Research On Z-source Converter Of Photovoltaic Generating System

In increasingly intense current energy environment,the solar energy as a part of .renewable energy sources,the recent urgent-need of energy supplement,will be the direction of energy development.Photovoltaic generating system is one of the indispensable component of new energy sources and growing rapidly.Coverter is the key element of PV generating system.To promote flexibility and reliability of adapting the large Photovoltaic Array voltage's ripple,Z-Source converter which has been exerted on Fuel Cell may be fit into PV generating system.Based on the profound analysis of Z-Source converter, PV generating system is researched.The main contents of this research are:1. The ayalysis of Z-Source converter operation principle is composition of topology,switch modes,equivalent circuit and control pluse.Lastly,the influence of abnormal operation case is present.2. Modeling Z-Source converter by using State-Space averaging method.There are two small signal models:a small signal Z-Source converter with inductive load model and small signal Z-Source converter viewed from the DC link model.Based on them,can get the transfer functions and analyze model.3. Comparing and analyzing simple control,maximum boost control,maximum constant boost control and modified SVM.Three closed-loop configuration for control system is built:the grid current loop,Z-Source capacitor voltage loop and PVA output voltage loop.The controller is designed by the root locus method and testified by open-loop Bode.4. Analyzing and summarizing photovoltaic cell basic principle and maximum power point track control.Simple photovoltaic cell model and PVA five parameters model are built.5. Designing the main circuit parameters for Z-Source.The Z-Source capacitance is chosen by restaining the ripple and the Z-Source inductance is chosen by avoiding abnormal operation case and restaining the ripple.Analysis is verified by simulation of matlab/simulink software.The comparison result shows that Z-Source converter is more reliable,more efficient and more adaptive for large PVA voltage's ripple.