Control Of Quasi-z-source Inverter In Concentrating Photovoltaic System

As one of the main technologies in solar energy utilization, photovoltaic powergeneration is now paid much attention by all the countries. How to effectively improve theefficiency and the conversion efficiency of photovoltaic inverter in the theory and applicationresearch is still hot in the academic circle at home and abroad.Currently the problems in photovoltaic power generation system are low efficiency andhigh expenses, and only about1/10of light energy can be transformed into electrical energy.Although the traditional frequency transformer isolated inverter is reliable on technicalperformance, the problems of low system efficiency, large volume, high cost are still serious.In view of the above problems, this thesis put forward the design scheme of quasi-Z-sourceinverter in concentrated photovoltaic concentrator system, so as to achieve the efficient andreliable DC input, AC output system.Firstly, the working principle of the photovoltaic cells was analyzed and the photovoltaiccell mathematical model was established, then the change law of the parameters was reflectedby the mathematical relationship, in the environment, the simulation model of PV arraydynamically was built based on Matlab/Simulink, the related simulation results were achieved.The principle of maximum power point tracking(MPPT) was discussed, the main methods ofMPPT were analyzed and researched, then combined with the dynamic simulation model ofphotovoltaic array based on Matlab/Simulink to verify the effectiveness of perturbation andobservation method.Secondly, aiming at the defects of traditional inverter, the working principle of quasi-Z-source inverter was analyzed, the parameters of the Z source impedance network weredesigned, the model of Z-source inverter was established, the DC bus voltage of quasi-Z-source inverter control strategy was designed to complete the controller designation.Finally, the modulation strategy of Z-source inverter was analyzed and the sinusoidalpulse width modulation(SPWM) modulation strategy of quasi-Z-source unique characteristicswas studied. The insertion mode of different modulation was analyzed, the maximum boostSPWM modulation strategies were improved, and the improved SPWM was proposed toreduce the difficulty of control. The DC bus controller was designed combined with SPWM modulation strategies in Matlab/Simulink environment, then the system model was built tovalidate the correctness of the theoretical analysis of simulation.