A Concept for Controlling Heat Pump Pools Using the Smart Grid Ready Interface

This paper introduces a control concept for aggregators to directly control a pool of residential heat pumps using market available technology. Smart meters are used for measuring the electric demand and the heat pumps' SG-Ready interfaces are used to trigger four different load-shifting strategies in the heat pump. The main idea of this paper is to use optimal control to calculate the setpoints for the pool and to track them using classic PID controls. The optimal control model as well as the implemented PID controller are both tailored to represent the available load shifting strategies. The characteristic response of the heat pump pool to a direct control signal is considered in the formulation of the optimal control problem. The control concept is tested with a pool of 284 heat pumps located in different buildings. The concept is demonstrated to realise an optimised operation of the pool respecting the variability of the prices on the day-ahead market for electricity. Tracking of a set-value for power consumption of the pool is presented. It showed that sending the signal to randomly selected heat pumps in the pool is similarly efficient as selecting from a priority list when not affecting the comfort of the occupants. Results indicate that control parameters should be continuously adjusted using an online estimation procedure to avoid oscillation.