US 4,363,101 A · Computerized power demand control in an electrochemical plant

Abstract

All line control is performed with a power demand control system to bring about ideal rate before the end of a demand period. Demand error is modified so as to project the demand toward a definite point on the ideal rate curve, then to follow the ideal rate toward the target. Correction at a chosen point in time takes into account a possible duration from ideal rate consumption by either choosing the ideal rate short of the target or by pointing exactly to the target. All lines are individually controlled by tap changing with variable deadband and hysteresis, and tap moves are estimated on the basis of individual wattage and amperage changes in a previous control cycle. The minimum between necessary tap moves and the tap moves possible within an upper and a lower limit in the cell line amperage is used for control. The system allows safe settings by the operator and establishes passwords to communicate with the computer system when protected steps are to be dealt with, by the engineer, for instance.

Claims14

Dependent claims

A method of controlling the loads in a plant facility while keeping the overall plant consumption within an assigned power demand limit, comprising the steps of:

measuring the actual power rate of consumption by said plant;
establishing successive demand periods for totalizing the power demand from the beginning of a demand period to the end thereof;
said power demand limit being assigned at the end of a demand period;
periodically calculating a demand error projected to be at the end of a demand period on the basis of actual power rate;
changing concurrently with said calculating step the demand error into a changed error by an amount sufficient to reach at a predetermined instant selected before the end of the demand period a power rate corresponding to the ideal rate of consumption at said predetermined instant;
and
controlling at least one of said loads in order to compensate for such said changed error, thereby reaching said assigned demand limit under the ideal rate at the end of the demand period.

4 more elements

In a power demand control system of a plant facility having a plurality of electrical loads which are controllably sheddable and a plurality of electrical loads which are selectively adjustable in relation to individual power rate consumption, said loads being supplied with energy from the power lines of a utility company, and including:

a utility company main kilowatt hour meter providing indication of present power demand of said plant facility;
means responsive to said main kilowatt hour meter and operative during successive demand periods for deriving an anticipated demand of energy at the end of a current demand period and establishing a demand error relative to an assigned demand limit not to be exceeded for the overall plant at the end of such demand period;
and
means responsive to said demand error for controlling said loads to minimize said error;
first means operative within a portion of said demand period immediately preceding a predetermined time interval counted from the end of said demand period for changing said demand error by a first amount sufficient to reach through operation of said controlling means with said adjustable loads a predetermined operative point at the beginning of said predetermined time interval;
and
second means operative from said predetermined operative point to establish with said adjustable load an ideal power rate for reaching said assigned demand limit at the end of said demand period.

4 more elements

Dependencies are inferred from the claim text.

Computerized power demand control in an electrochemical plant

Life of this patent

Computerized power demand control in an electrochemical plant

Life of this patent

Abstract

Claims14