DE102011006118A1 - Method for monitoring e.g. rail vehicle regenerative electric motor-generator drive unit that is utilized for producing electrical power, involves initiating system-side short circuit, and closing aperture of switch system immediately - Google Patents

Abstract

The method involves comparing a detected voltage at a filter capacitor (20) with two threshold values. A network-side short circuit is initiated, and an aperture of a switch system (14) is closed after expiration of a predetermined back-up time if the detected voltage falls below one of the threshold values. A system-side short circuit is initiated, and the aperture of the switch system is closed immediately if the detected voltage falls below the other threshold value, where a transformer (12) is connected with an electrical supply network (16) over the switch system. An independent claim is also included for a regenerative power system.

Description

The invention relates to a method for monitoring a regenerative energy system with a converter, with a filter with capacitor and with an inductor, in particular a transformer, which is connected via a switch system with an electrical supply network with a predetermined network frequency.

As a regenerative energy system in this context, a system is considered, which is connected to an electrical supply network, and at least temporarily feeds electrical energy into the same.

An example of this is a rail vehicle with a regenerative electric motor-generator drive unit. In the drive mode, such a rail vehicle is supplied with energy from a supply network and set in motion or held with the aid of the electric motor. In regenerative mode, however, the electric motor-generator drive unit acts as a generator and brakes the rail vehicle, wherein the electrical energy generated during the braking process is fed into the supply network.

Another example of a regenerative energy system is a wind turbine. This generates electrical energy depending on the prevailing weather conditions and feeds these into a connected supply network.

The characteristics of a supply network, such as the operation according to the DC or AC principle, the number of provided phases, the voltage amplitude or the mains frequency are typically predetermined and should not be changed by the supply of energy. Accordingly, in a regenerative energy system, the energy to be fed into the supply network is in most cases processed and thereby adapted to it. This adaptation takes place in many cases, inter alia with the aid of an inverter and an electronic filter.

To protect the regenerative energy system on the one hand and the supply network on the other hand, a timely separation of the regenerative energy system from the supply network is usually provided for the case of failure, especially in the case of a short circuit. For this purpose, the regenerative energy system via a switch system or a security system, for example, a fuse, connected to the supply network. In the event of a fault, the switch system is opened or the safety system is triggered so that the regenerative energy system is subsequently disconnected from the supply network.

On the other hand, there is the requirement that a system, which is intended for feeding energy into a supply network, must be able to contribute to a short-circuit clarification in the supply network. If a short circuit occurs within the supply network, the system should support the supply network and feed energy into it until a safety mechanism close to the short-circuit source triggers in the supply network.

Previous versions of serving for feed systems that are connected via a switch system with a supply network, react relatively sluggish due to the typical structural conditions of the switch system, so that the corresponding system after the occurrence of a short circuit for about 100 ms on the switch system with the Supply network is connected. If there is a short-circuit on the supply side, the system continues to feed energy into the supply network during this time and thus at least temporarily contributes to short-circuit clarification in the supply network. In addition to the switch system fuses are installed within the system to protect the regenerative energy system, especially in the case of a system-side short circuit. Unfavorable here is the fact that the triggering criteria for such a protection mechanism by the design of the protective elements, so the switch system and the fuses given and are thus very narrow.

The invention has for its object to provide a method for monitoring and in particular for the protection of a regenerative energy system. It is also an object of the invention to provide a correspondingly monitored regenerative energy system.

With regard to the method, the stated object is achieved according to the invention by the features of claim 1. The dependent claims contain, in part, advantageous and in part self-inventive developments of this invention.

The method is used for monitoring and in particular for the protection of a regenerative energy system, which is connected via a switch system with an electrical supply network with a predetermined network frequency. The regenerative energy system, hereinafter referred to as the energy system or just system, includes an inverter, a filter with a capacitor and a transformer. Instead of Transformers is provided in some cases, however, a simple inductance.

For the sake of clarity, the method is subdivided below into method steps. The method is, however, in the execution of neither bound to the order or their order. In a first method step, a voltage is detected at the capacitor. The capacitor is typically part of the electronic filter. However, in some cases, a voltage is also detected on, for example, a smoothing or storage capacitor.

In a further method step, the detected voltage is compared with a first threshold value and with a second threshold value. Depending on the result of this comparison, various conclusions and associated actions are envisaged, which will be carried out in a further procedural step. If the detected voltage at the capacitor does not fall below either of the two threshold values, then a fault-free operation of both the system and the supply network is concluded and a system reaction does not occur.

In the case of falling below the first threshold value is closed to a fault in the supply network and in particular to a network-side short circuit. Then, the opening of the switch system is initiated after a predetermined support time.

In the case of falling below the second threshold value, however, it is concluded that there has been an accident in the system itself and, in particular, a system-side short circuit. In this case, the opening of the switch system is initiated immediately.

Thus, such a method not only serves to detect an accident, but also to determine the type of accident and to respond in a suitable manner to the type of accident. This differentiation and the subsequent differentiated reaction make it possible to pursue the two objectives, namely the protection of the system on the one hand, and the support of the supply network for short-circuit clarification, on the other hand, virtually independently of one another.

Support time is the length of time in which the system continues to feed energy into the supply network and thus contributes to short-circuit clarification in the supply network. The protection of the system is guaranteed. Possible consequential damage to the system or personal injury is effectively avoided. In addition, no additional protective elements, in particular fuses, necessary. The design of such a system is virtually fuselage. As a result, the space required for the system is finally reduced and there is no additional power loss. In the event of a fault, therefore, no fuses must be replaced, which in turn reduces the need for spare parts.

According to an advantageous development of the method, the so-called short-circuit voltage of the transformer, ie about 5% to 10% of its rated voltage, is provided as the first threshold value. Furthermore, it is considered advantageous if the second threshold value corresponds to a voltage of <2% of the rated voltage. In addition, it is useful to provide for the support time a duration of up to 5 s. In this regard, a value range between 0.1 s and 2 s is preferred.

According to a preferred variant of the method, a mains-side short-circuit is closed only in the case of a shortfall of the first threshold value for the duration of a first minimum time, and the opening of the switch system is initiated after a predetermined support time has elapsed. With the help of this first minimum time so-called false triggering should be avoided. Such a false triggering occurs, for example, when the voltage detected at the capacitor falls below one of the threshold values, although there is neither a mains-side nor a system-side short-circuit. This is possible, for example, in the case of temporary operational transitions both in the supply network and in the system itself. Since voltage dips that are caused by such temporary operational transitions, typically have a short-term character, resulting false triggering is prevented if a minimum time adapted thereto is provided.

Typically, the duration of a typical temporary business transition correlates to the network frequency of the utility network or to the network period associated therewith. It is therefore appropriate for the minimum time to provide a range of values in the order of a network period. Preferred is a minimum time, which corresponds to 0.1 to 3 times the grid period.

According to a further preferred variant of the method, a short-circuit on the network side (system side) is not made until the second threshold value is undershot for a duration of a second minimum time, and the opening of the switch system is initiated immediately. The second minimum time is here as well as the first minimum time to prevent possible false triggering. For the simplest possible design of the method, the first minimum time and the second minimum time are usually identical. However, because at one Falling short of the second threshold may be a short circuit on the system side, which leads in most cases in a relatively short time to damage of components in the system, it is considered advantageous in some applications, for the first minimum time deviating from the second minimum time and especially smaller Specify time duration.

In an expedient development of the method, a current characterizing the state of charge of the capacitor is detected in addition to the voltage across the capacitor. The information thus obtained is used in particular for monitoring the capacitor itself, which, as a building block in the system, significantly influences the function and thus the life expectancy of the same.

With regard to the regenerative energy system, the stated object is achieved according to the invention by the features of claim 5. The claims referring back to it contain partially advantageous and partially inventive embodiments of this invention.

The regenerative energy system is connected via a switch system with an electrical supply network with a predetermined power frequency and includes a converter, a filter with a capacitor, an inductor or a transformer and at least one device for carrying out the method steps of the method. In the case of multiple devices, these may perform one or more method steps. If, by contrast, only one device is provided, then this performs all the method steps. Further variants of the device are given by the fact that the switch system, depending on the variant embodiment, is either a part of the energy-recoverable energy system or else part of the supply network.

According to a particularly advantageous embodiment, a so-called Active Line Module (ALM) is provided for the regenerative energy system. It is a microprocessor-controlled module based on IGBT (Insulated Gate Bipolar Transistor) with an actively and precisely controlled DC link, which controls an integrated converter on the basis of sensory data, such as current or voltage measurements, and thereby the recovery of Energy from the designated intermediate circuit regulated in the supply network.

Part of such an Active Line module is thus also an execution unit or device that is capable of performing all the steps in the process. This also includes a control of the switch system for demand-based separation of the regenerative energy system from the supply network. Some ALM variants are also programmable designed and provided with a memory, so that all parameters, such as the first threshold, the second threshold, the support time, the first minimum time and the second minimum time, arbitrarily specified and stored in a memory of the module can. Such a module can thus be advantageously adapted to the characteristics of different systems and different supply networks.

The invention will be explained in more detail with reference to a drawing. Show:

1 schematically a regenerative energy system with an active line module and with a mains transformer and with a switch system in the closed position, and

2 the energy system according to 1 with the switch system in an open position.

Corresponding parts are provided in both figures with the same reference numerals.

This in 1 and 2 schematically shown regenerative energy system 2 is constructed from a voltage source, symbolized by a storage capacitor 4 , an Active Line module 6 with a converter 8th and with a line filter 10 , a transformer 12 and a switch system 14 , With the help of the regenerative energy system 2 is electrical energy that is generated in a manner not shown and the storage capacitor 4 is available in a supply network symbolized by three connections 16 fed with three phases and a given mains frequency. For each of the three phases, the transformer points 12 a separate coil pair and the switch system 14 its own circuit breaker 14a . 14b . 14c on.

The net filter 10 is in adaptation to the three-phase supply network 16 also three-phase configured and constructed symmetrically as a star connection. Here are a filter inductance for each phase 18 and a filter capacity between each phase and a common star point 20 intended. Additionally, in some embodiments, this star point is grounded, in which case typically an additional noise suppression capacitor is placed between the star point and the ground. The line filter can also be constructed as a delta connection.

With the help of sensors 22 done by the Active Line module 6 a monitoring of the voltages Uf and the charging currents I _f to the filter capacitors 20 of the filter 10 , The voltages U _f at the filter capacitances 20 , also called filter voltages, are permanently - or more precisely compared to the system clock of the Active Line module - compared with two stored thresholds.

Since, in the case of a network-side short-circuit, the amplitude of the filter voltage associated with the affected phase drops to a minimum value, that of the short-circuit current of the converter 8th and the leakage inductance of the coil pair of the transformer 12 is dependent on the corresponding phase, a value is provided as the first threshold, which is between the amplitude of the filter voltage in normal operation and the component-dependent minimum value. In adaptation thereto, a value between the minimum value and zero is provided for the second threshold value, since in the case of a system-side and in particular filter-related short circuit the amplitude of the filter voltage typically drops to zero, at least to a very low residual voltage.

Join the Active Line module now 6 an undershooting of the first threshold, so first a first timer is started. If this shortfall for the duration of a stored minimum time, then a second timer is started and after the duration of a support time defined above a control command or control signal S is generated, as a result of which the circuit breaker 14a . 14b . 14c change to an open position. As a result, the regenerative power system becomes 2 from the supply network 16 separated.

If, on the other hand, the filter voltage again rises above the first threshold value within the minimum time, then the first timer is reset and stopped until a new undershooting of the first threshold value is detected.

In the case of falling below the second threshold, the first threshold is inevitably undershot and the first timer is started. If the filter voltage again exceeds the first threshold value within the minimum time, then the first timer is in turn reset and stopped until a new undershooting of the first threshold value is detected. If the amplitude rises above the second threshold value within the minimum time, but not above the first threshold value, the second timer is also started in this case and the control signal S for opening the circuit breaker is generated after expiration of the support time. If, on the other hand, the detected amplitude of the filter voltage is below the second threshold value for the entire duration of the minimum time, then the control signal S becomes for the switch system 14 generated without an additional delay and the system from the supply network 16 separated.

The illustrated monitoring of a single phase is provided by the Active Line module 6 performed in parallel for all three phases. In this case, a short circuit in one phase leads to the separation, ie the opening of all circuit breakers 14a . 14b . 14c , the regenerative energy system 2 from the supply network 16 ,

In summary, the invention relates to a method for monitoring and / or for the protection of a regenerative energy system 2 and a correspondingly monitored regenerative energy system 2 with an Active Line module 6 and preferably with a transformer 12 that has a switch system 14 with an electrical supply network 16 connected to a predetermined power frequency, one at a capacity 20 detected voltage is compared with a first threshold value and with a second threshold value, which is closed at a mains side and falls below the second threshold to a system-side short circuit when falling below the first threshold, whereupon the opening of the switch system 14 after expiration of a given support time or immediately initiated.

The invention is not limited to the above-described imple mentation example. Rather, other variants of the invention can be derived therefrom by the person skilled in the art without departing from the subject matter of the invention. In particular, all the individual features described in connection with the exemplary embodiment can also be combined with each other in other ways, without departing from the subject matter of the invention.

Claims (9)

Method for monitoring a regenerative energy system ( 2 ) with a converter ( 8th ), with a filter ( 10 ) with capacitor ( 20 ) and with an inductance ( 12 ), preferably a transformer ( 12 ), which via a switch system ( 14 ) with an electrical supply network ( 16 ) is connected to a predetermined mains frequency, - one of the capacitor ( 20 ) is compared with a first threshold value and with a second threshold value, - wherein when the first threshold falls below a threshold value closed circuit and the opening of the switch system ( 14 ) is initiated after a predetermined support time has elapsed, and - wherein, when the second threshold value is undershot, a system-side short-circuit is closed and the opening of the switch system ( 14 ) is initiated immediately. The method of claim 1, wherein only in the case of falling below the first threshold value for the duration of a first minimum time closed to a network-side short circuit and the opening of the switch system ( 14 ) is initiated after a predetermined support time has elapsed. Method according to one of claims 1 or 2, wherein closed only in the case of falling below the second threshold for the duration of a second minimum time to a network-side short circuit and the opening of the switch system ( 14 ) is initiated immediately. Method according to one of claims 1 to 3, wherein in addition to the voltage across the capacitor ( 20 ) the charge state of the capacitor ( 20 ) characterizing current is detected. Regenerative energy system ( 2 ) with a converter ( 8th ), with a filter ( 10 ) with capacitor ( 20 ) and with an inductance ( 12 ), preferably a transformer ( 12 ), which via a switch system ( 14 ) with an electrical supply network ( 16 ) is connected to a predetermined network frequency, in particular for carrying out the method according to one of claims 1 to 4, characterized by - means ( 6 . 22 ) for comparing one on the capacitor ( 20 ) detected voltage with a first threshold value and with a second threshold value, - means ( 6 ) for initiating the opening of the switch system ( 14 ) after the expiration of a given period of support, when the first threshold value has been reached, and - means ( 6 ) for directly initiating the opening of the switch system ( 14 ), when the second threshold is fallen short of. Regenerative energy system ( 2 ) according to claim 5, wherein the means ( 6 ) are suitable, in the case of falling below the first threshold for the duration of a first minimum time, the opening of the switch system ( 14 ) after expiration of the given support time. Regenerative energy system ( 2 ) according to one of claims 5 or 6, wherein the means ( 6 ) are suitable, in the case of falling below the second threshold for the duration of a second minimum time, the opening of the switch system ( 14 ) to initiate immediately. Regenerative energy system ( 2 ) according to claim 6 or 7, wherein the first and / or the second minimum time is adapted to a period of the mains frequency. Regenerative energy system ( 2 ) according to one of claims 5 to 8, wherein in addition means ( 6 . 22 ) for detecting a state of charge of the capacitor ( 20 ) characterizing stream are provided.

Images