Variable structure control method of grid-connected photovoltaic system

Abstract

The invention discloses a variable structure control method of a grid-connected photovoltaic system, used for controlling a two-stage circuit structure or a single-stage circuit structure. The method comprises the following steps of respectively determining each control point value, comprising V1-V6 and Vr1-Vr4, wherein a reference voltage value of a direct current bus is Vref, and an actual output voltage value of a photovoltaic battery array is VPV; and concretely controlling according to the following conditions: firstly, when the VPV of the photovoltaic battery array is ranging from V1 to V5, the grid-connected photovoltaic system works under the two-stage circuit structure and a two-stage control mode, and the set Vref of the reference voltage of the direct current bus is relevant to the size and the variation direction of the VPV; secondly, when the VPV of the photovoltaic battery array is ranging from V4 to V6, the grid-connected photovoltaic system works under the single-stage circuit structure and a single-stage control mode; and thirdly, when the VPV of the photovoltaic battery array is ranging from V4 to V5, the grid-connected photovoltaic system works under a hysteresis control mode. Through the method, the working voltage range is enlarged, and the equipment use efficiency is remarkably improved.

Description

technical field [0001] The invention belongs to the technical field of solar photovoltaic grid-connected power generation, and relates to a variable structure control method for a photovoltaic grid-connected power generation system. Background technique [0002] Photovoltaic grid-connected power generation technology is increasingly valued by governments of various countries, and many key technologies are expected to be resolved, especially novel circuit structures and control technologies are more urgent. [0003] The classic circuit structure is divided into single-stage circuit structure, two-stage or multi-stage circuit structure. One of the purposes of adopting a single-stage circuit structure is to reduce the number of transmission power stages and improve the overall efficiency of the system. However, the single-stage circuit structure is directly connected to the AC grid through grid-connected inverters, output filters (if isolated, including power frequency transfo...

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to provide a variable structure control method for a photovoltaic grid-connected power generation system, which solves the problem that the existing single-stage circuit structure and two-stage or multi-stage circuit structure have a small operating voltage range and are difficult to adapt to the grid-connected adjustment of the circuit needs, resulting in low efficiency of equipment use

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