A Harmonic Impedance Identification Method of Traction Network Based on Data Evolution Mechanism

Abstract

In railway electrification systems, the harmonic impedance of the traction network is of great value for avoiding harmonic resonance and electrical matching of impedance parameters between trains and traction networks. Therefore, harmonic impedance identification is beneficial to suppress harmonics and improve the power quality of the traction network. As a result of the coupling characteristics of the traction power supply system, the identification results of harmonic impedance may be inaccurate and controversial. In this context, an identification method based on a data evolution mechanism is proposed. At first, a harmonic impedance model is established and the equivalent circuit of the traction network is established. According to the harmonic impedance model, the proposed method eliminates the outliers of the measured data from trains by the Grubbs criterion and calculates the harmonic impedance by partial least squares regression. Then, the data evolution mechanism based on the sample coefficient of determination is introduced to estimate the reliability of the identification results and to divide results into several reliability levels. Furthermore, in the data evolution mechanism through adding new harmonic data, the low-reliability results can be replaced by the new results with high reliability and, finally, the high-reliability results can cover all frequencies. Moreover, the identification results based on the simulation data show the higher reliability results are more accurate than the lower reliability results. The measured data verify that the the data evolution mechanism can improve accuracy and reliability, and their results prove the feasibility and validation of the proposed method.

Non-Intrusive Load Monitoring Applied to AC Railways

“…Assessments of rolling stock distortions are carried out for several reasons: traditionally, compliance to limits of emission to prevent interference to signalling [29,30], and in general, excessive induction [31,32]; more recently, attention has been placed on power quality with respect to the rest of the network [33], to resonance triggering and consequential overvoltages [28,34,35]. Finally, distortion has implications for power and energy consumption [36][37][38]; this is gathering more attention, i.e., in order to improve the energy efficiency of electrified transportation systems [39] in a sustainability perspective.…”

Machine Learning for Energy Systems

“…The work by R.X. Yang et al [12], "A Harmonic Impedance Identification Method of Traction Network Based on Data Evolution Mechanism", proposed an identification method based on a data evolution mechanism to improve the identification accuracy of harmonic impedance. The harmonic impedance model and the equivalent circuit of the traction network were firstly studied.…”

Harmonic Overvoltage Analysis of Electric Railways in a Wide Frequency Range Based on Relative Frequency Relationships of the Vehicle–Grid Coupling System

“…The above NSPWM process can be intuitively understood from the perspective of signal transmission, compared with the switching frequency, the low-frequency original signal will produce additional high-frequency interference, and the high-frequency original signal will produce additional low-frequency interference. According to the above analysis, the relationship between the input and output signal of the NSPWM segment can be approximated by (5). ∂ k m represents the relationship between the kth harmonic component of the mth group of sideband harmonics in the output voltage spectrum and the modulation waveform signal.…”

“…∂ k m represents the relationship between the kth harmonic component of the mth group of sideband harmonics in the output voltage spectrum and the modulation waveform signal. In order to simplify the analysis, only the main 0th and 1st sideband harmonics are considered in Equation (5).…”

“…The method utilizes Re {Zin(jω)} > 0 as stability criterion, where Re {Zin(jω)} > 0 denotes the real part of input impedance of grid-connected converters port. When Zin(jω) does not satisfy the condition that the real part is greater than 0 at a certain frequency, the risk of harmonic instability is considered to exist [2][3][4][5][6].…”