Fault-tolerant control of power grids for security and availability

This paper presents a framework for fault-tolerant control of a modernizing electric power grid. The motivation for the new development hinges on the potential benefits of utilizing fast control devices and high sample rate measurement devices to enhance the grid´s resilience beyond that offered by the traditional protection devices. A set of quantifiable security indices based on a fault-coverage concept is used for selection of control actions and the times to exert them. Viewed as a discrete state stochastic process, the grid´s long-run availability is shown to be an increasing function of the security indices, whereas the security indices are decreasing functions of the level of uncertainty in the grid state information, the the level of imprecision of its dynamic model. An example of an aggregated two-area power system is used to demonstrate the principle and the computation involved in achieving a minimum risk control. It also illustrates how uncertainties cause delay in control actions and reduction in the critical clearance time in order to maintain a prescribed level of security.