Harmonic resonances in traction power supply systems (TPSSs) have attracted great attention due to their potentially destructive impact on the safe and stable operation of railways. Based on operation data acquired from Chinese railways, this paper presents a comprehensive review of this issue considering both academic and engineering requirements. Analysing actual incidents, the general patterns and effects of TPSS resonances are derived. The relation between the TPSS and the locomotive is illustrated by circuit models. Relevant methods for modeling locomotives and TPSSs are discussed. Both advanced resonance analysis methods giving general influence factors and a simplified resonance analysis explaining resonance features in a practical manner are discussed. Multiple groundbased and on-board solutions for resonance elimination are presented. At last, pre-identifying resonances in actual systems is investigated for addressing the open topic of resonance prevention.

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Abstract:With the rapid development of high-speed and heavy-haul railways throughout China, modern large power locomotives and electric multiple units (EMUs) have been applied in main railway lines. The high power requirements have brought about the problem of insufficient power supply capacity (PSC) of traction power supply systems (TPSSs). Thus, a convenient method of PSC assessment is meaningful and urgently needed. In this paper, a novel algorithm is proposed based on the Thévenin equivalent in order to calculate the PSC. In this algorithm, node voltage equations are converted into port characteristic equations, and the Newton-Raphson method is exploited to solve them. Based on this algorithm, the PSC of a typical high-speed railway is calculated through the repeated power flow (RPF). Subsequently, the effects of an optimized organization of train operations are analyzed. Compared to conventional algorithms, the proposed one has the advantages of fast convergence and an easy approach to multiple solutions and PV curves, which show vivid and visual information to TPSS designers and operators. A numerical analysis and case studies validate the effectiveness and feasibility of the proposed method, which can help to optimize the organization of train operations and design lines and enhance the reliability and safety of TPSSs.

Findings: This paper reveals that the Ohmic resistance accounts for much contribution to battery total polarization compared to charge transfer impedance. Practical implications:Experimental results demonstrate the efficacy of the model with the proposed identification method, which provides the foundation for battery charging optimization.-686-Journal of Industrial Originality/value: The paper analyzed the impedance characteristics of the lithium-ion battery based on EIS data, presented a charge polarization model with two RC networks, and estimated parameters like Ohmic resistance and charge transfer impedance.

Accidents related with high-order harmonic resonance seriously threaten the safety and stable operation of traction power supply systems (TPSSs). Generally, the resonant frequency of a TPSS, which is the crucial information for resonance suppression, cannot be accurately obtained through model-based methods due to the TPSS complexity. This study proposes a direct measuring method that harmonic currents at different frequencies and amplitudes are injected into the TPSS by a harmonic generator (HG). Then, the resonant frequency can be identified by measuring the harmonic response. The HG based on a single-phase cascaded H-bridge converter and its control algorithms are developed. Both simulations on a railway system model and experimental results on an equivalent resonant circuit are carried out to validate the feasibility and effectiveness of the proposed method.

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Many new types of locomotives are put to use in electric railway systems, resulting in instability problems such as high-order harmonic resonance occurring as a consequence of the interaction between the electrical locomotive (including electrical multiple units) and the traction network. In order to investigate this problem, this paper adopts the impedance-based approach to analyze the stability properties of the system interaction. The detailed impedance of the traction network is obtained by taking its distributed parameters into account. Then the locomotive converter with single-phase transient current control algorithm (TCCA), which can represent the locomotive when performing the impedance-based stability analysis, is modeled as the dq-frame impedance by single-phase dq decomposition. By plotting bode diagrams of the impedance for the traction network and the locomotive separately, and calculating the phase margin at the intersection point of the magnitude of the two impedances, the stability of the locomotive-network system is evaluated and thus the high-order harmonic resonance can be predicted. Moreover, a time-domain model of locomotivenetwork systems is established in this paper, which can reproduce the high-order harmonic resonance in the time domain as a first validation step of the analysis. Finally, a field test in a traction substation of the Beijing-Harbin Railway is carried out to finally validate the effectiveness of the proposed method. The stability analysis method in this paper is simple and effective without the need for a complex calculation of some norms or Eigenvalues. As a result, the high-order harmonic resonance can be predicted before a new type of locomotive is put into use.