Research On Control Strategy Of Microinverter And Power Optimizer For Modual Photovoltaic System

In order to promote changes in energy development and cope with environmental and climate change,many countries around the world are vigorously developing renewable energy.Solar energy has received extensive attention and research due to its advantages such as cleanliness,zero cost,and easy access.Among various types of photovoltaic applications,distributed photovoltaic systems represented by modular photovoltaic applications have developed rapidly in recent years and have a bright future.In a modular photovoltaic system,photovoltaic modules and grid-connected equipment represented by microinverters and power optimizers are the core equipment of the entire system.Therefore,the research on modular photovoltaic power generation technology is mainly reflected in the research on microinverter and power optimizer control technology.The control technology of the microinverter is significantly different from that of the power optimizer,but some functions also have similarities,that is,the control goal of the maximum power point tracking control of photovoltaic modules is required.Therefore,it is necessary to analyze the same part of the control function of the two before researching their respective control strategies.This article is based on the above ideas to study the control technology of microinverter and power optimizer.The research on the same parts of the microinverter and power optimizer control functions is mainly given in the second chapter of the paper.The second chapter of the paper first introduces a maximum power point tracking control method that can be universally applied to microinverters and power optimizers,—a maximum power point tracking control method based on direct power control.Based on theoretical analysis,the paper also carried out simulation and experimental verification based on the power optimizer platform.In addition,the article also extends the traditional maximum power point tracking control function and proposes a limited power point tracking control strategy.Based on direct power control,it can achieve flexible and stable control of the photovoltaic module's entire range.The third chapter focuses on the research of microinverter control strategies in modular photovoltaic applications.This paper considers that a major factor limiting the development of micro-inverters is its relatively high cost.In this chapter,after analyzing the advantages and disadvantages of traditional digital control strategies,a novel microinverter analog control strategy is proposed,in order to reduce the cost of microinverter through improved control methods.Based on the method described in Chapter 2,the design details of analog control are introduced,and the simulation and experimental verification based on the flyback microinverter platform are carried out.Chapter 4 focuses on the control strategy of the series-connected power optimizer system in modular photovoltaic applications.Because of the natural cross-coupling effect in the structure of the series-connected power optimizer system,the existence of this effect may lead to system instability,so Chapter 4 first analyzes the stability of the series system.Then based on the stability analysis,a low-cost control strategy that can improve the efficiency of the system is introduced and verified by experiments.