Stored-Program Control of DC Power Plants

This paper reports on an experimental computer-based data acquisition and control system for central office dc power plants. In this experiment, a microcomputer monitors the alarms and operational status of the rectifiers, batteries and distribution network which comprise the power plant. The microcomputer's control of the power plant is aimed at maximizing the efficiency of the plant by turning rectifiers on and off depending on the office load and the condition of the commercial ac input. The algorithm for controlling the rectifiers also equalizes their operating times and accounts for limited output capability due to ac phase failures. Additional computations are done to determine the net ampere-hour reserve available from the batteries based on the net charge flow into the batteries. Administration of the data available in the plant involves recording battery, rectifier and fuse alarms and critical voltages and currents in calendar time. A record of these events is used to deduce probable causes of troubles and to anticipate repair times, plant growth and feeder additions. This data is formatted and made available to an office control center or remote terminal. The hardware for the experimental system is configured using a DEC 11/03 Microcomputer and Hewlett-Packard Multiprogrammer, Scanner and Digital Multimeter interconnected on an IEEE 488 Bus. The software is written in C Language using the UNIX* operating system. The program structure uses a hardware clock interrupt to invoke measurement and control routines at prescribed intervals in calendar time.