EP4562730A1

EP4562730A1 - Multifunctional battery charging system

Info

Publication number: EP4562730A1
Application number: EP23748537.0A
Authority: EP
Inventors: Leonardus SLUIMAN; Juan Antonio CATENA OTREGA
Original assignee: Electroproject BV; Equans Infra & Energie BV
Current assignee: Electroproject BV; Equans Infra & Energie BV
Priority date: 2022-07-29
Filing date: 2023-07-28
Publication date: 2025-06-04
Also published as: WO2024023344A1; WO2024023345A1; EP4562731A1

Abstract

The present invention relates to a multifunctional battery charging system, configured to transfer electric energy between an electricity grid and one or more batteries, the system comprising: - a bi-directional transformer device, connectable to the electricity grid and configured to transform an AC grid voltage from the electricity grid into an AC system voltage, and vice versa - one or more preferably controllable bi-directional AC/DC converters, electrically connected to the transformer device and configured to transform the AC system voltage into a DC system voltage, and vice versa, - one or more bi-directional DC converters, electrically connected to the AC/DC converter and each configured to transform the DC system voltage into a DC interface voltage, and vice versa, - one or more electric interfaces, connected to the DC converters with each electric interface being connected to its own one or more parallel DC converters, and connectable to a battery and/or a source of renewable electric energy, configured to charge the battery by transferring electric energy obtained from the DC converter to the battery, and/or to transfer electric energy obtained from the battery to the DC converter.

Description

Title: Multifunctional battery charging system

Field of the invention

The present invention relates to a multifunctional battery charging system, configured to transfer electric energy between an electricity grid and one or more batteries. The present invention further relates to a method of charging a battery by means of a multifunctional battery charging system.

State of the art

At present, electricity is used more often to provide propulsion for vehicles, especially for road vehicles and watercrafts. The vehicles are thereto typically provided with batteries, which may be fixed in the vehicle or which may be exchangeable. The batteries do need to be charged once empty, for example when the vehicle is not in use. The batteries then need to be connected to the electricity grid temporarily to charge the batteries.

Several charging stations are known, which are typically adapted to the specific battery, or type of battery for which it is used. However, these known systems have the drawback that every type of battery requires its own charger. For example in container ports, both batteries of ships and of vehicles, like trucks and container handlers may need to be charged. Furthermore, it may be necessary to provide shore power to ships. The batteries of ships may be embodied as removable shipping containers, filled with battery cells, whereas the trucks may have fixed batteries. Accordingly, each type of vehicle presently requires its own charger, which is relatively cumbersome and requires relatively complex logistics.

For example, WO 2021/092658 A1 discloses a multimodal converter for use in electric vehicle charging stations for interfacing between at least one AC source and two DC sources, such a vehicle battery and a wind turbine or a solar panel array. This known converter relies on AC/DC converters and DC/DC converters that operate at certain fixed and predetermined voltages, which yields that each converter has be specifically manufactured and/or set for the sources that it is connected to, which reduces flexibility of the converter, for example making it impossible to connected different batteries to the converter.

Furthermore, it may be desired to use the batteries, once connected to the charging station, as a flexible buffer or sink for electric energy to provide for compensation of imbalances in the electricity grid. At present, this is not possible with existing charging stations.

Finally, it may also be desired to charge the batteries by means of sources of renewable electric energy, for example being present on the same site. At present, such sources may be connected to the electricity grid, having the drawback that efficiency is lost, as compared to when the renewable energy were to be used for charging directly.

Object of the invention

It is therefore an object of the invention to provide an improved multifunctional battery charging system, which allows multiple different types of batteries to be charged, for example in terms of capacity and/or voltage, and/or compensation of imbalances and/or direct DC connection of sources of renewable electric energy, or at least to provide an alternative battery charging system.

Detailed description

The present invention provides, according to a first aspect, a multifunctional battery charging system, configured to transfer electric energy between an electricity grid and one or more batteries, the system comprising: a bi-directional transformer device, connectable to the electricity grid and configured to transform an AC grid voltage from the electricity grid into an AC system voltage, and vice versa one or more bi-directional AC/DC converters, electrically connected to the transformer device and configured to transform the AC system voltage into a DC system voltage, and vice versa, one or more, preferably controllable, bi-directional DC converters, electrically connected to the AC/DC converter and each configured to transform the DC system voltage into a , preferably controllable, DC interface voltage, and vice versa, one or more electric interfaces, connected to the DC converters, e.g. with each interface being connected to its own one or more parallel DC converters, and connectable to a battery and/or a source of renewable electric energy, configured to:

• charge the battery by transferring electric energy obtained from the DC converter to the battery, and/or

• transfer electric energy obtained from the battery to the DC converter.

According to the present invention, a battery charging system is provided, which is able to charge batteries of multiple different types. For example, the present system is able to charge marine batteries, used for propulsion of ships, for example having a relatively high battery voltage of 1000 V and a battery capacity of 1 MWh. However, the present charging systems can be used to charge vehicles, like cars, with a relatively low battery voltage of 400 V and a battery capacity as low as 40 kWh. Moreover, all these different types of batteries, i.e. with different battery voltages, can be charged simultaneously with the present battery charging system. The present charging system can operate bi-directional, so that the battery can be charged, by transmitting electric energy from the electricity grid to the battery. Similarly, the battery can be discharged with the present charging system, by transmitting electric energy from the battery to the electricity grid.

The present multifunctional battery charging system is therefore able, in addition to the ability of regularly charging a battery, to compensate for imbalances in the electricity grid. Should there be a shortage of electric energy in the electricity grid, the present battery charging system is configured to discharge the battery to transfer electric energy towards the grid, whereas the battery charging system is also configured to charge the battery in case of an excess of electric energy in the electricity grid.

To this effect, the present battery charging system comprises a transformer device that is configured to transform the AC grid voltage in the electricity grid into an AC system voltage. Nonetheless, the AC grid voltage in the electricity grid may differ in dependence of the geographic location. The transformer device offers the benefit that the AC system voltage can be standardized, irrespective of the AC grid voltage in the electricity grid. As such, the same battery charging system can be used in various different locations, only requiring the transformer device to be adapted to a local AC grid voltage in the electricity grid.

The AC grid voltage may be 10 kV or more, which may qualify as a high voltage. However, the AC grid voltage is not necessarily a high voltage, as it may also be a low voltage, for example where the electricity grid is a rural network, such as a 400 V grid. The AC system voltage may be a low voltage, which may provide the benefit that safety regulations on low voltage equipment may be less strict than for high voltage equipment.

Alternatively, however, the AC grid voltage may be a low voltage and the AC system voltage may be a high voltage. This may be the case where the DC interface voltage to be supplied is relatively high and where the DC converters are not able to transform electricity at a large voltage difference. By having set the AC system voltage relatively high, i.e. and therefore also the DC system voltage, the DC converters may be able to output or absorb electricity at the relatively high DC interface voltage.

The transformer device is bi-directional, which means that the transforming of the voltage is carried out both when electricity is obtained from the electricity grid and when electricity is fed into the electricity grid.

The electricity grid may be connected to the transformer device with a 3-phase AC input line, subject to the AC grid voltage, for example by means of a 2 MVA grid connection. At the other side, the transformer device may be connected to one or more three-phase AC system voltage lines towards the other components of the battery charging system.

The battery charging system may further comprise a calibrated energy meter at its connection with the electricity grid, configured to register an amount of electric energy obtained from and fed into the electricity grid. This energy meter may monitor the amount of electric energy used to charge the batteries, but especially to monitor the electric energy obtained from the grid and fed into the grid for compensating the imbalances in the electricity grid, since economic benefits can be obtained on the basis of the amount of electric energy used for the compensation of imbalances.

The transformer device is electrically connected to the one or more bi-directional AC/DC converters. The AC/DC converters thereby receive electric energy from the transformer device at the AC system voltage to transform it into the DC system voltage or, oppositely, receive the electric energy from the battery at the DC system voltage to transform it into the AC system voltage towards the transformer device.

The AC/DC converters in the present battery charging system can be standardized components, since they are normally subject to the AC system voltage at one end and the DC system voltage at another end. These voltages, although being adjustable, can be standardized, irrespective of the geographic location of the battery charging system, i.e. irrespective of the local electricity grid, in terms of voltage, and the type of batteries that are to be charged. This standardization offers an economic improvement, compared to when different types of AC/DC converters were to be necessary.

The one or more bi-directional DC converters are electrically connected to the AC/DC converter and receive electric energy from the AC/DC converter at the DC system voltage to transform it into the DC interface voltage or, oppositely, receive the electric energy from the battery at the DC interface voltage to transform it into the DC system voltage towards the AC/DC converter.

The DC converters thereby form a link between the standardized DC voltage in the system, e.g. the DC system voltage, and the custom interfaces of the system, where the system is configured to output electric energy for charging the battery or where the system receives electric energy from the battery during discharging thereof. The DC converters may be controllable to receive and/or supply electric energy at the electric interface at a desired interface voltage, whilst being subject to the same and constant DC system voltage.

The DC converters are bi-directional as well, which allows them to output a desired DC interface voltage, whilst being fed with electric energy at one and the same DC system voltage. Accordingly, the DC converters are also configured to output electric energy at the DC system voltage, irrespective of the DC interface voltage at which electric energy is fed in to the DC converter from the battery.

The DC converters are each connected an electric interface, by means of which the system can output electric energy. The electric interface may be formed by wall sockets, for example when the battery charging system is used to charge batteries of electric vehicles. Additionally or alternatively, the electric interfaces may be wired connections to docking units for receiving exchangeable batteries.

In case multiple DC converters are provided in the battery charging system, the DC converters may all be placed in parallel, so that each of them is able to output or receive electric energy independent from the other DC converters. This may, for example, allow all DC interface voltages, from all DC converters, to be different from each other in dependence of the type of battery to which it is connected. Additionally, by having multiple DC converters arranged in parallel, selected parallel DC converters may be connected to a single electric interface to supply the DC interface voltage and power via the selected parallel DC converters. This has several advantages: Multiple DC converters may be more economically than a single DC converter having the same power rating. For example, the combined power rating of AC/DC converters may be substantially equal to the combined power rating of the DC converters, such that multiple DC converters can be used separately from each other when a relatively low power is required, and in parallel only when a relatively high power is required, thereby avoiding over dimensioning each of the DC converters. Secondly, the selected DC converters may operate at a more efficient power compared to a single DC converter. Further, redundancy may be provided by having multiple selected DC converters connected to an electric interface.

Accordingly, all electric interfaces are arranged parallel to each other, i.e. each electric interface being connected to its own one or more parallel DC converters, in order to output or receive the electric energy independently for all electric interfaces. Thus, an electric interface may be connected to a single DC converter, or - when multiple DC converters are provided - an electric interface may be connected to multiple DC converters that are arranged in parallel.

The charging system may only comprise, e.g. may consist of DC electric interfaces that are associated with a DC converter. As such, all electric interfaces are controllable via the DC converters, for example enabling the input or output voltage to be set. This allows that many different types of batteries can be charged and discharged with the present charging system, because the system is able to supply and withdraw electric energy at the right conditions to and from the battery. Likewise, it may enable that very many different types of sources of renewable electric energy can supply towards the present charging system, because the system is able to identify the relevant properties, in order to absorb electric energy at the right conditions from the sources.

During charging of the battery, electric energy may be obtained from the DC converter, i.e. from the electricity grid, and may be fed to the battery connected to the electric interface. Alternatively, when it is required to feed electric energy from the battery into the electricity grid, electric energy obtained from the battery and may be fed to the DC converter, i.e. further towards the electricity grid. In an embodiment, the one or more electric interfaces are further connectable to a source of renewable electric energy, wherein the one or more electric interfaces are configured to transfer electric energy obtained from the source of renewable electric energy to the DC converter. Examples of such sources of renewable electric energy are wind turbines or one or more photovoltaic panels.

According to this embodiment, one of the electric interfaces may be connected to the battery and another one of the electric interfaces may be connected to the source of renewable electric energy. The system is thereby able to both obtain electric energy from the renewable source and also, optionally even simultaneously, able to charge the batteries.

Similarly, the system may be also configured to both obtain electric energy from the renewable source and the battery, to feed a larger amount of electric energy into the electricity grid.

The connection with the renewable sources at the DC side of the system provides the benefit that no AC/DC conversion is needed in case it is desired to charge the batteries with renewable electric energy. In existing charging systems, the renewable electric energy is first converted into AC, fed into the grid, obtained from the grid by the charging system and converted into DC again. All these steps reduce the overall efficiency.

According to the present embodiment, the overall efficiency is thus improved. Furthermore, the present system is more flexible, since electric energy may be obtained from the renewable source at any DC voltage present, due to the ability of the DC converters to transform it into the DC system voltage.

Further flexibility is offered by the fact that, depending on the supply of renewable electric energy, one or more of the electric interfaces may be connected to one or more sources of renewable electric energy, which allows a single, standardized battery charging system to be used in various different applications.

In an embodiment, the one or more DC converters comprise multiple DC converters, and the DC converters are connected to the AC/DC converter in parallel via a DC system bus bar.

The DC system bus bar interconnects the DC converters at their sides that are subject to the DC system voltage. This parallel interconnection is the result of this unitary DC system voltage being present at all DC converters. With the DC converters being interconnected, all DC converters can be supplied with electric energy from the transformer device simultaneously, or can feed electric energy, obtained at their electric interfaces, towards the transformer device simultaneously.

Furthermore, the DC system bus bar allows that electric energy obtained at a first one of the electric interfaces can be transferred to a second one of the electric interfaces, without having to pass the transformer device, i.e. not requiring electric energy to be fed into the electricity grid or to be obtained therefrom. This may further reduce efficiency losses, since no conversion between AC and DC needs to be made.

In this case, the electric energy may be obtained by a first DC converter, connected to the first electric interface, by which it is transformed from a first DC interface voltage into the DC system voltage. The electric energy may be fed towards a second DC converter, via the DC system bus bar, after which the second DC converter is configured to transform the electric energy into a second DC interface voltage towards the second electric interface, connected to the battery.

In an embodiment, one of the electric interfaces is electrically connected to a DC interface bus bar and configured to be releasably connected to the battery for transferring electric energy between the DC converter and the battery.

According to this embodiment, a DC bus bar is also present at the interface side of the DC converters. The DC interface bus bar is connected to the electric interface that is connected to the battery. As such, all DC converters can be connected to that single battery electric interface, namely via the DC interface bus bar. This may offer the benefit that multiple DC converters can be used in parallel for transmitting electric energy to and from the battery, allowing relatively large charging or discharging currents to be achieved with modest DC converters that are, individually, not able to transmit such large currents.

Therewith, the cost of multiple smaller DC converters may be lower than that of a single DC converter having the same voltage and/or power rating as described hereinabove. Additionally, the multiple DC converters may operate more efficiently than a single DC converter at the same voltage and/or power.

The use of a DC interface bus bar for interconnecting multiple DC converters may offer a further benefit, since the DC converters can form a backup for each other, i.e. provide redundancy. In case one of the DC converters may be out of order, for example being broken down or in maintenance or repair, the other DC converters can be used to keep the battery charging system in function, even though one of the DC converters is not in use.

In a further embodiment, the one or more DC converters are each selectively connectable to the DC interface bus bar or to a single allocated one of the electric interfaces. This may offer the benefit that, dependent on the capacity of the battery and/or a desired charging and discharging current, the number of DC converters used for charging and discharging may be changed.

In case only a relatively small battery needs to be charged, a small number of DC converters may be connected to the DC interface bus bar to meet the charging requirements, whereas other DC converters can be used for other purposes, for example being connected to another battery or a source of renewable electric energy. In case large batteries are needed, the battery charging system is flexible, and allows multiple DC converters to charge the battery at the battery electric interface together.

The use of a battery charging system according to the present embodiment may be in particular beneficial where large batteries need to be charged, for example exchangeable batteries for ships, for only a short period of time and/or where large currents are received and/or supplied via the electric interface. During this short period, the relatively small DC converters can be combined and connected to the DC interface bus bar to meet the required large current, i.e. charging speed, whereas the DC converters can be disconnected from the DC interface bus bar outside this period. The individual DC converters can then, for example, each be used to charge relatively small vehicle batteries where only a single DC converter would already offer sufficient capacity.

The multiple DC converters, connectable at their interfaces, provide the benefit that the charging system is able to operate very flexibly, in dependence of the required electric power input or output at the electric interfaces. Hence, not all of the individual DC converters need to have an individual maximum power rating equal to the maximum power rating of the overall system and/or of the AC/DC converters. Instead, preferably, a combined maximum power rating of all DC converters operating in parallel is substantially similar to a combined maximum power rating of all AC/DC converters operating in parallel and/or to a maximum power rating of the overall system.

In an embodiment, the system comprises a further calibrated energy meter, i.e. a battery energy meter, at the battery electric interface. The battery energy meter is configured to register an amount of electric energy obtained from and fed into the battery connected to the battery electric interface. This battery energy meter may monitor the amount of electric energy used to charge the batteries, especially in case the battery is used for transportation purposes. In some jurisdictions, rewards are offered by authorities in case renewable electric energy is used for transportation purposes, like trucks or vessels.

These renewable energy units can be monitored by the battery energy meter at the DC battery electric interface, which offers the benefit that the energy is measured right before entering the battery in DC. Until present, the only possible way of measuring renewable energy units was via the network energy meter of the grid operator. However, this network energy meter is provided in the electricity grid, subject to the AC grid voltage in the grid. This implies that the renewable energy units with the network energy meter are not accurate, being subject to efficiency losses relative to the net electric energy fed into the grid, for example due to transformer devices and/or AC/DC conversion. The present battery energy meter may lack such losses and may offer more accurate measuring of renewable energy units. In an embodiment, the one or more AC/DC converters comprise multiple AC/DC converters, and the transformer device is connected to each of the AC/DC converters to form a branch for each of the AC/DC converters.

According to this embodiment, the electric energy obtained from the electricity grid is split up into multiple branches after transforming with the transformer device. Similarly, in case energy is fed into the electricity grid, the electric energy from the multiple branches is recombined into the transformer device. In particular, the transformer device comprises connections for each of the AC/DC converters, i.e. for each of the branches, so that the splitting into branches is carried out by the transformer device.

The multiple branches have the benefit that multiple AC/DC converters can form a backup for each other. In case one of the AC/DC converters may be out of order, for example being broken down or in maintenance or repair, the other AC/DC converters can be used to keep the battery charging system in function, even though one of the AC/DC converters is not in use.

The use of a battery charging system according to the present embodiment may be in particular beneficial where large batteries need to be charged, for example exchangeable batteries for ships, for only a short period of time. During this short period, multiple relatively small AC/DC converters of different branches can be combined and connected to the battery to meet the required large charging speed.

In a further embodiment, each of the branches comprises at least one of the DC converters. According to this embodiment, each of the branches is able to transform the DC system voltage into the DC interface voltage, independent of the other DC converters and the other AC/DC converters in the other branch, to further improve the flexibility of the present battery charging system.

In a further embodiment, each of the branches comprises a DC system bus bar in between its AC/DC converter and its at least one DC converter, wherein the DC system bus bars of the branches are electrically insulated from each other. Similar as when only a single AC/DC converter is present, as described above, does the present embodiment offer the benefit of having multiple DC converters arranged in parallel to each other, but in addition for each of the branches as well. This further increases the charging and discharging currents that can be obtained with the present battery charging system.

In the present embodiment, the DC system bus bars are electrically insulated from each other, which offers the benefit that, for example, one of the branches can be used to charge a battery directly from the grid, having multiple DC converters in a single branch charging in parallel to each other. The DC converters in the other branch can for example be connected to a source of renewable energy and to a smaller battery, in order to charge the smaller battery via the DC system bus bar with renewable electric energy, without passing the AC/DC converter of this branch.

Optionally, each of the branches has its DC converters connected to its own DC interface bus bar, so that the electric interfaces of each of the branches can be interconnected. This may offer the possibility to charge or charge a relatively large battery with each of the branches.

As a further option, the DC interface bus bars of different branches may be connectable to each other, in order to be able to charge and discharge batteries with all AC/DC converters and all DC converters operating in parallel to each other.

In an embodiment, the present battery charging system may have a single transformer device, connected to the electricity grid. The transformer device may be connected to two AC/DC converters to obtain two branches. Each other branch may comprise a single DC system bus bar, to which three DC converters are connected.

Each of the DC converters can be selectively connected with its own electric interface, i.e. having six individual electric interfaces. Furthermore, each of the branches has a single DC interface bus bar, to which the DC converters can also be selectively connected. The DC interface bus bars are each connected to a battery electric interface, so that each branch can charge a single, i.e. relatively large battery with three DC converters in parallel. The DC interface bus bars are also connectable to each other, to be able to charge a single battery with six DC converters, via both AC/DC converters.

In an embodiment, the transformer device is included in a first modular compartment, i.e. a power distribution unit, and the AC/DC converter and the DC converters are included in a second modular compartment, i.e. a power interface unit.

This modular layout of the battery charging system provides the benefit that all high voltage components, i.e. the transformer device and a grid connection between the battery charging system and the electricity grid, may be included in the first modular compartment. All low voltage components are included in a different compartment, i.e. the second modular compartment, and may therefore be subject to different regulations.

Furthermore, it was explained earlier that all components of the battery charging system can be standardized components, except for the transformer device, which needs to be adapted to the local electricity grid, for example to the AC grid voltage. With the present embodiment, the entire second modular compartment, i.e. power interface unit, can be used uniformly, due to the AC system voltage being standard, irrespective of the AC grid voltage in the electricity grid. Only the first modular compartment, i.e. the power distribution unit needs to be adapted towards local requirements, thereby improving flexibility of the present battery charging system. The modular compartments may be dedicated housings for the relevant components, each compartment for example being embodied as a modified shipping container, to improve the transportability and placement of the present battery charging system.

In a further embodiment, the system further comprises one or more battery docking devices, with which the battery charging system is connectable to the battery, wherein each battery docking device is included in a third modular compartment, i.e. a battery docking unit.

The battery docking device may be configured to receive a battery, for example allowing placement of the battery on the docking device. This may allow for an automated connection between the battery and the docking device, allowing the battery charging system to operate autonomously.

In an embodiment, the charging system may be provided with at least one interface sensor, for example comprising an interface sensor at each of the electric interfaces, configured to emit an interface sensor signal representative for an electric parameter at the respective electric interface. The interface sensor may for example comprise a voltage sensor, configured to measure or retrieve a voltage at the respective electric interface and to output a sensor signal representative for a voltage measured at the electric interface. As such, the voltage of a battery and/or source of renewable electric energy connected to that electric interface may be measured. Subsequently, the DC converter of that electric interface may be set on the measured voltage, in order to enable that the battery is charged at the right voltage and/or that the electric energy from the source of renewable electric energy is absorbed into the charging system at the right voltage.

Alternatively or additionally, the at least one interface sensor may be configured to directly retrieve a battery identifier from a battery connected to the respective electric interface, which battery identifier may comprise information about which battery is connected to the battery charging system, so that an operator of multiple batteries can track which batteries are charged and which batteries have been charged in the past and that the charging and discharging properties can be established on the basis of the battery identifier.

This embodiment may enable that very many different types of batteries can be charged and discharged with the present charging system, because the system is able to identify the relevant battery properties, in order to supply and withdraw electric energy at the right conditions to and from the battery. Likewise, it may enable that very many different types of sources of renewable electric energy can supply towards the present charging system, because the system is able to identify the relevant properties, in order to absorb electric energy at the right conditions from the sources. In an embodiment, the battery charging system further comprises a control device, configured to control the system, for example to control the one or more AC/DC converters and/or the one or more DC converters. The control device may be configured to control the components of the battery charging system, to allow the battery charging system to operate at desired voltages and/or phases, for example a pre-set AC system voltage or phase difference, DC system voltage and/or DC interface voltage. Furthermore, the control device may be configured to communicate with batteries that are connected to the electric interface, to optionally allow autonomous charging and discharging of the batteries.

In an embodiment, the control device is configured to control the DC converters, on the basis of whether the electric interfaces are connected to the battery or to the source of renewable electric energy, to transmit electric energy obtained from the electric interfaces connected to the source of electric energy towards the electric interfaces connected to the battery.

The control device may thereby determine whether any of the electric interfaces is connected to the source of renewable electric energy, and thus only required to obtain electric energy, or whether the electric interfaces are connected to the battery. In the latter case, the electric interface may be required to both feed and obtain electric energy, respectively during charging and discharging of the battery.

The control device of the battery charging system according to the present embodiment is then further configured to allow charging of the battery by means of electric energy obtained from the renewable source, preferably via two or more DC converters that are preferably arranged in parallel via the DC system bus bar, so that the charging can take place without obtaining electric energy from the electricity grid.

In an embodiment, the control device is further configured to control the system to selectively charge the battery by transferring electric energy obtained from the electricity grid to the electric interface connected to the battery and/or to selectively transfer electric energy obtained from the electric interface connected to the source of renewable electric energy to the electricity grid.

In a further embodiment, the control device is associated with the interface sensor, for example associated with each of the interface sensors at each of the electric interfaces, wherein the control device is further configured to control the DC converter associated with the interface sensor in dependence of the electric parameter, i.e. contained in the interface sensor signal, for example to set an output voltage and/or an input voltage of the DC converter in dependence of the measured voltage. This may enable that, when a battery is connected to the electric interface in order to be charged and/or when a source of renewable electric energy is connected to the electric interface in order to supply the charging system with renewable electric energy, the battery is charged at the right voltage and/or that the electric energy is absorbed into the charging system at the right voltage.

Alternatively or additionally, the at least one interface sensor may be configured to directly retrieve a battery identifier from a battery connected to the respective electric interface, which battery identifier may comprise information about which battery is connected to the battery charging system, so that an operator of multiple batteries can track which batteries are charged and which batteries have been charged in the past and that the charging and discharging properties can be established on the basis of the battery identifier

This embodiment may enable that very many different types of batteries can be charged and discharged with the present charging system, because the system is able to identify the relevant battery properties, in order to supply and withdraw electric energy at the right conditions to and from the battery. Likewise, it may enable that very many different types of sources of renewable electric energy can supply towards the present charging system, because the system is able to identify the relevant properties, in order to absorb electric energy at the right conditions from the sources.

The present system with multiple DC converters and/or one or more AC/DC converters may further provide that the compensating for imbalances may take place in different regimes. For example, one of the DC converters and associated battery or source of renewable electric energy may form a Frequency Containment Reserve (FCR) for the electricity grid, whereas another DC converter may deliver or absorb power to or from the electricity grid and yet another DC converter may be used for peak shaving. Additionally or alternatively, one or multiple AC/DC converters may provide for power factor correction by delivering or absorbing reactive power to or from the electricity grid.

These different regimes, which are explained in further detail below, may be entered simultaneously or one after another, depending on the available conditions. The ability to operate in different imbalance regime may provide that the current charging system can be used more flexibility, which is more cost effective, compared to when a separate, dedicated system were need to be provided for each of the regimes individually. In an embodiment, the battery charging system further comprises an imbalance module, connected to an external platform for monitoring imbalances in the electricity grid and configured to output an imbalance signal representative for imbalances in the electricity grid, wherein the control device is configured to control the system in dependence of the imbalance signal to selectively obtain electric energy from the electricity grid, and/or selectively feed electric energy into the electricity grid, in order to compensate for imbalances in the electricity grid. The imbalance module may be included in the battery charging system to allow the battery charging system to perform ancillary services for the electricity grid, by selectively obtaining electric energy from the electricity grid and by selectively feeding electric energy into the electricity grid, so that any imbalances can be compensated.

The ancillary services may be provided by the battery charging system on various different levels, i.e. time scales. In the following, several examples of ancillary services are mentioned, which are hereinafter referred to generically by means of “compensating for imbalances”.

As a first example, the battery charging system according to this embodiment may be used to form a Frequency Containment Reserve (FCR) for the electricity grid, which may be beneficial for stabilising frequency disturbances in the electricity grid, in order to compensate for disruptions. Severe frequency disturbances can lead to automatic load shedding and could, in the worst case, cause a blackout. The present battery charging system can be certified by the grid authorities to offer a certain volume of frequency containment reserve within a certain imbalance compensation time window, i.e. an FCR time window, for example a time window of several hours, depending on parameters of the battery charging system like maximum charging and discharging currents and battery capacities.

The battery charging system according to the present embodiment may, as a second example, be configured to deliver reactive power to the electricity grid or to absorb reactive power from the electricity grid. The battery charging system may be registered for a longer period of time, for example by means of yearly contracts.

Thirdly, the present battery charging system may be used to compensate for imbalances caused by under- or overloading of the electricity grid, also known as so-called “peak shaving”. This may occur when the demand for electric energy in the electricity grid is too high for the regular supply, in which case the battery of the battery charging system can be discharged to feed electric energy into the electricity grid. Oppositely, in case the supply of electric energy in the electricity grid is too high for the demand, the battery charging system may charge the battery to absorb electric energy from the electricity grid. The latter may be beneficial when the electricity grid relies on sources of renewable energy, like wind turbines or photovoltaic panels, that have respective large productivities in windy or sunny circumstances.

The battery charging system may also be used to avoid further imbalances of the electricity grid by local peak shaving, i.e. by using a connected sustainable energy source connected to an electric interface to charge the battery connected to the same or another electric interface, thereby limiting the amount of electric energy fed into the electricity grid.

As a final example, the present battery charging system may be able to provide electric energy to the electricity grid in case of a power outage or blackout, during which regular supplies of electricity cannot provide electric energy. The present battery charging system may form a backup in these situations, being able to discharge the battery.

In all of the above examples, economic benefits may be obtained from the grid authorities if these ancillary services are provided. These economic benefits may vary and can be dependent on a time frame during which the battery charging system is able to deliver the ancillary services, the extent, i.e. capacity, to which the ancillary services can be performed and to an actual amount of electric energy that is transferred between the battery charging system and the electricity when these ancillary services are carried out.

The battery charging system according to the present embodiment is thus able to both charge batteries and to perform ancillary services, by which economic benefits can be obtained, whilst still allowing the batteries to be charged within a predetermined timeframe.

When the battery charging system according to the present embodiment is used to perform ancillary services, the battery charging system is configured to charge the battery up to a required state of charge prior to being available for ancillary services, i.e. before the start of an imbalance compensation time window.

In an embodiment, the battery charging system further comprises the source of renewable electric energy, for example a wind turbine and/or one or more photovoltaic panels, wherein the source of renewable electric energy is electrically connected to one or more of the electric interfaces to supply electric energy to one or more of the DC converters, and wherein the system is configured to supply electric energy obtained from the renewable source to the other electric interfaces via the other DC converters, for example to a battery connected thereto, without requiring electric energy to be obtained from the electricity grid.

The sources of renewable electric energy are connected to one or more of the electric connectors, depending on the type and number of renewable sources. Each of the renewable sources is thereby configured to supply electric energy to the electric interfaces at the DC interface voltages, optionally each source with a different DC interface voltage. This offers the benefit that the renewable electric energy is supplied in DC already, thus not requiring any AC/DC conversion prior to feeding into the battery. This may offer a benefit over existing systems in which the renewable electric energy is obtained in AC, from the electricity grid, thus requiring AC/DC conversion that could reduce the overall efficiency.

Furthermore, the battery charging system according to the present embodiment has the benefit that the DC converters are able to receive renewable electric energy at their electric interfaces at any DC interface voltage, after which it is transformed into the DC system voltage. This offers a further improved flexibility, since the components of the battery charging system, i.e. the DC converters, do not require specific adaptation to the types of renewable sources that are connected to the electric interfaces. According to this embodiment, the battery charging system is configured to charge the battery by means of electric energy obtained from the renewable source, preferably via two or more DC converters that are preferably arranged in parallel via the DC system bus bar, so that the charging can take place without obtaining electric energy from the electricity grid.

In a further embodiment, the control device is further configured to control the system, in dependence of the imbalance signal to selectively feed electric energy obtained from the source of renewable electric energy to the electricity grid, in order to compensate for imbalances in the electricity grid.

As such, the electric energy obtained from the source of renewable electric energy may also be used to perform ancillary services with. In case there is a shortage of electric energy in the electricity grid, the renewable electric energy obtained from the renewable sources can also be fed into the electricity grid, in addition to the electric energy obtained from the battery. Furthermore, in case of an excess of electric energy in the electricity grid, the battery charging system may be configured to charge the battery both with electric energy obtained from the grid when ancillary services are performed and with electric energy obtained from the renewable source.

In an embodiment, the AC system voltage is in the range between 400 V and 1000 V, for example about 700 V. An AC voltage in this range may qualify as a low voltage, so that the safety regulations for the AC/DC converter may apply for low voltage equipment, which may be less strict than for high voltage equipment. Typically, the AC system voltage may be selected as large as possible to improve the efficiency of the system and to reduce electric currents, to reduce the size of the electric components.

In alternative embodiments, however, the AC system voltage may be in the range between 300 V and 1200 V. This wider range may be beneficial where the AC/DC converters and/or DC converters may not be able to transform electricity at a large voltage difference, so that the system may still be able to supply or absorb electricity at a desired DC interface voltage.

In an embodiment, the one or more AC/DC converters comprise an active rectifier device, for example an Active Front End (AFE). Such an active rectifier device may be configured to output a controllable DC system voltage when electric energy is obtained from the electricity grid, irrespective of the AC system voltage from the transformer device. Similarly, the active rectifier device may be configured to output a controllable AC system voltage when electric energy is fed into the electricity grid, irrespective of the DC system voltage from the DC converters. In an embodiment, the DC system voltage is in the range between 500 V and 1500 V, for example about 1100 V. A DC voltage in this range may qualify as a low voltage, so that the safety regulations for the DC converters may apply for low voltage equipment, which may be less strict than for high voltage equipment. Typically, the DC system voltage may be selected as large as possible to improve the efficiency of the system and to reduce electric currents, to reduce the size of the electric components.

In alternative embodiments, however, the DC system voltage may be in the range between 300 V and 1500 V. This wider range may be beneficial where the DC converters may not be able to transform electricity at a large voltage difference, so that the system may still be able to supply or absorb electricity at a desired DC interface voltage.

In an embodiment, the DC converters are each configured to adjust the DC interface voltage, e.g. independent of each other. As such, each of the DC converters may feed electric energy to its electric interface at its own DC interface voltage.

In a further embodiment, the DC interface voltage is adjustable in the range between 300 V and 1100 V. A DC system voltage in this range offers various possibilities for charging batteries, for example exchangeable batteries for vessels, which may operate at a DC battery voltage of 1000 V. However, the DC interface voltage may also be as low as 400 V, which is a typical DC battery voltage of electric vehicles.

According to a second aspect, the present invention provides a method of charging a battery by means of a multifunctional battery charging system as disclosed herein, in particular as recited in the preceding claims, the method comprising the steps of: electrically connecting a battery to an electric interface of the battery charging system, selectively charging and discharging the battery by means of the battery charging system, wherein the selective charging and discharging comprises:

• charging the battery by transferring electric energy obtained from the electricity grid to the battery, and/or

• discharging the battery by transferring electric energy obtained from the battery to the electricity grid.

The method according to the second aspect of the present invention may comprise one or more of the features and/or benefits of the battery charging system according to the first aspect of the invention, in particular as recited in the appended claims.

According to the present invention, one or more batteries can be charged by means of a battery charging system. The batteries may, but not need to, be of the same type and can also be charged simultaneously and independent of each other. For example, the present method may allow for charging of marine batteries, used for propulsion of ships, for example having a relatively high battery voltage of 1000 V and a battery capacity of 1 MWh. However, the present method can also be carried out to charge vehicles, like cars, with a relatively low battery voltage of 400 V and a battery capacity as low as 40 kWh. Preferably, the present system is able to charge multiple different types of batteries, i.e. with different battery voltages, simultaneously.

The present charging system can operate bi-directional, so that the battery can be charged, by transmitting electric energy from the electricity grid to the battery. Similarly, the battery can be discharged with the present charging system, by transmitting electric energy from the battery to the electricity grid.

The multifunctional battery charging system used in the present method is able, in addition to the ability of regularly charging a battery, to compensate for imbalances in the electricity grid. Should there be a shortage of electric energy in the electricity grid, the present battery charging system is configured to discharge the battery to transfer electric energy towards the grid, whereas the battery charging system is also configured to charge the battery in case of an excess of electric energy in the electricity grid.

During charging of the battery, electric energy may be obtained from the DC converter, i.e. from the electricity grid, and may be fed to the battery connected to the electric interface. Alternatively, when it is required to feed electric energy from the battery into the electricity grid, electric energy obtained from the battery and may be fed to the DC converter, i.e. further towards the electricity grid.

In an embodiment, the method further comprises the step of releasing the connection between the battery and the battery charging system after the battery has been charged to a desired state of charge. As such, the charged battery can be removed, for example exchanged with an empty battery, so that the empty battery can be charged in turn.

In an embodiment, the method further comprises, after the step of connecting and before the step of selectively charging, the step of measuring an electric parameter with an interface sensor provided at a respective electric interface, for example measuring a voltage with a voltage sensor at the respective electric interface. As such, the voltage of a battery and/or source of renewable electric energy connected to that electric interface can be measured. Subsequently, the DC converter of that electric interface may be set on the measured voltage, in order to enable that the battery is charged at the right voltage and/or that the electric energy from the source of renewable electric energy is absorbed into the charging system at the right voltage.

Alternatively or additionally, the electric parameter may comprise a battery identifier that is retrieved from a battery connected to the respective electric interface, which battery identifier may comprise information about which battery is connected to the battery charging system, so that an operator of multiple batteries can track which batteries are charged and which batteries have been charged in the past and that the charging and discharging properties can be established on the basis of the battery identifier

In an embodiment, the method further comprises the step of controlling the system, for example controlling the one or more AC/DC converters and/or the one or more DC converters, by means of a control device. The control device may control the components of the battery charging system, to allow the battery charging system to operate at desired voltages and/or phases, for example a pre-set AC system voltage or phase difference, DC system voltage and/or DC interface voltage. Furthermore, the control device may configured to communicate with batteries that are connected to the electric interface, to optionally allow autonomous charging and discharging of the batteries.

The steps of measuring of the electric parameter and of controlling may be carried out repeatedly during charging and discharging of the batteries, as certain parameters of the batteries, such as the battery voltage, may change over time during charging. A battery with a relatively low state of charge may typically operate at a lower battery voltage than the same battery at a relatively high state of charge. By measuring these parameters repeatedly and by controlling the AC/DC converters and/or the DC converters, the voltage may be adjusted at which the electric energy is supplied to and withdrawn from the battery during charging and discharging.

In a further embodiment, the controlling involves controlling the DC converters, on the basis of whether the electric interfaces are connected to the battery or to the source of renewable electric energy, to transmit electric energy obtained from the electric interfaces connected to the source of electric energy towards the electric interfaces connected to the battery.

In a further embodiment, the controlling involves controlling the system to selectively charge the battery by transferring electric energy obtained from the electricity grid to the electric interface connected to the battery and/or to selectively transfer electric energy obtained from the electric interface connected to the source of renewable electric energy to the electricity grid.

In an embodiment, the control device is associated with the interface sensor and the controlling involves controlling the DC converter associated with the interface sensor in dependence of the measured electric parameter, for example to set an output voltage and/or an input voltage of the DC converter in dependence of the measured voltage. This may enable that, when a battery is connected to the electric interface in order to be charged and/or when a source of renewable electric energy is connected to the electric interface in order to supply the charging system with renewable electric energy, the battery is charged at the right voltage and/or that the electric energy is absorbed into the charging system at the right voltage.

This may enable that very many different types of batteries can be charged and discharged with the present method, because the charging system is able to identify the relevant battery properties, in order to supply and withdraw electric energy at the right conditions to and from the battery. Likewise, it may enable that very many different types of sources of renewable electric energy can supply towards the present charging system, because the system is able to identify the relevant properties, in order to absorb electric energy at the right conditions from the sources.

In an embodiment, the method further comprises the step of: electrically connecting a source of renewable electric energy, for example a wind turbine and/or one or more photovoltaic panels, to another electric interface of the battery charging system, wherein the selective charging and discharging comprises:

• charging the battery by transferring electric energy obtained from the source of renewable electric energy to the battery, and/or

• transferring electric energy obtained from the source of renewable electric energy to the electricity grid.

According to this embodiment, one of the electric interfaces is connected to the battery and another one of the electric interfaces is connected to the source of renewable electric energy. This method thereby allows the battery charging system to both obtain electric energy from the renewable source and also, optionally even simultaneously, able to charge the batteries.

Similarly, the method allows the battery charging system to both obtain electric energy from the renewable source and the battery, to feed a larger amount of electric energy into the electricity grid.

The connection with the renewable sources at the DC side of the battery charging system provides the benefit that no AC/DC conversion is needed in case it is desired to charge the batteries with renewable electric energy. When charging methods are carried out by means of existing battery charging systems, the renewable electric energy is first converted into AC, fed into the grid, obtained from the grid by the charging system and converted into DC again. All these steps reduce the overall efficiency.

According to the present embodiment, the overall efficiency is thus improved. Furthermore, the present charging method is more flexible, since electric energy may be obtained from the renewable source at any DC voltage present, due to the ability of the DC converters to transform it into the DC system voltage.

Brief description of drawings

Further characteristics of the invention will be explained below, with reference to embodiments, which are displayed in the appended drawings, in which:

Figures 1 - 5 schematically depict an embodiment of the battery charging system according to the present invention in various different configurations.

Throughout the figures, the same reference numerals are used to refer to corresponding components or to components that have a corresponding function.

Detailed description of embodiments

Figures 1 - 5 schematically depict an embodiment of the battery charging system according to the present invention, to which is referred with reference numeral 1. The battery charging system 1 is configured to transfer electric energy between an electricity grid 100 and two batteries 200. The electricity grid 100 is connected to the transformer device 10 with a 3- phase AC input line, subject to an AC grid voltage VAC,H. In the present embodiment, the grid connection 100 is a 2 MVA grid connection and the AC grid voltage VAC.H is 10 kV.

The battery charging system 1 is able to charge batteries 200 of multiple different types, for example to charge marine batteries 200, used for propulsion of ships, that have a relatively high battery voltage of 1000 V and a battery capacity of 1 MWh. However, the present charging systems can be used to charge vehicles 201 with a relatively low battery voltage of 400 V and a battery capacity as low as 40 kWh. Especially, the present embodiment of the battery charging system 1 is able to charge multiple different types of batteries, i.e. with different battery voltages, simultaneously.

The present charging system 1 can operate bi-directional, so that the batteries 200 can be charged, by transmitting electric energy from the electricity grid 100 to the batteries 200. Similarly, the batteries 200 can be discharged with the present charging system 1 , by transmitting electric energy from the batteries 200 to the electricity grid 100. The present multifunctional battery charging system 1 is therefore able, in addition to the ability of regularly charging batteries 200, to compensate for imbalances in the electricity grid 100. Should there be a shortage of electric energy in the electricity grid 100, the present battery charging system 1 is configured to discharge the batteries 200 to transfer electric energy towards the grid 100, whereas the battery charging system 1 is also configured to charge the batteries 200 in case of an excess of electric energy in the electricity grid 100.

The battery charging system 1 further comprises an imbalance module 2, connected to an external platform for monitoring imbalances in the electricity grid 100 and configured to output an imbalance signal representative for imbalances in the electricity grid 100. A control device of the system 1 is configured to control the system 1 in dependence of the imbalance signal to selectively obtain electric energy from the electricity grid 100, and/or to selectively feed electric energy into the electricity grid 100, in order to compensate for imbalances in the electricity grid 100.

The battery charging system 1 comprises a calibrated energy meter 3 at its connection with the electricity grid 100, configured to register an amount of electric energy obtained from and fed into the electricity grid 100. This energy meter 3 is configured to monitor the amount of electric energy used to charge the batteries 200 and to monitor the electric energy obtained from the grid 100 and fed into the grid 100 for compensating the imbalances in the electricity grid 100.

The system 1 comprises a transformer device 10 that is connected to the electricity grid 100, configured to transform the AC grid voltage VAC.H from the electricity grid 100 into an AC system voltage VAC.L, and vice versa. The transformer device 10 is bi-directional, which implies that the transforming of the voltages VAC.H, VAC.L is carried out both when electricity is obtained from the electricity grid 100 and when electricity is fed into the electricity grid 100. Even though the AC grid voltage VAC.H in the electricity grid 100 may differ in dependence of the geographic location, is the transformer device 10 able to operate with a AC system voltage AC.L that can be standardized, irrespective of the AC grid voltage VAC.H in the electricity grid 100.

During use of the system 1 according to the present embodiment, the AC system voltage VAC.L is set in the range between 400 V and 1000 V, for example at about 700 V.

The transformer device 10 is electrically connected to two bi-directional AC/DC converters 20, so that a branch 21 is formed for each of the AC/DC converters 20, each configured to transform the AC system voltage VAC.L into a DC system voltage VDC.S, and vice versa. The AC/DC converters 20 in the present battery charging system 1 are standardized components, since they are normally subject to the AC system voltage VAC.L at one end and the DC system voltage VDC.S at another end.

The AC/DC converters 20 are embodied as Active Front Ends (AFE), configured to output a controllable DC system voltage VDC.S when electric energy is obtained from the electricity grid 100, irrespective of the AC system voltage VAC.L from the transformer device 10. Similarly, the Active Front Ends are configured to output a controllable AC system voltage VAC.L, e.g. at a controllable phase, when electric energy is fed into the electricity grid 10, irrespective of the DC system voltage VDC.S from the batteries 200.

These voltages VAC.L, VDC.S, although being adjustable, can be standardized, irrespective of the geographic location of the battery charging system 1 and the local electricity grid 100.

The present embodiment thereby provides that electric energy obtained from the electricity grid 100 is split up into two branches 21 after transforming with the transformer device 10. The AC/DC converters 20 thereby receive electric energy from the transformer device 10 at the AC system voltage VAC.L to transform it into the DC system voltage VDC.S. Similarly, in case electric energy is fed into the electricity grid 100, the electric energy from the multiple branches 21 is recombined by the transformer device 10. The AC/DC converters 20 thereby receive the electric energy from the batteries 200 at the DC system voltage DC.S to transform it into the AC system voltage VAC.L towards the transformer device 10.

The two branches 21 have the benefit that the AC/DC converters 20 can form a backup for each other. In case one of the AC/DC converters 20 may be out of order, the other AC/DC converter 20 can be used to keep the battery charging system 1 in working order. Also, the branches 21 are in particular beneficial with these exchangeable batteries 200 for ships being charged for a short period of time.

During use of the system 1 according to the present embodiment, the DC system voltage VDC.S is set in the range between 500 V and 1500 V, for example at about 1100 V

The system 1 further comprises six bi-directional DC converters 30, which are spread in two sets of three DC converters 30 arranged in parallel, in particular one set for each of the branches 21. The DC converters 30 are connected to the AC/DC converters 20 and are configured to transform the DC system voltage VDC.S into a DC interface voltage VDC.I, and vice versa. In particular, the DC converters 30 of a first one 21 of the branches are connected to a first one 20 of the AC/DC converters. Similarly, the DC converters 30’ of a second one 2T of the branches are connected to a second one 20’ of the AC/DC converters. Each of the branches 21 comprises three DC converters 30, so that each of the branches 21 is able to transform the DC system voltage VDC.S into the DC interface voltage VDC.I, independent of the other DC converters 30 and the other AC/DC converter 20 in the other branch 21 .

The bi-directional DC converters 30 are electrically connected to the AC/DC converter 20 and receive electric energy from the AC/DC converter 20 at the DC system voltage VDC.S to transform it into the DC interface voltage VDC.I or, oppositely, receive the electric energy from the battery 20 at the DC interface voltage VDC.I to transform it into the DC system voltage VDC.S towards the AC/DC converter 20.

The DC converters 30 thereby form a link between the standardized DC voltage in the system 1 , e.g. the DC system voltage VDC.S, and custom interfaces of the system 1 , where the system 1 is connected to the battery 200. The DC converters 30 are bi-directional as well, which allows them to output a desired DC interface voltage VDC.I, whilst being fed with electric energy at one and the same DC system voltage VDC,S. Accordingly, the DC converters 30 are also configured to output electric energy at the DC system voltage VDC.S, irrespective of the DC interface voltage VDC.I at which electric energy is fed in to the DC converter 30 from the battery 20.

The DC converters 30 are each configured to adjust the DC interface voltage VDC.I , independent of each other. As such, each of the DC converters 30 is able to feed electric energy to its electric interface at its own DC interface voltage DC.I, which may be adjustable in the range between 300 V and 1100 V.

Each of the branches 21 comprises a DC system bus bar 31 in between its AC/DC converter 20 and its three DC converters 30. The DC converters 30 are connected to their AC/DC converter 20 in parallel via their DC system bus bar 31. The DC system bus bar 31 interconnects the DC converters 30 at their sides that are subject to the DC system voltage VDC.S. The DC system bus bar 31 allows that electric energy can be transferred from a first DC converter 30 to a second DC converter 30, without having to pass the transformer device 10 and without requiring electric energy to be fed into the electricity grid 100 or to be obtained therefrom. In particular, renewable electric energy may be obtained from by a first DC converter 30, connected to source of renewable energy 300, by which it is transformed from a first DC interface voltage VDC.H into the DC system voltage VDC.S. The electric energy may be fed towards a second DC converter 30, via the DC system bus bar 31 , after which the second DC converter 30 is configured to transform the electric energy into a second DC interface voltage VDC,I2 towards the battery.

The DC system bus bar 31 of the first branch 21 is electrically insulated from the DC system bus bar 3T of the second branch 2T. The system 1 allows, as a result of the DC system bus bars 30 being electrically insulated from each other, that one of the branches 21 can be used to charge a battery 200 directly from the grid 100, having multiple DC converters 30 in that branch 21 charging in parallel to each other. The DC converters 30’ in the other branch 2T can for example be connected to a source of renewable energy 300 and to a vehicle 201 , in order to charge the vehicle 201 via the DC system bus bar 31 with renewable electric energy, without passing the AC/DC converter 20’ of this branch 2T.

The system further comprises two battery interfaces 41 , which are selectively connectable to the DC converters 30 and releasably connectable to one of the batteries 200. The battery interfaces 41 are configured to charge the batteries 200 by transferring electric energy obtained from the DC converters 30 to the batteries 200 and to transfer electric energy obtained from the batteries 200 to the DC converters 30. In between the battery interface 41 and the DC converters 30, respective DC interface bus bars 42 are provided. Each of the interface bus bars 42 is connected to all DC converters 30 of the branch 21 , so that all DC converters 30 of that branch 21 can be connected to a single battery interface 41. As such, multiple DC converters 30 can be used in parallel for transmitting electric energy to and from the batteries 200, allowing relatively large charging or discharging currents to be achieved with modest DC converters 30 that are, individually, not able to transmit such large currents.

The use of DC interface bus bars 42 for interconnecting multiple DC converters 30 offers a further benefit, since the DC converters 30 can form a backup for each other. In case one of the DC converters 30 may be out of order, the other DC converters 30 can be used to keep the battery charging system 1 in function.

The DC interface bus bars 42 of different branches 21 are furthermore connectable to each other by means of bus bar switches 43, in order to be able to charge and discharge batteries 200 with both AC/DC converters 200 and, at most, all six DC converters 30 operating in parallel to each other.

The system comprises a calibrated battery energy meter 3, at the battery interfaces 41. The battery energy meter 4 is configured to register an amount of electric energy obtained from and fed into the batteries 200 connected to the battery interfaces 41. This battery energy meter 4 is configured to monitor the amount of electric energy used to charge the batteries 200, since the batteries 200 are used for transportation purposes. In some jurisdictions, rewards are offered by authorities in case renewable electric energy is used for transportation purposes, like trucks or vessels. These renewable energy units are monitored by the battery energy meter 4 at the DC battery interfaces 41 , which offers the benefit that the energy is measured right before entering the batteries 200 in DC. The present battery energy meter 4 thereto lacks efficiency losses resulting from AC/DC conversion and offers more accurate measuring of renewable energy units.

The DC converters 30 are further each connectable to an electric interface 44, by means of which the system 1 can output electric energy or by means of which the system 1 is connectable to the sources of renewable electric energy 300. Examples of such sources of renewable electric energy 300 are wind turbines 301 or photovoltaic panels 302. The DC converters 30 are all placed in parallel, so that each of them is able to output or receive electric energy independent from the other DC converters 30. Accordingly, all electric interfaces 44 are arranged in parallel, i.e. each being connectable to its own DC converter 30, in order to output or receive the electric energy independently with all electric interfaces 44. Instead of a single DC converter 30, one or more of the electric interfaces 44 may be connected to multiple DC converters 30 that are arranged in parallel. Accordingly, electric interfaces may be connected or selectively connectable to multiple DC converters similarly as shown for the battery interfaces 41. For example, one of the two battery interfaces 41 shown could be provided as electric interface 44 by means of which the system 1 can input or output electric energy or by means of which the system 1 is connectable to the sources of renewable electric energy 300. For example, instead of a battery 200, wind turbines 301 , solar panels 302 or electric vehicles 201 may be connected to the system 1 .

Instead of two AC branches 21 , each with a single AC/DC converter 20 and a set of three DC converters 30, any combination of AC branchers 21 , AC/DC converters 20 and DC converters 30 may be provided, depending on the use case and required system voltages and power.

Each of the interfaces 44 comprises its own interface sensor, included in the interface 44 and configured to emit an interface sensor signal representative for an electric parameter at the respective electric interface 44, for example to measure the voltage at the interface 44. The interface sensor is associated with the control device, which is in turn configured to control the DC converter 30 of that electric interface 44 on the basis of the electric parameter, for example to enable that the battery 200 is charged at the right voltage and/or that the electric energy from the source of renewable electric energy 300 is absorbed into the charging system 1 at the right voltage.

The DC converters 30 are each selectively connectable to the DC interface bus bars 42 or to a single allocated one of the electric interfaces 44 by means of respective interface switches 45 for each of the DC converters 30. This offers the possibility to adjust the number of DC converters 30 used for charging and discharging of the batteries 200, dependent on the capacity of the batteries 200 and/or a desired charging and discharging current.

In the present embodiment, each AC converter 30 is provided with a respective switch 45 to select between a respective DC interface bus bar 42 and a respective electric interface 44. However multiple DC interface bus bars 42 may be provided with one or more battery interfaces and/or electric interfaces 44, and the switches 45 may selectively connect DC converters 30 to one of the multiple DC interface bus bars 42. This also allows to adjust the number of DC converters used for sources 300, 301 , 302, electric vehicles 201 or other connected devices.

The transformer device 10, the energy meter 3 and the imbalance module 2 are included in a first modular compartment of the system 1 , in particular a power distribution unit 5 of the system 1. The AC/DC converters 20 and the DC converters 30 are included in a second modular compartment of the system 1 , in particular in a power interface unit 6. All high voltage components of the system 1 , i.e. the transformer device 10 and a grid connection with the electricity grid 100 are thereby be included in the power distribution unit 5. All low voltage components are included in a different compartment, namely the power interface unit 6, and may therefore be subject to different regulations. The power distribution unit 5 and the power interface unit 6 are each embodied as modified shipping containers, to improve the transportability and placement of the units 5, 6. Furthermore, the two battery interfaces 41 are included in respective battery docking devices, with which the battery charging system 1 is connectable to the batteries 200. Each battery docking device forms a third modular compartment, namely a battery docking unit 7. The battery docking units 7 allow for placement of the exchangeable batteries 200 on themselves and may be configured to enable an automated connection between the battery 200 and the docking unit 7.

In figure 1 , the system 1 is displayed in a configuration in which two batteries 200, 200’ are connected to the respective docking units 7, 7’. The system 1 is connected to the electricity grid 100 and is configured to both charge batteries 200, 200’and to compensate for imbalances in the grid 100. The control device is thereby configured to control both charging of the batteries 200, 200’ and to control the system 1 , in dependence of the imbalance signal obtained from the imbalance module 2.

The imbalance signal comprises information about imbalances on various different levels, in particular different time scales. Examples hereof are the forming of a Frequency Containment Reserve (FCR) for the electricity grid 100, for stabilising frequency disturbances in the electricity grid 100. Secondly, the compensating of imbalances may concern the delivery of reactive power to the electricity grid 100 or the absorption of reactive power from the electricity grid 100. Thirdly, the compensating for imbalances may be done to compensate for under- or overloading of the electricity grid 100, also known as so-called “peak shaving”. As a final example, the compensating of imbalances may involve providing electric energy to the electricity grid 100 in case of a power outage or blackout.

The imbalance module 2 is included in the battery charging system 1 to allow the system 1 to perform the ancillary services for the electricity grid 100, as described above, which may be done by selectively obtaining electric energy from the electricity grid 100 and by selectively feeding electric energy into the electricity grid 100, so that any imbalances can be compensated.

In the configuration shown in figure 1 , the system 1 is connected to the grid 100 with the transformer device 10 and the AC/DC converters 20, 20’ are both connected to the transformer device 10 in parallel, over its respective branch 21 , 2T. The DC converters 30 of the first branch 21 are connected to the DC system bus bar 31 in parallel to each other. Accordingly, the interface switches 45 in the first branch 21 are arranged so that the DC converters are all connected to the first DC interface bus bar 42, connected to the first docking unit 7 via the bus bar switch 43 and the first battery electric interface 41. The same applies for the DC converters 30’ in the second branch 2T, which are all connected to the second docking unit 7’ in parallel.

The system 1 is configured to charge and discharge the first battery 200 by means of the AC/DC converter 20 and the DC converters 30 in the first branch 21 and to charge and discharge the second battery 200’ by means of the AC/DC converter 20’ and the DC converters 30’ in the second branch 2T. The bus bar switches 43 are arranged such that the interface bus bars 42, 42’ are electrically insulated from each other.

In case the imbalance signal obtained from the imbalance module 2 represents a shortage of electric energy in the electricity grid 100, the control device is configured to control the system 1 discharge the first battery 200 via the first branch 21 and/or to discharge the second battery 200’ via the second branch 2T, so that electric energy can be fed into the grid 100 from the batteries 200, 200’.

Similarly, in case the imbalance signal represents an excess of electric energy in the electricity grid 100, the control device is configured to control the system 1 charge the first battery 200 via the first branch 21 and/or to charge the second battery 200’ via the second branch 2T, so that electric energy can be obtained from the grid 100 and fed into the batteries 200, 200’.

Meanwhile, the control device is configured to control the system 1 to charge the batteries 200, 200’, so that the batteries 200, 200’ can be removed from the docking units 7, 7’ at a predetermined moment, in order to be used on the vessel. To this effect, the system 1 is controlled to charge the batteries 200, 200’ up to a predetermined minimum state of charge prior to being available for compensation the imbalances. In the embodiment shown in figure 1 , the predicted minimum required state of charge is about 70% of the maximum capacity of the batteries 200, 200’.

The system 1 is configured the log economic benefits that are obtained from the grid authorities when these ancillary services are provided, i.e. when the imbalances are compensated. This logging may, for example, be carried outby means of the calibrated energy meter 3 at the grid connection.

During charging of the batteries 200, 200’, the battery energy meter 4 is used to register a net amount of electric energy fed into the batteries 200, 200’ connected to the battery interfaces 41. On the basis hereof, renewable energy units fed into the batteries are monitored at the DC battery interfaces 41 , 4T, which may offer further subsidized economic benefits for the system 1.

During use of the system 1 , preferably at least one of the batteries 200, 200’ remains connected to the system 1 when another one of the batteries is disconnected after being charged to the desired state of charge. This may ensure that the system 1 may be able to compensate for the imbalances uninterrupted, which would not be possible when no batteries are connected to the docking units 7, 7’.

In figure 2, the system 1 is shown in a different configuration, compared to figure 1. In figure 2, the bus bar switch 43 connected to the first interface bus bar 42 is arranged in electric connection with the second battery electric interface 4T. In this configuration, all DC converters 30, 30’ are connected to the second battery electric interface 4T and are configured to charge or discharge the second battery 200’ in parallel. Instead, the first battery electric interface 41 and the first battery 200 are not in electric contact with the first interface bus bar 42. In this configuration, the first battery 200’ may be fully charged, to be removed from the first docking unit 7. A new, e.g. empty battery may be placed on the first docking unit 7, so that the system 1 can be returned to the configuration in figure 1 with the new battery.

In figure 3, the system 1 is displayed in a configuration in which a wind turbine 301 is connected to one of the second electric interfaces 44’, connected a first (left) one of the second DC converters 30’ and in which a plurality of photovoltaic panels 302 is connected to a second (middle) one of the second electric interfaces 44’, connected to another one of the second DC converters 30’. The third (right) one of the second DC converters 30’ is connected to the second DC interface bus bar 42’.

At the first branch 21 , the system 1 is configured to operate in a manner similar to the configuration in figure 1 , namely to charge the first battery 200 by means of electricity obtained from the electricity grid 100 and to compensate for imbalances in the grid 100 with the first battery 200.

In the second branch 2T, the system 1 obtains electric energy from the wind turbine 301 at a first DC interface voltage, fed into the first one of the second DC converters 30’, which transforms the electric energy from the wind turbine 301 into the second DC system voltage VDC.S in the second DC system bus bar 3T. The system 1 further obtains electric energy from the photovoltaic panels 302 at a second DC interface voltage, which may be different from the first DC interface voltage, which is fed into the second one of the second DC converters 30’, which then transforms the electric energy from the photovoltaic panels 302 into the second DC system voltage VDC.S in the second DC system bus bar 3T as well.

The third one of the second DC converters 30’ is configured to obtain the renewable electric energy from the second DC system bus bar 3T, without obtaining electric energy from the transformer device 10 and the second AC/DC converter 20’, and to transform it into the DC interface voltage VDC.I that is fed into the second DC interface bus bar 42’ and further towards the second battery electric interface 4T. The system 1 is thereby configured charge the second battery 200’ by means of the renewable electric energy obtained from the wind turbine 301 and the photovoltaic panels 302.

In figure 4, the system 1 is displayed in a configuration similar to the configuration in figure 3. As a difference, however, the first battery 200 is removed from the first docking unit 7 to be replaced by a new, empty battery. During this period in the absence of a battery at the first docking unit 7, the system 1 may either be temporarily disabled to perform ancillary services, i.e. to compensate for imbalances.

Alternatively, however, the system 1 in figure 4 may be configured to perform ancillary services with the second battery 200’, via the second AC/DC converter 20’ and the third (right) one of the second DC converters 30’. The system 1 may thereby be configured to charge the second battery 200’ by means of electric energy obtained from the grid 100, for compensating imbalances, and from the wind turbine 301 and the photovoltaic panels 302. Similarly, The system 1 may be configured to feed electric energy into the grid 100, for compensating imbalances, by obtaining electric energy from the second battery 200’, from the wind turbine 301 and the photovoltaic panels 302.

In figure 5, the system 1 is shown in a configuration in which it is, similar as in figures 1 - 3, configured to charge the first battery 200 with electric energy obtained from the grid 100 and to compensate for imbalances in the grid 100, both via its first branch 21. In the second branch 2T, the first (left) one of the second electric interfaces 44’ is connected to the wind turbine 301 , the second (middle) one of the second electric interfaces 44’ is connected to the battery of an electric vehicle 201 and the third (right) one of the second electric interfaces 44’ is connected to the photovoltaic panels 302. None of the second DC converters 30’ is connected to the second DC interface bus bar 42’, so none of the second DC converters 30’ is able to charge or discharge the second battery 200’.

Similar as in figure 3, is the system in figure 5 configured to obtain electric energy from the wind turbine 301 and from the photovoltaic panels 302, which is fed into the second DC system bus bar 3T by the respective first (left) one and third (right) one of the second DC converters 30’. The second (middle) one of the second DC converters 30’ is thereby configured to obtain the renewable electric energy from the second DC system bus bar 3T, without obtaining electric energy from the transformer device 10, and to transform it into the DC interface voltage VDC.I that is fed towards the second (middle) one of the second electric interfaces 44’ in order to charge the battery of the vehicle 201 connected thereto.

Optionally, the bus bar switches 43 may be arranged such, that both battery electric interfaces 41 , 4T, and therefore both batteries 200, 200’ become connected to the first interface bus bar 42. In this way, both batteries 200, 200’ may be charged via the first branch 21 and may both be used for ancillary services.

Claims

CLAIMS Multifunctional battery charging system, configured to transfer electric energy between an electricity grid and one or more batteries, the system comprising: a bi-directional transformer device, connectable to the electricity grid and configured to transform an AC grid voltage from the electricity grid into an AC system voltage, and vice versa one or more bi-directional AC/DC converters, electrically connected to the transformer device and configured to transform the AC system voltage into a DC system voltage, and vice versa, one or more controllable bi-directional DC converters, electrically connected to the AC/DC converter and each configured to transform the DC system voltage into a controllable DC interface voltage, and vice versa, one or more electric interfaces, connected to the DC converters, with each electric interface being connected to its own one or more parallel DC converters, and connectable to a battery, configured to:

• transfer electric energy obtained from the battery to the DC converter. Multifunctional battery charging system according to claim 1 , wherein the one or more electric interfaces are further connectable to a source of renewable electric energy, and wherein the one or more electric interfaces are configured to:

• transfer electric energy obtained from the source of renewable electric energy to the DC converter. Multifunctional battery charging system according to claim 1 or 2, wherein the one or more DC converters comprise multiple DC converters, and wherein the DC converters are connected to the AC/DC converter in parallel via a DC system bus bar. Multifunctional battery charging system according to any of the preceding claims, wherein one of the electric interfaces is electrically connected to a DC interface bus bar and configured to be releasably connected to the battery for transferring electric energy between the DC converter and the battery.

5. Multifunctional battery charging system according to claim 4, wherein the one or more DC converters are each selectively connectable to the DC interface bus bar or to a single allocated one of the electric interfaces.

6. Multifunctional battery charging system according to any of the preceding claims, wherein the one or more AC/DC converters comprise multiple AC/DC converters, and wherein the transformer device is connected to each of the AC/DC converters to form an AC branch for each of the AC/DC converters.

7. Multifunctional battery charging system according to claim 6, wherein each of the AC branches comprises at least one of the DC converters.

8. Multifunctional battery charging system according to claim 7, wherein each of the AC branches comprises a DC system bus bar in between its AC/DC converter and its at least one DC converter, and wherein the DC system bus bars of the AC branches are electrically insulated from each other.

9. Multifunctional battery charging system according to any of the preceding claims, wherein the transformer device is included in a first modular compartment, i.e. a power distribution unit, and wherein the AC/DC converter and the DC converters are included in a second modular compartment, i.e. a power interface unit.

10. Multifunctional battery charging system according to any of the preceding claims, further comprising at least one interface sensor, configured to emit an interface sensor signal representative for an electric parameter at the respective electric interface.

11. Multifunctional battery charging system according to any of the preceding claims, further comprising a control device, configured to control the system, for example to control the one or more AC/DC converters and/or the one or more DC converters.

12. Multifunctional battery charging system according to claims 10 and 11, wherein the control device is associated with the interface sensor, and wherein the control device is further configured to control the DC converter associated with the interface sensor in dependence of the electric parameter. Multifunctional battery charging system according to claim 11 or 12, further comprising an imbalance module, connected to an external platform for monitoring imbalances in the electricity grid and configured to output an imbalance signal representative for imbalances in the electricity grid, and wherein the control device is configured to control the system in dependence of the imbalance signal to: selectively obtain electric energy from the electricity grid, and/or selectively feed electric energy into the electricity grid, in order to compensate for imbalances in the electricity grid. Multifunctional battery charging system according to any of the preceding claims, further comprising a source of renewable electric energy, for example a wind turbine and/or one or more photovoltaic panels, wherein the source of renewable electric energy is electrically connected to one or more of the electric interfaces to supply electric energy to one or more of the DC converters, and wherein the system is configured to supply electric energy obtained from the renewable source to the other electric interfaces via the other DC converters, for example to a battery connected thereto, without requiring electric energy to be obtained from the electricity grid. Multifunctional battery charging system according to claims 13 and 14, wherein the control device is further configured to control the system, in dependence of the imbalance signal to selectively feed electric energy obtained from the source of renewable electric energy to the electricity grid, in order to compensate for imbalances in the electricity grid. Method of charging a battery by means of a multifunctional battery charging system according to any of the preceding claims, the method comprising the steps of: electrically connecting a battery to an electric interface of the battery charging system, selectively charging and discharging the battery by means of the battery charging system, wherein the selective charging and discharging comprises:

• discharging the battery by transferring electric energy obtained from the battery to the electricity grid. 17. Method according to claim 16, further comprising the step of: releasing the connection between the battery and the battery charging system after the battery has been charged to a desired state of charge.

18. Method according to claim 16 or 17, further comprising, after the step of connecting and before the step of selectively charging, and the step of measuring an electric parameter with an interface sensor provided at a respective electric interface.

19. Method according to claim 18, further comprising the step of controlling the system by means of a control device that is associated with the interface sensor, wherein the controlling involves controlling the DC converter associated with the interface sensor in dependence of the electric parameter.

20. Method according to any of the claims 16 - 19, further comprising the step of: electrically connecting a source of renewable electric energy to another electric interface of the battery charging system, wherein the selective charging and discharging comprises: