Power converter, charging device for an electric vehicle, and method for operating a power converter

Abstract

The invention relates to an electrical power converter for energy transfer between an AC voltage terminal and a DC voltage terminal. The power converter is characterized by a particularly simple and thus efficient and cost-effective configuration with a minimal number of required switching elements.

Description

[0001] R. 417111

[0002] - 1 -

[0003] Description

[0004] title

[0005] Power converter, charging device for an electric vehicle and method for operating a power converter

[0006] Technical field

[0007] The present invention relates to an electrical power converter and a method for operating such an electrical power converter. The present invention further relates to a charging device for an electric vehicle with such a power converter.

[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 example, the AC voltage from a low-voltage network can be used to recharge the electrical energy storage device. For this purpose, the single- or multi-phase AC voltage of the low-voltage network must be converted into a DC voltage suitable for recharging the electrical energy storage device using a suitable charging circuit. R. 417111

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[0011] For example, the publication DE 102017212834 A1 describes a circuit topology in which such a charging circuit includes components of the electric drive system.

[0012] Disclosure of the invention

[0013] The present invention provides an electrical power converter, a method for operating an electrical power converter, and a charging device for an electric vehicle, comprising the features of the independent claims. Further advantageous embodiments are the subject of the dependent claims.

[0014] Accordingly, the following is planned:

[0015] An electrical power converter comprising an AC input, a DC input, a transformer, a first circuit component, a second circuit component, and a switching matrix. The AC input is designed to be electrically coupled to a single-phase or multi-phase AC power supply. The DC input is designed to be electrically coupled to a DC power supply. The transformer comprises a primary and a secondary side. The second circuit component is arranged between the DC input and the secondary side of the transformer. In particular, the second circuit component is designed to rectify an AC voltage supplied at the secondary side of the transformer and supply it at the DC input.Additionally or alternatively, the second circuit component can also be designed to convert a DC voltage supplied at the DC terminal into an AC voltage and supply it at the secondary side of the transformer. The first circuit component comprises four bipolar switching elements arranged in series. A first bipolar switching element is arranged between the first node and a second node. R. 417111.

[0016] - 3 -

[0017] A second bipolar switching element is arranged between the second node and a third node. A third bipolar switching element is arranged between the third node and a fourth node. A fourth bipolar switching element is arranged between the fourth node and a fifth node. The second node is electrically coupled to a first terminal on the primary side of the transformer. The fourth node is electrically coupled to a second terminal on the primary side of the transformer. The switching matrix is ​​arranged between the AC terminal and the first circuit component. The switching matrix is ​​designed to couple the third node to a terminal of the AC terminal.Furthermore, the switching matrix is ​​designed to couple the first node and / or the fifth node to a connection point of the AC voltage connection.

[0018] Furthermore, the following is planned:

[0019] A charging device for an electric vehicle comprising a charging port and a power converter according to the invention. The charging port is designed to be electrically coupled to an AC voltage source. The AC voltage port of the power converter is electrically coupled to the charging port. Furthermore, the DC voltage port of the power converter is designed to be electrically coupled to an electrical energy storage device, for example, a traction battery of the electric vehicle.

[0020] Finally, the following is planned:

[0021] A method for operating an electrical power converter, an electrical power converter according to the invention. The method comprises a step for identifying an electrical voltage at one or more connection points of the AC voltage terminal. Furthermore, the method comprises a step for controlling the switching matrix in the power converter. By controlling the switching matrix in the power converter, the R. 417111

[0022] - 4 -

[0023] The connection points of the AC voltage terminal are selectively electrically coupled to the first, third, and fifth nodes of the first circuit component. The switching matrix is ​​controlled using the identified electrical voltages at the connection points of the AC voltage terminal. The method then includes a step for controlling the bipolar switching elements in the first circuit component. This control can be performed using a previously stored modulation scheme. Preferably, the method includes a step for controlling the switching elements in the second circuit component. This control can be performed using another previously stored modulation scheme.

[0024] Advantages of the invention

[0025] To charge an electric vehicle using electrical energy from an AC grid, it is necessary to rectify the AC voltage from the grid and adjust the output DC voltage to a level suitable for charging the vehicle's electrical energy storage system. Conversely, the electrical energy from the vehicle's energy storage system can also be used to operate an AC load or to feed electrical energy into an AC grid. For this, the DC voltage from the energy storage system must be converted into AC voltage and the voltage level adjusted to a target output voltage.To meet all the requirements, including galvanic isolation between the AC and DC voltage connections, conventional approaches have so far required relatively complex circuit topologies. These require a correspondingly large installation space and are also associated with high costs. R. 417111.

[0026] - 5 -

[0027] Based on this insight, the idea of ​​the present invention is therefore to create a concept for an electrical power converter between an AC voltage connection and a DC voltage connection, which enables bidirectional voltage conversion in a simple, cost-effective and efficient manner.

[0028] The concept according to the invention makes it possible to realize bidirectional energy transfer with a relatively small number of semiconductor switching elements and a simple transformer for galvanic isolation between the AC voltage side and the DC voltage side.

[0029] Furthermore, the concept according to the invention enables operation with one, two, or three electrical phases on the AC voltage side. Thus, the proposed electrical power converter can be used in a particularly versatile manner without requiring complex and therefore costly circuit topologies.

[0030] According to one embodiment, the four bipolar switching elements of the first circuit component each comprise a series connection of two anti-series connected unidirectional semiconductor switching elements. Such a combination of two unidirectional semiconductor switching elements enables the realization of a circuit arrangement that can block an electrical voltage regardless of the applied polarity.

[0031] According to an alternative embodiment, the four bipolar switching elements of the first circuit component each comprise a monolithic, bidirectionally switching semiconductor switching element. Such semiconductor switching elements are capable of reliably interrupting an electrical voltage regardless of the applied polarity.

[0032] According to one embodiment, the switching matrix is ​​designed to connect each phase terminal of the AC voltage connection to the first node, the third R, in a first operating mode. 417111

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[0034] to electrically couple the node and the fifth node. In this way, a three-phase coupling of the AC voltage connection with an AC voltage network is possible.

[0035] According to one embodiment, the switching matrix is ​​designed to electrically couple a first phase terminal of the AC voltage connection to the first node, a second phase terminal of the AC voltage connection to the fifth node, and a neutral terminal of the AC voltage connection to the third node in a second operating mode. In this way, the electrical converter can be coupled to the AC voltage network in a two-phase manner.

[0036] According to one embodiment, the switching matrix is ​​designed to electrically couple a first phase connection of the AC voltage connection to the first node and the fifth node in parallel in a third operating mode, and to electrically couple a neutral conductor connection of the AC voltage connection to the third node. In this way, a single-phase connection of the AC voltage connection to an AC voltage network is possible.

[0037] According to one embodiment, the power converter includes a further capacitor, preferably a fifth capacitor. The capacitor can be, for example, an electrolytic capacitor or another comparable capacitor with a large capacitance. In this fourth operating mode, the switching matrix can be configured to electrically couple a first phase terminal of the AC voltage terminal to the first node and to electrically couple a neutral terminal of the AC voltage terminal to the third node. Furthermore, for this fourth operating mode, the switching matrix can be configured to connect one terminal of the capacitor to the third node and another terminal of the capacitor to the fifth node. Such a circuit configuration is R. 417111

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[0039] It is possible to smooth the DC output voltage during power transfer from a single-phase AC connection to a DC connection. In particular, the capacitor smooths the AC ripple that occurs in the input AC voltage.

[0040] 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.

[0041] Brief description of the drawings

[0042] Further features and advantages of the invention are explained below with reference to the figures. These show:

[0043] Fig. 1 : a schematic representation of a basic circuit diagram of a power converter according to one embodiment;

[0044] Fig. 2: a schematic representation of a possible embodiment for a bidirectional switching element according to one embodiment;

[0045] Fig. 3: a schematic representation of a bidirectional switching element according to a further embodiment;

[0046] Figs. 4 to 7: Schematic representations of principle circuit diagrams for configurations of electrical power converters according to further embodiments; and R. 417111

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[0048] Fig. 8: a flowchart as it may form the basis of a method for operating an electrical power converter according to one embodiment.

[0049] Description of embodiments

[0050] Figure 1 shows a schematic representation of a basic circuit diagram for an electrical power converter 1 according to one embodiment. The electrical power converter 1 comprises an AC voltage connection 11 and a DC voltage connection 12. A single-phase or multi-phase AC electrical network or a single-phase or multi-phase electrical load can be connected to the AC voltage connection 11. A DC voltage network, for example the high-voltage network of an electric vehicle with an electrical energy storage device such as a traction battery, can be connected to the DC voltage connection 12.

[0051] The electrical converter 1 further comprises a transformer 20 with a primary side 21 and a secondary side 22. The leakage inductance of the transformer 20 is summarized here in the inductance L shown in Figure 1. Alternatively, in an equivalent circuit, the leakage inductance can be arranged as an additional inductance between a third capacitor C1 and the primary side of the transformer 20.

[0052] Furthermore, the power converter 1 comprises a first circuit component 40, a second circuit component 50, and a switching matrix 30. The second circuit component 50 can, for example, rectify the AC voltage supplied by the transformer 20 on the secondary side 22 during electrical power transfer from the AC terminal 11 to the DC terminal 12 and provide the rectified voltage at the DC terminal 12. During power transfer in the reverse direction from the DC terminal 12 towards the AC terminal 11, this second circuit component can rectify the voltage at the DC terminal 12.

[0053] - 9 -

[0054] The DC voltage supplied by the transformer 20 is converted into an AC voltage and supplied to the secondary side 22 of the transformer 20. For this purpose, the second circuit component 50 can, for example, contain four switching elements S5 to S8 in the form of two half-bridges or one full bridge. The switching elements S5 to S8 can, for example, be unipolar switching semiconductor switching elements. Since the basic operating principle of such a circuit component, preferably an inverter, is considered known, it will not be explained in detail here.

[0055] The first circuit component 40 comprises four bipolar switching elements S1 to S4 connected in series. A first switching element S1 is arranged between a first node K1 and a second node K2. A second switching element S2 is arranged between the second node K2 and the third node K3. A third switching element S3 is arranged between the third node K3 and the fourth node K4. The fourth switching element S4 is arranged between the fourth node K4 and the fifth node K5. The first node K1, the third node K3, and the fifth node K5 can be coupled to connection points of the AC voltage terminal 11 via the switching matrix 30. As will be explained in more detail below, different circuit configurations can be set depending on the operating mode.In parallel to the series connection of the first switching element S1 and the second switching element S2, a capacitor C3, preferably a first capacitor C3, can be provided between the first node K1 and the third node K3. Similarly, in parallel to the series connection of the third switching element S3 and the fourth switching element S4, a further capacitor C4, preferably a second capacitor C4, can be arranged between the third node K3 and the fifth node K5. Both capacitors C3 and C4 have a relatively low capacitance and primarily serve to filter high-frequency signals.

[0056] The primary side 21 of the transformer 20 can be electrically coupled to the second node K2 and the fourth node K4. R. 417111

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[0058] A capacitor C1, preferably a third capacitor C1, may be provided between the second node K2 and a first connection point of the primary side 21 of the transformer 20. Additionally or alternatively, a capacitor (not shown here) may be provided between the fourth node K4 and another connection point of the primary side 21 of the transformer 20. Optionally, another capacitor C2, preferably a fourth capacitor C2, may also be provided between a connection point of the secondary side 22 of the transformer 20 and the second circuit component 50.

[0059] Figure 2 shows a schematic representation of a circuit arrangement for a bipolar switching element, such as can be used for the bipolar switching elements S1 to S4 in the first circuit component 40. As can be seen from Figure 2, such a bipolar switching element can be realized by a series connection of two anti-series arranged unipolar switching semiconductor elements.

[0060] Figure 3 shows a schematic representation of an alternative bipolar switching semiconductor switching element according to an embodiment, which can also be used as switching element S1 to S4 for the first circuit component 40. This is a monolithic bidirectional switching semiconductor switching element which is capable of switching independently of the applied voltage polarity.

[0061] The control signals for the switching elements S1 to S4 of the first circuit component 40 and for the switching elements S5 to S8 of the second circuit component 50 can, for example, be generated by a control device 60 and provided to the switching elements S1 to S8. The control signals for the switching elements S1 to S8 can be generated based on a suitable modulation method. Preferably, in the modulation, in each half-bridge with the switching elements S1 / S2, S3 / S4, S5 / S6, and S7 / S8, either the high-side switch is turned on while the low-side switch is turned off, or vice versa. Preferably, for each R. 417111

[0062] - 11 -

[0063] The duty cycle or the clocking of, for example, the high-side switch is used as a degree of freedom for each half-bridge. Preferably, this results in four degrees of freedom for the four half-bridges. Preferably, the phase shift between the phases or the clocking of the individual half-bridges is varied, resulting preferably in three further degrees of freedom, for example, with respect to one of the half-bridges as a reference phase. The modulation can be adapted in advance, for example, based on numerical optimization. The resulting data for optimal modulation can be stored, for example, in a suitable memory device 61 of the control device 60.As part of the optimization, for example, the three voltages, i.e., the two input voltages between the first node K1 and the third node K3 and between the third node K3 and the fifth node K5, as well as the output voltage at the DC terminal 12, can be considered as slowly changing values ​​or

[0064] DC voltage values ​​are considered in relation to the switching element timing. For the combination of these three voltages, the available degrees of freedom can then be varied to ensure that, firstly, the desired average phase currents on the input side are maintained, and secondly, the losses within the converter 1 are minimized. Depending on the modulation, for example, the conduction losses in switches S1 to S8 and transformer 20 can be minimized, and / or the smoothest possible switching of the switching elements S1 to S8 can be ensured. By numerically optimizing the modulation parameters beforehand, the optimized parameters can be quickly read and applied at runtime.

[0065] Figure 4 shows a schematic representation of a basic circuit diagram of a power converter 1 according to one embodiment with three-phase connection to an AC power grid. For better illustration, the switching matrix 30 in the figures for this and the following embodiments has been replaced by the respective circuit configuration. As can be seen in Figure 4, with a three-phase connection, a first connection point for a first phase L1 can be connected to the first node K1, and a second phase connection for a second phase L2 can be connected to the third node K3R. 417111

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[0067] The third connection point for a third phase L3 can be connected to the fifth node K5. The further configuration of the power converter in this and subsequent embodiments corresponds to the configuration previously explained in connection with Figure 1.

[0068] Figure 5 shows a schematic representation of a basic circuit diagram for a power converter 1 according to an embodiment for a two-phase connection to the AC power grid. In this configuration, for example, a first connection point for a first electrical phase L1 can be connected to the first node K1, and a second connection point of the AC terminal 11 for a second phase L2 can be connected to the fifth node K5. The third node K3 can, in this case, be connected to a connection point of the AC terminal 11 for a neutral conductor N.

[0069] Figure 6 shows a schematic representation of a basic circuit diagram of an electrical power converter 1 according to an embodiment for single-phase connection to an AC power grid. In this operating mode, for example, the first node K1 and the fifth node K5 can be connected to a connection point for a first electrical phase L1, while the third node K3 is connected to a connection point of the AC power terminal 11 for a neutral conductor N.

[0070] Figure 7 shows a schematic representation of a basic circuit diagram of an electrical power converter 1 according to a further embodiment for single-phase connection to an AC power grid. In this embodiment, the power converter 1 includes a capacitor C5 with a higher capacitance, for example, an electrolytic capacitor C5. This additional capacitor C5, preferably a first capacitor C5, can be provided, for example, between the third node K3 and the fifth node K5. The third node K3 is connected to a terminal of the AC power supply 11 for a neutral conductor R. 417111

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[0072] The first node K1 is connected to a connection point of the AC voltage terminal 11 for a first electrical phase L1. This circuit configuration, as well as the connection of the first capacitor C5 with the increased capacitance, can also be set by the switching matrix 30. The additional first capacitor C5 serves to smooth the output current at the DC voltage terminal 12.

[0073] For this purpose, the first capacitor C5 stores a power ripple that corresponds to twice the mains frequency at the AC voltage connection 11.

[0074] Finally, Figure 8 shows a flowchart illustrating how a method for operating an electrical converter, specifically an electrical converter 1 as previously described in one embodiment, can be based. The method can, in principle, comprise any steps that may be necessary for implementing the electrical converter 1 according to one of the previously described embodiments. Similarly, the previously described embodiments of the electrical converter 1 can also comprise any components suitable for implementing the method described below.

[0075] In step 110, an electrical voltage is identified at one or more connection points of the AC voltage terminal 11. This allows, for example, the determination of whether a single-phase, two-phase, or three-phase AC voltage is present at the AC voltage terminal 11. Alternatively, the selection for single-phase, two-phase, or three-phase operation can also be made by other suitable means, such as a user setting or similar.

[0076] In step 120, the switching matrix 30 in the power converter 1 is activated. This allows selective coupling of the connection points of the AC voltage terminal 11 with the first node K1, the third node K3, and the fifth node K5 of the first circuit component 40. The switching matrix can be activated using the identified electrical voltages at the R. 417111

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[0078] Connection points of the AC voltage terminal 11 are then made. Subsequently, in step 130, the switching elements in the power converter 1, the bipolar switching elements S1 to S4 in the first circuit component 40, and preferably the switching elements S5 to S8 in the second circuit component 50, can be controlled. The control can be carried out using a previously stored modulation scheme.

[0079] In summary, the present invention relates to an electrical power converter for energy transfer between an AC voltage connection and a DC voltage connection. The power converter is characterized by a particularly simple and therefore efficient and cost-effective configuration with a minimal number of required switching elements.

Claims

R. 417111 - 15 - Claims 1. Electrical power converter (1), with: an AC voltage connection (11) designed to be electrically coupled to a single-phase or multi-phase AC voltage network; a DC connection (12) designed to be electrically coupled to a DC network; a transformer (20) with a primary side (21) and a secondary side (22); a first circuit component (40); a second circuit component (50) arranged between the DC terminal (12) and the secondary side (22) of the transformer (20), and designed to rectify an alternating voltage supplied at the secondary side (22) of the transformer (20) and to supply it at the DC terminal (12) and / or to convert a DC voltage supplied at the DC terminal (12) into an alternating voltage and to supply it at the secondary side (22) of the transformer (20); and a switching matrix (30) which is arranged between the AC voltage terminal (11) and the first circuit component (40), wherein the first circuit component (40) comprises four bipolar switching elements (S1, S2, S3, S4) arranged in series, wherein R. 417111 - 16 - a first bipolar switching element (S1) is arranged between a first node (K1) and a second node (K2), a second bipolar switching element (S2) is arranged between the second node (K2) and a third node (K3), a third bipolar switching element (S3) is arranged between the third node (K3) and a fourth node (K4), and a fourth bipolar switching element (S4) is arranged between the fourth node (K4) and a fifth node (K5), and wherein the second node (K2) is electrically coupled to a first connection point of the primary side (21) of the transformer (20), and the fourth node (K4) is electrically coupled to a second connection point of the primary side (21) of the transformer (20), and wherein the switching matrix (30) is designed to electrically couple the third node (K3) as well as the first node (K1) and / or the fifth node (K5) to a connection point of the AC voltage connection (11).

2. Power converter (1) according to claim 1, wherein the four bipolar switching elements (S1, S2, S3, S4) of the first circuit component (40) each comprise a series connection of two anti-series connected unidirectional semiconductor switching elements.

3. Power converter (1) according to claim 1, wherein the four bipolar switching elements (S1, S2, S3, S4) of the first circuit component (40) each comprise a monolithic bidirectional switching semiconductor switching element.

4. Power converter (1) according to one of claims 1 to 3, wherein the switching matrix (30) is designed to electrically couple one phase terminal (L1, L2, L3) of the AC voltage terminal (11) to the first node (K1), the third node (K3) and the fifth node (K5) in a first operating mode. R. 417111 - 17 - 5. Power converter (1) according to one of claims 1 to 4, wherein the switching matrix (30) is designed to electrically couple a first phase connection (L1, L2, L3) of the AC voltage connection (11) with the first node (K1) in a second operating mode, to electrically couple a second phase connection (L1, L2, L3) of the AC voltage connection (11) with the fifth node (K5), and to electrically couple a neutral conductor connection of the AC voltage connection (11) with the third node (K3).

6. Power converter (1) according to one of claims 1 to 5, wherein the switching matrix (30) is designed to electrically couple a first phase connection (L1, L2, L3) of the AC voltage connection (11) with the first node (K1) and the fifth node (K5) in a third operating mode, and to electrically couple a neutral conductor connection of the AC voltage connection (11) with the third node (3).

7. Power converter (1) according to one of claims 1 to 6, with a further capacitor (C5), wherein the switching matrix (30) is designed to electrically couple a first phase terminal (L1, L2, L3) of the AC voltage terminal (11) with the first node (K1) in a fourth operating mode, and to electrically couple a neutral terminal of the AC voltage terminal (11) with the third node (K3), and wherein the switching matrix (30) is designed to connect one terminal of the additional capacitor (C5) to the third node (K3) in the fourth operating mode and to connect another terminal of the additional capacitor (C5) to the fifth node (K5).

8. Power converter (1) according to one of claims 1 to 7, a control device (60) designed to control the four bipolar switching elements (S1, S2, S3, S4) of the first circuit component (40) according to a previously stored modulation scheme, R. 417111 - 18 - wherein the control device (60) comprises a storage device (61) designed to provide previously stored data for one or more modulation schemes.

9. Charging device for an electric vehicle, including: a charging port designed to be electrically coupled to an alternating current source; a power converter (1) according to any one of claims 1 to 8, wherein the AC voltage connection (11) is electrically coupled to the charging connection, and wherein the DC voltage connection (12) is designed to be electrically coupled to an electrical energy storage device of the electric vehicle.

10. Method for operating an electrical power converter (1) according to any one of claims 1 to 8, comprising the steps Identifying (110) an electrical voltage at one or more connection points of the AC voltage connection (11); Controlling (120) the switching matrix (30) in the power converter (1) for selective electrical coupling of the connection points of the AC voltage terminal (11) with the first node (K1), the third node (K3) and the fifth node (K5) of the first circuit component (40) using the identified electrical voltages at the connection points of the AC voltage terminal (11); and R. 417111 - 19 - Controlling (130) the bipolar switching elements (S1, S2, S3, S4) in the first circuit component (40) using a previously stored modulation scheme.

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