CN-115603371-B - Control method, circuit, device and medium for three-phase grid-connected converter

CN115603371BCN 115603371 BCN115603371 BCN 115603371BCN-115603371-B

Abstract

The application discloses a control method, a circuit, a device and a medium of a three-phase grid-connected converter, and relates to the technical field of alternating current and direct current power distribution systems. According to the control method of the three-phase grid-connected converter, the mathematical model of the three-phase grid-connected converter is built, the generation reason and the inhibition mechanism of leakage current are combined, and the voltage of the filter capacitor in the zero sequence loop is controlled to be a constant value through the PI regulator, so that the leakage current is effectively attenuated. And obtaining a grid voltage phase angle under a three-phase static coordinate system, carrying out coordinate transformation on the sampling quantity according to the phase angle, obtaining a modulation signal, and controlling a power switch tube in the grid-connected converter according to the modulation signal. In the scheme, only one connected lead is needed to be added between the middle point of the filter capacitor and the common point of the lower bridge arm, so that the cost is lower, and leakage current caused by the existence of parasitic capacitance of the power supply and distribution device on the DC side to the ground can be limited to a microampere level.

Inventors

SHEN BAOXING
YE HUIHUA
Lin Wangyifan
YU MEI
HUANG JIE
WU XIAOXIA
XU YAN
CHEN JUNHUA
WANG JIAN
PEI ZHONGCHEN
YU QINHAI
LIN LIN
LIU CHUANG
YU GUOFANG
ZENG SHAOHUA
YIN XIANGYU
LIU DAOHONG
YU HONGYUN
HAN ZIYU

Assignees

浙江华云清洁能源有限公司
东北电力大学

Dates

Publication Date: 20260512
Application Date: 20221031

Claims (9)

1. The control method of the three-phase grid-connected converter is characterized by comprising the following steps of: Acquiring common-mode voltage fluctuation characteristics of the grid-connected converter through Simulink simulation; When the middle point of the filter capacitor is connected with the common point of the lower bridge arm, controlling the voltage of the filter capacitor in the zero sequence loop to be a constant value through a PI regulator, and recording the voltage of the filter capacitor, wherein a connected lead is added between the middle point of the filter capacitor and the common point of the lower bridge arm; Establishing a dynamic mathematical model according to the grid-connected converter structure, and detecting and obtaining a grid phase angle of the grid side voltage under a static coordinate system; Acquiring a modulation signal according to the filter capacitor voltage and the grid phase angle; Controlling a bridge arm power switch tube according to the modulation signal; The obtaining a modulation signal according to the filter capacitor voltage and the grid phase angle includes: Performing park transformation on the switch side inductance current, the filter capacitor voltage and the filter capacitor current under the static coordinate system according to the phase angle of the power grid to obtain parameters under a synchronous rotation coordinate system; Comparing the zero sequence component of the filter capacitor voltage with a zero sequence voltage reference value, and obtaining the zero sequence reference value of the filter capacitor current through the PI regulator; and comparing the zero sequence reference value with the filter capacitor current to obtain a modulation ratio, and carrying out inverse transformation on the modulation ratio to obtain the modulation signal.
2. The method for controlling a three-phase grid-connected inverter according to claim 1, wherein the obtaining the common-mode voltage fluctuation characteristic of the grid-connected inverter through Simulink simulation comprises: And observing through the Simulink simulation to obtain the pulsating voltage on the parasitic capacitance of the direct current side, and obtaining the common mode voltage fluctuation characteristic through the leakage current generated by the pulsating voltage.
3. The method for controlling a three-phase grid-connected inverter according to claim 2, further comprising, before said controlling bridge arm power switching tubes according to said modulation signal: Detecting whether the modulation signal meets a preset standard or not; If yes, entering the step of controlling a bridge arm power switch tube according to the modulation signal; If not, alarming is carried out.
4. The control circuit of the three-phase grid-connected converter is characterized by comprising a three-phase alternating current power grid, an LCL filter, a three-phase voltage source type rectifier, a direct current bus, a control switch and a detection device; The input end of the three-phase alternating current power grid is grounded, and the output end of the three-phase alternating current power grid is connected with the input end of the LCL filter; The output end of the LCL filter is connected with the input end of the three-phase voltage source type rectifier; the output end of the three-phase voltage source type rectifier is connected with the direct current bus; the control switch is arranged between the middle point of the filter capacitor and the common point of the lower bridge arm, wherein a connecting wire is added between the middle point of the filter capacitor and the common point of the lower bridge arm; The detection device is connected with the control switch, when the control switch is disconnected, the detection device is used for acquiring the common mode voltage fluctuation characteristic of the grid-connected converter through Simulink simulation, when the control switch is closed, the detection device controls the filter capacitor voltage in the zero sequence loop to be a constant value through the PI regulator, records the filter capacitor voltage, establishes a dynamic mathematical model according to the grid-connected converter structure, detects and acquires the grid phase angle of the grid side voltage under the static coordinate system, acquires a modulation signal according to the filter capacitor voltage and the grid phase angle, and controls the bridge arm power switch tube according to the modulation signal; The obtaining a modulation signal according to the filter capacitor voltage and the grid phase angle includes: Performing park transformation on the switch side inductance current, the filter capacitor voltage and the filter capacitor current under the static coordinate system according to the phase angle of the power grid to obtain parameters under a synchronous rotation coordinate system; Comparing the zero sequence component of the filter capacitor voltage with a zero sequence voltage reference value, and obtaining the zero sequence reference value of the filter capacitor current through the PI regulator; and comparing the zero sequence reference value with the filter capacitor current to obtain a modulation ratio, and carrying out inverse transformation on the modulation ratio to obtain the modulation signal.
5. The three-phase grid-connected inverter control circuit according to claim 4, further comprising a positive DC bus capacitor and a negative DC bus capacitor; One end of the positive DC bus capacitor is connected with the positive electrode of the DC bus, and the other end of the positive DC bus capacitor is grounded; One end of the negative DC bus capacitor is connected with the negative electrode of the DC bus, and the other end of the negative DC bus capacitor is grounded.
6. The three-phase grid-connected inverter control circuit according to claim 5, further comprising a voltage stabilizing capacitor; the voltage stabilizing capacitor is arranged between the direct current bus and the common end of the upper bridge arm and the common end of the lower bridge arm of the three-phase voltage source type rectifier.
7. A three-phase grid-connected inverter control device, comprising: the simulation module is used for acquiring common-mode voltage fluctuation characteristics of the grid-connected converter through Simulink simulation; The recording module is used for connecting the filter capacitor middle point and the lower bridge arm common point, controlling the filter capacitor voltage in the zero sequence loop to be a constant value through the PI regulator, and recording the filter capacitor voltage, wherein a connecting wire is added between the filter capacitor middle point and the lower bridge arm common point; the detection module is used for establishing a dynamic mathematical model according to the grid-connected converter structure and detecting and obtaining a grid phase angle of the grid side voltage under a static coordinate system; The acquisition module is used for acquiring a modulation signal according to the filter capacitor voltage and the grid phase angle; the control module is used for controlling the bridge arm power switching tube according to the modulation signal; The acquisition module is specifically configured to: Performing park transformation on the switch side inductance current, the filter capacitor voltage and the filter capacitor current under the static coordinate system according to the phase angle of the power grid to obtain parameters under a synchronous rotation coordinate system; Comparing the zero sequence component of the filter capacitor voltage with a zero sequence voltage reference value, and obtaining the zero sequence reference value of the filter capacitor current through the PI regulator; and comparing the zero sequence reference value with the filter capacitor current to obtain a modulation ratio, and carrying out inverse transformation on the modulation ratio to obtain the modulation signal.
8. The control device of the three-phase grid-connected converter is characterized by comprising a memory, a control unit and a control unit, wherein the memory is used for storing a computer program; A processor for implementing the steps of the three-phase grid-connected inverter control method as claimed in any one of claims 1 to 3 when executing the computer program.
9. A computer-readable storage medium, characterized in that the computer-readable storage medium has stored thereon a computer program which, when executed by a processor, implements the steps of the three-phase grid-tie inverter control method as claimed in any one of claims 1 to 3.

Description

Control method, circuit, device and medium for three-phase grid-connected converter Technical Field The application relates to the technical field of alternating current and direct current distribution systems, in particular to a control method, a circuit, a device and a medium of a three-phase grid-connected converter. Background In recent years, with the development of power electronics technology, in order to adapt to the flexible access of distributed photovoltaic, energy storage and terminal load at the user side, building electrification has become a future development trend, and in order to realize electrical isolation between a power grid and a building power distribution system and ensure the power utilization safety of personnel in the building, the building power distribution system is usually connected with the power grid by adopting an isolated grid-connected converter with a power frequency or high-frequency transformer so as to eliminate potential safety hazards caused by leakage current, thereby causing low system efficiency and high input cost. Therefore, the application of the non-isolated three-phase grid-connected converter is becoming wider and wider. Fig. 1 is a circuit diagram of a topology of a conventional household three-phase grid-connected converter, as shown in fig. 1, the topology comprises a three-phase alternating current power grid, an LCL filter, a three-phase voltage source rectifier and a direct current bus part, wherein a common end of three-phase alternating current power grid side voltages ea, eb and ec is connected with the ground, a grounding resistor Rg is used for equivalent source side grounding resistance, a grid side voltage is connected with the three-phase voltage source rectifier through an LCL filter consisting of a three-phase power grid side filter inductance Lga, lgb, lgc, a filter capacitor Cfa, cfb, cfc and a switch side filter inductance Lfa, lfb, lfc, the three-phase voltage source rectifier consists of an A-phase first bridge arm, a B-phase second bridge arm and a C-phase third bridge arm, and the three bridge arms comprise two parallel power switching tubes, wherein U is used for representing an A-phase bridge arm midpoint, V is used for representing an A-phase bridge arm midpoint, and W is used for representing an A-phase bridge arm midpoint. The current non-isolated converter control mode for eliminating leakage current and common mode voltage is mainly realized by improving topology through a photovoltaic inverter, adding an additional fourth bridge arm and adopting an independent bridge arm control method based on inductance current feedback for control. In view of the above-mentioned technology, finding a control method of a three-phase grid-connected inverter, which is low in cost and can attenuate leakage current and stabilize common-mode voltage, is a problem to be solved by those skilled in the art. Disclosure of Invention The application aims to provide a control method, a circuit, a device and a medium of a three-phase grid-connected converter, so as to solve the problems that the current non-isolated converter control mode for eliminating leakage current and common mode voltage is mainly realized by improving topology of a photovoltaic inverter, an additional fourth bridge arm is added, an independent bridge arm control method based on inductance current feedback is adopted for control, the contradiction that the common mode voltage and the leakage current of the three-phase converter cannot be inhibited at the same time is overcome, but additional switching devices are added to cause higher cost and power loss, and in addition, the method cannot completely eliminate the leakage current of the photovoltaic inverter. In order to solve the technical problems, the application provides a control method of a three-phase grid-connected converter, comprising the following steps: Acquiring common-mode voltage fluctuation characteristics of the grid-connected converter through Simulink simulation; when the middle point of the filter capacitor is connected with the common point of the lower bridge arm, controlling the voltage of the filter capacitor in the zero sequence loop to be a constant value through a PI regulator, and recording the voltage of the filter capacitor; Establishing a dynamic mathematical model according to the grid-connected converter structure, and detecting and obtaining a grid phase angle of the grid side voltage under a static coordinate system; Acquiring a modulation signal according to the filter capacitor voltage and the grid phase angle; And controlling a bridge arm power switch tube according to the modulation signal. Preferably, the obtaining a modulation signal according to the filter capacitor voltage and the grid phase angle includes: Performing park transformation on the switch side inductance current, the filter capacitor voltage and the filter capacitor current under the static coordinate system according to the