Reverse engineering of a railcar prototype via energetic macroscopic representation approach

Application of dynamic programming to optimal energy management of grid-independent hybrid railcars

“…As it is well known, correct and fruitful DP exploitation entails reducing as much as possible model complexity, on the one hand, and, on the other hand, avoiding incurring in the “curse of dimensionality” issue. 38 The first requirement was accounted for by deriving, from the detailed energy macroscopic representation (EMR) model proposed in Agbli et al., 7 a simplified version, which is suitable for subsequent implementation within a DP optimization task, while retaining an acceptable accuracy level. Such a simplified approach (see section “Simplified railcar longitudinal model”) consists in estimating the power to be supplied by the hybrid powertrain first; then, the fuel consumption associated to the specific operating condition, as enabled by the DP-derived optimal EMS (see the “Optimal energy management” section), is evaluated.…”

“…The propulsion system referred to hereinafter was obtained by performing battery hybridization of the powertrain studied and modeled in a previous contribution. 7 Particularly, the baseline architecture consists of six driving axles and two DC buses, the latter two being connected to three power packs. A power pack (PWP) consists of a diesel engine unit integrated with its alternator and rectifier.…”

“…As shown in Figure 1, the latter variable is computed introducing a simplification with respect to the detailed model presented in Agbli et al. 7 Particularly, the piecewise f 1 function, originally consisting of two sub-functions, is converted in to one single function, i.e. the g 1 relationship, by averaging the above-mentioned sub-functions (holding valid in raising and descending P PWP mode, respectively).…”

“…Such a comparison indicated that the here-proposed model simplification ensures limiting the fuel consumption estimation error within the safe range ±3%. Considering the fact that the reference model 7 ensures prediction errors around 1%, the proposed backward modeling of railcar longitudinal dynamics can be deemed suitable for implementation within a DP optimization tool. It is worth noting that the above-discussed verification was carried-out on the same MPs used later on in the Results section; moreover, for sake of consistency with the model simplification target, the transmission efficiency η T (see Figure 1) was assumed to be constantly equal to 0.9.…”

“…Coradia iLint, the world’s first hydrogen-powered train, has been built by ALSTOM in this framework. Due to the current developmental phase, the hydrogen-powered train (hydrail) is now undergoing, 4 battery- as well as fly-wheel-based hybridization 5,6 of existing diesel-powered railcars which can substantially help train companies, such as the French SNCF as extensively discussed in a previous contribution, 7 in appropriately facing and managing the current transition phase. Nevertheless, it is worth remarking here that hydrail has recently marked some significant steps towards the achievement of techno-economic competitiveness, as confirmed by the fact that some hydrogen-powered regional trains are expected to experimentally enter in service in France by 2022.…”