Research On New Three-level Photovoltaic Grid-connected Inverter

Compared with the shortcomings of traditional energy resources and serious environmental pollution,new energy sources have huge development advantages such as small pollution,abundant resources and sustainable utilization.Among them,solar energy,as the most widely distributed new energy source in the world,has unique advantages such as low cost and sustainable development,and it has been considered as one of the most ideal energy sources.In solar power generation,photovoltaic grid-connected power generation system is a hot issue.Grid-connected inverter is the most critical link in photovoltaic power generation system,and it has very important theoretical and practical significance for its research.This paper analyzes the research status of photovoltaic grid-connected inverters at domestic and abroad,and basis on this,it does its own research..Firtly,In order to increase the conversion efficiency of the system and save the expense of design,this paper proposes a new three-level photovoltaic inverter topology.The front stage of the inverter adopts a new three-level boost circuit,and the latter stage adopts an CCT inverse.Compared with the traditional three-level inverter,the topology reduces the power-loss of the inverter system,improves the operational stability of the inverter system and the quality of the electric energy.Secondly,in order to increase the output power of the inverter,it is necessary to do maximum power point tracking in the Boost circuit of the inverter.The traditional perturbation observation method is based on the static photovoltaic curve,the tracking speed is slow,and the sudden change of the illumination intensity leads to the misjudgment of the algorithm.This paper firstly establishes a simplified model of photovoltaic cells,analyzes the causes of misjudgment by traditional perturbation methods,and finally proposes a maximum power point tracking method based on the rate of change of photovoltaic curves.Through simulation and experiment,it is proved that the method has the advantages of fast tracking rate,high tracking precision,and can solve the misjudgment problem brought by the environment.Thirdly,in order to solve the midpoint potential imbalance problem in the three-level topology,this paper proposes a new hybrid midpoint balance control strategy based on SVPWM.Then,the simulation proves that the method can effectively suppress the imbalance of the midpoint potential.