Ac / DC converter with star-connected matrix stage with bidirectional switches, hf transformer with 3 primary windings and primary cores as well as a secondary winding and a secondary-side full bridge

Abstract

Voltage converter arrangement for galvanically isolated power transmission between a multi-phase AC voltage terminal and a DC voltage terminal. The voltage converter arrangement comprises a transformer with three primary windings and one secondary winding. The three primary windings of the transformer are arranged on separate transformer cores, wherein the secondary winding encloses one limb of each of the transformer cores.

Description

[0001] R. 415147

[0002] - 1 -

[0003] Description

[0004] title

[0005] Voltage converter arrangement, charging circuit and method for operating a voltage converter arrangement

[0006] Technical field

[0007] The present invention relates to a voltage converter arrangement and a charging circuit for an electrical energy storage device with such a voltage converter arrangement. The present invention further relates to a method for operating a voltage converter arrangement. In particular, the present invention relates to a galvanically isolated voltage converter arrangement for converting electrical energy between a three-phase AC voltage connection and a DC voltage connection.

[0008] background

[0009] Vehicles that are fully or partially electrically powered generally have an electrical energy storage device, such as a traction battery. Such a device can provide a direct current (DC) voltage, which can be converted into a single- or multi-phase alternating current (AC) voltage suitable for powering an electric motor using a suitable circuit (inverter). When the vehicle is stationary, the electrical energy storage device can be recharged from an external energy source. (For charging the electrical R. 415147)

[0010] - 2 -

[0011] For example, the alternating current (AC) voltage of a low-voltage network can be used for energy storage. For this purpose, the single- or multi-phase AC voltage of the low-voltage network must be converted into a direct current (DC) voltage suitable for charging the electrical energy storage device using a suitable charging circuit.

[0012] For example, the publication DE 10 2017 212 834 A1 describes a circuit topology in which such a charging circuit includes components of the electric drive system.

[0013] For charging the electrical energy storage device in an electric vehicle, it is desirable to provide galvanic isolation between the external energy source, in particular the AC mains, and the vehicle's electrical system with the high-voltage battery.

[0014] Disclosure of the invention

[0015] The present invention provides a voltage converter arrangement, a charging circuit for an electrical energy storage device, and a method for operating a voltage converter arrangement with the features of the independent claims. Further advantageous embodiments are the subject of the dependent claims.

[0016] Accordingly, the following is planned:

[0017] A voltage converter arrangement comprising a DC input, an AC input, and a transformer, as well as several primary-side bridge circuits, a secondary-side bridge circuit, and a resonant assembly. The DC input is R. 415147.

[0018] - 3 - is designed to be coupled to a DC electrical network. This DC network may, for example, contain an electrical energy storage device such as the traction battery of an electric vehicle. The AC connection is designed to be coupled to a multi-phase AC electrical network. This AC network may, for example, be a low-voltage power supply network. The transformer comprises several primary windings and one secondary winding. In particular, a primary winding is provided for each electrical phase of the AC network that can be connected to the AC connection. Furthermore, a primary-side bridge circuit is arranged between each of the connection points of the AC connection and a node. Each primary-side bridge circuit comprises two half-bridges, each with two components arranged in series.Furthermore, each connection point of the two series-arranged components of a half-bridge is connected to a terminal point of a corresponding primary winding of the transformer. The secondary-side bridge circuit is electrically coupled to the secondary winding of the transformer. The resonant assembly is arranged between the secondary winding of the transformer and the secondary-side bridge circuit. The transformer comprises a separate transformer core for each primary winding. In particular, a primary winding is arranged on one leg of each of the multiple transformer cores. Furthermore, the secondary winding encloses one leg of each of the multiple transformer cores.

[0019] Furthermore, the following is planned:

[0020] A charging circuit for an electrical energy storage device with a voltage converter arrangement according to the invention. The AC voltage connection can be designed to be coupled to a multi-phase electrical energy source, for example, a multi-phase AC network such as a low-voltage power supply network. The DC voltage connection R. 415147

[0021] - 4 - can also be designed to be coupled with the electrical energy storage device.

[0022] Finally, the following is planned:

[0023] A method for operating a voltage converter arrangement, in particular a voltage converter arrangement according to the invention. In particular, the method comprises controlling the primary-side bridge circuits and / or the secondary-side bridge circuit, in which either the transformer voltage and transformer current on the primary side or the secondary side of the transformer are in phase.

[0024] Advantages of the invention

[0025] Conventional circuits currently available for charging an electric energy storage device in a motor vehicle typically use so-called unidirectional switching elements. These unidirectional switching elements are semiconductor devices that can block or control an electrical voltage in one direction, but do not exhibit this blocking property when the polarity is reversed. Therefore, special circuit topologies or two complementary unipolar switching elements arranged in series are required for use with alternating currents.

[0026] The present invention is based on the discovery that so-called bipolar semiconductor switching elements have recently become available, which can block and selectively switch an electrical voltage for both polarities. Based on such bipolar semiconductor switching elements, further novel concepts are therefore possible. R. 415147

[0027] - 5 -

[0028] Based on this finding, the present invention provides a voltage converter arrangement, in particular a galvanically isolated voltage converter arrangement, which is suitable for efficiently converting a supplied (multi-phase) alternating voltage into a direct voltage for charging an electrical energy storage device, such as the traction battery of an electric vehicle.

[0029] In particular, the use of a special transformer arrangement for galvanic isolation between the AC and DC voltage connections allows for a particularly clever, efficient and space-saving configuration.

[0030] Furthermore, the proposed concept according to the invention makes it possible to selectively control the load on the individual phases of the connected AC power network. This allows, for example, a targeted symmetrical load on the AC power network to be achieved. In addition, the reactive power component can also be adjusted and, in particular, minimized.

[0031] According to one embodiment, the primary-side bridge circuits each comprise two half-bridges. Each half-bridge can comprise two semiconductor switching elements connected in series. Alternatively, one half-bridge can comprise two semiconductor switching elements connected in series, while the other half-bridge comprises two capacitors connected in series. The switching elements of the primary-side bridge circuits can, in particular, be configured as bipolar switching semiconductor switching elements. R. 415147

[0032] - 6 -

[0033] According to one embodiment, the transformer comprises several cores. Each primary winding of the multiple primary windings can be arranged on one leg of one of the cores. Furthermore, the secondary winding can enclose one leg of each of the transformer's cores. In this way, the transformer arrangement according to the invention can be implemented particularly simply and efficiently.

[0034] According to one embodiment, the multiple cores of the transformer are designed as E-cores. Alternatively, the individual cores of the transformer can be designed as Ul-cores. E-cores and Ul-cores are readily available individual transformer cores, so that the transformer arrangement according to the invention can be implemented simply and cost-effectively.

[0035] According to one embodiment, the voltage converter arrangement includes a DC-DC converter. The DC-DC converter is arranged between the DC voltage terminal and another DC voltage terminal. In particular, the voltage converter is designed to convert a first DC voltage supplied at the DC voltage terminal into a second DC voltage and to supply the second DC voltage at the other DC voltage terminal. Additionally or alternatively, the DC-DC converter can be designed to convert a second DC voltage supplied at the other DC voltage terminal into a first DC voltage and to supply the first DC voltage at the DC voltage terminal. By using a DC-DC converter on the DC voltage side of the voltage converter arrangement, the voltage level of the electrical voltage supplied at the DC voltage terminal can be adjusted.Furthermore, the use of such a DC-DC converter can smooth or stabilize the electrical voltage supplied at the DC voltage connection. R. 415147.

[0036] - 7 -

[0037] According to one embodiment, the AC voltage connection comprises three connection points. Each connection point of the AC voltage connection is designed to be connected to a corresponding terminal of a three-phase AC voltage network. Accordingly, the transformer comprises three primary windings. Furthermore, in such a configuration, a primary-side bridge circuit is provided for each connection point of the AC voltage connection and its corresponding primary winding. This allows the voltage transformer arrangement to be connected to a three-phase AC voltage network, for example, a low-voltage network.

[0038] According to one embodiment, the voltage converter arrangement is designed to transfer electrical energy from the three connection points of the AC voltage terminal to the DC voltage terminal in a first operating mode. In particular, the voltage converter arrangement enables a balanced load across the three phases in such three-phase operation.

[0039] According to one embodiment, the voltage converter arrangement is designed to transfer electrical energy in a second operating mode only from one connection point of the AC voltage terminal to the DC voltage terminal. Accordingly, in this operating mode, electrical energy can be transferred when power requirements are low or when connecting to a power supply network that provides only a single-phase AC voltage.

[0040] According to one embodiment, the voltage converter arrangement is designed to transfer electrical energy from the DC terminal to the AC terminal in a third operating mode. Thus, electrical energy can also be transferred in the reverse direction, from the DC side to the AC side. For example, this makes it possible to feed electrical energy into a power supply network. R. 415147

[0041] - 8 -

[0042] The above embodiments and further developments can be combined with one another as appropriate. Further embodiments, further developments, and implementations of the invention also include combinations of features of the invention described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In particular, those skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention.

[0043] Brief description of the drawings

[0044] Further features and advantages of the invention are explained below with reference to the figures. These show:

[0045] Fig. 1 : a schematic representation of a basic circuit diagram of a charging circuit for an electrical energy storage device with a voltage converter arrangement according to one embodiment;

[0046] Fig. 2: a schematic representation of a basic circuit diagram of a charging circuit for an electrical energy storage device with a voltage converter arrangement according to a further embodiment;

[0047] Fig. 3: a schematic representation of a cross-section through a top view of a transformer as it may form the basis of a voltage transformer arrangement according to one embodiment;

[0048] Fig. 4: a schematic representation of a cross-section through a top view of a transformer as it may form the basis of a voltage transformer arrangement according to a further embodiment; and R. 415147

[0049] - 9 -

[0050] Fig. 5: a flowchart as it may form the basis of a method for operating a voltage converter arrangement according to one embodiment.

[0051] Description of embodiments

[0052] Figure 1 shows a schematic diagram of a charging circuit for an electrical energy storage device 3 according to one embodiment. The charging circuit comprises a voltage converter arrangement 1 with an AC voltage connection 11 and a DC voltage connection 12. An AC voltage network, in particular a three-phase AC voltage network 2, such as a low-voltage power supply network, can be connected to the AC voltage connection 11. Each connection point of the AC voltage connection 11 can be connected to one phase of the AC voltage network 2. A DC voltage network, for example the electrical system of an electric vehicle with an electrical energy storage device 3 such as a traction battery, can be connected to the DC voltage connection 12.As will be explained below in connection with Figure 2, a further DC voltage converter can be provided between the DC voltage connection 12 and the energy storage device 3.

[0053] Furthermore, the voltage converter arrangement 1 comprises a transformer 20, several primary-side bridge circuits 30, and a secondary-side bridge circuit 50. A resonant assembly 40 can also be provided between the transformer 20 and the secondary-side bridge circuit 50.

[0054] The transformer 20 comprises several primary windings 21, 22, 23 and one secondary winding 24. In particular, for each connection point, an electrical phase at the AC voltage connection 11 is a primary winding 21, R. 415147

[0055] - 10 -

[0056] 22, 23. Accordingly, a primary-side bridge circuit 30 is provided for each connection point of the AC voltage connection 11 and the corresponding primary winding 21, 22, 23.

[0057] Each bridge circuit 30 comprises two half-bridges, each with two components connected in series. In the embodiment shown in Figure 1, a first half-bridge comprises two semiconductor switching elements 30a arranged in series. These two semiconductor switching elements 30a are connected to a first terminal point of the corresponding primary winding 21, 22, 23 of the transformer 20. In this embodiment, the second half-bridge comprises two capacitors 30b arranged in series. The connection between these two capacitors 30b is connected to another terminal point of the corresponding primary winding 21, 22, 23. The two outer terminals of the two half-bridges are electrically connected to each other. One of the outer terminals is connected to the corresponding terminal point of the AC voltage connection 11. The other outer terminals of the half-bridges are connected to a node K.

[0058] The semiconductor switching elements 30a of the primary-side bridge circuit 30 can, in particular, be designed as bipolar switching semiconductor switching elements. Such semiconductor switching elements are capable of blocking electrical voltages in both directions, regardless of the applied polarity.

[0059] The secondary-side bridge circuit 50 comprises two half-bridges, each with two semiconductor switching elements connected in series. The semiconductor switching elements of the secondary-side bridge circuit 50 can also be unipolar switching semiconductor switching elements. The connection points between the two switching elements of a half-bridge are each electrically coupled to a terminal point of the secondary winding 24 of the transformer 20. A resonant assembly 40 can be provided between the secondary winding 24 and the secondary-side bridge circuit. For example, the resonant assembly 40 can be an R. 415147.

[0060] - 11 -

[0061] This involves a capacitor or a series circuit consisting of an inductor and a capacitor. The two outer terminals of the secondary-side bridge circuit 50 are connected to the corresponding terminals of the DC voltage terminal 12.

[0062] Figure 2 shows a schematic representation of a charging circuit with a voltage converter arrangement 1 according to a further embodiment. The voltage converter arrangement 1 according to Figure 2 differs from the previously described embodiment in that a DC voltage converter 60 is provided between the DC voltage terminal 12 and a further DC voltage terminal 13. Such a DC voltage converter 60 can convert the DC voltage provided by the secondary-side bridge circuit 50 or the electrical energy stored in a capacitor at the output of the secondary-side bridge circuit into a further DC voltage and provide this at the further DC voltage terminal 30. Thus, for example, even with a pulsating DC voltage at the DC voltage terminal 12, a constant voltage or a constant output power can be provided by the further DC voltage converter 60.

[0063] Additionally or alternatively, as also shown in Figure 2, it is also possible to implement the primary-side bridge circuit 30 by means of 2 half-bridges, each of which consists of two semiconductor switching elements connected in series, in particular two bipolar switching semiconductor switching elements 30a connected in series.

[0064] It is understood that, where sensible and applicable, the variations of the voltage transformer arrangement 1 according to Figure 1 and the voltage transformer arrangement 1 according to Figure 2 can also be combined with each other as desired. R. 415147

[0065] - 12 -

[0066] Figure 3 shows a schematic cross-section of a transformer 20, such as can form the basis of an embodiment of the voltage transformer arrangement 1. As can be seen in Figure 3, a separate transformer core 21a, 22a, 23a can be provided for each primary winding 21, 22, 23. In the embodiments shown in Figure 3, the transformer cores 21a, 22a, 23a can, for example, be Ul cores. Each primary winding 21, 22, 23 can be arranged around one leg of a corresponding core 21a, 22a, 23a. Furthermore, the secondary winding 24 can enclose one leg of each of the cores 21a, 22a, 23a. All primary windings 21, 22, 23 can have the same number of turns. Furthermore, the secondary winding 24 can also have a number of turns which corresponds to the number of turns of the primary windings 21, 22, 23.

[0067] Figure 4 shows a schematic representation of a cross-section through a transformer 20 according to an alternative embodiment. In the embodiment shown in Figure 4, the individual cores 21b, 22b, 23b of the transformer 20 are designed as E-cores. A primary winding 21, 22, 23 is arranged around one leg, in particular around a central leg, of each core 21b, 22b, 23b. Furthermore, the secondary winding 24 surrounds one leg, in particular a central leg, of each core 21b, 22b, 23b. The descriptions already given in connection with Figure 3 also apply to this embodiment.

[0068] For voltage conversion of a three-phase AC voltage at AC terminal 11 into a DC voltage at DC terminal 12, the switching elements 30a in the primary-side bridge circuits 30 can be controlled with a duty cycle of 50%. This generates rectangular voltages whose amplitudes are approximately half the respective instantaneous values ​​of the phase voltages at the corresponding terminals of the R. 415147

[0069] - 13 -

[0070] The AC voltage connection 11 corresponds to the switching elements of the secondary-side bridge circuit 50, which can be controlled either with a variable duty cycle or a constant duty cycle of 50%. The primary-side electrical voltages provided by the primary-side bridge circuits 20 and the secondary-side electrical voltage between the two connection points of the switching elements in the half-bridges of the secondary-side bridge circuit 50 are phase-shifted relative to each other. The respective phase shifts between the secondary-side electrical voltage and the phase shift between the primary-side electrical voltages and the secondary-side electrical voltage are used to regulate the phase currents between the AC voltage connection points and the corresponding bridge circuits 30 to the desired setpoints.

[0071] The section-wise sinusoidal current in the secondary winding 24 is regulated by the voltage applied across the resonant assembly 40. Thus, the secondary-side current can be regulated by the phase shifts between the primary-side electrical voltages described above and the secondary-side electrical voltage, as well as by the switching frequency of the secondary-side bridge circuit 50.

[0072] If only one phase is available at AC terminal 11 instead of several phases, the pulsating power can be transferred to the DC side at twice the mains frequency of this AC voltage. The control in this single-phase operation is analogous to the multi-phase operation; however, the setpoint of the transformer current amplitude follows only the instantaneous value of the one active phase. To minimize reactive power, the transformer current can be controlled so that the voltage at the corresponding primary winding 21, 22, 23 and the secondary-side transformer current are in phase. This is achieved by connecting the secondary-side bridge circuit 50 with a resistor. 415147

[0073] - 14 - corresponding combination of duty cycle for this secondary-side bridge circuit 50 and a phase shift between secondary-side transformer current and electrical voltage between the two nodes of the half-bridges of the secondary-side bridge circuit 50 is operated.

[0074] Figure 5 shows a schematic representation of a flowchart for a method for operating a voltage converter arrangement, in particular a voltage converter arrangement 1 according to the invention as described above. Accordingly, the method can, in principle, comprise any steps suitable for implementing the voltage converter arrangements 1 described above. Similarly, the voltage converter arrangements 1 described above can also comprise any components or units suitable for implementing the method described below.

[0075] In a first operating mode S1, electrical energy can be transferred from the AC voltage terminal 11 towards the DC voltage terminal 12. In this first operating mode S1, the electrical energy is transferred by means of a multiphase electrical voltage at the AC voltage terminal 11. In particular, for the operation of the voltage transformer arrangement 1, the primary-side bridge circuits 30 and / or the secondary-side bridge circuit 50 can be controlled, whereby the transformer voltage and the transformer current are in phase either on the primary side or the secondary side of the transformer 20.

[0076] In a second operating mode S2, energy transfer from the AC voltage terminal 11 towards the DC voltage terminal 12 can optionally take place, whereby only a single-phase AC voltage is provided at the AC voltage terminal 11. R. 415147

[0077] - 15 -

[0078] In another operating mode S3, energy transfer can also occur in the reverse direction, i.e., from the DC voltage terminal 12 towards the AC voltage terminal 11. In principle, either a multi-phase, in particular three-phase, AC voltage or a single-phase AC voltage can be provided at the AC voltage terminal 11. If a DC-DC converter 60 is provided between the DC voltage terminal 12 and another DC voltage terminal 13 in the voltage converter arrangement 1, it can be designed as a bidirectional DC-DC converter to also enable energy transfer in the reverse direction.

[0079] In summary, the present invention relates to a voltage converter arrangement for galvanically isolated power transmission between a multiphase AC voltage connection and a DC voltage connection. The voltage converter arrangement comprises a transformer with three primary windings and one secondary winding. The three primary windings of the transformer are arranged on separate transformer cores, with the secondary winding enclosing one leg of each transformer core.

Claims

R. 415147 - 16 - Claims 1. Voltage transformer arrangement (1), comprising: a DC voltage connection (12) designed to be coupled to a DC electrical network; an AC voltage connection (11) designed to be coupled to an AC electrical network (2); a transformer (20) with several primary windings (21, 22, 23) and a secondary winding (24), wherein a primary winding (21, 22, 23) is provided for each electrical phase of the AC network (2) that can be connected to the AC voltage connection (11);several primary-side bridge circuits (30), wherein a primary-side bridge circuit (30) is arranged between a connection point of the AC voltage terminal (11) and a node (K), wherein each primary-side bridge circuit (30) comprises two half-bridges, each with two components (30a, 30b) arranged in series, and wherein a connection point of the two components (30a, 30b) arranged in series of a half-bridge is connected to a connection point of a corresponding primary winding (21, 22, 23) of the transformer (20); a secondary-side bridge circuit (50) which is electrically coupled to the secondary winding (24) of the transformer (20); R. 415147 - 17 - a resonant assembly (40) arranged between the secondary winding (24) of the transformer (2) and the secondary-side bridge circuit (50), wherein the transformer (20) comprises a separate transformer core (21a, 22a, 23a; 21b, 22b, 23b) for each primary winding (21, 22, 23), wherein a primary winding of the multiple primary windings (21, 22, 23b) is arranged on one leg of each transformer core (21a, 22a, 23a; 21b, 22b, 23b) of the multiple transformer cores (21a, 22a, 23a; 21b, 22b, 23b), and wherein the secondary winding (24) connects one leg of each of the multiple transformer cores (21a, 22a, 23a; 21b, 22b, 23b).

2. Voltage converter arrangement (1) according to claim 1, wherein the primary-side bridge circuits (30) each comprise two half-bridges with two series-connected semiconductor switching elements (30a), or a half-bridge with two series-connected semiconductor switching elements (30a) and a half-bridge with two series-connected capacitors (30b), and wherein the switching elements (30a) of the primary-side bridge circuits (30) comprise bipolar switching semiconductor switching elements.

3. Voltage transformer arrangement (1) according to claim 1 or 2, wherein the multiple cores (21a, 22a, 23a; 21b, 22b, 23b) of the transformer (20) are configured as E-cores (21b, 22b, 23b) or as Ul-cores (21a, 22a, 23a).

4. Voltage converter arrangement (1) according to one of claims 1 to 3, comprising a DC voltage converter (60) arranged between the DC voltage terminal (12) and a further DC voltage terminal (13), and designed to convert a first DC voltage provided at the DC voltage terminal (12) into a second DC voltage and to provide the second DC voltage at the further DC voltage terminal (13) and / or to provide a second DC voltage provided at the further DC voltage terminal (13). R. 415147 - 18 - to convert into a first DC voltage and to provide the first DC voltage at the DC voltage terminal (12).

5. Voltage converter arrangement (1) according to one of claims 1 to 4, wherein the AC voltage connection (11) comprises three connection points designed to be connected to a three-phase AC voltage network, wherein the transformer (20) comprises three primary windings (21, 22, 23), and wherein a primary-side bridge circuit (30) is provided for each connection point of the AC voltage connection (11) and the respective corresponding primary winding (21, 22, 23).

6. Voltage converter arrangement (1) according to claim 5, wherein the voltage converter arrangement (1) is designed to transfer electrical energy from the three connection points of the AC voltage connection (11) to the DC voltage connection (12) in a first operating mode (S1).

7. Voltage converter arrangement (1) according to claim 5 or 6, wherein the voltage converter arrangement (1) is designed to transfer electrical energy in a second operating mode (S2) only from one connection point of the AC voltage connection (11) to the DC voltage connection (12).

8. Voltage converter arrangement (1) according to one of claims 5 to 7, wherein the voltage converter arrangement (1) is designed to transfer electrical energy from the DC voltage terminal (12) to the AC voltage terminal (11) in a third operating mode (S3), 9. Charging circuit for an electrical energy storage device (3), comprising: R. 415147 - 19 - a voltage converter arrangement (1) according to one of claims 1 to 8, wherein the AC voltage connection (11) is designed to be connected to a multi-phase electrical energy source, and wherein the DC voltage connection (12) is designed to be coupled to the electrical energy storage device (3).

10. Method for operating a voltage converter arrangement (1) according to any one of claims 1 to 8, wherein the method comprises controlling the primary-side bridge circuits (30) and / or the secondary-side bridge circuit (50), in which either the transformer voltage and transformer current on the primary side or the secondary side of the transformer (20) are in phase.

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