Coordinated Control of Once-through Boiler-turbine Units Using Feedforward-feedback Approach based on Stable Inversion

The structural features of the once-through boiler-turbine unit are nonlinear, strong coupling and multi-parameter, which affect the response ability of load of its coordinated control system. In order to improve the control performance of the once-through boiler-turbine coordinated system, a control method of feedforward-feedback control based on the nonlinear model of the once-through boiler-turbine unit was proposed in this article. First a nonlinear model that has certain accuracy and is fit for the controller design was established after reasonable reduce. Then the theory of stable inversion was introduced to seek the inversion solution of the nonlinear model. Feedforward control via inversion system leads the outputs of unit to the set points rapidly, while the feedback controller is designed for multivariable outputs to remove the tracking errors caused by external interference. Finally, simulation tests of the state disturbance and set point perturbation in different static operating conditions were carried out. Simulation results verify that the outputs of feedforward-feedback control method can track the set points accurately and fast.