Research On Current-Fed Z-Source Inverter-Based Photovoltaic Gird System

New energy technology is widely used in power generating system in recent years, especially the solar energy. Gird-connected inverter is the key to the power generating system. In order to improve photovoltaic (PV) grid system performance and the quality of gird electricity, Z-source inverter is used in the PV grid system. According to the analysis of Z-source inverter, the whole photovoltaic generating system is researched.The second chapter analyzes the ZSI topological and work principle. According to the different input power types, Z-source inverter is divided into:the voltage-fed and current-fed. Focus on analyzing the working principles and converter state.The third chapter analyzes solar battery physical properties, according to its physical characteristics parameters to build mathematical model. Introduce three commonly used maximum power point tracking (MPPT) methods and puts forward an improved incremental conductance.The fourth chapter analyzes the mathematical modeling of the current-fed Z-source inverter. According to the model transfer function draw the CFZSI small signal transfer function diagram. According to the transfer function CFZSI control strategy was researched and proposes three closed loop:PV array voltage loop, Z-source capacitance voltage loop and grid ac current loop.The fifth chapter designs the main circuit parameters of the current-fed Z-source inverter (CFZSI), according to inhibit dc voltage and high order harmonics source design Z-source capacitance; according to inhibit current harmonic design Z-source inductance; comprehensive fast current tracking characteristics and inhibit current harmonic design parallel inductance; and a simple design on the output of photovoltaic array capacitance, input of the Z-source impedance network diode and switch tube and diode of the inverter bridge.In the sixth chapter single-phase current-fed Z-source inverter PWM waves occur simulation module,photovoltaic array output capacitance filtering module,Z-source network module,ac grid-connected module,control system module of photovoltaic array voltage loop module,Z-source capacitance voltage loop module,grid current loop module are established. According to analyzes Z-source inverter's characteristics and the control system's three modules, gain the simulation waveform, which confirmed the raise or lower voltage function of Z-source inverter and the accuracy and stability of control system.Finally, this dissertation is summary and outlook the research work of the Z-source inverter.