A Flow Model for the Electrified Railway-Power Grid Hybrid Asymmetric Coupled System and its Linearized Method

Jul 16, 2026

In mountainous regions with a long-chain weak power grid where traction loads form a large share, interaction between the traction power supply system and the power grid becomes critical. Integrated power flow calculation (PFC) and linearized models are essential for joint planning of the power grid–traction network, yet prior work lacks sufficient characterization of EMU port loads and traction transformer connection-angle effects. This paper builds an integrated PFC model for the coupled system and provides a linearized hybrid phase decoupled method validated by simulations.

LanguageEnglish

CategoryResearch & Report

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Pages26

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Introduction

Motivation and background

Existing methods and research gap

Contributions and approach overview

arXiv :2607 . 11060v1 [ ee ss . SY] 13 Jul 2026 A Flow Model for the Electrified Railway-Power Grid Hybrid Asymmetric Coupled System and its Linearized Method Qiao Zhang, Zhigang Liu, Fellow, IEEE, Shibin Gao, Zhenzu Liu, Xiangyu Meng, Yunchuan Deng, Guinan Zhang, Bing Lu, and Yanming Lu Abstract In mountainous regions where traction loads constitute a significant portion of a long-chain weak power grid (PG) with sustainable energy, the interaction between the traction power supply system and the PG becomes increasingly evident. The integrated power flow calculation (PFC) method and its linearized model are quite important for the PG -traction network (TN) joint planning. However, existing research on the port load characteristics of the EMUs and the connection angle characteristics of traction transformers is insufficient, and there is a lack of effective methods for PFC or linearized PFC in systems that couple the PG with the traction network. To fill this gap, this paper proposes an integrated PFC model for the AT TN - PG coupled system, along with a linearized method. Firstly, according to the relationship of the phases between the PG and the AT traction network, the node admittance matrix of the coupled system has been constructed. Then, the issue of power injection equations being unable to deal with the EMUs port load is resolved by merging the contact line node and the rail node. Subsequently, the integrated PFC equations for the coupling system are established. Next, a hybrid phase linear decoupled power flow model for the coupling system is developed, employing the correspondence between the phases of the PG and the TN, as well as the phase angle differences among various nodes and branches. Numerical simulations conducted in a specific region demonstrate the necessity of an integrated PFC for the coupled system and validate both the accuracy and efficiency of the linearized model. Index Terms AT traction network, power grid, coupled system, flow method, linear flow method. NOMENCLATURE AT TN TSSTNPGS T R HPLD Vm DUM UHPkmLD θHPkmLD ABPG CBPG AD MAD MAE autotransformer traction network traction power supply system traction network–power grid coupled system transmission phase of the traction network return phase of the traction network hybrid phase linear decoupled voltage magnitude average error of the voltage magnitude voltage magnitude of the kth node of phase m calculated by the HPLD method voltage angle of the kth node of phase m calculated by the HPLD method phase A branch on the power grid side phase C branch on the power grid side angle difference maximum value of angle difference maximum value of angle error PG PFC EMUs ATPGS F PCC NR Va DUA UNkRm θNkRm BBPG TBTT AAD AAE VAD power grid power flow calculation electric multiple units AT traction network–power grid coupled system negative feeder phase of the traction network point of common coupling Newton–Raphson voltage angle average error of the voltage angle voltage magnitude of the kth node of phase m calculated by the NR method voltage angle of the kth node of phase m calculated by the NR method phase B branch on the power grid side phase T branch of the traction transformer average value of angle difference average value of angle error voltage angle difference I. INTRODUCTION WITH the development of economic levels, the planning and construction of railways in high-altitude mountainous areas have become increasingly urgent. However, these regions often experience low power loads and typically exhibit a long-chain weak power grid structure, with a small short-circuit capacity at the end of the chain. Once the railway is completed, the proportion of the traction load may reach 20 − 30% . At this point, the coupling between the traction network and the power grid becomes more stringent, as shown in Fig. 1. Traditional planning of TSSs treat

FAQs

What problem does the paper address in mountainous regions?

It addresses the tighter coupling between the traction power supply system and a long-chain weak power grid, where traction loads can reach 20–30% and make separate power-flow analysis difficult.

What new model does the paper propose?

It proposes an integrated PFC model for the traction network–power grid coupled system, together with a linearized method to enable tractable analysis and planning.

How does the linearized method improve practicality?

It develops a hybrid phase linear decoupled power flow model using phase correspondence and phase angle differences among nodes and branches, and simulations validate both accuracy and efficiency.

Jul 16, 2026

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