Control of single-phase Z-source inverter for a grid connected system

This paper presents a single-phase Z-source inverter as a power conditioning system for a grid-connected system. Z-source inverter is a single-stage topology that has buck-boost feature, which is possible because of additional shoot through state introduced in zero state of the conventional inverter pulse width modulation and provides desired output AC voltage. Small DG system with alternate energy sources requires power conditioning units with low cost, high efficiency and tolerance to wide range of input voltage variation and has to perform various functions such as dc-ac conversion, system control and achieve power quality norms. A two-loop control strategy, one Z-source capacitor voltage regulation and other for ac side control with inductor current feedback with voltage feed-forward is employed, which gives good transient response also suppress load and source disturbances effectively. Simulation results are presented to validate proposed control strategy and also open-loop results presented.