Ultra-supercritical(USC) unit is more and more popular in coal-fired power industry.In this paper,closed-loop identification based on subspace model identification(SMI) is introduced for superheated steam temperature system of USC unit.Closed-loop SMI is applied to building step response model of the unit directly.The parameters selection method is proposed to deal with the parameter sensitivity and improve the reliability of the model.Finally,the model is used in model identification of real USC unit.
超超临界机组是一个大而复杂的系统,具有机-炉耦合、动态非线性、大延时等特性。传统控制系统难以满足在节能减排及动态响应上的更高要求。为此采用模型辨识结合模型预测控制的方法对其进行建模和控制。建立了机组的闭环系统运行模型,在分析机组特点及预测控制器预测模型的需求的基础上,在模型辨识过程中,给出了一种子空间法和传统SISO(single input single output)辨识方法相结合的方法,以取得最终预测控制器所需的单位阶跃预测模型。实时仿真结果表明了所采用策略及方法的有效性。
Ultra-supercritical(USC) coal-fired unit is more and more popular in these years for its advantages.But the control of USC unit is a difficult issue for its characteristic of nonlinearity, large dead time and coupling among inputs and outputs. In this paper, model predictive control(MPC) method based on multi-model and double layered optimization is introduced for coordinated control of USC unit running in sliding pressure mode and fixed pressure mode. Three inputs(i.e. valve opening, coal flow and feedwater flow) are employed to control three outputs(i.e. output power, main steam temperature and main steam pressure). The step responses for the dynamic matrix control(DMC) are constructed using the three inputs by the three outputs under both pressure control mode. Piecewise models are built at selected operation points. In simulation, the output power follows load demand quickly and main steam temperature can be controlled around the setpoint closely in load tracking control. The simulation results show the effectiveness of the proposed methods.
