DE102018203388A1 - Precharging a DC link capacitor of a DC intermediate circuit - Google Patents

Abstract

The invention relates to a method for precharging an intermediate circuit capacitor (66) of a DC intermediate circuit (54) with electrical energy from an energy source (14) providing an AC voltage (18) with respect to a predetermined electrical reference potential (16, 40), in which the AC voltage ( 18) is rectified by means of a bridge rectifier (100) or an inversely operated polyphase inverter (20) to supply the energy provided by the power source (14) to the DC link capacitor (66), and at least one electrical potential of the DC link capacitor (66 ) DC link voltage is coupled by means of at least one Y-capacitor (42, 44) with the electrical reference potential (16, 40). The invention provides that during precharging only a first phase potential (P) of the AC voltage (18) is electrically coupled to the bridge rectifier (100) or the inversely operated polyphase inverter (20).

Description

The invention relates to a method for precharging a DC link capacitor of a DC intermediate circuit with electrical energy from an energy source providing an AC voltage with respect to a predetermined electrical reference potential, wherein the AC voltage is rectified by means of a bridge rectifier or an inversely operated polyphase inverter to provide the power source provided by the power source Supplying energy to the DC link capacitor, and at least one electrical potential of a DC link voltage provided by the rectification at the DC link capacitor is coupled to the electrical reference potential by means of at least one Y capacitor. The invention further relates to a precharging device for precharging a DC link capacitor of a DC intermediate circuit with electrical energy from an energy source providing an AC voltage with respect to a predetermined electrical reference potential, having a power source terminal for electrically coupling the power source, and a DC link terminal for connecting to the DC link capacitor, wherein the DC link capacitor to a rectifier unit which can be coupled to the energy source and rectifies the AC voltage by means of a bridge rectifier or an inverse polyphase inverter, to supply the energy supplied by the energy source to the DC link capacitor, and wherein at least one electrical potential of a DC link voltage provided by the rectification at the DC link capacitor by means of at least one Y-capacitor with the electrical n reference potential is coupled. Furthermore, the invention relates to a charging device for the energy-related coupling of an AC voltage with respect to a predetermined electrical reference potential providing energy source, with a power source terminal for electrically coupling the power source, an electrical system connection for connection to an electrical system of a motor vehicle, an electrically coupled to the electrical system DC link capacitor, a rectifier unit connected to the power source terminal and the intermediate circuit capacitor, which is configured to rectify the AC voltage by means of a bridge rectifier or an inversely operated polyphase inverter to supply the power provided by the energy source to the DC link capacitor, at least one Y capacitor connected to a first capacitor terminal the electrical reference potential and with a second capacitor terminal with a by rectifying a Coupling circuit DC voltage provided DC link capacitor is coupled, and a precharging device for precharging the DC link capacitor. Finally, the invention also relates to a motor vehicle with a vehicle electrical system having at least one electrical energy storage and a charging device connected to the electrical system for the energy-related coupling of a motor vehicle external electrical energy source.

The charging of an electrical energy storage device, in particular an electrical energy storage device of a motor vehicle, with electrical energy from an energy source such as a charging station, in particular an external vehicle, preferably a stationary charging station, is basically well known in the art, so that it is a separate printed Proof is not required. A motor vehicle usually includes an electrical system, in order to be able to supply its electrical equipment that is connected to the electrical system and also electrical units of the electrical system in a predeterminable manner with electrical energy. The electrical system thus serves the electrical power distribution.

In general, the electrical system comprises a DC voltage intermediate circuit, which in turn has the intermediate circuit capacitor and which is electrically coupled to the electrical energy storage. The electrical energy storage is used to store excess energy in the electrical system, as well as to provide this when needed for electrical energy for the electrical system. The electrical energy storage is often formed for this purpose by an accumulator or the like, which is able to chemically store electrical energy reversibly. In addition, the electrical energy store may also include an electrical capacitor. The electrical energy storage usually determines the amount of DC link voltage during normal operation.

In particular, in a motor vehicle, which is designed as an electrically driven motor vehicle, it can be provided that the electrical system is designed for operation at "high voltage". Usually then the value of the DC link voltage is a high voltage. The term "high voltage" means here an electrical voltage that is greater than about 60 V. The term "high-voltage" preferably corresponds to the ECE R 100 standard.

Especially in electrically driven motor vehicles, it is regularly necessary to charge their energy storage, which provides electrical energy for the intended driving, at regular intervals with energy. To For this purpose, the electrically driven motor vehicle is parked at a vehicle-external charging station and coupled with this energy technology. Frequently, the power engineering coupling is designed as a wired coupling by means of a charging cable, which can be coupled electromechanically detachable with the charging device of the motor vehicle. But even a wireless energy technology coupling using an alternating magnetic field can be provided. The vehicle-external charging station is usually formed stationary, for example, set up at a parking lot for the motor vehicle or the like.

The charging station provides an electrical voltage during a charging process, which is often a single-phase or multi-phase AC voltage. A common effective value for the single-phase AC voltage is, for example, about 230 V at a frequency of about 50 Hz. However, other single-phase AC voltages are possible, for example about 240 V at a frequency of about 60 Hz or the like. For example, for a three-phase AC voltage, the RMS value may be about 400V.

Of particular importance is the electric energy storage device in an electrically driven motor vehicle, which comprises an electric drive device by means of which the motor vehicle can be driven in the intended driving operation. Such a drive device usually comprises a vehicle electrical system connected, in particular with the DC voltage intermediate circuit of the electrical system electrically coupled inverter, to which in turn usually a rotating electric machine is connected, which is able to provide a mechanical drive power. Frequently, a three-phase electric machine is used for this purpose, for example in the manner of a synchronous machine, an asynchronous machine or the like.

Not only but especially in electrically driven vehicles, which may be formed for example by an electric vehicle or a hybrid vehicle, it is usually necessary to charge the energy storage regularly so that it can provide electrical energy for the intended driving operation. For this purpose, the motor vehicle has the electrically coupled to the electrical energy storage charger, which may be connected, for example, to the DC voltage intermediate circuit of the electrical system or which may also include in order to establish the electrical connection to the electrical energy storage. In addition, the charging device is electrically connected to a charging port of the motor vehicle, via which a power-technical connection to the vehicle-external charging station can be made usually solvable.

The motor vehicle external charging station can be formed, for example, by a charging station or the like. The motor vehicle external charging station can be either wired or wireless, for example by means of an alternating magnetic field or the like, coupled to the charging port of the motor vehicle to be able to promote electrical energy from the charging station to the electrical energy storage.

In order to produce the power engineering coupling, the charging device usually has an energy converter, for example in the manner of a rectifier, which may occasionally be coupled to a DC / DC converter or the like. In addition, a galvanic isolation is usually provided due to the electromagnetic compatibility and / or electrical safety, which separates the motor vehicle external charging station galvanically from the electrical system of the motor vehicle. The galvanic isolation is often formed by a transformer.

In general, the charging station for the purpose of energy supply provides the electrical AC voltage with respect to the predetermined electrical reference potential, which is usually formed by the ground potential. But it can also be another suitable ground potential or the like provided for this purpose. As a rule, since the electrical energy is taken from or provided by a public power supply network, the alternating voltage usually has an alternating voltage frequency which corresponds to that of the public power distribution network. In Europe and much of Asia, this is predominantly a frequency of about 50 Hz. In North America, however, the frequency is usually about 60 Hz.

Depending on the design of the charging station, a single-phase or even a polyphase, in particular a three-phase AC voltage can be provided. Especially when providing a single-phase AC voltage, specific problems may arise. In the case of a line-connected energy-related coupling, special requirements with regard to electrical safety and electromagnetic compatibility must be observed.

For this reason, a corresponding filter circuit is usually provided, for example, on the charging station side and / or on the motor vehicle side, so that the respective prescribed requirements can be met. However, this can result in a leakage current. The leakage current is an electric current which flows during normal operation of an electrical system in an undesirable current path. The current path is often formed by a protective conductor or a ground, which is or is usually electrically connected to the electrical reference potential. The electrical reference potential is usually the ground potential. However, it can also be another reference potential, for example a vehicle ground or the like. The level of the leakage current is usually limited by corresponding standards.

In many electrical applications, the leakage current is essentially determined by the filter circuit, which serves to comply with the electromagnetic compatibility, in particular with regard to conducted radio interference. To suppress such conducted radio interference often Y-capacitors are used in the filter circuit, which electrically couple a respective potential to be suppressed - here the potentials of the DC link voltage - with the respective reference potential, such as the motor vehicle mass or the like. This can result in that upon application of the alternating voltage, a corresponding alternating current flows through the at least one Y-capacitor, which at least partially determines the leakage current. In addition, the leakage current can also be dependent on further, in particular capacitive, couplings.

It has been shown that the leakage current can be influenced by certain measures. However, it has been found that some of the measures are at least partially dependent on which type of network system is provided by the power source or charging station. A network system type is, for example, a TN system, a TT system, an IT system, derivatives thereof and / or the like. The type of network system typically refers to a topology of the power grid through which the electrical energy is provided. In addition to the aforementioned types of network systems, which are usually found frequently in Europe, for example, the single-phase three-core network (English: split-phase electric power) is known, which has widespread use in North America. Since measures relating to electrical safety and electromagnetic compatibility may depend on the type of network system, it may be important to know which type of network system is provided by a power source or charging station.

To put the charging of the electrical energy storage in operation, the AC voltage of the charging station is turned on. At this time, the DC link voltage is usually close to zero. The intermediate circuit capacitor is therefore essentially discharged at this time. In this charge state, the connection of the AC voltage means that - depending on the phase position of the AC voltage - a very large current pulse may result and not only the charging station, but also the charging device, in particular the other units, for example, for rectification, energy conversion and / or the like are to be charged. This is very unfavorable for a number of technical reasons, which is why it is usually provided that the DC link capacitor is precharged before connecting the AC voltage to a DC link voltage, so that an unacceptably high current pulse when switching the AC voltage can be largely avoided. For this purpose, special pre-charging circuits are provided in the prior art, which pre-charge the intermediate circuit capacitor to the desired intermediate circuit voltage usually by using a bridgeable electrical resistance.

According to one embodiment in the prior art, it can be provided that the intermediate circuit capacitor can be charged by means of electrical energy of the electrical energy store or of the electrical system via a pre-charge resistor. However, this is not always possible and not possible with all on-board networks. A further embodiment provides that the intermediate circuit capacitor is charged via a likewise bridgeable Vorladewiderstand by the AC voltage of the charging station by this is electrically coupled to the AC voltage.

Even if these methods have proved successful, it proves to be disadvantageous in that on the one hand a correspondingly high-performance electrical resistance must be provided, which requires weight and installation space, and, moreover, the reliability of the precharging circuit formed thereby is limited. During normal operation, the resistor may fail so that the precharging function is lost. Damage to other units can then be the result.

A disadvantage of the prior art in the use of a pre-charge resistance, it turns out, moreover, that when using the pre-charge charging usually can not be realized up to the amplitude of the AC voltage. This results from the known charging curve of a capacitor via a resistor.

The invention has for its object to achieve an improved pre-charging and to reduce the requirement of the benefit of a pre-charge resistance as possible.

As a solution, the invention proposes a method, a pre-charging device, a charging device and a motor vehicle according to the independent claims.

Advantageous developments will become apparent from the features of the dependent claims.

With regard to a generic method, the invention particularly proposes that only a first phase potential of the alternating voltage is electrically coupled to the bridge rectifier or the inversely operated polyphase inverter during precharging.

With regard to a generic precharging device, it is proposed in particular that it has a switching unit which electrically couples the rectifier unit to the energy source and which is designed to electrically couple only a first phase potential of the AC voltage to the bridge rectifier or the inversely operated multiphase inverter during precharging.

With regard to a generic charging device, it is in particular proposed that the precharging device is designed according to the invention.

With regard to a generic motor vehicle, it is in particular proposed that the charging device is designed according to the invention.

The invention is based on the recognition that the AC voltage related to the reference potential can result in a charging effect occurring due to the Y capacitors connected on the DC side. This then causes a functionality in the manner of a charge pump, so that the DC link capacitor electrical charge can be supplied and thus the DC link voltage increases.

Among other things, the invention also makes use of the knowledge that the leakage current caused by the at least one Y capacitor can result in a corresponding charging of the intermediate circuit capacitor. Due to the fact that only one phase potential, here the first phase potential of the alternating voltage, is switched on electrically, the charging process, which otherwise would otherwise occur directly when fully connected, is avoided. Namely, the power consumption can be limited by the at least one Y capacitor, as will be explained further below. This effect can be used not only in PEN networks as Netzsystemart but also in particular in network types that provide, for example, a single-phase three-core network as a system type. A network system type is, for example, a TN system, a TT system, an IT system, derivatives thereof and / or the like. The type of network system typically refers to a topology of a utility grid that provides the electrical energy. In addition to the aforementioned types of network systems, which are usually found frequently in Europe, this is also known, for example, the single-phase three-core network (English: split-face electric power), which has widespread use in North America. In Europe, by contrast, the network system type of the PEN (protected earth neutral) is predominantly in use. Adapted to these network system types, the energy source, in particular the charging station, provides the electrical alternating voltage.

Among other things, the inventive concept is based on the fact that a capacitance value of the one or more Y capacitors is generally significantly smaller than the capacitance value of the intermediate circuit capacitor. Since, with respect to the precharge functionality according to the invention, these capacitors are connected in series, the precharge operation of the intermediate circuit capacitor is limited by the capacitance of the Y capacitor (s).

Due to the AC voltage, the intermediate circuit capacitor is cyclically supplied with each oscillation of the AC voltage by means of the Y capacitor or the Y capacitors a certain amount of charge, which is dependent inter alia on the electrical capacitance of the Y capacitor or the Y capacitors. As a result, the DC link capacitor is cyclically charged to an increasingly higher DC link voltage. The DC link voltage can be compared with a predetermined comparison value. If the intermediate circuit voltage is greater than the comparison value, then the precharge process can be terminated and the AC voltage can be fully switched on.

The invention thus makes it possible to completely save the precharging resistance, but at least to reduce its functionality and relevance.

Thus, the invention utilizes a special effect that can result in a bridge rectification in conjunction with at least one Y-capacitor. The bridge rectification may be provided, for example, by a bridge rectifier. Of course, it can also be realized by an inverter, if it is used in controlled manner in the manner of a bridge rectifier, in particular operated inversely. In this case, therefore, the inverter, the normal operation of a Motor vehicle can serve to apply an electrical machine of the motor vehicle according to electrical energy, used to rectify the AC voltage when charging the electrical energy storage. It can thereby at least partially provide the charging device of the electrically driven motor vehicle. This has the advantage that not only a rectification can be achieved, but also by a suitable control of the inverter in addition also a voltage adjustment can be realized, if necessary.

With the invention can thus also be achieved that the intermediate circuit DC voltage reaches a value which corresponds at least to the amplitude of the AC voltage. As a result, the known in the prior art undesirable effects, which at most reduce with the series resistor but can not be completely prevented, can be completely avoided.

Y capacitors are usually provided in on-board networks, in particular with regard to DC intermediate circuits, in order to be able to achieve electromagnetic compatibility (EMC) requirements. The leakage current can be determined in many electrical applications by appropriate filter circuits, which serve to comply with the electromagnetic compatibility, in particular with respect to conducted radio interference or the like. In particular for the suppression of such conducted radio interference, these Y capacitors are often used in the filter circuit, which electrically couple a respective potential to be suppressed, here at least one of the potentials of the DC link voltage, to the respective reference potential, for example a motor vehicle ground, ground potential and / or the like. This can result in that upon application of the alternating voltage, a corresponding alternating current flows through the Y-capacitor or the Y-capacitors, which at least partially determines the leakage current. Of course, the leakage current can of course also be dependent on further, in particular capacitive, couplings, for example in the electrical system of the motor vehicle.

However, the function of the invention is not limited to that the reference potential is directly electrically coupled to one of the potentials of the AC voltage of the power source. Rather, a different relationship may exist, for example by a, in particular fixed, potential offset or a potential difference ensures that the AC voltage with respect to the reference potential is not symmetrical or the like. It is important, however, that there is a given fixed relationship between the potentials of the AC voltage and the reference potential. In general, this is achieved by a suitable grounding, which is generally formed in Europe in that one of the potentials of the AC voltage is grounded. In North America, grounding is typically symmetrical to AC voltage according to the three-wire single-phase network.

The alternating voltage is usually provided with at least two potentials, one potential of which is a zero potential and the at least one other of the potentials is a phase potential, occasionally also called phase. Between these two potentials is usually the AC voltage. An AC voltage which has exclusively a zero potential and a phase potential is thus a single-phase AC voltage. In addition, multiphase alternating voltages are also in use, in particular three-phase alternating voltages, which have their own phase potential in addition to the zero potential for each of the respective phases. The phase potentials are usually different from each other, and usually differ in that they have a fixed phase shift at the same frequency and amplitude. Common in the prior art is the use of a three-phase AC voltage.

If a multiphase AC voltage is used for the invention, it may be provided that only a single one of the phase potentials for the method according to the invention is used for precharging the DC link capacitor. Only after the pre-charging then in addition to the zero potential and the other phase potentials are switched on. Depending on the configuration of the polyphase AC voltage, however, two or more phases can also be used for precharging the DC link capacitor according to the invention. It should be noted, however, that the charge pumping effect described above can continue to occur and can be used to pre-charge the DC link capacitor. This is usually possible if for each of the phase potentials of the polyphase AC voltage own separate rectification function is used with a respective own DC link capacitor, the DC link capacitors are electrically separated from each other so that the charge pumping effect - as described above - for each of the DC link capacitors individually can be used.

It is also proposed that, in the case of an alternating voltage having at least two phase potentials, at least one connection of the at least one Y capacitor during precharging is temporarily switched from the electrical reference potential to a different from the first phase potential second phase potential of the AC voltage. This development is not only suitable but especially for use in single-phase three-wire networks, in which only a limited pre-charging of the DC link capacitor can be achieved by using a single of the phase potentials. This results from the fact that the two phase potentials of the single-phase three-wire network are complementary in terms of phase position and thus only a pre-charging of the intermediate circuit capacitor can be achieved to about half the amplitude of the total AC voltage when using the ground potential as a reference potential. Although it is also possible - depending on the circuit topology - that with the charge pump effect, a higher DC link voltage than the amplitude of the half AC voltage can be achieved, however, the DC link capacitor can not be precharged to an intermediate circuit voltage corresponding to the AC voltage between the two phase potentials. So it would remain when switching the AC voltage using only one of the two phase potentials of the single-phase three-wire network, a significant voltage difference, so continue a very large current pulse can occur when switching.

In order to avoid this, it can be provided with this development that the at least one Y capacitor is at least temporarily not electrically coupled to the reference potential during precharging, but instead to the second phase potential. This provides an improved charge pumping effect. So that a rapid pre-charging as well as a timely achievement of a predetermined suitable intermediate circuit DC voltage can be achieved at the DC link capacitor. After reaching the predetermined intermediate circuit voltage, the at least one Y-capacitor can be switched back again so that it is now electrically coupled to the reference potential instead of the second phase potential of the AC voltage again.

It should be noted in this embodiment, however, that requirements are ensured in terms of electrical safety, because the Y capacitors are now not electrically connected to at least one of its terminals to the reference potential. Since the Y capacitors can often be electrically coupled with other, in particular touchable, system components, appropriate measures are provided here. Of course, this development is not limited to the application in single-phase three-wire networks, but can of course also generally in multi-phase AC voltages, for example in a three-phase AC voltage, are used. The basic considerations apply here equally in an adapted way.

Furthermore, it is proposed that the pre-charging be terminated as a function of a comparison of the DC link voltage detected by means of a voltage sensor with a predetermined comparison value. The process of pre-charging can thus be terminated automatically when a predetermined criterion is reached. This can be used to automatically perform a connection of the complete AC voltage. The predetermined comparison value is preferably selected such that, when the AC voltage is switched on, any possible current pulse can be neglected or even avoided. The predetermined comparison value can preferably also be determined in such a way that current pulses occurring under unfavorable conditions can not cause any damage to the circuit. Preferably, the predetermined comparison value is chosen as large as possible, so that a current pulse as small as possible, if not completely avoided.

Furthermore, it is proposed that subsequently for precharging a zero potential of the alternating voltage and / or further phase potentials of the alternating voltage be electrically coupled to the bridge rectifier or the inversely operated multiphase inverter. As a result, the complete connection of the AC voltage can be achieved. The intended operation of the precharge can thus be realized. There is now the supply of electrical energy from the power source to the DC voltage intermediate circuit in the intended known form to perform the charging of the energy storage. Characterized in that according to the invention, the pre-charging of the DC link capacitor has been realized, the problems occurring in the prior art can be largely avoided.

According to a development, it is proposed that a phase position is determined automatically at least with respect to the first phase potential and the coupling takes place as a function of the determined phase position. This embodiment is particularly suitable when the charge pumping effect is relatively low and the time for precharging the DC link capacitor would exceed a predetermined time. By determining the phase position and the dependent on this connection can be achieved that despite a possible voltage difference and the associated problem of the current pulse of the current pulse can be significantly reduced. If the connection is made in the region of a zero point of the alternating voltage, a possible current flow may be correspondingly smaller due to the possibly reduced voltage gradient. It can additionally advantageous that the DC link capacitor is no longer completely discharged but is already preloaded on a partial voltage of the amplitude of the AC voltage. Overall, thereby the use of the invention can be further improved.

It is also proposed that during the pre-charging a Netzsystemart is determined and the coupling takes place depending on the determined Netzsystemart and the determined phase position, at least with respect to the first phase potential. It can thereby be achieved that, depending on the network system type, a relevant phase position with regard to the relevant phase potential can be taken into account in order to carry out the coupling. It can thereby be achieved that the coupling takes place when a current load or the current pulse is as small as possible. For example, the coupling can already take place when the DC link voltage has not yet reached the value that it would have in the coupled state. The DC link capacitor is in this case only partially charged. Accordingly, the comparison value can be selected. In the case of a single-phase AC voltage in a PEN network, it is thus possible, for example, to couple in the region of a zero point of the AC voltage in order to keep the current pulse as small as possible. This allows, for example, to reduce the time for pre-charging. The DC link capacitor therefore does not need to be precharged to the full operating voltage in the intended charging mode. Of course, other constraints can be met herewith. The determination of the type of network system can be carried out, for example, by monitoring the behavior of the intermediate circuit voltage during precharging. For this purpose, it is also possible to examine a very wide variety of coupling states of the coupling. If, for example, it is not known from a potential of the alternating voltage whether it is a zero potential, this can be determined simply by coupling only this potential. If the charge pump effect appears, the potential is not coupled to the reference potential or the ground potential. If, on the other hand, there is no charge pumping effect, the potential is coupled to the reference potential or the ground potential. Further such investigations can at least gradually determine the network system type of the electrical energy source. Depending on this, it can then be determined in which phase position the coupling should preferably take place. It can thereby be taken into account that the optimum phase position for the coupling can be dependent on the type of network system.

According to a further development, it is proposed that in the case of a polyphase alternating voltage, separate rectifying and respective electrically isolated DC link capacitors be provided for each of the phases and each of the DC link capacitors during precharging only by means of the respective phase potential of the AC voltage across the respective bridge rectifier or the respective inversely operated polyphase Inverter is electrically coupled. Electrically separated with respect to the DC link capacitors means here that the at least one Y-capacitor, which is connected to the respective DC link capacitor, allows the respective charge pumping effect phase-related. Interactions of the DC link DC voltages provided at the respective DC link capacitors must be correspondingly suppressed in terms of circuitry. As a result, the charge pump effect can be used effectively and separately for each phase as described above. Of course, it is possible in such a configuration that, if only a single-phase AC voltage is available, the corresponding phase-related rectification branches are at least partially connected in parallel. In this case, of course, the DC link capacitors and the Y capacitors connected thereto can then be connected in parallel accordingly. Overall, this embodiment makes it possible to achieve high performance and at the same time to enable a high degree of flexibility with regard to different AC voltages.

In addition, it is proposed that, in the case of a polyphase alternating voltage with phase potentials having different phase angles, only one of the phase potentials of the alternating voltage be electrically coupled as a first phase potential to the bridge rectifier or the inversely operated polyphase inverter in a common rectification and a common intermediate circuit capacitor during precharging becomes. It can thereby be achieved that the invention can also be used for precharging a DC link capacitor, in which the rectification is carried out in three phases, for example by means of a B6 bridge. At the same time, of course, there is also the possibility that, if the energy source provides only a single-phase AC voltage, the functionality is still given.

Preferably, a capacitance value of the at least one Y capacitor is selected as a function of a capacitance value of the DC link capacitor. As a result, the charge pump effect can be adjusted specifically. For example, the capacitance value of the Y capacitor can be 100 nF. A capacitance value for the DC link capacitor may be, for example, 400 μF. Of course, the ratio, which in the may also be chosen smaller in order to enable the pre-charging within a predetermined time window in the intended manner, for example it can be provided that the ratio is only 1000, preferably about 500, more preferably less than or equal to about 100.

A further development provides that the at least one Y capacitor is electrically coupled during precharging by means of a switching element to the at least one electrical potential of the DC link voltage. In this development, the Y-capacitor is thus active only during pre-charging. It can therefore be at least partially deactivated outside the pre-charging period. Of course, it may be provided that not the full capacity of the at least one Y-capacitor is deactivated, but only a part thereof. For this purpose it can be provided that the Y-capacitor is provided by at least two separate capacitors. This embodiment can take into account that, in particular taking into account the electromagnetic compatibility, a different capacitance value of the Y capacitor is used in the intended operation of the charging of the electric energy storage device, as it makes sense for the pre-charging. Thus, for example, the case may occur that a larger capacitance value for the Y capacitor is useful for precharging the DC link capacitor than is used for the subsequent process of charging the electrical energy store. This can result, for example, in that a mean leakage current should not exceed a predetermined value. Other boundary conditions can be considered here accordingly. Overall, this development makes it possible to further design the invention flexibly.

The invention also includes developments of the method according to the invention, which have features as they have already been described in connection with the developments of the method according to the invention. For this reason, the corresponding developments of the method according to the invention are not described again here.

• 1 eine schematische Schaltbildansicht eines elektrischen Bordnetzes eines Elektrofahrzeugs als Kraftfahrzeug mit einer elektrischen Antriebseinrichtung, bei der das Elektrofahrzeug zum Aufladen eines Akkumulators des Bordnetzes als elektrischem Energiespeicher an eine Ladestation als Energiequelle angeschlossen ist, die ein einphasiges Wechselspannungsnetz bereitstellt;
• 2 in einer schematischen Diagrammdarstellung einen zeitlichen Verlauf eines Einschaltstroms beim Zuschalten einer durch die Ladestation bereitgestellten Wechselspannung bei einem entladenen Zwischenkreiskondensator im Bereich einer Nullstelle der Wechselspannung;
• 3 in einer schematischen Diagrammdarstellung wie 2 die Situation beim Zuschalten im Bereich einer maximalen Amplitude der Wechselspannung;
• 4 in einer schematischen Diagrammdarstellung wie 2 die Situation beim Zuschalten im Bereich der maximalen Amplitude der Wechselspannung unter Nutzung eines Vorwiderstands;
• 5 in einer schematischen Diagrammdarstellung einen zeitlichen Verlauf der Zwischenkreisgleichspannung am Zwischenkreiskondensator unter Nutzung eines Ladungspumpeneffekts bei einem Kapazitätsverhältnis von etwa 4000;
• 6 in einer schematischen Diagrammdarstellung einen zeitlichen Verlauf einer Zwischenkreisgleichspannung am Zwischenkreiskondensator unter Nutzung eines Ladungspumpeneffekts bei einem Kapazitätsverhältnis von etwa 100;
• 7 in einer schematischen Blockschaltbilddarstellung die Ladeeinrichtung für ein PEN-System als Netzsystemart;
• 8 in einer schematischen Blockschaltbilddarstellung eine Ladeeinrichtung für ein PEN-System, die ausgebildet ist, den Ladungspumpeneffekt zum Vorladen des Zwischenkreiskondensators zu nutzen;
• 9 in einer schematischen Blockschaltbilddarstellung eine Ladeeinrichtung für ein Dreileiter-Einphasennetz als Netzsystemart mit einem Vorwiderstand zum Vorladen des Zwischenkreiskondensators;
• 10 in einer schematischen Blockschaltbilddarstellung eine Ladeeinrichtung wie 9, die ausgebildet ist, den Ladungspumpeneffekt zum Vorladen des Zwischenkreiskondensators zu nutzen;
• 11 in einer schematischen Diagrammdarstellung einen zeitlichen Verlauf einer Zwischenkreisgleichspannung am Zwischenkreiskondensator für die Ladeeinrichtung gemäß 7;
• 12 in einer schematischen Diagrammdarstellung einen zeitlichen Verlauf einer Zwischenkreisgleichspannung am Zwischenkreiskondensator für die Ladeeinrichtung gemäß 8;
• 13 in einer schematischen Diagrammdarstellung einen zeitlichen Verlauf einer Zwischenkreisgleichspannung am Zwischenkreiskondensator für die Ladeeinrichtung gemäß 9;
• 14 in einer schematischen Diagrammdarstellung einen zeitlichen Verlauf einer Zwischenkreisgleichspannung am Zwischenkreiskondensator für die Ladeeinrichtung gemäß 10;
• 15 in einer schematischen Diagrammdarstellung einen zeitlichen Verlauf der Wechselspannung in einem TN-C-System; und
• 16 in einer schematischen Diagrammdarstellung wie 15 einen zeitlichen Verlauf der Wechselspannung in einem Einphasen-Dreileiternetz.

In the following an embodiment of the invention is described. This shows:

• 1 a schematic diagram of an electric vehicle electrical system of an electric vehicle as a motor vehicle with an electric drive device, in which the electric vehicle is connected to charge a battery of the electrical system as an electrical energy storage to a charging station as an energy source that provides a single-phase AC power supply;
• 2 in a schematic diagram representation of a time course of a switch-on when connecting an AC voltage provided by the charging station at a discharged DC link capacitor in the region of a zero point of the AC voltage;
• 3 in a schematic diagram representation like 2 the situation when switching in the range of a maximum amplitude of the AC voltage;
• 4 in a schematic diagram representation like 2 the situation when switching in the range of the maximum amplitude of the AC voltage using a Vorwiderstands;
• 5 in a schematic diagram representation of a time course of the DC link voltage on the DC link capacitor using a charge pumping effect at a capacity ratio of about 4000;
• 6 in a schematic diagram representation of a time course of a DC link voltage on the DC link capacitor using a charge pumping effect at a capacity ratio of about 100;
• 7 in a schematic block diagram representation of the charging device for a PEN system as Netzsystemart;
• 8th in a schematic block diagram representation of a charging device for a PEN system, which is designed to use the charge pumping effect for precharging the DC link capacitor;
• 9 in a schematic block diagram representation of a charging device for a three-wire single-phase network as Netzsystemart with a series resistor for precharging the DC link capacitor;
• 10 in a schematic block diagram representation of a charging device such 9 adapted to utilize the charge pumping effect for precharging the link capacitor;
• 11 in a schematic diagram representation of a time course of a DC link DC voltage on the DC link capacitor for the charging device according to 7 ;
• 12 in a schematic diagram representation of a time course of a DC link voltage on the DC link capacitor for the charging device according to 8th ;
• 13 in a schematic diagram representation of a time course of a DC link voltage on the DC link capacitor for the charging device according to 9 ;
• 14 in a schematic diagram representation of a time course of a DC link voltage on the DC link capacitor for the charging device according to 10 ;
• 15 in a schematic diagram representation of a time course of the AC voltage in a TN-C system; and
• 16 in a schematic diagram representation like 15 a time course of the AC voltage in a single-phase three-wire network.

The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention, which are to be considered independently of one another, which each further develop the invention independently of one another and thus also individually or in a different combination than the one shown as part of the invention. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

In the figures, functionally identical elements are each provided with the same reference numerals.

1 shows a schematic circuit diagram representation of a DC intermediate circuit 54 an electrical vehicle electrical system of an electric vehicle, not shown, as an electrically driven motor vehicle, to which an electric drive device 56 connected. The DC voltage intermediate circuit 54 includes a DC link capacitor 66 , to which a DC link voltage is applied. The electric drive device 56 includes a three-phase electric machine 58 , which is presently designed as a synchronous machine and which serves to drive the electric vehicle.

To the electric machine 58 is an inverter 60 connected, which is formed, a three-phase AC voltage network for the electric machine 58 provide. The inverter 60 includes a control unit 52 , by means of which the inverter 60 is suitably controlled with respect to the alternating voltage network, so that the electric machine 58 to provide the desired drive function during the intended driving operation of the electric vehicle. For this purpose, the inverter 60 three in the following still further explained inverter connections on which unnamed stator windings of the electric machine 58 are connected. The stator windings of the electric machine 58 are connected while driving at a common star point, not shown. The inverter 60 is still connected to the DC voltage intermediate circuit 54 connected, so that it is supplied with the DC link DC voltage.

At the DC voltage intermediate circuit 54 is also a high-voltage battery 10 as electrical energy storage via a switching unit 62 connected, which provides electrical energy for the intended operation of the electric vehicle. Thus, the high-voltage battery provides 10 at the same time the intermediate circuit DC voltage of the DC intermediate circuit 54 ready when driving.

Electrical potentials of the DC link voltage are across respective Y capacitors 42 . 44 coupled to a reference potential, which in this case by a mass 40 of the electric vehicle is formed. Through the Y capacitors 42 . 44 a radio interference in terms of common mode noise is achieved. The Y capacitors 42 . 44 act in this regard with a current-compensated choke 64 together. In the present embodiment, the electrical capacitance of each of the two Y capacitors 42 . 44 about 1 μF. The electrical capacity of the Y capacitors 42 . 44 If necessary, this can also be chosen differently.

A respective electrical voltage of potentials of the high-voltage battery 10 opposite to the mass 40 is as a reference voltage 38 represented between a positive electric potential of the high-voltage battery 10 and the crowd 40 is formed and corresponds to about half of the DC link voltage. Accordingly, there is an electrical voltage between the negative electric potential of the high-voltage battery 10 and the crowd 40 ,

During normal driving, the common mode potential on the DC link side is the one on the high-voltage battery 10 over the Y capacitors 42 . 44 to the mass 40 clamped. In contrast, the push-pull potential at the AC voltage side of the electric machine 58 around the crowd 40 jump, in time with the switching frequency of the inverter 60 ,

The inverter 60 in the present case has three series connections 22 . 24 . 26 from two semiconductor switches each 28 . 30 in the present case are formed by insulated gate bipolar transistors (IGBT). Of course, the semiconductor switches can also be formed by other transistors.

The series connections 22 . 24 . 26 are connected in parallel to the DC voltage intermediate circuit 54 connected. Each of the three series connections 22 . 24 . 26 has a respective middle connection 32 . 34 . 36 on which provide the inverter terminals, where the stator windings of the electric machine 58 are connected. The inverter 60 is thus like one B6 Inverter bridge formed and provides the three-phase AC power supply for driving.

1 shows in a schematic diagram representation of how the electrical system for charging the high-voltage battery 10 to a vehicle-external charging station 14 is connected, the electrical energy to charge the high-voltage battery 10 provides. The charging station 14 is a stationary charging station and has a network system type according to a TN-C system. The electric vehicle is for connection to the charging station 14 in the area of the charging station 14 off. About a not further shown wired connection, in this case a charging cable, and a charging-side switching unit 48 is the electrical system, as will be explained further below, to the charging station 14 connected.

In the present embodiment, a galvanic connection between the charging station 14 and the electrical system of the electric vehicle provided. Accordingly, a protective conductor terminal or a reference potential 16 , here earth potential, the charging station 14 with the crowd 40 electrically coupled to the electric vehicle.

To the charging station 14 To be able to connect to the electrical system of the electric vehicle is provided in this case that the neutral point of the electric machine 58 is opened and the corresponding terminals of the stator windings of the electric machine 58 to the respective phase terminals of the charging station 14 at least partially connected. This will be a charging station connection 48 provided by the electric vehicle.

About the stator windings of the electric machine 58 and the inverter 60 can then supply electrical energy to the high-voltage battery 10 respectively. For this purpose, the semiconductor switches or IGBTs here 28 . 30 of the inverter 60 by means of the control unit 52 of the inverter 60 controlled in a suitable manner. In the simplest case, however, they are uncontrolled, so that with an AC voltage 18 applied IGBTs 28 . 30 how diodes can act. In addition, the inverter can 60 provide a clocked energy converter, which makes use of the inductance of the stator windings of the electric machine 58 can realize an energy conversion in a suitable manner. This allows the high-voltage battery 10 electrical energy from the charging station 14 be supplied.

By means of a charging station provided net filter or a filter circuit 120 can be prevented that the reference potential 16 neither with respect to the DC link side nor with respect to the charging station side AC side jumps.

Depending on a respective switching pattern for the respective IGBTs 28 . 30 , which use a respective PWM pattern to realize the respective push-pull voltage with respect to the mains frequency of 50 Hz, different noise components are generated. The filter circuit 120 the charging station 12 is designed adapted for these disorders.

1 shows that the electrical system of the electric vehicle to the charging station 14 is connected, in the present case a single-phase AC voltage 18 provides. As a result, are from the inverter 60 in the present case only the series circuits 22 and 24 activated with respect to the energy conversion. Together with the stator windings of the electric machine 58 becomes thereby a clocked energy converter 20 educated. The clocked energy converter 20 has an energy storage port 50 on, with which he at the DC voltage intermediate circuit 54 and thus also on the high-voltage battery 10 connected. Thus, the clocked energy converter forms 20 a charging device 46 that is trained at the charging station 14 to be connected.

The central connections 32 and 34 the series connections 22 . 24 are correspondingly with a phase connection L (first phase potential) and a zero connection N (Zero potential) of the charging station 14 electrically connected. Charging station side is at the phase connection L opposite the zero connection N an AC voltage of 230 V at 50 Hz provided. The charging device 46 also has the filter circuit 120 on.

In addition, via a power supply, not shown, to which the charging station 14 connected, the zero connection N with a protective conductor connection as electrical reference potential 16 electrically coupled. The reference potential 16 is in this case the earth potential.

By means of the control unit 52 become the IGBTs 28 . 30 the series connections 22 . 24 controlled, so that a corresponding energy conversion can be realized. Thus, the charging station 14 taken from electrical energy and the high-voltage battery 10 be supplied. The crowd 40 is with the reference potential 16 electrically coupled.

The electrical potentials of the DC link voltage fluctuate in phase with approximately half the mains voltage amplitude with respect to the ground 40 with the AC voltage frequency. The resulting reference voltage 38 is therefore superimposed with an alternating voltage, so that over the Y-capacitors 42 . 44 a leakage current in the mass 40 is dissipated.

15 shows a schematic diagram of a time course of the AC voltage 18 a TN-C system, as it is often used in Europe. The ordinate is assigned to the voltage, whereas the abscissa is assigned to the time. The alternating voltage is sinusoidal and in the present case has an amplitude of about 325 V, so that it has an effective value of about 230 V. The frequency of the AC voltage is about 50 Hz. With a graph P is the course of the phase potential of the AC voltage 18 represented with respect to the time axis, which forms the abscissa in the present case. With another graph N that coincides with the time axis is the zero potential N of the corresponding neutral conductor. Out 15 it can be seen that the neutral conductor is grounded at the same time.

16 shows in a schematic diagram representation as 15 a time course of a single-phase AC voltage in a three-wire network, as it is usually used in North America. The ordinate is again associated with the voltage, whereas the abscissa correspondingly 15 associated with the time. With graphs P ₁ and P ₂ Two phase potentials of the single-phase three-wire network are shown, which are synchronized in time and each represent a sinusoidal voltage, wherein an effective value of each of the phases P ₁ and P ₂ an RMS value of about 115 V with respect to the zero potential N having. The phases P ₁ and P ₂ are symmetrical to the earth potential, which is the zero potential N equivalent.

2 shows a schematic diagram of a time course of a switch-on when connecting an AC voltage provided by the charging station at a discharged DC link capacitor in the region of a zero point of the AC voltage. In the diagram representation according to 2 an abscissa is assigned to the time. A left ordinate is associated with the voltage, whereas a right ordinate is associated with the electrical current flowing from the charging station 14 to the DC link capacitor 66 flows, is assigned. With a graph 14 is the course of the AC voltage 18 timely. The AC voltage 18 corresponds to how they are based on 15 was explained. With a graph 12 is the DC link voltage U _z shown. Another graph 16 is associated with the electrical current flowing into the DC link capacitor 66 flows. It can be seen that at time t = 0, the current jumps to a value greater than 40A. At about reaching the maximum amplitude of the AC voltage 18 the current takes up to a time t ₁ continuously until it reaches about zero. At this time, the DC link capacitor 66 then fully charged. How out 2 it can be seen, the components acted upon by the current flow are exposed to a comparatively large electric current.

3 shows in a presentation like 2 the situation when switching on during the maximum amplitude of the AC voltage 18 he follows. It can be seen that around the time t = 0s a very narrow current pulse occurs, the value of which is around 170kA. This current pulse is very short but very large, so from the rest of the diagram in accordance with 3 based on the graph 16 it can be seen that there is no longer a significant flow of electricity for the further course of time. It can be seen that the current-carrying components are subjected to a very significant electrical current. This is detrimental to these components and may even result in failure or failure of one or more components.

4 shows in a further schematic diagram representation as 2 the situation when switching in the range of the maximum amplitude of the AC voltage using a series resistor, which has a resistance of about 100Ω in the present case. The assignment of the axes and the graph corresponds to those as to the 2 and 3 , Out 4 It can be seen that the electric current can be considerably limited by the precharge resistance. Nevertheless, some time passes until the DC link voltage U _z has a value which is a connection of the AC voltage 18 while avoiding a large current pulse allowed by the series resistor is short-circuited by means of a suitable switching element. Out 4 it can be seen that the DC link voltage U _z reaches a value approximately equal to the amplitude of the AC voltage after about 1 second 18 equivalent. At this time, it is possible to short-circuit the series resistor, without a significant current pulse occurs. The current is also here with the graph 16 whereas the DC link voltage is indicated by the graph 12 is shown. The graph 14 sets the AC voltage 18 dar. From the diagram of 4 it can be seen that the maximum current is about 3,25A is when switching on the series resistor during the maximum amplitude of the AC voltage 18 he follows. The inrush current or current pulse is thus considerably smaller than in the to 2 and 3 described situations.

The invention now deals with the question of the intermediate circuit capacitor 66 to pre-charge and preferably to save the pre-charge resistance. In addition to be achieved with the invention that a pre-charging is no longer by the high-voltage battery 10 is necessary because this can not be realized in all systems.

To make this possible, it is provided to use a charge pumping effect, which results from the fact that at least one of the electrical potentials of the DC link voltage by means of Y capacitors 42 . 44 with the crowd 40 are coupled. In the present case, both electrical potentials of the DC link voltage by means of the Y capacitors 42 . 44 with the crowd 40 coupled. It uses the effect that the mass 40 with the earth potential 16 can be electrically coupled. For this purpose it is provided that the AC side of the charging station 14 only the phase potential P is switched on at the phase connection. The zero connection or the zero potential N does not stay connected. As a result, a charge pumping effect is achieved by means of which the intermediate circuit capacitor 66 using the Y capacitors 42 . 44 can be summoned. The idea is based on the fact that the charge pumping effect is inherently current-limited, because with each half-wave of the alternating voltage 18 only those in the Y capacitors 42 . 44 Stored electrical charge taken from the mains and the DC link capacitor 66 can be supplied. The charge pumping effect already occurs when only a single phase potential, which compared to the ground potential 16 alternates, is connected. Thus, by electrically coupling a single phase potential of the AC voltage 18 the DC link capacitor 66 be preloaded current limited. Only when the DC link DC voltage at the DC link capacitor 66 reaches a predetermined comparison value, then also the zero potential or the zero connection N be switched on. Then there is a company - as at the beginning of the 1 described - possible. For this embodiment of the precharge so is a precharge, as he said on the basis of 4 was explained, not required. In addition, of course, be taken into account that with this functionality, a phase angle of the AC voltage 18 can be determined, so a connection of the zero potential N or the zero terminal in synchronism with the phase position of the AC voltage 18 is possible.

5 shows in a further schematic diagram representation of a time course of the DC link DC voltage on the DC link capacitor using the charge pumping effect at a capacitance ratio of the DC link capacitor 66 to the summed values of the Y capacitors 42 . 44 of about 4000. In the diagram, the time axis is again assigned to the abscissa, the left ordinate is again a voltage in V assigned and the right ordinate a stream in A , With the graph 14 is again the AC voltage 18 represented here as a bar due to the resolution of the abscissa, it being noted that this is an AC voltage as in the previous one 2 to 4 explained.

The graph 12 again shows a voltage curve of the DC link DC voltage U _z It can be seen that the DC link voltage at about 30s the amplitude of the AC voltage 18 reached and then exceeds the time course. With a graph is a leakage current 70 or the current through the Y capacitors 42 . 44 shown. It can be seen that it is an alternating current whose amplitude is about 20 mA. At the leakage current 70 it is an alternating current that has a frequency like the AC voltage 18 having. When the diagram of 5 Underlying configuration is the capacity of the DC link capacitor 66 about 400μF, whereas the capacity of the Y capacitors 42 . 44 each is about 100nF.

6 shows in a diagram like 5 the conditions with a capacitance value of the DC link capacitor of about 10μF. The capacity of the Y capacitors 42 . 44 is unchanged. It can be seen that the maximum amplitude of the AC voltage 18 already reached after a time of about 0.75s. Charging can be much faster here than in the situation according to 5 respectively.

7 now shows a schematic block diagram representation of a charging device 98 for use in a PEN system as network system type. The charging device 98 is for connecting to a charging station 14 formed, the a three-phase AC voltage with the phase potentials P ₁ . P ₂ and P ₃ towards a zero potential N provides. In this embodiment, it is provided that the zero potential N with a ground potential 16 is electrically coupled. However, this need not necessarily be provided in this embodiment.

The charging device 98 comprises a charging-side switching unit 48 , which serves to provide a pre-charge functionality by means of precharging resistors for the DC link capacitors 66 provide. The switching unit 48 is formed as usual in the prior art and has for each of the phase potentials P ₁ . P ₂ and P ₃ a respective non-designated electrical resistance, by means of a likewise not designated respective electromechanical switching element can be shorted. The respective switching elements are - as in the 7 - Not shown, electromechanical switching contacts of an electromechanical contactor. For the purpose of precharging the DC link capacitors 66 are the respective switching elements in the open state, so that an electrical connection between the respective phase potentials P ₁ . P ₂ and P ₃ initially only on the respective electrical resistances. This allows the respective DC link capacitors 66 be pre-charged via the corresponding electrical resistors.

How out 7 is apparent, is for each of the phase potentials P ₁ . P ₂ and P ₃ the AC voltage of the charging station 14 a separate loading unit 78 the charging device 98 intended. Each of the loading units 78 is thereafter on the respective switching unit 48 to the respective phase potentials P ₁ . P ₂ and P ₃ connected. Between the respective DC link capacitors 66 the loading units 78 and the respective switching unit is a respective bridge rectifier 100 connected, the AC side with a respective connection also to the zero potential N the charging station 14 connected.

The charging station 14 thus provides a three-phase AC voltage at whose phase potentials P ₁ . P ₂ and P ₃ is shifted by a predetermined phase angle to each other. The phase angle is presently about 120 °.

For each of the phase potentials P ₁ . P ₂ and P ₃ the AC voltage of the charging station 14 is thus a separate loading unit 78 intended. Each loading unit 78 is thus designed to be able to use a single-phase AC voltage. This allows it when the charging station 14 provides only a single-phase AC voltage instead of a polyphase AC voltage, the charging units 78 parallel and thus the charging power of the charging device 98 even with a single-phase operation to enlarge. For this purpose, it is provided that the charging device 98 respective switching units 74 . 76 comprising, by means of not further described electromechanical switching elements, a switching between a three-phase and a single-phase operation of the charging device 98 allows. The function of the switching units 74 . 76 turns out 7 for the expert of course, so apart from further detailed explanations regarding the switching.

With the bridge rectifier 100 the applied AC voltage is rectified and according to the AC voltage a DC link DC voltage on the DC link capacitor 66 provided.

The loading unit 78 further comprises a PFC stage for adjusting a power factor, and a DC-DC converter including a half-bridge circuit 82 , a transformer 84 and a rectifier unit 88 includes. On the output side is the charging unit 78 to a respective electrical system 72 connected. The vehicle electrical system 72 can also be connected in parallel. The vehicle electrical system 72 can one or more high-voltage batteries - such as the high-voltage battery 10 - include.

8th now shows a charging device 98 as 7 , but now with the switching units 48 omitted with the respective pre-charging resistors. Instead, a respective electrical feedthrough is provided. The loading units 78 or their rectifier 100 are - in contrast to the embodiment according to 7 - now more about respective switching elements 90 with the crowd 40 electrically coupled. The crowd 40 is in to the charging station 40 connected state with the ground potential 16 electrically coupled, which in turn with the zero potential N is electrically coupled.

Furthermore, it is provided in the present case that the respective electrical potentials of the DC link capacitors 66 via respective Y-capacitors 42 . 44 with the crowd 40 are electrically coupled. The respective circumstances correspond to those, as they already are 7 why, in this regard, the comments made on 7 is referenced.

For precharging the DC link capacitors 66 is presently provided that the switching elements 90 are in the open switching state. This allows the through the Y capacitors 42 . 44 caused charge pumping effect can be used to the DC link capacitors 66 to preload accordingly. With regard to the basic functionality, reference is made to the preceding explanations in particular 5 directed.

By means of a voltage sensor, not shown, the respective DC link DC voltages at the respective DC link capacitors 66 and compared with a respective comparison value. As soon as the intermediate circuit DC voltage reaches the comparison value, the respective one of the switching elements 90 be closed, so that the intended charging operation of each of the loading units 78 can be realized. This charging device 98 according to 8th So it is characterized by the fact that pre-charging as in the charging device 98 according to 7 omitted.

The 9 and 10 now refer to an embodiment based on the 7 and 8th , this design provided for it is, to a single-phase three-core network of a charging station 92 to be connected. For this purpose, the charging device 98 according to 7 modified in that the loading units 78 Both the input side and output side are connected in parallel. It is a common switching unit 48 provided with a precharge resistor, which serves the respective DC link capacitors 66 in the known way vorzuladen. The charging device 98 is designed for two phase potentials P ₁ and P ₂ be connected, whereby an AC electrical voltage is provided, as described above with reference to 6 was explained. A middle connection of the AC voltage of the charging device 98 is at earth potential 16 electrically coupled. Further, a mass 40 the charging device 98 also with the earth potential 16 coupled.

In contrast to the previous embodiment, the center point grounding leads to the problem that the intermediate circuit DC voltage at the respective DC link capacitors 66 even after an infinite charging time, even if no electrical energy would be taken from the DC intermediate circuit, only the simple value of the amplitude of the AC voltage can reach. This theoretical end-of-charge voltage results from twice the common-mode voltage of the connected AC voltage, which in the present network system type is just half that of the PEN network system type. This also affects the charging behavior.

9 shows in case like 7 the pre-charging by means of an electrical resistance. Not only can the precharge process take a long time, but it can even happen that it can not be completely completed, so that when the corresponding switching element or a short circuiting of the electrical resistance, a large electric current pulse can still arise.

To reduce this current pulse can be in the circuit according to 9 be provided that a power-synchronous connection of the switching element of the switching unit 48 takes place, as has already been explained above.

10 now shows a charging device 98 based on the embodiment according to 8th but now adapted to a charging device 92 according to 9 to be connected. For this purpose, it is provided that the switching unit 48 by a switching element 94 is replaced. The pre-charge resistance is thus eliminated completely. In addition, the Y capacitors 42 . 44 not like in 8th represented directly with the mass 40 electrically coupled, but instead to another switching element 96 guided. The switching element 96 allows the respective connections of the Y capacitors 42 . 44 depending on the switching state of the switching element 96 either with the phase potential P ₁ or with the crowd 40 to couple electrically. As a result, the effects explained below with respect to the precharging of the respective DC link capacitors 66 be achieved.

By the in 10 shown circuit can be achieved that in a first switching position of the switching element 96 the Y capacitors 42 . 44 with the crowd 40 are electrically coupled. In the switching state of the precharge is the switching element 94 in the opened switching state. By means of the phase potential P ₂ Now takes a pre-charging the DC link capacitors 66 using the charge pumping effect as previously explained in detail. As has also been explained, however, this can only be a limited preloading of the DC link capacitors 66 be achieved.

To the DC link capacitors 66 It is better to be able to pre-charge to a higher DC link voltage, that after reaching a predetermined comparison value of the respective DC link DC voltages, the switching element 96 is switched so that the respective terminals of the Y capacitors 42 . 44 now with the phase potential P ₁ be electrically coupled. As a result, an improved charge pump effect can be achieved so that now the DC link capacitors 66 can be precharged to the required DC link voltage, so when connecting the phase potential P ₁ over the switching element 94 no current pulse needs to be made. At the same time with the connection of the switching element 94 can the switching element 96 be switched back so that the corresponding terminals of the Y capacitors 42 . 44 again with the crowd 40 be electrically coupled. This can be compared to the charging device 98 according to 9 provided a significantly improved functionality.

The with the charging devices 98 according to the 7 to 10 achievable functionalities are described below with reference to the schematic diagrams according to the 11 to 14 further explained.

In these diagrams, the abscissa is assigned to the time. A left ordinate is associated with the electrical voltage and a right ordinate with the electric current. In the diagrams is with 12 a respective graph is shown, the respective one of the DC link DC voltages to the respective one of the DC link capacitors 66 represents. With the graph 16 is a respective stream represented as provided by a respective one of the phase potentials.

The schematic diagram representation according to 11 refers to the circuit according to 7 , As can be seen, the charging device 98 according to 7 at the time t = 1s with the three-phase AC voltage of the charging station 14 applied. By means of the graph 12 It can be seen that the respective DC link DC voltages jump to approximately 320 V at time t = 1 s. Up to the time t = 3s, the intermediate circuit DC voltage continues to increase in each case to a value of about 440 V. At the time t = 1s is also based on the graph 16 a current pulse can be seen. This current pulse has a value of about 600 mA. After about 2s, the respective switching units 48 operated and shorted the corresponding pre-charge resistors. At time t = 3s, the intended charging operation of the charging device 98 recorded as the graphs 16 is apparent.

12 now shows a diagram like 11 , but for the circuit according to 8th , Again, at the time t = 1s, the AC voltage to the charger 98 given. It can be seen that from the time t = 1s the DC link DC voltage according to the graph 12 from 0 V to a voltage of about 440 V continuously increases. This is achieved by using the charge pump effect. Accordingly, by means of the graph 16 a fine Rippelstrom visible, which can be at least partially associated with the charge pump effect. At time t = 3s, the comparison value is due to the intermediate circuit DC voltages at the DC link capacitors 66 reached. At time t = 4s, the intended charging operation of the charging device 98 added. It can be seen that even without the precharge resistor, a reliable precharging of the DC link capacitor 66 can be reached.

The 13 and 14 Now refer to the corresponding circuits of 9 and 10 in which the charging device 98 to the charging station 92 is connected as explained above.

Out 13 that have a diagram like in the 11 and 12 , it can be seen that at time t = 1s the electrical connection to the charging station 92 will be produced. Based on the graph 12 It can be seen that charging takes place via the precharging resistor up to a precharging voltage of approximately 240V. The precharge operation is aborted at a time t = 8s, and the precharging resistance of the switching unit 48 will be shorted. It can be seen that due to the high voltage difference, a current pulse of about 0.2 A flows. At time t = 9s the intended charging operation is recorded.

14 now shows the effect of the circuit according to 10 using the charge pumping effect. As with the graph 12 it can be seen, the method begins with the switching on or activating the AC voltage of the charging station 92 at time t = 1s. For pre-charging the DC link capacitors 66 is provided that the switching element 96 the Y capacitors with the phase potential P ₁ coupled. This can improve the precharging of the DC link capacitors 66 be achieved, as shown by the graph 12 in 14 is apparent. At a time t = 3s, a voltage of almost 400 V is already present at the DC link capacitors 66 reached. At this time, the Y capacitors are switched by means of the switching element 96 again with the crowd 40 electrically coupled. This results in a voltage reduction with respect to the DC link voltage at the DC link capacitors 66 , At time t = 4s the intended charging operation is recorded. At this time, the switching element 94 already closed.

Overall, the embodiments show how, by means of the charge pumping effect, a precharging of the DC link capacitors can be achieved without a precharging resistor being required. Rather, the usually without existing Y capacitors can be used to realize the pre-charging of the DC link capacitors. As a result, not only can effort be saved, but in particular reliability and safety can also be increased.

Overall, it is also advantageous for the process control according to the invention if the DC voltage intermediate circuit is as far as possible not loaded by electrical consumers during precharging. As a result, the preloading can be accelerated in time. The connection of loads or loads on the electrical system should therefore preferably be done only after the precharge.

The exemplary embodiments serve exclusively to explain the invention and are not intended to limit this.

LIST OF REFERENCE NUMBERS

10

High-voltage battery

12

graph

14

charging station

16

ground

18

AC

20

energy converters

22

series connection

24

series connection

26

series connection

28

Semiconductor switches

30

Semiconductor switches

32

medium connection

34

medium connection

36

medium connection

38

reference voltage

40

Dimensions

42

Y-capacitor

44

Y-capacitor

46

loader

48

switching unit

50

Energy storage connection

52

control unit

54

Dc link

56

driving means

58

electric machine

60

inverter

62

switching unit

64

current-compensated choke

66

Link capacitor

70

leakage

72

board network

74

switching unit

76

switching unit

78

charging unit

82

Half-bridge circuit

84

transformer

88

Rectifier unit

90

switching element

92

charging station

94

switching element

96

switching element

98

loader

100

Bridge rectifier

N

Nullanpotential

P

phase potential

P ₁

phase potential

P ₂

phase potential

P ₃

phase potential

U _z

Intermediate circuit voltage

t1

time

Claims (13)

A method for precharging an intermediate circuit capacitor (66) of a DC intermediate circuit (54) with electrical energy from an energy source (14) providing an AC voltage (18) with respect to a predetermined electrical reference potential (16, 40), comprising: - the AC voltage (18) is rectified by means of a bridge rectifier (100) or an inversely operated polyphase inverter (20) in order to supply the energy provided by the energy source (14) to the DC link capacitor (66), and - at least one electrical potential of the DC link capacitor (66) rectified by provided DC link voltage by means of at least one Y-capacitor (42, 44) is coupled to the electrical reference potential (16, 40), characterized in that during pre-charging only a first phase potential (P) of the AC voltage (18) with the bridge rectifier (100) or inverse multiphase Wechselric Hter (20) is electrically coupled. Method according to Claim 1 , characterized in that at an AC voltage (18) having at least two phase potentials (P ₁ , P ₂ ), a connection of the at least one Y-capacitor (42, 44) during pre-charging at least temporarily from the electrical reference potential a (16, 40) one of the first phase potential (P ₁ ) different second phase potential (P ₂ ) of the AC voltage (18) is switched. Method according to Claim 1 or 2 , characterized in that the pre-charging is terminated depending on a comparison of the detected by a voltage sensor DC link voltage with a predetermined comparison value. Method according to one of the preceding claims, characterized in that then for pre-charging a zero potential (N) of the AC voltage (18) and / or further phase potentials (P ₁ , P ₂ ) of the AC voltage (18) with the bridge rectifier (100) or the inverse operated polyphase inverter (20) are electrically coupled. Method according to Claim 4 , characterized in that a phase position is determined automatically at least with respect to the first phase potential (P) and the coupling takes place depending on the determined phase position. Method according to one of the preceding claims, characterized in that during Vorladens a Netzsystemart is determined and the coupling takes place depending on the determined Netzsystemart and the determined phase position at least with respect to the first phase potential (P). Method according to one of the preceding claims, characterized in that in a polyphase AC voltage for each of the phases a separate rectifying and each electrically isolated DC link capacitors (66) are provided and each of the DC link capacitors (66) during precharge only by means of the respective phase potential of the AC voltage (18) is electrically coupled via the respective bridge rectifier (100) or the respective inversely operated polyphase inverter (20). Method according to one of the preceding claims, characterized in that in a polyphase AC voltage (18) with phase potentials (P ₁ , P ₂ ) having different phase angles from each other, with a common rectification and a common DC link capacitor (66) during precharge only one the phase potentials (P ₁ ) of the AC voltage (18) is electrically coupled as a first phase potential to the bridge rectifier (100) or to the inversely operated polyphase inverter (20). Method according to one of the preceding claims, characterized in that a capacitance value of the at least one Y-capacitor (42, 44) is selected as a function of a capacitance value of the intermediate circuit capacitor (66). Method according to one of the preceding claims, characterized in that the at least one Y-capacitor (42, 44) is electrically coupled during pre-charging by means of a switching element (96) with the at least one electrical potential (P ₁ ) of the DC link voltage. A precharge device for precharging an intermediate circuit capacitor (66) of a DC intermediate circuit (54) with electrical energy from an energy source (14) providing an AC voltage (18) with respect to a predetermined electrical reference potential (16, 40), comprising: - a power source terminal for electrically coupling the Energy source (14), and - a DC link connection for connection to the DC link capacitor (66), wherein the DC link capacitor (66) to a coupled to the energy source rectifier unit, the AC voltage by means of a bridge rectifier (100) or an inversely operated polyphase inverter (20) rectified, connected to supply the power source (14) provided energy to the DC link capacitor (66), and wherein at least one electrical potential of a DC link capacitor (66) provided by the intermediate DC link voltage by at least a Y-capacitor (42, 44) is coupled to the electrical reference potential (16, 40), characterized by a switching unit (48, 90, 96) which is adapted to electrically couple the rectifier unit with the power source (14) and during of precharging only a first phase potential (P) of the AC voltage (18) to the bridge rectifier (100) or the inversely operated multiphase inverter (20) to electrically couple. Charging means (46) for power coupling of an energy source (14) providing an AC voltage (18) with respect to a predetermined electrical reference potential (16, 40), comprising: - a power source terminal for electrically coupling the power source (14), - an onboard power supply terminal for connection to an electrical vehicle electrical system (72) of a motor vehicle, - an intermediate circuit capacitor (66) electrically coupled to the electrical system connection, - a rectifier unit connected to the power source connection and the intermediate circuit capacitor (66), which is designed to supply the AC voltage by means of a bridge rectifier (100) or a inverse-powered polyphase inverter (20) rectified to supply the energy supplied by the power source (14) to the DC link capacitor (66), - at least one Y-capacitor (42, 44) connected to a first capacitor terminal to the electrical reference potential (40) and with a second cond denatoranschluss is coupled to an intermediate circuit DC voltage provided by the rectification at the intermediate circuit capacitor (66), and - a precharging device for precharging the intermediate circuit capacitor (66), characterized in that the precharging device Claim 11 is trained. Motor vehicle with a least one electrical energy store (10) having on-board network (72) and a to the electrical system (72) connected to charging means (46) for energy-technical coupling a motor vehicle external electrical power source (14), characterized characterized in that the charging device (46) after Claim 12 is trained.

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