| With the vigorous construction and development of urban rail transit in China,the subway is favored for its advantages of convenient,quick,safe,comfortable and so on.At the same time as the extensive metro construction,the harmonic problems of the subway power supply system have also become the focus of common attention.The subway power supply system is an AC / DC hybrid system.A large number of nonlinear power electronic devices will produce harmonic waves,which will have adverse effects on the urban power system.Therefore,the harmonic research of the metro power supply system is very meaningful.This paper first introduces the structure and operation mode of the subway power supply system in detail,and analyzes the sources of harmonics in the subway power supply system.Then,it focuses on the analysis of the main harmonic source of the subway power supply system—the rectifier unit.The principle and characteristic harmonics and non-characteristic harmonics of the 6-pulse,12-pulse,and 24-pulse rectifier units are theoretically deduced and analyzed..After detailed analysis of the harmonic characteristics of the rectifier unit,the model of the various components of the subway power supply system was built based on the Matlab/Simulink platform targeting the subway power supply system with the most widely used 24 pulse rectifiers in China.Simulation analysis of harmonics with different loads and locomotive loads under different operating conditions.Subsequently,based on the study of the harmonic characteristics of the subway power supply system,this paper improves the harmonic power flow algorithm of the existing subway power supply system and designs a new harmonic power flow algorithm.The algorithm is based on the fundamental wave power flow calculation data,and the harmonic characteristics of the rectifier unit and the harmonic model of the AC side components of the subway power supply system are used to construct the harmonic equivalent network of the subway power supply system.The subway power supply system is first calculated.The first iteration of the harmonic flow,and then the calculation results into the power flow analysis of the fundamental wave current correction,the basic wave power flow calculation and harmonic power flow calculation results for each other's initial conditions,the two kinds of calculations each iteration until convergence.Finally,the harmonic power flow calculation program is written in M language,and the improved harmonic power flow algorithm and the program are verified through actual examples.The simulation results show the effectiveness of the algorithm,and show that the algorithm is more accurate than the original algorithm,and it has the advantages of good convergence and fast calculation speed. |
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