Torque ripple compensation in motor control system

Abstract

A method for operating a motor control system to dynamically compensate for low-frequency and / or high-frequency torque fluctuations. The method includes: receiving an input command; receiving a drive feedback signal representing a drive current in the motor; identifying harmonics in the drive feedback signal representing torque fluctuations in the motor; generating a torque fluctuation compensation signal based on the identified harmonics; and generating a motor drive control signal based on the input command, the current feedback signal, the torque fluctuation compensation signal, and a carrier signal with a certain phase shift.

Description

Technical Field

[0001] This disclosure generally relates to electric motor control systems. More specifically, this disclosure relates to AC electric motor control systems that provide harmonic torque ripple compensation. Background Technology

[0002] Alternating current (AC) motor systems are used in a variety of applications, including industrial installations and motor vehicles. These types of systems include AC motors and motor control systems. In response to an input command, the motor control system applies power from an energy source to the motor in a controlled manner, causing the motor to provide the commanded output. For example, in response to a torque command, the motor control system will cause the motor to transmit the requested torque on the motor's output shaft. While AC motor control systems typically attempt to provide a balanced sinusoidal drive current to produce a constant torque output from the motor, undesirable variations in the motor's torque output (often referred to as torque ripple) are inherent in many AC motors. For example, torque ripple is an inherent characteristic of many AC motors (such as internal permanent magnet motors) due to the placement of magnets at discrete locations around the motor's axis of rotation. There remains a need for improved AC motor control systems capable of reducing torque ripple. Summary of the Invention

[0003] The disclosed embodiments include an improved method for operating a motor control system to compensate for torque ripples. The embodiments include receiving an input command, receiving a drive feedback signal representing a drive current in the motor, identifying harmonics in the drive feedback signal representing motor torque ripples, generating a torque ripple compensation signal based on the identified harmonics, and generating a motor drive control signal based on the input command, the current feedback signal, and the torque ripple compensation signal.

[0004] In the example, identifying harmonics in the drive feedback signal includes identifying harmonics in the drive current; generating a torque ripple compensation signal includes generating a harmonic cancellation command; and generating a motor drive control signal includes summing the harmonic cancellation command and the input command. Summing the harmonic cancellation command and the input command can include summing the harmonic cancellation command and the input command in the dq reference coordinate system.

[0005] In these and other examples, the method further includes generating a dq reference coordinate system control feedback signal based on the drive feedback signal, and generating a motor drive control signal including a summed harmonic cancellation command and an input command based on the dq reference coordinate system, and generating a motor drive signal based on the dq reference coordinate system control feedback signal.

[0006] An example of this method is configured for use with a motor having multiple sets of windings. Generating torque ripple compensation signals may include determining the phase shift angle of a set of carrier signals, and generating motor drive control signals may include generating a set of motor drive control signals for each of the multiple sets of windings based on one of the carrier signals, and controlling the relative phase of the set of carrier signals based on the phase shift angle.

[0007] In the example, generating the torque ripple compensation signal also includes determining the phase shift angle of the carrier signal, and generating the motor drive control signal also includes generating the motor drive control signal based on the carrier signal having a specific phase shift angle.

[0008] In the example, generating a torque ripple compensation signal includes generating the signal based on the amplitude of the identified harmonics. Generating the torque ripple compensation signal may include generating a signal if the amplitude of the identified harmonics is greater than a predetermined level.

[0009] This method can be configured to control a multiphase motor. It can also be configured to control a motor with multiple sets of windings. In the example, the method further includes receiving a motor operating characteristic feedback signal and generating a motor drive control signal based on the motor operating characteristic feedback signal. In the example, the input command includes a torque command. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of a motor system including a motor control system according to an embodiment.

[0011] Figure 2 This is a schematic diagram of an electric motor control system according to an implementation method. Detailed Implementation

[0012] Figure 1This is a schematic diagram of a motor system 8, including a motor control system 10 and an alternating current (AC) motor 12, according to an embodiment. The output of the motor control system 10 is coupled to an inverter 14. The inverter 14 responds to the output of the motor control system 10 and controls the application of power from a source 16 to the motor 12. In addition to control input commands such as torque requests, the motor control system 10 also receives feedback inputs from components of the system 8. In the illustrated embodiment, for example, the motor control system 10 is coupled to receive feedback inputs representing the electrical operating characteristics of the motor 12 provided by a current sensor 18 and the mechanical operating characteristics of the motor provided by a solver system 20. As described in more detail below, in response to the control input commands and system feedback inputs, the motor control system 10 provides an output drive signal or command that causes the motor to provide a command output such as a torque level, while compensating for variations in output torque (referred to as torque ripple) caused by the inherent characteristics of the motor 12.

[0013] In this embodiment, motor 12 is a multiphase AC motor with rotor and stator windings. For example, motor 12 may be an internal permanent magnet (IPM) motor, an induction motor, or a synchronous motor. Although a six-phase motor 12 is described below as an exemplary embodiment, embodiments also include motors with fewer (e.g., three-phase) or more (e.g., nine-phase) phases. The power source may include a battery, a fuel cell, a conventional power grid, or any other energy source suitable for motor 12 and its applications, and in this embodiment is a direct current (DC) source.

[0014] The motor 12 operates in response to a voltage drive signal applied by the inverter 14. In embodiments including a six-phase motor 12, such as those described below, the motor control system 10 provides a voltage drive command V to the inverter 14. A V B V C V D V E V F (that is, V) A-F The voltage drive command can be a pulse-width modulation (PWM) signal. Inverter 14 processes the voltage drive command and applies the commanded voltage to the windings of motor 12. The applied voltage creates torque in the windings of motor 12, generating current, which causes the motor shaft to rotate. Inverter 14 can be any known or conventional design. Such inverter 14 typically includes multiple power switches to provide the PWM drive signal.

[0015] Voltage drive command V A-F Each of these corresponds to one phase winding of the motor 12. Therefore, the six-phase motor 12 embodiment described herein has six voltage drive commands V.A-F In an implementation, the six-phase motor 12 can be configured to include two sets of three-phase windings (e.g., a first set of windings and a second set of windings). For the purposes of convention and example, such as V... A-C The three voltage drive commands can be associated with and applied to the three windings in the first set of windings, and such as V D-F The three voltage drive commands can be applied to the three windings in the second set of windings.

[0016] The motor control system 10 may include a processor, a controller, digital logic circuitry, and / or a computer. The control system 10 may include or be coupled to memory (volatile memory such as RAM and non-volatile memory such as magnetic storage, ROM, and EEPROM), a communication interface (e.g., a wired serial or parallel data bus), inputs (such as switches, keypads, or communication interfaces), and outputs such as a display. The memory may store software, such as instructions representing algorithms or steps of the methods described herein, which are executed by the processor, controller, digital logic circuitry, and / or computer. The communication interface may include a communication module for sending and receiving messages and signals (e.g., input commands) over a network. The communication module is capable of communicating via one or more wireless or wired technologies (e.g., WiFi, Bluetooth, cellular networks, local area networks (LANs), and / or wide area networks (WANs)).

[0017] A current sensor 18 is coupled to the motor 12 and provides a signal representing the current (I) on each winding of the motor. In embodiments including a six-phase motor 12, such as those described below, the current sensor 18 provides a feedback signal I representing the current on each winding. A I B I C I D I E I F (i.e. I A-F The current sensor 18 can be any known or conventional device. In this embodiment, the current sensor 18 provides information representing the magnitude or level of the current in the windings of the motor 12. Using the current level information provided by the current sensor 18, the motor control system 10 can derive information about signal I. A-F The information provided indicates the relative phase of the current in the windings of the motor 12. In other embodiments, the current sensor 18 directly provides information about the phase of the motor winding current. Other embodiments of the motor system 8 include sensors that provide additional or alternative information representing the electrical operating characteristics of the motor 12.

[0018] The solver system 20 may include one or more sensors. In one embodiment, the solver system 20 includes an encoder or other position sensor that provides information about the rotational or angular position (θ) of the shaft of the motor 12. In another embodiment, the solver system 20 provides an angular position feedback signal θ. Using the shaft position information provided by the solver system 20, the motor control system 10 can derive information about the rotational or angular velocity (ω) of the shaft of the motor 12. In other embodiments, the solver system 20 directly provides information about the angular velocity of the shaft of the motor 12. Other embodiments of the solver system 20 provide information representing alternative or additional operating parameters of the motor 12.

[0019] In this embodiment, the motor control system 10 is configured to receive a control input command specifying the desired amount of torque to be generated by the motor 12. The motor control system 10 may also receive a current feedback signal I from the current sensor 18. A-F And the shaft angular position feedback signal from the solver device 20. The motor control system 10 processes torque control input commands and signals such as current feedback signals I. A-F Feedback signals, such as angular position feedback signal θ, are used to generate a voltage drive signal applied to inverter 14. In embodiments including a six-phase motor 12, such as those described below, the motor control system 10 generates a voltage drive signal V. A V B V C V D V E V F (that is, V) A-F Each voltage drive signal is associated with one of the motor windings. The motor control system 10 generates the voltage drive signal V based on a control algorithm. A-F In this implementation, the motor control system 10 implements flux-weakening (FW) and maximum-torque-ampere (MTPA) control algorithms to generate voltage drive signals as functions of input commands and feedback signals. The FW and MTPA algorithms are generally known, and any such conventional or other known algorithms suitable for the application of system 8 and / or motor 12 can be used.

[0020] The control algorithm implemented by the motor control system 10 also includes a torque ripple compensation component to reduce torque ripple in the motor 12. The motor control system 10 provides dynamic and instantaneous torque ripple compensation by providing compensation based on existing electrical or other operating characteristics of the motor 12 that contribute to torque ripple. As described in more detail below, the motor control system 10 analyzes the current feedback signal I... A-FThe parameters of the current contributing to torque ripple on the windings of motor 12 are identified. Then, the motor control system 10 generates a voltage drive signal to minimize or reduce torque ripple. In one embodiment, the torque ripple compensation component of the control algorithm identifies parameters related to low-frequency and high-frequency torque ripple.

[0021] Low-frequency torque ripples are harmonics of the fundamental frequency of the current in the windings of motor 12 (e.g., voltage drive command V). A-F (The fundamental frequency harmonics). To counteract or reduce low-frequency torque ripples, the dominant low-frequency harmonics are identified, and a voltage drive signal V is generated to reduce these harmonics by controlling the current in the windings. A-F High-frequency torque ripples are harmonics of the switching frequency and can be reduced in multiphase motors. For example, embodiments include a six-phase motor 12 comprising two sets of three-phase windings. Similarly, other embodiments include a motor 12 having more than two sets of windings. To counteract or reduce high-frequency torque ripples, the motor control system 10 alters and adjusts the relative phase of the carrier signal of the voltage drive command applied to the multiple sets of windings.

[0022] Figure 2 This is a functional schematic diagram of a motor control system 10 for a six-phase motor according to an embodiment. As shown, an input command is applied to a current command generator 40. The current command generator 40 also receives a motor feedback signal from the solver system 20. In this embodiment, the current command generator 40 may alternatively or additionally receive other input information, such as the signal characteristics of the power supply 16 (e.g., the DC voltage provided by the power supply). In response to the input command and the motor feedback signal, the current command generator 40 generates first and second sets of reference basic synchronous stator current commands I. dF1-ref I qF1-ref and I dF2-ref I qF2-ref Each set of reference base current commands is implemented as two components relative to the dq reference coordinate system and corresponds to one of the two sets of windings of the six-phase motor 12. In an embodiment, the motor control system 10 generates the reference base current command I using the FW and MTPA algorithms based on the requested torque command T, the angular velocity ω of the motor 12, and optionally other operating parameters of the motor system 8. dF1-ref I qF1-ref and I dF2-ref I qF2-ref The current command generator 40 can be operated according to conventional or other known motor control methods.

[0023] The summing junction 42 receives the reference basic current command I generated by the current command generator 40. dF1-ref IqF1-ref and I dF2-ref I qF2-ref The summation point 42 also receives the first and second group harmonic cancellation commands I. d1n-ref -I d1N-ref I q1n-ref -I q1N-ref and I d2n-ref -I d2N-ref I q2n-ref -I q2N-ref As described in more detail below, harmonic cancellation commands provide compensation for torque ripples identified in motor 12. Each group can have zero, one, or more cancellation commands n (0 ≤ n ≤ N), where each cancellation command n corresponds to one identified harmonic undergoing compensation. Each cancellation command in this group is implemented as two components relative to the dq reference coordinate system and corresponds to one of the two sets of windings of the six-phase motor 12. The summation point 42 superimposes the corresponding harmonic cancellation commands and the reference base current command to generate two sets of torque ripple compensation current reference signals I. dR1 I qR1 and I dR2 I qR2 Each set of current reference signals corresponds to one of the two windings of a six-phase motor and is implemented as two components relative to the dq reference coordinate system. The summation point 42 can generate the current reference signals according to conventional or other known motor control methods.

[0024] The PI (Proportional-Integral) controller 44 receives the current reference signal I generated by the summing point 42. dR1 I qR1 and I dR2 I qR2 The PI controller 44 also receives two sets of synchronous coordinate system feedback signals I generated by the reference coordinate system transformation 46. d1-feed I q1-feed and I d2-feed I q2-feed The synchronous coordinate system feedback signal includes information about the fundamental frequency and harmonic frequencies of the drive signal on motor 12. The PI controller 44 processes the current reference signal and the synchronous coordinate system feedback signal to generate two sets of intermediate voltage commands V. d1 V q1 and V d2 V q2 Each intermediate voltage command corresponds to one of the two windings of the six-phase motor 12. The PI controller 44 can generate intermediate voltage commands according to conventional or other known motor control methods.

[0025] Reference coordinate system transformer 46 receives two sets of α / β current feedback signals I α1-feed Iβ1-feed and I α2-feed I β2-feed Each of these corresponds to one of the two sets of windings of the six-phase motor 12, and generates a corresponding synchronous coordinate system quantity feedback signal according to conventional or other known motor control methods. According to conventional or other known motor control methods, the two sets of α / β current feedback signals are generated by the phase converter 48 based on the sensed current feedback signal I received from the current sensor 18. A-F produce.

[0026] Reference coordinate system transformer 50 receives intermediate voltage command V generated by PI controller 44. d1 V q1 and V d2 V q2 The reference coordinate system transformer 50 also receives motor feedback signals from the solver system 20, such as the angular position θ of the motor shaft. The reference coordinate system transformer 50 processes the intermediate voltage command and the motor feedback signal to generate two sets of stationary frame α / β voltage commands V. α1 V β1 and V α2 V β2 Each set of stationary coordinate system α / β voltage commands corresponds to one of the two windings of the six-phase motor 12. The reference coordinate system transformer 50 can generate stationary coordinate system α / β voltage commands according to conventional or other known motor control methods.

[0027] Phase transformer 52 receives α / β voltage command V generated by reference coordinate system transformer 50. α1 V β1 and V α2 V β2 And generate equivalent multiple sets of three-phase voltage drive control signals V a V b V c and V d V e V f (that is, V) a-f Multiple sets of voltage drive control signals are applied to modulator 54, and modulator 54 generates corresponding multiple sets of PWM voltage drive commands V. A-F Phase converter 52 can generate a voltage drive control signal according to conventional or other known motor control methods. In addition to the high-frequency, multi-winding-based torque ripple compensation function described below, modulator 54 can generate a voltage drive command according to conventional or other known motor control methods. For example, the voltage drive control signal can be a sinusoidal signal, and modulator 54 can construct a PWM voltage drive command from the intersection of a sawtooth or triangular carrier signal and the voltage drive control signal.

[0028] The torque ripple compensation function of the motor control system 10 can be provided by combining the harmonic identification unit 60 and the harmonic cancellation command generator 62 with other features of the motor control system 10, including the summing point 42 and the modulator 54. In one embodiment, the low-frequency torque compensation function is provided by the harmonic identification unit 60 and the harmonic cancellation command generator 62, which cooperate to generate a harmonic cancellation command applied to the summing point 42. In another embodiment, the high-frequency torque compensation function is provided by introducing a phase shift in the carrier signal for multiple windings based on the number of windings (e.g., a six-phase motor has two windings) and the carrier signal type (e.g., delta, sawtooth).

[0029] Harmonic identification unit 60 is connected to receive current feedback signal I A-F ,like Figure 2 As shown, the harmonic identification unit 60 processes the current feedback signal and identifies the fundamental frequency harmonics present in the signal and their amplitudes. The information provided by the harmonic identification unit 60 indicates the harmonic frequencies and amplitudes present in the drive current of the motor 12. These harmonic frequencies may be undesirable and may cause torque fluctuations. In an embodiment, the identified harmonics may include fundamental frequency harmonics (e.g., from the motor operating frequency). Conventional or other known signal processing methods (such as Fourier transform and signal strength detection) may be performed by the harmonic identification unit 60.

[0030] Harmonic cancellation command generator 62 receives the identified harmonic information (e.g., harmonic frequency and associated amplitude) and identifies the fundamental frequency harmonics that contribute to the compensable torque ripple. Harmonic cancellation command generator 62 then generates a harmonic cancellation command that provides compensation for the identified harmonics (e.g., minimizing or reducing torque ripple). The harmonic cancellation command is applied to summation point 42.

[0031] In one implementation, the harmonic cancellation command generator 62 can monitor the amplitude of harmonics (e.g., harmonics 1-N) at the operating frequency of the identified motor 12 and identify harmonics with amplitudes greater than a predetermined level. For example, the harmonic cancellation command generator can identify all harmonics with amplitudes greater than one level. In other implementations, the predetermined level can be different for different harmonics. One or more predetermined levels can be expected levels. The operator can select one or more predetermined levels (e.g., a range between 0% and 5% of the expected level).

[0032] After identifying the harmonics used for compensation, they are converted into direct-axis and quadrature-axis components (e.g., I0). dn I qn The harmonic cancellation command generator 62 generates multiple sets of harmonic cancellation commands I for each harmonic n. d1n-ref Iq1n-ref and I d2n-ref I q2n-ref When the summation point 42 coincides with the basic synchronous stator current command I dF1-ref I qF1-ref and I dF2-ref I qF2-ref When superimposed, the multiple sets of harmonic cancellation commands will result in the cancellation or minimization of harmonics. Each set of harmonic cancellation commands corresponds to one of the multiple windings of the motor 12. For example... Figure 2 As shown, a harmonic cancellation command is applied to summation point 42. The harmonic cancellation command can be based on unwanted frequencies (e.g., other than the fundamental signal) that can be removed or reduced from the electrical excitation to enhance system operation. For example, relatively strong harmonics may impair optimal system operation. In an embodiment, the motor control system 10 can identify harmonics (e.g., inherently relatively strong harmonics) that may impair the operation of the motor 12. The control system 10 can then determine which harmonic levels should be mitigated. For example, the controller can determine the presence of a third harmonic and a fifth harmonic, representing 30% and 20% of the fundamental frequency component, respectively. In this example, the control system 10 can, for example, be operated to limit the permissible relative amplitudes to 10% for the third harmonic and 0% for the fifth harmonic. The control system 10 can then generate reference signals for specifying the harmonics, and closed-loop control can be implemented accordingly. Examples of motor performance parameters that can be monitored and compensated (e.g., individually or simultaneously) include torque ripple, vibration, and efficiency. The harmonic cancellation command generated according to the embodiment can improve system performance. To improve system performance, thresholds such as those in the examples above can be made more stringent.

[0033] In one implementation, modulator 54 compensates for high-frequency harmonics by generating a phase shift between the carrier signals of the multiple windings. In an implementation of the six-phase motor 12, for example, modulator 54 generates a phase shift on the carrier signal of the first winding relative to the carrier signal of the second winding. Modulator 54 controls the phase shift angle of the carrier signals for the multiple windings based on the following formula:

[0034]

[0035] Where m is the order of magnitude of the dominant high-frequency torque ripple, depending on the type of carrier signal, and n is the number of windings. Since the dominant high-frequency torque ripple of a sawtooth carrier signal is at the switching frequency, m = 1 for a sawtooth carrier signal. Since the dominant high-frequency torque ripple of a delta carrier signal is twice the switching frequency, m = 2 for a delta carrier signal. For a six-phase motor, there are two windings, so n = 2. For a nine-phase motor, there are three windings, so n = 3. In the implementation of a six-phase motor, the phase shifts of the delta carrier signal and the sawtooth carrier signal should be 90 degrees and 180 degrees, respectively. In this case, the high-frequency harmonics generated by the two windings can cancel each other out.

[0036] It should be understood that the above description is illustrative and not restrictive. Many other embodiments will be apparent to those skilled in the art upon reading and understanding the above description. For example, features described in association with one embodiment may optionally be additionally or substituted for features described or associated with another embodiment. The motor control system may include one or both of the low-frequency compensation methods and high-frequency compensation methods described herein. The compensation methods described herein may be incorporated into motors having fewer or more phases. Therefore, the scope of the invention should be determined with reference to the appended claims and the full scope of their entitled equivalents.

Claims

1. A method for operating a motor control system, the method being used for a motor having multiple sets of windings, the method comprising: Receive input commands; Receive the drive feedback signal representing the drive current in the motor; Identify the harmonics representing motor torque fluctuations in the drive feedback signal; A torque ripple compensation signal is generated based on the identified harmonics; as well as Generating a motor drive control signal based on the input command, the drive feedback signal, and the torque ripple compensation signal includes: A set of motor drive signals is generated for each of the multiple sets of windings; as well as The phase shift between the carrier signals used for the multiple windings is controlled based on the number of windings and the magnitude of the dominant high-frequency torque fluctuations, which depend on the type of carrier signal.

2. The method according to claim 1, wherein: Identifying the harmonics in the drive feedback signal includes: identifying the harmonics of the drive current; Generating the torque ripple compensation signal includes: generating a harmonic cancellation command; and Generating the motor drive control signal includes summing the harmonic cancellation command and the input command.

3. The method of claim 2, wherein, Summing the harmonic cancellation command and the input command includes summing the harmonic cancellation command and the input command in the dq reference coordinate system.

4. The method according to claim 3, wherein: The method further includes: generating a dq reference coordinate system control feedback signal based on the driving feedback signal; and Generating the motor drive control signal includes: generating the motor drive control signal based on the summed harmonic cancellation command and the input command in the dq reference coordinate system, and based on the control feedback signal in the dq reference coordinate system.

5. The method according to claim 1, wherein: Generating the torque ripple compensation signal further includes: determining the phase shift angle of the carrier signal; and Generating the motor drive control signal further includes: generating the motor drive control signal based on the carrier signal having the phase shift angle of the carrier signal.

6. The method of claim 5, wherein, Generating the motor drive control signal includes: A set of motor drive control signals is generated for each of the multiple sets of windings based on a set of carrier signals; and The relative phase of the set of carrier signals is controlled based on the phase shift angle of the carrier signal.

7. The method of claim 1, wherein, Generating the motor drive control signal includes: A set of motor drive control signals is generated for each of the multiple sets of windings based on a set of carrier signals; and Control the relative phase of the set of carrier signals.

8. The method according to claim 1, wherein: Generating the torque ripple compensation signal includes: determining the phase shift angle of the carrier signal; and Generating the motor drive control signal includes: A set of motor drive control signals is generated for each of the multiple sets of windings based on a set of carrier signals; and Control the relative phase of the set of carrier signals.

9. The method of claim 1, wherein, Generating the torque ripple compensation signal includes generating the torque ripple compensation signal based on the amplitude of the identified harmonics.

10. The method of claim 1, wherein, Generating the torque ripple compensation signal includes generating the torque ripple compensation signal if the amplitude of the identified harmonic is greater than a predetermined level.

11. The method according to claim 1, wherein: The method also includes receiving feedback signals of motor operating characteristics; as well as Generating the motor drive control signal further includes generating the motor drive control signal based on the motor operating characteristic feedback signal.

12. The method of claim 1, wherein, The input commands include torque commands.

13. A motor control system for a motor having multiple sets of windings, the motor control system comprising: One or more processors; as well as A program memory, coupled to one or more processors, stores executable instructions that, when executed by the processor, cause the motor control system to: Receive input commands; Receive the drive feedback signal representing the drive current in the motor; Identify the harmonics representing motor torque fluctuations in the drive feedback signal; A torque ripple compensation signal is generated based on the identified harmonics; as well as Generating a motor drive control signal based on the input command, the drive feedback signal, and the torque ripple compensation signal includes: A set of motor drive signals is generated for each of the multiple sets of windings; as well as The phase shift between the carrier signals used for the multiple windings is controlled based on the number of windings and the magnitude of the dominant high-frequency torque fluctuations, which depend on the type of carrier signal.

14. The motor control system according to claim 13, wherein: Identifying the harmonics in the drive feedback signal includes: identifying the harmonics of the drive current; Generating the torque ripple compensation signal includes: generating a harmonic cancellation command; and Generating the motor drive control signal includes summing the harmonic cancellation command and the input command.

15. The electric motor control system of claim 14, wherein, Summing the harmonic cancellation command and the input command includes summing the harmonic cancellation command and the input command in the dq reference coordinate system.

16. The motor control system according to claim 15, wherein: Generating the torque ripple compensation signal includes: determining the phase shift angle of the carrier signal; and Generating the motor drive control signal includes: A set of motor drive control signals is generated for each of the multiple sets of windings based on a set of carrier signals; and Control the relative phase of the set of carrier signals.

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