Research And Design Of H6 Topology Photovoltaic Grid-Connected Inverter

Because of the increasing world energy crisis and the environmental pollution caused by fossil fuels,the development and utilization of renewable energy such as solar energy has been taken seriously.The research of grid-connected PV(Photo Voltaic)generation system with PV inverter as core part has made great progress.The PV inverter has to reduce its volume and improve its security to meet the needs of applications in residential houses and commercial office buildings.The improvement of system efficiency,response speed and power quality has also become a key issue.Under this background,the thesis focuses on PV inverter.The main works done include:1.Based on the characteristics of PV array,common maximum power point tracking(MPPT)algorithms are compared.A proved method combined of constant voltage method and variable step size perturbation and observation method is proposed to solve the contradiction between the accuracy and rapidity.And the simulation results verify its effectiveness.2.Based on the elaboration and comparison of H4 topology and H6 topology,the H6 topology with the characteristics of high efficiency and suppressing leakage current is adopted in this paper.3.A doubled closed-loop grid-connected control strategy based on power feed-forward control is proposed to improve the control effect and speed.The voltage outer-loop adoptes PI control and adds data filtering process of DC bus voltage.Power feed-forward control is introduced to speed up the response of system.A method of predictive deadbeat current control is proposed to reduce the current distortion due to the control delay,which is adopted in the current inner-loop.Simulation and experimental results verify the validity of the proposed control method.4.Based on the introduction the basic principle of islanding detection and conventional islanding detection methods,a periodic perturbation of bidirectional positive feedback active frequency drift method is proposed to reduce the impact of load property.And the simulation results show that the islanding can be detected effectively.5.A 3kW H6 topology single-phase PV inverter prototype is developed and built.The paper presents the hardware structure,circuit diagram of several parts,selection of core component and software flow chart.The results of performance test show that the inverter is able to reach the anticipate requirement.