Application of Trans Z-source Inverter in Photovoltaic Systems

In this paper a new photovoltaic system based on trans Z-source inverter(Trans-ZSI) is proposed. This inverter has been derived from quasi Z-source inverter recently. Trans Z-source network consists of one transformer and one capacitor. While maintaining all prominent features of pervious Z-source inverters, Trans Z-source inverter has several unique advantages such as increased voltage gain, reduced voltage stress and reduced components of impedance network. Due to these features, using trans Z-source inverter as a single stage converter in photovoltaic systems gives satisfactory results. In this paper the application of trans-ZSI in photovoltaic systems in both stand alone mode and grid connected mode has been investigated. By using the dynamic model of trans ZSI, the proper controllers for both stand alone mode and grid connected mode is designed. By controlling the shoot through duty ratio and modulation index, output voltage control has been performed in stand alone mode. Maximum power delivering and unity power factor is achieved through the use of controller in grid connected mode. Simulation results are presented to verify the ability of proposed system.