Research On The Off-grid Inverter Of The Photovoltaic Power Generation System

Nowadays, the energy crisis and environmental pollution problems have become more and more serious, restricting the sustainable development of the human society. To deal with these two issues effectively, many countries pay more attention to the use of the new energy, especially the solar energy. Photovoltaic power generation is one of the most important applications and research points. PV inverter is the core component of photovoltaic power generation system, which converting electrical energy, having a significant impact on overall system performance and cost. Research on inverter topology and digital control strategy is important for photovoltaic power generation system running economically, safely and reliably.This thesis is mainly devoted to the research of a two-stage structure inverter. The front stage is an interleaved full-bridge LLC resonant circuit, the back stage is the full-bridge inverter circuit. First, the working principle of the full-bridge LLC resonant circuit is researched. Based on this, the DC voltage gain, the resonance parameters impact on the converter, no-load and short circuit characteristics are analyzed, and the design method of the resonance parameters is given. Then, this paper conducts the full-bridge inverter mathematical model and the characteristics of the second order LC filter. The inverter control is dual closed loop on voltage and inductor current feedback. On this basis, the analog controller design method is proposed and discretized into a digital controller.Finally, on the basis of theoretical analysis and-parameter-design, a 1kW experimental prototype is designed and built. The experimental results verify the theoretical analysis and design feasibility.