Dynamic Performance of a Vector-current Controlled Unified Power Flow Controller Installed in a Real Chinese Power Network

Abstract

This paper examines the dynamic performance of a vector-current controlled unified power flow controller (UPFC) to be installed in an actual Chinese power network. This first UPFC of China, with a total rating of ±120MVA, has been in full operation since the end of 2015. This paper establishes the non-linear dynamic mathematical model of the vector-current controlled UPFC to be installed in the power network and carries out detailed examination on the dynamic performance of the UPFC and its impact on power system small-signal angular stability. The linearized model of the UPFC is derived afterwards. Based on the derived model, dynamic interactions among the multiple control functions of the UPFC are investigated by using the method of relative gain array (RGA). It is found that the vector-current controlled UPFC exhibits well decoupling performance among multiple control loops. This finding is further confirmed by the results of non-linear simulation. Moreover, modal analysis is conducted to examine the impact of the installation of the UPFC on the damping of electromechanical oscillation modes of the real power network. Conclusions of the modal analysis are further validated by the non-linear simulation results.