Automatic control method and system for thermal power plant parallel equipment
By combining PID closed-loop control and open-loop step adjustment, the problem of declining regulation performance of parallel equipment in thermal power plants after aging was solved, achieving stable operation of the equipment and efficient control of the system, and reducing maintenance costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 内蒙古聚达发电有限责任公司
- Filing Date
- 2026-03-16
- Publication Date
- 2026-05-12
AI Technical Summary
The PID closed-loop control of existing parallel equipment in thermal power plants suffers from decreased regulation performance after equipment aging, leading to hysteresis, overshoot, and oscillation, which affects system stability and economy.
A control method combining PID closed-loop control of the first regulating valve and open-loop step adjustment of the second regulating valve is adopted. By monitoring the opening degree of the first regulating valve, the second regulating valve is used to perform open-loop step adjustment within a preset range to maintain the stability of the controlled variable.
It improves the quality of equipment regulation, reduces the risk of equipment failure and downtime, enhances system stability and economic benefits, while reducing maintenance costs, and has flexibility and promotional value.
Smart Images
Figure CN122018284A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of thermal power plant equipment control technology, specifically to an automatic control method and system for parallel equipment in a thermal power plant. Background Technology
[0002] In thermal power plants, parallel equipment (such as multiple feedwater pumps, forced draft and induced draft fans, high-pressure / low-pressure heat exchangers, circulating water pumps, etc.) is a core component of the thermal and auxiliary systems. The core objective of automatic control of this type of equipment is to achieve "balanced load distribution, fault redundancy switching, and stable and efficient system operation," thereby avoiding system fluctuations caused by overload or insufficient output of a single piece of equipment.
[0003] Currently, the widely adopted technology is the Distributed Control System (DCS) hierarchical control: the system distributes the load evenly to each parallel device based on the total demand (such as boiler feedwater and furnace air volume) and the rated capacity or efficiency characteristics of each device, avoiding long-term full-load operation (shortened lifespan) or low-load operation (low efficiency) of a single device. Its control architecture is typically "total load command issued → local control layer (single device adjustment)" to achieve multi-device collaboration. For example, after the central control layer issues a command of "total air volume 80,000 m³ / h", the local layer automatically allocates 40,000 m³ / h output to each fan based on the rated capacity ratio of the two fans and adjusts the fan speed.
[0004] While existing methods are relatively mature in generating and distributing total load commands, they typically still rely on traditional PID closed-loop control after the command is issued to individual devices. However, as equipment operates for extended periods and ages, its dynamic characteristics often change, leading to decreased regulation performance and problems such as hysteresis, overshoot, or oscillation. Continuing to use a fixed-parameter PID control strategy not only makes precise regulation difficult but may also exacerbate equipment and system fluctuations, affecting overall operational stability and economy. Summary of the Invention
[0005] To address the problems existing in the background technology, this invention proposes an automatic control method and system for parallel equipment in thermal power plants, which improves the regulation quality of individual equipment and ensures the reliability and efficiency of the parallel equipment system under complex operating conditions.
[0006] To achieve the above objectives, the present invention adopts the following solution: An automatic control method for parallel equipment in a thermal power plant, applied to a system that jointly regulates the same controlled variable through a first regulating valve and a second regulating valve, includes the following: the first regulating valve adopts a closed-loop control mode, adjusting based on the deviation between the set value and the actual value of the controlled variable; monitoring the opening degree of the first regulating valve; when the opening degree of the first regulating valve is lower than a preset first threshold or higher than a preset second threshold, performing an open-loop step adjustment on the second regulating valve to change the controlled variable; the change in the controlled variable, through the closed-loop control loop of the first regulating valve, reverses the adjustment of the opening degree of the first regulating valve, causing it to return to the preset range formed by the first threshold and the second threshold.
[0007] Optionally, the open-loop step adjustment of the second regulating valve includes: when the opening degree of the first regulating valve is lower than the first threshold, decreasing the opening degree command of the second regulating valve by a preset step size; when the opening degree of the first regulating valve is higher than the second threshold, increasing the opening degree command of the second regulating valve by a preset step size.
[0008] Optionally, the preset step size is a fixed step size of 2% of the opening change.
[0009] Optionally, after each open-loop step adjustment, a preset waiting time is maintained until the adjusted quantity and the opening response of the first regulating valve stabilize. Then, it is determined again whether the opening of the first regulating valve is still outside the preset range. If so, the next step adjustment is performed.
[0010] Optionally, the preset waiting time is 60 seconds.
[0011] Optionally, a minimum opening limit is set for the second regulating valve, the minimum opening limit value being determined based on the unit's operating load.
[0012] Optionally, the relationship between the unit's operating load and the minimum opening limit value is determined through a preset correspondence, or obtained through interpolation when the load changes.
[0013] Optionally, it also includes interlocking control logic: when the first regulating valve is put into automatic mode, the regulating function of the second regulating valve is forced to be put into automatic mode; when the second regulating valve is switched to manual mode, the first regulating valve is forced to be switched to manual mode.
[0014] An automatic control system for parallel equipment in a thermal power plant includes a first regulating module, a status monitoring module, a second regulating module, a minimum opening protection module, an interlocking control module, and an anomaly handling module. The first adjustment module includes a PID controller and a first regulating valve, used to implement closed-loop control of the first regulating valve, so that it adjusts based on the deviation between the set value and the actual value of the controlled variable; the status monitoring module is electrically connected to the detection mechanism of the first regulating valve, used to monitor the opening degree of the first regulating valve in real time; the second adjustment module is electrically connected to the status monitoring module and the actuator of the second regulating valve respectively, used to perform open-loop step adjustment of the second regulating valve when the opening degree of the first regulating valve is lower than a first threshold or higher than a second threshold; The minimum opening protection module is electrically connected to the second regulating module and the unit load respectively; it is used to forcibly limit the output command to the minimum opening when the regulating command output by the second regulating module is less than the preset minimum opening and generate an alarm signal. The interlocking control module is electrically connected to the first regulating module and the second regulating module respectively, and is used to realize the signal interlocking of the first regulating valve and the second regulating valve; The anomaly handling module is electrically connected to the status monitoring module, the first adjustment module, and the second adjustment module, and is used to monitor abnormal situations in real time. The change in the controlled quantity is reversed through the closed-loop control circuit of the first regulating valve to adjust the opening of the first regulating valve, so that it returns to the preset range formed by the first threshold and the second threshold.
[0015] Optionally, the second regulating module performs open-loop step adjustment in the following manner: when the opening degree of the first regulating valve is lower than the first threshold, the opening degree command of the second regulating valve is reduced by a preset step size; when the opening degree of the first regulating valve is higher than the second threshold, the opening degree command of the second regulating valve is increased by a preset step size.
[0016] The beneficial effects of this invention are as follows: This method solves the problem that when one of the parallel equipment experiences deterioration in characteristics and reduced regulation performance due to long-term operation, using fixed-parameter PID closed-loop control often results in problems such as hysteresis, increased overshoot, and aggravated oscillation. This solution introduces an open-loop stepping-based regulation method, allowing the second regulating valve to perform range correction, thus constraining the degraded first regulating valve to operate within a range of good regulation characteristics. This ensures stable operation of the overall system, reduces the risk of downtime due to valve failure, and has significant economic benefits.
[0017] Secondly, this method uses an open-loop stepping mode to control the second regulating valve, which eliminates the need for complex models and large-scale modifications to the existing DCS system, saving manpower and resources and reducing maintenance costs. At the same time, the interlocking logic and minimum opening protection settings fully consider the on-site operational safety requirements, avoid human error caused by complex control logic, and ensure the reliability and efficiency of the parallel equipment system under complex operating conditions.
[0018] In addition, for different equipment, this solution only needs to readjust the preset range, step parameters and minimum opening correspondence according to the actual characteristics. The method itself does not need to be changed and can be promoted and applied in other systems such as thermal systems or auxiliary systems, which has flexibility and good promotion value. Attached Figure Description
[0019] Figure 1 This is a flowchart of the automatic control method for parallel equipment in a thermal power plant in the implementation of the present invention; Figure 2 This is a flowchart of the PID closed-loop control method used in the first regulating valve in this embodiment of the invention; Figure 3 This is a flowchart of the open-loop stepping control method used in the second regulating valve in this embodiment of the invention. Detailed Implementation
[0020] To make the present invention clearer and more understandable, the present invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the given embodiments are only one implementation method and do not represent all embodiments.
[0021] Example 1 Combination Figure 1 This invention provides an automatic control method for parallel equipment in a thermal power plant, aiming to improve the regulation quality of individual equipment and ensure the reliability and efficiency of the parallel equipment system under complex operating conditions. The automatic control method is applied to a system that jointly regulates the same controlled variable through a first regulating valve and a second regulating valve.
[0022] like Figure 2 As shown, the first regulating valve adopts a PID closed-loop control method; as Figure 3 As shown, the second regulating valve employs open-loop stepping control logic. The method includes the following steps: Step 1: The first regulating valve performs PID control based on the deviation between the setpoint and the actual value of the controlled variable. The setpoint is generated in real time by the upper-level control system according to the unit load command. The PID controller outputs control commands to the first regulating valve, causing its opening change to track the setpoint, thereby maintaining the stability of the controlled variable.
[0023] Step 2: Real-time acquisition of the opening signal of the first regulating valve to determine whether it is within a preset regulating range. In this embodiment, the preset range is greater than or equal to 30% and less than or equal to 60%, that is, the first threshold is 30% and the second threshold is 60%. It should be noted that this range is determined based on the characteristics of the first regulating valve and is not a unique range. Within this range, the first regulating valve has good regulating performance.
[0024] Step 3: If the opening of the first regulating valve is less than 30%, reduce the control command of the second regulating valve by 2% every 1 minute; wait 60 seconds after execution to allow the system response to stabilize, then return to Step 2 to reassess the opening of the first regulating valve. If it is still less than 30%, repeat this step until the opening rises to above 30%. Step 4: If the opening of the second regulating valve is greater than 60%, increase the control command of the second regulating valve by 2% every 1 minute; wait 60 seconds after execution to allow the system response to stabilize, then return to Step 2 to reassess the opening of the first regulating valve. If it is still greater than 60%, repeat this step until the opening falls below 60%. Step 5: To prevent the second regulating valve from being closed too narrowly and affecting system safety, a minimum opening limit is set. The minimum opening value is determined based on the unit's operating load, and the corresponding relationship used in this embodiment is shown in Table 1: Table 1 Correspondence
[0025] When the unit load falls between two adjacent points in the table, interpolation can be used to calculate the corresponding minimum opening. During the step adjustment process, if the calculated second regulating valve command is lower than the minimum opening corresponding to the current load, the command will take the minimum opening value and an alarm will be issued.
[0026] In addition, the interlocking control logic of the automatic control method includes: when the first regulating valve is put into automatic mode, the step adjustment function of the second regulating valve is forcibly put into automatic mode; when the second regulating valve is switched to manual mode, the first regulating valve is forcibly switched to manual mode.
[0027] Furthermore, if the second regulating valve has reached its minimum or full opening limit after continuous adjustment, and still cannot bring the first regulating valve back to the set normal opening range (i.e., the preset range), then automatic adjustment will stop and an alarm will be issued.
[0028] In summary, the above methods solve the problem of parallel equipment control under the background of equipment aging. Without increasing hardware investment or affecting the main system, they optimize the operating range of key equipment, extend the life of equipment, improve system stability, and reduce maintenance costs.
[0029] Example 2 This embodiment provides an automatic control system for parallel equipment in a thermal power plant, used to implement the control method in Embodiment 1. The automatic control system includes a first adjustment module, a status monitoring module, a second adjustment module, a minimum opening protection module, an interlocking control module, and an anomaly handling module.
[0030] The first regulating module includes a PID controller and a first regulating valve. The input of the PID controller is connected to the setpoint signal and the actual value feedback signal of the controlled variable, and the output is electrically connected to the actuator of the first regulating valve. The PID controller calculates the opening command in real time based on the deviation and performs closed-loop control on the first regulating valve.
[0031] The status monitoring module is electrically connected to the detection mechanism of the first regulating valve, and is used to collect the opening signal of the first regulating valve in real time and output the opening value to the second regulating module and the anomaly handling module.
[0032] The second adjustment module is electrically connected to the status monitoring module and the actuator of the second regulating valve, respectively, and is used to perform open-loop step adjustment according to the opening degree of the first regulating valve. The second adjustment module includes a step logic module and a timing module. Further, the step adjustment method includes: when the opening degree of the first regulating valve is less than 30%, the step logic module generates a decrease command by a preset step size of 2%, closing the second regulating valve; when the opening degree of the first regulating valve is greater than 60%, an increase command is generated by a preset step size of 2%, opening the second regulating valve. After each adjustment, the timing module is triggered to count down for 60 seconds. After the timing module expires, the latest opening degree from the status monitoring module is reread to determine whether further adjustment is needed.
[0033] The minimum opening protection module is electrically connected to the second regulating module and the unit load. When the command generated by the second regulating module is lower than the minimum opening, the minimum opening protection module will forcibly limit the output command to the minimum opening and issue an alarm signal.
[0034] The interlocking control module is electrically connected to the first regulating module and the second regulating module respectively to realize signal interlocking: when the first regulating valve is detected to be in automatic mode, the control mode of the second regulating module is automatically switched to automatic, that is, the step logic is enabled; when the second regulating valve is detected to be manually switched to manual mode, the control mode of the first regulating valve is also forced to switch to manual mode immediately.
[0035] The anomaly handling module is electrically connected to the status monitoring module, the first adjustment module, and the second adjustment module to monitor abnormal situations in real time. If the opening of the first adjustment valve still cannot return to the 30%~60% range after continuous adjustment by the second adjustment module, and the second adjustment valve has reached the minimum opening or full opening limit, the adjustment will stop and an alarm will be issued.
[0036] The above system does not require the establishment of complex models or large-scale modification of existing DCS systems, saving manpower and material resources, reducing maintenance costs, and the system can be promoted and applied in other systems such as thermal systems or auxiliary systems by simply retuning the preset intervals, step parameters and minimum opening correspondences, which has flexibility and good promotion value.
[0037] The specific embodiments of the present invention have been described in detail above with reference to the figures, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.
Claims
1. An automatic control method for parallel equipment in a thermal power plant, applied to a system in which the same controlled variable is jointly adjusted by a first regulating valve and a second regulating valve, characterized in that, The first regulating valve adopts a closed-loop control method, and adjusts based on the deviation between the set value and the actual value of the controlled variable; The opening degree of the first regulating valve is monitored; when the opening degree of the first regulating valve is lower than a preset first threshold or higher than a preset second threshold, an open-loop step adjustment is performed on the second regulating valve to change the controlled quantity; the change of the controlled quantity is reversed through the closed-loop control loop of the first regulating valve to adjust the opening degree of the first regulating valve in the opposite direction, so that it returns to the preset range formed by the first threshold and the second threshold.
2. The automatic control method for parallel equipment in a thermal power plant according to claim 1, characterized in that: The open-loop step adjustment of the second regulating valve includes: when the opening degree of the first regulating valve is lower than the first threshold, decreasing the opening degree command of the second regulating valve by a preset step size; when the opening degree of the first regulating valve is higher than the second threshold, increasing the opening degree command of the second regulating valve by a preset step size.
3. The automatic control method for parallel equipment in a thermal power plant according to claim 2, characterized in that: The preset step size is a fixed step size of 2% of the opening change.
4. The automatic control method for parallel equipment in a thermal power plant according to claim 1, characterized in that: After each open-loop step adjustment is performed, a preset waiting time is maintained until the adjusted quantity and the opening response of the first regulating valve stabilize. Then, it is determined again whether the opening of the first regulating valve is still outside the preset range. If so, the next step adjustment is performed.
5. The automatic control method for parallel equipment in a thermal power plant according to claim 4, characterized in that: The preset waiting time is 60 seconds.
6. The automatic control method for parallel equipment in a thermal power plant according to claim 1, characterized in that, Also includes: A minimum opening limit is set for the second regulating valve, and the minimum opening limit value is determined according to the unit's operating load.
7. The automatic control method for parallel equipment in a thermal power plant according to claim 6, characterized in that: The relationship between the unit's operating load and the minimum opening limit is determined by a preset correspondence, or obtained by interpolation when the load changes.
8. The automatic control method for parallel equipment in a thermal power plant according to claim 1, characterized in that, It also includes interlocking control logic: when the first regulating valve is put into automatic mode, the regulating function of the second regulating valve is forced to be put into automatic mode; when the second regulating valve is switched to manual mode, the first regulating valve is forced to be switched to manual mode.
9. An automatic control system for parallel equipment in a thermal power plant, used to implement the control method described in any one of steps 1-8, characterized in that: It includes a first adjustment module, a status monitoring module, a second adjustment module, a minimum opening protection module, an interlocking control module, and an anomaly handling module; The first adjustment module includes a PID controller and a first regulating valve, used to implement closed-loop control of the first regulating valve, so that it adjusts based on the deviation between the set value and the actual value of the controlled variable; the status monitoring module is electrically connected to the detection mechanism of the first regulating valve, used to monitor the opening degree of the first regulating valve in real time; the second adjustment module is electrically connected to the status monitoring module and the actuator of the second regulating valve respectively, used to perform open-loop step adjustment of the second regulating valve when the opening degree of the first regulating valve is lower than a first threshold or higher than a second threshold; The minimum opening protection module is electrically connected to the second regulating module and the unit load respectively; it is used to forcibly limit the output command to the minimum opening when the regulating command output by the second regulating module is less than the preset minimum opening and generate an alarm signal. The interlocking control module is electrically connected to the first regulating module and the second regulating module respectively, and is used to realize the signal interlocking of the first regulating valve and the second regulating valve; The anomaly handling module is electrically connected to the status monitoring module, the first adjustment module, and the second adjustment module, and is used to monitor abnormal situations in real time. The change in the controlled quantity is reversed through the closed-loop control circuit of the first regulating valve to adjust the opening of the first regulating valve, so that it returns to the preset range formed by the first threshold and the second threshold.
10. An automatic control system for parallel equipment in a thermal power plant, characterized in that: The second adjustment module performs open-loop step adjustment in the following ways: when the opening degree of the first adjustment valve is lower than the first threshold, the opening degree command of the second adjustment valve is reduced by a preset step size; when the opening degree of the first adjustment valve is higher than the second threshold, the opening degree command of the second adjustment valve is increased by a preset step size.