Design And Implementation Of DCS Control System For Steam Turbine

A certain power plant steam turbine system is employed as a research object,analyzing the structure of steam turbine,on the analysis of the structure of steam turbine,technological process and the requirements of steam turbine of the DCS control system.And the control system for steam turbine is redesigned from the hardware frame and software function based on Siemens PCS7 design platform.According to the technological requirements of steam turbine operation,phase control strategy is adopted to implement the speed control of the steam turbine.In the process of steam turbine acc,in order to ensure the steam turbine unit operation security and stable.The quick turn is needed when the speed reaches the critical zone.Therefore,the different rise speed rates sequence control is implemented.After reaching the rated speed,the PID control is involved,to keep the speed of the steam turbine within a certain range.When parallel operation,steam turbine power output must meet the requirements of the external load,and simultaneously,make the adjusted speed deviation within the tolerance range,Therefore double closed loops control is employed,the speed is controlled by the inner loop,and the power is controlled by the other.In the process of unit operation,even if the adjustment of the steam turbine valve opening unchanged,boiler fuel inconsistent quality will also cause the fluctuation of combustion conditions,leading to the variation in the turbine inlet steam parameters and power output,in further change the grid frequency changed,and the power supply quality dropped.The disturbance caused by the unit internal factors the unit active power and the power grid frequency is called "interference",to neutralize the influence of the " interference" of the unit,the power control signal is introduced in the steam turbine governing system,maintaining the power output of the unit meeting the requirements.When steam turbine load rejection occurs and the speed rise rapidly,the speed must be adjusted to a stable state quickly,to ensure the safety of the steam turbine unit.When steam turbine load rejection occurs,there are a lot of nonlinear and uncertain factors,and the over,traditional PID controller in the process of parameter setting become very tedious,moreover the control effect is not very ideal.Under this situation,the conventional PID adjustment cannot meets the control requirement.In consequence,the fuzzy control and PID control are combined to overcome it.The fuzzy controller is used to adjust the traditional three control parameters of PID controller online,and fuzzy logic reasoning adjusts parameters of PID controller automatically to adapt to the system dynamics,implementing the turbine speed fast track and stability.The effect of actual application has proved that this system has reached the requirement of process production,and the turbine speed can be automatically controlled.