PERFORMANCE INVESTIGATION OF UNIFIED POWER QUALITY CONDITIONER (UPQC)

Abstract

Power Quality (PQ) is used to describe the electrical phenomenon manifested in terms of variations in current, voltage and/or frequency that produce undesirable effects in the power system. The growing interest in the utilization of renewable energy resources for electric power generation is making the electric power distribution network more susceptible to power quality problems. Efficiency and cost are the major concerns in the transmission and distribution systems. In the last several years, there has been considerable interest in the development, use and application of active filters because of the increasing concern over power quality, at both distribution and consumer levels. Also there has been a need to control current & voltage harmonics, reactive power and voltage levels at different transmission levels. This work aims at giving a brief outlook into the field of active filters, mainly, Unified Power Quality Conditioners (UPQC) in a three phase three wire system. The circuit configurations, basic working principle, the control scheme used, compensation techniques used for the generation of reference currents and reference voltages has been studied in detail. Also, this thesis discusses a reduced DC-link voltage rated Unified Power Quality Conditioner (UPQC) which eliminates current and voltage harmonics in a distribution network thereby improving the quality of power. Series capacitors have been introduced in cascade with the coupling inductors on the shunt filter side of the UPQC. This topology helps in reducing the voltage rating of DC-link capacitor without compromising on the harmonic mitigation and thus acts as a cost effective solution in the distribution side. A simulation study of the traditional and new topology of UPQC have been made in a three phase three wire system and is compared with the conventional topology of UPQC. Simulation has been implemented in MATLAB/Simulink and the results obtained prove the robustness of the new topology.