INCREMENTAL FUZZY PI CONTROL OF A SOLAR POWER-PLANT

Between 1987 and 1997, considerable research effort has been devoted t o improving the efficiency of solar thermal power plants with distribu ted collectors, not only in the field of optical technology but also f rom the control and optimisation viewpoint. The article deals with thi s second aspect, and presents results obtained in the control of the d istributed solar collector field of the solar power plant of Almeria ( Spain) using a fuzzy logic control approach. A distributed collector f ield consists of a series of parabolic mirrors which reflect solar rad iation onto a pipe where oil gets heated while circulating. The object of the control system is to maintain the outlet oil temperature of th e field (collector field) at a desired level in spite of disturbances such as changes in the solar radiation level, mirror reflectivity or i nlet oil temperature. Since solar radiation cannot be adjusted this ca n only be achieved by adjusting the flow of oil. An incremental fuzzy PI controller (IFPIC) has been developed to cope with this control pro blem in which all parameters of a PI controller are updated online as a function of the operating conditions of the controlled plant, thus i mproving the behaviour of the classical fixed PI controllers which are usually employed. The strategy has been implemented in series with a simple feedforward controller which compensates for the disturbances a cting on the system. Simulation results using a nonlinear computer mod el of the field and real tests are provided.