Research On Photovoltaic Power Generation Converter System

With the development of the photovoltaic industry PV grid power systems are applied widely, so research PV power system converter is more and more important. This dissertation analyzes PV array output characteristic under different insolation and temperature and LCL filter PV power converter system control. This dissertation mainly researches on cascade type PV power converter system control strategy, and through the simulation and experiment verifies control strategy.Firstly, analyse various PV power system structures including centralized topology, series topology and DC module topology. After that analyse isolation type and non-isolated PV power converter system and multidrop PV power converter system structure. Discuss single phase basing on static axis and synchronous rotating frame control strategies, and research triphase basing on voltage oriented control and virtual flux linkage vector control strategy. Through the simulation results verify the single-phase and triphase PV grid system including single stage and twin-stage control strategy viability.Then this dissertation introduces PV equivalent circuit and output characteristic, and analyzes the hot-spot effect of shadow PV array. On the basis of PV mathematical physics model sets up PV simulation model, and through changing environment condition analyzes that series and parallel PV arrays is mainly affected by temperature or temperature illumination intensity. At last compare the efficiency of various PV power generation system structure.This dissertation studies cascade type PV power converter system, and analyses the same and mix unit cascade type photovoltaic inverter structure, and analyses cascade multilevel PV grid inverter pulse step modulation and carrier phase modulation method, and obtains the relationship of single polarity carrier phase modulation output frequency and switch frequency. At last this dissertation studies cascade multilevel photovoltaic PV grid inverter control and improved controlstrategy, and realizes separate unit working at the maximum power point, and analyses the methord of eliminating secondary ripple andastatic control result of PR better than P.Analyse PV grid inverter LCL filter damping method, passive damping and active damping control scheme.Set up PV grid inverter LCL filter virtual platform and prove virtual resistance and double-bandpass filter control method. At last set up single-phase single stage and double stage grid control system, three-phase grid control system and H bridge cascade grid control system experimental platform. This dissertation realizes single and three phase grid inverter control, and verifies that cascade grid control strategy is effective.