Power converter and method for exchanging electrical power
By using a clock-controlled semiconductor switch between the DC intermediate circuit and the bridge intermediate circuit, the safety issue of the power converter during ground faults is solved, thereby improving both safety and cost-effectiveness.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SMA SOLAR TECH AG
- Filing Date
- 2024-10-11
- Publication Date
- 2026-05-15
AI Technical Summary
Existing power converters lack effective safety protection measures in the event of a ground fault, which may result in unwanted high current flow, damage the equipment, and require expensive current-limiting fuses and additional structural space.
A clock-controlled semiconductor switch is used to establish and disconnect the connection between the DC intermediate circuit and the bridge intermediate circuit. The DC/DC converter limits the current during ground faults, avoiding the need for disconnection points and fuses in the current path.
It provides safety in the event of a ground fault, avoids unwanted current flow, reduces the risk of equipment damage, and lowers equipment costs and space requirements.
Smart Images
Figure CN122055893A_ABST
Abstract
Description
Technical Field
[0001] This application relates to a power converter and method for exchanging electrical power between a three-phase AC voltage network and a DC unit, particularly a battery. The power converter may, for example, be an AC / DC converter for charging an energy storage device, particularly a battery in a stationary battery system, or a traction battery of an electric vehicle, using DC power (DC, direct current; AC, alternating current), wherein DC power is taken from the AC voltage network as AC power and converted to DC power by the power converter. Background Technology
[0002] To convert AC power obtained from an AC voltage network into DC power (which can be used, for example, to power a DC load or charge a battery), a power converter may or may not be equipped with a transformer in the power path.
[0003] Power converters with transformers in the power path—especially those used to charge energy storage devices such as batteries in electric vehicles—include electrical isolation in the power path, which provides safety in the event of a ground fault on the energy storage side, and especially at the electric vehicle.
[0004] A power converter with an AC / DC inverter bridge is known from DE 20 2022 100 172 U1. In this power converter, to protect the split intermediate circuit capacitor on the DC side, an electrical connection can be connected between the center point of the split intermediate circuit capacitor on the DC side and the center point of the AC / DC inverter bridge, and can be disconnected as needed in the event of a semiconductor defect. This connection is always conductive during normal operation, i.e., in the absence of semiconductor defects. Summary of the Invention
[0005] Task The objective of this application is to provide an improved power converter and an improved method for exchanging electrical power between an AC voltage network and an energy storage device, particularly a battery.
[0006] Solution This task is accomplished by a power converter having the features of claim 1, a method having the features of claim 13, and an application having the features of claim 21. Embodiments are given in the dependent claims.
[0007] describe A power converter for ground fault-safe power exchange between a three-phase AC voltage network and a battery includes AC terminals, DC terminals, a bridge circuit, and a DC / DC converter. The AC terminals are configured for connection to the AC voltage network, and the DC terminals are configured for connection to the battery. A DC intermediate circuit with an applied DC voltage is arranged between the DC / DC converter and the DC terminals, and a bridge intermediate circuit with an applied bridge DC voltage is arranged between the DC / DC converter and the bridge circuit. The DC / DC converter has a clock-controlled semiconductor switch configured to generate a voltage conversion ratio between the DC intermediate circuit and the bridge intermediate circuit during power exchange. The DC / DC converter has at least one additional semiconductor switch with a controller configured to establish a connection between the DC intermediate circuit and the bridge intermediate circuit by controlling the additional semiconductor switch during power exchange and to interrupt the connection in the event of a ground fault.
[0008] The bridge circuit can be, in particular, an AC / DC inverter bridge that converts AC power from a three-phase AC voltage network into DC power. The bridge intermediate circuit is especially the intermediate circuit capacitor located on the DC side of the AC / DC inverter bridge. Based on its construction with both a bridge circuit and a DC / DC converter, the power converter can also be referred to as a transformerless two-stage power converter.
[0009] By employing an additional semiconductor switch to disconnect the connection between the DC intermediate circuit and the bridge intermediate circuit as needed, the power converter according to this application offers improved safety in the event of a ground fault. The advantage of the solution described here is that a disconnect point on the DC side is not required in the current path, which is expensive and requires structural space. Similarly, no further requirements are placed on the DC side regarding the use of fuses (e.g., regarding cascaded protection).
[0010] A ground fault can be a low-impedance connection to ground potential on the DC terminal side. If the three-phase AC voltage network is an AC voltage network with a fixed ground reference, high fault currents may flow through the power converter in certain situations, potentially causing a hazard. By employing additional semiconductor switches in the DC / DC converter as described above, unwanted and / or dangerous currents flowing through the power converter can be prevented in the event of a ground fault. This ensures the standard safety requirements under fault conditions. Furthermore, the power converter can be protected from damage due to overcurrent during fault conditions.
[0011] The intermediate circuit terminals of the DC / DC converter can be connected to opposite intermediate circuit terminals of the DC / DC converter via the at least one additional semiconductor switch. In the case of split DC intermediate circuits and split bridge intermediate circuits, connections can also be established between corresponding center points via the at least one additional semiconductor switch. By disconnecting the at least one connection as needed via the at least one additional semiconductor switch, the power converter can be made safe from ground short circuits.
[0012] The battery that can be connected to the power converter can be, in particular, a battery in a stationary or mobile battery system or a traction battery in an electric vehicle. The power converter can be configured to charge the battery from an AC voltage network when exchanging electrical power. In this embodiment, no further requirements are imposed on the battery system or electric vehicle, such as regarding cascading protection, when fuses are used.
[0013] The described power converter enables battery charging without the need for electrical isolation in the power path (i.e., especially without the need for a transformer in the power path). Charging via such an electrically isolated power converter, particularly by means of a transformerless power converter, offers advantages in terms of equipment cost, weight, and size compared to power converters with transformers. Ground short circuits on the DC side of the power converter (especially ground short circuits at or within the connected battery system or electric vehicle) and fault currents caused by corresponding potential shifts on the DC side can be handled without expensive current-limiting fuses.
[0014] Bridge intermediate circuits can be constructed, in particular, as split intermediate circuits. In the case of split bridge intermediate circuits, the center point can, for example, be located at the potential of the bridge center point of the bridge circuit. In a three-phase AC voltage network with a fixed ground reference, the bridge center point can, in particular, be located at the potential of the N conductor (i.e., ground potential), or have a fixed and / or adjustable potential reference relative to ground potential by means of the bridge circuit.
[0015] In implementations of the power converter, the DC / DC converter is constructed as a symmetrical DC / DC converter. A symmetrical DC / DC converter may have three terminals on one of two DC sides or on two DC sides, these three terminals being ordered according to their potentials. A corresponding intermediate terminal among the three terminals can be adjusted by the symmetrical DC / DC converter to the potential of the center potential of the corresponding other two terminals. In particular, the DC intermediate circuit can be implemented as a split intermediate circuit and has three terminals with corresponding potentials.
[0016] A symmetrical DC / DC converter, for example, can adjust the middle terminal of the three terminals of a split bridge intermediate circuit to the potential between the other two terminals of the split bridge intermediate circuit.
[0017] In an embodiment where the DC intermediate circuit between the DC terminal and the DC / DC converter is configured as a split intermediate circuit, the center point of the DC intermediate circuit can be adjusted to the center potential of the DC intermediate circuit by a symmetrical DC / DC converter, which substantially corresponds to the center potential of the bridge intermediate circuit.
[0018] In the implementation of the power converter, the at least one additional semiconductor switch is configured to establish a connection between the center potential of the split DC intermediate circuit and the center potential of the split bridge intermediate circuit during power exchange and to interrupt the connection in the event of a ground fault. This avoids fault currents between the DC intermediate circuit and the bridge intermediate circuit, which would flow through the previously existing connection at the center potential in the event of a ground fault. If the three-phase AC voltage network is an AC voltage network with a fixed ground reference, this can interrupt the connection between the center point of the DC intermediate circuit and the bridge center point, which can be at an N-conductor level.
[0019] In one embodiment of the power converter, two additional semiconductor switches are provided, each assigned to a terminal of the DC intermediate circuit, and the additional semiconductor switches are configured such that, during power exchange, one of the semiconductor switches controlled by the clock of the DC / DC converter establishes a corresponding connection between the corresponding terminal of the DC intermediate circuit and the corresponding terminal of the bridge intermediate circuit, and interrupts the corresponding connection in the event of a ground fault.
[0020] In one embodiment of the power converter, two additional semiconductor switches are provided, each assigned to a terminal of the bridge intermediate circuit, and the additional semiconductor switches are configured such that, during power exchange, one of the semiconductor switches controlled by the clock of the DC / DC converter establishes a corresponding connection between the corresponding terminal of the bridge intermediate circuit and the corresponding terminal of the DC intermediate circuit, and interrupts the corresponding connection in the event of a ground fault.
[0021] In one implementation of the power converter, a DC voltage is applied to the DC intermediate circuit and a bridge DC voltage is applied to the bridge intermediate circuit, wherein the DC / DC converter is configured to produce a voltage conversion ratio such that the DC voltage and thus the voltage on the connected battery are also less than the bridge DC voltage.
[0022] In implementations of the power converter, the DC voltage is limited to less than half of the bridge DC voltage. For example, the DC voltage, which may correspond to the battery voltage, may be between 300V and 1000V, such as about 500V or about 750V. The bridge DC voltage may be between 600V and 2000V, such as about 1000V or about 1500V.
[0023] In one embodiment of the power converter, the three-phase AC voltage network has a fixed reference relative to ground potential. DC terminals have DC conductors through which batteries can be connected. A ground fault is characterized by a low-impedance connection from one of the DC conductors at the DC terminals to ground potential.
[0024] In a method for ground fault-safe power exchange between a three-phase AC voltage network and a battery using the power converter, the DC / DC converter generates a voltage conversion ratio between a DC intermediate circuit and a bridge intermediate circuit by means of a clock-controlled semiconductor switch during power exchange. At least one additional semiconductor switch establishes a connection between the DC intermediate circuit and the bridge intermediate circuit during power exchange, and in the event of a ground fault, this connection is interrupted by opening this at least one additional semiconductor switch.
[0025] In an alternative method for ground fault-safe power exchange between a three-phase AC voltage network and a battery using a power converter, the power converter comprises a bridge circuit and a DC / DC converter. A DC intermediate circuit with a DC voltage is arranged between the DC / DC converter and the battery, and a bridge intermediate circuit with a bridge DC voltage is arranged between the DC / DC converter and the bridge circuit. The center potentials of the DC intermediate circuit and the bridge intermediate circuit are interconnected via RC components. In this method, when exchanging power, the DC / DC converter generates a voltage conversion ratio between the DC intermediate circuit and the bridge intermediate circuit using a clock-controlled semiconductor switch, such that the DC voltage is limited to less than half of the bridge DC voltage. The RC components allow for a partial disconnection of the center potentials of the DC intermediate circuit and the bridge intermediate circuit, which limits excessive fault current.
[0026] The described method allows for the toleration of potential shifts on the DC side of the power converter due to, for example, a ground fault, without generating large fault currents. Fault currents are limited by setting the voltage conversion ratio as described above because, at these potential ratios, the corresponding diodes in the bridge circuit will be cut off in the event of a ground fault. Therefore, fault currents are avoided by the described method. Thus, this method provides simple and economical safety in fault conditions.
[0027] Optionally, at least one additional semiconductor switch can establish a connection between the DC intermediate circuit and the bridge intermediate circuit when exchanging electrical power. In the event of a ground fault, the connection between the DC intermediate circuit and the bridge intermediate circuit can be interrupted by opening the at least one additional semiconductor switch.
[0028] In one embodiment of the method, the battery can be charged from an AC voltage network during power exchange.
[0029] Alternatively, the bridge intermediate circuit can be configured as a split intermediate circuit, and the DC / DC converter can be configured as a symmetrical DC / DC converter.
[0030] In one embodiment of the method, the DC intermediate circuit is configured as a split intermediate circuit. The split DC intermediate circuit has three terminals, each with a center potential and a potential that is either positive or negative relative to the center potential. A symmetrical DC / DC converter can then adjust the center potential of the split DC intermediate circuit to a potential between the other two terminals of the split DC intermediate circuit.
[0031] The at least one additional semiconductor switch can establish a connection between the center potential of the split DC intermediate circuit and the center potential of the split bridge intermediate circuit when exchanging electrical power. In the event of a ground fault, the connection between the DC intermediate circuit and the bridge intermediate circuit is interrupted by opening the at least one additional semiconductor switch.
[0032] In one embodiment of the method, two additional semiconductor switches are provided, each assigned to a terminal of the DC intermediate circuit. Each of these additional semiconductor switches establishes a connection between the corresponding terminal of the DC intermediate circuit and the corresponding terminal of the bridge intermediate circuit via a clock-controlled semiconductor switch of the DC / DC converter to generate the voltage conversion ratio during power exchange. In the event of a ground fault, this connection is interrupted by opening the corresponding additional semiconductor switch.
[0033] In one embodiment of the method, two additional semiconductor switches are provided, each assigned to a terminal of the bridge intermediate circuit. Each of these additional semiconductor switches establishes a connection between the corresponding terminal of the bridge intermediate circuit and the corresponding terminal of the DC intermediate circuit via a clock-controlled semiconductor switch of the DC / DC converter to generate the voltage conversion ratio during power exchange. In the event of a ground fault, this connection is interrupted by opening the corresponding additional semiconductor switch.
[0034] The described power converter and method are particularly useful for charging batteries in stationary or mobile battery systems or traction batteries in electric vehicles.
[0035] In another aspect, the power converter according to the invention may have a charging cable that provides additional protection for personnel operating the power converter. For example, the charging cable may have a conductive shielding layer (e.g., made of a metal mesh) that surrounds each conductor along the direction of the charging cable. This shielding layer may preferably be grounded via a grounding terminal, such that a conductor breakage or damage to the conductor insulation, and subsequent contact between the damaged portion and the shielding layer, specifically triggers a ground fault, which the power converter can respond to using the method according to the invention.
[0036] However, it is also conceivable that the high-current conductor of the charging cable is spirally wound around a protective conductor or a group of protective conductors. In the event of mechanical damage to the charging cable, this could cause the protective conductor or one of the protective conductors to break. A monitoring circuit that monitors the integrity of the protective conductor or multiple protective conductors (e.g., via resistance measurement) can detect such a break and trigger an appropriate response, such as shutting down the power converter and discharging the applied voltage. Existing control lines and / or temperature measuring lines can also be used as protective conductors, which are then spirally guided around the high-current conductor, so that external damage to the cable insulation has a high probability of breaking at least one protective conductor. Optical fibers with optical monitoring capabilities can also be used instead of electrical conductors. Attached Figure Description
[0037] The present application will be further explained and described below with the aid of embodiments shown in the accompanying drawings.
[0038] Figure 1 The schematic diagram illustrates one implementation including a battery system, a power converter, and an exemplary system including a three-phase AC voltage network.
[0039] Figure 2 The schematic diagram illustrates another implementation including a battery system, a power converter, and another exemplary system including a three-phase AC voltage network.
[0040] Figure 3 A first implementation of a DC / DC converter is schematically shown.
[0041] Figure 4 A second implementation of a DC / DC converter is schematically shown.
[0042] Figure 5 A third implementation of a DC / DC converter is schematically shown.
[0043] Figure 6 A fourth embodiment of a DC / DC converter is schematically illustrated.
[0044] Figure 7 A fifth embodiment of a DC / DC converter is schematically illustrated.
[0045] Figure 8 schematically shown Figure 1 The system has an equivalent diode diagram of a DC / DC converter.
[0046] Figure 9 schematically shown Figure 2 The system has an equivalent diode diagram of a DC / DC converter.
[0047] In the accompanying drawings, the same reference numerals are used for the same or similar elements. The illustrations in the accompanying drawings may not be drawn to scale. Detailed Implementation
[0048] Figure 1 A system comprising a battery 14, a power converter 10, and a three-phase AC voltage network 12 is schematically illustrated. The battery 14 is configured, for example, as a battery in a stationary or mobile battery system BS, particularly a traction battery for an electric vehicle (EV). A battery voltage UB is applied to the battery. Isolating switches BSS1 and BSS2 are arranged between the power converter 10 and the battery 14, which disconnect the corresponding DC conductors from the battery 14. Isolating switches BSS1 and BSS2 are configured, for example, as relays.
[0049] Power converter 10 has a DC terminal DCA. A DC conductor connects the DC terminal DCA of power converter 10, for example, via a plug connected to battery 14. The DC / DC converter 20 of power converter 10 can be disconnected from and connected to the DC terminal DCA via DC disconnect switches S1 and S2. DC disconnect switches S1 and S2 are configured as relays, for example. The corresponding DC conductors of power converter 10 are connected to ground potential via a capacitor (a so-called Y capacitor) between the DC intermediate circuit 18 of power converter 10 and the DC disconnect switches S1 and S2.
[0050] A DC intermediate circuit 18 is arranged between the DC disconnect switches S1 and S2 and the DC / DC converter 20. A DC voltage UDC is applied to the DC intermediate circuit 18. The DC / DC converter 20 is configured, for example, as a symmetrical DC / DC converter. A bridge intermediate circuit 22 is arranged between the DC / DC converter 20 and the bridge circuit 16. A bridge voltage UBR is applied to the bridge intermediate circuit 22. The bridge intermediate circuit 22 is split, and approximately half of the bridge voltage UBR / 2 is applied to each half of the split bridge intermediate circuit 22.
[0051] The bridge circuit 16 has a semiconductor switch (not shown) that can be clock-controlled by appropriate manipulation. By manipulating the clock-controlled semiconductor switch of the bridge circuit 16, the bridge circuit 16 converts AC power to DC power. Conversely, the bridge circuit 16 can also, in principle, convert DC power to AC power by manipulating the clock-controlled semiconductor switch.
[0052] Bridge circuit 16 is connected to AC terminal ACA of power converter 10. A three-phase AC voltage network 12 is connected to AC terminal ACA of power converter 10. AC voltage network 12 has conductors L1, L2, L3 for corresponding phases. AC voltage network 12 has a fixed reference relative to ground potential EP, for example, via protective conductor PE. An optional neutral conductor N may be provided, which can be connected to power converter 10.
[0053] Figure 1 The power converter 10 therefore has two stages, one stage having a bridge circuit 16 and the second stage having a DC / DC converter 20. Here, the DC intermediate circuit 18 is constructed as a simple, i.e., non-split intermediate circuit. The DC / DC converter 20 is constructed as a symmetrical DC / DC converter. The bridge intermediate circuit 22 is constructed as a split intermediate circuit. The split bridge intermediate circuit 22 has three terminals with corresponding potentials.
[0054] A symmetrical DC / DC converter can have three terminals on one or both DC sides, ordered by their potentials. The middle terminal can be adjusted to the center potential of the other two terminals using the symmetrical DC / DC converter. Figure 1 In the embodiment shown, the symmetrical DC / DC converter 20 is able to adjust the intermediate terminal of the bridge intermediate circuit 22 to the potential of the center between the other two terminals of the bridge intermediate circuit.
[0055] Figure 2 Another embodiment of the system is shown, comprising a battery 14 with a battery system BS, a three-phase AC voltage network 12, and a power converter 10.
[0056] according to Figure 2 The DC intermediate circuit 18 in this embodiment is configured as a split intermediate circuit. The split DC intermediate circuit 18 has three terminals with correspondingly different potentials, wherein the intermediate terminal has a potential located between the other two terminals of the DC intermediate circuit 18. Figure 2 The DC / DC converter 20 is configured as a symmetrical DC / DC converter, which can adjust the corresponding intermediate terminals of the intermediate circuits 18 and 22 to the potential of the center between the corresponding other terminals of the intermediate circuits 18 and 22.
[0057] exist Figure 3 A first embodiment of the DC / DC converter 20 according to this application is shown. The DC intermediate circuit 18 is non-split type, see [reference]. Figure 1 The DC / DC converter 20 shown is, for example, a symmetrical DC / DC converter. The DC / DC converter 20 has clock-controlled semiconductor switches 30.1, 30.2, 30.3, and 30.4, which are clock-controlled during power transfer between the AC terminal ACA and the DC terminal DCA, thereby cooperating with the inductor of the DC / DC converter 20 to set the voltage ratio between the two sides of the DC / DC converter 20.
[0058] In the first embodiment of the illustrated DC / DC converter 20, two additional semiconductor switches 24 are inserted into the corresponding DC conductors of the DC / DC converter 20. These additional semiconductor switches are not clock-controlled. The additional semiconductor switches 24 have corresponding freewheeling paths. These additional semiconductor switches 24 can be turned on under ground short-circuit conditions EF1, EF2. To avoid potential transfer currents (Umladeströme) between intermediate circuits 18, 22 that could damage, especially, the clock-controlled semiconductor switches 30.1, 30.2, 30.3, 30.4, in the event of a ground short-circuit EF1, EF2 fault, the additional semiconductor switches 24 are arranged in the corresponding DC conductors between the symmetrical DC intermediate circuit 18 and the bridge intermediate circuit 22 of the DC / DC converter 20. The additional semiconductor switches 24 are arranged in series with the inductor of the DC / DC converter 20. Since the additional semiconductor switches 24 block the inductor-driven current in the DC conductor when turned on, a freewheeling path via a diode or optionally a small capacitor (not shown) can be provided, for example. These small capacitors are preferably significantly smaller than the capacitors in intermediate circuits 18 and 22. Alternatively, in addition to the bridge intermediate circuit 22, another capacitor can be provided as the output capacitor of the DC / DC converter 20.
[0059] During the power transfer and the setting of the voltage conversion ratio of the DC / DC converter 20 by the clock-controlled semiconductor switches 30.1, 30.2, 30.3, and 30.4, an additional semiconductor switch 24 is closed, thereby establishing a connection between the bridge intermediate circuit 22 and the DC intermediate circuit 18.
[0060] Here, controller 31 operates semiconductor switch 24 and clock-controlled semiconductor switches 30.1, 30.2, 30.3, and 30.4. This controller is also capable of identifying ground short circuits EF1 and EF2 and appropriately operating these switches not only in normal operation mode but also under fault conditions. Ground short circuit identification is performed using known methods, such as differential current measurement. For simplicity, controller 31 is omitted from the following figures but may be included accordingly.
[0061] exist Figure 4 A second embodiment of the DC / DC converter 20 is shown. The DC intermediate circuit 18 is non-split. The DC / DC converter 20 shown is, for example, a symmetrical DC / DC converter 20. The DC / DC converter 20 has clock-controlled semiconductor switches 40.1, 40.2, and 40.3, which are clock-controlled during power transfer between the AC terminal ACA and the DC terminal DCA, and thus set the voltage ratio between the two sides of the DC / DC converter 20.
[0062] The illustrated DC / DC converter 20 is based on a type of DC / DC converter that can be called a Balanced Mode-Steller. This converter does not have a half-bridge with a center tap between the DC leads, but instead has only a clock-controlled semiconductor switch 40.2. Therefore, the bridge intermediate circuit 22 is no longer effectively split, but behaves like a single capacitor.
[0063] Compared to balanced mode choppers, Figure 4The embodiment shown includes an additional freewheeling diode and two additional semiconductor switches 26 inserted into the corresponding DC conductors of the DC / DC converter 20. These additional semiconductor switches 26 are closed during operation of the power converter 10 and can be opened in the event of a ground short circuit EF1, EF2. To prevent transfer currents that could potentially damage the clock-controlled semiconductor switches 40.1, 40.2, 40.3 between intermediate circuits 18, 22 in the event of a ground short circuit EF1, EF2 failure, the additional semiconductor switches 26 are arranged between the DC intermediate circuit 18 and the bridge intermediate circuit 22 of the symmetrical DC / DC converter 20. The additional semiconductor switches 26 are arranged in series with the inductors of the DC / DC converter 20. Since the additional semiconductor switches 26 block the inductor-driven current in the DC conductors when open, a freewheeling path via a diode or, optionally, a small capacitor (not shown) can be provided. These small capacitors are preferably significantly smaller than the capacitance of the intermediate circuits 18, 22. Alternatively, in addition to the bridge intermediate circuit 22, another capacitor can be provided as the output capacitor of the DC / DC converter 20.
[0064] During power delivery and the setting of the voltage conversion ratio of the DC / DC converter 20 by the clock-controlled semiconductor switches 40.1, 40.2, 40.3, an additional semiconductor switch 26 is closed, thereby establishing a connection between the bridge intermediate circuit 22 and the DC intermediate circuit 18.
[0065] exist Figure 5 A third embodiment of the DC / DC converter 20 is shown. The DC intermediate circuit 18 is non-split. The DC / DC converter 20 shown is, for example, a symmetrical DC / DC converter 20. The DC / DC converter 20 has clock-controlled semiconductor switches 50.1, 50.2, 50.3, and 50.4, which are clock-controlled during power transfer between the AC terminal ACA and the DC terminal DCA, and thus set the voltage ratio between the two sides of the DC / DC converter 20.
[0066] The DC / DC converter 20 shown is based on a type of DC / DC converter that can also be called a mirror-type steller. Figure 5The embodiment shown includes small capacitors that keep the commutation loop small and simultaneously fix a potential reference between the two sides of the DC / DC converter 20. Additional non-clock-controlled semiconductor switches 28 are mounted after these capacitors and are closed during normal operation of the power converter. These additional semiconductor switches 28 can be opened to disconnect the capacitive potential reference in the event of a ground short circuit EF1, EF2. Since this disconnection operates in one direction, the capacitance value can preferably be chosen to be small. These small capacitors are preferably significantly smaller than the capacitance of the intermediate circuits 18, 22. Simultaneously, these capacitors can be used as freewheeling current driven by the inductance of the DC / DC converter 20.
[0067] In the third embodiment of the DC / DC converter 20 shown, two additional semiconductor switches 28 are inserted into the corresponding DC conductors of the DC / DC converter 20. These additional semiconductor switches 26 can be opened under ground short-circuit conditions EF1, EF2. To avoid transfer currents that may occur between intermediate circuits 18, 22 and could damage the clock-controlled semiconductor switches 50.1, 50.2, 50.3, 50.4 in the event of a ground short-circuit EF1, EF2 fault, the additional semiconductor switches 28 are arranged between the DC intermediate circuit 18 and the bridge intermediate circuit 22 of the symmetrical DC / DC converter 20. Optionally, in addition to the bridge intermediate circuit 22, an additional capacitor may be provided as the output capacitor of the DC / DC converter 20.
[0068] During the power transfer and the setting of the voltage conversion ratio of the DC / DC converter 20 by the clock-controlled semiconductor switches 50.1, 50.2, 50.3, and 50.4, an additional semiconductor switch 28 is closed, thereby establishing a connection between the bridge intermediate circuit 22 and the DC intermediate circuit 18.
[0069] exist Figure 6 A fourth embodiment of the DC / DC converter 20 is shown. In this embodiment, the DC intermediate circuit 18 is split, having a lower DC intermediate circuit half and an upper DC intermediate circuit half, on which the DC intermediate circuit voltage UDC / 2 is reduced by approximately half. The DC / DC converter 20 shown is, for example, a symmetrical DC / DC converter 20. The DC / DC converter 20 has clock-controlled semiconductor switches 60.1, 60.2, 60.3, and 60.4, which are clock-controlled during power transfer between the AC terminal ACA and the DC terminal DCA, and thus set the voltage ratio between the two sides of the DC / DC converter 20.
[0070] exist Figure 6In the embodiment shown, the center point of the split intermediate circuits 18, 22 is connected via an additional semiconductor switch 32. The additional semiconductor switch 32 is not clock-controlled and can be turned on under ground short-circuit conditions EF3, EF4 to disconnect the potential connection between the DC intermediate circuit 18 and the bridge intermediate circuit 22.
[0071] During power delivery and the voltage setting of the associated clock-controlled semiconductor switches 60.1, 60.2, 60.3, and 60.4, i.e., during normal operation of the power converter 10, the additional semiconductor switch 32 is closed, enabling the establishment of a conduction connection via it and the problem-free symmetrical operation of the bridge circuit 16. Here, only a small amount of current flows through the additional semiconductor switch 32, resulting in almost no losses during normal operation during power delivery, and the additional semiconductor switch 32 can be constructed accordingly economically.
[0072] In the event of a ground short circuit EF3 or EF4, an additional semiconductor switch 32 can be opened to disconnect the center points of the DC intermediate circuit 18 and the bridge intermediate circuit 22, thus deactivating the conductive connection between these center points. Therefore, the DC intermediate circuit 18 is no longer effectively split, but behaves like a single capacitor. Because the connection of the intermediate circuit center points is thus disconnected in the fault condition, charge transfer between portions of the capacitance of the DC intermediate circuit 18 and the portion of the capacitance of the bridge intermediate circuit 22 is particularly prevented.
[0073] exist Figure 7 A fifth embodiment of the DC / DC converter 20 is shown. In this embodiment, the DC intermediate circuit 18 is split and has two intermediate circuit halves. The DC / DC converter 20 shown is, for example, a symmetrical DC / DC converter 20. The DC / DC converter 20 has clock-controlled semiconductor switches 70.1, 70.2, 70.3, and 70.4, which are clock-controlled during power transfer between the AC terminal ACA and the DC terminal DCA, and thus set the voltage ratio between the two sides of the DC / DC converter 20.
[0074] exist Figure 7 In the embodiment shown, the center points of the split intermediate circuits 18 and 22 are connected via RC member 72. Alternatively, the connection can be achieved via resistors or capacitors only.
[0075] A diode bridge is arranged in anti-parallel to the DC intermediate circuit 18. In the fifth embodiment of the DC / DC converter 20 shown, two additional semiconductor switches 34 are inserted into the corresponding DC conductors of the DC / DC converter 20. These semiconductor switches are not clock-controlled. The additional semiconductor switches 34 are arranged in series with the inductor of the DC / DC converter 20 and can be turned on under ground short-circuit conditions EF3, EF4. Since the additional semiconductor switches 34 block the inductor-driven current in the DC conductor when turned on, a freewheeling path is provided via the diode bridge.
[0076] During the power transfer and the setting of the voltage conversion ratio of the DC / DC converter 20 by the clock-controlled semiconductor switches 70.1, 70.2, 70.3, and 70.4, an additional semiconductor switch 34 is closed, thereby establishing a conduction connection through them.
[0077] The connection between the center point of the DC intermediate circuit 18 and the bridge intermediate circuit 22 via the RC member 72 can also be referred to as a soft connection. The RC member 72 attenuates resonances that may occur under other conditions and simultaneously limits the current to much lower values under fault conditions EF3 and EF4. Here, the inductors arranged in the DC / DC converter 20 can be constructed, for example, as coupled chokes, because they reduce interference excitation through coupling.
[0078] Figure 7 The fifth embodiment of the DC / DC converter 20 shown operates such that, when exchanging electrical power, the DC / DC converter generates a voltage conversion ratio between the DC intermediate circuit 18 and the bridge intermediate circuit 22 by means of clock-controlled semiconductor switches 70.1, 70.2, 70.3, and 70.4, such that the DC voltage UDC is limited to less than half of the bridge DC voltage UBR. In this operation mode of the fifth embodiment, the additional semiconductor switch 34 can optionally be omitted. In this operation mode, the freewheeling diode of the clock-controlled semiconductor switch 70.4 blocks half of the bridge voltage UBR / 2 when the ground short circuit EF3 and EF4 is applied, thereby preventing current from flowing through the clock-controlled semiconductor switch 70.4. The anode potential of the body diode of the clock-controlled semiconductor switch 70.1 is approximately higher than the DC voltage UDC than the ground potential EP, while the cathode potential is approximately half of the bridge DC voltage UBR / 2 than the ground potential EP. If the DC voltage UDC is less than half of the bridge DC voltage UBR / 2, the clock-controlled semiconductor switch 70.1 is turned off, and the circuit can thus operate without grounding short circuits.
[0079] Optionally, having according to Figures 3 to 7One of the DC / DC converters 20, the power converter 10, can operate such that the voltage of each half of the bridge intermediate circuit 22 is higher than the DC voltage UDC. Therefore, the freewheeling diodes of the DC / DC converter 20 are reliably cut off, and no corresponding ground current flows even under ground fault conditions EF1, EF2, EF3, EF4. In this operating mode, even under ground fault conditions EF1, EF2, EF3, EF4, the half of the bridge intermediate circuit will not be charged to the (however low) DC voltage UDC. Thus, the operation of the inverter is limited, as only half of the technically possible DC voltage UDC at a given bridge DC voltage UBR can be achieved as the battery voltage UB. However, the advantage of improved ground fault safety is provided. In particular, if the bridge circuit 16 is designed for a high bridge DC voltage UBR (e.g., 1500V), half of this (maximum) bridge DC voltage UBR on the DC intermediate circuit 18 is sufficient to charge the battery 14, which may have a maximum voltage of, for example, 400V, for a stationary or mobile battery system BS. For this operating mode, Figures 3 to 7 The DC / DC converter 20 may also be implemented without additional semiconductor switches 24, 26, 28, 32, 34.
[0080] according to Figures 3 to 7 The implementation methods can be combined to further improve fault tolerance.
[0081] exist Figure 8 The abstract form shows the basis Figure 1 The system. The DC intermediate circuit 18 is non-split type. Regarding the DC / DC converter 20, equivalent diodes ED1, ED2, ED3, and ED4 are additionally shown. These equivalent diodes ED1, ED2, ED3, and ED4 represent the symbolic equivalent circuit diagrams of the diodes of the clock-controlled semiconductor switches 30.1, 30.2, 30.3, 30.4 or 40.1, 40.2, 40.3 or 50.1, 50.2, 50.3, 50.4. See [link to diagram]. Figures 3 to 5Therefore, the DC / DC converter 20 of the first embodiment has clock-controlled semiconductor switches 30.1, 30.2, 30.3, and 30.4. The DC / DC converter 20 of the second embodiment has clock-controlled semiconductor switches 40.1, 40.2, and 40.3. The DC / DC converter 20 of the third embodiment has clock-controlled semiconductor switches 50.1, 50.2, 50.3, and 50.4. When the DC / DC converter 20 does not include the additional semiconductor switches according to this application, or when these additional semiconductor switches are in a closed state, the diodes of these clock-controlled semiconductor switches of the DC / DC converter 20 establish a unidirectional connection between the positive or negative DC wires on both sides of the DC / DC converter 20.
[0082] If a ground fault EF1 or EF2 occurs at the DC terminal DCA or at battery 14 of the battery system BS (e.g., in or at the traction battery of an electric vehicle), a low-impedance connection is established, particularly between one of the DC conductors between the power converter 10 and the battery system BS, and ground potential EP. In this case, various ground fault currents may occur. Here, the ground fault current flows through a circuit originating from the affected DC conductor, via ground potential EP, a given ground reference of the AC voltage network 12, bridge circuit 16, and DC / DC converter 20. In particular, the ground fault current may flow here via an explicit or implicit connection between the protective conductor PE of the AC voltage network 12 and the center point of the bridge intermediate circuit 22. Via DC / DC converter 20, the ground fault current may flow here via equivalent diodes ED1, ED2, ED3, and ED4 of DC / DC converter 20.
[0083] exist Figure 8In the example shown where a ground short circuit EF2 occurs on the negative DC conductor, the negative terminal of battery 14 (via ground short circuit EF2) and the center of bridge intermediate circuit 22 (via the ground reference of bridge circuit 16) are both at ground potential. Therefore, the upper half of bridge intermediate circuit 22 is effectively directly connected to battery 14 via equivalent diode ED2 and ground short circuit EF2, and is charged to the full battery voltage UB by the ground fault current flowing through the switch of DC / DC converter 20 corresponding to equivalent diode ED2. The fault current path here is from the positive terminal of battery 14 via the positive DC conductor, load switch S1, equivalent diode ED2, the upper half of the bridge intermediate circuit capacitor, bridge circuit 16, AC voltage network 12, protective conductor PE, and via ground short circuit fault EF2 to the negative terminal of battery 14. Here, equivalent diode ED2 can correspond to the body diode of clock-controlled semiconductor switch 30.1, 40.1, or 50.1. The ground fault current can be avoided by opening at least one additional semiconductor switch 24, 26, 28, in such a way that the additional semiconductor switch, according to Figures 3 to 5 The current path between the corresponding terminals of intermediate circuits 18 and 22 is interrupted. By saying that opening, the at least one additional semiconductor switch 24, 26, 28 takes advantage of the potential difference between the upper half of the bridge intermediate circuit 22 and the battery 14 due to the ground fault EF2 as a blocking voltage.
[0084] In the event of a ground short circuit EF1 on the positive DC conductor, both the positive terminal of battery 14 (via the ground short circuit EF1) and the center of bridge intermediate circuit 22 (via the ground reference of bridge circuit 16) are at ground potential. Consequently, the lower half of bridge intermediate circuit 22 is effectively directly connected to battery 14 via equivalent diode ED3 and ground short circuit EF1, and is charged to the full battery voltage UB by the ground fault current flowing through the switch of DC / DC converter 20 corresponding to equivalent diode ED3. The fault current path here is from the negative terminal of battery 14 via the negative DC conductor, load switch S2, equivalent diode ED3, the lower half of the bridge intermediate circuit capacitor, bridge circuit 16, AC voltage network 12, protective conductor PE, ground EP, and via ground short circuit fault EF1 to the positive terminal of battery 14. Here, equivalent diode ED3 can correspond to the body diode of clock-controlled semiconductor switches 30.4, 40.3, or 50.4. The ground fault current can be avoided by opening at least one additional semiconductor switch 24, 26, 28, in such a way that the additional semiconductor switch, according to Figures 3 to 5The current path between the corresponding terminals of intermediate circuits 18 and 22 is interrupted. By saying that opening, the at least one additional semiconductor switch 24, 26, 28 takes advantage of the potential difference between the lower half of the bridge intermediate circuit 22 and the battery 14 due to the ground fault EF1 as a blocking voltage.
[0085] exist Figure 9 The abstract form shows the basis Figure 2 The system. The DC intermediate circuit 18 is split. Regarding the DC / DC converter 20, equivalent diodes ED1, ED2, ED3, and ED4 are additionally shown. These equivalent diodes represent the symbolic equivalent circuit diagrams of the diodes for the clock-controlled semiconductor switches 60.1, 60.2, 60.3, 60.4 or 70.1, 70.2, 70.3, 70.4; see [link to diagram]. Figure 6 and Figure 7 Therefore, the DC / DC converter 20 of the fourth embodiment has clock-controlled semiconductor switches 60.1, 60.2, 60.3, and 60.4. The DC / DC converter 20 of the fifth embodiment has clock-controlled semiconductor switches 70.1, 70.2, 70.3, and 70.4. When the DC / DC converter 20 does not include the additional semiconductor switches according to this application, or when these additional semiconductor switches are in a closed state, the diodes of these clock-controlled semiconductor switches of the DC / DC converter 20 establish a unidirectional connection between the positive or negative DC wires on both sides of the DC / DC converter 20.
[0086] If a ground fault EF4 occurs at the DC terminal DCA or the battery 14 of the battery system BS (e.g., the traction battery of an electric vehicle), a low-impedance connection is established, particularly between one of the DC conductors between the power converter 10 and the battery system BS, and the ground potential EP. In this case, various ground fault currents may occur. Here, the ground fault current flows through a circuit originating from the affected DC conductor, via the ground potential EP, the given ground reference EP of the AC voltage network 12, the bridge circuit 16, and the DC / DC converter 20. Specifically, the ground fault current can flow here via an explicit or implicit connection between the protective conductor PE of the AC voltage network 12 and the center point of the bridge intermediate circuit 22. Via the DC / DC converter 20, the ground fault current can flow here either via a direct connection (particularly a direct connection between their center points) between the DC intermediate circuit 18 and the bridge intermediate circuit 22, or via the equivalent diodes ED1, ED2, ED3, and ED4 of the DC / DC converter 20.
[0087] exist Figure 9In the example shown, a ground fault EF4 occurring on the negative DC conductor at the DC terminal DCA of the split DC intermediate circuit 18 causes the lower half of the DC intermediate circuit 18 to be effectively short-circuited, thereby discharging the energy stored therein as a ground fault current. The fault current path returns from the negative DC conductor via the lower DC intermediate circuit capacitor, the connection of the intermediate circuit center point in the DC / DC converter 20, the bridge circuit 16, the AC voltage network 12, the protective conductor PE, the ground potential EP, and the ground fault EF4. The lower half of the DC intermediate circuit is thus short-circuited when the ground fault EF4 occurs and discharges via the ground potential EP. This fault current path is interrupted by opening an additional semiconductor switch 32, which withstands half of the DC intermediate circuit voltage UDC / 2 as a blocking voltage due to the short circuit caused by the ground fault EF4.
[0088] The ground fault EF4 on the negative DC conductor also causes the upper half of the DC intermediate circuit 18 to be effectively connected in series with the battery 14. This generates a ground fault current that charges the upper half of the DC intermediate circuit 18 from approximately half of the DC voltage UDC to the full battery voltage UB. The fault current path here is from the positive terminal of the battery 14 via the positive DC conductor, the upper DC intermediate circuit capacitor, the connection of the intermediate circuit center point in the DC / DC converter 20, the center point of the bridge intermediate circuit 22, the bridge circuit 16, the AC voltage network 12, the protective conductor PE, the ground potential EP, and the ground fault EF4 to the negative terminal of the battery 14. This ground fault current can be avoided by opening an additional semiconductor switch 32, which interrupts the current path between the center points of intermediate circuits 18 and 22 and absorbs the potential difference between the upper half of the bridge intermediate circuit 22 and the battery 14 caused by the ground fault EF4 as a blocking voltage.
[0089] Similarly, fault currents may occur when a ground short circuit EF3 occurs. Here, the corresponding other half of the DC intermediate circuit 18 is discharged or charged to the battery voltage UB. These fault currents can also be avoided by opening another semiconductor switch 32.
[0090] In addition to reference Figure 9 In addition to the fault current described, which can be avoided by another semiconductor switch 32, Figure 9 The system shown can also avoid combining Figure 8 The fault current via equivalent diodes (e.g., ED2 and / or ED3) is described in detail. For this purpose, the DC voltage UDC can be limited to less than half of the bridge DC voltage UBR / 2, or an additional semiconductor switch 34 can be used to interrupt the connection between the corresponding terminals of the bridge intermediate circuit 22 and the corresponding terminals of the DC intermediate circuit 18.
[0091] Otherwise, the described ground fault current flow—whether individually or in aggregate—could reach amplitudes unacceptable for standard reasons, damaging components and posing a potential health hazard, especially in the presence of personnel. Furthermore, resonant oscillations may occur between the capacitors and inductors involved in the power converter 10, which additionally increase the amplitude of the ground fault current. The described ground fault current flow can be reliably avoided by the described power converter and the described method.
[0092] List of reference numerals 10 Power Converter 12 Three-phase AC voltage network 14 batteries 16 Bridge circuit 18 DC intermediate circuits 20 DC / DC converters 22 Bridge intermediate circuit 31 Controller 24, 26, 28, 32, 34 Other semiconductor switches 30.1, 30.2, 30.3, 30.4 Clock-controlled semiconductor switches 40.1, 40.2, 40.3 Clock-controlled semiconductor switches 50.1, 50.2, 50.3, 50.4 Clock-controlled semiconductor switches 60.1, 60.2, 60.3, 60.4 Clock-controlled semiconductor switches 70.1, 70.2, 70.3, 70.4 Clock-controlled semiconductor switches UB battery voltage BSS1, BSS2 Battery System Relays BS Battery System Grounding faults at EF1, EF2, EF3, and EF4 DCA DC terminal ACA AC terminal S1, S2 switch relay UDC DC voltage UBR bridge voltage N neutral conductor PE protective conductor L1, L2, L3 conductors Equivalent diodes of ED1, ED2, ED3, and ED4 EP ground, ground potential
Claims
1. A power converter (10) for ground fault-safe power exchange between a three-phase AC voltage network (12) and a battery (14), wherein, The power converter (10) has an AC terminal (ACA), a DC terminal (DCA), a bridge circuit (16), and a DC / DC converter (20), wherein the AC terminal (ACA) is configured to be connected to the AC voltage network (12), and the DC terminal (DCA) is configured to be connected to the battery (14), wherein a DC intermediate circuit (18) with an applied DC voltage (UDC) is arranged between the DC / DC converter (20) and the DC terminal (DCA), and a bridge intermediate circuit (22) with an applied bridge DC voltage (UBR) is arranged between the DC / DC converter (20) and the bridge circuit (16), wherein the DC / DC converter (20) has a clock-controlled semiconductor switch (30.1-3). 0.4, 40.1-40.3, 50.1-50.4, 60.1-60.4, 70.1-70.4), the clock-controlled semiconductor switch is configured to generate a voltage conversion ratio between the DC intermediate circuit (18) and the bridge intermediate circuit (22) when exchanging electrical power, wherein the DC / DC converter (20) has at least one additional semiconductor switch (24, 26, 28, 32, 34) with a controller (31) configured to establish a connection between the DC intermediate circuit (18) and the bridge intermediate circuit (22) by manipulating the additional semiconductor switch (24, 26, 28, 32, 34) when exchanging electrical power and to interrupt the connection in the event of a ground fault (EF1, EF2, EF3, EF4).
2. The power converter according to claim 1, wherein, The battery (14) is arranged in a stationary or mobile battery system (BS) or is configured as a traction battery for an electric vehicle (EV).
3. The power converter according to claim 1 or 2, wherein, The power converter (10) is configured to charge the battery (14) from the AC voltage network (12) when exchanging electrical power.
4. The power converter according to any one of the preceding claims, wherein, The bridge intermediate circuit (22) is constructed as a split intermediate circuit.
5. The power converter according to any one of the preceding claims, wherein, The DC / DC converter (20) is configured as a symmetrical DC / DC converter.
6. The power converter according to claim 5, wherein, The DC intermediate circuit (18) is configured as a split intermediate circuit.
7. The power converter according to claim 6, wherein, The at least one additional semiconductor switch (32) is configured to establish a connection between the center potential of the split DC intermediate circuit (18) and the center potential of the split bridge intermediate circuit (22) when exchanging electrical power and to interrupt the connection in the event of a ground fault (EF1, EF2, EF3, EF4).
8. The power converter according to any one of claims 1 to 6, wherein, Two additional semiconductor switches (24, 26, 34) are provided, each of which is assigned to a terminal of the DC intermediate circuit (18). The additional semiconductor switches are configured to establish a corresponding connection between the corresponding terminal of the DC intermediate circuit (18) and the corresponding terminal of the bridge intermediate circuit (22) via one of the semiconductor switches (30.1, 30.4, 40.1, 40.3, 70.1, 70.4) controlled by the clock of the DC / DC converter (20) when exchanging electrical power, and to interrupt the corresponding connection in the event of a ground fault (EF1, EF2, EF3, EF4).
9. The power converter according to any one of claims 1 to 6, wherein, Two additional semiconductor switches (28) are provided, each assigned to a terminal of the bridge intermediate circuit (22), and the additional semiconductor switches are configured to establish a corresponding connection between the corresponding terminal of the bridge intermediate circuit (22) and the corresponding terminal of the DC intermediate circuit (18) via one of the clock-controlled semiconductor switches (50.1, 50.4) of the DC / DC converter when exchanging electrical power, and to interrupt the corresponding connection in the event of a ground fault (EF1, EF2, EF3, EF4).
10. The power converter according to any one of the preceding claims, wherein, The DC / DC converter (20) is configured to generate the voltage conversion ratio such that the DC voltage (UDC) is less than the bridge DC voltage (UBR).
11. The power converter according to any one of the preceding claims, wherein, The DC voltage (UDC) is limited to less than half of the bridge DC voltage (UBR).
12. The power converter according to any one of the preceding claims, wherein, The three-phase AC voltage network (12) has a fixed reference relative to the ground potential, and the ground faults (EF1, EF2, EF3, EF4) are characterized by a low-impedance connection from one of the DC conductors at the DC terminal (DCA) to the ground potential.
13. A method for ground fault-safe power exchange between a three-phase AC voltage network (12) and a battery (14) by means of a power converter (10), wherein, The power converter (10) has a bridge circuit (16) and a DC / DC converter (20), wherein a DC intermediate circuit (18) with a DC voltage (UDC) is arranged between the DC / DC converter (20) and the battery (14), and a bridge intermediate circuit (22) with a bridge DC voltage (UBR) is arranged between the DC / DC converter (20) and the bridge circuit (16). In this circuit, the DC / DC converter (20) uses clock-controlled semiconductor switches (30.1-30.4, 40.1-40.3, 50.1-50.4, 60.1-60.4, 70.1-70.4) to generate a voltage conversion ratio between the DC intermediate circuit (18) and the bridge intermediate circuit (22) when exchanging electrical power. At least one additional semiconductor switch (24, 26, 28, 32, 34) establishes a connection between the DC intermediate circuit (18) and the bridge intermediate circuit (22) when exchanging electrical power, and interrupts the connection by opening the at least one additional semiconductor switch (24, 26, 28, 32, 34) in the event of a ground fault (EF1, EF2, EF3, EF4).
14. A method for ground fault-safe power exchange between a three-phase AC voltage network (12) and a battery (14) by means of a power converter (10), wherein, The power converter (10) has a bridge circuit (16) and a DC / DC converter (10), wherein a DC intermediate circuit (18) with a DC voltage (UDC) is arranged between the DC / DC converter (20) and the battery (14), and a bridge intermediate circuit (22) with a bridge DC voltage (UBR) is arranged between the DC / DC converter (20) and the bridge circuit (16), wherein the center potentials of the DC intermediate circuit (18) and the bridge intermediate circuit (22) are interconnected via an RC member (72), wherein the DC / DC converter (20) generates a voltage conversion ratio between the DC intermediate circuit (18) and the bridge intermediate circuit (22) by means of a clock-controlled semiconductor switch (70.1-70.4) when exchanging electrical power, such that the DC voltage (UDC) is limited to less than half of the bridge DC voltage (UBR).
15. The method according to claim 14, wherein, At least one additional semiconductor switch (34) establishes a connection between the DC intermediate circuit (18) and the bridge intermediate circuit (22) when exchanging electrical power, and interrupts the connection by opening the at least one additional semiconductor switch (34) in the event of a ground fault (EF2, EF3, EF4).
16. The method according to any one of claims 13 to 15, wherein, When exchanging electrical power, the battery (14) is charged from the AC voltage network (12).
17. The method according to any one of claims 13 to 16, wherein, The bridge intermediate circuit (22) is configured as a split intermediate circuit, and the DC / DC converter (20) is configured as a symmetrical DC / DC converter.
18. The method according to any one of claims 13, 16 or 17, wherein, The DC intermediate circuit (18) is configured as a split intermediate circuit, and the at least one additional semiconductor switch (32) establishes a connection between the center potential of the split DC intermediate circuit (18) and the center potential of the split bridge intermediate circuit (22) when exchanging electrical power, and interrupts the connection by opening the at least one additional semiconductor switch (32) in the event of a ground fault (EF1, EF2, EF3, EF4).
19. The method according to any one of claims 13 to 17, wherein, Two additional semiconductor switches (24, 26, 34) are provided, each of which is assigned to a terminal of the DC intermediate circuit (18). When exchanging power, the respective additional semiconductor switches (24, 26, 34) establish a corresponding connection between the corresponding terminal of the DC intermediate circuit (18) and the corresponding terminal of the bridge intermediate circuit (22) via one of the clock-controlled semiconductor switches (30.1, 30.4, 40.1, 40.3, 70.1, 70.4) of the DC / DC converter (20), and interrupt the corresponding connection by opening the respective additional semiconductor switches (24, 26, 34) in the event of a ground fault (EF1, EF2, EF3, EF4).
20. The method according to any one of claims 13, 16 or 17, wherein, Two additional semiconductor switches (28) are provided, each of which is assigned to a terminal of the bridge intermediate circuit (22). When exchanging power, the respective additional semiconductor switches (28) establish a corresponding connection between the corresponding terminal of the bridge intermediate circuit (22) and the corresponding terminal of the DC intermediate circuit (18) via one of the clock-controlled semiconductor switches (50.1, 50.4) of the DC / DC converter (20), and interrupt the corresponding connection by opening the respective additional semiconductor switches (28) in the event of a ground fault (EF1, EF2, EF3, EF4).
21. The power converter (10) according to any one of claims 1 to 12 is used for charging the battery (14) of a stationary or mobile battery system (BS) or the traction battery of an electric vehicle (EV).