An effective control method for quasi-Z-source cascade multilevel three-phase grid-tie photovoltaic power system

An effective control method for a three-phase quasi-Z-source cascade multilevel inverter (qZS-CMI) based grid-tie photovoltaic (PV) power system is proposed. The control scheme achieves distributed maximum power point tracking (MPPT) and independent dc-link voltage balance for all quasi-Z-source H-bridge inverter (qZS-HBI) based PV modules, and balanced three-phase grid-injected power for the qZS-CMI based PV system. A system-level modeling, which can be used to design the controllers, is also disclosed. Simulation and experiment are carried out on a 7-level qZS-CMI based PV system to validate the proposed scheme.