Flexible control of UPQC for selective compensation of power quality problems

The unified power quality conditioner (UPQC) is a combination of back to back connected shunt and series active power filters (APFs) to a common DC link voltage, which compensates voltage and current based distortions, independently. Generally the power conditioning devices are designed for complete compensation, irrespective of the requirement/priority. In this paper flexibility of selective compensation is proposed in the control scheme of shunt APF while, the series APF is switched `on´ or `off´, as per the requirements. The shunt APF compensates the source current harmonics, reactive power and unbalance in source currents and their combinations, depending upon the limited rating of voltage source inverter (VSI). In this proposed control scheme of UPQC, the current/voltage control is applied over the fundamental supply currents/voltages instead of fast changing APFs currents/voltages, thus reducing the computational delay and the required number of sensors. The performance of the proposed control scheme of UPQC is validated through simulations using MATLAB software with its Simulink and Power System Block set toolboxes.