Hybrid Pulsewidth Modulated Single-Phase Quasi-Z-Source Grid-Tie Photovoltaic Power System

A hybrid pulsewidth modulated single-phase quasi-Z-source grid-tie photovoltaic (PV) power system is proposed. The hybrid pulse-width modulation (HPWM) combines the pulse-width modulation (PWM) and the pulse-amplitude modulation (PAM). The PWM works when the ac output voltage is lower than the dc source voltage; otherwise, the PAM operates the single-phase quasi-Z-source inverter (qZSI). The HPWM leads to the reduction of power loss, and the quasi-Z-source capacitance and inductance. An effective control strategy is proposed for the new PV power system to manage the maximum power point tracking (MPPT) of PV panel, grid-tie power injection, and dc-link voltage. A grid-tie current controller, combining a repetitive controller and a proportional-resonant regulator, achieves strong harmonic suppression, fast dynamic, and zero tracking error. A 500-W prototype is built to verify the new system. Power loss estimation and impedance design are detailed. Experimental tests validate the HPWM, new PV power system with higher efficiency, and the related control method.