Abstract
This paper proposes a generalized active disturbance rejection controller (GADRC) based hierarchical control structure for the boilerturbine unit. In the lower layer, a multivariable extended state observer (MESO) is developed to estimate the values of the lumped disturbances caused by modelling mismatches, fuel quality variation and wide range load variation. The influence of the disturbances is then compensated at the input side as a feedforward control. In the upper layer, the multi-objective optimization is devised to obtain the set-points by removing the plant behaviour variation from the optimized model in a feasible way. The lowpass filter acting on the lumped disturbances is designed to bridge the gap between the lower and upper layer. The impact of the feedthrough item is approximated by a first-order system and a two degree-of-freedom (2-DOF) control strategy is established to illustrate the set-point tracking and disturbance rejection properties of the controller. Simulation studies on a 1000MWe coal-fired ultra-supercritical boiler-turbine unit demonstrate that the proposed control strategy can achieve a satisfactory performance in cases of fuel quality variations, model-plant mismatches and wide range load variation.
Highlights
Boiler-turbine units are the core devices in modern fossil fuel fired power plants, in which the energy of the coal is transformed into steam thermal energy by the boiler to the rotation energy in the turbine and to the electrical energy through the synchronous generator
This paper presents a generalized active disturbance rejection control (GADRC) strategy for the boiler-turbine unit to achieve fast set-point tracking and disturbance rejection performance in the presence of internal uncertainties and external disturbances
The working principle of the proposed generalized active disturbance rejection controller (GADRC) is illustrated in figure 1, in which the disturbance compensation channel describes that the lumped disturbances are estimated by the multivariable extended state observer (MESO) and actively compensated by an appropriate gain Kd
Summary
Boiler-turbine units are the core devices in modern fossil fuel fired power plants, in which the energy of the coal is transformed into steam thermal energy by the boiler to the rotation energy in the turbine and to the electrical energy through the synchronous generator. The plant behavior variation and unknown disturbances caused by load varying, fuel quality change, coking and ash deposit in boiler, will degrade the performance of predesigned controller and affect the safe and economical operation of the plant For such a process plant, the conventional PID is still the most used control strategy. The incidental overshoot appeared in output tracking caused by the delayed coal transmission and variation of coal quality, which may influence the safe operation of the plant For these reasons, this paper presents a generalized active disturbance rejection control (GADRC) strategy for the boiler-turbine unit to achieve fast set-point tracking and disturbance rejection performance in the presence of internal uncertainties and external disturbances. A low-pass filter should be added on the estimated lumped disturbance, so that the multi-objective optimization is insensitive of high-frequency fluctuations and the solution of the optimization is more feasible
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