Abstract
A power system is considered to be fully observed when all bus voltages and currents are known. Phasor Measurement Unit (PMUs) opt to achieve system's observability when placed at selected buses throughout the system. Optimal PMU placement is concerned with determining the least count and position of PMUs needed to fully observe the system. This paper considers such optimization problem in the presence of zero injection buses (ZIBs). A novel solution is proposed where the system observability is modeled as a graph. A special transformation is presented to reduce the complexity of the optimization while factoring in the contribution of a ZIB to the system's observability. The optimization problem is then formulated as an integer linear program. Validation is conducted using different IEEE bus systems and using randomly generated power grid topologies. The results confirm the performance advantage of the proposed approach over competing scheme in the literature.