Island operation of a turbo expander

Abstract

The turbo expander can operate as a microgrid generator for islanding operation. The turbo expander can recover the energy lost during the pressure drop sequence to generate electricity. The pressurized process gas can rotate the turbine, thereby rotating the rotor within the stator of the turbo expander. The power electronics can include an islanding mode inverter for outputting an alternating current having a frequency and amplitude suitable for feeding power to the load. The power electronics can include a battery that is charged by the turbo expander and can supply power to start the turbo expander. The power electric can include a bidirectional inverter that sends surplus power from the turbo expander to the power grid and receives power from the power grid for starting.

Description

Technical Field

[0001] Claim of Priority This application claims the priority of U.S. Patent Application No. 17 / 804,265, filed on May 26, 2022, the entire content of which is incorporated herein by reference.

Background Art

[0002] The efficient and effective movement of gas from production areas to consumption areas uses large-scale and sophisticated transportation systems. The gas transported through pipelines can be pressurized and cross long distances through pipelines at high pressure. For example, natural gas transported through pipelines moves through the pipeline at high pressure. Natural gas is one of the major energy sources for many of our daily needs and activities. Natural gas is an attractive fossil fuel due to its abundance and relative cleanliness. As another example, hydrogen can also be transported at high pressure using pipelines. Hydrogen is a rapidly expanding global energy storage market. Hydrogen is used in many manufacturing processes from oil refining to food processing. Hydrogen is also used as a fuel source for gas turbines and in a wide range of fuel cells for power generation in the industrial and consumer transportation sectors. Other gases, including propane, oxygen, carbon dioxide, etc., can also be transported through high-pressure pipelines.

Summary of the Invention

[0003] Aspects of the embodiments include an apparatus including a generator. The generator includes a turbine wheel configured to receive a process gas, flow into an inlet of the turbine wheel, and rotate in response to expansion of the process gas flowing out of an outlet of the turbine wheel, a rotor coupled to the turbine wheel and configured to rotate with the turbine wheel, and a stationary stator. The generator generates an alternating current when the rotor within the stator rotates. The apparatus includes a power converter circuit coupled to the electrical output of the generator, the power converter circuit converting the alternating current from the generator into a direct current, and an islanding mode inverter circuit coupled to the electrical output of the rectifier circuit, the islanding mode inverter circuit converting the direct current from the rectifier circuit into an alternating current having a frequency and amplitude for supplying power to a load.

[0004] Aspects of the embodiments include a system including a generator and power electronics. The generator includes a turbine wheel configured to receive a process gas, flow into an inlet of the turbine wheel, and rotate in response to expansion of the process gas flowing out of an outlet of the turbine wheel, a rotor coupled to the turbine wheel and configured to rotate with the turbine wheel, and a stationary stator. The generator generates an alternating current when the rotor within the stator rotates. The power electronics includes a power converter circuit coupled to the electrical output of the generator, the power converter circuit converting the alternating current from the generator into a direct current, and an islanding mode inverter circuit coupled to the electrical output of the rectifier circuit, the islanding mode inverter circuit converting the direct current from the rectifier circuit into an alternating current having a frequency and amplitude for supplying power to a load.

[0005] Some aspects of the embodiments include a brake resistor rectifier coupled to the electrical output of the generator and a brake resistor assembly coupled to the output of the brake resistor rectifier.

[0006] In some implementations of the embodiments, the brake resistor assembly includes a brake resistor that is speed-controlled and current-regulated.

[0007] Some aspects of the embodiments include a battery coupled to a generator, the battery storing power received from the generator and supplying power to rotate a rotor within a stator.

[0008] In some implementations of the embodiments, the battery is coupled to a power converter circuit, the power converter circuit receiving an alternating current from the generator, converting the alternating current to a direct current for storage in the battery, receiving a direct current from the battery, and converting the direct current to an alternating current to supply power to the rotor.

[0009] Some aspects of the embodiments include a bidirectional inverter including an islanding mode inverter circuit and an active grid inverter that converts a direct current to an alternating current having a frequency and amplitude suitable for a power grid.

[0010] In some implementations of the embodiments, the bidirectional inverter supplies power to a load and supplies excess power to the power grid.

[0011] In some implementations of the embodiments, the bidirectional inverter supplies power from the power grid to the rotor to rotate the rotor within the stator before the process gas rotates the turbine wheel.

[0012] In some implementations of the embodiments, the generator comprises a three-phase permanent magnet synchronous generator.

[0013] Some aspects of the embodiments include a bidirectional inverter that conducts current to a load and conducts excess current to the power grid.

[0014] In some implementations of the embodiments, the bidirectional inverter comprises an active grid inverter that conducts power to the power grid and receives power from the power grid.

[0015] Aspects of the embodiments include flowing gas through a turbine wheel of a generator that is downstream of a flow control valve, generating an electric current by the generator, guiding the electric current generated by the generator to power electronics in islanding mode, and guiding an electric current from the power electronics in islanding mode to a load.

[0016] Some aspects of the embodiments include guiding excess electric current generated by the generator and not guided to the load through an active grid inverter to the power grid.

[0017] Some aspects of the embodiments include performing startup of the generator using power received from the power grid through an active grid inverter.

[0018] Some aspects of the embodiments include guiding excess electric current generated by the generator and not guided to the load to a battery.

[0019] Some aspects of the embodiments include performing startup of the generator using power received from the battery.

[0020] In some implementations, the islanding mode inverter circuit includes a circuit configuration that receives a direct current on a DC bus, converts the direct current to an alternating current, and adjusts the alternating current to a frequency and amplitude suitable for the load.

[0021] Some aspects of the embodiments include a master controller circuit that controls the flow of current to a braking resistor during a fault condition.

[0022] Some aspects of the embodiments include an active rectifier electrically connected between the generator and the braking resistor, and the master controller activates the active rectifier to conduct current from the generator to the braking resistor based on the presence of a fault condition when the fault condition is detected.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0024] Like reference numerals in the various drawings indicate like elements. The drawings are not to scale.

[0025] Natural gas, hydrogen, and other process gases are sometimes pressurized to facilitate efficient transport in pipelines that can be miles in length. Pipelines transport gas, for example, from production sites (such as wells) to processing facilities and from processing facilities to local distribution networks such as distribution networks in regions, cities, or districts or industrial plant networks at the site. To safely deliver and use the gas through the local distribution network, the process gas is depressurized (often using a pressure regulator) to a lower level. The pressure is stepped down at pressure letdown (PLD) stations to deliver to industrial, commercial, and residential end-users. PLD stations use control valves to achieve the required pressure drop but waste a significant amount of energy in the process. Additional control valves can be used elsewhere for pressure control, such as within pipelines between production and processing facilities, within sub-processes of processing facilities, and within end-user processes and piping. A turboexpander generator can be installed in parallel with the control valve to recover waste energy from the pressure drop and generate electricity. The electricity can be directed to the power grid or elsewhere. Similarly, a turboexpander generator can be installed at a gas storage facility upstream of one or more storage tanks to recover high-pressure gas discharged from a tanker truck through the turboexpander generator into the storage tank. Turboexpander generators are associated with other applications such as hydrogen liquefaction processes where cooled and pressurized gaseous hydrogen is expanded to the liquid state. The expansion can be carried out through a turboexpander generator to recover waste energy from the expansion and generate electricity. As described above, the electricity can be directed to the power grid or elsewhere so that it can be used to power compressors or other components of the liquefaction process. In each case, by recovering the energy lost from the pressure drop applications of natural gas and hydrogen, the turboexpander can also generate electricity while reducing CO2 emissions, increasing the overall efficiency of the plant, offsetting electricity costs, and generating additional revenue.

[0026] A power grid to which a turboexpander can supply power (and draw power therefrom) may be a national or regional power grid, a local power grid for a city or district, or a small grid, local grid, or microgrid such as an on-site grid that supplies power to a building, campus, industrial manufacturing or processing plant, or neighborhood.

[0027] FIG. 1 is a schematic diagram of a power generation system 100 coupled to a power grid 140, according to an embodiment of the present disclosure. The power generation system 100 can be added to a PLD station to capture energy from the expansion of a gas from a PLD process or for any of the other applications described above. The power generation system 100 includes a turboexpander 102 in parallel with a pressure control valve 130. The turboexpander 102 is axially arranged so that the turboexpander 102 can be attached in line with a pipe. The turboexpander 102 functions as a generator by generating electrical energy from the rotational kinetic energy derived from the expansion of a gas passing through a turbine wheel 104. For example, the rotation of the turbine wheel 104 can be used to rotate a rotor 108 within a stator 110, thereby generating electrical energy.

[0028] FIG. 1 is a schematic diagram of a power generation system 100 coupled to a power grid 140, according to an embodiment of the present disclosure. The power generation system 100 can be added to a PLD station to capture energy from the expansion of a gas from a PLD process. The power generation system 100 includes a turboexpander 102 in parallel with a pressure control valve 130. The turboexpander 102 is axially arranged so that the turboexpander 102 can be attached in line with a pipe. The turboexpander 102 functions as a generator by generating electrical energy from the rotational kinetic energy derived from the expansion of a gas passing through a turbine wheel 104. For example, the rotation of the turbine wheel 104 can be used to rotate a rotor 108 within a stator 110, thereby generating electrical energy.

[0029] The turboexpander 102 can include a high-performance high-speed permanent magnet generator. In certain embodiments, the turboexpander 102 includes a radial inflow expansion turbine wheel 104. The turboexpander 102 can also include low-loss active magnetic bearings (AMB) 116a, b. The rotor assembly can include a permanent magnet section with the turbine wheel 104 directly attached to the rotor hub. The rotor 108 can be levitated by a magnetic bearing system, creating a frictionless (or near-frictionless) interface between the dynamic and static components. The AMBs 116a, b facilitate lossless (or near-lossless) rotation of the rotor 108.

[0030] The turboexpander 102 is shown with process gas flowing through the system, which cools the generator section and eliminates the need for auxiliary cooling equipment. In some embodiments, a non-flow-through overhang type system can also be implemented. The power electronics for the turboexpander 118 combines, in some implementations, a variable speed drive (VSD) 166 and a magnetic bearing controller (MBC) 168 within one cabinet. The VSD enables a consistent and clean delivery of generated power from the turboexpander 102 to the power grid 140. The VSD 166 adjusts the frequency and amplitude of the generated current to match the local grid. After expansion, the gas exits the turboexpander 102 along the same axial path towards the downstream process.

[0031] The turboexpander 102 is shown as having a through-flow configuration. The through-flow configuration enables the process gas to flow from the inlet side of the turboexpander 102 to the outlet side of the turboexpander 102. The gas flows into the radial gas inlet 154 towards the turbine wheel 104 and into the axial gas outlet 156 from the turbine wheel 104. The gas then flows out of the outlet 156 through the generator, and the gas returns to the gas pipeline 170. Generally, the high-pressure process gas 120 is directed to flow into the turboexpander 102 through the flow control system 126. The flow control system 126 includes a flow or mass control valve and an emergency shut-off valve. The flow control system 126 can be electrically controlled from the power electronics 118 by the control line 164. In an embodiment, the housing 112 of the turboexpander is hermetically sealed. As described above, the turboexpander can be non-through-flow and overhung type without departing from the scope of the present disclosure. The high-pressure process gas 120 expands as it flows through the turbine wheel 104, resulting in a pressure drop of the process gas. The low-pressure process gas 128 exits the turboexpander. The expansion of the high-pressure process gas 120 through the turbine wheel 104 rotates the turbine wheel 104, which rotates the rotor 108. The rotation of the rotor 108 within the stator 110 generates electrical energy. The turboexpander 102 achieves a desired pressure drop and captures the energy from the pressure drop to generate electricity. A pressure control valve 130, such as a conventional pressure regulator, can be installed in parallel with the turboexpander 102. The pressure control valve 130 can be used to control the pressure of the high-pressure process gas 120 flowing through the turboexpander. Excess high-pressure process gas not directed into the turboexpander can be directed through the pressure control valve 130.

[0032] In some embodiments, the heater 122 can heat the high-pressure process gas 120 before flowing the gas to the turboexpander 102. For example, if the expansion of the gas through the turbine wheel 104 reduces the temperature of the process gas to the point where moisture in the gas freezes at the turbine wheel or other downstream locations within the pipeline, the pressurized process gas 120 can be heated by the heater 122. The heated high-pressure process gas 124 can then be directed into the turboexpander 102. Heating the process gas can prevent moisture from freezing when the gas expands and its temperature decreases.

[0033] The turboexpander 102 includes a turbine wheel 104. The turbine wheel 104 is shown as a radially-inflow turbine wheel, but other configurations such as an axial-flow turbine wheel are also within the scope of the present disclosure. In this example, the heated high-pressure process gas 124 is received from the inlet conduit 150 of the housing 112 and enters an inlet 154 that is radially oriented with respect to the turbine wheel 104. In certain embodiments, the fluid flows through the inlet conduit 150 and is split by a diverter to a radial inlet 154 that directs the flow to the radially-inflow portion of the turbine wheel 104. After expansion, the low-pressure process gas exits the turbine wheel 104 from an axially-oriented outlet 156 to an outlet conduit 152 of the housing 112.

[0034] The turbine wheel 104 can be directly fixed to the rotor 108 or the intermediate common shaft, for example, by means of fasteners, a rigid drive shaft, welding, or other methods. For example, the turbine wheel 104 can be received at one end of the rotor 108 and held by the shaft to the rotor 108. The shaft is screwed into the rotor 108 at one end and captures the turbine wheel 104 between the end of the rotor 108 and a nut received by the screw at the other end of the shaft. The turbine wheel 104 and the rotor 108 can be coupled without a gearbox and can rotate at the same speed. In other cases, the turbine wheel 104 can be indirectly coupled to the rotor 108, for example, by means of a gear train, a clutch mechanism, or other methods.

[0035] The turbine wheel 104 includes a plurality of turbine - wheel blades 106 that extend outwardly from the hub and react with the expanding process gas to rotate the turbine wheel 104. FIG. 1 shows a turbine wheel without a shroud, and each of the turbine blades 106 has an exposed blade tip that is oriented substantially radially and extends between a radial inlet 154 and an axial outlet 156. As will be described in more detail below, the blade tip seals substantially against a shroud 114 inside the housing 112. In certain cases, the turbine wheel 104 is a turbine wheel with a shroud.

[0036] In the configuration of the turbine wheel 104 without a shroud, the housing 112 includes an inwardly oriented shroud 114 that is present proximate to the turbine wheel blades 106 and that has little contact during operation. The proximity of the turbine wheel blades 106 and the shroud 114 substantially seals the passage of the process gas therebetween as the process gas flows through the turbine wheel 104. Some amount of the process gas may leak or pass between the turbine wheel blades 106 and the shroud 114, but the leakage is negligible in the operation of the turbine wheel 104. In certain cases, the leakage may be equivalent to other similar turbine / shroud surface interfaces without a shroud using conventional tolerances between the turbine wheel blades 106 and the shroud 114. The amount of leakage considered acceptable leakage may be predetermined. The operating parameters of the turbine generator can be optimized to reduce leakage. In an embodiment, the housing 112 is hermetically sealed to prevent the process gas from escaping from the radial inlet 154 of the turbine wheel 104.

[0037] The shroud 114 may be present at a specific distance from the turbine wheel blades 106 and is maintained at a constant distance from the turbine wheel blades 106 during operation of the turboexpander 102 by using a magnetic positioning device including an active magnetic bearing and a position sensor.

[0038] Bearings 116a and 116b are arranged to rotatably support the rotor 108 and the turbine wheel 104 with respect to the stator 110 and the shroud 114. The turbine wheel 104 is supported in a cantilevered manner by the bearings 116a, 116b. In an embodiment, the turbine wheel 104 may be supported in a non-cantilevered manner, and the bearings 116a and 116b may be arranged on the outlet side of the turbine wheel 104. In certain cases, one or more of the bearings 116a or 116b can include ball bearings, needle bearings, magnetic bearings, foil bearings, journal bearings, and the like.

[0039] Bearings 116a and 116b may be a combination of a radial bearing and a thrust bearing that support the rotor 108 in the radial and axial directions. Other configurations can also be utilized. Bearings 116a and 116b do not have to be of the same type.

[0040] In an embodiment where bearings 116a and 116b are magnetic bearings, a magnetic bearing controller (MBC) 168 is used to control magnetic bearings 116a and 116b. Position sensors 117a, 117b are used to detect the position or change in position of the turbine wheel 104 and / or rotor 108 relative to the housing 112 or other reference points (such as predetermined values). Position sensors 117a, 117b can detect axial and / or radial displacements. Magnetic bearings 116a and / or 116b can respond to information from position sensors 117a, 117b and adjust the detected displacement as needed. MBC 168 can receive information from position sensor(s) 117a, 117b, process the information, and provide control signals to magnetic bearings 116a, 116b. MBC 168 can communicate with various components of the turboexpander 102 via communication channel 162.

[0041] By using magnetic bearings 116a, 116b and position sensors 117a, 117b to maintain and / or adjust the position of the turbine wheel blade 106 so that it remains close to the shroud 114, it becomes possible to operate the turboexpander 102 without the need for a seal (e.g., without the need for a dynamic seal). The use of active magnetic bearings 116a, b in the turboexpander 102 eliminates not only physical contact between the rotating and stationary components but also lubrication, the lubrication system, and seals.

[0042] The turboexpander 102 may include one or more backup bearings. For example, during startup and shutdown, or in the event of a power outage that affects the operation of the magnetic bearings 116a and 116b, bearings can be used to rotatably support the turbine wheel 104 during that period. The backup bearings can include ball bearings, needle bearings, journal bearings, etc. As described above, the turboexpander 102 is configured to generate electricity in response to the rotation of the rotor 108. In certain instances, the rotor 108 can include one or more permanent magnets. The stator 110 includes a plurality of conductive coils. The current is generated by the rotation of the magnets within the coils of the stator 110. The rotor 108 and the stator 110 can be configured as a synchronous permanent magnet polyphase alternating current (AC) generator. The electrical output 160 can be, for example, a three-phase output. In certain instances, the stator 110 can include a plurality of coils (e.g., three or six coils for a 3-phase AC output). When the rotor 108 rotates, a voltage is induced in the stator coils. At any given instant, the magnitude of the voltage induced in the coils is proportional to the rate at which the magnetic field enclosed by the coils changes over time (i.e., the rate at which the magnetic field passes through the two sides of the coil). In the case where the rotor 108 is coupled to rotate at the same speed as the turbine wheel 104, the turboexpander 102 is configured to generate electricity at that speed. Such a turboexpander 102 is a so-called "high-speed" turbine generator. For example, in an embodiment, the turboexpander 102 can generate up to 280 kW at a continuous speed of 30,000 rpm. In an embodiment, the turboexpander can generate about 350 kW at a higher rotational speed (e.g., about 35,000 rpm).

[0043] In some embodiments, the design of the turbine wheel 104, the rotor 108, and / or the stator 110 can be based on the desired parameters of the output gas from the turboexpander 102. For example, the design of the rotor and the stator can be based on the desired temperature of the gas 128.

[0044] The turbo expander 102 can be coupled to the power electronics 118. The power electronics 118 can include a variable speed drive (VSD) 166 (or variable frequency drive) and a magnetic bearing controller (MBC) 168 (as described above).

[0045] The electrical output 160 of the turbo expander 102 is connected to a VSD 166 that can be programmed to meet specific power requirements. The VSD 166 can include an insulated-gate bipolar transistor (IGBT) rectifier for converting the variable frequency high voltage output from the turbo expander 102 to direct current (DC). The rectifier 210 can be a three-phase rectifier for three-phase AC input current. The inverter then converts the DC from the rectifier to AC for supplying to the power grid 140. The inverter can convert the DC to 380VAC - 480VAC at 50Hz - 60Hz for supplying to the power grid. The specific output of the VSD 166 depends on the power grid and the application. Other conversion values are also within the scope of the present disclosure. The VSD 166 samples the voltage and frequency of the grid and then changes the output voltage and frequency of the inverter to match the sampled voltage and frequency of the power grid 140 to match its output to the power grid 140.

[0046] The turbo expander 102 is also connected to the MBC 168 within the power electronics 118. The MBC 168 constantly monitors the position, current, temperature, and other parameters to ensure that the turbo expander 102 as well as the active magnetic bearings 116a and 116b are operating as desired. For example, the MBC 168 is coupled to the position sensors 117a, 117b to monitor the radial and axial positions of the turbine wheel 104 and the rotor 108. The MBC 168 can control the magnetic bearings 116a, 116b to selectively change the stiffness and damping characteristics of the magnetic bearings 116a, 116b as a function of the spin speed. The MBC 168 can also control synchronous cancellation including automatic balance control, adaptive vibration control, adaptive vibration cancellation, and unbalance force cancellation control.

[0047] The pressure drop system converts shaft power from the process flow. The turbo expander can support islanded operation. The turbo expander can continue to supply power to a location if the power grid that supplies power to that location is interrupted. The present disclosure describes components that can facilitate load matching between the shaft power generated by the process gas flow in the pressure drop station and the load demand. In this way, the turbo expander can support microgrid functionality for islanded operation.

[0048] The above-described turbo expander 102 includes exemplary features specific to the implementation form. Without departing from the scope of the present disclosure, specific features can be changed, added, deleted, or redesigned. For example, instead of or in addition to the AMB, other types of bearings such as ball bearings, fluid film bearings, etc. can be used. Different designs of rotors and stators such as brushless DC, induction type, etc. can be used. Other types of stator cooling architectures such as non-through-flow and overhang type architectures can be used.

[0049] FIG. 2 is a schematic diagram of an exemplary turbo expander system 200 that supports islanding operation without a grid source, according to an embodiment of the present disclosure. The turbo expander system 200 includes a turbo expander 102 as described above.

[0050] The turbo expander system 200 includes power electronics components 201 for supporting islanding operation. For example, a turbo expander power converter 202 electrically couples an electrical connection 160 of the turbo expander 102 to islanding mode power electronics (PE) 204. The power converter can convert AC power from the turbo expander 102 to DC, which can be stored in a battery 206 or routed to other locations on a DC bus. The turbo expander power converter 202 can convert the AC output of the turbo expander to DC and traverse the DC bus. In some embodiments, the turbo expander power converter 202 includes a rectifier circuit that includes electrical components capable of converting AC to DC. The DC from the turbo expander power converter 202 is input to the islanding mode PE 204. The islanding mode PE 204 can convert the DC to AC with a frequency and amplitude that matches the load 220.

[0051] The load 220 can be a device, printer, computer, lighting, telecommunications equipment, HVAC, air filter, or other critical system.

[0052] In an embodiment, the islanding mode PE 204 can include an inverter circuit. The inverter circuit can convert DC from the turbo expander power converter 202 to AC. The inverter circuit can include, for example, circuit elements that convert DC to AC with a frequency and amplitude (voltage) that matches the load 220. The inverter circuit can also support multiple loads with different power demands and parameters.

[0053] The power electronic device 201 can include a battery 206. The battery 206 can be coupled to the turbo expander 102 through a turbo expander power converter 202. The battery 206 can store the power output from the turbo expander 102. For example, the AC from the electrical connection part 160 can be converted into DC by the turbo expander power converter 202 and stored in the battery 206.

[0054] In an embodiment, the battery can facilitate the "dark start" of the turbo expander 102. When the power grid as the power source of the turbo expander is not connected, the battery 206 can supply the power necessary to start the rotation of the rotor of the turbo expander 102 through the bidirectional electrical connection part 160. In some embodiments, the battery 206 can assist in starting the rotor while the process gas begins to flow into the turbo expander inlet. After a while, when the process gas flow becomes sufficient to accelerate the rotor, the battery 206 can be disconnected from the turbo expander bidirectional connection part 160. The ability to dark start the turbo expander enables the turbo expander to function as a microgrid without a power grid as a power source.

[0055] The brake resistor assembly 208 is electrically connected to the electrical output 160 (e.g., the output of the generator) of the turbo expander 102. The brake resistor assembly 208 can have an impedance that is adjusted to enable efficient transfer of power from the turbo expander 102 to the brake resistor assembly 208. In an embodiment, the brake resistor assembly 208 comprises a speed-controlled and current-regulated brake resistor. The brake resistor assembly 208 can receive current directly (AC) from the turbo expander or through a rectifier circuit 210 (DC). The rectifier circuit 210 can convert the AC from the turbo expander 102 to DC. A current monitor 212 can be connected in parallel with the rectifier to monitor the current from the electrical output 160 of the turbo expander. In an embodiment, the rectifier circuit 210 includes an active rectifier circuit 210.

[0056] The battery 206 and the brake resistor 208 can mitigate turbocharger lag and provide seamless operation during the application and removal of step loads.

[0057] The load 220 can be any electrical load including critical loads at the location served by the turbo-expander system 200. Critical loads include, but are not limited to, lighting systems, food storage systems, air conditioning / heating systems, communication systems, and other loads considered important to the location.

[0058] FIG. 3 is a schematic diagram of an exemplary turbo-expander system 300 including a bi-directional inverter for islanding operation according to an embodiment of the present disclosure. The embodiment shown in FIG. 3 is backed up by a power grid 140. In the case of a system coupled to the power grid 140, power electronics uses the following bi-directional inverter system 304. The bi-directional inverter system 304 facilitates feeding power from the power grid 140 to the turbo expander 102 and also facilitates directing surplus power generated by the turbo expander 102 in excess of the load requirements of the load 220 back to the power grid 140. In some embodiments, when the power grid 140 is lost, the turbo expander 102 can function as a microgrid or backup power plant to supply power to the load 220.

[0059] The turbo-expander system 300 includes power electronics 302. Similar to the system 200 shown in FIG. 2, the turbo-expander system 300 includes a turbo expander 102 that can generate electricity from the rotation of a rotor within a stator using a process gas flow at a pressure drop station (for example). Similar to the system 200, the turbo-expander system 300 includes a brake resistor assembly 208 coupled to the electrical output 160 of the turbo expander 102. The brake resistor assembly 208 can have an impedance that is adjusted to enable efficient transfer of power from the turbo expander 102 to the brake resistor assembly 208. In an embodiment, the brake resistor assembly 208 comprises a brake resistor that is speed-controlled and current-regulated. The brake resistor assembly 208 can receive current directly (AC) from the turbo expander or through a rectifier circuit 210 (DC). The rectifier circuit 210 can convert AC from the turbo expander 102 to DC. A current monitor 212 can be connected in parallel to the rectifier to monitor the current from the electrical output 160 of the turbo expander.

[0060] The power electronics device 302 can include the battery 206. The battery 206 can be coupled to the turboexpander 102 through the turboexpander power converter 202. The battery 206 can store the power output from the turboexpander 102. For example, the AC from the electrical output 160 can be converted to DC by the turboexpander power converter 202 and stored in the battery 206. In an embodiment, the battery can facilitate the "dark start" of the turboexpander 102.

[0061] In an embodiment, the power electronics device 302 (and the power electronics device 201) can include different types of power storage devices. The power storage device can be charged using AC or DC. The power storage device can generally store the power from the turboexpander 102 and, in some embodiments, can store the power from the power grid. In an embodiment, the power storage device can be used to initiate the rotation of the rotor within the stator of the turboexpander 102 when a process gas flow is formed during a pressure drop sequence or other gas flow process.

[0062] To support the use of power from the power grid 140 and the delivery of power to the power grid, the power electronics device 302 includes a bidirectional inverter system 304. The bidirectional inverter system 304 includes an islanding mode inverter 204 and a power grid converter 308. The islanding mode inverter 204 can receive DC from the turboexpander power converter 202 and convert the DC to AC suitable for the load 220 (or loads).

[0063] The bidirectional inverter system 304 also includes a power grid converter 308. The power grid converter 308 can direct surplus power not used by the load 220 to the power grid 140. The active grid inverter can include electrical components capable of converting DC from the turboexpander power converter 202 into AC with a frequency and amplitude compatible with the power grid 140.

[0064] The power grid inverter 308 can also receive AC from the power grid and convert the AC from the power grid 140 into DC for traversing the DC bus towards the power converter 202. The power converter 202 can then convert the DC from the power grid inverter 308 into AC compatible with the turboexpander 102 to initiate the rotation of the rotor within the stator during the startup procedure. In an embodiment, the battery 206 can also be charged using power from the power grid 140.

[0065] The battery 206 of the turbo - expander system 200 can operate in the same manner as an uninterruptible power supply to continue supplying power to the load 220 in the event of a failure of the turboexpander 102. Similarly, in FIG. 3, in the event of a failure of the grid 140, the turboexpander 102 and the battery 206 can supply power to the load 220. In the event of a failure of both the grid 140 and the turboexpander 102, the battery 206 can supply power to the load 220. In any case, the islanding mode inverter 204 can adjust the DC input to AC power that mimics the grid 140 or the turboexpander 102 to seamlessly supply power to the load 220.

[0066] In any of the above scenarios, the power supplied by the battery 206 to the load 220 should mimic the grid power supplied to the load. Therefore, the islanding mode inverter 204 includes electronics for shaping the power from the battery to mimic grid power. In this way, the turbo expander system can support seamless operation of the load using the battery 206 even if the grid 140 and the turbo expander 102 fail. Similarly, the battery 206 and the grid 140 can be supplied by the turbo expander 102. The electrical components described herein facilitate the ability to supply power to the battery 206 and the grid 140 via the turbo expander 102 while ensuring that the load 220 continues to receive power during grid outages and / or turbo expander outages.

[0067] Furthermore, the battery 206 should have a sufficient charge or capacity to supply power to the load 220 for a certain period of time to enable the grid 140 or the turbo expander 102 to return online.

[0068] The master controller 230 can provide power management control to various components including output voltage shaping, output voltage control, reactive and active compensation of the load, and other power control functions. The master controller 230 can operate, stop, or control active rectifiers, inverters, converters, etc. to supply power to the correct components based on the operating state. The master controller is connected to and can control the turboexpander power converter 202, the islanding mode inverter 204, the brake resistor 208, the active rectifier 210, and the power grid converter 308. For example, a tripped breaker can indicate that the load 220 has been lost. To prevent an overspeed condition in the turboexpander 102, the master controller 230 can operate the active rectifier 210 to direct the power from the turboexpander 102 to the brake resistor assembly 208. The master controller 230 can also redirect power to the power electronic devices after an overspeed or other fault condition has been rectified. For example, if a breaker trips at the output of the power electronic devices, the master controller 230 can route power from the turboexpander 102 to the active rectifier 210 to allow the power to be dissipated by the brake resistor assembly 208. After the breaker is reset, the master controller 230 can reroute the power from the turboexpander 102 to the power electronic devices to supply the load.

[0069] Figure 4A is a schematic diagram 400 of an exemplary turboexpander converter according to an embodiment of the present disclosure. In Figure 4A, the turboexpander 102 is simplified as a three-phase permanent magnet synchronous AC generator 402. Although not shown, a current monitor can be coupled in parallel to the brake resistor assembly to monitor the current flowing through the brake resistor. A turboexpander power converter 404 similar to the turboexpander power converter 202 is shown. The turboexpander power converter 404 can be used to convert AC power from the generator 402 into DC power for the DC bus. The DC power can be stored in the battery 206 or sent to the islanding mode inverter 204 or the power grid converter 308.

[0070] The turboexpander power converter 404 can also convert DC power from the battery 206 or from the power grid converter 308 into AC power to drive the turboexpander during startup operation. The master controller 230 can be used to control the turboexpander power converter 404 to drive the current to or from the generator 402 based on the operating state. For example, the master controller 230 can receive power management control information that causes the master controller 230 to control the turboexpander power converter 404 to drive current from the battery 206 or the grid 140 to the generator 402 during startup. The master controller 230 can receive power management control information that causes the master controller 230 to control the turboexpander power converter 404 to drive current from the generator 402 to the DC bus to supply power to the battery 206, the grid 140, or the load 220. For example, the master controller 230 can activate the rectifier in the turboexpander power converter 404 based on the presence or absence of a fault condition in the load 220 or the grid 140.

[0071] FIG. 4B is a schematic diagram 450 of an exemplary islanding mode inverter 454 according to an embodiment of the present disclosure. The islanding mode inverter 454 is similar to the islanding mode inverter 204. The islanding mode inverter 454 can change DC current to AC current and supply AC power to the load 220. The islanding mode inverter 454 can adjust the power output from the islanding mode inverter 454 to mimic grid power. For example, the islanding mode inverter can include electrical components for adjusting AC power, including a sine filter 456. The output power to the load 220 mimics the power supplied to the load 220 by the grid 140 or the generator 402 so that the load 220 continues to operate when the grid is lost.

[0072] In an exemplary embodiment, the master controller 230 can receive information 458 that signals the master controller 230 to send battery power to the load through the islanding mode inverter 454. A tripped breaker can notify the master controller of a fault at the grid or elsewhere that causes the battery 206 to supply power to the load 220.

[0073] FIG. 5 is a process flow diagram 500 for supporting islanding operation using a turbo expander according to an embodiment of the present disclosure. In some embodiments, a power source can be used to initiate rotation of a rotor within a stator of the turbo expander. (502). The power source can be a battery connected to the turbo expander or a power grid connected to the turbo expander. The power source can assist in raising the rotor to a constant speed while the process gas flow forms a sufficient flow rate or mass to rotate the rotor at a desired speed to generate a desired output power. (504).

[0074] The load can be disconnected from the power grid. The turbo expander supplies power to the load during islanded operation, thereby functioning as a microgrid. The turbo expander power electronics can include islanded mode power electronics such as an islanded mode inverter to convert the current generated from the turbo expander into a current with a frequency and amplitude that matches the load. (506). The output current of the turbo expander can be used to power the load. (508). Surplus power not used by the load can be output to either a battery (or other power storage device) or the power grid. When the power grid is coupled to the turbo expander, an active grid inverter can convert the current generated from the turbo expander into a current with a frequency and amplitude that matches the power grid.

[0075] Therefore, the specification and drawings should be regarded in an illustrative rather than a limiting sense. Further, the foregoing use of embodiments and other illustrative language does not necessarily refer to the same embodiment or the same example, but can refer to different individual embodiments as well as potentially the same embodiment. In the above specification, specific illustrative embodiments have been described in detail. However, it will be apparent that various modifications and changes can be made without departing from the broader spirit and scope of the disclosure as set forth in the claims.

Claims

1. A generator, A process gas inlet coupled to a process gas pipeline and configured to receive high-pressure process gas from the process gas pipeline, A turbine wheel configured to receive high-pressure process gas from the process gas inlet, flow into the inlet of the turbine wheel, and rotate in response to the expansion of the process gas flowing out of the outlet of the turbine wheel, wherein the outlet of the turbine wheel is coupled to a downstream process gas pipeline for transferring low-pressure process gas downstream of the generator, A rotor coupled to the turbine wheel and configured to rotate with the turbine wheel, A stationary stator, wherein the generator comprises the stationary stator in which the rotor rotates to generate an alternating current, A generator, A power converter circuit coupled to the electrical output of the generator, the power converter circuit converting the alternating current from the generator into a direct current, An islanding mode inverter circuit coupled to the electrical output of the power converter circuit, the islanding mode inverter circuit converting the direct current from the power converter circuit into an alternating current having a frequency and amplitude for supplying power to an electrical load, and a device comprising: The generator is coupled in parallel to the electrical load and a power grid supplying power to the electrical load, and the device, Determines that the power grid no longer supplies power to the electrical load, Based on the determination that the power grid no longer supplies power to the electrical load, causes the islanding mode inverter to direct the power generated by the generator from the expansion of the high-pressure process gas received by the process gas pipeline to the load A master controller The device further comprising.

2. A brake resistor rectifier coupled to the electrical output of the generator, A brake resistor assembly coupled to the output of the brake resistor rectifier The device according to claim 1, further comprising.

3. The device according to claim 2, wherein the brake resistor assembly comprises a brake resistor whose speed is controlled and current is adjusted.

4. The apparatus according to claim 1, further comprising a battery coupled to the generator, the battery storing the power received from the generator and supplying power for rotating the rotor within the stator.

5. The battery is coupled to the power converter circuit, and the power converter circuit receives an alternating current from the generator and converts the alternating current into a direct current for storage in the battery, receives a direct current from the battery, converts the direct current into an alternating current, and supplies power to the rotor. The apparatus according to claim 4.

6. The islanding mode inverter circuit and an active grid inverter that converts a direct current into an alternating current having a frequency and amplitude compatible with a power grid The apparatus according to claim 1, comprising a bidirectional inverter.

7. The apparatus according to claim 6, wherein the bidirectional inverter supplies power to the load and supplies surplus power to the power grid.

8. The apparatus according to claim 6, wherein the bidirectional inverter supplies power from the power grid to the rotor for rotating the rotor within the stator before the process gas rotates the turbine wheel.

9. The islanding mode inverter circuit receives a direct current on a DC bus, converts the direct current into an alternating current, and adjusts the alternating current to a frequency and amplitude compatible with the load The apparatus according to claim 1, comprising a circuit configuration.

10. The apparatus according to claim 1, further comprising a master controller circuit for controlling the flow of current to a braking resistor during a fault condition.

11. The apparatus according to claim 10, further comprising an active rectifier electrically connected between the generator and the braking resistor, and the master controller operates the active rectifier to direct current from the generator to the braking resistor based on the presence of the fault condition when the fault condition is detected.

12. The apparatus according to claim 1, wherein the generator comprises a three-phase permanent magnet synchronous generator.

13. Receiving high-pressure process gas from a process gas pipeline at an inlet of a turbine wheel of a generator that exists downstream of a flow control valve of the process gas pipeline, wherein the generator is coupled in parallel to an electrical load and a power grid that supplies power to the electrical load; Flowing the high-pressure gas through the turbine wheel of the generator, wherein the flow of the high-pressure gas through the turbine wheel rotates a rotor coupled to the turbine wheel within a stator of the generator and expands the high-pressure gas; Generating an electric current by rotation of the rotor within the stator of the generator; Guiding the expanded process gas from an outlet of the generator to a downstream portion of the pipeline; Guiding the electric current generated by the generator to power electronics in islanding mode; Determining that the power grid has stopped supplying power to the electrical load; Based on the determination that the power grid has stopped supplying power to the electrical load, guiding an electric current from the power electronics in islanding mode to the electrical load; A method comprising the above.

14. The method according to claim 13, comprising guiding surplus electric current generated by the generator and not guided to the load through an active grid inverter to the power grid.

15. The method according to claim 14, comprising executing startup of the generator using power received from the power grid through the active grid inverter.

16. The method according to claim 13, comprising guiding surplus electric current generated by the generator and not guided to the load to a battery.

17. The method according to claim 16, comprising executing startup of the generator using power received from the battery.

18. A generator, A process gas inlet configured to be coupled to a process gas pipeline and receive high-pressure process gas from the process gas pipeline; A turbine wheel configured to receive high-pressure process gas from the process gas inlet, flow into the inlet of the turbine wheel, and rotate in response to the expansion of the process gas flowing out from the outlet of the turbine wheel, wherein the outlet of the turbine wheel is coupled to a downstream process gas pipeline for transferring low-pressure process gas downstream of the generator, and the turbine wheel; A rotor coupled to the turbine wheel and configured to rotate together with the turbine wheel; A fixed stator, wherein the generator generates an alternating current when the rotor in the stator rotates; A generator comprising the above; A power electronics system, A power converter circuit coupled to the electrical output of the generator, the power converter circuit converting the alternating current from the generator into a direct current; An islanding mode inverter circuit coupled to the electrical output of the rectifier circuit, the islanding mode inverter circuit converting the direct current from the rectifier circuit into an alternating current having a frequency and amplitude for supplying power to an electrical load; Comprising the above; The power electronics system is coupled in parallel to the electrical load and a power grid supplying power to the electrical load, and the power electronics system, Determines that the power grid no longer supplies power to the electrical load, Based on the determination that the power grid no longer supplies power to the electrical load, causes the islanding mode inverter to direct the power generated by the generator from the expansion of the high-pressure process gas received through the process gas pipeline to the load; A master controller Further comprising the above, a power electronics system; A system comprising the above.

19. The system according to claim 18, further comprising a bidirectional inverter that conducts current to the load and conducts surplus current to the power grid.

20. The system according to claim 19, wherein the bidirectional inverter comprises an active grid inverter that conducts power to the power grid and receives power from the power grid.

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