Power System Oscillations
Chapter 13: Wide-Area Control
Abstract
Inter-area oscillations are a phenomenon that affects an entire interconnection. They even have the potential of being destabilized causing widespread damage. The power system community has traditionally addressed this problem with power system stabilizers (PSSs). PSSs are devices that act on the excitation systems of rotating generators and have the ability to improve the dynamics of the system. These devices are usually fed with local signals. However, it has been shown that incorporating information to damping controllers from remote signals can lead to improved performance. In this chapter we assume that a suitable wide-area control actuator has been identified, using some of the analysis techniques discussed in Part I. Then the next task is to determine suitable local and remote PMU signals to be used as the input signal(s) to the damping controllers.
A superior input damping signal would result in an input-output transfer transfer function lacking zeros near or in the right half-plane (RHP) which are close to the inter-area modes, thus allowing the use of higher gain controllers to achieve sufficient inter-area damping. This chapter discusses two studies using different strategies to deal with the reliability of the remote signals. The first is a wide-area controller for the western interconnection that was tested in the actual system and demonstrated the benefits of using wide-area signals for damping control. This controller also shows why remote signals outperform local signals in damping applications. The chapter then presents the design of an adaptive wide-area controller. This controller uses an adaptive switching controller to compensate for network latencies in the remote synchrophasor signals to derive its control action.
