Project objectives
The aim of the project is to develop and implement a system to reduce peak power in traction substations managed by PGE Energetyka Kolejowa S.A. These facilities are characterized by significant load irregularity and large peak power values. This causes them to require large values of contracted power, which generates significant fixed costs. The system, built on the basis of an energy storage unit installed on the DC side via a bidirectional power electronic converter, is expected to make it possible to achieve a process innovation consisting in reducing the demand for contracted power and thus reducing the fixed costs associated with the energy distribution service provided by PGE Energetyka Kolejowa S.A. to the traction networks.
By using an energy storage facility, this can be accomplished without limiting the volume and parameters of distributed energy. The system is also expected to improve the stability of the output voltage on the DC side of the traction substation, which may also enable an increase in traction vehicle traffic and, consequently, an increase in the volume of distributed energy without having to increase the connection capacity. As a result, the impact of individual traction substations on the distribution networks feeding them is also expected to be reduced by reducing power fluctuations and peak power. This property is also planned for use in commercial system services involving temporary intentional, on-demand power curtailment. In both cases, this can contribute to the reduction of power losses in lines supplying traction stations and also to the reduction of load losses in station transformers. The Project will also result in the development and verification of a method for the selection of power reduction system components in traction stations, as well as the dimensioning of their technical parameters.
Traction energy storage PGE Energetyka Kolejowa S.A.
The most important result of the project is the largest traction energy storage facility in Europe. The prototype installation has a capacity of 5.5 MW and a guaranteed capacity after 10 years of 1.2 MWh. Its main purpose is to reduce the peak load on the distribution network resulting from rail traffic load. It allows to reduce the ordered power of the traction substation. The storage facility also makes it possible to improve the power quality of the traction network.
The proposed solution is unique on a global scale in many aspects. It is one of the first with this functionality and size, operating in the world, energy storage systems built on the overhead line. Although there are known solutions for the implementation of energy storage systems on the catenary network, but their main task is to improve the quality of voltage in the subway line and, importantly, these solutions are many times smaller in power and capacity. Secondly, due to the need to ensure the required reliability, the energy conversion system has a modular design. Thanks to this solution, even in the event of failure of one of the converter modules, continuous operation of the storage system with unchanged parameters is ensured. In the event of failure of subsequent modules, uninterruptible operation of the system is also ensured, but this time with less power. Another unique solution is the ability to ensure uninterrupted operation of the system in the event of exceeding the limits of the battery modules or even in the event of their fire - extinguishing covers only the faulty modules. In addition, the system has been configured in such a way as to allow adaptation of its operating parameters, for example, to changing train traffic (e.g., in a situation where the volume of train traffic increases).
A schematic description of the operation is indicated below:
The principle of the system is relatively simple. During the period when there is no train traffic on the railroad line, the storage is charged with low power from the national distribution network. When a vehicle is detected on the tracks, the storage gives up energy and provides the appropriate level of power. As a result, much less power is drawn from the national distribution network while the train is in motion, allowing a significant reduction in ordered peak power.
Energy storage consists of two main systems - the battery system and the energy conversion system:
- The battery system is the heart of the entire system - it is more than 4,000 lithium-ion batteries that store the transferred energy. Each battery is equipped with its own set of sensors to continuously monitor its basic parameters: voltage, current and temperature. The batteries are housed in 4 specially constructed containers and are equipped with dedicated cooling and fire protection systems.
- Energy conversion system - its main element is a state-of-the-art power electronic converter, whose task is to properly adjust the parameters of electricity transmitted from the storage facility to the catenary network. This is one of the first devices of this type in Poland.
- The operation of the entire installation is supervised by a control system, which ensures that the warehouse operates optimally and in accordance with the demand of the catenary network, as well as collecting data and parameters of the system's operation. The results obtained in the course of the research work will allow the development of appropriate standards for the implementation of further energy storages in other substations belonging to PGE Energetyka Kolejowa S.A.
The project is co-financed by the European Union with funds from the European Regional Development Fund under the Operational Programme Intelligent Development 2014-2020. The project is implemented under the competition of the National Centre for Research and Development: no. 8 of the Sectoral Programme "PBSE".
