A Robust Decentralized Wide Area Damping Controller for Wind Generators and FACTS Controllers Considering Load Model Uncertainties

This paper presents a systematic procedure to design a decentralized wide area damping controller for the wind farms and flexible ac transmission system (FACTS) controllers in a smart grid considering uncertainties in the load parameters. The effect of uncertainties in load parameters on damping of inter-area modes of oscillations is investigated through the probability collocation method. A robust $\boldsymbol {H_{\infty }}$ output feedback controller is then designed for the uncertain fuzzy system by satisfying linear matrix inequalities, which are obtained from the original bilinear matrix inequalities derived from the Lyapunov-based stability criterion. The input and output signals for the proposed controller are selected based on a joint observability/controllability index. The input signals are wide area signals obtained from the phasor measurement units and the output signals are fed to wind farm generators and the FACTS controllers. The input signal delay compensation is addressed in this paper. The performance of the controller has been tested on New England 39 bus system developed on real time digital simulator and on a practical large Indian power system under various operating scenarios and faults. Its effectiveness is also compared with a conventional power system stabilizer, local damping controllers, and an existing robust centralized wide area controller designed based on mixed $\boldsymbol {H_{2}} / \boldsymbol {H_{\infty }}$ output feedback synthesis.