Reactive Power Support in the Dynamic Voltage Stability Assessment of a Restructured Electric Power System

In recent years, the electricity sector undergoes a restructuring process, operationally and commercially, moving from a vertical integrated model to a market oriented model. With past and current difficulties in building new transmission lines and the significant increase in power transactions associated with competitive electricity markets, maintaining system security, with special regard to voltage instability/collapse issues, is more than ever one of the main concerns for market and system operators. Voltage is most readily controlled by adjustments to reactive power injections in power system. Reactive power can be produced and absorbed by both generation and transmission equipment. System operators, transmission owners, generators, customers, power marketers and government regulators need to pay close attention to voltage control. This paper is devoted to the study of the reactive power support for dynamic voltage stability of a restructured electric power system. A severe contingency situation was simulated. The automatic voltage regulators of the generating units and the mechanically switched shunt capacitors were modelled. The simulation results were obtained using the commercial transient software package EUROSTAG. Finally, some conclusions that provide a better understanding of the voltage collapse phenomena are pointed out.