Advanced control of a thermal power unit

Control at varying load of the steam pressure and the steam temperatures delivered by the steam generator has been performed by a multivariable numerical control system on a thermal power plant (250 MW) located at Martigues-Ponteau. This experiment has also allowed us to show off other evaluation criteria than traditional one in order to establish the effectiveness of a control system. The paper gives first the criteria list we have established, then describes the plant characteristics, interactions between variables, controlability difficulties, actuators saturation, non-linearities; the general principles of the method are given. Operating since April 1976, the advanced control system has been tested at various operating regimes to which a power plant is submitted, to compare it with the analog control system. Then the advanced control system has been used in normal operation for several thousand hours. The paper brings up the results of some of these comparative tests and the conclusions of the continuous use of the system. The noted improvement is obtained without increasing the sollicitations of actuators, essentialy through the multivariable and predictive control. The analysis of this advanced control system with respect to the new evaluation criteria, shows that this is a very effective system. The implementation of this method on a controller with microprocessor for a 2 inputs -2 outputs system will make easier the use of this advanced control system. Such a technic will allow an improvement of the thermal power plants flexibility as well as a reduction of stresses undergone by the thermal power plants equipment.