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 connected between a battery and a motor having a winding. A center tap of the battery is connected to a neutral point of the winding, whereby the battery, the inverter, and the motor are connected in a closed circuit. The system also includes a controller configured to control the inverter to pass circulating current from the battery through the closed circuit, thereby achieving a target temperature of the battery.

Description

Technical Field

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

[0002] The electrified 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 electrified vehicle. Summary of the invention

[0003] A system having an inverter and a controller is provided. The inverter is connected between a battery and a motor having a winding. The center tap of the battery is connected to the neutral point of the winding, whereby the battery, the inverter and the motor are connected in a closed circuit. The controller is configured to control the inverter so that a circulating current from the battery passes through the closed circuit, thereby achieving a target temperature of the battery.

[0004] The controller may control the inverter to control the amplitude and / or frequency of the circulating current.

[0005] The circulating current may be an alternating current (AC) square wave.

[0006] The system may further include a conductor having a switch movable between an open position and a closed position. When the switch is closed, the center tap of the battery is connected to the neutral point of the winding via the conductor. When the switch is open, the center tap of the battery is disconnected from the neutral point of the winding.

[0007] The controller may move the switch between the open position and the closed position. When the switch is in the open position, the inverter may drive the motor using power from the battery. When the switch is in the open position, the inverter may supply power received via the motor to the battery.

[0008] The battery may include a top battery pack and a bottom battery pack, wherein a cathode of the top battery pack and an anode of the bottom battery pack are connected together at the center tap of the battery. A voltage of the top battery pack and a voltage of the bottom battery pack may be substantially the same.

[0009] A method for use with an electric drive system (EDS) of a vehicle is provided. The EDS has a traction battery, a motor having a plurality of motor windings, and an inverter connected between the traction battery and the motor. The method includes connecting together a center tap of the traction battery and a neutral point of the motor windings, whereby the battery, the inverter, and the motor are connected in a closed circuit. The method also includes controlling the inverter to pass a circulating current from the traction battery through the closed circuit, whereby a target temperature of the traction battery is achieved.

[0010] The step of connecting the centre tap of the traction battery and the neutral point of the motor winding together may be performed only when the vehicle is not being propelled by the motor and the target temperature of the traction battery is not achieved.

[0011] The method may further include 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 controlling the inverter to drive the motor with power from the traction battery so that the motor propels the vehicle.

[0012] An EDS for a vehicle is provided, wherein the EDS has: a traction battery; a motor having a plurality of motor windings; and an inverter connected between the traction battery and the motor. The EDS also has a conductor having a switch movable between an open position and a closed position. When the switch is in the closed position, a center tap of the traction battery and a neutral point of the motor winding are connected together via the conductor, whereby when the switch is in the closed position, the traction battery, the inverter, and the motor are connected in a closed circuit. A controller associated with the EDS is configured to control the inverter when the switch is in the closed position so that a circulating current from the traction battery passes through the closed circuit, thereby generating heat to heat the traction battery and a transmission fluid of the motor.

[0013] The controller may move the switch to the closed 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.

[0014] The controller may move the switch to the open position when the vehicle is to be propelled by the motor, and may control the inverter to drive the motor with power from the traction battery so that the motor propels the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1A block diagram of a battery electric vehicle (BEV) having an electric drive system (EDS) including a traction battery, an inverter, and a motor is shown;

[0016] Figure 2 A functional diagram showing the traction battery, inverter and motor of the EDS and a controller for the EDS;

[0017] Figure 3 A circuit topology diagram showing the traction battery, inverter and motor of the EDS in an operating sequence with a fast charger according to a conventional arrangement for the fast charger to charge the traction battery;

[0018] Figure 4 A circuit topology diagram showing a traction battery, inverter and motor of an EDS having a self-heater arrangement operating in a heating mode using a controller to generate a circulating current from the traction battery so that heat is used to heat the traction battery and the transmission fluid of the motor, the amplitude and frequency of the circulating current being controllable according to the self-heater arrangement;

[0019] Figure 5 a schematic circuit diagram showing a control process for a self-heater arrangement operating in a heating mode;

[0020] Fig. 6A shows a graph with a curve of a square wave for generating a circulating current for a traction battery;

[0021] Figure 6B shows a graph with a curve for controlling the power switches of the inverter to generate a triangular wave of circulating current for the traction battery;

[0022] Fig. 7A A circuit topology diagram showing a self-heater arrangement with positive circulating current from the traction battery during a heating mode;

[0023] Figure 7B a circuit topology diagram showing a self-heater arrangement with negative circulating current from the traction battery during a heating mode; and

[0024] Figure 8Graphs showing simulation results of a self-heater arrangement during a heating mode, the graphs comprising: 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 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 implementing on and off switching of a top bridge group of power switches of an inverter versus time; and a sixth graph having a graph of control signals for implementing on and off switching of a bottom bridge group of power switches of an inverter versus 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 that may be embodied in various forms and alternative forms. The drawings are not necessarily drawn to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art to adopt the present disclosure in different ways.

[0026] Reference now 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) including 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, where the electrified vehicle does not have an engine. In other variations, the electrified vehicle may 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 EDS of the BEV 12 that is used to power the movement of the BEV. 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 drive shaft 20, which is mechanically connected to wheels 22 of the BEV 12. The motor 14 can provide propulsion capability to the BEV 12 and can also act as a generator. The motor 14 acting as a generator can recover energy that might normally be lost as heat in the friction braking system of the BEV 12.

[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 the 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 provides a DC voltage, while the motor 14 requires an alternating current (AC) current (e.g., a three-phase AC current) to function. The inverter 26 can convert the DC voltage into a three-phase AC current to operate the motor 14. In the regenerative mode, the inverter 26 can convert the three-phase AC current from the motor 14 used as a generator into a DC voltage compatible with the traction battery 24.

[0029] The traction battery 24 may be recharged by an external power source 36 (e.g., an electrical grid). The external power source 36 may be electrically connected to an electric vehicle supply equipment (EVSE) 38. The EVSE 38 provides circuitry and controls for controlling and managing the transfer of electrical energy between the external power source 36 and the BEV 12. The external power source 36 may provide DC or AC power to the EVSE 38. The EVSE 38 may 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 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 power delivery 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 controller may be a microprocessor-based device. The controller may communicate via a serial bus (e.g., a controller area network (CAN)) or via discrete conductors.

[0032] For example, there is a system controller 48 ("vehicle controller") 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 "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] Reference now Figure 2 , while continuing to refer to Figure 1 , shows a functional diagram of the traction battery 24, the inverter 26 and the motor 14 of the EDS and the controller 48 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 providing to the motor 14. In this way, the inverter 26 drives the motor 14 with the power from the traction battery 24 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 arranged between the traction battery and the inverter 26.

[0035] The controller 48 is operable to control the inverter 26 so that the inverter transfers power from the traction battery 24 for driving (i.e., motor driving) 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 transfer power from the traction battery 24 to the motor 14.

[0036] The inverter 26 includes three groups of paired power switch units 84 (ie, three groups of two power switch units 84 per pair equaling a total of six power switch units 84, as shown in FIG. Figure 2 ). Each pair of power switch units 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 pair of power switch units 84 is connected in parallel to the traction battery 24, and thus each pair of power switch units forms a phase of the inverter 26. The power switch 86 of each of the three phases (i.e., phase A, phase B, and phase C) is electrically connected to a corresponding winding of the three windings of the motor 14 via a power conductor 92. A current sensor 94 may be provided to monitor the current in the power conductor 92 (e.g., the current I of phase A). a , the current of phase B I b and the current I of phase C c). In this manner, the inverter 26 having three sets of paired power switch units 84 is a three-phase inverter operable to convert DC power from the traction battery 24 into three-phase AC power to provide to the motor 14.

[0038] As noted, the controller 48 is operable to control the on and off switching operation of the power switch 86 to enable the inverter 26 to convert a given DC power provided from the traction battery 24 to a 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 the current sensor 94 and signal inputs from the position sensor associated with the motor 14. The controller 48 transmits control signals to the individual power switches in the power switch 86 via control lines 96. The controller 48 includes control circuitry, algorithms, and other control elements for generating control signals. The power switch 86 controls the phase current (i.e., I a ,I b and I c ), the phase current is transmitted to the motor windings of the motor 14 via the power conductors 92 to generate power in the form of torque and / or speed based on the motor position and / or the 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. (Typically, the PWM control signal is such that when one power switch in a phase is turned on, the other power switch in the phase is turned off). In this way, 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 according to the operation of the power switch 86, such as thereby propelling 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. Generally, a temperature of the traction battery 24 in the range of approximately 10°C to 30°C or higher is preferred for fast charging and vehicle driving operation. For example, when the traction battery is cold, charging (particularly fast charging) of the traction battery 24 may be limited. 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 the motor 14 is generally best when the transmission fluid of the motor 14 is not cold. Therefore, it is desirable to maintain the temperature of the transmission fluid of the motor 14 above the cold temperature threshold. Specifically, it is desirable to be able to heat the motor transmission fluid when the motor transmission fluid 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, pumps, etc., and capable of circulating a heating fluid (i.e., a coolant) to the traction battery for heating the traction battery. The thermal arrangement also includes a coolant heater for heating the coolant that is circulating to the traction battery. The coolant heater is typically a resistive heater such as a positive temperature coefficient (PTC) heater. The problem is that such a resistive heater requires a relatively large amount of electricity for its operation. The electricity is provided by the traction battery, which thereby reduces the vehicle 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 a coolant heater), and some energy will be lost during this process. Then, the mechanical heat from the coolant starts to heat the traction battery, and a little more energy will be lost during this process. This makes the thermal arrangement relatively inefficient. In addition, the thermal arrangement as described is not suitable for heating the transmission fluid of the motor.

[0043] Reference now Figure 3 , while continuing to refer to Figure 1 and Figure 2 , shows a circuit topology diagram of the traction battery 24, inverter 26 and motor 14 of the EDS in an operating sequence with a fast charger 100, which is based on a conventional arrangement for charging a traction battery with a fast charger. Figure 3 , the fast charger 100 is a 400V DC fast charger. The 400V DC fast charger 100 can supply 400V DC power for traction battery charging.

[0044] Many EVSEs have 400V DC fast chargers, and the traction battery of many electrified vehicles is a 400V DC traction battery. Thus, the 400V DC fast charger was originally intended for charging a 400V DC traction battery. However, it has become popular for the traction battery to be an 800V DC traction battery. That is, it has become popular for BEVs to use an 800V DC traction battery and an 800V DC bus. Thus, the traction battery 24 will be considered to be an 800V DC traction battery, as shown in FIG. Figure 3 Instructions.

[0045] The 800V DC traction battery can supply 800V DC power for traction battery charging. In order for the traction battery 24 (i.e., the 800V DC traction battery) to have the best charging performance, an 800V DC fast charger should be used to charge the traction battery instead of the 400V DC fast charger 100. A problem occurs when the EVSE has a 400V DC fast charger but not an 800V DC fast charger.

[0046] Figure 3 The conventional arrangement shown provides a solution for charging the 800V DC traction battery 24 using a 400V DC fast charger 100. In this regard, the conventional arrangement employs a boost converter consisting of a motor winding (i.e., winding 102 of the motor 14) and an inverter 26. According to the conventional arrangement, as Figure 3 As shown, the 400V DC fast charger 100 is connected in parallel with the capacitor (C2) 104. The 400V DC fast charger 100 and the capacitor 104 connected in parallel therewith can be connected to the motor 14 via the first switch (K1) 106. Specifically, when the first switch 106 is closed (the first switch 106 is in Figure 3 When the first switch 106 is opened (shown as open in FIG—the controller 48 is operable to control the first switch 106 to open and close), the 400V DC fast charger 100 and the capacitor 104 connected in parallel therewith are connected between the neutral point 108 of the winding 102 of the motor 14 and the ground point 110 of the EDS. Then, the controller 48 controls the inverter 26 to operate in the voltage boost mode to boost the 400V DC voltage from the 400V DC fast charger 100 to an 800V DC voltage, and provide the 800V DC voltage to the traction battery 24 via the DC link capacitor 82 to charge the traction battery.

[0047] However, as described above, fast charging of traction battery 24, such as by using 400V DC fast charger 100, may be limited when the traction battery is cold. Thus, at low temperatures it is desirable to heat traction battery 24 to a temperature within an optimal temperature range to perform DC fast charging.

[0048] 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 problems of the thermal arrangement.

[0049] In operation of the self-heater arrangement during the heating mode, current from the traction battery 24 is circulated through the traction battery, the inverter 26, and the motor windings 102 to heat the traction battery and the transmission fluid of the motor. As explained in further detail below, in the heating mode, the traction battery 24, the inverter 26, and the motor 14 are connected in a closed circuit, and the controller 48 controls the inverter to pass the circulating current through the closed circuit. The circulating current generates heat, which heats the traction battery 24 and the transmission fluid of the motor 14. After the traction battery 24 is heated to a desired temperature by the circulating current, the heating mode can be terminated and the closed circuit of the traction battery 24, the inverter 26, and the motor 14 is disconnected. The 400 VDC fast charger 100 can then be connected to the EDS to charge the traction battery 24.

[0050] A feature of the self-heater arrangement is that the amplitude and frequency of the circulating current can be controlled by the controller 48. Thus, the self-heater arrangement is a self-heater arrangement in which the current amplitude and frequency are controllable.

[0051] Reference now Figure 4 , while continuing to refer to Figure 1 , Figure 2 and Figure 3 , a circuit topology diagram of the traction battery 24, inverter 26 and motor 14 of the EDS with a self-heater arrangement is shown. As described, the self-heater arrangement is operated in a heating mode using a controller 48 to generate a circulating current from the traction battery 24 to generate heat for heating the traction battery and the motor transmission fluid, and the amplitude and frequency of the circulating current are controllable.

[0052] The self-heater arrangement includes hardware circuitry 120 and a control algorithm executed by controller 48. The control algorithm involves controller 48 controlling hardware circuitry 120 and inverter 26 to operate in a particular manner, as described in detail below, whereby the control algorithm generates new operating modes and controllable circulating current amplitude and frequency.

[0053] Figure 4 The circuit topology diagram of FIG. 4 shows a circuit topology of a hardware circuit 120 including a self-heater arrangement. The hardware circuit 120 includes a conductor 122 and a second switch (K2) 124. The conductor 122 is connected from a center tap 126 of the traction battery 24 to the neutral point 108 of the winding 102 of the motor 14 through the second switch 124. Thus, when the second switch 124 is closed, the center tap 126 of the traction battery 24 is connected to the neutral point 108 of the motor winding 102 to have electrical continuity. The controller 48 is operable to control the second switch 124 to be opened and closed.

[0054] Therefore, when the second switch 124 is closed, (i) the traction battery 24 is Figure 2The common configuration shown is connected to the motor winding 102 via the inverter 26 , and (ii) the center tap 126 of the traction battery 24 is connected to the neutral point 108 of the motor winding 102 via a conductor 122 according to a configuration employing a hardware circuit 120 .

[0055] In contrast, when the second switch 124 is opened, the center tap 126 of the traction battery 24 and the neutral point 108 of the motor winding 102 are disconnected from each other to have electrical discontinuity. Therefore, when the second switch 124 is opened, the hardware circuit 120 does not actually exist, and the EDS has Figure 2 Common configuration shown.

[0056] As described, the traction battery 24 includes a center tap 126. The center tap 126 divides the traction battery 24 into a first series-connected battery pack 128a and a second series-connected battery pack 128b. In this example, the battery packs 128a and 128b are substantially identical battery packs having substantially the same voltage. Thus, since the traction battery 24 is an 800V DC battery, the battery packs 128a and 128b are each 400V DC battery packs. In this case, the voltage at the center tap 126 is 400V, the cathode of the first battery pack 128a (i.e., the top battery pack) and the anode of the second battery pack 128b (i.e., the bottom battery pack) are tied to the center tap 126 and are at a voltage of 400V, the voltage at the anode of the first battery pack 128a is 800V, and the voltage at the cathode of the second battery pack 128b is tied to the ground point 110 and is 0V.

[0057] As indicated, the self-heater arrangement utilizes the inverter 26 and the motor windings 102 to heat the traction battery 24. This also heats the transmission fluid of the motor 14.

[0058] The control algorithm of the self-heater arrangement implemented by the controller 48 provides three modes of operation.

[0059] The first operating mode is a vehicle propulsion mode, in which the EDS is used to propel the BEV 12, as is typically done. In the vehicle propulsion mode, the controller 48 opens the first switch (K1) 106, whereby the fast charger 100 (if present) is disconnected from the EDS, and the controller opens the second switch (K2) 124, whereby the hardware circuit 120 is effectively non-existent. Thus, the EDS has Figure 2 During the normal mode, the controller 48 controls the inverter 26 to drive the motor 14 with power from the traction battery 24 so that the motor propels the BEV 12. In this regard, 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 according to the operation of the power switch 86, thereby propelling the BEV 12.

[0060] The second operating mode is a charging mode, in which the fast charger 100 is used to charge the traction battery 24. In the charging mode, the fast charger 100 is present, and in this example, the fast charger is a 400V DC fast charger. The controller 48 closes the first switch (K1) 106, whereby the fast charger 100 is connected to the EDS, and the controller opens the second switch (K2) 124, whereby the hardware circuit 120 is not actually present. During the charging mode, the traction battery 24, which is an 800V DC traction battery, is charged by the fast charger 100 through the motor winding 102 and the inverter 26. The controller 48 controls the power switch 86 of the inverter 26 so that the motor winding 102 and the inverter work together to achieve a voltage step-up from 400V DC to 800V DC, and the traction battery 24 is charged with 800VDC electrical energy.

[0061] The third 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. The heating mode is available when the traction battery 24 needs to be heated to reach a desired temperature, the BEV 12 is not propelled by the motor 14, and the traction battery is not being charged, such as by a fast charger. In the heating mode, the controller 48 opens the first switch (K1) 106, thereby disconnecting the fast charger 100 (if present) from the EDS, and the controller closes the second switch (K2) 124, thereby connecting the center tap 126 of the traction battery 24 to the neutral point 108 of the motor winding 102. The controller 48 controls the traction battery 24 according to the control process 130 ( Figure 5 ) controls the power switch 86 of the inverter 26 to cause the traction battery 24 to generate a circulating current through the traction battery, the inverter 26, and the motor 14. The circulating current will heat the first and second battery packs 128a, 128b and the motor windings 102, which further heat the motor transmission fluid.

[0062] Reference now Figure 5 , while continuing to refer to Figure 4 , shows a schematic circuit diagram of a control process 130 for a self-heater arrangement operating in a heating mode. Figure 5 As shown, the control process 130 involves a closed loop control strategy to cause the traction battery 24 to generate a circulating current for causing heat. amp ) 132 is set by the controller 48 to control the amplitude of the circulating current. Specifically, the amplitude of the circulating current is I amp 1 / 2 (i.e., 0.5*I amp ). The current frequency variable (f0) 134 is set by the controller 48 to control the frequency of the circulating current. ref )136 is (i) current amplitude (I amp) and (ii) a square wave with amplitudes of +1 and -1 generated from square wave 135 with amplitudes of +1 and 0 ( Fig. 6A A graph showing a curve with a square wave 135 ).

[0063] The current sensor 94 in the inverter 26, which is designed for closed-loop control of the motor current in the vehicle propulsion mode, also measures the three-phase current of the inverter (the current I a , the current of phase B I b and the current I of phase C c ) is fed back to the controller 48. The controller 48 compares the sum of the phase currents (I a + Ib + Ic ) and the current reference (I ref ) 136 to generate a first error variable (Error1) 138 to heat the traction battery 24 during a closed-loop control strategy. The controller 48 adjusts the first error variable (Error1) 138 by assigning a positive or negative sign to the first error variable (Error1) 138 to reflect the corresponding positive or negative current command / feedback before passing it to the controller's proportional and integral (PI) regulator 140. After the first error variable (Error1) 138 is assigned a positive or negative sign, the second error variable (Error) 142 will be +Error1 or -Error1. The second error variable (Error) 142 is the input to the PI regulator 140. The process is synchronized by using a square wave 135 with +1 and 0 amplitudes ( Fig. 6A Again a graph with the curve of the square wave 135 is shown).

[0064] The controller 48 compares the output of the PI regulator 140 with the triangular wave 145 at the comparator 144 ( Figure 6B Graph showing a curve having a triangular wave 145) to generate a duty cycle to control the power switch 86 of the inverter 26. The switching frequency variable (f sw ) 147 is set by the controller 48 to control the frequency of the triangular wave 145, thereby defining the switching frequency of the power switch 86 of the inverter 26. Then, a PI regulator 140 controls the current of the motor winding 102 to track the positive current reference and the negative current reference, respectively.

[0065] Reference now Fig. 6A and Figure 6B , while continuing to refer to Figure 5 , respectively, a graph 150 with a curve of the square wave 135 and a graph 160 with a curve of the triangle wave 145 are shown.

[0066] like Fig. 6AAs shown, the square wave 135 has a 50% duty cycle and a period that is the inverse of the current frequency (f0) 134. Thus, the square wave 135 oscillates between +1 and 0 at a 50% duty cycle and has an oscillation frequency that is equal to the current frequency (f0) 134. In this manner, the current frequency (f0) 134 defines the frequency of the circulating current between the first battery pack 128a and the second battery pack 128b.

[0067] like Figure 6B As shown, the triangular wave 145 used as the carrier signal has a switching frequency (f sw )147. Thus, the triangular wave 145 oscillates between +1 and 0 and has a frequency equal to the switching frequency (f sw )147 oscillation frequency. In this way, the switching frequency (f sw ) 147 limits the switching frequency of the power switch 86 of the inverter 26 for generating a circulating current for the traction battery 24 .

[0068] refer to Figure 5 The control process 130 of the self-heater arrangement is shown and Figure 4 In the circuit topology shown, when the square wave 135 is at a high level (i.e., +1), the bottom bridge group (labeled as S2, S4, S6) of the power switch 86 of the inverter 26 is turned off, and the duty cycle controls the top bridge group (labeled as S1, S3, S5) of the power switch 86 of the inverter 26 to adjust the positive circulating current. Conversely, when the square wave 135 is at a low level (i.e., 0), the top bridge group (S1, S3, S5) of the power switch 86 is turned off, and the duty cycle controls the bottom bridge group (S2, S4, S6) of the power switch 86 to adjust the negative circulating current.

[0069] Reference now Fig. 7A and Figure 7B , respectively, show circuit topologies 170 and 180 of a self-heater arrangement during a heating mode, wherein the positive circulating current is drawn from the traction battery 24 ( Fig. 7A ), and the negative circulating current comes from the traction battery ( Figure 7B ). Each circuit topology diagram 170 and 180 shows an equivalent circuit when the EDS is operated in a heating mode.

[0070] refer to Fig. 7A , when the motor winding current (i.e., phase current I a +I b +l c The sum of the phase currents I a +l b +l c is positive), half of the motor winding current (I batt1) flows out of the top battery pack 128a, and the other half of the motor winding current (I batt2 ) flows into the bottom battery pack 128b. In other words, when the motor winding current is positive, the top battery pack 128a transfers energy to the bottom battery pack 128b.

[0071] refer to Figure 7B , when the motor winding current is negative (i.e., the phase current I a +I b +I c is negative), half of the motor winding current (I batt2 ) flows out of the bottom battery pack 128b, and the other half of the motor winding current (I batt1 ) flows into the top battery pack 128a. In other words, when the motor winding current is negative, the bottom battery pack 128b transfers energy to the top battery pack 128a.

[0072] The motor winding current indicates the circulating current. After each cycle of the positive motor winding current and the negative motor winding current, the top battery pack 128a and the bottom battery pack 128b have the same state of charge (SOC). The controller 48 can control the frequency of the cycle as needed. The controller 48 can adjust the amplitude of the motor winding current as needed. According to the current cycling process, the top battery pack 128a and the bottom battery pack 128b and the motor 14 are heated.

[0073] Now refer to Figure 8 Simulation results depicting the demonstration of a self-heater arrangement of the EDS heating the traction battery 24 and the transmission fluid of the motor 14 during a heating mode. Figure 8 Graphs of simulation results are shown, including a first graph 200 having a curve 202 of voltage of the traction battery 24 versus time; a second graph 210 having a curve 212 of current of the top battery pack 128a versus time; a third graph 220 having a curve 222 of current of the second battery pack 128b versus time; a fourth graph 230 having a curve 232 of current of the motor winding 102 versus time; a fifth graph 240 having a curve 242 of control signals for implementing on and off switching of the top bridge group (S1, S3, S5) of the power switch 86 versus time; and a sixth graph 250 having a curve 252 of control signals for implementing on and off switching of the bottom bridge group (S2, S4, S6) of the power switch 86 versus time.

[0074] The voltage of the traction battery 24 (V batt ) is 800 V, as confirmed by curve 202 of graph 200. In this simulation, the current reference Iamp =200A, current frequency f0 = 50Hz, and switching frequency f sw =10kHz. Since the current reference I amp =200A, so the battery current amplitude is 100A. Therefore, in the case where the current frequency f0 in the square wave is 50Hz, the top battery group 128a and the bottom battery group 128b alternately have positive current and negative current with a current amplitude of 100A in the square wave with a frequency of 50Hz, as confirmed by curve 212 in the graph 210 and curve 222 in the graph 220, respectively. Since the top battery group 128a and the bottom battery group 128b alternately have positive current and negative current with a current amplitude of 100A in the square wave with a frequency of 50Hz, each phase current I a ,I b and I c In a square wave with a frequency of 50 Hz, there is an amplitude of 66.67 A. This is confirmed by curve 232 of graph 230 , which indicates the current of one of the motor windings 102 versus time.

[0075] Curve 242 of graph 240 shows the relationship between the control signal for implementing the on and off switching of the top bridge group (S1, S3, S5) of power switch 86 versus time. The switching frequency is 10 kHz, and the duty cycle D is controlled by the current closed-loop regulator PI. Similarly, curve 252 of graph 250 shows the relationship between the control signal for implementing the on and off switching of the bottom bridge group (S2, S4, S6) of power switch 86 versus time. Again, the switching frequency is 10 kHz, and the duty cycle D is controlled by the current closed-loop regulator PI.

[0076] As described, the present disclosure provides an EDS for an electrified vehicle, wherein the EDS includes a traction battery, an inverter, and a motor having a self-heater arrangement. To implement the self-heater arrangement, (i) the EDS also includes a hardware circuit having a contactor (i.e., a second switch (K2) 124) and a connecting line (i.e., a connector 122) between a center tap of the traction battery and a neutral point of a motor winding, and (ii) the controller adopts a new control strategy and operation mode to operate the inverter, the motor winding, and the traction battery so as to generate a circulating current therethrough.

[0077] In more detail, the controller adopts a new current loop control strategy to make the EDS generate a current that circulates between the two (top and bottom) battery packs and the motor windings. This control method creates a new operating mode for the traction battery, inverter and motor, where the battery current is a smooth square wave, and its amplitude and frequency are adjustable. The top and bottom battery packs are heated by the square AC current, while the battery packs always maintain the same state of charge during the process.

[0078] The self-heater arrangement utilizes the already existing traction battery, inverter and motor windings, with only additional cost-effective components (ie, a second switch and connector) being added.

[0079] The self-heater arrangement makes the ambient temperature irrelevant to the operation of the electrified vehicle. In this regard, the traction battery temperature and the coolant temperature are automatically controlled to maintain them within a desired range. As a result, the traction battery and the motor transmission fluid achieve enhanced performance regardless of the ambient temperature. This eliminates the need to use a separate coolant heater as described above.

[0080] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms of the present disclosure. In fact, the words used in this specification are descriptive rather than restrictive, and it should be understood that various changes can be made without departing from the spirit and scope of the present disclosure. In addition, the features of various implementation embodiments can be combined to form other embodiments of the present disclosure.

[0081] According to the present invention, a system is provided, which has: an inverter, which is connected between a battery and a motor having a winding; a center tap of the battery is connected to a neutral point of the winding, whereby the battery, the inverter and the motor are connected in a closed circuit; and a controller, which is configured to control the inverter so that a circulating current from the battery passes through the closed circuit, thereby achieving a target temperature of the battery.

[0082] According to an embodiment: the controller is further configured to control the inverter to control the amplitude of the circulating current.

[0083] According to an embodiment: the controller is further configured to control the inverter to control the frequency of the circulating current.

[0084] According to an embodiment: the circulating current is an alternating current (AC) square wave.

[0085] According to an embodiment, the present invention is also characterized by: a conductor having a switch movable between an open position and a closed position; wherein, when the switch is closed, the center tap of the battery is connected to the neutral point of the winding via the conductor; and when the switch is open, the center tap of the battery is disconnected from the neutral point of the winding.

[0086] According to an embodiment: the controller is configured to move the switch between the open position and the closed position.

[0087] According to an embodiment: the inverter is configured to drive the motor using power from the battery when the switch is in the open position.

[0088] According to an embodiment: the inverter is configured to supply the battery with power received via the motor when the switch is in the open position.

[0089] According to an embodiment: the battery comprises a top battery pack and a bottom battery pack; and a cathode of the top battery pack and an anode of the bottom battery pack are connected together at the center tap of the battery.

[0090] According to an embodiment: the voltage of the top battery group and the voltage of the bottom battery group are substantially the same.

[0091] According to the present invention, a method for use with an electric drive system of a vehicle includes the electric drive system having: a traction battery: a motor, the motor having a plurality of motor windings; and an inverter, the inverter connected between the traction battery and the motor, the method comprising: connecting together a center tap of the traction battery and a neutral point of the motor, whereby the battery, the inverter and the motor are connected in a closed circuit; and controlling the inverter to pass a circulating current from the traction battery through the closed circuit, whereby a target temperature of the traction battery is achieved.

[0092] In one aspect of the invention, the method comprises: controlling the inverter to control the amplitude of the circulating current.

[0093] In one aspect of the invention, the method comprises: controlling the inverter to control the frequency of the circulating current.

[0094] In one aspect of the invention: connecting the center tap of the traction battery and the neutral point of the motor winding together is performed only when the vehicle is not propelled by the motor and a target temperature of the traction battery is not achieved.

[0095] 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 controlling the inverter to drive the motor with power from the traction battery so that the motor propels the vehicle.

[0096] 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 connected between the battery and the motor; a conductor having a switch movable between an open position and a closed position; wherein when the switch is in the closed position, a center tap of the traction battery and a neutral point of the motor winding are connected together via the conductor, whereby when the switch is in the closed position, the traction battery, the inverter and the motor are connected in a closed circuit; and a controller configured to control the inverter when the switch is in the closed position so that a circulating current from the traction battery passes through the closed circuit, thereby generating heat to heat the traction battery and a transmission fluid of the motor.

[0097] According to an embodiment: the controller is further configured to control the inverter to control the amplitude and / or frequency of the circulating current.

[0098] According to an embodiment: the circulating current is a square wave circulating current.

[0099] According to an embodiment: the controller is configured to move the switch to the closed position when the vehicle is not propelled by the motor and target temperatures of the traction battery and the motor windings are not achieved.

[0100] According to an embodiment: the controller is configured to move the switch to the open position when the vehicle is to be propelled by the motor, and the controller is further configured to control the inverter to drive the motor with power from the traction battery so that the motor propels the vehicle.

Claims

1. A system comprising: an inverter connected between the battery and a motor having a winding; The center tap of the battery is connected to the neutral point of the winding, whereby the battery, the inverter and the motor are connected in a closed circuit; as well as A controller is configured to control the inverter to pass a circulating current from the battery through the closed circuit, thereby achieving a target temperature of the battery.

2. The system of claim 1, wherein: The controller is further configured to control the inverter to control the amplitude and / or frequency of the circulating current.

3. The system of claim 1, wherein: The circulating current is an alternating current (AC) square wave.

4. The system of claim 1, further comprising: a conductor having a switch movable between an open position and a closed position; wherein, when the switch is closed, the center tap of the battery is connected to the neutral point of the winding via the conductor; and When the switch is open, the center tap of the battery is disconnected from the neutral point of the winding.

5. The system of claim 4, wherein: The inverter is configured to drive the motor using power from the battery when the switch is in the open position.

6. The system of claim 4, wherein: The inverter is configured to supply power received via the motor to the battery when the switch is in the open position.

7. The system of claim 1, wherein: The battery includes a top battery pack and a bottom battery pack; and The cathode of the top battery pack and the anode of the bottom battery pack are connected together at the center tap of the battery.

8. The system of claim 7, wherein: The voltage of the top battery group and the voltage of the bottom battery group are substantially the same.

9. A method for use with an electric drive system of a vehicle, the electric drive system having: a traction battery; A motor having a plurality of motor windings; and an inverter connected between a traction battery and the motor, the method comprising: connecting the center tap of the traction battery and the neutral point of the motor winding together, whereby the battery, the inverter and the motor are connected in a closed circuit; as well as The inverter is controlled to pass a circulating current from the traction battery through the closed circuit, thereby achieving a target temperature of the traction battery.

10. The method of claim 9, further comprising: The inverter is controlled to control the amplitude and / or frequency of the circulating current.

11. The method of claim 9, wherein: Connecting the center tap of the traction battery and the neutral point of the motor winding together is performed only when the vehicle is not being propelled by the motor and the target temperature of the traction battery is not achieved.

12. The method of claim 9, further comprising: 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; as well as The inverter is controlled to drive the motor using power from the traction battery so that the motor propels the vehicle.

13. An electric drive system for a vehicle, the electric drive system comprising: Traction batteries; a motor having a plurality of motor windings; an inverter connected between the battery and the motor; a conductor having a switch movable between an open position and a closed position; wherein when the switch is in the closed position, the center tap of the traction battery and the neutral point of the motor winding are connected together via the conductor, whereby when the switch is in the closed position, the traction battery, the inverter and the motor are connected in a closed circuit; as well as A controller is configured to control the inverter when the switch is in the closed position to pass circulating current from the traction battery through the closed circuit, thereby generating heat to heat the traction battery and a transmission fluid of the motor.

14. The electric drive system of claim 13, wherein: The controller is further configured to control the inverter to control the amplitude and / or frequency of the circulating current.

15. The electric drive system of claim 13, wherein: The controller is configured to move the switch to the closed 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.

Images