Cascaded voltage control of three-phase four-leg inverter for OFF grid solar photovoltaic applications

Abstract

Solar photovoltaics (PV) is one of the popular renewable energy sources in tropical countries like India which can help in supplementing the rising demand of electrical energy. DC input from solar PV strings needs to be converted into AC component both for ON and for OFF grid applications. Three-phase inverters are used for the above inversion when power levels are high. In OFF grid applications, task of maintaining stable terminal voltage across the loads lies with the inverter in the absence of utility grid. It also has to supply variety of balanced and unbalanced loads. In this paper, cascaded voltage control scheme, for a three-phase four-leg inverter, is developed. Parameters of the proportional resonant controllers (PR) are tuned using bode plot techniques. Simulations results are presented for operation under different loading conditions.