| A large number of scientific and technical problems arise with large-scale engineering construction of electrified railway. With the building of the new electrified railway, the expanding capacity of existed electrified railway, the improving of locomotive technology and the development of power system, researches on power quality influenced by the new electrified railway and the effection to the planning of power grid are important.Firstly, for a large number of measured data of feeder current from traction substation, the distribution characteristics and digital characteristic were statistically analyzed. Statistical results show that the charged effective coefficient reflects the fluctuation of charged load current in some degree. The distribution of the ratio between the95%probability value and the average value of charged traction load current centralized relatively. The average ratio is about2.4.Probability density function for feeder current of traction substation is fitted by using β function through the theory of stochastic process and method of numerical analysis on the basis of summarizeing and analyzing the distribution characteristics of traction load. Error anlaysis verifies the effectiveness of the proposed method. As a new electrified railway traction load, according to the basic information derived from railway departments, the prediction model of new electrified railway traction load can be obtained. The feeder current sampleis obtained by using Monte Carlo method.Taking a subnetwork supplied by regional power grid substation as an example, the influence of negative sequence unbalance caused by the new electrified railway is evaluated.Considering the complexity of harmonic,"stage3" evaluation method was proposed by IEC. The third stage evaluation method is applicative for the traction distortion load. According to the bearing harmonic capacity abundance of electric equipment of the MV and LV system, and the comprehensive penetration coefficient method is put forward for IEC "Stage3about harmonic emission limit.The influence of harmonic caused by the new electrified railway traction load is evaluated through the example.Finally, for the increasingly prominent negative sequence problem in traction power supply system, cophased traction power supply technology is proposed because it is the best comprehensive solution for negative sequence power quality and electrical neutral section. Mathematical modeling of Power Flow Controller for comprehensive compensation is built in this paper. Aiming at any wiring transformers, the general expression for PFC comprehensive compensating current is given.Then the method for PFC comprehensive capacity configuration taking complete and flexible compensation as the objectives is designed. Three different traction loads are used. The PFC comprehensive capacity configuration scheme is analysed and compared according to two compensation objectives. Example analysis results that adopting the configuration method proposed in this paper, the objective of satisfaction compensation within full load can be attained by PFC. The proposed method reduces project cost obviously. |
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