Turbine and motor double-drive magnetic levitation natural gas expansion recompression unit, system and method

Abstract

The invention relates to the technical field of natural gas treatment, and particularly discloses a turbine and motor double-drive magnetic levitation natural gas expansion recompression unit, system and method, and the turbine and motor double-drive magnetic levitation natural gas expansion recompression unit comprises a natural gas expansion machine, a high-speed synchronous motor and a natural gas compressor which are coaxially and rigidly connected; the magnetic suspension supporting system comprises an expansion side magnetic suspension bearing arranged at the output end of the natural gas expansion machine and a compression side magnetic suspension bearing arranged at the input end of the compressor, and is used for realizing non-contact suspension and torque transmission of the rotor; the electric control unit comprises an electric appliance cabinet and a pressure sensor, a converter and a main controller are arranged in the electric appliance cabinet, the converter is connected with a power grid and the high-speed synchronous motor, and the main controller dynamically adjusts the operation mode and power of the high-speed synchronous motor by taking the outlet pressure of the natural gas compressor as a control variable. The natural gas compressor is driven by the natural gas expansion machine and the highly synchronous motor, the unit with the reverse power generation function is adopted, the operation flexibility of the unit is improved, and the comprehensive utilization rate of energy is remarkably increased.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas processing, and in particular to a turbine and motor dual-driven magnetic levitation natural gas expansion and recompression unit, system and method. Background Art

[0002] In natural gas pipeline pressure regulating stations, liquefied natural gas (LNG) receiving stations, and high-pressure natural gas decompression and utilization, high-pressure natural gas often needs to be reduced to pipeline pressure. Traditional throttle valve decompression methods waste a significant amount of pressure energy. Using an expander instead of a throttle valve can recover this pressure energy and use it to drive a compressor to boost the pressure of another stream of low-pressure natural gas or other loads, thus saving energy. However, existing technologies have the following problems: In the existing technology, the use of oil bearings in turbines has the following problems: first, lubricating oil will leak into natural gas, contaminating the process medium and affecting the back-end process and product purity; second, the operation and maintenance of the oil-bearing turbine expander is large and the transmission efficiency is low.

[0003] In addition, existing natural gas expansion and recompression units usually use an expander to drive the compressor alone. This operating mode has the following defects: First, when the compressor power is greater than the expander power, the compressor outlet parameters will not meet the process requirements; second, when the compressor power is less than the expander power, the industry usually uses a bypass pressure reducing valve to reflux into the compressor inlet to adjust the power. This method wastes the work of the expander and has low energy utilization.

[0004] Based on this, those skilled in the art have proposed a magnetic levitation natural gas expansion and recompression unit, system and method driven by both turbine and motor, providing a new solution to the above technical problems. Summary of the Invention

[0005] Based on this, it is necessary to provide a magnetic levitation natural gas expansion and recompression unit, system and method driven by both turbine and motor to address the problems raised in the above background technology.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: The turbine and motor dual-driven magnetic levitation natural gas expansion and compression unit specifically includes: Coaxial rigidly connected natural gas expander, high-speed synchronous motor and natural gas compressor; A magnetic suspension support system, comprising an expansion-side magnetic suspension bearing provided at the output end of the natural gas expander and a compression-side magnetic suspension bearing provided at the input end of the compressor, for achieving contactless suspension of the rotor and torque transmission; Electronic control unit: includes an electrical cabinet and a pressure sensor. The electrical cabinet has a built-in converter and a main controller. The converter connects the power grid and the high-speed synchronous motor. The main controller uses the outlet pressure of the natural gas compressor as a control variable to dynamically adjust the operating mode and power of the high-speed synchronous motor.

[0007] Optionally, the expansion-side magnetic bearing and the compression-side magnetic bearing are both five-degree-of-freedom active electromagnetic bearings, and are integrated with displacement sensors to monitor the radial and axial displacements of the rotor in real time; The magnetic suspension support system is connected to an independent magnetic bearing controller and dynamically adjusts the coil current of the magnetic bearing based on a PID or H∞ control algorithm to stabilize the rotor suspension posture.

[0008] Optionally, the high-speed synchronous motor is a permanent magnet synchronous motor; the converter is an IGBT bidirectional converter, which is used to realize switching between the motor mode, generator mode and idling mode of the high-speed synchronous motor.

[0009] A natural gas expansion and recompression system, comprising: Data acquisition module: acquires in real time the outlet pressure of the natural gas compressor, the natural gas mass flow rate, the inlet and outlet pressures and temperatures of the natural gas expander, the rotor displacement and speed, and the target outlet pressure of the natural gas compressor; Power decision module: calculates the expansion power of the natural gas expander and the target pressure power requirement of the natural gas compressor based on the collected data, where the target pressure power requirement is the compression power required by the natural gas compressor to reach the target outlet pressure, and performs: When the target pressure required power is greater than the expansion power, instructing the high-speed synchronous motor to operate in a motor mode; When the target pressure required power is less than the expansion power, instructing the high-speed synchronous motor to operate in a generator mode; When the target pressure required power is equal to the expansion power, an instruction is given to disconnect the high-speed synchronous motor from the power grid; Pressure closed-loop module: dynamically adjusts the input and output power of the high-speed synchronous motor based on the deviation between the target pressure and the actual pressure of the natural gas compressor.

[0010] Optionally, the pressure closed-loop module adopts feedforward and feedback composite control, the feedforward term generates the target pressure demand power corresponding to the target outlet pressure based on the natural gas compressor characteristic curve, and the feedback term corrects the pressure deviation through the PID algorithm.

[0011] Optionally, a high-pressure natural gas pipeline network is connected to the inlet of the natural gas expander for inputting high-pressure natural gas; a low-pressure natural gas pipeline network is connected to the inlet of the natural gas compressor for inputting natural gas to be pressurized; the outlet of the natural gas compressor is connected to the downstream process pipeline network, and its target outlet pressure is determined by the downstream process requirements; the power grid is connected to the converter to realize the input or feedback of electric energy.

[0012] A natural gas expansion and recompression method comprises the following steps: S1: The rotor is lifted to a suspended state through the expansion-side magnetic bearing and the compression-side magnetic bearing; S2: High-pressure natural gas drives the natural gas expander to work and reduce pressure, while low-pressure natural gas is fed into the natural gas compressor; S3: Calculate the real-time expansion power of the natural gas expander and the target pressure power requirement of the natural gas compressor, and decide the operating mode of the high-speed synchronous motor; S4: Based on the target pressure of the natural gas compressor, the power of the high-speed synchronous motor is adjusted to achieve coordinated optimization of pressure and energy efficiency.

[0013] Optionally, in step S3, the real-time calculation of the expansion power and the compression power is achieved by the following steps: S31: Dynamic acquisition of expansion power: S311: Real-time monitoring of the natural gas mass flow, inlet pressure and temperature, and outlet pressure and temperature of the natural gas expander inlet; S312: Based on the thermodynamic characteristics of natural gas, convert the pressure and temperature data into corresponding inlet specific enthalpy values ​​and outlet specific enthalpy values; S313: Outputting real-time expansion power based on the product of the inlet flow rate and the inlet / outlet specific enthalpy difference, combined with the efficiency characteristics of the natural gas expander; S32: Target pressure required power acquisition: S321: Collecting the natural gas mass flow, inlet pressure and temperature, and target outlet pressure of the natural gas compressor; S322: Based on the natural gas mass flow, inlet pressure and temperature, and target outlet pressure in S321, and in combination with the efficiency model of the natural gas compressor, output the target pressure demand power that meets the target outlet pressure.

[0014] Optionally, step S4 includes: S41: Pressure deviation response mechanism S411: When it is detected that the actual outlet pressure of the natural gas compressor is lower than the target outlet pressure, in the motor mode, the input power of the high-speed synchronous motor is increased to increase the speed of the natural gas compressor; in the generator mode, the power output is reduced to increase the pneumatic load of the natural gas compressor; S412: When it is detected that the compressor outlet pressure is higher than the target outlet pressure, a reverse adjustment operation is performed; S42: Energy Efficiency Optimization Strategy S421: Prioritize the use of the output power of the natural gas expander to drive the natural gas compressor; S422: Compensation is performed only when power imbalance occurs through energy interaction between the high-speed synchronous motor and the grid; S423: The optimization goal is to minimize the system's net energy dependence on the power grid.

[0015] Optionally, a security protection module is provided, wherein the security protection module includes a hierarchical response mechanism: Level 1 response: When a single operating parameter is detected to continuously deviate from the normal operating range, the unit output power is automatically reduced; Secondary response: When multiple related parameters are detected to deviate from the normal operating range, or the rotor dynamic stability index exceeds the preset tolerance, the following actions are performed: Close the natural gas expander inlet valve to cut off the power source; Disconnect the high-speed synchronous motor from the electrical grid; Level 3 response: A mechanical backup bearing is set up. When the risk of rotor suspension loss of control is detected, the system switches to the mechanical backup bearing system for emergency landing and shutdown. Among them, the execution of the third-level response action automatically includes the first-level and second-level response actions.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention eliminates the traditional gearbox by coaxially rigidly connecting the natural gas expander, high-speed synchronous motor, and natural gas compressor. Instead, it uses magnetic bearings to connect the natural gas expander, high-speed synchronous motor, and natural gas compressor, eliminating the lubrication system and effectively preventing lubricating oil from contaminating the natural gas. This significantly reduces maintenance costs and complexity and improves system reliability.

[0017] The present invention adopts a natural gas expander and a highly synchronous motor to dual-drive the natural gas compressor and has a reverse power generation function, which increases the operating flexibility of the unit. When the expansion power is less than the target pressure required power, the high-speed synchronous motor and the natural gas expander jointly drive the natural gas compressor; when the expansion power is greater than the target pressure required power, the excess power is reversely transmitted to the power grid through the high-speed synchronous motor, thereby increasing energy utilization. When the expansion power is equal to the target pressure required power, the natural gas expander directly drives the natural gas compressor, and energy is directly utilized with the highest efficiency. By switching between the three modes, the comprehensive energy utilization rate is significantly improved and energy waste is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the solutions in the present invention, a brief introduction will be given below to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 A schematic diagram of the overhead structure of a magnetically levitation natural gas expansion and recompression unit driven by both a turbine and a motor; Figure 2 This is a schematic diagram of the axial structure of a magnetic levitation natural gas expansion and recompression unit driven by both a turbine and a motor; Figure 3 This is a schematic diagram of the structure of a magnetic levitation natural gas expansion and recompression unit driven by both turbine and motor; Figure 4 The schematic diagram of a magnetically levitation natural gas expansion and compression unit driven by both a turbine and a motor; Figure 5 This is a schematic block diagram of the natural gas expansion and recompression method.

[0020] The markings in the figure are as follows: 1. Natural gas expander; 2. Natural gas compressor; 3. High-speed synchronous motor; 4. Expansion-side magnetic bearing; 5. Compression-side magnetic bearing; 6. Magnetic bearing controller; 7. Electrical cabinet. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0022] Please refer to Figure 1-5 The present invention provides a turbine and motor dual-driven magnetic levitation natural gas expansion and recompression unit, which specifically includes: The natural gas expander 1 is used to receive high-pressure natural gas, expand it to reduce the pressure to the process requirement, and then output it to the back-end process; the output shaft of the natural gas expander 1 transmits power through the expansion-side magnetic bearing 4.

[0023] Natural gas compressor 2, used to receive and compress low-pressure natural gas to the target outlet pressure before outputting; The natural gas expander 1, high-speed synchronous motor 3 and natural gas compressor 2 are coaxially rigidly connected. The expander adopts a high-speed centripetal turbine and a motor dual-drive to achieve seamless switching between the three modes of "dual-drive power supplement - direct drive high efficiency - reverse power generation and revenue creation", effectively eliminating power imbalance loss, and converting surplus expansion power into grid-connected power, greatly improving the energy efficiency of the system.

[0024] The magnetic suspension support system includes an expansion-side magnetic suspension bearing 4 located at the output end of the natural gas expander 1 and a compression-side magnetic suspension bearing 5 located at the input end of the compressor. These support systems are used to achieve contactless suspension and torque transmission for the rotor. By utilizing electromagnetic field coupling to achieve non-mechanical contact torque transmission, the system completely eliminates the lubricating oil system, preventing lubricating oil from contaminating natural gas. This effectively addresses the wear, leakage, and temperature runaway problems associated with traditional oil-lubricated bearings under high-speed operating conditions. The expansion-side magnetic bearing 4 and the compression-side magnetic bearing 5 are respectively arranged at the key support positions of the output shaft of the natural gas expander 1 and the input shaft of the natural gas compressor 2 to achieve contactless suspension, support and torque transmission of the rotor; this magnetic bearing system completely replaces the traditional oil lubrication system.

[0025] The expansion-side magnetic bearing 4 and the compression-side magnetic bearing 5 are both five-degree-of-freedom active electromagnetic bearings. Their stator cores are made of laminated silicon steel sheets, and the coil windings are embedded in liquid cooling channels. They also have integrated displacement sensors. The radial displacement sensor is embedded in the inner wall of the bearing stator, and the axial displacement sensor is located on the rotor end face. The detection accuracy is less than or equal to 0.1μm, and the bandwidth is greater than or equal to 1kHz. They monitor the radial and axial displacements of the rotor in real time. The magnetic levitation support system is connected to an independent magnetic bearing controller 6 and dynamically adjusts the coil current of the magnetic bearing based on the PID or H∞ control algorithm to stabilize the rotor suspension posture. The control target is to maintain the rotor radial suspension gap of 50±5μm, so as to take into account both air gap efficiency and anti-disturbance capability, and the axial gap of 30±3μm to match the thrust balance requirements of the natural gas compressor.

[0026] In an optional embodiment, a mechanical protection bearing is provided, which is arranged outside the magnetic suspension bearing, with a gap of 100 μm between it and the rotor, and the surface is coated with a diamond-like wear-resistant coating to protect the rotor system during emergency landing.

[0027] Electronic control unit: includes an electrical cabinet 7 and a pressure sensor. The electrical cabinet 7 has a built-in converter and a main controller. The converter connects the power grid and the high-speed synchronous motor 3. The main controller uses the outlet pressure of the natural gas compressor 2 as the control variable to dynamically adjust the operating mode and power of the high-speed synchronous motor 3.

[0028] The converter includes a rectifier unit, a DC bus, an inverter unit, a grid-connected unit, and a control board.

[0029] The control system receives the pressure sensor signal from the outlet of the natural gas compressor 2, takes the outlet pressure as the control variable, and dynamically adjusts the electric power input or output to the high-speed synchronous motor 3 to ensure that the outlet pressure of the natural gas compressor 2 is stable at the target outlet pressure and minimize the energy consumption of the system operation.

[0030] The high-speed synchronous motor 3 is a permanent magnet synchronous motor; the converter is an IGBT bidirectional converter, which is used to switch the high-speed synchronous motor 3 between the motor mode, generator mode and idling mode; The converter has three working mode interfaces: Motor mode: absorbs DC power from the grid and converts it into variable frequency AC power to drive the motor; Generator mode: The variable frequency AC power generated by the rectifier motor is fed back to the grid through the grid-connected unit; Idle mode: The grid connection is disconnected and the DC bus capacitor maintains the floating charge voltage.

[0031] In another embodiment, a natural gas expansion and recompression system includes: Data acquisition module: real-time acquisition of the outlet pressure of natural gas compressor 2, natural gas mass flow, inlet and outlet pressures and temperatures of natural gas expander 1, rotor displacement and speed; The high-speed synchronous motor 3 has a rotor coaxially and rigidly connected to the output shaft of the natural gas expander and the input shaft of the natural gas compressor.

[0032] The Kalman filter algorithm is used to fuse multi-sensor data to eliminate interference signals such as pressure pulsation and electromagnetic noise in real time. The sampling frequency is ≥100 Hz, ensuring that the control response delay is less than 10 ms. Power decision module: Calculates the expansion power of natural gas expander 1 and the target pressure power requirement of natural gas compressor 2 based on the collected data. The target pressure power requirement is the compression power required by natural gas compressor 2 to reach the target outlet pressure, and performs the following operations: When the target pressure required power is greater than the expansion power, the high-speed synchronous motor 3 is instructed to operate in the motor mode; When the target pressure required power is less than the expansion power, the high-speed synchronous motor 3 is instructed to operate in generator mode; When the target pressure required power is equal to the expansion power, the command is issued to disconnect the high-speed synchronous motor 3 from the power grid; Pressure closed-loop module: Regardless of the operating mode of the high-speed synchronous motor 3, the control system always uses the compressor outlet pressure as the key controlled variable and dynamically adjusts the input and output power of the high-speed synchronous motor 3 based on the deviation between the target pressure and the actual pressure of the natural gas compressor 2.

[0033] The pressure sensor feeds real-time pressure signals back to the electrical cabinet control system. The control system then compares the actual pressure with the set target outlet pressure to determine the pressure deviation. Based on this pressure deviation and its changing trend, the control system dynamically adjusts the work capacity of natural gas compressor 2 by fine-tuning the input or output power of high-speed synchronous motor 3, thereby eliminating the pressure deviation and ensuring that the outlet pressure remains stable at the target value. This adjustment process also takes into account the principle of optimal energy efficiency within the current operating mode, such as prioritizing expansion power in dual-drive mode and maximizing power generation in reverse power generation mode, thereby minimizing global energy consumption while maintaining stable pressure.

[0034] In electric mode, the converter increases the output power of the inverter unit to increase the motor torque, thereby increasing the compressor speed and thus increasing the outlet pressure.

[0035] In power generation mode, the converter reduces the output power of the grid-connected unit, which reduces the motor power generation load, thereby increasing the compressor load and increasing the outlet pressure.

[0036] It should be noted that the unit should be equipped with a comprehensive protection system, including but not limited to: overspeed protection, vibration limit protection (based on magnetic bearing displacement signals), bearing temperature protection, intake and exhaust pressure and temperature protection, motor overcurrent, overvoltage, undervoltage protection, and grid fault protection. Once a protection condition is triggered, the unit will shut down or reduce load according to the preset safety logic.

[0037] The pressure closed-loop module adopts feedforward and feedback compound control. The feedforward term generates the target pressure demand power corresponding to the target outlet pressure based on the characteristic curve of natural gas compressor 2, and the feedback term corrects the pressure deviation through the PID algorithm. In the forward feedback control channel, the three-dimensional characteristic curve of the compressor, i.e., the flow-pressure ratio-efficiency mapping table, is pre-stored. By inputting the target outlet pressure and real-time flow, the target pressure demand power corresponding to the target outlet pressure is obtained; In the feedback adaptive channel, the deviation ΔP between the actual pressure and the target outlet pressure is monitored, and fuzzy rules are used to dynamically adjust the PID parameters. If |ΔP|>0.1 MPa, the proportional gain is increased to achieve rapid deviation correction; if ΔP is continuously negative, the integral effect is enhanced to eliminate the steady-state error, and the final output power correction amount ΔPa; When the high-speed synchronous motor 3 is in motor mode, the final power instruction is: the power at the actual pressure plus the power correction amount ΔPa; when the high-speed synchronous motor 3 is in generator mode, the final power instruction is: the power at the actual pressure minus the power correction amount ΔPa.

[0038] The high-pressure natural gas pipeline network is connected to the inlet of the natural gas expander 1 for inputting high-pressure natural gas; the low-pressure natural gas pipeline network is connected to the inlet of the natural gas compressor 2 for inputting natural gas to be pressurized; the outlet of the natural gas compressor 2 is connected to the downstream process pipeline network, and its target outlet pressure is determined by the downstream process requirements; the power grid is connected to the converter to realize the input or feedback of electric energy.

[0039] A natural gas expansion and recompression method comprises the following steps: Step S1: Magnetic levitation safety start: The rotor is lifted to a suspended state by the expansion-side magnetic bearing 4 and the compression-side magnetic bearing 5. The suspension control of the magnetic bearings is divided into two stages. In the first stage, a step current is applied to the magnetic bearings to lift the rotor to a suspension height of 50μm. In the second stage, a PID or H∞ controller intervenes to stabilize the rotor to a working clearance of 100±5μm. After the rotor radial vibration is detected to be less than 0.8mm / s, the natural gas valve is allowed to open. Step S2: Operating condition perception and dynamic power estimation: High-pressure natural gas drives the natural gas expander 1 to work and reduce pressure, while low-pressure natural gas is input into the natural gas compressor 2; (1) Real-time perception of expansion power: Collect the natural gas mass flow, inlet and outlet pressures and temperatures at the expander inlet; Query the real-time physical property database to obtain specific enthalpy values: Based on pressure and temperature data, combined with the natural gas physical property database, determine the inlet specific enthalpy value and the outlet specific enthalpy value; Combined with the expander efficiency curve, output the real-time expansion power of the natural gas expander 1; The specific calculation process is as follows: the real-time expansion power can be obtained by multiplying the flow rate by the specific enthalpy difference and then multiplying it by the adiabatic efficiency of the expander.

[0040] (2) Target compression power decision: Receive the target outlet pressure set by the downstream process and calculate the target required power of the natural gas compressor 2 based on the compressor adiabatic model and the real-time inlet flow and pressure; The real-time calculation of expansion power and compression power is achieved through the following steps: Dynamic acquisition of expansion power: (1) Real-time monitoring of the natural gas mass flow, inlet pressure and temperature, and outlet pressure and temperature at the inlet of natural gas expander 1; (2) Based on the thermodynamic characteristics of natural gas, the pressure and temperature data are converted into the corresponding inlet specific enthalpy and outlet specific enthalpy values. The specific enthalpy values ​​are obtained by real-time querying the natural gas physical property database; (3) Output the real-time expansion power based on the product of the inlet flow rate and the difference between the inlet and outlet specific enthalpy values, combined with the expander efficiency characteristics; Target pressure required power acquisition: (1) Collect the natural gas mass flow rate, inlet pressure and temperature, and target outlet pressure at the inlet of natural gas compressor 2; (2) Based on the adiabatic index and gas constant of natural gas, the theoretical adiabatic compression work is calculated. Combined with the efficiency model of the compressor, the target pressure demand power that meets the target outlet pressure is output.

[0041] Step S3: Three-mode adaptive switching When the target power demand is greater than the expansion power, the high-speed synchronous motor 3 operates in motor mode. At this time, the converter draws power from the grid to drive the high-speed synchronous motor 3 to output compensation power. In this state, the expander and the motor jointly drive the compressor. When the target power demand is less than the expansion power, the high-speed synchronous motor 3 operates in generator mode. At this time, the surplus power of the natural gas expander 1 drives the high-speed synchronous motor 3 to generate electricity, and the converter is connected to the grid to output electrical energy. When the target required power is equal to the expansion power, the high-speed synchronous motor 3 operates in motor mode. At this time, the connection between the high-speed synchronous motor 3 and the power grid is disconnected, and the DC bus maintains the floating charge voltage. In this state, the expander directly drives the compressor to operate.

[0042] Step S4: Taking the target pressure of the natural gas compressor 2 as a benchmark, the power of the high-speed synchronous motor 3 is adjusted to achieve coordinated optimization of pressure and energy efficiency; Pressure deviation response mechanism (1) When it is detected that the actual outlet pressure of the natural gas compressor 2 is lower than the target outlet pressure, in the motor mode, the input power of the high-speed synchronous motor 3 is increased to increase the speed of the natural gas compressor 2; in the generator mode, the power output is reduced to increase the pneumatic load of the natural gas compressor 2; (2) When it is detected that the compressor outlet pressure is higher than the target outlet pressure, a reverse regulation operation is performed; Energy efficiency optimization strategy (1) Prioritizing the use of the output power of the natural gas expander 1 to drive the natural gas compressor 2; (2) Compensation is performed only when power imbalance occurs through energy interaction between the high-speed synchronous motor 3 and the grid; (3) The optimization goal is to minimize the system’s net energy dependence on the power grid.

[0043] Set up a security protection module, which includes a hierarchical response mechanism: Level 1 response: When a single operating parameter is detected to continuously deviate from the normal operating range, the unit output power is automatically reduced; Secondary response: When multiple related parameters are detected to deviate from the normal operating range, or the rotor dynamic stability index exceeds the preset tolerance, the following actions are performed: Close the air inlet valve of the natural gas expander 1 to cut off the power source; Disconnect the electrical connection between the high-speed synchronous motor 3 and the power grid; Level 3 response: A mechanical backup bearing is set up. When the risk of rotor suspension loss of control is detected, the system switches to the mechanical backup bearing system for emergency landing and shutdown. Among them, the execution of the third-level response action automatically includes the first-level and second-level response actions.

[0044] Those skilled in the art will clearly understand that for the sake of convenience and brevity, the division of the above-mentioned functional modules is only used as an example for illustration. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. The specific working processes of the above-mentioned systems, devices, and units can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

Claims

1. A turbine and motor dual-driven magnetic levitation natural gas expansion and compression unit, characterized in that: include: A natural gas expander (1), a high-speed synchronous motor (3) and a natural gas compressor (2) that are coaxially rigidly connected; A magnetic suspension support system comprising an expansion-side magnetic suspension bearing (4) provided at the output end of the natural gas expander (1) and a compression-side magnetic suspension bearing (5) provided at the input end of the compressor, for achieving contactless suspension of the rotor and torque transmission; The electric control unit comprises an electric cabinet (7) and a pressure sensor. The electric cabinet (7) has a built-in converter and a main controller. The converter is connected to the power grid and the high-speed synchronous motor (3). The main controller uses the outlet pressure of the natural gas compressor (2) as a control variable to dynamically adjust the operating mode and power of the high-speed synchronous motor (3).

2. The turbine and motor dual-drive magnetic levitation natural gas expansion and recompression unit according to claim 1, characterized in that: The expansion-side magnetic suspension bearing (4) and the compression-side magnetic suspension bearing (5) are both five-degree-of-freedom active electromagnetic bearings, and are integrated with displacement sensors to monitor the radial and axial displacements of the rotor in real time; The magnetic suspension support system is connected to an independent magnetic bearing controller (6) and dynamically adjusts the coil current of the magnetic bearing based on a PID or H∞ control algorithm to stabilize the rotor suspension posture.

3. The turbine and motor dual-drive magnetic levitation natural gas expansion and compression unit according to claim 1, characterized in that: The high-speed synchronous motor (3) is a permanent magnet synchronous motor; the converter is an IGBT bidirectional converter, which is used to realize switching between the motor mode, the generator mode and the idling mode of the high-speed synchronous motor (3).

4. A natural gas expansion and recompression system according to any one of claims 1 to 3, characterized in that: include: Data acquisition module: real-time acquisition of the outlet pressure of the natural gas compressor (2), the natural gas mass flow rate, the inlet and outlet pressures and temperatures of the natural gas expander (1), the rotor displacement and speed, and the target outlet pressure of the natural gas compressor (2); Power decision module: calculates the expansion power of the natural gas expander (1) and the target pressure demand power of the natural gas compressor (2) based on the collected data, wherein the target pressure demand power is the compression power required by the natural gas compressor (2) to reach the target outlet pressure, and executes: When the target pressure required power is greater than the expansion power, instructing the high-speed synchronous motor (3) to operate in motor mode; When the target pressure required power is less than the expansion power, instructing the high-speed synchronous motor (3) to operate in a generator mode; When the target pressure required power is equal to the expansion power, an instruction is given to disconnect the high-speed synchronous motor (3) from the power grid; A pressure closed-loop module dynamically adjusts the input and output power of the high-speed synchronous motor (3) based on the deviation between the target pressure and the actual pressure of the natural gas compressor (2).

5. The natural gas expansion and recompression system according to claim 4, characterized in that: The pressure closed-loop module adopts feedforward and feedback composite control, wherein the feedforward term generates a target pressure demand power corresponding to the target outlet pressure based on the characteristic curve of the natural gas compressor (2), and the feedback term corrects the pressure deviation through a PID algorithm.

6. The natural gas expansion and recompression system according to claim 4, characterized in that: The high-pressure natural gas pipeline network is connected to the inlet of the natural gas expander (1) for inputting high-pressure natural gas; the low-pressure natural gas pipeline network is connected to the inlet of the natural gas compressor (2) for inputting natural gas to be pressurized; the outlet of the natural gas compressor (2) is connected to the downstream process pipeline network, and its target outlet pressure is determined by the downstream process requirements; the power grid is connected to the converter to realize the input or feedback of electric energy.

7. A natural gas expansion and recompression method, characterized in that: The following steps are involved: S1: lifting the rotor to a suspended state through the expansion side magnetic suspension bearing (4) and the compression side magnetic suspension bearing (5); S2: High-pressure natural gas drives the natural gas expander (1) to perform work and reduce pressure, while low-pressure natural gas is input into the natural gas compressor (2); S3: Calculate the real-time expansion power of the natural gas expander (1) and the target pressure power requirement of the natural gas compressor (2), and decide the operation mode of the high-speed synchronous motor (3); S4: Taking the target pressure of the natural gas compressor (2) as a benchmark, the power of the high-speed synchronous motor (3) is adjusted to achieve coordinated optimization of pressure and energy efficiency.

8. The natural gas expansion and recompression method according to claim 7, characterized in that: In step S3, the real-time calculation of the expansion power and compression power is achieved by the following steps: S31: Dynamic acquisition of expansion power; S311: Real-time monitoring of the natural gas mass flow rate, inlet pressure and temperature, and outlet pressure and temperature of the natural gas expander (1); S312: Based on the thermodynamic characteristics of natural gas, convert the pressure and temperature data into corresponding inlet specific enthalpy values ​​and outlet specific enthalpy values; S313: Outputting the real-time expansion power of the natural gas expander (1) based on the product of the inlet flow rate and the difference between the inlet and outlet specific enthalpy values ​​and the efficiency characteristics of the expander; S32: target pressure required power acquisition; S321: Collecting the natural gas mass flow rate, inlet pressure and temperature, and target outlet pressure of the natural gas compressor (2); S322: Based on the natural gas mass flow, inlet pressure and temperature, and target outlet pressure in S321, and in combination with the efficiency model of the natural gas compressor (2), output the target pressure demand power that meets the target outlet pressure.

9. The natural gas expansion and recompression method according to claim 7, characterized in that: The step S4 comprises: S41: Pressure deviation response mechanism; S411: When it is detected that the actual outlet pressure of the natural gas compressor (2) is lower than the target outlet pressure, in the motor mode, the input electric power of the high-speed synchronous motor (3) is increased to increase the speed of the natural gas compressor (2); in the generator mode, the power output is reduced to increase the pneumatic load of the natural gas compressor (2); S412: When it is detected that the compressor outlet pressure is higher than the target outlet pressure, a reverse adjustment operation is performed; S42: Energy efficiency optimization strategy; S421: Prioritizing the use of the output power of the natural gas expander (1) to drive the natural gas compressor (2); S422: Compensation is performed only when there is power imbalance through energy interaction between the high-speed synchronous motor (3) and the grid; S423: The optimization goal is to minimize the system's net energy dependence on the power grid.

10. The natural gas expansion and recompression method according to any one of claims 7 to 9, characterized in that: Set up a security protection module, which includes a hierarchical response mechanism: Level 1 response: When a single operating parameter is detected to continuously deviate from the normal operating range, the unit output power is automatically reduced; Secondary response: When multiple related parameters are detected to deviate from the normal operating range, or the rotor dynamic stability index exceeds the preset tolerance, the following actions are performed: Close the air inlet valve of the natural gas expander (1) to cut off the power source; Disconnecting the high-speed synchronous motor (3) from the electrical grid; Level 3 response: A mechanical backup bearing is set up. When the risk of rotor suspension loss of control is detected, the system switches to the mechanical backup bearing system for emergency landing and shutdown. Among them, the execution of the third-level response action automatically includes the first-level and second-level response actions.

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