Power System Contingencies

Power system voltage control has a hierarchy structure with three levels: the primary, secondary, and the tertiary voltage control. Over the past 20 yrs, one of the most successful measures proposed to improve power system voltage regulation has been the application of secondary voltage control, initiated by the French electricity company, EDF, and followed by some other electricity utilities in European countries.

The secondary voltage control closes the control loop of the references value setting of controllers at the primary level. The primary objective of secondary voltage control is to achieve better voltage regulation in power systems. In addition, it brings in the extra benefit of improvement of power system voltage stability, for this application, several methods to design secondary voltage controllers have been proposed.

The useful concept of secondary voltage control is explored for a new application-the elimination of the voltage violations in power system contingencies. For this particular application, the coordination of various secondary voltage controllers is proposed to be based on a multi agent request -and- answer type of protocol to between any two agents. The resulted secondary voltage control can only cover the location where voltage controllers are installed. This paper presents results of significant progresses in investigating this new application to eliminate voltage violations in power system contingencies via secondary voltage control.

A collaboration protocol, expressed graphically as finite state machine, is proposed for the coordination among multiple FACTS voltage controllers. The coordinated secondary voltage control is suggested to cover multiple locations to eliminate voltage violations in the adjacent locations to a voltage controller. A novel scheme of a learning fuzzy logic control is proposed for the design of the secondary voltage controller. A key parameter of the learning fuzzy logic controller is proposed to be trained through off-line simulation with the injection of artificial loads in the controller's adjacent locations.