Power control device for an electric machine and method for disconnecting an electric machine from an electrical energy storage device

Abstract

Power control device (LS) for an electric machine (EM) with a DC voltage terminal (GA) and an inverter (IN) connected between the DC voltage terminal (GA) and an AC voltage terminal (WA) for connecting the electric machine (EM) and comprising a semiconductor bridge circuit (11-23; H1-H24), wherein the power control device comprises a controller (C, C1) connected to the semiconductor bridge circuit (11-23; H1-H24) for control purposes, wherein the semiconductor bridge circuit (11-23; H1, H11, H21) comprises at least one first semiconductor switch (11-13; H1, H11, H21) located between the AC voltage terminal (WA) and a first potential (P; EA1) of the DC voltage terminal (GA), and the power control device (LS) further comprises at least one second semiconductor switch (S1) connected anti-series to the at least one first semiconductor switch (11-13; H1-H21) and connected to the first potential (P; EA1) of the DC voltage terminal, wherein the controller (C; C1, C2) further comprises a disconnect signal input (FE) configured to receive a disconnect signal in the form of an error signal and the controller (C; C1, C2) is configured to permanently open the at least one first semiconductor switch and the at least one second semiconductor switch when the error signal occurs and wherein the power control device further comprises a DC-DC converter via which the DC-DC terminal (GA) is connected to the inverter (IN) and wherein the at least one first semiconductor switch (H11) is part of the semiconductor bridge circuit and the at least one second semiconductor switch (S1) is part of the DC-DC converter.

Description

[0001] It is known to equip a vehicle with an electric drive, with an electrical energy storage device in the form of an accumulator supplying the energy to operate the electric drive. Relatively high power levels are required to propel a vehicle, so the drive must also be designed for this power. In order to reduce the conductor diameter and the current to be controlled while maintaining the same (high) power, relatively high operating voltages are used for electric drives and their energy storage devices. For example, voltage levels of more than 300 volts can occur, in particular more than 350 volts, for example 400 volts, or even 600 volts, or 800 volts.

[0002] Since these high voltages pose a high safety risk, care must be taken to ensure that the contact voltage is safe, for example during maintenance or in the event of an accident.

[0003] The publication DE 10 2016 209 905 A1 describes an inverter with at least two phase current terminals connected to the electrical machine. Disconnectors are provided that can disconnect the phases of the electrical machine in a controlled manner, for example, to disconnect a star point of the electrical machine.

[0004] The publication DE 10 2014 211 207 A1 describes a converter circuit with bidirectional switches connected in series between a central potential terminal of a DC power supply and a converter circuit. These switches can be opened in the event of a short circuit.

[0005] In order to ensure that the contact voltage is safe, contactors are used, i.e. electromechanical switches that separate the energy storage device from the rest of the vehicle's electrical system.

[0006] Such electromechanical switches must be designed for high holding currents (corresponding to the maximum traction power) and, in particular, high switching capacities to ensure reliable switching and interrupt the current flow. This is associated with high costs, even if switching events are rare and limited to maintenance or accidents.

[0007] It is an object of the invention to show a possibility with which in particular the costs for the realization of a reliable separation process can be reduced.

[0008] This object is achieved by the power control device and by the method according to the independent claims. Further embodiments, features, properties, and advantages will become apparent from the description and the accompanying figures.

[0009] It is proposed to use semiconductor switches that already perform the functions of an inverter and / or a DC-DC converter to disconnect the electrical energy storage device. This allows at least one potential of the energy storage device to be disconnected without the need for an electromechanical isolating switch (to disconnect this potential). At least one of the two isolating switches (one isolating switch per potential of the energy storage device) can be omitted. To prevent current flow in both directions (relative to the energy storage device), two semiconductor switches that are arranged anti-serially to each other are opened when a fault signal is present. Both semiconductor switches are part of an inverter or part of an inverter and a DC-DC converter. The two semiconductor switches (i.e.The first and second semiconductor switches (i.e., the first and second semiconductor switches) are connected in series (directly or indirectly) between an AC terminal and a DC terminal of the power control device. In a current path leading from the AC terminal to the DC terminal, the two semiconductor switches (i.e., the first and second semiconductor switches) are connected in series and are anti-serial to each other. In other words, the operating directions of the first and second semiconductor switches, in which they are controllable by external signals, are opposite to each other, with the operating directions being considered in a current path leading from the AC terminal to the DC terminal.

[0010] It is possible for both (i.e., the at least one first and the at least one second) of the anti-serially connected semiconductor switches to be part of the bridge circuit of an inverter. The power control device provides that one of these two semiconductor switches (namely, the at least one first semiconductor switch) is part of the bridge circuit of the inverter, and the at least one other semiconductor switch (namely, the second) can be part of a DC-DC converter. Such a DC-DC converter can be connected, for example, between the energy storage device and the inverter, for example to bring the operating voltage of the inverter to a desired level or to keep it constant.

[0011] A power control device for an electrical machine is described. In particular, this relates to a power control device in a vehicle electrical system. The electrical machine can be an electrical machine of a traction drive, a starter generator, or another component, for example, an electric air conditioning compressor. The power control device has a DC voltage connection and an inverter. The inverter is provided between the DC voltage connection and an AC voltage connection of the power control device. The AC voltage connection is provided for connecting the electrical machine. The power control device is provided for an electrical machine in that the power control device has an inverter that can output (or also receive) a three-phase current at the AC voltage connection. The inverter has a semiconductor bridge circuit.The inverter is unidirectional or bidirectional and is particularly designed to generate an alternating voltage, in particular a three-phase current, at the AC voltage terminal from a direct voltage present at the DC voltage terminal or at a DC voltage side of the inverter. For this purpose, the individual semiconductor switches of the semiconductor bridge circuit are specifically controlled in a known manner.

[0012] The power drive device comprises at least one controller. This controller is drivingly connected to the semiconductor bridge circuit, in particular to its semiconductor switches. The controller has an isolating signal input at which an isolating signal can be received, wherein the controller is configured to open the at least one first and the at least one second semiconductor switch upon receipt of an isolating signal. The controller (or another controller), together with the semiconductor bridge circuit, is configured to convert a DC voltage at the DC voltage terminal into a three-phase current for delivery to the AC voltage terminal. It is possible for the inverter to be connected directly to the DC voltage terminal, i.e., without changing the voltage level. However, the power drive device provides for the inverter to be connected indirectly to the DC voltage terminal via a DC-DC converter.The controller is preferably configured to control the semiconductor bridge circuit, converting a direct current at the direct voltage terminal into a three-phase current for output at the alternating voltage terminal. However, this function can also be implemented in another controller, which is preferably connected to the controller configured to open semiconductor switches upon the occurrence of a disconnect signal, or operates in coordination with it via a common (higher-level) control unit.

[0013] The semiconductor bridge circuit has at least one first semiconductor switch connected between the AC voltage terminal and a first potential of the DC voltage terminal. In other words, the at least one first semiconductor switch is connected between the AC voltage terminal and a potential rail having the first potential. At least one second semiconductor switch of the power control device is connected anti-serially to the at least one first semiconductor switch. The first and second semiconductor switches are connected in series one after the other between the DC voltage terminal and the AC voltage terminal (directly or indirectly via another component, such as an inductor). The at least one second semiconductor switch is connected to the first potential (i.e., to a first potential rail) of the DC voltage terminal.The at least one first and at least one second semiconductor switch are provided in series between the DC voltage terminal and the AC voltage terminal.

[0014] The controller has an isolating signal input. This is set up to receive an isolating signal. The isolating signal corresponds to an error signal which represents an error which requires the electrical machine to be disconnected. The controller is set up to open the at least one first semiconductor switch and the at least one second semiconductor switch when the isolating signal occurs. The isolating signal can be represented, for example, by a specific level or by a specific signal sequence. The controller can be composed of one or more individual control elements, wherein each control element has such an isolating signal input. In particular when the at least one first semiconductor switch is in another bridge circuit oris provided on a different component than the at least one second semiconductor switch, then multiple control elements can be provided (preferably one per component), each of which has a corresponding isolation signal input. A higher-level control unit can also be provided, to which the control unit(s) is / are subordinate.

[0015] According to a first possibility, it is conceivable that the at least one first semiconductor switch and the at least one second semiconductor switch are provided in the same component (and in particular are configured to jointly implement a function). Therefore, the at least one first semiconductor switch and the at least one second semiconductor switch can be part of the semiconductor bridge circuit or each part of the inverter. The semiconductor bridge circuit therefore has at least two semiconductor switches that are connected anti-serially to one another between the AC voltage connection and the DC voltage connection. The semiconductor switches are, in particular, switches that can be controlled by external signals. The semiconductor switches are, in particular, configured to control (in particular to switch) current in a flow direction according to a signal at a control input.Furthermore, the semiconductor switch may not be able to control the current flow according to an external control signal in an opposite current flow direction, particularly if the semiconductor switch has inverse diodes or body diodes that bridge the relevant switching element opposite to the flow direction (in controllable operation). This is the case, for example, with field-effect transistors such as MOSFETs and IGBTs. Field-effect transistors such as MOSFETs or IGBTs are therefore preferably used as semiconductor switches in the power control device mentioned here (and the method mentioned here). In order to prevent current flow in both directions, at least one first and at least one second semiconductor switch are provided, which are connected in series but opposite to one another in their operating direction (in which control of the current flow is possible by means of external signals).In other words, the source-drain and collector-emitter directions of the first and second semiconductor switches can be opposite to each other. Such an anti-serial series connection refers to the consideration of current flow between the AC voltage terminal and the DC voltage terminal.

[0016] It is possible for the semiconductor bridge circuit to be, in particular, an H-bridge circuit. The at least one first semiconductor switch and the at least one second semiconductor switch are part of this H-bridge circuit. In this way, only one controller can be provided, namely the one that controls the semiconductor switches of the H-bridge circuit and which further has an isolating signal input, as described herein. As a result, the at least one first and the at least one second semiconductor switches are given a further function, namely the function of isolating the electrical machine from the energy storage device or from the DC voltage connection, in addition to the usual function of the inverter of generating a three-phase current at the AC voltage connection from the DC voltage at the DC voltage connection.

[0017] An H-bridge circuit comprises two series circuits or branches for each phase of the AC voltage connection.

[0018] Each series circuit comprises two semiconductor switches connected in series, which extend in particular between the two supply potentials of the DC voltage connection (e.g., ground and a positive supply potential). The at least one first semiconductor switch and the at least one second semiconductor switch belong to the same phase and are assigned to different series circuits (of the same phase). The first and second semiconductor switches are connected to the same supply potential, in particular to the positive supply potential of the inverter.

[0019] The AC voltage connection has several phases, with each phase being connected to a connection point between two series-connected semiconductor switches. The H-bridge circuit comprises a full-bridge circuit for each phase, with the bridge between the two branches (which are each provided by two series-connected semiconductor switches) being formed by an inductor. One of the two branches is connected to the DC voltage connection (directly or indirectly via a DC-DC converter), while the other series circuit of the same phase is connected to a phase of the AC voltage connection (or the electrical machine). In particular, the first and second semiconductor switches are connected in series for one phase, for several phases, or for all phases, in particular via the inductor or via the bridge that connects the two branches of the H-bridge circuit.

[0020] Apart from the first possibility mentioned above, the power control device provides that the at least one first semiconductor switch is part of the inverter or the semiconductor bridge circuit, and the at least one second semiconductor switch belongs to a different component (and in particular a different function) and is part of a DC-DC converter. Therefore, the power control device can comprise a further component in the form of a DC-DC converter, wherein this component is connected in series between the DC voltage input (for connecting the energy storage device) and the inverter. The DC-DC converter or this component has semiconductor switches, at least one of which forms the second semiconductor switch. In other words, the at least one second semiconductor switch is part of the DC-DC converter or this component. The first semiconductor switch is part of the semiconductor bridge circuit or part of the inverter.The DC-DC converter is, in particular, a synchronous converter with two semiconductor switches connected in series. The ends of the resulting series circuit are connected to the inverter or its DC side.

[0021] The DC-DC converter further comprises an energy storage device, for example in the form of an inductance or a capacitor. In particular, an inductance of the DC-DC converter can be connected between the first potential or the DC voltage connection of the power control device and the connection point of the two semiconductor switches, which, as mentioned, are connected in series. A controller can be provided which controls both the component or the DC-DC converter and the inverter, and which further comprises an isolating signal input. Such a controller is designed to open at least one first and at least one second semiconductor switch upon receipt of an isolating signal or an error signal. Furthermore, a first controller can be provided which controls the semiconductor switches orcontrols the bridge circuit of the inverter, and a second controller can be provided which controls the semiconductor switches of the DC-DC converter or the component. Both controllers preferably each have an isolating signal input. Both controllers are configured to open the respective semiconductor switches upon receipt of an isolating signal or an error signal. The first component is configured to open the at least one first semiconductor switch when an isolating signal is received. The second controller is configured to open the at least one second semiconductor switch when an isolating signal is received.

[0022] Finally, a higher-level control unit can be provided, as well as a first and a second controller, wherein the first controller controls the semiconductor switches of the component or the DC-DC converter, and the second controller controls the semiconductor switches of the inverter or its bridge circuit. The first and the second controller are connected downstream of the higher-level control unit. The higher-level control unit can have an isolating signal input. The higher-level control is connected to the first and the second controller in a controlling manner. The first and the second controller, as well as the higher-level control unit, are configured to open the at least one first semiconductor switch and the at least one second semiconductor switch upon receipt of an error signal or isolating signal (in particular at the isolating signal input of the higher-level control unit).

[0023] The semiconductor bridge circuit (of the inverter) can be a fully controlled three-phase bridge circuit. For each phase, two semiconductor switches are connected in series and connected to the DC voltage terminal. The AC voltage terminals correspond to the connection points between the semiconductor switches. In particular, the semiconductor bridge circuit is a B6C pushbutton or, more generally, a BnC bridge, where n represents the number of phases multiplied by two. The capital letter C in this abbreviation indicates that the switching elements of the bridge circuit can be controlled by external signals. Here, too, the semiconductor switches are preferably field-effect transistors such as MOSFETs or IGBTs. The at least one first semiconductor switch is connected between the DC-DC converter and the AC voltage terminal.The at least one first semiconductor switch is thus a switch in the series circuit of two switches, which constitutes one branch or phase of the full-bridge circuit. The at least one second semiconductor switch is part of the DC-DC converter or a component connected between the semiconductor bridge circuit of the inverter and the DC voltage terminal. In particular, the at least one second semiconductor switch is connected to the first potential via the storage element (of the DC-DC converter, which forms the component). The storage element is, in particular, an inductor, via which the semiconductor switches of the DC-DC converter are connected to the first potential.

[0024] The first potential is, in particular, the positive potential of the energy storage device (which feeds the inverter). Ground can be used, in particular, as the second potential of the DC voltage connection. Provision can be made for an electromechanical or other element to interrupt the connection between the ground connection of the energy storage device and the inverter (in particular between the energy storage device connection and the DC-DC converter, if present). Provision can be made for at least one of the controllers or the higher-level control unit to open this isolating switch at the second potential (downstream of the ground connection of the energy storage device) upon receipt of a corresponding isolating signal or error signal, preferably simultaneously with the opening of the first and second semiconductor elements.The energy storage device is preferably a high-voltage energy storage device with an operating voltage of over 60 volts, in particular over 120 volts, and preferably over 300 or 360 volts. For example, the operating voltage of the energy storage device can be 400 volts, 600 volts, or even 800 volts. The energy storage device is, for example, a lithium-based battery with several galvanic cells connected in series (based on lithium technology). The energy storage device is, in particular, a traction storage device of the vehicle's electrical system.

[0025] The controller, the controllers, or the higher-level control unit can further be configured to permanently open the at least one first and the at least one second semiconductor switch, in particular until a reset signal is present. Furthermore, these control elements of the power control device can be configured to control the at least one first and the at least one second semiconductor switch in an open state after a disconnect signal has occurred, in particular until a reset signal is received. The error or disconnect signal can be provided by a body controller or by a safety device configured to detect a maintenance condition and / or configured to detect an accident or an impending accident.One (or more) controllers can be provided that control the semiconductor switches of the inverter for converting AC voltage into DC voltage and / or the semiconductor switches of the DC-DC converter for converting DC voltage into DC voltage (of a different level). At least one further controller can be provided that controls the at least one first and / or the at least one second semiconductor switch to open when an isolating signal has been received. However, it can also be provided that the at least one controller that controls the conversion function also opens the first and / or second semiconductor switch when an isolating signal is received. While the semiconductor switches to be opened upon receipt of an isolating signal are part of the inverter and possibly also part of a DC-DC converter, it can be provided that the relevant controllers are separate with regard to these functions (conversion and isolating).

[0026] As mentioned, the at least one first semiconductor switch and the at least one second semiconductor switch are transistors which have a body diode or inverse diode. This is particularly necessary in field-effect transistors due to the structure of the semiconductor switch. It can also be provided that a diode is connected as a discrete component in anti-parallel to a semiconductor switch. In this case, as in the case of inverse diodes, it is possible for current to flow in the event of current flows opposite to the operating direction or usual forward direction of the semiconductor switch, in particular independently of external control. To prevent current from flowing opposite to the operating direction, the first and second semiconductor switches are connected in anti-serial to one another (seen from the DC connection towards the AC connection).

[0027] Furthermore, a method for disconnecting an electrical machine from an electrical energy storage device is described. First, a disconnection signal is detected. When this is detected, at least one first semiconductor switch and at least one second semiconductor switch are opened. These are anti-serial to one another. The semiconductor switches are provided between the electrical machine or its AC connection and a DC voltage connection, in particular a first potential of the DC voltage connection. The DC voltage connection and the AC voltage connection are, as mentioned, preferably connections of a power control device which is present between the energy storage device and the electrical machine in order to control the power supply from the battery to the electrical machine. The at least one first semiconductor switch is part of an inverter which is provided between the electrical energy storage device (orthe DC voltage connection) and the electrical machine (or the AC voltage connection). It is conceivable that the at least one second semiconductor is also part of an inverter. However, the power control device provides that the second semiconductor switch is part of another component that is provided between the energy storage device and the electrical machine, namely a DC-DC converter. The method preferably uses the components of the power control device.

[0028] It is possible that when the first and second semiconductor switches are opened, two semiconductor switches that are part of a semiconductor bridge circuit of the inverter are opened. The opening of the first and second semiconductor switches can therefore be implemented by opening at least one first and at least one second semiconductor switch of the semiconductor bridge circuit of the inverter. In this case, the at least one first and at least one second semiconductor switch would be part of the inverter. In other words, two semiconductor switches that are anti-serial to one another and are part of the inverter are opened as the first and second semiconductor switches. The inverter in this case comprises, in particular, an H-bridge. Furthermore, the first and second semiconductor switches are connected to the same (DC) potential.

[0029] The method provides that opening the at least one first semiconductor switch comprises opening at least one semiconductor switch that is part of a semiconductor bridge circuit of the inverter. In this respect, this corresponds to the previously mentioned method. However, according to the claimed method, opening the at least one second semiconductor switch comprises opening at least one semiconductor switch that is part of a DC-DC converter. The DC-DC converter is connected between the energy storage device and the inverter. In other words, a semiconductor switch of the inverter is opened as the first semiconductor switch, and a semiconductor switch of the DC-DC converter is opened as the second semiconductor switch. The signs of the supply potentials to which the first and second semiconductor switches are connected are identical.Preferably, all semiconductor switches of the inverter are opened as (several) first semiconductor switches connected to the same supply potential (i.e., to a supply potential with the same sign as the supply potential to which the second semiconductor switch is connected).

[0030] During operation of the DC-DC converter for converting DC voltage, the semiconductor switch that is also opened (permanently) when the isolating signal occurs is repeatedly opened and closed.

[0031] The opening of the respective semiconductor switch upon receipt of or due to the disconnect signal involves an opening phase that is significantly longer than the opening phase of a semiconductor switch during operation of the DC-DC converter. In particular, after receipt of a disconnect signal, the open state of the at least one first and the at least one second semiconductor switch persists until a reset signal is present.

[0032] The Fig. 1 and Fig. 2 show vehicle electrical systems with a power control and serve to explain in more detail the procedure and the power control device described here.

[0033] The Fig. 1 illustrates, by way of example, a vehicle electrical system in which a power control device LS connects an electrical energy storage device ES, in particular a rechargeable battery, to an electrical machine EM. In order to generate an alternating current from the direct voltage of the energy storage device ES, the power control device LS comprises an inverter IN with a semiconductor bridge circuit formed by the switches 11, 12, 13, 21, 22, and 23. The bridge circuit of the inverter IN is a B6C bridge, wherein a branch is provided for each phase, which branch comprises two semiconductors connected in series. A first branch relating to a first phase of the electrical machine is formed by the semiconductor switches 11 and 21, a further branch (relating to a second phase) is formed by the semiconductor switches 12 and 22, and a third branch (relating to a third phase) is formed by the semiconductor switches 13 and 23. Thus, the Fig. The embodiment shown in Figure 1 is three-phase, but the number of phases is not limited to this number. In particular, six phases can also be used.

[0034] Each branch contains a connection point A1, A2, and A3 where the semiconductor switches of that branch are connected. The serially connected semiconductor switches of each branch are connected to a positive and a negative supply potential of the inverter IN. Connection points A1 - A3 are routed to an AC voltage terminal WA and correspond to the phase connections of the electrical machine.

[0035] A DC-DC converter, shown here as a synchronous converter, comprises a series circuit of two semiconductor switches S1 and S2. The ends of this series circuit are connected to the inverter IN. The connection point between the two switches S1 and S2 is connected to a first potential P of the energy storage device ES via an inductor IND. The DC-DC converter and the inverter IN are also connected to ground M, which also corresponds to the ground of the energy storage device and can also be referred to as the second potential.

[0036] The power control device LS is connected to the electric machine EM via an AC voltage connection WA. The inverter is connected either directly to the first potential P or, as shown, to the energy storage device ES via the optional DC-DC converter.

[0037] In the illustrated embodiment, a controller C1, which may be part of the inverter, part of the power control device, or provided externally, controls the semiconductor switches 11 to 23 of the inverter IN to generate a three-phase current at the alternating voltage output WA from the direct voltage applied to the inverter during normal operation. This three-phase current generates a rotating magnetic field in the electric machine. The inverter can also be bidirectional and configured to convert an alternating voltage applied to the alternating voltage terminal WA into a direct voltage for supplying the energy storage device ES.

[0038] Another controller C2 controls the switches S1 and S2 of the DC-DC converter. The controller C2 is configured to control the switches to convert one DC voltage (into another DC voltage).

[0039] Both controllers C1 and C2 each have a disconnect signal input FE1, FE1', at which a disconnect signal or a fault signal can be detected. Controllers C1 and C2 are configured to open switches upon receipt of such a disconnect signal. In the case of controller C1, this is at least switch 11, but switches 12 and 13, and thus all switches located between the AC terminal WA and the supply potential of the inverter (corresponding to the positive output of the DC-DC converter), can also be opened.

[0040] The controller C2 of the DC-DC converter is configured to open switch S1 upon receipt of the disconnection signal. Starting from the AC voltage terminal WA and following a current path to the first potential P, switch 11 and switch S1 (of the DC-DC converter DCD) are connected in anti-serial relation to each other, so that despite their inverse diodes (e.g., inverse diode 1 of switch 11), no current can flow in either direction. This results in a complete disconnection between the DC voltage terminal GA (to which the energy storage device ES is connected to the power control device ELS) and the AC voltage terminal WA. The two switches connected in anti-serial relation to each other in the disconnection case belong, according to the example of the Fig. 1 different components of the power control device, namely the inverter IN and the DC-DC converter. Both switches, connected in reverse series, are connected to the same supply potential, namely the positive supply potential of the inverter (corresponding to the positive output potential of the DC-DC converter). In this case, the first and second semiconductor switches are directly connected to each other (but with opposite operating directions).

[0041] In the illustrated embodiment, controllers C1 and C2 are configured to open the semiconductor switches upon receipt of such a disconnect signal. It may be provided that at least one controller is used for the conversion function for the inverter IN and the DC-DC converter DCDC, while at least a second controller is used for the function of opening the first and second semiconductor switches (which includes a disconnect signal input FE and possibly also a disconnect signal input FE').

[0042] In the Fig. 2 shows another vehicle electrical system as an example, which serves to further explain a possible procedure.

[0043] Here, too, an energy storage device ES is connected to an electrical machine EM via the power control device. The power control device LS has a DC voltage connection GA, to which the energy storage device is connected, and an AC voltage connection WA, to which the electrical machine EM is connected. Here, too, the electrical machine EM and the AC voltage connection WA of the power control device LS are multi-phase. An (optional) DC / DC converter can be provided, which is connected between the DC voltage connection GA and the inverter IN of the power control device LS, or no DC / DC converter can be provided, although this can be implemented differently depending on the operating voltages used for the energy storage device and the electrical machine.

[0044] The inverter IS comprises a multi-phase H-bridge circuit. Each phase of the H-bridge circuit of the inverter IN comprises two branches, each of which comprises two series-connected semiconductor switches. In each phase of the H-bridge circuit, one branch or a series connection of two semiconductor switches is connected to a DC potential EA1, EA2 of the inverter (which can correspond to the terminals of the energy storage device). In other words, in each phase of the H-bridge circuit, one branch or a series connection of two semiconductor switches is connected to a DC voltage side of the inverter IN or to a DC voltage terminal of the inverter.

[0045] In each phase, a second branch or a second series circuit of two semiconductor switches is connected to the AC voltage terminal WA. The first branches or the first series circuits, which are connected to the DC voltage potential GA1, GA2 or to the energy storage device ES, are the semiconductor switches H1, H2 for the first phase, H11, H12 for the second phase, and H21, H22 for the third phase. The series circuits of two semiconductor switches shown on the left can be considered the DC side of the inverter, while the other branches or series circuits (H3, H4, H13, H14, H23, H24) can be considered the AC side.

[0046] Capacitors C21, C22, and C23 are connected in parallel to the branches of the AC side of the inverter. An inductor L1, L2, and L3 is connected in series as a bridge element between the branches of each phase. In terms of the electric machine, the multiphase H-bridge circuit is thus connected in series between the DC voltage terminal GA and the AC voltage terminal WA.

[0047] A controller C, which may be part of the power control device, is configured to control the semiconductor switches H1 to H24 during normal operation to convert the DC voltage at the DC voltage terminal GA or at the supply potentials EA1, EA2 into an AC voltage at the AC voltage terminal WA. Optionally, the power control device is also bidirectional, so that the controller C can be configured to convert an AC voltage at the AC voltage terminal WA into a DC voltage at the DC voltage terminal GA.

[0048] The controller C comprises a disconnect signal input SE at which a disconnect signal can be received. The controller C is configured to open the switches located between the phase connections of the AC voltage connection WA and the DC voltage connection GA when an error signal or disconnect signal occurs at the input SE. For the upper phase, these are switches H1 and H3, for the middle phase, these are switches H11 and H13, and for the lower phase, these are switches H21 and H23. In the embodiment shown, the switches that are opened upon a disconnect signal are the switches connected to the first potential of the energy storage device ES, in the case shown, the potential EA1, which can correspond to a positive pole. Complementary embodiments are also conceivable.Leading from the AC terminal WA to the DC terminal GA, the switches opened by control C in each phase are anti-serial to each other. This results in a complete separation between the AC terminal WA and the DC terminal GA.

[0049] Alternatively, a controller C with a separation signal input FE can be provided as shown, which realizes the opening step, while a further controller controls the semiconductor switches of the inverter in normal operation to generate a three-phase current.

[0050] It is intended that the control for opening the semiconductor switches has priority when an isolating signal is present if this control does not correspond to the control that controls the semiconductor switches for normal operation (=converting voltage).

[0051] It should be noted that also in the Fig. 1 when a separation signal occurs, at least one switch is opened (such as switch 11 or also switches 11, 12 and 13), which are located between the AC voltage connection and the first potential P, which is in the Fig. 1 can correspond to the positive supply potential.

[0052] In the examples shown, Fig. 1 and Fig. 2 Furthermore, an additional isolating switch can be provided in the ground path, which is connected (directly) downstream of the energy storage device and which is also opened when an error signal or isolating signal occurs.

[0053] As mentioned, the opening of the switches (including the further switch) is permanent and lasts until a reset signal, in particular from the control C, C1 and C2, has been received. While in the Fig. 1 preferably both at least one switch of the inverter and one switch of the DC-DC converter DCDC are opened when an error signal occurs in order to provide two switches in an open state that are anti-serial to one another, it is in the embodiment of the Fig. 2 possible that two switches of the inverter itself are opened, in the case of Fig. 2, switches H1 and H3, as well as switches H11 and H13, and switches H21 and H23. The anti-serial switches, which are opened in the event of an isolation signal, are connected in series to semiconductor switches that are directly connected to ground or to a potential that does not correspond to the first potential.

[0054] The following applies to both figures and also to other embodiments: A power control device for an electrical machine is described. An inverter IN of the device is connected between a DC voltage connection GA of the device and an AC voltage connection WA for the electrical machine EM. The power control device has a controller, downstream of which a semiconductor bridge circuit of the inverter IN is connected in a controlling manner. The semiconductor bridge circuit has at least one first semiconductor switch, which is located between the AC voltage connection and a first potential of the DC voltage connection. A second semiconductor switch of the power control device is anti-serial to the at least one first semiconductor switch and is connected to the first potential of the DC voltage connection. The controller has an isolating signal input for receiving an isolating signal.The controller opens the at least one first and the at least one second semiconductor switch when a disconnect signal occurs.

[0055] A method for disconnecting an electrical machine EM from an electrical energy storage device ES is also described, in which, upon detection of a disconnection signal, at least one first and at least one second semiconductor switch (connected anti-serially for this purpose) are opened. The semiconductor switches are connected between the electrical machine EM and a first potential of a DC voltage terminal GA. The semiconductor switches are part of an inverter and a DC-DC converter between the inverter IN and the energy storage device ES.

Claims

[1] Power control device (LS) for an electrical machine (EM) with a DC voltage connection (GA) and an inverter (IN) which is connected between the DC voltage connection (GA) and an AC voltage connection (WA) for connecting the electrical machine (EM) and which comprises a semiconductor bridge circuit (11-23; H1-H24), wherein the power control device comprises a controller (C, C1) which is connected in a controlling manner to the semiconductor bridge circuit (11-23; H1-H24), wherein the semiconductor bridge circuit (11-23; H1, H11, H21) has at least one first semiconductor switch (11-13; H1, H11, H21) which is located between the AC voltage terminal (WA) and a first potential (P; EA1) of the DC voltage terminal (GA), and the power control device (LS) further comprises at least one second semiconductor switch (S1) which is connected anti-serially to the at least one first semiconductor switch (11-13; H1 - H21) and is connected to the first potential (P; EA1) of the DC voltage terminal, wherein the controller (C; C1, C2) further comprises an isolating signal input (FE) configured to receive an isolating signal in the form of an error signal, and the controller (C; C1, C2) is configured to permanently open the at least one first semiconductor switch and the at least one second semiconductor switch when the error signal occurs, and wherein the power drive device further comprises a DC-DC converter (DCDC) via which the DC voltage terminal (GA) is connected to the inverter (IN), and wherein the at least one first semiconductor switch (H11) is part of the semiconductor bridge circuit, and the at least one second semiconductor switch (S1) is part of the DC-DC converter (DCDC). [2] The power drive device according to claim 1, wherein the DC-DC converter (DCDC) comprises a storage element (IND) and at least one semiconductor switch (S1) connected between the storage element (IND) and the inverter (IN), said at least one semiconductor switch (S1) forming the at least one second semiconductor switch. [3] Power control device according to claim 2, wherein the semiconductor bridge circuit is a fully controlled three-phase bridge circuit and the at least one first semiconductor switch (11) is connected between the DC-DC converter (DCDC) and the AC voltage terminal (WA), wherein the at least one second semiconductor switch (S1) is connected to the first potential (P) via the storage element (IND). [4] Power drive device according to one of the preceding claims, wherein the controller is arranged to permanently open the at least one first and the at least one second semiconductor switch until a reset signal is present. [5] Method for separating an electrical machine (EM) from an electrical energy storage device (ES), comprising: Detecting a separation signal in the form of an error signal; and Permanently opening at least one first semiconductor switch (11-13; H1, H11, H21) and at least one second semiconductor switch (S1; H3, H13, H23) which is connected anti-serially to the first semiconductor switch, wherein the semiconductor switches are present between the electrical machine (EM) and a first potential (P, EA1) of a DC voltage connection (GA), wherein at least one of the first and second semiconductor switches is part of an inverter (IN) which is connected between the electrical energy store (ES) and the electrical machine (EM), wherein the permanent opening of the at least one first semiconductor switch comprises: opening at least one semiconductor switch which is part of a semiconductor bridge circuit of the inverter (IN), and the opening of the at least one second semiconductor switch comprises: opening at least one semiconductor switch which is part of a direct current converter (DCDC) which is connected between the energy storage device (ES) and the inverter (IN). [6] The method of claim 5, wherein the at least one first and the at least one second semiconductor switch are permanently opened by a controller until a reset signal is present.

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