Primary frequency support from local control of large-scale heat pumps

Increasing penetration of volatile renewable sources in the electric power system increases the need of new sources of balancing capacity. As a power-to-x technology, heat pumps (HPs) couple the electricity and heating systems, while offering a potential source of regulating capacity. This paper presents new findings on primary frequency support from large-scale HPs through local droop and synthetic inertia control methods with the objective of improving the system frequency control performance following a disturbance. The complexity and operation of large-scale HPs are different from the common model representation of HPs as thermostatically controllable load, which makes the existing studies and HP frequency support methods inaccurate. This work applies a state space model representation of the large-scale HPs, which enables a performance evaluation of existing local frequency control methods. Simulation results show the improved grid frequency control performance following a disturbance supported by large-scale HPs. Simultaneously, the heat and power response of large-scale HPs with frequency control support is compared to that of small-scale HPs.