Broadcast communication by system frequency modulation

Load controllers available today can measure AC system frequency and react to frequency deviations. A system operator can communicate to frequency sensitive loads by changing the set-points of the system´s dispatchable frequency regulation resources. Explicitly signaling system state by generating off-nominal system frequency values is a novel narrowband broadcast communications channel between system operators and frequency sensitive distributed energy resources (FS-DER). The feasibility of the proposed system is evaluated on an existing island power system in Denmark. This study shows that within standard frequency quality constraints, 4 distinct symbols are feasible on the island. However, the overarching imperative of system stability prevents the symbols from having arbitrary meanings. Higher frequency values must translate into greater consumption from loads, and vice versa. Within these constraints, the proposed system would allow operators to dispatch FS-DER in a robust manner, without using an external digital control channel. By dispatching FS-DER, their well known role as a power balancing resource can be expanded to include energy balancing services.