Inverter switching frequency control system and method

Abstract

An electric motor control system includes: a voltage command module configured to determine a target d-axis voltage and a target q-axis voltage of the electric motor; a target frequency module configured to: selectively set a target switching frequency to a first predetermined switching frequency; and selectively set the target switching frequency to a second predetermined switching frequency, the second predetermined switching frequency being at least 2 kHz greater than the first predetermined switching frequency; and a switching module configured to: determine a target pulse width modulation (PWM) duty cycle for each phase of the electric motor based on the target d-axis voltage and the target q-axis voltage; and switch the branches of inverter modules connected to each phase of the electric motor according to the target PWM duty cycle and the target switching frequency.

Description

Technical Field

[0001] The information provided in this section is for the purpose of generally presenting the context of this disclosure. The work of the currently attributed inventors within the scope described in this section, and aspects of the description that may not conform to the prior art at the time of filing, are neither expressly nor impliedly acknowledged as prior art with respect to this disclosure.

[0002] This disclosure relates to inverters for vehicle motors, and in particular to systems and methods for controlling the switching of inverters. Background Technology

[0003] Some types of vehicles consist solely of an internal combustion engine that generates propulsive torque. Electric vehicles may not include an internal combustion engine, instead relying on one or more electric motors for propulsion.

[0004] Hybrid vehicles include both an internal combustion engine and one or more electric motors. Some types of hybrid vehicles utilize both electric motors and internal combustion engines to achieve higher fuel efficiency than using only the internal combustion engine. Other types of hybrid vehicles utilize both electric motors and internal combustion engines to achieve greater torque output than the internal combustion engine alone could achieve.

[0005] Some example types of hybrid vehicles include parallel hybrid vehicles, series hybrid vehicles, and other types. In a parallel hybrid vehicle, the electric motor works in parallel with the engine to combine the power and range advantages of the engine with the efficiency and regenerative braking advantages of the electric motor. In a series hybrid vehicle, the engine drives a generator to produce electricity for the electric motor, which in turn drives the transmission. This allows the electric motor to take on some of the engine's power responsibilities, thereby allowing for the use of a smaller and potentially more efficient engine. Summary of the Invention

[0006] In one feature, the motor control system includes: a voltage command module configured to determine a target d-axis voltage and a target q-axis voltage of the motor; a target frequency module configured to: selectively set a target switching frequency to a first predetermined switching frequency; and selectively set the target switching frequency to a second predetermined switching frequency, the second predetermined switching frequency being at least 2 kHz greater than the first predetermined switching frequency; and

[0007] The switching module is configured to: determine the target pulse width modulation (PWM) duty cycle of each phase of the motor based on the target d-axis voltage and the target q-axis voltage; and switch the branches (legs) of the inverter modules connected to each phase of the motor with the target PWM duty cycle and the target switching frequency.

[0008] In a further feature, the target frequency module is configured to determine whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on the torque and speed of the motor.

[0009] In a further feature, the target frequency module is configured to: based on the torque and the speed, within the fundamental electrical period of the sinusoidal phase current, set a start time and period for setting the target switching frequency to the second predetermined switching frequency; and set the target switching frequency to the second predetermined switching frequency at the start time of the period.

[0010] In a further feature, the target frequency module is configured to determine whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on the d-axis current of the motor.

[0011] In a further feature, the target frequency module is configured to: set a start time and period for setting the target switching frequency to the second predetermined switching frequency based on the d-axis current of the motor; and set the target switching frequency to the second predetermined switching frequency at the start time of the period.

[0012] In a further feature, the target frequency module is configured to determine whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on the q-axis current of the motor.

[0013] In a further feature, the target frequency module is configured to: set a start time and period for setting the target switching frequency to the second predetermined switching frequency based on the q-axis current of the motor; and set the target switching frequency to the second predetermined switching frequency at the start time of the period.

[0014] In a further feature, the target frequency module is configured to determine whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on at least one current of at least one phase of the motor.

[0015] In a further feature, the target frequency module is configured to: set a start time and period for setting the target switching frequency to the second predetermined switching frequency based on the at least one current of the at least one phase of each phase; and set the target switching frequency to the second predetermined switching frequency at the start time of the period.

[0016] In a further feature, the target frequency module is configured to determine whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on the stator current, wherein the stator current is equal to the square root of the sum of (a) the square of the d-axis current of the motor and (b) the square of the q-axis current of the motor.

[0017] In a further feature, the target frequency module is configured to: set a start time and period for setting the target switching frequency to the second predetermined switching frequency based on the stator current; and set the target switching frequency to the second predetermined switching frequency at the start time of the period.

[0018] In a further feature, the first predetermined switching frequency is 10 kHz.

[0019] In a further feature, the second predetermined switching frequency is approximately 15 kHz.

[0020] In a further feature, the second predetermined switching frequency is approximately 20 kHz.

[0021] In a further feature, the voltage command module is configured as follows:

[0022] The target d-axis voltage and the target q-axis voltage of the motor are determined by minimizing a first error between the d-axis current of the motor and the target d-axis current of the motor, and a second error between the q-axis current of the motor and the target q-axis current of the motor.

[0023] In a further feature, the current command module is configured to set the target d-axis current and the target q-axis current based on the torque request of the motor.

[0024] In a further feature, the target frequency module is configured to selectively set the target switching frequency to the second predetermined switching frequency within six different cycles during the period of the basic electrical cycle of the sinusoidal phase current.

[0025] In a further feature, the motor control method includes: determining a target d-axis voltage and a target q-axis voltage of the motor; selectively setting a target switching frequency to a first predetermined switching frequency; selectively setting the target switching frequency to a second predetermined switching frequency, the second predetermined switching frequency being at least 2 kHz greater than the first predetermined switching frequency; determining a target pulse width modulation (PWM) duty cycle for each phase of the motor based on the target d-axis voltage and the target q-axis voltage; and switching the branches of the inverter module connected to each phase of the motor with the target PWM duty cycle and the target switching frequency, respectively.

[0026] In a further feature, the motor control method further includes: determining whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on the torque and speed of the motor.

[0027] In a further feature, the motor control method further includes: based on the torque and the speed, within the basic electrical cycle of the sinusoidal phase current, setting a start time and period for setting the target switching frequency to the second predetermined switching frequency; and setting the target switching frequency to the second predetermined switching frequency at the start time of the period.

[0028] Further applicability of this disclosure will become apparent from the detailed description, claims, and drawings. The detailed description and specific examples are for illustrative purposes only and are not intended to limit the scope of this disclosure.

[0029] Option 1. A motor control system, comprising:

[0030] A voltage command module configured to determine the target d-axis voltage and the target q-axis voltage of the motor;

[0031] The target frequency module is configured as follows:

[0032] Selectively set the target switching frequency to a first predetermined switching frequency; and

[0033] Selectively setting the target switching frequency to a second predetermined switching frequency, wherein the second predetermined switching frequency is at least 2 kHz higher than the first predetermined switching frequency; and

[0034] The switching module is configured as follows:

[0035] Based on the target d-axis voltage and the target q-axis voltage, the target pulse width modulation (PWM) duty cycle of each phase of the motor is determined; and

[0036] The switches of the branches of the inverter modules connected to each phase of the motor are switched according to the target PWM duty cycle and the target switching frequency.

[0037] Option 2. According to the motor control system described in Option 1, the target frequency module is configured to: determine whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on the torque and speed of the motor.

[0038] Option 3. The motor control system according to Option 2, wherein the target frequency module is configured as follows:

[0039] Based on the torque and the speed, within the basic electrical cycle of the sinusoidal phase current, the start time and period for setting the target switching frequency to the second predetermined switching frequency are determined; and

[0040] At the start time of the cycle, the target switching frequency is set to the second predetermined switching frequency.

[0041] Option 4. According to the motor control system described in Option 1, the target frequency module is configured to: determine whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on the d-axis current of the motor.

[0042] Option 5. The motor control system according to Option 4, wherein the target frequency module is configured as follows:

[0043] Based on the d-axis current of the motor, the start time and period for setting the target switching frequency to the second predetermined switching frequency are determined; and

[0044] At the start time of the cycle, the target switching frequency is set to the second predetermined switching frequency.

[0045] Option 6. The motor control system according to Option 1, wherein the target frequency module is configured to: determine whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on the q-axis current of the motor.

[0046] Option 7. The motor control system according to Option 6, wherein the target frequency module is configured as follows:

[0047] Based on the q-axis current of the motor, the start time and period for setting the target switching frequency to the second predetermined switching frequency are determined; and

[0048] At the start time of the cycle, the target switching frequency is set to the second predetermined switching frequency.

[0049] Option 8. The motor control system according to Option 1, wherein the target frequency module is configured to: determine whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on at least one current of at least one phase of the motor.

[0050] Option 9. The motor control system according to Option 8, wherein the target frequency module is configured as follows:

[0051] Based on the at least one current of at least one phase in each of the phases, a start time and period for setting the target switching frequency to the second predetermined switching frequency are determined; and

[0052] At the start of the cycle, the target switching frequency is set to the second predetermined switching frequency.

[0053] Scheme 10. The motor control system according to Scheme 1, wherein the target frequency module is configured to: determine whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on the stator current, wherein the stator current is equal to the square root of the sum of (a) the square of the d-axis current of the motor and (b) the square of the q-axis current of the motor.

[0054] Option 11. The motor control system according to Option 10, wherein the target frequency module is configured as follows:

[0055] Based on the stator current, the start time and period for setting the target switching frequency to the second predetermined switching frequency are determined; and

[0056] At the start of the cycle, the target switching frequency is set to the second predetermined switching frequency.

[0057] Option 12. The motor control system according to Option 1, wherein the first predetermined switching frequency is 10kHz.

[0058] Option 13. The motor control system according to Option 12, wherein the second predetermined switching frequency is approximately 15 kHz.

[0059] Option 14. The motor control system according to Option 12, wherein the second predetermined switching frequency is approximately 20 kHz.

[0060] Option 15. The motor control system according to Option 1, wherein the voltage command module is configured as follows:

[0061] The target d-axis voltage and the target q-axis voltage of the motor are determined by minimizing a first error between the d-axis current of the motor and the target d-axis current of the motor, and a second error between the q-axis current of the motor and the target q-axis current of the motor.

[0062] Option 16. The motor control system according to Option 15 further includes a current command module, which is configured to set the target d-axis current and the target q-axis current based on the torque request of the motor.

[0063] Option 17. The motor control system according to Option 1, wherein the target frequency module is configured to selectively set the target switching frequency to the second predetermined switching frequency in six different cycles during the period of the basic electrical cycle of the sinusoidal phase current.

[0064] Option 18. A motor control method, comprising:

[0065] Determine the target d-axis voltage and the target q-axis voltage of the motor;

[0066] Selectively set the target switching frequency to a first predetermined switching frequency;

[0067] The target switching frequency is selectively set to a second predetermined switching frequency, which is at least 2 kHz higher than the first predetermined switching frequency.

[0068] Based on the target d-axis voltage and the target q-axis voltage, the target pulse width modulation (PWM) duty cycle of each phase of the motor is determined; and

[0069] The switches of the branches of the inverter modules connected to each phase of the motor are switched according to the target PWM duty cycle and the target switching frequency.

[0070] Solution 19. The motor control method according to Solution 18 further includes: determining whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on the torque and speed of the motor.

[0071] Option 20. The motor control method according to Option 19 further includes:

[0072] Based on the torque and the speed, within the fundamental electrical cycle of the sinusoidal phase current, the start time and period for setting the target switching frequency to the second predetermined switching frequency are determined; and

[0073] At the start time of the cycle, the target switching frequency is set to the second predetermined switching frequency. Attached Figure Description

[0074] This disclosure will be more fully understood through a detailed description and accompanying drawings, in which:

[0075] Figure 1 This is a functional block diagram of an example vehicle system;

[0076] Figure 2 This is a functional block diagram of an example propulsion control system;

[0077] Figure 3This is a schematic diagram of an embodiment of the power control system;

[0078] Figure 4 This is a schematic diagram of an embodiment of the inverter module;

[0079] Figure 5 This is a functional block diagram of an example motor control module;

[0080] Figure 6 This is an example graph showing how the pulse width modulation (PWM) duty cycle changes over time;

[0081] Figure 7 This is a flowchart describing an example method for setting a target switching frequency for an inverter module and controlling the inverter module to switch at the target switching frequency; and

[0082] Figure 8 This is an example graph showing the current and ripple tracking pulse over time.

[0083] In the accompanying drawings, reference numerals may be used repeatedly to refer to similar and / or identical parts. Detailed Implementation

[0084] The vehicle's inverter module includes branches of switches that regulate (a) the current flow from the battery to the motor and (b) the current flow from the motor to the battery. A direct current (DC) bus capacitor may be connected between the inverter module and the battery. The switching of these branches is controlled using a pulse width modulation (PWM) signal. A fixed, predetermined switching frequency for the PWM signal may be used, such as 10 kHz for automotive applications.

[0085] According to this application, the control module uses a predetermined switching frequency in some cases, but a second (higher) predetermined switching frequency in others, such as when the AC current ripple to the inverter output / input of the motor would be higher. The use of the second predetermined switching frequency reduces system losses, reduces AC current ripple and total harmonic distortion (THD), reduces motor noise, vibration, and acoustic harshness (NVH), and reduces the probability of resonance. For example, the second predetermined switching frequency can be twice the predetermined switching frequency (e.g., 20 kHz).

[0086] Now for reference Figure 1 , Figure 1A functional block diagram of an example vehicle system is shown. Although a vehicle system for a hybrid vehicle is shown and described below, this disclosure is also applicable to electric vehicles (including pure electric vehicles) that do not include an internal combustion engine, fuel cell vehicles, autonomous vehicles, semi-autonomous vehicles, non-autonomous vehicles, and other types of vehicles. Furthermore, while vehicle examples are provided, this application is also applicable to non-vehicle implementations.

[0087] Engine 102 can combust an air / fuel mixture to produce drive torque. Engine control module (ECM) 114 controls engine 102. For example, ECM 114 can control the actuation of engine actuators such as throttle valve, one or more spark plugs, one or more fuel injectors, valve actuators, camshaft phaser, exhaust gas recirculation (EGR) valve, one or more superchargers, and other suitable engine actuators. In some types of vehicles (e.g., electric vehicles), engine 102 may be omitted.

[0088] Engine 102 can output torque to transmission 195. Transmission control module (TCM) 194 controls the operation of transmission 195. For example, TCM 194 can control gear selection and one or more torque transmission devices (e.g., torque converter, one or more clutches, etc.) within transmission 195.

[0089] The vehicle system includes one or more electric motors, such as motor 198. The electric motor can function as either a generator or a motor at a given time. When used as a generator, the motor converts mechanical energy into electrical energy. For example, electrical energy can be used to charge battery 199. When used as a motor, the motor generates torque that can be used, for example, to propel the vehicle. While an example of an electric motor is provided, a vehicle may include multiple electric motors.

[0090] The motor control module 196 controls the current from the battery 199 to the motor 198 and from the motor 198 to the battery 199. The motor control module 196 applies electrical energy from the battery 199 to the motor 198 so that the motor 198 outputs positive torque, for example, for vehicle propulsion. The battery 199 may include, for example, one or more cells and / or a battery pack.

[0091] The electric motor 198 can output torque, for example, to the input shaft or output shaft of the transmission 195. The clutch 200 can be engaged to couple the electric motor 198 to the transmission 195, or disengaged to decouple the electric motor 198 from the transmission 195. One or more gear mechanisms can be implemented between the output of the clutch 200 and the input of the transmission 195 to provide a predetermined ratio between the rotation of the electric motor 198 and the rotation of the input of the transmission 195.

[0092] The electric motor control module 196 can also selectively convert the vehicle's mechanical energy into electrical energy. More specifically, when the electric motor 198 is driven by the transmission 195 and the electric motor control module 196 is not supplying electrical energy to the electric motor 198 from the battery 199, the electric motor 198 generates and outputs electrical energy through back electromotive force (EMF). The electric motor control module 196 can then charge the battery 199 using the electrical energy output by the electric motor 198.

[0093] Now for reference Figure 2 , Figure 2 A functional block diagram of an example propulsion control system is shown. The driver torque module 204 determines a driver torque request 208 based on driver input 212. Driver input 212 may include, for example, accelerator pedal position (APP), brake pedal position (BPP), cruise control input, and / or autonomous input. In various embodiments, the cruise control input may be provided by an adaptive cruise control system that attempts to maintain at least a predetermined distance between the vehicle and objects in its path. Autonomous input may be provided by an autonomous driving system that controls the vehicle's movement from one location to another while avoiding objects and other vehicles. The driver torque module 204 may use one or more lookup tables or equations to determine the driver torque request 208, which associate the driver input with the driver torque request. The accelerator pedal position (APP) and brake pedal position (BPP) may be measured using one or more accelerator pedal position (APP) sensors and brake pedal position (BPP) sensors, respectively.

[0094] Driver torque request 208 can be an axle torque request. Axle torque (including axle torque requests) refers to the torque at the wheels. As discussed further below, propulsion torque (including propulsion torque requests) differs from axle torque in that propulsion torque can refer to the torque at the transmission input shaft.

[0095] The axle torque arbitration module 216 arbitrates the driver torque request 208 and other axle torque requests 220. Axle torque (torque at the wheels) can have various sources, including engine 102 and / or one or more electric motors, such as electric motor 198. Examples of other axle torque requests 220 include, but are not limited to, torque reduction requests from the traction control system when positive wheel slippage is detected, torque increase requests to counteract negative wheel slippage, brake management requests to reduce axle torque to ensure that the axle torque does not exceed the brakes' ability to hold the vehicle when it stops, and vehicle overspeed torque requests to reduce axle torque to prevent the vehicle from exceeding a predetermined speed. The axle torque arbitration module 216 outputs one or more axle torque requests 224 based on the arbitration result between the received axle torque requests 208 and 220.

[0096] In a hybrid vehicle, the hybrid module 228 can determine how much of one or more axle torque requests 224 should be generated by the engine 102 and how much of one or more axle torque requests 224 should be generated by the electric motor 198. For simplicity, the example using electric motor 198 will continue, but multiple electric motors may also be used. The hybrid module 228 outputs one or more engine torque requests 232 to the propulsion torque arbitration module 236. The engine torque requests 232 indicate the requested torque output of engine 102.

[0097] The hybrid module 228 also outputs an electric motor torque request 234 to the electric motor control module 196. The electric motor torque request 234 indicates the requested torque output (positive or negative) of the electric motor 198. In vehicles where the engine 102 is omitted (e.g., in an electric vehicle) or where the engine 102 is not connected to the vehicle's output propulsion torque, the axle torque arbitration module 216 may output an axle torque request and the electric motor torque request 234 may be equal to that axle torque request.

[0098] In the example of an electric vehicle, ECM 114 can be omitted, and the driver torque module 204 and axle torque arbitration module 216 can be implemented within the electric motor control module 196. In the electric vehicle, the driver torque module 204 can input the driver torque request 208 to the electric motor control module 196, and components related to controlling the engine actuator can be omitted.

[0099] The propulsion torque arbitration module 236 converts the engine torque request 232 from the axle torque domain (torque at the wheels) to the propulsion torque domain (e.g., torque at the transmission input shaft). The propulsion torque arbitration module 236 arbitrates the converted torque request before it is combined with other propulsion torque requests 240. Examples of other propulsion torque requests 240 include, but are not limited to, torque reduction requests for engine overspeed protection and torque increases requests to prevent stalling. As a result of the arbitration, the propulsion torque arbitration module 236 may output one or more propulsion torque requests 244.

[0100] Actuator control module 248 controls actuators 252 of engine 102 based on propulsion torque request 244. For example, based on propulsion torque request 244, actuator control module 248 can control throttle opening, spark timing from spark plugs, fuel injection timing and quantity from fuel injectors, cylinder drive / deactivation, intake and exhaust valve phases, output of one or more boosting devices (e.g., turbochargers, superchargers, etc.), EGR valve opening, and / or one or more other engine actuators. In various embodiments, propulsion torque request 244 can be adjusted or modified by actuator control module 248 before use to generate torque reserve.

[0101] The motor control module 196 controls the switching of the inverter module based on the motor torque request 234, as discussed further below. The inverter module converts direct current (DC) to alternating current (AC). The inverter module applies AC power to the motor 198. The switching of the inverter module controls the torque of the motor 198. The inverter module also converts the electricity generated by the motor 198 back to DC power and outputs DC power to the battery 199, for example, to charge the battery 199.

[0102] The inverter module includes multiple switches, such as switches with three branches. The motor control module switches the switches to apply alternating current (AC) to the motor 198 to drive it. For example, the inverter module may generate n-phase AC and apply it to (e.g., a, b, and c, or u, v, and w) the n stator windings of the motor 198. In many embodiments, n equals 3. The magnetic flux generated by the current flowing through the stator windings drives the rotor of the motor 198. The rotor is connected to and drives the output shaft of the motor 198 to rotate. The output shaft of the motor 198 is connected to one or more wheels of the vehicle.

[0103] In various implementations, one or more filters (e.g., capacitors) may be electrically connected between the inverter module and the battery 199. For example, one or more filters may be implemented to filter electrical energy flowing into and out of the battery 199. For example, a filter including one or more capacitors and resistors may be electrically connected in parallel with the battery 199 and the inverter module.

[0104] Figure 3 This is a schematic diagram of an embodiment of the power control system. As described above, battery 199 may also be referred to as or include a battery pack.

[0105] The high (positive, DC+) and low (negative, DC-) sides 304 and 308 are connected to the positive and negative terminals of battery 199, respectively. One or more capacitors, such as capacitor 312, are connected in parallel with battery 199 between high side 304 and low side 308. The capacitors stabilize the DC bus and provide a low-impedance voltage source to the inverter module, as battery 199 may have higher impedance.

[0106] Inverter module 316 includes three branches, each connected to each phase of motor 198. Inverter module 316 controls the current flowing to the branch / phase of motor 198. Inverter module 316 converts DC power from high-side and low-side 304 and 308 into three-phase AC power and outputs the AC power to motor 198.

[0107] Figure 4 This is a schematic diagram of an embodiment of inverter module 316. Inverter module 316 includes three branches. Each branch is connected to each phase of motor 198.

[0108] The first branch 512 includes first and second switches 516 and 520. Each switch 516 and 520 includes a first terminal, a second terminal, and a control terminal. Each of the switches 516 and 520 can be an insulated-gate bipolar transistor (IGBT), a field-effect transistor (FET), such as a metal-oxide-semiconductor FET (MOSFET), or another suitable type of switch. In the example of IGBT and FET, the control terminal is referred to as the gate.

[0109] The first terminal of the first switch 516 is connected to the high side 304. The second terminal of the first switch 516 is connected to node 504. The second terminal of the second switch 520 may be connected to the low side 308. Node 504 is connected to the second terminal of the first switch 516, the first terminal of the second switch 520, and the first phase (e.g., a) of the motor 198.

[0110] The first branch 12 may include first and second diodes 524 and 528, respectively, connected in anti-parallel to switches 516 and 520. In other words, the anode of the first diode 524 may be connected to the second terminal of the first switch 516, and the cathode of the first diode 524 may be connected to the first terminal of the first switch 516. The anode of the second diode 528 may be connected to the second terminal of the second switch 520, and the cathode of the second diode 528 may be connected to the first terminal of the second switch 520. Diodes 524 and 528 form one phase of a three-phase rectifier for converting electrical energy from the motor 198 into electrical energy for the battery 199. However, diodes 524 and 528 may be omitted, for example, if switches 516, 540, 556, 520, 544, and 560 are MOSFETs (with built-in diodes). Diodes 524 and 528 may be included if the power module includes IGBTs.

[0111] Inverter module 316 also includes a second branch 532 and a third branch 536. The second branch 532 and the third branch 536 may (circuitarily) be similar to or identical to the first branch 512. In other words, the second and third branches 532 and 536 may each include corresponding switches and diodes connected in the same manner as the first branch 512, similar to switches 516 and 520 and diodes 524 and 528. For example, the second branch 532 includes switches 540 and 544 and anti-parallel diodes 548 and 552. Node 542 is connected to the first terminal of switch 544 and the second stator winding of motor 198 (e.g., b). The third branch 536 includes switches 556 and 560 and anti-parallel diodes 564 and 568. Node 570 is connected to the first terminal of switch 560 and the third stator winding of motor 198 (e.g., c). Similar to diodes 524 and 528, diodes 548, 552, 564, and 568 can be omitted.

[0112] The control terminals of the inverter module 316 switch are connected to a switch signal 576 from the motor control module 196. The motor control module 196 generates the switch signal 576 such that the high-side switch of the branch is turned on and the low-side switch of the branch is turned off, and vice versa. The motor control module 196 uses pulse width modulation (PWM) control to generate the switch signal 576.

[0113] The control signals for the gates of the low-side switches 520, 544, and 560 can be reversed so that the control signals applied to the low-side switches 520, 544, and 560 are opposite in polarity to the control signals applied to the gates of the high-side switches 516, 540, and 556.

[0114] Figure 5This is a functional block diagram of an embodiment of the motor control module 196. The switching module 604 uses a pulse width modulation (PWM) signal to control the switching of switches 516 and 520. For example, the switching module 604 applies a PWM signal to the control terminals of switches 516, 520, 540, 544, 556, and 560. When the high-side switch is closed, electrical energy flows from battery 199 to motor 198 to drive motor 198.

[0115] Considering the inversion of the signals applied to the gates of low-side switches 520, 544, and 560, the states of the high-side and low-side switches for each phase are complementary (opposite). For example, when the high-side switch 516 of the first branch 512 is on, the low-side switch 520 of the first branch 512 is off, and vice versa. When the high-side switch 540 of the second branch 532 is on, the low-side switch 544 of the second branch 532 is off, and vice versa. When the high-side switch 556 of the third branch 536 is on, the low-side switch 560 of the third branch 536 is off, and vice versa.

[0116] The PWM signals provided to the second and third branches 532 and 536 can be phase-shifted relative to each other, or phase-shifted from the PWM signals provided to the switches 516 and 520 of the first branch 512. For example, the PWM signal for each branch can be phase-shifted by 120° from each of the other branches (360° / 3 branches = 120° offset per branch). Thus, the current through the stator windings (phases) of the motor 198 can be phase-shifted by 120° from each other. Different types of PWM schemes for three-phase voltage source inverters can be used, such as space vector modulation, sinusoidal delta modulation, third harmonic injection modulation, discontinuous modulation, or other suitable PWM schemes.

[0117] The current command module 608 determines the d-axis current command (Id command) and q-axis current command (Iq command) of the motor 198 based on the motor torque request 234, the (mechanical) rotor speed 632 of the motor 198, and the DC bus voltage 610. The current command module 608 may use one or more equations and / or lookup tables to determine the d-axis and q-axis current commands, which associate the motor torque request, rotor speed, and DC bus voltage with the d-axis and q-axis current commands.

[0118] The d-axis current command and the q-axis current command are together by Figure 5412 is shown in the diagram. Voltage sensor 611 measures the DC bus voltage 610, such as the voltage on the DC bus capacitor, between battery 199 and inverter module 316 (e.g., between high side 304 and low side 308). The axis of the magnetic field or rotor winding field is called the rotor direct axis or d-axis. The axis 90 degrees after the d-axis is called the quadrature axis or q-axis.

[0119] Rotor speed 632 is the (mechanical) rotational speed of the rotor of motor 198. For example, rotor speed sensor 636 can be used to measure rotor speed 632. In various embodiments, rotor speed 632 can be determined by a rotor speed module based on one or more other parameters, such as the change of rotor position over time, where the position is determined based on current 640 of motor 198. In various embodiments, rotor speed sensor 636 can determine the rotor position, and rotor speed sensor 636 (or speed module, such as the speed module of motor control module 196) can determine rotor speed 632 based on the change of rotor position over time (e.g., using the mathematical derivative of position with respect to time). Current sensor 642 can measure phase current 640, for example, in a corresponding branch of inverter module 316. In various embodiments, one or more phase currents 640 can be estimated.

[0120] The voltage command module 656 (which may be referred to as a current regulator) determines the voltage command for motor 198 based on the d-axis current command, the q-axis current command, the d-axis current of motor 198, and the q-axis current of motor 198. The d-axis voltage command and the q-axis voltage command are together determined by... Figure 5 660 is shown in Figure 660. In various embodiments, the voltage command module 656 can use closed-loop control to generate voltage commands 660, based on or adjusting the d-axis and q-axis currents 644 toward or to the d-axis and q-axis current commands 612, respectively. The reference frame (FOR) module 648 can convert the phase current 640 into d-axis and q-axis currents 644 by applying Clarke and Parker transformations.

[0121] The switching module 604 determines the duty cycle of the PWM signal to be applied to the switches of inverter module 316 based on the d-axis and q-axis voltage commands to generate voltage for motor 198. For example, the switching module 604 may use one or more schemes (e.g., algorithms) to determine the PWM duty cycle, which utilize equations or lookup tables that associate voltage commands with the PWM duty cycle. Example PWM schemes for three-phase voltage source inverters include, but are not limited to, space vector modulation, sinusoidal-triangular modulation, third harmonic injection modulation, and discontinuous modulation. The switching module 604 switches the switches of inverter module 316 based on the PWM duty cycle of each phase and the target switching frequency 670. The duty cycle of a phase corresponds to the period during which the high-side switch of that phase is turned on (off) within the period corresponding to the target switching frequency 670 (period = 1 / target switching frequency). The PWM scheme may have a fixed switching frequency and modulated duty cycle.

[0122] The target frequency module 674 sets the target switching frequency 670. The target frequency module 674 can set the target switching frequency 670 for each phase. More specifically, the target frequency module 674 sets the target switching frequency for the first phase, the second phase, and the third phase of the inverter module 316. The target switching frequency for each phase can be the same.

[0123] The target frequency module 674 can set the target switching frequency 670 of a phase to a first predetermined switching frequency for a specified time period within the basic electrical cycle or period of the phase current, when the current ripple of that phase is less than a predetermined value. The first predetermined switching frequency can be, for example, 10 kHz or another suitable switching frequency. This provides a first predetermined number (e.g., 3) of on-cycles for the high-voltage side switches within each cycle of the phase current. The target frequency module 674 can perform this operation for each phase.

[0124] The target frequency module 674 can set the target switching frequency 670 of a phase to a second predetermined switching frequency for a specified time length within the basic electrical cycle or period of the phase current when the current ripple of that phase is greater than a predetermined value. The second predetermined switching frequency is greater than the first predetermined switching frequency. The second predetermined switching frequency can be, for example, about 15 kHz, about 20 kHz, or another suitable switching frequency that is at least 2 kHz greater than the first predetermined switching frequency. This provides a second predetermined number of on-time cycles for the high-voltage side switch within each cycle of the phase current (e.g., 6 in an example where the second predetermined switching frequency is twice the first predetermined switching frequency). The sum of the time lengths of the first and second predetermined switching frequencies is the basic electrical cycle of the current. "About" can refer to + / - 10% of the set value. Using the second (higher) predetermined switching frequency may increase the losses of the inverter module 316 (e.g., switching). However, using the second predetermined switching frequency can reduce AC current ripple, reduce motor 198 losses, reduce total system losses, reduce the root mean square (RMS) current and losses of the DC bus capacitor, and reduce total harmonic distortion (THD) of the AC current. The use of a second predetermined switching frequency can also reduce the noise, vibration, and acoustic harshness (NVH) of the motor, reduce potential resonance, and make the motor torque smoother.

[0125] The target frequency module 674 can set the period (duration) for setting the target switching frequency 670 to the second predetermined switching frequency, as well as the timing of that period, based on the torque 669 and speed 632 of the motor 198. The target frequency module can use one or more equations or lookup tables to set the period and timing (e.g., start) for using the second predetermined switching frequency, which associate the motor torque and speed with the period and timing for using the second predetermined switching frequency.

[0126] The torque sensor 668 can measure the current torque 669 of the motor 198. In various embodiments, the current torque 669 can be estimated by the torque estimation module based on one or more parameters.

[0127] As an alternative to determining the period and timing of using the second predetermined switching frequency based on the current torque 669 and speed 632, the target frequency module 674 can set the target switching frequency 670 as the period of the second predetermined switching frequency and the timing of that period based on the three-phase current setting. For example, the target frequency module 674 can set the period of using the second predetermined switching frequency for each phase and the timing of that period based on the ripple current content of the first, second, and third phases (Ia, Ib, Ic).

[0128] As an alternative to determining the period and timing of using the second predetermined switching frequency based on the current torque 669 and speed 632, the target frequency module 674 can set the target switching frequency 670 as the period of the second predetermined switching frequency and the timing of that period based on at least one of the d-axis current and q-axis current 644. For example, the target frequency module 674 can use one or more equations and / or lookup tables to set the period and timing of the first, second, and third phases using the second predetermined switching frequency, which correlate the d-axis and / or q-axis current ripple with the period and timing of each phase.

[0129] As an alternative to determining the period and timing of using the second predetermined switching frequency based on the current torque 669 and speed 632, the target frequency module 674 can set the period of a phase at which the target switching frequency 670 is set to the second predetermined switching frequency, and the timing of that period, based on the magnitude of the stator current space vector (Iss). The target frequency module 674 can determine the stator current space vector based on the d-axis current and the q-axis current 644. For example, the target frequency module 674 can set the stator current based on the square root of the sum of (a) the square of the d-axis current and (b) the square of the q-axis current, or set the stator current to be equal to the square root of the sum of (a) the square of the d-axis current and (b) the square of the q-axis current. For example, the target frequency module 674 can use one or more equations and / or lookup tables to set the period and timing of each phase using the second predetermined switching frequency, said one or more equations and / or lookup tables relating the stator current ripple to the period and timing of each phase.

[0130] The switching module 604 switches the switches of each phase of the inverter module 316 based on the PWM duty cycle and the target switching frequency of each phase.

[0131] Figure 6 This is an example diagram illustrating the gate signal applied to the first phase (phase A) 704 of motor 198 during a portion of a fundamental electrical cycle or loop, the gate signal applied to the second phase (phase B) 708 of motor 198, and the gate signal applied to the third phase (phase C) 712 of motor 198. A positive 1 gate signal may indicate that the high-side switch of that phase (e.g., 516 of the first phase 512) is closed and the low-side switch of that phase (e.g., 520 of the first phase 512) is open. A negative 1 gate signal may indicate that the high-side switch of that phase (e.g., 516 of the first phase 512) is open and the low-side switch of that phase (e.g., 520 of the first phase 512) is closed.

[0132] The left column 716 of the chart shows the gate signals for each phase, with the target switching frequency remaining constant. In other words, Figure 6 The chart in the left column 716 only used the first predetermined switching frequency.

[0133] The right column 720 includes graphs of the gate signals applied to the first phase (phase A) 724 of the motor 198, graphs of the gate signals applied to the second phase (phase B) 728 of the motor 198, and graphs of the gate signals applied to the third phase (phase C) 732 of the motor 198. The graphs in the right column 720 show the gate signals for each phase, selectively using a first predetermined switching frequency and a second predetermined switching frequency. Graph 736 shows whether the first predetermined switching frequency or the second predetermined switching frequency is used. More specifically, when the signal in graph 736 is at 2, the second predetermined switching frequency is used, while when the signal in graph 736 is at 1, the first predetermined switching frequency is used. As shown in graphs 724, 728, and 732, switching is more frequent when the (higher) second predetermined switching frequency is used. For example, when using the first predetermined switching frequency, three PWM cycles per phase period can be used; when using the second predetermined switching frequency, six PWM cycles per phase period can be used.

[0134] The current ripple pattern repeats six times the fundamental electrical frequency of the sinusoidal phase current. Since the aim is to reduce current ripple, six controls and changes are made to predetermined switching frequencies 1 and 2 within the cycle of the alternating current. The start time and duration of each switching frequency are determined using the aforementioned ripple standard, which can be done in real time or pre-calibrated (e.g., using a lookup table).

[0135] Figure 7 This is a flowchart depicting an example method for selectively changing (e.g., doubling) the switching frequency of inverter module 316 and controlling the switching of inverter module 316. Control begins at 804, where motor torque request 234 is determined as described above.

[0136] At 808, the current command module 608 determines the d-axis current command and the q-axis current command, as described above. At 812, the voltage command module 656 determines the d-axis voltage command and the q-axis voltage command based on the d-axis current command, the d-axis current, the q-axis current command, and the q-axis current.

[0137] At 816, the switching module 816 determines the target duty cycle for each phase based on the d-axis voltage command and the q-axis voltage command, respectively. At 820, the target frequency module 674 determines the target switching frequency 670 based on at least one of the following: (1) the motor torque 669 and speed 632; (2) the d-axis current; (3) the q-axis current; (4) the stator current; and (5) at least one of the phase currents. The target frequency module 674 sets the target switching frequency 670 to a first predetermined switching frequency (e.g., 10 kHz) or a second predetermined switching frequency (e.g., 20 kHz).

[0138] In 824, the switching module 604 switches the switches of each phase according to the target duty cycle and the target switching frequency. Although Figure 7 The example shows the end, but control can return to 804 for the next control loop. Figure 8 Here are example graphs showing the changes of phase current 804, d-axis current 808, q-axis current 812, ISS 816, and ripple tracking pulse 820 over time.

[0139] The foregoing description is illustrative in nature and is not intended to limit this disclosure, its application, or use. The broad teachings of this disclosure can be implemented in many forms. Therefore, while this disclosure includes specific examples, its true scope should not be limited thereto, as other modifications will become apparent upon examination of the accompanying drawings, specification, and appended embodiments. It should be understood that one or more steps within a method may be performed in a different order (or simultaneously) without altering the principles of this disclosure. Furthermore, although each embodiment is described above as having certain features, any one or more features of any embodiment of this disclosure may be implemented in any other embodiment and / or combined with features of any other embodiment, even if such combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and substitutions of one or more embodiments remain within the scope of this disclosure.

[0140] Various terms are used to describe spatial and functional relationships between components (e.g., modules, circuit components, semiconductor layers, etc.), including “connection,” “joint,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “set.” Unless explicitly described as “direct,” when describing a relationship between first and second components in the foregoing disclosure, the relationship can be a direct relationship in which no other intermediate components exist between the first and second components, or an indirect relationship in which one or more intermediate components (spatially or functionally) exist between the first and second components. In this document, the phrase “at least one of A, B, and C” should be understood to mean logical (A or B or C) using the non-exclusive logical “OR,” and should not be understood to mean “at least one of A, at least one of B, and at least one of C.”

[0141] In a diagram, the direction of the arrow typically indicates the flow of information (such as data or instructions) related to the diagram. For example, when components A and B exchange various information, but the information transmitted from component A to component B is relevant to the diagram, the arrow can point from component A to component B. This unidirectional arrow does not mean that no other information is transmitted from component B to component A. Furthermore, for information sent from component A to component B, component B can send a request for or confirmation of receipt of the information to component A.

[0142] In this application, including in the definitions below, the term "circuit" may be used instead of the terms "module" or "controller". The term "module" may refer to, belong to, or include: application-specific integrated circuits (ASICs); digital, analog, or mixed-signal analog / digital discrete circuits; digital, analog, or mixed-signal analog / digital integrated circuits; combinational logic circuits; field-programmable gate arrays (FPGAs); processor circuitry (shared, dedicated, or grouped) that executes code; memory circuitry (shared, dedicated, or grouped) that stores code executed by the processor circuitry; other suitable hardware elements that provide the functions described above; or combinations of some or all of the above, such as in a system-on-a-chip.

[0143] A module may include one or more interface circuits. In some examples, the interface circuit may include a wired or wireless interface for connecting to a local area network (LAN), the Internet, a wide area network (WAN), or a combination thereof. The functionality of any given module disclosed herein can be distributed among multiple modules connected via the interface circuit. For example, multiple modules can allow for load balancing. In another example, a server (also known as a remote or cloud) module may perform some functions on behalf of a client module.

[0144] The term "code" as used above can include software, firmware, and / or microcode, and can refer to programs, routines, functions, classes, data structures, and / or objects. The term "shared processor circuit" includes a single processor circuit that executes some or all of the code from multiple modules. The term "group processor circuit" includes a processor circuit that, in conjunction with additional processor circuitry, executes some or all of the code from one or more modules. "Multiprocessor circuit" includes multiple processor circuits on a discrete die, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination thereof. The term "shared memory circuit" includes a single memory circuit that stores some or all of the code from multiple modules. The term "group memory circuit" includes a memory circuit that, in conjunction with additional memory, stores some or all of the code from one or more modules.

[0145] The term "memory circuit" is a subset of the term "computer-readable medium." As used herein, the term "computer-readable medium" does not include transient electrical or electromagnetic signals propagated through a medium (e.g., on a carrier wave); therefore, the term "computer-readable medium" can be considered tangible and non-transient. Non-limiting examples of non-transient, tangible computer-readable media include non-volatile memory circuits (e.g., flash memory circuits, erasable programmable read-only memory circuits, or mask read-only memory circuits), volatile memory circuits (e.g., static random access memory circuits or dynamic random access memory circuits), magnetic storage media (e.g., analog or digital magnetic tape or hard disk drives), and optical storage media (e.g., CDs, DVDs, or Blu-ray discs).

[0146] The apparatus and methods described in this application can be implemented, in part or in whole, by a special-purpose computer created by configuring a general-purpose computer to perform one or more specific functions contained in a computer program. The aforementioned function blocks, flowchart elements, and other components serve as a software specification that can be translated into a computer program through the routine work of a skilled technician or programmer.

[0147] A computer program includes processor-executable instructions stored on at least one non-transitory, tangible, computer-readable medium. A computer program may also include or depend on stored data. A computer program may include a basic input / output system (BIOS) that interacts with the hardware of a special-purpose computer, device drivers that interact with specific devices of the special-purpose computer, one or more operating systems, user applications, background services, background applications, etc.

[0148] Computer programs may include: (i) descriptive text to be parsed, such as HTML (Hypertext Markup Language), XML (Extensible Markup Language), or JSON (JavaScript Object Markup); (ii) assembly code; (iii) object code generated from source code by a compiler; (iv) source code executed by an interpreter; (v) source code compiled and executed by a just-in-time (JIT) compiler, etc. As an example only, source code can be written using the syntax of the following languages: C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, JavaScript®, HTML5 (Hypertext Markup Language version 5), Ada, ASP (Active Server Pages), PHP (Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic®, Lua, MATLAB, SIMULINK, and Python®.

Claims

1. A motor control system, comprising: A voltage command module configured to determine the target d-axis voltage and the target q-axis voltage of the motor; The target frequency module is configured as follows: Selectively set the target switching frequency to a first predetermined switching frequency; and Selectively setting the target switching frequency to a second predetermined switching frequency, wherein the second predetermined switching frequency is at least 2 kHz higher than the first predetermined switching frequency; and The switching module is configured as follows: Based on the target d-axis voltage and the target q-axis voltage, the target pulse width modulation (PWM) duty cycle of each phase of the motor is determined; and The switches of the branches of the inverter modules connected to each phase of the motor are switched according to the target PWM duty cycle and the target switching frequency. The target frequency module is configured such that when the current ripple of a phase of the motor is less than a predetermined value, the target switching frequency of that phase is set to a first predetermined switching frequency within a specified time period; and when the current ripple of that phase is greater than a predetermined value, the target switching frequency of that phase is set to a second predetermined switching frequency within a specified time period.

2. The motor control system according to claim 1, wherein, The target frequency module is configured to determine whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on the torque and speed of the motor.

3. The motor control system according to claim 2, wherein, The target frequency module is configured as follows: Based on the torque and the speed, within the basic electrical cycle of the sinusoidal phase current, the start time and period for setting the target switching frequency to the second predetermined switching frequency are determined. as well as At the start time of the cycle, the target switching frequency is set to the second predetermined switching frequency.

4. The motor control system according to claim 1, wherein, The target frequency module is configured to determine whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on the d-axis current of the motor.

5. The motor control system according to claim 4, wherein, The target frequency module is configured as follows: Based on the d-axis current of the motor, the start time and period for setting the target switching frequency to the second predetermined switching frequency are determined; and At the start time of the cycle, the target switching frequency is set to the second predetermined switching frequency.

6. The electric motor control system according to claim 1, wherein, The target frequency module is configured to determine whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on the q-axis current of the motor.

7. The motor control system according to claim 6, wherein, The target frequency module is configured as follows: Based on the q-axis current of the motor, the start time and period for setting the target switching frequency to the second predetermined switching frequency are determined; and At the start time of the cycle, the target switching frequency is set to the second predetermined switching frequency.

8. The motor control system according to claim 1, wherein, The target frequency module is configured to determine whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on at least one current of at least one phase of the motor.

9. The electric motor control system according to claim 8, wherein, The target frequency module is configured as follows: Based on the at least one current of at least one phase in each phase, the start time and period for setting the target switching frequency to the second predetermined switching frequency are determined; as well as At the start of the cycle, the target switching frequency is set to the second predetermined switching frequency.

10. The motor control system according to claim 1, wherein, The target frequency module is configured to determine whether to set the target switching frequency to the first predetermined switching frequency or the second predetermined switching frequency based on the stator current, wherein the stator current is equal to the square root of the sum of (a) the square of the d-axis current of the motor and (b) the square of the q-axis current of the motor.

11. The motor control system according to claim 10, wherein, The target frequency module is configured as follows: Based on the stator current, the start time and period for setting the target switching frequency to the second predetermined switching frequency are determined; and At the start of the cycle, the target switching frequency is set to the second predetermined switching frequency.

12. The motor control system according to claim 1, wherein, The first predetermined switching frequency is 10kHz.

13. The motor control system according to claim 12, wherein, The second predetermined switching frequency is 15kHz.

14. The motor control system according to claim 12, wherein, The second predetermined switching frequency is 20kHz.

15. The motor control system according to claim 1, wherein, The voltage command module is configured as follows: The target d-axis voltage and the target q-axis voltage of the motor are determined by minimizing a first error between the d-axis current of the motor and the target d-axis current of the motor, and a second error between the q-axis current of the motor and the target q-axis current of the motor.

16. The motor control system according to claim 15, further comprising a current command module, the current command module being configured to set the target d-axis current and the target q-axis current based on the torque request of the motor.

17. The motor control system according to claim 1, wherein, The target frequency module is configured to selectively set the target switching frequency to the second predetermined switching frequency within six different cycles during the period of the basic electrical cycle of the sinusoidal phase current.

18. A method for controlling an electric motor, comprising: Determine the target d-axis voltage and the target q-axis voltage of the motor; Selectively set the target switching frequency to a first predetermined switching frequency; The target switching frequency is selectively set to a second predetermined switching frequency, which is at least 2 kHz higher than the first predetermined switching frequency. Based on the target d-axis voltage and the target q-axis voltage, the target pulse width modulation (PWM) duty cycle of each phase of the motor is determined respectively; as well as The switches of the branches of the inverter modules connected to each phase of the motor are switched according to the target PWM duty cycle and the target switching frequency. Specifically, when the current ripple of a phase of the motor is less than a predetermined value, the target switching frequency of that phase is set to a first predetermined switching frequency within a specified time period; when the current ripple of that phase is greater than a predetermined value, the target switching frequency of that phase is set to a second predetermined switching frequency within a specified time period.

19. The electric motor control method according to claim 18, further comprising: The target switching frequency is determined to be either the first predetermined switching frequency or the second predetermined switching frequency based on the torque and speed of the motor.

20. The electric motor control method according to claim 19, further comprising: Based on the torque and the speed, within the basic electrical cycle of the sinusoidal phase current, the start time and period for setting the target switching frequency to the second predetermined switching frequency are determined. as well as At the start time of the cycle, the target switching frequency is set to the second predetermined switching frequency.

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