Use of the Thermal Inertia of Trains for Contributing to Primary Frequency Control and Inertia of Electric Power Systems

The current trend of massively incorporating renewable-based generation into power systems is affecting frequency stability. This generation does not inherently provide inertia owing to its electronic interface. Therefore, many approaches have been proposed to address the problem of inertia weakening. Beyond the new trends of making new generation and storage responsive to grid needs, this study addresses the problem from the role of consumers. The use of railway consumption to contribute to frequency control tasks, without affecting train circulation, is proposed. For the first time, the provision of virtual inertia combined with primary frequency control is presented. This is achieved by means of the power consumption of ventilation and air conditioning systems, while maintaining the thermal comfort of passengers. To illustrate this new concept, a case study of a real metro line is presented. The results demonstrate the benefits of using the thermal inertia of trains to contribute to grid frequency control. Also, some insights into technical requirements and possible issues are provided. An appropriate combination of primary frequency control and virtual inertia can reduce technical requirements and provide better frequency performance.