A study on the dynamic responses of a PWM based UPFC and its application to power system

This paper presents the analysis of the dynamic responses of PWM (pulse width modulation) based UPFC (unified power flow controller) and its interaction with a power system. Detailed switching-level simulation is performed using EMTP (Electromagnetic Transient Program) and its dynamic responses are analyzed. Based on the simulation results, the appropriate equivalent impedances of UPFC voltage-source model which represents similar dynamic responses with PWM based UPFC are determined by an optimization routine. This paper also analyzes the influence of control parameters and the power system strength on the performance of UPFC. Finally this paper shows that the performance of UPFC is improved by control parameter tuning when UPFC is installed in a weak power system.