Electrically driven vehicle and method for operating same

Abstract

The invention relates to an electrically driven vehicle (13) having an electric circuit (14), comprising a drive inverter (1) and an electric drive machine (2), wherein: the drive inverter (1) is electrically connected to the drive machine (2) by means of a plurality of lines (3) in order to transmit an alternating voltage generated by the drive inverter (1) to the drive machine (2); active power filtering is provided for reducing switching losses of the drive inverter (1); a power factor correction filter (5) is arranged as part of an on-board charger for charging a high-voltage battery (9) of the vehicle (13) by means of a high-voltage vehicle electrical system (10); a changeover matrix (6) is arranged in order to connect the power factor correction filter (5) selectively to the lines (3), in a travel mode, in order to implement the active power filtering, or to AC charging terminals (U, V, W) of an alternating-voltage charging station, in a charging mode; the electrical circuit (14) is further configured for an operating mode for travel using the power factor correction filter (5); the power factor correction filter (5) is coupled to the drive machine (2) via the switching matrix (6) and provides a three-phase system for the drive machine (2) using information from a motor position sensor, while the drive inverter (1) is inactive.

Description

[0001] Mercedes-Benz Group AG

[0002] Electrically powered vehicle and method for its operation

[0003] The invention relates to an electrically powered vehicle according to the preamble of claim 1 and a method for operating it according to the preamble of claim 5.

[0004] During operation of a vehicle with an electric drive motor, losses occur in an inverter used to control the drive motor. These losses take the form of conduction losses at the semiconductor components and switching losses. The switching losses should be reduced as much as possible.

[0005] Switching losses arise from the simultaneous presence of a voltage and a current across the semiconductor. The product of these two time-dependent quantities and integration over the duration of the switching process yields the energy loss per switching operation. The switching power loss during driving consists of the sum of the power losses per switching operation, differentiated over time. It can be reduced in various ways.

[0006] - Reducing the switching frequency (number of switching operations per second): However, this increases the harmonic content of the AC voltage to the drive motor, resulting in additional iron losses in the drive motor. Furthermore, the DC link capacitor is subjected to greater stress due to the higher harmonic content and either ages faster or needs to be larger. Additionally, reducing the switching frequency leads to an increase in voltage ripple in the DC high-voltage system, which can stress other high-voltage components or impair their function.

[0007] - Reduction of the DC high-voltage voltage to be switched: However, this entails additional effort, for example, the use of a three-level inverter instead of a two-level inverter or the use of a voltage converter upstream of the inverter. - Shortening the switching time, which reduces energy loss by shortening the integration time: Increasing the dll / dt or dl / dt values ​​causes overvoltages at the semiconductor itself, which can destroy the semiconductor. Furthermore, high dll / dt values ​​damage the insulation of the stator windings in the drive motor.

[0008] Circuits for reducing harmonics are known from the prior art, enabling the inverter to operate at the fundamental frequency. Such filters are called Integrated Active Filters (IAF) or Active Power Filters (APF). These applications target solar inverters and PFC (Power Factor Correction) stages. They are suitable for reducing switching losses and / or the capacitance of the inverter's DC link capacitor.

[0009] The inverter's function lies in fundamental frequency switching, but without phase shift between the AC current and the AC fundamental frequency voltage. The harmonic content is reduced by selectively injecting a compensation current. This compensation current is set in a DC / DC converter with a storage inductor and can assume both positive and negative values. Its time waveform corresponds to a triangular current with three times the AC fundamental frequency of the inverter. The power output is set via a downstream DC / DC converter. Therefore, the power is controlled by the voltage difference between the source and the load. The selector assigns the current impressed in the inductor to the correct AC phase. Consequently, the Integrated Active Filter (IAF) or Active Power Filter (APF) also requires additional components, e.g.,...in the form of a resistor, a choke, six semiconductor switches as selectors, and two additional fast-switching semiconductors to generate a triangular current in the coil. This additional effort is comparable to that of three-level inverters or additional DC / DC converters.

[0010] JP 5713282 B2 describes the provision of a current conversion device without electrolytic capacitors that can reduce a harmonic current flowing in a system power supply. The current conversion device includes a three-phase inverter connected to a capacitor on one DC side and to a three-phase system on one AC side to convert current between the DC and AC sides, and an instantaneous reactive power compensator connected to the three-phase inverter on the AC side to compensate for the instantaneous reactive power due to a harmonic current generated by the operation of the three-phase inverter to provide a sinusoidal system current for the three phases.

[0011] T. Soeiro, T. Friedli and JW Kolar, "Three-phase high power factor mains interface concepts for Electric Vehicle battery charging systems", 2012 Twenty-Seventh Annual IEEE Applied Power Electronics Conference and Exposition (APEC), Orlando, FL, USA, 2012, pp. 2603-2610, doi: 10.1109 / APEC.2012.6166190 describes the use of an active power filter in an electrically powered vehicle.

[0012] The invention is based on the objective of providing a novel electrically powered vehicle and a method for its operation.

[0013] The problem is solved according to the invention by an electrically powered vehicle with the features of claim 1 and by a method with the features of claim 5.

[0014] Advantageous embodiments of the invention are the subject of the dependent claims.

[0015] An electrically powered vehicle with an electrical circuit is proposed, comprising an inverter and an electric drive motor, wherein the inverter is electrically connected to the drive motor via several lines to transmit an alternating voltage generated by the inverter to the drive motor, wherein active power filtering is provided to reduce switching losses of the inverter, wherein a power factor correction filter is arranged as part of an on-board charger for charging a high-voltage battery of the vehicle via a high-voltage on-board power supply, wherein a switching matrix is ​​arranged to selectively connect the power factor correction filter to the lines in a driving mode to implement the active power filtering, or to connect it to AC charging terminals of an AC charging station in a charging mode.According to the invention, the electrical circuit is further configured for an operating mode for driving with the power factor correction filter, wherein the power factor correction filter is coupled to the drive machine via the switching matrix and provides a three-phase system for the drive machine using information from a motor position sensor, while the drive inverter is inactive.

[0016] According to the invention, the power factor correction filter has three half-bridges, each consisting of two semiconductor switches and a choke connected to the center tap of the half-bridge.

[0017] According to the invention, the power factor correction filter with its chokes is connected to the switching matrix via an EMC filter. Alternatively, according to the invention, the power factor correction filter with its chokes is connected directly to the switching matrix, and the EMC filter is arranged between the AC charging terminals and the switching matrix. Alternatively, according to the invention, the center taps of the half-bridges of the power factor correction filter are connected directly to the switching matrix, and the EMC filter and the chokes are arranged between the AC charging terminals and the switching matrix.

[0018] In one embodiment, the on-board charger further comprises a bulk capacitor and an isolated DC / DC converter connected to the high-voltage on-board power supply.

[0019] In one embodiment, switching elements for connecting the high-voltage potentials of the power factor correction filter and the drive inverter are arranged between the power factor correction filter and the isolated DC / DC converter.

[0020] In one embodiment, a contactor is arranged between a positive DC charging terminal and a positive high-voltage potential of the high-voltage battery and / or a contactor between a negative DC charging terminal and a negative high-voltage potential of the high-voltage battery and / or a contactor between the positive DC charging terminal and a star point of the electric drive machine.

[0021] According to one aspect of the present invention, a method for operating the electrically powered vehicle described above is proposed.

[0022] According to the invention, the power factor correction filter is coupled to the drive motor via the switching matrix and, using information from a motor position sensor, establishes a three-phase system for the drive motor while the drive inverter is inactive. In one embodiment, the power factor correction filter is supplied with power for operating the drive motor via the isolated DC / DC converter.

[0023] Alternatively, the power factor correction filter is supplied with power directly from the high-voltage battery via the switching elements.

[0024] The present invention proposes connecting the AC outputs of the onboard charger's power factor controller (PFC) to the AC terminals of the electric motor. This allows the PFC to be used as an inverter for propulsion when driving at low power levels, while the actual drive inverter, designed for significantly higher power, remains inactive. This enables the PFC to efficiently control the drive at low power levels, particularly in areas where the drive inverter is less efficient (due to its high-power design). Since the onboard charger's PFC is not required for charging while driving, this function is easy to implement.

[0025] The solution according to the invention enables an improvement in efficiency when operating at low power levels. Due to the smaller chip area of ​​the PFC MOSFETs, switching losses are lower compared to operation with the drive inverter. A boost function is provided during DC charging from 400 V to 800 V. Furthermore, a redundant operating option (at low power levels) is provided in the event of a drive inverter failure or opening of the main battery contactors, particularly if the isolating DC / DC converter has its own access to the battery.

[0026] Exemplary embodiments of the invention are explained in more detail below with reference to drawings.

[0027] This shows:

[0028] Fig. 1 shows a schematic view of an electrical circuit with a drive inverter.

[0029] Fig. 2 shows a schematic circuit diagram of a first embodiment of a connection on an AC side of a power factor correction filter,

[0030] Fig. 3 is a schematic circuit diagram of a second embodiment of the connection on the AC side of the power factor correction filter, Fig. 4 is a schematic circuit diagram of a third embodiment of the connection on the AC side of the power factor correction filter, and Fig. 5 is a schematic view of an electrically powered vehicle.

[0031] Corresponding parts are marked with the same reference symbols in all figures.

[0032] Figure 1 is a schematic view of an electrical circuit 14 with a drive inverter 1, for example a two-level inverter, for controlling an electric drive motor 2 of a vehicle 13, for example a passenger car, a commercial vehicle or a bus.

[0033] The electric drive machine 2 can, for example, be designed as a permanent magnet synchronous machine.

[0034] The drive inverter 1 is electrically connected to the drive machine 2 via several lines 3 to transmit an alternating voltage from the drive inverter 1 to the drive machine 2. A bidirectional three-phase power factor correction filter 5 (PFC) is connected to the lines 3 via further lines 4. The power factor correction filter 5 is shown as a three-phase example. However, the three-phase power factor correction filter 5 could also be formed, for example, by three single-phase power factor correction filters 5.

[0035] Furthermore, a switching matrix 6 is arranged to selectively connect the power factor correction filter 5 either in a driving mode via the additional lines 4 to the lines 3 between the drive inverter 1 and the drive motor 2, or in a charging mode to AC charging terminals U, V, W of an AC charging station. The switching matrix 6 can, for example, have three changeover switches for switching one phase each, which can preferably be switched together. The changeover switches can be designed as relays or as semiconductor switches.

[0036] The drive inverter 1 operates in fundamental frequency clock mode, meaning its clock frequency is identical to the rotational frequency of the drive machine 2. The drive inverter 1 has several semiconductor switches S1 to S6, for example, MOSFETs or IGBTs, which form three half-bridges and are controlled by a controller (not shown). The duty cycle of each semiconductor switch S1 to S6 is, for example, 0.5. This means that each semiconductor switch S1 to S6 is always on for one half-cycle and off for the other. The three half-bridges are phase-shifted by 120° in their clocking sequence.

[0037] The power control of the drive inverter 1 is achieved, for example, by controlling the phase shift between an alternating current and the generation of an AC fundamental wave by switching the semiconductor switches S1 to S6 (or in other words: by controlling a torque-generating current iq).

[0038] The power factor correction filter 5 is part of an on-board charger for charging a high-voltage battery 9 of the vehicle 13 via a high-voltage electrical system 10. The on-board charger also includes a bulk capacitor 11 and an isolated DC / DC converter 12 for feeding power into the high-voltage electrical system 10. The DC / DC converter 12 is, for example, only active during charging mode and inactive during driving mode.

[0039] Instead of the two-level inverter used as drive inverter 1, another inverter topology is also conceivable, for example a three-level inverter such as a T-type or NPC inverter. The AC connections of the bidirectional three-phase power factor correction filter 5 (PFC) are connected to the AC connection points between the drive inverter 1 and the electric machine 2 via the switching matrix 6. There are three possible connection options for the power factor correction filter 5, which are explained below.

[0040] Optionally, a connection between the high-voltage potentials HV+ and HV- can be established between the power factor correction filter 5 and the isolated DC / DC converter 12. Mechanical switches (boost / drive_P) or semiconductor switches (boost / drive_N) can be used as switching elements for this purpose. This connection between the drive inverter 1 and the power factor correction filter 5 on the DC side allows for separate power design between the power factor correction filter 5 and the isolated DC / DC converter 12. Additionally, a contactor DC_P_800 can optionally be provided between the positive DC charging terminal P and the positive high-voltage potential of the battery 9. Furthermore, a contactor DC_N can be provided between a negative DC charging terminal N and the negative high-voltage potential of the battery 9.Furthermore, a contactor DC_P_400 can be provided between the positive DC charging terminal P and a star point 7 of the electric machine 2.

[0041] The power factor correction filter 5 has three half-bridges, each consisting of two semiconductor switches S7 to S12 and one choke L4, L5, L6 connected to the center tap of the half-bridge.

[0042] Figure 2 is a schematic circuit diagram of a first embodiment of the connection on the AC side of the power factor correction filter 5. In this embodiment, the power factor correction filter 5 with its chokes L4, L5, L6 is connected to the switching matrix 6 via an EMC filter 15.

[0043] An advantage of this design is that the motor current is smoothed by the chokes L4, L5, L6. Furthermore, common-mode electromagnetic interference (CM-EMC) can be dampened by discharging the motor's stray inductances L1, L2, L3. Additionally, motor bearing currents can be reduced.

[0044] Figure 3 is a schematic circuit diagram of a second embodiment of the connection on the AC side of the power factor correction filter 5. In this embodiment, the power factor correction filter 5 with its chokes L4, L5, L6 is directly connected to the switching matrix 6, while the EMC filter 15 is arranged between the AC charging terminals U, V, W and the switching matrix 6.

[0045] The advantage here is that the motor current is smoothed by the chokes L4, L5, L6. Only chokes L4, L5, L6 need to be rated for the motor currents. The EMC filter 15 can be rated for the AC charging currents.

[0046] Figure 4 is a schematic circuit diagram of a third embodiment of the connection on the AC side of the power factor correction filter 5. In this embodiment, the center taps of the half-bridges of the power factor correction filter 5 are connected directly to the switching matrix 6, while the EMC filter 15 and the inductors L4, L5, L6 are arranged between the AC charging terminals U, V, W and the switching matrix 6. An advantage of this is that the inductors L4, L5, L6 and the EMC filter 15 only need to be designed for the AC charging power, while the full DC voltage can be applied to the electric machine 2 (no inductive voltage divider). Possible operating modes of the electrical circuit 14 are described below.

[0047] When operating with the power factor correction filter 5, the AC outputs of the power factor correction filter 5 are coupled to the AC inputs of the electric machine 2 via the switching matrix 6. The drive inverter 1 is inactive. The power factor correction filter 5 provides the three-phase system for the electric machine 2. The power factor correction filter 5 requires information from a motor position sensor.

[0048] On the DC side, the power factor correction filter 5 initially draws its power via the isolated DC / DC converter 12. For this configuration, the optional switching elements Boost / Drive_P and Boost / Drive_N are not required. The maximum possible driving power and DC boost power corresponds to either the power of the power factor correction filter 5 or the power of the isolated DC / DC converter 12 (the weaker component determines the maximum driving power). The efficiency of the isolated DC / DC converter 12 slightly reduces the overall efficiency.

[0049] In a second variant, the power factor correction filter 5 is supplied directly from battery 9 via the optional switching elements Boost / Drive_P and Boost / Drive_N. The isolated DC / DC converter 12 is inactive. Therefore, there are no efficiency losses due to the isolated DC / DC converter 12. The driving power and the DC boost power thus correspond to the power of the power factor correction filter 5. It is possible to design the power of the power factor correction filter 5 and the isolated DC / DC converter 12 differently, for example, 50 kW for the power factor correction filter 5 and 11 kW for the isolated DC / DC converter 12.

[0050] When operating with the power factor correction filter 5 as an active power filter, the power factor correction filter 5 adds a compensating current to each current on the lines 3 to the drive motor 2, resulting in a sinusoidal current in the drive motor 2. Since no power is transmitted via the harmonics, the isolated DC / DC converter 12 in the onboard charger can remain passive or deactivated. The bulk capacitor 11 serves as an energy storage device to provide an AC compensation current through the power factor correction filter 5. The drive inverter 1 can be operated at the fundamental frequency switching frequency at operating points with lower AC currents. This can be important in real-world driving conditions. This allows for increased efficiency (reduction of the switching frequency and thus reduction of switching power losses). Additional iron losses in the drive motor 2 can be avoided.Furthermore, it is advantageous to use the power factor correction filter 5 of the on-board charger, which is already present in the vehicle 13, as an active power filter (APF - Active Power Filter).

[0051] When driving with only the drive inverter 1, the switch position of the switching matrix 6 is unrestricted, provided that the switching elements Boost / Drive_P and Boost / Drive_N are either not present or open. If the switching elements Boost / Drive_P and Boost / Drive_N are closed, the switching matrix 6 must assume the position that establishes a connection from the power factor correction filter 5 to the electric machine 2 to ensure that the AC charging terminals U, V, and W are de-energized.

[0052] The power factor correction filter 5 is inactive and only the drive inverter 1 takes over the control of the electric machine 2.

[0053] During AC charging, the switch position of the switching matrix 6 is such that a connection is established between the AC charging terminals U, V, W and the power factor correction filter 5. To enable galvanically isolated AC charging, the switching elements Boost / Drive_P and Boost / Drive_N must be open, if present. The power factor correction filter 5 and the isolated DC / DC converter 12 are active.

[0054] When DC charging with voltage boosting, i.e., when charging a battery 9 whose voltage is higher than that supplied by a DC charging station, voltage matching is required. For this purpose, the AC terminals of the power factor correction filter 5 are also connected to the AC inputs of the electric motor 2. The neutral point 7 of the electric motor 2 is brought out and connected to the DC charging terminal P. The DC charging terminal N is directly connected to one terminal of the battery 9. The power factor correction filter 5 now acts as a boost converter, which, through the switching operation of the motor leakage inductance L1, L2, L3 or the series connection of the motor leakage inductance L1, L2, L3 and the chokes L4, L5, L6 of the power factor correction filter 5, raises the voltage of the DC charging station to the battery voltage.By specifying a charging current to be set in the power factor correction filter 5, the charging process can be carried out with the desired power.

[0055] If the DC charging station can provide an output voltage that is greater than or equal to the battery voltage, then charging can be carried out with a direct connection between the DC charging station and battery 9. To avoid routing the DC charging currents through the electric machine 2 and the drive inverter 1, the contactor DC_P_800 can be optionally provided as a bypass. Closing this contactor DC_P_800 connects the second terminal of battery 9 directly to the DC charging station.

[0056] Figure 5 is a schematic view of an electrically powered vehicle 13 in which the electrical circuit 14 according to Figure 1 may be arranged.

[0057] Reference symbol list

[0058] 1 drive inverter

[0059] 2 Drive machine, electric machine

[0060] 3 lines

[0061] 4 more lines

[0062] 5 power factor correction filters

[0063] 6 Switching matrix

[0064] 7 Star Point

[0065] 9 high-voltage battery, battery

[0066] 10 High-voltage electrical system

[0067] 11 Bulk capacitor

[0068] 12 DC / DC converters

[0069] 13 vehicles

[0070] 14 electrical circuit

[0071] 15 EMC filters

[0072] Boost / Drive_P Switch Element

[0073] Boost / Drive_N switching element

[0074] P, N DC charging port

[0075] DC_P_800 Contactor

[0076] DC_P_400 Contactor

[0077] DC_N Schütz

[0078] L1 to L3 Motor stray inductance

[0079] L4 to L6 throttle

[0080] S1 to S12 semiconductor switches

[0081] U, V, W AC- Ladeanschluss

Claims

Mercedes-Benz Group AG Patent claims 1. Electrically powered vehicle (13) with an electrical circuit (14) comprising a drive inverter (1) and an electric drive motor (2), wherein the drive inverter (1) is electrically connected to the drive motor (2) via several lines (3) to transmit an alternating voltage generated by the drive inverter (1) to the drive motor (2), wherein active power filtering is provided to reduce switching losses of the drive inverter (1), wherein a power factor correction filter (5) is arranged as part of an on-board charger for charging a high-voltage battery (9) of the vehicle (13) via a high-voltage electrical system (10), wherein the power factor correction filter (5) has three half-bridges, each consisting of two semiconductor switches (S7 to S12) and each of an inductor (L4, L5, L6) connected to the center tap of the half-bridge, characterized in that a switching matrix (6) is arranged,to optionally connect the power factor correction filter (5) to the lines (3) in a driving mode to implement active power filtering, or to connect it to AC charging terminals (U, V, W) of an AC charging station in a charging mode, and the electrical circuit (14) is further configured for an operating mode for driving with the power factor correction filter (5), wherein the power factor correction filter (5) is coupled to the drive machine (2) via the switching matrix (6) and provides a three-phase system for the drive machine (2) using information from a motor position sensor, while the drive inverter (1) is inactive, - wherein the power factor correction filter (5) with its chokes (L4, L5, L6) is connected to the switching matrix (6) via an EM filter (15), or - where the power factor correction filter (5) with its chokes (L4, L5, L6) directly connected to the switching matrix (6) and the EMC filter (15) is arranged between the AC charging terminals (U, V, W) and the switching matrix (6), or - wherein the center taps of the half-bridges of the power factor correction filter (5) are directly connected to the switching matrix (6) and the EMC filter (15) and the chokes (L4, L5, L6) are arranged between the AC charging terminals (U, V, W) and the switching matrix (6).

2. Electrically powered vehicle (13) according to claim 1, characterized in that the on-board charger further comprises a bulk capacitor (11) and an isolated DC / DC converter (12) connected to the high-voltage on-board power supply (10).

3. Electrically powered vehicle (13) according to claim 2, characterized in that switching elements (Boost / Drive_P, Boost / Drive_N) for connecting high-voltage potentials between the power factor correction filter (5) and the drive inverter (1) are arranged between the power factor correction filter (5) and the isolated DC / DC converter (12).

4. Electrically powered vehicle (13) according to one of the preceding claims, characterized in that a contactor (DC_P_800) is arranged between a positive DC charging terminal (P) and a positive high-voltage potential of the high-voltage battery (9) and / or a contactor (DC_N) is arranged between a negative DC charging terminal (N) and a negative high-voltage potential of the high-voltage battery (9) and / or a contactor (DC_P_400) is arranged between the positive DC charging terminal (P) and a star point (7) of the electric drive machine (2).

5. Method for operating the electrically powered vehicle (13) according to one of the preceding claims, characterized in that the power factor correction filter (5) is coupled to the drive machine (2) via the switching matrix (6) for driving and provides a three-phase system for the drive machine (2) using information from a motor position sensor, while the drive inverter (1) is inactive.

6. Method according to claim 5, characterized in that the power factor correction filter (5) is supplied with power for the operation of the drive machine (2) via the isolated DC / DC converter (12).

7. Method according to claim 5, characterized in that the power factor correction filter (5) is supplied with power directly from the high-voltage battery (9) via the switching elements (Boost / Drive_P, Boost / Drive_N).

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