Masahiro Sekoguchi

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.

Mathematical model for a combined cycle plant and its implementation in an analogue power system simulator

Large-scale blackouts due to a cascade trip of gas turbine generators have been reported. From the viewpoint of improving power system reliability, the behaviors of gas turbine generating plants and combined cycle plants during the occurrence of a large disturbance in the power system should be clarified. In this paper, a block diagram representing dynamic behaviors of a combined cycle plant, derived from process physical relationships, is described and a modeling method of a multi-shaft type combined cycle plant is proposed. Simulation methods of the combined cycle plant in an analog power system simulator are shown.

Power system transient stability enhancement by STATCOM with nonlinear control system

A nonlinear control approach is applied to static synchronous compensator (STATCOM), which is one of the FACTS devices. Here, the nonlinear controller is designed locally based on mathematical models of one of the generators, STATCOM and transmission lines in a multi-machine system. The influence of the proposed controller, which controls the terminal voltage of STATCOM, on the power system stability is tested by digital dynamic simulations. As a result of the simulation, it has been made clear that the STATCOM can improve the transient stability in the 3-machine loop system. In the case of the IEEJ West 10-machine system, the effectiveness is also discussed.