Patent US 4,181,950

Power demand control on a plant having a plurality of load units of production, each operating between a starting time and an ending time to provide individual production outputs, is exercised by automatically shedding or restoring such load units in order to maintain power demand within an assigned demand limit. The control system provides adaptive priority determination by storing an image of the ON, or OFF, status of the load units into at least two memories (memory I and memory II) on a last ON, first OFF basis for the loads to be shed, and on a last OFF, first ON basis for the loads to be restored. Loads that are ON are stored in a first (ON) memory (memory I); loads that are being held OFF by the controller are stored in a second (DCOFF) memory (memory III). Also provided is a third memory (OFF) (memory II) to store the status of load units which are out of production and under independent control either after ending production or while being made ready to start production. Such independent control is interfaced with automatic power demand control by storing OFF status load units that were under independent controls but are now available for processing production into the second memory at the lowest priority and those having ended production being stored into the third memory at the highest priority. Load units which change status under power demand control to minimize demand error have their status locations in the first and second memory exchanged in preparation of subsequent automatic demand control during the demand control period. The load position in the first and second memories may be modified by the controller operators to enhance the probability of a given load turning ON or staying ON.