Research On Fast Calculation Method Of The Minimum Break Point Set In On-line Relay Coordination

The disadvantages of off-line relay coordination mode become increasinglyprominent, because of flexible and polytropic grid operation mode. And the unreasonablesettings have become a major security risk which could lead to blackouts accident.On-line coordination can completely solve the problems, so it has caused a wide range ofacademic research. Break point set is the key calculation step in on-line coordination,which need a long calculation time. In addition, it plays an important role in impactingprotection setting’s performance. Therefore, the fast calculation method of the optimalbreak point set has become one of the most important research directions in on-linecoordination. If the optimal break point set is calculated on-line directly, it is difficult tomeet the requirement of real-time applications. For this reason, the calculation of theoptimal break point set in on-line coordination is converted to the “off-line calculation,off-line assessment, on-line update” of the minimum break point set (MBPS). The maincontents are as follows:An optimization method which contains the space distribution characteristics hasbeen proposed for MBPS computation. In order to realize parallel computation of theMBPS, the proposed method combines MBPS’s space discrete characteristics andclustering characteristics with binary particle swarm optimization algorithm. For thisreason, the optimization algorithm’s convergence speed and success rate have beenimproved greatly. What more, according to MBPS’s symmetry characteristics, it is easyto obtain a number of MBPSs quickly which locate in different places.On the basis of the above research, the structural vulnerability assessment model ofthe MBPS has been built. In the model, the break point’s vulnerability assessment isconverted to its line’s structure vulnerability assessment. And the vulnerabilityassessment indicator which contains both betweenness centrality measurement andcloseness centrality measurement has been proposed. It can fully embody the impact ofpower flow transfer when the line is disconnected. According to this model, it is easy to obtain the MBPS whose vulnerability is lowest.After the MBPS getting from off-line assessment was applied to on-line coordination,a method for updating it has been proposed which can apply to arbitrary topologychanging. The proposed method deduces the evolution law of break point after the linecommissioning and outage or bus-tie switch open and close. According to theequivalence relation between this law and coordination sequence, the MBPS can beupdated based on relay incidence matrix, whose calculation speed is fast. At the sametime, the proposed method can obtain the minimum (or minimal) break point set in thecase of arbitrary topology changing.In addition, on-line verification is also a research hotspot in relay coordination. Inorder to improve the efficiency of parallel verification calculation, an optimal partitionmethod based on virtual node impedance matrix and boundary nodes migration has beenproposed. In this method, the nodes are classified by applying the heuristic rule to thevirtual node impedance matrix elements for achieving the initial partition result quickly.Then through migrating the boundary nodes based on the initial partition result and theshortest verification time as the objective function, the partition result which has a higherparallel efficiency can be obtained. At last, the proposed method has approximate lineartime complexity and fast calculation speed.