阅读说明：本技术 一种多机串联运行的单轴压缩机组系统及其控制方法 (Multi-machine series running single-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单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单轴离心压缩机组；低压机组通过变频电机驱动,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-machine series running single-shaft compressor set system and a control method thereof, and mainly solves 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 single-shaft centrifugal compressor units; the low-pressure unit is driven by a variable 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 and the first output pipeline of the high-pressure unit; 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 single-shaft compressor set 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 single-shaft centrifugal compressor units;

the low-pressure unit (1) is driven by a variable frequency motor (9), the inlet of the low-pressure unit is communicated with the outside atmosphere through a flow regulating device (21), the outlet of the low-pressure unit is respectively connected with the inlet of the high-pressure unit (2) and a first output pipeline (3), and a pipeline between the outlet of the low-pressure unit (1) and the inlet of the high-pressure unit (2) is provided with a check valve (10), a third stop valve (11) and a regulating valve (12) connected with the third stop valve (11) in parallel;

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 (9), 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-series operating single-shaft compressor train system according to claim 1, wherein: the low-pressure unit (1) and the high-pressure unit (2) are respectively a three-section type single-shaft centrifugal compressor unit.

3. The multi-series operating single-shaft compressor train system according to claim 1, wherein: the flow regulating device (21) is a throttle valve or a guide vane.

4. The multiple series operated single 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), six heat exchangers (18) and a heat exchanger.

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

6. The multi-series operating single-shaft compressor train system according to 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-series operating single-shaft compressor train system according to 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 (22), and an outlet flowmeter (20) is arranged on the output main pipeline (22).

8. A control method of a single-shaft compressor set system with multiple sets of compressors running in series is characterized by comprising the following steps:

step one, a throttle valve or a guide vane is in a small opening degree, a low-pressure cylinder anti-surge valve (6) is fully opened, a low-pressure unit (1) is started in a frequency conversion mode, after the low-pressure unit (1) is started to the minimum working rotating speed, the throttle valve or the guide vane is slowly opened, the 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 rotating speed of the low-pressure unit (1) is slowly increased to the rated rotating speed in the inflation process; the initial pressure of the high-pressure air storage tank (15) is less than 1 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 1.2-1.6 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 rotating speed, the low-pressure unit (1) still inflates a high-pressure air storage tank (15) through the first output pipeline (3), the adjusting 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 back 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, the low-pressure unit (1) operates at the maximum working rotating speed, and the high-pressure unit (2) operates at the minimum working rotating speed;

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, gradually reducing the rotating speed of the low-pressure unit (1), and gradually reducing the air charging amount of the low-pressure unit (1) to the high-pressure air storage tank (15) in the process when the low-pressure unit (1) reaches the minimum working rotating speed until the back pressure of the high-pressure air storage tank (15) closes the first one-way valve (13); 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 a throttle valve or a guide vane, and reducing the pressure and flow 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, wherein the high-pressure unit (2) runs in a high-efficiency area; in the process, the high-pressure unit (2) starts to charge air into the high-pressure air storage tank (15), and the charging amount is gradually increased;

step four, slowly opening a throttle valve or a guide vane along with the improvement of the inflation back pressure of the high-pressure air storage tank (15), and simultaneously gradually and alternately increasing the rotating speed of the low-pressure unit (1) and 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), closing the second one-way valve (17) by the back pressure of the high-pressure air storage tank (15), then closing the second cut-off valve (16), and completing inflation.

9. The control method of the multi-series operated single-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-machine series running single-shaft compressor set system 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 do 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 configuration of compressors of the existing series compressor unit, and provides a multi-unit series operation single-shaft compressor unit system and a control method thereof.

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

a single-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 single-shaft centrifugal compressor units; the low-pressure unit is driven by a variable 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.

Further, the low-pressure unit and the high-pressure unit are three-section type single-shaft centrifugal compressor units respectively.

Further, the flow regulating device is a throttle or a guide vane.

Furthermore, the heat exchanger comprises six heat exchangers 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 control method of the multi-machine series operation single-shaft compressor set system, which comprises the following steps:

step one, a throttle valve or a guide vane is in a small opening degree, a low-pressure cylinder anti-surge valve is fully opened, a low-pressure unit is started in a frequency conversion mode, the throttle valve or the guide vane is slowly opened after the low-pressure unit is started to the minimum working rotating speed, the anti-surge valve is slowly closed, the high-pressure air storage tank is inflated at a constant flow rate through a first output pipeline, and the rotating speed is slowly increased to the rated rotating speed in the inflating process of the low-pressure unit; the initial pressure of the high-pressure air storage tank is less than 1 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 1.2-1.6 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 rotating 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, and at the moment, the low-pressure unit operates at the maximum working rotating speed and the high-pressure unit operates at the minimum working rotating speed;

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, gradually reducing the rotating speed of the low-pressure unit, and gradually reducing the air charging amount of the low-pressure unit to the high-pressure air storage tank in the process when the low-pressure unit reaches the minimum working rotating speed until the back pressure of the high-pressure air storage tank closes the first one-way valve; slowly closing the high-pressure anti-surge valve, increasing the exhaust pressure of the high-pressure unit, simultaneously reducing the inlet flow of the low-pressure unit through a throttle valve or a guide vane, and reducing the pressure and flow of the outlet of the low-pressure unit and the inlet of the high-pressure unit until the high-pressure anti-surge valve is completely closed, and the high-pressure unit operates in a high-efficiency area; in the process, the high-pressure unit starts to charge the high-pressure air storage tank, and the charging amount is gradually increased;

step four, slowly opening a throttle valve or a guide vane along with the increase of the inflation back pressure of the high-pressure air storage tank, and simultaneously gradually and alternately increasing the rotating speed of the low-pressure unit and the high-pressure unit to continuously increase the exhaust pressure of the high-pressure unit, 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, when the inflation flow reaches the inflation low threshold value, closing the low-pressure unit and the high-pressure unit, closing the second one-way valve by the back pressure of the high-pressure air storage tank, then closing the second cut-off 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 single-shaft centrifugal compressor unit, and the single-shaft centrifugal compressor unit has the characteristics of stability and reliability and is the best choice for coping with frequent starting and stopping of compressed air energy storage at present. In the series machine operation scheme of the single-shaft unit, the high-pressure unit and the low-pressure unit are adjusted by variable rotating speed, and the optimal comprehensive operation efficiency of the single-shaft unit is realized by a matching control method.

3. The low-pressure unit and the high-pressure unit are respectively three-section single-shaft compressor units, the design working condition loads of the compressors are uniformly matched by the arrangement, and the minimum cylinder number and the maximum number of compression sections are realized at the same time.

Drawings

FIG. 1 is a schematic diagram of one embodiment of a multi-unit tandem single-shaft compressor train system according to the present invention;

FIG. 2 is a schematic diagram of a multi-unit tandem single-shaft compressor train system according to a second embodiment of 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-variable frequency motor, 10-check valve, 11-third cut-off valve, 12-regulating valve, 13-first check valve, 14-first cut-off valve, 15-high pressure air storage tank, 16-second cut-off valve, 17-second check valve, 18-heat exchanger, 19-air filter, 20-outlet flowmeter, 21-flow regulating device, 22-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-running single-shaft compressor set system and a control method thereof, wherein the system and the method are a multi-machine series-running wide back pressure system and an optimized control method, and aims to quickly start and stop and realize high efficiency in the whole running process, reduce the emptying or backflow working condition and improve the running efficiency of a compressed air energy storage system.

Example one

As shown in fig. 1, the multi-unit series operation single-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 single-shaft centrifugal compressor units; the low-pressure unit 1 is driven by a variable frequency motor 9, the inlet of the low-pressure unit is communicated with the outside atmosphere through a flow regulating device 21 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 pipeline between the outlet of the low-pressure unit 1 and the inlet of the high-pressure unit 2 is provided with 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; 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 9, 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 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 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 second 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 single-shaft centrifugal compressor units, and the single-shaft (single-shaft) units have stable and reliable characteristics and are the best choice for coping with frequent starting and stopping of compressed air energy storage at present. However, the single-shaft unit low-voltage unit 1 has a small pressure ratio and a narrow adjusting range, and based on the situation, the low-voltage unit 1 is driven by the variable-frequency motor 9, and the problems of low efficiency and narrow adjusting range of the single-shaft unit can be effectively solved by adjusting the variable rotating speed. Therefore, in the tandem operation scheme of the single-shaft unit, the high-pressure unit and the low-pressure unit 1 are adjusted by variable rotating speed, and by matching process operation, more efficient and wider pressure ratio adjusting range can be realized, and the optimal comprehensive operation efficiency of the single-shaft unit is realized.

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 and the high-pressure unit 2 are three-section single-shaft compressor units respectively, and this arrangement makes the compressor design condition load match uniform, and simultaneously realizes the minimum cylinder number and the maximum number of compression sections. In addition, six 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.

In this embodiment, the flow regulating device 21 may specifically be a throttle or a guide vane. The throttle valve or the guide vane can control the inflation speed, and the damage of the high-pressure unit 2 caused by quick inflation is avoided. Meanwhile, the inflating constant flow adjusting mode of the single-shaft unit can also have variable rotating speed except for a throttle valve or a guide vane, and the problems of low efficiency and narrow adjusting range of the single-shaft unit can be effectively solved by increasing the variable rotating speed for adjustment. The first output pipeline 3 and the second output pipeline 4 are both provided with outlet flow meters 20, and the two outlet flow meters 20 are arranged. Because the air inflation can be fast or slow, the load-up of the unit needs to be provided with a control variable, and the high-efficiency adjustment of the constant-flow air delivery 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, the initial energy storage working pressure is set to be 1MPa, the operation state analysis of the compressor under different back pressures of 1MPa, 2MPa, 3MPa and … 10MPa is completed, and a configuration scheme is formed. When the energy storage pressure exceeds 1.2-1.6 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 aggregate 1 operates, the low pressure anti-surge valve of the low pressure aggregate 1 may be opened to achieve a constant outlet pressure of the compressor of the low pressure aggregate 1. 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. And (3) starting the high-pressure unit 2 to the minimum working rotating speed, and then continuously closing the anti-surge valve until the pressure ratio is gradually established. The above process is described in detail by the following steps, that is, the method for controlling a multi-unit series single-shaft compressor set system provided by the invention specifically comprises the following steps:

step one, a throttle valve or a guide vane is in a small opening degree, a low-pressure cylinder anti-surge valve 6 is fully opened, a low-pressure unit 1 is started in a frequency conversion mode, after the low-pressure unit 1 is started to the minimum working rotating speed, the throttle valve or the guide vane is slowly opened, meanwhile, the 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 rotating speed of the low-pressure unit 1 is slowly increased to the maximum working rotating speed (rated rotating speed) in the inflating process; the initial pressure of the high-pressure air storage tank 15 is less than 1 MPa;

when the low-pressure unit 1 is initially inflated, an inlet throttle valve or a guide vane of the low-pressure unit 1 has a small degree of tightness; 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 a throttle valve or a guide vane is 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 1.2-1.6 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 2 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 rotating 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 in rear of 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, the low-pressure unit 1 operates at the maximum working rotating speed, and the high-pressure unit 2 operates at the minimum working rotating speed; at the moment, the high-pressure storage tank is still inflated only by the low-pressure unit 1;

step three, gradually reducing the rotating speed of the low-pressure unit 1, and gradually reducing the air charging amount of the low-pressure unit 1 to the high-pressure air storage tank 15 in the operation process after the low-pressure unit 1 reaches the minimum working rotating speed until the back pressure of the high-pressure air storage tank 15 closes the first one-way valve 13;

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 a throttle valve or a guide vane, and reducing the pressure and flow 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; in the process, the high-pressure unit 2 starts to charge the high-pressure air storage tank 15, and the charging amount is gradually increased;

step four, slowly opening a throttle valve or a guide vane along with the increase of the inflation back pressure of the high-pressure air storage tank 15, and gradually and alternately increasing the rotating speeds of the low-pressure unit 1 and the high-pressure unit 2 to continuously increase the exhaust pressure of the high-pressure unit 2; in order to realize the efficient 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 efficient adjustment is achieved;

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, closing the second one-way valve 17 by the back pressure of the high-pressure air storage tank 15, then closing the second cut-off valve 16, 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 outlet line 3 and the second outlet line 4 are connected to the high-pressure air storage tank 15 through an outlet main line 22, and an outlet flow meter 20 is arranged on the outlet main line 22, which can reduce the arrangement of the outlet flow meter 20, so that the cost of the system can be further reduced.

The control method of the multi-unit series operation single-shaft compressor set system provided by the embodiment specifically comprises the following steps:

step one, a throttle valve or a guide vane is in a small opening degree, a low-pressure cylinder anti-surge valve 6 is fully opened, a low-pressure unit 1 is started in a frequency conversion mode, after the low-pressure unit 1 is started to the minimum working rotating speed, the throttle valve or the guide vane is slowly opened, meanwhile, the 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 rotating speed of the low-pressure unit 1 is slowly increased to the maximum working rotating speed (rated rotating speed) in the inflating process; the initial pressure of the high-pressure air storage tank 15 is less than 1 MPa;

when the low-pressure unit 1 is initially inflated, an inlet throttle valve or a guide vane of the low-pressure unit 1 has a small degree of tightness; 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 a throttle valve or a guide vane is 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 pressurized starting process; the high-pressure unit 2 can be started under pressure, and the operation of opening a throttle valve or a guide vane for the second time is omitted in the high-pressure starting machine, 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, gradually reducing the rotating speed of the low-pressure unit 1, and gradually reducing the air charging amount of the low-pressure unit 1 to the high-pressure air storage tank 15 in the operation process after the low-pressure unit 1 reaches the minimum working rotating speed until the back pressure of the high-pressure air storage tank 15 closes the first one-way valve 13;

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 a throttle valve or a guide vane, and reducing the pressure and flow 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; in the process, the high-pressure unit 2 starts to charge the high-pressure air storage tank 15, and the charging amount is gradually increased;

step four, slowly opening a throttle valve or a guide vane along with the increase of the inflation back pressure of the high-pressure air storage tank 15, and gradually and alternately increasing the rotating speeds of the low-pressure unit 1 and the high-pressure unit 2 to continuously increase the exhaust pressure of the high-pressure unit 2; in order to realize the efficient 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 efficient adjustment is achieved;

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, closing the second one-way valve 17 by the back pressure of the high-pressure air storage tank 15, then closing the second cut-off valve 16, and completing inflation.