Optimal placement of PMUs in power system network for voltage stability estimation under contingencies

Voltage stability has been considered as an important threat to power researchers and utilities since last few decades. With placement of Phasor Measurement Units (PMUs) at few selected locations, it may be quite possible to monitor voltage stability of power system network. This paper proposes optimal placement of PMUs considering impact of voltage stability based critical contingencies. Contingencies have been ranked based on voltage stability margin (the distance between the base case operating point and nose point). Variations in voltage stability margin caused by changing load patterns have also been considered while deciding critical contingencies. PMUs have been placed in the system based on results of binary integer linear programming run under system intact case and voltage stability based critical contingency cases. Effectiveness of proposed PMUs placement approach has been established by comparing nose curves obtained using PMUs measurements and pseudo-measurements under increased demands, with offline estimation of nose curves based on the results of continuation power flow. Case studies have been performed on a standard IEEE 14-bus system and practical 246-bus Northern Regional Power Grid (NRPG) system representing power network of nine states of India, with the help of Power System Analysis Toolbox (PSAT) software.