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 half-bridge circuit (9) with a plurality of supply 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 first feed node (37a; 37b; 47a) which is coupled to the half-bridge circuit (9); a second feed node (37a; 37b; 47b) which is coupled to a reference potential rail (4) of the energy storage device (1); a buck converter (31, 32, 33; 41, 32, 33) which is coupled between the first feed node (37a; 37b; 47a) and the second feed node (37a; 37b; 47b), and which is designed to supply a direct current (I L ) to provide for charging the energy storage modules (3); and a supply circuit (35; 44, 45) which is coupled to input terminals of the buck converter (31, 32, 33; 41, 32, 33) and which is designed to supply at least a temporary DC charging voltage (U N) for the buck converter (31, 32, 33; 41, 32, 33), wherein the half-bridge circuit (9) has a plurality of diodes (9a) which are each coupled between the first feed nodes (37a; 37b; 47a) and one of the plurality of feed terminals (8a, 8b, 8c), wherein the half-bridge circuit (9) has a plurality of commutation chokes (9b) which are each coupled between the plurality of diodes (9a) and the first feed nodes (37a; 37b; 47a).

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 a significantly higher 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 derived from the voltage of a single energy storage module, with the maximum possible phase output voltage being determined by 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] German patent application 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. The first electromechanical device contains several windings connected to the first bidirectional DC-AC inverter.The drive inverter circuit further includes a charging bus having a first conductor connected to the multiple windings of the first electromechanical device, the charging bus being configured to transfer a charging current to the first electromechanical device or to receive a charging current from it in order to charge the first energy storage device via the first electromechanical device and via 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] German patent application DE 10 2009 054 820 A1 discloses a power supply system comprising an electrical energy storage system, in particular a battery system, with several storage modules, a device for determining the state variables of the storage modules, and an energy transfer unit for transferring energy between the storage modules and a downstream electrical device. The energy transfer unit is provided to have several DC choppers connected in parallel and / or in series at their outputs, with each DC chopper being connectable to a storage module of the energy storage system. The power supply system includes a control device for controlling the DC choppers based on the determined state variable of the respective connected storage module.

[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 of the present invention, a charging circuit for an energy storage device is provided, comprising 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, a half-bridge circuit with a plurality of feed terminals, each coupled to one of the output terminals of the energy storage device, a first feed node coupled to the half-bridge circuit, a second feed node coupled to a reference potential rail of the energy storage device, a buck converter coupled between the first feed node and the second feed node, designed to provide a direct current for charging the energy storage modules, and a feed circuit coupled to input terminals of the buck converter.and which is designed to provide a charging DC voltage for the buck converter, at least temporarily.

[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, the supply terminals of which are each coupled to one of the output terminals of the energy storage device, and the second supply node of which is coupled to a reference potential rail of the energy storage device, and a DC voltage tap arrangement.The DC voltage tap arrangement has a reference terminal coupled to the second feed node of the charging circuit and a boost converter coupled between the first feed node of the charging circuit and the reference terminal. This boost converter is designed to provide a DC voltage at the tap terminals of the DC voltage tap arrangement, depending on the potential between the half-bridge circuit and the reference terminal. The inductor of the buck converter of the charging circuit also serves as the inductor of the boost converter of the DC voltage tap arrangement.

[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 half-bridge circuit, which has a plurality of 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] The 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 DC voltage can be fed into the outputs of the energy storage device for charging energy storage cells. For this purpose, a diode half-bridge is provided as a power supply to the output terminals of the energy storage device, by means of which a charging current of the charging circuit can be routed through all output terminals. It is particularly advantageous that a diode half-bridge of a DC tap arrangement can be used as the power supply for the charging circuit, which is already present for providing another DC voltage level, for example, for supplying an intermediate circuit capacitor of the vehicle electrical system 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 design 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, and consequently the installation space and weight of the system, particularly in an electric drive system, for example, 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 half-bridge circuit can have a plurality of diodes, each of which is coupled between the first feed nodes and one of the plurality of feed terminals. In an advantageous embodiment, the half-bridge circuit can have a plurality of commutation chokes, each of which is coupled between the plurality of diodes and the first feed nodes. This allows fluctuations, in particular high-frequency fluctuations at certain times during the activation of the energy storage device, of the potentials at the output terminals to be compensated for or buffered.

[0021] According to a further embodiment of the charging circuit according to the invention, the buck converter can comprise a converter choke, a freewheeling diode, and a semiconductor switch. In an advantageous embodiment, the semiconductor switch can be a power semiconductor switch, for example a MOSFET switch or an IGBT switch.

[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 DC charging voltage for charging the energy storage modules via the buck converter.

[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 buck converter.

[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 tap terminals of the DC voltage tap arrangement.

[0026] According to a further embodiment of the drive system according to the invention, the drive system can further comprise a second reverse polarity protection diode, which is coupled between the input terminals of the charging circuit.

[0027] According to one embodiment of the method according to the invention, the method can further include the step of stepping down the charging DC voltage with a buck converter which has a converter choke, a freewheeling diode, and a semiconductor switch.

[0028] 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 the semiconductor switch of the buck converter depending on the detected operating state.

[0029] 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.

[0030] 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

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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 common terminals 8a, 8b, and 8c on the one hand and via a reference terminal 8d on the other. A DC voltage U can be drawn from 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.

[0043] The DC voltage tap arrangement 8 comprises a half-bridge circuit 9, which is coupled via busbars 8a, 8b, 8c to each of the output terminals 1a, 1b, 1c of the energy storage device 1. The busbars 8a, 8b, 8c can, for example, be coupled to the phase lines 2a, 2b, and 2c of the system 200, respectively. The half-bridge circuit 9 can comprise a plurality of diodes 9a, each of which is coupled to one of the busbars 8a, 8b, and 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 at a common busbar of the half-bridge circuit 9. This ensures that the highest current potential of the phase lines 2a, 2b, and 2c is present at the busbar of the half-bridge circuit 9. Additionally, a number of commutation chokes 9b can optionally be provided, each coupled between the diodes 9a and the collecting point.The commutation chokes 9b can buffer potential fluctuations which may occur temporarily in the respective phase lines 2a, 2b and 2c due to control-related step potential changes, so that the diodes 9a are less stressed by frequent commutation processes.

[0044] The DC voltage tap arrangement 8 further comprises a reference terminal 8d, which is coupled to a reference potential rail 4 of the energy storage device 1. A potential difference therefore exists between the common point of the half-bridge circuit 9 and the reference terminal 8d, which can be boosted by a boost converter 14 coupled between the half-bridge circuit 9 and the reference terminal 8d. The boost converter 14 is designed to generate a DC voltage U, depending on the potential between the half-bridge circuit 9 and the reference terminal 8d. ZKThe DC voltage tap arrangement 8 is to be provided at the tap terminals 8e and 8f. 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 reference terminal 8d. Alternatively, the converter inductor 10 can also be provided between the reference terminal 8d 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 output tap 8f and the control switching element 12.

[0045] 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.

[0046] 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 point of the half-bridge circuit 9 and the reference terminal 8d 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.

[0047] 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 14. 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.

[0048] The number of diodes 9a in the half-bridge circuit 9 is in Fig. Figure 4 is given as an example with three diodes 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 circuit 9 is equally possible, depending on which phase voltages are generated by the energy storage device 1.

[0049] 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 diodes 9a are connected with their cathodes to the phase lines 2a, 2b, 2c of the energy storage device 1. In the DC voltage tap arrangement 8 of the Fig. Therefore, at a collection point of the half-bridge circuit 9, the lowest current potential of the phase lines 2a, 2b, 2c is always present. This also applies to the DC voltage tap arrangement 8 of the Fig. 5. A potential difference exists between the collecting point of the half-bridge circuit 9 and the reference terminal 8d, which is converted by the boost converter 14 to a DC voltage U. ZK can be increased.

[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 N This 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. Nsignificantly reduced. An output voltage U can be applied to feed nodes 37a and 37b of the charging circuit 30. L the 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 arrangement to be charged, such as a series of energy storage modules 5 or a branch of an energy storage device 1 as in the Fig. 1 to 5 are shown, or alternatively, the duty cycle of the buck converter implemented via the semiconductor switch 33 can be used. It may also be possible to use the input voltage U applied across the intermediate circuit capacitor 35. N as a 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 circuit arrangements (not shown), for example, inverter full bridges or the like. The charging AC voltage preferably has 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 converter bridge. 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 device 1 as in the Fig. Figures 1 to 5 are shown, or alternatively, the DC component of the pulsating DC 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 difference between the 10 systems shown, 400, 500 and 600, is that the respective charging circuit 30 or 40 and the DC voltage tap arrangement 8, in particular, share the converter choke 10 or 31 or 41 required for the buck converter and the boost converter 14, as well as the half-bridge 9.

[0059] In Fig. 8 is the one in Fig. 6 shown charging circuit 30 with the in Fig. The system 200 shown in Figure 4, which comprises an energy storage device 1 and a DC tap arrangement 8, is combined to form a system 400. The half-bridge circuit 9 of the DC tap arrangement 8 is used as a supply circuit for the charging circuit 30 by connecting the input terminal 36b of the charging circuit 30 to a node 38 between the converter inductor 10 and the diode 11 of the boost converter 14 of the DC tap arrangement 8. In this way, the converter inductor 10 can also function as the converter inductor 31 of the buck converter of the charging circuit 30. The supply node 37b of the charging circuit 30 is coupled to the cathode common point of the half-bridge circuit 9 and, via the diodes 9a of the half-bridge circuit 9, is connected to each of the common terminals 8a, 8b, and 8c. The common terminals 8a, 8b, 8c of the DC voltage tap arrangement 8 thus serve as supply terminals 8a, 8b, 8c of the charging circuit 30.The second feed 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. L The current can flow via the second feed node 37a, the reference potential rail 4, the energy storage modules 3 of the power supply branches Z, the half-bridge circuit 9, the first feed node 37b, the converter choke 31, and node 38 back to the charging circuit 30. The diodes 9a of the half-bridge circuit 9 ensure that electrical energy can actually be supplied to the energy storage modules 3, since the freewheeling diode 32 provides an alternative current return path when the semiconductor switch 33 is closed.

[0060] An optional reverse polarity protection diode 39b can be coupled between the tap terminals 8e, 8f of the DC voltage tap arrangement 8, which can protect the intermediate circuit capacitor 13 from negative charging by possible reverse currents that may occur in an active operation of the charging circuit 30.

[0061] Likewise, 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 when the charging circuit 30 is deactivated and the DC voltage tap arrangement 8 is activated.

[0062] The freewheeling diode 32 additionally serves to protect the control switching element 12 of the DC voltage tap arrangement 8 from the occurrence of negative collector-emitter voltages when the control switching element 12 is permanently switched on during the charging operation of the charging circuit 30. This is necessary if the control switching element 12 of the DC voltage tap arrangement 8 does not have a defined and sufficient reverse blocking capability. If, on the other hand, the control switching element 12 has a defined and sufficient reverse blocking capability, the freewheeling diode 32 can be omitted and replaced by an electrically conductive connection.

[0063] 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 L In this way, the charging current I can be L be regulated. To ensure an even distribution of the charging current I LTo 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 circuit 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.

[0064] In Fig. 9 is the one in Fig. 7 shown charging circuit 40 with the in Fig. The system 200 shown in Figure 4, 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 the power supply for the charging circuit 40 by connecting the anode common point of the full-bridge rectifier circuit 44 of the charging circuit 40 to a node 48 between the converter inductor 10 and the output diode 11 of the boost converter 14 of the DC tap arrangement 8. In this way, the converter inductor 10 can also function as the converter inductor 41 of the buck converter of the charging circuit 40. The power supply node 47b of the charging circuit 40 is coupled to the cathode common point of the half-bridge circuit 9 and, via the diodes 9a of the half-bridge circuit 9, is connected to one of the common terminals 8a, 8b, 8c.The common terminals 8a, 8b, 8c of the DC tap arrangement 8 thus serve as 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, so that a charging current I. L The current can flow via the second feed node 47a, the reference potential rail 4, the energy storage modules 3 of the power supply branches Z, the half-bridge circuit 9, the first feed node 47b, the converter choke 41, and node 48 back to the charging circuit 40. The diodes 9a of the half-bridge circuit 9 ensure that electrical energy can actually be supplied to the energy storage modules 3, since the freewheeling diode 32 provides an alternative current return path when the semiconductor switch 33 is closed.

[0065] As an alternative to pulsed control of the semiconductor switch 33 to reduce the charging DC voltage, the semiconductor switch 33 can also remain permanently closed, since a freewheeling state can also be achieved by setting the instantaneous value of the pulsating charging DC voltage u. N can be set to the value 0. This can be achieved, for example, by specifying appropriate time intervals during which the charging AC voltage is... ch the value 0 at the primary winding of transformer 45 is achieved. This is accomplished by varying the duty cycle of the charging DC voltage u in this way. N Their DC component can be varied. Furthermore, a reverse polarity protection diode 39b can be provided, which can protect the intermediate circuit capacitor 13 from negative charging due to possible reverse currents that may occur during active operation of the charging circuit 40.

[0066] Fig. Figure 10 shows a schematic representation of a system 600, which is formed by combining the charging circuit 30 from Fig. 6 with a System 300 from 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.

[0067] All switching elements of the specified circuit arrangements can include power semiconductor switches, for example, normally blocking or normally conducting n- or p-channel MOSFET switches or corresponding IGBT switches. When using power semiconductor switches with defined and sufficient reverse blocking capability, the corresponding series circuits with diodes can be omitted.

[0068] 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.

[0069] 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 of the buck converter of the charging circuit can be permanently opened, thus deactivating the charging circuit. This deactivation can, in particular, be independent of the operation of the DC voltage tap arrangement 8 of the 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's buck converter can be intermittently closed, depending on the function of the buck converter, so that the charging circuit is in an active state and the energy storage device 1 can be charged. For this purpose, the actuator switching element 12 of the DC tap arrangement 8 can be permanently closed, thus ensuring a freewheeling path for the buck converter via the freewheeling diode 32.Alternatively, the buck converter functionality can be omitted in a charging mode if the semiconductor switch 33 is permanently closed. In this case, the control switching element 12 of the DC tap arrangement 8 can also optionally be disabled, since the freewheeling path of the buck converter via the freewheeling diode 32 is not used.

[0070] In step S2 of the procedure 20, a direct current I can be generated at least temporarily. L depending on a charging DC voltage U N This occurs in step S4, which in a half-bridge circuit 9 has a plurality of feed connections 8a, 8b, 8c, each of which is coupled to one of the output connections 1a, 1b, 1c of the energy storage device 1, and can be fed into the energy storage modules 3. The direct current I LIn step S5, the current 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 ensures that a charging current flows through the energy storage modules 3 of the energy storage device 1, at least temporarily.

[0071] As explained above, for example, depending on the state of charge of the energy storage modules 3 or on the size of the grid-supplied DC charging voltage U N In an optional step S3, the charging DC voltage U is reduced. NThis is achieved with the buck converter, which comprises a converter inductor 31 or 41, a freewheeling diode 32, and a semiconductor switch 33. The semiconductor switch 33 can be controlled in an intermittent or pulsed switching mode to set a desired charging voltage. A particular advantage is that the buck converter shares the converter inductor 31 or 41 and the half-bridge circuit 9 with the DC voltage tap arrangement 8. This reduces the component requirements of the electric drive system without impairing the functionality of the DC voltage tap arrangement 8 or the charging circuit 30 or 40.

[0072] The charging current I L This can be achieved by varying the DC charging voltage U N, can be influenced and thus controlled by varying the output voltages of the branches Z of the energy storage device 1 and optionally by varying the duty cycle of the intermittent semiconductor switch 33.

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 half-bridge circuit (9) with a plurality of supply 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 first feed node (37a; 37b; 47a) which is coupled to the half-bridge circuit (9); a second feed node (37a; 37b; 47b) which is coupled to a reference potential rail (4) of the energy storage device (1); a buck converter (31, 32, 33; 41, 32, 33) which is coupled between the first feed node (37a; 37b; 47a) and the second feed node (37a; 37b; 47b), and which is designed to supply a direct current (I L ) to provide for charging the energy storage modules (3); and a supply circuit (35; 44, 45) which is coupled to input terminals of the buck converter (31, 32, 33; 41, 32, 33) and which is designed to supply at least a temporary DC charging voltage (U N) for the buck converter (31, 32, 33; 41, 32, 33), wherein the half-bridge circuit (9) has a plurality of diodes (9a) which are each coupled between the first feed nodes (37a; 37b; 47a) and one of the plurality of feed terminals (8a, 8b, 8c), wherein the half-bridge circuit (9) has a plurality of commutation chokes (9b) which are each coupled between the plurality of diodes (9a) and the first feed nodes (37a; 37b; 47a). [2] Charging circuit (30; 40) according to claim 1, wherein the buck converter comprises a converter choke (31; 41), a freewheeling diode (32), and a semiconductor switch (33). [3] Charging circuit (30) according to claim 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 buck converter (31, 32, 33). [4] Charging circuit (40) according to claim 2, wherein the supply circuit comprises a transformer (45) whose primary winding is coupled between input terminals (46a; 46b) of the charging circuit (30), 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 buck converter (41, 32, 33). [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 2 to 4, the supply terminals (8a, 8b, 8c) of which are each coupled to one of the output terminals (1a, 1b, 1c) of the energy storage device (1), and the second supply node (37a; 37b; 47b) of which 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 the first feed nodes (37a; 37b; 47a) 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 between the half-bridge circuit (9) and the reference terminal (8d). ZK ) to provide at tap terminals (8e, 8f) of the DC tap arrangement (8), wherein the converter choke (31; 41) of the buck converter of the charging circuit (30; 40) represents the converter choke (10) of the boost converter (14) of the DC voltage tap arrangement (8). [6] Electric drive system (400; 500; 600) according to claim 5, 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. [7] Electric drive system (400; 500; 600) according to one of claims 5 and 6, further comprising: a first reverse polarity protection diode (39a) which is coupled between the tap terminals (8e, 8f) of the DC voltage tap arrangement (8). [8] Electric drive system (400; 500; 600) according to one of claims 5 to 7, further comprising: a second reverse polarity protection diode (39b; 42) 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) which has a plurality of feed terminals (8a, 8b, 8c) each 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: Low-voltage charging (U) (S3) N) with a buck converter (31, 32, 33; 41, 32, 33) which includes a converter choke (31; 41), a freewheeling diode (32), and a semiconductor switch (33). [11] Method (20) according to claim 10, 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 buck converter (31, 32, 33; 41, 32, 33) depending on the detected operating state. [12] Method (20) according to one of claims 9 to 11, 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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