A hierarchical framework for demand-side frequency control

This paper aims to develop a hierarchical framework for demand-side frequency control. The framework involves two decision layers. The top layer determines a control gain for the aggregated load response on each bus using robust decentralized control theory. The second layer involves a large number of devices, which switch probabilistically during contingencies so that the aggregated power change matches the desired droop amount according to the control gains determined in the top layer. The proposed framework is based on the classical nonlinear multi-machine power system model, and can deal with time-varying system operating conditions while respecting the physical constraints of individual devices. Realistic simulation results based on a 68-bus system are provided to demonstrate the effectiveness of the proposed strategy.