Three-Phase Power Flow For The Distribution Network With The Distributed Generation

The world is facing serious challenges from energy and the environment, and exploring new energy technologies is imminent. Thus, distributed generation gets more and more attention of experts in the field of global power because of its advantages. Distributed generation brings tremendous impact on the aspects of the grid structure, power loss and voltage distribution when providing necessary power to the distribution network. To do careful research, distribution network with distributed generation must be based on the power flow calculation. Therefore, in this thesis, three-phase power flow problem of distribution network with distributed generation has been researched in-depth:1. The impact of distributed generation grid to distribution network was studied and summarized, and all the calculation methods of power flow and three-phase power flow so far were analysised and compared. On this basis, the core idea was drawn up which was about a three-phase power flow with Newton method. Combined with the Newton method, the three-phase model of electrical components were established in distribution network, and a variety of distributed generation were divided into four node types and given detailed processing methods.2. The principle of three-phase Newton power flow and initial value sensitivity seriously affecting the convergence were analyzed in detail. Aiming at this problem, this thesis put forward the convergence theorem of Newton-like power flow algorithm, and gave the detailed proof. The proposed theorem gave a sufficient condition for convergence of Newton-like power flow algorithm and solved the problems of slow convergence rate and no convergence because of improper initial value selection when using the Newton-like algorithm power flow solutions. The correctness and validity of the convergence theorem of Newton-like power flow algorithm was proved by the simulation of IEEE node system and the power flow instance analysis of Tongliao grid distribution system.3. The N-GA three-phase power flow calculation method was proposed which combined Newton method with genetic algorithm for the features of multi-node and complex structure of distribution network with distributed generation and the inherent difficulty of initial value selection. The method used global optimization ability of genetic algorithm to select initial value of Newton method in three-phase power flow calculation, solving the problem of the blindness of initial value selection. Meanwhile, the iteration times estimated theorem of Newton-like power flow algorithm was presented to calculate the maximum number of iterations, which increases the rational of initial value selection in power flow calculation. The correctness and validity of the N-GA three-phase power flow calculation was proved by the simulation of IEEE 33 node system, which could prove the speed and accuracy of this method in balanced and unbalanced three phase system.Finally, main concluding remarks are summarized and presented at the end of this thesis as well as some interesting problems which deserve further study.