Dual Controller Differential Pressure Regulation
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Solution Overview
Problem
Existing control methods for differential pressure in membrane processes, such as chlor-alkali electrolysis, face challenges in maintaining simultaneous operation of fine and coarse control valves, leading to unstable and slow regulation, especially during startup or load fluctuations.
Innovation Solution
A control device comprising a fine controller and a coarse controller, where the fine controller adjusts a manipulated variable based on a reference variable and a controlled variable, and the coarse controller adjusts a second manipulated variable based on the fine controller's output, allowing both actuators to operate continuously and react to changes effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If split-range control is used with two control valves of different sizes, then the control range is divided into areas for fine and coarse control, but the operating times of the two control valves are subject to difficult-to-maintain conditions and cannot work simultaneously in an overlap range
Solution Approach 1:
A GAP controller is introduced as an intermediary between the fine and coarse controllers. This mediator translates the fine controller's output signal into a form that the coarse controller can process, enabling seamless handover and simultaneous operation of both valves through x-tracking and dead zone mechanisms
Solution Approach 2:
The control system dynamically adjusts which valve is active based on real-time operating conditions. The fine controller operates during normal conditions while the coarse controller activates during startup or disruption scenarios, with dynamic switching enabled by the GAP controller's dead zone and x-tracking functions
2Adaptability or versatility
If a large control valve is used for pressure control, then the control range is extended, but the valve can only be adjusted to a limited extent due to larger line cross-section requiring very slow parameter set
Solution Approach 1:
The control function is segmented between two valves: the large valve handles coarse pressure adjustments and startup scenarios, while the small valve handles fine pressure control during normal operation. This segmentation allows each valve to operate in its optimal performance range
Solution Approach 2:
The system dynamically switches between coarse and fine control modes based on operating conditions. During startup or disruption scenarios, the coarse valve with slow parameters is used, while during normal operation, the fine valve with faster parameters takes over for rapid response
Data Source
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AI summary
The device has a fine controller (1) for comparing a reference variable (w1) with a control variable (x1) to determine a control variable (y1). The former control variable is dependent on a measured value of state variable. The reference variable gives a desired value of state variable. A coarse controller (3) compares other reference variable (w2) with control variable (x2) to determine the control variable (y2). The variable (y1) is supplied to fine control member (2) and other variable (y2) is supplied to coarse control member (4). The state variable is influenced by the control members. Independent claims are also included for the following: (1) a differential pressure controlling device comprising two connected measuring points (2) a method for regulating state variable of a process.