阅读说明：本技术 一种低压旁路控制系统阀后压力控制方法 (Method for controlling pressure behind valve of low-pressure bypass control system ) 是由 孙建国 程江南 范双双 马全乐 康君 戴云飞 于海东 李越男 赵新宇 马志国 郭 于 2021-07-28 设计创作，主要内容包括：一种低压旁路控制系统阀后压力控制方法,涉及发电厂机组控制技术领域。本发明是为了解决减压阀后压力过大,一来容易导致减压阀后温度过高,进而使低旁减压阀快关,造成再热器压力迅速升高,引起再热器安全门动作；二来容易导致凝汽器真空度的下降,进而造成机组低真空保护动作停机的问题。本发明当低压旁路控制系统处于自动控制状态时,将低旁减压阀后最大压力和低旁减压阀后实际压力之差的PI调节结果作为低旁减压阀指令,当低压旁路控制系统处于手动控制状态时,将最大低旁减压阀开度作为低旁减压阀指令；选取低旁减压阀指令和再热器指令中的最小值作为低旁减压阀的最终指令,并利用该最终指令对低旁减压阀的开度进行控制。(A method for controlling the pressure behind a valve of a low-pressure bypass control system relates to the technical field of power plant unit control. The invention aims to solve the problems that the temperature behind the pressure reducing valve is easily overhigh due to overlarge pressure behind the pressure reducing valve, so that the pressure of a low-side pressure reducing valve is quickly closed, the pressure of a reheater is quickly increased, and the action of a safety door of the reheater is caused; secondly, the vacuum degree of the condenser is easily reduced, and the low-vacuum protection action of the unit is stopped. When the low-pressure bypass control system is in an automatic control state, a PI (proportional integral) regulation result of the difference between the maximum pressure behind the low-bypass pressure reducing valve and the actual pressure behind the low-bypass pressure reducing valve is used as a low-bypass pressure reducing valve instruction, and when the low-pressure bypass control system is in a manual control state, the opening degree of the maximum low-bypass pressure reducing valve is used as a low-bypass pressure reducing valve instruction; and selecting the minimum value of the low bypass pressure reducing valve instruction and the reheater instruction as a final instruction of the low bypass pressure reducing valve, and controlling the opening of the low bypass pressure reducing valve by using the final instruction.)

1. A method for controlling the pressure behind the valve of a low-pressure bypass control system is characterized in that,

when the low-pressure bypass control system is in an automatic control state, a PI (proportional integral) regulation result of the difference between the maximum pressure behind the low-bypass pressure reducing valve and the actual pressure behind the low-bypass pressure reducing valve is used as a low-bypass pressure reducing valve instruction, and when the low-pressure bypass control system is in a manual control state, the opening degree of the maximum low-bypass pressure reducing valve is used as a low-bypass pressure reducing valve instruction;

and selecting the minimum value of the low bypass pressure reducing valve instruction and the reheater instruction as a final instruction of the low bypass pressure reducing valve, and controlling the opening of the low bypass pressure reducing valve by using the final instruction.

2. The method of claim 1, wherein the reheater instructions are: PI regulation result of difference between reheater actual pressure and reheater set pressure.

3. The method of claim 1, wherein the maximum post-low-pressure-bypass-relief-valve pressure X is a maximum post-low-pressure-bypass-relief-valve pressure X₁And actual pressure X after low side pressure reducing valve₂PI regulation result Q of the difference₁The expression is as follows:

wherein k is_pFor proportional coefficient of PI regulation, k_iFor the integral coefficient of the PI regulation,the integral is represented.

4. The method of claim 2, wherein the reheater actual pressure Y is set to be equal to or greater than the reheater actual pressure Y₁And reheater set pressure Y₂PI regulation result Q of the difference₂The expression is as follows:

wherein k is_pFor proportional coefficient of PI regulation, k_iFor the integral coefficient of the PI regulation,the integral is represented.

5. The method for controlling the pressure after the valve of the low-pressure bypass control system according to the claim 1, 2, 3 or 4, wherein the maximum pressure after the low-pressure bypass reducing valve is the maximum pressure allowed by the unit design.

Technical Field

The invention belongs to the technical field of power plant unit control, and particularly relates to pressure behind a valve.

Background

The existing generating sets of I and II stages of power plants adopt thermal power generating sets with the rated power of 330 MW. The low-pressure bypass control system is mainly used for recovering working quality and ensuring smooth running of the unit impact rotation and the unit reverse cutting cylinder in a unit starting or accident state. The low-pressure bypass control system comprises a low bypass pressure reducing valve and a low bypass temperature reducing valve, and relates to a reheater pressure control system and a temperature control system behind the low bypass pressure reducing valve. In the reheater pressure control loop, a pressure set value is generated by the primary pressure of the steam turbine, and a reheater pressure measured value is output through a PI regulator after being deviated from the set value so as to control the opening of the low-bypass pressure reducing valve. The low side temperature reducing valve is a two-position control valve of a linked switch, and when the opening degree of the low side pressure reducing valve is more than 2%, the first-stage temperature reducing valve is linked; when the opening degree of the low by-pass reducing valve is more than 2% and the pressure behind the valve is more than 3.7bar, the two-stage temperature reducing valve is connected.

If the pressure behind the pressure reducing valve is continuously increased, the temperature behind the pressure reducing valve is easily overhigh, and when the temperature is higher than a certain value, the low bypass pressure reducing valve is quickly closed, so that the pressure of a reheater is quickly increased, and the action of a safety door of the reheater is caused. Moreover, the continuous increase of the pressure behind the pressure reducing valve can also cause the reduction of the vacuum degree of the condenser, thereby causing the shutdown of the low-vacuum protection action of the unit.

Disclosure of Invention

The invention aims to solve the problems that the temperature behind the pressure reducing valve is easily overhigh due to overlarge pressure behind the pressure reducing valve, so that the pressure of a low-side pressure reducing valve is quickly closed, the pressure of a reheater is quickly increased, and the action of a safety door of the reheater is caused; secondly, the vacuum degree of the condenser is easily reduced, and further the low vacuum protection action of the unit is stopped, and a method for controlling the pressure behind the valve of the low-pressure bypass control system is provided.

A method for controlling the pressure behind a valve of a low-pressure bypass control system specifically comprises the following steps:

when the low-pressure bypass control system is in an automatic control state, a PI (proportional integral) regulation result of the difference between the maximum pressure behind the low-bypass pressure reducing valve and the actual pressure behind the low-bypass pressure reducing valve is used as a low-bypass pressure reducing valve instruction, and when the low-pressure bypass control system is in a manual control state, the opening degree of the maximum low-bypass pressure reducing valve is used as a low-bypass pressure reducing valve instruction;

and selecting the minimum value of the low bypass pressure reducing valve instruction and the reheater instruction as a final instruction of the low bypass pressure reducing valve, and controlling the opening of the low bypass pressure reducing valve by using the final instruction.

Further, the reheater instructions are: PI regulation result of difference between reheater actual pressure and reheater set pressure.

Further, the maximum pressure X after the low-side pressure reducing valve₁And actual pressure X after low side pressure reducing valve₂PI regulation result Q of the difference₁The expression is as follows:

wherein k is_pFor proportional coefficient of PI regulation, k_iFor the integral coefficient of the PI regulation,the integral is represented.

Further, the reheater actual pressure Y₁And reheater set pressure Y₂PI regulation result Q of the difference₂The expression is as follows:

wherein k is_pFor proportional coefficient of PI regulation, k_iFor the integral coefficient of the PI regulation,the integral is represented.

Further, the maximum pressure behind the low-side pressure reducing valve is the maximum pressure allowed by the unit design.

The invention has the beneficial effects that:

1. in the production operation process, if the pressure behind the pressure reducing valve is continuously increased, the temperature behind the pressure reducing valve is easily overhigh, and when the temperature is higher than a certain value, the low-side pressure reducing valve is quickly closed, so that the pressure of a reheater is quickly increased, and the action of a reheater safety door is caused. The invention automatically controls the actual pressure after the low side pressure reducing valve, and can avoid the actual pressure after the low side pressure reducing valve from exceeding the maximum pressure after the low side pressure reducing valve, thereby avoiding the occurrence of the action of the safety door.

2. In the production operation process, the continuous increase of the pressure behind the pressure reducing valve can also cause the reduction of the vacuum degree of the condenser, thereby causing the shutdown of the low-vacuum protection action of the unit. The invention can avoid the problem of unit tripping caused by the reduction of the vacuum degree of the condenser due to overhigh pressure after the low-side pressure reducing valve.

3. The invention can effectively and automatically control the back pressure of the pressure reducing valve, reduce the labor intensity of operators in the starting or accident state of the unit and avoid the misoperation of the operators.

Drawings

Fig. 1 is a schematic diagram illustrating a method for controlling a post-valve pressure of a low-pressure bypass control system according to the present invention.

Detailed Description

The first embodiment is as follows: specifically describing the present embodiment with reference to fig. 1, the method for controlling the pressure after the valve in the low-pressure bypass control system according to the present embodiment includes:

when the low-pressure bypass control system is in an automatic control state, the maximum pressure X after the low-pressure bypass reducing valve allowed by the unit design is used₁And actual pressure X after low side pressure reducing valve₂PI regulation result Q of the difference₁As the low side pressure reducing valve command, the expression is as follows:

and when the low-pressure bypass control system is in a manual control state, taking the opening degree of the maximum low bypass reducing valve as a command of the low bypass reducing valve.

The actual pressure Y of the reheater₁And reheater set pressure Y₂PI regulation result Q of the difference₂As a reheater instruction, the expression is:

and selecting the minimum value of the low bypass pressure reducing valve instruction and the reheater instruction as a final instruction of the low bypass pressure reducing valve, and controlling the opening of the low bypass pressure reducing valve by using the final instruction.

In the above formula, k_pFor proportional coefficient of PI regulation, k_iFor the integral coefficient of the PI regulation,the integral is represented.

In the production operation process, if the pressure behind the pressure reducing valve is continuously increased, the temperature behind the pressure reducing valve is easily overhigh, and when the temperature is higher than a certain value, the low-side pressure reducing valve is quickly closed, so that the pressure of a reheater is quickly increased, and the action of a reheater safety door is caused. The embodiment automatically controls the actual pressure behind the low-side pressure reducing valve, and can avoid the actual pressure behind the low-side pressure reducing valve from exceeding the maximum pressure behind the low-side pressure reducing valve, thereby avoiding the action of the safety door.

In addition, in the production operation process, the continuous increase of the pressure behind the pressure reducing valve can also cause the reduction of the vacuum degree of the condenser, thereby causing the shutdown of the low-vacuum protection action of the unit. This embodiment can avoid the condenser vacuum that the low side relief valve back pressure is too high to lead to reduce, and the unit tripping operation problem that arouses.

Moreover, the pressure behind the pressure reducing valve can be effectively and automatically controlled, the labor intensity of operators is reduced when the unit is started or in an accident state, and misoperation of the operators is avoided.