# Analysis of Hybrid and Plug-In Hybrid Alternative Propulsion Systems for Regional Diesel-Electric Multiple Unit Trains

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## Abstract

**:**

## 1. Introduction

- A method to support a hypothetical conversion of a conventional regional DMU vehicle to its hybrid and plug-in hybrid counterparts, equipped with the prominent ESS technologies and newly developed causal and easy-to-implement real-time power control, allowing for a realistic estimation of fuel savings;
- A comparative analysis of alternative propulsion systems in a case study of a selected benchmark vehicle and railway line in the northern Netherlands, providing the railway undertaking with an assessment of potential benefits in terms of reduction of produced GHG emissions and energy costs.

## 2. Configuration of Standard, Hybrid, and Plug-In Hybrid Propulsion Systems

## 3. Modeling and Control of Alternative Propulsion Systems

#### 3.1. Simulation Model

^{®}/Simulink

^{©}environment using the OPEUS Simulink toolbox [59]. The model of a hybrid DEMU [37] was extended to include different power sources (i.e., ICE, pantograph, LB, and DLC) and to capture the dynamics of ESSs using typically available parameters published by the manufacturers. The simulation model (Figure 2) allowed for the simulation of different configurations by disconnecting components not included in the respective system. According to the backward orientation of the model, the inputs encompass the train velocity and geometry profiles of the track, and the main outputs are cumulative fuel and electricity demand. The arrows designate the numerical evaluation sequence, opposite to the physical power flow. Due to the high efficiencies of the power converters, their dynamics were omitted in the model, with their efficiencies assumed to be ~100%. However, they were considered in the physical system for controlling the power flows and dispatching different system components according to the implemented energy management strategy (see Section 3.2). The braking rheostat was used only for assessing the balance of power flows in the system. The description of the low-order models for the system components is provided in the remainder of this section.

#### 3.1.1. Vehicle

#### 3.1.2. Axle Gear

#### 3.1.3. Electric Motor

#### 3.1.4. Auxiliaries

#### 3.1.5. Diesel Generator Set

#### 3.1.6. Pantograph

#### 3.1.7. Lithium-Ion Battery

#### 3.1.8. Double-Layer Capacitor

#### 3.2. Energy Management Strategy

- Removing emissions and noise in terminal stops by switching off the ICE and supplying auxiliary systems from an ESS or electric power grid;
- Improving fuel economy by maximizing regenerative braking energy and its later use in powering traction and auxiliary systems;
- Increasing overall ICE-G efficiency by avoiding low load operation;
- Supporting ICE-G by an ESS during high power demand phases (acceleration).

#### 3.2.1. FSM Control for HDEMU Vehicle

#### 3.2.2. FSM Control for PHDEMU Vehicle

## 4. Case Study of the Dutch Northern Regional Railway Lines

#### 4.1. Benchmark Railway Vehicle

#### 4.2. Benchmark Railway Line Selection

- Charging facilities located only in terminal stations with long layover times;
- Charging facilities located in terminal stations and an additional fast charging facility located in Buitenpost, a common short stop for the two services.

#### 4.3. Comparative Assessment Results

^{®}/Simulink

^{©}simulation model described in Section 3, with the adopted fixed time step $\Delta t=0.1\mathrm{s}$, the ode3 (Bogacki-Shampine) solver used for numerical integration, and implemented hysteresis cycles of ${\sigma}_{\mathrm{LB}}^{\mathrm{hyst}}=5\%$ and ${\sigma}_{\mathrm{DLC}}^{\mathrm{hyst}}=20\%$ for LB and DLC, respectively. Due to its causal nature, the proposed FSM control cannot guarantee the SoC sustenance. Therefore, each HDEMU and PHDEMU configuration was simulated twice, with the initial SoC set to ${\sigma}_{\mathrm{ESS}}=50\%$, and then replaced with the final value obtained in the first simulation run. This allowed for a fair comparison between different configurations. The maximum power from the grid ${P}_{\mathrm{pan}}^{\mathrm{max}}$ was determined from the national railway traction grid characteristics, namely 1500 V DC voltage and current limitation of 2000 A [77]. To account for a difference in weight due to additional components, optimized vehicle speed profiles that comply with the timetable, vehicle, and track parameters were pre-calculated using a bi-section algorithm [78] for each vehicle configuration. For the sake of brevity, detailed simulation results are given in Appendix A (Figure A1, Figure A2 and Figure A3), with the main results summarized in Table 4.

_{2}e/l and for grey electricity reflecting a national power mix of 0.556 kgCO

_{2}e/kWh [82] were assumed. Since all national trains on the electrified lines run on the electricity produced from wind power since 2017 [83], an alternative scenario considered the utilization of green electricity coming from the same source, with the emission factor equal to zero. For the calculation of energy costs, an average diesel price of 1.237 EUR/l [84] and a railway traction electricity price of 0.024137 EUR/kWh [77] were adopted.

## 5. Discussion

_{2}e per kWh of battery capacity [90], contributing 31–46% to the total GHG impact from vehicle production [91]. Even though these relative contributions would be significantly lower for railway vehicles due to their much higher utilization and longer life cycle, further investigation in terms of detailed life cycle assessment (LCA) [92] is needed in order to assess the overall environmental impact of a particular solution.

## 6. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## Nomenclature

Abbreviations | |

AC | Alternating current |

BEMU | Battery-electric multiple unit |

DC | Direct current |

DEMU | Diesel-electric multiple unit |

DLC | Double-layer capacitor |

DMU | Diesel multiple unit |

DP | Dynamic programming |

ECMS | Equivalent consumption minimization strategy |

EM | Electric motor |

EMS | Energy management strategy |

ESS | Energy storage system |

EVSE | Electric vehicle supply equipment |

FCMU | Fuel-cell multiple unit |

FSM | Finite state machine |

G | Generator |

GHG | Greenhouse gasses |

GTW | Gelenktriebwagen |

HDEMU | Hybrid diesel-electric multiple unit |

HEV | Hybrid electric vehicle |

HVAC | Heating, ventilation, and air conditioning |

ICE | Internal combustion engine |

IS | Intermediate stop |

LB | Lithium-ion battery |

LCA | Life cycle assessment |

LCC | Life cycle costs |

LTO | Li titanium oxide |

NMC | Nickel manganese cobalt |

PHDEMU | Plug-in hybrid diesel-electric multiple unit |

PHEV | Plug-in hybrid electric vehicle |

PMP | Pontryagin’s minimum principle |

RB | Rule-based |

RU | Railway undertaking |

SoC | State-of-charge |

TS | Terminal stop |

Parameters | |

${a}_{\mathrm{max}}$ | Maximum acceleration $\left[\mathrm{m}/{\mathrm{s}}^{2}\right]$ |

${a}_{\mathrm{min}}$ | Maximum deceleration $\left[\mathrm{m}/{\mathrm{s}}^{2}\right]$ |

${C}_{\mathrm{DLC}}$ | Capacitance of the double-layer capacitor $\left[\mathrm{F}\right]$ |

${d}_{\mathrm{w}}$ | Wheel diameter $\left[\mathrm{m}\right]$ |

${E}_{\mathrm{DLC}}$ | Energy content of the double-layer capacitor $\left[\mathrm{Kwh}\right]$ |

${E}_{\mathrm{LB}}^{\mathrm{max}}$ | Energy content of the battery $\left[\mathrm{Kwh}\right]$ |

${E}_{\mathrm{LB}}^{\mathrm{use}}$ | Usable energy content of the battery $\left[\mathrm{Kwh}\right]$ |

${F}_{\mathrm{w}}^{\mathrm{max}}$ | Maximum (starting) tractive effort at the wheel $\left[\mathrm{N}\right]$ |

$g$ | Gravitational acceleration $\left[\mathrm{m}/{\mathrm{s}}^{2}\right]$ |

${i}_{\mathrm{ag}}$ | Constant gear ratio $\left[-\right]$ |

${I}_{\mathrm{DLC}}^{\mathrm{max},\mathrm{ch}}$ | Allowed maximum charging current for double-layer capacitor $\left[\mathrm{A}\right]$ |

${I}_{\mathrm{DLC}}^{\mathrm{max},\mathrm{dch}}$ | Allowed maximum discharging current for double-layer capacitor $\left[\mathrm{A}\right]$ |

${I}_{\mathrm{LB}}^{\mathrm{cont},\mathrm{ch}}$ | Allowed maximum continuous charging current of the battery $\left[\mathrm{A}\right]$ |

${I}_{\mathrm{LB}}^{\mathrm{cont},\mathrm{dch}}$ | Allowed maximum continuous discharging current of the battery $\left[\mathrm{A}\right]$ |

${I}_{\mathrm{LB}}^{\mathrm{peak},\mathrm{ch}}$ | Allowed peak (pulse) charging current of the battery $\left[\mathrm{A}\right]$ |

${I}_{\mathrm{LB}}^{\mathrm{peak},\mathrm{dch}}$ | Allowed peak (pulse) discharging current of the battery $\left[\mathrm{A}\right]$ |

${m}_{\mathrm{DLC}}$ | Weight of the double-layer capacitor $\left[\mathrm{kg}\right]$ |

${m}_{\mathrm{LB}}$ | Weight of the battery $\left[\mathrm{kg}\right]$ |

${m}_{\mathrm{pax}}$ | Total weight of passengers $\left[\mathrm{kg}\right]$ |

${m}_{\mathrm{tare}}$ | Empty vehicle mass $\left[\mathrm{kg}\right]$ |

${m}_{\mathrm{v}}$ | Total vehicle mass $\left[\mathrm{kg}\right]$ |

${P}_{\mathrm{aux},\mathrm{const}}$ | Constant auxiliaries power $\left[\mathrm{W}\right]$ |

${p}_{\mathrm{cool}}$ | Cooling power coefficient $\left[-\right]$ |

${P}_{\mathrm{EM}}^{\mathrm{rated}}$ | Rated power of the electric motor $\left[\mathrm{W}\right]$ |

${P}_{\mathrm{G}}^{\mathrm{opt}}$ | Optimal level of electrical power from the diesel generator $\left[\mathrm{W}\right]$ |

${P}_{\mathrm{ICE}}^{\mathrm{rated}}$ | Rated power of the internal combustion engine $\left[\mathrm{W}\right]$ |

${P}_{\mathrm{pan}}^{\mathrm{max}}$ | Maximum power from the charging grid $\left[\mathrm{W}\right]$ |

${Q}_{\mathrm{LB}}$ | Nominal capacity of the battery $\left[\mathrm{As}\right]$ |

${R}_{\mathrm{dch}}$ | Self-discharging resistance of the double-layer capacitor $\left[\mathrm{\Omega}\right]$ |

${R}_{\mathrm{DLC}}$ | Internal resistance of the double-layer capacitor $\left[\mathrm{\Omega}\right]$ |

${R}_{\mathrm{LB}}^{\mathrm{ch}}$ | Battery internal resistance during charging $\left[\mathrm{\Omega}\right]$ |

${R}_{\mathrm{LB}}^{\mathrm{dch}}$ | Battery internal resistance during discharging $\left[\mathrm{\Omega}\right]$ |

${r}_{0}$ | Davis equation coefficient (constant term) $\left[\mathrm{N}\right]$ |

${r}_{1}$ | Davis equation coefficient (linear term) $\left[\mathrm{N}/\left(\mathrm{M}/\mathrm{S}\right)\right]$ |

${r}_{2}$ | Davis equation coefficient (quadratic term) $[\mathrm{N}/{\left(\mathrm{M}/\mathrm{S}\right)}^{2}]$ |

${s}_{\mathrm{cr}}$ | Line-specific critical track section $\left[\mathrm{m}\right]$ |

${s}_{\mathrm{ts}}$ | Position of the terminal stop $\left[\mathrm{m}\right]$ |

${t}_{\mathrm{peak}}^{\mathrm{ch}}$ | Time limit for the allowed battery pulse charging current $\left[\mathrm{s}\right]$ |

${t}_{\mathrm{peak}}^{\mathrm{dch}}$ | Time limit for the allowed battery pulse discharging current $\left[\mathrm{s}\right]$ |

${U}_{\mathrm{DLC}}^{\mathrm{max}}$ | Maximum voltage of the double-layer capacitor $\left[\mathrm{V}\right]$ |

${U}_{\mathrm{DLC}}^{\mathrm{min}}$ | Minimum voltage of the double-layer capacitor $\left[\mathrm{V}\right]$ |

${U}_{\mathrm{LB}}^{\mathrm{max}}$ | Maximum battery voltage $\left[\mathrm{V}\right]$ |

${U}_{\mathrm{LB}}^{\mathrm{min}}$ | Minimum battery voltage $\left[\mathrm{V}\right]$ |

${v}_{\mathrm{max}}$ | Maximum velocity $\left[\mathrm{m}/\mathrm{s}\right]$ |

$\Delta t$ | Simulation (integration) time step $\left[\mathrm{s}\right]$ |

${\eta}_{\mathrm{ag}}$ | Constant efficiency of the gearbox $\left[-\right]$ |

$\lambda $ | Rotating mass factor $\left[-\right]$ |

$\rho $ | Fuel density $\left[\mathrm{kg}/\mathrm{L}\right]$ |

${\sigma}_{\mathrm{ESS}}^{\mathrm{hyst}}$ | Energy storage system hysteresis cycle for the state-of-charge $\left[-\right]$ |

${\sigma}_{\mathrm{ESS}}^{\mathrm{lim}}$ | State-of-charge limit for the energy storage system $\left[-\right]$ |

${\sigma}_{\mathrm{ESS}}^{\mathrm{min}}$ | Minimum state-of-charge for the energy storage system $\left[-\right]$ |

${\sigma}_{\mathrm{LB}}^{\mathrm{max}}$ | Maximum battery state-of-charge $\left[-\right]$ |

${\sigma}_{\mathrm{LB}}^{\mathrm{min}}$ | Minimum battery state-of-charge $\left[-\right]$ |

Dynamic variables | |

$a$ | Vehicle acceleration $[{\mathrm{m}/\mathrm{s}}^{2}]$ |

${b}_{\mathrm{el}}$ | Binary indicator for the track electrification status $\left[-\right]$ |

${B}_{\mathrm{ICE}}$ | Total fuel consumption $\left[\mathrm{L}\right]$ |

${E}_{\mathrm{pan}}$ | Total electrical energy consumption $\left[\mathrm{Ws}\right]$ |

$Flag$ | Binary indicator for the state-of-charge hysteresis cycle $\left[-\right]$ |

${F}_{\mathrm{w}}$ | Tractive/braking effort at the wheel $\left[\mathrm{N}\right]$ |

${I}_{\mathrm{DLC}}$ | Current of the double-layer capacitor $\left[\mathrm{A}\right]$ |

${I}_{\mathrm{DLC}}^{\mathrm{max}}$ | Maximum current of the double-layer capacitor $\left[\mathrm{A}\right]$ |

${I}_{\mathrm{DLC}}^{\mathrm{min}}$ | Minimum current of the double-layer capacitor $\left[\mathrm{A}\right]$ |

${I}_{\mathrm{LB}}$ | Battery current $\left[\mathrm{A}\right]$ |

${I}_{\mathrm{LB}}^{\mathrm{max}}$ | Maximum battery current $\left[\mathrm{A}\right]$ |

${I}_{\mathrm{LB}}^{\mathrm{max},\mathrm{ch}}$ | Maximum battery charging current defined by the manufacturer $\left[\mathrm{A}\right]$ |

${I}_{\mathrm{LB}}^{\mathrm{max},\mathrm{dch}}$ | Maximum battery discharging current defined by the manufacturer $\left[\mathrm{A}\right]$ |

${I}_{\mathrm{LB}}^{\mathrm{min}}$ | Minimum battery current $\left[\mathrm{A}\right]$ |

${P}_{\mathrm{aux}}$ | Total auxiliaries power $\left[\mathrm{W}\right]$ |

${P}_{\mathrm{dem}}$ | Total requested power for traction and auxiliaries $\left[\mathrm{W}\right]$ |

${P}_{\mathrm{DLC}}$ | Power of the double-layer capacitor $\left[\mathrm{W}\right]$ |

${P}_{\mathrm{DLC}}^{\mathrm{max}}$ | Maximum power of the double-layer capacitor $\left[\mathrm{W}\right]$ |

${P}_{\mathrm{DLC}}^{\mathrm{min}}$ | Minimum power of the double-layer capacitor $\left[\mathrm{W}\right]$ |

${P}_{\mathrm{EM}}$ | Electric power of the electric motor $\left[\mathrm{W}\right]$ |

${P}_{\mathrm{ESS}}^{\mathrm{max}}$ | Maximum power of the energy storage system $\left[\mathrm{W}\right]$ |

${P}_{\mathrm{ESS}}^{\mathrm{min}}$ | Minimum power of the energy storage system $\left[\mathrm{W}\right]$ |

${P}_{\mathrm{G}}$ | Electrical output power of the generator $\left[\mathrm{W}\right]$ |

${P}_{\mathrm{ICE}}$ | Mechanical output power of the internal combustion engine $\left[\mathrm{W}\right]$ |

${P}_{\mathrm{LB}}$ | Power of the battery $\left[\mathrm{W}\right]$ |

${P}_{\mathrm{LB}}^{\mathrm{max}}$ | Maximum power of the battery $\left[\mathrm{W}\right]$ |

${P}_{\mathrm{LB}}^{\mathrm{min}}$ | Minimum power of the battery $\left[\mathrm{W}\right]$ |

${P}_{\mathrm{pan}}$ | Electric power received via pantograph $\left[\mathrm{W}\right]$ |

${R}_{\mathrm{c}}$ | Curve resistances $\left[\mathrm{N}\right]$ |

${R}_{\mathrm{g}}$ | Grade resistances $\left[\mathrm{N}\right]$ |

${R}_{\mathrm{LB}}$ | Battery internal resistance $\left[\mathrm{\Omega}\right]$ |

${R}_{\mathrm{v}}$ | Vehicle resistances $\left[\mathrm{N}\right]$ |

$s$ | Distance traveled $\left[\mathrm{m}\right]$ |

$t$ | Time $\left[\mathrm{s}\right]$ |

${t}_{\mathrm{cnt}}^{\mathrm{ch}}$ | Battery pulse charging time counter $\left[\mathrm{s}\right]$ |

${t}_{\mathrm{cnt}}^{\mathrm{dch}}$ | Battery pulse discharging time counter $\left[\mathrm{s}\right]$ |

${T}_{\mathrm{EM}}$ | Torque at the mechanical output of the electric motor $\left[\mathrm{Nm}\right]$ |

${T}_{\mathrm{w}}$ | Torque at the wheel $\left[\mathrm{Nm}\right]$ |

${U}_{\mathrm{DLC}}$ | Terminal voltage of the double-layer capacitor $\left[\mathrm{V}\right]$ |

${U}_{\mathrm{LB}}$ | Battery terminal voltage $\left[\mathrm{V}\right]$ |

${U}_{\mathrm{OC}}$ | Battery open circuit voltage $\left[\mathrm{V}\right]$ |

$v$ | Vehicle velocity $\left[\mathrm{m}/\mathrm{s}\right]$ |

$\gamma $ | Angle of the slope $\left[\mathrm{rad}\right]$ |

${\eta}_{\mathrm{EM}}$ | Efficiency of the electric motor $\left[-\right]$ |

${\eta}_{\mathrm{G}}$ | Efficiency of the generator $\left[-\right]$ |

${\sigma}_{\mathrm{DLC}}$ | State-of-charge of the double-layer capacitor $\left[-\right]$ |

${\sigma}_{\mathrm{LB}}$ | Battery state-of-charge $\left[-\right]$ |

$\varphi $ | Curve radius $\left[\mathrm{m}\right]$ |

$\psi $ | Specific fuel consumption $\left[\mathrm{Kg}/\mathrm{Ws}\right]$ |

${\omega}_{\mathrm{EM}}$ | Rotational speed of the electric motor $\left[\mathrm{rad}/\mathrm{s}\right]$ |

${\omega}_{\mathrm{ICE}}$ | Rotational speed of the internal combustion engine $\left[\mathrm{rad}/\mathrm{s}\right]$ |

${\omega}_{\mathrm{w}}$ | Rotational speed of the wheel $\left[\mathrm{rad}/\mathrm{s}\right]$ |

## Appendix A

**Figure A1.**Simulation results for a standard DEMU vehicle on (

**a**) stopping service and (

**b**) express service.

**Figure A2.**Simulation results for a HDEMU vehicle on stopping and express service, respectively: (

**a**,

**b**) with LB ESS; and (

**c**,

**d**) with DLC ESS.

**Figure A3.**Simulation results for a PHDEMU vehicle on stopping and express service, respectively: (

**a**,

**b**) LB ESS with charging at TSs; (

**c**,

**d**) LB ESS with charging at TSs and IS; (

**e**,

**f**) DLC ESS with charging at TSs; and (

**g**,

**h**) DLC ESS with charging at TSs and IS.

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**Figure 1.**Simplified schematic representation of (

**a**) standard, (

**b**) hybrid, and (

**c**) plug-in hybrid system architectures for a diesel-electric multiple unit vehicle.

**Figure 2.**Layout of the simulation model for the assessment of the alternative diesel-electric multiple-unit propulsion system configurations.

**Figure 7.**(

**a**) Efficiency map of an electric motor; (

**b**) specific fuel consumption of an internal consumption engine; and (

**c**) lithium-ion battery module open circuit voltage as a function of state-of-charge.

**Figure 8.**(

**a**) Position and (

**b**) schematic representation of the Northern lines in the Netherlands; and (

**c**) track layout for the railway line Leeuwarden-Groningen with indicated locations for charging facilities, stops for stopping and express service, track geometry, and maximum allowed speed.

**Figure 9.**Total GHG emissions depending on the propulsion system, charging location, and electricity production configurations; and estimated potential reduction compared to a standard diesel-electric multiple unit.

**Figure 10.**Estimated fuel costs for different propulsion system and charging location configuration, and potential reduction compared to a standard diesel-electric multiple unit.

Parameter | Unit | Value | Description |
---|---|---|---|

${m}_{\mathrm{tare}}$ | t | 70.4 | Tare weight ^{1} |

$\lambda $ | - | 0.05 | Rotating mass factor ^{2} |

${m}_{\mathrm{pax}}$ | t | 7 | Total passengers weight ^{3} |

${r}_{0}$ | N | 1001 | Davis equation coefficient (constant term) ^{2} |

${r}_{1}$ | N/(km/h) | 22.3 | Davis equation coefficient (linear term) ^{2} |

${r}_{2}$ | N/(km/h)^{2} | 0.1 | Davis equation coefficient (quadratic term) ^{2} |

${d}_{\mathrm{w}}$ | m | 0.86 | Powered wheel diameter ^{4} |

${i}_{\mathrm{ag}}$ | - | 1.7218 | Axle gear ratio ^{5} |

${\eta}_{\mathrm{ag}}$ | - | 0.97 | Axle gear efficiency ^{6} |

${v}_{\mathrm{max}}$ | km/h | 140 | Maximum velocity ^{4} |

${a}_{\mathrm{max}}$ | m/s^{2} | 1.05 | Maximum acceleration ^{2} |

${a}_{\mathrm{min}}$ | m/s^{2} | −1 | Maximum deceleration ^{2} |

${F}_{\mathrm{w}}^{\mathrm{max}}$ | kN | 80 | Maximum (starting) tractive effort at the wheel ^{4} |

${P}_{\mathrm{w}}^{\mathrm{max}}$ | kW | 600 | Maximum power at the wheel ^{4} |

${P}_{\mathrm{EM}}^{\mathrm{rated}}$ | kW | 2 × 400 | EM rated power ^{1} |

${P}_{\mathrm{ICE}}^{\mathrm{rated}}$ | kW | 2 × 390 | ICE rated power ^{1} |

${P}_{\mathrm{aux},\mathrm{const}}$ | kW | 50 | Constant auxiliaries power ^{3} |

${p}_{\mathrm{cool}}$ | - | 0.01 | Cooling power coefficient ^{3} |

$\rho $ | g/L | 825 | Fuel density (diesel) ^{6} |

^{1}Giro Batalla and Feenstra [71];

^{2}Personal communication with Arriva;

^{3}Assumed values;

^{4}Stadler Bussnang AG [72];

^{5}Calculated as the ratio between the maximum rotational speed of the GTW’s EM provided in [71] and the maximum rotational speed of the wheel derived from the maximum vehicle speed;

^{6}Adopted from Prohl [59].

Parameter | Unit | Value | Description |
---|---|---|---|

LB module ^{1} | |||

${Q}_{\mathrm{LB}}$ | Ah | 45 | Nominal capacity |

${I}_{\mathrm{LB}}^{\mathrm{cont},\mathrm{ch}}/{I}_{\mathrm{LB}}^{\mathrm{cont},\mathrm{dch}}$ | A | −160/160 | Minimum/maximum continuous current |

${I}_{\mathrm{LB}}^{\mathrm{peak},\mathrm{ch}}/{I}_{\mathrm{LB}}^{\mathrm{peak},\mathrm{dch}}$ | A | −350/350 | Minimum/maximum pulse current |

${t}_{\mathrm{peak}}^{\mathrm{dch}}/{t}_{\mathrm{peak}}^{\mathrm{dch}}$ | s | 10 | Allowed time for pulse current |

${U}_{\mathrm{LB}}^{\mathrm{min}}/{U}_{\mathrm{LB}}^{\mathrm{max}}$ | V | 18/32.4 | Minimum/maximum voltage |

${R}_{\mathrm{LB}}^{\mathrm{ch}}/{R}_{\mathrm{LB}}^{\mathrm{dch}}$ | Ω | 0.006 | Internal resistance charge/discharge |

${\sigma}_{\mathrm{LB}}^{\mathrm{min}}/{\sigma}_{\mathrm{LB}}^{\mathrm{max}}$ | % | 10/90 | Minimum/maximum SoC ^{2} |

${E}_{\mathrm{LB}}^{\mathrm{max}}$ | kWh | 1.24 | Energy content |

${E}_{\mathrm{LB}}^{\mathrm{use}}$ | kWh | 0.922 | Usable energy content ^{3} |

${m}_{\mathrm{LB}}$ | kg | 15 | Weight |

DLC module ^{4} | |||

${C}_{\mathrm{DLC}}$ | F | 63 | Rated capacitance |

${I}_{\mathrm{DLC}}^{\mathrm{max},\mathrm{ch}}/{I}_{\mathrm{DLC}}^{\mathrm{max},\mathrm{dch}}$ | A | −240/240 | Minimum/maximum continuous current |

${U}_{\mathrm{DLC}}^{\mathrm{min}}/{U}_{\mathrm{DLC}}^{\mathrm{max}}$ | V | 12.5/125 | Minimum/maximum voltage |

${R}_{\mathrm{DLC}}$ | Ω | 0.018 | Internal resistance |

${E}_{\mathrm{DLC}}$ | kWh | 0.14 | Energy content |

${m}_{\mathrm{DLC}}$ | kg | 61 | Weight |

Station | Distance (km) | Departure Time (hh:mm) | |||
---|---|---|---|---|---|

Stopping Service ^{1} | Express Service | ||||

Lw → Gn | Gn → Lw | Lw → Gn | Gn → Lw | ||

Leeuwarden | 0 | hh: 51 | hh + 2:40 (arrival) | hh: 44 | hh + 2:16 (arrival) |

Leeuwarden C. | 3.34 | hh: 54 | hh + 2:35 | - | - |

Hurdegaryp | 9.83 | hh + 1:01 | hh + 2:30 | - | - |

Feanwalden | 14.00 | hh + 1:05 | hh + 2:25 | - | - |

De Westereen | 17.24 | hh + 1:08 | hh + 2:20 | - | - |

Buitenpost | 24.74 | hh + 1:16 | hh + 2:15 | hh + 1:00 | hh + 2:00 |

Grijskerk | 35.71 | hh + 1:23 | hh + 2:06 | - | - |

Zuidhorn | 42.35 | hh + 1:30 | hh + 2:01 | - | - |

Groningen | 54.05 | hh + 1:39 (arrival) | hh + 1:51 | hh + 1:18 (arrival) | hh + 1:42 |

^{1}Stopping service departure times also reported in [37].

**Table 4.**Energy consumption, GHG emissions, and energy costs for standard, hybrid, and plug-in hybrid vehicle configurations.

Service | Configuration | ESS | Charging Option ^{1} | Energy Consumption | GHG Emissions ^{2}[kgCO _{2}e] | Energy Costs [EUR] | |
---|---|---|---|---|---|---|---|

Fuel [L] | Electricity [kWh] | ||||||

Stopping | DEMU | - | - | 106.31 | - | 343.38 | 131.51 |

HDEMU | LB | - | 92.01 | - | 297.19 | 113.82 | |

DLC | - | 72.43 | - | 233.95 | 89.60 | ||

PHDEMU | LB | TSs | 75.77 | 41.01 | 267.54 (244.74) | 94.72 | |

TSs + IS | 75.84 | 47.44 | 271.34 (244.96) | 94.96 | |||

DLC | TSs | 50.38 | 63.43 | 197.99 (162.73) | 63.85 | ||

TSs + IS | 46.04 | 100.55 | 204.62 (148.71) | 59.38 | |||

Express | DEMU | - | - | 140.40 | - | 453.49 | 173.67 |

HDEMU | LB | - | 126.80 | - | 409.56 | 156.85 | |

DLC | - | 87.11 | - | 281.37 | 107.76 | ||

PHDEMU | LB | TSs | 106.61 | 49.61 | 371.93 (344.35) | 133.07 | |

TSs + IS | 118.58 | 49.84 | 410.72 (383.01) | 147.89 | |||

DLC | TSs | 61.98 | 83.48 | 246.61 (200.20) | 78.68 | ||

TSs + IS | 60.49 | 104.81 | 253.66 (195.38) | 77.36 |

^{1}TS: Terminal stop, IS: Intermediate stop;

^{2}The values in brackets were calculated for the scenarios that consider green electricity for ESS charging.

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**MDPI and ACS Style**

Kapetanović, M.; Vajihi, M.; Goverde, R.M.P. Analysis of Hybrid and Plug-In Hybrid Alternative Propulsion Systems for Regional Diesel-Electric Multiple Unit Trains. *Energies* **2021**, *14*, 5920.
https://doi.org/10.3390/en14185920

**AMA Style**

Kapetanović M, Vajihi M, Goverde RMP. Analysis of Hybrid and Plug-In Hybrid Alternative Propulsion Systems for Regional Diesel-Electric Multiple Unit Trains. *Energies*. 2021; 14(18):5920.
https://doi.org/10.3390/en14185920

**Chicago/Turabian Style**

Kapetanović, Marko, Mohammad Vajihi, and Rob M. P. Goverde. 2021. "Analysis of Hybrid and Plug-In Hybrid Alternative Propulsion Systems for Regional Diesel-Electric Multiple Unit Trains" *Energies* 14, no. 18: 5920.
https://doi.org/10.3390/en14185920