High frequency alternating current battery heating using voltage command

Abstract

High frequency alternating current battery heating using voltage commands. A method for heating a battery pack of an electrified powertrain having an electric motor includes determining a temperature of the battery pack. In response to the battery temperature being less than a predetermined threshold temperature, the method includes performing a self-heating mode of the battery pack. This includes injecting a high-frequency direct-axis alternating voltage waveform that minimizes the output torque and prevents rotation of the rotor of the electric motor. As a result of the voltage injection, an AC current waveform is applied to the battery pack. The controller includes a temperature sensor configured to determine a temperature of the battery pack and a processor configured to perform the method. A motor vehicle includes a controller, an electrified powertrain having a battery pack and an electric motor, and road wheels connected to and powered by the electric motor.

Description

[0001] introduce

[0002] The present disclosure relates to an electrical system having an electrochemical battery pack connected to an alternating current (AC) powered electric motor via an inverter, such as a traction power inverter module of a motor vehicle, and a computer-based control method for internally heating the constituent battery cells of the battery pack using a high frequency AC current waveform.

[0003] Advanced hybrid electric and all-electric motor vehicles include one or more electric traction motors. Each traction motor is activated by the controlled discharge of a traction lithium-ion battery pack or a battery pack having a battery chemistry suitable for the application. In cold ambient conditions, the constituent cells of the battery pack are typically warmed to a threshold temperature before off-board charging. However, a motor vehicle may lack a resident fluid thermal management system (TMS), or the heating response of an available on-board TMS may be suboptimal for a given charging scenario or prevailing weather conditions. Summary of the invention

[0004] Disclosed herein are circuit topologies and associated control methods for heating an electrochemical battery pack of an electrified powertrain, such as a hybrid electric vehicle or a battery electric vehicle. The present solution enables internal heating ("self-heating") of the battery pack based on selective high-frequency alternating current (AC) current. In particular, self-heating is initiated by transmitting direct-axis (d-axis) and quadrature-axies (q-axis) voltage commands to a power inverter module (PIM) of the electrified powertrain, where the PIM is in turn connected to an electric traction motor. Zero-sequence voltage commands may also be used in certain implementations, such as when the traction motor has a neutral connection point.

[0005] When the d-axis voltage command is manipulated in accordance with the present disclosure, the q-axis voltage command is set to zero. Therefore, a high-frequency AC current waveform is generated as a result of the d-axis voltage command, and then a high-frequency AC current waveform is applied across the electrode terminals of the battery pack for heating of the battery pack. That is, the present method includes creating an unbalanced AC current in the traction motor, which ultimately results in an AC current in the battery pack. As part of the present control strategy, the angular position of the rotor of the aforementioned traction motor can be controlled in a closed loop to minimize residual rotor torque, which otherwise may result from slight changes from zero in the q-axis voltage command, and / or a reluctance torque or magnetic torque can be created via a total voltage command to maintain a desired rotor position.

[0006] In particular, a method for heating a battery pack of an electrified powertrain having at least one electric motor includes determining a temperature of the battery pack via a temperature sensor, wherein the temperature is considered herein as a measured battery temperature. In response to a set of entry conditions, the method includes executing a self-heating mode of the battery pack via an electronic controller, including injecting a high-frequency AC voltage waveform onto the d-axis of the electric motor, i.e., across the terminals of the electric motor. This occurs by heating the battery pack via a d-axis voltage command in combination with a zero quadrature axis (q-axis) voltage command. The entry condition may include the measured battery temperature being less than a lower temperature limit.

[0007] Embodiments of the method may include applying an AC current waveform across electrode terminals of the battery pack during the self-heating mode in response to injecting a high frequency AC voltage waveform into a d-axis of the electric motor.

[0008] The method may include detecting a threshold rotation of a rotor of the electric motor and adjusting a total voltage command via the electronic controller in response to the threshold rotation of the rotor.

[0009] Injecting the high frequency AC voltage waveform onto the d-axis of the electric motor may include generating a pulsating d-axis voltage command via a closed-loop position control routine of the rotor. Generating the pulsating d-axis voltage command may include using a linear combination of varying d-axis voltage commands and / or using a constant d-axis voltage command. Generating the pulsating d-axis voltage command may also include using a varying zero-sequence voltage command and / or using a constant zero-sequence voltage command.

[0010] In one or more implementations, the electronic controller includes a current regulator. In some embodiments, the method may include selectively increasing an injection frequency of a d-axis voltage injection and a bandwidth of the current regulator via the electronic controller. The method may also include changing from voltage control of the electric motor to current control of the electric motor when the injection frequency of the d-axis voltage injection is within the bandwidth of the current regulator.

[0011] The methods disclosed herein may further include determining a control angle of the electric motor during the self-heating mode, and then using the control angle to maintain an angular position of a rotor of the electric machine during the self-heating mode.

[0012] Embodiments may include calculating the reluctance torque when the control angle exceeds a calibrated value, and thereafter using the reluctance torque to reposition the rotor.Alternatively, the method may include calculating the magnetic torque when the control angle exceeds a calibrated value, and thereafter using the magnetic torque to reposition the rotor.

[0013] Also disclosed herein is an electronic controller for use with an electrified powertrain having a battery pack and an electric motor. In a possible configuration, the electronic controller includes a temperature sensor and a processor. The temperature sensor is configured to measure the temperature of the battery pack. The processor, in communication with the temperature sensor, receives the temperature of the battery pack from the temperature sensor as a measured battery temperature. In response to a set of entry conditions, the conditions including the measured battery temperature being less than a lower temperature limit, the electronic controller is configured to execute a self-heating mode of the battery pack, including injecting a high-frequency AC voltage waveform into the d-axis of the electric motor via a d-axis voltage command in combination with a zero q-axis voltage command, thereby heating the battery pack.

[0014] Also disclosed herein is a motor vehicle having road wheels and an electrified powertrain having a battery pack and an electric motor having a rotor connected to one or more of the road wheels. The motor vehicle also includes an electronic controller having a temperature sensor configured to determine the temperature of the battery pack, and a processor in communication with the temperature sensor. The processor in this particular embodiment is configured to receive the temperature of the battery pack as a measured battery temperature. In response to a set of entry conditions including the measured battery temperature being less than a lower temperature limit, a self-heating mode of the battery pack is executed by commanding a high-frequency AC voltage waveform to be injected onto the d-axis of the electric motor. This occurs via a d-axis voltage command in combination with a zero q-axis voltage command, and the battery pack is heated by causing an AC current waveform to be applied across the electrode terminals of the battery pack.

[0015] A method for heating a battery pack of an electrified powertrain system having a battery pack and an electric motor, comprising: determining the temperature of the battery pack as a measured battery temperature via a temperature sensor; and executing a self-heating mode of the battery pack via an electronic controller in response to a set of entry conditions, comprising: injecting a high-frequency alternating current (AC) voltage waveform onto a direct axis (d-axis) of the electric motor as a d-axis voltage injection via a d-axis voltage command combined with a zero orthogonal axis (q-axis) voltage command, thereby initiating an AC current waveform sufficient to heat the battery pack; and in response to the injection of the high-frequency AC voltage waveform, applying an AC current waveform across electrode terminals of the battery pack during the self-heating mode, wherein the entry conditions include the measured battery temperature being less than a lower temperature limit.

[0016] The electronic controller includes a current regulator, and the method further includes selectively increasing, via the electronic controller, an injection frequency of the d-axis voltage injection and a bandwidth of the current regulator.

[0017] detecting a threshold rotation of a rotor of the electric motor; and adjusting a total voltage command via an electronic controller in response to the threshold rotation of the rotor to maintain a desired rotor position of the rotor.

[0018] Injecting a high frequency AC voltage waveform onto a d-axis of the electric motor includes generating a pulsed d-axis voltage command.

[0019] Generating the pulsed d-axis voltage command includes using a varying d-axis voltage command and / or using a linear combination of a constant d-axis voltage command.

[0020] Generating the pulsating d-axis voltage command includes using a varying zero-sequence voltage command and / or using a constant zero-sequence voltage command.

[0021] The electronic controller includes a current regulator having a bandwidth, the method further comprising changing from voltage control of the electric motor to current control of the electric motor when an injection frequency of the d-axis voltage injection is within the bandwidth of the current regulator.

[0022] Further comprising: determining a control angle of the electric motor during the self-heating mode; and using the control angle to maintain an angular position of a rotor of the electric machine during the self-heating mode.

[0023] Further comprising: calculating the reluctance torque when the control angle exceeds a calibrated value; and repositioning the rotor using the reluctance torque.

[0024] Further comprising: calculating the magnetic torque when the control angle exceeds a calibrated value; and repositioning the rotor using the magnetic torque.

[0025] An electronic controller for use with an electrified powertrain having a battery pack and an electric motor, comprising: a temperature sensor configured to measure the temperature of the battery pack; and a processor in communication with the temperature sensor, wherein the processor is configured to: receive the temperature of the battery pack as a measured battery temperature; and in response to a set of entry conditions, including the measured battery temperature being less than a lower temperature limit, execute a self-heating mode for the battery pack, including injecting a high-frequency alternating current (AC) voltage waveform into a direct axis (d-axis) of the electric motor via a d-axis voltage command combined with a zero orthogonal axis (q-axis) voltage command, thereby heating the battery pack.

[0026] The processor is further configured to, in response to injecting the high frequency unbalanced AC voltage waveform across the electric motor, apply the AC waveform across the electrode terminals of the battery pack to heat the battery pack during the self-heating mode.

[0027] The processor is configured to detect a threshold rotation of a rotor of the electric machine and to adjust the total voltage command via the processor in response to the threshold rotation.

[0028] The processor is configured to generate a pulsed d-axis voltage command such that negligible torque is applied to the rotor during the self-heating mode.

[0029] The processor is configured to generate the pulsed d-axis voltage command using a varying d-axis voltage command and / or using a linear combination of a constant d-axis voltage command.

[0030] The processor is configured to generate the pulsating d-axis voltage command using a varying zero-sequence voltage command and / or using a constant zero-sequence voltage command.

[0031] The processor is configured to determine a control angle during the self-heating mode, and to use the control angle to maintain a desired angular position of the rotor of the electric machine for a duration of the self-heating mode.

[0032] The processor is configured to: determine when the control angle exceeds a calibrated value; calculate a reluctance torque or a magnetic torque when the control angle exceeds the calibrated value; and command the reluctance torque or the magnetic torque to reposition the rotor.

[0033] A motor vehicle comprising: road wheels; an electrified powertrain having a battery pack and an electric motor having a rotor connected to one or more of the road wheels; and an electronic controller comprising: a temperature sensor configured to determine a temperature of the battery pack; and a processor in communication with the temperature sensor, wherein the processor is configured to: receive the temperature of the battery pack as a measured battery temperature; and in response to a set of entry conditions including the measured battery temperature being less than a lower temperature limit, command a high frequency alternating current (AC) voltage waveform to a direct axis (d-axis) of the electric motor to heat the battery pack via a d-axis voltage command combined with an orthogonal axis (q-axis) command of zero, thereby applying an AC current waveform across electrode terminals of the battery pack to execute a self-heating mode of the battery pack.

[0034] The electronic controller is configured to determine a control angle during the self-heating mode, and to use the control angle to maintain the angular position of the rotor for a duration of the self-heating mode.

[0035] The above features and advantages and other features and advantages of the present teachings are readily apparent from the following detailed description of some of the best modes and other embodiments for carrying out the present teachings as defined in the appended claims when considered in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A representative motor vehicle having an electrified powertrain is illustrated in which a battery pack is heated via the control methods detailed herein.

[0037] Figure 2A is a circuit diagram depicting an exemplary electronic controller that may be used to perform aspects of the self-heating method of the present disclosure that may be used for rotor positioning / locking using reluctance torque.

[0038] Figure 2B It depicts Figure 2A A circuit diagram of an alternative embodiment of an electronic controller that can be used for rotor positioning / locking using magnetic torque.

[0039] Figure 3 Representative circuit topologies for injecting a pulsating current waveform into a battery pack via a direct-axis (d-axis) voltage command in accordance with aspects of the present disclosure are illustrated.

[0040] Figure 4A , 4B 4C and 4C are vector diagrams that together illustrate the application of pulsating current output.

[0041] Figure 5A , 5B and 5C correspond to Figure 4A , 4B and 4C control variables.

[0042] Figure 6 yes Figure 1 A simplified illustration of the rotor of an electric motor within an electrified powertrain.

[0043] Figures 7A-7D is a representative time plot of parameters according to the present disclosure.

[0044] Figure 8 is described for self-heating Figure 1 A flow chart of an exemplary method of a battery pack.

[0045] The present disclosure may be embodied or modified in alternative forms, wherein representative embodiments are shown in the accompanying drawings and described in detail below. The inventive aspects of the present disclosure are not limited to the disclosed embodiments. On the contrary, the present disclosure is intended to cover alternatives that fall within the scope of the disclosure as defined by the appended claims. DETAILED DESCRIPTION

[0046] Referring to the drawings, wherein like reference numerals correspond to like or similar parts throughout the several views, Figure 1 An electrified powertrain system 10 is illustrated in FIG. In one or more embodiments, the electrified powertrain system 10 that can be used on a motor vehicle 12 includes a high voltage traction battery pack (B HV ) 14. The traction battery pack 14 is connected to a direct current (DC) voltage bus 15 via a main battery contactor set 16. A power inverter module ("DC / AC") 18, hereinafter referred to as inverter 18 for simplicity, is electrically connected to the traction battery pack 14 via the DC voltage bus 15, wherein the illustrated open state of the contactor set 16 corresponds to a disconnected state of the traction battery pack 14.

[0047] exist Figure 1 In the illustrated embodiment, the electric traction motor (M E) 20 is connected to the alternating current (AC) side of the inverter 18. Although a single electric traction motor 20 and a single inverter 18 are shown for simplicity of illustration, the present disclosure can be extended to a multi-inverter / multi-motor powertrain, as will be appreciated by those skilled in the art. Thus, the DC voltage (VDC) present on the DC voltage bus 15 is converted to an AC voltage (VAC) suitable for exciting the individual phase windings of the electric traction motor 20. When excited, the rotor 20R of the electric traction motor 20 produces an output torque (T O ), where the output torque (T O ) is directed via an output member 200 coupled to the rotor 20R. The rotation of the output member 200 is ultimately transferred to one or more drive shafts 17, and ultimately to one or more driven road wheels 21 connected to the drive shafts 17, where for simplicity, Figure 1 Two driven road wheels 21 are illustrated in FIG.

[0048] High Frequency AC Self-Heating Mode: AC-based internal heating of the traction battery pack 14 ("self-heating") as contemplated herein requires the selective application of a high frequency alternating current to the traction battery pack 14. In one possible / non-limiting implementation, the term "high frequency" as used herein may include approximately 200 Hertz (Hz) to 1 kHz or more. However, the maximum bandwidth of typical current controllers used in the AC motor control art is typically less than 200 Hz, and is therefore insufficient for optimal AC-based self-heating of the traction battery pack 14. That is, the greater the difference between the signal frequency and the available controller bandwidth, the greater the resulting error between the commanded d-axis value and the actual d-axis value.

[0049] Method 100, an exemplary embodiment of which is referred to below Figure 8 description, and is therefore coded as Figure 1 The method 100 is a method for implementing computer readable instructions executed by an electronic controller (C) 50 of / in communication with the electrified powertrain 10 to address this potential problem. Execution of the method 100 involves the selective use of an oscillating direct axis (d-axis) voltage command in combination with a zero quadrature axis (q-axis) voltage command. As a result of the manipulation of the voltage commands on the d-axis and q-axis ("dq-axis"), a high frequency AC current is ultimately applied across the electrode terminals of the traction battery pack 14 to heat the traction battery pack 14, as described herein with reference to FIGS. 2-7D.

[0050] Still reference Figure 1 A representative motor vehicle 12 may include a low voltage / auxiliary battery (B LV) 22, such as a 12-15V lead-acid battery. The auxiliary battery 22 can be connected to an auxiliary power module ("DC / DC") 24, i.e., a DC-to-DC converter, which is connected to the battery pack 14, as shown. The operation of the auxiliary power module 24 allows for the relatively high voltage levels on the DC voltage bus 15, such as 60V-300V or more, to be reduced to a 12-15V auxiliary level suitable for powering various low-voltage electrical devices on the motor vehicle 12.

[0051] As appreciated by those skilled in the art, the inverter 18 includes solid-state power switches (not shown), such as IGBTs or MOSFETS. During the AC self-heating mode described herein, the individual ON / OFF conduction states of the various power switches are controlled by the electronic controller 50 or another dedicated processor via pulse width modulation (PWM) or another suitable switching technique. It is possible that during the execution of the method 100, the DC voltage bus 15 may be connected to several other DC devices. However, when the battery temperature of the traction battery pack 14, such as measured or estimated, calculated or otherwise determined by the temperature sensor 14S, remains below a specified lower temperature limit suitable for charging, such as approximately 32-35°F, the electronic controller 50 may not permit charging of the traction battery pack 14. In this case, the electronic controller 50 will execute computer-readable instructions embodying the method 100, thereby initiating the self-heating mode described herein.

[0052] Within the scope of the present disclosure, the electronic controller 50 includes one or more processors 52 and a memory 54. Each processor 52 is configured to receive or generate an input signal (CC I ). Input signal (CC I ) may include the measured battery temperature (T BAT ), a mode signal (CC) indicating the current operating mode of the electrified powertrain system 10 10 ), such as the speed and on / off state of the motor vehicle 12, and the measured rotor position (θ) from the rotational position sensor 20S of the electric traction motor 20 R ), the rotation position sensor 20S is, for example, a resolver, an encoder or a Hall effect sensor. R ) indicates the actual angular position of the rotor 20R and is a measured value, from which the electronic controller 50 can determine other related control values, such as motor speed, electrical angle, etc.

[0053] In response to the input signal (CC I), the electronic controller 50 is configured to execute the method 100 as one or more algorithms or instruction sets, wherein as part of the method 100, the electronic controller 50 ultimately outputs a signal (CC O ) is transmitted to the inverter 18. Output signal (CC O ) include on / off state commands or PWM signals for controlling the conductive state of individual power switches (not shown) of inverter 18. Computer readable code or instructions for implementing method 100 may be stored in a tangible, non-transitory portion of memory 54, where memory 54 embodies a computer-readable storage medium, such as magnetic or optical media, CD-ROM, and / or solid-state / semiconductor memory (e.g., various types of RAM or ROM).

[0054] The term "controller" and related terms such as control module, module, control, control unit, processor, and the like refer to one or various combinations of application specific integrated circuit(s) (ASICs), field programmable gate arrays (FPGAs), electronic circuit(s), central processing unit(s), such as microprocessor(s), and associated non-transitory memory components in the form of memory and storage devices (read-only, programmable read-only, random access, hard drive, etc.). The non-transitory components of the memory 54 are those components capable of storing machine-readable instructions in the form of one or more software or firmware programs or routines, combinational logic circuit(s), input / output circuit(s) and devices, signal conditioning and buffering circuits, and other components that can be accessed by the processor(s) 52 to provide the described functionality.

[0055] (One or more) input / output circuits and devices include analog / digital converters and related devices that monitor inputs from sensors, monitoring such inputs at a preset sampling frequency or in response to a triggering event. Software, firmware, programs, instructions, control routines, codes, algorithms and similar terms mean a set of instructions executable by a controller, including calibration and lookup tables. Each controller executes (one or more) control routines to provide the desired functionality. Routines can be executed at regular intervals, such as at intervals of approximately 50-100 microseconds (ms) during ongoing operation. Alternatively, routines can be executed in response to the occurrence of a triggering event.

[0056] D-axis voltage command: As is appreciated in the art, the d-axis and q-axis commands in the context of motor control are used as adjustable setpoints or control "knobs" or "handles" that the electronic controller 50 can access when controlling the flux and torque settings of the electric traction motor 20. In geometric terms, the d-axis and q-axis are single-phase representations of flux contributions of separate sinusoidal phase quantities occurring at the same angular velocity. In particular, the d-axis is aligned / in-phase with the permanent magnet field of the rotor 20R and is the specific axis that primarily produces flux. When executing the self-heating mode, the d-axis current can be manipulated using the d-axis voltage command, as described below.

[0057] The torque production of the electric traction motor 20 is primarily produced on its q-axis, which is generally aligned with the rotating field of the stator, i.e., 90° out-of-phase with the magnetic field of the rotor 20R. During the current self-heating mode, the q-axis voltage command is therefore set to zero to minimize the torque generation and resulting movement of the motor vehicle 12. The q-axis command is used in the motor control strategy to influence torque production. However, during the self-heating mode considered herein, the q-axis voltage command is purposefully set to zero and maintained there for the duration of the self-heating mode. Despite this control action, visible changes in the q-axis current may still result, and therefore other techniques for minimizing or preventing movement of the rotor 20R are described below. The d-axis voltage command for this portion is controlled to provide a high-frequency AC component to the traction battery pack 14 and create an imbalance across the output phases of the electric traction motor 20 during the self-heating mode.

[0058] When the rotor 20R of the electric traction motor 20 is not rotating, i.e., maintained at zero speed, there is no cross-coupling effect between the d-axis and the q-axis (due to the back-electromotive force from the permanent magnet flux and the stator induced flux). Therefore, the d-axis voltage command can be derived using an open-loop method herein. Due to inductance nonlinearity (saturation), the voltage command can be defined by a lookup table herein and is not calculated in real time. However, even when the rotor 20R is at zero speed, Figure 1 Slight asymmetries in the electric traction motor 20 may still produce small cross-coupling effects between the d-axis and the q-axis, where the control actions contemplated herein are used to counteract such effects.

[0059] When using e.g. Figure 1When a rotor position sensor such as the position sensor 20S shown in FIG. 1 is used, position errors may also result in a small amount of residual torque and resulting d-axis current injection during the contemplated d-axis voltage control. Because rotation of the rotor 20R is undesirable when heating the traction battery pack 14, the present control method may optionally incorporate generation of a pulsating d-axis voltage command via a closed-loop position control routine with respect to the angular position of the rotor 20R, as shown in FIG. Figure 2A and Figure 2B Doing so will help ensure that negligible torque is applied to the rotor 20R during the self-heating mode to avoid potential movement of the motor vehicle 12 .

[0060] Zero-sequence voltage command: A zero-sequence voltage command may be applied in one or more configurations of the electric traction motor 20 to generate a balanced set of phase voltages. For example, in a balanced three-phase system, the individual phase voltages may be represented using complex numbers, where the zero-sequence voltage represents a voltage signal applied simultaneously to all three electrical phases, nominally a, b, and c phases. The application of the balanced voltage signal causes current to flow through the stator windings of such a machine, which in turn produces a rotating magnetic field with a zero net magnetic field in each direction. Zero-sequence voltage commands that do not contribute to mechanical torque generation may be selectively used herein to modify the magnetic field generated in the electric traction motor 20 during the envisioned self-heating mode. That is, although a neutral connection point is typically not present in an AC motor constructed for use in an electrified powertrain 10, such a motor configuration may be used in some, unlike residential electrical systems. In such a case, the zero-sequence voltage command adds another handle that may be used for optimal performance in the self-heating mode.

[0061] Reference now Figure 2A and Figure 2B , the method 100 may be implemented by Figure 1 The electronic controller 50 via the control logic 50L ( Figure 2A ) or 150L( Figure 2B ) collection to achieve this. Figure 1 A simplified representation of the electrified powertrain 10 includes a traction battery pack 14, an inverter 18, and an electric traction motor 20, along with associated resistors (R1, R2), capacitors (C1), and inductors (L1) representing the equivalent resistance, capacitance, and inductance of various circuit components, such as a DC link capacitor, traction battery pack 14, and associated wiring. Figure 1 The electronic controller 50 shown in FIG. 1 may be programmed with computer readable instructions embodying control logic 50L or 150L. Figure 2A and Figure 2BIn a non-limiting configuration, the control logic 50L or 150L includes a voltage command block 55 and a closed-loop position control block 58 .

[0062] In the voltage command box 55, the d-axis voltage command (V d ), q-axis voltage command (V q ) and the optional zero-sequence voltage command (V0) selection value. The q-axis voltage command is set to zero, that is, V q =0 to effectively eliminate torque generation as noted above. The zero sequence voltage command (V0) is likewise set to zero, but may also be set to a non-zero value in certain embodiments of the electric traction motor 20 having a neutral connection point. The dq-to-abc reference frame conversion is performed by transformation block 57 such that representative three-phase voltage commands in the nominal abc reference frame are provided to the inverter 18 as output signals (CC O ) part, for example as a PWM signal from an inverter control unit or a PWM control box 56.

[0063] exist Figure 2A The closed loop position control block 58 is also shown in the block diagram of FIG. 50 , which is used for the purpose of rotor positioning / locking using reluctance torque in one or more embodiments, as described in detail below. Here, the operation control logic 50L Figure 1 The electronic controller 50 determines the reference angle (θ e，ref )(block 60), i.e., the initial value, and the measured electrical angle (θ e )(frame 51), that is, where P is the number of pole pairs and θ m is the mechanical angle between the rotor 20R and the stator (not shown). Therefore, a hypothetical embodiment of an electric traction motor 20 having two pole pairs (P=2) would have an electrical angle equal to the mechanical angle. This result may be processed via a proportional-integral-derivative (PID) control block 64 and then integrated at an integrator block 66 To generate and introduce a small error value (θ e，err_gen ). For the purpose of maintaining its angular position Figure 1 The generated error value (θ) of the residual torque generated on the rotor 20R e，err_gen ) at the node (N1) from the measured electrical angle (θ e ) is subtracted from the block 51, where the change over time, ie, ω(t), is fed into the transformation block 57 to track the change in electrical angle in real time. Another node (N2) can be used to determine (θ e ) when correcting the sensor-based offset error (θ e，err ), as understood in the art.

[0064] use Figure 2A The exemplary control logic 50L, Figure 1 The electronic controller 50 can slowly increase the d-axis voltage command (V d ) to allow for closed loop position control to react in the event of a residual torque being generated by voltage injection. Closed loop control of the rotor 20R is achieved using a closed loop position control block 58, but alternative topologies may also be assumed. These may include, for example, a PID control block 64 including zero gain, a PID controller in series with an integrator block 66, or the use of a lead / lag compensator or other suitable technique. The output from the PWM control block 56 ultimately controls the output phase voltage (V abc，0 ), phase current (I abc ) and the commanded torque (T q ), where the output signal (CC O ) includes these values ​​or these values ​​are included as separate signals.

[0065] Generates pulsating d-axis current (I d ) when executed as part of the self-heating mode described herein may include using a varying d-axis voltage command (V d ) and / or a constant d-axis voltage command (V d ), and possibly using a varying zero-sequence voltage command (V0) and / or a constant zero-sequence voltage command (V0). The zero-sequence voltage command (V0) may be added independently of whether the electric traction motor 20 has a neutral connection point. However, as will be appreciated by one of ordinary skill in the art, embodiments of the electric traction motor 20 lacking such a neutral connection point will not experience zero-sequence current circulation.

[0066] Figure 2B The diagram shows Figure 2A The control logic 150L is an alternative control logic to the control logic 50L. For the purpose of rotor positioning and locking, the control logic 150L can use magnetic torque instead of reluctance torque. q The current is not high frequency, so it is possible to use the current regulator directly for this low frequency component even with the bandwidth limitation of the controller 50 operating as a current controller. In parallel, the d-axis voltage injection described herein is still responsible for the AC heating of the traction battery pack 14 .

[0067] Relative to Figure 2A The circuit topology and control logic of 50L, Figure 2B Blocks 55 and 58 are used in a modified manner and a current regulator block 59 is added. Here, block 58 above determines the q-axis current command (i ) based on the output of integrator 66, for example via a lookup table. q * ), and the q-axis current command (iq * ) is fed into a current regulator 59, such as a PID controller with limited bandwidth. The output of block 55 is added to the output of the current regulator block 59, with the sum being fed into block 57. In other words, instead of Figure 2A The same small error value (θ e，err_gen ) and subtract that value from the output of block 51, but instead use the current controller block directly. For the purpose of rotor positioning / locking during AC heating of the traction battery pack 14, such an approach can be used to control the magnetic torque as explained below.

[0068] Brief reference Figure 3 ,exist Figure 2A and Figure 2B The zero-sequence voltage command (V0) illustrated as having a zero value in FIG. 1 may alternatively have a non-zero value in some implementations, for example using logic 70 that performs a linear combination of the varying and / or constant voltage commands 72 as noted above. Similar combinations may be performed to generate the d-axis voltage command (V d The corresponding switching blocks 74A and 74B can be controlled to output the d-axis voltage command (V d ) and the desired resulting waveform of the zero-sequence voltage command (V0) as shown.

[0069] exist Figure 3 At block 75, the q-axis voltage command (V q ) As in Figure 2A and Figure 2B PWM control of the electric traction motor 20 of FIG. 2 via the inverter 18 uses a conversion block 57 via Figure 2A and Figure 2B PWM control block 56 is performed. When the electric traction motor 20 lacks a neutral point, as is common in vehicle propulsion applications, the effect is infinite impedance and lack of zero-sequence current circulation. Therefore, if so desired, the zero-sequence voltage command (V0) can be added and controlled to a non-zero value regardless of whether the electric traction motor 20 has a neutral connection point.

[0070] Figure 4A , 4B and 4C respectively illustrate the electric traction motor 20 ( Figure 1 , 2A and 2B) of the d-axis, q-axis and representative a-axis, b-axis and c-axis of the nominal abc reference frame of a non-limiting three-phase embodiment. Figure 4A Depicted are a (non-zero) d-axis voltage component and a zero-valued q-axis component as used herein during a self-heating mode.

[0071] Figure 5A The corresponding magnitude plots of the dq variables are shown in Figure 5B A similar plot for the abc variables is shown in . The nominal amplitude is Figure 5A , 5B and 5C are plotted on the vertical axis, and time (t) in seconds (s) is plotted on the horizontal axis, wherein Figure 5A and Figure 5B Corresponds to Figure 4C A vector diagram of . Figure 4B Again, it is a vector diagram, in particular the vector diagram of the zero-sequence voltage command (V0) mentioned above. Figure 4C The vector diagram further illustrates Figure 4A and Figure 4B The vector diagram of the phase current I a ,I b and I c exist Figure 5C The magnitude is shown in the plot. Figure 5C The unbalanced nature of the phase current is illustrated in itself, where as part of the present method 100, the AC current waveform is ultimately applied to Figure 1 The electrode terminals of the traction battery pack 14 are used for AC-based self-heating.

[0072] Rotor Positioning / Locking: Now refer to Figure 6 , presents a highly simplified illustration of the rotor 20R, illustrating its south pole (S) and north pole (N). The inertia of the rotor 20R and the inertia of the load connected thereto, e.g. Figure 1 The (one or more) drive shafts 17 and road wheels 21 of the present invention will filter out the high-frequency electromagnetic torque components that may be present. When an unbalanced high-frequency AC current is injected via a d-axis voltage command according to method 100, the magnetic torque component will average to zero. However, when d-axis voltage injection is performed according to the present method 100, the reluctance torque will have a non-zero average value. Therefore, one aspect of the present disclosure includes using the reluctance torque in a controlled manner to maintain the desired angular position of the rotor 20R.

[0073] The amplitude of the d-axis voltage command used as part of the method 100 may also be slowly increased to allow the closed loop position control of the rotor 20R to react to minor torque generation during the self-heating mode. Signal injection may be accomplished in a rotating or stationary reference frame using αβ or abc voltage signals as understood in the art. Due to slight harmonics, some rotor positions may be less affected by torque fluctuations than others when a high frequency AC waveform is injected. For example, at key-off of the motor vehicle 12, Figure 1 The rotor 20R can be selectively positioned to a predetermined "optimal" angular position.

[0074] Furthermore, with respect to using the reluctance torque for the purpose of position control of the rotor 20R, one may consider the following equation to determine the torque (T):

[0075]

[0076] Component ψ m i q decreases to zero because when a high frequency AC current is injected via the d-axis voltage command, the q-axis current (i q ) has an average value of zero. However, in some embodiments, the electronic controller 50 may command the injection of a DC component on the q-axis to m i q The term affects the torque. Additionally, the q-axis and d-axis currents can be expressed as follows:

[0077]

[0078]

[0079] where θ err is the angular difference between the real dq-axis reference frame aligned with the north pole of the rotor and the virtual reference frame, and are the corresponding d-axis and q-axis current components in the real reference frame, and and are the corresponding d-axis and q-axis current components on the virtual reference frame of the controller 50. When these expressions are considered When multiplied together, it is expressed as follows:

[0080]

[0081]

[0082]

[0083] Where P is the number of poles of the electric traction motor 20. By creating a small error (θ err ), as referenced above Figure 2A As explained, it is possible to induce a small average amount of reluctance torque. This induced reluctance torque is then applied to the rotor 20R to maintain the desired angular position of the rotor 20R during the self-heating mode of the battery pack 14. Alternatively, Figure 2B The circuit topology can be used to generate a small average amount of magnetic torque, Used for positioning / locking the rotor 20R.

[0084] Reference now Figures 7A-7D In some implementations, the method 100 will result in a zero q-axis voltage command, i.e., V q=0, and for the purposes of this example, results in a zero-sequence voltage that is also zero, i.e., V0 = 0. However, the d-axis voltage command will tend to be within a representative time period (t) and a representative voltage range (±V d ) Fig. 7A For the same time period, the d-axis current command (I d ) will also vary as shown. In addition to pure sinusoidal signals, other waveforms are possible, such as triangle waves, square waves, etc.

[0085] like Figure 7B As shown in the figure, Fig. 7A The high frequency d-axis voltage command (V d ) can result in a q-axis current (I q ) small change 80. When self-heating by method 100 Figure 1 When the traction battery pack 14 is connected, this current change can cause a slight rotation of the rotor 20R. Figure 2A or Figure 2B In one or more of the embodiments described, closed loop control may be established over the angular position of the rotor 20R to maintain the rotor 20R at a desired angular position, and possibly initially set the rotor 20R to such a position prior to the self-heating mode.

[0086] Ideally, when heated Figure 1 When the battery pack 14 is set, the angular position of the rotor 20R will not change. However, the closed loop control response may see a small / negligible movement within the calibration window, such as + / - 5x10 -3 Radians, such as Figure 7C As represented by the position trajectory 82 in . Fig.7D The resulting battery current (i BAT ), wherein the battery current circulates in the traction battery 14. Therefore, the battery 14 is supplied with a high frequency AC current waveform, i.e., i d , while the heating, as mentioned above, is itself determined by the d-axis voltage command (V d ) inductive.

[0087] Figure 8 The heating Figure 1 An embodiment of the method 100 of the electric powertrain 10 with the battery pack 14 connected to the electric traction motor 20 is provided. For clarity of description, Figure 8 Organized into discrete process steps, code segments, or blocks, wherein each block of method 100 is executed and thus Figure 1 The electronic controller 50 executes.

[0088] At block B102, the method 100 includes determining the temperature (T BAT ), which can be obtained by Figure 1 The temperature sensor 14S performs the measurement of the battery temperature (T BAT ) is then transmitted to the electronic controller 50, such as via a controller area network (CAN) message bus. The method 100 proceeds to block B104.

[0089] At block B104, the electronic controller 50 determines whether a predetermined set of entry conditions have been met. For example, the conditions considered in block B104 may include a measured battery temperature (T BAT ) is less than the calibrated minimum temperature limit (T CAL Although other temperature values ​​may be used as the minimum temperature limit (T CAL ), but in one or more embodiments, a temperature limit of approximately 32-35°F may be appropriate. Other conditions may also be considered, including but not limited to receiving a user request for self-heating, for example via a cellular phone or touch screen (not shown), Figure 1 The motor vehicle 12 is in a closed state / stationary park, etc. In response to the entry conditions being met, the method 100 proceeds to box B106, wherein when the entry conditions are not met, the method 100 instead proceeds to box B102.

[0090] At box B106, the method 100 next includes executing the aforementioned self-heating mode of the battery pack 14 via the electronic controller 50. This includes at least one of: d ) and the q-axis voltage command (V q ) combines to inject a high frequency AC waveform into the traction battery pack 14 and control the position of the rotor 20R in a closed loop during the self-heating mode (see Figure 2A and Figure 2B ) to minimize the output torque (T o ), ideally zero or within an existing gear lash tolerance. That is, gear lash in the electric traction motor 20 may allow for small movements of the rotor 20R without movement of the motor vehicle 12, and thus interference may occur beyond such predetermined gear lash limits.

[0091] Block B106 may include generating an unbalanced AC waveform in the electric motor via the electronic controller 50 and applying the AC waveform across the electrode terminals of the traction battery pack 14. The electronic controller 50 may have a bandwidth of less than about 200 Hz, in which case generating the unbalanced AC waveform may include generating an AC waveform having a frequency of at least 200 Hz to 1 kHz. As part of block B106, the method 100 may also include detecting a threshold rotation of the rotor 20R, such as using Figure 1 In such a case, generating the unbalanced AC waveform may include adjusting the injection angle via the electronic controller 50 in response to the threshold rotation, thereby counteracting the threshold rotation.

[0092] exist Figure 8 The closed-loop control routine executed in block B106 may also include generating a pulsating d-axis voltage command (V d ), so that negligible electromagnetic torque is generated during the self-heating mode. Figure 3 As described, this action may require using a linear combination of varying and / or constant d-axis voltage commands, and may use varying and / or constant zero-sequence voltage commands. The method 100 then proceeds to block B108.

[0093] Block B108 includes determining the angular position (θ R ) is in the calibration position (θ CAL ) within the predetermined tolerance, i.e., θ R ≈θ CAL When the angular position is not within a predetermined tolerance, such as Figure 7C The 5×10 -3 radians, the method 100 proceeds to block B109. Block B108 may include determining a control angle during the self-heating mode, and then using the control angle to maintain the position of the rotor 20R for the duration of the self-heating mode, such as when the control angle exceeds a calibrated value. The control angle as used herein is Figure 1 The control signal (CC O ) is applied to a specific angle of the electric traction motor 20. The method 100 instead proceeds to block B110.

[0094] In box B109 (GEN T R), the electronic controller 50 may generate a reluctance torque as described above, and then apply the reluctance torque to reposition the rotor 20R. In one or more embodiments, generating the reluctance torque may include generating a small difference in the virtual reference angle, such as 1-2°. In one or more embodiments, block B109 may include selectively injecting a DC voltage waveform into the d-axis of the electric traction motor 20 to maintain the rotor 20R at a predetermined angular position. The method 100 then returns to block B108.

[0095] At box B110 ("XC?"), the electronic controller 50 can determine whether an exit condition exists for exiting the method 100. Representative conditions can include an electrical fault, or perhaps a threshold rotation of the rotor 20R, which indicates that the motor vehicle 12 moves through a resident amount that is more than the gear play in the electric traction motor 20. When the motor vehicle 12 is equipped with front / rear cameras or sensors, the movement of the motor vehicle 12 (and the closed-loop control of the rotor 20R) can be coordinated with data from such sensors. When such a fault condition has been detected, the method 100 proceeds to box B112. When a fault condition is not detected, box B102 is performed instead.

[0096] Frame B112 ("EXT") includes exiting the method 100 and interrupting the self-heating mode. In such a case, the method 100 can be restarted from frame B102 at the next ignition-off cycle of the motor vehicle 12, or can be blocked until maintenance has been performed depending on the nature of the fault detected in frame B110.

[0097] Self-heating can be performed in various situations Figure 1 The proposed method 100 is for charging the traction battery pack 14 of the embodiment of the present invention. For example, the method 100 may be performed when one or more high voltage loads, such as an AC compressor control module, an auxiliary power module 24, or a high voltage heater (not shown), are operable on the DC voltage bus 15 and connected to the traction battery pack 14. The method 100 may also be performed when the traction battery pack 14 is actively charged, such as via a DC fast charging process. This may occur regardless of whether the HV loads are operable on the DC voltage bus 15.

[0098] The electronic controller 50 may optionally selectively use the voltage control method of the present disclosure. For example, the controller 50 may change from voltage control to current control based on the injection frequency of the d-axis voltage injection. This action may require switching to current control when, for example, it is determined based on a threshold comparison that the injection frequency is within the existing bandwidth of the current regulator controller 59.

[0099] If current control is used, the injection frequency and bandwidth of the electronic controller 50 acting as a current regulator can be selectively increased to improve control. For example, the bandwidth of the current regulator can be modified by adjusting controller gains such as proportional and integral gains. The gain values ​​of the electronic controller 50 can be defined using a lookup table, where the input to the lookup table is the highest frequency component of the d-axis current command. Alternatively, algebraic functions such as linear, nonlinear, polynomial, and piecewise linear can be used to define each controller gain based on the input (the highest frequency component of the d-axis current command).

[0100] In addition to other ancillary benefits, Figure 8 The method 100 solves the problem of limited AC current injection for battery self-heating at higher frequencies while minimizing the rotation of the rotor 12R due to excess residual torque. The use of the method 100 also enables the traction battery pack 14 to be uniformly heated faster than conventional methods, such as before charging. In this way, the implementation of the present technical solution can help improve Figure 1 The operating range of the motor vehicle 12 is improved without the need for additional hardware. In view of the previous disclosure period, those skilled in the art will easily appreciate these and other attendant benefits of the present disclosure.

[0101] The specific implementation scheme and the accompanying drawings or each figure are support and description of this teaching, but the scope of this teaching is limited only by the claims. Although the best mode and some of the other embodiments for implementing this teaching have been described in detail, there are various alternative designs and embodiments to practice this teaching defined in the appended claims.

Claims

1. A method for heating a battery pack of an electrified powertrain having a battery pack and an electric motor, comprising: determining a temperature of the battery pack as a measured battery temperature via a temperature sensor; and In response to the set of entry conditions, a self-heating mode of the battery pack is executed via the electronic controller, including: injecting a high frequency alternating current (AC) voltage waveform onto a direct axis (d-axis) of the electric motor as a d-axis voltage injection via a d-axis voltage command combined with a quadrature axis (q-axis) voltage command of zero, thereby initiating an AC current waveform sufficient to heat the battery pack; and In response to injecting the high frequency AC voltage waveform, an AC current waveform is applied across the electrode terminals of the battery pack during a self-heating mode, wherein an entry condition includes a measured battery temperature being less than a lower temperature limit.

2. The method according to claim 1, wherein: The electronic controller includes a current regulator, the method further comprising: The injection frequency of the d-axis voltage injection and the bandwidth of the current regulator are selectively increased via an electronic controller.

3. The method according to claim 2, further comprising: detecting a threshold rotation of a rotor of an electric motor; and In response to a threshold rotation of the rotor, the total voltage command is adjusted via the electronic controller to maintain a desired rotor position of the rotor.

4. The method according to claim 1, wherein: Injecting a high frequency AC voltage waveform onto a d-axis of the electric motor includes generating a pulsed d-axis voltage command.

5. The method according to claim 4, wherein: Generating the pulsed d-axis voltage command includes using a varying d-axis voltage command and / or using a linear combination of a constant d-axis voltage command.

6. The method according to claim 5, wherein: Generating the pulsating d-axis voltage command includes using a varying zero-sequence voltage command and / or using a constant zero-sequence voltage command.

7. The method according to claim 1, wherein: The electronic controller includes a current regulator having a bandwidth, the method further comprising: When the injection frequency of the d-axis voltage injection is within the bandwidth of the current regulator, a change is made from voltage control of the electric motor to current control of the electric motor.

8. The method according to claim 1, further comprising: determining a control angle of the electric motor during a self-heating mode; and During the self-heating mode, the control angle is used to maintain the angular position of the rotor of the electric machine.

9. The method according to claim 8, further comprising: When the control angle exceeds the calibration value, the reluctance torque is calculated; and Reluctance torque is used to reposition the rotor.

10. The method according to claim 1, further comprising: When the control angle exceeds a calibrated value, calculating the magnetic torque; and Use magnetic torque to reposition the rotor.

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