Research On Grid-Connected Optimal Operation And Island Partition For Distributed Generation In Distrbution Networks

Distributed generation(DG) has many advantages so that it can alleviate energy crises, reduce environmental pollutions and improve power supply reliability, which has been widely used in the power system recently. DG is mainly connected to the power system in grid mode or island mode through distribution networks, which has great influence on the original mode of distribution networks. Studying on grid-connected optimal operation and island partition for distributed generation is of great significance to develop the DG technology and ensure the safe and reliable operation of the distribution networks. In this paper, The above two topics are studied. The main work is presented as follow:(1) An issue is researched in which the power factor of DG is optimzed on the basis that the largest capacity of DG is full used. A power factor optimization model is propose which takes reducing the whole loss of distribution networks as the optimization goal and considers some constrains concerning system operation and capacities of facilities. Then Particle Swarm Optimization (PSO) is introduced, and PSO is employed to the above model. The correctness of the proposed model and algorithm is verified by the calculation results of IEEE33-bus system, and the positive impacts of power factor optimization on the economic and stable operation of distribution networks are researched.(2) Takeing photovoltaic generators as the research object, a new strategy of dynamic islanding partition of microgird with distributed photovoltaic generators upon distributed network failures is proposed based on sufficient recognitions about the matching between daily patterns of photovoltaic generators and load curves of different industrys. In this strategy, photovoltaic power will be supplied to important loads preferentially, then the rest power will be supplied to unimportant loads. As for the latter, a optimization model is established. In the model the amount of photovoltaic power supplied to unimportant loads based on their industry attributes will be optimized in time. After the optimization, a power island will be made out, which takes the photovoltaic generator as the root node. What is more, the fusions of islands are also took into acconut. The suggested strategy is assessed through some simulation experiments with the PG&E69-bus system, the outcome shows that the strategy can produce reasonable islanding scheme after faults in distributed network and effectively improve the self-healing ability of the gird. In each island formed, the matching between daily patterns of photovoltaic generators and load curves of different industrys is appreciable.