DC Railway Simulation Including Controllable Power Electronic and Energy Storage Devices

Abstract

This work presents a comprehensive set of steady state models to be included in power flow simulation studies of DC railway networks. This simulation framework covers all important aspects and features of each element of modern DC railways. The proposed models are simplified to achieve the maximum simulation speed while keeping the required accuracy. Not only non-reversible, controlled and uncontrolled reversible substations are considered, but also on-board and off-board accumulation systems. The train model can consider the low network receptivity (overvoltage protection for trains equipped with regenerative braking) and overcurrent protection. It is also possible to include in the simulation DC/DC links between nodes of the railway network at the same or different voltage. To date, there is no other work able to conjugate all the mentioned models in a complex multi-train scenario.

Analysis, Evaluation and Simulation of Railway Diesel-Electric and Hybrid Units as Distributed Energy Resources

“…Another policy is energy storage both on board or off-board [16]. It is important clustering these solutions into AC [17] and DC [18] railway systems because specific problems and solutions are quite different (power flows to the public power system, phase balance, load sharing between feeder stations, reactive voltage support or transformer connections). DC systems are still in use in many railways where the power demand and distance are not critical, but AC systems are preferred for high-speed or heavy haul freight systems.…”

Optimal Energy Management of Railroad Electrical Systems with Renewable Energy and Energy Storage Systems

“…A comprehensive set of steady-state approaches to be included in the power flow simulation studies of direct current (DC) railway systems is proposed in [3]. An approach for the optimal operation of railroad electrical systems considering RERs, regenerative braking, and hybrid energy storage systems is proposed in [4].…”

Modeling, Simulationand Analysis of On-Board Hybrid Energy Storage Systems for Railway Applications

“…Pseudo-static models have been traditionally less accurate, but much faster [11]. They are usually combined with power flow solvers that must be able to manage the 2 of 21 complex non-smooth and non-derivable characteristics presented by the new power electronic devices installed within the railways [12].…”

“…Wayside energy storage can be an alternative to the on-board accumulation systems and in some cases can also be better. In [12,25], the authors mentioned that for choosing the correct infrastructure/train configuration, multiple cases should be analyzed, and all possible technologies should be compared, like for instance reversible substations, wayside energy storage, and on-board energy storage. In order to take advantage of the power regenerated by the trains, the most common solution used in the past was: (1) to optimize the schedule, so when one train is accelerating, another train is braking (this solution is quite difficult to achieve without automatic driving systems); (2) the use of reversible substations; in this case, railway manufacturers are quite reluctant to change the conventional non-controlled diode-based substations because they are inexpensive and robust, so nearly all reversible substations are formed with an IGBT bridge in parallel with the diode bridge; the infrastructure keeps using the diodes to transfer power from AC to DC, and they use the IGBT to put power back into the DC system.…”

“…This approach reduces the complexity of the mathematical model without reducing the accuracy when compared with previous proposed models [28]. The model has been embedded in a commercial software package that uses a modified current injection method to solve the power flow problem [12]; the solver allows combining regenerative trains with diode-based non-reversible substations. It must be remarked that even when there is the possibility of combining regenerative trains with Voltage Source Converter (VSC)-based reversible substations [29,30], in the vast majority of the cases, the existing infrastructures and also the new ones use non-controlled and non-reversible substations due to their robustness, reliability, and low cost [31].…”