Due to large delay and inertia of unit control system at the boiler side,the load response time of the conventional coordinated control strategy is usually long and the load change speed is below 2％ of the full load in one minute.To solve this problem,this paper proposes a novel load control strategy based on back pressure regulation.On the premise of safe back pressure,this control strategy takes the condenser cooling water flow as a new control variable for the steam turbine load.When the steam turbine load order is changed,the back pressure will be changed immediately to decrease the variance.And when the steam turbine load is close to the load order,the back pressure will be recovered to its normal value to ensure energy-saving and prepare for the next load dispatch.Tests on the simulator show that the condenser back pressure and steam turbine power would arrive at another steady values in 30 seconds after the cooling water flow changed.The static and dynamic models between the cooling water flow and the turbine power were set up based on the mechanism analysis and identification.A novel load-change strategy based on continuous back-pressure regulation was firstly proposed:the back pressure regulation is activated mainly in the initial control period,and the coordinated control is mainly used at the end of the control.Simulation were conducted on a 300 MW coal-fired unit and the results prove that this control strategy shortens the responding time and accelerates the load change speed.%传统火电机组协调控制策略受限于锅炉侧的大迟延大惯性,其变负荷响应时间较长,一般不超过额定负荷的2 ％/min.本文提出一种基于背压调节的新型变负荷控制策略,在保证机组运行在安全背压的前提下,将循环水流量作为机组负荷的控制变量,当机组负荷出现偏差时,背压调节快速动作,减小偏差;而当机组负荷接近负荷指令时,背压调节恢复机组初始背压,保证机组运行的经济性,同时为下次变负荷调节做准备.在仿真机进行背压调节试验,结果表明湿冷机组循环水流量发生变化后30s内机组背压和出力都将达到另一稳态值;在此基础上通过机理分析与试验曲线辨识,建立了湿冷机组循环水流量变化对机组出力影响的静态、动态模型;将背压连续调节作为机炉协调控制的辅助手段,建立了基于背压连续调节的新型变负荷控制策略,即背压调节用于机组变负荷控制的初始阶段,末期由协调控制完成.在某300 MW燃煤直流锅炉再热机组进行仿真,仿真结果表明该方案缩短了机组变负荷跨出死区的响应时间,提升了机组的变负荷速率.
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