Nonlinear optimal control applied to STATCOM for power system stabilization

This paper presents the results of simulator test for improvement of power system stability by applying a nonlinear optimal control to a static synchronous compensator (STATCOM). The STATCOM using the self-commutated converter was selected for this study among FACTS devices, and the power system oscillation damping control and voltage control were designed by using the approach of nonlinear optimal control based on the differential geometry theory. The capability of STATCOM supplies the reactive power at low voltage is larger than conventional SVC, and reactive power of STATCOM can be controlled continuously at high speed. The stabilizing control system was investigated supposing that STATCOM is used in the nonlinear operating points. Specifically, the stabilizing effects by nonlinear control theory were compared with the effects by linear control theory. It was confirmed that nonlinear control was more effective compared with linear control. Moreover, system conditions where nonlinear control operates effectively were clarified.