Research On Power Quality Of Regional Power Grid Affected By Electrified Railways

The rapid development of electrified railway power system has some adverse effects on the power system. Harmonics and negative sequence are two fundamental reasons for the power quality problems caused by traction load. Combined with specific regional power grid model, assessing and forecasting the impact on power quality has their practical significance.Firstly, the load characteristics of electrified railway traction are studied in this paper, using mathematical statistics and a combination fitting method of least squares and simulated annealing to establish traction station feeder current probability model. And the traction load harmonic process is regarded as two-dimensional random process. With the two dimensional random variables composed by the amplitude and phase of the harmonic accounted relatively independence, the mathematical model of random fluctuations is established accordingly. Secondly, on the basis of the information and data of the existing electrified railway traction substation, using Monte Carlo sampling methods to generate traction load samples according to the boundary conditions of new traction station, thereby the harmonics and negative sequence current of traction station access point are obtained and the quality parameters on the accessing point are predicted in addition. Furthermore, a three-phase flow calculation model of regional power grid is built in PSCAD/EMTDC. Through the grid simulation, the distribution of the grid power quality parameters caused by traction load can be obtained intuitively. Besides, the additional loss on the regional power grid caused by harmonics and negative sequence current of electric railway is quantitative analyzed in this paper. Finally, the three-phase SVC compensation scheme is proposed for the electrified railway impact on the grid, which compensation capacity is reasonably optimized.This paper relies on a specific project, combines with large amounts of operation data of Qinhuangdao electrified railway, conducts quantitative research on the traction load impact on the regional power grid in depth and provides an important theoretical basis and guidance for further assessment of electrified railway traction station and dispatching management and other areas.