Study of Z-source inverter for grid-connected PV systems

This paper presents a Z-source inverter for photovoltaic (PV) grid-connected generating system. The Z-source inverter employs a unique LC network to couple the inverter power circuit to the diode front end and can be shoot through to boost the DC link voltage. In order to explain the operating principle, the entire control configuration is analyzed. By controlling sinusoidal modulation index, the grid-connected current inner loop is adopted, which ensures the system working in limit power factor. The Z-source capacitor voltage outer loop is adopted, which ensures the voltage stabilization. By controlling the shoot-through duty cycle, the PV array output voltage is controlled and the maximum power point tracking (MPPT) is realized. Lastly, a 3 kW Z-Source inverter circuit has been built and the experiment results have validated the operating principle.