Quasi-Z-source inverter (QZSI) is a new topology, which has been proposed to be simple and realize the single stage energy conversion in recent years. Due to the unique impedance network structure, it has the characteristic of shoot-through. In this paper the voltage-source QZSI is applied to grid-connected photovoltaic system. Firstly the operating principle of QZSI is deep analyzed, and then a grid-connected photovoltaic system using a QZSI is proposed. In order to conform to the requirement of grid-connection, the decoupling control thought of active current and reactive current by d-q rotating coordinate system and the modified PWM strategy of this system are studied. The rationality and feasibility of the proposed control strategy is verified through MATLAB/Simulink.
11-kV Series-Connected H-Bridge Multilevel Converter for Direct Grid Connection of Renewable Energy Systems