CN114278548A

CN114278548A - Constant pressure vessel overshoot protection system

Info

Publication number: CN114278548A
Application number: CN202111665108.9A
Authority: CN
Inventors: 李泽辉; 刘伯钊
Original assignee: Yolico Electric Wuxi Co ltd
Current assignee: Yolico Electric Wuxi Co ltd
Priority date: 2021-12-31
Filing date: 2021-12-31
Publication date: 2022-04-05
Anticipated expiration: 2041-12-31
Also published as: CN114278548B

Abstract

The invention relates to the technical field of frequency converter control, in particular to an overshoot protection system for a constant-pressure vessel, which can meet the quick response requirement of a client, simultaneously can not generate the situation that pressure is easy to overshoot and the system is damaged, and comprises a first PID adjusting system, a second PID adjusting system and a third PID adjusting system which are arranged in parallel, wherein the first PID adjusting system, the second PID adjusting system and the third PID adjusting system respectively comprise a P parameter, an I parameter and a D parameter; the first PID adjusting system is used for controlling the control object under the condition that the feedback value is not more than 50% of the target value; the second PID adjusting system is used for controlling the control object under the condition that the feedback value is 51-80% of the target value, and the response speed of the second PID adjusting system is slower than that of the first PID adjusting system; the third PID adjustment system is used for controlling the control object under the condition that the feedback value is 81-100% of the target value.

Description

Constant pressure vessel overshoot protection system

Technical Field

The invention relates to the technical field of frequency converter control, in particular to an overshoot protection system for a constant-pressure container.

Background

At present, industrial air compressors or vacuum machines all need constant-pressure control of a frequency converter, and can achieve energy conservation and environmental protection to the greatest extent. After having generally used converter constant voltage control, when load demand appears, in order to guarantee that the pressure is invariable, the converter will improve gas supply volume through PID's feedback increase revolution, and in order to guarantee that the response is quick, PID's adjustment can be very quick, and traditional PID control mechanism is shown in figure 1, and P is proportional gain, and I is the integral, and D is the differential, in small-size tolerance system, has very big potential safety hazard in applying it to small-size tolerance system occasionally.

For example, in the case that the air pressure capacity of the refrigerator is 2L and the target pressure is set to 50kPa, the conventional PID pressure control is seriously modulated due to the small vacuum system sealed by the compressor of the refrigerator, because the PID generally performs the next action according to the feedback of the pressure sensor, and when the pressure sensor reaches the set pressure, the frequency converter generally reduces the work by reducing the output frequency. However, because the refrigerator compressor is a closed system, the vacuum pressure will gradually rise in the process of the frequency converter decelerating to 0. This situation can cause severe overshoot, damage to the weak gas pipes in the system, and even damage to the compressor or cause severe consequences of gas pipe explosion when overshoot is severe.

Disclosure of Invention

In order to solve the problem that the system is damaged due to the fact that pressure is easy to process due to rapid response when traditional PID control is applied to an existing small-sized gas system, the invention provides an overshoot protection system for a constant-pressure container, which can meet the rapid response requirement of a customer, and meanwhile, the situation that pressure is easy to overshoot and the system is damaged can not be generated.

The technical scheme is as follows: the overshoot protection system for the constant-pressure vessel comprises a first PID adjusting system and is characterized by further comprising a second PID adjusting system and a third PID adjusting system which are arranged in parallel, wherein the first PID adjusting system, the second PID adjusting system and the third PID adjusting system respectively comprise a P parameter, an I parameter and a D parameter; the first PID adjusting system is used for controlling the control object under the condition that the feedback value is not more than 50% of the target value; the second PID adjusting system is used for controlling the control object under the condition that the feedback value is 51-80% of the target value, the response speed of the second PID adjusting system is slower than that of the first PID adjusting system, and when the feedback value is 70-80% of the target value, the acceleration time adjusting module is used for prolonging the response time; the third PID adjusting system is used for controlling the control object under the condition that the feedback value is 81-100%, the integral accumulation in the PID parameter before the third PID adjusting system is cleared when in operation, the speed is slower than the response speed of the second PID adjusting system, and the increase of the pressure is realized by adjusting the deceleration time module.

After the invention is adopted, three sets of parallel PID adjusting systems are utilized to control a controlled object and add an acceleration time module and a deceleration time module, and the three sets of PID adjusting systems are respectively used for different feedback value intervals, under the condition that the feedback value is larger, the response speed is properly slowed down, but the quick response requirement of a client is still met, meanwhile, the pressure can not overshoot, and the condition of system damage is avoided.

Drawings

FIG. 1 is a schematic diagram of a conventional PID control mechanism;

FIG. 2 is a schematic diagram of the PID control mechanism of the present invention.

Detailed Description

Referring to fig. 2, the overshoot protection system for the constant-pressure vessel comprises a first PID adjusting system, a second PID adjusting system and a third PID adjusting system which are arranged in parallel, wherein the first PID adjusting system comprises a P1 parameter, an I1 parameter and a D1 parameter, the second PID adjusting system comprises a P2 parameter, an I2 parameter and a D2 parameter, and the third PID adjusting system comprises a P3 parameter, an I3 parameter and a D3 parameter.

The first PID adjusting system participates in pressure parameter adjustment when the system is just started, is used for controlling a control object under the condition that the feedback value is not more than 50% of the target value, responds to the speed, and does not actively adjust the acceleration time module and the deceleration time module.

The second PID adjusting system is used for controlling the control object under the condition that the feedback value is 51-80% of the target value, the response speed of the second PID adjusting system is slower than that of the first PID adjusting system and is generally reduced by 50%, and when the feedback value is 70-80% of the target value, the acceleration time adjusting module is used for prolonging the response time by 0.5-2 s;

the third PID adjusting system is used for controlling a control object under the condition that the feedback value is 81-100%, and for automatic switching, the third PID adjusting system clears the integral accumulation in the PID parameters before running and has the speed slower than the response speed of the second PID adjusting system, and because of a closed system, the pressure increase in the period is achieved by slowly decelerating by adjusting the deceleration time. When the feedback value is 95-100%, the frequency converter slowly reaches the target value at the lowest frequency of 2Hz, and the final result is 0.5s, and the increase changes every 1%.

Under the condition that a 2L hermetic compressor is vacuumized, when the set pressure is 50kpa, the pressure precision can reach 0.1%, the possibility that the pressure container and the system are damaged due to overlarge pressure is avoided, the set pressure value can be reached within 10s, and the requirement of a client on quick response speed is met.

Claims

1. The overshoot protection system for the constant-pressure vessel comprises a first PID adjusting system and is characterized by further comprising a second PID adjusting system and a third PID adjusting system which are arranged in parallel, wherein the first PID adjusting system, the second PID adjusting system and the third PID adjusting system respectively comprise a P parameter, an I parameter and a D parameter; the first PID adjusting system is used for controlling the control object under the condition that the feedback value is not more than 50% of the target value; the second PID adjusting system is used for controlling the control object under the condition that the feedback value is 51-80% of the target value, the response speed of the second PID adjusting system is slower than that of the first PID adjusting system, and when the feedback value is 70-80% of the target value, the acceleration time adjusting module is used for prolonging the response time; the third PID adjusting system is used for controlling the control object under the condition that the feedback value is 81-100%, the integral accumulation in the PID parameter before the third PID adjusting system is cleared when in operation, the speed is slower than the response speed of the second PID adjusting system, and the increase of the pressure is realized by adjusting the deceleration time module.