Quasi Z-source inverter for photovoltaic system connected to single phase AC grid

Abstract

A novel photovoltaic system based on quasi Z-source inverter (qZSI) which is connected to a single phase grid is proposed in this paper. Quasi Z-source inverter is a recently developed topology derived from Z-source inverter (ZSI). qZSI is a one-stage power conditioner that employs a capacitor-inductor network for connecting inverter to photovoltaic module. By means of controlling shoot-through duty cycle, the objective of tracking maximum power point can be accomplished. In comparison with ZSI, qZSI benefits some prominent privileges such as lower component ratings and source constant dc current. In this paper, through introducing an appropriate control structure, qZSI is used for connecting photovoltaic system to single phase grid. In the control structure, maximum power with unit power factor and low THD current is delivered to grid by controlling modulation index via PIS controller. Presuming voltage stabilization, the amount of power delivered to grid is regulated through the use of controller of qZSI capacitor voltage. qZSI is also utilized to control the shoot-through duty cycle in order to achieve maximum power point tracking (MPPT). Simulation results are provided to demonstrate the competence of the system.