Hybrid pulsewidth modulated single-phase quasi-Z-source grid-tie Photovoltaic power system

A hybrid pulsewidth modulated single-phase quasi-Z-source inverter (qZSI) based grid-tie Photovoltaic (PV) power system is proposed. The hybrid pulsewidth modulation (HPWM) conducts PWM when the required ac output voltage is lower than the dc source voltage, otherwise it performs pulse-amplitude modulation (PAM) for the single-phase qZSI. The low-frequency ripple voltage of dc link is utilized, resulting in reductions of quasi-Z-source inductance and capacitance, as well as power devices' switching actions. Control strategy of the proposed system is further presented to track the maximum power points of the PV panel and to inject the extracted PV power into grid. A grid-tie current controller, combining with the plug-in repetitive control and proportional-resonant regulator, is employed to achieve strong harmonic suppression, fast convergence, and zero tacking error. The system dynamic model is disclosed to design controllers. Simulation and experimental results demonstrate validity of the proposed system.