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多变量控制在基准锅炉中的应用研究

Comparative Study on Multivariable Control and Its Application for Benchmark Boiler

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【作者】 ULEMJ DAMIRAN(巨力)

【导师】 谭文

【作者基本信息】 华北电力大学(北京), 控制理论与控制工程, 2016, 博士

【摘要】 从工业革命到今天为止,工业自动化控制系统变得越来越复杂。在电力系统和化工系统中,通常使用多种类型燃料的汽包锅炉来产生蒸汽。在火力发电厂的自动控制系统中,锅炉控制是最重要的任务之一。锅炉控制系统是一个多变量输入、多变量输出(MIMO)、非线性和强耦合的动态过程,具有很大的惯性和复杂的数学模型,输入输出参数之间相互影响,是一个强耦合系统。此外,锅炉控制过程通常工作在一个存在广泛干扰的条件下。目前,传统PID控制器在锅炉控制系统广泛应用,但是PID并不能很好的处理系统的非线性和多变量特性。因此,传统的控制方法不能满足汽包锅炉控制系统的控制要求。本文重点研究一个基准锅炉系统的多变量智能控制技术,并对其存在的问题进行了探讨。具体内容包括:1. 为了提高控制系统的鲁棒性,针对基准锅炉设计了H∞回路成形控制器。为了控制器实现的方便,将高阶H∞控制降阶为一个多变量PID控制器,并且针对系统存在输入约束问题,采用了抗回绕的补偿措施。2. 为了处理系统耦合以及输入约束,针对基准锅炉设计了模型预测控制。模型预测控制在每个采样时刻内进行优化,可以将系统耦合及输入约束等问题综合考虑。3. 为了提高系统抗干扰的能力,针对基准锅炉设计了自抗扰控制。自抗扰控制通过扩张状态观测器对系统内扰和外绕进行估计,可以达到更好的抑制性能。针对系统输入约束,采用了针对自抗扰控制的抗回绕补偿措施。本文对上述三种控制方法在基准锅炉的设计、整定、以及仿真进行了详细讨论。仿真结果表明所采用的多变量控制方法可以获得比常规PID控制更好的控制效果,特别地,H∞回路成形方法在这三种方法中具有最好的扰动抑制性能,但是解耦性能最差;预测控制具有最好的解耦性能。因此,为了提高基准锅炉的控制性能,本文建议采用H∞回路成形方法。

【Abstract】 From the beginning of the industrial revolution until present day, the industrial automation control system has become more and more complex and highly sophisticated. Electricity market and chemical industry for producing steam usually use multi-type-fuel-fired drum boiler. Boiler control is one of the most important tasks in automatic control system in thermal power plants. Boiler control system is a multivariable input multivariable output (MIMO), nonlinear dynamic process with large inertia and strong coupling. Moreover, boiler control process usually works in a wide range of operating conditions. The conventional proportional-integral-derivative (PID) controllers are widely used in this process, however, conventional control method may not achieve the desired requirement and performance for a drum boiler control system.This thesis focuses on the design and performance of multivariable control techniques for a benchmark boiler control.The main contents include:1.To improve the robustness of the system against uncertainties, H∞ loop shaping approach is applied to the Benchmark boiler. To implement the resulted high-order H∞ controller, a multivariable PID controller is obtained by approximation. Anti-windup scheme is implemented to take the input constraints of the system into consideration.2. To deal with the coupling and input constraints of the system, model predictive control (MPC) is applied to the Benchmark boiler. MPC performs an optimization process at each sample, which can take the coupling and input constraints into consideration naturally.3. To improve the disturbance rejection performance, active disturbance rejection control (ADRC) is applied to the Benchmark boiler. ADRC uses an extended state observer to estimate the generalized disturbance and try to attenuate it quickly. To overcome the effects of the input constraints of the system, the error between the computed output and the real output of the actuator is fed back to the extended state observer to avoid the windup.The above-mentioned three control methods are discussed in the thesis. The controller design, tuning and simulation for Benchmark boiler are illustrated in detail. Simulation results show that the proposed multivariable control techniques can achieve better performance than the conventional PID control for the Benchmark boiler. Moreover, it is shown that H∞ loop shaping control achieves the best load rejection performance for the Benchmark boiler, but the worst decoupling performance; while MPC achieves the best decoupling performance. So H∞ loop shaping control and MPC is recommended for the Benchmark boiler to improve its control performance.

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