Motor overmodulation control method based on real-time voltage harmonic detection and compensation

Abstract

The invention relates to the technical field of motor control, in particular to a motor overmodulation control method based on real-time voltage harmonic detection and compensation. Main harmonic components in output voltage are detected in real time in an overmodulation state, a voltage intelligent compensation strategy is provided, an extra harmonic voltage signal is superposed on the basis of fundamental voltage, the signal is opposite to the harmonic components in time sequence, a compensation signal capable of effectively inhibiting harmonic waves is generated, and finally, the harmonic components in the output voltage are detected in real time. A compensation signal is fused into an original voltage modulation signal through a closed-loop control system, effective suppression of harmonic waves in an over-modulation state is achieved, the electric energy quality of a motor system is remarkably improved, the operation efficiency is optimized, and the service life of the whole driving system is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a motor overmodulation control method based on real-time voltage harmonic detection and compensation. Background Art

[0002] In the field of modern motor control technology, servo motor drive systems are widely used due to their advantages such as high efficiency, energy saving and high controllability. However, in order to improve the bus voltage utilization of the servo drive, expand the speed regulation range of the motor, and quickly respond to load requirements and provide greater instantaneous torque output, the servo drive uses overmodulation technology to improve the bus voltage utilization, thereby achieving a maximum phase voltage amplitude that can be provided under the conventional PWM state to enhance the transient response capability and load capacity of the motor. When the servo drive is overmodulated, the output waveform will produce significant harmonic distortion and generate harmonic voltage. These nonlinear effects will not only reduce the efficiency of the motor system and increase losses, but may also have adverse effects on the motor and the power grid, such as increased vibration, increased noise, reduced power quality and shortened equipment life.

[0003] At present, harmonic current suppression methods are mostly used to improve the above problems. For example, announcement number CN117013911A, titled "A method for suppressing harmonic current of a permanent magnet synchronous motor", proposes a specific harmonic current suppression method, which aims to reduce the impact of harmonic current on motor performance. Harmonic current is suppressed by adjusting the duty cycle of the PWM signal. Due to the need for complex calculations, the real-time performance of this method will be affected. Harmonic voltage is indirectly obtained by extracting harmonic current, and delays will occur especially when processing high-speed changing current signals. Summary of the invention

[0004] In order to solve the deficiencies of the prior art, the present invention provides a motor overmodulation control method based on real-time voltage harmonic detection and compensation.

[0005] The present invention is achieved through the following technical solutions:

[0006] A motor overmodulation control method based on real-time voltage harmonic detection and compensation comprises the following steps:

[0007] Step 1: Input the speed loop target value into the speed loop PI controller. The speed loop target value is the set speed given value. The speed feedback value is calculated by collecting the value of the motor encoder. The output value of the speed loop is obtained through the PI controller. q * .

[0008] Step 2: The output value of the speed loop obtained in step 1 q *As the given value of the q-axis current control loop, the given value of the d-axis current control loop is i d * , where i d * =0; d-axis current component i d As the current feedback value of the d-axis, the q-axis current component i q As the current feedback value of the q axis; then i d The d-axis current PI control loop obtains U d ,i q The q-axis current PI control loop obtains U q , U d , U q And the motor electrical angle θ is obtained by inverse transformation of park α and U β .

[0009] Step 3: Use high-speed data acquisition equipment to continuously collect the output voltage signal of the motor drive system in real time, and convert the continuous motor three-phase voltage analog signal into a discrete voltage digital signal sequence u[N], where N is the number of sampling points.

[0010] Perform fast Fourier transform on the voltage digital signal sequence u[N], and separate the amplitude and phase of the odd harmonics in the signal according to the known sampling rate and fundamental frequency, as follows:

[0011] The amplitude Au[k] and phase of the U-phase odd harmonic component U[k] Where, k = 1, 3, 5, ...;

[0012] The expression of the odd harmonic component U[k] of phase U is:

[0013] The expression (3) of U[k] is simplified to the complex form:

[0014] U[k]=a+bj (4),

[0015] Among them, a represents a real number; b represents an imaginary number; j represents the unit of the imaginary number; n = 0, 1, 2...(N-1);

[0016] Then the amplitude Au[k] of the U-phase odd harmonic component U[k] is: Phase of the U-phase odd harmonic component U[k] for:

[0017] After determining the amplitude and phase of the odd harmonic component of phase U, calculate the harmonic distortion rate Hu[k] of each harmonic. The calculation formula of the harmonic distortion rate Hu[k] is:

[0018]

[0019] Then the calculation results are recorded as the amplitude and phase of the harmonic distortion rate Hu[k] of the U phase greater than 2%, and the amplitude and phase of the harmonic distortion rate greater than 2% are recorded as Au[fb] and

[0020] Then the harmonic voltage of the odd harmonics with harmonic distortion rate greater than 2% in phase U is:

[0021]

[0022] Then the harmonic voltage of the odd harmonics with V-phase harmonic distortion greater than 2% is:

[0023]

[0024] The above harmonic voltage expressions (8) and (9) are transformed into the following equations through Clark transformation:

[0025] U kα =U fb (10)

[0026]

[0027] The total U is obtained by adding the harmonic voltages of the odd harmonics in formulas (10) and (11) αsum and U βsum .

[0028] Step 4: Add the U calculated in step 3 to the original voltage calculated in step 2. αsum and U βsum , get the compensation regulated output voltage U α * and U β * ,

[0029] U α * =U α -U αsum (12)

[0030] U β * =U β -U βsum (13);

[0031] Step 5: After signal compensation is completed, it enters overmodulation. During overmodulation, the control strategy adopts the minimum phase error method. The phase of the reference voltage vector outside the modulatable area remains unchanged, and the amplitude outside the modulatable area is reduced to 2*U dc / π, where U dc Represents the DC bus voltage, and the corrected Us , U s Represents the stator terminal voltage vector amplitude, according to U s Calculate the corrected U α * and U β * .

[0032] Step 6: According to the corrected U α * and U β * , the values ​​Ta, Tb, and Tc of the three-phase comparator are calculated through the SVPWM overmodulation link to generate a PWM signal to drive the motor.

[0033] In step 2, i d and i q The following process is used to obtain: Two phases of the three-phase stator current of the motor are i a and i b , the motor electrical angle is θ, and the stator current i is taken a and i b After the Clark transformation of abc / αβ and the Park transformation of αβ / dq, it is transformed into the d-axis current component i in the two-phase rotating coordinate system d and the q-axis current component i q .

[0034] The present invention proposes a voltage intelligent compensation strategy by real-time detection of the main harmonic components in the output voltage under the overmodulation state. An additional harmonic voltage signal is superimposed on the fundamental voltage. The signal will be opposite to the harmonic component in timing, and a compensation signal for effectively suppressing harmonics is generated. Finally, the compensation signal is integrated into the original voltage modulation signal through a closed-loop control system to achieve effective suppression of harmonics under the overmodulation state, significantly improve the power quality of the motor system, optimize the operating efficiency, and extend the service life of the overall drive system.

[0035] Beneficial effects of the present invention:

[0036] 1. The present invention adopts a voltage overmodulation control strategy and uses a minimum phase error method to minimize the harmonic distortion rate of the output voltage and achieve the best linearity.

[0037] 2. The present invention realizes continuous monitoring and dynamic compensation of output voltage harmonics through a closed-loop control system, so that even under changing working conditions, a good harmonic suppression effect can be maintained, thereby ensuring the stability and reliability of the motor drive system.

[0038] 3. The present invention effectively suppresses the voltage waveform distortion caused by overmodulation technology by real-time detection and intelligent compensation of the harmonic components in the output voltage of the motor drive system, thereby improving the voltage output quality of the system.

[0039] 4. The present invention adopts overmodulation technology to enhance motor performance, reduce the impact of harmonics on motor efficiency, enable the motor to utilize bus voltage to a higher degree, thereby increasing instantaneous torque output and expanding the speed regulation range, and improving the overall operating efficiency of the motor and its control system.

[0040] 5. The present invention effectively suppresses and compensates harmonics, reduces energy loss caused by nonlinear effects, and improves the overall operating efficiency of the motor system.

[0041] 6. The present invention reduces the impact of harmonics on power equipment, reduces the additional heat, vibration and other potential damages caused by harmonics, and helps to effectively extend the service life of the motor and its related electrical components. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a flow chart of the motor overmodulation control process of real-time voltage harmonic detection and intelligent compensation of the present invention;

[0043] Figure 2 Partitioning for SVPWM vector and modulation;

[0044] Figure 3 It is the overmodulation minimum phase error correction strategy. DETAILED DESCRIPTION

[0045] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0046] The technical solution for implementing the present invention is as follows:

[0047] Step 1: Input the speed loop target value into the speed loop PI controller. The speed loop target value is the set speed given value N. * , by collecting the value of the motor encoder and then calculating the speed feedback value N, the output value i of the speed loop is obtained through the PI controller q * .

[0048] Step 2: The output value of the speed loop obtained in step 1 q * As the given value of the q-axis current control loop, the given value of the d-axis current control loop is i d * , where i d *=0; d-axis current component i d As the current feedback value of the d-axis, the q-axis current component i q As the current feedback value of the q axis.

[0049] Among them, the above i d and i q The following process is used to obtain: Two phases of the three-phase stator current of the motor are i a and i b , the motor electrical angle is θ, and the stator current i is taken a and i b After the Clark transformation of abc / αβ and the Park transformation of αβ / dq, it is finally transformed into the d-axis current component i in the dq two-phase rotating coordinate system. d and the q-axis current component i q ,i d and i q They are used as the current feedback values ​​of the d-axis and q-axis respectively.

[0050] Then the d-axis current component i d The d-axis current PI control loop obtains U d , q-axis current component i q The q-axis current PI control loop obtains U q , then U d , U q And the motor electrical angle θ is obtained by inverse transformation of park α and U β , U α and U β The expressions are as follows:

[0051] U α =U d cosθ-U q sinθ (1),

[0052] U β =U d sinθ+U q cosθ (2).

[0053] Step 3: Voltage harmonic detection and feedback module.

[0054] This step specifically includes the following steps:

[0055] Step 31: The output voltage signal of the motor drive system is continuously collected in real time by high-speed data acquisition equipment, and the continuous motor three-phase voltage analog signal is converted into a discrete voltage digital signal sequence u[N], where N is the number of sampling points.

[0056] Step 32: Perform fast Fourier transform on the voltage digital signal sequence u[N], and separate the amplitude and phase of the odd harmonics in the signal according to the known sampling rate and fundamental frequency, as follows:

[0057] The amplitude Au[k] and phase of the U-phase odd harmonic component U[k] Where, k = 1, 3, 5, ...;

[0058] The expression of the odd harmonic component U[k] of phase U is:

[0059] As mentioned above, U[k] is the complex spectral component corresponding to the odd harmonics, so the U[k] expression (3) can be simplified to the following complex form:

[0060] U[k]=a+bj (4),

[0061] Among them, a represents a real number; b represents an imaginary number; j represents the unit of the imaginary number; n = 0, 1, 2...(N-1).

[0062] Then the amplitude Au[k] of the U-phase odd harmonic component U[k] is: Phase of the U-phase odd harmonic component U[k] for:

[0063] Step 33: After determining the amplitude and phase of the odd harmonic component of the U phase, calculate the harmonic distortion rate relative to the fundamental amplitude, thereby obtaining the harmonic distortion rate Hu[k] of each harmonic. The calculation formula of the harmonic distortion rate Hu[k] is:

[0064]

[0065] Then, based on the above calculation results, the amplitude and phase of the harmonic distortion rate Hu[k] of the U phase greater than 2% are recorded. The amplitude and phase of the harmonic distortion rate greater than 2% are recorded as Au[fb] and

[0066] The harmonic voltage of the odd harmonics with harmonic distortion rate greater than 2% in phase U is:

[0067]

[0068] Due to the symmetry of the three-phase system, the amplitude of the harmonics of the same order in each phase is equal, and the phase difference is The V-phase harmonic voltage can be calculated from the U-phase harmonic voltage, so the harmonic voltage of the odd harmonics with a V-phase harmonic distortion rate greater than 2% is:

[0069]

[0070] The above harmonic voltage expressions (8) and (9) are transformed into the following equations through Clark transformation:

[0071] U kα =U fb (10)

[0072]

[0073] The total U is obtained by adding the harmonic voltages of the odd harmonics in formulas (10) and (11) αsum and U βsum .

[0074] Step 4: Harmonic voltage compensation control loop.

[0075] The specific steps include:

[0076] Step 41: U calculated based on the result of step 3 αsum and U βsum , add the U calculated in step 3 to the original voltage calculated in step 2 αsum and U βsum , the signal will be opposite to the harmonic component in timing, and the compensation signal that can offset or reduce the harmonic component is synthesized according to the compensation strategy to obtain the compensated regulated output voltage U α * and U β * ,

[0077] U α * =U α -U αsum (12)

[0078] U β * =U β -U βsum (13).

[0079] Step 42: Voltage harmonic detection feedback compensation forms a compensation regulating output voltage U α * and U β * , continuously detect the harmonic components of the output voltage, and continuously correct the compensation signal through the above-mentioned feedback compensation mechanism until the main odd harmonic distortion rate is controlled within 1%.

[0080] Step 5: After signal compensation is completed, it enters overmodulation. During overmodulation, the control strategy adopts the minimum phase error method. The phase of the reference voltage vector outside the modulatable area remains unchanged, and the amplitude outside the modulatable area is reduced to 2*U dc / π,U dcRepresents the DC bus voltage, and the corrected U s , U s Represents the stator terminal voltage vector amplitude, according to U s Calculate the corrected U α * and U β * .

[0081] Step 6: According to the corrected U α * and U β * , the values ​​Ta, Tb, and Tc of the three-phase comparator are calculated through the SVPWM overmodulation link to generate a PWM signal to drive the motor.

[0082] The present invention may also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A motor overmodulation control method based on real-time voltage harmonic detection and compensation, characterized in that: The steps include: Step 1: Input the speed loop target value into the speed loop PI controller. The speed loop target value is the set speed given value. The speed feedback value is calculated by collecting the value of the motor encoder. The output value of the speed loop is obtained through the PI controller. q * ; Step 2: The output value of the speed loop obtained in step 1 q * As the given value of the q-axis current control loop, the given value of the d-axis current control loop is i d * , where i d * =0; d-axis current component i d As the current feedback value of the d-axis, the q-axis current component i q As the current feedback value of the q axis; then i d The d-axis current PI control loop obtains U d ,i q The q-axis current PI control loop obtains U q , U d , U q And the motor electrical angle θ is obtained by inverse transformation of park α and U β ; Step 3: Use high-speed data acquisition equipment to continuously collect the output voltage signal of the motor drive system in real time, and convert the continuous motor three-phase voltage analog signal into a discrete voltage digital signal sequence u[N], where N is the number of sampling points; Perform fast Fourier transform on the voltage digital signal sequence u[N], and separate the amplitude and phase of the odd harmonics in the signal according to the known sampling rate and fundamental frequency, as follows: The amplitude Au[k] and phase of the U-phase odd harmonic component U[k] Where, k = 1, 3, 5, ...; The expression of the odd harmonic component U[k] of phase U is: The expression (3) of U[k] is simplified to the complex form: U[k]=a+bj (4), Among them, a represents a real number; b represents an imaginary number; j represents the unit of the imaginary number; n = 0, 1, 2...(N-1); Then the amplitude Au[k] of the U-phase odd harmonic component U[k] is: Phase of the U-phase odd harmonic component U[k] for: After determining the amplitude and phase of the odd harmonic component of phase U, calculate the harmonic distortion rate Hu[k] of each harmonic. The calculation formula of the harmonic distortion rate Hu[k] is: Then the calculation results are recorded as the amplitude and phase of the harmonic distortion rate Hu[k] of the U phase greater than 2%, and the amplitude and phase of the harmonic distortion rate greater than 2% are recorded as Au[fb] and Then the harmonic voltage of the odd harmonics with harmonic distortion rate greater than 2% in phase U is: Then the harmonic voltage of the odd harmonics with V-phase harmonic distortion greater than 2% is: The above harmonic voltage expressions (8) and (9) are transformed into the following equations through Clark transformation: IN kα =U fb (10), The total U is obtained by adding the harmonic voltages of the odd harmonics in formulas (10) and (11) αsum and U βsum ; Step 4: Add the U calculated in step 3 to the original voltage calculated in step 2. αsum and U βsum , get the compensation regulated output voltage U α * and U β * , IN α * =U α -IN αsum (12), IN β * =U β -IN βsum (13); Step 5: After signal compensation is completed, it enters overmodulation. During overmodulation, the control strategy adopts the minimum phase error method. The phase of the reference voltage vector outside the modulatable area remains unchanged, and the amplitude outside the modulatable area is reduced to 2*U dc / π, where U dc Represents the DC bus voltage, and the corrected U s , U s Represents the stator terminal voltage vector amplitude, according to U s Calculate the corrected U α * and U β * ; Step 6: According to the corrected U α * and U β * , the values ​​Ta, Tb, and Tc of the three-phase comparator are calculated through the SVPWM overmodulation link to generate a PWM signal to drive the motor.

2. The motor overmodulation control method based on real-time voltage harmonic detection and compensation according to claim 1 is characterized in that: In step 2, i d and i q The following process is used to obtain: Two phases of the three-phase stator current of the motor are i a and i b , the motor electrical angle is θ, and the stator current i is taken a and i b After the Clark transformation of abc / αβ and the Park transformation of αβ / dq, it is transformed into the d-axis current component i in the two-phase rotating coordinate system d and the q-axis current component i q .

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