Control system and method for load distribution of parallel compressor units

Abstract

The present invention discloses a control system and method for load distribution of parallel compressor units, and relates to the field of industrial automation control. The calculation results can be used to determine whether the actual operating states of each unit are the same, and the main controller controls the corresponding sub-controller to ensure the load balance of each unit. The system includes: a main controller, which is used to determine the target operating point and target surge point corresponding to each unit, and calculate the first target slope from each target operating point to the corresponding operating curve origin, and the second target slope from each target surge point to the operating curve origin, determine the slope ratio of the second target slope to the first target slope, compare multiple slope ratios, generate a comparison result, and if the comparison result indicates that the multiple slope ratios are inconsistent, the main controller sends a load balance instruction to the sub-controller to perform load distribution control; the sub-controller calls the performance controller and anti-surge controller of the unit for conventional control.

Description

Technical Field

[0001] The present invention relates to the field of industrial automation control, and in particular to a control system and method for load distribution of parallel compressor units. Background Art

[0002] With the continuous development of industrial automation control technology, equipment such as compressors have emerged. Compressors are important equipment in the production process of industrial enterprises. Sometimes, in order to meet the fluctuations of process loads, such as seasonal changes from winter to summer, planned adjustments to oil and gas field production, etc., multiple units need to be operated in parallel.

[0003] In related technologies, most of them use the equal surge margin method to balance the operating conditions of multiple units to ensure that the compressor units operate under the same load. Among them, the surge margin is the main indicator to measure the surge performance of the compressor, which is directly related to the stability of the compressor.

[0004] However, for multiple different units, the equal surge margin method cannot truly reflect whether the actual operating status of each unit is the same, which can easily cause the compressor to enter a surge state, shut down, or even damage the equipment. It can also cause the compressors to not operate at the same performance level and the operating load to be unbalanced, causing some units to enter the surge zone prematurely or some units to enter the surge zone with a delay. Summary of the invention

[0005] In view of this, the present application provides a control system and method for load distribution of parallel compressor units. The main purpose is to solve the technical problem that the equal surge margin method cannot truly reflect whether the actual operating status of each unit is the same, which may easily cause the compressor to enter a surge state, shut down, or even damage the equipment.

[0006] According to a first aspect of the present invention, there is provided a control system for load distribution of parallel compressor units, the system comprising: a main controller, a sub-controller;

[0007] The main controller is used to read the operation curves of multiple units, determine the target operation point and target surge point corresponding to each of the units, and calculate a first target slope from each of the target operation points to the corresponding operation curve origin, and a second target slope from each of the target surge points to the operation curve origin, determine a slope ratio of the second target slope to the first target slope, obtain a plurality of slope ratios, compare the plurality of slope ratios, generate a comparison result, and if the comparison result indicates that the plurality of slope ratios are inconsistent, the main controller sends a load balancing instruction to the sub-controller to perform load distribution control;

[0008] The sub-controller, in response to the load balancing instruction sent by the main controller, calls the performance controller and anti-surge controller of the unit to perform conventional control.

[0009] Optionally, the system further comprises: a performance control valve;

[0010] The main controller is configured to send a load balancing instruction to the sub-controller if the comparison result indicates that the multiple slope ratios are inconsistent, and the sub-controller performs performance control on the compressor unit through proportional integral derivative PID control;

[0011] The sub-controller, in response to the load balancing instruction sent by the main controller and based on the performance control requirement sent by the main controller, operates the corresponding performance control valve to move the target operating point of the compressor group to a specified position;

[0012] The performance control valve is used to adjust the speed or inlet throttling according to the operation instruction sent by the sub-controller.

[0013] Optionally, the sub-controller is used to maintain performance control and keep the operating state by using the branch pipe instrument measurement value if the comparison result indicates that the multiple slope ratios are consistent.

[0014] Optionally, the system further comprises: an anti-surge valve;

[0015] The anti-surge valve is used to prevent the compressor unit from entering the surge zone, and upon receiving the adjustment signal from the sub-controller, controls the compressor unit to avoid the surge danger zone before the target operating point reaches the specified position.

[0016] Optionally, the main controller includes: a load performance control module and a load balancing control module;

[0017] The load performance control module is used to control the performance indicators of the plurality of units to meet the overall process requirements;

[0018] The load balancing control module is used to determine whether a balance state is reached between the plurality of units.

[0019] According to a second aspect of the present invention, a method for controlling load distribution of parallel compressor sets is provided, the method comprising:

[0020] The main controller reads the operation curves of the multiple units and determines the target operation point and the target surge point corresponding to each of the units;

[0021] The main controller calculates a first target slope from each of the target operating points to the corresponding origin of the operating curve, and a second target slope from each of the target surge points to the origin of the operating curve, determines a slope ratio of the second target slope to the first target slope, obtains a plurality of slope ratios, compares the plurality of slope ratios, and generates a comparison result;

[0022] If the comparison result indicates that the multiple slope ratios are inconsistent, the main controller sends a load balancing instruction to the sub-controller to perform load distribution control;

[0023] The sub-controller, in response to the load balancing instruction sent by the main controller, calls the performance controller and anti-surge controller of the compressor unit to perform conventional control.

[0024] Optionally, the method further comprises:

[0025] Detecting the inlet pressure and the outlet pressure of the compressor unit;

[0026] When it is detected that the inlet pressure is in a depressurized state or the outlet pressure is in an overpressure state, the anti-surge valve selects an opening time according to a corresponding preset value so as to achieve an energy-saving effect.

[0027] Optionally, the method further comprises:

[0028] Obtaining a main measurement variable of the main controller or the sub-controller, and determining whether the main measurement variable is valid;

[0029] If the main measured variable is valid, the main controller or the sub-controller performs PID control based on the main measured variable to maintain the operating state of the compressor unit;

[0030] If the main measurement variable fails, the main controller or the sub-controller executes a replacement strategy, selects a loop signal where a preset replacement variable indicated by a preset replacement relationship is located, and replaces the main measurement variable.

[0031] Optionally, the method further comprises:

[0032] When the main controller fails, the sub-controller switches to a single-machine control state and maintains operation according to the respective set values; or,

[0033] When the main controller fails, the compressor unit executes a backup strategy and calls the backup main controller to achieve continuous control of load distribution.

[0034] According to a third aspect of the present invention, there is provided a control cabinet having a computer program stored thereon, wherein the control cabinet comprises an external independent control cabinet and a system control cabinet, wherein the external independent control cabinet and the system control cabinet are arranged side by side, and the computer program is arranged in the external independent control cabinet, or integrated in the PLC of the system control cabinet, and when the computer program is executed, the control method for load distribution of the above-mentioned parallel compressor groups is implemented.

[0035] The present invention provides a control system and method for load distribution of parallel compressor sets. The main controller reads the operation curves of multiple sets to determine the target operation point and target surge point corresponding to each set. Then, the first target slope from each target operation point to the corresponding operation curve origin and the second target slope from each target surge point to the operation curve origin are calculated, and the slope ratio of the second target slope to the first target slope is determined to obtain multiple slope ratios. The multiple slope ratios are compared to generate a comparison result. If the comparison result indicates that the multiple slope ratios are inconsistent, the main controller sends a load balancing instruction to the sub-controller to perform load distribution control. Finally, the sub-controller responds to the load balancing instruction sent by the main controller and calls the performance controller and anti-surge controller of the compressor set for conventional control. The curve of each set is read by the algorithm built into the main controller, and calculation is performed after reading. Then, the actual operation status of each set is determined by the calculation result, that is, whether it is running under the same load. If the operating loads of multiple sets are inconsistent, the main controller controls the corresponding sub-controller to ensure the load balance of each set.

[0036] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0038] Figure 1A A schematic diagram showing the composition of another control system for load distribution of parallel compressor units provided by an embodiment of the present invention;

[0039] Figure 1B A schematic diagram of distribution signals of another control system for load distribution of parallel compressor units provided by an embodiment of the present invention is shown;

[0040] Figure 1CA schematic diagram showing the composition of another control system for load distribution of parallel compressor units provided by an embodiment of the present invention;

[0041] Figure 2 A flow chart of a method for controlling load distribution of parallel compressor sets provided in an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0042] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0043] This embodiment provides a control system for load distribution of parallel compressor units, in which the main controller reads the operating curves of multiple units to determine the target operating point and target surge point corresponding to each unit. Then, the first target slope from each target operating point to the origin of the corresponding operating curve and the second target slope from each target surge point to the origin of the operating curve are calculated, and the slope ratio of the second target slope to the first target slope is determined to obtain multiple slope ratios. The multiple slope ratios are compared to generate a comparison result. If the comparison result indicates that the multiple slope ratios are inconsistent, the main controller sends a load balancing instruction to the sub-controller to perform load distribution control. Finally, the sub-controller responds to the load balancing instruction sent by the main controller and calls the performance controller and anti-surge controller of the compressor unit for conventional control. The curve of each unit is read by the algorithm built into the main controller, and calculations are performed after reading. Then, the actual operating status of each unit is determined by the calculation results, that is, whether it is running under the same load. If the operating loads of multiple units are inconsistent, the main controller controls the corresponding sub-controller to ensure that the loads of each unit are balanced, such as Figure 1A As shown in FIG. 1 , the control system for load distribution of the parallel compressor units includes: a main controller 21 and a sub-controller 22. Taking the parallel connection of two units A and B as an example, if the load distribution signal of the two units in parallel is detailed Figure 1BAs shown, it includes a process inlet main pipe (Suction), an inter-stage gasification main pipe (Induction), and a process outlet main pipe (discharge). Unit function cabinet A, unit function cabinet B, unit A, and unit B. Among them, unit control cabinet A includes an inlet anti-surge controller (Inlet anti-surge controller), an inlet master controller (Inlet master control), an inlet slave controller (Inlet slave controller), an inter-stage gasification anti-surge controller (Induction anti-surgecontroller), an inter-stage gasification master controller (Induction master control), an inter-stage gasification sub-controller (Induction slave controller), and an inter-stage performance controller (Induction performancecontroller). Unit control cabinet B includes an inlet anti-surge controller, an inlet sub-controller, an inlet performance controller, an inter-stage gasification anti-surge controller, an inter-stage gasification sub-controller, and an inter-stage performance controller. Units A and B are connected to the corresponding unit control cabinets respectively.

[0044] The main controller 21 reads the operation curves of multiple units, determines the target operation point and target surge point corresponding to each unit, and calculates the first target slope from each target operation point to the corresponding operation curve origin, and the second target slope from each target surge point to the operation curve origin. Determine the slope ratio of the second target slope to the first target slope, obtain multiple slope ratios, compare the multiple slope ratios, and generate a comparison result. If the comparison result indicates that the multiple slope ratios are inconsistent, the main controller sends a load balance instruction to the sub-controller for load distribution control. In order to realize the real-time transmission of load distribution data, the controller executes a tracking strategy, that is, a strategy that is always in a "hot standby" state. Specifically, the main controller 21 executes load distribution control, performs proportional integral differential PID control, outputs to the sub-controller 22 for performance control, and sends a load balance instruction to the sub-controller 22. In fact, the load distribution control is mainly implemented by two internal control modules: a load performance control module, which is used to control the performance indicators of multiple units to meet the overall process requirements, and a load balance control module, which is used to determine whether a balance state is reached between multiple units.

[0045] The sub-controller 22, in response to the load balancing instruction sent by the main controller, calls the performance controller and anti-surge controller of the compressor unit to perform routine control. Specifically, in response to the load balancing instruction sent by the main controller 21, based on the performance control requirements sent by the main controller 21, the corresponding performance control valve is operated to move the target operating point of the unit to the specified position. The performance control valve performs speed adjustment or inlet throttling adjustment according to the operating instructions sent by the sub-controller. Furthermore, if the comparison result indicates that multiple slope ratios are consistent, the sub-controller 22 performs automatic PID control using the performance control loop according to the preset logic to always maintain the compressor performance to meet the requirements and maintain the operating state. The specific interface between the main controller and the sub-controller, such as Figure 1C As shown, it includes, HIC manual control; PLC (Programmable logic controller); PI (pressure indicate), PIC pressure indication control; PY pressure control actuator; PV pressure control valve; ZI valve position feedback indication; ZIT valve position indication transmitter; Inductionprocess GAS inter-stage aeration process gas.

[0046] In addition, during the actual operation, when the main measured variable of the main controller 21 or the sub-controller 22 fails, the main controller or the sub-controller executes the replacement strategy, selects the loop signal of the preset replacement variable indicated by the preset replacement relationship, and replaces the main measured variable. When the outlet pressure of the unit is overpressure or the inlet pressure is underpressure, it can be opened in advance or delayed according to the preset value, wherein the advance or delay of the opening time of the anti-surge valve can be achieved by artificially setting means through the UCP control cabinet / OWS operation station / EWS engineer station. The delay or advance time should be able to meet the working conditions. When the main controller 21 fails, the sub-controller 22 switches to the single-machine control state, maintains operation according to the set value, or realizes continuous control of load distribution through the backup controller without causing any impact. The number of backup main controllers in the backup strategy is at least 1 and at most n-1. For example, if there are 5 units in total, the backup strategy of control can be realized with a maximum of four and a minimum of one main controller. Based on the real-time data transmission of the tracking strategy and the reasonable configuration of the backup strategy, the switching action under the failure state is realized.

[0047] In one embodiment, Figure 2As shown, a control method for load distribution of parallel compressor sets based on a control system for load distribution of parallel compressor sets is provided, wherein the main controller reads the operation curves of multiple sets to determine the target operation point and target surge point corresponding to each set. Then, the first target slope from each target operation point to the origin of the corresponding operation curve and the second target slope from each target surge point to the origin of the operation curve are calculated, and the slope ratio of the second target slope to the first target slope is determined to obtain multiple slope ratios, and the multiple slope ratios are compared to generate a comparison result. If the comparison result indicates that the multiple slope ratios are inconsistent, the main controller sends a load balancing instruction to the sub-controller to perform load distribution control. Finally, the sub-controller responds to the load balancing instruction sent by the main controller and calls the performance controller and anti-surge controller of the compressor set for conventional control. The curve of each set is read by the algorithm built into the main controller, and calculation is performed after reading. Then, the actual operation status of each set is determined by the calculation result, that is, whether it is running under the same load. If the operating loads of multiple sets are inconsistent, the main controller controls the corresponding sub-controller to ensure the load balance of each set. The method comprises the following steps:

[0048] 201. The main controller reads the operating curves of multiple units and determines the target operating point and target surge point corresponding to each unit.

[0049] Among them, the main controller is the controller that controls all units to achieve load balance and meet performance standards. In each unit, as long as it is the main controller, it is used to uniformly control and coordinate all units. The built-in algorithm of the main controller will read the data of the curve of each unit and determine the target operating point corresponding to each unit. It should be noted that the compressor operating curve is a two-dimensional curve. The target operating point refers to the operating point on the operating curve, which represents the instantaneous operating state of the compressor. An operating point contains multiple parameters such as flow, pressure, composition, speed, power, etc. Any different parameters will result in different operating points on the operating curve. Furthermore, the main controller identifies the operating curve of each unit and finally obtains multiple target operating points, that is, each unit corresponds to a target operating point.

[0050] 202. The main controller calculates a first target slope from each target operating point to the corresponding operating curve origin, and a second target slope from each target surge point to the operating curve origin, determines a slope ratio of the second target slope to the first target slope, obtains multiple slope ratios, compares the multiple slope ratios, and generates a comparison result.

[0051] Furthermore, the present application provides a new type of calculation method, namely the slope proportional method. The ratio of the slope k1 of the line connecting the operating point to the origin to the slope k2 of the line connecting the surge point to the origin is used to determine whether each unit is operating under the same load. The slope proportional method can be directly applied to the judgment between different units, is not limited by the operating conditions, and can achieve accurate judgment when facing different units. Specifically, the main controller calculates the first target slope from each target operating point to the corresponding origin of the operating curve, and the second target slope from each target surge point to the origin of the operating curve, determines the slope ratio of the second target slope to the first target slope, and obtains multiple slope ratios. Then, multiple slope ratios are compared to generate a comparison result. For example, when load distribution is performed on two different units, under the same operating condition, the second target slope from the surge point to the origin of unit A is Ks0, and the first target slope from the operating point to the origin is Kn0; the second target slope from the surge point to the origin of unit B is Ks0', and the first target slope from the operating point to the origin is Kn0', then Ks0 / Kn0=Ks0' / Kn0'.

[0052] 203. If the comparison result indicates that the multiple slope ratios are inconsistent, the main controller sends a balanced load instruction to the sub-controller to perform load distribution control. The sub-controller responds to the balanced load instruction sent by the main controller and calls the performance controller and anti-surge controller of the compressor unit to perform conventional control.

[0053] In an embodiment of the present application, if the comparison result indicates that the slope values ​​of multiple target slopes are inconsistent, it means that the units are not operating under the same load. At this time, the main controller sends a load balancing instruction to the sub-controller to perform load distribution control.

[0054] Specifically, if the comparison result indicates that the values ​​of multiple target slopes are inconsistent, the load distribution control is put into use, and the main controller performs proportional integral differential PID control, and outputs it to the sub-controller for performance control, such as controlling the final actuator in the loop, adjusting the speed or changing the valve position, etc. It should be noted that the sub-controller can be an inlet sub-controller, an inter-stage gasification sub-controller, an anti-surge controller, etc. In the actual application process, the sub-controller that the main controller needs to operate in order to balance the load can be called a sub-controller, and the present application does not specifically limit the model and function of the sub-controller. Further, the main controller sends a balanced load instruction to the sub-controller for anti-surge control. The sub-controller responds to the balanced load instruction sent by the main controller, and based on the performance control requirements sent by the main controller, operates the corresponding performance control valve to move the target operating point of the unit to the specified position. In addition, if the comparison result indicates that the slope values ​​of multiple target slopes are consistent, the load distribution control is offline, and the sub-controllers perform performance control functions separately. Specifically, the sub-controller uses the performance control loop to perform automatic PID control according to the preset logic, and always maintains the compressor performance to meet the requirements and maintains the operating state. When the main controller performs load distribution, it needs to rely on two internal control modules, namely the load performance control module and the load balance control module. The load performance control module mainly realizes that the performance indicators of each unit meet the overall process requirements, and the load balance control module mainly realizes whether the units are in a balanced state. It includes the five-coordinate parameters required for anti-surge, the set points for performance control, and some surge over-limit, separation and other diagnoses, with complete coverage.

[0055] Furthermore, in the face of different numbers of units, different overall performance of the units, different standby rates of the unit main controllers, etc., the present application provides a variety of control strategies to ensure stable operation of the system.

[0056] In the actual application process, the main measured variable of the main controller or the sub-controller is obtained to determine whether the main measured variable is valid. Whether it is the load distribution main controller or the sub-controller, a replacement strategy can be adopted to set 1-2 additional replacement variables as a replacement solution when the main performance fails. For example, the value obtained by the original system comes from the measured pressure of the main pipe, and now it is changed to the pressure measured from the branch pipe or other positions. Among them, the main performance refers to the overall process performance control index, generally with the inlet or outlet pressure and flow rate of the compressor main pipe network as the measurement variable. The replacement variable refers to other instrument measurement values ​​that can replace the main measurement variable when the main measurement variable fails. When the main performance fails, the controller will select the signal of the loop where the replacement variable is located according to the established logic. If the main measurement variable is valid, the main controller or sub-controller performs PID control based on the main measurement variable to maintain the operating state of the compressor unit. If the main measurement variable fails, the main controller or sub-controller executes the replacement strategy, selects the loop signal where the preset replacement variable indicated by the preset replacement relationship is located, and replaces the main measurement variable.

[0057] After a failure occurs in the transmitter, communication circuit, controller power supply, etc., a fallback strategy can be adopted, that is, another processing method is used to replace the failed method as a protection method. For example, when the instrument is redundantly configured, the two-out-of-two logic is often used, and after one of the instruments fails, the strategy will become one-out-of-one logic, using the fallback strategy to achieve the stability of safety protection.

[0058] When the outlet pressure of the compressor unit is overpressured or the inlet pressure is underpressured, if the boundary strategy is in effect, the anti-surge valve may be selectively opened in advance or delayed according to the preset value to ensure that the adjustment behavior of the compressor will not affect the upstream and downstream pipelines. In fact, the advance or delay of the opening time of the anti-surge valve can be achieved through the UCP control cabinet / OWS operation station / EWS engineer station by artificially setting means to achieve early or delayed opening. The delay or advance time should be able to meet the working conditions, for example, 2-3 seconds in advance for unstable or low-frequency abnormal conditions. Under stable conditions, the delay time should be as long as possible before the surge line is not triggered, usually 10 seconds. In addition, when the load distribution main controller is powered off or the communication fails, the sub-controller cannot receive the signal sent by the main controller, and the sub-controller will switch to the single-machine control state. In this state, the sub-controller does not receive any signals from other sub-controllers, and only maintains operation according to their own set values. In other words, each unit will maintain the main control variable unchanged, but because there is no signal exchange between the units, the state of each unit will be different.

[0059] In actual operation, it is difficult to simultaneously meet the requirements of no process fluctuations and safe and stable operation of the compressor. In the face of this situation, the fault buffer strategy will confirm with the operation and maintenance personnel and implement a new treatment method. The core idea is to prevent unnecessary waste caused by process fluctuations and give the operator time to decide the optimal solution. This strategy will minimize the impact of process fluctuations and improve safety and economy. For example, when the system detects inlet pressure fluctuations, there will be an input premise-before the new instruction arrives, no related actions are performed and the timing starts, and the action will not start until the preset time is reached. In this way, there is sufficient time to receive the new strategy. The new treatment method utilizes the unit safety margin but does not affect the unit safety, does not stop the machine, and continues to meet the process, production and other processes to improve economy.

[0060] Through the description of the above implementation methods, those skilled in the art can clearly understand that the present application can be implemented by hardware, or by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of the present application can be embodied in the form of a software product, which can be stored in a control cabinet. Specifically, the control cabinet includes an external independent control cabinet and a system control cabinet, wherein the external independent control cabinet and the system control cabinet are arranged side by side, and the computer program of the software product can be arranged in the external independent control cabinet, or integrated in the PLC of the system control cabinet to execute the methods described in each implementation scenario of the present application.

[0061] Those skilled in the art will appreciate that the accompanying drawings are merely schematic diagrams of a preferred implementation scenario, and the modules or processes in the accompanying drawings are not necessarily required for implementing the present application.

[0062] Those skilled in the art will appreciate that the modules in the device in the implementation scenario can be distributed in the device in the implementation scenario according to the implementation scenario description, or can be changed accordingly and located in one or more devices different from the implementation scenario. The modules in the above implementation scenario can be combined into one module, or can be further split into multiple sub-modules.

[0063] The above application serial numbers are for description only and do not represent the advantages or disadvantages of the implementation scenarios.

[0064] The above disclosure only discloses several specific implementation scenarios of the present application. However, the present application is not limited thereto, and any changes that can be conceived by technicians in this field should fall within the scope of protection of the present application.

Claims

1. A control system for load distribution of parallel compressor units, characterized in that: The system comprises: a main controller and a sub-controller; The main controller is used to read the operation curves of multiple units, determine the target operation point and target surge point corresponding to each of the units, and calculate a first target slope from each of the target operation points to the corresponding operation curve origin, and a second target slope from each of the target surge points to the operation curve origin, determine a slope ratio of the second target slope to the first target slope, obtain a plurality of slope ratios, compare the plurality of slope ratios, generate a comparison result, and if the comparison result indicates that the plurality of slope ratios are inconsistent, the main controller sends a load balancing instruction to the sub-controller to perform load distribution control; The sub-controller, in response to the load balancing instruction sent by the main controller, calls the performance controller and anti-surge controller of the compressor unit to perform conventional control.

2. The control system for load distribution of parallel compressor units according to claim 1, characterized in that: The system also includes: a performance control valve; The main controller is configured to send a load balancing instruction to the sub-controller if the comparison result indicates that the multiple slope ratios are inconsistent, and the sub-controller performs performance control on the compressor unit through proportional integral derivative PID control; The sub-controller, in response to the load balancing instruction sent by the main controller and based on the performance control requirement sent by the main controller, operates the corresponding performance control valve to move the target operating point of the compressor group to a specified position; The performance control valve is used to adjust the speed or inlet throttling according to the operation instruction sent by the sub-controller.

3. The control system for load distribution of parallel compressor units according to claim 1, characterized in that: The sub-controller is used to perform automatic PID control using a performance control loop according to a preset logic if the comparison result indicates that the multiple slope ratios are consistent, so as to always maintain the compressor performance to meet the requirements and maintain the operating state.

4. The control system for load distribution of parallel compressor units according to claim 1, characterized in that: The system further comprises: an anti-surge valve; The anti-surge valve is used to prevent the compressor unit from entering the surge zone, and upon receiving the adjustment signal from the sub-controller, controls the compressor unit to avoid the surge danger zone before the target operating point reaches the specified position.

5. The control system for load distribution of parallel compressor units according to claim 1, characterized in that: The main controller includes: a load performance control module and a load balancing control module; The load performance control module is used to control the performance indicators of the plurality of units to meet the overall process requirements; The load balancing control module is used to determine whether a balance state is reached between the plurality of units.

6. A method for controlling load distribution of parallel compressor sets based on a control system for load distribution of parallel compressor sets, characterized in that: include: The main controller reads the operation curves of the multiple units and determines the target operation point and the target surge point corresponding to each of the units; The main controller calculates a first target slope from each of the target operating points to the corresponding origin of the operating curve, and a second target slope from each of the target surge points to the origin of the operating curve, determines a slope ratio of the second target slope to the first target slope, obtains a plurality of slope ratios, compares the plurality of slope ratios, and generates a comparison result; If the comparison result indicates that the multiple slope ratios are inconsistent, the main controller sends a load balancing instruction to the sub-controller to perform load distribution control; The sub-controller, in response to the load balancing instruction sent by the main controller, calls the performance controller and anti-surge controller of the compressor unit to perform conventional control.

7. The method according to claim 6, characterized in that The method further comprises: Detecting the inlet pressure and the outlet pressure of the compressor unit; When it is detected that the inlet pressure is in a depressurized state or the outlet pressure is in an overpressure state, the anti-surge valve selects an opening time according to a corresponding preset value so as to achieve an energy-saving effect.

8. The method according to claim 6, characterized in that The method further comprises: Obtaining a main measurement variable of the main controller or the sub-controller, and determining whether the main measurement variable is valid; If the main measured variable is valid, the main controller or the sub-controller performs PID control based on the main measured variable to maintain the operating state of the compressor unit; If the main measurement variable fails, the main controller or the sub-controller executes a replacement strategy, selects a loop signal where a preset replacement variable indicated by a preset replacement relationship is located, and replaces the main measurement variable.

9. The method according to claim 6, characterized in that The method further comprises: When the main controller fails, the sub-controller switches to a single-machine control state and maintains operation according to the respective set values; or, When the main controller fails, the compressor unit executes a backup strategy and calls the backup main controller to achieve continuous control of load distribution.

10. A control cabinet having a computer program stored thereon, characterized in that: The control cabinet includes an external independent control cabinet and a system control cabinet, wherein the external independent control cabinet and the system control cabinet are arranged side by side, and the computer program is arranged in the external independent control cabinet, or integrated in the PLC of the system control cabinet, and when the computer program is executed, the steps of the method described in any one of claims 6 to 9 are implemented.

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