Control and filter design of three-phase inverters for high power quality grid connection

TLDR

In distributed generation and micro‑grids, inverter use demands low‑distortion, high‑quality power export, yet switching‑frequency effects and existing grid voltage distortion can degrade quality, and filters can attenuate these components but affect control bandwidth and grid impedance. The study proposes a filter incorporating an isolating transformer and a complementary controller to reject grid disturbances, preserve waveform quality, and enable real and reactive power control. The authors implement this filter and controller in discrete time and validate the design experimentally. Experimental results confirm the discrete‑time implementation achieves the intended performance.

Abstract

The trend toward using inverters in distributed generation systems and micro-grids has raised the importance of achieving low-distortion, high-quality power export from inverters. Both switching frequency effects and pre-existing grid voltage distortion can contribute to poor power quality. A well designed filter can attenuate switching frequency components but has an impact on the control bandwidth and the impedance presented to grid distortion. This paper describes a filter designed to incorporate an isolating transformer and the design of a complementary controller that rejects grid disturbance, maintains good waveform quality and achieves real and reactive power control. A realistic discrete time implementation is discussed and validated with experimental results.