Research On Optimization Strategy Of Black-start And Network Reconfiguration Of Power Systems

The extensive blackout occurred in recent years has proved that the widespread blackout is a serious threat to the modern power systems. As the scale of power system becomes larger and the modern society is more dependent on the power supply excessively, the damage due to widespread blackout is more and more severe. Therefore, as one of self-rescue measures, the research on power system black-start restoration and its optimization technique is of great importance to relieving restoration burdens, speeding up the system restorationre process, reducing the economic loss and social influence resulting from faults.After thoroughly investigating the previous work about the black-start issue, the optimization technique about balck start stage and network reconfiguration has been studied systematically, the main work of this thesis is described as following:1. An assessment method of power system black-start schemes considering subsequent restoration efficiency is proposed and its sensitivity is analysed. First, the interdependence of black-start and follow-up system restoration process is analysed thoroughly, the indexes reflecting subsequent restoration efficiency is extracted, and all indexes is conformed to construct a new assessment index system. Then, Fuzzy Analytic Hierarchy Process algorithm is proposed to evaluate the black-start schemes. And last, the sensitivity of the assessment result is analysed, and the marginal weight coefficient and marginal index which can lead to the change of the rank of black-start schemes are calculated.2. An extended black-start optimization decision-making method is proposed. Firstly, the black-start restoration process is analysed thoroughly, a novel extended black-start strategy is proposed, in which a single black-start source can be used to start more than one power plant simultaneously. Secondly, the mathematic optimazation model of the extended black-start strategy is presented by analysing the restoration target and the consideration of the constraints of generator's start-up and power system's operation comprehensive. Thirdly, the solving method is studied by analysing the optimazation modle, and the solution algorhthem is develped to determine the best extended black-start scheme.3. A hierarchical optimization method of unit restarting during network reconfiguration is proposed. In view of the layered feature of units'restarting during network reconfiguration, the unit restarting process during the network reconfiguration is treated as a two-layer restoration process, the network-layer unit restarting, and the plant-layer unit restarting, respectively. First, the interaction between the network-layer unit restarting and the plant-layer unit restarting is analysed, the model of layered unit restarting is established by the study of optimization target and the consideration of the generator's start-up, run scheduling and power system's operating constraints comprehensive. Then, rule processing and optimization calculation are combined to determine the units'restarting sequence.4. An optimization method of loads recovery during network reconfiguration is proposed. First, the characteristics of loads recovery during network reconfiguration is analysed. Second, the loads'comprehensive importance is evaluated by comprehensivly considering the load recovery cost, load characteristics, load importance and the influence of the load restoration to the succeeding network reconstruction comprehensivly, and their comprehensive weights are calculated. Third, the loads' recovery optimization model is presented, which the optimization target is to maximize the total weighted loads with all constraints being satisfied, then, the solving method is studied, and the loads'recovery optimization during network reconfiguration is realized.5. An optimization method of network reconfiguration is proposed by introducing a two-layer unit-restarting framework for power system restoration. First, the continuous restoring process of network reconfiguration is changed into a multi-step sequential process through partitioning the time axis for the system restoration, a global optimization strategy of "modeling on discrete time steps, optimizing on the whole process" is developed, and the optimization of the network reconfiguration is modeled as a multi-objective optimization problem of the network-layer unit restarting, the plant-layer unit restarting and the important loads recovery. Second, the overall multi-objective optimization model is bulit based on the built optimization modles of network-layer unit restarting, the plant-layer unit restarting and the important loads recovery. Third, the lexicographic optimization method is employed to solve the multi-objective optimization problem by integrating the solving processes of the three sub-problems. The proposed optimization method of network reconfiguration can determine the restarting sequence of all the units and realize the coordinative optimization of the unit restarting and restoration of the important loads.