A dynamic demand response control strategy for isolated microgrid with primary frequency regulation

Electric water heaters (EWHs) are considered as suitable devices for demand response (DR) load control and can be aggregated to participate in primary frequency regulation services for microgrids. However, achieving accurate frequency control of the microgrid through the load response of EWHs while reducing frequency rebound remains a challenge. This paper proposes a dynamic DR load control strategy for primary frequency regulation in microgrids that utilizes EWHs as responsive loads. First, an aggregated model is developed to aggregate EWH clusters based on their physical characteristics. Then, the coefficients of the local frequency curve equation are obtained using the least squares method to predict the nadir of frequency fluctuations. The maximum frequency deviation is calculated based on the nadir of the frequency. Furthermore, an EWH cluster switch control strategy is established based on the EWH temperature and the maximum frequency deviation to determine the switching sequence of EWHs. The simulation results point out that the control algorithm proposed in this study is capable of accurately regulating the frequency of the microgrid within the aggregated capacity range of the EWHs while also the user's comfort is almost unaffected.