Coordinated Optimization of Parameters of PSS and UPFC-PODCs to Improve Small-Signal Stability of a Power System with Renewable Energy Generation

Abstract

The ever-increasing penetration of intermittent renewable energy generation from wind farms (WFs) and photovoltaic (PV) plants has significant impacts on the stability of the power system concerned. This paper examined the effect of the power oscillation damping controller (PODC), consisting of a power system stabilizer (PSS) and a unified power flow controller (UPFC), on the stability of a power system with doubly fed induction generators (DFIGs) based WFs and PV plants. The small-signal stability of a power system with intermittent renewable energy generation was enhanced by coordinately adjusting the parameters of damping controllers of the PSS and UPFC-PODC, as formulated as a multiobjective optimization and solved by the steepest descent algorithm (SDA). The well-coordinated application can suppress significantly the low-frequency oscillation (LFO). In addition, an index based on eigenvalues and damping ratios is proposed to measure the damping change of the power system. A four-machine, two-area sample power system was employed to test the proposed method through several designed scenarios, including changing the tie-line transmission power, increasing wind power and PV outputs, and changing WF and PV plant access points. The performance of the proposed method was demonstrated through small-disturbance eigenvalue analysis and short-circuit fault dynamic time-domain simulation. Simulation results showed that simultaneous optimization of parameters among different controllers effectively suppresses local and interarea oscillations.