Electric drive system for vehicle comprising traction battery, inverter and motor

Abstract

The present disclosure provides a vehicle electric drive system including a traction battery, an inverter, and a motor. A system for an electrically powered vehicle, such as a battery electric vehicle (BEV), includes an inverter configured to drive a motor having a motor winding with power from a battery according to a configuration of a power switch of the inverter. The system also includes a capacitor connected between a center tap of the battery and a neutral point of the motor winding, whereby the capacitor and the motor winding form an LC circuit. The system also includes a controller configured to operate the power switch in a zero current switching mode with a switching frequency dependent on a resonant frequency of the LC circuit to thereby circulate a current between the battery, the inverter, and the motor, the current heating the battery and the motor windings.

Description

Technical Field

[0001] The present disclosure relates to utilizing windings of a traction battery, inverter, and motor of an electric drive system of an electrified vehicle to heat the traction battery and transmission fluid of the motor. Background Art

[0002] The electric vehicle includes an electric drive system having a traction battery, an inverter, and a motor. The motor is powered by electrical energy from the traction battery via the inverter to propel the electric vehicle. Summary of the Invention

[0003] A system is provided having an inverter, a capacitor, and a controller. The inverter is configured to drive a motor having a winding using power from a battery based on a configuration of a first power switch of the inverter. The capacitor is connected between a center tap of the battery and a neutral point of the winding. The controller is configured to operate the first power switch in a zero current switching (ZCS) mode to achieve target temperatures for the battery and the winding.

[0004] The capacitor and the winding form an LC circuit.The controller may be configured to operate the first power switch in the ZCS mode by operating the first power switch at a switching frequency that depends on a resonant frequency of the LC circuit.

[0005] The switching frequency may depend on the resonant frequency of the LC circuit according to the following equation:

[0006] fsw=fresonant / t(2*k)

[0007] where f sw is the switching frequency, f resonant is the resonant frequency of the LC circuit, and k is a positive integer.

[0008] The inverter may be further configured to drive the motor using power from the battery according to a configuration of a second power switch of the inverter. In this case, the controller may be further configured to operate the first and second power switches in the ZCS mode by alternately turning on one of the power switches and turning off the other of the power switches.

[0009] The controller that alternately turns on and off the power switch may alternately turn on and off the power switch at a duty cycle of 50%.

[0010] The system may further include a contactor connected in series with the capacitor between the center tap of the battery and the neutral point of the winding. The contactor is movable between a first position, in which electrical continuity is established between the center tap of the battery and the neutral point of the winding via the capacitor, and a second position, in which electrical discontinuity is established between the center tap of the battery and the neutral point of the winding.

[0011] The controller may be further configured to move the contactor to the first position when the target temperature of the battery and the winding is not achieved.

[0012] A method for use with an electric drive system (EDS) for a vehicle is provided. The EDS includes a traction battery; a motor having motor windings; and an inverter configured to drive the motor using power from the traction battery based on the configuration of upper and lower power switches in a bridge arm of the inverter. The method includes connecting a center tap of the traction battery and a neutral point of the motor windings using a capacitor, whereby the capacitor and the motor windings form an LC circuit. The method also includes alternately turning on one of the power switches and turning off the other of the power switches at a switching frequency that depends on the resonant frequency of the LC circuit, thereby circulating current between the traction battery, the inverter, and the motor, the current heating the traction battery and the motor windings.

[0013] Connecting the center tap of the traction battery and the neutral point of the motor windings together using the capacitor may be performed only when the vehicle is not being propelled by the motor and target temperatures of the traction battery and the motor windings are not achieved.

[0014] The method may further include: (i) disconnecting the center tap of the traction battery and the neutral point of the motor winding from each other when the vehicle is to be propelled by the motor; and (ii) operating the power switch of the inverter to drive the motor with power from the traction battery, so that the motor propels the vehicle.

[0015] An electric drive system (EDS) for a vehicle is provided. The EDS includes a traction battery; a motor having motor windings; an inverter configured to drive the motor using power from the traction battery based on the configuration of upper and lower power switches in a bridge arm of the inverter; and a capacitor connecting a center tap of the traction battery and a neutral point of the motor windings, whereby the capacitor and the motor windings form an LC circuit. The EDS also includes a controller configured to alternately turn on one of the power switches and turn off the other of the power switches at a switching frequency that depends on the resonant frequency of the LC circuit, thereby circulating current between the traction battery, the inverter, and the motor, the current heating the traction battery and the motor windings.

[0016] The EDS may further include a contactor connected in series with the capacitor between the center tap of the traction battery and the neutral point of the motor winding. The contactor is movable between a first position, in which electrical continuity is established between the center tap of the traction battery and the neutral point of the motor winding via the capacitor, and a second position, in which electrical discontinuity is established between the center tap of the traction battery and the neutral point of the motor winding.

[0017] The controller may be further configured to move the contactor to the first position when the vehicle is not being propelled by the motor and target temperatures of the traction battery and the motor windings are not achieved.

[0018] The controller may be further configured to move the contactor to the second position and operate the power switch of the inverter to drive the motor with power from the traction battery when the vehicle is to be propelled by the motor, so that the motor propels the vehicle.

[0019] The traction battery may include a first cell group and a second cell group, wherein a cathode of the first cell group and an anode of the second cell group are connected together at the center tap of the traction battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 shows a block diagram of a battery electric vehicle (BEV) having an electric drive system including a traction battery, an inverter, and a motor;

[0021] Figure 2 A functional diagram showing the traction battery, inverter, and motor of the electric drive system;

[0022] Figure 3 shows a functional diagram of the traction battery, inverter and motor of an electric drive system having a self-heater arrangement;

[0023] Figure 4 shows a first graph with curves of control signals for enabling switching on and off of a top bridge group of power switches of an inverter with respect to time during a heating mode of a self-heater arrangement; and a second graph with curves of control signals for enabling switching on and off of a bottom bridge group of power switches of an inverter with respect to time during a heating mode of the self-heater arrangement; and

[0024] Figure 5 Graphs showing simulation results from a self-heater arrangement during a heating mode, the graphs including: a first graph having a graph of voltage of a traction battery versus time; a second graph having a graph of current of a first of two battery packs forming the traction battery versus time; a third graph having a graph of current of a second of the two battery packs forming the traction battery versus time; a fourth graph having a graph of current of one of the windings of a motor versus time; a fifth graph having a graph of control signals for enabling switching on and off of a top bridge group of power switches of an inverter with respect to time; and a sixth graph having a graph of control signals for enabling switching on and off of a bottom bridge group of power switches of the inverter with respect to time. DETAILED DESCRIPTION

[0025] Detailed embodiments of the present disclosure are disclosed herein; however, it should be understood that the disclosed embodiments are merely examples of the present disclosure, which may be embodied in various forms and alternatives. The drawings are not necessarily drawn to scale; some features may be exaggerated or minimized to illustrate details of particular components. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as a representative basis for teaching one skilled in the art to employ the present disclosure in various ways.

[0026] Now refer to Figure 1, a block diagram of an electrified vehicle 12 in the form of a battery electric vehicle (BEV) is shown. The BEV 12 has an electric drive system (EDS) that includes one or more motors ("motors") 14, a traction battery ("battery" or "battery pack") 24, and a power electronics module in the form of an inverter 26 (or inverter system controller (ISC)). In the BEV configuration, the traction battery 24 provides all propulsion power, wherein the electrified vehicle does not have an engine. In other variations, the electrified vehicle can be a plug-in (or non-plug-in) hybrid electric vehicle (HEV) that also has an engine.

[0027] The motor 14 is the portion of the BEV 12's EDS that powers the BEV's movement. In this regard, the motor 14 is mechanically connected to a transmission 16 of the BEV 12. The transmission 16 is mechanically connected to a driveshaft 20, which is mechanically connected to wheels 22 of the BEV 12. The motor 14 can provide propulsion to the BEV 12 and can also operate as a generator. Acting as a generator, the motor 14 can recover energy that would normally be lost as heat in the BEV 12's friction braking system.

[0028] The traction battery 24 stores electrical energy that can be used by the motor 14 to propel the BEV 12. The traction battery 24 typically provides a high voltage (HV) direct current (DC) output. The traction battery 24 is electrically connected to an inverter 26. The motor 14 is also electrically connected to the inverter 26. The inverter 26 provides the ability to transfer energy bidirectionally between the traction battery 24 and the motor 14. For example, the traction battery 24 may provide a DC voltage, while the motor 14 may require three-phase alternating current (AC) to function. The inverter 26 may convert the DC voltage into three-phase AC current to operate the motor 14. In regenerative mode, the inverter 26 may convert the three-phase AC current from the motor 14, which acts as a generator, into a DC voltage compatible with the traction battery 24.

[0029] The traction battery 24 can be recharged by an external power source 36 (e.g., the electrical grid). The external power source 36 can be electrically connected to electric vehicle supply equipment (EVSE) 38. The EVSE 38 provides circuitry and controls to control and manage the transfer of electrical energy between the external power source 36 and the BEV 12. The external power source 36 can provide DC or AC power to the EVSE 38. The EVSE 38 can have a charging connector 40 for plugging into the charging port 34 of the BEV 12.

[0030] A power conversion module 32 of the BEV 12, such as an onboard charger having a DC / DC converter, may condition the power supplied from the EVSE 38 to provide appropriate voltage and current levels to the traction battery 24. The power conversion module 32 may interface with the EVSE 38 to coordinate the delivery of power to the traction battery 24.

[0031] The various components described above may have one or more associated controllers to control and monitor the operation of the components. The controllers may be microprocessor-based devices. The controllers may communicate via a serial bus (e.g., a controller area network (CAN)) or via separate conductors.

[0032] For example, a system controller 48 ("vehicle controller") is present to coordinate the operation of the various components. The controller 48 includes electronics, software, or both to perform the necessary control functions for operating the BEV 12. The controller 48 may be a combined vehicle system controller and powertrain control module (VSC / PCM). Although the controller 48 is shown as a single device, the controller 48 may include multiple controllers in the form of multiple hardware devices, or multiple software controllers with one or more hardware devices. In this regard, references to a "controller" herein may refer to one or more controllers.

[0033] The traction battery 24 may have one or more temperature sensors (such as thermistors) in communication with the controller 48 to provide data indicative of the temperature of the traction battery for the controller to monitor the temperature of the traction battery. The BEV 12 may also include a temperature sensor to provide data indicative of the ambient temperature for the controller 48 to monitor the ambient temperature.

[0034] Now refer to Figure 2 , while continuing to refer to Figure 1 , shows a functional diagram of the traction battery 24, inverter 26, and motor 14 of the EDS. As described above, the inverter 26 is coupled between the traction battery 24 and the motor 14. The inverter 26 converts the DC power provided from the traction battery 24 into AC power for supply to the motor 14. In this way, the inverter 26 utilizes the power from the traction battery 24 to drive the motor 14 to propel the BEV 12 by the motor. The DC link capacitor (V dc ) 82 is connected in parallel with the traction battery 24 and is provided between the traction battery and the inverter 26 .

[0035] The controller 48 is operable to control the inverter 26 so that the inverter moves power from the traction battery 24 for driving (i.e., motoring) the motor 14. Specifically, the controller 48 controls the power switch 86 of the inverter 26 to open and close (e.g., turn on and off) according to a selected switching frequency and a selected duty cycle of the inverter to move power from the traction battery 24 to the motor 14.

[0036] The inverter 26 includes three groups of paired power switch units 84 (ie, 3×2=a total of 6 power switch units 84, as shown in FIG. Figure 2). Each group of power switch cells 84 includes two power switches 86 connected at a common bridge node (i.e., an upper power switch and a lower power switch in each of the three bridge legs or "phases" of the inverter 26). In this example, each power switch 86 is a transistor in the form of an insulated gate bipolar transistor (IGBT).

[0037] Each set of paired power switch cells 84 is connected in parallel to the traction battery 24, and thus each set of paired power switch cells forms a phase of the inverter 26. The power switch 86 of each of the three phases is electrically connected to a corresponding one of the three windings of the motor 14 via power conductors 92. A current sensor 94 may be provided to monitor the current in the power conductors 92. In this manner, the inverter 26 having three sets of paired power switch cells 84 is a three-phase inverter that is operable to convert DC power from the traction battery 24 into three-phase AC power to provide to the motor 14.

[0038] As indicated, the controller 48 is operable to control the on and off switching operation of the power switches 86 so that the inverter 26 converts the given DC power provided by the traction battery 24 into the desired AC power to be provided to the motor 14. In operation, the controller 48 receives motor control commands and controls the state of the inverter 26 to provide motor drive functions. The controller 48 monitors signal inputs from position sensors associated with the motor 14 and from current sensors 94. The controller 48 transmits control signals to each of the power switches 86 via control lines 96. The controller 48 includes control circuitry, algorithms, and other control elements that generate the control signals. The power switches 86 control the phase currents (i.e., ia, ib, and ic) that are delivered to the motor windings of the motor 14 via power conductors 92 to generate power in the form of torque and / or rotational speed based on the motor position and / or motor speed.

[0039] When controlling the inverter 26 to drive the motor 14 with the desired AC power, the controller 48 controls the operation of the power switch 86 according to a pulse width modulation (PWM) control strategy. In this regard, the controller 48 generates a PWM control signal having a selected carrier switching frequency and a selected duty cycle. The power switch 86 is turned on and off in response to the PWM control signal according to the switching frequency and duty cycle of the PWM control signal. In this manner, the power switch 86 is driven at a specific switching frequency, and within each cycle of the switching frequency, the power switch can operate at a specified duty cycle. The motor 14 is driven accordingly based on the operation of the power switch 86, such as to propel the BEV 12.

[0040] The performance of the traction battery 24 (such as in the form of a lithium-ion traction battery) is generally optimal when the traction battery is not cold. Therefore, it is desirable to maintain the temperature of the traction battery 24 above a cold temperature threshold. Specifically, it is desirable to be able to heat the traction battery when the traction battery 24 is cold so that the traction battery is no longer cold.

[0041] Likewise, the performance of motor 14 is generally optimal when the transmission fluid of motor 14 is not cold. Therefore, it is desirable to maintain the temperature of the transmission fluid of motor 14 above a cold temperature threshold. Specifically, it is desirable to be able to heat the motor transmission fluid when it is cold so that the motor transmission fluid is no longer cold.

[0042] Typically, an electrified vehicle also includes a thermal arrangement having a heating circuit consisting of conduits and a pump, and capable of circulating a heated fluid (i.e., coolant) to the traction battery for heating the traction battery. The thermal arrangement also includes a coolant heater for heating the coolant circulating to the traction battery. The coolant heater is typically a resistive heater, such as a positive temperature coefficient (PTC) heater. A problem is that such resistive heaters require a relatively large amount of electricity to operate. This electricity is provided by the traction battery, thereby reducing the vehicle's range, or by an external power source, such as when the traction battery is being recharged. In operation, the thermal arrangement first converts electrical energy into mechanical heat (using the coolant heater), with some energy lost during this process. The mechanical heat from the coolant then begins to heat the traction battery, with some energy again lost during this process. This makes the thermal arrangement relatively inefficient. Furthermore, the thermal arrangement as described is not suitable for heating the transmission fluid of the motor.

[0043] According to the present disclosure, the traction battery 24, inverter 26, and motor 14 of the EDS have a self-heater arrangement for heating the traction battery and the motor's transmission fluid. The self-heater arrangement implements a relatively efficient and relatively cost-effective self-heater for the traction battery 24 and the motor's transmission fluid to overcome the issues of the thermal arrangement. That is, the self-heater arrangement uses the traction battery 24, inverter 26, and motor 14 (specifically, the motor's windings) to implement a relatively efficient and relatively cost-effective heater.

[0044] Now refer to Figure 3 , while continuing to refer to Figure 1 and Figure 2 , shows a functional diagram of the traction battery 24, inverter 26, and motor 14 with a self-heater arrangement. The self-heater arrangement includes hardware circuitry 100 and a control algorithm executed by the controller 48. The control algorithm generally involves the controller 48 controlling the hardware circuitry 100 and the inverter 26 to operate in a particular manner, as described in detail below.

[0045] Figure 3The functional diagram of FIG. 1 shows the circuit topology of the hardware circuit 100 including the self-heater arrangement. Figure 3 As shown, hardware circuit 100 includes a capacitor (C2) 102, a contactor (J) 104, and a conductor 106. Capacitor 102 has a relatively small capacitance, such as approximately 10 μF. Conductor 106 connects from a center tap 108 of traction battery 24 through capacitor 102 and contactor 104 to a neutral point 110 of a winding 112 of motor 14. Therefore, when contactor 104 is closed, the center tap 108 of traction battery 24 and the neutral point 110 of motor winding 112 are connected through capacitor 102 to provide electrical continuity. Controller 48 is operable to control the opening and closing of contactor 104.

[0046] Thus, when the contactor 104 is closed, (i) the traction battery 24 Figure 2 The common configuration shown is connected to the motor winding 112 via the inverter 26 , and (ii) the center tap 108 of the traction battery 24 is connected to the neutral point 110 of the motor winding 112 via the capacitor 102 according to the configuration employing the hardware circuit 100 .

[0047] Thus, when the contactor 104 is open, the center tap 108 of the traction battery 24 and the neutral point 110 of the motor winding 112 are disconnected from each other to have electrical discontinuity. Thus, when the contactor 104 is open, the hardware circuit 100 is effectively non-existent and the EDS has Figure 2 Common configuration shown.

[0048] As noted, traction battery 24 includes a center tap 108. Center tap 108 divides traction battery 24 into a first series-connected battery pack 114a and a second series-connected battery pack 114b. In this example, battery packs 114a and 114b are substantially identical battery packs with substantially the same voltage. For example, traction battery 24 is an 800V battery, with battery packs 114a and 114b each being a 400V battery pack. In this case, the voltage at center tap 108 is 400V, the cathode of second battery pack 114b and the anode of first battery pack 114a are connected to center tap 108 and are at a voltage of 400V, the voltage at the anode of second battery pack 114b is 800V, and the voltage at the cathode of first battery pack 114a is 0V.

[0049] The self-heater arrangement utilizes the inverter 26 and the motor windings 112 to heat the traction battery 24. This also heats the transmission fluid of the motor 14.

[0050] The control algorithm implemented by the controller 48 for the self-heater arrangement provides two modes of operation. The first mode of operation is a normal mode in which the EDS is used to propel the BEV 12 as is normally done. In the normal mode, the controller 48 controls the contactor 104 to open, whereby the hardware circuit 100 is effectively absent and the EDS has Figure 2 The second operating mode is a heating mode, in which the EDS is used to heat the traction battery 24 and the transmission fluid of the motor 14. In the heating mode, the controller 48 controls the contactor 104 to close, thereby connecting the center tap 108 of the traction battery 24 and the neutral point 110 of the motor winding 112 through the capacitor 102.

[0051] In the normal mode of the EDS, the contactor 104 is open. When the BEV 12 is propelled by the motor 14, the inverter 26 utilizes the power flow between the traction battery 24 and the motor to drive the motor. The controller 48 controls the operation of the power switch 86 of the inverter 26, such as according to a conventional PWM control strategy. The motor 14 is driven accordingly based on the operation of the power switch 86, thereby propelling the BEV 12.

[0052] In the heating mode of the EDS, the contactor 104 is closed, and the BEV 12 is not propelled by the motor 14. When it is desired to heat the traction battery 24, the controller 48 closes the contactor 104 while the BEV 12 is not propelled by the motor 14. With the center tap 108 of the traction battery 24 and the neutral point 110 of the motor windings 112 connected via the capacitor 102 when the contactor 104 is closed, the motor windings act as coupled inductors (i.e., the three motor windings act as three coupled inductors), with the motor windings and capacitor forming an LC circuit. The controller 48 operates the inverter 26 in zero current switching (ZCS) mode according to a selected control strategy based on the resonant frequency of the LC circuit. That is, the controller 48 controls the power switches 86 of the inverter 26 to operate the inverter in ZCS mode according to the selected control strategy.

[0053] More specifically, in the heating mode, the controller 48 controls the power switch 86 of the inverter 26 according to the selected control strategy so that the motor winding 112 and the capacitor 102 are used to achieve resonant operation. The resonant frequency (f resonant ) is defined by the following equation:

[0054]

[0055] L1 is the inductance of the motor winding 112 , and C2 is the capacitance of the capacitor 102 .

[0056] The power switch 86 of the inverter 26 is operated according to a selected control strategy for achieving resonant operation so that the resonant current (I batt ) flows through the traction battery 24. The resonant current (I batt ) has an amplitude defined by the following equation:

[0057]

[0058] V batt1 is the voltage at the center tap 108 of the traction battery 24 .

[0059] The resonant current circulates between the traction battery 24, the inverter 26, and the motor 14, which generates heat throughout the EDS. In this way, the traction battery 24 and the transmission fluid of the motor 14 are heated.

[0060] Now refer to Figure 4 , while continuing to refer to Figure 3 , the selected control strategy employed by the controller 48 during the heating mode will be described in more detail. Likewise, the controller 48 employs the selected control strategy to control the power switch 86 of the inverter 26 for the inverter to operate in the ZCS mode.

[0061] Figure 4 A first graph 120 is shown with a graph 122 of a first control signal of the controller 48 for enabling switching on and off of the top bridge group of the power switch 86 during the heating mode. Figure 3 , where the top bridge groups of power switches 86 of the three bridge legs of inverter 26 are shown labeled S1 , S3 , and S5 . Figure 4 Also shown is a second graph 130 having a graph 132 of a second control signal of the controller 48 for switching the bottom bridge group of the power switch 86 on and off during the heating mode. Figure 3 , the bottom bridge groups of power switches 86 of the three legs of inverter 26 are labeled S2 , S4 , and S6 .

[0062] Graphs 120 and 130 depict control strategies used by controller 48 to operate inverter 26 with zero current switching when the center tap 108 of traction battery 24 and the neutral point 110 of motor winding 112 are connected through capacitor 102 during heating mode to heat traction battery 24 and transmission fluid of motor 14 .

[0063] During the heating mode, the controller 48 operates according to the selected control strategy by switching the motor winding 112 at a switching frequency (f sw) operates the power switch to operate each power switch 86 in ZCS mode. According to the following equation, the switching frequency (f sw ) depends on the resonant frequency of the LC circuit (f resonant ):

[0064] fsw=fresonant / (2*k)where k=1,2,3,...(3)

[0065] Accordingly, the switching frequency (f sw ) is defined by the following equation:

[0066] T=2*k / fresonant (4)

[0067] More specifically, according to the selected control strategy, the controller 48(a) switches at a switching frequency (f sw ) turns on the top bridge group of power switches S1, S3 and S5, while the switching frequency (f sw ) turns off the bottom bridge set of power switches S2, S4 and S6, and (b) switches at a switching frequency (f sw ) turns off the top bridge group of power switches S1, S3 and S5, while the switching frequency (f sw ) turns on the bottom bridge group of power switches S2, S4, and S6. Therefore, power switches S1, S3, and S5 are turned on, while power switches S2, S4, and S6 are turned off; and power switches S1, S3, and S5 are turned off, while power switches S2, S4, and S6 are turned on.

[0068] The controller 48 sends a signal to the power switches S1, S3 and S5. Figure 4 The first control signal represented by curve 122 in the graph 120 is used to switch the switching frequency (f sw ) turns on and off these power switches. Accordingly, the controller 48 sends a signal to the power switches S2, S4 and S6. Figure 4 The second control signal represented by curve 132 in the graph 130 is used to switch the switching frequency (f sw ) turns these power switches off and on. In this way, the top bridge group of power switches S1, S3 and S5 and the bottom bridge group of power switches S2, S4 and S6 are alternately turned on and off.

[0069] As noted, the top and bottom groups of power switches are alternately turned on and off in this manner to generate a resonant current (I batt ), the resonant current circulates between the traction battery 24, the inverter 26 and the motor 14. The circulating resonant current (Ibatt ) generates heat throughout the EDS, which heats the traction battery 24 and the transmission fluid of the motor 14. In this way, target temperatures for the traction battery 24 and the motor windings 112 can be achieved.

[0070] As indicated, the switching frequency (f sw ) depends on the resonant frequency (f resonant ) and a positive integer k. Regardless of the value of k, there is always no switching loss. The circulating resonant current (Ibatt) heats the first battery pack 114a and the second battery pack 114b at a high frequency and will continuously heat the motor winding 112, which further heats the transmission fluid of the motor 14.

[0071] Now refer to Figure 5 Simulation results depicting the demonstration of the self-heater arrangement of the EDS heating the traction battery 24 and the transmission fluid of the motor 14 during a heating mode. Figure 5 Graphs illustrating simulation results include a first graph 140 having a graph 142 of the voltage of the traction battery 24 versus time; a second graph 150 having a graph 152 of the current of the second battery pack 114 b versus time; a third graph 160 having a graph 162 of the current of the first battery pack 114 a versus time; a fourth graph 170 having a graph 172 of the current of the motor winding 112 versus time; a fifth graph 180 having a graph 182 of the control signal for enabling the top bridge group of the power switch 86 to be turned on and off relative to time; and a sixth graph 190 having a graph 192 of the control signal for enabling the bottom bridge group of the power switch 86 to be turned on and off relative to time.

[0072] In this simulation, the voltage of the traction battery 24 (V batt ) is 800 V, as confirmed by curve 142 of graph 140. The inductance of each of the three motor windings 112 is 200 μH, and the capacitance of capacitor 102 is 10 μF. Therefore, the resonant frequency (f resonant ) is 6164Hz. In this simulation, k=2. Therefore, the switching frequency (f sw ) is 1540Hz.

[0073] As shown by curves 152 and 162 of graphs 150 and 160, respectively, second battery pack 114b and first battery pack 114a alternately undergo two complete cycles of current flow. Consequently, second battery pack 114b and first battery pack 114a alternately heat at a frequency of 1540 Hz. All six power switches S1, S2, S3, S4, S5, and S6 implement zero-current switching (ZCS), resulting in no switching losses, as confirmed by graph 170. In this simulation, the traction battery current amplitude is 155 A. By using capacitor 102 with an appropriate capacitance, the traction battery current amplitude can be designed to optimally match the traction battery characteristics.

[0074] As described, the present disclosure provides an EDS for an electrified vehicle, wherein the EDS includes a traction battery, an inverter, and a motor with a self-heater arrangement. To implement the self-heater arrangement, the EDS further includes a hardware circuit having a capacitor, a contactor, and connecting wiring between the center tap of the traction battery and the neutral point of the motor winding through the capacitor and the contactor. The self-heater arrangement utilizes the inverter and motor windings, with only cost-effective components (i.e., capacitors, contactors, and connecting wiring) added. The self-heater arrangement achieves zero-current switching, and the inverter has zero switching losses, resulting in high efficiency.

[0075] The self-heating arrangement makes ambient temperature irrelevant to the operation of the electrified vehicle. In this regard, the traction battery temperature and coolant temperature are automatically controlled to maintain them within a desired range. As a result, the traction battery and motor-transmission fluid achieve optimal performance regardless of ambient temperature. This eliminates the need for a separate coolant heater as described above.

[0076] Switching frequency (f sw ) is just the resonant frequency f resonant of where k is a positive integer. This reduces the demands on the power switches when achieving resonant operation. Furthermore, even at relatively low switching frequencies, the resonant frequency can be quite high, allowing the passive components to be quite small.

[0077] Although exemplary embodiments have been described above, these embodiments are not intended to describe all possible forms of the present disclosure. Indeed, the terms used in this specification are descriptive rather than restrictive, and it should be understood that various changes may be made without departing from the spirit and scope of the present disclosure. In addition, the features of various implementation embodiments may be combined to form other embodiments of the present disclosure.

[0078] According to the present invention, a system is provided, comprising: an inverter configured to drive a motor having a winding using power from a battery according to a configuration of a first power switch of the inverter; a capacitor connected between a center tap of the battery and a neutral point of the winding; and a controller configured to operate the first power switch in a zero current switching mode to thereby achieve a target temperature of the battery and the winding.

[0079] According to one embodiment: the capacitor and the winding form an LC circuit, and the controller is configured to operate the first power switch in the zero current switching mode by operating the first power switch at a switching frequency that depends on a resonant frequency of the LC circuit.

[0080] According to one embodiment, the switching frequency depends on the resonant frequency of the LC circuit according to the following equation:

[0081] fsw=fresonant / (2*k)

[0082] where f sw is the switching frequency, f resonant is the resonant frequency of the LC circuit, and k is a positive integer.

[0083] According to one embodiment: the inverter is further configured to drive the motor using power from the battery according to the configuration of the second power switch of the inverter; and the controller is further configured to operate the first power switch and the second power switch in the zero current switching mode by alternately turning on one of the power switches and turning off the other power switch.

[0084] According to one embodiment, the controller that alternately turns on and off the power switch alternately turns on and off the power switch at a duty cycle of 50%.

[0085] According to one embodiment, the switching frequency depends on the resonant frequency of the LC circuit according to the following equation:

[0086] fsw=fresonant / (2*k)

[0087] where f sw is the switching frequency, f resonant is the resonant frequency of the LC circuit, and k is a positive integer.

[0088] According to one embodiment, the present invention is further characterized by: a contactor, which is connected in series with the capacitor between the center tap of the battery and the neutral point of the winding, and the contactor can be moved between a first position and a second position, in which, in the first position, electrical continuity between the center tap of the battery and the neutral point of the winding via the capacitor is established, and in the second position, electrical discontinuity between the center tap of the battery and the neutral point of the winding is established.

[0089] According to one embodiment: the controller is further configured to move the contactor to the first position when the target temperature of the battery and the winding is not achieved.

[0090] According to the present invention, a method for use with an electric drive system of a vehicle includes: a traction battery; a motor having a plurality of motor windings; and an inverter configured to drive the motor using power from the traction battery according to the configuration of upper and lower power switches in a bridge arm of the inverter. The method includes: connecting a center tap of the traction battery and a neutral point of the motor windings together using a capacitor, whereby the capacitor and the motor windings form an LC circuit; and alternately turning on one of the power switches and turning off the other of the power switches at a switching frequency that depends on the resonant frequency of the LC circuit, thereby circulating current between the traction battery, the inverter, and the motor, the current heating the traction battery and the motor windings.

[0091] In one aspect of the invention: the switching frequency depends on the resonant frequency of the LC circuit according to the following equation:

[0092] fsw=fresonant / (2*k)

[0093] where f sw is the switching frequency, f resonant is the resonant frequency of the LC circuit, and k is a positive integer.

[0094] In one aspect of the present invention, the alternating switching on and off of the power switch is performed at a duty cycle of 50%.

[0095] In one aspect of the invention, connecting the center tap of the traction battery and the neutral point of the motor windings together using the capacitor is performed only when the vehicle is not propelled by the motor and target temperatures of the traction battery and the motor windings are not achieved.

[0096] In one aspect of the present invention, the method includes: disconnecting the center tap of the traction battery and the neutral point of the motor winding from each other when the vehicle is to be propelled by the motor; and operating the power switch of the inverter to drive the motor with power from the traction battery, so that the motor propels the vehicle.

[0097] According to the present invention, an electric drive system for a vehicle is provided, the electric drive system having: a traction battery; a motor having a plurality of motor windings; an inverter configured to drive the motor using power from the traction battery according to a configuration of upper and lower power switches in a bridge arm of the inverter; a capacitor connecting a center tap of the traction battery and a neutral point of the motor winding, whereby the capacitor and the motor winding form an LC circuit; and a controller configured to alternately turn on one of the power switches and turn off the other of the power switches at a switching frequency that depends on a resonant frequency of the LC circuit, thereby circulating current between the traction battery, the inverter, and the motor, the current heating the traction battery and the motor windings.

[0098] According to one embodiment, the switching frequency depends on the resonant frequency of the LC circuit according to the following equation:

[0099] fsw=fresonant / (2*k)

[0100] where f sw is the switching frequency, f resonant is the resonant frequency of the LC circuit, and k is a positive integer.

[0101] According to one embodiment, the controller that alternately turns on and off the power switch alternately turns on and off the power switch at a duty cycle of 50%.

[0102] According to one embodiment, the invention is further characterized by a contactor connected in series with the capacitor between the center tap of the traction battery and the neutral point of the motor winding, the contactor being movable between a first position in which electrical continuity between the center tap of the traction battery and the neutral point of the motor winding via the capacitor is established, and a second position in which electrical discontinuity between the center tap of the traction battery and the neutral point of the motor winding is established.

[0103] According to one embodiment, the invention is further characterized in that the controller is further configured to move the contactor to the first position when the vehicle is not propelled by the motor and target temperatures of the traction battery and the motor windings are not achieved.

[0104] According to one embodiment: the controller is further configured to move the contactor to the second position when the vehicle is to be propelled by the motor, and operate the power switch of the inverter to drive the motor with power from the traction battery so that the motor propels the vehicle.

[0105] According to one embodiment, the traction battery comprises a first battery group and a second battery group, and the cathode of the first battery group and the anode of the second battery group are connected together at the center tap of the traction battery.

Claims

1. A system comprising: an inverter configured to drive a motor having a winding using power from a battery according to a configuration of a first power switch of the inverter; a capacitor connected between a center tap of the battery and a neutral tap of the winding; as well as A controller is configured to operate the first power switch in a zero current switching mode to thereby achieve a target temperature of the battery and the winding.

2. The system of claim 1, wherein: The capacitor and the winding form an LC circuit, and the controller is configured to operate the first power switch in the zero current switching mode by operating the first power switch at a switching frequency that depends on a resonant frequency of the LC circuit.

3. The system of claim 2, wherein: The switching frequency depends on the resonant frequency of the LC circuit according to the following equation: fsw=fresonant / (2*k) where f sw is the switching frequency, f resonant is the resonant frequency of the LC circuit, and k is a positive integer.

4. The system of claim 2, wherein: The inverter is further configured to drive the motor using power from the battery according to a configuration of a second power switch of the inverter; and The controller is further configured to operate the first power switch and the second power switch in the zero current switching mode by alternately turning on one of the power switches and turning off another one of the power switches.

5. The system of claim 4, wherein: The controller that alternately turns on and off the power switch alternately turns on and off the power switch at a duty ratio of 50%.

6. The system of claim 1, further comprising: A contactor connected in series with the capacitor between the center tap of the battery and the neutral tap of the motor winding, the contactor being movable between a first position in which electrical continuity between the center tap of the battery and the neutral tap of the winding via the capacitor is established, and a second position in which electrical discontinuity between the center tap of the battery and the neutral tap of the winding is established.

7. The system of claim 6, wherein: The controller is further configured to move the contactor to the first position when the target temperature of the battery and the winding is not achieved.

8. A method for use with an electric drive system for a vehicle, the electric drive system having: a traction battery; a motor having a plurality of motor windings; and an inverter configured to drive the motor with power from the traction battery according to a configuration of upper and lower power switches in a bridge arm of the inverter, the method comprising: connecting together a center tap of the traction battery and a neutral tap of the motor winding using a capacitor, whereby the capacitor and the motor winding form an LC circuit; as well as One of the power switches is alternately turned on and the other of the power switches is turned off at a switching frequency that depends on the resonant frequency of the LC circuit to thereby circulate current between the traction battery, the inverter, and the motor, the current heating the traction battery and the motor windings.

9. A method for use with an electric drive system of a vehicle as claimed in claim 8, wherein: Connecting together the center tap of the traction battery and the neutral tap of the motor winding using the capacitor is performed only when the vehicle is not being driven and target temperatures of the traction battery and the motor winding are not achieved.

10. An electric drive system for a vehicle, the electric drive system comprising: Traction batteries; a motor having a plurality of motor windings; an inverter configured to drive the motor using power from the traction battery according to a configuration of upper and lower power switches in a bridge leg of the inverter; a capacitor connecting together a center tap of the traction battery and a neutral tap of the motor winding, whereby the capacitor and the motor winding form an LC circuit; as well as a controller configured to alternately turn on one of the power switches and turn off another of the power switches at a switching frequency that depends on a resonant frequency of the LC circuit to thereby circulate a current between the traction battery, the inverter, and the motor, the current heating the traction battery and the motor windings.

11. The electric drive system for a vehicle as claimed in claim 10, wherein: The switching frequency depends on the resonant frequency of the LC circuit according to the following equation: fsw=fresonant / (2*k) where f sw is the switching frequency, f resonant is the resonant frequency of the LC circuit, and k is a positive integer; and The controller that alternately turns on and off the power switch alternately turns on and off the power switch at a duty ratio of 50%.

12. The electric drive system for a vehicle as claimed in claim 10, further comprising: a contactor connected in series with the capacitor between the center tap of the traction battery and the neutral tap of the motor winding, the contactor being movable between a first position in which electrical continuity between the center tap of the traction battery and the neutral tap of the motor winding via the capacitor is established, and a second position in which electrical discontinuity between the center tap of the traction battery and the neutral tap of the motor winding is established.

13. The electric drive system for a vehicle as claimed in claim 12, further comprising: The controller is further configured to move the contactor to the first position when the vehicle is not being propelled by the motor and target temperatures of the traction battery and the motor windings are not achieved.

14. The electric drive system for a vehicle as claimed in claim 12, wherein: The controller is further configured to move the contactor to the second position and operate the power switch of the inverter to drive the motor with power from the traction battery when the vehicle is to be propelled by the motor so that the motor propels the vehicle.

15. The electric drive system for a vehicle as claimed in claim 10, wherein: The traction battery includes a first battery pack and a second battery pack; and The cathode of the first battery group and the anode of the second battery group are connected together at the center tap of the traction battery.

Images