An Efficient Power Quality Enhancement for a Renewable Source Connected Inverter

Abstract

This paper proposes cascaded voltage and current control strategy for inverter in micro grids. Thisstrategy gives excellent performance of THD (total harmonic distortion)for both inverter local loadvoltage and grid current and it improves the power quality. Many of the new types of distributed energy resources (DER) are inverter based, such as photovoltaics (PV), wind, microturbines, and fuel cells. Inverters with energy storage enable new functionality such as peak shaving, energy arbitrage, and seamless islanding, i.e. UPS functionality. Herea cascaded current–voltage control strategy is proposed for inverters to concurrently progress the power quality of the inverter local load voltage and the current switched with the grid.In general control scheme comprises an inner voltage loop and an outer current loop, with both controllers designed using the H^∞ repetitive control approach. This leads to a very low total harmonic distortion in both the inverter local load voltage and the current exchanged with the grid at the same time.Our proposed control approach can be employed to single-phase inverters as well as three-phase four-wire inverters. It allows grid-connected inverters to inject balanced clean currents to the grid even when the local loads (if any) are unbalanced and/or nonlinear.