Voltage stability assessment and enhancement of a large power system using static and dynamic approaches

Voltage instability initiated by induction motor dynamics has been an important issue in power system operation. The voltage instability in a power system having significant induction motor loads can be manifested either in the form of delayed voltage recovery or in the form of voltage collapse. When a power system is subjected to a disturbance in the presence of considerable induction motor loads, static analysis alone is not sufficient to determine the control actions required to restore the system voltages. Time domain simulations are required to obtain useful indications to deal with controls depending on system time evolution. The present study focuses on the application of a mix of various static and dynamic approaches to analyze and enhance the voltage stability of power systems. Static analysis is used mainly to select critical contingencies based on voltage stability margins whereas the dynamic analysis is used to find the mechanism of voltage collapse. The propagation of impact of faults from the transmission level to the distribution level is observed to examine the mechanism of voltage collapse and to determine the corrective action to mitigate the detrimental effect of the voltage collapse. The impact of induction motors on voltage stability is examined using trajectory sensitivity analysis. A novel technique based on a trajectory sensitivity index is proposed to find the suitable location for dynamic reactive power support. In this regard, the viability of FACTs controllers such as SVC and STATCOM is examined. Accordingly, the latter is found more effective for providing corrective action against voltage collapse.