AC railway power network with integration of renewable energy sources

Kano, Nakaret ORCID: 0009-0002-4850-426X (2023). AC railway power network with integration of renewable energy sources. University of Birmingham. Ph.D.

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Abstract

Currently, 25 kV 50/60 Hz AC electrical railway systems are the global standard for mainline and high-speed rail. However, high-speed trains consume substantial energy from the power supply, contributing to carbon emissions and climate change. Most electricity is generated by fossil fuel-based steam turbine generators, including power for railways. To reduce carbon emissions, it is crucial to decrease reliance on fossil fuels and explore renewable energy sources. While studies exist on integrating renewables into the power grid, few have examined their connection to railway power supply systems. This thesis aims to identify a suitable scheme for integrating renewable energy and an energy storage system to decarbonize the traction power network.

The thesis reviews the AC railway traction power supply system, including transformer connections and feeding arrangements. It explores solar PV farms, wind farms, and energy storage systems. A simulation model is developed to verify the findings using a case study of a high-speed railway route.

Proposed renewable integration schemes for the AC railway traction network are presented and simulated. The case study results show that connecting the RES to a three-phase railway power network yields the lowest power losses, requires less investment, and provides greater long- term cost savings. Furthermore, all schemes based on a 400 kV transmission system meet the UK's restriction of 1.5% voltage unbalance factor (VUF). Integrating 120 MW of RES in the case study reduces CO2 emissions by 50%.

A scheme integrating solar PV farms and large-scale energy storage into the railway power supply is introduced. It studies energy flow, storage benefits, and renewable sources. The main control strategy is to reduce system energy costs by using regenerative braking energy and purchasing low-priced energy. Results show effective utilization of captured regen energy, though not all can be absorbed. The scheme with energy storage exhibits lower electricity costs and carbon emissions compared to the benchmark scheme. Integration of PV farms in the benchmark scheme reduces net electricity cost and carbon tax. Employing both PV farms and energy storage achieves the lowest electricity cost and carbon emissions.

A concept to decarbonize electric railways by integrating solar PV farms, wind farms, and an energy storage system (ESS) has been proposed. An energy management system was developed to calculate energy flow and cost, considering contact wire loss and conversion loss. The Brute Force Algorithm was used to optimize the capacity and location of the PV farm, wind farm, and ESS for the lowest daily expenses. The High Speed 2 Railway in the UK was used as a case study. Implementing ESS and renewable energy sources (RESs) significantly reduced global cost and carbon emissions. The ESS alone eliminated around 1.3% of the global cost by absorbing and reusing regenerative energy. Including PV and wind farms increased this figure to 10% and 62% respectively. Taking all factors into account, establishing a wind power plant was found to be the more cost-effective option. The study also showed that the ideal installation sites for the plants and ESS varied depending on the scenario.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):