Digital positioner for electric controlled valve and method thereof

Abstract

The invention discloses a digital electric valve positioner and a method thereof. The positioner consists of a control unit, an I / P electric conversion unit, a valve position feedback unit and a malfunction diagnosis unit. By the configuration of the flux characteristic parameters of the positioner, the working flux characteristic aberration which is caused by the factors such as a change of the pressure drop ratio of the adjusting valve, etc. is corrected, which is based on that a plurality of flux characteristics and action directions of the adjusting valve integration are provided. The control to the valve position of the adjusting valve is based on a Fuzzy-PI dual-mode no-interference shifting algorithm. Depending on the internal relationship between the valve position given value, the valve position feedback value and the valve film head pressure which are arranged by a control center and applying a rule-based knowledge reasoning, the malfunction diagnosis is realized through that the user selects to release or partly release the valve film head pressure during the stuck freeing operation. The valve displacement / electric conversion of the valve position feedback unit depends on a non-contact magnetic sensitive potentiometer. The man-machine interaction adopts a touch screen technique, and the control unit is accessed in a control network by an Ethernet interface.

Description

technical field [0001] The invention belongs to the technical category of valve positioner for electric regulating valves, and in particular refers to a valve positioner with the functions of distortion correction and fault diagnosis of the working flow characteristics of the regulating valve. Digital electro-valve positioner for valve displacement / electrical switching devices. Background technique [0002] Pneumatic actuators for industrial processes consist of electric valve positioners, pneumatic actuators and regulating valves. The basic function of the electric valve positioner is to control the difference between the given value of the valve position of the control valve output by the control center and the feedback value of the valve position of the control valve, and to control the pneumatic actuator and the opening of the control valve (flow rate) according to the preset algorithm. ), and the valve position feedback unit feeds back the real-time valve position valu...

AI Technical Summary

Problems solved by technology

First of all, the control system is designed based on the inherent flow characteristics of the control valve, and the actual working conditions of the control valve after it is put into operation are far from the test conditions of the inherent flow characteristics. Ignoring the objective fact that the working flow characteristics of the control valve is distorted will inevitably lead to control Quality decline; taking oil refining enterprises as an example, the pressure drop loss of the control valve accounts for about 20%-40% of the power consumption of the enterprise. With the decrease of the pressure drop ratio, the distortion of the working flow characteristics is more serious, and the negative impact on the control quality is catastrophic

Secondly, the valve position of the regulating valve adopts a 5-contact switch control algorithm. Although it has good robustness and fast dynamic response performance, it has the disadvantage of poor steady-state tracking accuracy of the valve position.

In addition, the failure rate of keyboard input in human-computer interaction is high, and the stability and reliability of contact potentiometers for valve displacement / electrical conversion are unsatisfactory; fault diagnosis, especially the fault handling strategy, lacks the overall concept of the control system. Take the position stuck fault as an example, the valve position feedback value is invalid due to the valve position stuck, so the deviation between it and the given position of the valve position cannot be eliminated, so the pressure of the valve diaphragm head tends to the upper limit of the air source pressure

Once the fault is eliminated, the regulating valve is fully closed (air-closed valve) or fully opened (air-opened valve), which not only makes the working condition of the pneumatic actuator fluctuate sharply, but also undoubtedly causes major interference to the entire control system, and even causes a safety accident.

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