Power System Optimal Power Flow Under Voltage Caonstrains Margin

Optimal Power Flow (OPF) is a large-scale, multi-constrained, nonlinear optimization problem. By solving the OPF problem can achieve targets of optimize existing resources, reduce the cost of power generation and reduce transmission losses, improve system transmission capacity and so on. It has the technical and economic significance of the traditional power flow calculation can not be realized. Optimal Power Flow has been a challenging issue; the majority of scholars have done a lot of it. Objective function of a traditional power flow optimization method is usually expressed as that minimizing the active transmission power loss under rigid voltage constrains, but neglects the soft characteristics of voltage constrains. It can raise the voltage of some bus too close to its boundary, thus becoming hidden trouble of system security. Therefore, study on optimal power flow under the voltage safety margin has very important significance.This paper reviewed the development of optimal power flow and optimal power flow model and optimization method of research; pointed out the problems of the optimal were faced. Discussed the mathematical model of OPF, and the theoretical foundation and basic principles of the Primal-dual interior point algorithm in detail; deduced the mathematical model of nonlinear programming problem in detail by primal-dual interior-point algorithm. Introduce the theory of fuzzy mathematics and definitions of fuzzy set and membership function. Fuzzy modeling for the OPF problem according to the fuzzy set theory, and then based on fuzzy set theory and the maximum satisfaction method turn the fuzzy optimal power flow model into a maximum satisfactory degree problem. On this basis, reactive power optimization model with fuzzy constraints was established, and then the original optimization problem was transformed into the maximum satisfaction optimization problem. Finally the model was solved by Primal-dual interior point algorithm. Using Ward & Hale 6 and IEEE 30 bus system as an example for simulation, discusses the impact on the optimization results with different "soft constraints" margin, compares the optimize performance between fuzzy optimization and non-fuzzy optimization algorithm, proves the validity and accuracy of the model; To deal with different dimensions, conflicting multi-objective optimization problem, the fuzzy set theory is led in and the mathematical model is derived by which the fuzzy multi-objective constraint can be transformed into crisp single objective constrain, which is solved by the original-dual interior point algorithm. The paper carried out simulation and verification by Ward & Hale 6 and IEEE 14 standard examples. The results show the effectiveness and correctness of the fuzzy programming algorithm.