Power system stability increase by secondary voltage regulation applied to the South Africa transmission grid

Due to growing competition in the electricity market, the drive for efficient, stable and secure grid operation makes voltage control in the transmission grid relevant. A solution that has potential is to increase the effectiveness of the ancillary service by automatic fast control. The paper describes a Wide Area Voltage Regulation (V-WAR) that fits this framework. The V-WAR is based on Secondary and Tertiary Voltage Regulations (SVR; TVR). Currently ESKOM-TAP is investigating this kind of V-WAR for application in South Africa (SA). The V-WAR is a hierarchical closed-loop control system that operates beyond the conventional regulating and emergency control types by implementing innovative, timely and coordinated control of the main reactive power resources that are situated in the field. The proposed V-WAR is simple, has a control structure that is easy to implement and provides the means to achieve smart objectives that could never be attained without it. The SVR application is described, shown to have a robust selection of pilot nodes, control power stations and areas in the SA transmission grid. The control loop dynamics and characteristics of SVR are presented and significant objects achieved due to its effective functionality are highlighted. The noticeable improvement in voltage and angular stability and in saving grid operation at voltage closed to the maximum continuous value, are the main paper issues. Jointly to other relevant results (already presented at IEEE-PES GM2010 and here simply remembered) such as less switching maneuvers at compensating equipment, system loss reduction, minimization of the generator control effort by moving from Primary Voltage Regulation (PVR) to SVR, all these benefits significantly contribute to justify the V-WAR application in SA.