The Research On Robust Control Of Thermal Process

In thermal power plant,the dynamic behavior of the main steam temperature is a process with large time-delay,big inertia, nonlinearity and time variance.Using the conventional PID control technique,system performance is not satisfied.The issue of robust control for uncertain systems has been an active area in scientific research.Robust control theory is often to identify a bounding set such that all the admissible uncertainties fall within this set and yet it is not too difficult to analyze mathematically.This dissertation is mainly on the study of the robust control of the thermal process in the frequency domain and time domain.In frequency domain,mixed Sensitivity H_∞robust control and Smith predictor H_∞robust control were study.The selection of weighting function was discussed in the mixed sensitivity H_∞robust control,according to the action of the weighting function.In the design of Smith predictor robust controller,Maclaurin series was used to substitute for the changes of process parameters,and then the robust problem of time-delay process was shifted into that of delay-free process.These two control strategies were used in the thermal process.Simulation results showed that these methods can effectively restrain the changes of the process and improve system robustness.The non-fragile robust control for uncertain systems was studied in time domain.The non-fragile robust controller was acquired by the LMIs.This method was used to control the thermal process.Simulation results showed that the system performance was satisfied when the parameters of the object and controller were changed.Finally,the robust control of the uncertain systems with input-delay was discussed based on the characteristic of thermal process.An improved reduction method was used to achieve the robust controller of the uncertain systems with input-delay and simulation result demonstrates the effectiveness and superiority of the method.