Electric water heater modeling and control strategies for demand response

Demand response (DR) has a great potential to provide balancing services at normal operating conditions and emergency support when a power system is subject to large disturbances. Effective DR control strategies can help relieve balancing and frequency response burdens on conventional generators in addition to reducing generation and transmission investments needed to meet peak demands. This paper discusses modeling residential electric water heaters (EWH) in households and tests their responses with various control strategies implementing DR. The open-loop response of EWH to a centralized control signal is studied by adjusting temperature settings to provide balancing services; and two types of decentralized controllers are tested to provide frequency support following generator trips. EWH models are included in a simulation platform capable of performing electromechanical simulations, which contains 147 households in a distribution feeder. Simulation results show the effectiveness of EWH responses and its dependence on hot water usage. These results provide insight and suggest the need for control strategies to achieve better performance in demand response implementations.