Automatic generation control in a deregulated power system

Load-frequency control (LFC) is used for many years as part of the Automatic Generation Control (AGC) in power systems around the world. In the synchronous Nordic power system, however, this function (termed secondary control) has so far been handled with manual control actions. Increased operational strain due to new HVDC connections in the next decade will make it increasingly difficult to maintain the current manual control system. In this paper a model of the interconnected power systems of Norway and Sweden is used to show how introduction of AGC might aid the system operator in handling the increased strain. However, the classical LFC based on the Area Control Error is difficult to implement in a deregulated environment. An alternative concept is thus introduced where selected units are automatically following load changes on the HVDC connections. This ramp following controller (RFC) supported by manual control seems to be a promising option.