| China's high-speed railway network provides convenient and safe transportation,and also enhances China's influence in the world.However,the electric locomotive as a non-linear load on the power grid can cause harmonic pollution.In this paper,the harmonic analysis and harmonic modeling of AC-DC-AC type CRH2 EMUs are studied.The simulation model of CRH2 high-speed EMU traction drive system was established by EMTP-ATP,and the grid side voltage and current harmonic waveforms of EMU under different operating conditions were obtained.The amplitude and phase angle characteristics of the grid side current are studied under different working conditions.For the FFT analysis of the spectrum leakage problem of harmonics,by comparing the difference of adjacent periodic waveforms,find the appropriate time domain truncation window length,so that the frequency resolution is higher than the resolution of the FFT analysis locomotive harmonics,Therefore,the calculation of the harmonics and interharmonics of the current characteristics of the network side is more accurate;When using FFT to perform harmonic analysis on EMUs,considering the influence of EMU inverter-traction motor system,the harmonic amplitude of the current characteristics of the grid side increases,and new interharmonics are generated.It laid the foundation for harmonic modeling of EMU.The active fluctuation method is proposed,which uses the capacitor switching,changing the resistance of the transformer and the harmonic source injection method to form the fluctuation.It is used for the harmonic impedance measurement of the EMU.The effects of the advantages and disadvantages of the three methods and the magnitude of the fluctuation on the measured harmonic impedance and harmonic source results are analyzed.Among them,the harmonic source injection method constitutes the fluctuation amount,which can artificially control the injection harmonics,adjust the harmonic fluctuation of PCC,and is superior to the harmonic impedance measurement method of capacitor switching and changing the resistance of the transformer,The calculation result is more accurate.A model that can effectively describe the harmonic characteristics of high-speed EMUs--uncoupled harmonic Norton model is established,and the validity of the model is verified by error analysis;The ARMAFIT is used to fit the harmonic impedance of the EMU,and the EMU harmonic model is built in the ATP,which is of great significance for evaluating and analyzing the influence of electrified railway traction load harmonics on power quality of power system. |
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