PMU placement for optimal three-phase state estimation performance

The future ‘smart’ grid will see increasing deployments of intelligent electronic devices (IED), that sense the state variables of the grid at more locations than present. It is anticipated that sensory devices with Phasor Measurement Unit (PMU)-like capabilities will find deployment within the changing distribution sub-system, to provide greater operational efficiency. However, due to the current high cost of PMU installation, their deployment in the distribution network will continue to be selective for the foreseeable future. Much of the prior literature on PMU placement has focused on how to obtain full observability with minimal number of PMUs for a single-phase power network. Very little work exists for the placement problem for three-phase distribution grid. We further observe that there typically exist multiple minimal-PMU sets that achieve full network observability, affording additional degree of freedom to select an optimal choice among this set. We define the desired solution as the PMU placement that also achieves best overall state estimation performance. Accordingly, we derive the state estimator of all buses in a three-phase network and propose a) greedy algorithm and b) integer programming optimization method to determine the optimal solution. The comparative performance of these two methods is presented via evaluation of transmission and distribution test networks.