Simulation of Fly Back PV Micro Inverter Using Decoupling Capacitor

An electrolytic capacitors used as a decoupling reservoir which restrict the lifetime of photovoltaic (PV) micro inverters. This has led to the development of several improved decoupling circuits that can reduce the capacitor value to allow the use of non electrolytic types. The project focus on selection of the minimum decoupling capacitor value for the proper operation of discontinuous conduction mode fly back PV micro inverters by considering the total harmonic distortion (THD) and PV power utilization ratio. A decoupling capacitor selection method for single-stage and two-stage fly back inverters is proposed. The results presented show that the decoupling capacitor value influences the THD more than PV power utilization. For single-stage inverters, the decoupling capacitor is placed across the PV output terminals, and should be sized according to the desired THD limit instead of PV power utilization. For two-stage inverters, the control method of the dc–dc converter determines the stage where the decoupling function takes place. Thus, the PV side decoupling capacitor should be dimensioned according to the PV power utilization ratio, and the inverter side decoupling capacitor should be selected according to the desired THD limitation. The corresponding voltage ripple limits for THD and PV power utilization ratio satisfy the IEC standard values of 5% and 9.6%, respectively.