Smart outlet system with fast frequency tracking for power system frequency control using distributed appliances

A method to control a power grid frequency, comprising:

• distributing a plurality of outlet devices each containing a relay over a grid;
• continuously measuring the power grid frequency providing power to each of the distributed outlet devices, wherein the each of the distributed outlet devices is plugged into an outlet;
• updating a value of the power grid frequency using an extended Kalman filter within the each of the distributed outlet devices at a low-voltage single-phase distribution level by determining the state transition of extended Kalman filter:
• xc[t+1]=cos(xω[t]/ƒs)xc[t]−sin(xω[t]/ƒs)xs[t]+ϵc[t],
• xs[t+1]=sin(xω[t]/ƒs)xc[t]+cos(xω[t]/ƒs)xs[t]+ϵs[t],
• xω[t+1]=xω[t]+ϵω[t],
• where ƒs is the sampling frequency;
• xc, xs and xω consist of the state of the extended Kalman filter;
• t is the time;
• and ϵc, ϵs, and ϵω are the noise;
• determining and sending a threshold to the each of the distributed outlet devices at and by a cloud control center;
• tracking a frequency change within 0.2 second or 10 cycles and enabling a fast frequency response in response to a frequency fluctuation;
• and
• switching off the relay in the each of the distributed outlet devices that provides power to an appliance based on the result of comparing the power grid frequency with the threshold sent from the cloud control center.