SOGI-based grid voltage positive and negative sequence separation and feed-forward compensation method

Abstract

The application discloses a SOGI-based power grid voltage positive and negative sequence separation and feedforward compensation method, which comprises the following steps: step 1, collecting three-phase voltage and obtaining voltage signals after transformation; step 2, constructing a cross-coupled SOGI-FLL module, inputting the voltage signals obtained in step 1 into the cross-coupled SOGI-FLL module for frequency self-adaption to obtain output signals; step 3, constructing a positive and negative sequence separation module, and performing algebraic separation of positive and negative sequence components of the output signals of step 2; step 4, constructing a feedforward compensation module, and performing current instruction calculation and current feedforward amount calculation on the separated positive and negative sequence components of step 3; and step 5, inputting the feedforward compensation obtained in step 4 into a PWM power unit after inverse Clarke transformation to drive. The application solves the problems of low separation precision, high calculation complexity and incapability of directly converting negative sequence information into a feedforward disturbance suppression signal in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of power electronics and smart grid control technology, specifically relating to a method for separating positive and negative sequence of grid voltage and feedforward compensation based on SOGI. Background Technology

[0002] In medium- and high-voltage flexible distribution systems, negative sequence components often appear in the grid voltage due to load asymmetry, single-phase grounding faults, or nonlinear loads. This imbalance can cause double-frequency active power fluctuations on the input side of grid-connected equipment, which in turn can lead to DC bus voltage oscillations, threatening the stable operation of the system.

[0003] Existing technologies use a dual dq phase-locked loop (PLL) structure to separate positive and negative sequence components, which has the following drawbacks: (1) It relies on the dynamic tracking capability of the PLL, and the response lags when the frequency changes abruptly, resulting in a decrease in separation accuracy; (2) It requires multiple coordinate transformations (abc→αβ→dq). + / dq - (3) The negative sequence component is usually only used for monitoring or indirect compensation and does not directly participate in current feedforward, so the suppression effect is limited.

[0004] Therefore, there is an urgent need for a method that has high separation accuracy, low computational complexity, and can directly convert negative-order information into feedforward perturbation suppression signals. Summary of the Invention

[0005] The purpose of this invention is to provide a method for separating positive and negative sequence of grid voltage based on SOGI and for feedforward compensation, which solves the problems of low separation accuracy, high computational complexity, and inability to directly convert negative sequence information into feedforward disturbance suppression signals in existing technologies.

[0006] The technical solution adopted in this invention is a grid voltage positive and negative sequence separation and feedforward compensation method based on SOGI, which is implemented according to the following steps: Step 1: Acquire three-phase voltages and transform them to obtain voltage signals; Step 2: Construct a cross-coupled SOGI-FLL module. Input the voltage signal obtained in Step 1 into the cross-coupled SOGI-FLL module for frequency adaptation to obtain the output signal. Step 3: Construct a positive and negative order separation module to perform algebraic separation of positive and negative order components on the output signal of Step 2; Step 4: Construct a feedforward compensation module to perform current command calculation and current feedforward calculation on the positive and negative sequence components separated in Step 3, respectively. Step 5: The feedforward compensation obtained in step 4 is then input into the PWM power unit after inverse Clarke transformation for driving.

[0007] The invention is further characterized in that: Step 1: Acquire three-phase grid voltage using voltage sensors , , For three-phase power grid voltage , , Perform Clarke transformation to the two-phase αβ stationary coordinate system to obtain the voltage signal. and ; , (1).

[0008] Step 2 specifically involves: Step 2.1, the cross-coupled SOGI-FLL module includes a first SOGI module and a second SOGI module. Both the first SOGI module and the second SOGI module integrate a frequency adaptive frequency locking loop. The first SOGI module and the second SOGI module share the same adaptive angular frequency ω′. Both the first SOGI module and the second SOGI module include a summation unit and a gain unit. Step 2.2, convert the voltage signal Input the first SOGI module to obtain the output signal. , , to voltage signal Input the second SOGI module to obtain the output signal. , ; , It is an in-phase signal. , Orthogonal signals α The channel satisfies the following differential relation, for β The same applies to channels; , (2) in, d The differential symbol, dt The symbol for the differential time; Step 2.3, Orthogonal output of the first SOGI module Feedback to the input summation point of the second SOGI module, the second SOGI module's Feedback is sent to the input of the first SOGI module, forming a closed loop of frequency synchronization and sequence component decoupling. The first SOGI module and the second SOGI module are connected through... , Interconnection, the frequency adaptive frequency-locked loop dynamically adjusts the adaptive angular frequency according to the error signal. This enables frequency adaptive tracking.

[0009] The FLL frequency update law in step 2.3 is: (3); in, >0 represents the FLL gain, ensuring that the adaptive angular frequency ω′ converges quickly to the actual grid frequency; Taking the first SOGI module as an example, the error signal is as follows: (4).

[0010] In step 3, the output signal from step 2 will be... , , , The input positive and negative sequence separation module performs algebraic operations, and the cross-coupled SOGI-FLL module automatically inverts the quadrature output of the negative sequence component, thus separating the positive sequence component of the grid voltage. , and negative order components , ; (5) (6) (7) (8).

[0011] Step 4 specifically involves: Step 4.1, Set the target value of the DC bus voltage. Vdc_ref With feedback sample value Vdc_fbk Both are input to the voltage outer loop PI controller for power calculation, generating an active power command. , the orthogonal components , As a synchronization reference signal, the current command is then calculated. , Finally, the main current command is obtained. , ; Step 4.2, transfer the negative-order components. , As a feedforward compensation amount, a compensation current command is generated proportionally via feedforward. , As a current feedforward quantity, it achieves disturbance feedforward suppression; Step 4.3: Combine the main current command obtained in step 4.1 with the compensation current command obtained in step 4.2 to obtain the final current command; , (12).

[0012] Step 4.2 specifically involves: , (9) in, This is the feedforward gain coefficient, with a value of 0.02 A / V.

[0013] Feedforward gain coefficient Based on the system equivalent impedance Adjustment; (10) Feedforward gain Online adaptive; (11) in, This is the DC voltage frequency double-harmonic ripple detection value.

[0014] Step 5 specifically involves: Step 5.1, Three-phase power grid current sampling , , The current signal is obtained by performing a Clarke transformation to the two-phase αβ stationary coordinate system. and ; Step 5.2, the current signal from step 5.1 , and the current command obtained in step 4.3 , The input current inner-loop PI controller synthesizes two-phase voltage commands. , ; Step 5.3, transfer the two-phase voltage command , After inverse Clarke transformation, the three-phase voltage command is obtained. , , , drives the PWM power unit.

[0015] The beneficial effects of this invention are: This invention, based on the SOGI-based grid voltage positive and negative sequence separation and feedforward compensation method, constructs a cross-coupled second-order generalized integrator-frequency-locked loop (SOGI-FLL) module, in... αβIn a stationary coordinate system, the positive and negative sequence components of the grid voltage are directly extracted, and the negative sequence component is directly used for current feedforward compensation. This invention is applicable to grid-connected converters, power electronic transformers, and power quality management devices. This invention does not require a phase-locked loop or rely on a rotating coordinate system. It is a computationally efficient and physically meaningful method for positive and negative sequence separation and feedforward compensation. Under grid voltage imbalance conditions, it effectively suppresses DC bus voltage oscillations and power fluctuations, improves the system's dynamic response speed and steady-state accuracy, and also enhances the system's robustness and control performance. Attached Figure Description

[0016] Figure 1 This is a flowchart of the SOGI-based grid voltage positive and negative sequence separation and feedforward compensation method of the present invention; Figure 2 To construct an internal signal flow diagram of the cross-coupled SOGI-FLL module structure for this invention; Figure 3 This is the algebraic operation logic diagram for positive and negative order separation and feedforward compensation of the present invention. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0018] Example 1 This invention relates to a method for separating positive and negative sequence of grid voltage based on SOGI and for feedforward compensation, the process of which is as follows: Figure 1 As shown, the specific implementation steps are as follows: Step 1: Acquire three-phase voltages and transform them to obtain voltage signals; Step 2: Construct a cross-coupled SOGI-FLL module. Input the voltage signal obtained in Step 1 into the cross-coupled SOGI-FLL module for frequency adaptation to obtain the output signal. Step 3: Construct a positive and negative order separation module to perform algebraic separation of positive and negative order components on the output signal of Step 2; Step 4: Construct a feedforward compensation module to perform current command calculation and current feedforward calculation on the positive and negative sequence components separated in Step 3, respectively. Step 5: The feedforward compensation obtained in step 4 is then input into the PWM power unit after inverse Clarke transformation for driving.

[0019] Example 2 This invention relates to a grid voltage positive and negative sequence separation and feedforward compensation method based on SOGI, which is implemented according to the following steps: Step 1: Acquire three-phase voltages and transform them to obtain voltage signals; Three-phase power grid voltage is collected using a voltage sensor. , , For three-phase power grid voltage , , Perform Clarke transformation to the two-phase αβ stationary coordinate system to obtain the voltage signal. and ; Step 2: Construct a cross-coupled SOGI-FLL module. Input the voltage signal obtained in Step 1 into the cross-coupled SOGI-FLL module for frequency adaptation to obtain the output signal. Step 3: Construct a positive and negative order separation module to perform algebraic separation of positive and negative order components on the output signal of Step 2; Step 4: Construct a feedforward compensation module to perform current command calculation and current feedforward calculation on the positive and negative sequence components separated in Step 3, respectively. Step 5: The feedforward compensation obtained in step 4 is then input into the PWM power unit after inverse Clarke transformation for driving.

[0020] Example 3 This invention relates to a grid voltage positive and negative sequence separation and feedforward compensation method based on SOGI, which is implemented according to the following steps: Step 1: Acquire three-phase voltages and transform them to obtain voltage signals; Three-phase power grid voltage is collected using a voltage sensor. , , For three-phase power grid voltage , , Perform Clarke transformation to the two-phase αβ stationary coordinate system to obtain the voltage signal. and ; Step 2: Construct a cross-coupled SOGI-FLL module. Input the voltage signal obtained in Step 1 into the cross-coupled SOGI-FLL module for frequency adaptation to obtain the output signal. Step 2.1, the cross-coupled SOGI-FLL module includes a first SOGI module and a second SOGI module. Both the first SOGI module and the second SOGI module integrate a frequency adaptive frequency locking loop. The first SOGI module and the second SOGI module share the same adaptive angular frequency ω′. Both the first SOGI module and the second SOGI module include a summation unit and a gain unit. Step 2.2, convert the voltage signal Input the first SOGI module to obtain the output signal. , , to voltage signal Input the second SOGI module to obtain the output signal. , ; Step 2.3, Orthogonal output of the first SOGI module Feedback to the input summation point of the second SOGI module, the second SOGI module's Feedback is sent to the input of the first SOGI module, forming a closed loop of frequency synchronization and sequence component decoupling. The first SOGI module and the second SOGI module are connected through... , Interconnection, the frequency adaptive frequency-locked loop dynamically adjusts the adaptive angular frequency according to the error signal. This enables frequency adaptive tracking.

[0021] Step 3: Construct a positive and negative order separation module to perform algebraic separation of positive and negative order components on the output signal of Step 2; Step 4: Construct a feedforward compensation module to perform current command calculation and current feedforward calculation on the positive and negative sequence components separated in Step 3, respectively. Step 5: The feedforward compensation obtained in step 4 is then input into the PWM power unit after inverse Clarke transformation for driving.

[0022] Example 4 This invention relates to a grid voltage positive and negative sequence separation and feedforward compensation method based on SOGI, which is implemented according to the following steps: Step 1: Acquire three-phase voltages and transform them to obtain voltage signals; Three-phase power grid voltage is collected using a voltage sensor. , , For three-phase power grid voltage , , Perform Clarke transformation to the two-phase αβ stationary coordinate system to obtain the voltage signal. and ; Step 2: Construct a cross-coupled SOGI-FLL module. Input the voltage signal obtained in Step 1 into the cross-coupled SOGI-FLL module for frequency adaptation to obtain the output signal. Step 2.1, the cross-coupled SOGI-FLL module includes a first SOGI module and a second SOGI module. Both the first SOGI module and the second SOGI module integrate a frequency adaptive frequency locking loop. The first SOGI module and the second SOGI module share the same adaptive angular frequency ω′. Both the first SOGI module and the second SOGI module include a summation unit and a gain unit. Step 2.2, convert the voltage signal Input the first SOGI module to obtain the output signal. , , to voltage signal Input the second SOGI module to obtain the output signal. , ; Step 2.3, Orthogonal output of the first SOGI module Feedback to the input summation point of the second SOGI module, the second SOGI module's Feedback is sent to the input of the first SOGI module, forming a closed loop of frequency synchronization and sequence component decoupling. The first SOGI module and the second SOGI module are connected through... , Interconnection, the frequency adaptive frequency-locked loop dynamically adjusts the adaptive angular frequency according to the error signal. This enables frequency adaptive tracking.

[0023] Step 3: Construct a positive and negative order separation module to perform algebraic separation of positive and negative order components on the output signal of Step 2; Output signal from step 2 , , , The input positive and negative sequence separation module performs algebraic operations, and the cross-coupled SOGI-FLL module automatically inverts the quadrature output of the negative sequence component, thus separating the positive sequence component of the grid voltage. , and negative order components , ; Step 4: Construct a feedforward compensation module to perform current command calculation and current feedforward calculation on the positive and negative sequence components separated in Step 3, respectively. Step 5: The feedforward compensation obtained in step 4 is then input into the PWM power unit after inverse Clarke transformation for driving.

[0024] Example 5 This invention relates to a grid voltage positive and negative sequence separation and feedforward compensation method based on SOGI, which is implemented according to the following steps: Step 1: Acquire three-phase voltages and transform them to obtain voltage signals; Three-phase power grid voltage is collected using a voltage sensor. , , For three-phase power grid voltage , , Perform Clarke transformation to the two-phase αβ stationary coordinate system to obtain the voltage signal. and ; , (1).

[0025] Step 2: Construct a cross-coupled SOGI-FLL module. Input the voltage signal obtained in Step 1 into the cross-coupled SOGI-FLL module for frequency adaptation to obtain the output signal. Step 2.1, the cross-coupled SOGI-FLL module includes a first SOGI module and a second SOGI module, such as Figure 2 As shown, both the first SOGI module and the second SOGI module integrate a frequency adaptive frequency-locked loop (FLL). The first SOGI module and the second SOGI module share the same adaptive angular frequency ω′, and the initial value of the resonant frequency is set to... , =50Hz or 60Hz It is set to the rated frequency of the power grid to adapt to power grid frequency fluctuations and improve dynamic response capabilities.

[0026] Both the first and second SOGI modules include summation units and gain units (damping coefficients). The critical damping balances both dynamic and steady-state performance; the integrator uses a trapezoidal integration rule for discretization to ensure digital stability; the cross-coupling path is implemented through the DSP's hardware multiplier, increasing computation by less than 5%. Step 2.2, convert the voltage signal Input the first SOGI module to obtain the output signal. , , to voltage signal Input the second SOGI module to obtain the output signal. , ; , It is an in-phase signal. , Orthogonal signals α The channel satisfies the following differential relation, for β The same applies to channels; , (2) in, d The differential symbol, dt The symbol for differential time.

[0027] Step 2.3, Orthogonal output of the first SOGI module Feedback to the input summation point of the second SOGI module, the second SOGI module's Feedback is sent to the input of the first SOGI module, forming a closed loop of frequency synchronization and sequence component decoupling. The first SOGI module and the second SOGI module are connected through... , Interconnected, frequency adaptive frequency-locked loop (FLL) dynamically adjusts adaptive angular frequency based on error signal. This enables frequency adaptive tracking.

[0028] The FLL frequency update law is: (3); in >0 represents the FLL gain, ensuring that the adaptive angular frequency ω′ converges quickly to the actual grid frequency.

[0029] Taking the first SOGI module as an example, the error signal is as follows: (4).

[0030] Step 3: Construct a positive and negative order separation module to perform algebraic separation of positive and negative order components on the output signal of Step 2; Output signal from step 2 , , , The input positive and negative sequence separation module performs algebraic operations, and the cross-coupled SOGI-FLL module automatically inverts the quadrature output of the negative sequence component (ensuring this through dynamic adjustment of the cross-coupling and FLL), thus separating the positive sequence component of the grid voltage. , and negative order components , ; (5) (6) (7) (8).

[0031] Step 4: Construct a feedforward compensation module to perform current command calculation and current feedforward calculation on the positive and negative sequence components separated in Step 3, respectively. Step 4.1, Set the target value of the DC bus voltage. Vdc_ref With feedback sample value Vdc_fbk Both are input to the voltage outer loop PI controller for power calculation, generating an active power command. , the orthogonal components , As a synchronization reference signal, the current command is then calculated. , Finally, the main current command is obtained. , ; Step 4.2, transfer the negative-order components. , As a feedforward compensation amount, a compensation current command is generated proportionally via feedforward. , As a current feedforward quantity, it achieves disturbance feedforward suppression, such as Figure 3 As shown; , (9) in, This is the feedforward gain coefficient.

[0032] Feedforward gain coefficient Based on the system equivalent impedance Adjustment; (10) Feedforward gain Online adaptive; (11) in, This is the DC voltage frequency double-harmonic ripple detection value.

[0033] In this embodiment, the feedforward gain coefficient The value is 0.02 A / V.

[0034] Step 4.3: Combine the main current command obtained in Step 4.1 with the compensation current command obtained in Step 4.2. , (12).

[0035] Step 5: The feedforward compensation obtained in step 4 is then input into the PWM power unit after inverse Clarke transformation for driving.

[0036] Step 5.1, Three-phase power grid current sampling , , The current signal is obtained by performing a Clarke transformation to the two-phase αβ stationary coordinate system. and ; Step 5.2, the current signal from step 5.1 , and the current command obtained in step 4.3 , The input current inner-loop PI controller synthesizes two-phase voltage commands. , ; Step 5.3, transfer the two-phase voltage command , After inverse Clarke transformation, the three-phase voltage command is obtained. , , , drives the PWM power unit.

[0037] Example 6 This invention presents a grid voltage positive and negative sequence separation and feedforward compensation method based on SOGI. The effect of DC voltage fluctuation under voltage imbalance is verified by MATLAB simulation.

[0038] Existing technologies using a dual-dq PLL method for comparison show DC bus voltage fluctuations reaching 120 V (±8%). This invention employs PI control for the current loop, with a control period of 25 µs and a positive-sequence component. , Calculate and generate active / reactive power commands; negative sequence components , Converted to current feedforward quantity , (in The value is added to the reference value of the current controller to achieve disturbance suppression; when k = 1.414, the fluctuation is reduced to 22 V (±1.5%), and the system completes positive and negative sequence separation within 0.02 s, with fast dynamic response.

[0039] The results show that under a 20% voltage imbalance condition, the DC bus voltage fluctuation is reduced from ±8% by the traditional method to ±1.5%. It requires only two SOGI modules and four addition / multiplication operations, making it suitable for real-time operation on embedded platforms such as DSPs or MCUs with low resource consumption. It is highly versatile: it can be seamlessly integrated into various grid-connected converter control systems without modifying the main control architecture, and is compatible with dq decoupling or pure αβ control strategies. This invention has a simple structure, high computational efficiency, and significantly improves power control accuracy and system stability under unbalanced grid conditions.

[0040] This invention presents a grid voltage positive and negative sequence separation and feedforward compensation method based on SOGI. It directly separates and extracts positive and negative sequence components in the αβ stationary coordinate system, eliminating the need for a phase-locked loop and rotating coordinate transformation. It requires only two SOGI modules and algebraic operations, resulting in lightweight computation and efficient positive and negative sequence separation in the stationary coordinate system. The negative sequence information is directly converted into a feedforward disturbance suppression signal for feedforward compensation control, making it suitable for embedded real-time control. It exhibits strong robustness, maintaining high-precision separation even with grid frequency deviations, and fast dynamic response (separation can be completed within one cycle). It effectively suppresses power fluctuations by directly converting the negative sequence voltage component into a current feedforward signal, effectively offsetting the second harmonic active power fluctuations caused by the negative sequence current. The method is computationally efficient, has a fast dynamic response, good compensation effect, and achieves good steady-state accuracy.

Claims

1. A method for separating positive and negative sequence voltages and providing feedforward compensation based on SOGI, characterized in that, The specific steps are as follows: Step 1: Acquire three-phase voltages and transform them to obtain voltage signals; Step 2: Construct a cross-coupled SOGI-FLL module. Input the voltage signal obtained in Step 1 into the cross-coupled SOGI-FLL module for frequency adaptation to obtain the output signal. Step 3: Construct a positive and negative order separation module to perform algebraic separation of positive and negative order components on the output signal of Step 2; Step 4: Construct a feedforward compensation module to perform current command calculation and current feedforward calculation on the positive and negative sequence components separated in Step 3, respectively. Step 5: The feedforward compensation obtained in step 4 is then input into the PWM power unit after inverse Clarke transformation for driving.

2. The method for separating positive and negative sequence grid voltages and providing feedforward compensation based on SOGI according to claim 1, characterized in that, Step 1: Acquire three-phase grid voltage using voltage sensors , , For three-phase power grid voltage , , Perform Clarke transformation to the two-phase αβ stationary coordinate system to obtain the voltage signal. and ; , （1）。 3. The method for separating positive and negative sequence of grid voltage and feedforward compensation based on SOGI according to claim 2, characterized in that, Step 2 specifically involves: Step 2.1, the cross-coupled SOGI-FLL module includes a first SOGI module and a second SOGI module. Both the first SOGI module and the second SOGI module integrate a frequency adaptive frequency locking loop. The first SOGI module and the second SOGI module share the same adaptive angular frequency ω′. Both the first SOGI module and the second SOGI module include a summation unit and a gain unit. Step 2.2, convert the voltage signal Input the first SOGI module to obtain the output signal. , , to voltage signal Input the second SOGI module to obtain the output signal. , ; , It is an in-phase signal. , Orthogonal signals α The channel satisfies the following differential relation, for β The same applies to channels; ， （2） in, d The differential symbol, dt The symbol for the differential time; Step 2.3, Orthogonal output of the first SOGI module Feedback to the input summation point of the second SOGI module, the second SOGI module's Feedback is sent to the input of the first SOGI module, forming a closed loop of frequency synchronization and sequence component decoupling. The first SOGI module and the second SOGI module are connected through... , Interconnection, the frequency adaptive frequency-locked loop dynamically adjusts the adaptive angular frequency according to the error signal. This enables frequency adaptive tracking.

4. The method for separating positive and negative sequence of grid voltage and feedforward compensation based on SOGI according to claim 3, characterized in that, The FLL frequency update law in step 2.3 is: （3）； in, >0 represents the FLL gain, ensuring that the adaptive angular frequency ω′ converges quickly to the actual grid frequency; Taking the first SOGI module as an example, the error signal is as follows: （4）。 5. The method for separating positive and negative sequence of grid voltage and feedforward compensation based on SOGI according to claim 4, characterized in that, In step 3, the output signal from step 2 will be... , , , The input positive and negative sequence separation module performs algebraic operations, and the cross-coupled SOGI-FLL module automatically inverts the quadrature output of the negative sequence component, thus separating the positive sequence component of the grid voltage. , and negative order components , ; （5） （6） （7） （8）。 6. The method for separating positive and negative sequence of grid voltage and feedforward compensation based on SOGI according to claim 5, characterized in that, Step 4 specifically involves: Step 4.1, Set the target value of the DC bus voltage. Vdc_ref With feedback sample value Vdc_fbk Both are input to the voltage outer loop PI controller for power calculation, generating an active power command. , the orthogonal components , As a synchronization reference signal, the current command is then calculated. , Finally, the main current command is obtained. , ; Step 4.2, transfer the negative-order components. , As a feedforward compensation amount, a compensation current command is generated proportionally via feedforward. , As a current feedforward quantity, it achieves disturbance feedforward suppression; Step 4.3: Combine the main current command obtained in step 4.1 with the compensation current command obtained in step 4.2 to obtain the final current command; ， （12）。 7. The method for separating positive and negative sequence of grid voltage and feedforward compensation based on SOGI according to claim 6, characterized in that, Step 4.2 specifically involves: ， （9） in, This is the feedforward gain coefficient, with a value of 0.02 A / V; Feedforward gain coefficient Based on the system equivalent impedance Adjustment; （10） Feedforward gain Online adaptive; （11） in, This is the DC voltage frequency harmonic ripple detection value.

8. The method for separating positive and negative sequence of grid voltage and feedforward compensation based on SOGI according to claim 7, characterized in that, Step 5 specifically involves: Step 5.1, Three-phase power grid current sampling , , The current signal is obtained by performing a Clarke transformation to the two-phase αβ stationary coordinate system. and ; Step 5.2, the current signal from step 5.1 , and the current command obtained in step 4.3 , The input current inner-loop PI controller synthesizes two-phase voltage commands. , ; Step 5.3, transfer the two-phase voltage command , After inverse Clarke transformation, the three-phase voltage command is obtained. , , , drives the PWM power unit.

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