Negative sequence control-based control method for grid-side converter of grid-forming type permanent magnet synchronous motor

Abstract

The invention discloses a negative sequence control-based control method for a grid-side converter of a grid-forming type permanent magnet synchronous motor, and relates to the technical field of virtual synchronous machine control. According to the method, permanent magnet synchronous motor network side control under the unbalanced weak power grid condition is divided into network construction type control, positive sequence double-closed-loop control and negative sequence closed-loop control, cooperative compensation control is added to the positive sequence double-closed-loop control, and corresponding positive sequence voltage and current components are compensated according to the power grid unbalance degree. Aiming at the problem that the existing permanent magnet synchronous motor control technology is difficult to realize stable operation under the unbalanced weak power grid, a negative sequence control mode is combined with a network construction mode, a cooperative compensation control mode is added, a negative sequence current component can be effectively inhibited, the stability of the permanent magnet synchronous motor under the unbalanced weak power grid is greatly improved, and the stability of the permanent magnet synchronous motor under the unbalanced weak power grid is improved. And stable operation under a severe power grid condition is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of virtual synchronous machine control, and in particular to a grid-side converter control method of a grid-forming permanent magnet synchronous motor based on negative sequence control. Background Art

[0002] In order to solve the problem of system instability caused by the permanent magnet synchronous motor when the grid has an unbalanced fault or is connected to an unbalanced load after being connected to a weak grid, relevant scholars from various countries have proposed positive and negative sequence separation control based on the existing traditional grid-following control strategy, thereby suppressing the negative sequence current generated by the system. As the short-circuit ratio of the future power grid is facing a trend of continuous reduction, the traditional grid-forming permanent magnet synchronous motor's current imbalance suppression strategy not only cannot meet the suppression requirements of negative sequence voltage under weak grids, but also puts the system at risk of instability. Therefore, it is necessary to explore the unbalanced stator voltage suppression strategy of the grid-forming permanent magnet synchronous motor under weak grid operating conditions.

[0003] There are many academic papers that have studied the stability of virtual synchronous machines, such as:

[0004] 1) The document "Excitation Control Strategy of Grid-connected Doubly-fed Induction Generator under Unbalanced Grid Voltage" was published in Journal of Wuhan University, Vol. 42, No. 1, pp. 110-113 in 2009. The proposed strategy is based on the positive and negative sequence synchronous coordinate system, and uses a proportional controller to achieve the following of the inner loop positive sequence control command and the suppression of unbalanced components such as stator current and active power.

[0005] 2) Literature "PIR Control of the Rotor Side of Doubly Fed Wind Induction Generator under Unbalanced Voltage" 2018 Journal of Electric Power System and Automation, Vol. 30, No. 9, pp. 128-133 Based on the positive sequence synchronous coordinate system, the negative sequence component of the rotor current is suppressed by a proportional resonant controller;

[0006] 3) The document “Hybrid direct power control strategy for doubly-fed induction generators under unbalanced voltage conditions”, 2022, Electric Power Automation Equipment, Vol. 42, No. 6, pp. 199-205, calculates the rotor current reference value for different control targets such as unbalanced rotor current, active power, reactive power, and torque ripple;

[0007] 4) The document “Multi-objective Model Predictive Control of Doubly Fed Generators under Unbalanced Grid Voltage”, 2019 Proceedings of the CSEE, Vol. 39, No. 13, pp. 3917-3930, proposes a multi-objective control strategy based on model prediction under unbalanced voltage. By adjusting the weight coefficients, flexible suppression of each control objective is achieved.

[0008] Based on the above documents, the prior art has the following deficiencies:

[0009] 1. Only the grid-following operation state is considered. Under weak grid conditions, the existence of the phase-locked loop in the grid-following control will have a negative impact on system stability;

[0010] 2. The positive and negative sequence dual-loop control of the doubly-fed asynchronous motor is set as a proportional link. There is a static error in the steady state and it cannot accurately follow the given value;

[0011] 3. It is impossible to switch between different operating modes for different grid conditions, and it cannot better adapt to the operating conditions of permanent magnet synchronous motors. Summary of the invention

[0012] The technical problem to be solved by the present invention is that the existing control scheme of permanent magnet synchronous motor is difficult to adapt to the harsh conditions of unbalanced weak power grid, and its stability is threatened. Specifically, the present invention proposes a control method for grid-type permanent magnet synchronous motor grid-side converter based on negative sequence control. The control method can realize the stable operation of permanent magnet synchronous motor under unbalanced weak power grid conditions through grid-type control and positive and negative sequence separation control and coordinated compensation control, and greatly improves the robustness of permanent magnet synchronous motor grid-connected system.

[0013] The object of the present invention is achieved in this way. The present invention provides a control method for a grid-type permanent magnet synchronous motor grid-side converter based on negative sequence control, and the circuit topology structure applying the control method includes a permanent magnet synchronous motor, a machine-side converter, a DC bus capacitor, a grid-side converter, an LC filter, a grid impedance and a three-phase grid connected in sequence, and the LC filter includes a filter inductor and a filter capacitor; the permanent magnet synchronous motor is controlled separately by two loops, positive sequence and negative sequence, under the condition of unbalanced weak grid operation, and the specific steps are as follows:

[0014] Step 1: Sample the grid-connected point voltage and record it as the grid-connected voltage u ga ,u gb ,u gc , sample the three-phase current on the grid-side converter side and record it as the three-phase grid-side current i wa ,i wb ,i wc , sample the three-phase voltage on the grid-side converter side and record it as the three-phase grid-side voltage u wa ,u wb ,u wc ;

[0015] Step 2: Input the grid voltage u in the decoupling software phase-locked loop of the dual synchronous coordinate system ga ,u gb ,u gc , three-phase grid side voltage u wa ,u wb ,u wc and three-phase grid-side current i wa ,iwb ,i wc , complete the transformation of the above three sets of parameters from the three-phase stationary coordinate system to the positive and negative synchronous rotating coordinate system, and the specific output is: dq axis grid-connected voltage positive sequence component Positive sequence component of voltage on the dq axis grid side Negative sequence component of dq axis grid side voltage Positive sequence component of dq axis grid side current Negative sequence component of dq axis grid side current

[0016] Step 3: According to the positive sequence component of the voltage on the dq axis grid side and the positive sequence component of the dq axis grid side current The active power positive sequence component of the output after filtering is obtained through the power calculation equation and reactive power positive sequence component

[0017] Step 4: According to the positive sequence component of the active power output after filtering The positive sequence component of harmonic frequency is obtained by constructing the active power control equation And calculate the positive sequence control angle s is the Laplace operator; then according to the positive sequence component of the active power output after filtering and reactive power positive sequence component By constructing the network reactive power control equation, the given value of the positive sequence component of the voltage on the d-axis network side is obtained.

[0018] Step 5: Introduce virtual impedance Z v , introduce voltage coordination coefficient K u and current coordination coefficient K i , and satisfy the boundary condition K u +K i =1; the dq axis grid side current positive sequence component corrected by the current coordination coefficient is obtained through calculation and recorded as the corrected dq axis grid side current positive sequence component The voltage positive sequence component of the dq axis grid side after voltage coordination coefficient correction is obtained and recorded as the corrected dq axis grid side voltage positive sequence component Set 0 as the input value of the cooperative compensation control loop, and convert the corrected dq axis grid side current positive sequence component and the corrected dq axis grid side voltage positive sequence component As feedback input, the positive sequence component of the dq axis current cooperative compensation value is output after passing through the resonant controller and PI controller.

[0019] Step 6: Set the positive sequence component of the voltage on the d-axis grid side to a given value As the input of the positive sequence voltage control outer loop of the grid-side converter, the positive sequence component of the d-axis grid-side voltage As the feedback input of the positive sequence voltage control outer loop of the grid-side converter, it outputs the given value of the positive sequence component of the dq axis grid-side current after PI control. Set the positive sequence component of the dq axis grid side current to a given value Positive sequence component of dq axis grid side current As the feedback input of the positive sequence current control inner loop of the grid-side converter, the positive sequence component of the dq axis current cooperative compensation value As the feedback input compensation value of the positive sequence current control inner loop of the grid-side converter, the output after PI control is the positive sequence component of the dq axis grid-side voltage modulation wave after coordinated compensation control.

[0020] Step 7: Set 0 as the negative sequence current loop input and set the negative sequence component of the dq axis grid side current As feedback input, after PI control, the negative sequence component of the voltage modulation wave on the dq axis grid side is output

[0021]

[0022] Step 8: The positive sequence component of the dq axis grid side voltage modulation wave after the coordinated compensation control obtained in step 6 And the negative sequence component of the dq axis grid side voltage modulation wave obtained in step 7 The grid-side converter switch voltage modulation wave is obtained through the decoupling software phase-locked loop inverse coordinate transformation of the dual synchronous coordinate system to complete the control of the grid-side converter.

[0023] Preferably, the power calculation equation in step 3 is:

[0024]

[0025] In the formula, ω f is the cut-off frequency of the LC filter.

[0026] Preferably, the network active power control equation and network reactive power control equation in step 4 are respectively:

[0027]

[0028] Where P set is the virtual synchronous machine active power command value, ω n is the rated angular frequency of the power grid, D is the active damping coefficient of the virtual synchronous machine, J is the virtual moment of inertia, Q set is the reactive power command value of the virtual synchronous machine, and n is the reactive-frequency droop coefficient.

[0029] Preferably, the corrected positive sequence component of the dq axis grid side current in step 5 is and the corrected dq axis grid side voltage positive sequence component The calculation formulas are:

[0030]

[0031] The dq axis current cooperative compensation value positive sequence component The calculation formula is:

[0032]

[0033] In the formula, K P2 is the proportional coefficient of the PI controller used in the cooperative compensation control, K I2 is the integral coefficient of the PI controller used in the cooperative compensation control, G R (s) is the resonant controller transfer function, and its expression is:

[0034]

[0035] In the formula, k r is the resonance gain coefficient; ω c is the cut-off frequency, and ω2 is the resonant frequency.

[0036] Preferably, the given value of the positive sequence component of the dq axis grid side current in step 6 is The calculation formula is:

[0037]

[0038] In the formula, K uP is the proportional coefficient of the PI controller used in the outer loop of the positive sequence voltage control of the grid-side converter, K uI The integral coefficient of the PI controller used in the outer loop of the positive sequence voltage control of the grid-side converter;

[0039] The positive sequence component of the dq axis grid side voltage modulation wave after coordinated compensation control The calculation formula is:

[0040]

[0041] In the formula, ω n is the rated angular frequency of the power grid, K iP is the proportional coefficient of the inner loop of the positive sequence current control, K iI is the integral coefficient of the inner loop of the positive sequence current control, L f is the inductance value of the filter inductor.

[0042] Preferably, the negative sequence component of the dq axis grid side voltage modulation wave in step 7 The calculation formula is:

[0043]

[0044] In the formula, K P1 is the PI controller proportional coefficient used in the negative sequence current loop, K I1 It is the integral coefficient of the PI controller used in the negative sequence current loop.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] 1. The present invention further considers the influence of weak grid on permanent magnet synchronous motor under the condition of unbalanced grid, and adopts grid-forming control. Compared with grid-following control, the grid-forming permanent magnet synchronous motor has better grid support and stability under the condition of weak grid;

[0047] 2. The present invention is simple to implement, uses a meshed control outer loop, and separates the positive and negative sequence components for control, which can ensure the stable operation of the permanent magnet synchronous motor under an unbalanced weak power grid, and at the same time can suppress the negative sequence current generated by the system.

[0048] 3. Compared with the simple proportional control method, the present invention adopts positive sequence component double closed-loop control, which can achieve zero static error following command value;

[0049] 4. The present invention uses single-loop control in the negative sequence component, which can ensure rapid suppression of the negative sequence current of the system.

[0050] 5. The present invention adds a coordinated compensation control on the positive sequence component side, which can compensate the voltage according to the imbalance of voltage and current, and can better adapt to the grid conditions of the motor operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A circuit topology diagram for applying the control method of the present invention;

[0052] Figure 2 This is a network control structure diagram corresponding to step 3-step 4 of the present invention;

[0053] Figure 3 It is the positive sequence and negative sequence current control structure diagram;

[0054] Figure 4 This is the structure diagram of the positive sequence double closed loop control for the added collaborative compensation control;

[0055] Figure 5 The voltage waveform of the grid-side converter under SCR=2 and Udroop=10%;

[0056] Figure 6 The grid-side converter current waveform is SCR=2, Udroop=10%;

[0057] Figure 7 This is the effect diagram of unbalanced current suppression of the grid-side converter;

[0058] Figure 8 This is the effect diagram of unbalanced voltage suppression of the grid-side converter;

[0059] Fig. 9 This is a diagram of the power pulsation suppression effect. DETAILED DESCRIPTION

[0060] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0061] Figure 1 The circuit topology diagram of the control method of the present invention is as follows: Figure 1 It can be seen that the system includes a permanent magnet synchronous motor, a machine-side converter, a DC bus capacitor, a grid-side converter, an LC filter, a grid impedance and a three-phase grid which are connected in sequence, and the LC filter includes a filter inductor and a filter capacitor.

[0062] exist Figure 1 in, u dc is the DC bus capacitor voltage, L f is the inductance of the filter inductor, C f is the capacitance of the filter capacitor, L grid is the inductance value in the grid line impedance, R grid is the resistance value in the grid line impedance.

[0063] Figure 2 This is the network control structure diagram corresponding to step 3-step 4 of the present invention, Figure 3 It is the positive sequence and negative sequence current control structure diagram. Figure 4 The positive sequence double closed-loop control structure diagram of the added collaborative compensation control is composed of Figure 2-Figure 4 It can be seen that the permanent magnet synchronous motor of the present invention is controlled separately by the positive sequence and negative sequence loops under the unbalanced weak power grid operation condition. The specific control steps are as follows:

[0064] Step 1: Sample the grid-connected point voltage and record it as the grid-connected voltage u ga ,u gb ,u gc , sample the three-phase current on the grid-side converter side and record it as the three-phase grid-side current i wa ,i wb ,i wc , sample the three-phase voltage on the grid-side converter side and record it as the three-phase grid-side voltage u wa ,u wb ,u wc .

[0065] Step 2: Input the grid voltage u in the decoupling software phase-locked loop of the dual synchronous coordinate system ga ,u gb ,u gc , three-phase grid side voltage uwa ,u wb ,u wc and three-phase grid-side current i wa ,i wb ,i wc , complete the transformation of the above three sets of parameters from the three-phase stationary coordinate system to the positive and negative synchronous rotating coordinate system, and the specific output is: dq axis grid-connected voltage positive sequence component Positive sequence component of voltage on the dq axis grid side Negative sequence component of dq axis grid side voltage Positive sequence component of dq axis grid side current Negative sequence component of dq axis grid side current

[0066] Step 3: According to the positive sequence component of the voltage on the dq axis grid side and the positive sequence component of the dq axis grid side current The active power positive sequence component of the output after filtering is obtained through the power calculation equation and reactive power positive sequence component

[0067] In this embodiment, the power calculation equation is:

[0068]

[0069] In the formula, ω f is the cut-off frequency of the LC filter. In this embodiment, ω is taken f =150rad / s.

[0070] Step 4: According to the positive sequence component of the active power output after filtering The positive sequence component of harmonic frequency is obtained by constructing the active power control equation And calculate the positive sequence control angle s is the Laplace operator; then according to the positive sequence component of the active power output after filtering and reactive power positive sequence component By constructing the network reactive power control equation, the given value of the positive sequence component of the voltage on the d-axis network side is obtained.

[0071] In this embodiment, the network active power control equation and the network reactive power control equation are respectively:

[0072]

[0073] Where P set is the virtual synchronous machine active power command value, ω n is the rated angular frequency of the power grid, D is the active damping coefficient of the virtual synchronous machine, J is the virtual moment of inertia, Q setis the reactive power command value of the virtual synchronous machine, n is the reactive power-frequency droop coefficient, and in this embodiment, P is taken set =2MW, take ω n =50rad / s, take J=0.075, take D=23.78, take Q set =0kW, take n=-0.00008.

[0074] Step 5: Introduce virtual impedance Z v , introduce voltage coordination coefficient K u and current coordination coefficient K i , and satisfy the boundary condition K u +K i =1; the dq axis grid side current positive sequence component corrected by the current coordination coefficient is obtained through calculation and recorded as the corrected dq axis grid side current positive sequence component The positive sequence component of the dq grid voltage after correction by the voltage coordination coefficient is recorded as the corrected positive sequence component of the dq grid voltage Set 0 as the input value of the cooperative compensation control loop, and convert the corrected dq axis grid side current positive sequence component and the corrected dq axis grid side voltage positive sequence component As feedback input, the positive sequence component of the dq axis current cooperative compensation value is output after passing through the resonant controller and PI controller.

[0075] In this embodiment, the corrected dq axis grid side current positive sequence component and the corrected dq axis grid side voltage positive sequence component The calculation formulas are:

[0076]

[0077] The dq axis current cooperative compensation value positive sequence component The calculation formula is:

[0078]

[0079] In the formula, K P2 is the proportional coefficient of the PI controller used in the cooperative compensation control, K I2 is the integral coefficient of the PI controller used in the cooperative compensation control, G R (s) is the resonant controller transfer function, and its expression is:

[0080]

[0081] In the formula, k r is the resonance gain coefficient; ω c is the cut-off frequency, and ω2 is the resonant frequency.

[0082] In this embodiment, k r =10, K P2 =0.07, K I2 =20.

[0083] Step 6: Set the positive sequence component of the voltage on the d-axis grid side to a given value As the input of the positive sequence voltage control outer loop of the grid-side converter, the positive sequence component of the d-axis grid-side voltage As the feedback input of the positive sequence voltage control outer loop of the grid-side converter, it outputs the given value of the positive sequence component of the dq axis grid-side current after PI control. Set the positive sequence component of the dq axis grid side current to a given value Positive sequence component of dq axis grid side current As the feedback input of the positive sequence current control inner loop of the grid-side converter, the positive sequence component of the dq axis current cooperative compensation value As the feedback input compensation value of the positive sequence current control inner loop of the grid-side converter, the output after PI control is the positive sequence component of the dq axis grid-side voltage modulation wave after coordinated compensation control.

[0084] In this embodiment, the given value of the positive sequence component of the dq axis grid side current is The calculation formula is:

[0085]

[0086] In the formula, K uP is the proportional coefficient of the PI controller used in the outer loop of the positive sequence voltage control of the grid-side converter, K uI The integral coefficient of the PI controller used in the outer loop of the positive sequence voltage control of the grid-side converter;

[0087] The positive sequence component of the dq axis grid side voltage modulation wave after coordinated compensation control The calculation formula is:

[0088]

[0089] In the formula, ω n is the rated angular frequency of the power grid, K iP is the proportional coefficient of the inner loop of the positive sequence current control, K iI is the integral coefficient of the inner loop of the positive sequence current control, L f is the inductance value of the filter inductor.

[0090] In this embodiment, K iP =5, K iI =30, K uP =0.05, K uI =15,L f=0.00035H.

[0091] Step 7: Set 0 as the negative sequence current loop input and set the negative sequence component of the dq axis grid side current As feedback input, after PI control, the negative sequence component of the voltage modulation wave on the dq axis grid side is output

[0092]

[0093] In this embodiment, the negative sequence component of the dq axis grid side voltage modulation wave The calculation formula is:

[0094]

[0095] In the formula, K P1 is the PI controller proportional coefficient used in the negative sequence current loop, K I1 It is the integral coefficient of the PI controller used in the negative sequence current loop.

[0096] In this embodiment, K P1 =0.1, K I1 =15.

[0097] Step 8: The positive sequence component of the dq axis grid side voltage modulation wave after the coordinated compensation control obtained in step 6 And the negative sequence component of the dq axis grid side voltage modulation wave obtained in step 7 The grid-side converter switch voltage modulation wave is obtained through the decoupling software phase-locked loop inverse coordinate transformation of the dual synchronous coordinate system to complete the control of the grid-side converter.

[0098] In order to demonstrate the beneficial effects of the present invention, a hardware-in-the-loop experimental platform was used to verify the present invention.

[0099] Figure 5 The three-phase grid voltage waveform under different voltage compensation coefficients and different grid imbalance coefficients under the condition of grid short circuit ratio SCR = 2 and grid imbalance Udroop = 10%. The horizontal axis is time. The time unit of the upper half is 200ms / div, that is, each small grid is 200ms, and the unit of the lower half is 20ms / div, that is, each small grid is 20ms. The vertical axis is the three-phase grid voltage u wa ,u wb ,u wc The amplitude is 180V / div, i.e. 180V per small grid, ε u is the voltage imbalance.

[0100] Figure 6The three-phase grid-side current waveforms under the conditions of grid short-circuit ratio SCR = 2 and grid imbalance Udroop = 10% are shown in the figure. The horizontal axis is time. The time unit of the upper half is 200ms / div, that is, each small grid is 200ms, and the unit of the lower half is 20ms / div, that is, each small grid is 20ms. The vertical axis is the three-phase grid-side current i wa ,i wb ,i wc The amplitude is in units of 210A / div, which means 210A per small grid. Figure 7 ε i is the current imbalance.

[0101] according to Figure 5 , Figure 6 It can be seen that on the basis of positive and negative sequence separation control, the coordinated compensation control is added, and by adjusting K u ,K i The voltage and current coordination coefficient can further improve the voltage and current waveforms on the grid-side converter side.

[0102] Figure 7 , Figure 8 The figure is a diagram showing the suppression effect of unbalanced current and voltage of the grid-side converter after the grid-type positive-negative sequence separation control of the present invention is applied. Compared with the permanent magnet synchronous motor without the positive-negative sequence separation control, it can be observed that the waveforms of the current and voltage of the grid-side converter of the present invention are better, and the unbalanced current and voltage are significantly suppressed. Figure 7 The horizontal axis is time. The time unit in the upper part is 200ms / div, that is, each small grid is 200ms. The unit in the lower part is 20ms / div, that is, each small grid is 20ms. The vertical axis is the three-phase grid-side current i wa ,i wb ,i wc The amplitude is in units of 250A / div, which means 250A per small grid. Figure 8 The horizontal axis is time. The time unit of the upper part is 200ms / div, that is, each small grid is 200ms. The unit of the lower part is 20ms / div, that is, each small grid is 20ms. The vertical axis is the three-phase grid side voltage u wa ,u wb ,u wc The amplitude is in units of 200V / div, i.e. 200V per small grid.

[0103] Fig. 9 It is a diagram of the power oscillation suppression results after applying the grid-type positive and negative sequence separation control and cooperative compensation control of the present invention. It can be observed that after the positive and negative sequence separation control, the oscillation amplitudes of the active power Ps and the reactive power Qs can be effectively suppressed, and by adjusting the voltage cooperative compensation coefficient, the power oscillation problem of the permanent magnet synchronous motor in an unbalanced weak power grid can be further improved.

Claims

1. A control method for a grid-type permanent magnet synchronous motor grid-side converter based on negative sequence control, wherein the circuit topology structure to which the control method is applied comprises a permanent magnet synchronous motor, a machine-side converter, a DC bus capacitor, a grid-side converter, an LC filter, a grid impedance and a three-phase grid connected in sequence, wherein the LC filter comprises a filter inductor and a filter capacitor; characterized in that: The permanent magnet synchronous motor is controlled separately by the positive sequence loop and the negative sequence loop under the condition of unbalanced weak power grid operation. The specific steps are as follows: Step 1: Sample the grid-connected point voltage and record it as the grid-connected voltage u ga ,u gb ,u gc , sample the three-phase current on the grid-side converter side and record it as the three-phase grid-side current i wa ,i wb ,i wc , sample the three-phase voltage on the grid-side converter side and record it as the three-phase grid-side voltage u wa ,u wb ,u wc ; Step 2: Input the grid voltage u in the decoupling software phase-locked loop of the dual synchronous coordinate system ga ,u gb ,u gc , three-phase grid side voltage u wa ,u wb ,u wc and three-phase grid-side current i wa ,i wb ,i wc , complete the transformation of the above three sets of parameters from the three-phase stationary coordinate system to the positive and negative synchronous rotating coordinate system, and the specific output is: dq axis grid-connected voltage positive sequence component Positive sequence component of voltage on the dq axis grid side Negative sequence component of dq axis grid side voltage Positive sequence component of dq axis grid side current Negative sequence component of dq axis grid side current Step 3: According to the positive sequence component of the voltage on the dq axis grid side and the positive sequence component of the dq axis grid side current The positive sequence component of active power output after filtering is obtained through the power calculation equation and reactive power positive sequence component Step 4: According to the positive sequence component of the active power output after filtering The harmonic frequency positive sequence component is obtained by constructing the active power control equation And calculate the positive sequence control angle s is the Laplace operator; then according to the positive sequence component of the active power output after filtering and reactive power positive sequence component By constructing the network reactive power control equation, the given value of the positive sequence component of the voltage on the d-axis network side is obtained. Step 5: Introduce virtual impedance Z v , introduce voltage coordination coefficient K u and current coordination coefficient K i , and satisfy the boundary condition K u +K i =1; the dq axis grid side current positive sequence component corrected by the current coordination coefficient is obtained through calculation and recorded as the corrected dq axis grid side current positive sequence component The voltage positive sequence component of the dq axis grid side after voltage coordination coefficient correction is obtained and recorded as the corrected dq axis grid side voltage positive sequence component Set 0 as the input value of the cooperative compensation control loop, and convert the corrected dq axis grid side current positive sequence component and the corrected dq axis grid side voltage positive sequence component As feedback input, the positive sequence component of the dq axis current cooperative compensation value is output after passing through the resonant controller and PI controller. Step 6: Set the positive sequence component of the voltage on the d-axis grid side to a given value As the input of the positive sequence voltage control outer loop of the grid-side converter, the positive sequence component of the d-axis grid-side voltage As the feedback input of the outer loop of the positive sequence voltage control of the grid-side converter, it outputs the given value of the positive sequence component of the dq axis grid-side current after PI control. Set the positive sequence component of the dq axis grid side current to a given value Positive sequence component of dq axis grid side current As the feedback input of the positive sequence current control inner loop of the grid-side converter, the positive sequence component of the dq axis current cooperative compensation value As the feedback input compensation value of the positive sequence current control inner loop of the grid-side converter, the output after PI control is the positive sequence component of the dq axis grid-side voltage modulation wave after coordinated compensation control. Step 7: Set 0 as the negative sequence current loop input and set the negative sequence component of the dq axis grid side current As feedback input, after PI control, the negative sequence component of the voltage modulation wave on the dq axis grid side is output Step 8: The positive sequence component of the dq axis grid side voltage modulation wave after the coordinated compensation control obtained in step 6 And the negative sequence component of the dq axis grid side voltage modulation wave obtained in step 7 The grid-side converter switch voltage modulation wave is obtained through the decoupling software phase-locked loop inverse coordinate transformation of the dual synchronous coordinate system to complete the control of the grid-side converter.

2. A method for controlling a grid-side converter of a grid-connected permanent magnet synchronous motor based on negative sequence control according to claim 1, characterized in that: The power calculation equation in step 3 is: In the formula, ω f is the cut-off frequency of the LC filter.

3. The method for controlling a grid-side converter of a grid-connected permanent magnet synchronous motor based on negative sequence control according to claim 1, characterized in that: The active power control equation and reactive power control equation of the network in step 4 are: Where P set is the virtual synchronous machine active power command value, ω n is the rated angular frequency of the power grid, D is the active damping coefficient of the virtual synchronous machine, J is the virtual moment of inertia, Q set is the reactive power command value of the virtual synchronous machine, and n is the reactive-frequency droop coefficient.

4. The method for controlling a grid-side converter of a grid-connected permanent magnet synchronous motor based on negative sequence control according to claim 1, characterized in that: The positive sequence component of the dq axis grid side current after correction in step 5 and the corrected dq axis grid side voltage positive sequence component The calculation formulas are: The dq axis current cooperative compensation value positive sequence component The calculation formula is: In the formula, K P2 is the proportional coefficient of the PI controller used in the cooperative compensation control, K I2 is the integral coefficient of the PI controller used in the cooperative compensation control, G R (s) is the resonant controller transfer function, and its expression is: In the formula, k r is the resonance gain coefficient; ω c is the cut-off frequency, and ω2 is the resonant frequency.

5. The method for controlling a grid-side converter of a grid-connected permanent magnet synchronous motor based on negative sequence control according to claim 1, characterized in that: Step 6: The given value of the positive sequence component of the dq axis grid side current The calculation formula is: In the formula, K uP is the proportional coefficient of the PI controller used in the outer loop of the positive sequence voltage control of the grid-side converter, K uI The integral coefficient of the PI controller used in the outer loop of the positive sequence voltage control of the grid-side converter; The positive sequence component of the dq axis grid side voltage modulation wave after coordinated compensation control The calculation formula is: In the formula, ω n is the rated angular frequency of the power grid, K iP is the proportional coefficient of the inner loop of the positive sequence current control, K iI is the integral coefficient of the inner loop of the positive sequence current control, L f is the inductance value of the filter inductor.

6. The method for controlling a grid-side converter of a grid-connected permanent magnet synchronous motor based on negative sequence control according to claim 1, characterized in that: Step 7: Negative sequence component of the voltage modulation wave on the dq axis grid side The calculation formula is: In the formula, K P1 is the PI controller proportional coefficient used in the negative sequence current loop, K I1 It is the integral coefficient of the PI controller used in the negative sequence current loop.

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