| State estimation is the core of EMS’s guarantee towards the quality of real-time data of the power system and basis for EMS online advanced software applications. Observability of power system is the necessary condition of state estimation, the algorithm of which have a direct affect on the smoothly running and accuracy of state estimation.Two types of missing judgment problems currently exist in topological observability analysis based on the solvability condition of power flow. Based on the fact that there can only be one unknown state voltage parameter in one measurement island, this paper presents a method of adjacency table of boundary nodes with injection measurement that can systematically analyze and observe these missing judgment problems. The first type of missing judgment, which indicates that even the overall network is not mergeable, yet the partial network can be combined, is settled by using combination of local equations solvability and heuristic search algorithm after proposing the concept of injection deficiency of the boundary nodes with injection measurements. After analyzing the conditions and requirements of two networks with intersection that can be judged together, this paper solved the second type of missing judgment that the power flow of two unsolvable networks is solvable when combined through the necessary conditions derived from analysis. In addition, when the system is judged unobservable, the improved algorithm put forward the automatically appending of pseudo measurements by the revised adjacency table of boundary nodes with injection measurement after merge operation, besides pseudo measurements can be guaranteed all key measurements. Finally, this paper gives the comprehensively improved topological observability analysis method based on the solvability condition of power flow, whose implementation is by means of adjacency table of boundary nodes with injection measurement. An IEEE14-node system, a15-node case and a Hebei southern grid example were used to test the validity of the method. |
