Comparative evaluation of performance of different control strategies on UPQC connected distribution system

This paper presents a comparative analysis of steady state behaviour of UPQC with three different control techniques, when connected to a distribution system to protect sensitive loads against power quality problems. The control strategies based only on hysteresis, SPWM and a combination of both for controlling the firing pulses of shunt and series APFs of UPQC are discussed. In common, PI control is used for maintaining DC link voltage. PSCAD/EMTDC is used to model the UPQC connected to a RL load. The simulated model is tested with all the three control strategies and the results are verified for voltage sag and swell compensation. A comparison is made between the control schemes, taking in account of the current through shunt APF and current at the point of common coupling (PCC). The results are appreciable when hysteresis type control is applied to shunt APF and SPWM control to series APF.