Linear PV Power Plant Integration into Electrical Railway Microgrid via MVDC Architecture

Switzerland proves the feasibility of installing PV panels between railway tracks while maintaining safe railway operation and infrastructure maintenance. Considering the approximately 5200 km of railway tracks and numerous multimodal transport hubs, the railway represents a largely untapped resource for renewable energy generation in Switzerland. From a technical perspective, REN exhibits characteristics that are favorable for renewable energy integration. It is designed to supply highly variable traction loads from moving trains and is therefore inherently robust to power fluctuations. Moreover, railway standards allow voltage variations of up to ±30% of the nominal catenary voltage, which is significantly higher than the

±10% typically permitted in conventional distribution networks. Such flexibility and robustness make REN suitable for the integration of renewable energy sources such as LPV.

The main objective of this work is to explore the integration of LPV installations into a railway microgrid (Rail-MG) while respecting electrical and operational constraints. Conventional PV system architectures are not directly applicable to LPV installations longer than one kilometer due to challenges such as mismatch losses caused by non-uniform irradiance and shading, Paris Session 2026

August 23 to 28

Palais des Congrès, Paris, France voltage variation limits, and the need to minimize the number of power converters for economic and maintenance reasons. To address these challenges, this paper focuses on a design and sizing methodology for LPV systems installed between railway tracks. In addition, a Rail-MG case study is introduced and simulated to assess the technical feasibility of LPV integration and to evaluate its impact on railway electrification system. The key results and conclusions are summarized as follows:

• The LPV power plant features a modular layout with a PV block length of 6 m, resulting in string and array lengths of 60 m and 120 m, over an approximately 4 km LPV installation.

The length of the LPV segments controlled by each MPPT module is designed to be very short around 60m, which mitigates the adverse effects of potential shading or non-uniform irradiance on PV production efficiency. The total PV production reaches 864 kWp at the

MPP interfaced through 32 LV DC/DC converters rated at 28 kW, together with two MV

DC/DC converters rated at 432 kW. • The LVDC and MVDC networks are sized based on voltage rise and power loss constraints.

For the LVDC network, a 95 mm² cable limits the voltage rise to 3% at peak PV output. For the MVDC network, a cable cross-section of 10 mm² is theoretically sufficient for 10 kV/20 kV operation, however, the minimum commercially available cross-section is 50 mm² for 10 kV/20 kV MV cables. When operating at 20 kV MVDC network, the selected 50 mm² cable achieves a transmission efficiency of 99.9%, ensuring efficient power transfer. • Simulation results confirm the technical feasibility of integrating LPV systems into RailMG. More importantly, LPV deployment into Rail-MG diversifies the energy mix for electric mobility, enhances grid resilience by reducing dependence on centralized generation, and contributes to the decarbonization of electric transport systems. This work also highlights an opportunity to optimize railway power flow by leveraging regenerative braking and BESS alongside PV generation, to be explored in the next step.