Contribution of the thermal inertia of trains to the primary frequency control of electric power systems

Abstract

There is a wide consensus about substituting fossil fuel-based electric generation with renewable resource-based one. However, the displacement of conventional power plants with power electronics-interfaced plants implies several technical issues that must be addressed. Among these needs, providing ancillary services to electric power systems is fundamental to maintain power quality and system reliability. There is a considerable amount of literature about providing ancillary services from renewable power plants and an increasingly important effort to complement these services with loads. However, the contribution of railway systems to these services has been less explored. Considering the world-wide expansion of railway systems, it is appropriate to consider them as relevant contributors to ancillary services. The present work presents a novel approach to assess the possibilities of contribution of railways to grid primary frequency control based on the thermal inertia of trains. This approach aims at determining how railways can support frequency control tasks without affecting the circulation time of trains and thermal comfort of passengers. This paper proposes to act on the power consumption of the air conditioning system of trains as the way of making the train whole consumption responsive to frequency deviations. In addition, the paper proposes a methodology for analyzing the effectivity of the approach. It defines the extent of the modeling detail of railway and electric power system, and the coupling between them. To validate the feasibility, its application is illustrated with a case study. The results show that frequency deviations can be reduced without affecting passengers’ thermal comfort.