Research On Penetration Ratio And Coordinated Optimization Algorithm Of Distribution Power System With Distributed Generations

The integration of distributed generation(DG) units made distribution power network transform to an active network with many power sources all over itself, which brought significant effects to the planning, operating, power quality and relay protection of distribution network. So it was a urgent problem to be solved that how to alleviate the adverse impact to power network of DG such as photovoltaic and wind turbine while improving penetration ratio of DG capacity in power system.As to the problem of penetration of DG units in distribution network, this paper established a bi-level programming problem considering the uncertainty of the power load and the static security constraints based on optimization form to solve the maximum allowable penetration capacity in distribution network. The method of transforming the bi-level programming of solving the maximum penetration of DG units to single-level programming was proposed. Then the trust region sequential quadratic programming (TRSQP) method was used to solve the single-level programing problem. The factors which affect the DG maximum penetration were analyzed in the simulation. DG optimal control for the operation of distribution networks with DG units was also investigated in this paper. Considering the objectives of minimal line loss, minimal voltage deviation and maximum DG active power output, the multi-objective optimization was transformed to single objective optimization to calculate the optimal active and reactive power output of DG units. The TRSQP method was used to solve the problem. Numerical tests compared with the primal-dual interior-point method (PDIPM) and sequential linear programming method (SLPM) were provided, indicating TRSQP for distributed generation control optimization was fast, robust, and applicable in online condition. The simulation result showed the proposed optimal algorithm could solve the DG optimal dispatching problem fast and accurately.The coordinated voltage control problem for distribution network with the integration of DG was studied at last. The objective of the proposed control method was to minimize the active power loss in the distribution lines, as well as to decrease the number of switching device operation, while maintaining the grid voltage within the allowed range. The reactive optimization mathematical model of distribution network with both dispatchable and non-dispatchable DG units were established. The method of transforming the complex coordinated reactive optimization formulation to traditional mixed-integer constrained optimization problem was proposed, which then could be solved by using branch-and-bound method and TRSQP. The simulation result showed the proposed algorithm could solve the coordinated voltage control problem and the coordinated control method had a better economic benefits than the conventional one.