Control and design of a current source united power quality conditioner with fault current limiting ability

This study proposes control and design methods for a current source united power-quality conditioner (CS-UPQC). Unipolar modulation and parameter design methods are proposed for the series CS converter. The proposed modulation method doubles the equivalent switching frequency, which makes it possible to reduce the filter size and improve the control dynamics. Modified repetitive control schemes are presented for the voltage and current compensation strategies, which provide large open-loop control gains at the integral multiple of the fundamental frequency and guarantee good harmonics compensation performance. A fault current limiting scheme is also presented, which limits the fault current effectively by utilising the large DC link inductor of the CS-UPQC. Simulation results in Matlab/Simulink are presented to clarify the theory and feasibility of the proposed approaches.