Research On Coordinated Control Technique Of Boiler-Turbine Unit

At present, in power system, unit power plants with great power and big parameters have been widely used. It is required that the boiler-turbine-generator set react to the load demand quickly, and make sure that it can perform safely, stably and economically at the same time. But the unit boiler-turbine-generator set can be considered as a two-input-two-output system. The inputs are combustion of input fuel and the turbine valve; the outputs are main steam pressure of the boiler and the power from the boiler turbine generator, which are interdependent and coupled greatly. Therefore, the fastness and the stability of the boiler-turbine-generator set are contradicted.This paper researches on the three control methods of the boiler-turbine-generator set, boiler following control, turbine following control and the coordinated boiler-turbine control; and then simulate them. Through simulation, the advantages and the disadvantages of every method are illustrated; and the superiorities of coordinated boiler-turbine control are verified.To solve the coupling of the coordinated control system (CCS), decoupling networks are designed. Two methods are adopted, the one-way decoupling and the Inverse Nyquist Array, which implement the static near decoupling and the dynamic near decoupling of the control plant respectively.To improve the responding time of the load demand of the electric network, and to restrain the disturbance, the Gershgorin bands method is proposed in the paper to calculate the ultimate gain and the ultimate frequency of every object after dynamic near decoupling of the plant. After that, the refined Ziegler-Nichols method is applied to tune parameters of the controllers of the boiler and the turbine. Through simulation, compared to the conventional PID control, the GB method has greater ability on robustness and disturb-resistance.With respect to the big inertia and large-time delay of the boiler, to get better performance of the CCS, the boiler fuzzy self-adaptive controller is designed. The bad effect is eliminated, the overshoot of the generate power is decreased, and the fluctuation of the steam pressure is decreased, too. Through simulation, the robustness and the disturb-resistibility of the method proposed is...