A vehicle electrical system having a power inverter and an electric motor for step-down voltage

Abstract

Examples of vehicle electrical systems include a rechargeable energy storage system (RESS) having a first voltage and a power inverter electrically connected to the RESS. The system also includes an electric motor having a plurality of motor windings, where each motor winding includes a multiphase terminal electrically connected to the power inverter. The electric motor also includes a neutral terminal disposed separately from the multiphase terminal. The system also includes an accessory load connected to the neutral terminals of the power inverter and the electric motor, where the accessory load requires a second voltage lower than the first voltage. Current flows through the motor windings to reduce the first voltage to the second voltage. The power inverter is configured to cycle between a first and a second operating state such that the power inverter reduces the first voltage to the second voltage.

Description

Technical Field

[0001] The present invention relates to a vehicle electrical system, and more particularly, to a vehicle electrical system having a power inverter and an electric motor for reducing battery voltage. Background Art

[0002] The propulsion system of a pure battery electric vehicle (BEV) typically includes one or more high-voltage multi-phase electric motors, which exist in the form of an electric generator set or a traction motor. The electric motor delivers power to or draws power from a rechargeable direct current (DC) battery pack. The energized electric motor can adjust the torque of each gear set of the propulsion system to achieve optimal system efficiency. The BEV also includes a separate DC / DC converter for reducing the voltage of the battery pack to support a voltage lower than the available voltage of the battery pack for accessory loads. The DC / DC converter may increase the cost, mass, and volume of the vehicle electrical system.

[0003] The propulsion system typically also includes a power inverter module having semiconductor switches, which are controlled by pulse width modulation or other switching control signals to convert the battery output voltage into an alternating current (AC) output voltage. The AC output voltage of the power inverter module is ultimately transmitted to the respective phase windings of the electric motor. The energized electric motor provides torque or other driving force to the propulsion system of the vehicle.

[0004] Therefore, although existing vehicle electrical systems include DC / DC converters to achieve their intended purposes, there is still a need for a new and improved vehicle electrical system to address these issues. Summary of the Invention

[0005] According to several aspects of the present disclosure, a vehicle electrical system includes a rechargeable energy storage system (RESS) having a first voltage and a power inverter electrically connected to the RESS. The system further includes an electric motor having a plurality of motor windings, wherein each motor winding includes a multi-phase terminal electrically connected to the power inverter. The motor winding further includes a neutral terminal disposed separately from the multi-phase terminal. The system further includes an accessory load selectively connected to the neutral terminal of the RESS or the electric motor, wherein the second voltage required by the accessory load is lower than the first voltage. Current flows through at least one of the motor windings to reduce the voltage from the first voltage of the RESS to the second voltage of the accessory load. The power inverter is configured to cycle between a first operating state in which the power inverter connects the RESS to the plurality of motor windings of the electric motor and a second operating state in which the power inverter disconnects the connection between the RESS and the motor winding and interrupts the current delivered to the motor winding, such that the power inverter reduces the first voltage of the RESS to the second voltage of the accessory load.

[0006] In one aspect, the system further includes an accessory load switch disposed between the neutral terminal of the electric motor and the accessory load. The accessory load switch is configured to transition between a closed state that allows current to flow from the electric motor to the accessory load and an open state that prevents current from flowing to the accessory load.

[0007] In another aspect, the motor windings are a plurality of inductors.

[0008] In another aspect, the power inverter includes a set of semiconductor inverter switches configured to convert direct current into alternating current.

[0009] In another aspect, each semiconductor inverter switch includes a voltage-controlled switching device.

[0010] In another aspect, the voltage-controlled switching device includes at least one of a silicon insulated-gate bipolar transistor (IGBT), a silicon carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET), a silicon (Si) superjunction MOSFET, a gallium nitride (GaN) field-effect transistor (FET), a SiC junction field-effect transistor (JFET), a wide-bandgap (WBG) or ultra-wide-bandgap (UWBG) semiconductor power switching device.

[0011] In another aspect, the power inverter includes a plurality of phase legs, each phase leg including a pair of semiconductor inverter switches, and each phase leg being connected to a respective one of the inductors.

[0012] In another aspect, the plurality of phase legs includes first, second, and third phase legs, and at least one of the semiconductor inverter switches of the first, second, and third phase legs is pulse-width modulated to cause current to flow through an associated one of the first, second, and third phase legs.

[0013] In another aspect, the system further includes a ripple inductor connected in series between the neutral terminal of the electric motor and the accessory load, wherein the ripple inductor is configured to mitigate current ripple and torque disturbance.

[0014] In another aspect, the accessory load switch is a contactor.

[0015] According to several aspects of the present disclosure, a vehicle electrical system includes a rechargeable energy storage system (RESS) having a first voltage and a power inverter electrically connected to the RESS. The system further includes an electric motor having a plurality of motor windings, wherein each motor winding includes a multi-phase terminal electrically connected to the power inverter. The motor windings further include a neutral terminal disposed separately from the multi-phase terminals. The system further includes an accessory load selectively connected to the neutral terminal of the RESS or the electric motor. A second voltage required by the accessory load is lower than the first voltage. The system further includes a controller electrically connected to the power inverter and configured to transmit a plurality of control signals to the power inverter in response to the controller receiving a command for a buck operation. The power inverter may be set in a first operating state that connects the RESS to the motor windings of the electric motor, and, in response to the power inverter receiving an associated control signal from the controller, the power inverter may also be set in a second operating state that disconnects the connection between the RESS and the motor windings. The power inverter is configured to cycle between the first and second operating states such that the power inverter and the electric motor reduce the first voltage of the RESS to the second voltage of the accessory load.

[0016] In one aspect, the system further includes an accessory load switch disposed between the neutral terminal of the electric motor and the accessory load. The accessory load switch is configured to switch between a closed state that allows current to flow from the electric motor to the accessory load and an open state that prevents current from flowing to the accessory load.

[0017] In another aspect, the accessory load includes at least one of a propulsion support system, a climate control system, and a driver comfort system.

[0018] In another aspect, the motor windings are a plurality of inductors.

[0019] In another aspect, the power inverter includes a set of semiconductor inverter switches configured to convert direct current into alternating current.

[0020] In another aspect, each semiconductor inverter switch includes a voltage-controlled switching device.

[0021] In another aspect, the power inverter includes a plurality of phase legs, each phase leg including a pair of semiconductor inverter switches, and each phase leg being connected to a respective one of the inductors.

[0022] In another aspect, the phase legs include a first phase leg and a second phase leg, and at least one of the semiconductor inverter switches of the first phase leg and the second phase leg performs pulse width modulation such that current flows through an associated one of the first phase leg and the second phase leg.

[0023] According to several aspects of the present disclosure, a method of operating a vehicle electrical system is provided. The system includes a rechargeable energy storage system (RESS), a power inverter, and an electric motor including a plurality of motor windings. The system also includes an accessory load connected to the motor windings of the electric motor. The method includes generating, by a controller, a plurality of control signals in response to the controller receiving a command for buck operation. In response to the power inverter receiving the control signals from the controller, the power inverter cycles between a first and a second operating state. In response to the power inverter cycling between the first and the second operating state, the power inverter and the electric motor reduce a first voltage of the RESS to a second voltage for supporting the accessory load.

[0024] In one aspect, the method further includes generating, by the controller, first and second control signals in response to the controller receiving a command for buck operation. The method further includes placing the power inverter in a first operating state in response to the power inverter receiving the first control signal from the controller. The method further includes electrically connecting, by the power inverter, the RESS to the motor windings of the electric motor, which in turn is electrically connected to the accessory load, in response to the power inverter being placed in the first operating state. The method further includes placing the power inverter in a second operating state in response to the power inverter receiving the second control signal from the controller. The method further includes disconnecting, by the power inverter, the electrical connection between the RESS and the motor windings of the electric motor in response to placing the power inverter in the second operating state. The method further includes reducing, by the power inverter and the electric motor, the first voltage of the RESS to the second voltage of the accessory load in response to electrically connecting, by the power inverter, the RESS to the motor windings of the electric motor and disconnecting the electrical connection between the RESS and the motor windings of the electric motor.

[0025] From the description provided herein, further applicable fields will become apparent. It should be understood that the description and specific examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way.

[0027] Figure 1 is a perspective view of an example of a motor vehicle having a vehicle electrical system connected to an off-vehicle power source.

[0028] Figure 2 is Figure 1 a block diagram of the system shown, showing a system having a power inverter and an electric motor for reducing a voltage from a first voltage of a rechargeable energy storage system (RESS) to a second voltage of an accessory load.

[0029] Figure 3A isFigure 2 Circuit schematic of the system shown, showing the power inverter in a first operating state, in which the power inverter electrically connects the RESS to the motor, and the motor is in turn electrically connected to the accessory load.

[0030] Figure 3B is Figure 2 Circuit schematic of the system shown, showing the power inverter in a second operating state, in which the power inverter disconnects the electrical connection between the RESS and the motor.

[0031] Figure 4 is Figure 1 Block diagram of another example of the system shown, showing a system with a single-pole double-throw switch for connecting the accessory load to the motor or the RESS.

[0032] Figure 5A is Figure 4 Circuit schematic of the system shown, showing the power inverter in a first operating state, in which the power inverter electrically connects the RESS to the motor, and the motor is in turn electrically connected to the accessory load.

[0033] Figure 5B is Figure 4 Circuit schematic of the system shown, showing the power inverter in a second operating state, in which the power inverter disconnects the electrical connection between the RESS and the motor.

[0034] Figure 6 is Figure 1 Block diagram of another example of the system shown.

[0035] Figure 7 is a flowchart showing an example of a method for operating Figure 2 the system shown. Detailed Description

[0036] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

[0037] The present disclosure describes a motor vehicle 100 having an electrical system ( Figure 2 , Figure 3A and Figure 3B ). Figure 1) An example of which, the electrical system is used to reduce the voltage of the on-vehicle rechargeable energy storage system 104 (RESS) when charging the RESS 104 to support one or more accessory loads 106. As described in detail below, the system 102 includes a power inverter 108 having a set of switches 110 and an electric motor 112 having a plurality of motor windings L1-L3 connected to the switches 110. The system 102 also includes a controller 116 and an inverter controller 180, which are used to selectively switch one or more switches 110 between an open state and a closed state so as to be able to conduct electric power from the RESS through the motor windings L1-L3 to reduce the first voltage of the RESS and support the second voltage of the accessory load 106.

[0038] Reference Figure 1 , An example of the motor vehicle 100 is a plug-in electric vehicle having a body 118, a plurality of drive wheels 120, and the system 102. The system 102 may include a DC charging circuit 128 ( Figure 2 ), which combines the propulsion / traction drive components of the vehicle 100. The general functions of these components may include providing power to the electric motor 112 (such as a traction motor) to generate motor torque and transmit it to the drive wheels 120 in order to provide torque or other driving force to the drive wheels 120, or for performing other useful work on the vehicle 100.

[0039] The system 102 can be used as part of any mobile system having an off-vehicle power source 122, such as a DC fast charging station arranged at a fixed location and configured to charge the RESS 104. During DC fast charging operation, the charging cable 124 and the charging port 126 electrically connect the DC charging circuit 128 ( Figure 2 ) to the DC fast charging station 122. The body 118 may define or include the charging port 126 at a location accessible to the user. A non-limiting example of the charging cable 124 may be an SAE J1772 charging connector, CHAdeMO, or another suitable regional or national standard charging plug or connector. The present teachings are independent of the specific charging standard ultimately adopted in the DC fast charging operation involving the DC fast charging station 122, so the examples described herein are merely illustrative. In other non-limiting examples, the system can be used as part of a fixed or mobile power plant, robot, or platform. The system can also be used as part of an aircraft, ship, and rail vehicle. For the sake of consistency in illustration, the application of the system as a component of the motor vehicle 100 will be described below, and the present disclosure is not limited to such an embodiment.

[0040] Now refer to Figure 3A and Figure 3B, the system 102 includes a RESS 104, and the shown RESS 104 may include one or more high-voltage, independently rechargeable battery packs. Non-limiting examples of RESS include multi-cell lithium-ion battery packs, zinc-air battery packs, nickel-metal hydride battery packs, and lead-acid DC battery packs. The RESS 104 is adapted to store high-voltage electrical energy for propelling the vehicle. The RESS 104 may be a deep-cycle, high-ampere capacity battery system rated at a first voltage. The first voltage may be in the range between 400 volts and about 800 volts direct current (VDC). However, it is conceivable that the rated first voltage of the RESS 104 is higher than 800 VDC, depending on the vehicle driving range, the vehicle gross weight, and the rated power of the various loads drawing power from the RESS 104. As Figure 3A , Figure 3B , Figure 5A and Figure 5B shown, a DC link capacitor Ci may be connected between the positive and negative terminals. The RESS 104 may be electrically connected to a high-voltage DC bus 136 and a power inverter 108 to control the transfer of electrical energy to and from the electric motor 112.

[0041] The system 102 also includes a power inverter 108 that selectively connects the RESS 104 to the electric motor 112. The power inverter 108 may be part of a traction power inverter module (TPIM) that connects an off-vehicle power source 122, such as an off-vehicle DC fast charger or a vehicle, to the RESS 104. The power inverter 108 may include a set 110 of semiconductor inverter switches S1 - S6 ("inverter switches") that cooperatively convert the direct current of the RESS 104 into alternating current to power the electric motor 112 through high-frequency switching. Each inverter switch S1 - S6 may be implemented as a voltage-controlled switching device in the form of: silicon insulated-gate bipolar transistors (IGBTs), silicon carbide (SiC) metal-oxide semiconductor field-effect transistors (MOSFETs), silicon (Si) superjunction MOSFETs, gallium nitride (GaN) field-effect transistors (FETs), SiC junction field-effect transistors (JFETs), wide-bandgap (WBG) or ultra-wide-bandgap (UWBG) semiconductor power switching devices, or other suitable switches having corresponding gates to which a gate signal is applied to change the on / off state of a given switch.

[0042] One or more inverter switches may be associated with each phase of a three-phase motor 112. In this example, for each phase of the three-phase traction motor 112, the inverter switch includes at least a pair of semiconductor switches. Each pair of switches, such as switches S1 and S2 (phase A), switches S3 and S4 (phase B), and switches S5 and S6 (phase C), may be referred to as a phase leg of the power inverter 108. For example, the power inverter 108 may include at least three (3) phase legs. In this example, the inverter switches S1 - S6 are contactors adapted to close under an electrical load to ensure the instantaneous or near-instantaneous delivery of power to the vehicle's propulsion system and drive any number of on-vehicle accessories. The power inverter 108 may incorporate multiple phases and corresponding motor control modules that are operable to receive motor control commands and thereby control the inverter state to provide drive or regenerative functionality for the motor.

[0043] System 102 also includes a motor 112 having motor windings L1 - L3, each winding having a multi-phase terminal 132 electrically connected to the power inverter 108 ( Figure 2 ). The motor windings L1 - L3 also include a neutral terminal 134 ([[]] Figure 2 ) that is separately disposed from the multi-phase terminal 132. In this example, the motor is a three-phase traction motor 112 having three windings L1 - L3 and associated terminals 132, and the motor windings L1 - L3 are inductors. Each inductor L1 - L3 is electrically connected to a corresponding one of the three phase terminals of the power inverter 108. Inductor L4 may be electrically connected to the neutral terminal of the motor 112 and positioned in series with one or more of the motor windings L1 - L3 to reduce (e.g., mitigate) current ripple and torque disturbances. Although only three motor windings L1 - L3 are shown as such, it should be understood that the traction motor 112 may include additional motor windings 166 depending on the motor configuration.

[0044] System 102 may also include one or more accessory loads 106, which are electrically connected to the neutral terminal 134 of the power inverter 108 and the motor 112, where the second voltage required by the accessory load 106 is lower than the first voltage of the RESS 104. The accessory load 106 may be represented as Vload 138, and the filter capacitor Co may be electrically connected across the two ends of Vload 138. Continuing with the previous example where the RESS104 may be adapted to store approximately eight hundred (800) VDC, the accessory load 106 may require a second voltage, such as approximately 400 VDC. However, it is contemplated that the voltage of the accessory load 106 may be any voltage lower than the first voltage of the RESS 104. Non-limiting examples of accessory loads may include at least one of a propulsion support system, a climate control system, and a driver comfort system. In other examples where the system includes multiple accessory loads, it is contemplated that the accessory loads may include various loads that are different from each other and draw power from the RESS 104.

[0045] Continuing with this example, where the accessory load 106 is supported by a second voltage that is lower than the available first voltage of the RESS 104. System 102 also includes an accessory load switch 140 disposed between the neutral terminal 134 of the motor 112 and the accessory load 106 for controlling the buck operation. The accessory load switch 140 is configured to transition between a closed state that allows current to flow from the motor 112 to the accessory load 106 and an open state that prevents current from flowing to the accessory load 106. System 102 also includes an accessory load switch 142 disposed between the RESS104 and the accessory load for allowing current to flow directly from the RESS 104 to the accessory load without voltage reduction, for example when the voltage of the accessory load is equal to the available voltage of the RESS 104.

[0046] The system also includes a controller 116 and an inverter controller 180, which are electrically connected to the inverter switches S1 - S6 of the power inverter 108 and the accessory load switches 140, 142. The controller 116 and / or the inverter controller 180 are configured to transmit a plurality of control signals to the inverter switches S1 - S6 and the accessory load switches 140, 142, so as to allow current to flow from the RESS 104 through the motor windings L1 - L3 to the accessory load 106 during a first operating state ( Figure 3A ), and prevent current from flowing from the RESS 104 through the motor windings L1 - L3 to the accessory load 106 during a second operating state ( Figure 3B ).

[0047] Each of the controller 116 and the inverter controller 180 includes at least one processor and a sufficient amount of memory for storing computer-readable instructions. The memory includes tangible, non-transitory memory, such as read-only memory, whether optical, magnetic, flash, or other memory. The controller 116 and / or the inverter controller 180 also includes a sufficient amount of random access memory, electrically erasable programmable read-only memory, etc., as well as high-speed clocks, analog-to-digital and digital-to-analog circuits, and input / output circuits and devices, and appropriate signal conditioning and buffering circuits. The controller 116 and / or the inverter controller 180 can receive a charging request signal from one or more electronic control units (ECUs) of the vehicle 100. For example, the ECU can provide a signal indicating that the RESS 104 needs to supply a reduced voltage supported by a second voltage (i.e., lower than the first voltage of the RESS 104) to an accessory load, and the controller 116 and / or the inverter controller 180 can initiate a step-down DC-DC operation as described below. If the RESS 104 can directly supply the required voltage to the accessory load, the controller 116 can send control signals to the switches 140, 142 such that the switch 140 is opened and the switch 142 is closed.

[0048] In one example, the inverter controller 180 can receive signals from the controller 116 and / or from sensors within the traction motor 112. For example, the traction motor 112 can include phase current sensors and / or rotor position sensors and provide signals indicating the phase current and / or rotor position, respectively. The inverter controller 180 can control the semiconductor switches S1 - S6 by providing signals to one or more gates to cause the semiconductor switches to transition between an open state and a closed state, as discussed in more detail below.

[0049] In some embodiments, the software of the controller 116 and / or the inverter controller 180 can be updated based on over-the-air programming. For example, the software update can be transmitted from a data source (such as an original equipment manufacturer (OEM)) to the controller 116 via one or more suitable communication networks. The over-the-air update can provide the required parameters for one or more switches S1 - S6 to adjust the charging power by adjusting the inverter control signals (such as current commands, frequencies, duty cycles, phase shifts, etc.) according to the charging power level via the inverter controller 180.

[0050] The power inverter 108 is configured in a first operating state in which the power inverter 108 connects the RESS 104 to the motor windings L1 - L3 of the motor 112 ( Figure 3A ) and a second operating state in which the power inverter 108 disconnects the connection between the RESS and the motor windings L1 - L3 of the motor 112 and interrupts the current supplied to the motor windings L1 - L3 ( Figure 3B) so that the power inverter 108 reduces the first voltage of the RESS 104 to a second voltage of the accessory load 106.

[0051] like Figure 3A As shown, the power inverter 108 is placed in a first operating state, in which one or more of the inverter switches S1, S3, and S5 are placed in a closed state, the inverter switches S2, S4, and S6 are placed in an open state, and the accessory load switch 142 is placed in a closed state so that current flows from the RESS 104 to the associated inductors L1-L3. In response to the inverter switches S1-S6 and the accessory load switch 140 receiving control signals from the controller 116 and / or the inverter controller 180, the associated motor windings L1-L3 perform a step-down conversion. In the example shown, in response to the inverter switch S1 and the accessory load switch 140 being placed in a closed state and the inverter switches S2-S6 being placed in an open state, current flows through the inductors L1, L4. Similarly, in response to the inverter switch S5 and the accessory load switch 140 being placed in a closed state and the inverter switches S1-S4 and S6 being placed in an open state, current flows through the inductors L2, L4. In response to the inverter switch S3 and the accessory load switch 140 being placed in a closed state and the inverter switches S1, S2, and S4-S6 being placed in an open state, current flows through the inductors L3, L4. The inverter switches S1, S3, and / or S5 may be affected by a pulse width modulation signal from the inverter controller 180 to switch the inverter switches S1, S3, and S5 between an open state and a closed state. In this non-limiting example, the duty cycle may be fifty percent (50%).

[0052] refer to Figure 3B, the power inverter 108 is placed in a second operating state in which each of the inverter switches S1, S3, and S5 is placed in an open state to prevent current from flowing from the RESS 104 to the associated inductors L1 - L3 of the motor 112. One or more of the inverter switches S2, S4, and S6 are placed in a closed state to allow current to continue flowing from one or more of the associated inductors L1 - L3 to the accessory load 106. In the example shown, in response to the accessory load switch 142 and the inverter switch S2 being placed in the closed state and the inverter switches S1 - S3, S5, and S6 being placed in the open state, current flows from the inductors L1, L4 to the accessory load 106. In another example, in response to the accessory load switch 142 and the inverter switch S6 being placed in the closed state and the inverter switches S1 - S5 being placed in the open state, current flows from the inductors L2, L4 to the accessory load 106. In yet another example, in response to the accessory load switch 142 and the inverter switch S4 being placed in the closed state and the inverter switches S1 - S3, S5, and S6 being placed in the open state, current flows from the inductors L3, L4 to the accessory load 106. It is contemplated that any one or more of the inductors can continue to supply power to the accessory load when the RESS is disconnected from the inductor. The inverter switches S2, S4, and / or S6 can be affected by a pulse width modulation signal from the inverter controller 180 to switch the inverter switches S2, S4, and S6 between the open state and the closed state. In this non - limiting example, the duty cycle can be fifty percent (50%).

[0053] Reference Figure 4 、 Figure 5A and Figure 5B , another example of an electrical system 202 is similar to Figure 2 、 Figure 3A and Figure 3B the system 102 shown and its identical components are labeled with the same reference numerals incremented by 100. Although Figure 2 、 Figure 3A and Figure 3B the system shown includes accessory load switches 140, 142, the system 202 has a single - pole double - throw switch 244 that selectively connects the accessory load 206 to the motor 212 or the RESS 204.

[0054] Reference Figure 6 , another example of an electrical system 302 is similar to Figure 2 、 Figure 3A and Figure 3B the system 102 shown and its identical components are labeled with the same reference numerals incremented by 200. Although Figure 2 、 Figure 3A and Figure 3BThe illustrated system 102 includes an accessory load switch 140 disposed between the neutral terminal 134 of the electric motor 112 and the accessory load 106, but the system 302 includes an off-vehicle switch 350 disposed between the neutral terminal 134 of the electric motor 112 and the off-vehicle power source 322. Although Figure 2 , Figure 3A and Figure 3B system 102 includes an accessory load switch 142 disposed between the RESS 104 and the accessory load 104, but the system 302 includes an off-vehicle switch 352 disposed between the RESS 304 and the off-vehicle power source 322. The system 302 also includes an off-vehicle switch 352 disposed between the RESS 304 and the off-vehicle power source 322. During buck operation, switches 350, 354 can move to a closed state and switch 352 can move to an open state so that the power inverter 308 and the electric motor 312 can reduce the voltage of the RESS to support the off-vehicle power source 322 or charge the off-vehicle power source 322. Additionally, when the rated voltages of the RESS 304 and the off-vehicle power source 322 are a common voltage, switches 352 and 354 can move to a closed state while switch 350 can move to an open state. The off-vehicle power source 322 can be the RESS of another vehicle for V2V charging operations. In other non-limiting examples, the off-vehicle power source can alternatively be an accessory load, such as a power tool that receives electrical energy from the system 300 of a truck.

[0055] Referring Figure 7 to Figure 2 , a flowchart of an exemplary method 300 for operating the illustrated system 102 to support one or more accessory loads 106 of the vehicle 100 is provided. The blocks in method 400 can be executed by the controller 116 and the inverter controller 180. Method 400 begins at block 402 where the controller 116 determines whether the controller 116 has received a charging signal associated with buck operation. For example, one or more ECUs associated with the accessory load 106 can send a charging signal indicating that the accessory load 106 needs to be charged to the inverter controller 180. If the controller 116 has received the charging signal, the method proceeds to block 404. If the controller 116 has not received the charging signal, the method 400 repeats block 402.

[0056] At block 404, the controller 116 and / or the inverter controller 180 generates one or more control signals. The control signals can be voltage signals that cause the switches S1 - S6 of the power inverter 108 to transition between an open state and a closed state. More specifically, in this example, the controller 116 and / or the inverter controller 180 generates a first control signal associated with the RESS 104 that is electrically connected to one or more of the inductors L1 - L3 of the motor windings, and the controller 116 and / or the inverter controller 180 generates a second control signal associated with the RESS 104 that is electrically disconnected between one or more of the inductors L1 - L3 of the motor windings. The controller 116 also transmits control signals to the accessory load switches 140, 142 to cause the switches 140, 142 to transition to a desired operating state, such as an open state or a closed state.

[0057] At block 406, in response to the power inverter 108 receiving a control signal from the inverter controller 180, the power inverter 108 cycles between a first and a second operating state. More specifically, in response to the power inverter 108 receiving a first control signal from the inverter controller 180, the power inverter 108 is placed in the first operating state. In the first operating state, one or more of the inverter switches S1 - S3 are placed in the closed state, while each of the inverter switches S4 - S6 is placed in the open state. The inverter switches S1, S3, and / or S5 can be affected by the first control signal in the form of a pulse width modulation signal from the inverter controller 180 such that during the first operating state, the inverter switches S1, S3, and S5 transition between the open state and the closed state. In response to the power inverter 108 receiving a second control signal from the inverter controller 180, the power inverter 108 is placed in the second operating state. In the second operating state, each of the inverter switches S1 - S3 is placed in the open state, while one or more of the inverter switches S4 - S6 are placed in the closed state. The inverter switches S2, S4, and / or S6 can be affected by the second control signal in the form of a pulse width modulation signal from the inverter controller 180 such that during the second operating state, the inverter switches S2, S4, and S6 transition between the open state and the closed state.

[0058] At block 408, the power inverter 108 electrically connects the RESS 104 to one or more of the motor windings L1 - L3 of the electric motor 112, and in response to the power inverter being placed in a first operating state, current flows from the RESS 104 through one or more of the motor windings L1 - L3 to the accessory load 106. In response to the power inverter 108 being placed in a second operating state, the power inverter disconnects the electrical connection between the RESS 104 and the motor windings L1 - L3 of the electric motor 112, and current does not flow from the RESS 104 to the motor windings L1 - L3. As described above, the inverter 108 and the motor windings L1 - L3 act as a buck converter by causing current to flow from the inverter 108 through the motor windings L1 - L3 of the electric motor 112 in order to reduce the voltage from a first voltage (e.g., 800V) to a second voltage (e.g., 400V). In this example, the accessory load switch 142 is also in a closed state to effect the connection between the accessory load 106 and the motor windings L1 - L3.

[0059] At block 410, in response to the power inverter 108 cycling between the first and second operating states, the power inverter 108 and the electric motor 112 reduce the voltage from the available first voltage of the RESS 104 to the second voltage that supports the accessory load 106.

[0060] At block 412, the controller 116 determines whether the controller 116 has received a termination charging signal from one or more ECUs associated with the accessory load 106. If the controller 116 has not received a termination charging signal, the method 400 returns to block 404. If the controller 116 has received a termination charging signal, the method 400 proceeds to block 414.

[0061] At block 414, the controller 116 and / or the inverter controller 180 transmit signals to switch the inverter switches S1 - S6 and the accessory load switches 140, 142 so that the RESS 104 delivers power to the electric motor 112.

[0062] The description of the present disclosure is merely exemplary in nature, and variations that do not depart from the gist of the present disclosure are intended to fall within the scope of the present disclosure. Such variations should not be regarded as departing from the spirit and scope of the present disclosure.

Claims

1. A vehicle electrical system, comprising: A rechargeable energy storage system (RESS) having a first voltage; A power inverter electrically connected to the RESS; A motor having a plurality of motor windings, wherein each of the motor windings includes a multi-phase terminal electrically connected to the power inverter, and the motor further has a neutral terminal disposed separately from the multi-phase terminal; and An accessory load selectively connected to one of the RESS and the neutral terminal of the motor, wherein the accessory load requires a second voltage; A first accessory load switch disposed between the neutral terminal of the motor and the accessory load; A second accessory load switch disposed between the RESS and the accessory load; Wherein the power inverter includes semiconductor switches S1, S3, and S5, each of the semiconductor switches S1, S3, and S5 is disposed between the RESS and a corresponding one of the multi-phase terminals, and includes semiconductor switches S2, S4, and S6, each of the semiconductor switches S2, S4, and S6 is connected between the accessory load and a corresponding one of the multi-phase terminals, wherein the semiconductor switches S1 - S6 cooperate to convert direct current (DC) electricity from the RESS into alternating current (AC) electricity for powering the motor by high-frequency switching; Wherein the power inverter is configured to cycle between: A first operating state, wherein the power inverter connects the RESS to the plurality of motor windings of the motor such that current flows from the RESS through the multi-phase terminals to the accessory load via closing the first accessory load switch, opening the second accessory load switch, closing one of the semiconductor switches S1, S3, and S5, and opening the remaining semiconductor switches S1 - S6; A second operating state, wherein the power inverter disconnects the RESS from the plurality of motor windings of the motor and interrupts the current to the motor windings, such that the power inverter reduces the first voltage of the RESS to the second voltage of the accessory load by closing the first accessory load switch, opening the second accessory load switch, opening the semiconductor switches S1, S3, and S5 to disconnect the RESS from the multi-phase terminals, and closing one or more of the remaining semiconductor switches S2, S4, and S6 to allow current to flow from one or more of the multi-phase terminals to the accessory load; and A third operating state, wherein the RESS directly charges the accessory load without reducing the voltage by opening the first accessory load switch and closing the second accessory load switch.

2. The vehicle electrical system according to claim 1, wherein, The accessory load includes at least one of a propulsion support system, a climate control system, and a driver comfort system.

3. The vehicle electrical system according to claim 1, wherein, The plurality of motor windings includes a plurality of inductors.

4. The vehicle electrical system according to claim 3, wherein, The semiconductor switches S1 - S6 are configured to convert DC electricity into AC electricity.

5. The vehicle electrical system according to claim 4, wherein, Each of the semiconductor switches includes a voltage-controlled switching device.

6. The vehicle electrical system according to claim 5, wherein, The voltage-controlled switching device includes at least one of a silicon insulated gate bipolar transistor (IGBT), a silicon carbide (SiC) metal oxide semiconductor field effect transistor (MOSFET), a silicon (Si) super junction MOSFET, a gallium nitride (GaN) field effect transistor (FET), a SiC junction field effect transistor (JFET), and a wide bandgap (WBG) or ultra-wide bandgap (UWBG) semiconductor power switching device.

7. The vehicle electrical system according to claim 4, wherein, The power inverter includes a plurality of phase arms, each of the phase arms includes a pair of semiconductor switches, and each of the phase arms is connected to a corresponding one of the inductors.

8. The vehicle electrical system according to claim 7, wherein, The plurality of phase arms includes first, second, and third phase arms, and at least one of the semiconductor switches of the first, second, and third phase arms performs pulse width modulation such that current flows through an associated one of the first, second, and third phase arms.

9. The vehicle electrical system according to claim 8 further includes a ripple inductor connected in series between the neutral terminal of the motor and the accessory load, wherein, The ripple inductor is configured to mitigate current ripple and torque disturbance.

10. The vehicle electrical system according to claim 9, wherein, The at least one accessory load switch includes a contactor.

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