Locating minimum number of PMUs for preand post-disturbance monitoring of power systems

In this study, the post-disturbance coherency of buses is added to the conventional phasor measurement unit (PMU) placement problem to find the minimum number of PMUs at different depths of unobservability. To do that, different scenarios are defined based on probabilistic parameters. Then, in each scenario, central buses are determined based on the similarity of post-disturbance variations using subtractive clustering algorithm. The central bus in each area is the bus that its postdisturbance variations are similar to the highest number of buses in the area. The PMU placement problem is then solved considering the number of scenarios where each bus has been selected as a central bus. The resulted placement scheme is more suitable for monitoring the power system dynamics compared to the conventional method. In order to reduce the number of PMUs, the placement problem is solved for higher depths of unobservability. In each depth, the voltage phasor of unobservable buses is obtained using state estimation methods. The results of applying the proposed methodology on 68-bus, 16-machine system show its better performance compared to the conventional method.