采用可编程逻辑控制器直接负荷控制讲述.docx

Direct load control using a programmable logic controller Abstract This paper presents a fully automated programmable logic controller (PLC) based direct load control system. Unlike other existing systems, it gives the consumer the privilege to share in the load shedding policy. After receiving the warning alarm from the PC at the utility control center, the consumer has the chance to switch off any desired load. If he does not act within a predefined period, the PLC will take the required action based on the scenario decided by the utility. Having the consumer decide his own priorities release the utility company from blind decisions. This is one of the most important contributions of the proposed system. Also the load restoration process is scheduled to avoid the creation of a new peak during reenergization. This is done using 48 built-in timers with an accuracy of less than one cycle (10 ms). The hardware at the customer side may be integrated with a digital energy meter to form a complete energy management system. ? 1999 Elsevier Science S.A. All rights reserved. Keywords: Programmable logic controller; Load control; Energy management 1.Introduction Today, electric utilities are facing a rapid increase in demand. Increasing the generation capacity and expanding the transmission and distribution networks are not sufficient on long-term basis. Many utilities attempt to use the existing plants and facilities more effectively rather than try to build new power plants. As the cost of producing electricity increases, utilities are extending their activities into the customer domain. In order to increase efficiency, utilities are controlling how electric energy is used. Thus they shift from a supply only viewpoint to demand side activities. These activities and measures are known as demand side management (DSM). The DSM measures are classified into direct load control (DLC) or indirect load control. A great deal of research and development has occurr