Automatic control method for correcting differential action

Abstract

The application discloses an automatic control method for correcting differential action, and steps are as follows: 1) real-time detection of a measurement value state of a unit controlled operation parameter, judgment of whether the parameter is in a valid positive value interval; 2) judgment of whether the system is in a dynamic adjustment process, input of differential adjustment action, and real-time recording of a minimum value of the differential action in a current adjustment period; 3) when the differential output is reduced to the minimum value in the current period, the differential action is quickly attenuated to 1 / 2 of the minimum value; 4) after the differential action is stabilized to the value, the original differential control output logic is restored to continue adjustment until a controlled variable deviation is zeroed and the parameter is restored to stability, and then the differential adjustment action is cut off. The application belongs to the technical field of operation optimization control of thermal power units, and solves problems that, when a small disturbance exists in a field measurement signal in the prior art, a control system appears periodic oscillation, dynamic overshoot is increased, and a controlled variable repeatedly fluctuates.

Description

Technical Field

[0001] This invention belongs to the field of thermal power unit operation optimization control technology, and relates to an automatic control method for correcting differential action. Background Technology

[0002] During long-term continuous operation of thermal power units, key operating conditions such as unit load, main steam pressure, and main steam temperature are constantly changing. Simultaneously, the inherent nonlinear characteristics of various automatic control systems within the unit continuously affect the quality of system regulation. Since the initial parameters of the PID controller are all tuned based on rated operating conditions, when the operating conditions of the thermal power unit deviate, the fixed PID parameters cannot adapt to the changing operating characteristics, making it difficult for conventional PID control to achieve ideal dynamic and steady-state regulation effects.

[0003] To address this issue, conventional PID control incorporates derivative action, leveraging its anticipatory regulation characteristics to predict the changing trend of the controlled variable, effectively suppressing system fluctuations and dynamic overshoot, accelerating system response, and improving the dynamic regulation characteristics of the unit's control system. However, the derivative element has significant control limitations. Its output is directly related to the rate of change of the controlled variable and is highly sensitive to high-frequency jitter and random fluctuations in the measured signal. In particular, when there are minor disturbances in the field measurement signal, the derivative element will generate a large high-frequency output, causing frequent jitter and frequent actions in the actuator. This leads to problems such as periodic oscillations, increased dynamic overshoot, and repeated fluctuations in the controlled variable in the control system. In severe cases, it can cause the regulation curve to oscillate continuously or even diverge, significantly reducing the stability and control accuracy of the unit's automatic control system. Summary of the Invention

[0004] The purpose of this invention is to provide an automatic control method for correcting differential action, which solves the problems in the prior art where the differential element generates a large high-frequency output when there is a small disturbance in the field measurement signal, causing the actuator to jitter and move frequently, which in turn leads to periodic oscillations, increased dynamic overshoot, and repeated fluctuations of the controlled variable in the control system.

[0005] The technical solution adopted in this invention is an automatic control method for correcting differential action, implemented according to the following steps: Step 1: Monitor the measured values ​​of the controlled operating parameters of the unit in real time and determine whether the parameters are within the valid positive value range; Step 2: If the measured value of the controlled parameter is positive, determine that the system is in a dynamic adjustment process, engage the derivative adjustment action, and record the minimum value of the derivative action in the current adjustment cycle in real time. Step 3: When the differential output drops to the minimum value of this cycle, control the differential action to quickly decay to 1 / 2 of the minimum value; Step 4: After the derivative action stabilizes to this value, restore the original derivative control output logic and continue to adjust until the controlled variable deviation returns to zero and the parameter returns to stability, then cut off the derivative adjustment action.

[0006] The beneficial effects of this invention are that the control method can achieve precise on-demand input and dynamic correction of the differential action, avoiding the drawbacks of conventional differential control with full input and unconstrained output. It fundamentally solves the problems of overshoot, system oscillation and severe parameter fluctuation caused by differential control, and effectively improves the adjustment accuracy and operational stability of the automatic control system of thermal power units under changing operating conditions. Attached Figure Description

[0007] Figure 1 This is the minimum value logic scheme with clearing function in the method of this invention; Figure 2 This is the differential correction logic scheme in the method of the present invention; Figure 3 This is a waveform diagram of the modified differential control in the method of this invention; Figure 4 This is the curve showing the equal amplitude fluctuation between the actual measured value and the set value in Embodiment 1 of the method of the present invention; Figure 5 This is the differential action curve formed based on the controlled quantity in Embodiment 2 of the method of the present invention; Figure 6 This is the curve showing that the measured value in Embodiment 3 of the method of the present invention is within the positive valid range; Figure 7 These are the curves of the minimum differential value and the minimum 1 / 2 differential value in Embodiment 4 of the method of the present invention; Figure 8 These are the differential curve, differential minimum curve, and 1 / 2 differential minimum curve of embodiment 5 of the method of the present invention; Figure 9 The curve in Embodiment 6 of the method of the present invention shows that the measured value is positive and falls within the valid positive value range. Detailed Implementation

[0008] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0009] This invention provides an automatic control method for correcting differential action. Addressing the shortcomings of conventional differential control, such as poor regulation performance and susceptibility to system oscillation, this method superimposes a steady-state correction control strategy on the original differential control logic. This can quickly drive the controlled parameters towards stability and accurately optimize the differential input and output process.

[0010] The automatic control method for correcting differential action according to the present invention is implemented according to the following steps: Step 1: Monitor the measured values ​​of the controlled operating parameters of the unit in real time and determine whether the parameters are within the valid positive value range; like Figure 2 The measured value is subtracted from the set value using adder SUM1 to obtain the deviation between the measured value and the set value. When the output value of the high limit module HIGHMON1 is greater than 0, it indicates that the measured value is above the set value, and the parameter is judged to be in the valid positive value range. Figure 3 Point ① in the middle.

[0011] When the output value of the high-limit module HIGHMON1 is less than 0, it indicates that the measured value is below the set value, meeting the switching condition of the switching module TRANSFER3. All N channels are activated, and the assignment module AVALGEN5 is set to 0, indicating that the parameter is in a non-valid positive value range. (See...) Figure 3 Point ④.

[0012] Step 2: If the measured value of the controlled parameter is positive, determine that the system is in a dynamic adjustment process, engage the derivative adjustment action, and record the minimum value of the derivative action in the current adjustment cycle in real time. like Figure 2 When the measured value is different from the set value by adder SUM1, the difference is then compared with the difference between adder SUM2 by adder LEADLAG module, forming a differential action.

[0013] (Note: The LEADLAG function used in the logic is a non-linear lead / lag function with the function symbol: OUT=(K1 X IN1)+ (K2 X OLDIN1) +(K3X OLDOUT). The LEADLAG module has two parameters, LEAD and LAG. When LEAD=0 and LAG>0, the module is a pure lag module, i.e., an inertial module, and its lag function is used in this logic.)

[0014] When the HIGHMON1 module is greater than 0, the measured value is determined to be positive and within the valid positive value range. This serves as the switching condition for the TRANSFER3 module, and the Y-path is turned on, at which point the differential action is engaged.

[0015] Reference Figure 1 The minimum value logic scheme with zeroing function in this invention is implemented by the coordinated action of the pulse module ONESHOT, the assignment module AVALGEN1, the assignment module AVALGEN2, the switching module TRANSFER1, the minimum value module MIN, and the multiplication module MULTIPLY1; the output of the adder SUM2 is used as the differential action to enter the minimum value MIN module: when the deviation is less than 0, that is, when the lower limit module LOWMON1 is less than 0 (see the lower limit module LOWMON1), the minimum value is determined by the following steps: Figure 2As shown), the pulse module ONESHOT=500ms is triggered, which serves as the switching condition for the switching module TRANSFER1. The Y-path is turned on, and the assignment module AVALGEN1=0 outputs. This output value is multiplied by the output value of the minimum value MIN module.

[0016] The significance of the minimum value logic is as follows: when the measured value is less than the set value and the deviation value is less than 0, the minimum value MIN is cleared to zero. After the pulse module ONESHOT=500ms is triggered, the switching module TRANSFER1 turns on N channels, and the assignment module AVALGEN2=1 outputs. This output value is multiplied by the output value of the MIN module (minimum value module) in the multiplication module MULTIPLY1 to form the minimum value. This minimum value is then used as one of the inputs of the MIN module and is taken as the smaller of the real-time differential value of the other input (the output of the adder SUM2). This achieves the minimum value logic scheme with a clearing function.

[0017] The function of the minimum value logic is to reset the minimum value to zero before the measured value of the controlled operating parameter falls within the valid positive range. Figure 3 Point ⑤, when the differential action equals 0, as... Figure 3 At point ⑥, when the differential action is less than 0, the minimum value in the interval between point ⑥ and point ② is equal to the real-time differential value.

[0018] When correcting the differential action, the minimum value of the multiplication module MULTIPLY1 is multiplied by the assignment module AVALGEN3=0.5 in the multiplication module MULTIPLY2 to form a 1 / 2 minimum value, thus obtaining the differential feedforward curve, as shown below. Figure 3 As shown, in the interval between point ① and point ②, the real-time differential value is equal to the minimum value, the difference of SUM3 is 0, the HIGHMON3 module is greater than 0 and will not be triggered, the triggering condition of the AND module is not met, the N-way conduction of the switching module TRANSFER2 is turned on, and the real-time differential value is output.

[0019] Step 3: When the differential output drops to the minimum value of this cycle, control the differential action to quickly decay to 1 / 2 of the minimum value; Figure 3 In the process, starting from point ②, after the differential output drops to the minimum value of this cycle, it is triggered by the AND module under the following conditions: the real-time differential value is greater than the minimum value, the difference of SUM3 is greater than 0, and the HIGHMON3 module is greater than 0. The second trigger condition is that the difference between the 1 / 2 minimum value of the multiplication module MULTIPLY2 output and the real-time differential value at SUM4 is greater than 0. When both of these trigger conditions are met, the Y-path of the switching module TRANSFER2 is turned on, and the 1 / 2 minimum value curve is output. This situation continues until the end of point ③.

[0020] Step 4: After the derivative action stabilizes to this value, restore the original derivative control output logic and continue to adjust until the controlled variable deviation returns to zero and the parameter returns to stability, then cut off the derivative adjustment action.

[0021] Figure 3 In the middle, starting from point ③, the real-time differential value is equal to the minimum value, the difference of the adder module SUM3 is 0, the high limit module HIGHMON3 is greater than 0 and will not be triggered, the trigger condition of the AND module is not met, the N-way conduction of the switching module TRANSFER2 is turned on, and the real-time differential value is output. This situation continues until point ④ ends, and the differential action is cut off. When the HIGHMON1 module is greater than 0, it indicates that the measured value is in the valid positive value range. This serves as the switching condition for the TRANSFER3 switching module. The Y-channel is turned on, and the output of the TRANSFER2 switching module enters the Y-channel. At this time, the differential correction action is engaged. The difference between the differential action and PIDout is calculated in the adder SUM5 to form the actuator instruction. When the HIGHMON1 module is less than 0, it indicates that the measured value is in the non-valid positive value range, and the differential action is deactivated.

[0022] This enables precise, on-demand input and dynamic correction of differential action, fundamentally solving the problems of overshoot and system oscillation caused by differential control, and effectively improving the adjustment accuracy and operational stability of the automatic control system under varying operating conditions of thermal power units.

[0023] Example 1 The specific implementation of the steps described above in this invention is as follows: Step 1: Monitor the measured values ​​of the controlled operating parameters of the unit in real time and determine whether the parameters are within the valid positive value range; Step 2: If the measured value of the controlled parameter is positive, determine that the system is in a dynamic adjustment process, engage the derivative adjustment action, and record the minimum value of the derivative action in the current adjustment cycle in real time. Step 3: When the differential output drops to the minimum value of this cycle, control the differential action to quickly decay to 1 / 2 of the minimum value; Step 4: After the derivative action stabilizes to this value, restore the original derivative control output logic and continue to adjust until the controlled variable deviation returns to zero and the parameter returns to stability, then cut off the derivative adjustment action.

[0024] In this embodiment, the measured values ​​of the controlled operating parameters fluctuate around the set value by a constant amplitude due to a mismatch in the module's PID parameters. This result is consistent with... Figure 4 The corresponding display.

[0025] Figure 4 This is a curve showing the equal amplitude fluctuation between the actual measured value and the set value at the production site.

[0026] Example 2 The specific implementation of the steps described above in this invention is as follows: Step 1: Monitor the measured values ​​of the controlled operating parameters of the unit in real time and determine whether the parameters are within the valid positive value range; Step 2: If the measured value of the controlled parameter is positive, determine that the system is in a dynamic adjustment process, engage the derivative adjustment action, and record the minimum value of the derivative action in the current adjustment cycle in real time. Step 3: When the differential output drops to the minimum value of this cycle, control the differential action to quickly decay to 1 / 2 of the minimum value; Step 4: After the derivative action stabilizes to this value, restore the original derivative control output logic and continue to adjust until the controlled variable deviation returns to zero and the parameter returns to stability, then cut off the derivative adjustment action.

[0027] The conventional solution involves using the deviation between the actual field measurement and the setpoint, applying the lag effect of the LEADLAG function (lead=0, lag=x, where x is set according to the object being measured, typically 5~30), to form a conventional differential action in SUM2. This result is consistent with... Figure 5 The corresponding display.

[0028] Figure 5 This is the differential action curve formed based on the controlled variable.

[0029] Example 3 The specific implementation of the steps described above in this invention is as follows: Step 1: Monitor the measured values ​​of the controlled operating parameters of the unit in real time and determine whether the parameters are within the valid positive value range; Step 2: If the measured value of the controlled parameter is positive, determine that the system is in a dynamic adjustment process, engage the derivative adjustment action, and record the minimum value of the derivative action in the current adjustment cycle in real time. Step 3: When the differential output drops to the minimum value of this cycle, control the differential action to quickly decay to 1 / 2 of the minimum value; Step 4: After the derivative action stabilizes to this value, restore the original derivative control output logic and continue to adjust until the controlled variable deviation returns to zero and the parameter returns to stability, then cut off the derivative adjustment action.

[0030] In this embodiment, when the deviation between the actual measured value and the set value is greater than 0, it indicates that the measured value is in the valid positive value range, the condition that HIGHMON1 is greater than 0 is met, the output is 1, and the condition for differential action to be engaged is met. This result is consistent with... Figure 6 The corresponding display.

[0031] Figure 6 For the measured value to be within the positive effective interval curve, the differential action input condition is satisfied.

[0032] Example 4 The specific implementation of the steps described above in this invention is as follows: Step 1: Monitor the measured values ​​of the controlled operating parameters of the unit in real time and determine whether the parameters are within the valid positive value range; Step 2: If the measured value of the controlled parameter is positive, determine that the system is in a dynamic adjustment process, engage the derivative adjustment action, and record the minimum value of the derivative action in the current adjustment cycle in real time. Step 3: When the differential output drops to the minimum value of this cycle, control the differential action to quickly decay to 1 / 2 of the minimum value; Step 4: After the derivative action stabilizes to this value, restore the original derivative control output logic and continue to adjust until the controlled variable deviation returns to zero and the parameter returns to stability, then cut off the derivative adjustment action.

[0033] In this embodiment, when the deviation between the actual measured value and the set value is less than 0, and the condition that LOWMON1 is less than 0 is met, the output is 1, and the pulse module emits a pulse of ONESHOT=500ms with a value of 1. During this period... The switching condition for the switching module TRANSFER1 is that the Y-path is on, the assignment module AVALGEN1 outputs 0, and this output value is multiplied by the output value of the minimum value module MIN, resulting in 0. This 0 value is then used as one of the inputs to the minimum value module MIN and its real-time differential value (the output of adder SUM2) is taken as the smaller value. Therefore, the minimum value is switched to 0. When the pulse module ONESHOT ends after 500ms, the switching module TRANSFER1's N-path is on, the assignment module AVALGEN2 outputs 1, and this output value is multiplied by the output value of the minimum value module MIN in the multiplication module MULTIPLY1 to form the minimum value. This achieves a minimum value logic scheme with a clearing function. This result is consistent with... Figure 7 The corresponding display.

[0034] Figure 7 These are the curves for the minimum value of the differential and the minimum value of the half-differential.

[0035] Example 5 The specific implementation of the steps described above in this invention is as follows: Step 1: Monitor the measured values ​​of the controlled operating parameters of the unit in real time and determine whether the parameters are within the valid positive value range; Step 2: If the measured value of the controlled parameter is positive, determine that the system is in a dynamic adjustment process, engage the derivative adjustment action, and record the minimum value of the derivative action in the current adjustment cycle in real time. Step 3: When the differential output drops to the minimum value of this cycle, control the differential action to quickly decay to 1 / 2 of the minimum value; Step 4: After the derivative action stabilizes to this value, restore the original derivative control output logic and continue to adjust until the controlled variable deviation returns to zero and the parameter returns to stability, then cut off the derivative adjustment action.

[0036] like Figure 8 It can be seen that during the period when the pulse module emits a pulse of ONESHOT=500ms (1), the minimum value output is switched from its original minimum value to 0. After the pulse module emits ONESHOT=500ms and the pulse disappears, this minimum value of 0 is reversed and compared with the input real-time differential value in the minimum value module's MIN logic judgment. Since the real-time differential value is positive, the minimum value remains 0, and the 1 / 2 minimum value also remains 0. When point ⑥ is reached, the input real-time differential value begins to be less than 0, and the minimum value is equal to the real-time differential value, showing the same curve, continuing until point ②. After point ②, the minimum value remains unchanged. This result is consistent with... Figure 8 The corresponding display.

[0037] Figure 8 These are the differential curve, the differential minimum curve, and the 1 / 2 differential minimum curve.

[0038] Example 6 The specific implementation of the steps described above in this invention is as follows: Step 1: Monitor the measured values ​​of the controlled operating parameters of the unit in real time and determine whether the parameters are within the valid positive value range; Step 2: If the measured value of the controlled parameter is positive, determine that the system is in a dynamic adjustment process, engage the derivative adjustment action, and record the minimum value of the derivative action in the current adjustment cycle in real time. Step 3: When the differential output drops to the minimum value of this cycle, control the differential action to quickly decay to 1 / 2 of the minimum value; Step 4: After the derivative action stabilizes to this value, restore the original derivative control output logic and continue to adjust until the controlled variable deviation returns to zero and the parameter returns to stability, then cut off the derivative adjustment action.

[0039] Figure 9 For a curve where the measured value is positive and within the effective positive range, the differential action condition is met. The correction differential moves from 0 → differential value → 1 / 2 differential minimum value → differential value. Due to the effect of the correction differential, the measured value quickly converges and adjusts to near the set value, achieving the control effect. This result is consistent with... Figure 9 The corresponding display.

Claims

1. An automatic control method for correcting differential action, characterized in that, Follow these steps: Step 1: Monitor the measured values ​​of the controlled operating parameters of the unit in real time and determine whether the parameters are within the valid positive value range; Step 2: If the measured value of the controlled parameter is positive, determine that the system is in a dynamic adjustment process, engage the derivative adjustment action, and record the minimum value of the derivative action in the current adjustment cycle in real time. Step 3: When the differential output drops to the minimum value of this cycle, control the differential action to quickly decay to 1 / 2 of the minimum value; Step 4: After the derivative action stabilizes to this value, restore the original derivative control output logic and continue to adjust until the controlled variable deviation returns to zero and the parameter returns to stability, then cut off the derivative adjustment action.

2. The automatic control method for correcting differential action according to claim 1, characterized in that, In step 1, the specific process is as follows: The difference between the measured value and the set value is obtained by adding the SUM1. When the HIGHMON1 module is greater than 0, it means that the measured value is above the set value, and the parameter is judged to be in the valid positive value range. When the HIGHMON1 module is less than 0, it means that the measured value is below the set value, which meets the switching condition of the TRANSFER3 module. N channels are turned on, the assignment module AVALGEN5 is set to 0, and the parameter is judged to be in the non-valid positive value range.

3. The automatic control method for correcting differential action according to claim 1, characterized in that, Step 2, the specific process is as follows: When the measured value is different from the set value by adder SUM1, the difference is then compared with the difference between the LEADLAG module and adder SUM2, forming a differential action. When the HIGHMON1 module is greater than 0, the measured value is determined to be positive and within the valid positive value range. This serves as the switching condition for the TRANSFER3 module, and the Y-path is turned on. At this time, the differential action is engaged. Using the output of adder SUM2 as the differential action, it enters the minimum value MIN module: when the deviation is less than 0, that is, the lower limit module LOWMON1 is less than 0, the pulse module ONESHOT=500ms is triggered, which serves as the switching condition for the switching module TRANSFER1. The Y-path is turned on, and the assignment module AVALGEN1=0 is output. This output value is multiplied by the output value of the minimum value MIN module.

4. The automatic control method for correcting differential action according to claim 3, characterized in that, The specific process is as follows: When the differential action is corrected, the minimum value of the multiplication module MULTIPLY1 is multiplied by the assignment module AVALGEN3=0.5 in the multiplication module MULTIPLY2 to form 1 / 2 of the minimum value, thus obtaining the differential feedforward curve. The real-time differential value is equal to the minimum value, the difference of SUM3 is 0, the high limit module HIGHMON3 is greater than 0 and will not be triggered, the triggering condition of the AND module is not met, the N-way conduction of the switching module TRANSFER2 is turned on, and the real-time differential value is output.

5. The automatic control method for correcting differential action according to claim 4, characterized in that, The logical meaning of the minimum value is as follows: when the measured value is less than the set value and the deviation value is less than 0, the minimum value MIN is cleared to zero. After the pulse module ONESHOT=500ms is triggered, the switching module TRANSFER1 turns on N channels, and the assignment module AVALGEN2=1 outputs. This output value is multiplied by the output value of the MIN module in the multiplication module MULTIPLY1 to form the minimum value. This minimum value is then used as one of the inputs of the MIN module and is the smaller of the output of the real-time differential value adder SUM2.

6. The automatic control method for correcting differential action according to claim 1, characterized in that, Step 3, the specific process is as follows: After the differential output drops to the minimum value of this cycle, it triggers the AND module under the following conditions: the real-time differential value is greater than the minimum value, the difference of SUM3 is greater than 0, and the HIGHMON3 module is greater than 0. Under the following conditions: the difference between the 1 / 2 minimum value of the multiplication module MULTIPLY2 output and the real-time differential value at SUM4 is greater than 0. When both of these conditions are met, the Y-path of the switching module TRANSFER2 is turned on, and the 1 / 2 minimum value curve is output.

7. The automatic control method for correcting differential action according to claim 1, characterized in that, Step 4, the specific process is as follows: When the real-time differential value equals the minimum value, the difference in adder module SUM3 is 0, the high limit module HIGHMON3 is greater than 0 and will not trigger, the trigger condition of AND module AND is not met, the N-way conduction of switching module TRANSFER2 is turned on, the real-time differential value is output, and the differential action is cut off.

8. The automatic control method for correcting differential action according to claim 1, characterized in that, Step 4, the specific process is as follows: When the HIGHMON1 module is greater than 0, it indicates that the measured value is in the valid positive value range. This serves as the switching condition for the TRANSFER3 switching module. The Y-channel is turned on, and the output of the TRANSFER2 switching module enters the Y-channel. At this time, the differential correction action is engaged. The difference between the differential action and PIDout is calculated in the adder SUM5 to form the actuator instruction. When the HIGHMON1 module is less than 0, it indicates that the measured value is in the non-valid positive value range, and the differential action is deactivated.

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