Performance Evaluation of Three-Phase Unified Power Quality Conditioner controlled using SRF

This paper discusses the performance evaluation of three-phase three-wire Unified Power Quality Conditioner (UPQC) using Synchronous Reference Frame (SRF) Theory. The core objective of any electrical utility is to supply quality power to load end uninterruptedly with constant frequency, sinusoidal balanced rms voltage and current. Electrical and electronic equipment such as variable speed drives, Switch-mode power supplies (SMPS), high penetration of non-linear loads injects lot of harmonics in supply current of the system thereby affects the neighboring loads and source as well. On the other hand, compressors, induction motors, pumps etc. draw high input surge current during starting thereby creating sag/swell in system voltage. To compensate power quality concerns associated with both current and voltage, a device called UPQC considered to be the most prevalent device for sensitive and critical loads. It consists of shunt and series Active Power Filters (APF) which are connected back-to-back using dc-link capacitor. A PI controller is used for the balancing of delink capacitor voltage. UPQC is used to alleviate harmonics in load voltage, supply current; and balances the load voltage of the distribution system. In this paper, UPQC is designed, modeled, controlled and simulated for different disturbances in source voltage i.e. sag/swell, polluted grid. Results are presented to analyze the total harmonic distortion (THD) in voltage and current, power flow and dc-link voltage for nonlinear load using Simulink based MATLAB model.