Modeling and design of multi-loop closed loop controller for Z-source inverter for distributed generation

This paper presents the modelling and designing of a multi loop controller for Z-source inverters used in distributed generation systems. Z-source inverter is recently proposed converter capable of operating in buck and boost modes. Hence it is more suitable for DG applications over the other alternative converter topologies. When employing the Z-source inverter in DG applications, closed loop controlling is necessary to achieve good reference tacking and disturbance rejection properties. Hence this paper focuses on developing such closed loop controllers. The system was modelled mathematically and transfer functions were obtained. Closed loop controllers were designed by considering Z-source inverter as a combination of VSI and boost converter. Proposed controllers would minimize the effects of non-minimum phase characteristics present in the DC side and a cushioning method was employed to mitigate the transferring of DC side disturbances into the AC side. Proper operation and validity of designed controller was proved with simulations in Matlab/Simulink and experiments carried out using a laboratory prototype.