Optimal control of SMES systems for maximum power system stability and damping

Abstract

Fast development of power electronics and computers has provided the basis for an accelerated development of various flexible AC transmission systems (FACTS). Some of these systems have already been successfully applied while others are constantly being evaluated for future applications in order to improve the transmission capability, stability and dynamic performance of existing power systems. Superconducting energy storage systems (SMES) represent an interesting prospective FACTS technology since they can generate/absorb active and reactive power in rapid response to power system requirements. SMES' systems are considered for a variety of applications: automatic generation control; fast spinning reserve; peak generation and load sh fting; improving stability, dynamics, transmission efficiency and voltage performance; etc. A number of such applications have been studied and a few experimental systems have been built and evaluated. SMES application is particularly interesting for long transmission systems such as Hydro-Quebec's, for example. This paper presents the use of the optimal control of SMES systems to achieve transient stability and damping of the power system. The synthesis of an optimal controller is illustrated on a two-machine equivalent for simplicity. Solving this problem yields some important conclusions with regard to the control and efficiency of active and reactive power when applied to improve system stability and damping. Implementation aspects of the optimal control for large power systems are discussed.