SRF and real power theory based control of a nine switch converter based UPQC

A conventional Unified Power Quality Conditioner (UPQC) is a back-to-back shunt and series converters with a dc-link capacitor, requires 12 switches to resolve voltage and current related power quality issues. Recently a nine-switch UPQC (NS-UPQC) is proposed, but suffers with certain limitations like limited reference amplitude and phase shift, twice the rated dc-link voltage and increased stress on the semiconductor devices. To overcome these issues, in this paper nine-switch UPQC (NS-UPQC) is investigated using Synchronous Reference Frame (SRF) and Real Power Theory (P-Theory) with harmonic extraction based control schemes. The nine-switch UPQC (NS-UPQC) model with the proposed control schemes are developed in Matlab/Simulink software and its performance is examined under various conditions like load voltage and supply current harmonics, supply unbalanced currents, voltage sag/swell. %THDs of voltage and current are also analyzed in this work.