Research On The Control Technology Of Parallel Inverters In Photovoltaic System

With the development of modern power electronic technology, the photovoltaictechnology is improved continuously. Three-phase inverter is an important part of thephotovoltaic system, and it plays an important role in the distributed generation system,wind-light complementary system and the battery energy storage system, etc. In order toincrease the stability and the capacity of the system, the technology of modular powersystems should be paid more attention. It breaks the limitations of the power that the controltechnology of the parallel modular power systems. In the meantime, because it was designedwith redundant structure, it could improve the flexibility and reliability of the photovoltaicsystem. Therefore, the control technology of parallel inverters has become an importantresearch direction in power electronics area and it has great significance.Firstly, the mathematical model of three-phase inverter is established and its operatingcharacteristics are studied in this paper. Based on the double closed loop control technologyof the inverter, the control method which could satisfy the output index of the photovoltaicsystem will be researched, and the optimal control method will be researhed base on thedemand of the system. Secondly, the frequency-domain analysis of the various filters’transferfunctions is done. The application of LCL filter and the parallel control tecology are studiedin the photovoltaic system. The optimal filter parameters are designed. The model of thesystem which has parallel inverters is established in this paper, and the causes of generatingcircular current are studied. According to the results of analyzing the parallel power modules,the fuzzy control technology is used for intelligent controller in the system.A democratic master-slave control method is used for controlling the parallel invertersin this paper. The average current feedback control technology and the improved fuzzycontrol technology are used for the intelligent controller in this system. The systemsimulation model is built by using MATLAB in this paper, and the simulation results meet thedesign requirements. According to the research a photovoltaic system which has two parallrlinverters is built. It can be proved that the proposed method in this paper could control theparallel inverters by the testing of the equipment.