Dynamic Stability Improvement of Power System with Simultaneous and Coordinated Control of DFIG and UPFC using LMI

This paper presents an enhancement of the dynamic stability of a power system equipped with both a unified power flow controller (UPFC) and a doubly-fed induction generator (DFIG) by using the LMI technique . We use all UPFC main basic PI controllers and its power oscillation damping (POD) supplementary controller. A more complete model of DFIG and both rotor-side converter (RSC) and grid-side converter (GSC) dynamics with their controllers are considered, too. These two devices controllers are simultaneously coordinated and optimized with compromising between their control variables parameters. The particle swarm optimization (PSO) algorithm is used to optimize the objective function based on eigenvalues and damping ratio to reach the best parameters and variables of controllers of both UPFC and DFIG. Linear matrix inequality (LMI) is applied to the whole system linearized model to reach optimally modified eigenvalues. Within the steady state and dynamic study, we consider practical line thermal capacity and UPFC power rating, too. Simulation results in 39-bus 10-machine New-England power systems illustrate the capability of the applied method. The results demonstrate that coordinated control of these two devices besides using LMI results in more damping of system modes oscillations and more stability in the power system.