Research On Control Strategy Of High Frequency Isolated Quasi Z Source Photovoltaic Inverter

Since the 21 st century,with the traditional three major energy depletion,as well as the use of traditional energy in the process of pollution,leading to the direction of human green to the development of new energy.One of its solar energy reserves,green pollution,a wide range of distribution and other advantages,as a green new energy power generation trends.Photovoltaic grid-connected power is the core of the grid-connected inverter,the traditional grid-connected inverter is a concentrated inverter,which will lead to its anti-shadow ability is poor,the DC link bus voltage is higher,the system loss is large,Prone to failure and other shortcomings,this proposed miniature inverter,to solve the above problems.This thesis first analyzes the background of the development of photovoltaic micro inverter in the domestic and foreign research status,and the output characteristics of PV modules are analyzed;based on the comparison of the commonly used maximum power point tracking algorithm,the perturbation and observation method was improved,and the simulation shows that the improved algorithm has higher tracking speed and then.Comparative analysis of the topological structure of several photovoltaic inverter circuit,for their shortcomings,the topology of high frequency isolated quasi Z source is introduced,and the topology,working principle and development of Z source inverter are described.And choose simple boost SPWM modulation technology as the modulation strategy of this thesis;Secondly,the control strategy of isolated quasi Z source inverter is studied,based on the small signal model,the structure of the system is analyzed,through the double closed-loop control of the secondary capacitor voltage and the grid connected current,the grid connected control of the system is realized.According to the traditional PI regulator in the grid current control,can not be achieved without static error tracking and disturbance can not solve the problem.This thesis introduces the quasi-proportional resonant regulator to control the grid-connected current,and theoretically compare the performance of the two controllers,the quasi PR regulator can well eliminate the steady-state error and anti disturbance ability is better than PI controller.Finally,in the case of 300 W based photovoltaic grid connected inverter model in saber software,the controller designed in this thesis the simulation,combined with the RT-LAB experimental platform for experimental study of semi physical build,results show the effectiveness of the proposed method.