A new switching strategy for single stage boost inverter fed by solar PV system

Solar photovoltaic (PV) system are attaining world wide popularity due to their clean generation mechanism and energy security. The dc voltage obtained from PV system is usually lower than the peak value of the required output voltage of inverter and varies in a wide range. A power transformer is required to step-up the output voltage or a dc-dc converter is required to boost the input dc voltage, in addition to the dc-ac inverter, which increase cost and circuit complexity. Z-source single stage inverters with bulk inductors and capacitors are used in some topologies, but the harmonic content in the output is relatively high. In this paper, a solar photovoltaic (PV) fed single stage boost inverter feeding a three phase induction motor is explained with mathematical expressions and computer simulations. A time independent pulse width modulation technique is adopted in this system, which generates symmetrical gate pulse pattern resulting in smooth output waveforms. The dc link inductor can be kept very low as the inductor current is maintained constant by this discrete switching control strategy. This system is simple, cost effective and can be used for stand-alone solar applications. Results obtained from this system confirm the effectiveness of new discrete switching strategy and prove its capability to perform real time.