Application of embedded Z-Source inverters in Grid connected photovoltaic systems

Abstract

This paper proposes the use of the embedded Z-Source (EZ-source) inverters in photovoltaic (PV) grid interconnection. Being different from the traditional Z-source inverter, EZ-source inverters are constructed by inserting dc sources into the X-shaped impedance network so that the dc input current flows smoothly during the whole switching period unlike the traditional Z-source inverter. Fully parallel embedded Z-Source (FPEZ-source) inverters are one of the EZ-source inverters topologies with two isolated dc sources are embedded with each inductor of X-shaped network in series and so we can use two PV panel in this structure. The control system consist of two parts: one part adjusts the shoot through time for maximum power point tracking (MPPT) by simple dp/dv method and another part generate the reference current for FPEZ-source inverter to inject maximum available power of PV array to grid with high quality and maintain DC link capacitor voltage in its reference value. The performance of proposed structure and control strategy is validated with simulation results obtained using PSCAD/EMTDC software.