Dual Current Loop Control for a Third-Order Passive Damped Filter Based Quasi-Z-Source Inverter

Abstract

An Impedance Source Inverter (ZSI) offers a solution to low output renewable energy sources, because it provides an unconventional high boost. The interaction of Quasi-Z-Source (qZS) inverter with the load side raises stability concerns. Multiple resonant features need attention when grid is connected. In this paper, the resonant feature of a third order filter based on a qZS inverter is explored, and DC and AC sides dynamic characteristics are analyzed for optimum size selection of passive components. Coupled response of a qZS inverter and the AC side filter is presented. For input variation, a closed loop control is established to take care of stability and the multiple resonant feature. A voltage loop and a dual current loop are used for DC and AC side dynamics respectively. Controllers are designed to mitigate input side disturbance. Results are provided for two design cases (case I, II), the need for damping is highlighted, and measured results validate the design and control methodology.