There are several control system involved in BESS for primary frequency regulation: EMS, SMS, PCS and Batteries.
EMS shall calculate the quantity of active power necesary when a frequency perturbation ocurs and send the set-points to SMS and then to PCS.
But, if I need that response of active power (P) different to "step function", for example a ramp or a PI, what should be the system that I should program this function? EMS, SMS or PCS?