Load imbalance compensation topology based on interphase power mutual aid and control method thereof

Abstract

The invention provides a load unbalance compensation topology based on interphase power mutual aid and a control method thereof. The compensation topology comprises a direct current filtering unit, an active compensation unit, an alternating current filtering unit, a load, a sampling unit, a control unit and a driving unit. The output end of the direct-current filtering unit is connected with the input end of the active compensation unit, the output end of the active compensation unit is connected with the input end of the alternating-current filtering unit, and the output end of the alternating-current filtering unit is connected with a load; the input end of the sampling unit is connected with a load, the feedback end of the sampling unit is connected with the input end of the control unit, the output end of the control unit is connected with the input end of the driving unit, and the output end of the driving unit is connected with the input end of the active compensation unit. According to the invention, the compensation device current and the load distortion current are mutually offset, the purpose of compensating the unbalanced current is achieved, and the problem that the voltage and current of a three-phase power grid are unbalanced is solved.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically a load imbalance compensation topology based on phase-to-phase power mutual assistance and its control method. Background Technology

[0002] In the actual operation of power systems, three-phase load imbalance is a long-standing and critical problem that urgently needs to be solved. With the rapid development of the social economy and the large-scale connection of various electrical equipment, the complexity and uncertainty of power load have increased significantly, making the three-phase load imbalance situation increasingly serious.

[0003] Three-phase load imbalance can trigger a series of adverse consequences, posing a serious threat to the safe, stable, and economical operation of the power system. From the grid side, unbalanced three-phase loads lead to asymmetry in three-phase voltage and current, resulting in negative sequence components. Negative sequence currents generate additional losses and heat in generators, reducing their efficiency and lifespan. Simultaneously, negative sequence components can interfere with relay protection devices and automatic devices in the power system, affecting their normal operation and reducing the reliability of power system operation. Furthermore, three-phase load imbalance increases line losses, reduces grid transmission efficiency, and increases the operating costs of power companies.

[0004] From the user's perspective, three-phase load imbalance can cause some phase voltages to be too high or too low, affecting the normal operation of electrical equipment. Excessive voltage may damage the insulation of electrical equipment and shorten its lifespan; insufficient voltage will result in insufficient output from the equipment, preventing it from performing properly and impacting the user's production and daily life. For example, for some precision electronic equipment that requires high voltage stability, voltage fluctuations caused by three-phase load imbalance may cause malfunctions or even damage the equipment, resulting in significant economic losses for the user.

[0005] Currently, there are some compensation technologies and methods for three-phase load imbalance, but they all have certain limitations. For example, traditional capacitor compensation mainly compensates for reactive power and cannot effectively solve the active power imbalance caused by three-phase load imbalance. On the other hand, some early load compensation devices are complex in structure, expensive, and have unsatisfactory compensation effects, making it difficult to meet the needs of modern power systems for efficient and accurate compensation.

[0006] Therefore, developing a compensation topology and its control method that can effectively solve the three-phase load imbalance problem, and that is simple in structure, low in cost, and has a significant compensation effect, has important practical significance and broad application prospects. Summary of the Invention

[0007] The purpose of this application is to provide a load imbalance compensation topology and its control method based on phase-to-phase power mutual assistance, which effectively solves the three-phase load imbalance problem, and has a simple structure, low cost and significant compensation effect.

[0008] To achieve the above objectives, this application provides the following technical solution:

[0009] This application provides a load imbalance compensation topology based on phase-to-phase power mutual assistance. The compensation topology includes a DC filter unit, an active compensation unit, an AC filter unit, a load, a sampling unit, a control unit, and a drive unit.

[0010] The output of the DC filter unit is connected to the input of the active compensation unit, the output of the active compensation unit is connected to the input of the AC filter unit, and the output of the AC filter unit is connected to the load. The input of the sampling unit is connected to the load, the feedback of the sampling unit is connected to the input of the control unit, the output of the control unit is connected to the input of the drive unit, and the output of the drive unit is connected to the input of the active compensation unit.

[0011] The active compensation unit includes a switching transistor. , , , , , , , , , , , pin S and , , pin S and , , After pin D is connected to the inductor Connected to the input terminal, , pin D and , Connected to pin D, , Pin S is connected to the neutral line of the power grid. The switching transistors are all selected from one of the following semiconductor devices with switching characteristics: GaN, MOSFET, IGBT, and BJT.

[0012] The inverter capacitor in the DC filter unit negative electrode and After the positive terminal is connected, it is connected to the neutral line of the power grid. The positive electrode and , , Connected to pin D, negative electrode and , , The pin S is connected.

[0013] The AC filter unit adopts one of the structure networks with filtering characteristics, namely C, LC, or LCL. The AC filter unit is used to filter out high-frequency components in the active compensation unit and reduce output harmonics.

[0014] When the AC filter unit adopts a C input filter circuit, the AC filter unit is a filter capacitor. The positive terminal of the filter capacitor is connected to the output terminal of the active compensation unit and the load input terminal, and the negative terminals of the capacitor are connected to each other.

[0015] When the AC filter unit adopts an LC input filter circuit, the AC filter unit includes a filter inductor and a filter capacitor. The positive terminal of the filter inductor is connected to the output terminal of the active compensation unit, and the negative terminal is connected to the positive terminal of the filter capacitor and the load input terminal. The negative terminals of the filter capacitors are connected to each other.

[0016] When the AC filter unit adopts an LCL input filter circuit, the AC filter unit includes two filter inductors and one filter capacitor. The positive terminal of the first filter inductor is connected to the output terminal of the active compensation unit, and the negative terminal is connected to the positive terminal of the filter capacitor and the positive terminal of the second filter inductor. The negative terminal of the second filter inductor is connected to the load input terminal, and the negative terminals of the filter capacitors are connected to each other.

[0017] A control method for load imbalance compensation based on inter-phase power mutual assistance, implemented based on the three-phase unbalanced load compensation topology described above, includes the following steps:

[0018] S1: Regarding the grid voltage Load current Inverter output current Bus voltage , After sampling, the grid voltage is first phase-locked; then the current is transformed into positive and negative zero sequence to extract the positive sequence current on the load side. Negative sequence current Zero-sequence current Extract the positive sequence current output from the inverter. Negative sequence current Zero-sequence current .

[0019] S2: Convert bus voltage , The current bus voltage value is obtained by adding them together. The voltage difference is obtained by subtracting the desired bus voltage from the current, and then processed by a PI controller to obtain the current command for the bus voltage. ; bus voltage , Subtraction yields the bus voltage difference After passing through the PI controller, the current command for bus voltage equalization is obtained. ;

[0020] S3: Oriented by grid voltage, positive sequence current. After Park transformation and passing through a high-pass filter, the higher harmonics and reactive components of the positive sequence current in the dq coordinate system can be obtained. and , and Doing bad things The difference between the current and the expected value is sent to the PI controller, and after inverse Park transformation, the positive sequence current command is obtained.

[0021] S4: Directed by grid voltage, negative sequence current. The negative sequence current in the dq coordinate system can be obtained through the Park transformation. and The negative sequence current of the inverter output current After Park transformation, we obtain and ,Will and and and The difference is fed into the PI controller, and after inverse Park transformation, a negative sequence current command is obtained.

[0022] S5: Zero-sequence current With the zero-sequence component of the inverter output current The difference is sent to the PR controller to obtain the zero-sequence compensation current command, which is then compared with the bus equalization current command. After differential calculation, the data is sent to the PR controller to obtain the zero-sequence current command.

[0023] S6: The current commands of the positive sequence, negative sequence, and zero sequence are added together to obtain the current command of the three-phase unbalanced load compensation system. After SPWM modulation, the PWM signal of the three-phase bridge arm is obtained.

[0024] Compared with the prior art, the beneficial effects of the present invention are: it realizes the mutual cancellation of the compensation device current and the load distortion current, achieves the purpose of compensating for unbalanced current, and solves the problem of voltage and current imbalance in three-phase power grid. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a topology diagram of a load imbalance compensation device based on phase-to-phase power mutual assistance according to an embodiment of the present invention.

[0027] Figure 2 This is a specific circuit diagram of the load imbalance compensation device based on phase-to-phase power mutual assistance when the filter circuit adopts an LCL filter circuit in an embodiment of the present invention.

[0028] Figure 3 This is a structural diagram of a filter circuit that can be used in the embodiments of the present invention.

[0029] Figure 4 This is a control structure diagram of a load imbalance compensation device based on phase-to-phase power mutual assistance in an embodiment of the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will now be described with reference to the accompanying drawings. It should be noted that similar reference numerals and letters in the following drawings indicate similar items; therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0031] The terms “comprising,” “including,” or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0032] The terms “first,” “second,” etc., are used only to distinguish one entity or operation from another, and should not be construed as indicating or implying relative importance, nor as requiring or implying any such actual relationship or order between these entities or operations.

[0033] Embodiments of the present invention provide a three-phase load imbalance compensation topology based on interphase power mutual assistance and its corresponding control method. Figures 1-4The figures shown are a schematic diagram and a circuit diagram of an embodiment of a three-phase load imbalance compensation topology based on interphase power mutual assistance according to the present invention.

[0034] like Figure 1 As shown, Figure 1 This is a topology diagram of a load imbalance compensation device based on phase-to-phase power mutual assistance, which includes a DC filter unit 1, an active compensation unit 2, an AC filter unit 3, a load 4, a sampling unit 501, a control unit 601, and a drive unit 701.

[0035] The specific circuit diagram of the load imbalance compensation device based on interphase power mutual assistance is as follows: Figure 2 As shown, the output terminal of DC filter unit 1 is connected to the input terminal of active compensation unit 2, the output terminal of active compensation unit 2 is connected to the input terminal of AC filter unit 3, and the output terminal of AC filter unit 3 is connected to load 4; the input terminal of sampling unit 501 is connected to load 4, the feedback terminal of sampling unit 501 is connected to the input terminal of control unit 601, the output terminal of control unit 601 is connected to the input terminal of drive unit 701, and the output terminal of drive unit 701 is connected to the input terminal of active compensation unit 2.

[0036] The DC filter unit 1 and inverter capacitor mentioned above negative electrode and After the positive terminal is connected, it is connected to the neutral line of the power grid. The positive electrode and , , Connected to pin D, negative electrode and , , The pin S is connected, and the type of switching transistor selected is one of the semiconductor devices with switching characteristics such as GaN, MOSFET, IGBT and BJT.

[0037] The active compensation unit 2 includes a switching transistor. , , , , , , , , , , , pin S and , , pin S and , , After pin D is connected to the inductor Connected to the input terminal, , pin D and , Connected to pin D, , Pin S is connected to the neutral line of the power grid. The switching transistors are all selected from one of the semiconductor devices with switching characteristics, such as GaN, MOSFET, IGBT and BJT.

[0038] Furthermore, the switching transistors can be cascaded using one or more of the following semiconductor devices with switching characteristics: GaN, MOSFET, IGBT, and BJT. The source of the first switching transistor is connected to the drain of the second switching transistor, the source of the second switching transistor is connected to the drain of the third switching transistor, and so on. The drain of the first switching transistor is the drain of the cascaded switch, and the source of the last switching transistor is the source of the cascaded switch.

[0039] Furthermore, the output filter circuit 3 adopts one of the structural networks with filtering characteristics, such as C, LC, or LCL. The input filter circuit 3 is used to filter out high-frequency components in the single-stage resonant converter and reduce input harmonics.

[0040] When the input filter circuit 3 adopts a C input filter circuit, such as Figure 3 As shown in (a), the AC filter unit 3 is a filter capacitor. The positive terminal of the filter capacitor is connected to the output terminal of the active compensation unit 2 and the input terminal of the load 4, and the negative terminals of the capacitor are connected to each other.

[0041] When the input filter circuit 3 adopts an LC input filter circuit, such as Figure 3 As shown in (b), the AC filter unit 3 includes a filter inductor and a filter capacitor. The positive terminal of the filter inductor is connected to the output terminal of the active compensation unit 2, and the negative terminal is connected to the positive terminal of the filter capacitor and the input terminal of the load 4. The negative terminals of the filter capacitors are connected to each other.

[0042] When the input filter circuit 3 adopts an LCL input filter circuit, such as Figure 3 As shown in (c), the AC filter unit 3 includes two filter inductors and one filter capacitor. The positive terminal of the first filter inductor is connected to the output terminal of the active compensation unit 2, and the negative terminal is connected to the positive terminal of the filter capacitor and the positive terminal of the second filter inductor. The negative terminal of the second filter inductor is connected to the input terminal of the load 4, and the negative terminals of the filter capacitors are connected to each other.

[0043] Figure 4 This is a control structure diagram of a load imbalance compensation device based on phase-to-phase power mutual assistance in an embodiment of the present invention. Further, the control device based on phase-to-phase power mutual assistance for load imbalance compensation includes a phase-locked loop, a coordinate transformation unit, a control algorithm, a modulation strategy unit, and a drive unit.

[0044] The phase-locked loop (PLL) input is the input power supply voltage signal. The PLL output is connected to the control algorithm input terminal, the output terminal is connected to the coordinate transformation unit input terminal, the coordinate transformation unit output terminal is connected to the control algorithm input terminal, the control algorithm output terminal is connected to the modulation strategy input terminal, and the modulation strategy output terminal is connected to the drive circuit input terminal for outputting the modulation signal.

[0045] Furthermore, the phase-locked loop is used to control the frequency and phase of the internal oscillation signal using an externally input reference signal, so that the output voltage and the input voltage maintain a fixed phase difference. The phase-locked loop can be a phase-locked method with phase-locking characteristics, such as an improved EPLL based on hybrid filtering, a single-phase phase-locked loop based on cascaded delay signal cancellation, or a phase-locked loop based on a second-order generalized integrator.

[0046] Furthermore, in the control algorithm, controller one is used to control the bus voltage, controller two is used to control the bus voltage difference, controller three is used to control the d-axis component of the positive sequence current, controller four is used to control the q-axis component of the positive sequence current, controller five is used to control the d-axis component of the negative sequence current, controller six is ​​used to control the q-axis component of the negative sequence current, and controller seven is used to control the zero-sequence compensation current. The controller can be one or more of the following: proportional-integral-derivative, proportional resonant controller, sliding mode control, etc.

[0047] Furthermore, the modulation strategy is used to output the duty cycle and switching frequency modulation signal of the mode selected by the mode selection unit.

[0048] Furthermore, the driving circuit is used to convert modulation into switching network control logic to realize the control of the active compensation unit;

[0049] Furthermore, a control method based on inter-phase power mutual assistance for load imbalance compensation is implemented, comprising the following steps:

[0050] S1: Regarding the grid voltage Load current Inverter output current Bus voltage , After sampling, the grid voltage is first phase-locked; then the current is transformed into positive and negative zero sequence to extract the positive sequence current on the load side. Negative sequence current Zero-sequence current Extract the positive sequence current output from the inverter. Negative sequence current Zero-sequence current .

[0051] S2: Convert bus voltage , The current bus voltage value is obtained by adding them together. The voltage difference is obtained by subtracting the desired bus voltage from the current, and then processed by a PI controller to obtain the current command for the bus voltage. ; bus voltage , Subtraction yields the bus voltage difference After passing through the PI controller, the current command for bus voltage equalization is obtained. ;

[0052] S3: Oriented by grid voltage, positive sequence current. After Park transformation and passing through a high-pass filter, the higher harmonics and reactive components of the positive sequence current in the dq coordinate system can be obtained. and , and Doing bad things The difference between the current and the expected value is sent to the PI controller, and after inverse Park transformation, the positive sequence current command is obtained.

[0053] S4: Directed by grid voltage, negative sequence current. The negative sequence current in the dq coordinate system can be obtained through the Park transformation. and The negative sequence current of the inverter output current After Park transformation, we obtain and ,Will and and and The difference is fed into the PI controller, and after inverse Park transformation, a negative sequence current command is obtained.

[0054] S5: Zero-sequence current With the zero-sequence component of the inverter output current The difference is sent to the PR controller to obtain the zero-sequence compensation current command, which is then compared with the bus equalization current command. After differential calculation, the data is sent to the PR controller to obtain the zero-sequence current command.

[0055] S6: The current commands of the positive sequence, negative sequence, and zero sequence are added together to obtain the current command of the three-phase unbalanced load compensation system. After SPWM modulation, the PWM signal of the three-phase bridge arm is obtained.

[0056] Furthermore, a control method based on phase-to-phase power mutual assistance for load imbalance compensation, wherein the controller has one parameter , ; Controller two parameters , ; Controller three parameters , Controller four parameters , Controller five parameters , ; Controller six parameters , ; Controller seven parameters , The determination process is as follows:

[0057] (1) First, fix the bus voltage to the standard voltage, and the upper and lower bus voltages are both half of the bus voltage. Set the initial values ​​of the initial parameters of controller one and two to 0. First, adjust the parameters of controller three to seven.

[0058] (2) Calculate the parameters of controller three and controller four, and debug them respectively. and Check the inverter output current. If the positive-sequence component oscillates, then decrease it. and Continue adjusting until the waveform oscillations are eliminated, then proceed to process (3); otherwise, proceed to process (2) to continue adjusting. and ;

[0059] (3) Fix and Value, debugging and Check the inverter output current. Does the positive-order component fluctuate? If so, then decrease it. and Continue until the waveform oscillation is eliminated, then proceed to process (4); otherwise, proceed to process (3) to continue debugging. and ;

[0060] (4) Determine , and , The final values ​​are used as the coefficients of controller three and controller four;

[0061] (5) Calculate the parameters of controller five and controller six, and debug them respectively. and Check the inverter output current. If the negative-order component oscillates, then decrease it. and Continue adjusting until the waveform oscillations are eliminated, then proceed to process (6); otherwise, proceed to process (5) to continue adjusting. and ;

[0062] (6) Fix and Value, debugging and Check the inverter output current. Does the negative order component fluctuate? If so, then decrease. and Continue until the waveform oscillation is eliminated, then proceed to process (7); otherwise, proceed to process (6) to continue debugging. and ;

[0063] (7) Determine , and , The final values ​​are used as the coefficients of controller two and controller three;

[0064] (8) Adjust the seven parameters of the controller. The initial value is set to 0;

[0065] (9) Debug first Check the inverter output current. Does the zero-sequence component oscillate? If so, then decrease. Continue until the waveform oscillation is eliminated, then proceed to process (10); otherwise, proceed to step (9) to continue debugging. ;

[0066] (10) Fixed Value, debugging Check the inverter output current. Does the zero-order component fluctuate? If so, then decrease. Continue until the waveform oscillation is eliminated, then proceed to process (11); otherwise, proceed to process (6) to continue debugging. ;

[0067] (11) to determine , The final value is used as the controller's seven coefficients;

[0068] (12) Adjust one parameter of the controller. The initial value is set to 0;

[0069] (13) First debug Check if the bus voltage is oscillating; if so, reduce it. Continue until the waveform oscillation is eliminated, then proceed to process (14); otherwise, proceed to step (13) to continue debugging. ;

[0070] (14) Fixed Value, debugging Check if the bus voltage is fluctuating; if so, reduce it. Continue until the waveform oscillation is eliminated, then proceed to process (15); otherwise, proceed to process (14) to continue debugging. ;

[0071] (15) to determine and The final value is used as a coefficient of the controller;

[0072] (16) Adjust the two parameters of the controller. The initial value is set to 0;

[0073] (17) First debug Check if the bus voltage difference is oscillating; if so, reduce it. Continue until the waveform oscillation is eliminated, then proceed to process (18); otherwise, proceed to step (17) to continue debugging. ;

[0074] (18) Fixed Value, debugging Check if the line voltage difference fluctuates; if so, reduce it. Continue until the waveform oscillation is eliminated, then proceed to process (19); otherwise, proceed to process (18) to continue debugging. ;

[0075] (19) to determine and The final value is used as the second coefficient of the controller;

[0076] (20) Based on operations (1)-(19), the output control loop parameters are finally obtained. , , , , , , , , , ;

[0077] The beneficial effects of the technical solution provided by this invention are: the invention realizes the compensation of three-phase unbalanced load, and improves the working range and efficiency of the system.

[0078] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A load imbalance compensation topology based on interphase power mutual assistance, characterized in that, The compensation topology includes a DC filter unit (1), an active compensation unit (2), an AC filter unit (3), a load (4), a sampling unit (501), a control unit (601), and a drive unit (701). The output of the DC filter unit (1) is connected to the input of the active compensation unit (2), the output of the active compensation unit (2) is connected to the input of the AC filter unit (3), and the output of the AC filter unit (3) is connected to the load (4); the input of the sampling unit (501) is connected to the load (4), the feedback of the sampling unit (501) is connected to the input of the control unit (601), the output of the control unit (601) is connected to the input of the drive unit (701), and the output of the drive unit (701) is connected to the input of the active compensation unit (2).

2. The three-phase unbalanced load compensation topology as described in claim 1, characterized in that, The active compensation unit (2) includes a switching transistor. , , , , , , , , , , , pin S and , , pin S and , , After pin D is connected to the inductor Connected to the input terminal, , pin D and , Connected to pin D, , Pin S is connected to the neutral line of the power grid. The switching transistors are all selected from one of the following semiconductor devices with switching characteristics: GaN, MOSFET, IGBT, and BJT.

3. A three-phase unbalanced load compensation topology as described in claim 2, characterized in that, The inverter capacitor in the DC filter unit (1) negative electrode and After the positive terminal is connected, it is connected to the neutral line of the power grid. The positive electrode and , , Connected to pin D, negative electrode and , , The pin S is connected.

4. A three-phase unbalanced load compensation topology as described in claim 1, characterized in that, The AC filter unit (3) adopts one of the structure networks with filtering characteristics, such as C, LC, or LCL. The AC filter unit (3) is used to filter out high-frequency components in the active compensation unit (2) and reduce output harmonics. When the AC filter unit (3) adopts a C input filter circuit, the AC filter unit (3) is a filter capacitor. The positive terminal of the filter capacitor is connected to the output terminal of the active compensation unit (2) and the input terminal of the load (4), and the negative terminals of the capacitor are connected to each other. When the AC filter unit (3) adopts an LC input filter circuit, the AC filter unit (3) includes a filter inductor and a filter capacitor. The positive terminal of the filter inductor is connected to the output terminal of the active compensation unit (2), and the negative terminal is connected to the positive terminal of the filter capacitor and the input terminal of the load (4). The negative terminals of the filter capacitors are connected to each other. When the AC filter unit (3) adopts an LCL input filter circuit, the AC filter unit (3) includes two filter inductors and one filter capacitor. The positive terminal of the first filter inductor is connected to the output terminal of the active compensation unit (2), and the negative terminal is connected to the positive terminal of the filter capacitor and the positive terminal of the second filter inductor. The negative terminal of the second filter inductor is connected to the input terminal of the load (4), and the negative terminals of the filter capacitors are connected to each other.

5. A control method for load imbalance compensation based on inter-phase power mutual assistance, implemented based on the three-phase unbalanced load compensation topology described in any one of claims 1-4, characterized in that, It includes the following steps: S1: Regarding the grid voltage Load current Inverter output current Bus voltage , After sampling, the grid voltage is first phase-locked; then the current is transformed into positive and negative zero sequence to extract the positive sequence current on the load side. Negative sequence current Zero-sequence current Extract the positive sequence current output from the inverter. Negative sequence current Zero-sequence current ; S2: Convert bus voltage , The current bus voltage value is obtained by adding them together. The voltage difference is obtained by subtracting the desired bus voltage from the current, and then processed by a PI controller to obtain the current command for the bus voltage. ; bus voltage , Subtraction yields the bus voltage difference After passing through the PI controller, the current command for bus voltage equalization is obtained. ; S3: Oriented by grid voltage, positive sequence current. After Park transformation and passing through a high-pass filter, the higher harmonics and reactive components of the positive sequence current in the dq coordinate system can be obtained. and , and Doing bad things The difference between the current and the expected value is sent to the PI controller, and after inverse Park transformation, the positive sequence current command is obtained. S4: Directed by grid voltage, negative sequence current. The negative sequence current in the dq coordinate system can be obtained through the Park transformation. and The negative sequence current of the inverter output current After Park transformation, we obtain and ,Will and and and The difference is fed into the PI controller, and after inverse Park transformation, a negative sequence current command is obtained. S5: Zero-sequence current With the zero-sequence component of the inverter output current The difference is sent to the PR controller to obtain the zero-sequence compensation current command, which is then compared with the bus equalization current command. After differential calculation, the zero-sequence current command is obtained by sending it to the PR controller. S6: The current commands of the positive sequence, negative sequence, and zero sequence are added together to obtain the current command of the three-phase unbalanced load compensation system. After SPWM modulation, the PWM signal of the three-phase bridge arm is obtained.

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