A fluid control system

Abstract

This invention discloses a fluid control system applied to a fluid system. The fluid system includes a high-pressure fluid cylinder and a low-pressure fluid cylinder; the high-pressure fluid cylinder contains the fluid to be adjusted; the high-pressure fluid cylinder and the low-pressure fluid cylinder are connected and controlled by a first valve; the fluid control system includes a first deviation device, an adjustment activation system, and a PID controller; the first deviation device is used to determine a first deviation between the current pressure value of the fluid to be adjusted and a preset pressure threshold; the adjustment activation system is used to output a high-level state value when the first deviation falls within a trigger adjustment range, and to output a low-level state value when the first deviation falls within a stop adjustment range; the PID controller is used to control the valve position of the first valve in response to the state values. By setting the trigger adjustment range and the stop adjustment range, automatic adjustment of the current pressure value of the fluid to be adjusted in the high-pressure fluid cylinder is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat supply, in particular to a fluid control system. BACKGROUND

[0002] Nuclear energy as a clean, efficient and stable energy, can provide users with a steady stream of heat, so nuclear heat supply is gradually becoming another way of nuclear energy supply.

[0003] The existing nuclear power unit after large-scale heat supply modification, under rated operating conditions, the steam pressure entering the high pressure cylinder of the steam turbine is designed to remain basically unchanged. Each stage of blade in the high pressure cylinder has a difference in pressure difference due to heat supply extraction. The last stage and the penultimate stage of the high pressure cylinder are closer to the high pressure cylinder exhaust side, and the extracted steam has a larger pressure difference under the same flow rate. If the current pressure is not controlled, when the heat supply steam quantity increases to a certain amount, the further reduction of the current pressure will endanger the safety of the high pressure blade. In order to ensure the safety of the high pressure blade, the current pressure needs to be controlled after the heat supply modification.

[0004] The current pressure control usually adopts PID (Proportional Integral Derivative) control, which is realized by adjusting the ICV (Intercept valve) valve. Although the control of the current pressure is realized, when the current pressure value fluctuates greatly or the variable changes rapidly, the pressure cannot be adjusted adaptively according to the change of the pressure. SUMMARY

[0005] The present application provides a fluid control system to realize the automatic adjustment of the current pressure value of the fluid in the high pressure cylinder.

[0006] The present application provides a fluid control system, which is applied to a fluid system; the fluid system comprises a fluid high pressure cylinder and a fluid low pressure cylinder; wherein the fluid high pressure cylinder contains a fluid to be adjusted; the fluid high pressure cylinder is in communication with the fluid low pressure cylinder and is controlled by a first valve.

[0007] The fluid control system comprises a first deviation device, an adjustment activation system and a PID controller.

[0008] The first deviation device is used to determine the first deviation between the current pressure value of the fluid to be adjusted and a preset pressure threshold.

[0009] An input end of the adjustment activation system is connected with an output end of the first deviation device, and an output end of the adjustment activation system is connected with a control end of the PID controller, for outputting a high level state value when the first deviation belongs to a trigger adjustment interval, and outputting a low level state value when the first deviation belongs to a stop adjustment interval.

[0010] A variable input end of the PID controller is connected with the output end of the first deviation device, a follow input end of the PID controller is set as a preset follow value, and an output end of the PID controller is connected with the first valve, for performing valve position control on the first valve in response to the state value.

[0011] Further, the adjustment activation system comprises a first comparator, a second comparator, a third comparator, a fourth comparator, a first OR gate, a first AND gate and an RS flip-flop.

[0012] Input ends of the first comparator, the second comparator, the third comparator and the fourth comparator are respectively connected with the output end of the first deviation device.

[0013] Output ends of the first comparator and the second comparator are respectively connected with a set end of the RS flip-flop through logical OR operation of the first OR gate, for defining the trigger adjustment interval.

[0014] Output ends of the third comparator and the fourth comparator are respectively connected with a reset end of the RS flip-flop through logical AND operation of the first AND gate, for defining the stop adjustment interval.

[0015] A first state end of the RS flip-flop is connected with the control end of the PID controller.

[0016] Further, the adjustment activation system further comprises:

[0017] A variable stop adjustment loop is connected in series between the first state end of the RS flip-flop and the reset end of the RS flip-flop, for outputting a high level when a high level state value of the first state end exceeds a preset threshold value.

[0018] Further, the variable stop adjustment loop comprises a delay timer, a first NOT gate, a second AND gate and a second OR gate.

[0019] The delay timer is connected in series between one input end of the second AND gate and the first state end of the RS flip-flop.

[0020] The first NOT gate is connected in series between an output end of the first OR gate and another input end of the second AND gate.

[0021] One input end of the second OR gate is connected with the output end of the second AND gate, another input end of the second OR gate is connected with the output end of the second AND gate, and the output end of the second OR gate is connected with the reset end of the RS flip-flop.

[0022] Further, the fluid control system further comprises a deviation decomposition system;

[0023] A control end of the deviation decomposition system is connected with the first state end of the RS flip-flop, a variable input end of the deviation decomposition system is connected with the output end of the first deviation device, and an output end of the deviation decomposition system is connected with a variable input end of the PID controller;

[0024] The deviation decomposition system is used for decomposing the first deviation value with large step change into adjustment parameters with small step change according to a preset sampling period, and inputting the decomposed adjustment parameters as inputs of the variable input end of the PID controller.

[0025] Further, the deviation decomposition system comprises a first switch, a first rate limiter and a second deviation device;

[0026] A variable input end of the first switch is connected with the output end of the first deviation device, a control end of the first switch is connected with the first state end of the RS flip-flop, and an output end of the first switch is connected with a variable input end and a follow-up input end of the first rate limiter respectively;

[0027] A control end of the first rate limiter is connected with the first state end of the RS flip-flop, and an output end of the first rate limiter is connected with a negative input end of the second deviation device;

[0028] A positive input end of the second deviation device is connected with the output end of the first deviation device, and an output end of the second deviation device is connected with the variable input end of the PID controller;

[0029] The first switch and the first rate limiter are respectively provided with preset parameter values.

[0030] Further, the fluid system further comprises a heat supply system; the fluid high-pressure cylinder is communicated with the heat supply system and is controlled by a second valve;

[0031] The fluid control system further comprises a rate limiting loop, which is used for controlling a valve position of the second valve according to a preset safety rate corresponding to a corresponding safety fault when different safety faults occur in the fluid system.

[0032] Further, the rate limiting circuit comprises a switch group, a third OR gate, a second switch and a second rate limiter.

[0033] The switch group comprises at least two third switches connected in cascade through corresponding variable input terminals and output terminals.

[0034] The control terminals of each of the third switches are inputted with transient values of safety faults, and the fixed value input terminals of each of the third switches are set with preset safety rates of corresponding safety faults.

[0035] The variable input terminal of the first third switch in the switch group is set with a preset standard rate, and the output terminal of the last third switch in the switch group is connected with the fixed value input terminal of the second rate limiter in the same direction of rate adjustment.

[0036] The transient values of different safety faults are connected with the control terminal of the second switch after logical OR operation through the third OR gate.

[0037] The fixed value input terminal of the second switch is set with a preset percentage, the variable input terminal of the second switch is set with a preset control instruction, and the output terminal of the second switch is connected with the variable input terminal of the second rate limiter.

[0038] The control terminal of the second rate limiter is set with a preset level signal.

[0039] Further, the severity of different safety faults is sequentially increased according to the hierarchical order of the connected third switches, and correspondingly, the numerical value of the preset safety rate of the safety fault is monotonously changed based on the direction of rate adjustment according to the change of the hierarchical order.

[0040] Further, the fluid high-pressure cylinder is a steam turbine high-pressure cylinder; the fluid low-pressure cylinder is a steam turbine low-pressure cylinder; the fluid to be regulated is steam; the current pressure value is a current exhaust steam pressure; the first valve is a cut-off valve; and the second valve is a steam extraction regulating valve.

[0041] It should be understood that the details described in this section are not intended to identify key or critical features of the embodiments of the application or to limit the scope of the application. Other features of the application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative effort.

[0043] Figure 1 is a principle architecture diagram of a fluid control system according to an embodiment of the application;

[0044] Figure 2 is a specific architecture diagram of a fluid control system according to an embodiment of the application;

[0045] Figure 3 is a specific implementation diagram of a fluid control system according to an embodiment of the application;

[0046] Figure 4 is a specific architecture diagram of a fluid system according to an embodiment of the application;

[0047] Figure 5 is a down rate limit circuit diagram of a second valve according to an embodiment of the present application;

[0048] Figure 6 is an up rate limit circuit diagram of a second valve according to an embodiment of the present application;

[0049] Figure 7 is a specific implementation diagram of a down rate limit circuit diagram according to an embodiment of the present application. DETAILED DESCRIPTION

[0050] In order to make the personnel in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0051] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to only those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0052] Figure 1 A principle architecture diagram of a fluid control system according to an embodiment of the present application is provided, the embodiment can be applied to the case of adjusting step deviation of a process system, and the fluid control system can be implemented by software and / or hardware, wherein the hardware part can be implemented by an analog circuit and / or a digital circuit, and the present application does not make any limitation in this regard.

[0053] Referring to Figure 1 In the embodiment, the fluid control system 10 is applied to a fluid system 20; the fluid system 20 includes a fluid high-pressure cylinder and a fluid low-pressure cylinder; wherein the fluid high-pressure cylinder contains a fluid to be adjusted; the fluid high-pressure cylinder is in communication with the fluid low-pressure cylinder and is controlled by a first valve. The pressure of the fluid to be adjusted in the fluid high-pressure cylinder is usually higher than the pressure of the fluid to be adjusted in the fluid low-pressure cylinder.

[0054] The fluid control system 10 comprises a first deviator 110, an adjustment activation system 120 and a PID controller 130.

[0055] The first deviator 110 is configured to determine a first deviation between a current pressure value of the fluid to be adjusted and a preset pressure threshold value.

[0056] The fluid to be adjusted can be a single-phase fluid, and the preset pressure threshold value of the fluid to be adjusted is used to represent the expected output of the fluid system 20 and can be artificially set according to actual conditions or experience values or determined through a large number of experiments, which are not limited in the embodiments of the present application.

[0057] The input end of the adjustment activation system 120 is connected to the output end of the first deviator 110, the output end of the adjustment activation system 120 is connected to the control end A of the PID controller 130, and the adjustment activation system 120 is configured to output a high-level state value when the first deviation belongs to a trigger adjustment interval and output a low-level state value when the first deviation belongs to a stop adjustment interval.

[0058] The variable input end of the PID controller 130 is connected to the output end of the first deviator 110, the follow-up input end T of the PID controller 130 is set to a preset follow-up value, and the output end of the PID controller 130 is connected to the first valve and is configured to control the valve position of the first valve in response to the state value. The preset follow-up value can be artificially set according to actual conditions or experience values or determined through a large number of experiments, which are not limited in the embodiments of the present application.

[0059] The trigger adjustment interval can be understood as an interval in which the adjustment of the first valve is triggered when the current pressure value of the fluid to be adjusted deviates from the interval. When the current pressure value of the fluid to be adjusted approaches the preset pressure threshold value, the first deviation between the preset pressure threshold value and the current pressure value is in a smaller interval, which is called a stop adjustment interval. The absolute value of the boundary value of the stop adjustment interval is designed to be smaller than the absolute value of the boundary value of the trigger adjustment interval, and the deviation between the two intervals is mainly used to avoid the situation that when the adjustment of the current pressure value of the fluid to be adjusted is completed, the current pressure value deviates from the trigger adjustment interval due to normal fluctuations or other reasons, the adjustment is triggered, and the adjustment is started again after the adjustment is completed and the current pressure value reenters the trigger adjustment interval, which repeatedly causes the valve to frequently move. The absolute value of the stop adjustment interval is set to be smaller than the absolute value of the trigger interval, which can widen the deviation and prevent the normal fluctuations of the current pressure value of the fluid to be adjusted from triggering the adjustment.

[0060] The state value is used to represent the high and low of the level, and can be represented by at least one of a number and a letter, for example, a high level can be represented by 1, and a low level can be represented by 0. The trigger adjustment interval and the stop adjustment interval can be artificially set according to actual conditions or empirical values, or determined through a large number of experiments, and the embodiments of the present application do not make any limitation on this. For example, a high level output is represented by the number 1, a low level output is represented by the number 0, the trigger adjustment interval is set to be greater than A and less than -A, the stop adjustment interval is set to be greater than -B and less than B, when the first deviation is greater than A or less than -A, at this time, the first output of the adjustment activation system is activated, and when -B is less than or equal to the first deviation and the first deviation is less than or equal to B, at this time, the adjustment activation system outputs 0, wherein the values of A and B are real numbers, and the absolute value of A is greater than the absolute value of B. Specifically, the values of A and B can be set or adjusted based on the process parameters of the fluid system.

[0061] The fluid control system of the present application comprises a first deviation device, an adjustment activation system and a PID controller. The first deviation device is used to determine the first deviation between the current pressure value of the fluid to be adjusted and the preset pressure threshold value. The input end of the adjustment activation system is connected with the output end of the first deviation device, the output end of the adjustment activation system is connected with the control end A of the PID controller, and the adjustment activation system is used to output a high level state value when the first deviation belongs to the trigger adjustment interval, and output a low level state value when the first deviation belongs to the stop adjustment interval. The variable input end S of the PID controller is connected with the output end of the first deviation device, the follow-up input end T of the PID controller is set to a preset follow-up value, and the output end of the PID controller is connected with the first valve, and is used to control the valve position of the first valve in response to the state value. By setting the trigger adjustment interval and the stop adjustment interval, different level state values are output according to the interval where the first deviation is located, so as to control the valve position of the first valve by the PID controller, and the automatic adjustment of the current pressure value of the fluid in the high pressure cylinder is realized.

[0062] The current pressure value is controlled by the PID controller and is realized by adjusting the first valve. If the parameters of the PID controller are adjusted to achieve an ideal large step adjustment, the output of the PID controller will change greatly. This change causes the first valve to be adjusted greatly and violently in a short time, which causes the sliding parts of the first valve, i.e. the moving and static parts, to be rubbed too much, affects the service life of the first valve and related supporting parts, and challenges the reliability of the first valve.

[0063] Optionally, referring to Figure 2 , the adjustment activation system comprises a first comparator, a second comparator, a third comparator, a fourth comparator, a first OR gate, a first AND gate and an RS flip-flop.

[0064] The input ends of the first comparator, the second comparator, the third comparator and the fourth comparator are connected with the output end of the first biaser respectively; the output end of the first comparator and the output end of the second comparator are connected with the setting end S of the RS flip-flop after logical or operation by the first or gate, for limiting the trigger adjustment interval; the output end of the third comparator and the output end of the fourth comparator are connected with the reset end R of the RS flip-flop after logical and operation by the first and gate, for limiting the stop adjustment interval; the first state end Q of the RS flip-flop is connected with the control end of the PID controller 130.

[0065] Optionally, Figure 2The adjustment activation system 120 in the control system is set, the trigger adjustment interval is ≥ A, ≤ -A, when the current pressure value minus the first deviation of the preset pressure threshold ≥ A, the S end of the RS trigger is input, the first output of the RS trigger is to the A end of the PID controller 130, the PID automatic adjustment function is activated, the valve adjusts the valve opening according to the instruction of the PID controller 130, the current pressure value is adjusted to < A, the PID automatic adjustment does not stop, and continues to adjust to the first deviation ≤ B of the current pressure value and the current pressure value threshold, B is one of the stop adjustment intervals, until the first deviation of the current pressure value and the current pressure value threshold is ≥ A again, the PID controller 130 triggers the automatic adjustment again; the adjustment process in the opposite direction, when the first deviation of the current pressure value and the current pressure value threshold is ≤ -A, the S end of the RS trigger is input, the first output of the RS trigger is to the A end of the PID controller 130, the PID automatic adjustment function is activated, the first valve adjusts the valve opening according to the instruction of the PID controller 130 and the related circuit, the current pressure value is adjusted, the first deviation of the current pressure value and the preset pressure threshold is adjusted to > -A, the PID automatic adjustment does not stop, and continues to adjust to the first deviation ≤ -B of the current pressure value and the preset pressure threshold, -B is the other stop adjustment interval, until the first deviation of the current pressure value and the preset pressure threshold is 1 ≤ -A, the PID controller 130 triggers the automatic adjustment again. The deviation of the trigger adjustment interval and the stop adjustment interval can avoid the following situation: after the current pressure value adjustment is completed, if the current pressure value exceeds the trigger adjustment interval due to normal fluctuations and the like, the adjustment is triggered, the adjustment is completed, the trigger interval is reentered, the adjustment is triggered, and the process is repeatedly repeated, which can cause the valve to frequently move and cause excessive wear of the sliding parts of the valve. However, the above process has a contradiction: when the deviation of the current pressure value and the preset pressure threshold is ≥ A, it exceeds the trigger adjustment interval, the PID controller 130 is triggered to automatically adjust, and the deviation is also ≥ -B, which exceeds the stop adjustment interval, and the PID controller 130 needs to be stopped to automatically adjust, which is contradictory, and the loop stops adjusting; similarly, when the first deviation of the current pressure value and the preset pressure threshold is ≤ -A, it exceeds the trigger adjustment interval, the PID controller 130 is triggered to automatically adjust, and the first deviation is also ≤ B, which exceeds the stop adjustment interval, and the PID controller 130 needs to be stopped to automatically adjust, which is also contradictory, and the loop stops adjusting, and this situation needs to be avoided.

[0066] Optionally, the present application designs Figure 2The first or gate 125 and the first and gate 126, when the first deviation of the current pressure value and the preset pressure threshold value is ≥ A or ≤ -A, the S end of the RS flip-flop is input (S = 1, R = 0, Q = 1), the first output of the RS flip-flop is input to the A end of the PID controller 130, and the PID automatic adjustment function is activated. The first deviation ≥ A or ≤ -A is connected by the OR logic of the first or gate 125; when the first deviation ≥ -B and ≤ -B, the output of the RS flip-flop is 0 to the A end of the PID controller 130 through the R end of the RS flip-flop, and the PID automatic adjustment function is locked. The PID controller 130 follows the feedback value of the valve of the T port, and the first deviation ≥ -B and ≤ -B is connected by the AND logic of the first and gate 126. After such design, when the first deviation of the current pressure value and the preset pressure threshold value is ≥ A, although the first deviation is also ≥ -B, the first deviation is not ≤ B at the same time, and the AND gate of the first and gate 126 plays a role at this time, preventing the signal from being sent to the R end of the RS flip-flop. When the first deviation of the current pressure value and the preset pressure threshold value is ≤ -A, although the first deviation is also ≤ B, the first deviation is not ≥ -B at the same time, and the AND gate of the first and gate 126 plays a role at this time, preventing the signal from being sent to the R end of the RS flip-flop. Through such logical combination, the above-mentioned contradiction can be avoided.

[0067] Specifically, the first deviation of the current pressure value and the preset pressure threshold value is calculated by the following formula: Figure 3For example, the trigger adjustment interval is set to be ≥ 0.03 MPa, ≤ -0.03 MPa, and the first deviation of the current pressure value minus the preset pressure threshold is ≥ 0.03 MPa, and the RS trigger connected behind is triggered to complete the automatic adjustment function of the PID controller 130, and the first valve adjusts the valve opening according to the instruction of the PID controller 130 to control the current pressure, and the first deviation of the current pressure value minus the preset pressure threshold is adjusted to be < 0.03 MPa, and the PID automatic adjustment does not stop, and continues to adjust until the first deviation of the current pressure value minus the preset pressure threshold is ≤ 0.01 MPa, and the adjustment stops, and 0.01 MPa is one of the stop adjustment intervals, and until the next time the first deviation of the current pressure value minus the preset pressure threshold is ≥ 0.03 MPa, the PID controller 130 is triggered again to automatically adjust; the adjustment process in the opposite direction, when the first deviation of the current pressure value minus the preset pressure threshold is ≤ -0.03 MPa, the RS trigger connected behind is triggered to complete the automatic adjustment function of the PID controller 130, and the first valve adjusts the valve opening according to the instruction of the PID controller 130 and the related circuit to control the current pressure value, and the first deviation of the current pressure value minus the preset pressure threshold is adjusted to be > -0.03 MPa, and the PID automatic adjustment does not stop, and continues to adjust until the first deviation of the current pressure value minus the current pressure value is ≥ -0.01 MPa, and the adjustment stops, and -0.01 MPa is another stop adjustment interval, and until the next time the first deviation of the current pressure value minus the preset pressure threshold is ≤ -0.03 MPa, the PID controller 130 is triggered again to automatically adjust. The deviation of the trigger adjustment interval and the stop adjustment interval can avoid the current pressure value from being adjusted, and once the current pressure value is adjusted due to its own normal fluctuation and exceeds the trigger adjustment interval, the trigger adjustment is triggered, and after the adjustment is completed and the trigger interval is re-entered, the adjustment is triggered again, and the process is repeatedly repeated, which can cause the first valve to move frequently, causing the first valve sliding part to be excessively worn. However, the above process has a contradiction, when the first deviation of the current pressure value minus the preset pressure threshold is ≥ 0.03 MPa, which exceeds the trigger adjustment interval, the PID controller 130 is triggered to automatically adjust, and the deviation at this time is also ≥ -0.01 MPa, which exceeds the stop adjustment interval, and it is required to stop the PID controller 130 from automatically adjusting; similarly, when the first deviation of the current pressure value minus the preset pressure threshold is ≤ -0.03 MPa, which exceeds the trigger adjustment interval, the PID controller 130 is triggered to automatically adjust, and the deviation at this time is also ≤ 0.01 MPa, which exceeds the stop adjustment interval, and it is required to stop the PID controller 130 from automatically adjusting, which causes a contradiction.

[0068] The present application designs Figure 3The combination of the middle 120, when the current pressure value minus the first deviation of the preset pressure threshold ≥ 0.03MPa or ≤-0.03MPa, the S end of the RS trigger is input, the first output of the RS trigger is connected to the A end of the PID controller 130, and the PID automatic adjustment function is activated. The first deviation ≥ 0.03MPa or ≤-0.03MPa is connected by the "or" logic of the first or gate 125; when the first deviation ≥-0.01MPa and ≤-0.03MPa, after the second or gate 129, the R end of the RS trigger is input, and the output 0 of the RS trigger is connected to the A end of the PID controller 130, and the PID automatic adjustment function is locked. The PID controller 130 follows the feedback value of the first valve of the T port. The first deviation ≥-0.01MPa and ≤-0.03MPa is connected by the "and" logic of the first and gate 126. After such design, when the first deviation of the current pressure value minus the preset pressure threshold ≥ 0.03MPa, although the first deviation is also ≥-0.01MPa, the design of the first and gate 126 makes the first deviation not ≤0.01MPa at the same time. At this time, the "and" gate of the first and gate 126 plays a role, preventing the signal from being sent to the R end of the RS trigger. When the first deviation of the current pressure value minus the preset pressure threshold ≤-0.03MPa, although the deviation is also ≤0.01MPa, the first deviation is not ≥-0.01MPa at the same time. At this time, the "and" gate of the first and gate 126 plays a role, preventing the signal from being sent to the R end of the RS trigger.

[0069] Optionally, continuing to refer to Figure 2 , the adjustment activation system 120 further comprises: a variable stop adjustment circuit connected in series between the first state end Q of the RS trigger and the reset end R of the RS trigger, for outputting a high level when the high level state value of the first state end exceeds the preset threshold.

[0070] The variable stop adjustment circuit comprises a delay timer, a first NOT gate, a second AND gate and a second OR gate. The delay timer is connected in series between one input end of the second AND gate and the first state end Q of the RS trigger. The first NOT gate is connected in series between the output end of the first OR gate and the other input end of the second AND gate. One input end of the second OR gate is connected with the output end of the second AND gate, the other input end of the second OR gate is connected with the output end of the first AND gate, and the output end of the second OR gate is connected with the reset end R of the RS trigger.

[0071] Optionally, the present application forms a loop with the first NOT gate 127 "NOT" logic, the delay and the second AND gate 128 "AND" logic in the adjustment activation system 120 as a variable stop adjustment loop. The loop is relative to the value setting of the stop adjustment interval. The stop adjustment is variable, not fixed, and more flexible. Its function is as follows: first, when the first deviation of the current pressure value and the preset pressure threshold is ≥ A or ≤ -A, the RS flip-flop output is 1 (S = 1, R = 0, Q = 1), and the PID starts to automatically adjust the current pressure value. When the adjustment makes the first deviation not satisfy ≥ A or ≤ -A, the first NOT gate 127 "NOT" logic is set to 1, at the same time, the first deviation does not reach the stop adjustment interval, and the RS flip-flop output continues to be 1 (S = 0, R = 0, Q remains unchanged = 1). The delay output is 1, and the two input ports of the second AND gate 128 "AND" logic are set to 1. The RS flip-flop R end is set to 1 through the second OR gate 129 "OR" logic, and the reset output end is set to 0, so that the PID automatic adjustment function is stopped, and the valve is also stopped at the current position. Thus, the valve stops moving when the first deviation does not reach the stop adjustment interval. To avoid the current pressure value deviation being too small when triggering the adjustment interval and the stop, the time of the delay needs to be set. The loop after the stop adjustment interval of the first AND gate 126 "AND" logic and the variable stop adjustment loop is connected to the second OR gate 129 "OR" logic, which means that any one inlet is set to 1 to output 1 to reset the RS flip-flop, regardless of who sets 1 first between the stop adjustment interval and the variable stop adjustment interval. If the variable stop adjustment interval is earlier than the stop adjustment interval, the PID automatic adjustment process can be terminated in advance to avoid the valve moving too frequently. Such a design combination is also more flexible.

[0072] Optionally, continuing to refer to Figure 2 , the fluid control system 10 further comprises a deviation decomposition system 140.

[0073] The control end of the deviation decomposition system 140 is connected with the first state end Q of the RS flip-flop, the variable input end R of the deviation decomposition system 140 is connected with the output end of the first deviation, and the output end of the deviation decomposition system 140 is connected with the variable input end S of the PID controller 130. The deviation decomposition system 140 is used for decomposing the first deviation value with large step change into adjustment parameters with small step change according to a preset sampling period, and taking the decomposed adjustment parameters as the input of the variable input end S of the PID controller 130. The preset sampling period can be set in the computer where the first rate limiter is located.

[0074] The large step change can be understood as a change condition with a change amplitude greater than a first preset threshold. The small step change can be understood as a change condition with a change amplitude less than a second preset threshold. The first preset threshold and the second preset threshold can be empirical values or experimental values, and the first preset threshold is greater than the second preset threshold.

[0075] Optionally, continuing to refer to Figure 2 , the deviation decomposition system 140 comprises a first switch 141, a first rate limiter 142 and a second deviation 143.

[0076] The variable input end R of the first switch 141 is connected with the output end of the first deviation 110, the control end A of the first switch 141 is connected with the first state end Q of the RS flip-flop, and the output end of the first switch 141 is connected with the variable input end S and the follow-up input end T of the first rate limiter 142 respectively; the control end A of the first rate limiter 142 is connected with the first state end Q of the RS flip-flop, and the output end of the first rate limiter 142 is connected with the negative input end of the second deviation 143; the positive input end of the second deviation 143 is connected with the output end of the first deviation 110, and the output end of the second deviation 143 is connected with the variable input end S of the PID controller 130; the preset parameter values (E and F in the formula (1) in the first switch 141 and the first rate limiter 142 respectively) are set in the fixed value input end S of the first switch 141 and the fixed value input end U and D of the first rate limiter 142 respectively, wherein the preset parameter values can be artificially set according to actual conditions or empirical values, or determined through a large number of experiments, and the embodiments of the present application do not make any limitation in this aspect. Figure 2 Figure 3 The preset parameter values (E and F in the formula (1) in the first switch 141 and the first rate limiter 142 respectively) are set in the fixed value input end S of the first switch 141 and the fixed value input end U and D of the first rate limiter 142 respectively, wherein the preset parameter values can be artificially set according to actual conditions or empirical values, or determined through a large number of experiments, and the embodiments of the present application do not make any limitation in this aspect.

[0077] ​In order to make the PID controller 130 and the auxiliary adjustment loop have the ability to adapt to various steps, the deviation decomposition system 140 loop designed by the present application is selected, which is a computer-centered digital control based on a sampling-data control system. The preset sampling period set in the computer by the first rate limiter can be very short, for example, 50 milliseconds. The PID data entering the computer is a signal based on periodic sampling. After digital processing by the computer, the current pressure value can be decomposed into a very small value, which is then continuously accumulated and sent to the PID controller 130 every preset sampling period for uninterrupted processing, so that the PID controller 130 only needs to focus on the design of small step parameters. The specific method is that the first switch 141 is switched to the first deviation input when the PID controller 130 is in automatic adjustment, and the 142 is a rate limiter, the inlet selects the S port when the PID controller 130 is in automatic adjustment; the U port uplink rate limiting and the D port downlink rate limiting play the role of deviation change limiting, the rate limiter outlet is connected to the negative terminal of the second deviation 143, the first deviation is connected to the positive terminal of the second deviation 143, and the second deviation output by the second deviation 143 enters the S port inlet of the PID controller 130. By adjusting the values of the U port and the D port of the first rate limiter 142, the output of the first rate limiter 142 is changed, the output of the second deviation 143 is changed, and the deviation amount entering the PID controller 130 in each computer period is changed, so that the PID controller 130 only needs to set the basic adjustment parameter proportional coefficient, integral time constant and differential time constant of relatively small step, which can ensure that the PID controller 130 output link can adapt to large and small step deviations, and can also control the adjustment precision based on small step PID adjustment within a reasonable range. The deviation decomposition system 140 part makes it unnecessary to bind a specific or dedicated PID controller, and only the basic adjustment function of the PID provided by various manufacturers can realize the adjustment and control function of adapting to large and small steps in a wide range.

[0078] In the heating condition, the current pressure value is changed due to the unexpected event on the heating side or the change of the need of the extraction of the heating steam, at this time, the second valve is adjusted passively or actively, which causes the change of the current pressure value exceeding a certain limit value, the PID controller controls the valve position of the first valve to keep the current pressure value around the constant value. When the second valve is opened, more heating steam is extracted, the current pressure value is smaller, the first valve needs to be closed to maintain the current pressure value; when the second valve is closed, less heating steam is extracted, the current pressure value is larger, the first valve needs to be opened to maintain the current pressure value. However, the basic adjustment parameters of the PID controller are difficult to adapt to a wide range of step disturbances if the process system is determined, if the adjustment parameters adapt to small step disturbances, overshoot will occur when large step disturbances occur, and even the regulation activation system 120 cannot be stable, the current pressure value will eventually diverge or oscillate; if the adjustment parameters are set to adapt to large step disturbances, the regulation activation system 120 will have overshoot or the regulation accuracy cannot meet the requirements. Among them, the overshoot phenomenon refers to the case that the current pressure value is greater than the preset pressure threshold.

[0079] Optionally, referring to Figure 4 , the fluid system 20 further comprises a heating system; the fluid high-pressure cylinder is in communication with the heating system and is controlled by the second valve; the fluid control system 20 further comprises a rate limiting loop 150 for controlling the valve position of the second valve according to the preset safety rate corresponding to the corresponding safety fault in the case of different safety faults of the fluid system. It can be understood that the control of the second valve will directly affect the current pressure value of the fluid to be adjusted in the fluid high-pressure cylinder, thereby indirectly affecting the subsequent valve position control of the first valve.

[0080] Optionally, the rate limiting loop comprises a switch group, a third OR gate, a second switch and a second rate limiter.

[0081] The switcher group includes at least two third switches cascaded together via corresponding variable inputs and outputs. The control terminal of each third switch receives transient values ​​of different safety faults, and the setpoint input of each third switch is set with a preset safety rate for the corresponding safety fault. The variable input of the first third switch in the switcher group is set to a preset standard rate, and the output of the last third switch in the switcher group is connected to the setpoint input of the second rate limiter, which is aligned with the rate adjustment direction. The transient values ​​of different safety faults are logically ORed through a second OR gate and then connected to the control terminal of the second switcher. The setpoint input of the second switcher is set to a preset percentage, the variable input of the second switcher is set to a preset control command, and the output of the second switcher is connected to the variable input of the second rate limiter. The control terminal of the second rate limiter is set to a preset level signal. The value of the preset level signal can be manually set based on actual conditions or experience, or determined through extensive testing; this embodiment of the invention does not impose any limitations on this.

[0082] Optionally, connecting the output of the third switch at the end of the switch group 151 to the fixed input terminal of the second rate limiter 154 that is aligned with the rate adjustment direction includes: when the change at the output terminal changes from large to small, the output of the third switch in the switch group 151 is connected to the fixed input terminal D of the second rate limiter 154 where the rate adjustment direction is downward. See, for example... Figure 5 When the output changes from small to large, the output of the third switch in switch group 151 is connected to the fixed input U of the second rate limiter 154, where the rate adjustment direction is upward. See, for example... Figure 6 .

[0083] by Figure 5 For example, switch group 151 includes at least two third switches cascaded together through corresponding variable input terminals R and output terminals; the control terminal A of each third switch is input with transient values ​​of different safety faults, and the setpoint input terminal S of each third switch is set with the preset safety rate of the corresponding safety fault; the variable input terminal R of the first third switch in switch group 151 is set with the preset standard rate, and the output terminal of the last third switch in switch group 151 is connected to the setpoint input terminal D of the second rate limiter 154, which is consistent with the rate adjustment direction; the transient values ​​of different safety faults are logically ORed by the third OR gate 152 and then connected to the control terminal A of the second switch 153; the setpoint input terminal S of the second switch 153 is set with a preset percentage, the variable input terminal R of the second switch 153 is set with a preset control command, and the output terminal of the second switch 153 is connected to the variable input terminal S of the second rate limiter 154; the control terminal A of the second rate limiter 154 is set with a preset level signal.

[0084] The severity of different safety faults increases sequentially with the hierarchical order of the connected third switch (where the maximum hierarchical level is N). Correspondingly, the preset safety rate of the safety fault changes monotonically with the hierarchical order, based on the direction of rate adjustment. The preset safety rate can be manually set based on actual conditions or experience, or determined through extensive experimentation; this embodiment of the invention does not impose any limitations on this. For example, the preset safety rate can be a preset percentage per minute.

[0085] The action of the second valve will cause the current pressure value to deviate from the preset pressure threshold, but the control of the current pressure value is determined by... Figure 2 The first valve is used for control and regulation. When the second valve actuates, it will cause the regulating valve to actuate in conjunction with the second valve due to the change in the current pressure value. The second valve and the regulating valve have a linked relationship. Optionally, see [link to relevant documentation]. Figure 5 Each third switch corresponds to a transient condition, which refers to a significant system malfunction requiring the closure of the second valve. The closure of the second valve reduces fluid flow, causing the current pressure to rise, which is then regulated by the regulating valve. When a transient occurs, the outlet of the second switch 153 switches from the R end to the S end. Figure 5 The transient value increases with the severity of the transient, ensuring that the rate at the S end of the corresponding second switch 153 is obtained when the most severe transient occurs. Simultaneously, the transient value switches the second switch 153 from the R end command to 0 and changes according to the rate at the D end of the second rate limiter 154, controlling the second valve to close at a predetermined rate. The change in current pressure value increases at the corresponding rate. Designing a rate loop avoids large steps at the inlet of the PID controller for the regulating valve, allowing the deviation to change gradually. The PID controller does not need to be configured with parameters for large steps. This configuration minimizes the frequency of operation of the first valve (such as a hydraulic, pneumatic, or electric regulating valve), avoids excessive wear on the sliding parts of the actuator, and extends the service life and maintenance interval of the actuator.

[0086] Taking the high-pressure fluid cylinder as the high-pressure cylinder of the steam turbine; the low-pressure fluid cylinder as the low-pressure cylinder of the steam turbine; the fluid to be adjusted as steam; the current pressure value as the current exhaust pressure; and the second valve as an extraction steam regulating valve as an example. (See also...) Figure 7, each switch corresponds to a unit transient, which means that the system has a major fault, the second valve needs to be closed, the closing of the second valve causes the extraction steam to decrease, and the current exhaust pressure value of the high-pressure cylinder of the steam turbine increases due to the decrease in extraction steam. When the transient occurs, the second switch 153 outlet is switched from the R end to the S end. In order to make the second valve get a more smooth current pressure value rate change when the transient occurs, slow down the impact of large steps, control the current pressure value not to develop to the alarm value or the trip value (previously set by the technical personnel), Figure 7 The "first transient" in the above formula has the lowest severity, and the "third transient" has the highest severity. If the "first transient", the "second transient" and the "third transient" occur at the same time or two of them occur, it can be seen from the design of the present application that the loop will select the rate of the S end of the third switch closer to the second rate limiter. Ensure that the second valve can act according to the rate designed under the current most serious condition. At the same time, the transient switches the second switch 153 from the R end of the command 50% to the S end of the command -5% / min, and executes the second valve to full closing according to the rate of the D end of the second rate limiter. The -5% / min of the S end is a forced negative command to ensure that the valve is closed in place.

[0087] Optionally, in the embodiment of the present application, the fluid high-pressure cylinder is a steam turbine high-pressure cylinder; the fluid low-pressure cylinder is a steam turbine low-pressure cylinder; the fluid to be adjusted is steam; the current pressure value is the current exhaust pressure; the first valve is a cut-off valve; and the second valve is an extraction steam regulating valve.

[0088] Note that the above is only a preferred embodiment of the present application and the technical principle applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and those skilled in the art can make various obvious changes, readjustments and substitutions without departing from the scope of the present application. Therefore, although the present application has been described in more detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the appended claims.

Claims

1. A fluid control system, characterized by, The application is applied to a fluid system; the fluid system comprises a fluid high-pressure cylinder and a fluid low-pressure cylinder; wherein the fluid high-pressure cylinder contains fluid to be regulated; the fluid high-pressure cylinder is communicated with the fluid low-pressure cylinder and is controlled by a first valve; The fluid control system comprises a first deviation device, a regulation activation system and a proportional-integral-derivative (PID) controller; The first deviation device is used for determining a first deviation between a current pressure value of the fluid to be regulated and a preset pressure threshold value; An input end of the regulation activation system is connected with an output end of the first deviation device, an output end of the regulation activation system is connected with a control end of the PID controller, and the regulation activation system is used for outputting a high-level state value when the first deviation belongs to a trigger regulation interval and outputting a low-level state value when the first deviation belongs to a stop regulation interval; A variable input end of the PID controller is connected with the output end of the first deviation device, a follow-up input end of the PID controller is set as a preset follow-up value, and an output end of the PID controller is connected with the first valve, and the PID controller is used for controlling a valve position of the first valve in response to the state value; The regulation activation system comprises a first OR gate, a first AND gate, an RS flip-flop and a variable stop regulation loop; A first state end of the RS flip-flop is connected with the control end of the PID controller; The variable stop regulation loop is connected in series between the first state end of the RS flip-flop and a reset end of the RS flip-flop, and is used for outputting a high level when a high-level state value of the first state end exceeds a preset threshold value; The variable stop regulation loop comprises a delay timer, a first NOT gate, a second AND gate and a second OR gate; The delay timer is connected in series between one input end of the second AND gate and the first state end of the RS flip-flop; The first NOT gate is connected in series between an output end of the first OR gate and another input end of the second AND gate; One input end of the second OR gate is connected with an output end of the second AND gate, another input end of the second OR gate is connected with an output end of the first AND gate, and an output end of the second OR gate is connected with the reset end of the RS flip-flop.

2. The fluid control system of claim 1, wherein, The regulation activation system comprises a first comparator, a second comparator, a third comparator and a fourth comparator; Input ends of the first comparator, the second comparator, the third comparator and the fourth comparator are respectively connected with an output end of the first deviation device; An output end of the first comparator and an output end of the second comparator are respectively connected with a set end of the RS flip-flop after logical OR operation through the first OR gate, and are used for defining the trigger regulation interval; An output end of the third comparator and an output end of the fourth comparator are respectively connected with a reset end of the RS flip-flop after logical AND operation through the first AND gate, and are used for defining the stop regulation interval.

3. The fluid control system of claim 1, wherein, The application further comprises a deviation decomposition system. The control end of the deviation decomposition system is connected with the first state end of the RS flip-flop, the variable input end of the deviation decomposition system is connected with the output end of the first deviation device, and the output end of the deviation decomposition system is connected with the variable input end of the PID controller; The deviation decomposition system is used for decomposing the first deviation value with large step change into adjustment parameters with small step change according to a preset sampling period, and taking the decomposed adjustment parameters as the input of the variable input end of the PID controller.

4. The fluid control system of claim 3, wherein, The deviation decomposition system comprises a first switch, a first rate limiter and a second deviation device; The variable input end of the first switch is connected with the output end of the first deviation device, the control end of the first switch is connected with the first state end of the RS flip-flop, and the output end of the first switch is connected with the variable input end and the follow-up input end of the first rate limiter respectively; The control end of the first rate limiter is connected with the first state end of the RS flip-flop, and the output end of the first rate limiter is connected with the negative input end of the second deviation device; The positive input end of the second deviation device is connected with the output end of the first deviation device, and the output end of the second deviation device is connected with the variable input end of the PID controller; The constant value input end of the first switch and the constant value input end of the first rate limiter are respectively provided with preset parameter values.

5. The fluid control system of any one of claims 1-4, wherein, The fluid system further comprises a heat supply system; the fluid high-pressure cylinder is communicated with the heat supply system and is controlled through a second valve; The fluid control system further comprises a rate limiting loop for controlling the valve position of the second valve according to a preset safety rate corresponding to a corresponding safety fault when different safety faults occur in the fluid system.

6. The fluid control system of claim 5, wherein, The rate limiting loop comprises a switch group, a third OR gate, a second switch and a second rate limiter. The switch group comprises at least two third switches connected in cascade through corresponding variable input ends and output ends. The control end of each third switch is inputted with a transient value of a different safety fault, and the constant value input end of each third switch is provided with a preset safety rate of a corresponding safety fault. The variable input end of the first third switch in the switch group is provided with a preset standard rate, and the output end of the last third switch in the switch group is connected with the constant value input end of the second rate limiter in the same direction of rate adjustment. The transient values of different safety faults are connected with the control end of the second switch after logical OR operation through the third OR gate. The constant value input end of the second switch is provided with a preset percentage, the variable input end of the second switch is provided with a preset control instruction, and the output end of the second switch is connected with the variable input end of the second rate limiter. The control end of the second rate limiter is provided with a preset level signal.

7. The fluid control system according to claim 6, wherein: The severity of different security faults increases in turn along a hierarchical order of connected third switches, and the preset security rate of the security faults monotonously changes based on the rate adjustment direction along with the change of the hierarchical order.

8. The fluid control system of claim 5, wherein, The fluid high-pressure cylinder is a steam turbine high-pressure cylinder, the fluid low-pressure cylinder is a steam turbine low-pressure cylinder, the fluid to be regulated is steam, the current pressure value is a current exhaust steam pressure, the first valve is a cut-off valve, and the second valve is a steam extraction regulating valve.

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