Fully decoupled fixed-time cascade control of three-phase voltage source converters with LC output filter

Abstract

This paper presents a fully decoupled fixed-time cascade control system of three-phase voltage source converters (VSCs) with LC output filter. The proposed controller has a cascade structure and it is designed in the synchronous reference frame d-q. The outer loop is for voltage control and the inner loop is for current control. A fixed-time controller is developed for voltage regulation and reference tracking before the desired pre-fixed time despite the unknown disturbances. The current controller uses PI controllers for current regulation and feedforward terms to decouple the direct and quadrature of voltage and current control loops. Unlike the conventional PI-based synchronous reference frame VSC control, the proposed approach provides better control performance with smaller and smoother control signal and enables the d-q components of voltage and current to be fully decoupled. A comparative simulation study with the conventional control system is provided to highlight the effectiveness of the proposed approach.