Universal energy-saving and stable air supply control method for air compression system of iron and steel plant

Abstract

The invention relates to the technical field of steel plant air compression, and discloses a steel plant air compression system universal energy-saving and stable air supply control method which comprises the following steps that S1, the total air consumption demand Q of a steel plant compressed air pipe network is monitored in real time; s2, executing a load segmentation control strategy based on the total gas consumption demand Q; s3, loading and unloading operation of the power frequency air compressor and rotation speed adjustment of the variable frequency air compressor are controlled in a coordinated mode through a central energy-saving control unit; and S4, a pressure buffer tank is arranged on an output pipeline of the variable-frequency air compressor and used for stabilizing the pressure of the pipe network. The total air consumption demand Q is divided into two sections, the power frequency machine is started and stopped according to the N + 1 principle, and the frequency converter is supplemented for continuous quantity supplement, so that the system can operate only with the minimum necessary unit in any load scene, energy waste caused by over-start and over-stop in a traditional scheme is avoided, and overall reduction of compressed air production energy consumption is realized.

Description

Technical Field

[0001] This invention relates to the field of compressed air technology in steel plants, specifically to a universal energy-saving and stable air supply control method for compressed air systems in steel plants. Background Technology

[0002] In the steel production process, the air compressor system is a key power source that provides compressed air to various production equipment. Its energy consumption accounts for a considerable proportion of the total energy consumption of steel plants. The traditional control method of air compressor system in steel plants has many drawbacks, which seriously affect energy utilization efficiency and corporate economic benefits.

[0003] A search revealed Chinese patent CN108361186A, which discloses an optimization method for an air compressor system in a steel plant. Based on historical data, it establishes a compressed air pressure and flow demand model for each user; it reads real-time compressed air data from each user and optimizes the compressed air pressure and flow demand model accordingly, setting a pressure setpoint for the compressed air pipeline network. This invention employs cluster optimization, enabling scientific start-up, shutdown, and loading / unloading operations for air compressors, achieving precise control of the compressed air pipeline network pressure, reducing the pressure level of the compressed air pipeline network, and decreasing energy consumption.

[0004] However, the traditional solutions mentioned above mostly adopt a relatively extensive control mode. When faced with different gas demand, they lack precise load segmentation and coordinated operation mechanisms. For example, in low-load scenarios, it is difficult to meet large gas demand if only a single frequency converter is used. Furthermore, unreasonable start-up and shutdown methods not only waste energy but also frequently impact equipment and shorten its service life. Based on this, the present invention designs a universal energy-saving and stable gas supply control method for air compressor systems in steel plants to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a universal energy-saving and stable air supply control method for air compressor systems in steel plants, which solves the problem of lack of precise load segmentation and coordinated operation mechanism in the background technology.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A universal energy-saving and stable air supply control method for air compressor systems in steel plants includes the following steps:

[0008] Step S1: Monitor the total air consumption demand Q of the compressed air pipeline network in the steel plant in real time;

[0009] Step S2, based on the total gas consumption demand Q, execute the load segmentation control strategy:

[0010] When Q≤V1, only the variable frequency air compressor is started, and the formula is followed. The speed of the variable frequency air compressor is adjusted to match the air demand; where V1 is the maximum air output of the variable frequency air compressor.

[0011] When Q > V1, calculate the starting base N of the industrial frequency air compressor and actually start K = N + 1 industrial frequency air compressors; where V2 is the rated air output of a single industrial frequency air compressor.

[0012] Calculate the remaining gas demand Qr. ;

[0013] Start the variable frequency air compressor and follow the formula. Adjust its rotation speed to replenish the remaining gas demand;

[0014] Step S3: The loading and unloading operations of the industrial frequency air compressor and the speed adjustment of the variable frequency air compressor are coordinated and controlled by the central energy-saving control unit.

[0015] Step S4: Install a pressure buffer tank on the output pipeline of the variable frequency air compressor to stabilize the pipeline pressure.

[0016] Preferably, in the load segmentation control strategy:

[0017] The range of the remaining gas demand Qr is 0-V1;

[0018] When V1 < Q ≤ V2, K = 1;

[0019] When V2 < Q ≤ (V1 + V2), K = 2;

[0020] When (V1+V2)<Q≤(2×V2), K=2;

[0021] When (2×V2)<Q≤(2×V2+V1), K=3; and so on.

[0022] Preferably, the central energy-saving control unit performs the following operations:

[0023] Step S31: Real-time acquisition of pipeline pressure, flow signals, and air compressor unit operating status signals;

[0024] Step S32: Calculate the total gas consumption demand Q based on the collected signals;

[0025] Step S33: Execute the load segmentation control strategy according to Q to generate start / stop commands for the power frequency air compressor and speed setpoints for the variable frequency air compressor;

[0026] Step S34: Select the industrial frequency air compressor to be started or stopped based on the preset priority rules. The priority rules are used to balance the cumulative running time or number of start-stop cycles of multiple industrial frequency air compressors.

[0027] Preferably, the volume V of the pressure buffer tank satisfies the following condition:

[0028] ;

[0029] Where: Qmax is the maximum allowable instantaneous gas consumption fluctuation value of the system, ΔQmax≤V1;

[0030] T is the maximum pressure recovery time set by the system.

[0031] ΔP is the maximum allowable fluctuation amplitude of pipeline pressure in the system.

[0032] Preferably, the industrial frequency air compressor is a centrifugal air compressor; the variable frequency air compressor is a screw air compressor.

[0033] Preferably, the system is configured with one variable frequency screw air compressor with a maximum air output V1 of 7,560 m³. 3 / h; The system is configured with multiple industrial frequency centrifugal air compressors, and the rated air output V2 of each compressor is 15,000 m³ / h. 3 / h.

[0034] When Q ≤ 7560 m³ / h, the control unit only sends a start command to the variable frequency screw air compressor. At the same time, the module M3 outputs a speed setpoint that is linearly proportional to Q, so that the variable frequency compressor runs at a speed of (Q / 7560) × 100%, thereby accurately matching the air consumption within the continuous adjustment range of 0% to 100%. During this stage, all industrial frequency centrifugal air compressors remain in a stopped or unloaded state to avoid ineffective energy consumption.

[0035] When Q > 7560 m3 / h, module M3 first calculates the starting base N of the power frequency generator and generates a starting sequence of K = N + 1 power frequency generators; then it calculates the remaining gas demand Qr = Q - N × 15000 and sends a speed command of (Qr / 7560) × 100% to the frequency converter to achieve accurate compensation of Qr by the frequency converter.

[0036] Preferably, the central energy-saving control unit is an ES360 energy-saving control unit; the ES360 energy-saving control unit includes:

[0037] Module M1, the data acquisition module, is used to collect pipeline pressure, flow rate, and unit operating status in real time;

[0038] Module M2, the module load calculation module, is used to calculate the gas consumption Q in real time based on the collected data and determine the load segment;

[0039] Module M3, the unit scheduling module, is used to execute the N+1 start-up logic and inverter compensation calculation, and generate start-stop commands for the power frequency generator and the inverter speed setpoint.

[0040] Module M4, the fault self-diagnosis module, automatically starts the standby fixed-frequency air compressor or adjusts the speed setting value of the variable-frequency air compressor according to the priority rules when any operating air compressor fault is detected, and issues an alarm signal.

[0041] Preferably, the central energy-saving control unit interacts with the factory's existing DCS and PLC systems via a communication interface.

[0042] Preferably, when the pipeline pressure exceeds the set upper limit Pmax + 0.02 MPa for a continuous period of Δt, the central energy-saving control unit executes an unloading sequence that first reduces pressure and then stops.

[0043] Step A: First, reduce the speed of the variable frequency air compressor to the minimum allowable speed;

[0044] Step B: If the pressure is still higher than the upper limit, unload one industrial frequency air compressor in sequence according to the priority rules.

[0045] Step C: Repeat steps A and B until the pressure returns to the target range, thereby avoiding a sudden drop in pressure caused by the simultaneous unloading of multiple power frequency machines.

[0046] Preferably, when the pipeline pressure is continuously lower than the set lower limit Pmin - 0.02 MPa for a period of Δt, the central energy-saving control unit executes a loading sequence of first raising and then starting:

[0047] Step a: First, increase the speed of the variable frequency air compressor to 100%;

[0048] Step b: If the pressure is still below the lower limit, start the next industrial frequency air compressor according to the N+1 principle.

[0049] Step c: Repeat steps a and b until the pressure returns to the target range, thereby suppressing instantaneous pressure fluctuations to within 0.02 MPa.

[0050] As shown by the above technical solution, when the pipeline pressure exceeds the set upper limit Pmax + 0.02MPa for a continuous time interval Δt, module M3 executes a "reduce first, then stop" unloading sequence: first, the variable frequency drive speed is reduced to the minimum allowable value; if the pressure still does not return to the target range, the fixed frequency drive with the longest cumulative running time is unloaded according to the priority rules, and the above steps are repeated until the pressure returns to the target range. This tiered unloading strategy effectively avoids a sudden drop in pipeline pressure caused by the simultaneous unloading of multiple fixed frequency drives.

[0051] When the pipeline pressure is lower than the set lower limit Pmin - 0.02MPa for a continuous Δt time, module M3 executes the "rise first, start later" loading sequence: first, the speed of the inverter is increased to 100%; if the pressure still does not rise back to the target range, the next industrial frequency machine with the shortest cumulative running time is started according to the N+1 principle, and the above steps are repeated until the pressure is restored, ensuring that the instantaneous pressure fluctuation is always ≤0.02MPa.

[0052] The core of this invention lies in constructing a three-in-one control system integrating precise load segmentation, variable frequency and mains frequency complementary linkage, and active pressure suppression. It precisely matches the start-up and shutdown baseline of the mains frequency generator using the N+1 principle, and accurately compensates for the remaining gas volume Qr using the continuous stepless adjustment characteristics of the variable frequency generator, ensuring efficient operation of the minimum necessary unit under any load and minimizing ineffective energy consumption. A pressure buffer tank absorbs instantaneous fluctuations, and combined with the unloading sequence of first reducing and then stopping and the loading sequence of first increasing and then starting executed by the central controller, it actively intervenes in pipeline pressure changes, strictly constraining pressure fluctuations within ±0.02MPa. The central controller also balances the operating load of the mains frequency generator through priority rules, significantly reducing the number of start-ups and shutdowns. The synergistic effect of these three systems achieves a significant reduction in the energy consumption of the compressed air system and an extension of equipment lifespan, while providing the extremely high gas supply stability necessary for steel production.

[0053] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0054] 1. This invention divides the total air demand Q into two segments and starts and stops the fixed frequency generator according to the N+1 principle, and then supplements it with the variable frequency generator for continuous replenishment. The system can operate with only the minimum necessary units under any load scenario, avoiding the energy waste caused by excessive start-stop in the traditional solution, and realizing an overall reduction in compressed air production energy consumption.

[0055] 2. In this invention, the central energy-saving control unit evenly allocates the start-stop tasks of each industrial frequency machine according to the priority rules of cumulative running time or number of start-stop times, so that the number of start-stop times of a single industrial frequency machine per day is reduced from more than 30 times in the traditional way to less than 5 times. This significantly reduces mechanical shock and electrical stress, reduces wear and tear of parts and the probability of failure, thereby extending the service life of the whole machine and reducing maintenance workload.

[0056] 3. In this invention, a pressure buffer tank with a volume that is precisely calculated based on the instantaneous air consumption fluctuation is configured at the outlet of the frequency converter. Combined with a two-way pressure suppression sequence of "first decrease and then stop, first increase and then start", the pressure fluctuation of the pipeline network is continuously constrained within the allowable range, eliminating the sudden rise or fall of pressure caused by sudden load changes, and providing a continuous and stable compressed air source for the steel production line. Attached Figure Description

[0057] Figure 1 This is the control flowchart of the present invention;

[0058] Figure 2 This is a working logic diagram of the central controller of the present invention;

[0059] Figure 3 This is a flowchart illustrating the pressure fluctuation suppression process of the present invention.

[0060] Figure 4 This is a diagram showing the structure and control relationship of the compressed air system of the present invention. Detailed Implementation

[0061] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] Example 1;

[0063] Please see Figures 1-4 In this embodiment of the invention, a universal energy-saving and stable air supply control method for an air compressor system in a steel plant includes the following steps:

[0064] Step S1: Monitor the total air consumption demand Q of the compressed air pipeline network in the steel plant in real time;

[0065] Step S2, based on the total gas demand Q, execute the load segmentation control strategy:

[0066] When Q≤V1, only the variable frequency air compressor is started, and the formula is followed. The speed of the variable frequency air compressor is adjusted to match the air demand; where V1 is the maximum air output of the variable frequency air compressor.

[0067] When Q > V1, calculate the starting base N of the industrial frequency air compressor and actually start K = N + 1 industrial frequency air compressors; where V2 is the rated air output of a single industrial frequency air compressor.

[0068] Calculate the remaining gas demand Qr. ;

[0069] Start the variable frequency air compressor and follow the formula. Adjust its speed to replenish the remaining gas demand;

[0070] Step S3: The loading and unloading operations of the industrial frequency air compressor and the speed adjustment of the variable frequency air compressor are coordinated and controlled by the central energy-saving control unit.

[0071] Step S4: Install a pressure buffer tank on the output pipeline of the variable frequency air compressor to stabilize the pipeline pressure.

[0072] In the load segmentation control strategy:

[0073] The range of remaining gas demand Qr is 0-V1;

[0074] When V1 < Q ≤ V2, K = 1;

[0075] When V2 < Q ≤ (V1 + V2), K = 2;

[0076] When (V1+V2)<Q≤(2×V2), K=2;

[0077] When (2×V2)<Q≤(2×V2+V1), K=3; and so on.

[0078] The central energy-saving control unit performs the following operations:

[0079] Step S31: Real-time acquisition of pipeline pressure, flow signals, and air compressor unit operating status signals;

[0080] Step S32: Calculate the total gas consumption demand Q based on the collected signals;

[0081] Step S33: Execute the load segmentation control strategy according to Q to generate start / stop commands for the industrial frequency air compressor and speed setpoints for the variable frequency air compressor;

[0082] Step S34: Select the industrial frequency air compressor to be started or stopped based on the preset priority rules. The priority rules are used to balance the cumulative running time or number of start-stop cycles of multiple industrial frequency air compressors.

[0083] The volume V of the pressure buffer tank satisfies the following condition:

[0084] ;

[0085] Where: Qmax is the maximum allowable instantaneous gas consumption fluctuation value of the system, ΔQmax≤V1;

[0086] T is the maximum pressure recovery time set by the system.

[0087] ΔP is the maximum allowable fluctuation amplitude of pipeline pressure in the system.

[0088] A fixed-frequency air compressor is a centrifugal air compressor; a variable-frequency air compressor is a screw air compressor.

[0089] The system is configured with one variable frequency screw air compressor with a maximum air output V1 of 7,560 m³. 3 / h; The system is configured with multiple industrial frequency centrifugal air compressors, and the rated air output V2 of each unit is 15,000 m³ / h. 3 / h.

[0090] The working principle of this invention is as follows: The total air consumption demand Q of the compressed air pipeline network is first collected in real time by flow sensors installed on the pipeline trunk line and simultaneously transmitted to the ES360 energy-saving control unit. The module M2 inside the control unit dynamically analyzes Q based on the received instantaneous flow data and the set algorithm, and assigns it to the corresponding load segment.

[0091] When Q≤7560m 3 At / h, the control unit only sends a start command to the variable frequency screw air compressor, and at the same time outputs a speed setpoint that is linearly proportional to Q through module M3, so that the variable frequency compressor runs at a speed of (Q / 7560)×100%, thereby accurately matching the air consumption within the continuous adjustment range of 0% to 100%; during this stage, all industrial frequency centrifugal air compressors remain in a stopped or unloaded state to avoid ineffective energy consumption.

[0092] When Q > 7560m 3 At / h, module M3 first calculates the starting base N of the power frequency machine and generates the starting sequence of K = N + 1 power frequency machines; then it calculates the remaining gas demand Qr = Q - N × 15000 and sends a speed command of (Qr / 7560) × 100% to the frequency converter to achieve accurate compensation of Qr by the frequency converter.

[0093] Throughout the process, the central energy-saving control unit continuously monitors the operating status of each unit through module M4. In the event of a unit failure, the backup frequency unit is immediately called up and reordered according to the rule of the shortest cumulative running time to ensure the continuity of gas supply. At the same time, the pressure buffer tank installed at the outlet of the frequency converter absorbs and releases instantaneous gas volume fluctuations through its volume V, so that the pressure fluctuation amplitude of the pipeline network is always suppressed within ±0.02MPa, thereby providing stable compressed air for downstream process equipment.

[0094] Example 2;

[0095] Please see Figures 1-4 In this embodiment of the invention, the central energy-saving control unit is an ES360 energy-saving control unit; the ES360 energy-saving control unit includes:

[0096] Module M1, the data acquisition module, is used to collect pipeline pressure, flow rate, and unit operating status in real time;

[0097] Module M2, the module load calculation module, is used to calculate the gas consumption Q in real time based on the collected data and determine the load segment;

[0098] Module M3, the unit scheduling module, is used to execute the N+1 start-up logic and inverter compensation calculation, and generate start-stop commands for the power frequency generator and inverter speed setpoints.

[0099] Module M4, the fault self-diagnosis module, automatically starts the standby fixed-frequency air compressor or adjusts the speed setting value of the variable-frequency air compressor according to the priority rules when any operating air compressor fault is detected, and issues an alarm signal.

[0100] The central energy-saving control unit interacts with the factory's existing DCS and PLC systems via a communication interface.

[0101] When the pipeline pressure exceeds the set upper limit Pmax + 0.02 MPa for a continuous period of Δt, the central energy-saving control unit executes an unloading sequence that first reduces pressure and then stops.

[0102] Step A: First, reduce the speed of the variable frequency air compressor to the minimum allowable speed;

[0103] Step B: If the pressure is still higher than the upper limit, unload one industrial frequency air compressor in sequence according to the priority rules.

[0104] Step C: Repeat steps A and B until the pressure returns to the target range, thereby avoiding a sudden drop in pressure caused by the simultaneous unloading of multiple power frequency machines.

[0105] When the pipeline pressure is continuously lower than the set lower limit Pmin - 0.02 MPa for a period of Δt, the central energy-saving control unit executes a loading sequence of first raising and then starting:

[0106] Step a: First, increase the speed of the variable frequency air compressor to 100%;

[0107] If the pressure is still below the lower limit in step b, start the next industrial frequency air compressor according to the N+1 principle;

[0108] Step c: Repeat steps a and b until the pressure returns to the target range, thereby suppressing instantaneous pressure fluctuations to within 0.02 MPa.

[0109] The working principle of this invention is as follows: the ES360 energy-saving control unit and the existing DCS and PLC systems of the steel plant are used to conduct bidirectional data interaction through a standard communication interface to achieve coordinated operation between the air compressor station layer and the plant control layer.

[0110] When the pipeline pressure exceeds the set upper limit Pmax + 0.02MPa for a continuous time interval Δt, module M3 executes a "reduce first, then stop" unloading sequence: first, the variable frequency drive speed is reduced to the minimum allowable value; if the pressure still does not return to the target range, the fixed frequency drive with the longest cumulative running time is unloaded according to priority rules, and the above steps are repeated until the pressure returns to the target range. This tiered unloading strategy effectively avoids a sudden drop in pipeline pressure caused by the simultaneous unloading of multiple fixed frequency drives.

[0111] When the pipeline pressure is lower than the set lower limit Pmin - 0.02MPa for a continuous Δt time, module M3 executes the "rise first, start later" loading sequence: first, the speed of the inverter is increased to 100%; if the pressure still does not rise back to the target range, the next industrial frequency machine with the shortest cumulative running time is started according to the N+1 principle, and the above steps are repeated until the pressure is restored, ensuring that the instantaneous pressure fluctuation is always ≤0.02MPa.

[0112] In addition, the pipeline pressure, flow rate and unit status signals collected in real time by module M1 are processed by module M2 and then synchronously sent to the DCS / PLC system through the communication interface, providing real-time decision-making basis for the plant's energy management system. At the same time, the DCS / PLC system can also issue new pressure settings or maintenance commands, and the ES360 unit will automatically adjust the control strategy accordingly to achieve cross-system collaborative optimization.

[0113] Example 3;

[0114] Please see Figures 1-4 Taking the No. 3 air compressor station of an oxygen plant in a steel company as a specific application scenario, the station was originally equipped with eight Atlas ZH15000 centrifugal air compressors, each with a rated air production capacity of 15,000 m³ / h. The original control system was a single-unit independent pressure control. In this embodiment, an Atlas ZR900 variable frequency screw air compressor with a maximum air production capacity of 7,560 m³ / h was added on site and connected to an ES360 energy-saving control unit. It achieves bidirectional data communication with the existing DCS system in the station through the Profinet interface.

[0115] During on-site operation, the ES360 unit obtains the total gas consumption demand Q in real time through the vortex flow meter installed at the main pipe outlet. When the measured Q is 5200 m³ / h, the control unit determines that the current load is in the "variable frequency motor only operation segment", instructs the variable frequency motor to run at 68.8% speed, and keeps all the fixed frequency motors shut down. The instantaneous power is reduced from 1870kW in the traditional solution to 820kW in the variable frequency motor. As the steelmaking pace accelerated, Q rapidly increased to 18400 m³ / h. The control unit immediately implemented a load segmentation strategy: first, it calculated N = ⌊18400 / 15000⌋ = 1, obtaining the starting base N = 1 for the power frequency chiller, and then started the two centrifuges with the shortest cumulative running time in sequence according to the principle of K = N + 1 = 2; subsequently, it calculated the remaining gas demand Qr = 18400 - 1 × 15000 = 3400 m³ / h, and issued a speed setting of 3400 / 7560 × 100% = 44.9% to the frequency converter to achieve precise replenishment. The entire loading process took 38 seconds, and the pipeline pressure fluctuation amplitude was controlled within 0.015 MPa.

[0116] When Q drops to 9800 m³ / h during the night shift, the ES360 unit follows the "reduce first, then stop" unloading sequence: first, the inverter speed is reduced to 30% of the minimum allowable value. Since the pipeline pressure is still higher than the set upper limit of 0.82 MPa, the line frequency machine with the longest cumulative running time is unloaded according to the priority rule. Then, the inverter speed is reduced to 65% to make up for the remaining demand. The entire unloading process takes 45 seconds, avoiding a sudden drop in pressure caused by the simultaneous shutdown of multiple line frequency machines.

[0117] After 30 days of continuous operation, the control method described in this application reduced the daily start-up and shutdown frequency of the power frequency generator from an average of 32 times to 4.2 times. The variable frequency generator operated continuously with an average daily speed of 64%, and based on an annual operating time of 8000 hours, the annual power consumption of the station decreased from 256 million kWh to 179.2 million kWh, resulting in electricity cost savings of approximately 4.61 million yuan. Simultaneously, the pipeline pressure stability improved from ±0.08 MPa to within ±0.02 MPa.

[0118] Working Principle: Taking the real-time acquired total compressed air demand Q of the pipeline network as the core input, the load segmentation control strategy precisely maps Q to the variable frequency-industrial frequency coordinated operation mode. Under the centralized scheduling of the ES360 energy-saving control unit, the variable frequency screw compressor undertakes continuous adjustment and fine compensation, while the industrial frequency centrifugal compressor performs staged start-stop and high-load support. The two complement each other to achieve on-demand air supply. At the same time, the pressure buffer tank and the bidirectional pressure suppression sequence of "lowering before stopping and raising before starting" work together to strictly control the pipeline pressure fluctuation within ±0.02 MPa. The control unit also uses priority rules to balance the cumulative running time or start-stop frequency of each industrial frequency compressor, and interacts with the factory's DCS / PLC system in real time through the communication interface to form a universal energy-saving and stable air supply control system for the air compressor system of the steel plant across levels.

[0119] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A universal energy-saving and stable air supply control method for air compressor systems in steel plants, characterized in that, Includes the following steps: Step S1: Monitor the total air consumption demand Q of the compressed air pipeline network in the steel plant in real time; Step S2, based on the total gas consumption demand Q, execute the load segmentation control strategy: When Q≤V1, only the variable frequency air compressor is started, and the formula is followed. The speed of the variable frequency air compressor is adjusted to match the air demand; where V1 is the maximum air output of the variable frequency air compressor. When Q > V1, according to Calculate the starting base N for the industrial frequency air compressor, and actually start K=N+1 industrial frequency air compressors; where V2 is the rated air output of a single industrial frequency air compressor; Calculate the remaining gas demand Qr. ; Start the variable frequency air compressor and follow the formula. Adjust its rotation speed to replenish the remaining gas demand; Step S3: The loading and unloading operations of the industrial frequency air compressor and the speed adjustment of the variable frequency air compressor are coordinated and controlled by the central energy-saving control unit. Step S4: Install a pressure buffer tank on the output pipeline of the variable frequency air compressor to stabilize the pipeline pressure.

2. The universal energy-saving and stable air supply control method for air compressor systems in steel plants according to claim 1, characterized in that, In the load segmentation control strategy: The range of the remaining gas demand Qr is 0-V1; When V1 < Q ≤ V2, K = 1; When V2 < Q ≤ (V1 + V2), K = 2; When (V1+V2)<Q≤(2×V2), K=2; When (2×V2)<Q≤(2×V2+V1), K=3.

3. The universal energy-saving and stable air supply control method for air compressor systems in steel plants according to claim 2, characterized in that, The central energy-saving control unit performs the following operations: Step S31: Real-time acquisition of pipeline pressure, flow signals, and air compressor unit operating status signals; Step S32: Calculate the total gas consumption demand Q based on the collected signals; Step S33: Execute the load segmentation control strategy according to Q to generate start / stop commands for the power frequency air compressor and speed setpoints for the variable frequency air compressor; Step S34: Select the industrial frequency air compressor to be started or stopped based on the preset priority rules. The priority rules are used to balance the cumulative running time or number of start-stop cycles of multiple industrial frequency air compressors.

4. The universal energy-saving and stable air supply control method for air compressor systems in steel plants according to claim 1, characterized in that, The volume V of the pressure buffer tank satisfies the following condition: ； Where: Qmax is the maximum allowable instantaneous gas consumption fluctuation value of the system, ΔQmax≤V1; T is the maximum pressure recovery time set by the system. ΔP is the maximum allowable fluctuation amplitude of pipeline pressure in the system.

5. The universal energy-saving and stable air supply control method for air compressor systems in steel plants according to claim 1, characterized in that: The industrial frequency air compressor is a centrifugal air compressor; the variable frequency air compressor is a screw air compressor.

6. The universal energy-saving and stable air supply control method for air compressor systems in steel plants according to claim 1, characterized in that: The system is configured with one variable frequency screw air compressor with a maximum air output V1 of 7,560 m³. 3 / h; The system is configured with multiple industrial frequency centrifugal air compressors, and the rated air output V2 of each compressor is 15,000 m³ / h. 3 / h.

7. The universal energy-saving and stable air supply control method for air compressor systems in steel plants according to claim 3, characterized in that: The central energy-saving control unit is an ES360 energy-saving control unit; the ES360 energy-saving control unit includes: Module M1, the data acquisition module, is used to collect pipeline pressure, flow rate, and unit operating status in real time; Module M2, the module load calculation module, is used to calculate the gas consumption Q in real time based on the collected data and determine the load segment; Module M3, the unit scheduling module, is used to execute the N+1 start-up logic and inverter compensation calculation, and generate start-stop commands for the power frequency generator and the inverter speed setpoint. Module M4, the fault self-diagnosis module, automatically starts the standby fixed-frequency air compressor or adjusts the speed setting value of the variable-frequency air compressor according to the priority rules when any operating air compressor fault is detected, and issues an alarm signal.

8. The universal energy-saving and stable air supply control method for air compressor systems in steel plants according to claim 1, characterized in that: The central energy-saving control unit interacts with the factory's existing DCS and PLC systems via a communication interface.

9. A universal energy-saving and stable air supply control method for an air compressor system in a steel plant according to claim 1, characterized in that: When the pipeline pressure exceeds the set upper limit Pmax + 0.02 MPa for a continuous period of Δt, the central energy-saving control unit executes an unloading sequence that first reduces pressure and then stops. Step A: First, reduce the speed of the variable frequency air compressor to the minimum allowable speed; Step B: If the pressure is still higher than the upper limit, unload one industrial frequency air compressor in sequence according to the priority rules. Step C: Repeat steps A and B until the pressure returns to the target range, thereby avoiding a sudden drop in pressure caused by the simultaneous unloading of multiple power frequency machines.

10. A universal energy-saving and stable air supply control method for an air compressor system in a steel plant according to claim 1, characterized in that: When the pipeline pressure is continuously lower than the set lower limit Pmin - 0.02 MPa for a period of Δt, the central energy-saving control unit executes a loading sequence of first raising and then starting: Step a: First, increase the speed of the variable frequency air compressor to 100%; Step b: If the pressure is still below the lower limit, start the next industrial frequency air compressor according to the N+1 principle. Step c: Repeat steps a and b until the pressure returns to the target range, thereby suppressing instantaneous pressure fluctuations to within 0.02 MPa.

Images