Voltage stability and voltage recovery: Load dynamics and dynamic VAR sources

Two of the most frequent causes of power system voltage instability are voltage recovery following faults, and voltage collapse during transient swings. We propose methods for the identification and mitigation of these phenomena by appropriate usage of control devices such as dynamic VAR sources. We also propose a method for the reliable simulation of these phenomena, called "the time continuation method". This method combines the efficiency of power flow techniques and the capabilities of transient stability models. It is based on a quadratic model of the power system, including generators, voltage regulators and dynamic loads consisting mainly of induction motors. This model explains recently observed voltage stability and voltage recovery phenomena. Numerical experiments with visualizations are presented for the purpose of quantifying the phenomena and identifying the major affecting parameters. It is shown that proper combinations of static and dynamic reactive power sources can alleviate the risk of voltage instability. Finally, we propose a methodology for selecting the location and size and mix of static and dynamic VAR resources for the purpose of alleviating the risk of voltage instability and slow voltage recovery.