Reseach On Pv Off-grid Inverter And PWM Control Method

The energy consumption pushes the states all over the world to increase their investment in renewable energy development, however, the establishment of large-scale photovoltaic power or wind power plants requires huge area of land and investment, and they also need regular maintenance. There are many applications in the small and medium off-grid photovoltaic power generation equipments, such as street lamps, lights, transmitters and so on. The aim of this issue is to design an off-grid photovoltaic inverter and the PWM control scheme, in the practical application process, which can be connected to MPPT module directly to provide high-quality AC power.This article has designed off-grid photovoltaic inverter hardware, using transformerless single-phase full-bridge topology with HPWM modulation, to make a significant reduction on the harmonic content in the output waveform while reducing the loss of switching devices. Improved filter design method, considering the output current ripple and filter capacitor impedance, ensure low output voltage ripple, and reduce the size of the filter to make low cost as well. Through the establishment of off-grid Inverter simulation model, to calculate the RMS voltage closed-loop control parameters, which ensure high output voltage stability and dynamic response characteristics, using DC power supply to make the test of dynamic response process and the steady-state performance on the fluctuations of bus voltage and load mutation. By introducing the repetitive controller, which modified the RMS voltage control loop method, to it can ensure that the output voltage not occur oscillation at the crossing point. Design the experiment of off-grid photovoltaic inverter combined with MPPT modules, to test launched system and bus voltage fluctuation. Using the RMS voltage control loop with repetitive controller, the power of off-grid photovoltaic inverter can reach 5kVA.The issue did the actual circuit simulation and experiment which verified the feasibility of photovoltaic devices under the bus fluctuations and load mutations, the entire system output voltage is stable.