A method for compensating DC bias error of rotary transformer output signal

Abstract

The present invention relates to a method for compensating a DC offset error in a resolver output signal. The resolver is connected to a built-in permanent magnet synchronous motor. The method comprises the following steps: a current acquisition step: acquiring the three-phase current of the built-in permanent magnet synchronous motor, performing a 3 / 2 conversion on the three-phase current, and obtaining a q-axis feedback current; a DC offset error extraction step: inputting the q-axis feedback current into a preset DC offset error extraction module to obtain a DC offset error; an error compensation step: compensating the resolver output signal using the DC offset error; and a DC offset error extraction module: extracting the DC offset error based on the amplitude of a sine-cosine ripple term in the q-axis feedback current whose frequency is the motor electrical frequency. Compared with the prior art, the present invention improves the accuracy of rotor position estimation in a resolver soft decoding scheme and enhances the quality of motor torque output.

Description

Technical Field

[0001] The present invention relates to the field of rotary transformer control, and in particular to a method for compensating a DC offset error of a rotary transformer output signal. Background Art

[0002] Interior permanent magnet synchronous motors (IPMS) offer advantages such as high efficiency, high power density, and a simple and compact structure. With the development of power electronics, they are widely used in electric vehicles, renewable energy generation, and industrial servo drives. In IPMMS systems using field-oriented control, position sensors are often used to acquire real-time rotor position signals due to the control method's requirements. Common position sensors include photoelectric encoders and resolvers.

[0003] As a position and speed sensor, resolvers offer advantages such as high robustness and safe and reliable operation. In recent years, they have been widely used in motor control applications such as electric vehicles. Generally speaking, using resolvers to extract rotor position and speed can be done through either hardware decoding or software decoding. Both methods share similar principles: the resolver receives a sinusoidal excitation input signal and two sinusoidal output signals containing the absolute rotor position. These signals are converted into digital signals by a resolver-to-digital converter (RDC), extracting position and speed information.

[0004] Due to the high cost of hardware decoding chips, the use of software decoding solutions to extract rotor position and speed information is becoming increasingly common. During software decoding of resolvers, the sampled resolver output signal can contain DC offset errors due to influences from external circuits, AD sampling, and the resolver itself. This DC offset error in the resolver output signal affects the rotor position obtained through software decoding, causing fluctuations in the dq axis currents at the same frequency as the electrical frequency. This, in turn, causes fluctuations in the motor torque, affecting the motor's torque output characteristics and reducing system efficiency. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for compensating the DC bias error of the rotary transformer output signal in order to overcome the defect of the above-mentioned prior art that the DC bias contained in the rotary transformer output signal affects the rotor position due to external circuits and sampling.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for compensating a DC bias error in a rotary transformer output signal, wherein the rotary transformer is connected to a built-in permanent magnet synchronous motor, the method comprising the following steps:

[0008] Current collection step: collecting the three-phase current of the built-in permanent magnet synchronous motor, performing a 3 / 2 conversion on the three-phase current, and obtaining a q-axis feedback current;

[0009] DC bias error extraction step: inputting the q-axis feedback current into a preset DC bias error extraction module to obtain a DC bias error;

[0010] Error compensation step: using the DC offset error to compensate the output signal of the resolver;

[0011] The DC bias error extraction module extracts the sine-cosine ripple term having a frequency equal to the motor electrical frequency from the q-axis feedback current, thereby calculating the DC bias error.

[0012] Furthermore, the DC bias error extraction module is provided with a phase delay compensation unit and a component extraction unit.

[0013] The phase delay compensation unit is used to obtain the phase delay of the sine-cosine ripple term;

[0014] The component extraction unit extracts the amplitude of the sine ripple component and the amplitude of the cosine ripple component from the sine-cosine ripple term according to the phase delay amount.

[0015] Furthermore, the calculation expression of the phase delay amount in the phase delay compensation unit is:

[0016] θ delay =θ delay1 +θ delay2

[0017]

[0018] Where θ delay is the phase delay amount in the phase delay compensation unit, θ delay1 is the phase delay component of the q-axis feedback current, θ delay2 is the phase delay component of the bandpass filter, P is the number of motor pole pairs, ω cc is the current loop bandwidth, and n is the motor speed.

[0019] Furthermore, the component extraction unit subtracts the amplitude of the sine-cosine ripple term from 0, and then inputs the results into a preset first integrator and a second integrator respectively, and controls the opening and closing of the first integrator and the second integrator based on the phase delay amount to obtain the amplitude of the sine ripple component and the amplitude of the cosine ripple component.

[0020] Furthermore, the horizontal coordinate of the sine-cosine ripple term corresponds to the motor rotor position, the value of the motor rotor position is within the range of 0 to 2pi, and the motor rotor position is phase compensated by the phase delay amount;

[0021] The first integrator is turned on when the motor rotor position after phase compensation is between 0 and pi, and is turned off in other cases. The first integrator is used to obtain the definite integral of the sinusoidal fluctuation component in the sine-cosine fluctuation term to obtain the amplitude of the sinusoidal fluctuation component.

[0022] Furthermore, the horizontal coordinate of the sine-cosine ripple term corresponds to the motor rotor position, the value of the motor rotor position is within the range of 0 to 2pi, and the motor rotor position is phase compensated by the phase delay amount;

[0023] The second integrator is turned on when the motor rotor position after phase compensation is between pi / 2 and 3pi / 2, and is turned off in other cases. The second integrator is used to obtain the definite integral of the cosine fluctuation component in the sine-cosine fluctuation term to obtain the amplitude of the cosine fluctuation component.

[0024] Furthermore, the amplitude of the sine ripple component and the amplitude of the cosine ripple component correspond to the DC bias of the sine signal and the cosine signal in the output signal of the rotary transformer. According to the amplitude of the sine ripple component and the amplitude of the cosine ripple component, the DC bias compensation is performed on the sine signal and the cosine signal in the output signal of the rotary transformer to obtain the compensated rotary transformer output signal.

[0025] Furthermore, the DC bias error extraction module uses a bandpass filter to extract the sine-cosine ripple term of the q-axis feedback current whose frequency is the motor electrical frequency.

[0026] Furthermore, the bandpass filter is a finite impulse response bandpass filter whose center frequency is the electrical frequency.

[0027] Furthermore, the rotary transformer output signal DC offset error compensation method is used in a built-in permanent magnet synchronous motor control system using a soft decoding solution.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] (1) The present invention analyzes the DC bias error of the dq-axis current of the rotary transformer, and obtains the magnitude of the DC bias error by extracting the amplitude of the sine-cosine ripple term of the q-axis feedback current whose frequency is the motor electrical frequency, thereby compensating the output signal of the rotary transformer, thereby improving the accuracy of the rotor position estimation in the rotary transformer soft decoding scheme and improving the motor torque output quality.

[0030] (2) The present invention takes into account that the error frequency in the q-axis current fluctuation term is related to the motor speed, so there is a phase delay between the actual rotor position and the q-axis fluctuation term, and the phase delay increases with the speed increase; therefore, a phase delay compensation unit is set up, and the q-axis current fluctuation frequency and the current closed-loop bandwidth and bandpass filter are considered at the same time to perform phase delay compensation, which is conducive to extracting accurate resolver error information. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is an overall principle diagram of the method of the present invention applied to a built-in permanent magnet synchronous motor system;

[0032] Figure 2 This is a partial schematic diagram of the DC bias error extraction module of the present invention. DETAILED DESCRIPTION

[0033] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0034] Example 1

[0035] This embodiment provides a method for compensating a DC offset error in a resolver output signal, which is used in a built-in permanent magnet synchronous motor control system using a soft decoding solution. The resolver is connected to the built-in permanent magnet synchronous motor. The method includes the following steps:

[0036] Current acquisition steps: Collect the three-phase current of the built-in permanent magnet synchronous motor, perform a 3 / 2 conversion on the three-phase current, and obtain the q-axis feedback current;

[0037] DC bias error extraction step: inputting the q-axis feedback current into a preset DC bias error extraction module to obtain the DC bias error;

[0038] Error compensation steps: using DC bias error to compensate the output signal of the resolver;

[0039] The DC bias error extraction module includes a DC bias error extraction unit, a phase delay compensation unit and a component extraction unit.

[0040] The following describes in detail each unit in the DC bias error extraction module and the specific implementation process of this method.

[0041] 1. DC bias error extraction unit

[0042] The DC bias error extraction unit extracts the DC bias error according to the amplitude of the sine-cosine ripple term in the q-axis feedback current, the frequency of which is the motor electrical frequency.

[0043] This embodiment uses a bandpass filter to extract the amplitude of the sine-cosine ripple term in the q-axis feedback current whose frequency is the motor electrical frequency. The bandpass filter is specifically a finite impulse response bandpass filter whose center frequency is the electrical frequency.

[0044] 2. Phase delay compensation unit

[0045] The phase delay compensation unit is used to obtain the phase delay of the sine and cosine ripple terms. The calculation expression of the phase delay is:

[0046] θ delay =θ delay1 +θ delay2

[0047]

[0048] Where θ delay is the phase delay amount in the phase delay compensation unit, θ delay1 is the phase delay component of the q-axis feedback current, θ delay2 is the phase delay component of the bandpass filter, P is the number of motor pole pairs, ω cc is the current loop bandwidth, and n is the motor speed.

[0049] 3. Component extraction unit

[0050] The component extraction unit extracts the amplitude of the sine ripple component and the amplitude of the cosine ripple component from the sine-cosine ripple term according to the phase delay. The amplitude of the sine ripple component and the amplitude of the cosine ripple component correspond to the DC offset of the sine signal and the cosine signal in the output signal of the resolver.

[0051] Based on the amplitudes of the sine and cosine components, DC offset compensation is performed on the resolver output signal to obtain a compensated resolver output signal. This compensated resolver output signal is then input into a resolver-to-digital converter to calculate the rotor position angle.

[0052] Specifically, the component extraction unit subtracts the amplitude of the sine and cosine ripple terms from 0, and then inputs them into the preset first integrator and second integrator respectively, controls the opening and closing of the first integrator and the second integrator based on the phase delay amount, and obtains the amplitude of the sine ripple component and the amplitude of the cosine ripple component.

[0053] The horizontal coordinate of the sine-cosine ripple term corresponds to the motor rotor position, and the value of the motor rotor position is within the range of 0 to 2pi. The motor rotor position is phase compensated by the phase delay amount;

[0054] The first integrator is turned on when the motor rotor position after phase compensation is between 0 and pi, and is turned off in other cases. The first integrator is used to obtain the definite integral of the sinusoidal fluctuation component in the sine-cosine fluctuation term to obtain the amplitude of the sinusoidal fluctuation component.

[0055] The second integrator is turned on when the motor rotor position after phase compensation is between pi / 2 and 3pi / 2, and is turned off in other cases. The second integrator is used to obtain the definite integral of the cosine fluctuation component in the sine-cosine fluctuation term to obtain the amplitude of the cosine fluctuation component.

[0056] 4. Specific implementation process

[0057] A method for compensating a DC offset error of a resolver output signal comprises the following steps:

[0058] S1: In a built-in permanent magnet synchronous motor control system using a soft decoding solution, the motor's three-phase currents (a, b, and c) are collected. After a 3 / 2 transformation, the q-axis feedback current is input into the DC bias error extraction module. The output is the DC bias error.

[0059] S2: Compensate the DC bias error output by the DC bias error extraction module to the two resolver output signals respectively, and use the compensated resolver output signals to extract the angle and speed.

[0060] The specific implementation steps of the DC bias error extraction module in step S1 are as follows:

[0061] 1) After demodulating the resolver output signal (extracting the envelope), the following signal is obtained:

[0062]

[0063] Where E is the amplitude of the feedback signal, V dc1 、V dc2 They are the DC error components contained in the sine and cosine signals respectively.

[0064] Multiply the signal of formula (1) by the trigonometric function of the rotor position feedback value and make the difference, and the error information is as follows:

[0065]

[0066] When the closed-loop system controls err to 0, the error in the angle can be expressed as follows:

[0067]

[0068] Substituting this error into the coordinate transformation, the d-axis and q-axis current models containing the error information can be obtained:

[0069]

[0070] Where β is the current angle; is the estimated value of the rotor position.

[0071] Calculation yields:

[0072]

[0073] By analyzing the q-axis (or d-axis) current in Equation (5), it can be concluded that the q-axis current consists of a DC component and a sine-cosine ripple term at the motor's electrical frequency. The amplitude of the ripple term is the DC offset error. Therefore, after extracting this frequency ripple term using a bandpass filter and integrating it, the DC offset error can be extracted.

[0074] 2) If Figure 2 As shown, a finite impulse response (FIR) bandpass filter (BPF) with a center frequency of electrical frequency is used to extract the sine and cosine ripple terms contained in the q-axis current, and then the sine and cosine ripple terms are input into a phase delay compensation unit for phase delay compensation, the compensated sine and cosine ripple terms are subtracted from 0, and then the signal is input into integrator 1 and integrator 2, wherein integrator 1 acts when the rotor position after phase compensation is between 0 and pi, with the purpose of obtaining the amplitude of the sine ripple component in the signal; integrator 2 acts when the rotor position after phase compensation is between pi / 2 and 3pi / 2, with the purpose of obtaining the amplitude of the cosine ripple component in the signal.

[0075] In some cases, the bandpass filter can only display the amplitude of the sine and cosine ripple terms, and the amplitude of the sine and cosine ripple terms corresponds to the motor rotor position. At this time, the phase delay amount is first calculated by the phase delay compensation unit to perform phase compensation on the motor rotor position, and integrator 1 and integrator 2 both perform integration operations based on the amplitude of the sine and cosine ripple terms corresponding to the motor rotor position after phase compensation.

[0076] The amplitude of the sine wave component and the amplitude of the cosine wave component are the DC bias of the resolver output sine signal and cosine signal respectively. After the resolver output signal is compensated, the resolver output signal is input into the resolver / digital converter to calculate the rotor position angle.

[0077] The phase delay compensation unit described in step 2) is specifically implemented as follows:

[0078] Because the error frequency in the q-axis current fluctuation term is related to the motor speed, there is a phase delay between the actual rotor position and the q-axis fluctuation term. This phase delay increases with speed. To extract accurate resolver error information, this phase delay needs to be compensated.

[0079] Taking into account the q-axis current fluctuation frequency and the current closed-loop bandwidth, the phase delay can be calculated as follows:

[0080]

[0081] where ω cc is the current loop bandwidth, and P is the number of motor pole pairs.

[0082] In addition, since the FIR bandpass filter is needed to extract the fluctuation signal, this part of the delay θ delay2 Compensation is also required. The phase angle to be compensated depends on the design parameters of the filter. The total phase delay θ delay =θ delay1 +θ delay2 .

[0083] like Figure 1 As shown in the figure, it is the overall principle diagram of the method of the present invention applied to the built-in permanent magnet synchronous motor system. In the built-in permanent magnet synchronous motor system, T e The signal enters the MTPA & weak magnetic table unit (MTPA is the maximum torque current ratio control of PMSM), generating signal i dref and i qref , then flows into the PI current controller to generate a signal v d and v q , after Park inverse transform unit 1, generates signal v α and v β , signal v α and v β , same as V dc They flow into the space vector pulse width modulation unit SVPWM together to generate the PWM_Signals signal (pulse width modulation signal) and flow into the voltage source inverter VSI. The output end of the voltage source inverter VSI is connected to the 3 / 2 conversion unit 2 and the built-in permanent magnet synchronous motor IPMSM respectively. The rotary transformer Resolver connected to the built-in permanent magnet synchronous motor IPMSM outputs the rotary output signal and flows into the rotary / digital converter; the voltage source inverter VSI transmits the three-phase current signal i to the 3 / 2 conversion unit 2 abc , 3 / 2 conversion unit 2 generates d-axis feedback current i d and q-axis feedback current i q , where i q The DC bias compensation module compensates for the DC bias error of the resolver output signal of the resolver / digital converter, thereby extracting the angle and speed.

[0084] Among them, T e 、i dref 、iqref 、v d 、v q 、v α 、v β and V dc They are motor torque command, d-axis reference current, q-axis reference current, d-axis voltage, q-axis voltage, α-axis voltage, β-axis voltage and DC bus voltage respectively.

[0085] The DC bias detection and compensation method of the rotary transformer output signal of this embodiment solves the problem of inaccurate position signal estimation and fluctuation in dq-axis current and torque caused by the DC bias error in the rotary transformer output signal in the built-in permanent magnet synchronous motor vector control system using a soft decoding scheme, and has the following beneficial effects: The DC bias detection and compensation method of the rotary transformer output signal of this embodiment, in the built-in permanent magnet synchronous motor control system using a soft decoding scheme, when the rotary transformer output signal has a DC bias error due to sampling and other problems, the DC bias error in the rotary transformer output signal can be compensated and corrected in real time by online calculation of the amplitude of the DC bias error, thereby improving the accuracy of rotor position estimation in the rotary transformer soft decoding scheme and improving the motor torque output quality.

[0086] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for compensating a DC bias error in a rotary transformer output signal, wherein the rotary transformer is connected to a built-in permanent magnet synchronous motor, characterized in that: The method comprises the following steps: Current collection step: collecting the three-phase current of the built-in permanent magnet synchronous motor, performing a 3 / 2 conversion on the three-phase current, and obtaining a q-axis feedback current; DC bias error extraction step: inputting the q-axis feedback current into a preset DC bias error extraction module to obtain a DC bias error; Error compensation step: using the DC offset error to compensate the output signal of the resolver; The DC bias error extraction module extracts the sine and cosine fluctuation terms with a frequency equal to the motor electrical frequency from the q-axis feedback current, thereby calculating the DC bias error; The DC bias error extraction module is provided with a phase delay compensation unit and a component extraction unit. The phase delay compensation unit is used to obtain the phase delay of the sine-cosine ripple term; The component extraction unit extracts the amplitude of the sine fluctuation component and the amplitude of the cosine fluctuation component from the sine-cosine fluctuation term according to the phase delay; The component extraction unit subtracts the amplitude of the sine and cosine ripple terms from 0, and then inputs the subtraction into a preset first integrator and a preset second integrator, respectively. The first integrator and the second integrator are turned on and off based on the phase delay amount to obtain the amplitude of the sine ripple component and the amplitude of the cosine ripple component. The amplitude of the sine wave component and the amplitude of the cosine wave component are the DC offset errors; The horizontal coordinate of the sine-cosine ripple term corresponds to the motor rotor position, the value of the motor rotor position is within the range of 0 to 2pi, and the motor rotor position is phase compensated by the phase delay amount; The first integrator is turned on when the motor rotor position after the phase compensation is between 0 and pi, and is turned off in other cases. The first integrator is used to obtain the definite integral of the sinusoidal fluctuation component in the sine-cosine fluctuation term to obtain the amplitude of the sinusoidal fluctuation component; The second integrator is turned on when the motor rotor position after phase compensation is between pi / 2 and 3pi / 2, and is turned off in other cases. The second integrator is used to obtain the definite integral of the cosine fluctuation component in the sine-cosine fluctuation term to obtain the amplitude of the cosine fluctuation component.

2. The method for compensating a DC offset error of a resolver output signal according to claim 1, wherein: The calculation expression of the phase delay amount in the phase delay compensation unit is: i delay =θ delay1 +θ delay2 Where θ delay is the phase delay amount in the phase delay compensation unit, θ delay1 is the phase delay component of the q-axis feedback current, θ delay2 is the phase delay component of the bandpass filter, P is the number of motor pole pairs, ω cc is the current loop bandwidth, and n is the motor speed.

3. The method for compensating a DC offset error of a resolver output signal according to claim 1, wherein: According to the amplitude of the sine ripple component and the amplitude of the cosine ripple component, DC offset compensation is performed on the sine signal and the cosine signal in the resolver output signal to obtain a compensated resolver output signal.

4. The method for compensating a DC offset error of a resolver output signal according to claim 1, wherein: The DC bias error extraction module uses a bandpass filter to extract the sine-cosine ripple term with a frequency equal to the motor electrical frequency from the q-axis feedback current.

5. The method for compensating a DC offset error of a resolver output signal according to claim 4, wherein: The bandpass filter is a finite impulse response bandpass filter with a center frequency being an electrical frequency.

6. The method for compensating a DC offset error of a resolver output signal according to claim 1, wherein: The rotary transformer output signal DC offset error compensation method is used in a built-in permanent magnet synchronous motor control system using a soft decoding solution.

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