Design of a hybrid hierarchical demand response control scheme for the frequency control

Conventionally, the frequency of the power system is controlled by matching the electric supply to the varying demand. Some recent studies demonstrated that demand response (DR) can also contribute to the frequency control. However, most of the research works focus on the overall control strategy of DR, whereas the DR parameters are usually randomised rather than carefully designed. In this study, a hybrid hierarchical DR control scheme is designed to support frequency control. The parameters settings are discussed in detail. Instead of randomising the parameters for individual DR controllers, this study proposes a systematic way to design the parameters such as frequency threshold and minimum off-time for individual controllers, so that aggregation of DR can provide primary frequency control smoothly just like thermal generators. Furthermore, the control system is formulated as a multi-objective optimisation problem. The parameters such as the recovery rate of DR and the integral gain of secondary frequency control is optimised so that the maximum deviation, overshoot and oscillations of the frequency can be properly minimised. The proposed method is verified on numerical examples.