Research Of Technologies Of Transformer Less Single Phase Grid-connected Photovoltaic Inverter

Electric energy is a necessity for social production and human life. Energy crisis and environmental crisis and other factors have promoted the wide use of photovoltaic power generation system. Photovoltaic grid-connected inverter is the core part of the photovoltaic power generation system. Usually, the main type of the household photovoltaic power generation system is the non-isolated single phase photovoltaic inverter.First of all, the advantages and disadvantages of the non isolated PV inverter are analyzed in the paper, and the common mode current, the auxiliary power supply and the dual path MPPT are introduced. The operation state, control logic and state switching of the inverter are described, and the state diagram is drawn. The control strategies of Maximum Power Point Tracing for the inverter circuit with preceding stage Boost circuit and with post stage Boost circuit are demonstrated, and the control flow chart is established. The control strategy of current loop for the Boost circuit is proposed on the basis of the Boost voltage monocyclic control, so the photovoltaic inverter can work with the DC source simulated as the solar panels. It is convenient for production and testing in this situation.In view of the characteristics of photovoltaic inverter, the boost circuit, inverter circuit, communication circuit and monitoring system are analyzed, and the selection principle and calculation method of power inductors, bus capacitors and so on are presented. According to the characteristics of photovoltaic power generation system, the working principle and detection method of the automatic circuit breaker, the PV of the ground insulation detection circuit, the leakage current detection circuit, and the illumination detection are analyzed.Photovoltaic inverter is a part of the photovoltaic power generation system, the whole system security is not only related to the inverter, but also with the household electrical distribution system, inverter and photovoltaic substrate installation and other factors are closely related. According to the characteristics of household electrical distribution system and installation location, the corresponding grounding method and fault protection scheme are put forward.According to the theoretical analysis results, the 5KW double boost single phase photovoltaic inverter is designed, and the corresponding test is verified. The correctness of the analysis is verified. The inverter has passed the rigorous testing of CQC and TUV, and has entered the stage of mass production.