Grid-connected three-phase unbalanced output control algorithm for alternating-current stable direct-current bus voltage

Abstract

The invention discloses a grid-connected three-phase unbalanced output control algorithm for alternating-current stable direct-current bus voltage, relates to the technical field of circuits, and aims to solve the technical problems of bus voltage fluctuation and power distribution caused when a three-phase unbalanced load is accessed and an inverter performs three-phase unbalanced output scheduling in the prior art. Comprising the steps of obtaining common connection point power of each phase of an inverter; obtaining a single-phase active power reference value of the inverter according to the power of the common connection point of each phase; the total power reference value of the inverter is calculated according to the single-phase active power reference value of the inverter, and the total active power reference value of the inverter is calculated according to the power reference value of each phase; according to the method, the actual power needing to be compensated for by the inverter is calculated in real time, accurate dispatching and distribution of the power can be achieved, energy loss is reduced, efficiency is improved, the output of the bus voltage control loop is redistributed, the power output of each phase can be matched with the load requirement to the maximum extent, and the overall efficiency of the system is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of circuit technology, and in particular to a grid-connected three-phase unbalanced output control algorithm for AC-stabilized DC bus voltage. Background Art

[0002] With the development of new energy technologies, distributed photovoltaic power generation and energy storage have become increasingly popular, and users' requirements for the stability and safety of household energy storage systems have gradually increased. Household energy storage systems mainly include distributed power sources, energy storage systems, local loads and power grids. The performance of its control algorithm directly affects the stability and energy efficiency of the entire system.

[0003] Three-phase unbalanced load is a common operating condition in power systems, especially in distribution networks and household scenarios. The imbalance of three-phase loads often leads to voltage asymmetry and current fluctuations. Voltage imbalance will produce negative-sequence components and zero-sequence components, increase the harmonic content of the system, reduce the operating efficiency of equipment, and may cause damage to certain sensitive equipment (such as computers and communication equipment). In such scenarios, the degradation of power quality caused by voltage fluctuations and uneven power distribution affects the overall operating efficiency of the inverter. Especially in household environments where three-phase unbalanced loads are more common, the AC-side control strategy of traditional inverters makes it difficult to achieve effective control of unbalanced output while maintaining a constant voltage on the DC bus.

[0004] Common regulation methods, such as strategies based on fixed power factor or simple proportional control, can alleviate voltage fluctuations to a certain extent, but their response speed and regulation accuracy cannot meet the needs of actual dynamic loads. In severe cases, it may cause system instability and even bus voltage fluctuations. This problem is particularly prominent in home energy storage scenarios, because user load types and power requirements are variable, and a single control algorithm cannot adapt to such a complex power environment.

[0005] Most of the inverter grid-connected solutions on the current market focus on the current control on the AC side under the condition of constant voltage input on the DC side. The control algorithm of some inverters realizes the inverter power dispatch under grid connection while stabilizing the DC bus on the AC side. However, the latter has significant deficiencies in unbalanced output control. This is mainly reflected in the following aspects:

[0006] 1. Insufficient coordination control between stable DC bus voltage and unbalanced output on the AC side:

[0007] 2. Complexity of power distribution under constant voltage of DC bus:

[0008] 3. Insufficient dynamic response capability of inverter power dispatch under unbalanced load:

[0009] Based on the above situation, the present invention proposes a control algorithm for stabilizing the three-phase unbalanced output of the DC bus on the AC side. Summary of the invention

[0010] The embodiment of the present invention provides a grid-connected three-phase unbalanced output control algorithm for AC-stabilized DC bus voltage, so as to at least solve the technical problems of bus voltage fluctuation and power distribution caused by the inverter performing three-phase unbalanced output scheduling when the three-phase unbalanced load is connected in the prior art. The load power imbalance can be calculated according to the actual load size, and the three-phase inverter unbalanced output scheduling can be completed. At the same time, the problem of single-phase output power overload damaging the load and equipment when the load is suddenly added or unloaded can be prevented;

[0011] To achieve the above object, the embodiments of the present invention adopt the following technical solutions:

[0012] A grid-connected three-phase unbalanced output control algorithm for AC-DC bus voltage stabilization, comprising:

[0013] S1, obtaining the power of each phase common connection point of the inverter;

[0014] S2. Obtaining a single-phase active power reference value of the inverter according to the power of each phase common connection point;

[0015] S3, calculating the total power reference value of the inverter according to the single-phase active power reference value of the inverter, and calculating the total active power reference value of the inverter according to the power reference value of each phase;

[0016] S4, calculating the active power imbalance of each phase according to the active power reference value of each phase of the inverter and the total active power reference value of the inverter;

[0017] S5. Redistribute the bus voltage loop output according to the degree of imbalance to obtain reference values ​​of various inverter currents;

[0018] S6, calculating the current flowing through the common connection point of each phase according to the current value obtained by the current Hall sensor of each phase output port of the inverter and the current value obtained by the circuit Hall sensor of each phase of the load port;

[0019] S7, calculating the power that needs to be compensated for each phase of the inverter according to the current and voltage of the common connection point, and outputting the power to the power imbalance calculation module;

[0020] S8, the power imbalance calculation module calculates the current imbalance coefficient of each phase of the inverter;

[0021] S9, the bus voltage loop obtains the output of the bus voltage loop through the PI controller according to the bus voltage reference value;

[0022] S10. Calculate a current output reference value of each phase of the inverter according to the current unbalance coefficient calculated by the unbalance calculation module and the output of the bus voltage loop.

[0023] Furthermore, in S1, the power at the common connection point is calculated by calculating the inverter output and the load side power through the Hall current sensors on the AC side and the load side of the inverter.

[0024] Furthermore, the power P_A of the common connection point of phase A is calculated based on the inverter output and the load phase A power, the power P_B of the common connection point of phase B is calculated based on the inverter output and the load phase B power, and the power P_C of the common connection point of phase C is calculated based on the inverter output and the load phase C power.

[0025] Furthermore, the reference value of the inverter output power can be calculated from the power of each phase common connection point calculated in step S1, then the reference value of the inverter output power of phase A is P_InvRefA=P_A, the reference value of the inverter output power of phase B is P_InvRefB=P_B, and the reference value of the inverter output power of phase C is P_InvRefC=P_C.

[0026] Further, in S6, the power of the A-phase inverter output is calculated to be P_InvA=I_InvA*U_InvA, the power of the B-phase inverter output is P_InvB=I_InvB*U_InvB, and the power of the C-phase inverter output is P_InvC=I_InvC*U_InvC. At the same time, the A-phase load power is calculated to be P_LoadA=I_LoadA*U_LoadA, the B-phase load power is P_LoadB=I_LoadB*U_LoadB, and the C-phase load power is P_LoadC=I_LoadC*U_LoadC. Then, the power of the A-phase common connection point is P_A=P_InvA-P_LoadA, the power of the B-phase common connection point is P_B=P_InvB-P_LoadB, and the power of the C-phase common connection point is P_C=P_InvC-P_LoadC.

[0027] Further, in S7, specifically, P_InvRef=P_InvRefA+P_InvRefB+P_InvRefC,

[0028] Among them, P_InvRef is the total inverter output power reference value, P_InvRefA, P_InvRefB, and P_InvRefC are the inverter A phase, B phase, and C phase output power reference values ​​respectively. The A phase inverter output power reference value is P_InvRefA=P_A, the B phase inverter output power reference value is P_InvRefB=P_B, and the C phase inverter output power reference value is P_InvRefC=P_C.

[0029] Furthermore, in S8

[0030] Unb_factorA=P_InvRefA / P_InvRef, Unb_factorB=P_InvRefB / P_InvRef, Unb_factorC=P_InvRefC / P_InvRef,

[0031] Among them, Unb_factorA, Unb_factorB, and Unb_factorC are the unbalance coefficients of the inverter output power respectively, and P_InvRefA, P_InvRefB, and P_InvRefC are the reference values ​​of the inverter output power respectively.

[0032] The beneficial effect is that the grid-connected three-phase unbalanced output control algorithm for AC-stabilized DC bus voltage provided by the embodiment of the present invention optimizes the bus voltage fluctuation and power distribution problems caused by the access to three-phase unbalanced loads and the inverter performing three-phase unbalanced output scheduling in the prior art. The present invention proposes to calculate the power that the actual inverter needs to compensate in real time based on the power of the actual common connection point, which can realize accurate scheduling and allocation of power, reduce energy loss and improve efficiency. The present invention redistributes the output of the bus voltage control loop so that the power output of each phase can not only match the load demand to the maximum extent, but also control the stability of the bus voltage, thereby significantly improving the overall efficiency of the system.

[0033] In the prior art, due to insufficient power dispatching control of three-phase unbalanced loads, the inverter is easily unstable in connection with the power grid under complex loads. The control algorithm of the present invention achieves a more stable power grid connection by calculating the imbalance and adjusting the output power, and through the protection logic during three-phase unbalanced output, it can have better grid adaptability when the load changes frequently. In addition, the protection logic can forcibly balance the three-phase power output when the output single-phase is overloaded, which improves the efficiency and stability when the unbalanced load suddenly changes or is abnormal, and also reduces the equipment failure rate caused by the unbalanced load, thereby improving the reliability of the entire household energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is one of the circuit schematics of this application;

[0035] Figure 2 This is the second circuit schematic diagram of this application;

[0036] Figure 3 This is the third circuit schematic diagram of this application;

[0037] Figure 4 This is a flowchart of the grid-connected three-phase unbalanced output control algorithm for AC and DC bus voltage stabilization in this application. DETAILED DESCRIPTION

[0038] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0039] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] Most of the inverter grid-connected solutions on the current market focus on the current control on the AC side under the condition of constant voltage input on the DC side. The control algorithm of some inverters realizes the inverter power dispatch under grid connection while stabilizing the DC bus on the AC side. However, the latter has significant deficiencies in unbalanced output control. This is mainly reflected in the following aspects:

[0041] 1. Insufficient coordination control between stable DC bus voltage and unbalanced output on the AC side:

[0042] Traditional inverter control algorithm

[0043] The methods usually focus on DC bus voltage control, maintaining the stability of DC bus voltage through PI or PID regulators. However, when the load is asymmetric or the power demand fluctuates, these controllers can only output balanced three-phase current, which is difficult to cope with the variable unbalanced power demand in actual applications. For household loads, especially when single-phase loads dominate, the existing technology performs poorly in the coordination of AC side voltage regulation and unbalanced output control, which may cause voltage fluctuations or frequency drift.

[0044] 2. Complexity of power distribution under constant voltage of DC bus:

[0045] Under this control algorithm, the energy storage system needs to achieve inverter output at a fixed DC voltage. However, when the load is unbalanced or changes dynamically, how to effectively distribute power under constant voltage conditions becomes a major difficulty. Existing technologies mostly use static distribution methods or simple power factor correction for adjustment, but these methods show hysteresis and instability in practical applications, especially when facing transient load changes, it is difficult to respond quickly and maintain voltage stability.

[0046] 3. Insufficient dynamic response capability of inverter power dispatch under unbalanced load:

[0047] Unbalanced output power dispatch control is particularly important under dynamic loads. Most current control strategies are based on the assumption of balanced loads. When the actual load is unbalanced and changes dramatically, the response speed of traditional algorithms is insufficient, and the delay and instability in the regulation process will affect the overall performance of the system. This lag is more obvious in the control system of the DC bus on the AC side, because the system needs to complete complex power regulation and dispatch under a fixed bus voltage, and existing technologies are difficult to ensure its stability and flexibility.

[0048] To solve the above problems, the embodiment of the present application discloses a grid-connected three-phase unbalanced output control algorithm for AC-stabilized DC bus voltage, which can calculate the load active power imbalance when connected to the grid, and redistribute the current reference value of each phase inverter circuit according to the total reference value of the inverter three-phase current output by the bus voltage loop. On this basis, unbalanced output single-phase overload protection logic is added, and the unbalanced output algorithm is used to ensure the normal operation and safety of the household inverter when it is connected to the three-phase unbalanced load.

[0049] The control algorithm includes: obtaining the grid-side power of each phase of the inverter; calculating the output power reference value of each phase of the inverter according to the grid-side power of each phase; calculating the actual output total power reference value according to the output power reference value of each phase; calculating the output power imbalance according to the actual output total power reference value and the output power reference value of each phase; obtaining the inverter bus voltage value; calculating the bus voltage output, that is, the total reference value of the inverter current loop current amplitude, through the PI controller parameters and the bus voltage reference value; calculating the actual current output reference value of each phase at the inverter according to the output power imbalance and the output of the bus voltage loop.

[0050] The following describes a three-phase unbalanced output control method provided by an embodiment of the present application. The three-phase unbalanced output control method can be applied to the above scenario, and specifically includes the following steps:

[0051] S1, obtaining the power of each phase common connection point of the inverter;

[0052] The power at the common connection point is calculated by calculating the inverter output and load side power through the Hall current sensors on the inverter AC side and the load side.

[0053] See also Figure 1 According to the inverter output and the load A phase power, the power of the A phase common connection point is calculated as P_A = P_InvA-P_LoadA. According to the inverter output and the load B phase power, the power of the B phase common connection point is calculated as P_B = P_InvB-P_LoadB. According to the inverter output and the load C phase power, the power of the C phase common connection point is calculated as P_C = P_InvC-P_LoadC.

[0054] S2. Obtaining a single-phase active power reference value of the inverter according to the power of each phase common connection point;

[0055] Specifically, the power of each phase common connection point calculated in step S1 can be used to calculate the reference value of the inverter output power, then the A-phase inverter output power reference value is P_InvRefA=P_A, the B-phase inverter output power reference value is P_InvRefB=P_B, and the C-phase inverter output power reference value is P_InvRefC=P_C.

[0056] S3, calculating the total power reference value of the inverter according to the single-phase active power reference value of the inverter, and calculating the total active power reference value of the inverter according to the power reference value of each phase;

[0057] S4, calculating the active power imbalance of each phase according to the active power reference value of each phase of the inverter and the total active power reference value of the inverter;

[0058] S5. Redistribute the bus voltage loop output according to the degree of imbalance to obtain reference values ​​of various inverter currents;

[0059] The control loop of the three-phase unbalanced control method in this embodiment is introduced below.

[0060] See also Figure 2 , Figure 2 The power calculation module receives the voltage and current values ​​of each phase of the inverter and the load, and the output end is connected to the power imbalance calculation module. The power imbalance module receives the reference value of each phase inverter power, and the output end is connected to the multiplier of the bus voltage loop output. Figure 3 The output end of the bus voltage loop subtractor is connected to the bus voltage loop PI controller, the input end of the unbalance coefficient multiplier is connected to the output of the bus voltage loop PI controller, the output end is connected to the inverter current loop subtractor, the input end of each phase current loop PI controller is connected to the output end of each phase inverter current subtractor is connected to the SPWM modulator.

[0061] S6, calculating the current flowing through the common connection point of each phase according to the current value obtained by the current Hall sensor of each phase output port of the inverter and the current value obtained by the circuit Hall sensor of each phase of the load port;

[0062] See also Figure 1 , the power of the A-phase inverter output is calculated to be P_InvA=I_InvA*U_InvA, the power of the B-phase inverter output is P_InvB=I_InvB*U_InvB, and the power of the C-phase inverter output is P_InvC=I_InvC*U_InvC. At the same time, the A-phase load power is calculated to be P_LoadA=I_LoadA*U_LoadA, the B-phase load power is P_LoadB=I_LoadB*U_LoadB, and the C-phase load power is P_LoadC=I_LoadC*U_LoadC. Then the power of the A-phase common connection point is P_A=P_InvA-P_LoadA, the power of the B-phase common connection point is P_B=P_InvB-P_LoadB, and the power of the C-phase common connection point is P_C=P_InvC-P_LoadC.

[0063] S7, calculating the power that needs to be compensated for each phase of the inverter according to the current and voltage of the common connection point, and outputting the power to the power imbalance calculation module;

[0064] Specifically, P_InvRef=P_InvRefA+P_InvRefB+P_InvRefC,

[0065] Among them, P_InvRef is the total inverter output power reference value, P_InvRefA, P_InvRefB, and P_InvRefC are the inverter A phase, B phase, and C phase output power reference values ​​respectively. The A phase inverter output power reference value is P_InvRefA=P_A, the B phase inverter output power reference value is P_InvRefB=P_B, and the C phase inverter output power reference value is P_InvRefC=P_C.

[0066] S8, the power imbalance calculation module calculates the current imbalance coefficient of each phase of the inverter;

[0067] Specifically,

[0068] Unb_factorA=P_InvRefA / P_InvRef, Unb_factorB=P_InvRefB / P_InvRef, Unb_factorC=P_InvRefC / P_InvRef,

[0069] Among them, Unb_factorA, Unb_factorB, and Unb_factorC are the unbalance coefficients of the inverter output power respectively, and P_InvRefA, P_InvRefB, and P_InvRefC are the reference values ​​of the inverter output power respectively.

[0070] The protection logic of unbalanced output under this control algorithm is introduced below.

[0071] S9, the bus voltage loop obtains the output of the bus voltage loop, i.e. the total inverter current reference value of the three phases, through the PI controller according to the bus voltage reference value;

[0072] S10. Calculate a current output reference value of each phase of the inverter according to the current unbalance coefficient calculated by the unbalance calculation module and the output of the bus voltage loop.

[0073] Exemplarily, the A-phase inverter current is given as I_InvRefA=I_BusOut*Unb_factorA, the B-phase inverter current is given as I_InvRefB=I_BusOut*Unb_factorB, and the C-phase inverter current is given as I_InvRefC=I_BusOut*Unb_factorC.

[0074] In the example of the present application, what is different from other algorithms is that the output of the bus voltage loop is the reference value of the current of each phase calculated according to the unbalance coefficient of each phase of the inverter, so it does not affect the control of the bus voltage loop.

[0075] The protection logic of unbalanced output under this control algorithm is introduced below.

[0076] In this specific example, when the inverter has an unbalanced three-phase output, the current and power output of each phase need to be within a certain limit range to ensure the normal and safe operation of the inverter and prevent damage to the load and the inverter itself due to control instability.

[0077] According to the above-mentioned control strategy of three-phase unbalanced output, the output current reference value at the inverter is calculated by calculating the actual power output unbalance coefficient and redistributing the bus voltage loop output. When calculating the unbalance coefficient, the actual compensation power of each phase and the unbalance coefficient of other phases are limited. When the power that the inverter actually needs to compensate exceeds the single-phase allowable unbalanced output limit, the three-phase current unbalance coefficient output by the unbalance calculation module is 1 / 3, and the inverter output current is redistributed according to the bus voltage loop output, forcing the inverter to balance the output, and preventing the inverter from being damaged by the load and the inverter due to the overload of the single-phase output.

[0078] Specifically, the output unbalance coefficient of phase A on the inverter side is Unb_factorA=P_InvRefA / P_InvRef, and the amplitude limit range is 0 to 1. The output unbalance coefficient of phase B on the inverter side is Unb_factorB=P_InvRefB / P_InvRef, and the amplitude limit range is (1-Unb_factorA) to 1. The output unbalance coefficient of phase B at the inverter is Unb_factorC=P_InvRefC / P_InvRef, and the amplitude limit range is (1-Unb_factorA-Unb_factorB) to 1. When a certain inverter output power reference value exceeds the overload value set in the inverter, the three-phase output is forced to be balanced. At this time, the unbalance coefficients of each phase of the inverter are 1 / 3, which can effectively prevent damage to the inverter or load caused by single-phase output overload.

[0079] The key technical point of the present invention is that while controlling the bus, the inverter side calculates the power value that needs to be dispatched for each phase of the inverter, redistributes the bus voltage loop output, ensures the stability of the bus voltage, and realizes three-phase unbalanced output. Based on this control algorithm, a protection logic is proposed, which can detect the output power size in real time when the inverter has three-phase unbalanced output, and make an overload judgment based on the calculated power value that needs to be compensated for each phase of the inverter, to prevent the inverter from overloading when the load suddenly changes, thereby damaging the load or inverter.

[0080] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0081] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A grid-connected three-phase unbalanced output control algorithm for AC-DC bus voltage stabilization, characterized in that: S1, obtaining the power of each phase common connection point of the inverter; S2. Obtaining a single-phase active power reference value of the inverter according to the power of each phase common connection point; S3, calculating the total power reference value of the inverter according to the single-phase active power reference value of the inverter, and calculating the total active power reference value of the inverter according to the power reference value of each phase; S4, calculating the active power imbalance of each phase according to the active power reference value of each phase of the inverter and the total active power reference value of the inverter; S5. Redistribute the bus voltage loop output according to the degree of imbalance to obtain reference values ​​of various inverter currents; S6, calculating the current flowing through the common connection point of each phase according to the current value obtained by the current Hall sensor of each phase output port of the inverter and the current value obtained by the circuit Hall sensor of each phase of the load port; S7, calculating the power that needs to be compensated for each phase of the inverter according to the current and voltage of the common connection point, and outputting the power to the power imbalance calculation module; S8, the power imbalance calculation module calculates the current imbalance coefficient of each phase of the inverter; S9, the bus voltage loop obtains the output of the bus voltage loop through the PI controller according to the bus voltage reference value; S10. Calculate a current output reference value of each phase of the inverter according to the current unbalance coefficient calculated by the unbalance calculation module and the output of the bus voltage loop.

2. The grid-connected three-phase unbalanced output control algorithm for AC-DC bus voltage stabilization according to claim 1 is characterized in that: In S1, the power of the common connection point is calculated by calculating the inverter output and the load side power through the Hall current sensors on the inverter AC side and the load side.

3. The grid-connected three-phase unbalanced output control algorithm for AC-DC bus voltage stabilization according to claim 2 is characterized in that: The power of the common connection point of phase A is calculated based on the inverter output and the power of phase A of the load, P_A=P_InvA-P_LoadA; the power of the common connection point of phase B is calculated based on the inverter output and the power of phase B of the load, P_B=P_InvB-P_LoadB; the power of the common connection point of phase C is calculated based on the inverter output and the power of phase C of the load, P_C=P_InvC-P_LoadC.

4. The grid-connected three-phase unbalanced output control algorithm for AC-DC bus voltage stabilization according to claim 3 is characterized in that: The reference value of the inverter output power can be calculated from the power of each phase common connection point calculated in step S1, then the reference value of the inverter output power of phase A is P_InvRefA=P_A, the reference value of the inverter output power of phase B is P_InvRefB=P_B, and the reference value of the inverter output power of phase C is P_InvRefC=P_C.

5. The grid-connected three-phase unbalanced output control algorithm for AC-DC bus voltage stabilization according to claim 4 is characterized in that: In S6, it is calculated that the power of the A-phase inverter output is P_InvA=I_InvA*U_InvA, the power of the B-phase inverter output is P_InvB=I_InvB*U_InvB, and the power of the C-phase inverter output is P_InvC=I_InvC*U_InvC. At the same time, it is calculated that the A-phase load power is P_LoadA=I_LoadA*U_LoadA, the B-phase load power is P_LoadB=I_LoadB*U_LoadB, and the C-phase load power is P_LoadC=I_LoadC*U_LoadC. Then the power of the A-phase common connection point is P_A=P_InvA-P_LoadA, the power of the B-phase common connection point is P_B=P_InvB-P_LoadB, and the power of the C-phase common connection point is P_C=P_InvC-P_LoadC.

6. The grid-connected three-phase unbalanced output control algorithm for AC-DC bus voltage stabilization according to claim 5 is characterized in that: Specifically in S7, P_InvRef=P_InvRefA+P_InvRefB+P_InvRefC, Among them, P_InvRef is the total inverter output power reference value, P_InvRefA, P_InvRefB, and P_InvRefC are the inverter A phase, B phase, and C phase output power reference values ​​respectively. The A phase inverter output power reference value is P_InvRefA=P_A, the B phase inverter output power reference value is P_InvRefB=P_B, and the C phase inverter output power reference value is P_InvRefC=P_C.

7. The grid-connected three-phase unbalanced output control algorithm for AC-DC bus voltage stabilization according to claim 6 is characterized in that: S8 Unb_factorA=P_InvRefA / P_InvRef, Unb_factorB=P_InvRefB / P_InvRef, Unb_factorC=P_InvRefC / P_InvRef, Among them, Unb_factorA, Unb_factorB, and Unb_factorC are the unbalance coefficients of the inverter output power respectively, and P_InvRefA, P_InvRefB, and P_InvRefC are the reference values ​​of the inverter output power respectively.

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