Rule-based control for STATCOM to increase power system stability

As a major FACTS (flexible AC transmission systems) project in China, a ±20 MVAr STATCOM (static synchronous compensator) will be put into operation in Henan province, Central China in 1998. The STATCOM is expected to supply fast voltage control and enhance the damping of inter-area electromechanical oscillations of the system. This paper analyzes the conflicts between these control objectives and discusses the existence of the deadpoint of a STATCOM damping controller. Based on the analytical conclusions, a rule-based controller, which employs bang-bang, fuzzy logic or fixed-parameter PI control strategy according to the operation state, of the system, is designed to compromise the control objectives. Nonlinear digital simulation results show the advantages of the proposed controller over the conventional fixed-parameter PI controller