A Direct Digital Control System for a Steam Power Plant

Abstract

The application of a computer for the direct digital control of boiler-turbine-generator unit A in Fusina electric power station is described.

The main purpose of the project is to provide experimental evidence of the possible merits of advanced digital control techniques in steam plants, with special reference to checking actual performance and limitations of the most promising control algorithms so far proposed. The essential features of the process-control oriented “MATRAN” language (derived from Fortran, with suitable additions and simplifications) and real-time executive, which were here developed to enhance off-line compiling and on-line program sequence management capabilities of the CII-10020 computer used, are briefly recalled.

Both the software and the data acquisition and control interface equipment were especially designed to allow flexible testing of non-conventional control algorithms and structures.

MATRAN-implemented application programs for input and output data handling, operator’s console and display, plant supervision, security and control, priority scheduling of program executions, have been written in modular form, to allow easy exchange of the different types of control algorithms to be tested and compared.

Both single input-single output (digital transposition of PID, dead-beat, with load- dependent parameters and with more general adaptive actions) and multi-input/multi-output (non interacting, linear optimal) control algorithms have been considered. Part of them has been tested in the laboratory of the Centro Ricerca di Automatica — ENEL, by connecting the DDC system to a hybrid computer and simulating several significant plant conditions. A rather accurate model of the boiler-turbine-generator unit and of the existing conventional analog control system input-output equipment (including transducers, servomotors, limit-stops and automatic-to-manual switches) has been implemented on the hybrid computer.

Some results of the extensive laboratory tests are given. The second phase of DDC system and control algorithms performance tests is presently under way.