Wide-range reliable stabilization of time-delayed power systems

Abstract

Steam valve control is usually discarded in power system stability due to belief in its slow response. The present manuscript makes use of it as a backup control in the case of failure of the main fast excitation control. The model describing system dynamics as a function of the two controllers, with wide range loading conditions, is derived in a norm-bounded format. Linear matrix inequalities are derived as a sufficient condition to obtain reliable controllers that provide good oscillation damping when both controllers are sound or even in the case of failure of either one. The design scheme is robust in the sense that it keeps reliable stability against wide load changes as well. A single machine infinite bus system is presented to illustrate the proposed design procedure and exhibit its performance. Results of excitation and governor controller testing show that the desired performance could be fulfilled from light load to heavy load conditions. System performance shows a remarkable improvement of dynamic stability by obtaining a well-damped oscillation time response even in the case of failure of either controller. Extension of the proposed controller to multiarea load-frequency control with time delay is also presented.

Robust automatic generation control with saturated input using the ellipsoid method

“…The controller is given by K = YP −1 . Moreover, ellipsoid E, which is defined in (3), bounds the reachable sets of the system (1) with disturbance constraint (2) and control constraint (6). Note that the above matrix inequality (8) is nonlinear in the scalar α > 0.…”

“…It allows some states to be shared between the controllers. Load‐frequency control with communication network delays is also presented in Soliman et al and Dey et al…”

“…A control strategy that maintains stability against controller failure is termed reliable control. A 2‐area system controlled by 2 stabilizers, 1 for each, the LFC that maintains the stability of the global system when either controller fails or when both controllers are sound, is termed reliable control …”

“…A 2-area system controlled by 2 stabilizers, 1 for each, the LFC that maintains the stability of the global system when either controller fails or when both controllers are sound, is termed reliable control. 6 The LFC in the presence of nonlinearities in power systems is presented in Tsay. 7 The governor dead-band nonlinearities have been considered during the controller design to minimize the effect of sustained oscillation by using optimization techniques.…”

“…13 It allows some states to be shared between the controllers. Load-frequency control with communication network delays is also presented in Soliman et al and Dey et al 6,14 Control system constraints have caught the attention of many researchers, e.g., Chen et al, 15 and the references therein. One of these approaches is the positive invariance that is based on avoiding the constraint on the control signal to prevent saturation in the closed-loop.…”