PID (Proportion Integration Differentiation) control system of marine steam-water heat exchanger

Abstract

The invention relates to a PID control system of a marine steam-water heat exchanger, which comprises a PID controller, a steam regulating valve, a flow meter, a temperature sensor and a control module, the control module is connected with the flow meter and used for receiving a cooling water inlet flow value and outputting a preset valve position coarse adjustment signal to the steam regulating valve, an outlet of the steam regulating valve is connected with a heat exchanger, and the temperature sensor is connected with the heat exchanger. The PID controller collects the hot water outlet temperature value of the heat exchanger through the temperature sensor to serve as a feedback value and outputs a control signal to the steam adjusting valve, PID valve position adjustment is conducted on the steam adjusting valve to serve as steam adjusting valve position fine adjustment, and a double-loop control system is formed. According to the control system, the temperature of the hot water outlet can be controlled, the valve position opening degree of the steam adjusting valve is controlled through the two parameters of the cold water inlet flow and the temperature of the hot water outlet, and therefore the control target of accurate control over the temperature of the hot water outlet is achieved.

Description

Technical Field

[0001] The present invention relates to a PID control system for the hot water outlet temperature of a water system heated by steam through a heat exchanger. Steam and water exchange heat through the heat exchanger, and the hot water outlet temperature is controlled and adjusted by an electric regulating valve on a steam pipeline. The invention belongs to the field of process control technology. Background Art

[0002] At present, the hot water outlet temperature control for this type of hot water heating heat exchanger is generally regulated and controlled by a steam regulating valve, and the hot water outlet temperature is regulated by changing the steam volume. The PID control strategy is usually used to control the regulating valve.

[0003] In view of the particularity of marine steam-water heat exchangers, simple PID control cannot achieve accurate control of the outlet water temperature. The main reasons are: 1. Since there are generally a large number of marine water supply users, it is easy to cause the water flow to change quickly, which makes it easy for the outlet water temperature to fluctuate. 2. And because steam-heated water has the characteristic of fast heating rate, when the temperature sensor set in the hot water outlet pipeline is used as feedback, it is easy to cause lag in the outlet water temperature control. 3. The action rate of the usual electric control valve cannot keep up with the changes in input conditions. Therefore, based on actual ship experience, a simple PID control strategy cannot meet the control requirements of this system.

[0004] In order to solve the above problems and meet the requirements of hot water outlet temperature control accuracy of steam-water heat exchanger, the control strategy is improved. A double-loop control system is proposed, which controls the valve position of the steam regulating valve through the double-loop control strategy of two parameters: cold water inlet flow rate and hot water outlet temperature, so as to achieve accurate control of hot water outlet temperature. Summary of the invention

[0005] The present invention aims to provide a PID control system for a marine steam-water heat exchanger, which controls the valve position opening of a steam regulating valve through a double-loop control strategy of two parameters, namely, cold water inlet flow and hot water outlet temperature, thereby achieving precise control of the hot water outlet temperature.

[0006] To achieve the above-mentioned purpose, the technical solution of the present invention is: a PID control system for a marine steam-water heat exchanger, comprising a PID controller, a steam regulating valve, a flow meter, a temperature sensor, and a control module. The control module is connected to the flow meter to receive the cooling water inlet flow value and output a preset valve position coarse adjustment signal to the steam regulating valve. The outlet of the steam regulating valve is connected to the heat exchanger. The PID controller collects the hot water outlet temperature value of the heat exchanger as a feedback value through the temperature sensor, and outputs a control signal to the steam regulating valve for performing PID valve position adjustment on the steam regulating valve as a fine adjustment of the steam regulating valve position, thereby forming a dual-loop control system.

[0007] Furthermore, the control module is used to segment the cold water flow value and divide the flow into multiple segment intervals.

[0008] Furthermore, the control module inputs a preset valve position value in each cold water flow interval obtained according to test data or calculation, and the valve position is a preset coarse adjustment valve position.

[0009] Furthermore, after the steam regulating valve reaches the preset valve position to roughly adjust the flow rate to be stable, the PID controller outputs a control signal to the steam regulating valve based on the collected hot water outlet temperature value as a feedback value, and performs PID valve position adjustment on the steam regulating valve.

[0010] Beneficial effects of the present invention:

[0011] 1. It compensates for the hot water temperature fluctuation caused by large fluctuations in the cooling water inlet flow rate and improves the control accuracy.

[0012] 2. Compensated for the fast heating rate of the steam-water heat exchanger and the control lag when the temperature sensor set in the hot water outlet pipeline is used as feedback, thereby improving the control rate of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a principle block diagram of the control system of the present invention;

[0014] Figure 2 It is the schematic diagram of the heat exchanger heating system. DETAILED DESCRIPTION

[0015] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0016] like Figure 1 As shown in FIG2 , an improved PID control system for a marine steam-water heat exchanger of the present invention comprises a PID controller, a steam regulating valve 1 , a flow meter, a temperature sensor 2 , and a control module.

[0017] The control module is connected to the flow meter to receive the cooling water inlet flow value, and outputs the initial valve position value of the steam regulating valve that is calculated to match the flow as a preset valve position coarse adjustment signal to the steam regulating valve. The outlet of the steam regulating valve 1 is connected to the heat exchanger 3. The PID controller collects the hot water outlet temperature value of the heat exchanger through the temperature sensor 2 as a feedback value, and outputs a control signal to the steam regulating valve 1, which is used to perform PID valve position adjustment on the steam regulating valve as a fine adjustment of the steam regulating valve position, forming a dual-loop control system.

[0018] In the system, the first link is the coarse adjustment of the preset valve position, and the second link is the fine adjustment of the PID control valve position. Through the double-loop control, the hot water outlet temperature control accuracy is higher and the control rate is faster.

[0019] The control module uses a PLC controller. The control module collects the cold water inlet flow, divides the cold water flow value, divides the flow into multiple sections, and obtains the preset valve position value in each cold water flow interval based on the input test data or calculation. The valve position is a preset coarse adjustment valve position, and the steam regulating valve will first move to the preset valve position. Then after the flow stabilizes, the PID controller uses the collected hot water outlet temperature value as the feedback value to adjust the PID valve position of the steam regulating valve. The valve position adjustment is a fine adjustment based on the coarse adjustment valve position, which can control the outlet water temperature more accurately and make the outlet water temperature fluctuation range smaller. If the cold water flow suddenly changes to other section flow intervals, the PID adjustment is suspended, and the PID adjustment is continued after the travel to the preset valve position of the section.

[0020] The control system of the present invention can control the hot water outlet temperature by controlling the valve position opening of the steam regulating valve through the strategy of two parameters: cold water inlet flow rate and hot water outlet temperature, thereby achieving the control goal of precise control of the hot water outlet temperature.

[0021] The control system of the present invention has been implemented and verified on more than 10 seagoing vessels. According to feedback from actual ship users, the technical solution of the control system is superior to the pure PID adjustment control solution, and the hot water outlet temperature control is more accurate and faster.

Claims

1. A PID control system for a marine steam-water heat exchanger, characterized in that: It includes a PID controller, a steam regulating valve, a flow meter, a temperature sensor, and a control module. The control module is connected to the flow meter to receive the cooling water inlet flow value and output a preset valve position coarse adjustment signal to the steam regulating valve. The outlet of the steam regulating valve is connected to the heat exchanger. The PID controller collects the hot water outlet temperature value of the heat exchanger as a feedback value through the temperature sensor, and outputs a control signal to the steam regulating valve for performing PID valve position adjustment on the steam regulating valve as a fine adjustment of the steam regulating valve position, thereby forming a dual-loop control system.

2. The PID control system of a marine steam-water heat exchanger according to claim 1, characterized in that: The control module is used to segment the cold water flow value and divide the flow into multiple section intervals.

3. The PID control system of a marine steam-water heat exchanger according to claim 1, characterized in that: The control module inputs a preset valve position value in each cold water flow interval obtained according to test data or calculation, and the valve position is a preset coarse adjustment valve position.

4. The PID control system of a marine steam-water heat exchanger according to claim 1, characterized in that: After the steam regulating valve reaches the preset valve position to roughly adjust the flow rate to be stable, the PID controller uses the collected hot water outlet temperature value as the feedback value, outputs a control signal to the steam regulating valve, and performs PID valve position adjustment on the steam regulating valve.

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