Charging circuit for an energy storage device and method for charging an energy storage device

Abstract

Charging circuit (30; 40) for an energy storage device (1), which has a plurality of power supply branches (Z) each with a plurality of energy storage modules (3) for generating an alternating voltage at a plurality of output terminals (1a, 1b, 1c) of the energy storage device (1), comprising: a first half-bridge circuit (9) with a plurality of first feed terminals (8a, 8b, 8c), each of which is coupled to one of the output terminals (1a, 1b, 1c) of the energy storage device (1); a second half-bridge circuit (15) with a plurality of second feed terminals (8g, 8h, 8i), each of which is coupled to one of the output terminals (1a, 1b, 1c) of the energy storage device (1); a first feed node (37a; 37b; 47a) which is coupled to the first half-bridge circuit (9) or the second half-bridge circuit (15); a second feed node (37a; 37b; 47b) which is coupled to a reference potential rail (4) of the energy storage device (1); a supply circuit (35; 44, 45) which is coupled between the first and second supply nodes (37a; 37b; 47a, 47b) and which is designed to supply at least a temporary DC charging voltage (U N ) to provide; a converter choke (31; 41) which is coupled between one of the feed nodes (37a; 37b; 47a, 47b) and the feed circuit (35; 44, 45); and a semiconductor switch (33) which is coupled between one of the feed nodes (37a; 37b; 47a, 47b) and the feed circuit (35; 44, 45), wherein the first and / or second half-bridge circuit (9; 15) each have a plurality of first or second diodes (9a; 15a) which are each coupled between the common point of the half-bridge circuit (9; 15) and one of the plurality of first or second feed terminals (8a, 8b, 8c; 8g, 8h, 8i), wherein the first and / or second half-bridge circuit (9; 15) have a plurality of commutation chokes (9b; 15b) which are each coupled between the plurality of first or second diodes (9a; 15a) and the common point of the half-bridge circuit (9; 15).

Description

[0001] The invention relates to a charging circuit for an energy storage device and a method for charging an energy storage device, in particular for charging a battery direct converter with a DC voltage. State of the art

[0002] It is becoming clear that in the future, both in stationary applications, such as wind turbines or solar power plants, and in vehicles, such as hybrid or electric vehicles, electronic systems will increasingly be used that combine new energy storage technologies with electric drive technology.

[0003] The injection of multiphase current into an electric machine is typically accomplished by a converter in the form of a pulse-width modulation (PWM) inverter. For this purpose, a direct current (DC) voltage supplied by a DC link can be converted into a multiphase alternating current (AC) voltage, for example, a three-phase AC voltage. The DC link is supplied by a string of battery modules connected in series. To meet the power and energy requirements of a given application, several battery modules are often connected in series to form a traction battery.

[0004] Connecting multiple battery modules in series presents the problem that if a single battery module fails, the entire string fails. Such a failure of the power supply string can lead to a failure of the entire system. Furthermore, temporary or permanent reductions in the performance of a single battery module can lead to performance reductions in the entire power supply string.

[0005] Document US 5,642,275 A describes a battery system with integrated inverter functionality. Systems of this type are known as multilevel cascaded inverters or battery direct inverters (BDIs). Such systems comprise DC power sources in multiple energy storage module strings, which can be directly connected to an electric machine or an electrical grid. Single-phase or multi-phase supply voltages can be generated. The energy storage module strings consist of multiple energy storage modules connected in series, with each energy storage module having at least one battery cell and an associated controllable coupling unit. This coupling unit allows, depending on control signals, the respective associated battery cell to be bypassed or connected to the respective energy storage module string.The coupling unit can be designed to additionally allow the associated at least one battery cell to be connected with reverse polarity to the respective energy storage module string, or even to interrupt the respective energy storage module string. By appropriately controlling the coupling units, e.g., using pulse-width modulation, suitable phase signals for controlling the phase output voltage can also be provided, thus eliminating the need for a separate pulse inverter. The pulse inverter required for controlling the phase output voltage is therefore, in effect, integrated into the BDI.

[0006] Compared to conventional systems, BDIs typically exhibit higher efficiency, greater reliability, and significantly lower harmonic content in their output voltage. Reliability is ensured, among other things, by the ability to bridge defective, failed, or underperforming battery cells in the power supply strings through appropriate control of their associated coupling units. The phase output voltage of an energy storage module string can be varied and, in particular, adjusted in steps by appropriately controlling the coupling units. The output voltage steps are determined by the voltage of a single energy storage module, with the maximum possible phase output voltage being the sum of the voltages of all energy storage modules in an energy storage module string.

[0007] For example, the publications DE 10 2010 027 857 A1 and DE 10 2010 027 861 A1 disclose battery direct inverters with multiple battery module strings which can be directly connected to an electric machine.

[0008] A constant DC voltage is not available at the output of BDIs because the energy storage cells are distributed across different energy storage modules, and their coupling devices must be specifically controlled to generate a voltage level. Due to this distribution, a BDI is essentially not available as a DC voltage source, for example, for powering the electrical system of an electric vehicle. Consequently, charging the energy storage cells via a conventional DC voltage source is not readily possible.

[0009] The publication DE 10 2009 044 281 A1 discloses a drive inverter circuit comprising a first energy storage device configured to output a DC voltage, a first bidirectional DC-AC inverter connected to the first energy storage device, and a first electromechanical device containing several windings connected to the first bidirectional DC-AC inverter.

[0010] German patent application DE 10 2004 031 216 A1 discloses a device and a method for charge balancing of energy storage devices connected in series. Energy is extracted from the entire capacitor module, consisting of the individual energy storage devices connected in series, and fed to an AC voltage bus. The voltage on the AC voltage bus rises until it corresponds to the lowest double-layer capacitor voltage plus one, or in the second embodiment plus two, diode voltages. This achieves a very efficient recharging of the most discharged capacitor.

[0011] The publication DE 10 2009 054 820 A1 discloses an energy supply system with an electrical energy storage system comprising several storage modules, in particular a battery system, a determining device for determining state variables of the storage modules and an energy transfer unit for transferring energy between the storage modules and a downstream electrical device.

[0012] Therefore, there is a need for a charging circuit for an energy storage device and a method for operating it, with which energy storage cells of the energy storage device can be charged using a direct current. Disclosure of the invention

[0013] According to one aspect, the present invention provides a charging circuit for an energy storage device, which has a plurality of power supply branches, each with a plurality of energy storage modules for generating an alternating voltage at a plurality of output terminals of the energy storage device, comprising a first half-bridge circuit with a plurality of first supply terminals, each of which is coupled to one of the output terminals of the energy storage device, a second half-bridge circuit with a plurality of second supply terminals, each of which is coupled to one of the output terminals of the energy storage device, a first supply node coupled to the first half-bridge circuit, a second supply node coupled to a reference potential rail of the energy storage device, and a supply circuit coupled between the first and second supply nodes.and which is designed to provide a charging DC voltage at least temporarily, a converter choke coupled between one of the supply nodes and the supply circuit, and a semiconductor switch coupled between one of the supply nodes and the supply circuit.

[0014] According to a further aspect, the present invention provides an electric drive system comprising an energy storage device which has a plurality of energy supply branches, each with a plurality of energy storage modules for generating an alternating voltage at a plurality of output terminals of the energy storage device, a charging circuit according to the invention, one of whose feed nodes is coupled to the output terminals of the energy storage device via the diodes of a first or via the diodes of a second half-bridge circuit, and the other of whose feed nodes is coupled to a reference potential rail of the energy storage device, and a DC voltage tap arrangement.The DC voltage tap arrangement includes a boost converter connected between the feed nodes of the charging circuit that are connected to the common point of one of the two half-bridge circuits and the common point of the other half-bridge circuit. This boost converter is designed to provide a DC voltage at the tap terminals of the DC voltage tap arrangement, depending on the potential difference between the first and second half-bridge circuits. The diodes of the second half-bridge circuit couple its common point to the output terminals of the energy storage device. Additionally, the common point of the second half-bridge circuit can be coupled to the reference potential rail of the energy storage device via an additional balancing diode.

[0015] According to a further aspect, the present invention provides a method for charging an energy storage device, which has a plurality of energy supply branches, each with a plurality of energy storage modules for generating an alternating voltage at a plurality of output terminals of the energy storage device, comprising the steps of at least temporarily generating a direct current depending on a charging direct voltage, feeding the direct current into the energy storage modules via a first half-bridge circuit, which has a plurality of first supply terminals, each of which is coupled to one of the output terminals of the energy storage device, into the output terminals of the energy storage device, and returning the direct current via a reference potential rail of the energy storage device. Advantages of the invention

[0016] An idea of ​​the present invention is to couple a circuit with the outputs of an energy storage device, in particular a battery direct converter, by which a direct current can be fed into the outputs of the energy storage device for charging energy storage cells. For this purpose, it is provided that a diode half-bridge is coupled to each of the output terminals of the energy storage device as a supply device, by means of which a charging current from the charging circuit can be led into the energy storage device via all output terminals and out again via its reference potential rail.It is particularly advantageous that one of two diode half-bridges of a DC tap arrangement can be used as the power supply device for the charging circuit, which is already available to provide another DC voltage layer, for example to supply an intermediate circuit capacitor of the vehicle network from the energy storage device.

[0017] A significant advantage of this charging circuit is its compatibility with a DC power tap arrangement, meaning that the charging circuit and the DC power tap arrangement do not interfere with each other during operation. Another advantage is that the number of components required for the simultaneous implementation of a charging circuit and a DC power tap arrangement can be kept low, as several components have dual functionality. This reduces the number of components required, thereby decreasing the installation space and weight of the system, particularly in an electric drive system, such as in an electric vehicle.

[0018] Advantageously, it is possible to select between active operation of the charging circuit on the one hand and the DC tap arrangement on the other, depending on the operating state of the energy storage device. For example, in a driving mode of an electric vehicle with an energy storage device that has both a charging circuit and a DC tap arrangement, the DC tap arrangement can be activated, while in a rest or standstill mode of the vehicle, the charging circuit can be activated.

[0019] By using a diode half-bridge as a power supply device, it can advantageously be ensured that charging energy can be supplied to the energy storage device, since the energy storage device has a bipolar voltage control range for each power supply branch.

[0020] According to one embodiment of the charging circuit according to the invention, the charging circuit can further include a balancing diode which is coupled between one of the feed nodes and the reference potential rail of the energy storage device.

[0021] According to one embodiment of the charging circuit according to the invention, the first and / or second half-bridge circuits can have a plurality of first and second diodes, respectively, each coupled between one of the input terminals of the boost converter of the DC tap arrangement and each of the plurality of first and second supply terminals. In an advantageous embodiment, the half-bridge circuits can have a plurality of first and second commutation chokes, each coupled between the plurality of first and second diodes and the respective input terminal of the boost converter. This allows fluctuations, particularly high-frequency fluctuations at certain times during the activation of the energy storage device, in the potentials at the output terminals to be compensated for or buffered.

[0022] According to a further embodiment of the charging circuit according to the invention, the supply circuit can have a supply capacitor which is coupled between the input terminals of the charging circuit and which is designed to provide the charging DC voltage for charging the energy storage modules via the converter choke.

[0023] According to a further embodiment of the charging circuit according to the invention, the supply circuit can include a transformer whose primary winding is coupled between the input terminals of the charging circuit, and a full-bridge rectifier which is coupled to the secondary winding of the transformer and which is designed to provide a pulsating DC charging voltage for charging the energy storage modules via the converter choke.

[0024] According to one embodiment of the drive system according to the invention, the drive system can further comprise an n-phase electric machine with n phase connections, which is coupled to the output connections of the energy storage device, wherein n ≥ 1.

[0025] According to a further embodiment of the drive system according to the invention, the drive system can further comprise a first reverse polarity protection diode which is coupled between the input terminals of the charging circuit.

[0026] According to one embodiment of the method according to the invention, the method can further include the step of detecting an operating state of the energy storage device and selectively opening or closing the semiconductor switch of the charging circuit depending on the detected operating state.

[0027] According to one embodiment of the method according to the invention, the method can be used to charge an energy storage device of an electrically powered vehicle with an electric drive system according to the invention.

[0028] Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings. Brief description of the drawings

[0029] They show: Fig. 1 a schematic representation of a system with an energy storage device; Fig. 2 a schematic representation of an energy storage module of an energy storage device; Fig. 3 a schematic representation of an energy storage module of an energy storage device; Fig. 4 a schematic representation of a system with an energy storage device and a DC voltage tap arrangement according to an embodiment of the invention; Fig. 5 a schematic representation of a system with an energy storage device and a DC voltage tap arrangement according to a further embodiment of the present invention; Fig. 6 a schematic representation of a charging circuit for a power supply branch of an energy storage device according to a further embodiment of the invention; Fig. 7 a schematic representation of a charging circuit for a power supply branch of an energy storage device according to a further embodiment of the invention; Fig. 8 a schematic representation of a system with an energy storage device, a charging circuit and a DC voltage tap arrangement according to a further embodiment of the invention; Fig. 9 a schematic representation of a system comprising an energy storage device, a charging circuit and a DC voltage tap arrangement according to a further embodiment of the present invention; Fig. 10 a schematic representation of a system comprising an energy storage device, a charging circuit and a DC voltage tap arrangement according to a further embodiment of the present invention; and Fig. 11 a schematic representation of a method for charging an energy storage device according to a further embodiment of the present invention.

[0030] Fig. Figure 1 shows a schematic representation of a system 100 with an energy storage device 1 for converting the DC voltage provided in energy storage modules 3 into an n-phase AC voltage. The energy storage device 1 comprises a plurality of power supply branches Z, of which in Fig. Figure 1 shows three examples suitable for generating a three-phase alternating voltage, for example for a three-phase machine 2. However, it is clear that any other number of power supply branches Z is also possible. The power supply branches Z can have a multitude of energy storage modules 3 connected in series within the power supply branches Z. Examples are shown in Figure 1. Fig. Figure 1 shows three energy storage modules 3 per power supply branch Z, although any other number of energy storage modules 3 is also possible. The energy storage device 1 has an output connection 1a, 1b and 1c on each of the power supply branches Z, which are each connected to phase lines 2a, 2b and 2c respectively.

[0031] The system 100 can further include a control device 6 which is connected to the energy storage device 1 and by means of which the energy storage device 1 can be controlled to provide the desired output voltages at the respective output terminals 1a, 1b, 1c.

[0032] The energy storage modules 3 each have two output terminals 3a and 3b, via which an output voltage of the energy storage modules 3 can be provided. Since the energy storage modules 3 are connected in series at the primary end, the output voltages of the energy storage modules 3 add up to a total output voltage, which can be provided at the respective output terminals 1a, 1b and 1c of the energy storage device 1.

[0033] Exemplary configurations of the energy storage modules 3 are shown in the Fig. 2 and Fig. Figure 3 shows in greater detail. The energy storage modules 3 each comprise a coupling device 7 with several coupling elements 7a, 7c, and optionally 7b and 7d. The energy storage modules 3 also each comprise an energy storage cell module 5 with one or more energy storage cells 5a to 5k connected in series.

[0034] The energy storage cell module 5 can, for example, comprise batteries 5a to 5k connected in series, such as lithium-ion batteries. The number of energy storage cells 5a to 5k in the module is... Fig. 2 and Fig. The 3 energy storage modules shown are two examples, but any other number of energy storage cells 5a to 5k is also possible.

[0035] The energy storage cell modules 5 are connected via connecting cables to input terminals of the associated coupling device 7. The coupling device 7 is in Fig. 2. This is exemplified as a full bridge circuit with two coupling elements 7a, 7c and two coupling elements 7b, 7d. Each coupling element 7a, 7b, 7c, 7d can have an active switching element, for example, a semiconductor switch, and a freewheeling diode connected in parallel. The coupling elements 7a, 7b, 7c, 7d can be configured as MOSFET switches, which already have an intrinsic diode, or as IGBT switches. Alternatively, it is possible to configure only two coupling elements 7a, 7d with one active switching element each, so that – as in Fig. 3 is shown as an example - an asymmetrical half-bridge circuit is implemented.

[0036] The coupling elements 7a, 7b, 7c, 7d can be controlled in this way, for example using the [function / method] shown in Fig. The control device 6 shown in Figure 1 indicates that the respective energy storage cell module 5 is selectively connected between the output terminals 3a and 3b, or that the energy storage cell module 5 is bypassed. With reference to Fig. 2. For example, the energy storage cell module 5 can be connected in the forward direction between the output terminals 3a and 3b by setting the active switching element of coupling element 7d and the active switching element of coupling element 7a to a closed state, while setting the two remaining active switching elements of coupling elements 7b and 7c to an open state. A bridging state can be set, for example, by setting the two active switching elements of coupling elements 7a and 7b to a closed state, while keeping the two active switching elements of coupling elements 7c and 7d in an open state. A second bridging state can be set by keeping the two active switching elements of coupling elements 7a and 7b in an open state, while setting the two active switching elements of coupling elements 7c and 7d to a closed state.Finally, the energy storage cell module 5 can, for example, be connected in reverse between the output terminals 3a and 3b by setting the active switching element of coupling element 7b and the active switching element of coupling element 7c to a closed state, while setting the two remaining active switching elements of coupling elements 7a and 7d to an open state. Analogous considerations can be made for the asymmetric half-bridge circuit in . Fig. 3. By appropriately controlling the coupling devices 7, individual energy storage cell modules 5 of the energy storage modules 3 can therefore be selectively integrated into the series connection of an energy supply branch with any polarity.

[0037] System 100 serves as an example in Fig. 1 for supplying a three-phase electric machine 2, for example in an electric drive system for an electric vehicle. However, it can also be provided that the energy storage device 1 is used to generate electrical current for a power supply network 2. The power supply branches Z can be connected at their end connected to a star point to a reference potential 4 (reference potential bar). The reference potential 4 can, for example, be a ground potential. Even without any further connection to a reference potential located outside the power supply device 1, the potential of the ends of the power supply branches Z connected to a star point can be defined as the reference potential 4.

[0038] To generate a phase voltage between the output terminals 1a, 1b, and 1c on the one hand and the reference potential rail 4 on the other, typically only a portion of the energy storage cell modules 5 of the energy storage modules 3 are required. Their coupling devices 7 can be controlled such that the total output voltage of a power supply branch Z can be adjusted in steps within a rectangular voltage / current range between the negative voltage of a single energy storage cell module 5 multiplied by the number of energy storage modules 3 and the positive voltage of a single energy storage cell module 5 multiplied by the number of energy storage modules 3 on the one hand, and the negative and positive nominal current through a single energy storage module 3 on the other.

[0039] Such an energy storage device 1 as in Fig. The device shown in Figure 1 exhibits different potentials at its output terminals 1a, 1b, and 1c at various times during operation and therefore cannot be used directly as a DC voltage source. Particularly in electric drive systems of electrically powered vehicles, it is often desirable to supply the vehicle's electrical system, for example, a high-voltage or low-voltage system, from the energy storage device 1. Therefore, a DC voltage tap arrangement is provided, which is designed to be connected to an energy storage device 1 and, when supplied by it, to provide a DC voltage, for example, for the electrical system of an electrically powered vehicle.

[0040] Fig. Figure 4 shows a schematic representation of a system 200 with an energy storage device 1 and a DC voltage tap arrangement 8. The DC voltage tap arrangement 8 is coupled to the energy storage device 1 via first busbars 8a, 8b and 8c on the one hand and via second busbars 8g, 8h and 8i on the other. A DC voltage U can be applied to tap terminals 8e and 8f. ZK The DC voltage tap arrangement 8 can be tapped. A DC-DC converter (not shown) for the electrical system of an electric vehicle can be connected to the tap terminals 8e and 8f, or – with suitable adjustment between the voltage U – ZK between the tap terminals 8e and 8f and the on-board power supply - this on-board power supply can be connected directly.

[0041] The DC voltage tap arrangement 8 comprises a first half-bridge circuit 9, which is coupled via the first common terminals 8a, 8b, 8c to each of the output terminals 1a, 1b, 1c of the energy storage device 1. The first common terminals 8a, 8b, 8c can, for example, be coupled to the phase lines 2a, 2b, and 2c of the system 200, respectively. The first half-bridge circuit 9 can comprise a plurality of first diodes 9a, each of which is coupled to one of the common terminals 8a, 8b, 8c, such that the anodes of the diodes 9a are coupled to the phase lines 2a, 2b, and 2c, respectively. The cathodes of the diodes 9a can be connected together at a common common point of the first half-bridge circuit 9. As a result, the highest current potential of the phase lines 2a, 2b and 2c is present at the collection point of the half-bridge circuit 9.Optionally, a number of first commutation chokes 9b can be provided, each coupled between the first diodes 9a and the common point of the first half-bridge circuit 9. The first commutation chokes 9b can buffer potential fluctuations that may temporarily occur in the respective phase lines 2a, 2b, and 2c due to control-induced stepped potential changes, thus reducing the load on the first diodes 9a from frequent commutation processes.

[0042] Similarly, the DC voltage tap arrangement 8 has a second half-bridge circuit 15, which is coupled via the second busbars 8g, 8h, 8i to each of the output terminals 1a, 1b, 1c of the energy storage device 1. The second busbars 8g, 8h, 8i can, for example, be coupled to the phase lines 2a, 2b, and 2c of the system 200, respectively. The second half-bridge circuit 15 can have a plurality of second diodes 15a, each of which is coupled to one of the second busbars 8g, 8h, 8i, such that the cathodes of the diodes 15a are coupled to the phase lines 2a, 2b, and 2c, respectively. The anodes of the diodes 15a can be connected at a common busbar of the second half-bridge circuit 15. As a result, the lowest current potential of the phase lines 2a, 2b and 2c is present at the collection point of the second half-bridge circuit 15.Optionally, a number of second commutation chokes 15b can be provided, each coupled between the second diodes 15a and the common point of the second half-bridge circuit 15. The second commutation chokes 15b can buffer potential fluctuations that may temporarily occur in the respective phase lines 2a, 2b, and 2c due to control-induced stepped potential changes, thus reducing the stress on the second diodes 15 from frequent commutation processes.

[0043] The half-bridge circuits 9 and 15 are each coupled via their common points to one of two input terminals of a boost converter 14. A potential difference exists between the common points, which can be increased by the boost converter 14. The boost converter 14 is designed to generate a DC voltage U, depending on the potential difference between the half-bridge circuits 9 and 15.ZK The DC voltage taps 8e and 8f of the DC tap arrangement 8 are to be provided. The boost converter 14 can, for example, have a converter inductor 10 and an output diode 11 connected in series, the center tap of which couples a control switching element 12 to the second half-bridge circuit 15. Alternatively, the converter inductor 10 can also be provided between the second half-bridge circuit 15 and the control switching element 12, or two converter inductors 10 can be provided at both input terminals of the boost converter 14. The same applies to the output diode 11, which can alternatively also be provided between the tap terminal 8f and the control switching element 12.

[0044] The controller switching element 12 can, for example, include a power semiconductor switch, such as a MOSFET switch or an IGBT switch. For instance, an n-channel IGBT, which is normally off, can be used for the controller switching element 12. However, it should be clear that any other power semiconductor switch can also be used for the controller switching element 12.

[0045] It is possible to omit the actuator switching element 12, or to leave the actuator switching element 12 in a permanently blocked state, particularly if the potential difference between the common points of the half-bridge circuits 9 and 15 always lies within an input voltage range defined by another component connected to the tap terminals 8e, 8f. In this case, the output diode 11 can also be omitted in some embodiments.

[0046] The DC voltage tap arrangement 8 can further include an intermediate circuit capacitor 13, which is connected between the tap terminals 8e, 8f of the DC voltage tap arrangement 8, and which is designed to buffer the current pulses output by the boost converter 14 and thus provide a smoothed DC voltage U at the output of the boost converter. ZK to generate. The intermediate circuit capacitor 13 can then be used, for example, to supply a DC voltage converter of an electrically powered vehicle's electrical system, or in certain cases this electrical system can also be connected directly to the intermediate circuit capacitor 13.

[0047] The number of diodes in half-bridge circuits 9 and 15 is in Fig. Figure 4 shows three diodes each as an example and is adapted to the number of output terminals 1a, 1b, 1c of the energy storage device 1. It should be clear that any other number of diodes in the half-bridge circuits 9 and 15 is equally possible, depending on which phase voltages are generated by the energy storage device 1.

[0048] Fig. Figure 5 shows a schematic representation of a system 300 with an energy storage device 1 and a DC voltage tap arrangement 8. The system 300 differs from the one in Fig. The difference in system 200 shown in Figure 4 is essentially that the DC voltage tap arrangement 8 additionally has a reference terminal 8d, which is coupled to a reference potential rail 4 of the energy storage device 1. Balancing diodes 16a and 17a are connected between the common points of the half-bridge circuits 9 and 15 and the reference terminal 8d. The cathode of the first balancing diode 16a is coupled to the common point of the first half-bridge circuit 9, and the anode of the second balancing diode 17a is coupled to the common point of the second half-bridge circuit 15.

[0049] The potentials present at the common points of the half-bridge circuits 9 and 15 can be limited, respectively, by the reference potential at the reference terminal 8d, via the balancing diodes 16a and 17a. This ensures a sufficiently high potential difference between the input terminals of the boost converter 14, even at low stator voltages in the phase lines 2a, 2b, 2c, for example at low speeds or when the electric machine 2 is stationary, by raising or lowering the neutral potential of the electric machine 2 by a uniform value.The neutral potential of the electric machine 2 can be shifted relative to the reference potential by uniformly increasing or decreasing the output voltages at the multiple output terminals 1a, 1b, 1c of the energy storage device 1, provided that the potential difference between the currently highest and lowest potentials at the output terminals 1a, 1b, 1c of the energy storage device 1 falls below a predetermined threshold. This means that the output potentials of all power supply branches Z are raised or lowered by a uniform value without affecting the stator voltages and / or stator currents of the electric machine 2. To compensate for fluctuations caused by commutation processes, additional commutation chokes 16b and 17b, respectively, can be connected in series with the respective compensating diodes 16a and 17a.The balancing diode 16a allows the neutral potential of the electric machine 2 to be shifted towards negative values ​​by preventing the potential at the common point of the first half-bridge circuit 9 from falling below the reference potential. Similarly, the balancing diode 17a allows the neutral potential of the electric machine 2 to be shifted towards positive values ​​by preventing the potential at the common point of the second half-bridge circuit 15 from rising above the reference potential. It is also possible to implement the DC tap arrangement 8 with only one of the two balancing diodes 16a or 17a. In this case, a shift of the neutral potential of the electric machine 2 relative to the reference potential is only possible in one direction.

[0050] To connect the energy storage modules 3 of the energy storage device 1 of the Fig. 4 or Fig. To charge the DC voltage tap assembly 8, it is necessary to implement a charging circuit that is compatible with it and, in particular, does not impair its functionality. Preferably, the charging circuit should also utilize components of the DC voltage tap assembly 8 to minimize the number of components and the required installation space.

[0051] The Fig. 6 and Fig. Figure 7 shows schematic representations of charging circuits 30 and 40, which can be used, for example, to charge a power supply branch Z of an energy storage device 1.

[0052] Fig. Figure 6 shows a schematic representation of a charging circuit 30, which has input terminals 36a, 36b, to which a charging DC voltage U is applied. N can be fed in. The charging DC voltage U NThis can be generated by (not shown) circuit arrangements, for example, DC-DC converters, controlled or regulated rectifiers with power factor correction (PFC), or the like. The charging DC voltage U N This can be provided, for example, by a power supply network connected on the input side. The charging circuit 30 can also include an intermediate circuit capacitor 35, across which a DC voltage can be tapped and which dampens the effect of pulsating currents on both the input and output sides of the charging circuit 30, or of switching operations within the charging circuit 30 itself, on the DC charging voltage U. N significantly reduced. An output voltage U can be applied to feed nodes 37a and 37b of the charging circuit 30. Lthe charging circuit 30 is tapped, which is used to charge an energy storage arrangement connected to the feed nodes 37a and 37b, for example a series of energy storage modules 5 or a branch of an energy storage device 1 as in the Fig. Numbers 1 to 5 are shown and can be used.

[0053] The charging circuit 30 comprises a semiconductor switch 33, a freewheeling diode 32, and a converter inductor 31, which implement a buck converter. It is understood that the arrangement of the semiconductor switch 33 and / or the converter inductor 31 in the respective current paths of the charging circuit 30 can be varied, so that, for example, the converter inductor 31 can also be arranged between the freewheeling diode 32 and the feed node 37b. Likewise, the semiconductor switch 33 can also be connected between the freewheeling diode 32 and the input terminal 36b. The control variable for the charging current I flowing through the converter inductor 31 is...L For example, the output voltage of an energy storage module to be charged, or alternatively the duty cycle of the buck converter implemented via the semiconductor switch 33, can serve as the control variable for the charging current I. It may also be possible to use the input voltage drop across the DC link capacitor 35 as the control variable for the charging current I. L to use.

[0054] The buck converter can, for example, also be operated in a state with a constant duty cycle of 1, so that the semiconductor switch 33 can remain permanently closed. It may also be possible to omit the semiconductor switch 33 and the freewheeling path with the freewheeling diode 32.

[0055] Fig. Figure 7 shows a schematic representation of a charging circuit 40, which has input terminals 46a, 46b, to which a charging AC voltage u is applied. ch can be fed in. The charging AC voltage u chThis can be generated by (not shown) circuit arrangements, for example, inverter full bridges or the like. The charging AC voltage u ch preferably exhibits a rectangular, discontinuous or continuous waveform and a high fundamental frequency. The charging AC voltage u ch This can be provided, for example, by a power supply network connected at the input side with a downstream AC or inverter circuit. The charging circuit 40 can further include a transformer 45 whose primary winding is coupled to the input terminals 46a, 46b. The secondary winding of the transformer 45 can be coupled to a full-bridge rectifier circuit 44 consisting of four diodes, at the output of which a pulsating DC voltage U is generated. Ncan be tapped. The interval length of the pulsating DC voltage can be varied by varying the time intervals in which the AC charging voltage applied to the primary winding of transformer 45 is applied. ch and thus the corresponding secondary voltage at the secondary winding of transformer 45 also has the value 0. An output voltage U can be applied to feed nodes 47a and 47b of the charging circuit 40. L the charging circuit 40 is tapped, which is used to charge an energy storage arrangement connected to the feed nodes 47a and 47b, for example a series of energy storage modules 5 or a branch of an energy storage device 1 as in the Fig. Numbers 1 to 5 are shown and can be used.

[0056] The charging circuit 40 includes a freewheeling diode 42 and a converter choke 41, the converter choke 41 being used to smooth the pulsating DC voltage u provided by the full-bridge rectifier circuit 44. N It serves this purpose. It is self-evident that the arrangement of the converter choke 41 in the respective current paths of the charging circuit 40 can be varied, so that, for example, the converter choke 41 can also be connected between the freewheeling diode 42 and the feed node 47b. The control variable for the charging current I flowing through the converter choke 41 is... L For example, the output voltage of an energy storage arrangement to be charged, such as a series of energy storage modules 5 or a branch of the energy storage arrangement 1 as in the Fig. 1 to 5 are shown, or alternatively the DC component U. N the pulsating direct voltage U N be used.

[0057] In another embodiment, the freewheeling diode 42 can be omitted entirely. In this case, the diodes of the full-bridge rectifier circuit 44 additionally take over the function of the freewheeling diode 42. This saves one component, but in return reduces the efficiency of the charging circuit 40.

[0058] In the Fig. 8, Fig. 9 and Fig. Figure 10 shows exemplary embodiments of the charging circuits 30 and 40 of the Fig. 6 or Fig. 7 with the systems 200 or 300 of the Fig. 4 and Fig. 5 can be combined. One advantage of this is that it is found in the Fig. 8, Fig. 9 and Fig. The systems 400, 500 and 600 shown in Figure 10 are characterized in that the respective charging circuit 30 and 40 and the DC voltage tap arrangement 8 in particular use the half-bridge circuits 9 and 15 in common.

[0059] In Fig. 8 is the one in Fig. 6 shown charging circuit 30 with the in Fig. 4 or Fig. The system 200 or 300 shown in Figure 5, which comprises an energy storage device 1 and a DC tap arrangement 8, is combined to form a system 400. The half-bridge circuits 9 of the DC tap arrangement 8 are used as a supply circuit for the charging circuit 30 by connecting the supply node 37b of the charging circuit 30 to the cathode common point of the first half-bridge circuit 9. This connection is then coupled via the diodes 9a of the first half-bridge circuit 9 to each of the common terminals 8a, 8b, 8c. The common terminals 8a, 8b, 8c of the DC tap arrangement 8 thus serve as the first supply terminals 8a, 8b, 8c of the charging circuit 30. The second supply node 37a of the charging circuit 30 is coupled to the reference potential rail 4 of the energy storage device 1, so that a charging current I Lvia the second feed node 37a, the reference potential rail 4, the energy storage modules 3 of the power supply branches Z, the first half-bridge circuit 9, the first feed node 37b and the converter choke 31 back into the charging circuit 30.

[0060] An optional reverse polarity protection diode 39a can be coupled between the input terminals of the charging circuit 30, which protects the intermediate circuit capacitor 35 of the charging circuit 30 from negative charging by possible reverse currents when the charging circuit 30 is deactivated and the DC voltage tap arrangement 8 is activated.

[0061] Additionally, a balancing diode 17a is provided, which is coupled via the reference terminal 8d of the DC voltage tap arrangement 8 between the anode common point of the second half-bridge circuit 15 and the second supply node 37a. The balancing diode 17a ensures that the anode common point of the second half-bridge circuit 15 always has a potential that cannot exceed 0. This allows a sufficiently high input voltage to be supplied to the boost converter 14 of the DC voltage tap arrangement 8 even during operation with a small potential difference between the common points of the half-bridge circuits 9 and 15, e.g., at low speed of the electric motor 2 or when stationary, by shifting the star point potential of the electric motor 2 towards positive values.Furthermore, the diode 17a automatically protects the control switching element 12 of the DC voltage tap arrangement 8 from the occurrence of negative collector-emitter voltages, even if the control switching element 12 is permanently conducting during the charging operation of the charging circuit 30. If this possibility of increasing the input voltage of the boost converter 14 described above is not to be used, the compensating diode 17a can also be omitted without replacement.

[0062] The output potentials of the output terminals 1a, 1b, 1c of the energy storage device 1 can be set to a uniform, in particular negative, value in a charging mode, i.e., when the charging circuit is activated. If the magnitude of this value is less than the value of the DC charging voltage U L , so the charging current I increases L , the magnitude of this value is greater than the value of the charging DC voltage U L , so the charging current I decreases LIn this way, the charging current I can be L be regulated. To ensure an even distribution of the charging current I L To ensure the individual power supply branches Z of the energy storage device 1 are supplied with power, a controller can specify deviations between the output potentials of the power supply branches Z. For this purpose, the commutation chokes 9b of the half-bridge circuits 9 can be used as balancing chokes. The commutation chokes 9b can, for example, also be arranged on one, two, or three cores such that only deviations between the charging currents through the individual branches can induce magnetic fields, while the total charging current I L However, not.

[0063] In Fig. 9 is the one in Fig. 7 shown charging circuit 40 with the in Fig. 4 or Fig. The system 200 or 300 shown in Figure 5, which comprises an energy storage device 1 and a DC tap arrangement 8, is combined to form a system 500. The half-bridge circuit 9 of the DC tap arrangement 8 is used as a supply circuit for the charging circuit 40 by connecting the supply node 47b of the charging circuit 40 to the cathode common point of the first half-bridge circuit 9. This connection is thus coupled via the first diodes 9a of the first half-bridge circuit 9 to each of the common terminals 8a, 8b, 8c. The common terminals 8a, 8b, 8c of the DC tap arrangement 8 therefore serve as the first supply terminals 8a, 8b, 8c of the charging circuit 40. The second supply node 47a of the charging circuit 40 is coupled to the reference potential rail 4 of the energy storage device 1 via a semiconductor switch 33, so that a charging current I Lvia the second feed node 47a, the reference potential rail 4, the energy storage modules 3 of the power supply branches Z, the first half-bridge circuit 9, the first feed node 47b and the converter choke 41 back into the charging circuit 40.

[0064] The semiconductor switch 33 remains permanently closed during charging operation, whereby a freewheeling state is achieved by setting the instantaneous value of the pulsating DC charging voltage U. Ncan be set to the value 0. This can be achieved, for example, by appropriately controlling the primary winding of the transformer 45. By opening the semiconductor switch 33 when the charging circuit 40 is deactivated, it can be ensured that, particularly when the DC voltage tap arrangement 8 is activated, no short circuit occurs at the input of the boost converter 14 via the diode 42 or the full-bridge rectifier circuit 44, which would prevent the proper operation of the DC voltage tap arrangement 8.

[0065] As already in the Fig. In the system 400 shown in Figure 8, a balancing diode 17a is also provided in the system 500 shown here, for which the same statements apply as already made in the description of system 400 based on the Fig. 8 were made.

[0066] In both systems 400 and 500, the second balancing diodes 16a of systems 200 and 300 respectively are omitted, as otherwise a current path would be established which would affect the charging current I L would bypass the energy storage unit 1, and therefore charging would not be possible.

[0067] Fig. Figure 10 shows a schematic representation of a System 600, which, like the one in Fig. 8. System 400 shown through a combination of the charging circuit 30. Fig. 6 with a system 200 or 300 from Fig. 4. or Fig. 5. System 600 differs from system 400 essentially in that the charging circuit 30 is connected to the DC tap arrangement 8 with reversed polarity, and that during charging of the energy storage device 1, the power supply branches are set to a uniform, in particular positive, output potential. It should also be clear that a system with reversed polarity can also be formed by combining the charging circuit 40 from Fig. 7 with a System 300 from Fig. 5 can be implemented. In these cases, only the one already in may be used as a balancing diode. Fig. The existing diode 16a is used between the reference potential rail 4 and the cathode common point of the half-bridge circuit 9. However, a balancing diode 17a must not be provided between the anode common point of the half-bridge circuit 15 and the reference potential rail 4, as this would create a current path which would affect the charging current I. L would bypass the energy storage unit 1, and therefore charging would not be possible.

[0068] All switching elements of the specified circuit arrangements can include power semiconductor switches, for example, normally blocking or normally conducting n- or p-channel IGBT switches or corresponding MOSFET switches. When using reverse-blocking power semiconductor switches, the corresponding parallel diode connections can be omitted.

[0069] Fig. Figure 11 shows a schematic representation of a method 20 for charging an energy storage device, in particular an energy storage device 1, as in connection with the Fig. 1 to 10 are described. Method 20 can, for example, be used to charge an energy storage device 1 of an electrically powered vehicle with an electric drive system 400, 500 or 600. Fig. 8, Fig. 9 or 10 can be used.

[0070] In an optional step S1, the operating state of the energy storage device 1 can first be detected. If, for example, the operating state of the energy storage device 1 is a state in which the energy storage device 1 provides an AC voltage at the output terminals 1a, 1b, 1c, for example for the operation of an electric machine 2 of an electric vehicle, the semiconductor switch 33 can be permanently opened, thus deactivating the charging circuit. This deactivation can be performed independently of the operation of the DC voltage tap arrangement 8. Fig.8 to 10, so that the energy storage device 1 can continue to provide a DC voltage for the vehicle's electrical system during operation. If the operating state of the energy storage device 1 is one in which it does not provide an AC voltage at the output terminals 1a, 1b, 1c, for example, when an electrically powered vehicle is stationary or in standby mode, the semiconductor switch 33 of the charging circuit can be permanently closed, so that the charging circuit is in an active state and the energy storage device 1 can be charged. The actuator switching element 12 of the DC voltage tap arrangement 8 can either be opened or closed during charging, since no freewheeling path of the charging circuit via the actuator switching element 12 is required.

[0071] In step S2 of the procedure 20, a direct current I can be generated at least temporarily. L depending on the DC component U N a pulsating DC charging voltage u N This process takes place in step S3, which can be fed into the energy storage modules 3 via one of the half-bridge circuits 9 or 15, each of which has a plurality of feed connections 8a, 8b, 8c or 8g, 8h, 8i respectively, each of which is coupled to one of the output connections 1a, 1b, 1c of the energy storage device 1. The direct current I L In one step, S4 can be fed back into the charging circuit via a reference potential rail 4 of the energy storage device 1. Since the energy storage device 1 is operated in a bipolar voltage control range, the half-bridge circuit 9 or 15 ensures that a charging current flows through the energy storage modules 3 of the energy storage device 1, at least temporarily.

[0072] The charging current I L The current is routed via the converter choke 31 or 41 of the charging circuit 30 or 40. The semiconductor switch 33 is permanently closed during charging operation, since a freewheeling diode between the charging circuit and one of the half-bridge devices 9 or 15 would prevent the operation of the DC tap arrangement 8 due to the short circuit that would then occur across the respective half-bridge device 9 or 15 and the converter choke 31 or 41.

Claims

[1] Charging circuit (30; 40) for an energy storage device (1), which has a plurality of power supply branches (Z) each with a plurality of energy storage modules (3) for generating an alternating voltage at a plurality of output terminals (1a, 1b, 1c) of the energy storage device (1), comprising: a first half-bridge circuit (9) with a plurality of first feed terminals (8a, 8b, 8c), each of which is coupled to one of the output terminals (1a, 1b, 1c) of the energy storage device (1); a second half-bridge circuit (15) with a plurality of second feed terminals (8g, 8h, 8i), each of which is coupled to one of the output terminals (1a, 1b, 1c) of the energy storage device (1); a first feed node (37a; 37b; 47a) which is coupled to the first half-bridge circuit (9) or the second half-bridge circuit (15); a second feed node (37a; 37b; 47b) which is coupled to a reference potential rail (4) of the energy storage device (1); a supply circuit (35; 44, 45) which is coupled between the first and second supply nodes (37a; 37b; 47a, 47b) and which is designed to supply at least a temporary DC charging voltage (U N ) to provide; a converter choke (31; 41) which is coupled between one of the feed nodes (37a; 37b; 47a, 47b) and the feed circuit (35; 44, 45); and a semiconductor switch (33) which is coupled between one of the feed nodes (37a; 37b; 47a, 47b) and the feed circuit (35; 44, 45), wherein the first and / or second half-bridge circuit (9; 15) each have a plurality of first or second diodes (9a; 15a) which are each coupled between the common point of the half-bridge circuit (9; 15) and one of the plurality of first or second feed terminals (8a, 8b, 8c; 8g, 8h, 8i), wherein the first and / or second half-bridge circuit (9; 15) have a plurality of commutation chokes (9b; 15b) which are each coupled between the plurality of first or second diodes (9a; 15a) and the common point of the half-bridge circuit (9; 15). [2] Charging circuit (30; 40) according to claim 1, comprising: a balancing diode (16a; 17a) which is coupled between the half-bridge circuit (9; 15) which is not connected to one of the feed nodes (37a; 37b; 47a, 47b) and the reference potential rail (4) of the energy storage device (1). [3] Charging circuit (30) according to one of claims 1 or 2, wherein the supply circuit has a supply capacitor (35) which is coupled between input terminals (36a; 36b) of the charging circuit (30) and which is designed to supply the DC charging voltage (U N ) to provide for charging the energy storage modules (3) via the converter choke (31). [4] Charging circuit (40) according to one of claims 1 or 2, wherein the supply circuit comprises a transformer (45) whose primary winding is coupled between input terminals (46a; 46b) of the charging circuit (40), and a full-bridge rectifier (44) which is coupled to the secondary winding of the transformer (45) and which is designed to provide a pulsating DC charging voltage (U N ) to provide for charging the energy storage modules (3) via the converter choke (41). [5] Electric drive system (400; 500; 600), with: an energy storage device (1) which has a plurality of power supply branches (Z) each with a plurality of energy storage modules (3) for generating an alternating voltage at a plurality of output terminals (1a, 1b, 1c) of the energy storage device (1); a charging circuit (30; 40) according to one of claims 1 to 4, the first feed node (37a; 37b; 47a) of which is coupled via the diodes (9a; 15a) of a first or a second half-bridge circuit (9; 15) via first or second feed terminals (8a, 8b, 8c; 8g, 8h, 8i) each to one of the output terminals (1a, 1b, 1c) of the energy storage device (1), and the second feed node (37a; 37b; 47b) is coupled to a reference potential rail (4) of the energy storage device (1); and a DC voltage tap arrangement (8) which comprises: a reference connection (8d) which is coupled to the second feed node (37a; 37b; 47b) of the charging circuit (30; 40); and a boost converter (14) which is coupled between that half-bridge circuit (9; 15) which is not coupled to one of the feed nodes (37a; 37b; 47a; 47b) of the charging circuit (30; 40) and the reference terminal (8d), and which is designed to generate a DC voltage (U) depending on the potential difference between the half-bridge circuits (9; 15). ZK ) to be provided at tap terminals (8e, 8f) of the DC tap arrangement (8). [6] Electric drive system (400; 500; 600) according to claim 5, comprising: a balancing diode (16a; 17a) which is coupled between the half-bridge circuit (9; 15) which is not connected to one of the feed nodes (37a; 37b; 47a, 47b) and the reference potential rail (4) of the energy storage device (1). [7] Electric drive system (400; 500; 600) according to claim 5 or 6, further comprising: an n-phase electrical machine (2) with n phase terminals, which is coupled to the output terminals (1a, 1b, 1c) of the energy storage device (1), where n ≥ 1. [8] Electric drive system (400; 500; 600) according to one of claims 5 to 7, further comprising: a first reverse polarity protection diode (39a) which is coupled between the input terminals of the charging circuit (30; 40). [9] Method (20) for charging an energy storage device (1), comprising a charging circuit according to claim 1 comprising the steps: at least temporary generation (S2) of a direct current (I L ) depending on a charging DC voltage (U N ); Feed-in (S4) of direct current (I L ) into the energy storage modules (3) via a half-bridge circuit (9; 15), which has a multitude of feed connections (8a, 8b, 8c; 8g, 8h, 8i) each of which are coupled to one of the output terminals (1a, 1b, 1c) of the energy storage device (1), into the output terminals (1a, 1b, 1c) of the energy storage device (1); and Return (S5) of the direct current (I L ) via a reference potential rail (4) of the energy storage device (1). [10] Method (20) according to claim 9, further comprising the step: Detection (S1) of an operating state of the energy storage device (1) and Selective opening of the semiconductor switch (33) of the charging circuit (30; 40) depending on the detected operating state. [11] Method (20) according to one of claims 9 and 10, wherein the method (20) is used to charge an energy storage device (1) of an electrically powered vehicle with an electric drive system (400; 500; 600) according to one of claims 5 to 8.

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