阅读说明：本技术 一种多机串联运行的多轴压缩机组系统及其控制方法 (Multi-machine series-operation multi-shaft compressor set system and control method thereof ) 是由 侯佑松 周根标 陈余平 汤本凯 王小坤 奚忠 刘侃 徐海霞 朱安安 乔社宁 刘丹 于 2021-10-27 设计创作，主要内容包括：本发明提供一种多机串联运行的多轴压缩机组系统及其控制方法,主要解决现有串联压缩机组的压缩机运行效率低、压缩机配置复杂的问题。该系统包括低压机组、高压机组、第一输出管路、第二输出管路、高压防喘振阀、低压防喘振阀、放空阀和放空消音器；低压机组和高压机组均为多段式多轴离心压缩机组；低压机组通过工频电机驱动,其进口与外界大气连通,出口分别与高压机组的入口、第一输出管路连接；高压机组通过变频电机驱动,高压机组的出口与第二输出管路连接；高压防喘振阀的进口与高压机组的出口连接,出口连接在高压机组进口和调节阀出口之间的管路上；低压防喘振阀的进口与低压机组的出口连接,出口与外界大气连通。(The invention provides a multi-shaft compressor set system with multiple sets running in series and a control method thereof, which mainly solve the problems of low running efficiency and complex configuration of compressors of the existing series compressor set. The system comprises a low-pressure unit, a high-pressure unit, a first output pipeline, a second output pipeline, a high-pressure anti-surge valve, a low-pressure anti-surge valve, an emptying valve and an emptying silencer; the low-pressure unit and the high-pressure unit are both multi-section multi-shaft centrifugal compressor units; the low-pressure unit is driven by a power frequency motor, the inlet of the low-pressure unit is communicated with the outside atmosphere, and the outlet of the low-pressure unit is respectively connected with the inlet of the high-pressure unit and a first output pipeline; the high-voltage unit is driven by the variable frequency motor, and an outlet of the high-voltage unit is connected with the second output pipeline; the inlet of the high-pressure anti-surge valve is connected with the outlet of the high-pressure unit, and the outlet of the high-pressure anti-surge valve is connected to a pipeline between the inlet of the high-pressure unit and the outlet of the regulating valve; the inlet of the low-pressure anti-surge valve is connected with the outlet of the low-pressure unit, and the outlet is communicated with the outside atmosphere.)

1. A multi-shaft compressor unit system with multiple machines operating in series is characterized in that: the device comprises a low-pressure unit (1), a high-pressure unit (2), a first output pipeline (3), a second output pipeline (4), a high-pressure anti-surge valve (5), a low-pressure anti-surge valve (6), an emptying valve (7) and an emptying silencer (8);

the low-pressure unit (1) and the high-pressure unit (2) are both multi-section multi-shaft centrifugal compressor units;

the low-pressure unit (1) is driven by a power frequency motor, the inlet of the low-pressure unit is communicated with the outside atmosphere through a flow regulating device (9), the outlet of the low-pressure unit is respectively connected with the inlet of the high-pressure unit (2) and the first output pipeline (3), and a check valve (10), a third cut-off valve (11) and a regulating valve (12) connected with the third cut-off valve (11) in parallel are arranged on a pipeline between the outlet of the low-pressure unit (1) and the inlet of the high-pressure unit (2);

the first output pipeline (3) is connected with a high-pressure air storage tank (15) through a first one-way valve (13) and a first cut-off valve (14);

the high-pressure unit (2) is driven by a variable frequency motor, an outlet of the high-pressure unit (2) is connected with a second output pipeline (4), and the second output pipeline (4) is connected with a high-pressure air storage tank (15) through a second one-way valve (17) and a second cut-off valve (16);

the inlet of the high-pressure anti-surge valve (5) is connected with the outlet of the high-pressure unit (2), and the outlet of the high-pressure anti-surge valve (5) is connected to a pipeline between the inlet of the high-pressure unit (2) and the outlet of the regulating valve (12);

the inlet of the low-pressure anti-surge valve (6) is connected with the outlet of the low-pressure unit (1), and the outlet of the low-pressure anti-surge valve (6) is communicated with the outside atmosphere;

and the inlet of the emptying valve (7) is connected with the outlet of the high-pressure unit (2), and the outlet of the emptying valve (7) is communicated with the outside atmosphere through an emptying silencer (8).

2. The multi-machine series operated multi-shaft compressor train system of claim 1, wherein: the low-pressure unit (1) is a six-section type multi-shaft centrifugal compressor unit, and the high-pressure unit (2) is a two-section type multi-shaft centrifugal compressor unit.

3. The multi-machine series operated multi-shaft compressor train system of claim 1, wherein: the flow regulating device (9) is a guide vane.

4. The multiple-unit, series-operated, multiple-shaft compressor train system according to claim 1, 2 or 3, wherein: the heat exchanger comprises a low-pressure unit (1), a high-pressure unit (2), a first output pipeline (3), a second output pipeline (4), eight heat exchangers (18) and a heat exchanger.

5. The multi-machine series operated multi-shaft compressor train system of claim 4, wherein: an air filter (19) is further arranged at the inlet of the low-pressure unit (1).

6. The multi-machine series operated multi-shaft compressor train system of claim 5, wherein: and outlet flow meters (20) are arranged on the first output pipeline (3) and the second output pipeline (4).

7. The multi-machine series operated multi-shaft compressor train system of claim 5, wherein: the outlets of the first output pipeline (3) and the second output pipeline (4) are connected with a high-pressure air storage tank (15) through an output main pipeline (21), and an outlet flowmeter (20) is arranged on the output main pipeline (21).

8. A control method of a multi-shaft compressor set system with multi-machine series operation is characterized by comprising the following steps:

the method comprises the following steps that firstly, guide vanes are in a small opening degree, a low-pressure anti-surge valve (6) is fully opened, a low-pressure unit (1) is started in a power frequency mode or in a frequency conversion mode, the guide vanes are slowly opened after the start is finished, the low-pressure anti-surge valve (6) is slowly closed, a high-pressure air storage tank (15) is inflated at a constant flow rate through a first output pipeline (3), and the initial pressure of the high-pressure air storage tank (15) is 3-4 MPa;

step two, starting the high-pressure unit (2) through a) a low-pressure starting process or b) a pressurized starting process;

a) when the back pressure of the high-pressure air storage tank (15) exceeds 4.0-5.0 MPa, the check valve (10) is automatically opened, meanwhile, the regulating valve (12) is opened, part of air at the outlet of the low-pressure unit (1) is input into the high-pressure unit (2), the high-pressure unit (2) is in an inflation state, when the inflation pressure of the high-pressure unit (2) reaches 2-5 bar, the high-pressure unit (2) is inflated, and the regulating valve (12) is closed; the high-pressure unit (2) is started in a frequency conversion mode and runs at the lowest working rotating speed, and the high-pressure anti-surge valve (5) is in a fully-opened state;

in the process that the high-pressure unit (2) operates at the lowest working speed, the low-pressure unit (1) still inflates the high-pressure air storage tank (15) through the first output pipeline (3), the regulating valve (12) is opened, the air pressure in the high-pressure unit (2) is inflated to be equal to the exhaust pressure of the low-pressure unit (1), the pressure in front of a valve of the third cut-off valve (11) is equal to the pressure in rear of the valve, the third cut-off valve (11) is opened, the low-pressure unit (1) and the high-pressure unit (2) are completely communicated, at the moment, guide vanes at the inlet of the low-pressure unit are fully opened and operate at the rated working condition, the high-pressure unit (2) operates at the minimum working speed, the low-pressure unit (1) still inflates the high-pressure air storage tank (15) through the first output pipeline (3), and the inflation flow is gradually reduced;

b) opening a regulating valve (12), after the high-pressure unit (2) is inflated until the internal pressure of the high-pressure unit (2) is equal to the exhaust pressure of the low-pressure unit (1), opening a third cut-off valve (11), completing the conduction of the low-pressure unit (1) and the high-pressure unit (2), and then starting the high-pressure unit (2) to a minimum running state through frequency conversion;

step three, slowly closing the high-pressure anti-surge valve (5), increasing the exhaust pressure of the high-pressure unit (2), and simultaneously reducing the inlet flow of the low-pressure unit (1) through the guide vane; reducing the pressure of an outlet of the low-pressure unit (1) and the pressure of an inlet of the high-pressure unit (2) until the high-pressure anti-surge valve (5) is completely closed, and operating the high-pressure unit (2) in a high-efficiency area; in the process, the high-pressure unit (2) starts to inflate the high-pressure air storage tank (15), the inflation quantity is gradually increased, the low-pressure unit (1) inflates the high-pressure air storage tank (15) and gradually decreases until the back pressure of the high-pressure air storage tank (15) closes the first one-way valve (13);

step four, slowly opening a guide vane along with the increase of the inflation backpressure of the high-pressure air storage tank (15), and simultaneously gradually increasing the rotating speed of the high-pressure unit (2) to continuously increase the exhaust pressure of the high-pressure unit (2), wherein the compressor is controlled to be under the set optimal inflation flow all the time in the process;

and step five, with the gradual increase of the back pressure of the high-pressure air storage tank (15), when the inflation flow reaches the inflation low threshold value, closing the low-pressure unit (1) and the high-pressure unit (2), or until the back pressure of the high-pressure air storage tank (15) closes the second one-way valve (17), and completing inflation.

9. The control method of a multi-machine series-operated multi-shaft compressor train system according to claim 8, wherein: the compression temperature of each section of the low-pressure unit (1) and the high-pressure unit (2) is controlled to be less than 150 ℃.

Technical Field

The invention belongs to the field of compressed air energy storage, and particularly relates to a multi-shaft compressor set system with multiple machines operating in series and a control method thereof.

Background

Due to the intermittent and unstable characteristics of renewable energy power generation, energy storage devices are configured at the power generation end, the power transmission and distribution end and the user end of the power grid in a great necessity. Compressed air energy storage systems are a hot spot of current research.

The basic principle of compressing air is as follows: the electric energy of a power grid is consumed by the motor to drive the compressor to compress the air to do work, and the pressure energy of the compressed air is stored. When the power grid is in a high load period, the turbine expander is driven to generate electricity through high-pressure air. The compressed air can be stored through waste rock caverns, pressure vessels and the like, and when the vessels are adopted, the volume requirement on the vessels is higher and higher along with the increase of energy storage power. In order to reduce the volume requirement of the container or the rock cavern to the maximum extent, the pressure energy of the compressed air needs to be fully utilized during power generation, the compressed air pressure energy can be changed from 10-100% in the primary energy storage and power generation process, and thus, the back pressure of the compressor is the same as the process of changing from 10-100% in the compressed air energy storage process.

Because the final pressure of stored energy is generally very high and is generally more than 10MPa, a plurality of compressors are often required to work simultaneously to achieve the target. However, the pressure in the energy storage container is low when the compressor initially works, and 1 compressor is usually enough. However, as the energy storage progresses, the subsequent compressor is required to be gradually incorporated into the compression sequence, meanwhile, because the time of the energy storage period is very limited, rapid and reliable incorporation and rapid load establishment are required, and meanwhile, in order to reduce manual operation, the requirement of intelligent automatic control is required to be achieved.

The condition that current industry was used has many the series connection to use occasionally, but often the operating mode is invariable (backpressure is invariable), and does not have the frequent start-stop operating mode that opens and stop daily, and the compressor of many series connections is when this kind of running mode is worked, and compressor operating efficiency is low, the compressor configuration is complicated, is difficult to the practicality.

Disclosure of Invention

The invention aims to solve the problems of low operation efficiency and complex compressor configuration of the existing series compressor unit, and provides a multi-unit series operation multi-shaft compressor unit system and a control method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

a multi-shaft compressor set system with multiple sets running in series comprises a low-pressure set, a high-pressure set, a first output pipeline, a second output pipeline, a high-pressure anti-surge valve, a low-pressure anti-surge valve, an emptying valve and an emptying silencer, wherein the low-pressure set is connected with the high-pressure set through the first output pipeline; the low-pressure unit and the high-pressure unit are both multi-section multi-shaft centrifugal compressor units; the low-pressure unit is driven by a power frequency motor, the inlet of the low-pressure unit is communicated with the outside atmosphere through a flow regulating device, the outlet of the low-pressure unit is respectively connected with the inlet of the high-pressure unit and a first output pipeline, and a check valve, a third cut-off valve and an adjusting valve connected with the third cut-off valve in parallel are arranged on a pipeline between the outlet of the low-pressure unit and the inlet of the high-pressure unit; the first output pipeline is connected with the high-pressure air storage tank through a first one-way valve and a first cut-off valve; the high-pressure unit is driven by a variable frequency motor, an outlet of the high-pressure unit is connected with a second output pipeline, and the second output pipeline is connected with a high-pressure air storage tank through a second stop valve and a second one-way valve; the inlet of the high-pressure anti-surge valve is connected with the outlet of the high-pressure unit, and the outlet of the high-pressure anti-surge valve is connected to a pipeline between the inlet of the high-pressure unit and the outlet of the regulating valve; the inlet of the low-pressure anti-surge valve is connected with the outlet of the low-pressure unit, and the outlet of the low-pressure anti-surge valve is communicated with the outside atmosphere; and the inlet of the emptying valve is connected with the outlet of the high-pressure unit, and the outlet of the emptying valve is communicated with the external atmosphere through an emptying silencer.

Furthermore, the low-pressure unit is a six-section type multi-shaft centrifugal compressor unit, and the high-pressure unit is a two-section type multi-shaft centrifugal compressor unit.

Further, the flow regulating device is a guide vane.

And the eight heat exchangers are arranged between two adjacent sections of compressors in the low-pressure unit and the high-pressure unit and on the first output pipeline and the second output pipeline.

Further, an air filter is arranged at the inlet of the low-pressure unit.

Furthermore, the first output pipeline and the second output pipeline are both provided with outlet flow meters.

Furthermore, outlets of the first output pipeline and the second output pipeline are connected with the high-pressure air storage tank through an output main pipeline, and an outlet flow meter is arranged on the output main pipeline.

Meanwhile, the invention also provides a multi-machine series operation multi-shaft compressor set system control method, which comprises the following steps:

the method comprises the following steps that firstly, guide vanes are in a small opening degree, a low-pressure anti-surge valve 6 is fully opened, a low-pressure unit 1 is started in a power frequency mode or in a frequency conversion mode, the guide vanes are slowly opened after the start is finished, the low-pressure anti-surge valve 6 is slowly closed, a high-pressure air storage tank 15 is inflated at a constant flow rate through a first output pipeline 3, and the initial pressure of the high-pressure air storage tank 15 is 3-4 MPa;

step two, starting the high-pressure unit through a) a low-pressure starting process or b) an under-pressure starting process;

a) when the back pressure of the high-pressure air storage tank exceeds 4.0-5.0 MPa, the check valve is automatically opened, meanwhile, the regulating valve is opened, part of air at the outlet of the low-pressure unit is input into the high-pressure unit, so that the high-pressure unit is in an inflation state, when the inflation pressure of the high-pressure unit reaches 2-5 bar, the high-pressure unit completes inflation, and the regulating valve is closed; the high-voltage unit is started in a frequency conversion mode and runs at the lowest working rotating speed, and the high-voltage anti-surge valve is in a fully open state;

when the high-pressure unit operates at the lowest working speed, the low-pressure unit still inflates the high-pressure air storage tank through the first output pipe, the regulating valve is opened, the air pressure in the high-pressure unit is inflated to be equal to the exhaust pressure of the low-pressure unit, the pressure in front of a valve of the third cut-off valve is equal to the pressure in back of the valve, the third cut-off valve is opened, the low-pressure unit and the high-pressure unit are completely communicated, at the moment, guide vanes at the inlet of the low-pressure unit are fully opened and operate at a rated working condition, the high-pressure unit operates at the minimum working speed, the low-pressure unit still inflates the high-pressure air storage tank through the first output pipe, and the inflation flow is gradually reduced;

b) opening a regulating valve, after the high-pressure unit is inflated until the internal pressure of the high-pressure unit is equal to the exhaust pressure of the low-pressure unit, opening a third cut-off valve to complete the conduction of the low-pressure unit and the high-pressure unit, and then starting the high-pressure unit to a minimum running state through frequency conversion;

step three, slowly closing the high-pressure anti-surge valve, increasing the exhaust pressure of the high-pressure unit, and simultaneously reducing the inlet flow of the low-pressure unit through the guide vane;

reducing the pressure of an outlet of the low-pressure unit and the pressure of an inlet of the high-pressure unit until the high-pressure anti-surge valve is completely closed, and operating the high-pressure unit in a high-efficiency area; in the process, the high-pressure unit starts to inflate the high-pressure air storage tank, the inflation quantity is gradually increased, the low-pressure unit gradually decreases the inflation of the high-pressure air storage tank until the back pressure of the high-pressure air storage tank closes the first one-way valve;

step four, slowly opening the guide vane along with the increase of the inflation back pressure of the high-pressure air storage tank, and simultaneously gradually increasing the rotating speed of the high-pressure unit to continuously increase the exhaust pressure of the high-pressure unit, wherein the compressor is always controlled to be under the set optimal inflation flow in the process;

and step five, with the gradual increase of the back pressure of the high-pressure air storage tank, when the flow of the unit reaches an inflation low threshold value, closing the unit, or until the back pressure of the high-pressure air storage tank closes the second one-way valve, and completing inflation.

Further, the compression temperature of each section of the low-pressure unit and the high-pressure unit is controlled to be less than 150 ℃.

Compared with the prior art, the invention has the following beneficial effects:

1. the invention provides a compressed air energy storage unit without wide back pressure and with multiple machines in series operation, which can realize the high-efficiency operation of the compressor unit in the wide back pressure process, thereby improving the efficiency of an air energy storage system and ensuring that each compressor in the air inflation process is in a high-efficiency working range in the whole process.

2. The system adopts a multi-section multi-shaft centrifugal compressor set, the low-pressure unit adopts constant rotating speed adjustment, the configuration cost of the compressor is low, and efficient inflation in a low-back-pressure inflation area is realized through an independent inflation mode; meanwhile, the low-pressure unit can run at a rated working condition in a normal time region and is efficient, and the high-pressure unit is completely controlled in a wide backpressure change range in the process from the middle of inflation to the subsequent process and is realized by adopting optimal variable-speed regulation.

3. The low-pressure unit adopts a six-stage scheme, can quickly reach a rated working state and output stable compression high-quality compression heat, and is convenient to recover the compression heat. The high-pressure unit is of a two-stage structure, only two stages of impellers are provided, the variable-speed adjustment can be easily matched, and the widest efficient working area is obtained.

Drawings

FIG. 1 is a schematic diagram of a multi-shaft compressor train system for multi-machine series operation according to one embodiment of the present invention;

FIG. 2 is a schematic diagram of a multi-shaft compressor train system with multiple trains running in series according to the present invention.

Reference numerals: 1-low pressure unit, 2-high pressure unit, 3-first output pipeline, 4-second output pipeline, 5-high pressure anti-surge valve, 6-low pressure anti-surge valve, 7-blow-off valve, 8-blow-off silencer, 9-flow regulating device, 10-check valve, 11-third cut-off valve, 12-regulating valve, 13-first one-way valve, 14-first cut-off valve, 15-high pressure air storage tank, 16-second cut-off valve, 17-second one-way valve, 18-heat exchanger, 19-air filter, 20-outlet flowmeter, 21-output main pipeline.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood by those skilled in the art that these embodiments are only for explaining the technical principle of the present invention and are not intended to limit the scope of the present invention.

The invention provides a multi-machine series-operation multi-shaft compressor set system and a control method thereof, wherein the system and the method are a multi-machine series-connection wide back pressure system and an optimized control method, and aims to quickly start and stop and realize high efficiency in the whole operation process, reduce the emptying or backflow working condition and improve the operation efficiency of a compressed air energy storage system.

Example one

As shown in fig. 1, the multi-unit series-operation multi-shaft compressor train system provided by this embodiment includes a low-pressure unit 1, a high-pressure unit 2, a first output pipeline 3, a second output pipeline 4, a high-pressure anti-surge valve 5, a low-pressure anti-surge valve 6, a blow-down valve 7 and a blow-down muffler 8; the low-pressure unit 1 and the high-pressure unit 2 are both multi-section multi-shaft centrifugal compressor units; the low-pressure unit 1 is driven by a power frequency motor, the inlet of the low-pressure unit is communicated with the outside atmosphere through a flow regulating device 9 and an air filter 19, the outlet of the low-pressure unit is respectively connected with the inlet of the high-pressure unit 2 and the first output pipeline 3, and a check valve 10, a third cut-off valve 11 and a regulating valve 12 connected with the third cut-off valve 11 in parallel are arranged on a pipeline between the outlet of the low-pressure unit 1 and the inlet of the high-pressure unit 2; the first output pipeline 3 is connected with a high-pressure air storage tank 15 through a first check valve 13 and a first cut-off valve 14; the high-pressure unit 2 is driven by a variable frequency motor, the outlet of the high-pressure unit 2 is connected with a second output pipeline 4, and the second output pipeline 4 is connected with a high-pressure air storage tank 15 through a second stop valve 16 and a second one-way valve 17; the inlet of the high-pressure anti-surge valve 5 is connected with the outlet of the high-pressure unit 2 after passing through a heat exchanger 18, the outlet of the high-pressure anti-surge valve 5 is connected on a pipeline between the inlet of the high-pressure unit 2 and the outlet of the regulating valve 12, namely the outlet joint of the high-pressure anti-surge valve 5 is positioned at the downstream of the outlet of the regulating valve 12; the inlet of the low-pressure anti-surge valve 6 is connected with the outlet of the low-pressure unit 1, and the outlet of the low-pressure anti-surge valve 6 is communicated with the outside atmosphere; the inlet of the atmospheric valve 7 is connected with the outlet of the high-pressure unit 2, and the outlet of the atmospheric valve 7 is communicated with the outside atmosphere through an atmospheric silencer 8.

The low-pressure unit 1 and the high-pressure unit 2 are both multi-section multi-shaft centrifugal compressor units, the low-pressure unit 1 adopts guide vane constant rotating speed adjustment, the compressor configuration cost is low, and efficient inflation in a low-back-pressure inflation area is realized through an independent inflation mode; through process configuration and reasonable pressure ratio distribution, the low-pressure unit 1 can operate at a rated working condition in a normal time region and is efficient, and the high-pressure unit 2 is completely controlled in a wide backpressure change range in the middle of inflation to the subsequent process and is realized by adopting optimal variable-speed regulation. Meanwhile, the low-voltage unit 1 does not need to adopt variable-speed regulation, so that the frequency converter is reduced, and the cost is saved.

The low-pressure unit 1 and the high-pressure unit 2 are multi-section centrifugal compressor units, and in order to realize higher compression efficiency, the compression temperature of each section of the compressor is controlled to be less than 150 ℃, and the cost is reduced by adopting the multi-section compressor in consideration of reducing the number of the compressors as much as possible. In this embodiment, the low-pressure unit 1 adopts a six-stage scheme, and the low-pressure six-stage scheme can make the first-stage pressure ratio as much as possible, and can reach the rated working state more quickly to output more stable compression high-quality compression heat, thereby obtaining more stable compression heat sources for recovery. Therefore, the eight heat exchangers 18 between two adjacent sections of compressors in the low-pressure unit 1 and the high-pressure unit 2 and on the first output pipeline 3 and the second output pipeline 4 can recover energy in the system. The high-pressure unit 2 is of a two-section structure, only two stages of impellers are arranged, the variable-speed adjustment can be easily matched, the widest efficient working area is obtained, the range of simulation parameters can realize the efficient operation of the backpressure from 5-10 MPa, and almost all available variable-speed intervals are completely utilized.

In this embodiment, the flow regulating means 9 may in particular be a guide vane. The guide vane can control the inflation speed, and the damage of the high-pressure unit 2 caused by quick inflation is avoided. The first output pipeline 3 and the second output pipeline 4 are both provided with an outlet flowmeter 20, and the two outlet flowmeters 20 are arranged in total. Because the inflation can be fast or slow, the unit load-up needs to be provided with a control variable, and the high-efficiency adjustment of the constant-flow gas transmission of the unit can be realized through the flow control output by the outlet flowmeter 20.

When the system operates, the final energy storage pressure of the storage tank is set to be 9-11 MPa, the pressure is the optimal inflation pressure, and the initial energy storage working pressure is set to be 3-4 MPa. When the energy storage pressure exceeds 4.0-5.0 MPa, the high-voltage unit 2 needs to be involved in working, the low-voltage unit 1 works in a state of small flow and maximum pressure ratio, the low-voltage unit 1 runs at the highest rotating speed, and the running point is close to an anti-surge line; the gas circuits of the two low-pressure units are separated by a third cut-off valve 11 on the pipeline leading from the outlet of the low-pressure unit 1 to the inlet of the high-pressure unit 2, so that the compressor of the high-pressure unit 2 is not influenced when the compressor of the low-pressure unit 1 works alone. As the low pressure train 1 operates, the low pressure train 1 anti-surge valve may open to achieve a constant outlet pressure of the low pressure train 1 compressor. The mode can realize that the compression work consumed by unit effective air compression is the lowest, and full-automatic operation in automatic loading and stringing machines is realized.

When the low-pressure unit 1 works to be close to the maximum pressure ratio, a bypass valve (namely an adjusting valve 12) of a third stop valve 11 at the outlet of the low-pressure unit 1 is opened until the third stop valve 11 is fully opened, and the high-pressure unit 2 and a pipeline are filled with air with the pressure equal to that of the outlet of the low-pressure unit 1; at this time, the low pressure unit 1 operates, and the high pressure anti-surge valve 5 is opened and maintained at a constant opening degree. The stored energy charging is temporarily stopped due to insufficient pressure ratio. The method for controlling the multi-compressor unit system with multiple units running in series specifically comprises the following steps:

the method comprises the following steps that firstly, guide vanes are in a small opening degree, a low-pressure anti-surge valve 6 is fully opened, a low-pressure unit 1 is started in a power frequency mode or in a frequency conversion mode, the guide vanes are slowly opened after the start is finished, the low-pressure anti-surge valve 6 is slowly closed, a high-pressure air storage tank 15 is inflated at a constant flow rate through a first output pipeline 3, and the initial pressure of the high-pressure air storage tank 15 is 3-4 MPa;

when the low-pressure unit 1 is initially inflated, the inlet guide vane of the low-pressure unit has a small degree of closeness; at the moment, flow signals of the first output pipeline 3 and the second output pipeline 4 of the high-pressure air storage tank 15 are collected, and guide vanes are gradually opened in the inflation process according to the flow signals, so that the low-pressure unit 1 adopts constant-flow inflation to realize high-efficiency inflation;

step two, starting the high-voltage unit 2 through a low-voltage starting process;

when the back pressure of the high-pressure air storage tank 15 exceeds 4.0-5.0 MPa (different working performances of compressors are different, the back pressure value changes), the check valve 10 is automatically opened (the check valve 10 is in an automatically opened state due to the work of the low-pressure unit 1), meanwhile, the regulating valve 12 is opened, part of air at the outlet of the low-pressure unit 1 is input into the high-pressure unit 2, the high-pressure unit 2 is in an inflation state, the inflation pressure of the high-pressure unit is in a low-pressure state, and when the inflation pressure of the high-pressure unit 2 reaches 2-5 bar, the inflation of the high-pressure unit 2 is completed, and the regulating valve 12 is closed; the high-voltage unit 2 is started in a frequency conversion mode and runs at the lowest working rotating speed, and the high-voltage anti-surge valve 5 is in a fully-opened state in the process;

in the process that the high-pressure unit 2 operates at the lowest working speed, the low-pressure unit 1 still inflates air to the high-pressure air storage tank 15 through the first output pipeline 3, the regulating valve 12 is opened, the air pressure in the high-pressure unit 2 is inflated to be equal to the exhaust pressure of the low-pressure unit 1, the pressure in front of the third cut-off valve 11 is equal to the pressure behind the third cut-off valve, the third cut-off valve 11 is opened, the low-pressure unit 1 and the high-pressure unit 2 are completely communicated, at the moment, guide vanes at the inlet of the low-pressure unit are fully opened and operate at the rated working condition, the high-pressure unit 2 operates at the minimum working speed, and the low-pressure unit 1 still inflates air to the high-pressure air storage tank 15 through the first output pipeline 3 and the inflation flow is gradually reduced;

step three, slowly closing the high-pressure anti-surge valve 5, increasing the exhaust pressure of the high-pressure unit 2, simultaneously reducing the inlet flow of the low-pressure unit 1 through the guide vane, and reducing the pressure of the outlet of the low-pressure unit 1 and the inlet of the high-pressure unit 2 until the high-pressure anti-surge valve 5 is completely closed, and the high-pressure unit 2 operates in a high-efficiency area; at the moment, the inlet guide vane of the low-pressure unit 1 has a small degree of closeness;

in the process, the high-pressure unit 2 starts to inflate the high-pressure air storage tank 15, the inflation quantity is gradually increased, and the low-pressure unit 1 inflates the high-pressure air storage tank 15 and gradually decreases until the back pressure of the high-pressure air storage tank 15 closes the first one-way valve 13;

step four, slowly opening the guide vane along with the increase of the charging backpressure of the high-pressure air storage tank 15, and simultaneously gradually increasing the rotating speed of the high-pressure unit 2 to continuously increase the exhaust pressure of the high-pressure unit 2; in order to realize the high-efficiency operation of the compressor, the compressor is always controlled to be under the optimal inflation flow according to flow signals on the first output pipeline 3 and the second output pipeline 4 of the high-pressure air storage tank 15, so that the high efficiency is obtained;

and step five, with the gradual increase of the back pressure of the high-pressure air storage tank 15, after the high-pressure unit 2 gradually reaches the rated rotating speed and the flow of the unit reaches the inflation low threshold value, closing the unit, or closing the second one-way valve 17 until the back pressure of the high-pressure air storage tank 15 is closed, and completing inflation.

Example two

As shown in fig. 2, this embodiment is substantially the same as the system arrangement of the first embodiment, except that the outlets of the first output pipeline 3 and the second output pipeline 4 are connected to the high-pressure air storage tank 15 through an output main pipeline 21, and an outlet flow meter 20 is arranged on the output main pipeline 21, which can reduce the arrangement of the outlet flow meter 20, so that the cost of the system is further reduced. The control method of the multi-compressor unit system with multi-compressor series operation provided by the embodiment specifically comprises the following steps:

the method comprises the following steps that firstly, guide vanes are in a small opening degree, a low-pressure anti-surge valve 6 is fully opened, a low-pressure unit 1 is started in a power frequency mode or in a frequency conversion mode, the guide vanes are slowly opened after the start is finished, the low-pressure anti-surge valve 6 is slowly closed, a high-pressure air storage tank 15 is inflated at a constant flow rate through a first output pipeline 3, and the initial pressure of the high-pressure air storage tank 15 is 3-4 MPa;

when the low-pressure unit 1 is initially inflated, the inlet guide vane of the low-pressure unit has a small degree of closeness; at the moment, flow signals of the first output pipeline 3 and the second output pipeline 4 of the high-pressure air storage tank 15 are collected, and guide vanes are gradually opened in the inflation process according to the flow signals, so that the low-pressure unit 1 adopts constant-flow inflation to realize high-efficiency inflation;

step two, the high-pressure unit 2 can be started under pressure, and the operation of opening guide vanes for the second time is omitted when the high-pressure unit is started under pressure, but the starting torque is larger;

opening a regulating valve 12, after the high-pressure unit 2 is inflated until the internal pressure of the high-pressure unit 2 is equal to the exhaust pressure of the low-pressure unit 1, opening a third cut-off valve 11 to complete the conduction of the low-pressure unit 1 and the high-pressure unit 2, and then starting the high-pressure unit 2 to a minimum running state through frequency conversion;

step three, slowly closing the high-pressure anti-surge valve 5, increasing the exhaust pressure of the high-pressure unit 2, simultaneously reducing the inlet flow of the low-pressure unit 1 through the guide vane, and reducing the pressure of the outlet of the low-pressure unit 1 and the inlet of the high-pressure unit 2 until the high-pressure anti-surge valve 5 is completely closed, and the high-pressure unit 2 operates in a high-efficiency area; at the moment, the inlet guide vane of the low-pressure unit 1 has a small degree of closeness;

in the process, the high-pressure unit 2 starts to inflate the high-pressure air storage tank 15, the inflation quantity is gradually increased, and the low-pressure unit 1 inflates the high-pressure air storage tank 15 and gradually decreases until the back pressure of the high-pressure air storage tank 15 closes the first one-way valve 13;

step four, slowly opening the guide vane along with the increase of the charging backpressure of the high-pressure air storage tank 15, and simultaneously gradually increasing the rotating speed of the high-pressure unit 2 to continuously increase the exhaust pressure of the high-pressure unit 2; in order to realize the high-efficiency operation of the compressor, the compressor is always controlled to be under the optimal inflation flow according to flow signals on the first output pipeline 3 and the second output pipeline 4 of the high-pressure air storage tank 15, so that the high efficiency is obtained;

and step five, with the gradual increase of the back pressure of the high-pressure air storage tank 15, after the high-pressure unit 2 gradually reaches the rated rotating speed and the flow of the unit reaches the inflation low threshold value, closing the unit, or closing the second one-way valve 17 until the back pressure of the high-pressure air storage tank 15 is closed, and completing inflation.