Delay-Scheduled Controllers for Inter-Area Oscillations Considering Time Delays

Unlike the existing views that was introduced the existence of delay caused by the transmission of wide area measurement system data (WAMS) into the controllers input of the power oscilation damping (POD) by communication networks as a reason for poor performance of the POD controllers. This paper shows that the presence of time delay in the feedback loop may improve the performance of a POD controller in reducing inter-area oscilations. In fact, in a situation where the design and implementation of a POD controller for an FACT device is not easy without delays, in order to compensate for the delay effectively. In this work, a delayed scheduling method to design POD controllers is proposed. At first modeling of power system with delay as a design parameter was established. Then, the power oscillation damping delay scheduling (PODDS) based on objective function of the spectral abscissa was designed and the sufficient condition about stability of the closed-loop system is given. To evaluate the accuracy of the proposed control function and feasibility study, a four-machine power system for numerical simulation was used. The simulation results show that the controller designed in a wide range of delay changes decreases the power system oscilations without restricting SVC performance.