A SOC-feedback Control Scheme for Fast Frequency Support with Hybrid Battery/Supercapacitor Storage System

Providing fast frequency regulation by means of energy storage systems is currently considered as a viable solution to low-inertia issues, caused by power electronics-interfaced generators. In particular, hybrid energy storage systems, composed by more energy storage technologies having different power and energy ratings, can optimally support the frequency regulation. A supercapacitor/battery storage system, for example, can exploit the supercapacitor dynamic active power response for synthetic inertia control, while the battery can provide primary and secondary frequency regulation. However, the optimal energy management of hybrid energy storage systems during transients needs to be addressed further in literature. In this paper, a State of Charge (SOC) feedback control scheme is proposed, that adjusts the active power output reference depending on the state of charge, avoiding excessive stress on the components and limiting the state of charge excursions. Control system parameters are optimally tuned minimizing a weighted multi-objective function in the solution of an optimal control problem. Test results adopting different weights are presented and discussed.