An assessment of available measures to reduce traction energy use in railway networks

In order to increase the utilization rate of the regenerative braking energy (RBE), reduce the operation cost, and improve the power quality of traction power supply system (TPSS) in high-speed railway, a supercapacitor (SC)-based energy storage system (SCESS) integrated railway static power conditioner (RPC) is presented in this article. In this scheme, the SC is connected onto the dc link of the RPC via a bidirectional dc–dc converter. A hierarchical control strategy, with an energy management layer and a converter control layer, is presented. Four operation modes and transition conditions of SCESS-RPC are elaborated in detail in the energy management layer. To obtain rapid and stable control performance, in the converter control layer, a passivity-based control (PBC)-based nonlinear controller is designed for the RPC, and an optimal control strategy based on the linear quadratic regulator with integral action (LQRI) is adopted for the bidirectional dc–dc converter. By means of simulations and experiments, the feasibility of the proposed topology and control strategy are verified.

Supercapacitor Integrated Railway Static Power Conditioner for Regenerative Braking Energy Recycling and Power Quality Improvement of High-Speed Railway System

This paper proposes an energy storage system (ESS) for recycling the regenerative braking energy in the high-speed railway. In this case, a supercapacitor-based storage system is integrated at the DC bus of the back to back converter that is connected to the two power phases of the traction power system (TPS). In order to ensure the suitability of the ESS in the TPS, the operation modes are classified by considering the load conditions of the TPS and the state-of-charge limit of the supercapacitor. Then, a master-slave control strategy with a central controller is proposed. In which, the central controller realizes the flexible management for all operation modes, by means of the state machine logic. Meanwhile, the master-slave control serves for coordinating the operation of the multiple converters according to the commands from the central controller. Finally, the capabilities of the proposed ESS are validated by sufficient experiments under different operation modes and the simulation based on the field data.

An Energy Storage System for Recycling Regenerative Braking Energy in High-Speed Railway

Auxiliary-battery-based substations (ABSs) can enhance conventional railway feeder systems. In particular, ABSs make dc feeders located in areas far from the ac grid able to power high-performance passenger and freight trains and store their braking energy. This paper proposes a techno-economic method to define size, position along the track, and control parameters of an ABS, with the goal to minimize the annual cost of energy. Our approach takes into account the replacements of battery modules within the ABS’s expected lifetime in order to reduce costs. Numerical simulations are carried out assuming a new-generation high-performance train on a real Italian 3-kV dc railway system equipped with one ABS. Although, in some cases, ABSs are already cheaper solutions compared to new traditional substations, the proposed sizing method allows obtaining a further reduction in the ABS cost.

Techno-economic Sizing of Auxiliary-Battery-Based Substations in DC Railway Systems

Today, in the railway sector there is considerable interest in studying the best ways of exploiting train braking energy, in order to achieve a reduction in energy costs and better stabilisation of grid voltage. Among the various on-board or wayside measures proposed, one of the most promising solutions is based on using wayside energy storage systems (WESSs). A WESS is a storage installation which can be integrated into mass transit systems in urban areas as well as into long-distance railway lines. It can operate as a smart storage system able to provide relevant benefits in terms of recovering surplus regeneration braking energy, voltage stabilisation, reduction of peak power demand. For these purposes, an effective and flexible simulator is essential to provide all the elements needed to focus and compare feasible configurations and operations. This study examines the problem of introducing the WESS technology in real railway infrastructure. It proposes a method based on a simulator of the WESS system integrated into the infrastructure and carries out the results of dynamic simulations referring to real operating data of the system and vehicles. The results highlight the performance of the WESS in terms of energy and power exchange, also discussing economic aspects.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-est.2019.0005

Impact on railway infrastructure of wayside energy storage systems for regenerative braking management: a case study on a real Italian railway infrastructure

After the 3.11 earthquake in Tohoku district in Japan, energy saving and renewable energy utilization become one of the important problems in Japan. East Japan Railway Company, as a public transportation company, tries to contribute to solve these problems by realizing eco-friendly railway transportation system. In this paper, three realized and under construction projects are summarized which enhance efficiency of traction power supply system. First project is installation of lithium ion battery at Haijima Substation on February 20th, 2013 to make use of regenerative power in d.c. traction power supply. Second project is the power conversion application to be installed at Ushiku sectioning post for a.c. traction power supply and will start operation in the end of 2013 fiscal year. The last project but not least one is “zero-emission station” realized at Hiraizumi Station on June 28th, 2013. The total electric power of the station is supplied from solar power even in the evening using lithium ion batteries. The detail of the operation data of “zero emission station” is shown in this paper.

Possibility of energy saving by introducing energy conversion and energy storage technologies in traction power supply system

Previously, some energy storage systems were installed to compensate for voltage drop and to avoid regenerative brake cancelation in d.c. 750V and 1.5kV traction power supply system in Japan. The fly wheel and Lithium-ion (Li-ion) battery, nickel metal hydride (Ni-MH) battery and electric double layer capacitor (EDLC) were used as a storage device. In East Japan Railway Company, Li-ion battery system was installed at HAIJIMA Substation (SS) on Ome Line and started operation on February 20 th , 2013. It is the first application of the energy storage system mainly not for voltage drop compensation but for regenerative energy utilization. In this paper, the effect of Li-ion battery system installed at HAIJIMA SS is evaluated based on the measured data during the practical operation and it is shown that it contributes to more than 5% reduction of total traction power supply at HAIJIMA Substation. The future plan of energy storage application is also mentioned.

Lithium-ion battery installation in traction power supply system for regenerative energy utilization Initial report of effect evaluation after half a year operation

PROBLEM TO BE SOLVED: To provide a power storage device capable of correcting a proper charge or discharge starting voltage regardless of a tap switching operationSOLUTION: The power storage device is configured to adjust storage or discharge of power in a DC-side load by constituting a DC power source from an AC power source including internal impedance through a rectifier The power storage device includes: a power control circuit for adjusting the storage or discharge of the power in accordance with a difference between the charge and discharge starting voltages and a DC voltage; and a correction circuit for correcting the charge and discharge starting voltages in accordance with an input voltage of the rectifier Therefore, during a discharging operation of the power storage device, the discharge starting voltage is kept constant

Power storage device

Two Lithium ion battery systems have already installed at practical traction substations, HAIJIMA SS and OKEGAWA SS, to utilize regenerative energy in d.c. 1.5kV traction power supply system of East Japan Railway Company. In this paper, the effect of energy storage system for energy saving by making use of regenerative energy is evaluated in detail. According to our experiences, the annual effects of energy storage systems at HAIJIMA SS and OKEGAWA SS are 400MWh/year and 600 or 700MWh/year, respectively.

Masateru Tojo

Papers

Possibility of energy saving by introducing energy conversion and energy storage technologies in traction power supply system

Lithium-ion battery installation in traction power supply system for regenerative energy utilization Initial report of effect evaluation after half a year operation

Power storage device

Effect evaluation of Li-ion battery for regenerative energy utilization in traction power supply system