一次调频设置问题引起机组甩负荷的实例及分析

为分析某650 MW火电机组发生的异常甩负荷事故,在数字电液系统（DEH）中构建了该机组精确的锅炉-汽轮机对象模型,并利用DEH的仿真功能对事故过程进行了重现,对事故原因进行了分析。分析结果表明导致机组在控制方式切换时甩负荷的主要原因在于机组一次调频设置不合理,其在控制方式切换时的循环叠加效应使得总阀位指令大幅异常变化,最终引起甩负荷。利用实时仿真技术分析了相关参数对事故程度的影响,结果表明DEH控制器处理周期、汽机转速、机组负荷对事故均有影响。最后提出了通过规范设计并增加仿真试验以验证一次调频功能合理性的建议。

Case Study on Load Rejection Caused by Configuration Problems of Primary Frequency Regulation

To analyze the load rejection accident happened in a 650-MW thermal generation unit, an accurate boiler-turbine model of the unit is built in the Digital Electronic Hydraulic (DEH, for short) system. By using the simulation function of DEH, the course of the accident is reproduced to find out the causes. The result indicates that the immediate cause of the load rejection during the control mode switchover lies in the irrational primary frequency regulation configuration, of which the superimposed effects make the valve position demand to be changed abnormally by a great margin. Furthermore, the influences of the related parameters on the load rejection are studied with real- time simulation. It is indicated that the DEH processing cycle, the turbine speed and the load condition are all related to the load rejection. At the end, the suggestions of normalizing the design and taking more simulative tests to verify the design rationality of primary frequency regulation are put forward.