Unified power quality controller

Abstract

The invention provides a topological structure of a unified power quality controller with inertia support and frequency modulation capabilities and a control system design method, and aims to solve the problems of low power quality, poor power system stability and the like of a high-proportion new energy power grid. The system adopts a novel topological structure and is mainly composed of a series compensation module, a parallel compensation module and a power control inductor. Wherein the series compensation module controls reactive power by controlling voltage at two ends of an internal transformer, and is responsible for improving voltage quality of a power grid and ensuring stable transmission of electric energy; and the parallel compensation module is responsible for maintaining the constant amplitude of the load voltage and controlling the active power of the power grid by controlling the phase of the load voltage. According to the method, the electric energy quality and the system stability are remarkably improved, the method is suitable for an electric power system under variable load conditions, and technical support is provided for efficient and safe operation.

Description

Technical Field

[0001] The invention relates to the technical field of power electronics, and in particular to a unified power quality controller. Background Art

[0002] With the increasing complexity of power systems and the widespread use of renewable energy, power quality issues are becoming increasingly prominent, including voltage fluctuations, harmonic interference, and frequency fluctuations. These issues not only affect the safe operation of power equipment, but may also cause equipment damage and economic losses. Traditional power quality control methods often find it difficult to achieve effective coordination and unified management of multiple issues.

[0003] In recent years, VSG (Virtual Synchronous Generator) technology has emerged as an emerging control strategy to support grid stability by providing voltage and frequency support. Currently, there is no unified power quality controller that effectively utilizes VSG technology in the prior art. Summary of the invention

[0004] The embodiment of the present invention provides a unified power quality controller to effectively improve the flexibility and efficiency of power quality control.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme.

[0006] A unified power quality controller includes: a parallel compensation module, a series compensation module and a power control inductor L1, wherein the parallel compensation module is composed of a power converter, a filter inductor, a filter capacitor and an isolation transformer, which is equivalent to a parallel voltage source U p The series compensation module is composed of a power converter, a filter inductor, a filter capacitor and an isolation transformer, which is equivalent to an equivalent series voltage source U s ; Series voltage source U s One end of the grid voltage source U g One end is connected to the series voltage source U s The other end of the power control inductor L1 is connected to one end of the power control inductor L1, and the other end of the power control inductor L1 is connected to the parallel voltage source U p One end is connected to the parallel voltage source U p The other end is connected to the grid voltage source U g The other end of the load is connected to the equivalent current source I L Connected in parallel with the parallel voltage source U p superior.

[0007] Preferably, the parallel voltage source U p By controlling the parallel voltage source U pThe amplitude of is maintained constant to control the phase difference of the voltage across the power control inductor L1, thereby controlling the active power; the series voltage source U s The reactive power is controlled by controlling the amplitude difference of the voltage across the power control inductor L1.

[0008] Preferably, the series voltage source U s The given value is the difference between the reference voltage and the grid voltage, and the reference voltage is formed by integrating the amplitude generated by the reactive power control of the virtual synchronous generator and the grid voltage phase; the parallel voltage source U p The voltage amplitude is the rated value of the load voltage, and the phase is the phase generated by the active power control of the virtual synchronous generator.

[0009] Preferably, when applied to a single-phase single-wire scenario, the power quality controller is composed of a parallel compensation module, a series compensation module and a second filter inductor L2 for power control; the parallel compensation module is composed of a first inverter INV1, a first filter inductor L1 and a first filter capacitor C1; the series compensation module is composed of a second inverter INV2, a third filter inductor L3, a first single-phase transformer T1 and a second filter capacitor C2;

[0010] One end of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form a first AC connection point AC1, and the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form a third AC connection point AC3; the third AC connection point AC3 is connected to one end of the load, and the other end of the load is connected to the other end of the first filter capacitor C1 to form a second AC connection point AC2; the other end of the AC output end of the first inverter INV1 is connected to the second AC connection point AC2, the second AC connection point AC2 is connected to one end of the single-phase power grid, and the other end of the single-phase power grid is connected to one end of the primary side of the first single-phase transformer T1 to form a fourth AC connection point AC4; the other end of the primary side of the first single-phase transformer T1 is connected to one end of the second filter inductor L2 to form a fifth AC connection point AC5; the other end of the second filter inductor L2 is connected to the third AC connection point AC3; one end of the AC connection point of the second inverter INV2 is connected to the third filter One end of the third filter inductor L3 is connected to one end of the secondary side of the first single-phase transformer T1 to form a seventh AC connection point AC7; the other end of the AC connection point of the second inverter INV2 is connected to the other end of the secondary side of the first single-phase transformer T1 to form an eighth AC connection point AC8; the two ends of the second filter capacitor C2 are respectively connected to the fourth AC connection point AC4 and the fifth AC connection point AC5 or the seventh AC connection point AC7 and the eighth AC connection point AC8, the high voltage end of the DC output end of the first inverter INV1 is connected to the high voltage end of the DC output end of the second inverter INV2 to form a first DC connection point DC1; the low voltage end of the DC output end of the first inverter INV1 is connected to the low voltage end of the DC output end of the second inverter INV2 to form a second DC connection point DC2; the two ends of the third filter capacitor C3 are respectively connected to the first DC output point DC1 and the second DC output point DC2.

[0011] Preferably, the phase angle difference of the voltages across the second filter inductor L2 determines the active power of the current flowing through the second filter inductor L2, and the amplitude difference of the voltages across the second filter inductor L2 determines the reactive power of the current flowing through the second filter inductor L2; the potential difference between the fifth AC connection point AC5 and the second AC connection point AC2 is the first voltage U1, and the potential difference between the third AC connection point AC3 and the second AC connection point AC2 is the second voltage U2;

[0012] The grid-connected active power is realized by controlling the phase difference between the first voltage U1 and the second voltage U2, and the phase difference is realized by adjusting the phase of the second voltage U2. The given value of the phase of the second voltage U2 is generated by the active power control of the virtual synchronous generator. The given value of the amplitude of the second voltage U2 is set to the rated value of the load voltage amplitude. The given value of the amplitude and phase of the second voltage U2 is integrated to obtain the given value of the second voltage U2. The second voltage U2 is the output voltage of the parallel compensation module, because the given value of the output voltage of the parallel compensation module is the given value of the second voltage U2.

[0013] The difference in amplitude between the first voltage U1 and the second voltage U2 determines the reactive power of the current flowing through the second filter inductor L2. The first voltage U1 is equal to the sum of the grid voltage and the output voltage of the series compensation module, and the amplitude of the second voltage U2 is controlled to keep the rated value of the load voltage unchanged. The amplitude of the first voltage U1 is controlled by controlling the output voltage of the series compensation module, thereby controlling the amplitude difference between the first voltage U1 and the second voltage U2, and further controlling the reactive power of the current flowing through the second filter inductor L2. The given value of the phase of the first voltage U1 is the same as that of the grid. The amplitude of the first voltage U1 is generated by the reactive control of the virtual synchronous generator. The given value of the amplitude and phase of the first voltage U1 is integrated to obtain the given value of the first voltage U1. The given value of the output voltage of the series compensation module is the difference between the given value of the first voltage and the grid voltage.

[0014] Preferably, when applied to a three-phase three-wire scenario, the power quality controller is composed of a parallel compensation module, a series compensation module, and a seventh filter inductor L7, an eighth filter inductor L8, and a ninth filter inductor L9 for power control; the series compensation module adopts two forms: three single-phase commutation bridge forms and one three-phase commutation bridge form, and the parallel compensation module adopts an inverter module composed of a three-phase commutation bridge;

[0015] The parallel compensation module is composed of a first inverter INV1, a first filter inductor L1, a second filter inductor L2, a third filter inductor L3, a first filter capacitor C1, a second filter capacitor C2 and a third filter capacitor C3. The first phase of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form a first connection point a1 of phase a, and the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form a second connection point a2 of phase a, and the second connection point a2 of phase a is connected to the first phase of the load; the second phase of the AC output end of the first inverter INV1 is connected to one end of the second filter inductor L2 to form a second connection point a1 of phase b. A connection point b1, the other end of the second filter inductor L2 is connected to one end of the second filter capacitor C2 to form a b-phase second connection point b2, and the b-phase second connection point b2 is connected to the second phase of the load; the third phase of the AC output end of the first inverter INV1 is connected to one end of the third filter inductor L3 to form a c-phase first connection point c1, the other end of the third filter inductor L3 is connected to one end of the third filter capacitor C3 to form a c-phase second connection point c2, and the c-phase second connection point c2 is connected to the third phase of the load; the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are connected to each other to form a first AC output terminal AC1;

[0016] The series compensation module adopts three single-phase commutation bridge forms, and its series inverter module is composed of a second single-phase inverter INV2, a third single-phase inverter INV3, a fourth single-phase inverter INV4, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6. The AC output of the second single-phase inverter INV2 One end of the AC output end of the second single-phase inverter INV2 is connected to the other end of the secondary side of the first single-phase transformer T1 to form the seventh connection point a7 of the a phase; one end of the AC output end of the third single-phase inverter INV3 is connected to one end of the fifth filter inductor L5 to form the third connection point b3 of the b phase; the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form the fourth connection point a4 of the a phase; the other end of the AC output end of the second single-phase inverter INV2 is connected to the other end of the secondary side of the first single-phase transformer T1 to form the seventh connection point a7 of the a phase; one end of the AC output end of the third single-phase inverter INV3 is connected to one end of the fifth filter inductor L5 to form the third connection point b3 of the b phase; The other end of the inductor L5 is connected to one end of the secondary side of the second single-phase transformer T2 to form the fourth connection point b4 of the b phase, and the other end of the AC output end of the third single-phase inverter INV3 is connected to the other end of the secondary side of the second single-phase transformer T2 to form the seventh connection point b7 of the b phase; one end of the AC output end of the fourth single-phase inverter INV4 is connected to one end of the sixth filter inductor L6 to form the third connection point c3 of the c phase, the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to form the fourth connection point c4 of the c phase, and the other end of the AC output end of the fourth single-phase inverter INV4 is connected to the other end of the secondary side of the third single-phase transformer T3 to form the seventh connection point c7 of the c phase; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side of the first single-phase transformer T1 or the two ends of the secondary side, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side of the second single-phase transformer T2 or the two ends of the secondary side, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side of the third single-phase transformer T3 or the two ends of the secondary side;

[0017] The series compensation module adopts a three-phase commutation bridge form, and its series inverter module is composed of a second three-phase inverter INV2, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6; the first phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fourth filter inductor L4 to form the a-phase third connection point a3, and the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form the a-phase fourth connection point a4; the second phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fifth filter inductor L5 to form the b-phase third connection point b3, and the other end of the fifth filter inductor L5 is connected to the second One end of the secondary side of the single-phase transformer T2 constitutes the fourth connection point b4 of the b phase; the third phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the sixth filter inductor L6 to constitute the third connection point c3 of the c phase, and the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to constitute the fourth connection point c4 of the c phase; the other ends of the secondary sides of the first single-phase transformer T1, the second single-phase transformer T2, and the third single-phase transformer T3 are connected to each other to form the second AC output terminal AC2; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the first single-phase transformer T1, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the second single-phase transformer T2, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the third single-phase transformer T3;

[0018] One end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to the first phase of the power grid to form the fifth connection point a5 of the a phase, the other end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to one end of the seventh filter inductor L7 to form the sixth connection point a6 of the a phase, and the other end of the seventh filter inductor L7 is connected to the second connection point a2 of the a phase; one end of the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b5 of the b phase, and the The other end of the primary side is connected to one end of the eighth filter inductor L8 to form the sixth connection point b6 of the b phase, and the other end of the eighth filter inductor L8 is connected to the second connection point b2 of the b phase; one end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to the third phase of the power grid to form the fifth connection point c5 of the c phase, the other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the ninth filter inductor L9 to form the sixth connection point c6 of the c phase, and the other end of the ninth filter inductor L9 is connected to the second connection point c2 of the c phase;

[0019] The high voltage end of the DC output end of the parallel inverter module is connected to the high voltage end of the DC output end of the series inverter module to form a first DC connection point DC1, the low voltage end of the DC output end of the parallel inverter module is connected to the low voltage end of the DC output end of the series inverter module to form a second DC connection point DC2, and the two ends of the seventh filter capacitor C7 are respectively connected to the first DC output point DC1 and the second DC output point DC2.

[0020] Preferably, the phase angle difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9 respectively determines the active power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9, and the amplitude difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9 respectively determines the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9; the potential difference between the sixth AC connection point a6 of the a phase and the first AC output terminal AC1 is the first voltage U1, the potential difference between the second AC connection point a2 of phase a and the first AC output terminal AC1 is the second voltage U2; the potential difference between the sixth AC connection point b6 of phase b and the first AC output terminal AC1 is the third voltage U3, and the potential difference between the second AC connection point b2 of phase b and the first AC output terminal AC1 is the fourth voltage U4; the potential difference between the sixth AC connection point c6 of phase c and the first AC output terminal AC1 is the fifth voltage U5, and the potential difference between the second AC connection point c2 of phase c and the first AC output terminal AC1 is the sixth voltage U6;

[0021] The grid-connected active power is realized by controlling the phase difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6, and the phase difference is realized by adjusting the phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively, and the given values ​​of the phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are generated by the active power control of the virtual synchronous generator; the three-phase voltages of the load voltage are respectively the same as the second voltage U2, the fourth voltage U4 and the sixth voltage U6, The given values ​​of the amplitudes of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are set as the rated value of the load voltage amplitude; the given values ​​of the amplitudes and phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 can be respectively integrated to obtain the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6, and the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are the three-phase output voltages of the parallel compensation module, and the given values ​​of the three-phase output voltages of the parallel compensation module are respectively the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6;

[0022] The grid-connected reactive power is realized by controlling the amplitude difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6. The first voltage U1 is equal to the sum of the first phase voltage of the power grid and the first phase output voltage of the series compensation module, the third voltage U3 is equal to the sum of the second phase voltage of the power grid and the second phase output voltage of the series compensation module, the fifth voltage U5 is equal to the sum of the third phase voltage of the power grid and the third phase output voltage of the series compensation module, and the amplitudes of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are controlled to keep the load voltage rated value unchanged. The amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled by controlling the output voltage of the series compensation module, and the first voltage U1 is controlled to be equal to the second voltage U2, the third voltage U3 is controlled to be equal to the fourth voltage U4, and the fifth voltage U5 is controlled to be equal to the sixth voltage U6. The amplitude difference is used to control the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9 respectively; the given values ​​of the phases of the first voltage U1, the third voltage U3 and the fifth voltage U5 are the same as those of the power grid, the amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are generated by the reactive power control of the virtual synchronous generator, and the given values ​​of the amplitudes and phases of the first voltage U1, the third voltage U3 and the fifth voltage U5 can be integrated to obtain the given values ​​of the first voltage U1, the third voltage U3 and the fifth voltage U5, the given value of the first phase output voltage of the series compensation module is the difference between the given value of the first voltage U1 and the power grid voltage, the given value of the second phase output voltage of the series compensation module is the difference between the given value of the third voltage U3 and the power grid voltage, and the given value of the third phase output voltage of the series compensation module is the difference between the given value of the first voltage U1 and the power grid voltage.

[0023] Preferably, when applied to a three-phase four-wire scenario, the power quality controller is composed of a parallel compensation module, a series compensation module, and a seventh filter inductor L7, an eighth filter inductor L8, and a ninth filter inductor L9 for power control; the series compensation module adopts two forms: three single-phase commutation bridge forms and one three-phase commutation bridge form, and the parallel compensation module adopts two forms: a four-bridge arm form and a split capacitor form;

[0024] The series compensation module adopts three single-phase commutation bridge forms, and its series inverter module is composed of a second single-phase inverter INV2, a third single-phase inverter INV3, a fourth single-phase inverter INV4, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6. One end of the AC output end of the second single-phase inverter INV2 is connected to the fourth filter inductor L4 to form the a-phase third connection point a3, the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form the a-phase fourth connection point a4, the other end of the AC output end of the second single-phase inverter INV2 is connected to the other end of the secondary side of the first single-phase transformer T1 to form the a-phase seventh connection point a7; one end of the AC output end of the third single-phase inverter INV3 is connected to one end of the fifth filter inductor L5 to form the b-phase third connection point b3, the fifth filter inductor L4 is connected to the first single-phase transformer T1 to form the a-phase fourth connection point a4, the second end of the AC output end of the second single-phase inverter INV2 is connected to the first single-phase transformer T1 to form the a-phase seventh connection point a7; one end of the AC output end of the third single-phase inverter INV3 is connected to one end of the fifth filter inductor L5 to form the b-phase third connection point b3, the fifth filter inductor L4 is connected to the first single-phase transformer T1 to form the a-phase seventh connection point a8. The other end of the inductor L5 is connected to one end of the secondary side of the second single-phase transformer T2 to form the fourth connection point b4 of the b phase, and the other end of the AC output end of the third single-phase inverter INV3 is connected to the other end of the secondary side of the second single-phase transformer T2 to form the seventh connection point b7 of the b phase; one end of the AC output end of the fourth single-phase inverter INV4 is connected to one end of the sixth filter inductor L6 to form the third connection point c3 of the c phase, the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to form the fourth connection point c4 of the c phase, and the other end of the AC output end of the fourth single-phase inverter INV4 is connected to the other end of the secondary side of the third single-phase transformer T3 to form the seventh connection point c7 of the c phase; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side of the first single-phase transformer T1 or the two ends of the secondary side, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side of the second single-phase transformer T2 or the two ends of the secondary side, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side of the third single-phase transformer T3 or the two ends of the secondary side;

[0025] The series compensation module adopts a three-phase commutation bridge form, and its series inverter module is composed of a second three-phase inverter INV2, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6; the first phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fourth filter inductor L4 to form the a-phase third connection point a3, and the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form the a-phase fourth connection point a4; the second phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fifth filter inductor L5 to form the b-phase third connection point b3, and the other end of the fifth filter inductor L5 is connected to the secondary side of the second single-phase transformer T2. One end of the sixth filter inductor L6 constitutes the fourth connection point b4 of the b phase; the third phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the sixth filter inductor L6 to constitute the third connection point c3 of the c phase, and the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to constitute the fourth connection point c4 of the c phase; the other ends of the secondary sides of the first single-phase transformer T1, the second single-phase transformer T2, and the third single-phase transformer T3 are connected to each other to form the second AC output terminal AC2, and the second AC output terminal AC2 is connected to the neutral line; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the first single-phase transformer T1, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the second single-phase transformer T2, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the third single-phase transformer T3;

[0026] One end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to the first phase of the power grid to form the fifth connection point a5 of the a phase, the other end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to one end of the seventh filter inductor L7 to form the sixth connection point a6 of the a phase, and the other end of the seventh filter inductor L7 is connected to the second connection point a2 of the a phase; one end of the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b5 of the b phase, and the The other end of the primary side is connected to one end of the eighth filter inductor L8 to form the sixth connection point b6 of the b phase, and the other end of the eighth filter inductor L8 is connected to the second connection point b2 of the b phase; one end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to the third phase of the power grid to form the fifth connection point c5 of the c phase, the other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the ninth filter inductor L9 to form the sixth connection point c6 of the c phase, and the other end of the ninth filter inductor L9 is connected to the second connection point c2 of the c phase;

[0027] The parallel compensation module in the form of four bridge arms is composed of a first inverter INV1, a first filter inductor L1, a second filter inductor L2, a third filter inductor L3, a tenth filter inductor L 10 , a first filter capacitor C1, a second filter capacitor C2 and a third filter capacitor C3, the first inverter INV1 uses an additional branch, the first phase of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form the a phase first connection point a1, the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form the a phase second connection point a2, the a phase second connection point a2 is connected to the first phase of the load; the second phase of the AC output end of the first inverter INV1 is connected to one end of the second filter inductor L2 to form the b phase first connection point b1, the other end of the second filter inductor L2 is connected to one end of the second filter capacitor C2 to form the b-phase second connection point b2, and the b-phase second connection point b2 is connected to the second phase of the load; the third phase of the AC output end of the first inverter INV1 is connected to one end of the third filter inductor L3 to form the c-phase first connection point c1, the other end of the third filter inductor L3 is connected to one end of the third filter capacitor C3 to form the c-phase second connection point c2, and the c-phase second connection point c2 is connected to the third phase of the load; the additional branch of the AC output end of the first inverter INV1 is connected to the tenth filter inductor L 10 One end of the N-phase first connection point n1, the tenth filter inductor L 10 The other end of the first filter capacitor C1 is connected to the neutral line to form the N-phase second connection point n2; the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are connected to each other to form a first AC output terminal AC1, and the first AC output terminal AC1 is connected to the N-phase second connection point n2; the high voltage end of the DC output end of the first inverter INV1 is connected to the high voltage end of the DC output end of the series inverter module to form a first DC connection point DC1, the low voltage end of the DC output end of the first inverter INV1 is connected to the low voltage end of the DC output end of the series inverter module to form a second DC connection point DC2, and the two ends of the seventh filter capacitor C7 are respectively connected to the first DC output point DC1 and the second DC output point DC2;

[0028] The parallel compensation module in the form of split capacitors is composed of a first inverter INV1, a first filter inductor L1, a second filter inductor L2, a third filter inductor L3, a first filter capacitor C1, a second filter capacitor C2 and a third filter capacitor C3. The first phase of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form a first connection point a1 of phase a, and the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form a second connection point a2 of phase a, and the second connection point a2 of phase a is connected to the first phase of the load; the second phase of the AC output end of the first inverter INV1 is connected to one end of the second filter inductor L2 to form a first connection point b1 of phase b, and the other end of the second filter inductor L2 is connected to one end of the second filter capacitor C2 to form a second connection point b2 of phase b, and the second connection point b2 of phase b is connected to the second phase of the load; the third phase of the AC output end of the first inverter INV1 is connected to one end of the third filter inductor L3 to form a first connection point c of phase c1, the other end of the third filter inductor L3 is connected to one end of the third filter capacitor C3 to form the second connection point c2 of the c phase, and the second connection point c2 of the c phase is connected to the third phase of the load; the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are connected to each other to form the first AC output terminal AC1, and the first AC output terminal AC1 is connected to the neutral line; the high voltage end of the DC output end of the first inverter INV1 is connected to the high voltage end of the DC output end of the series inverter module to form the first DC connection point DC1, the low voltage end of the DC output end of the first inverter INV1 is connected to the low voltage end of the DC output end of the series inverter module to form the second DC connection point DC2, one end of the seventh filter capacitor C7 is connected to the first DC output point DC1, one end of the eighth filter capacitor C8 is connected to the second DC output point DC2, the other ends of the seventh filter capacitor C7 and the eighth filter capacitor C8 are connected to each other to form the N phase first connection point n1, and the N phase first connection point n1 is connected to the neutral line.

[0029] Preferably, the phase angle difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9 respectively determines the active power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9, and the amplitude difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9 respectively determines the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9; the potential difference between the sixth AC connection point a6 of the a phase and the first AC output terminal AC1 is the first voltage U1, the potential difference between the second AC connection point a2 of phase a and the first AC output terminal AC1 is the second voltage U2; the potential difference between the sixth AC connection point b6 of phase b and the first AC output terminal AC1 is the third voltage U3, and the potential difference between the second AC connection point b2 of phase b and the first AC output terminal AC1 is the fourth voltage U4; the potential difference between the sixth AC connection point c6 of phase c and the first AC output terminal AC1 is the fifth voltage U5, and the potential difference between the second AC connection point c2 of phase c and the first AC output terminal AC1 is the sixth voltage U6;

[0030] The grid-connected active power is realized by controlling the phase difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6, and the phase difference is realized by adjusting the phase of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively, and the given values ​​of the phase of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are generated by the active power control of the virtual synchronous generator; the three-phase voltage of the load voltage is the same as the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively , the given values ​​of the amplitudes of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are set to the rated value of the load voltage amplitude; the given values ​​of the amplitudes and phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are respectively integrated to obtain the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6, and the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are the three-phase output voltages of the parallel compensation module, and the given values ​​of the three-phase output voltages of the parallel compensation module are the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively;

[0031] The grid-connected reactive power is realized by controlling the amplitude difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6. The first voltage U1 is equal to the sum of the first phase voltage of the power grid and the first phase output voltage of the series compensation module, the third voltage U3 is equal to the sum of the second phase voltage of the power grid and the second phase output voltage of the series compensation module, the fifth voltage U5 is equal to the sum of the third phase voltage of the power grid and the third phase output voltage of the series compensation module, the amplitudes of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are controlled to keep the load voltage rated value unchanged, and the amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled by controlling the output voltage of the series compensation module, thereby controlling the first voltage U1 and the second voltage U2, the third voltage U3 and the fourth voltage U4, and the fifth voltage U5 and the sixth voltage The amplitude difference of U6 is used to control the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9 respectively; the given values ​​of the phases of the first voltage U1, the third voltage U3 and the fifth voltage U5 are the same as those of the power grid, the amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are generated by the reactive power control of the virtual synchronous generator, and the given values ​​of the amplitudes and phases of the first voltage U1, the third voltage U3 and the fifth voltage U5 are integrated to obtain the given values ​​of the first voltage U1, the third voltage U3 and the fifth voltage U5, the given value of the first phase output voltage of the series compensation module is the difference between the given value of the first voltage U1 and the power grid voltage, the given value of the second phase output voltage of the series compensation module is the difference between the given value of the third voltage U3 and the power grid voltage, and the given value of the third phase output voltage of the series compensation module is the difference between the given value of the first voltage U1 and the power grid voltage.

[0032] It can be seen from the technical solutions provided by the above-mentioned embodiments of the present invention that the method of the present invention can effectively improve the flexibility and efficiency of power quality control and meet the needs of modern power systems by combining VSG technology with UPQC (Unified Power Quality Conditioner). In particular, it can make adjustment responses faster when facing power grid fluctuations or load changes. This flexible power regulation capability not only improves the voltage regulation performance of the system, but also effectively copes with frequency changes and load fluctuations in the power grid.

[0033] Additional aspects and advantages of the present invention will be given in part in the following description, which will become obvious from the following description, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0035] Figure 1 This is a circuit schematic diagram of a unified power quality controller with inertia support and frequency modulation capabilities according to the present invention.

[0036] Figure 2 This is the single-phase single-wire topology structure described in the embodiment of the present invention.

[0037] Figure 3 The series compensation module described in the embodiment of the present invention adopts a three-phase three-wire topology structure in the form of a three-phase commutation bridge.

[0038] Figure 4 The series compensation module described in the embodiment of the present invention adopts a three-phase three-wire topology structure in the form of three single-phase commutation bridges.

[0039] Figure 5 The series compensation module described in the embodiment of the present invention adopts a three-phase commutation bridge form, and the parallel compensation module adopts a three-phase four-wire topology structure in the form of four bridge arms.

[0040] Figure 6 The series compensation module described in the embodiment of the present invention adopts a three-phase commutation bridge form, and the parallel compensation module adopts a three-phase four-wire topology structure in the form of a split capacitor.

[0041] Figure 7 The series compensation module described in the embodiment of the present invention adopts three single-phase commutation bridges, and the parallel compensation module adopts a three-phase four-wire topology structure in the form of four bridge arms.

[0042] Figure 8 The series compensation module described in the embodiment of the present invention adopts a three-phase four-wire topology structure in the form of three single-phase commutation bridges, and the parallel compensation module adopts a three-phase four-wire topology structure in the form of split capacitors.

[0043] Fig. 9 This is the control strategy of the virtual synchronous generator described in the embodiment of the present invention. DETAILED DESCRIPTION

[0044] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0045] It will be understood by those skilled in the art that, unless expressly stated, the singular forms "one", "said", and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. In addition, the "connection" or "coupling" used herein may include wireless connection or coupling. The term "and / or" used herein includes any unit and all combinations of one or more associated listed items.

[0046] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0047] To facilitate understanding of the embodiments of the present invention, several specific embodiments will be further explained below with reference to the accompanying drawings, and each embodiment does not constitute a limitation on the embodiments of the present invention.

[0048] The embodiment of the present invention provides a unified power quality controller with inertia support and frequency modulation capabilities, and its circuit schematic diagram is as follows: Figure 1 As shown, it includes: a parallel compensation module, a series compensation module and a power control inductor L1. The parallel compensation module is composed of a power converter, a filter inductor, a filter capacitor and an isolation transformer, and can be equivalent to a parallel voltage source U p The series compensation module is composed of a power converter, a filter inductor, a filter capacitor and an isolation transformer, and can be equivalent to an equivalent series voltage source U s ; Series voltage source U s One end of the grid voltage source U g One end is connected to the series voltage source U s The other end of the power control inductor L1 is connected to one end of the power control inductor L1, and the other end of the power control inductor L1 is connected to the parallel voltage source U p One end is connected to the parallel voltage source U p The other end is connected to the grid voltage source U g The other end of the load is connected to the equivalent current source I L Connected in parallel with the parallel voltage source Up superior.

[0049] The control principle mainly includes parallel voltage source control and series voltage source control. The parallel voltage source U p The active power is controlled by controlling the phase angle difference of the voltage across the power control inductor L1 to protect the parallel voltage source U p Parallel critical load, control parallel voltage source U p The amplitude of the capacitor is kept constant, thereby improving the voltage quality of the key load connected in parallel with the capacitor; the series voltage source U s The power control inductor L1 controls the voltage amplitude difference across the two ends to control the reactive power; the series voltage source U s The given value is the difference between the reference voltage and the grid voltage, which is formed by integrating the amplitude generated by the reactive power control of the virtual synchronous generator and the grid voltage phase; the parallel voltage source U p The voltage amplitude is the rated value of the load voltage, and the phase is the phase generated by the active power control of the virtual synchronous generator.

[0050] The single-phase single-wire system of the unified power quality controller with inertia support and frequency regulation capability is composed of a parallel compensation module, a series compensation module and a second filter inductor L2 for power control, such as Figure 2As shown; the parallel compensation module is composed of a first inverter INV1, a first filter inductor L1 and a first filter capacitor C1; the series compensation module is composed of a second inverter INV2, a third filter inductor L3, a first single-phase transformer T1 and a second filter capacitor C2; one end of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form a first AC connection point AC1, and the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form a third AC connection point AC3, and the third AC connection point AC3 is connected to the negative The other end of the load is connected to one end of the first filter capacitor C1 to form a second AC connection point AC2, the other end of the AC output end of the first inverter INV1 is connected to the second AC connection point AC2, the second AC connection point AC2 is connected to one end of the single-phase power grid, the other end of the single-phase power grid is connected to one end of the primary side of the first single-phase transformer T1 to form a fourth AC connection point AC4, the other end of the primary side of the first single-phase transformer T1 is connected to one end of the second filter inductor L2 to form a fifth AC connection point AC5, the second filter The other end of the wave inductor L2 is connected to the third AC connection point AC3; one end of the AC connection point of the second inverter INV2 is connected to one end of the third filter inductor L3 to form a sixth AC connection point AC6, the other end of the third filter inductor L3 is connected to one end of the secondary side of the first single-phase transformer T1 to form a seventh AC connection point AC7, and the other end of the AC connection point of the second inverter INV2 is connected to the other end of the secondary side of the first single-phase transformer T1 to form an eighth AC connection point AC8; the two ends of the second filter capacitor C2 are respectively connected to the fourth AC Connection point AC4 and the fifth AC connection point AC5 or the seventh AC connection point AC7 and the eighth AC connection point AC8; the high voltage end of the DC output end of the first inverter INV1 is connected to the high voltage end of the DC output end of the second inverter INV2 to form a first DC connection point DC1, the low voltage end of the DC output end of the first inverter INV1 is connected to the low voltage end of the DC output end of the second inverter INV2 to form a second DC connection point DC2, and the two ends of the third filter capacitor C3 are respectively connected to the first DC output point DC1 and the second DC output point DC2.

[0051] The control design method of the single-phase single-wire system specifically includes parallel compensation module control and series compensation module control; the phase difference of the voltage across the second filter inductor L2 determines the active power of the current flowing through the second filter inductor L2, and the amplitude difference of the voltage across the second filter inductor L2 determines the reactive power of the current flowing through the second filter inductor L2; the potential difference between the fifth AC connection point AC5 and the second AC connection point AC2 is the first voltage U1, and the potential difference between the third AC connection point AC3 and the second AC connection point AC2 is the second voltage U2. The grid-connected active power is achieved by controlling the phase difference between the first voltage U1 and the second voltage U2, and the phase difference is achieved by adjusting the phase of the second voltage U2, and the given value of the phase of the second voltage U2 is generated by the active power control of the virtual synchronous generator; since the load voltage is the same as the second voltage U2, in order to protect the load and maintain the load terminal voltage at the rated value, the given value of the amplitude of the second voltage U2 is set to the rated value of the load voltage amplitude; the given value of the amplitude and phase of the second voltage U2 can be integrated to obtain the given value of the second voltage U2, and the second voltage U2 is the output voltage of the parallel compensation module (that is, the voltage across the first filter capacitor C1 of the parallel compensation module), so the given value of the output voltage of the parallel compensation module is the given value of the second voltage U2. The difference in amplitude between the first voltage U1 and the second voltage U2 determines the reactive power of the current flowing through the second filter inductor L2. Since the first voltage U1 is equal to the sum of the grid voltage and the output voltage of the series compensation module, and the amplitude of the second voltage U2 is controlled to keep the load voltage rating unchanged, the amplitude of the first voltage U1 is controlled by controlling the output voltage of the series compensation module, thereby controlling the amplitude difference between the first voltage U1 and the second voltage U2, and further controlling the reactive power of the current flowing through the second filter inductor L2. In order to minimize the amplitude of the output voltage of the series compensation module, the given value of the phase of the first voltage U1 is the same as that of the grid. The amplitude of the first voltage U1 is generated by the reactive control of the virtual synchronous generator. The given value of the first voltage U1 can be obtained by integrating the given values ​​of the amplitude and phase of the first voltage U1. The given value of the output voltage of the series compensation module (i.e., the voltage across the primary side of the first single-phase transformer T1 in the series compensation module) is the difference between the given value of the first voltage and the grid voltage. When the grid frequency fluctuates, the virtual synchronous generator control can enable the unified power quality controller to respond to changes in the grid frequency and adjust the active power output through the parallel compensation module to help maintain the stability of the grid frequency; the series compensation module further stabilizes the grid voltage and improves the power quality by adjusting the reactive power.

[0052] The three-phase three-wire system of the unified power quality controller with inertia support and frequency modulation capability is composed of a parallel compensation module, a series compensation module and a seventh filter inductor L7, an eighth filter inductor L8 and a ninth filter inductor L9 for power control; wherein the series compensation module can be in two forms: a three-phase commutation bridge form (such as Figure 3As shown) and three single-phase commutation bridge forms (as Figure 4 As shown), the parallel compensation module uses an inverter module consisting of a three-phase commutation bridge (as shown Figure 3 , Figure 4 shown).

[0053] like Figure 3 , Figure 4 As shown, the parallel compensation module is composed of a first inverter INV1, a first filter inductor L1, a second filter inductor L2, a third filter inductor L3, a first filter capacitor C1, a second filter capacitor C2 and a third filter capacitor C3. The first phase of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form a first connection point a1 of the a phase, and the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form a second connection point a2 of the a phase. The a phase second connection point a2 is connected to the first phase of the load; the second phase of the AC output end of the first inverter INV1 is connected to one end of the second filter inductor L2 to form a b phase. A connection point b1, the other end of the second filter inductor L2 is connected to one end of the second filter capacitor C2 to form a b-phase second connection point b2, and the b-phase second connection point b2 is connected to the second phase of the load; the third phase of the AC output end of the first inverter INV1 is connected to one end of the third filter inductor L3 to form a c-phase first connection point c1, the other end of the third filter inductor L3 is connected to one end of the third filter capacitor C3 to form a c-phase second connection point c2, and the c-phase second connection point c2 is connected to the third phase of the load; the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are connected to each other to form a first AC output terminal AC1.

[0054] like Figure 3As shown, a series compensation module in the form of a three-phase commutation bridge is composed of a second three-phase inverter INV2, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6; the first phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fourth filter inductor L4 to form the a-phase third connection point a3, and the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form the a-phase fourth connection point a4; the second phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fifth filter inductor L5 to form the b-phase third connection point b3, and the other end of the fifth filter inductor L5 is connected to the second single-phase transformer T1. One end of the secondary side of the transformer T2 constitutes the fourth connection point b4 of the b phase; the third phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the sixth filter inductor L6 to constitute the third connection point c3 of the c phase, and the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to constitute the fourth connection point c4 of the c phase; the other ends of the secondary sides of the first single-phase transformer T1, the second single-phase transformer T2, and the third single-phase transformer T3 are connected to each other to form the second AC output terminal AC2; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the first single-phase transformer T1, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the second single-phase transformer T2, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the third single-phase transformer T3.

[0055] like Figure 4As shown, the series compensation module in the form of three single-phase commutation bridges is composed of a second single-phase inverter INV2, a third single-phase inverter INV3, a fourth single-phase inverter INV4, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6. One end of the AC output end of the second single-phase inverter INV2 is connected to the fourth filter inductor L4 to form the a-phase third connection point a3, the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form the a-phase fourth connection point a4, the other end of the AC output end of the second single-phase inverter INV2 is connected to the other end of the secondary side of the first single-phase transformer T1 to form the a-phase seventh connection point a7; one end of the AC output end of the third single-phase inverter INV3 is connected to one end of the fifth filter inductor L5 to form the b-phase third connection point b3, the fifth filter inductor L5 is connected to the sixth filter capacitor C6, and the fifth filter capacitor C6 is connected to the sixth filter capacitor C6. The other end of the AC output end of the third single-phase inverter INV3 is connected to one end of the secondary side of the second single-phase transformer T2 to form the fourth connection point b4 of the b phase, and the other end of the AC output end of the third single-phase inverter INV3 is connected to the other end of the secondary side of the second single-phase transformer T2 to form the seventh connection point b7 of the b phase; one end of the AC output end of the fourth single-phase inverter INV4 is connected to one end of the sixth filter inductor L6 to form the third connection point c3 of the c phase, the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to form the fourth connection point c4 of the c phase, and the other end of the AC output end of the fourth single-phase inverter INV4 is connected to the other end of the secondary side of the third single-phase transformer T3 to form the seventh connection point c7 of the c phase; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the first single-phase transformer T1, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the second single-phase transformer T2, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the third single-phase transformer T3.

[0056] One end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to the first phase of the power grid to form the fifth connection point a5 of the a phase, the other end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to one end of the seventh filter inductor L7 to form the sixth connection point a6 of the a phase, and the other end of the seventh filter inductor L7 is connected to the second connection point a2 of the a phase; one end of the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b5 of the b phase, and the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b6 of the b phase. The other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the eighth filter inductor L8 to form the sixth connection point b6 of phase b, and the other end of the eighth filter inductor L8 is connected to the second connection point b2 of phase b; one end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to the third phase of the power grid to form the fifth connection point c5 of phase c, the other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the ninth filter inductor L9 to form the sixth connection point c6 of phase c, and the other end of the ninth filter inductor L9 is connected to the second connection point c2 of phase c.

[0057] The high voltage end of the DC output end of the parallel inverter module is connected to the high voltage end of the DC output end of the series inverter module to form a first DC connection point DC1, the low voltage end of the DC output end of the parallel inverter module is connected to the low voltage end of the DC output end of the series inverter module to form a second DC connection point DC2, and the two ends of the seventh filter capacitor C7 are respectively connected to the first DC output point DC1 and the second DC output point DC2.

[0058] The control design method for the three-phase three-wire system specifically includes parallel compensation module control and series compensation module control. The phase angle difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the active power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9, and the amplitude difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9; the potential difference between the sixth AC connection point a6 of the a phase and the first AC output terminal AC1 is the first voltage U1 , the potential difference between the second AC connection point a2 of phase a and the first AC output terminal AC1 is the second voltage U2; the potential difference between the sixth AC connection point b6 of phase b and the first AC output terminal AC1 is the third voltage U3, and the potential difference between the second AC connection point b2 of phase b and the first AC output terminal AC1 is the fourth voltage U4; the potential difference between the sixth AC connection point c6 of phase c and the first AC output terminal AC1 is the fifth voltage U5, and the potential difference between the second AC connection point c2 of phase c and the first AC output terminal AC1 is the sixth voltage U6.

[0059] The grid-connected active power is realized by controlling the phase difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6, and the phase difference is realized by adjusting the phase of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively, and the given values ​​of the phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are generated by the active power control of the virtual synchronous generator; since the three-phase voltages of the load voltage are respectively the same as the second voltage U2, the fourth voltage U4 and the sixth voltage U6, in order to protect the load and maintain the load terminal voltage at the rated value, the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are respectively The given values ​​of the amplitudes of the second voltage U4 and the sixth voltage U6 are set to the rated value of the load voltage amplitude; the given values ​​of the amplitudes and phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 can be integrated respectively to obtain the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6, and the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are the three-phase output voltages of the parallel compensation module (that is, the voltages across the first filter capacitor C1, the second filter capacitor C2 and the third filter capacitor C3 of the parallel compensation module), so the given values ​​of the three-phase output voltage of the parallel compensation module are the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively.

[0060] The grid-connected reactive power is realized by controlling the amplitude difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6. Since the first voltage U1 is equal to the sum of the first phase voltage of the power grid and the first phase output voltage of the series compensation module, the third voltage U3 is equal to the sum of the second phase voltage of the power grid and the second phase output voltage of the series compensation module, and the fifth voltage U5 is equal to the sum of the third phase voltage of the power grid and the third phase output voltage of the series compensation module, and the amplitudes of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are controlled to keep the load voltage rating unchanged, the amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled by controlling the output voltage of the series compensation module, thereby controlling the amplitude difference between the first voltage U1 and the second voltage U2, the third voltage U3 and the fourth voltage U4, and the fifth voltage U5 and the sixth voltage U6, and then respectively controlling the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9; in order to minimize the amplitude of the output voltage of the series compensation module, the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled to keep the load voltage rating unchanged. The given values ​​of the phases of U3 and the fifth voltage U5 are the same as those of the power grid. The amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are generated by the reactive power control of the virtual synchronous generator. The given values ​​of the amplitudes and phases of the first voltage U1, the third voltage U3 and the fifth voltage U5 can be integrated to obtain the given values ​​of the first voltage U1, the third voltage U3 and the fifth voltage U5. The given value of the first phase output voltage of the series compensation module (i.e., the voltage across the primary side of the first single-phase transformer T1 in the series compensation module) is the difference between the given value of the first voltage U1 and the power grid voltage. The given value of the second phase output voltage of the series compensation module (i.e., the voltage across the primary side of the second single-phase transformer T2 in the series compensation module) is the difference between the given value of the third voltage U3 and the power grid voltage. The given value of the third phase output voltage of the series compensation module (i.e., the voltage across the primary side of the third single-phase transformer T3 in the series compensation module) is the difference between the given value of the first voltage U1 and the power grid voltage.

[0061] When the grid frequency fluctuates, the virtual synchronous generator control can enable the unified power quality controller to respond to changes in the grid frequency and adjust the active power output through the parallel compensation module to help maintain the stability of the grid frequency; the series compensation module further stabilizes the grid voltage and improves the power quality by adjusting the reactive power.

[0062] The three-phase four-wire system of the unified power quality controller with inertia support and frequency modulation capability is composed of a parallel compensation module, a series compensation module and a seventh filter inductor L7, an eighth filter inductor L8 and a ninth filter inductor L9 for power control, such as Figure 5-Figure 8 As shown; the series compensation module can take two forms: three single-phase commutation bridges and one three-phase commutation bridge, and the parallel compensation module can take two forms: four-bridge arm form and split capacitor form.

[0063] like Figure 7 and Figure 8 As shown, the series compensation module in the form of three single-phase commutation bridges is composed of a second single-phase inverter INV2, a third single-phase inverter INV3, a fourth single-phase inverter INV4, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6. One end of the AC output end of the second single-phase inverter INV2 is connected to the fourth filter inductor L4 to form the a-phase third connection point a3, the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form the a-phase fourth connection point a4, the other end of the AC output end of the second single-phase inverter INV2 is connected to the other end of the secondary side of the first single-phase transformer T1 to form the a-phase seventh connection point a7; one end of the AC output end of the third single-phase inverter INV3 is connected to one end of the fifth filter inductor L5 to form the b-phase third connection point b3, the fifth filter inductor L5 is connected to the sixth filter capacitor C6, and the fifth filter capacitor C6 is connected to the sixth filter capacitor C6. The other end of the AC output end of the third single-phase inverter INV3 is connected to one end of the secondary side of the second single-phase transformer T2 to form the fourth connection point b4 of the b phase, and the other end of the AC output end of the third single-phase inverter INV3 is connected to the other end of the secondary side of the second single-phase transformer T2 to form the seventh connection point b7 of the b phase; one end of the AC output end of the fourth single-phase inverter INV4 is connected to one end of the sixth filter inductor L6 to form the third connection point c3 of the c phase, the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to form the fourth connection point c4 of the c phase, and the other end of the AC output end of the fourth single-phase inverter INV4 is connected to the other end of the secondary side of the third single-phase transformer T3 to form the seventh connection point c7 of the c phase; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the first single-phase transformer T1, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the second single-phase transformer T2, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the third single-phase transformer T3.

[0064] like Figure 5 and Figure 6As shown, a series compensation module in the form of a three-phase commutation bridge is composed of a second three-phase inverter INV2, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6; the first phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fourth filter inductor L4 to form the a-phase third connection point a3, and the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form the a-phase fourth connection point a4; the second phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fifth filter inductor L5 to form the b-phase third connection point b3, and the other end of the fifth filter inductor L5 is connected to one end of the secondary side of the second single-phase transformer T2 The third phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the sixth filter inductor L6 to form the third connection point c3 of the c phase, and the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to form the fourth connection point c4 of the c phase; the other ends of the secondary sides of the first single-phase transformer T1, the second single-phase transformer T2, and the third single-phase transformer T3 are connected to each other to form the second AC output terminal AC2, and the second AC output terminal AC2 is connected to the neutral line; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the first single-phase transformer T1, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the second single-phase transformer T2, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the third single-phase transformer T3.

[0065] One end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to the first phase of the power grid to form the fifth connection point a5 of the a phase, the other end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to one end of the seventh filter inductor L7 to form the sixth connection point a6 of the a phase, and the other end of the seventh filter inductor L7 is connected to the second connection point a2 of the a phase; one end of the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b5 of the b phase, and the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b6 of the b phase. The other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the eighth filter inductor L8 to form the sixth connection point b6 of phase b, and the other end of the eighth filter inductor L8 is connected to the second connection point b2 of phase b; one end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to the third phase of the power grid to form the fifth connection point c5 of phase c, the other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the ninth filter inductor L9 to form the sixth connection point c6 of phase c, and the other end of the ninth filter inductor L9 is connected to the second connection point c2 of phase c.

[0066] like Figure 5 and Figure 7As shown, the parallel compensation module in the form of four bridge arms is composed of a first inverter INV1, a first filter inductor L1, a second filter inductor L2, a third filter inductor L3, a tenth filter inductor L 10 , a first filter capacitor C1, a second filter capacitor C2 and a third filter capacitor C3, the first inverter INV1 uses an additional branch (a fourth half-bridge inverter), the first phase of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form a first connection point a1 of the a phase, the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form a second connection point a2 of the a phase, and the a phase second connection point a2 is connected to the first phase of the load; the second phase of the AC output end of the first inverter INV1 is connected to one end of the second filter inductor L2 to form a b phase The first inverter INV1 has a first connection point b1, and the other end of the second filter inductor L2 is connected to one end of the second filter capacitor C2 to form a second connection point b2 of the b phase, and the second connection point b2 of the b phase is connected to the second phase of the load; the third phase of the AC output end of the first inverter INV1 is connected to one end of the third filter inductor L3 to form a first connection point c1 of the c phase, and the other end of the third filter inductor L3 is connected to one end of the third filter capacitor C3 to form a second connection point c2 of the c phase, and the second connection point c2 of the c phase is connected to the third phase of the load; the additional branch of the AC output end of the first inverter INV1 is connected to the tenth filter inductor L 10 One end of the N-phase first connection point n1, the tenth filter inductor L 10 The other end of the first filter capacitor C1 is connected to the neutral line to form the N-phase second connection point n2; the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are connected to each other to form the first AC output terminal AC1, and the first AC output terminal AC1 is connected to the N-phase second connection point n2; the high-voltage end of the DC output end of the first inverter INV1 is connected to the high-voltage end of the DC output end of the series inverter module to form a first DC connection point DC1, and the low-voltage end of the DC output end of the first inverter INV1 is connected to the low-voltage end of the DC output end of the series inverter module to form a second DC connection point DC2, and the two ends of the seventh filter capacitor C7 are respectively connected to the first DC output point DC1 and the second DC output point DC2.

[0067] like Figure 6 and Figure 8As shown, the parallel compensation module in the form of a split capacitor is composed of a first inverter INV1, a first filter inductor L1, a second filter inductor L2, a third filter inductor L3, a first filter capacitor C1, a second filter capacitor C2 and a third filter capacitor C3. The first phase of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form the first connection point a1 of the a phase, and the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form the second connection point a2 of the a phase, and the second connection point a2 of the a phase is connected to the first phase of the load; the second phase of the AC output end of the first inverter INV1 is connected to one end of the second filter inductor L2 to form the first connection point b1 of the b phase, and the other end of the second filter inductor L2 is connected to one end of the second filter capacitor C2 to form the second connection point b2 of the b phase, and the second connection point b2 of the b phase is connected to the second phase of the load; the third phase of the AC output end of the first inverter INV1 is connected to one end of the third filter inductor L3 to form the first connection point of the c phase c1, the other end of the third filter inductor L3 is connected to one end of the third filter capacitor C3 to form the second connection point c2 of the c phase, and the second connection point c2 of the c phase is connected to the third phase of the load; the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are connected to each other to form the first AC output terminal AC1, and the first AC output terminal AC1 is connected to the neutral line; the high voltage end of the DC output end of the first inverter INV1 is connected to the high voltage end of the DC output end of the series inverter module to form the first DC connection point DC1, the low voltage end of the DC output end of the first inverter INV1 is connected to the low voltage end of the DC output end of the series inverter module to form the second DC connection point DC2, one end of the seventh filter capacitor C7 is connected to the first DC output point DC1, one end of the eighth filter capacitor C8 is connected to the second DC output point DC2, the other ends of the seventh filter capacitor C7 and the eighth filter capacitor C8 are connected to each other to form the N phase first connection point n1, and the N phase first connection point n1 is connected to the neutral line.

[0068] The control design method for the three-phase four-wire system specifically includes parallel compensation module control and series compensation module control. The phase angle difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the active power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9, and the amplitude difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9; the potential difference between the sixth AC connection point a6 of the a phase and the first AC output terminal AC1 is the first voltage U1 , the potential difference between the second AC connection point a2 of phase a and the first AC output terminal AC1 is the second voltage U2; the potential difference between the sixth AC connection point b6 of phase b and the first AC output terminal AC1 is the third voltage U3, and the potential difference between the second AC connection point b2 of phase b and the first AC output terminal AC1 is the fourth voltage U4; the potential difference between the sixth AC connection point c6 of phase c and the first AC output terminal AC1 is the fifth voltage U5, and the potential difference between the second AC connection point c2 of phase c and the first AC output terminal AC1 is the sixth voltage U6.

[0069] The grid-connected active power is realized by controlling the phase difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6, and the phase difference is realized by adjusting the phase of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively, and the given values ​​of the phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are generated by the active power control of the virtual synchronous generator; since the three-phase voltages of the load voltage are respectively the same as the second voltage U2, the fourth voltage U4 and the sixth voltage U6, in order to protect the load and maintain the load terminal voltage at the rated value, the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are respectively The given values ​​of the amplitudes of the second voltage U4 and the sixth voltage U6 are set to the rated value of the load voltage amplitude; the given values ​​of the amplitudes and phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 can be integrated respectively to obtain the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6, and the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are the three-phase output voltages of the parallel compensation module (that is, the voltages across the first filter capacitor C1, the second filter capacitor C2 and the third filter capacitor C3 of the parallel compensation module), so the given values ​​of the three-phase output voltage of the parallel compensation module are the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively.

[0070] The grid-connected reactive power is realized by controlling the amplitude difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6. Since the first voltage U1 is equal to the sum of the first phase voltage of the power grid and the first phase output voltage of the series compensation module, the third voltage U3 is equal to the sum of the second phase voltage of the power grid and the second phase output voltage of the series compensation module, and the fifth voltage U5 is equal to the sum of the third phase voltage of the power grid and the third phase output voltage of the series compensation module, and the amplitudes of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are controlled to keep the load voltage rating unchanged, the amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled by controlling the output voltage of the series compensation module, thereby controlling the amplitude difference between the first voltage U1 and the second voltage U2, the third voltage U3 and the fourth voltage U4, and the fifth voltage U5 and the sixth voltage U6, and then respectively controlling the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9; in order to minimize the amplitude of the output voltage of the series compensation module, the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled to keep the load voltage rating unchanged. The given values ​​of the phases of U3 and the fifth voltage U5 are the same as those of the power grid. The amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are generated by the reactive power control of the virtual synchronous generator. The given values ​​of the amplitudes and phases of the first voltage U1, the third voltage U3 and the fifth voltage U5 can be integrated to obtain the given values ​​of the first voltage U1, the third voltage U3 and the fifth voltage U5. The given value of the first phase output voltage of the series compensation module (i.e., the voltage across the primary side of the first single-phase transformer T1 in the series compensation module) is the difference between the given value of the first voltage U1 and the power grid voltage. The given value of the second phase output voltage of the series compensation module (i.e., the voltage across the primary side of the second single-phase transformer T2 in the series compensation module) is the difference between the given value of the third voltage U3 and the power grid voltage. The given value of the third phase output voltage of the series compensation module (i.e., the voltage across the primary side of the third single-phase transformer T3 in the series compensation module) is the difference between the given value of the first voltage U1 and the power grid voltage.

[0071] When the grid frequency fluctuates, the virtual synchronous generator control can enable the unified power quality controller to respond to changes in the grid frequency and adjust the active power output through the parallel compensation module to help maintain the stability of the grid frequency; the series compensation module further stabilizes the grid voltage and improves the power quality by adjusting the reactive power.

[0072] Example 1

[0073] This embodiment describes a single-phase single-wire unified power quality controller system with inertia support and frequency modulation capabilities, such as Figure 2 As shown, it aims to improve the power quality and solve problems such as low power factor and power loss.

[0074] The topological structure of the single-phase single-wire system consists of a series compensation module, a parallel compensation module and a power control inductor L2.

[0075] The parallel compensation module is composed of a first inverter INV1, a first filter inductor L1 and a first filter capacitor C1; the series compensation module is composed of a second inverter INV2, a third filter inductor L3, a first single-phase transformer T1 and a second filter capacitor C2.

[0076] One end of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form a first AC connection point AC1, the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form a third AC connection point AC3, the third AC connection point AC3 is connected to one end of the load, the other end of the load is connected to the other end of the first filter capacitor C1 to form a second AC connection point AC2, the other end of the AC output end of the first inverter INV1 is connected to the second AC connection point AC2, the second AC connection point AC2 is connected to one end of the single-phase power grid, the other end of the single-phase power grid is connected to one end of the primary side of the first single-phase transformer T1 to form a fourth AC connection point AC4, the other end of the primary side of the first single-phase transformer T1 is connected to one end of the second filter inductor L2 to form a fifth AC connection point AC5, the other end of the second filter inductor L2 is connected to the third AC connection point AC3; one end of the AC connection point of the second inverter INV2 is connected to the third One end of the filter inductor L3 is connected to form a sixth AC connection point AC6, the other end of the third filter inductor L3 is connected to one end of the secondary side of the first single-phase transformer T1 to form a seventh AC connection point AC7, and the other end of the AC connection point of the second inverter INV2 is connected to the other end of the secondary side of the first single-phase transformer T1 to form an eighth AC connection point AC8; the two ends of the second filter capacitor C2 are respectively connected to the fourth AC connection point AC4 and the fifth AC connection point AC5 or the seventh AC connection point AC7 and the eighth AC connection point AC8; the high voltage end of the DC output end of the first inverter INV1 is connected to the high voltage end of the DC output end of the second inverter INV2 to form a first DC connection point DC1, the low voltage end of the DC output end of the first inverter INV1 is connected to the low voltage end of the DC output end of the second inverter INV2 to form a second DC connection point DC2, and the two ends of the third filter capacitor C3 are respectively connected to the first DC output point DC1 and the second DC output point DC2.

[0077] The control design method specifically includes parallel compensation module control and series compensation module control; the phase difference of the voltage across the second filter inductor L2 determines the active power of the current flowing through the second filter inductor L2, and the amplitude difference of the voltage across the second filter inductor L2 determines the reactive power of the current flowing through the second filter inductor L2; the potential difference between the fifth AC connection point AC5 and the second AC connection point AC2 is the first voltage U1, and the potential difference between the third AC connection point AC3 and the second AC connection point AC2 is the second voltage U2.

[0078] The grid-connected active power is achieved by controlling the phase difference between the first voltage U1 and the second voltage U2, and the phase difference is achieved by adjusting the phase of the second voltage U2, and the given value of the phase of the second voltage U2 is generated by the active power control of the virtual synchronous generator; since the load voltage is the same as the second voltage U2, in order to protect the load and maintain the load terminal voltage at the rated value, the given value of the amplitude of the second voltage U2 is set to the rated value of the load voltage amplitude; the given value of the amplitude and phase of the second voltage U2 can be integrated to obtain the given value of the second voltage U2, and the second voltage U2 is the output voltage of the parallel compensation module (that is, the voltage across the first filter capacitor C1 of the parallel compensation module), so the given value of the output voltage of the parallel compensation module is the given value of the second voltage U2.

[0079] The difference in amplitude between the first voltage U1 and the second voltage U2 determines the reactive power of the current flowing through the second filter inductor L2. Since the first voltage U1 is equal to the sum of the grid voltage and the output voltage of the series compensation module, and the amplitude of the second voltage U2 is controlled to keep the load voltage rating unchanged, the amplitude of the first voltage U1 is controlled by controlling the output voltage of the series compensation module, thereby controlling the amplitude difference between the first voltage U1 and the second voltage U2, and further controlling the reactive power of the current flowing through the second filter inductor L2. In order to minimize the amplitude of the output voltage of the series compensation module, the given value of the phase of the first voltage U1 is the same as that of the grid. The amplitude of the first voltage U1 is generated by the reactive control of the virtual synchronous generator. The given value of the first voltage U1 can be obtained by integrating the given values ​​of the amplitude and phase of the first voltage U1. The given value of the output voltage of the series compensation module (i.e., the voltage across the primary side of the first single-phase transformer T1 in the series compensation module) is the difference between the given value of the first voltage and the grid voltage.

[0080] The control strategy of virtual synchronous generator is as follows Fig. 9 As shown, P ref is the given value of active power, P e is the actual value of active power, J is the moment of inertia, D P is the damping coefficient, ω g is the grid angular frequency, θ is the phase angle of the second voltage U2; first, the difference between the given value and the actual value of the active power is used as input and transferred to the grid frequency link, and its transfer function is The difference in active power is converted into a torque difference, and the torque difference and the virtual damping signal are input into the transfer function: The active inertia link outputs a frequency increment signal Δω, and the virtual damping signal is the virtual damping coefficient D p The virtual inertia link simulates the inertial characteristics of the system to frequency changes, helping the system to remain stable when the frequency fluctuates. The virtual damping link is used to increase the system damping, aiming to reduce oscillation and improve the stability of the system. n The phase angle of the second voltage U2 is generated by adding the phase angle of the second voltage U2 through the integral link. ref is the given value of reactive power, Q e is the actual value of reactive power, K q is the reactive power-voltage inertia coefficient. First, the difference between the given value and the actual value of reactive power is taken as input and input into the transfer function: The reactive inertia link outputs a voltage increment signal ΔE, a frequency increment signal ΔE and a rated amplitude U of the grid voltage. g Add together to generate the amplitude given value E of the first voltage U1 m In order to adjust the output of reactive power, thereby ensuring that the system can effectively respond to reactive power changes according to the needs of the power grid, the generated signal is subtracted from the grid voltage amplitude to obtain the final amplitude difference.

[0081] When the grid frequency fluctuates, the virtual synchronous generator control enables the unified power quality controller to respond to the change of grid frequency and adjust the active power output through the grid-connected compensation module to help maintain the stability of the grid frequency. The series compensation module further stabilizes the grid voltage and improves the power quality by adjusting the reactive power.

[0082] Example 2

[0083] The topology of a three-phase three-wire system using a three-phase commutation bridge is as follows: Figure 3 As shown, it is composed of a series compensation module, a parallel compensation module and a seventh filter inductor L7, an eighth filter inductor L8 and a ninth filter inductor L9 for power control.

[0084] The parallel compensation module is composed of a first inverter INV1, a first filter inductor L1, a second filter inductor L2, a third filter inductor L3, a first filter capacitor C1, a second filter capacitor C2 and a third filter capacitor C3. The first phase of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form a first connection point a1 of the a phase, and the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form a second connection point a2 of the a phase. The a phase second connection point a2 is connected to the first phase of the load; the second phase of the AC output end of the first inverter INV1 is connected to one end of the second filter inductor L2 to form a first connection point a1 of the b phase. Connection point b1, the other end of the second filter inductor L2 is connected to one end of the second filter capacitor C2 to form the b-phase second connection point b2, and the b-phase second connection point b2 is connected to the second phase of the load; the third phase of the AC output end of the first inverter INV1 is connected to one end of the third filter inductor L3 to form the c-phase first connection point c1, the other end of the third filter inductor L3 is connected to one end of the third filter capacitor C3 to form the c-phase second connection point c2, and the c-phase second connection point c2 is connected to the third phase of the load; the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are connected to each other to form the first AC output terminal AC1.

[0085] The series inverter module is composed of a second three-phase inverter INV2, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6; the first phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fourth filter inductor L4 to form the a-phase third connection point a3, and the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form the a-phase fourth connection point a4; the second phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fifth filter inductor L5 to form the b-phase third connection point b3, and the other end of the fifth filter inductor L5 is connected to one end of the secondary side of the second single-phase transformer T2. The third end of the AC output end of the second three-phase inverter INV2 is connected to one end of the sixth filter inductor L6 to form the third connection point c3 of the c phase, and the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to form the fourth connection point c4 of the c phase; the other ends of the secondary sides of the first single-phase transformer T1, the second single-phase transformer T2, and the third single-phase transformer T3 are connected to each other to form the second AC output terminal AC2; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the first single-phase transformer T1, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the second single-phase transformer T2, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the third single-phase transformer T3. One end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to the first phase of the power grid to form the fifth connection point a5 of the a phase, the other end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to one end of the seventh filter inductor L7 to form the sixth connection point a6 of the a phase, and the other end of the seventh filter inductor L7 is connected to the second connection point a2 of the a phase; one end of the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b5 of the b phase, and the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b6 of the b phase. The other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the eighth filter inductor L8 to form the sixth connection point b6 of phase b, and the other end of the eighth filter inductor L8 is connected to the second connection point b2 of phase b; one end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to the third phase of the power grid to form the fifth connection point c5 of phase c, the other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the ninth filter inductor L9 to form the sixth connection point c6 of phase c, and the other end of the ninth filter inductor L9 is connected to the second connection point c2 of phase c.

[0086] The high voltage end of the DC output end of the parallel inverter module is connected to the high voltage end of the DC output end of the series inverter module to form a first DC connection point DC1, the low voltage end of the DC output end of the parallel inverter module is connected to the low voltage end of the DC output end of the series inverter module to form a second DC connection point DC2, and the two ends of the seventh filter capacitor C7 are respectively connected to the first DC output point DC1 and the second DC output point DC2.

[0087] The control design method of the system specifically includes parallel compensation module control and series compensation module control. The phase angle difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the active power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9, and the amplitude difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9; the potential difference between the sixth AC connection point a6 of the a phase and the first AC output terminal AC1 is the first voltage U1 , the potential difference between the second AC connection point a2 of phase a and the first AC output terminal AC1 is the second voltage U2; the potential difference between the sixth AC connection point b6 of phase b and the first AC output terminal AC1 is the third voltage U3, and the potential difference between the second AC connection point b2 of phase b and the first AC output terminal AC1 is the fourth voltage U4; the potential difference between the sixth AC connection point c6 of phase c and the first AC output terminal AC1 is the fifth voltage U5, and the potential difference between the second AC connection point c2 of phase c and the first AC output terminal AC1 is the sixth voltage U6.

[0088] The grid-connected active power is realized by controlling the phase difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6, and the phase difference is realized by adjusting the phase of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively, and the given values ​​of the phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are generated by the active power control of the virtual synchronous generator; since the three-phase voltages of the load voltage are respectively the same as the second voltage U2, the fourth voltage U4 and the sixth voltage U6, in order to protect the load and maintain the load terminal voltage at the rated value, the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are respectively The given values ​​of the amplitudes of the second voltage U4 and the sixth voltage U6 are set to the rated value of the load voltage amplitude; the given values ​​of the amplitudes and phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 can be integrated respectively to obtain the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6, and the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are the three-phase output voltages of the parallel compensation module (that is, the voltages across the first filter capacitor C1, the second filter capacitor C2 and the third filter capacitor C3 of the parallel compensation module), so the given values ​​of the three-phase output voltage of the parallel compensation module are the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively.

[0089] The grid-connected reactive power is realized by controlling the amplitude difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6. Since the first voltage U1 is equal to the sum of the first phase voltage of the power grid and the first phase output voltage of the series compensation module, the third voltage U3 is equal to the sum of the second phase voltage of the power grid and the second phase output voltage of the series compensation module, and the fifth voltage U5 is equal to the sum of the third phase voltage of the power grid and the third phase output voltage of the series compensation module, and the amplitudes of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are controlled to keep the load voltage rating unchanged, the amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled by controlling the output voltage of the series compensation module, thereby controlling the amplitude difference between the first voltage U1 and the second voltage U2, the third voltage U3 and the fourth voltage U4, and the fifth voltage U5 and the sixth voltage U6, and then respectively controlling the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9; in order to minimize the amplitude of the output voltage of the series compensation module, the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled to keep the load voltage rating unchanged. The given values ​​of the phases of U3 and the fifth voltage U5 are the same as those of the power grid. The amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are generated by the reactive power control of the virtual synchronous generator. The given values ​​of the amplitudes and phases of the first voltage U1, the third voltage U3 and the fifth voltage U5 can be integrated to obtain the given values ​​of the first voltage U1, the third voltage U3 and the fifth voltage U5. The given value of the first phase output voltage of the series compensation module (i.e., the voltage across the primary side of the first single-phase transformer T1 in the series compensation module) is the difference between the given value of the first voltage U1 and the power grid voltage. The given value of the second phase output voltage of the series compensation module (i.e., the voltage across the primary side of the second single-phase transformer T2 in the series compensation module) is the difference between the given value of the third voltage U3 and the power grid voltage. The given value of the third phase output voltage of the series compensation module (i.e., the voltage across the primary side of the third single-phase transformer T3 in the series compensation module) is the difference between the given value of the first voltage U1 and the power grid voltage.

[0090] When the grid frequency fluctuates, the virtual synchronous generator control can enable the unified power quality controller to respond to changes in the grid frequency and adjust the active power output through the parallel compensation module to help maintain the stability of the grid frequency; the series compensation module further stabilizes the grid voltage and improves the power quality by adjusting the reactive power.

[0091] Example 3

[0092] The topology of a three-phase three-wire system using three single-phase commutation bridges is as follows: Figure 4 As shown, it is composed of a parallel compensation module, a series compensation module and a seventh filter inductor L7, an eighth filter inductor L8 and a ninth filter inductor L9 for power control.

[0093] The parallel compensation module is composed of a first inverter INV1, a first filter inductor L1, a second filter inductor L2, a third filter inductor L3, a first filter capacitor C1, a second filter capacitor C2 and a third filter capacitor C3. The first phase of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form a first connection point a1 of the a phase, and the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form a second connection point a2 of the a phase. The a phase second connection point a2 is connected to the first phase of the load; the second phase of the AC output end of the first inverter INV1 is connected to one end of the second filter inductor L2 to form a first connection point a1 of the b phase. Connection point b1, the other end of the second filter inductor L2 is connected to one end of the second filter capacitor C2 to form the b-phase second connection point b2, and the b-phase second connection point b2 is connected to the second phase of the load; the third phase of the AC output end of the first inverter INV1 is connected to one end of the third filter inductor L3 to form the c-phase first connection point c1, the other end of the third filter inductor L3 is connected to one end of the third filter capacitor C3 to form the c-phase second connection point c2, and the c-phase second connection point c2 is connected to the third phase of the load; the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are connected to each other to form the first AC output terminal AC1.

[0094] The series inverter module is composed of a second single-phase inverter INV2, a third single-phase inverter INV3, a fourth single-phase inverter INV4, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6. One end of the AC output end of the second single-phase inverter INV2 is connected to the fourth filter inductor L4 to form a third connection point a3 of the a phase, and the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form a fourth connection point a4 of the a phase. The other end of the AC output end of the second single-phase inverter INV2 is connected to the other end of the secondary side of the first single-phase transformer T1 to form a seventh connection point a7 of the a phase; one end of the AC output end of the third single-phase inverter INV3 is connected to one end of the fifth filter inductor L5 to form a third connection point b3 of the b phase, and the other end of the fifth filter inductor L5 is connected to the first One end of the secondary side of the second single-phase transformer T2 constitutes the fourth connection point b4 of the b phase, and the other end of the AC output end of the third single-phase inverter INV3 is connected to the other end of the secondary side of the second single-phase transformer T2 to constitute the seventh connection point b7 of the b phase; one end of the AC output end of the fourth single-phase inverter INV4 is connected to one end of the sixth filter inductor L6 to constitute the third connection point c3 of the c phase, the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to constitute the fourth connection point c4 of the c phase, and the other end of the AC output end of the fourth single-phase inverter INV4 is connected to the other end of the secondary side of the third single-phase transformer T3 to constitute the seventh connection point c7 of the c phase; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the first single-phase transformer T1, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the second single-phase transformer T2, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the third single-phase transformer T3.

[0095] One end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to the first phase of the power grid to form the fifth connection point a5 of the a phase, the other end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to one end of the seventh filter inductor L7 to form the sixth connection point a6 of the a phase, and the other end of the seventh filter inductor L7 is connected to the second connection point a2 of the a phase; one end of the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b5 of the b phase, and the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b6 of the b phase. The other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the eighth filter inductor L8 to form the sixth connection point b6 of phase b, and the other end of the eighth filter inductor L8 is connected to the second connection point b2 of phase b; one end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to the third phase of the power grid to form the fifth connection point c5 of phase c, the other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the ninth filter inductor L9 to form the sixth connection point c6 of phase c, and the other end of the ninth filter inductor L9 is connected to the second connection point c2 of phase c.

[0096] The high voltage end of the DC output end of the parallel inverter module is connected to the high voltage end of the DC output end of the series inverter module to form a first DC connection point DC1, the low voltage end of the DC output end of the parallel inverter module is connected to the low voltage end of the DC output end of the series inverter module to form a second DC connection point DC2, and the two ends of the seventh filter capacitor C7 are respectively connected to the first DC output point DC1 and the second DC output point DC2.

[0097] The control design method of the system specifically includes parallel compensation module control and series compensation module control. The phase angle difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the active power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9, while the amplitude difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9; the potential difference between the sixth AC connection point a6 of the a phase and the first AC output terminal AC1 is the first voltage U1 , the potential difference between the second AC connection point a2 of phase a and the first AC output terminal AC1 is the second voltage U2; the potential difference between the sixth AC connection point b6 of phase b and the first AC output terminal AC1 is the third voltage U3, and the potential difference between the second AC connection point b2 of phase b and the first AC output terminal AC1 is the fourth voltage U4; the potential difference between the sixth AC connection point c6 of phase c and the first AC output terminal AC1 is the fifth voltage U5, and the potential difference between the second AC connection point c2 of phase c and the first AC output terminal AC1 is the sixth voltage U6.

[0098] The grid-connected active power is realized by controlling the phase difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6, and the phase difference is realized by adjusting the phase of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively, and the given values ​​of the phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are generated by the active power control of the virtual synchronous generator; since the three-phase voltages of the load voltage are respectively the same as the second voltage U2, the fourth voltage U4 and the sixth voltage U6, in order to protect the load and maintain the load terminal voltage at the rated value, the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are respectively The given values ​​of the amplitudes of the second voltage U4 and the sixth voltage U6 are set to the rated value of the load voltage amplitude; the given values ​​of the amplitudes and phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 can be integrated respectively to obtain the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6, and the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are the three-phase output voltages of the parallel compensation module (that is, the voltages across the first filter capacitor C1, the second filter capacitor C2 and the third filter capacitor C3 of the parallel compensation module), so the given values ​​of the three-phase output voltage of the parallel compensation module are the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively.

[0099] The grid-connected reactive power is realized by controlling the amplitude difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6. Since the first voltage U1 is equal to the sum of the first phase voltage of the power grid and the first phase output voltage of the series compensation module, the third voltage U3 is equal to the sum of the second phase voltage of the power grid and the second phase output voltage of the series compensation module, and the fifth voltage U5 is equal to the sum of the third phase voltage of the power grid and the third phase output voltage of the series compensation module, and the amplitudes of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are controlled to keep the load voltage rating unchanged, the amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled by controlling the output voltage of the series compensation module, thereby controlling the amplitude difference between the first voltage U1 and the second voltage U2, the third voltage U3 and the fourth voltage U4, and the fifth voltage U5 and the sixth voltage U6, and then respectively controlling the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9; in order to minimize the amplitude of the output voltage of the series compensation module, the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled to keep the load voltage rating unchanged. The given values ​​of the phases of U3 and the fifth voltage U5 are the same as those of the power grid. The amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are generated by the reactive power control of the virtual synchronous generator. The given values ​​of the amplitudes and phases of the first voltage U1, the third voltage U3 and the fifth voltage U5 can be integrated to obtain the given values ​​of the first voltage U1, the third voltage U3 and the fifth voltage U5. The given value of the first phase output voltage of the series compensation module (i.e., the voltage across the primary side of the first single-phase transformer T1 in the series compensation module) is the difference between the given value of the first voltage U1 and the power grid voltage. The given value of the second phase output voltage of the series compensation module (i.e., the voltage across the primary side of the second single-phase transformer T2 in the series compensation module) is the difference between the given value of the third voltage U3 and the power grid voltage. The given value of the third phase output voltage of the series compensation module (i.e., the voltage across the primary side of the third single-phase transformer T3 in the series compensation module) is the difference between the given value of the first voltage U1 and the power grid voltage.

[0100] When the grid frequency fluctuates, the virtual synchronous generator control can enable the unified power quality controller to respond to changes in the grid frequency and adjust the active power output through the parallel compensation module to help maintain the stability of the grid frequency; the series compensation module further stabilizes the grid voltage and improves the power quality by adjusting the reactive power.

[0101] Example 4

[0102] This embodiment describes a unified power quality controller system with inertia support and frequency modulation capabilities, in which the series compensation module adopts a three-phase commutation bridge form, and the parallel compensation module adopts a three-phase four-wire topology structure in the form of four bridge arms, such as Figure 5 The system improves the power quality through series compensation modules and parallel compensation modules, provides voltage and frequency stability for the power grid, and provides protection for the load.

[0103] The topological structure of the three-phase four-wire system consists of a parallel compensation module, a series compensation module, and a seventh filter inductor L7, an eighth filter inductor L8, and a ninth filter inductor L9 for power control.

[0104] The series inverter module is composed of a second three-phase inverter INV2, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6; the first phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fourth filter inductor L4 to form a third connection point a3 of the a phase, and the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form a fourth connection point a4 of the a phase; the second phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fifth filter inductor L5 to form a third connection point b3 of the b phase, and the other end of the fifth filter inductor L5 is connected to one end of the secondary side of the second single-phase transformer T2 to form a fourth connection point b of the b phase. Point b4; the third phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the sixth filter inductor L6 to form the c-phase third connection point c3, and the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to form the c-phase fourth connection point c4; the other ends of the secondary sides of the first single-phase transformer T1, the second single-phase transformer T2, and the third single-phase transformer T3 are connected to each other to form the second AC output terminal AC2, and the second AC output terminal AC2 is connected to the neutral line; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the first single-phase transformer T1, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the second single-phase transformer T2, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the third single-phase transformer T3.

[0105] One end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to the first phase of the power grid to form the fifth connection point a5 of the a phase, the other end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to one end of the seventh filter inductor L7 to form the sixth connection point a6 of the a phase, and the other end of the seventh filter inductor L7 is connected to the second connection point a2 of the a phase; one end of the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b5 of the b phase, and the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b6 of the b phase. The other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the eighth filter inductor L8 to form the sixth connection point b6 of phase b, and the other end of the eighth filter inductor L8 is connected to the second connection point b2 of phase b; one end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to the third phase of the power grid to form the fifth connection point c5 of phase c, the other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the ninth filter inductor L9 to form the sixth connection point c6 of phase c, and the other end of the ninth filter inductor L9 is connected to the second connection point c2 of phase c.

[0106] The parallel compensation module is composed of a first inverter INV1, a first filter inductor L1, a second filter inductor L2, a third filter inductor L3, a tenth filter inductor L 10 , a first filter capacitor C1, a second filter capacitor C2 and a third filter capacitor C3, the first inverter INV1 uses an additional branch (a fourth half-bridge inverter), the first phase of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form a first connection point a1 of the a phase, the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form a second connection point a2 of the a phase, and the a phase second connection point a2 is connected to the first phase of the load; the second phase of the AC output end of the first inverter INV1 is connected to one end of the second filter inductor L2 to form a b phase The first inverter INV1 has a first connection point b1, and the other end of the second filter inductor L2 is connected to one end of the second filter capacitor C2 to form a second connection point b2 of the b phase, and the second connection point b2 of the b phase is connected to the second phase of the load; the third phase of the AC output end of the first inverter INV1 is connected to one end of the third filter inductor L3 to form a first connection point c1 of the c phase, and the other end of the third filter inductor L3 is connected to one end of the third filter capacitor C3 to form a second connection point c2 of the c phase, and the second connection point c2 of the c phase is connected to the third phase of the load; the additional branch of the AC output end of the first inverter INV1 is connected to the tenth filter inductor L 10 One end of the N-phase first connection point n1, the tenth filter inductor L 10The other end of the first filter capacitor C1 is connected to the neutral line to form the N-phase second connection point n2; the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are connected to each other to form the first AC output terminal AC1, and the first AC output terminal AC1 is connected to the N-phase second connection point n2; the high-voltage end of the DC output end of the first inverter INV1 is connected to the high-voltage end of the DC output end of the series inverter module to form a first DC connection point DC1, and the low-voltage end of the DC output end of the first inverter INV1 is connected to the low-voltage end of the DC output end of the series inverter module to form a second DC connection point DC2, and the two ends of the seventh filter capacitor C7 are respectively connected to the first DC output point DC1 and the second DC output point DC2.

[0107] The control design method of the system specifically includes parallel compensation module control and series compensation module control. The phase angle difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the active power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9, while the amplitude difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9; the potential difference between the sixth AC connection point a6 of the a phase and the first AC output terminal AC1 is the first voltage U1 , the potential difference between the second AC connection point a2 of phase a and the first AC output terminal AC1 is the second voltage U2; the potential difference between the sixth AC connection point b6 of phase b and the first AC output terminal AC1 is the third voltage U3, and the potential difference between the second AC connection point b2 of phase b and the first AC output terminal AC1 is the fourth voltage U4; the potential difference between the sixth AC connection point c6 of phase c and the first AC output terminal AC1 is the fifth voltage U5, and the potential difference between the second AC connection point c2 of phase c and the first AC output terminal AC1 is the sixth voltage U6.

[0108] The grid-connected active power is realized by controlling the phase difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6, and the phase difference is realized by adjusting the phase of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively, and the given values ​​of the phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are generated by the active power control of the virtual synchronous generator; since the three-phase voltages of the load voltage are respectively the same as the second voltage U2, the fourth voltage U4 and the sixth voltage U6, in order to protect the load and maintain the load terminal voltage at the rated value, the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are respectively The given values ​​of the amplitudes of the second voltage U4 and the sixth voltage U6 are set to the rated value of the load voltage amplitude; the given values ​​of the amplitudes and phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 can be integrated respectively to obtain the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6, and the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are the three-phase output voltages of the parallel compensation module (that is, the voltages across the first filter capacitor C1, the second filter capacitor C2 and the third filter capacitor C3 of the parallel compensation module), so the given values ​​of the three-phase output voltage of the parallel compensation module are the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively.

[0109] The grid-connected reactive power is realized by controlling the amplitude difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6. Since the first voltage U1 is equal to the sum of the first phase voltage of the power grid and the first phase output voltage of the series compensation module, the third voltage U3 is equal to the sum of the second phase voltage of the power grid and the second phase output voltage of the series compensation module, and the fifth voltage U5 is equal to the sum of the third phase voltage of the power grid and the third phase output voltage of the series compensation module, and the amplitudes of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are controlled to keep the load voltage rating unchanged, the amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled by controlling the output voltage of the series compensation module, thereby controlling the amplitude difference between the first voltage U1 and the second voltage U2, the third voltage U3 and the fourth voltage U4, and the fifth voltage U5 and the sixth voltage U6, and then respectively controlling the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9; in order to minimize the amplitude of the output voltage of the series compensation module, the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled to keep the load voltage rating unchanged. The given values ​​of the phases of U3 and the fifth voltage U5 are the same as those of the power grid. The amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are generated by the reactive power control of the virtual synchronous generator. The given values ​​of the amplitudes and phases of the first voltage U1, the third voltage U3 and the fifth voltage U5 can be integrated to obtain the given values ​​of the first voltage U1, the third voltage U3 and the fifth voltage U5. The given value of the first phase output voltage of the series compensation module (i.e., the voltage across the primary side of the first single-phase transformer T1 in the series compensation module) is the difference between the given value of the first voltage U1 and the power grid voltage. The given value of the second phase output voltage of the series compensation module (i.e., the voltage across the primary side of the second single-phase transformer T2 in the series compensation module) is the difference between the given value of the third voltage U3 and the power grid voltage. The given value of the third phase output voltage of the series compensation module (i.e., the voltage across the primary side of the third single-phase transformer T3 in the series compensation module) is the difference between the given value of the first voltage U1 and the power grid voltage.

[0110] When the grid frequency fluctuates, the virtual synchronous generator control can enable the unified power quality controller to respond to changes in the grid frequency and adjust the active power output through the parallel compensation module to help maintain the stability of the grid frequency; the series compensation module further stabilizes the grid voltage and improves the power quality by adjusting the reactive power.

[0111] Example 5

[0112] This embodiment describes a unified power quality controller system with inertia support and frequency modulation capability, in which the series compensation module adopts a three-phase commutation bridge form and the parallel compensation module adopts a split capacitor form. Figure 6 The system improves the power quality through series compensation modules and parallel compensation modules, provides voltage and frequency stability for the power grid, and provides protection for the load.

[0113] The topological structure of the three-phase four-wire system consists of a parallel compensation module, a series compensation module, and a seventh filter inductor L7, an eighth filter inductor L8, and a ninth filter inductor L9 for power control.

[0114] The series inverter module is composed of a second three-phase inverter INV2, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6; the first phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fourth filter inductor L4 to form a third connection point a3 of the a phase, and the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form a fourth connection point a4 of the a phase; the second phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fifth filter inductor L5 to form a third connection point b3 of the b phase, and the other end of the fifth filter inductor L5 is connected to one end of the secondary side of the second single-phase transformer T2 to form a fourth connection point b of the b phase. Point b4; the third phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the sixth filter inductor L6 to form the c-phase third connection point c3, and the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to form the c-phase fourth connection point c4; the other ends of the secondary sides of the first single-phase transformer T1, the second single-phase transformer T2, and the third single-phase transformer T3 are connected to each other to form the second AC output terminal AC2, and the second AC output terminal AC2 is connected to the neutral line; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the first single-phase transformer T1, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the second single-phase transformer T2, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the third single-phase transformer T3.

[0115] One end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to the first phase of the power grid to form the fifth connection point a5 of the a phase, the other end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to one end of the seventh filter inductor L7 to form the sixth connection point a6 of the a phase, and the other end of the seventh filter inductor L7 is connected to the second connection point a2 of the a phase; one end of the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b5 of the b phase, and the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b6 of the b phase. The other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the eighth filter inductor L8 to form the sixth connection point b6 of phase b, and the other end of the eighth filter inductor L8 is connected to the second connection point b2 of phase b; one end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to the third phase of the power grid to form the fifth connection point c5 of phase c, the other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the ninth filter inductor L9 to form the sixth connection point c6 of phase c, and the other end of the ninth filter inductor L9 is connected to the second connection point c2 of phase c.

[0116] The parallel compensation module is composed of a first inverter INV1, a first filter inductor L1, a second filter inductor L2, a third filter inductor L3, a first filter capacitor C1, a second filter capacitor C2 and a third filter capacitor C3. The first phase of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form a first connection point a1 of phase a, and the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form a second connection point a2 of phase a, and the second connection point a2 of phase a is connected to the first phase of the load; the second phase of the AC output end of the first inverter INV1 is connected to one end of the second filter inductor L2 to form a first connection point b1 of phase b, and the other end of the second filter inductor L2 is connected to one end of the second filter capacitor C2 to form a second connection point b2 of phase b, and the second connection point b2 of phase b is connected to the second phase of the load; the third phase of the AC output end of the first inverter INV1 is connected to one end of the third filter inductor L3 to form a first connection point c1 of phase c, and the third filter inductor L3 is connected to one end of the third filter capacitor C3 to form a second connection point c2 of phase c. The other end of the wave inductor L3 is connected to one end of the third filter capacitor C3 to form the second connection point C2 of the C phase, and the second connection point C2 of the C phase is connected to the third phase of the load; the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are connected to each other to form the first AC output terminal AC1, and the first AC output terminal AC1 is connected to the neutral line; the high voltage end of the DC output end of the first inverter INV1 is connected to the high voltage end of the DC output end of the series inverter module to form the first DC connection point DC1, the low voltage end of the DC output end of the first inverter INV1 is connected to the low voltage end of the DC output end of the series inverter module to form the second DC connection point DC2, one end of the seventh filter capacitor C7 is connected to the first DC output point DC1, one end of the eighth filter capacitor C8 is connected to the second DC output point DC2, the other ends of the seventh filter capacitor C7 and the eighth filter capacitor C8 are connected to each other to form the N phase first connection point n1, and the N phase first connection point n1 is connected to the neutral line.

[0117] The control design method of the system specifically includes parallel compensation module control and series compensation module control. The phase angle difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the active power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9, while the amplitude difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9; the potential difference between the sixth AC connection point a6 of the a phase and the first AC output terminal AC1 is the first voltage U1 , the potential difference between the second AC connection point a2 of phase a and the first AC output terminal AC1 is the second voltage U2; the potential difference between the sixth AC connection point b6 of phase b and the first AC output terminal AC1 is the third voltage U3, and the potential difference between the second AC connection point b2 of phase b and the first AC output terminal AC1 is the fourth voltage U4; the potential difference between the sixth AC connection point c6 of phase c and the first AC output terminal AC1 is the fifth voltage U5, and the potential difference between the second AC connection point c2 of phase c and the first AC output terminal AC1 is the sixth voltage U6.

[0118] The grid-connected active power is realized by controlling the phase difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6, and the phase difference is realized by adjusting the phase of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively, and the given values ​​of the phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are generated by the active power control of the virtual synchronous generator; since the three-phase voltages of the load voltage are respectively the same as the second voltage U2, the fourth voltage U4 and the sixth voltage U6, in order to protect the load and maintain the load terminal voltage at the rated value, the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are respectively The given values ​​of the amplitudes of the second voltage U4 and the sixth voltage U6 are set to the rated value of the load voltage amplitude; the given values ​​of the amplitudes and phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 can be integrated respectively to obtain the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6, and the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are the three-phase output voltages of the parallel compensation module (that is, the voltages across the first filter capacitor C1, the second filter capacitor C2 and the third filter capacitor C3 of the parallel compensation module), so the given values ​​of the three-phase output voltage of the parallel compensation module are the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively.

[0119] The grid-connected reactive power is realized by controlling the amplitude difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6. Since the first voltage U1 is equal to the sum of the first phase voltage of the power grid and the first phase output voltage of the series compensation module, the third voltage U3 is equal to the sum of the second phase voltage of the power grid and the second phase output voltage of the series compensation module, and the fifth voltage U5 is equal to the sum of the third phase voltage of the power grid and the third phase output voltage of the series compensation module, and the amplitudes of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are controlled to keep the load voltage rating unchanged, the amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled by controlling the output voltage of the series compensation module, thereby controlling the amplitude difference between the first voltage U1 and the second voltage U2, the third voltage U3 and the fourth voltage U4, and the fifth voltage U5 and the sixth voltage U6, and then respectively controlling the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9; in order to minimize the amplitude of the output voltage of the series compensation module, the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled to keep the load voltage rating unchanged. The given values ​​of the phases of U3 and the fifth voltage U5 are the same as those of the power grid. The amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are generated by the reactive power control of the virtual synchronous generator. The given values ​​of the amplitudes and phases of the first voltage U1, the third voltage U3 and the fifth voltage U5 can be integrated to obtain the given values ​​of the first voltage U1, the third voltage U3 and the fifth voltage U5. The given value of the first phase output voltage of the series compensation module (i.e., the voltage across the primary side of the first single-phase transformer T1 in the series compensation module) is the difference between the given value of the first voltage U1 and the power grid voltage. The given value of the second phase output voltage of the series compensation module (i.e., the voltage across the primary side of the second single-phase transformer T2 in the series compensation module) is the difference between the given value of the third voltage U3 and the power grid voltage. The given value of the third phase output voltage of the series compensation module (i.e., the voltage across the primary side of the third single-phase transformer T3 in the series compensation module) is the difference between the given value of the first voltage U1 and the power grid voltage.

[0120] When the grid frequency fluctuates, the virtual synchronous generator control can enable the unified power quality controller to respond to changes in the grid frequency and adjust the active power output through the parallel compensation module to help maintain the stability of the grid frequency; the series compensation module further stabilizes the grid voltage and improves the power quality by adjusting the reactive power.

[0121] Example 6

[0122] This embodiment describes a unified power quality controller system with inertia support and frequency modulation capabilities, in which the series compensation module adopts three single-phase commutation bridges and the parallel compensation module adopts a three-phase four-wire topology structure in the form of four bridge arms, such as Figure 7 The system improves the power quality through series compensation modules and parallel compensation modules, provides voltage and frequency stability for the power grid, and provides protection for the load.

[0123] The topological structure of the three-phase four-wire system consists of a parallel compensation module, a series compensation module, and a seventh filter inductor L7, an eighth filter inductor L8, and a ninth filter inductor L9 for power control.

[0124] The series inverter module is composed of a second single-phase inverter INV2, a third single-phase inverter INV3, a fourth single-phase inverter INV4, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6. One end of the AC output end of the second single-phase inverter INV2 is connected to the fourth filter inductor L4 to form a third connection point a3 of the a phase, and the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form a fourth connection point a4 of the a phase. The other end of the AC output end of the second single-phase inverter INV2 is connected to the other end of the secondary side of the first single-phase transformer T1 to form a seventh connection point a7 of the a phase; one end of the AC output end of the third single-phase inverter INV3 is connected to one end of the fifth filter inductor L5 to form a third connection point b3 of the b phase, and the other end of the fifth filter inductor L5 is connected to the first One end of the secondary side of the second single-phase transformer T2 constitutes the fourth connection point b4 of the b phase, and the other end of the AC output end of the third single-phase inverter INV3 is connected to the other end of the secondary side of the second single-phase transformer T2 to constitute the seventh connection point b7 of the b phase; one end of the AC output end of the fourth single-phase inverter INV4 is connected to one end of the sixth filter inductor L6 to constitute the third connection point c3 of the c phase, the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to constitute the fourth connection point c4 of the c phase, and the other end of the AC output end of the fourth single-phase inverter INV4 is connected to the other end of the secondary side of the third single-phase transformer T3 to constitute the seventh connection point c7 of the c phase; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the first single-phase transformer T1, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the second single-phase transformer T2, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the third single-phase transformer T3.

[0125] One end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to the first phase of the power grid to form the fifth connection point a5 of the a phase, the other end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to one end of the seventh filter inductor L7 to form the sixth connection point a6 of the a phase, and the other end of the seventh filter inductor L7 is connected to the second connection point a2 of the a phase; one end of the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b5 of the b phase, and the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b6 of the b phase. The other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the eighth filter inductor L8 to form the sixth connection point b6 of phase b, and the other end of the eighth filter inductor L8 is connected to the second connection point b2 of phase b; one end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to the third phase of the power grid to form the fifth connection point c5 of phase c, the other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the ninth filter inductor L9 to form the sixth connection point c6 of phase c, and the other end of the ninth filter inductor L9 is connected to the second connection point c2 of phase c.

[0126] The parallel compensation module is composed of a first inverter INV1, a first filter inductor L1, a second filter inductor L2, a third filter inductor L3, a tenth filter inductor L 10 , a first filter capacitor C1, a second filter capacitor C2 and a third filter capacitor C3, the first inverter INV1 uses an additional branch (a fourth half-bridge inverter), the first phase of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form a first connection point a1 of the a phase, the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form a second connection point a2 of the a phase, and the a phase second connection point a2 is connected to the first phase of the load; the second phase of the AC output end of the first inverter INV1 is connected to one end of the second filter inductor L2 to form a b phase The first inverter INV1 has a first connection point b1, and the other end of the second filter inductor L2 is connected to one end of the second filter capacitor C2 to form a second connection point b2 of the b phase, and the second connection point b2 of the b phase is connected to the second phase of the load; the third phase of the AC output end of the first inverter INV1 is connected to one end of the third filter inductor L3 to form a first connection point c1 of the c phase, and the other end of the third filter inductor L3 is connected to one end of the third filter capacitor C3 to form a second connection point c2 of the c phase, and the second connection point c2 of the c phase is connected to the third phase of the load; the additional branch of the AC output end of the first inverter INV1 is connected to the tenth filter inductor L 10 One end of the N-phase first connection point n1, the tenth filter inductor L 10The other end of the first filter capacitor C1 is connected to the neutral line to form the N-phase second connection point n2; the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are connected to each other to form the first AC output terminal AC1, and the first AC output terminal AC1 is connected to the N-phase second connection point n2; the high-voltage end of the DC output end of the first inverter INV1 is connected to the high-voltage end of the DC output end of the series inverter module to form a first DC connection point DC1, and the low-voltage end of the DC output end of the first inverter INV1 is connected to the low-voltage end of the DC output end of the series inverter module to form a second DC connection point DC2, and the two ends of the seventh filter capacitor C7 are respectively connected to the first DC output point DC1 and the second DC output point DC2.

[0127] The control design method of the system specifically includes parallel compensation module control and series compensation module control. The phase angle difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the active power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9, while the amplitude difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9; the potential difference between the sixth AC connection point a6 of the a phase and the first AC output terminal AC1 is the first voltage U1 , the potential difference between the second AC connection point a2 of phase a and the first AC output terminal AC1 is the second voltage U2; the potential difference between the sixth AC connection point b6 of phase b and the first AC output terminal AC1 is the third voltage U3, and the potential difference between the second AC connection point b2 of phase b and the first AC output terminal AC1 is the fourth voltage U4; the potential difference between the sixth AC connection point c6 of phase c and the first AC output terminal AC1 is the fifth voltage U5, and the potential difference between the second AC connection point c2 of phase c and the first AC output terminal AC1 is the sixth voltage U6.

[0128] The grid-connected active power is realized by controlling the phase difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6, and the phase difference is realized by adjusting the phase of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively, and the given values ​​of the phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are generated by the active power control of the virtual synchronous generator; since the three-phase voltages of the load voltage are respectively the same as the second voltage U2, the fourth voltage U4 and the sixth voltage U6, in order to protect the load and maintain the load terminal voltage at the rated value, the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are respectively The given values ​​of the amplitudes of the second voltage U4 and the sixth voltage U6 are set to the rated value of the load voltage amplitude; the given values ​​of the amplitudes and phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 can be integrated respectively to obtain the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6, and the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are the three-phase output voltages of the parallel compensation module (that is, the voltages across the first filter capacitor C1, the second filter capacitor C2 and the third filter capacitor C3 of the parallel compensation module), so the given values ​​of the three-phase output voltage of the parallel compensation module are the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively.

[0129] The grid-connected reactive power is realized by controlling the amplitude difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6. Since the first voltage U1 is equal to the sum of the first phase voltage of the power grid and the first phase output voltage of the series compensation module, the third voltage U3 is equal to the sum of the second phase voltage of the power grid and the second phase output voltage of the series compensation module, and the fifth voltage U5 is equal to the sum of the third phase voltage of the power grid and the third phase output voltage of the series compensation module, and the amplitudes of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are controlled to keep the load voltage rating unchanged, the amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled by controlling the output voltage of the series compensation module, thereby controlling the amplitude difference between the first voltage U1 and the second voltage U2, the third voltage U3 and the fourth voltage U4, and the fifth voltage U5 and the sixth voltage U6, and then respectively controlling the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9; in order to minimize the amplitude of the output voltage of the series compensation module, the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled to keep the load voltage rating unchanged. The given values ​​of the phases of U3 and the fifth voltage U5 are the same as those of the power grid. The amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are generated by the reactive power control of the virtual synchronous generator. The given values ​​of the amplitudes and phases of the first voltage U1, the third voltage U3 and the fifth voltage U5 can be integrated to obtain the given values ​​of the first voltage U1, the third voltage U3 and the fifth voltage U5. The given value of the first phase output voltage of the series compensation module (i.e., the voltage across the primary side of the first single-phase transformer T1 in the series compensation module) is the difference between the given value of the first voltage U1 and the power grid voltage. The given value of the second phase output voltage of the series compensation module (i.e., the voltage across the primary side of the second single-phase transformer T2 in the series compensation module) is the difference between the given value of the third voltage U3 and the power grid voltage. The given value of the third phase output voltage of the series compensation module (i.e., the voltage across the primary side of the third single-phase transformer T3 in the series compensation module) is the difference between the given value of the first voltage U1 and the power grid voltage.

[0130] When the grid frequency fluctuates, the virtual synchronous generator control can enable the unified power quality controller to respond to changes in the grid frequency and adjust the active power output through the parallel compensation module to help maintain the stability of the grid frequency; the series compensation module further stabilizes the grid voltage and improves the power quality by adjusting the reactive power.

[0131] Example 7

[0132] This embodiment describes a unified power quality controller system with inertia support and frequency modulation capability, in which the series compensation module adopts three single-phase commutation bridges and the parallel compensation module adopts a split capacitor. Figure 8 The system improves the power quality through series compensation modules and parallel compensation modules, provides voltage and frequency stability for the power grid, and provides protection for the load.

[0133] The topological structure of the three-phase four-wire system consists of a parallel compensation module, a series compensation module, and a seventh filter inductor L7, an eighth filter inductor L8, and a ninth filter inductor L9 for power control.

[0134] The series inverter module is composed of a second single-phase inverter INV2, a third single-phase inverter INV3, a fourth single-phase inverter INV4, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6. One end of the AC output end of the second single-phase inverter INV2 is connected to the fourth filter inductor L4 to form a third connection point a3 of the a phase, and the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form a fourth connection point a4 of the a phase. The other end of the AC output end of the second single-phase inverter INV2 is connected to the other end of the secondary side of the first single-phase transformer T1 to form a seventh connection point a7 of the a phase; one end of the AC output end of the third single-phase inverter INV3 is connected to one end of the fifth filter inductor L5 to form a third connection point b3 of the b phase, and the other end of the fifth filter inductor L5 is connected to the first One end of the secondary side of the second single-phase transformer T2 constitutes the fourth connection point b4 of the b phase, and the other end of the AC output end of the third single-phase inverter INV3 is connected to the other end of the secondary side of the second single-phase transformer T2 to constitute the seventh connection point b7 of the b phase; one end of the AC output end of the fourth single-phase inverter INV4 is connected to one end of the sixth filter inductor L6 to constitute the third connection point c3 of the c phase, the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to constitute the fourth connection point c4 of the c phase, and the other end of the AC output end of the fourth single-phase inverter INV4 is connected to the other end of the secondary side of the third single-phase transformer T3 to constitute the seventh connection point c7 of the c phase; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the first single-phase transformer T1, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the second single-phase transformer T2, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the third single-phase transformer T3.

[0135] One end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to the first phase of the power grid to form the fifth connection point a5 of the a phase, the other end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to one end of the seventh filter inductor L7 to form the sixth connection point a6 of the a phase, and the other end of the seventh filter inductor L7 is connected to the second connection point a2 of the a phase; one end of the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b5 of the b phase, and the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b6 of the b phase. The other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the eighth filter inductor L8 to form the sixth connection point b6 of phase b, and the other end of the eighth filter inductor L8 is connected to the second connection point b2 of phase b; one end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to the third phase of the power grid to form the fifth connection point c5 of phase c, the other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the ninth filter inductor L9 to form the sixth connection point c6 of phase c, and the other end of the ninth filter inductor L9 is connected to the second connection point c2 of phase c.

[0136] The parallel compensation module is composed of a first inverter INV1, a first filter inductor L1, a second filter inductor L2, a third filter inductor L3, a first filter capacitor C1, a second filter capacitor C2 and a third filter capacitor C3. The first phase of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form a first connection point a1 of phase a, and the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form a second connection point a2 of phase a, and the second connection point a2 of phase a is connected to the first phase of the load; the second phase of the AC output end of the first inverter INV1 is connected to one end of the second filter inductor L2 to form a first connection point b1 of phase b, and the other end of the second filter inductor L2 is connected to one end of the second filter capacitor C2 to form a second connection point b2 of phase b, and the second connection point b2 of phase b is connected to the second phase of the load; the third phase of the AC output end of the first inverter INV1 is connected to one end of the third filter inductor L3 to form a first connection point c1 of phase c, and the third filter inductor L3 is connected to one end of the third filter capacitor C3 to form a second connection point c2 of phase c. The other end of the wave inductor L3 is connected to one end of the third filter capacitor C3 to form the second connection point C2 of the C phase, and the second connection point C2 of the C phase is connected to the third phase of the load; the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are connected to each other to form the first AC output terminal AC1, and the first AC output terminal AC1 is connected to the neutral line; the high voltage end of the DC output end of the first inverter INV1 is connected to the high voltage end of the DC output end of the series inverter module to form the first DC connection point DC1, the low voltage end of the DC output end of the first inverter INV1 is connected to the low voltage end of the DC output end of the series inverter module to form the second DC connection point DC2, one end of the seventh filter capacitor C7 is connected to the first DC output point DC1, one end of the eighth filter capacitor C8 is connected to the second DC output point DC2, the other ends of the seventh filter capacitor C7 and the eighth filter capacitor C8 are connected to each other to form the N phase first connection point n1, and the N phase first connection point n1 is connected to the neutral line.

[0137] The control design method of the system specifically includes parallel compensation module control and series compensation module control. The phase angle difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the active power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9, while the amplitude difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9; the potential difference between the sixth AC connection point a6 of the a phase and the first AC output terminal AC1 is the first voltage U1 , the potential difference between the second AC connection point a2 of phase a and the first AC output terminal AC1 is the second voltage U2; the potential difference between the sixth AC connection point b6 of phase b and the first AC output terminal AC1 is the third voltage U3, and the potential difference between the second AC connection point b2 of phase b and the first AC output terminal AC1 is the fourth voltage U4; the potential difference between the sixth AC connection point c6 of phase c and the first AC output terminal AC1 is the fifth voltage U5, and the potential difference between the second AC connection point c2 of phase c and the first AC output terminal AC1 is the sixth voltage U6.

[0138] The grid-connected active power is realized by controlling the phase difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6, and the phase difference is realized by adjusting the phase of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively, and the given values ​​of the phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are generated by the active power control of the virtual synchronous generator; since the three-phase voltages of the load voltage are respectively the same as the second voltage U2, the fourth voltage U4 and the sixth voltage U6, in order to protect the load and maintain the load terminal voltage at the rated value, the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are respectively The given values ​​of the amplitudes of the second voltage U4 and the sixth voltage U6 are set to the rated value of the load voltage amplitude; the given values ​​of the amplitudes and phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 can be integrated respectively to obtain the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6, and the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are the three-phase output voltages of the parallel compensation module (that is, the voltages across the first filter capacitor C1, the second filter capacitor C2 and the third filter capacitor C3 of the parallel compensation module), so the given values ​​of the three-phase output voltage of the parallel compensation module are the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively.

[0139] The grid-connected reactive power is realized by controlling the amplitude difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6. Since the first voltage U1 is equal to the sum of the first phase voltage of the power grid and the first phase output voltage of the series compensation module, the third voltage U3 is equal to the sum of the second phase voltage of the power grid and the second phase output voltage of the series compensation module, and the fifth voltage U5 is equal to the sum of the third phase voltage of the power grid and the third phase output voltage of the series compensation module, and the amplitudes of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are controlled to keep the load voltage rating unchanged, the amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled by controlling the output voltage of the series compensation module, thereby controlling the amplitude difference between the first voltage U1 and the second voltage U2, the third voltage U3 and the fourth voltage U4, and the fifth voltage U5 and the sixth voltage U6, and then respectively controlling the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9; in order to minimize the amplitude of the output voltage of the series compensation module, the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled to keep the load voltage rating unchanged. The given values ​​of the phases of U3 and the fifth voltage U5 are the same as those of the power grid. The amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are generated by the reactive power control of the virtual synchronous generator. The given values ​​of the amplitudes and phases of the first voltage U1, the third voltage U3 and the fifth voltage U5 can be integrated to obtain the given values ​​of the first voltage U1, the third voltage U3 and the fifth voltage U5. The given value of the first phase output voltage of the series compensation module (i.e., the voltage across the primary side of the first single-phase transformer T1 in the series compensation module) is the difference between the given value of the first voltage U1 and the power grid voltage. The given value of the second phase output voltage of the series compensation module (i.e., the voltage across the primary side of the second single-phase transformer T2 in the series compensation module) is the difference between the given value of the third voltage U3 and the power grid voltage. The given value of the third phase output voltage of the series compensation module (i.e., the voltage across the primary side of the third single-phase transformer T3 in the series compensation module) is the difference between the given value of the first voltage U1 and the power grid voltage.

[0140] When the grid frequency fluctuates, the virtual synchronous generator control can enable the unified power quality controller to respond to changes in the grid frequency and adjust the active power output through the parallel compensation module to help maintain the stability of the grid frequency; the series compensation module further stabilizes the grid voltage and improves the power quality by adjusting the reactive power.

[0141] In summary, the parallel compensation module of the embodiment of the present invention suppresses voltage harmonics and protects the critical loads connected in parallel with the filter capacitor by controlling the voltage amplitude of the filter capacitor to be constant. This mechanism effectively improves the quality of electric energy, especially the suppression of harmonics and voltage fluctuations. The series compensation module ensures the stable transmission of electric energy by controlling the voltage across the transformer, further improves the overall power quality of the power system, and reduces voltage fluctuations. The DC ends of the two inverters are connected in parallel through filter capacitors, which effectively balances the transfer and storage of energy. This design not only improves the response speed of the system, but also significantly enhances the stability of the system, especially when facing power grid fluctuations or load changes, it can make faster adjustment responses.

[0142] The present invention introduces a control method for a virtual synchronous generator, which provides inertia support and frequency support for the power grid through a parallel compensation module and a series compensation module. By simulating the inertial response and frequency regulation capability of a traditional synchronous generator, the system can quickly provide active power support when the power grid frequency fluctuates, help stabilize the power grid frequency, and improve the dynamic performance of the power system. The system realizes independent regulation of active power and reactive power by controlling the parallel and series compensation modules. The parallel module regulates the active power by controlling the phase angle of the filter capacitor voltage, and the series module regulates the reactive power by controlling the voltage at both ends of the single-phase transformer. This flexible power regulation capability not only improves the voltage regulation performance of the system, but also effectively copes with frequency changes and load fluctuations in the power grid.

[0143] Those skilled in the art can understand that the accompanying drawings are only schematic diagrams of an embodiment, and the modules or processes in the accompanying drawings are not necessarily required to implement the present invention.

[0144] It can be known from the description of the above implementation methods that those skilled in the art can clearly understand that the present invention can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which can be stored in a storage medium such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in the various embodiments of the present invention or certain parts of the embodiments.

[0145] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. The device and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0146] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention 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 unified power quality controller, characterized in that: include: The parallel compensation module, the series compensation module and the power control inductor L1, the parallel compensation module is composed of a power converter, a filter inductor, a filter capacitor and an isolation transformer, which is equivalent to a parallel voltage source U p The series compensation module is composed of a power converter, a filter inductor, a filter capacitor and an isolation transformer, which is equivalent to an equivalent series voltage source U s ; Series voltage source U s One end of the grid voltage source U g One end is connected to the series voltage source U s The other end of the power control inductor L1 is connected to one end of the power control inductor L1, and the other end of the power control inductor L1 is connected to the parallel voltage source U p One end is connected to the parallel voltage source U p The other end is connected to the grid voltage source U g The other end of the load is connected to the equivalent current source I L Connected in parallel with the parallel voltage source U p superior.

2. The unified power quality controller according to claim 1, characterized in that: The parallel voltage source U p By controlling the parallel voltage source U p The amplitude of the series voltage source U is maintained constant to control the phase difference of the voltage across the power control inductor L1, thereby controlling the active power; s The reactive power is controlled by controlling the amplitude difference of the voltage across the power control inductor L1.

3. The unified power quality controller according to claim 2, characterized in that: The series voltage source U s The given value is the difference between the reference voltage and the grid voltage, and the reference voltage is formed by integrating the amplitude generated by the reactive power control of the virtual synchronous generator and the grid voltage phase; the parallel voltage source U p The voltage amplitude is the rated value of the load voltage, and the phase is the phase generated by the active power control of the virtual synchronous generator.

4. The power quality controller according to claim 1, characterized in that: When applied to a single-phase single-wire scenario, the power quality controller is composed of a parallel compensation module, a series compensation module and a second filter inductor L2 for power control; the parallel compensation module is composed of a first inverter INV1, a first filter inductor L1 and a first filter capacitor C1; the series compensation module is composed of a second inverter INV2, a third filter inductor L3, a first single-phase transformer T1 and a second filter capacitor C2; One end of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form a first AC connection point AC1, and the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form a third AC connection point AC3; the third AC connection point AC3 is connected to one end of the load, and the other end of the load is connected to the other end of the first filter capacitor C1 to form a second AC connection point AC2; the other end of the AC output end of the first inverter INV1 is connected to the second AC connection point AC2, the second AC connection point AC2 is connected to one end of the single-phase power grid, and the other end of the single-phase power grid is connected to one end of the primary side of the first single-phase transformer T1 to form a fourth AC connection point AC4; the other end of the primary side of the first single-phase transformer T1 is connected to one end of the second filter inductor L2 to form a fifth AC connection point AC5; the other end of the second filter inductor L2 is connected to the third AC connection point AC3; one end of the AC connection point of the second inverter INV2 is connected to the third filter One end of the third filter inductor L3 is connected to one end of the secondary side of the first single-phase transformer T1 to form a seventh AC connection point AC7; the other end of the AC connection point of the second inverter INV2 is connected to the other end of the secondary side of the first single-phase transformer T1 to form an eighth AC connection point AC8; the two ends of the second filter capacitor C2 are respectively connected to the fourth AC connection point AC4 and the fifth AC connection point AC5 or the seventh AC connection point AC7 and the eighth AC connection point AC8, the high voltage end of the DC output end of the first inverter INV1 is connected to the high voltage end of the DC output end of the second inverter INV2 to form a first DC connection point DC1; the low voltage end of the DC output end of the first inverter INV1 is connected to the low voltage end of the DC output end of the second inverter INV2 to form a second DC connection point DC2; the two ends of the third filter capacitor C3 are respectively connected to the first DC output point DC1 and the second DC output point DC2.

5. The power quality controller according to claim 4, characterized in that: The phase angle difference of the voltage across the second filter inductor L2 determines the active power of the current flowing through the second filter inductor L2, and the amplitude difference of the voltage across the second filter inductor L2 determines the reactive power of the current flowing through the second filter inductor L2; the potential difference between the fifth AC connection point AC5 and the second AC connection point AC2 is the first voltage U1, and the potential difference between the third AC connection point AC3 and the second AC connection point AC2 is the second voltage U2; The grid-connected active power is realized by controlling the phase difference between the first voltage U1 and the second voltage U2, and the phase difference is realized by adjusting the phase of the second voltage U2. The given value of the phase of the second voltage U2 is generated by the active power control of the virtual synchronous generator. The given value of the amplitude of the second voltage U2 is set to the rated value of the load voltage amplitude. The given value of the amplitude and phase of the second voltage U2 is integrated to obtain the given value of the second voltage U2. The second voltage U2 is the output voltage of the parallel compensation module, because the given value of the output voltage of the parallel compensation module is the given value of the second voltage U2. The difference in amplitude between the first voltage U1 and the second voltage U2 determines the reactive power of the current flowing through the second filter inductor L2. The first voltage U1 is equal to the sum of the grid voltage and the output voltage of the series compensation module, and the amplitude of the second voltage U2 is controlled to keep the rated value of the load voltage unchanged. The amplitude of the first voltage U1 is controlled by controlling the output voltage of the series compensation module, thereby controlling the amplitude difference between the first voltage U1 and the second voltage U2, and further controlling the reactive power of the current flowing through the second filter inductor L2. The given value of the phase of the first voltage U1 is the same as that of the grid. The amplitude of the first voltage U1 is generated by the reactive control of the virtual synchronous generator. The given value of the amplitude and phase of the first voltage U1 is integrated to obtain the given value of the first voltage U1. The given value of the output voltage of the series compensation module is the difference between the given value of the first voltage and the grid voltage.

6. The power quality controller according to claim 1 is characterized in that, when applied to a three-phase three-wire scenario, the power quality controller is composed of a parallel compensation module, a series compensation module, and a seventh filter inductor L7, an eighth filter inductor L8, and a ninth filter inductor L9 for power control; the series compensation module adopts two forms: three single-phase commutation bridge forms and one three-phase commutation bridge form, and the parallel compensation module adopts an inverter module composed of a three-phase commutation bridge; The parallel compensation module is composed of a first inverter INV1, a first filter inductor L1, a second filter inductor L2, a third filter inductor L3, a first filter capacitor C1, a second filter capacitor C2 and a third filter capacitor C3. The first phase of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form a first connection point a1 of phase a, and the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form a second connection point a2 of phase a, and the second connection point a2 of phase a is connected to the first phase of the load; the second phase of the AC output end of the first inverter INV1 is connected to one end of the second filter inductor L2 to form a second connection point a1 of phase b. A connection point b1, the other end of the second filter inductor L2 is connected to one end of the second filter capacitor C2 to form a b-phase second connection point b2, and the b-phase second connection point b2 is connected to the second phase of the load; the third phase of the AC output end of the first inverter INV1 is connected to one end of the third filter inductor L3 to form a c-phase first connection point c1, the other end of the third filter inductor L3 is connected to one end of the third filter capacitor C3 to form a c-phase second connection point c2, and the c-phase second connection point c2 is connected to the third phase of the load; the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are connected to each other to form a first AC output terminal AC1; The series compensation module adopts three single-phase commutation bridge forms, and its series inverter module is composed of a second single-phase inverter INV2, a third single-phase inverter INV3, a fourth single-phase inverter INV4, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6. The AC output of the second single-phase inverter INV2 One end of the AC output end of the second single-phase inverter INV2 is connected to the other end of the secondary side of the first single-phase transformer T1 to form the seventh connection point a7 of the a phase; one end of the AC output end of the third single-phase inverter INV3 is connected to one end of the fifth filter inductor L5 to form the third connection point b3 of the b phase; the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form the fourth connection point a4 of the a phase; the other end of the AC output end of the second single-phase inverter INV2 is connected to the other end of the secondary side of the first single-phase transformer T1 to form the seventh connection point a7 of the a phase; one end of the AC output end of the third single-phase inverter INV3 is connected to one end of the fifth filter inductor L5 to form the third connection point b3 of the b phase; The other end of the inductor L5 is connected to one end of the secondary side of the second single-phase transformer T2 to form the fourth connection point b4 of the b phase, and the other end of the AC output end of the third single-phase inverter INV3 is connected to the other end of the secondary side of the second single-phase transformer T2 to form the seventh connection point b7 of the b phase; one end of the AC output end of the fourth single-phase inverter INV4 is connected to one end of the sixth filter inductor L6 to form the third connection point c3 of the c phase, the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to form the fourth connection point c4 of the c phase, and the other end of the AC output end of the fourth single-phase inverter INV4 is connected to the other end of the secondary side of the third single-phase transformer T3 to form the seventh connection point c7 of the c phase; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side of the first single-phase transformer T1 or the two ends of the secondary side, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side of the second single-phase transformer T2 or the two ends of the secondary side, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side of the third single-phase transformer T3 or the two ends of the secondary side; The series compensation module adopts a three-phase commutation bridge form, and its series inverter module is composed of a second three-phase inverter INV2, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6; the first phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fourth filter inductor L4 to form the a-phase third connection point a3, and the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form the a-phase fourth connection point a4; the second phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fifth filter inductor L5 to form the b-phase third connection point b3, and the other end of the fifth filter inductor L5 is connected to the second One end of the secondary side of the single-phase transformer T2 constitutes the fourth connection point b4 of the b phase; the third phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the sixth filter inductor L6 to constitute the third connection point c3 of the c phase, and the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to constitute the fourth connection point c4 of the c phase; the other ends of the secondary sides of the first single-phase transformer T1, the second single-phase transformer T2, and the third single-phase transformer T3 are connected to each other to form the second AC output terminal AC2; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the first single-phase transformer T1, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the second single-phase transformer T2, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the third single-phase transformer T3; One end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to the first phase of the power grid to form the fifth connection point a5 of the a phase, the other end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to one end of the seventh filter inductor L7 to form the sixth connection point a6 of the a phase, and the other end of the seventh filter inductor L7 is connected to the second connection point a2 of the a phase; one end of the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b5 of the b phase, and the The other end of the primary side is connected to one end of the eighth filter inductor L8 to form the sixth connection point b6 of the b phase, and the other end of the eighth filter inductor L8 is connected to the second connection point b2 of the b phase; one end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to the third phase of the power grid to form the fifth connection point c5 of the c phase, the other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the ninth filter inductor L9 to form the sixth connection point c6 of the c phase, and the other end of the ninth filter inductor L9 is connected to the second connection point c2 of the c phase; The high voltage end of the DC output end of the parallel inverter module is connected to the high voltage end of the DC output end of the series inverter module to form a first DC connection point DC1, the low voltage end of the DC output end of the parallel inverter module is connected to the low voltage end of the DC output end of the series inverter module to form a second DC connection point DC2, and the two ends of the seventh filter capacitor C7 are respectively connected to the first DC output point DC1 and the second DC output point DC2.

7. The power quality controller according to claim 6 is characterized in that the phase angle difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the active power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9, and the amplitude difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9 respectively determines the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8, and the ninth filter inductor L9; between the sixth AC connection point a6 of the a phase and the first AC output terminal AC1 The potential difference between the a-phase second AC connection point a2 and the first AC output terminal AC1 is a first voltage U1, and the potential difference between the a-phase second AC connection point a2 and the first AC output terminal AC1 is a second voltage U2; the potential difference between the b-phase sixth AC connection point b6 and the first AC output terminal AC1 is a third voltage U3, and the potential difference between the b-phase second AC connection point b2 and the first AC output terminal AC1 is a fourth voltage U4; the potential difference between the c-phase sixth AC connection point c6 and the first AC output terminal AC1 is a fifth voltage U5, and the potential difference between the c-phase second AC connection point c2 and the first AC output terminal AC1 is a sixth voltage U6; The grid-connected active power is realized by controlling the phase difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6, and the phase difference is realized by adjusting the phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively, and the given values ​​of the phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are generated by the active power control of the virtual synchronous generator; the three-phase voltages of the load voltage are respectively the same as the second voltage U2, the fourth voltage U4 and the sixth voltage U6, The given values ​​of the amplitudes of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are set as the rated value of the load voltage amplitude; the given values ​​of the amplitudes and phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 can be respectively integrated to obtain the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6, and the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are the three-phase output voltages of the parallel compensation module, and the given values ​​of the three-phase output voltages of the parallel compensation module are respectively the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6; The grid-connected reactive power is realized by controlling the amplitude difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6. The first voltage U1 is equal to the sum of the first phase voltage of the power grid and the first phase output voltage of the series compensation module, the third voltage U3 is equal to the sum of the second phase voltage of the power grid and the second phase output voltage of the series compensation module, the fifth voltage U5 is equal to the sum of the third phase voltage of the power grid and the third phase output voltage of the series compensation module, and the amplitudes of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are controlled to keep the load voltage rated value unchanged. The amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled by controlling the output voltage of the series compensation module, and the first voltage U1 is controlled to be equal to the second voltage U2, the third voltage U3 is controlled to be equal to the fourth voltage U4, and the fifth voltage U5 is controlled to be equal to the sixth voltage U6. The amplitude difference is used to control the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9 respectively; the given values ​​of the phases of the first voltage U1, the third voltage U3 and the fifth voltage U5 are the same as those of the power grid, the amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are generated by the reactive power control of the virtual synchronous generator, and the given values ​​of the amplitudes and phases of the first voltage U1, the third voltage U3 and the fifth voltage U5 can be integrated to obtain the given values ​​of the first voltage U1, the third voltage U3 and the fifth voltage U5, the given value of the first phase output voltage of the series compensation module is the difference between the given value of the first voltage U1 and the power grid voltage, the given value of the second phase output voltage of the series compensation module is the difference between the given value of the third voltage U3 and the power grid voltage, and the given value of the third phase output voltage of the series compensation module is the difference between the given value of the first voltage U1 and the power grid voltage.

8. The power quality controller according to claim 1 is characterized in that, when applied to a three-phase four-wire scenario, the power quality controller is composed of a parallel compensation module, a series compensation module, and a seventh filter inductor L7, an eighth filter inductor L8, and a ninth filter inductor L9 for power control; the series compensation module adopts two forms: three single-phase commutation bridge forms and one three-phase commutation bridge form, and the parallel compensation module adopts two forms: a four-bridge arm form and a split capacitor form; The series compensation module adopts three single-phase commutation bridge forms, and its series inverter module is composed of a second single-phase inverter INV2, a third single-phase inverter INV3, a fourth single-phase inverter INV4, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6. One end of the AC output end of the second single-phase inverter INV2 is connected to the fourth filter inductor L4 to form the a-phase third connection point a3, the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form the a-phase fourth connection point a4, the other end of the AC output end of the second single-phase inverter INV2 is connected to the other end of the secondary side of the first single-phase transformer T1 to form the a-phase seventh connection point a7; one end of the AC output end of the third single-phase inverter INV3 is connected to one end of the fifth filter inductor L5 to form the b-phase third connection point b3, the fifth filter inductor L4 is connected to the first single-phase transformer T1 to form the a-phase fourth connection point a4, the second end of the AC output end of the second single-phase inverter INV2 is connected to the first single-phase transformer T1 to form the a-phase seventh connection point a7; one end of the AC output end of the third single-phase inverter INV3 is connected to one end of the fifth filter inductor L5 to form the b-phase third connection point b3, the fifth filter inductor L4 is connected to the first single-phase transformer T1 to form the a-phase seventh connection point a8. The other end of the inductor L5 is connected to one end of the secondary side of the second single-phase transformer T2 to form the fourth connection point b4 of the b phase, and the other end of the AC output end of the third single-phase inverter INV3 is connected to the other end of the secondary side of the second single-phase transformer T2 to form the seventh connection point b7 of the b phase; one end of the AC output end of the fourth single-phase inverter INV4 is connected to one end of the sixth filter inductor L6 to form the third connection point c3 of the c phase, the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to form the fourth connection point c4 of the c phase, and the other end of the AC output end of the fourth single-phase inverter INV4 is connected to the other end of the secondary side of the third single-phase transformer T3 to form the seventh connection point c7 of the c phase; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side of the first single-phase transformer T1 or the two ends of the secondary side, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side of the second single-phase transformer T2 or the two ends of the secondary side, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side of the third single-phase transformer T3 or the two ends of the secondary side; The series compensation module adopts a three-phase commutation bridge form, and its series inverter module is composed of a second three-phase inverter INV2, a fourth filter inductor L4, a fifth filter inductor L5, a sixth filter inductor L6, a first single-phase transformer T1, a second single-phase transformer T2, a third single-phase transformer T3, a fourth filter capacitor C4, a fifth filter capacitor C5 and a sixth filter capacitor C6; the first phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fourth filter inductor L4 to form the a-phase third connection point a3, and the other end of the fourth filter inductor L4 is connected to one end of the secondary side of the first single-phase transformer T1 to form the a-phase fourth connection point a4; the second phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the fifth filter inductor L5 to form the b-phase third connection point b3, and the other end of the fifth filter inductor L5 is connected to the secondary side of the second single-phase transformer T2. One end of the sixth filter inductor L6 constitutes the fourth connection point b4 of the b phase; the third phase of the AC output end of the second three-phase inverter INV2 is connected to one end of the sixth filter inductor L6 to constitute the third connection point c3 of the c phase, and the other end of the sixth filter inductor L6 is connected to one end of the secondary side of the third single-phase transformer T3 to constitute the fourth connection point c4 of the c phase; the other ends of the secondary sides of the first single-phase transformer T1, the second single-phase transformer T2, and the third single-phase transformer T3 are connected to each other to form the second AC output terminal AC2, and the second AC output terminal AC2 is connected to the neutral line; the two ends of the fourth filter capacitor C4 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the first single-phase transformer T1, the two ends of the fifth filter capacitor C5 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the second single-phase transformer T2, and the two ends of the sixth filter capacitor C6 are respectively connected to the two ends of the primary side or the two ends of the secondary side of the third single-phase transformer T3; One end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to the first phase of the power grid to form the fifth connection point a5 of the a phase, the other end of the primary side of the first single-phase transformer T1 of the series compensation module is connected to one end of the seventh filter inductor L7 to form the sixth connection point a6 of the a phase, and the other end of the seventh filter inductor L7 is connected to the second connection point a2 of the a phase; one end of the primary side of the second single-phase transformer T2 of the series compensation module is connected to the second phase of the power grid to form the fifth connection point b5 of the b phase, and the The other end of the primary side is connected to one end of the eighth filter inductor L8 to form the sixth connection point b6 of the b phase, and the other end of the eighth filter inductor L8 is connected to the second connection point b2 of the b phase; one end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to the third phase of the power grid to form the fifth connection point c5 of the c phase, the other end of the primary side of the third single-phase transformer T3 of the series compensation module is connected to one end of the ninth filter inductor L9 to form the sixth connection point c6 of the c phase, and the other end of the ninth filter inductor L9 is connected to the second connection point c2 of the c phase; The parallel compensation module in the form of four bridge arms is composed of a first inverter INV1, a first filter inductor L1, a second filter inductor L2, a third filter inductor L3, a tenth filter inductor L 10 , a first filter capacitor C1, a second filter capacitor C2 and a third filter capacitor C3, the first inverter INV1 uses an additional branch, the first phase of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form the a phase first connection point a1, the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form the a phase second connection point a2, the a phase second connection point a2 is connected to the first phase of the load; the second phase of the AC output end of the first inverter INV1 is connected to one end of the second filter inductor L2 to form the b phase first connection point b1, the other end of the second filter inductor L2 is connected to one end of the second filter capacitor C2 to form the b-phase second connection point b2, and the b-phase second connection point b2 is connected to the second phase of the load; the third phase of the AC output end of the first inverter INV1 is connected to one end of the third filter inductor L3 to form the c-phase first connection point c1, the other end of the third filter inductor L3 is connected to one end of the third filter capacitor C3 to form the c-phase second connection point c2, and the c-phase second connection point c2 is connected to the third phase of the load; the additional branch of the AC output end of the first inverter INV1 is connected to the tenth filter inductor L 10 One end of the N-phase first connection point n1, the tenth filter inductor L 10 The other end of the first filter capacitor C1 is connected to the neutral line to form the N-phase second connection point n2; the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are connected to each other to form a first AC output terminal AC1, and the first AC output terminal AC1 is connected to the N-phase second connection point n2; the high voltage end of the DC output end of the first inverter INV1 is connected to the high voltage end of the DC output end of the series inverter module to form a first DC connection point DC1, the low voltage end of the DC output end of the first inverter INV1 is connected to the low voltage end of the DC output end of the series inverter module to form a second DC connection point DC2, and the two ends of the seventh filter capacitor C7 are respectively connected to the first DC output point DC1 and the second DC output point DC2; The parallel compensation module in the form of split capacitors is composed of a first inverter INV1, a first filter inductor L1, a second filter inductor L2, a third filter inductor L3, a first filter capacitor C1, a second filter capacitor C2 and a third filter capacitor C3. The first phase of the AC output end of the first inverter INV1 is connected to one end of the first filter inductor L1 to form a first connection point a1 of phase a, and the other end of the first filter inductor L1 is connected to one end of the first filter capacitor C1 to form a second connection point a2 of phase a, and the second connection point a2 of phase a is connected to the first phase of the load; the second phase of the AC output end of the first inverter INV1 is connected to one end of the second filter inductor L2 to form a first connection point b1 of phase b, and the other end of the second filter inductor L2 is connected to one end of the second filter capacitor C2 to form a second connection point b2 of phase b, and the second connection point b2 of phase b is connected to the second phase of the load; the third phase of the AC output end of the first inverter INV1 is connected to one end of the third filter inductor L3 to form a first connection point c of phase c1, the other end of the third filter inductor L3 is connected to one end of the third filter capacitor C3 to form the second connection point c2 of the c phase, and the second connection point c2 of the c phase is connected to the third phase of the load; the other ends of the first filter capacitor C1, the second filter capacitor C2, and the third filter capacitor C3 are connected to each other to form the first AC output terminal AC1, and the first AC output terminal AC1 is connected to the neutral line; the high voltage end of the DC output end of the first inverter INV1 is connected to the high voltage end of the DC output end of the series inverter module to form the first DC connection point DC1, the low voltage end of the DC output end of the first inverter INV1 is connected to the low voltage end of the DC output end of the series inverter module to form the second DC connection point DC2, one end of the seventh filter capacitor C7 is connected to the first DC output point DC1, one end of the eighth filter capacitor C8 is connected to the second DC output point DC2, the other ends of the seventh filter capacitor C7 and the eighth filter capacitor C8 are connected to each other to form the N phase first connection point n1, and the N phase first connection point n1 is connected to the neutral line.

9. The power quality controller according to claim 8, characterized in that: The phase angle difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9 respectively determines the active power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9, and the amplitude difference of the voltage across the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9 respectively determines the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9; the potential difference between the sixth AC connection point a6 of the a phase and the first AC output terminal AC1 is the first voltage U1 , the potential difference between the second AC connection point a2 of phase a and the first AC output terminal AC1 is the second voltage U2; the potential difference between the sixth AC connection point b6 of phase b and the first AC output terminal AC1 is the third voltage U3, and the potential difference between the second AC connection point b2 of phase b and the first AC output terminal AC1 is the fourth voltage U4; the potential difference between the sixth AC connection point c6 of phase c and the first AC output terminal AC1 is the fifth voltage U5, and the potential difference between the second AC connection point c2 of phase c and the first AC output terminal AC1 is the sixth voltage U6; The grid-connected active power is realized by controlling the phase difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6, and the phase difference is realized by adjusting the phase of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively, and the given values ​​of the phase of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are generated by the active power control of the virtual synchronous generator; the three-phase voltage of the load voltage is the same as the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively , the given values ​​of the amplitudes of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are set to the rated value of the load voltage amplitude; the given values ​​of the amplitudes and phases of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are respectively integrated to obtain the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6, and the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are the three-phase output voltages of the parallel compensation module, and the given values ​​of the three-phase output voltages of the parallel compensation module are the given values ​​of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 respectively; The grid-connected reactive power is realized by controlling the amplitude difference between the first voltage U1 and the second voltage U2, between the third voltage U3 and the fourth voltage U4, and between the fifth voltage U5 and the sixth voltage U6. The first voltage U1 is equal to the sum of the first phase voltage of the power grid and the first phase output voltage of the series compensation module, the third voltage U3 is equal to the sum of the second phase voltage of the power grid and the second phase output voltage of the series compensation module, the fifth voltage U5 is equal to the sum of the third phase voltage of the power grid and the third phase output voltage of the series compensation module, the amplitudes of the second voltage U2, the fourth voltage U4 and the sixth voltage U6 are controlled to keep the load voltage rated value unchanged, and the amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are controlled by controlling the output voltage of the series compensation module, thereby controlling the first voltage U1 and the second voltage U2, the third voltage U3 and the fourth voltage U4, and the fifth voltage U5 and the sixth voltage The amplitude difference of U6 is used to control the reactive power of the current flowing through the seventh filter inductor L7, the eighth filter inductor L8 and the ninth filter inductor L9 respectively; the given values ​​of the phases of the first voltage U1, the third voltage U3 and the fifth voltage U5 are the same as those of the power grid, the amplitudes of the first voltage U1, the third voltage U3 and the fifth voltage U5 are generated by the reactive power control of the virtual synchronous generator, and the given values ​​of the amplitudes and phases of the first voltage U1, the third voltage U3 and the fifth voltage U5 are integrated to obtain the given values ​​of the first voltage U1, the third voltage U3 and the fifth voltage U5, the given value of the first phase output voltage of the series compensation module is the difference between the given value of the first voltage U1 and the power grid voltage, the given value of the second phase output voltage of the series compensation module is the difference between the given value of the third voltage U3 and the power grid voltage, and the given value of the third phase output voltage of the series compensation module is the difference between the given value of the first voltage U1 and the power grid voltage.

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