Harmonic injection control system and method for suppressing harmonics and current overshoot

Abstract

The present invention provides a harmonic injection control system and method for suppressing harmonics and current overshoot, which belongs to the field of permanent magnet motor and drive control. Based on the drawbacks of the traditional harmonic injection control strategy, the harmonic current component of the three-phase current of the permanent magnet synchronous motor is extracted, and the extracted harmonic current component is calculated and PI controlled to obtain an accurate harmonic voltage component, which is then injected into the input terminal u of the SVPWM. α and u β , using the overmodulation processing function in the SVPWM module, the voltage vector action time inside the SVPWM is controlled within the switching cycle, and finally the SVPWM module emits a PWM waveform. The present invention not only realizes the harmonic suppression function of the traditional harmonic injection method, but also has a better suppression effect on the overshoot problem of the motor phase current when the motor changes speed or the load changes suddenly.

Description

Technical Field

[0001] The invention belongs to the field of AC motor and drive control, and relates to a harmonic injection control system and method for suppressing harmonics and current overshoot. Background Art

[0002] Permanent magnet synchronous motor has the advantages of small size, light weight, high power density and high operating efficiency. Compared with DC motor, its structure is simpler and easier to repair and maintain. Compared with asynchronous motor, its stator current and stator resistance loss are reduced, and the rotor parameters are measurable and the control performance is good, so it is widely used.

[0003] However, relevant research has found that in the application of traditional permanent magnet synchronous motors, due to the influence of factors such as the nonlinear factors of the inverter, dead time and switching characteristics, the sinusoidality of the output current decreases and there are more harmonics in the motor, which not only affects the stability of the hardware system and causes the accuracy and reliability of motor control to decrease, but also generates electromagnetic noise and interference, which will cause certain harm to people's health.

[0004] The harmonic injection method is a classic harmonic suppression method. It extracts the harmonic components of the three-phase current, calculates the harmonic voltage value and injects it into the control loop. The harmonic components in the three-phase current are reduced by adjusting the control loop. The traditional harmonic injection method injects the harmonic components into the three-phase modulation wave that generates the PWM wave. When the motor is running at variable speed or loading, the injected harmonic components are large due to the poor current waveform. Injecting them will cause the amplitude of the three-phase modulation wave to increase sharply, resulting in serious current overshoot. The accuracy of the harmonic component extraction is also one of the key factors that determine the performance of the harmonic injection method. Therefore, the traditional harmonic injection method has obvious disadvantages and needs to be improved. Summary of the invention

[0005] To solve the above problems, the present invention discloses a harmonic injection control method for suppressing harmonics and current overshoot, which particularly improves the safety performance of the permanent magnet synchronous motor by suppressing current overshoot and effectively suppresses the harmonic components in the motor.

[0006] The present invention adopts the following technical solutions to achieve the above-mentioned purpose:

[0007] A harmonic injection control system for suppressing harmonics and current overshoot includes a low-order harmonic identification module, a new harmonic voltage compensation module and an improved SVPWM module. The low-order harmonic identification module is used to extract the nth current harmonic in the three-phase current signal and filter the redundant harmonic components to obtain the accurate nth current component. The new harmonic voltage compensation module includes a harmonic voltage calculation module and a PI controller module. The harmonic voltage calculation and PI controller output are performed based on the nth current component to form an accurate nth harmonic voltage component, and the harmonic injection component is obtained through coordinate conversion. The improved SVPWM module includes a sector judgment module, a vector action time calculation module, a modulation processing module and a PWM wave generation module. The sector judgment module determines the sector position of the voltage vector based on the harmonic injection component, the vector action time calculation module obtains the voltage vector action time, the modulation processing module fixes the vector action time within the switching cycle, and generates the PWM wave required by the inverter based on the PWM wave generation module. The control method includes a low-order harmonic identification module, a new harmonic voltage compensation module and an improved SVPWM module.

[0008] Preferably, the low-order harmonic identification module includes a dq coordinate transformation module and a low-pass filter, and obtains the three-phase current signal as the input of the dq coordinate transformation module. The d-axis current and q-axis current are obtained after coordinate transformation and input into the low-pass filter to filter out other harmonic components and obtain the required n-th d-axis current and n-th q-axis current.

[0009] Preferably, the new harmonic voltage compensation module includes a d-axis harmonic voltage PI controller, a q-axis harmonic voltage PI controller, a harmonic voltage calculation module and a dq / αβ coordinate transformation module. Based on the nth d-axis current and the nth q-axis current, the nth d-axis and q-axis harmonic voltages are output through the harmonic voltage calculation module and the d-axis and q-axis PI controllers, and are input into the dq / αβ coordinate transformation module to obtain the α-axis and β-axis nth harmonic injection components.

[0010] Preferably, the system also includes a vector control module, based on which α-axis and β-axis voltage reference components are generated. The harmonic injection component is an additional input of the SVPWM module. The α-axis and β-axis voltage reference components and the α-axis and β-axis nth harmonic injection components are synthesized and input into the sector judgment module in the improved SVPWM module to obtain the sector position.

[0011] The present invention also discloses a control method for a harmonic injection control system for suppressing harmonics and current overshoot, comprising the following steps:

[0012] Step 1: Get the three-phase current signal i of the motor a ,i b and i cIn order to suppress the nth harmonic current in the motor, the phase current in the motor is transformed into nth dq coordinates, the nth d-axis current and q-axis current components are extracted, and the harmonic components above nth are filtered out by a low-pass filter to obtain the accurate nth d-axis and q-axis current components i dnth 、i qnth ;

[0013] Step 2, based on the accurate n-th d-axis and q-axis current components i dnth 、i qnth , calculate the n-th dq axis voltage components, and at the same time perform n-th d-axis and q-axis voltage feedback adjustment through the PI controller to obtain more accurate n-th d-axis and q-axis voltage components u dnth 、u qnth , and perform dq / αβ coordinate transformation to obtain the nth harmonic injection component u of α-axis and β-axis αnth 、u βnth ;

[0014] Step 3: αnth 、u βnth The injection loop is connected to the input side of the SVPWM module, combined with the α-axis voltage reference component u generated by vector control α and the β-axis voltage reference component u β Determine the sector position of the voltage vector and calculate the time T of the voltage vector action 4 / T 6 The time of the fixed voltage vector action is in the switching period T through the overmodulation process in SVPWM. S The motor control loop adjusts the output PWM wave in a closed loop by injecting harmonic components, thereby achieving three-phase current harmonic suppression and current overshoot relief in the motor.

[0015] Preferably, in step 1, the transformation matrix of the dq coordinate transformation is:

[0016]

[0017] The method to filter out harmonic components above n is:

[0018] y(t)=K·u(t)+(1-K)·y(t-1) (2)

[0019] Among them, y(t) is the output signal at the current moment t, that is, the target subharmonic component except the high-order harmonic component, u(t) is the input signal, K∈(0,1), and y(t-1) is the output signal at the previous moment.

[0020] As a preference, in step 2, a more accurate n-th d-axis and q-axis voltage component u is obtained. dnth 、u qnth The method is:

[0021]

[0022] Among them, u dnth is the n-th d-axis voltage, u dnth_PI is the PI controller output of the n-th d-axis voltage, ω is the electrical angular velocity of the motor, L q is the quadrature axis inductance of the motor, i qnth is the n-th q-axis current of the motor, R s is the phase resistance of the motor, u qnth is the nth q-axis voltage, L d is the quadrature axis inductance of the motor, i dnth is the nth d-axis current of the motor, u qnth_PI is the PI controller output of the n-th q-axis voltage.

[0023] Preferably, in step 3, the n-th d-axis voltage and the n-th q-axis voltage are transformed into a two-phase stationary coordinate system by dq / αβ coordinate transformation, and used as an additional input u of the SVPWM module. αnth and u βnth , that is, harmonic injection, and the total input of SVPWM will be overmodulated to fix the voltage vector action time within the switching cycle, where the dq / αβ coordinate transformation matrix and overmodulation processing are shown as follows:

[0024]

[0025]

[0026] Among them, C 2r / 2s is the dq / αβ coordinate transformation matrix, θ is the electrical angle, Tx is the action time of voltage vector x, Ty is the action time of voltage vector y, T S is the switching cycle.

[0027] Preferably, in step 3, the harmonic component is injected into the modulation wave of SVPWM, and the generated three-phase modulated PWM wave y(t) is expressed as:

[0028]

[0029] Among them, ε is the normalization coefficient, M represents the modulation ratio, U d is the bus voltage, θ e is the phase angle of the modulation wave.

[0030] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0031] (1) Compared with the traditional harmonic injection method, the present invention injects harmonic components into the modulation wave output by SVPWM. The control loop adjusts the output PWM wave of the control loop through the injected harmonic components in a closed loop, thereby achieving the three-phase current harmonic suppression and current overshoot relief in the motor, and has a better harmonic suppression effect;

[0032] (2) Compared with the traditional harmonic injection method, it has a better improvement effect on the current overshoot problem in situations such as permanent magnet motor loading or speed change. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the improved harmonic injection SVPWM control principle diagram of the present invention

[0034] Figure 2 This is the control principle diagram of the low-order harmonic identification module in the present invention.

[0035] Figure 3 This is the control principle diagram of the new harmonic voltage compensation module in the present invention.

[0036] Figure 4 This is a comparison of the conventional and improved SVPWM control principle diagrams in the present invention.

[0037] Figure 5 This is the harmonic suppression effect diagram of the present invention

[0038] Figure 6 This is the current overshoot suppression effect diagram of the present invention DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] The present invention is based on the drawbacks of the traditional harmonic injection control strategy. By extracting the harmonic current components of the three-phase current of the permanent magnet synchronous motor, the extracted harmonic current components are combined with the output of the PI controller through the n-th dq axis voltage calculation to form a more accurate harmonic voltage component with closed-loop feedback; finally, different from the traditional harmonic injection method, the harmonic components are injected into the modulation wave output by the SVPWM, that is, injected into the input terminal u of the SVPWM. α and u β, using the overmodulation processing function in the SVPWM module, the voltage vector action time inside the SVPWM is controlled within the switching cycle to prevent the voltage vector action time from being too long and causing current overshoot; the control loop closes the loop by injecting harmonic components to adjust the output PWM wave of the control loop, so as to achieve the three-phase current harmonic suppression and current overshoot relief in the motor, and has a good suppression effect on the motor mid-phase current overshoot problem when the motor changes speed or sudden load changes.

[0041] like Figure 1 As shown, the purpose of the present invention is to provide a harmonic injection control system suitable for suppressing harmonics and current overshoot, the system comprising: a low-order harmonic identification module, a novel harmonic voltage compensation module and an improved SVPWM module; the low-order harmonic identification module comprises a dq coordinate transformation and a low-pass filter, which is used to extract the nth current harmonic in the three-phase current signal and filter the redundant harmonic components to obtain the accurate nth current component; the novel harmonic voltage compensation module comprises a d-axis harmonic voltage PI controller, a q-axis harmonic voltage PI controller, a harmonic voltage calculation module and a dq / αβ coordinate transformation, based on The n-th current component is respectively subjected to harmonic voltage calculation and PI controller output to form an accurate n-th harmonic voltage component, and the harmonic injection component is obtained through coordinate transformation; the improved SVPWM module includes a sector judgment module, a vector action time calculation module, a modulation processing module and a PWM wave generation module, the sector judgment module determines the sector position of the voltage vector based on the harmonic injection component, the vector action time calculation module obtains the action time of the voltage vector, the modulation processing module fixes the vector action time within the switching cycle, and the PWM wave required by the inverter is issued based on the PWM wave generation module.

[0042] This embodiment takes the suppression of the fifth harmonic current as an example:

[0043] The low-order harmonic identification module includes: Figure 2 As shown, firstly, the three-phase current in the motor is detected by using components such as current sensors to obtain the three-phase current signal i of the permanent magnet synchronous motor. a ,i b and i c , use it as the input of the low-order harmonic identification module, through the fifth dq coordinate transformation, and then filter out other harmonic components through a low-pass filter to obtain the accurate fifth-order d-axis current i d5th and the fifth q-axis current i q5th .

[0044] The new harmonic voltage compensation module includes: Figure 3 As shown, the module input is the fifth d-axis current i d5th and the fifth q-axis current i q5th , through the fifth d-axis harmonic voltage calculation and d-axis PI controller output ud5th_PI Forming accurate fifth d-axis harmonic voltage u d5th , through the fifth q-axis harmonic voltage calculation and q-axis PI controller output u q5th_PI Forming the accurate fifth q-axis harmonic voltage u q5th , and then the fifth d-axis harmonic voltage u d5th and the fifth q-axis harmonic voltage u q5th Input dq / αβ coordinate transformation to obtain the additional input of the SVPWM module: the fifth harmonic injection component u of the α axis α5th and the fifth harmonic injection component u of the β axis β5th , that is, the harmonic injection component.

[0045] The improved SVPWM link includes: Figure 4 As shown, the improved SVPWM link is used to generate PWM wave, and the input is the α-axis voltage reference component u generated by vector control. α and the β-axis voltage reference component u β And the α-axis fifth harmonic injection component u generated by the new harmonic voltage compensation module α5th and the fifth harmonic injection component u of the β axis β5th The synthesized component passes through the SVPWM sector judgment module to determine the sector position of the voltage vector, and then passes through the vector action time calculation module to calculate the voltage vector action time T 4 / T 6 Then, the modulation processing module fixes the vector action time at the switching period T S Finally, it passes through the PWM wave generation module to generate the PWM wave required by the inverter.

[0046] Combination Figures 2 to 6 The present invention also discloses a harmonic injection control method for suppressing harmonics and current overshoot.

[0047] Step 1: Get the three-phase current signal i of the motor a ,i b and i c In order to suppress the nth harmonic current in the motor, the phase current in the motor is transformed into nth dq coordinates, the nth d-axis current and q-axis current components are extracted, and the harmonic components above nth are filtered out by a low-pass filter to obtain the accurate nth d-axis and q-axis current components i dnth 、i qnth .

[0048] Step 2, based on the accurate n-th d-axis and q-axis current components i dnth 、i qnth , calculate the n-th dq axis voltage components, and at the same time perform n-th d-axis and q-axis voltage feedback adjustment through the PI controller to obtain more accurate n-th d-axis and q-axis voltage components udnth 、u qnth , and perform dq / αβ coordinate transformation to obtain the nth harmonic injection component u of α-axis and β-axis αnth 、u βnth ;

[0049] Step 3: αnth 、u βnth The injection loop is connected to the input side of the SVPWM module, combined with the α-axis voltage reference component u generated by vector control α and the β-axis voltage reference component u β Determine the sector position of the voltage vector and calculate the time T of the voltage vector action 4 / T 6 , the time of the fixed voltage vector action is in the switching period T through the overmodulation process in SVPWM S The motor control loop adjusts the output PWM wave in a closed loop by injecting harmonic components, thereby achieving three-phase current harmonic suppression and current overshoot relief in the motor.

[0050] This embodiment takes the suppression of the fifth harmonic current in a permanent magnet synchronous motor as an example:

[0051] Step 1: Use current sensors and other components to obtain the three-phase current signal i of the permanent magnet synchronous motor. a ,i b and i c , use it as the input of the low-order harmonic identification module, through the fifth dq coordinate transformation, and then filter out other harmonic components through a low-pass filter to obtain the accurate fifth-order d-axis current i d5th and the fifth q-axis current i q5th . Among them, the transformation matrix of dq coordinate transformation is

[0052]

[0053] The method to filter out harmonic components above n is: y(t) = K·u(t) + (1-K)·y(t-1),

[0054] Among them, y(t) is the output signal at the current time t, u(t) is the input signal, K∈(0,1), and y(t-1) is the output signal at the previous time.

[0055] Step 2: Input the new harmonic voltage compensation module, calculate the fifth d-axis harmonic voltage and output u through the d-axis PI controller d5th_PI Forming accurate fifth d-axis harmonic voltage u d5th , through the fifth q-axis harmonic voltage calculation and q-axis PI controller output u q5th_PI Forming the accurate fifth q-axis harmonic voltage u q5th :

[0056]

[0057] where u d5th is the fifth d-axis voltage, u d5th_PI is the PI controller output of the fifth d-axis voltage, ω is the electrical angular velocity of the motor, L q is the quadrature axis inductance of the motor, i q5th is the fifth q-axis current of the motor, R s is the phase resistance of the motor, u q5th is the fifth q-axis voltage, L d is the quadrature axis inductance of the motor, i d5th is the fifth d-axis current of the motor, u q5th_PI is the PI controller output of the fifth q-axis voltage.

[0058] Then the fifth d-axis harmonic voltage u d5th and the fifth q-axis harmonic voltage u q5th Input dq / αβ coordinate transformation to obtain the additional input of the SVPWM module: the fifth harmonic injection component u of the α axis α5th and the fifth harmonic injection component u of the β axis β5th , that is, the harmonic injection component.

[0059] Among them, the dq / αβ coordinate transformation matrix is ​​as follows:

[0060]

[0061]

[0062] Taking the first sector of SVPWM as an example, T 4 is the action time of voltage vector 4, T 6 is the action time of voltage vector 6, T S is the switching cycle.

[0063] Step 3: α5th 、u β5th The α-axis voltage reference component u generated by vector control α and the β-axis voltage reference component u β The new reference component is input into the SVPWM module, and the overmodulation process in SVPWM is used to fix the action time of the voltage vector within the switching cycle. The control loop adjusts the output PWM wave of the control loop through the injected harmonic component in a closed loop to drive the inverter to work, thereby achieving the three-phase current harmonic suppression and current overshoot relief in the motor.

[0064] Specifically,

[0065] The entire loop is based on the fifth d-axis current i d5th and the fifth q-axis current iq5th The calculated fifth harmonic injection component u of the α axis α5th and the fifth harmonic injection component u of the β axis β5th The control loop is adjusted to reduce the three-phase current signal i a ,i b and i c The fifth harmonic current component of the current is extracted more accurately through the d-axis PI controller and the q-axis PI controller. The dq / αβ coordinate transformation matrix is ​​shown as follows:

[0066] C 2r / 2s is the dq / αβ coordinate transformation matrix, and θ is the electrical angle.

[0067] Injecting harmonic components into the modulation wave of SVPWM, the overmodulation process in SVPWM is used to alleviate the current overshoot when the motor is loaded or the speed is changed. The overmodulation process is as follows:

[0068]

[0069] Taking the first sector of SVPWM as an example, T 4 is the action time of voltage vector 4, T 6 is the action time of voltage vector 6, T S is the switching cycle.

[0070] Compared with the traditional harmonic injection, which injects harmonic components into the modulation wave of SVPWM, the three-phase modulation wave y(t) after injection is expressed by the following formula:

[0071]

[0072] Where ε is the normalization coefficient, M represents the modulation ratio, and U d is the bus voltage, θ e is the phase angle of the modulation wave. It can be seen that if the first term and the second term of the modulation wave are in phase, the three-phase modulation wave will appear in a soaring state.

[0073] Figure 5 It is the phase current waveform diagram before and after adding the suppression algorithm. It can be seen from the figure that the phase current waveform is obviously smoother after adding the suppression algorithm. Figure 6 It is the waveform diagram of the current overshoot suppression situation of the traditional harmonic suppression method and the improved harmonic suppression method. It can be seen from the figure that when the motor is idling, when the speed jumps from 400r / min to 600r / min, the current overshoot generated is reduced from 3.4A to 2.6A.

[0074] The present invention aims to provide a harmonic injection control method for suppressing harmonics and current overshoot, which particularly improves the safety performance of permanent magnet synchronous motor operation by limiting current overshoot and suppresses harmonic components in the motor.

[0075] The above embodiments are only for illustrating the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the present invention.

Claims

1. A harmonic injection control system for suppressing harmonics and current overshoot, characterized in that: Including low-order harmonic identification module, new harmonic voltage compensation module and improved SVPWM module, The low-order harmonic identification module is used to extract the nth current harmonic in the three-phase current signal and filter the redundant harmonic components to obtain the accurate nth current component; The novel harmonic voltage compensation module includes a harmonic voltage calculation module and a PI controller module, which respectively perform harmonic voltage calculation and PI controller output based on the nth order current component to form an accurate nth order harmonic voltage component, and obtain a harmonic injection component through coordinate transformation; The improved SVPWM module includes a sector judgment module, a vector action time calculation module, a modulation processing module and a PWM wave generation module. The sector judgment module determines the sector position of the voltage vector based on the harmonic injection component. The vector action time calculation module obtains the action time of the voltage vector. The modulation processing module fixes the action time of the vector within the switching cycle. The PWM wave generation module generates the PWM wave required by the inverter. The generated three-phase modulated PWM wave y(t) is expressed as: Among them, ε is the normalization coefficient, M represents the modulation ratio, U d is the bus voltage, θ e is the phase angle of the modulation wave.

2. The harmonic injection control system for suppressing harmonics and current overshoot according to claim 1, characterized in that: The low-order harmonic identification module includes a dq coordinate transformation module and a low-pass filter. The three-phase current signal is obtained as the input of the dq coordinate transformation module. The d-axis current and q-axis current are obtained after coordinate transformation and input into the low-pass filter to filter out other harmonic components and obtain the required n-th d-axis current and n-th q-axis current.

3. The harmonic injection control system for suppressing harmonics and current overshoot according to claim 2, characterized in that: The novel harmonic voltage compensation module includes a d-axis harmonic voltage PI controller, a q-axis harmonic voltage PI controller, a harmonic voltage calculation module and a dq / αβ coordinate transformation module. Based on the n-th d-axis current and the n-th q-axis current, the harmonic voltage calculation module and the d-axis and q-axis PI controllers output the n-th d-axis and q-axis harmonic voltages, and input them into the dq / αβ coordinate transformation module to obtain the α-axis and β-axis n-th harmonic injection components.

4. The harmonic injection control system for suppressing harmonics and current overshoot according to claim 3, characterized in that: The system also includes a vector control module, based on which α-axis and β-axis voltage reference components are generated. The harmonic injection component is an additional input of the SVPWM module. The α-axis and β-axis voltage reference components and the α-axis and β-axis nth harmonic injection components are synthesized and input into the sector judgment module in the improved SVPWM module to obtain the sector position.

5. The control method of the harmonic injection control system for suppressing harmonics and current overshoot according to any one of claims 1 to 4, characterized in that: The following steps are included: Step 1: Get the three-phase current signal i of the motor a ,i b and i c In order to suppress the nth harmonic current in the motor, the phase current in the motor is transformed into nth dq coordinates, the nth d-axis current and q-axis current components are extracted, and the harmonic components above nth are filtered out by a low-pass filter to obtain the accurate nth d-axis and q-axis current components i dnth 、i qnth ; Step 2, based on the accurate n-th d-axis and q-axis current components i dnth 、i qnth , calculate the n-th dq axis voltage components, and at the same time perform n-th d-axis and q-axis voltage feedback adjustment through the PI controller to obtain more accurate n-th d-axis and q-axis voltage components u dnth 、u qnth , and perform dq / αβ coordinate transformation to obtain the nth harmonic injection component u of α-axis and β-axis αnth 、u βnth ; Step 3: αnth 、u βnth The injection loop is connected to the input side of the SVPWM module, combined with the α-axis voltage reference component u generated by vector control α and the β-axis voltage reference component u β Determine the sector position of the voltage vector, calculate the action time of the voltage vector, and fix the action time of the voltage vector in the switching period T through the overmodulation process in SVPWM S The motor control loop adjusts the output PWM wave in a closed loop by injecting harmonic components, thereby achieving three-phase current harmonic suppression and current overshoot relief in the motor.

6. The control method of the harmonic injection control system for suppressing harmonics and current overshoot according to claim 5, characterized in that: In step 1, the transformation matrix of dq coordinate transformation is The method to filter out harmonic components above n is: y(t)=K·u(t)+(1-K)·y(t-1) (2) Among them, y(t) is the output signal at the current time t, u(t) is the input signal, K∈(0,1), and y(t-1) is the output signal at the previous time.

7. The control method of the harmonic injection control system for suppressing harmonics and current overshoot according to claim 6, characterized in that: In step 2, the more accurate n-th d-axis and q-axis voltage components u are obtained. dnth 、u qnth The method is: Among them, u dnth is the n-th d-axis voltage, u dnth_PI is the PI controller output of the n-th d-axis voltage, ω is the electrical angular velocity of the motor, L q is the quadrature axis inductance of the motor, i qnth is the n-th q-axis current of the motor, R s is the phase resistance of the motor, u qnth is the nth q-axis voltage, L d is the quadrature axis inductance of the motor, i dnth is the nth d-axis current of the motor, u qnth_PI is the PI controller output of the n-th q-axis voltage.

8. The control method of the harmonic injection control system for suppressing harmonics and current overshoot according to claim 7, characterized in that: In step 3, the n-th d-axis voltage and the n-th q-axis voltage are transformed into the two-phase stationary coordinate system through dq / αβ coordinate transformation as the additional input u of the SVPWM module. αnth and u βnth , i.e., the harmonic component, where the dq / αβ coordinate transformation matrix is ​​as follows: Among them, C 2r / 2s is the dq / αβ coordinate transformation matrix, and θ is the electrical angle.

9. The control method of the harmonic injection control system for suppressing harmonics and current overshoot according to claim 8, characterized in that: The harmonic component is injected into the modulation wave of SVPWM, and the three-phase modulated PWM wave generated after the overmodulation process in SVPWM is used, where the overmodulation process is: T x is the voltage vector x action time, T y is the action time of voltage vector y, T S is the switching cycle.

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