Research On Single Phase Household Photovoltaic Grid Connected Inverter

With the increasing problem of energy shortage and environmental pollution,clean and renewable energy has been widely concerned.Solar energy is considered as the most promising new energy because of its abundant and non-pollution.Photovoltaic grid-connected inverter is the core component and the key to good performance and market promotion of photovoltaic power generation system.In this paper,the related research on the household photovoltaic grid-connected inverter is carried out,which aims to provide the technical basis for the utility and marketization of PV inverter.By contrast,a two-stage photovoltaic grid-connected inverter topology scheme based on a half bridge LLC resonant converter is adopted.The working principle of half bridge LLC resonant converter is analysed,and the fundamental component method is used to simplify the circuit.The influence of resonant parameters on the converter voltage gain characteristics is studied,and the resonant parameters are designed on this basis.In order to avoid the reverse recovery problem of MOSFET diode and reduce the switching loss,inverter circuit adopts MOSFET and IGBT hybrid bridge and uses unipolar SPWM control to improve the efficiency of the system.In this paper,the MPPT algorithm of photovoltaic cells is studied,and an improved incremental conductance method is introduced,which avoids the shortcomings of the traditional incremental conductance method and consider both the steady state accuracy and tracking speed of the system.The control scheme of two-stage photovoltaic grid-connected inverter is analyzed in detail,which is use the former LLC resonant converter to realize the MPPT control of the photovoltaic cell and the boost control of the input voltage,and the after level inverter circuit used to realize the control of DC link voltage and the grid inverter control.The double closed loop PI control is used to realize the closed-loop control of the inverter,and the grid voltage feed-forward control is added to suppress the disturbance of the grid voltage and improve the waveform quality?Based on the theoretical analysis,the MATLAB simulation model is established to verify the feasibility and effectiveness of the system.Finally,the hardware and software ofthe system are designed.An experimental prototype of 1kW based on TMS320F28035 digital control is designed,a preliminary test was completed to further verify the correctness and feasibility of the theoretical analysis.