Adaptive tuning algorithm for single‐phase Z‐source inverters

Abstract

This study proposes an adaptive tuning algorithm for dynamic adjustment of the saturation limits for the shoot-through duty ratio (STDR) and modulation index of a Z-source inverter. This adaptive tuning is crucial in Z-source inverter applications where wide fluctuations in dc source voltage are expected. Even though a standalone application is chosen here to demonstrate the validity of an adaptive tuning algorithm, the proposed algorithm is equally valid for other applications using Z-source inverter based topologies also. The effects of non-idealities on dc-link voltage and ac output voltages are investigated, and STDR expressions for which the dc-link voltage is maximal are derived. Subsequently, these expressions are utilised to define the saturation limit of the STDR in the proposed adaptive tuning algorithm. The transient phenomenon of state-switching behaviour in a Z-source inverter under closed-loop operation is analysed for different perturbed conditions. A laboratory prototype of a 250 VA single-phase Z-source inverter is built to demonstrate the proposed adaptive tuning algorithm. The proposed algorithm and associated control laws are implemented using a dsPIC30f6010 microcontroller. The effectiveness of the closed-loop controlled single-phase Z-source inverter system is tested with linear and non-linear loads. The measured results are in close agreement with analytical investigations.