A Study On Optimal PMU Placement Based On Coherency Identification Of Generating Sets

PMU can collect state information of power system with accurate time produced by GPS,thus it can measure every node data synchronously. For the consideration of economy andtechnology, it is not practical that PMU is put in every node. So the optimization of PMUallocation is regarded by manyscholars. The paper distinguishes generators bythe characteristicsof coherent generator group after fault. The rotor angle surge curves of all generators in the samegroup are similar. If every coherent generator group assigns a PMU which represents thecharacteristics of the group, this method can realize the measurement of total system with leastPMUs.Based on coherency identification theory, this paper identifies generators correlationaccordingtoreachabilityGrammiamofsystemmodel.Themethodisfastandexact,andprovidesnecessary and sufficient condition for generator correlation recognition. Then generators aregrouped bytheir correlation usingimproved graph traversal algorithm.Thus a novel approach forPMUoptimizationallocationisdeveloped.The paper presents the result of coherent generator group identification in Huazhong powersystem using the proposed approach under the condition of basic load, stochastic load andmaximal load. On the basis of hierarchical clustering arithmetic, the coherent generator groupswith analogical characteristics are united in the result of above example using group averagemethod. In the end, the new comprehensive result of coherent generator group identification isachieved. Then every group is assigned a PMU. So a scheme of PMU optimization allocation isobtained.