Research On Grid Planning of Power System Including UPFC

Unified Power Flow Controller (UPFC) has been applied in our country and deployed in Nanjing and Suzhou, Jiangsu province. Suzhou's project has the highest voltage level and the largest capacity UPFC project in the world. These installed UPFC have an impact on power grid planning, but there is few research on it. How to make the use of the high voltage and large power flow control ability of UPFC to reduce the planning cost and improve system reliability is an urgent problem to be solved. In this paper, the grid expansion planning including UPFC is studied to achieve economy and reliability at the same time. Firstly, the basic principle of UPFC is introduced, and the influence of UPFC on grid planning is analyzed. Taking the newly added UPFC parameters and N−1 constraints into account, the mathematical model of power network planning with UPFC is established, and the genetic algorithm is improved to solve the problem. Finally, an example of grid planning with UPFC is given. The planning results show that considering the reliability will increase the cost of new lines, but it can better maintain the safe operation of the grid and reduce the comprehensive cost. Installation of UPFC and proper adjustment of its parameters can significantly reduce the cost and improve the reliability.

I. Introduction

Compared with the traditional power system control mode, FACTS has faster response speed, better controllability and stronger control ability. UPFC is the most powerful among all FACTS, which has a variety of control methods and can adjust local bus voltage and transmission line trend. The first UPFC demonstration project of 220kv was put into operation in Nanjing, Jiangsu Province in 2015, which was used to solve the power flow problem of Nanjing Western Ring Network. In 2017, UPFC of higher voltage grade 500kv has been installed in Suzhou, from which the maximum power consumption capacity of Suzhou power grid can be improved by about 1.3 million kw. This is the highest voltage level and largest capacity UPFC in the world at present. A lot of research on UPFC have been made for the last fewer years. the function of UPFC in improving the total transmission capacity of power grid is studied [2]. The influence of different control modes of UPFC on power grid is analyzed, and the best scheme with maximum transmission capacity and minimum power consumption is found. Paper[3] discusses the UPFC control mode and various aspects of the settings, and evaluates its impact on the stability of power systems. The main factors affecting the location and volume of UPFC are studied, and an optimization method is proposed to solve the problem of location and volume of UPFC in reference[4]. The economic indicators of power loss or coal consumption for power generation have been considered in paper [5]–[8]. It can be seen that most of the literature on UPFC is about the locating and sizing or power flow optimization. The grid expansion planning including a installed UPFC has not been studied in depth.