Potentials of using electric-thermal sector coupling for frequency control: A review

Power and heat are the two most important sectors in modern energy systems. Microgrid, as the basic block of the future power sector, is turning into a low-inertia system as the renewable energy penetration level continues to rise. Since battery energy storage systems are still costly, the flexibility in microgrids is currently limited, which makes frequency control challenging. On the contrary, as a result of the high thermal inertia and affordable thermal energy storage systems, the heat sector has a large amount of unused flexibility. With the trend of decarbonization, the heat sector is increasingly being electrified, granting the opportunity for combined operation between the power and heat sectors. Utilizing the flexibilities in heating systems for microgrid fre-quency control is an essential step toward sector coupling and multi-energy operations. This paper analyzes the flexibilities of combined-heat-and-power (CHP) and power-to-heat (PtH) systems through several key perfor-mance indicators. In addition, the available control strategies and existing practices of frequency control based on CHPs and PtH systems are reviewed. Finally, future research directions on sector-coupled frequency control are provided based on the gathered information.