Approach on nonlinear control theory for designing STATCOM controller

The static synchronous compensator (STATCOM) can improve the static and dynamic voltage stability of the bus on power system and keep the voltage of the electric network in the receivable operating mode. STATCOM can also improve the system damping and restrain effectively the oscillation. The paper linearized the nonlinear state equations of STATCOM by the exact linearization method of the nonlinear control theory and obtained the linearized state equations , then computed the closed-loop dominant poles according to the system performance index in time domain and utilized the Ackermann algorithm to work out the state feedback matrix. Control input signals of pulse width modulation (PWM) could be obtained by the computation, which controlled the devices of the power electronics conduction or shutoff. The paper expressed the simulation results of power system dynamical process that three-phase grounding fault happened in the load-bus side of one infinite-system and power load with STATCOM. STATCOM operated under the state feedback control and the general proportional integral control (PI control) respectively. At last, the two results were compared and analyzed and it was evident that the state feedback controller based on the state equations linearized exactly could realize the anticipative demand and realize the voltage support effectively.