Closed-Loop Compensation for Current Measurement Offset Error in an AC Motor Drive

Abstract

The present application discloses a closed-loop compensation for current measurement offset errors in an AC motor drive. Systems and methods for compensating current measurement offset errors in a permanent magnet synchronous motor (PMSM) drive are disclosed. The systems and methods include: reading an output voltage command signal; extracting features of the current measurement offset error from the output voltage command signal; and compensating the current measurement offset error in the closed loop based on the features using a feedback path.

Description

Technical Field

[0001] This disclosure relates to current measurement offset errors and, in particular, to systems and methods for closed-loop compensation of current measurement offset errors in permanent magnet synchronous motor drives. Background Art

[0002] Vehicles such as cars, trucks, sport utility vehicles, crossovers, minivans, or other suitable vehicles may include an electric power steering (EPS) system. Such an EPS system typically includes an electric motor for providing steering assistance during operation of the vehicle. To provide such steering assistance, the EPS system may drive the electric motor according to a torque control method. The electric motor may include a permanent magnet synchronous motor (PMSM) drive. When using a PMSM drive, the EPS system may utilize field-oriented control (FOC). FOC transforms the alternating current (AC) phase motor voltage and current signals in a stationary reference coordinate system to a synchronously rotating reference coordinate system (commonly referred to as the d / q-axis reference coordinate system), where the motor voltage and current become direct current (DC) quantities. FOC torque control is typically achieved through a closed-loop current control method that employs a current regulator to minimize the error between the commanded current and the measured current, thereby achieving perfect current tracking. Thus, current control requires measuring the motor current, which can be achieved by measuring the phase currents of the PMSM drive, and then the phase currents are transformed to the synchronous coordinate system via the park transform to perform control in the synchronous reference coordinate system.

[0003] When a certain magnitude of offset error occurs in the phase current measurement, the closed-loop current controller operating in the synchronous reference coordinate system adjusts the motor voltage to match the measured result of the motor current with the commanded current. Since the measurement result is incorrect, the current controller causes the actual motor current to become incorrect. This failure mode can lead to motor torque and current errors related to the motor position, which may be perceived as large torque ripple on the motor shaft and may be greater than the rated motor current (designed by hardware). When the torque ripple caused by the phase current measurement offset error exceeds a certain threshold, the offset error may generate a motor torque in a direction opposite to the motor torque command. When used in an EPS system, a failure that generates torque in a direction opposite to the desired motor torque command results in the following: the inability to provide steering assistance to the driver, and the driver ultimately needs to apply greater force compared to the situation where the vehicle is operating in the manual steering mode (i.e., without an active EPS system). Summary of the Invention

[0004] This disclosure generally relates to the detection of current measurement offset errors.

[0005] One aspect of the disclosed embodiments includes a system for compensating current measurement offset errors in an alternating current (AC) motor drive. The system includes a processor and a memory. The memory includes instructions that, when executed by the processor, cause the processor to: read an output voltage signal, extract a signature of the current measurement offset error from the output voltage signal, and compensate for the current measurement offset error in a closed loop based on the signature using a feedback path.

[0006] Another aspect of the disclosed embodiments includes a method for compensating current measurement offset errors in an alternating current (AC) motor drive. The method includes: reading an output voltage signal, extracting a signature of the current measurement offset error from the output voltage signal, and compensating for the current measurement offset error in a closed loop based on the signature using a feedback path.

[0007] Another aspect of the disclosed embodiments includes an electronic device. The electronic device includes a processor and a memory. The memory includes instructions that, when executed by the processor, cause the processor to: read an output voltage signal, extract a signature of the current measurement offset error from the output voltage signal, and compensate for the current measurement offset error in a closed loop based on the signature using a feedback path.

[0008] These and other aspects of the present disclosure are disclosed in the following detailed description of the embodiments, the appended claims, and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be emphasized that, according to common practice, the various features of the drawings are not drawn to scale. Instead, for clarity, the dimensions of the various features are arbitrarily enlarged or reduced.

[0010] Figure 1A-1C An alternating current (AC) motor drive system with closed-loop current measurement offset error compensation in accordance with the principles of the present disclosure is generally shown.

[0011] Figure 2 A controller system in accordance with the principles of the present disclosure is generally shown.

[0012] Figure 3 is a flowchart generally showing a method for closed-loop compensation of current measurement offset errors in an AC motor drive in accordance with the principles of the present disclosure. DETAILED DESCRIPTION

[0013] The following discussion pertains to various embodiments of the present disclosure. Although one or more of these embodiments may be preferred, the disclosed embodiments should not be construed as or otherwise used to limit the scope of the present disclosure, including the claims. Additionally, those skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is only intended to be an exemplary discussion of that embodiment and is not intended to imply that the scope of the present disclosure, including the claims, is limited to that embodiment.

[0014] Some machines (e.g., vehicles, boats, airplanes, drones, power equipment, yard equipment, pumps, compressors, etc.) may include an alternating current (AC) motor drive that controls an AC motor in a closed loop. A current measurement system may be included in the closed loop to measure the current output of a synchronous motor. Machines using a current measurement system may be affected by current measurement offset errors.

[0015] Current measurement offset errors are caused by non-idealities or faults in current measurement. Current measurement offset errors may be caused by an incorrect measurement of the current output from the AC motor by a current estimator. In a closed-loop system using a current regulator, the current regulator generates a desired output voltage signal to make the measured current equal to the commanded current. In this case, when the measured current is different from the commanded current, the output voltage signal will be incorrect (e.g., different from the expected output voltage signal based on the commanded current) because the current regulator is attempting to match the measured current (e.g., which is different from the commanded current) to the commanded current.

[0016] Gradual changes in the measurement circuit (e.g., operational amplifier (op-amp), offset drift, etc.) may result in smaller current measurement offset errors. A fault in the measurement circuit may result in larger current measurement offset errors. As discussed, if left undetected and / or unmitigated, the fault mode will result in motor torque and current errors related to the motor position, which may be perceived as large torque fluctuations at the motor shaft and may be greater than the rated motor current (of the hardware design). When the torque fluctuations caused by phase current measurement offset errors exceed a certain threshold, the offset error may generate a motor torque in a direction opposite to the motor torque command. When used in an EPS system, a fault that generates torque in a direction opposite to the desired motor torque command results in the inability to provide steering assistance to the driver, and the driver ultimately needs to apply more force compared to the case where the vehicle is operating in the manual steering mode (i.e., without an active EPS system).

[0017] Accordingly, systems and methods such as those described herein can be configured to address the above problems by providing techniques for electronically compensating current measurement offset errors in any AC motor drive and current measurement system. In some embodiments, the systems and methods described herein are capable of detecting, learning, and compensating for the effects of current measurement offset errors on an AC motor drive. For example, using closed-loop compensation control, the effects of current measurement offset errors can be at least partially compensated for.

[0018] In some embodiments, the systems and methods described herein can be configured to provide techniques for real-time detection of inter-phase current measurement offset errors in an AC motor drive and a current measurement system. The systems and methods described herein can be configured to use various mathematical models to extract the characteristics of current measurement offset errors, use a closed-loop compensator to compensate for current measurement offset errors, and correct current measurement offset errors.

[0019] In some embodiments, the systems and methods described herein can be configured to change the measured current in real time to regulate the operation of an AC motor drive, thereby controlling the AC motor in a more desirable manner. The systems and methods described herein can result in enhanced AC motor performance, extended AC motor life, enhanced steering, and enhanced customer experience of a machine including the AC motor.

[0020] The disclosed techniques are applicable to any electric motor drive having an alternating current (AC) motor and any current measurement architecture (a current measurement architecture involving both in-line and low side aspects). A low side current measurement system can refer to placing a current sensor in series with a load between the load and ground. An in-line current measurement system can refer to placing a current sensor in series with a circuit such that the current flowing through the circuit also flows through the current sensor. Additionally, the disclosed embodiments can be implemented by a processor to perform real-time detection, identification, and / or correction while the AC motor is operating. The disclosed embodiments can also be implemented by a processor at the end of line (EOL) of a manufacturing plant's production line.

[0021] Figure 1AGenerally shown is an alternating current (AC) motor drive system 100 (referred to herein as "the system") in accordance with the principles of the present disclosure. The system 100 can include a current command generator 102, a current regulator 104, a current measurement offset error compensation controller 106, a pulse width modulator 108, an inverter 110, an AC motor 112, a current sensor 114, and a current estimator 116. In some embodiments, the current regulator 104, the pulse width modulator 108, the inverter 110, the AC motor 112, the current sensor 114, and the current estimator 116 form a closed-loop current control system. The depicted AC motor drive system 100 also includes another closed-loop within the current control system. For example, the current regulator 104, the current measurement offset error compensation controller 106, the current sensor 114, and the current estimator 116 form a closed-loop current measurement offset error compensation system. It should be noted that fewer or more components may be included in the system 10 as needed to perform the techniques disclosed herein, and the depicted components are for illustrative purposes.

[0022] In some embodiments, the closed-loop current measurement offset error compensation system can operate as follows. The current regulator 104 receives a command or reference current and outputs a corresponding output voltage command signal. The current measurement offset error compensation controller 106 receives the output voltage signal. The current measurement offset error compensation controller 106 includes a current measurement offset error compensator 106A and an adder module 106B.

[0023] Figure 1B A detailed block diagram of the current measurement offset error compensation controller 106 in accordance with the principles of the present disclosure is shown. The offset error feature extraction module 118 extracts the features of the current measurement offset error. This error is subtracted from the zero command, i.e., the negative of the error is calculated and sent to the closed-loop compensator 120, which generates a basic current offset correction signal. The coordinate system transformation module 122 transforms the pre-transformed current offset correction signal to generate a final current offset correction signal. The final current offset correction signal is added to the current estimate at the adder module 106B to determine the measured current that is input to the current regulator 104, thereby closing the loop.

[0024] With the foregoing description, additional details and operation of the AC motor drive system 100 will now be discussed. The AC motor 112 can generate a rotational force or a linear force for powering a machine (e.g., those described herein). The AC motor 112 can include a constant speed motor or other suitable motor. The AC motor drive system 100 can selectively control the electrical energy supplied to the AC motor 112. The AC motor drive system 100 can supply electrical energy to the AC motor 112 in varying amounts and at varying frequencies, thereby indirectly controlling the speed and torque of the AC motor 112.

[0025] The current measurement system 170 may include a current sensor 114 and a current estimator 116. The current sensor 114 may include any suitable current sensor configured to sense or measure the current in a circuit. The current sensor may provide a signal indicative of the current to the current estimator 116. The current sensor may be configured to receive a signal indicative of the current and measure the amount of current output by the AC motor 112 (e.g., based on the current indicated by the signal). The current estimator 116 may be configured to send the stationary reference frame current of the AC motor 112 or transform the measured current into a synchronous reference frame using the position estimate of the AC motor 112.

[0026] The current command generator 102 may receive a torque command The current command generator 102 may generate a commanded current I based on the torque command * . The current command may be composed of a direct axis (d-axis) current component and a quadrature axis (q-axis) current component . The current regulator 104 receives the commanded current and transmits an output voltage command signal V * to the pulse width modulator 108. The voltage command may be composed of a d-axis component and a q-axis component . The pulse width modulator 108 may control the ratio of the time that the output voltage signal is high compared to the time that the output voltage signal is low over a constant time period, which may control the direction of the AC motor 112. The inverter 110 may include a voltage source inverter or other suitable inverter and may be configured to change the frequency of the supplied electrical energy provided to the AC motor 112 to control the speed of the AC motor 112. The AC motor 112 may receive the output voltage signal V as an input. The AC motor 112 may use the input to generate an amount of current I as an output, which may be equal to the commanded current or different from the commanded current (e.g., when there is a current measurement offset error).

[0027] The current I output from the AC motor 112 may be sensed by the current sensor 114 to determine the measured current The current estimator 116 may receive the measured current and determine the estimated current The current estimator 116 of the current measurement system 170 outputs the estimated current to the current regulator 104. Thus, as depicted, the system 100 uses a closed loop. However, as discussed, in some cases, the measured current may be incorrect due to circuit degradation, drift, etc.

[0028] The current regulator 104 can receive the estimated current and compare it with the commanded current. If there is any variation, the current regulator 104 can send an output voltage command signal V * , which will cause the estimated current to closely match the commanded current I * . Thus, since the commanded current I * is constant (or slowly varying), and the estimated current equals the commanded current I * , the estimated current is also constant. When there is an offset error in the current measurement system, the current regulator 104 can include a pulsating component in the output voltage command signal V * .

[0029] The current measurement offset error compensation controller 106 reads the output voltage command signal from the current regulator 104. The current measurement offset error compensation controller 106 can include a current measurement offset error compensator 106A, which includes an offset error feature extraction module 118, a closed-loop compensator 120, and a coordinate system transformation module 122. As will be described, the offset error feature extraction module 118 can use a mathematical model to extract the features of the current measurement offset error from the output voltage command signal. The offset error feature extraction module 118 can identify the features of the current measurement offset error as the pulsation frequency of the first electrical order in the output voltage command signal. In some embodiments, the offset error feature extraction module 118 can use an adaptive band-pass filter to extract the features, as Figure 1C shown. The adaptive band-pass filter can be configured to perform pre-filtering in the synchronous coordinate system before transformation, or use an adaptive low-pass filter in the (adaptively) tuned pseudo-stationary coordinate system according to the pulsation frequency (i.e., the pulsation frequency of the first electrical order) being equal to the synchronous frequency. In some embodiments, the offset error feature extraction module 118 can perform direct sine error extraction on the output voltage command signal. In some embodiments, the offset error feature extraction 118 can perform demodulation to convert the sine part of the output voltage command signal into a DC signal, and then perform low-pass filtering.

[0030] As will be described, the closed-loop compensator 120 can receive the features and use an adaptive resonator for the sine features to generate a basic current offset correction, or use a conventional integrator for the DC features to generate a basic current offset correction. As Figure 1C depicted, in the case of the sine features of the current measurement offset error extracted from the output voltage command signal, a resonant controller can be used to generate a basic offset correction. The resonant controller receives a pseudo-command input ΔV equal to zeroc * from the filtered sinusoidal voltage component ΔV c and generate a basic current offset correction signal The resonant controller is inherently adaptive, i.e., designed to eliminate any error at its input at its critical frequency, which in this case is equal to the estimated synchronous frequency The coordinate system transformation module 122 converts the basic current offset correction signal into a final current offset correction signal by applying a position-dependent reference coordinate system transformation that utilizes the estimated electrical position of the reference coordinate system transformation The addition module 106B adds the final current offset error correction signal to the estimated current to compensate for the current measurement offset error and generate a compensated estimated current The compensated estimated current is sent in real time to the current regulator 104 to mitigate any effects of the current measurement offset error

[0031] The following discussion pertains to the mathematical models used in the systems and methods described herein. The measured current with an offset error in the stationary reference coordinate system can be mathematically represented as:

[0032]

[0033]

[0034] where ΔI α and ΔI β are the offset errors in the stationary reference coordinate system and represent the deviations of the measured current and from the actual currents I α and I β respectively

[0035] When the estimated d / q currents and are transformed into the synchronous reference coordinate system using the reference coordinate system transformation the estimated d / q currents and become:

[0036]

[0037]

[0038] where ΔI d and ΔI qis the current measurement error in the synchronous reference frame, I d and I q are the actual currents, and and

[0039] Note that the transformation matrix is

[0040]

[0041]

[0042] where X can represent voltage or current.

[0043] Assuming that the high-performance current regulator has a sufficiently high bandwidth, the estimated current can be assumed to be approximately equal to the commanded current, thus distorting the actual current. The actual current can be expressed as

[0044]

[0045] Then the pulsating component of the voltage command can be calculated as:

[0046]

[0047]

[0048] where and ω e , R, L d , L q are the synchronous frequency (motor speed), motor resistance, d-axis inductance, and q-axis inductance, respectively. Therefore, when there is a current measurement offset error, an adaptive band-pass filter tuned at the synchronous frequency can be used to filter the output voltage command to extract the pulsating component ΔV c , as Figure 1C shown. Note that ΔV c is equal to ΔV * given in Equation 5. Then the resonant controller 120 operates on the error feature and outputs the basic offset error correction term This basic offset error correction term is transformed by the reference frame transformation module 122 into the final offset error correction term and added to the estimated current at the adder module 106B to obtain the final estimated current in the synchronous reference frame This final estimated current is input to a current regulator 104. This closed-loop system forces the current measurement offset error to zero, thereby reducing the ripple in the output current caused by the offset error in the measured current.

[0049] Figure 2 Generally shows a controller system 200 in accordance with the principles of the present disclosure. The controller system 200 includes a current measurement offset error compensation controller 106 communicatively coupled to a memory 202. The current measurement offset error compensation controller 106 may include a processor. The processor may include any suitable processor, such as those described herein. The memory 202 may store instructions that, when executed by the current measurement offset error compensation controller 106, cause the current measurement offset error compensation controller 106 to perform at least the techniques disclosed herein. Specifically, the computer instructions, when executed by the current measurement offset error compensation controller 106, may cause the current measurement offset error compensation controller 106 to perform the operations of method 300, as further described below with reference to Figure 3 is further described.

[0050] Figure 3 is a flowchart generally showing a method 300 for electronically compensating for current measurement offset error in an AC motor drive in accordance with the principles of the present disclosure. At 302, method 300 reads an output voltage command signal. For example, the current regulator 104 may generate the output voltage command signal. At 304, method 300 extracts the characteristics of the current measurement offset error from the output voltage command signal. In some embodiments, the output voltage command signal may include only a constant portion, and in some embodiments, the output voltage command signal may include a constant portion and a sinusoidal portion. If the output voltage command signal includes only a constant portion, there may be no current measurement offset error because the sinusoidal portion of the output voltage signal represents the ripple including the characteristics of the current measurement offset error. Thus, when the output voltage signal includes a constant portion and a sinusoidal portion, when the characteristic has a frequency of the first electrical order (i.e., at the synchronous frequency), the sinusoidal portion is extracted as the characteristic of the current measurement offset error. The sinusoidal portion may correspond to the pulsating portion of the output voltage signal and may be caused by the current regulator 104 causing the estimated current output from the current estimator 116 to be equal to the commanded current.

[0051] In some embodiments, to extract the characteristics of the current measurement offset error from the output voltage command signal, method 300 further includes directly extracting a sinusoidal error from the output voltage command signal. In some embodiments, to extract the characteristics of the current measurement offset error from the output voltage command signal, method 300 further includes transforming the output voltage command signal to transform the sinusoidal portion into a direct current (DC) characteristic and filtering the DC characteristic.

[0052] At 306, method 300 uses a feedback path to compensate for current measurement offset errors in the closed loop based on the feature. In some embodiments, method 300 compensates for current measurement offset errors in real time (e.g., less than 2 seconds) as the AC motor driver operates the AC motor 112. In some embodiments, method 300 uses a feedback path based on the feature to compensate for current measurement offset errors in the closed loop by: generating a correction term that compensates for the current measurement offset error, applying the correction term to the estimated current to output a compensated estimated current to the current regulator 104, and verifying that the subsequent output voltage signal received from the current regulator 104 via the feedback path does not include a current measurement offset error.

[0053] In some embodiments, when method 300 directly extracts the sine error as a feature, method 300 can also compensate for current measurement offset errors based on the feature by inputting the feature into an adaptive resonator to output a correction term. The correction term can correct the current measurement offset error. The adaptive resonator is capable of processing AC signals of any frequency. In some embodiments, method 300 calculates a correction term for the current measurement offset error in the stationary reference coordinate system and adds the transformed final correction term to the current estimated in the synchronous coordinate system.

[0054] In some embodiments, when method 300 transforms the output voltage command signal to convert the sine portion to a DC feature and filters the DC feature, method 300 can also compensate for current measurement offset errors based on the DC feature by inputting the DC feature into a conventional integrator to output a DC correction term. The DC correction term can directly correct the current measurement offset error in the synchronous reference coordinate system.

[0055] In any embodiment, the compensated estimated current can be sent to the current regulator 104 so that the current regulator 104 provides an output voltage command signal that lacks the characteristics of the current measurement offset error.

[0056] In some embodiments, a system for compensating for current measurement offset errors in an alternating current (AC) motor driver includes a processor and a memory including instructions. The instructions, when executed, cause the processor to: read an output voltage command signal, extract a feature of the current measurement offset error from the output voltage command signal, and use a feedback path based on the feature to compensate for current measurement offset errors in the closed loop.

[0057] In some embodiments, to compensate for current measurement offset errors in a closed loop using a feedback path based on features, the instructions further cause the processor to: generate a correction term that compensates for the current measurement offset errors, apply the correction term to the estimated current to output a compensated estimated current to a current regulator, and verify that a subsequent output voltage command signal received via the feedback path from the current regulator does not include the current measurement offset errors. In some embodiments, compensation for the current measurement offset errors is performed in real time as the AC motor driver operates the AC motor. In some embodiments, to extract features of the current measurement offset errors from the output voltage command signal, the instructions further cause the processor to: directly extract a sinusoidal error from the output voltage command signal. In some embodiments, to compensate for the current measurement offset errors based on the features, the instructions further cause the processor to: input the features into an adaptive resonator to output a correction term. In some embodiments, the instructions further cause the processor to: compensate for the current measurement offset errors in a stationary reference frame by adding the transformed correction term to the estimated current in a synchronous coordinate system. In some embodiments, to extract features of the current measurement offset errors from the output voltage command signal, the instructions further cause the processor to: transform the features into a DC signal. In some embodiments, to compensate for the current measurement offset errors based on the features, the instructions further cause the processor to: input the DC signal into a conventional integrator to output a DC correction term. In some embodiments, the instructions further cause the processor to: directly add the DC correction term to the estimated current in a synchronous coordinate system.

[0058] In some embodiments, a method for compensating current measurement offset errors in an alternating current (AC) motor driver includes: reading an output voltage command signal, extracting features of the current measurement offset errors from the output voltage command signal, and using a feedback path based on the features to compensate for the current measurement offset errors in a closed loop.

[0059] In some embodiments, to compensate for current measurement offset errors in a closed loop using a feedback path based on a feature, the method further includes: generating a correction term to compensate for the current measurement offset error, applying the correction term to the estimated current to output a compensated estimated current to a current regulator, and verifying that a subsequent output voltage command signal received via the feedback path from the current regulator does not include a current measurement offset error feature. In some embodiments, the method further includes: compensating for the current measurement offset error in real time as the AC motor driver operates the AC motor. In some embodiments, to extract a feature of the current measurement offset error from the output voltage command signal, the method further includes: extracting a sine component from the output voltage command signal. In some embodiments, to compensate for the current measurement offset error based on the feature, the method further includes: inputting the feature into an adaptive resonator to output a correction term. In some embodiments, the method further includes: compensating for the current measurement offset error by: transforming the correction term in a stationary reference frame and adding it to the estimated current in a synchronous reference frame. In some embodiments, to extract a feature of the current measurement offset error from the output voltage command signal, the method further includes: converting the feature to a DC signal. In some embodiments, to compensate for the current measurement offset error based on the feature, the method further includes: inputting the DC signal into a conventional integrator to output a DC correction term. In some embodiments, the method further includes: adding the DC correction to the estimated current in the synchronous reference frame and directly compensating for the current measurement offset error in the synchronous reference frame.

[0060] In some embodiments, an electronic device includes a processor and a memory storing instructions. The instructions, when executed, cause the processor to: read an output voltage command signal, extract a feature of a current measurement offset error from the output voltage command signal, and compensate for the current measurement offset error in a closed loop based on the feature using a feedback path.

[0061] In some embodiments, to extract the characteristics of the current measurement offset error from the output voltage command signal, the instructions further cause the processor to: extract a sine component from the output voltage command signal. In some embodiments, to compensate for the current measurement offset error based on the characteristics, the instructions further cause the processor to: input the characteristics into an adaptive resonator to output a correction term. In some embodiments, the instructions further cause the processor to: compensate for the current measurement offset error by transforming the correction term in the stationary reference coordinate system and adding it to the estimated synchronous coordinate system current. In some embodiments, to extract the characteristics of the current measurement offset error from the output voltage command signal, the instructions further cause the processor to: convert the characteristics into a DC signal. In some embodiments, to compensate for the current measurement offset error based on the characteristics, the instructions further cause the processor to: input the DC signal into a conventional integrator to output a DC zero command. In some embodiments, the instructions further cause the processor to: convert the DC zero command into a sine zero command, and compensate for the current measurement offset error in the stationary reference coordinate system by applying the sine zero command to the d / q measured current.

[0062] The foregoing discussion is intended to illustrate the principles of the invention and various embodiments. Once the above disclosure is fully understood, many variations and modifications will become apparent to those skilled in the art. The following claims are intended to be construed to include all such variations and modifications.

[0063] The word "example" is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as an "example" is not necessarily to be construed as more preferred or advantageous than other aspects or designs. Rather, the use of the word "example" is intended to present concepts in a concrete fashion. As used in this application, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless otherwise specified or clear from the context, "X includes A or B" is intended to mean any of the natural inclusive permutations. That is, if X includes A; X includes B; or X includes both A and B, then "X includes A or B" is satisfied in any of the foregoing instances. Additionally, the articles "a / an" used in this application and the appended claims should generally be construed to mean "one or more" unless otherwise specified or clearly indicated to the contrary from the context. Further, unless so described, the use of the term "embodiment" or "an embodiment" throughout the specification does not necessarily refer to the same embodiment or implementation.

[0064] Implementations of the systems, algorithms, methods, instructions, etc. described herein can be implemented in hardware, software, or any combination thereof. The hardware can include, for example, a computer, an intellectual property (IP) core, an application specific integrated circuit (ASIC), a programmable logic array, an optical processor, a programmable logic controller, microcode, a microcontroller, a server, a microprocessor, a digital signal processor, or any other suitable circuitry. In the claims, the term "processor" should be understood to include any of the foregoing hardware, individually or in combination. The terms "signal" and "data" may be used interchangeably.

[0065] As used herein, the term module can include a packaged functional hardware unit designed to be used with other components, a set of instructions executable by a controller (e.g., a processor executing software or firmware), processing circuitry configured to perform a particular function, and a self - contained hardware or software component interfacing with a larger system. For example, a module can include an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), circuitry, digital logic circuitry, analog circuitry, a combination of discrete circuitry, gate circuits, and other types of hardware, or combinations thereof. In other embodiments, a module can include a memory that stores instructions executable by a controller to implement the features of the module.

[0066] In addition, in one aspect, for example, the systems described herein can be implemented using a general - purpose computer or a general - purpose processor having a computer program that, when executed, implements any of the corresponding methods, algorithms, and / or instructions described herein. Additionally or alternatively, for example, a special - purpose computer / processor can be utilized that can include other hardware for implementing any of the methods, algorithms, or instructions described herein.

[0067] Furthermore, all or part of the implementations of the present disclosure can take the form of a computer program product accessible from, for example, a computer - usable or computer - readable medium. A computer - usable or computer - readable medium can be any device that can tangibly contain, store, communicate, or transport a program for use by or in connection with any processor. The medium can be, for example, an electrical, magnetic, optical, electromagnetic, or semiconductor device. Other suitable media can also be used.

[0068] The above - described embodiments, implementations, and aspects have been described to allow an easy understanding of the present invention and not to limit the present invention. On the contrary, the present invention is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which scope should be given the broadest interpretation to cover all such modifications and equivalent structures as are permitted by law.

Claims

1. A system for compensating current measurement offset errors in an alternating current (AC) motor drive, the system comprising: a processor; and a memory including instructions that, when executed by the processor, cause the processor to: read an output voltage command signal; directly extract a characteristic of the current measurement offset error from the output voltage command signal; and apply the characteristic to an estimated current to compensate for the current measurement offset error in a closed loop using a feedback path.

2. The system according to claim 1, wherein to compensate for the current measurement offset error in the closed loop using the feedback path based on the characteristic, the instructions further cause the processor to: generate a correction term for compensating the current measurement offset error; apply the correction term to the estimated current to output a compensated estimated current to a current regulator; and verify that a subsequent output voltage command signal received from the current regulator via the feedback path does not include the current measurement offset error.

3. The system according to claim 1, wherein compensation for the current measurement offset error is performed in real time as the AC motor drive operates the AC motor.

4. The system according to claim 1, wherein to extract the characteristic of the current measurement offset error from the output voltage command signal, the instructions further cause the processor to: extract a sine component at a synchronous frequency from the output voltage command signal.

5. The system according to claim 4, wherein to compensate for the current measurement offset error based on the characteristic, the instructions further cause the processor to: input the characteristic into an adaptive resonator to output a correction term.

6. The system according to claim 5, wherein the instructions further cause the processor to: compensate for the current measurement offset error in a synchronous reference coordinate system by transforming the correction term and adding the transformed correction term to the estimated current in the synchronous coordinate system.

7. The system according to claim 1, wherein to extract the characteristic of the current measurement offset error from the output voltage command signal, the instructions further cause the processor to: convert the characteristic into a DC signal.

8. The system according to claim 7, wherein to compensate for the current measurement offset error based on the characteristic, the instructions further cause the processor to: input the DC signal into a conventional integrator to output a DC correction term.

9. The system according to claim 8, wherein the instructions further cause the processor to: apply the DC correction term to the current estimated in the synchronous coordinate system to directly compensate for the current measurement offset error in the synchronous reference coordinate system.

10. A method for compensating current measurement offset errors in an AC motor drive, the method comprising: reading an output voltage command signal; directly extracting a characteristic of the current measurement offset error from the output voltage command signal; and applying the characteristic to an estimated current to compensate for the current measurement offset error in a closed loop using a feedback path.

11. The method according to claim 10, wherein To use the feedback path to compensate for the current measurement offset error based on the said characteristics, the method further includes: Generating a correction term command for compensating the current measurement offset error; Applying the correction term to the estimated current to output the compensated estimated current to a current regulator; and Verifying that the subsequent output voltage command signal received from the current regulator via the feedback path does not include the current measurement offset error.

12. The method according to claim 10, further including: Compensating for the current measurement offset error in real time as the AC motor driver operates the AC motor.

13. The method according to claim 10, wherein, To extract the characteristics of the current measurement offset error from the output voltage command signal, the method further includes: extracting a sine component at the synchronous frequency from the output voltage command signal.

14. The method according to claim 13, wherein, To compensate for the current measurement offset error based on the said characteristics, the method further includes: inputting the said characteristics into an adaptive resonator to output a correction term.

15. The method according to claim 14, further including: Directly compensating for the current measurement offset error in the stationary reference coordinate system by transforming the correction term and adding the transformed correction term to the estimated current in the synchronous coordinate system.

16. The method according to claim 10, wherein, To extract the characteristics of the current measurement offset error from the output voltage command signal, the method further includes: converting the said characteristics into a DC signal.

17. The method according to claim 16, wherein, To compensate for the current measurement offset error based on the said characteristics, the method further includes: inputting the DC signal into a conventional integrator to output a DC correction term.

18. The method according to claim 17, further including: Applying the DC correction term to the current estimated in the synchronous coordinate system to directly compensate for the current measurement offset error in the synchronous reference coordinate system.

19. An electronic device, including: A processor; and A memory, the memory including instructions which, when executed by the processor, cause the processor to: Read an output voltage command signal; Directly extract the characteristics of the current measurement offset error from the output voltage command signal; and Apply the said characteristics to the estimated current to use the feedback path to compensate for the current measurement offset error in the closed loop.

20. The electronic device according to claim 19, wherein: To extract the characteristics of the current measurement offset error from the output voltage command signal, the instructions further cause the processor to: convert the said characteristics into a DC signal; To compensate for the current measurement offset error based on the said characteristics, the instructions further cause the processor to: input the DC signal into a conventional integrator to output a DC correction term; and The instructions further cause the processor to: apply the DC correction term to the current estimated in the synchronous coordinate system to directly compensate for the current measurement offset error in the synchronous reference coordinate system.

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