Research On The Flexible Transmission Expansion Planning Based On The Genetic Algorithm

Network planning is an important part of power system planning. The purpose of network planning is to determine an optimal network structure according to load growth and generation expansion schemes during the planning periods so as to deliver the power to loads economically and reliably. The discipline of network planning is to minimize the investment cost while delivering power safely. Power system is an integral and incorporating big plants or high voltage transmission lines into the system will affect the operation and development of power system in the future. Every county will invest a great number of money to strength the power system to guarantee customers’demand. Eliminating a small percent of these investment cost will save a large number of money. Consequentially, no matter from the economical perspective or technical perspective, transmission expansion planning has significantly meanings.This paper made out a group of transmission planning schemes based on the genetic algorithm according to the topology of system and the position of new load and new generators while considering the static constraints and stability constraint. The stability constraint is keeping a safe margin between the normal operation point and the limit operation point which is computed by continuation power flow. Because of the increasing of uncertainties, such as load variation, new energy power and so on, the optimal scheme obtained by genetic algorithm may not be the optimal one in practical condition. So improvements to schemes are needed. Therefore, this paper defined the conception of flexible transmission expansion planning as follows. The scheme with the least improvements is the flexible transmission expansion planning scheme while satisfying the reliability and stability under uncertainties. The improvements of schemes were made out with the Monte Carlo Method and the Sensitivity analysis. In order to check the reliability of the flexible transmission expansion planning scheme and the effectiveness of this method, this paper simulated the flexible transmission expansion planning scheme under different conditions based on the prime-dual interior point method. For the output of shunt capacity is discrete variables, this paper presented a method to cope with the discrete variables of optimal power flow. This method added the discrete variables into the inequality constraints of the model. Results demonstrated that the flexible transmission expansion planning scheme can adapt to different operation conditions very well. And also it checked the effectiveness of the method of the flexible transmission expansion planning based on the genetic algorithm, Monte Carlo method and the sensitivity method.