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Zhao J.,Hohai University | Fan X.,Hohai University | Lin C.,Beijing Kedong Electrical Control System Cooperation Ltd | Wei W.,Beijing Kedong Electrical Control System Cooperation Ltd
Journal of Modern Power Systems and Clean Energy | Year: 2015

As the integration of distributed generations (DGs) transforms the traditional distribution network into the active distribution network, voltage stability assessments (VSA) of transmission grid and distribution grid are not suitable to be studied separately. This paper presents a distributed continuation power flow method for VSA of global transmission and distribution grid. Two different parameterization schemes are adopted to guarantee the coherence of load growth in transmission and distribution grids. In the correction step, the boundary bus voltage, load parameter and equivalent power are communicated between the transmission and distribution control centers to realize the distributed computation of load margin. The optimal multiplier technique is used to improve the convergence of the proposed method. The three-phase unbalanced characteristic of distribution networks and the reactive capability limits of DGs are considered. Simulation results on two integrated transmission and distribution test systems show that the proposed method is effective. © The Author(s) 2015.

Lin J.,Tongji University | Yang T.,Tianjin University | Hu S.,State Grid Corporation of China | Liu H.,State Grid Corporation of China | And 2 more authors.
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2015

To accurately and rapidly identify the key power flow transfer section following a cleared line due to its fault or overload, a new fast search method is proposed based on the random fuzziness clustering algorithm and the shortest path algorithm. Firstly, the vectors of line power components obtained by power flow tracking are classified using the random fuzziness clustering method with the capability of adaptive determination of the optimal cluster number, leading to an initial transfer section formed by parallel line set of fault or overloaded line, to avoid the problem probably of multi-selection or missed-selection lines of the random fuzziness clustering algorithm due to the inappropriate classification number given in advance. Then for each branch in the initial transfer section, the shortest path is obtained by searching from one end of fault or overloaded line to another end and simultaneously passing the corresponding branch. All the branches in the shortest path, having the same power flow direction as that of the fault or overloaded line, are considered as the candidate lines of the key transfer section. The key power flow transfer section is finally checked out by the simple distribution factor. The method proposed has significantly improved the recognition accuracy by taking advantage of both the branch power component clustering key section selecting method and the shortest path selecting method. The results of a number of samples show its effect and validity. ©, 2015, State Grid Electric Power Research Institute Press. All right reserved.

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