Reconfiguration Of Distribution Network And Service Restoration With Distributed Generation

As a useful supplement to centralized power generation, distributed generation(DG), which bas been widely studied because it can be decreasing network losses, improving voltage profiles and reduc ing environmental pollution, etc. While DG accesses to distribution network, it brings changes to topological structure and power flow of distribution network. As one of the impor tant means to reduce network losses and improve reliability, distribution network reconfiguration can be divided into network optimization reconstruction of the normal distribution system and service restoration after network failure. Network reconfigurati on is the process of adjusting the network topology by altering the status of switches, which can help to enhance the reliability and economy of power system. So it has the theoretical and practical significance to study the distribution network reconfiguration and se rvice restoration with DGs.As a fundamental task for power system analysis and the results of the calculation, power flow calculation will affect the accuracy of the network reconfiguration. Traditional power flow algorithm is based on constant power load, which does not take into account the load voltage characteristic. T herefore, a power flow algorithm model of distribution system with DGs considering static load characteristics is proposed in this paper. Based on the analysis of operation and control of several typical DGs, different types of DGs can be classified into PQ, PQ(V), PV, PI type nodes. A forward-backward sweep method based on branch current and nodal voltage is employed to solve the power flow model. Simulation with IEEE 33 buses system was carried out to illustrate the stability and validity of the proposed method. T he results show that the presented method is flexible and is available to solve power flow of distribution network with DGs, which are prepared for the following network reconstruction.A distribution network reconstruction model with DGs considering for load voltage characteristics is presented in this paper, then a quantum genetic algorithm(QGA) based on binary-coding is applyed to solve the reconstruction model. Adaptive dynamic quantum rotation, quantum crossover and mutation mechanisms were developed in QGA, which can enhance population diversity and convergence ability. By adopting the loop matrix and hierarchical search strategy, infeasible solutions can effectively be avoided. T he effectiveness and robustness of the proposed method are verified by an IEEE 33-bus system and PG&E69-bus system with single-type DGs, multi-type DGs and without DG.A distribution system service restoration method with DGs islanding strategy is proposed considering serious failures occur which result in large area power blackout. This method is divided into two sub problems, that is, islanding operation and residual network reconfiguration(RRN). T he island partition is applied for po wer load in out-of-service area by considering the load priority and the equivalent electrical distance on the basis of the operation performance of DG s. And the RRN is a comprehensive optimization covering line losses and switching times for the residual network. T he RRN solutions are obtained by the QGA, where the switch states are expressed by binary qubits. Moreover, the simulation results of IEEE-33 bus system with DGs validate that the proposed method is reliable and effective.