Study On Off-Grid Photovoltaic Inverter Using Dual Controllers

Off-grid photovoltaic inverter is one of the core equipments of independent photovoltaic power generation system. The converter structure, detection circuit and control strategy have been studied to develope a small off-grid photovoltaic inverter.Basing on basic structure of the off-grid small inverter, a push-pull forward DC-DC converter and full-bridge DC-AC converter for the two-stage circuit have been choosen.And then the dual controllers also have been studied. The simulation models of push-pull forward DC-DC converter and full-bridge DC-AC power converter have been established by Matlab/Simulink tool. Meanwhile the SPWM and PWM signal also have been generated as driving signals for DC-DC converter and DC-AC converter.At last the simulation model has been simulated and the useful parameters of inverter have been obtained by this simulation module.Hardware circuits and control programs are designed. Hardware circuits mainly include:the two stage power converters, DC-DC converters, DC-AC converter, detection circuit, signal sampling circuit of DC bus, main controller circuit and auxiliary power supplies etc. Control programs include:the high DC voltage sampling and processing, PWM and SPWM signal generation, sampling and processing for AC output voltage and current, as well as the mian programs.At last prototype inverter is made and then experiments are carried out to prove whether this prototype inverter works normally in this paper. With some experiments we can conclude that satisfactory results are achieved from the experimental data and waveforms.