Coordination of storage and generation in power system frequency control using an Hα approach

This study proposes a novel H_∞-based approach called advanced frequency control (AFC) to integrate storage into frequency control. The objective is to split the task of balancing frequency deviations introduced by renewable energy source (RES) and load variations according to the capabilities of storage and generators. Hence, via frequency dependent weighting functions, a so-called frequency separation objective is achieved: the conventional generators mainly balance the low-frequency components of the RES and load variations while the energy storage devices compensate the high-frequency components. First, a state-space structure-preserving model of the power system is derived, which is needed for the design of the controller. In order to enable the controller design for storage devices located at buses with no generators, a model for the frequency at such a bus is developed. Then, AFC controllers are synthesised through decentralised static output feedback to reduce the complexity in the practical implementation of such controllers. An existing linear matrix inequality algorithm is improved and employed to solve the involved H_∞ problem. Finally, the WECC 9-bus test system is used to verify the performance of the AFC design.