Traction power systems for electrified railways:evolution,state of the art,and future trends

Traction power systems(TPSs)play a vital role in the operation of electrified railways.The transformation of conventional railway TPSs to novel structures is not only a trend to promote the development of electrified railways toward high-efficiency and resilience but also an inevitable requirement to achieve carbon neutrality target.On the basis of sorting out the power supply structures of conventional AC and DC modes,this paper first reviews the characteristics of the existing TPSs,such as weak power supply flexibility and low-energy efficiency.Furthermore,the power supply structures of various TPSs for future electrified railways are described in detail,which satisfy longer distance,low-carbon,high-efficiency,high-reliability and high-quality power supply requirements.Meanwhile,the application prospects of different traction modes are discussed from both technical and economic aspects.Eventually,this paper introduces the research progress of mixed-system electrified railways and traction power supply technologies without catenary system,speculates on the future development trends and challenges of TPSs and predicts that TPSs will be based on the continuous power supply mode,employing power electronic equipment and intelligent information technology to construct a railway comprehensive energy system with renewable energy.

Integrated Configuration and Control Strategy for PV Generation in Railway Traction Power Supply Systems

Recently,electric railways have experienced a rapid development causing an increasing power demand.Due to the flexible installation available at trackside land along railways,photovoltaic(PV)generation is suggested as an extension to the traction power supply system(TPSS)in railways.First,this paper proposes a three-phase integrated configuration for PV generation connected to a two-phase traction network and the on-site consumption of solar resources alongside railways.In this configuration,another inverse V/V transformer is used to maintain a balanced three-phase low voltage(LV)AC bus from a two-phase traction network.It is more convenient for accessing PV generation units.Then,in order to mitigate the negative sequence currents caused by electric trains,an individual phase current(IPC)control strategy for PV converters is developed for power quality improvement.It can not only supply the locomotive with asymmetrical currents,but also provide feedback to the grid through symmetrical currents.All the implementation and calculations are conducted in the three-phase stationary reference frame without any sequence extracting and power compensations.Finally,simulation results are presented to validate the effectiveness of the proposed IPC control strategy.

Integrated Railway Smart Grid Architecture Based on Energy Routers

Railway power system is an inseparable part of the power system,therefore,the intelligent architecture of the railway power system should also be focused on.The unique power supply characteristics of the railway power system are analyzed and integrated railway smart grid architecture based on energy routers is proposed.Importantly,three corresponding resilient mode control methods are suggested for the proposed architecture.In the fourth section,a simulation model corresponding to the resilient control mode is built and the simulation results prove the feasibility of the proposed control mode.Equally,for the novel network-connected backbone router(NCBR),a 1000 kVA,27.5/10 kV NCBR engineering prototype is used to prove its effectiveness in practical applications.Finally,a differentiation analysis is given,followed by conclusions regarding the traditional power system and proposed system.