Control Engineering of Steam Turbine Valve
The control valve for a large steam turbine in a power plant has the characteristic of nonlinearity. The turbine must, however, be operated linearly by an automatic control system in the power plant. It is found that the flow increase is much greater for a given valve position change near the closed end of travel than near the open end. The steam flow in the system being proportional to the ultimate desired quantity of the turbine, it is preferable to have linear operation. The automatic control can be applied to this nonlinear system to maintain the frequency of electricity constant by adjusting the control valve opening to the desired valve position. If the valve is opened less near the closed end of travel and greater near the open end, the desired linearization will be achieved. In this paper the Valve Engineered Logic Analysis (VELA) has adopted the electro hydraulic control (EHC) as well as the digital electro hydraulic control (DEHC) for linearization. Transfer functions of the valve position loop are obtained according to the different locations of nonlinear signal produced at the input to valve position loop or in the feedback. They are derived from setting particular conditions to achieve the linear control. For convenient modeling of the control system, it is necessary to approximate the valve curve with two or three straight lines. This approximation is a usual practice in setting up the control system of power plants. The transfer functions of the valve position loop are obtained according to the different locations of the nonlinear signal produced at the input to the valve position loop or in the feedback. This paper gives an idea about a valve position loop with nonlinear compensation at the input. The unit gain is used at the feedback. This network is simplified to a pure integrator instead of the complicated transfer function of a real actuator.
Control valve Operational Amplifier Diode Linearization Feedback Feedforward
B. Halimi Kune Y. Suh
Seoul National University 599 Gwanak-Ro, Gwanak-Gu, Seoul, 151-744, Korea Seoul National University 599 Gwanak-Ro, Gwanak-Gu, Seoul, 151-744, Korea；PHILOSOPHIA, Inc. 599 Gwan
国际会议
上海
英文
1368-1374
2010-10-10（万方平台首次上网日期，不代表论文的发表时间）