A methodology for the redesign of frequency control for AC networks

This paper describes a methodology for redesigning an ac network frequency control considering the cost of control, network security, reliability, and markets. This methodology was used to implement changes in the Southern African network and in Eskom as one of the control areas in this network. Most networks have frequency control strategies and targets that have been inherited from other networks. There is no existing methodology to use when starting anew. Most optimization strategies assume that the best control is the tightest frequency control as this is the most reliable. The cheapest solution is not to move the generator or customer at all from an optimal position. This has to be traded against the cost of not having any reliability. The new frequency control strategy implemented in Eskom has reduced the generator movement by over 80% without a major impact on the customer or on the reliability of the network. Regulation energy costs have also dropped as dispatch is done more closely to merit order. The inadvertent energy to neighboring control areas has shown no negative impact.