Power controller using dual deadbands for reducing oscillatory load manipulations

Claim 1

In a power demand control system associated with a plant having loads supplied with electrical energy from utility power lines including: means for selecting loads selected to be switched from one of an ON and OFF status to the other in accordance with a priority schedule to maximize production while maintaining within a deadband about an assigned demand limit reference signal the energy consumed by the plant; and means for measuring the power consumed from said power lines for a predetermined number N of equal time intervals, each defined between two consecutive said sampling instants; the combination of: first means responsive to the power measured by said measuring means during (N-1) consecutive said time intervals ending at a present sampling instant for providing a first signal representative of the (N-1) time interval demand of energy consumed during said (N-1) consecutive time intervals; second means responsive to said measuring means and to said first means for predicting at said present sampling instant the deviation of demand during the time interval subsequent to said present sampling instant and for providing a second signal representative of the amount of power consumed at said sampling instant if maintained constant during said subsequent time interval; third means for comparing said demand limit reference signal to the sum of said first and second signals as a representation of predicted demand for N time intervals for deriving an error relative to said demand limit; and means for switching a selected load in response to said error exceeding said demand deadband, thereby to maintain the assigned demand limit within the demand deadband, while minimizing load switching manipulation.