A composite superconducting micro-grid system applied to suppress offshore wind power fluctuation

Abstract

The application provides a composite superconducting microgrid system applied to suppressing offshore wind power fluctuation, offshore wind power is transmitted to the shore by flexible DC transmission technology and is incorporated into a main power grid and a water electrolysis hydrogen production device, a composite superconducting system composed of a superconducting generator, a superconducting step-up transformer, a liquid hydrogen-superconducting hybrid submarine AC / DC cable and a superconducting energy storage is established in the transmission process, the composite superconducting system is convenient for large-capacity power transmission and reduces the cost. A microgrid system of offshore wind power, the composite superconducting system, hydrogen storage and fuel cells is further established, the storage, utilization and conversion technology of wind energy-chemical energy-electric energy hybrid energy are realized, the microgrid system has the advantages of being clean, environmentally friendly and capable of being locally consumed, effectively combines the advantages of superconducting energy storage and fuel cells, suppresses offshore wind power fluctuation, and improves the quality of electric energy for power users. In the whole process, the circulation conversion between hydrogen and liquid hydrogen and the flow detection of the liquid hydrogen relay booster station can better cool the composite superconducting system, realize the comprehensive utilization of hydrogen energy and the composite superconducting system, and avoid the high operation and maintenance cost required by the traditional refrigeration mode.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of superconducting microgrids, and particularly relates to a composite superconducting microgrid system applied to offshore wind power and a working method. BACKGROUND

[0002] In the process of rapid global industrialization today, the contradiction between energy demand and environmental pollution has become a problem that needs to be solved urgently. Renewable energy is the key to solving the energy crisis and realizing sustainable development. Wind power has become the third largest renewable energy generation method after hydropower due to its advantages such as easy development and low construction cost. Offshore wind power has advantages such as abundant resources, high power utilization rate, and proximity to power load centers for easy power consumption, and is becoming a global focus.

[0003] The intermittent and random nature of wind power generation results in poor power quality. Because energy storage has the characteristics of bidirectional power and flexible adjustment capability, configuring energy storage is a solution to the system instability and other problems caused by wind power generation. Energy storage technology can be divided into energy storage (pumped storage, fuel cells, etc.) and power storage (superconducting energy storage, supercapacitor energy storage, etc.). Energy storage systems have long discharge time, large capacity density, but relatively slow power response speed and are not suitable for frequent and fast charging and discharging. Power storage has the advantages of fast response speed and large power density. Therefore, combining the two types of energy storage can reduce costs and provide good power quality.

[0004] Among many energy storage technologies, hydrogen energy storage uses excess power generated by wind power to electrolyze water to produce hydrogen, and stores hydrogen. When needed, hydrogen is used to generate electricity through fuel cells or gas turbines. Hydrogen energy generation has the advantages of long discharge time and no pollution, and can be used to smooth wind power fluctuations. It can also be used as an effective means of energy consumption, significantly reducing carbon emissions. Superconducting energy storage technology uses the zero-resistance current-carrying characteristics of superconducting materials below the critical temperature to construct a magnet coil to store electromagnetic energy. Through a current transformer, power exchange with the grid is achieved, and the technology has the advantages of fast response and independent four-quadrant operation.

[0005] At present, most offshore wind farms adopt high-voltage alternating current grid connection mode, but need to install reactive power compensation device to solve the problem of alternating current cable capacitance charging current, so under the rapid development of high-power power electronic devices, flexible direct current transmission is widely recognized due to its advantages of less harmonic content, no commutation failure and independent power regulation. The offshore wind power grid connection structure based on flexible direct current transmission includes offshore wind turbine, step-up transformer, alternating current submarine cable, offshore converter station, direct current submarine cable, onshore converter station and main power grid. The traditional doubly-fed induction generator and permanent magnet synchronous generator are difficult to meet the problem of large-scale offshore wind turbine capacity, when the high-temperature superconducting generator is used, the wind turbine generator is direct-driven, which increases the reliability and reduces the maintenance cost, and due to the light weight and small size, the design requirements of offshore wind turbine support structure and the like are reduced, and the construction cost of the wind farm is reduced. The carrying capacity of the traditional submarine cable is insufficient and a large amount of electric energy is lost, so the superconducting cable is used to replace the traditional submarine transmission line to meet the large-capacity load center. If the step-up transformer also uses a superconducting transformer, the weight of the transformer can be effectively reduced, the noise is reduced, the service life of the transformer is also prolonged in the low-temperature environment, the construction and maintenance costs are reduced, and the influence on the surrounding marine organisms is small.

[0006] Since all superconducting devices need to work in a low-temperature environment, the temperature of liquid hydrogen is about 20K and is obtained by electrolysis of water to produce hydrogen, so the superconducting cable can be installed in the liquid hydrogen transmission pipeline, and the magnet in the superconducting transformer and the superconducting energy storage device is immersed in the Dewar containing liquid hydrogen. However, during the operation of the system, the superconducting transformer and the superconducting energy storage device will inevitably have thermal disturbance and certain heat leakage, and the liquid hydrogen pipeline end of the superconducting submarine cable connected in the room temperature environment will also have heat loss. SUMMARY

[0007] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a composite superconducting microgrid system and working method applied to offshore wind power, which combines hydrogen energy storage and superconducting energy storage to better realize the regulation of grid voltage, frequency, active and reactive power, and at the same time, combines various superconducting devices to increase transmission capacity and reduce loss, and further reduces cost.

[0008] The present application is realized by the following technical solutions:

[0009] The application discloses a composite superconducting micro-grid system applied to suppressing offshore wind power fluctuation, and has the characteristics that the system comprises offshore superconducting wind turbine generators, a superconducting step-up transformer, liquid hydrogen-superconducting hybrid submarine AC cables, an offshore converter station, a liquid hydrogen relay booster station, liquid hydrogen-superconducting hybrid submarine DC cables, an onshore converter station, a main power grid, water electrolysis hydrogen production equipment, hydrogen liquefaction equipment, fuel cells and a superconducting energy storage device.

[0010] Further, the offshore superconducting generator adopts a semi-superconducting generator with stator windings made of normal conductive material and rotor windings made of superconductive material, and the cryogenic cooling of the high-temperature superconductor uses liquid helium or liquid neon; the cryogenic gas is transported to the low-temperature container of the rotor coil through a rotating sealing good rotating cold transport vacuum pipeline; the superconducting generator does not use liquid hydrogen for cooling, so as to reduce the investment and construction cost of transporting liquid hydrogen to the higher fan.

[0011] Further, the superconducting step-up transformer is composed of a three-phase laminated core, a spiral high-temperature superconducting winding, a ring-shaped Dewar for cooling only the transformer winding, a current lead and a refrigeration unit for cooling the superconducting winding with liquid hydrogen.

[0012] Further, the liquid hydrogen-superconducting hybrid submarine AC cable adopts a three-core type AC cable, and each core cable has the structure from inside to outside as follows: a liquid hydrogen transmission pipeline, a superconducting layer, a low-temperature insulation layer and a superconducting shielding layer; the liquid hydrogen transmission pipeline is made of a stainless steel corrugated pipe; the superconducting layer and the superconducting shielding layer are both made of second-generation superconducting tapes YBCO; the low-temperature insulation layer is made of polypropylene laminated paper; the three single-phase cables are twisted and arranged in a liquid hydrogen low-temperature Dewar pipeline; the Dewar pipe is externally provided with an ethylene-propylene rubber insulated lead jacket waterproof layer and a protection layer made of thick steel wire armoring polypropylene fiber for waterproofing and corrosion prevention.

[0013] Further, the liquid hydrogen-superconducting hybrid submarine DC cable adopts a single-pole coaxial cable, and the structure from inside to outside is in turn: a liquid hydrogen inner transmission pipeline, a superconducting layer, a low-temperature insulation layer, a liquid hydrogen outer transmission pipeline, an adiabatic layer and a protective layer. The materials used for the liquid hydrogen inner transmission pipeline, the superconducting layer, the low-temperature adiabatic layer and the protective layer are consistent with those of the liquid hydrogen-superconducting hybrid submarine AC cable. The liquid hydrogen outer transmission pipeline is a gap between the low-temperature insulation layer and the adiabatic layer. The two liquid hydrogen pipelines adopt single-end counterflow refrigeration. The adiabatic layer is sleeved with a coaxial double-layer stainless steel bellows and is vacuumized between the two layers and embedded with multiple layers of radiation-proof metal foils, so that the superconducting layer is always in a low-temperature environment to maintain a superconducting state.

[0014] Preferably, the AC power output by the offshore superconducting wind turbine is boosted by a superconducting booster transformer and then transmitted to an AC bus of an offshore converter station through a liquid hydrogen-superconducting hybrid submarine AC cable. The offshore converter station converts the AC power into DC power and transmits the DC power to a DC bus of an onshore converter station through a liquid hydrogen-superconducting hybrid submarine DC cable. The onshore converter station inverts the DC power into AC power and connects the AC power to a main power grid and a water electrolysis hydrogen production device, thereby realizing centralized grid connection of offshore wind turbine based on flexible DC power transmission.

[0015] Further, the hydrogen of the fuel cell is derived from hydrogen gas stored in a gas tank after water electrolysis hydrogen production. The hydrogen inlet amount and the first DC chopper in the fuel cell are controlled according to the load and the electrical characteristics detected by the main power grid, so as to adjust the power generated.

[0016] Further, the superconducting energy storage magnets in the superconducting energy storage device are in a superconducting state in a Dewar filled with liquid hydrogen, and are charged and discharged through a second DC chopper.

[0017] Preferably, the electric energy generated by the offshore wind power is used to produce hydrogen in the water electrolysis hydrogen production device and store the hydrogen in a gas tank. Part of the hydrogen gas in the gas tank is used for power generation by the fuel cell, and part of the hydrogen gas is liquefied into liquid hydrogen by a hydrogen liquefaction device and stored in a liquid tank. Part of the liquid hydrogen in the liquid tank is used to cool the superconducting magnets in the superconducting energy storage device, and part of the liquid hydrogen is used in the liquid hydrogen-superconducting hybrid submarine AC and DC cables and the superconducting booster transformer. Not only is the composite superconducting system placed in a low-temperature environment of liquid hydrogen, but also the raw material for the fuel cell is supplemented.

[0018] Preferably, the superconducting energy storage device and the fuel cell control their respective choppers to charge or discharge according to the electrical characteristics of the DC bus, thereby realizing power fluctuation suppression of offshore wind power generation.

[0019] Preferably, the liquid tank is connected to the liquid hydrogen transmission pipeline in the liquid hydrogen-superconducting hybrid submarine AC / DC cable through a liquid hydrogen pump, and finally connected to the superconducting booster transformer, and the controller on the liquid hydrogen relay booster station determines whether the liquid hydrogen pump is needed to supplement the insufficient liquid hydrogen in the pipeline by monitoring the flow rate of the liquid hydrogen in the liquid hydrogen transmission pipeline, thereby avoiding the loss of superconductivity of the liquid hydrogen-superconducting hybrid submarine AC / DC cable due to insufficient liquid hydrogen.

[0020] Preferably, the liquid hydrogen in the liquid tank enters the Dewar through the liquid inlet pipe to cool the superconducting energy storage device, and the heat generated by the superconducting energy storage magnet in the superconducting energy storage device during operation vaporizes the liquid hydrogen in the Dewar to produce hydrogen gas, which enters the gas tank through the exhaust pipe.

[0021] Preferably, the liquid level in the annular Dewar of the superconducting booster transformer changes when the transformer is working, and when the liquid level drops to a certain extent, the liquid hydrogen pump of the refrigerator sends liquid hydrogen into the Dewar through the liquid inlet pipe of the transformer, and the hydrogen gas after vaporization enters the liquid hydrogen pump through the exhaust pipe of the transformer and becomes liquid hydrogen after passing through the heat exchanger to continue to circulate and use, thereby improving the utilization rate of hydrogen energy.

[0022] Preferably, the liquid level in the Dewar of the superconducting energy storage device changes during operation of the superconducting energy storage device, and the intelligent control switch on the liquid inlet pipe controls the opening and closing of the liquid inlet pipe according to the signal sensed by the liquid level sensor in the Dewar, and the intelligent control switch on the exhaust pipe controls the opening and closing of the exhaust pipe according to the gas pressure sensed by the pressure sensor in the Dewar, so that the liquid surface in the Dewar is always above the superconducting energy storage magnet, thereby providing a low-temperature environment for the superconducting energy storage device by using the gas-liquid conversion of hydrogen, and realizing the mixed use of liquid hydrogen and superconducting energy storage.

[0023] The purpose of the present application is also to provide a specific step of a composite superconducting microgrid system applied to the suppression of offshore wind power fluctuation, which comprises:

[0024] S1, power generation, the offshore superconducting generator set converts wind energy into electrical energy, and the electrical energy is boosted by the superconducting booster transformer and then transmitted to the offshore converter station by the liquid hydrogen-superconducting hybrid submarine AC cable, thereby realizing the conversion of offshore wind energy and electrical energy;

[0025] S2, conversion, the offshore converter station converts three-phase AC power into DC power by using flexible DC power transmission, and the DC power is transmitted to the onshore converter station by the liquid hydrogen-superconducting hybrid submarine DC cable, and the onshore converter station converts the DC power into AC power, thereby preferentially meeting the electricity demand of the water electrolysis hydrogen production equipment and the superconducting energy storage device, and the surplus electrical energy is transmitted to the main power grid, thereby realizing the rational distribution of electrical energy.

[0026] S3, hydrogen storage, hydrogen production equipment electrolysis of water to receive shore converter sent to the electrical energy, electrolysis of water to produce hydrogen, hydrogen storage tank, hydrogen liquefaction equipment into the tank hydrogen into liquid hydrogen, liquid hydrogen storage tank, the conversion of electrical energy and hydrogen energy and hydrogen and liquid hydrogen;

[0027] S4, power smoothing, hydrogen tank can be used as raw material for fuel cell, liquid hydrogen along the liquid pipe into the Dewar superconducting energy storage device, liquid hydrogen over its superconducting energy storage magnet to achieve immersion cooling, fuel cell and superconducting energy storage device through the electrical characteristics of the connected DC bus to determine the control of the respective DC chopper charge and discharge, and then realize the power fluctuation of offshore wind power smoothing;

[0028] In S2, due to the long distance of liquid hydrogen-superconducting hybrid submarine DC cable, the liquid hydrogen pump may not be able to deliver liquid hydrogen to the superconducting booster transformer, so the liquid hydrogen relay booster station is added, when the liquid hydrogen flow rate in the liquid hydrogen transmission pipeline is detected to be lower than the lower threshold, the liquid hydrogen pump on the liquid hydrogen relay booster station is started to supplement the insufficient liquid hydrogen in the pipeline;

[0029] In S2, when the liquid level of the Dewar in the superconducting booster transformer refrigerator is detected to drop to the minimum set value, the liquid inlet valve is opened to allow the liquid hydrogen in the liquid tank to supplement, when the liquid hydrogen in the transformer tank is insufficient, the liquid hydrogen pump on the liquid hydrogen relay booster station supplements the liquid hydrogen;

[0030] In S3, the hydrogen in the tank is used to meet the needs of the hydrogen liquefaction equipment, and the surplus hydrogen can be used for fuel cells, and the liquid hydrogen in the tank is used to meet the needs of the superconducting energy storage device, the liquid hydrogen-superconducting hybrid submarine AC / DC cable and the superconducting booster transformer, so as to ensure that they are in a low-temperature environment for a long time;

[0031] In S4, when the liquid level of the Dewar is lower than the minimum threshold, the liquid level sensor opens the intelligent control switch on the liquid inlet pipe to allow the liquid hydrogen to enter the superconducting energy storage device, and the liquid hydrogen is easily gasified by the heat generated by the operation of the superconducting energy storage device, when the hydrogen pressure in the Dewar is higher than the maximum threshold, the intelligent control switch on the exhaust pipe is opened according to the gas pressure sensed by the pressure sensor in the Dewar to allow the hydrogen to enter the tank;

[0032] In S4, when controlling the respective DC chopper of the fuel cell and the superconducting energy storage device, a filter can be used, the high-frequency component of the power fluctuation is borne by the superconducting energy storage device, and the low-frequency component is borne by the fuel cell.

[0033] Compared with the prior art, the present application has the following beneficial effects:

[0034] 1) This invention utilizes the near-zero resistance and zero loss characteristics of superconductivity to establish a composite superconducting system consisting of a superconducting generator, a superconducting step-up transformer, a superconducting cable, and a superconducting energy storage, which facilitates large-capacity power transmission and reduces costs. At the same time, it uses low-temperature, environmentally friendly liquid hydrogen to maintain the working environment temperature of the superconducting submarine AC / DC cable installed in the liquid hydrogen pipeline. By detecting the flow rate in the liquid hydrogen transmission pipeline, the liquid hydrogen pump in the liquid hydrogen relay booster station is controlled, thereby effectively solving the thermal leakage problem of the superconducting step-up transformer and the superconducting submarine cable.

[0035] 2) This invention establishes a microgrid system integrating offshore wind power, a composite superconducting system, hydrogen storage, and fuel cells. It realizes the storage, utilization, and conversion technology of hybrid energy of wind energy, chemical energy, and electrical energy, which has the advantages of being clean, environmentally friendly, and capable of local consumption. It effectively utilizes the characteristics of superconducting energy storage, such as millisecond-level response speed, extremely high conversion efficiency, near-infinite charge-discharge cycle count, and high power density. At the same time, it utilizes the characteristics of fuel cells, such as long discharge time, high energy density, and no pollution. After high- and low-frequency filtering of the power generated by offshore wind power, it controls the superconducting energy storage and fuel cell charge-discharge, thereby smoothing out power fluctuations and improving the quality of electricity for power users.

[0036] 3) By utilizing the cyclic conversion between hydrogen gas and liquid hydrogen, the composite superconducting system is cooled, realizing the comprehensive utilization of hydrogen energy and the composite superconducting system, and avoiding the high operation and maintenance costs required by traditional refrigeration methods. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the composite superconducting microgrid system structure for mitigating power fluctuations in offshore wind power according to the present invention;

[0038] Figure 2 This is a schematic diagram of the superconducting step-up transformer structure of the present invention;

[0039] Figure 3 This is a schematic diagram of the liquid hydrogen-superconducting hybrid submarine AC cable structure of the present invention;

[0040] Figure 4 This is a schematic diagram of the liquid hydrogen-superconducting hybrid submarine DC cable structure of the present invention;

[0041] Figure 5 This is a schematic diagram of the superconducting energy storage device of the present invention.

[0042] The figure is marked as: 1 - offshore superconducting wind turbine; 2 - superconducting booster transformer; 201 - liquid hydrogen tank; 202 - liquid outlet valve; 203 - transformer refrigerator dewar; 204 - transformer liquid hydrogen pump; 205 - heat exchanger; 206 - transformer exhaust pipe; 207 - transformer liquid inlet pipe; 208 - current lead; 209 - transformer winding; 210 - transformer ring dewar; 211 - transformer core; 212 - transformer refrigerator; 3 - liquid hydrogen-superconducting hybrid submarine AC cable; 301 - liquid hydrogen transmission pipeline; 302 - superconducting layer; 303 - low-temperature insulation layer; 304 - superconducting shielding layer; 305 - liquid hydrogen low-temperature dewar pipeline; 306 - waterproof layer; 307 - protective layer; 4 - liquid hydrogen relay booster station; 5 - offshore converter station; 6 - liquid hydrogen-superconducting hybrid submarine DC cable; 601 - liquid hydrogen inner transmission pipeline; 602 - superconducting layer; 603 - low-temperature insulation layer; 604 - liquid hydrogen outer transmission pipeline; 605 - thermal insulation layer; 606 - protective layer; 7 - onshore converter station; 8 - main power grid; 9 - superconducting energy storage device; 901 - superconducting energy storage device dewar; 902 - superconducting energy storage magnet; 903 - liquid inlet pipe intelligent control switch; 904 - exhaust pipe intelligent control switch; 10 - fuel cell; 11 - water electrolysis hydrogen production equipment; 12 - gas tank; 13 - hydrogen liquefaction equipment; 14 - liquid tank; 15 - first DC chopper; 16 - second DC chopper; 17 - DC bus; 18 - AC bus; 19 - liquid inlet pipe; 20 - exhaust pipe; 21 - liquid hydrogen pump. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be further described below in combination with the drawings of the embodiments of the present application. In the drawings, the same reference signs represent the same or similar functional devices or equipment throughout. The described embodiments are part of the embodiments of the present application, and the described content and directional words are not limited to the embodiments, but are detailed explanations of the present application rather than limitations.

[0044] In one broad embodiment of the present application, a composite superconducting microgrid system for smoothing offshore wind power fluctuations is shown in FIG. 1. Figure 1 characterized in that it comprises an offshore superconducting generator set 1, a superconducting booster transformer 2, a liquid hydrogen-superconducting hybrid submarine AC cable 3, an offshore converter station 4, a liquid hydrogen relay booster station 5, a liquid hydrogen-superconducting hybrid submarine DC cable 6, an onshore converter station 7, a main power grid 8, a superconducting energy storage device 9, a fuel cell 10, water electrolysis hydrogen production equipment 11 and hydrogen liquefaction equipment 13. The offshore superconducting generator set 1, the superconducting booster transformer 2, the liquid hydrogen-superconducting hybrid submarine AC and DC cables 3, 6 and the superconducting energy storage device 9 constitute a composite superconducting system.

[0045] The AC power output by the offshore superconducting wind turbine 1 is boosted by the superconducting booster transformer 2 and gathered on the AC bus 18, transmitted to the offshore converter station 4 through the liquid hydrogen-superconducting hybrid submarine AC cable 3, converted into DC power by the offshore converter station 4 and transmitted to the DC bus 17 of the onshore converter station 7 through the liquid hydrogen-superconducting hybrid submarine DC cable 6, and then inverted into AC power by the onshore converter station 7 and connected to the main power grid 8 and the water electrolysis hydrogen production equipment 11, realizing offshore wind power grid connection based on flexible DC power transmission; the superconducting energy storage device 9 and the fuel cell 10 control the respective DC choppers 15, 16 to charge and discharge according to the electrical characteristics on the DC bus 17, thereby stabilizing the power fluctuation of the offshore wind power generation device.

[0046] The electric energy generated by the offshore wind power is used to produce hydrogen in the water electrolysis hydrogen production equipment 11 and stored in the gas tank 12, part of the hydrogen in the gas tank 12 is used for power generation by the fuel cell 10, and part of the hydrogen is liquefied into liquid hydrogen by the hydrogen liquefaction equipment 13 and stored in the liquid tank 14, part of the liquid hydrogen in the liquid tank 14 is used to cool the superconducting energy storage magnet 902 in the superconducting energy storage device 9, and part of the liquid hydrogen is used in the liquid hydrogen-superconducting hybrid submarine AC and DC cables 3, 6; wherein the hydrogen raw material of the fuel cell 10 is derived from the hydrogen stored in the gas tank 12 after water electrolysis, and the hydrogen inlet amount and the first DC chopper 15 in the battery are controlled according to the load and the electrical characteristics detected by the main power grid, so as to adjust the power generated.

[0047] The structure of the superconducting booster transformer 2 is shown in Fig. 2. Figure 2 The superconducting booster transformer 2 is composed of a current lead 208, a spiral high-temperature superconducting winding 209, a ring-shaped Dewar 210 which only cools the transformer winding, a three-phase laminated iron core 211, and a refrigerator 212 which uses liquid hydrogen to cool the superconducting winding. The liquid level of the liquid hydrogen in the ring-shaped Dewar 210 changes during the operation of the transformer. When the liquid level drops to a certain extent, the liquid hydrogen pump 204 of the refrigerator will send liquid hydrogen into the Dewar through the liquid inlet pipe 207, and the hydrogen gas after gasification will enter the heat exchanger 205 through the exhaust pipe 206 and then become liquid hydrogen for continuous circulation. When the liquid hydrogen in the Dewar 203 of the transformer refrigerator drops to the lowest set value, the liquid outlet valve 202 is opened to supplement the liquid hydrogen in the Dewar. When the liquid hydrogen in the liquid tank 201 of the transformer drops to the lowest set value, the liquid inlet valve on the liquid tank is opened and the liquid hydrogen pump on the liquid hydrogen relay booster station is used to supplement the liquid hydrogen.

[0048] The structure of the liquid hydrogen-superconducting hybrid submarine AC cable is shown in Fig. 3. Figure 3, the three same core type AC cable, each phase cable is from inside to outside: liquid hydrogen transmission pipeline 301, superconducting layer 302, low temperature insulation layer 303 and superconducting shielding layer 304, liquid hydrogen transmission pipeline 301 is made of stainless steel bellows, superconducting layer 302 and superconducting shielding layer 304 are made of second generation superconducting tape YBCO, low temperature insulation layer 303 is made of polypropylene laminated paper, three single-phase cables are twisted and loaded into liquid hydrogen low temperature Dewar pipeline 305, the Dewar tube is externally provided with ethylene-propylene rubber insulation lead sleeve waterproof layer 306, protection layer 307 made of coarse steel wire armoring polypropylene fiber is waterproof and anticorrosive.

[0049] The structure of the liquid hydrogen-superconducting hybrid submarine DC cable is as shown in the accompanying Figure 4 , the single pole coaxial cable, from inside to outside: liquid hydrogen inner transmission pipeline 601, superconducting layer 602, low temperature insulation layer 603, liquid hydrogen outer transmission pipeline 604, thermal insulation layer 605 and protection layer 606, the materials used for liquid hydrogen inner transmission pipeline 601, superconducting layer 602, low temperature insulation layer 603 and protection layer 606 are consistent with those of the liquid hydrogen-superconducting hybrid submarine AC cable 3, liquid hydrogen outer transmission pipeline 604 is the gap between the low temperature insulation layer 603 and the thermal insulation layer 605, the two liquid hydrogen pipelines adopt single-end counterflow refrigeration, the low temperature insulation layer is sleeved with coaxial double-layer stainless steel bellows, vacuum is extracted between the two layers and multiple layers of radiation-proof metal foils are embedded.

[0050] The liquid tank 14 is connected to the liquid hydrogen-superconducting hybrid submarine DC cable 6, the liquid hydrogen relay booster station 5 and the liquid hydrogen-superconducting hybrid submarine AC cable 3 in sequence through the liquid hydrogen pump 21, and finally connected to the liquid tank 201 at the superconducting booster transformer 2, the controller on the liquid hydrogen relay booster station 5 judges whether the liquid hydrogen pump is needed to supplement the insufficient liquid hydrogen in the pipeline and the liquid hydrogen tank 201 of the superconducting booster transformer by monitoring the flow rate of the liquid hydrogen in the liquid hydrogen transmission pipeline in the submarine cable.

[0051] The structure of the superconducting energy storage device is as shown in the accompanying Figure 5 The liquid hydrogen in the liquid tank 14 enters the Dewar 901 through the liquid inlet pipe 19 to cool the superconducting energy storage device so that the superconducting energy storage magnet 902 is in a superconducting state, but the heat generated by the superconducting energy storage magnet 902 during operation will vaporize the liquid hydrogen in the Dewar to produce hydrogen gas, which enters the gas tank through the exhaust pipe 20, so the liquid level and pressure in the Dewar will also change, the intelligent control switch 903 on the liquid inlet pipe 19 controls the opening and closing of the liquid inlet pipe according to the signal sensed by the liquid level sensor in the Dewar, and the intelligent control switch 904 on the exhaust pipe 20 controls the opening and closing of the exhaust pipe according to the gas pressure sensed by the pressure sensor in the Dewar, so that the liquid level in the Dewar 901 always covers the superconducting energy storage magnet 902.

[0052] The application also provides a specific step of the composite superconducting microgrid system for smoothing offshore wind power fluctuation as described above, which comprises:

[0053] S1, power generation, the offshore superconducting generator set 1 converts wind energy into electrical energy, the electrical energy is boosted by the superconducting booster transformer 2 and transmitted to the offshore converter station 4 by the liquid hydrogen-superconducting hybrid submarine AC cable 3, realizing the conversion of offshore wind energy and electrical energy;

[0054] S2, conversion, the offshore converter station 4 converts three-phase AC power into DC power by flexible DC transmission, the DC power is transmitted to the onshore converter station by the liquid hydrogen-superconducting hybrid submarine DC cable 6, and the onshore converter station 7 converts the DC power into AC power, which is preferentially used for the superconducting energy storage device 9 and the water electrolysis hydrogen production equipment 11, and the surplus electrical energy is transmitted to the main power grid 8, realizing the rational distribution of electrical energy;

[0055] S3, hydrogen production and storage, the water electrolysis hydrogen production equipment 11 receives electrical energy from the onshore converter and performs water electrolysis to produce hydrogen, which is stored in the gas tank 12, the hydrogen gas in the gas tank is converted into liquid hydrogen by the hydrogen liquefaction equipment 13, and the liquid hydrogen is stored in the liquid tank 14, realizing the conversion of electrical energy and hydrogen energy, as well as hydrogen gas and liquid hydrogen;

[0056] S4, power smoothing, the hydrogen gas in the gas tank can be used as raw material for the fuel cell 10, the liquid hydrogen enters the Dewar 901 of the superconducting energy storage device 9 along the liquid inlet pipe 19, and the liquid hydrogen flows over the superconducting energy storage magnet 902 to achieve immersion cooling, the superconducting energy storage device 9 and the fuel cell 10 control their respective DC choppers by judging the electrical characteristics on the DC bus connected to them, thereby realizing the smoothing of power fluctuations in offshore wind power generation;

[0057] In S2, due to the long transmission distance of the liquid hydrogen-superconducting hybrid submarine DC cable 6, the liquid hydrogen pump 21 may not be able to completely deliver the liquid hydrogen to the superconducting booster transformer 2, so the liquid hydrogen relay booster station 5 is added, when the flow rate of the liquid hydrogen in the liquid hydrogen transmission pipeline is lower than the lower threshold, the liquid hydrogen pump on the liquid hydrogen relay booster station 5 is started to supplement the insufficient liquid hydrogen in the pipeline;

[0058] In S3, the hydrogen gas in the gas tank 12 preferentially meets the needs of the hydrogen liquefaction equipment 13, and the surplus hydrogen gas can be used for the fuel cell 10, the liquid hydrogen in the liquid tank 14 preferentially meets the needs of the superconducting energy storage device 9, the liquid hydrogen-superconducting hybrid submarine AC / DC cable 3, 6, and the superconducting booster transformer 2, to ensure that they are in a low-temperature environment for a long time;

[0059] In S4, when the liquid level of liquid hydrogen in Dewar 901 is lower than the minimum threshold, the signal sensed by the liquid level sensor will open the intelligent control switch 903 on the liquid inlet pipe 19 to let liquid hydrogen into the superconducting energy storage device 9. Liquid hydrogen is easily vaporized by the heat generated when the superconducting energy storage device is running. When the hydrogen pressure in Dewar 901 is higher than the maximum threshold, the intelligent control switch 904 on the exhaust pipe 20 controls the exhaust pipe according to the gas pressure sensed by the pressure sensor in Dewar 901 to open the on-off switch to let hydrogen into the gas tank.

[0060] In S4, when controlling the direct current chopper of the superconducting energy storage device 9 and the fuel cell 10 respectively, a filter can be used. The high-frequency component of the power fluctuation is borne by the superconducting energy storage device, and the low-frequency component is borne by the fuel cell.

[0061] Finally, it should be noted that the above embodiments described only the preferred technical solutions of the present application, and equivalent changes made to the system described in the present application are included in the protection scope of the present application. Related technical personnel in the technical field to which the present application belongs can make further modifications and improvements or make equivalent substitutions or arbitrary combinations of some technical features with reference to the described embodiments, as long as the essence of the corresponding technical solution does not deviate from the technical spirit and scope of the present application, and no creative labor is obtained. All other embodiments obtained under the premise that the technical solution belongs to the protection scope of the present application.

Claims

1. A composite superconducting microgrid system applied to smoothen offshore wind power fluctuation, characterized in that, The application relates to a superconducting power generation system, which comprises offshore superconducting wind turbine generators (1), superconducting step-up transformers (2), liquid hydrogen-superconducting hybrid submarine AC cables (3), liquid hydrogen relay booster stations (4), offshore converter stations (5), liquid hydrogen-superconducting hybrid submarine DC cables (6), onshore converter stations (7), main power grids (8), superconducting energy storage devices (9), fuel cells (10), water electrolysis hydrogen production equipment (11) and hydrogen liquefaction equipment (13); the superconducting step-up transformers (2) are connected to the offshore converter stations (5) through the liquid hydrogen-superconducting hybrid submarine AC cables (3), the offshore converter stations (5) are connected to the onshore converter stations (7) through the liquid hydrogen-superconducting hybrid submarine DC cables (6), the onshore converter stations (7) convert and distribute electric energy to the main power grids (8) and the water electrolysis hydrogen production equipment (11) directly connected to the onshore converter stations (7), the hydrogen liquefaction equipment (13) is communicated with a gas tank (12) of the water electrolysis hydrogen production equipment and stores liquid hydrogen in a liquid tank (14), the superconducting energy storage devices (9) are communicated with the gas tank (12) and the liquid tank (14), the fuel cells (10) are connected to the gas tank (12), and the superconducting energy storage devices (9) and the fuel cells (10) are connected to a DC bus (17) of the onshore converter stations (7) through respective DC choppers; The AC electric energy output by the offshore superconducting wind turbine generators (1) is boosted by the superconducting step-up transformers (2) and gathered on an AC bus (18), and then transmitted to the offshore converter stations (5) through the liquid hydrogen-superconducting hybrid submarine AC cables (3); the offshore converter stations (5) convert the AC electric energy into DC electric energy and transmit the DC electric energy to the DC bus (17) of the onshore converter stations (7) through the liquid hydrogen-superconducting hybrid submarine DC cables (6); and the onshore converter stations (7) convert the DC electric energy into AC electric energy and input the AC electric energy into the main power grids (8) and the water electrolysis hydrogen production equipment (11); wherein, The offshore superconducting wind turbine generators (1) are semi-superconducting generators with stator windings made of normal conductive material and rotor windings made of superconductive material; the cryogen for the high-temperature superconductor is liquid helium or liquid neon, and the cryogen is delivered to the low-temperature container of the rotor coil through a rotating sealing good rotating cryogenic delivery vacuum pipeline; The superconducting step-up transformers (2) are composed of current leads (208), spiral high-temperature superconducting windings (209), annular Dewar (210) for cooling only the transformer windings, three-phase laminated iron cores (211) and cryogenic machines (212) for cooling the superconducting windings with liquid hydrogen; The liquid hydrogen level in the annular Dewar (210) of the superconducting step-up transformers changes during the operation of the transformers; when the liquid hydrogen level drops to a certain degree, the liquid hydrogen pump (204) of the cryogenic machine (212) sends liquid hydrogen into the Dewar through the liquid inlet pipe (207), and the hydrogen gas after being vaporized enters the liquid hydrogen pump through the exhaust pipe (206) and is changed into liquid hydrogen through the heat exchanger (205) to continue the circulation. The liquid hydrogen-superconducting hybrid submarine AC cable (3) adopts three concentric type AC cables, each phase cable has the structure from inside to outside as follows: liquid hydrogen transmission pipeline (301), superconducting layer (302), low temperature insulation layer (303) and superconducting shielding layer (304), the liquid hydrogen transmission pipeline (301) is made of stainless steel bellows, the superconducting layer (302) and the superconducting shielding layer (303) are both made of second generation superconducting tape YBCO, and the low temperature insulation layer (303) is made of polypropylene laminated paper; the three single-phase cables are twisted and arranged in the liquid hydrogen low temperature Dewar pipeline (305), the Dewar tube is externally provided with an ethylene-propylene rubber insulation lead sleeve waterproof layer (306) and a coarse steel wire armored polypropylene fiber protective layer (307) for waterproofing and corrosion prevention. The liquid hydrogen-superconducting hybrid submarine DC cable (6) adopts a single-pole coaxial cable, which has the structure from inside to outside as follows: liquid hydrogen inner transmission pipeline (601), superconducting layer (602), low temperature insulation layer (603), liquid hydrogen outer transmission pipeline (604), heat insulation layer (605) and protective layer (606), the materials of the liquid hydrogen inner transmission pipeline (601), the superconducting layer (602), the low temperature insulation layer (603) and the protective layer (606) are consistent with those of the liquid hydrogen-superconducting hybrid submarine AC cable, the liquid hydrogen outer transmission pipeline (604) is a gap between the electric insulation layer and the heat insulation layer, the two liquid hydrogen pipelines adopt single-end counter-flow refrigeration, the heat insulation layer (605) is made of coaxial double-layer stainless steel bellows, vacuum is extracted between the two layers, and multiple layers of radiation-proof metal foils are embedded in the coaxial double-layer stainless steel bellows. The electric energy generated by the offshore wind power is used to produce hydrogen in the water electrolysis hydrogen production equipment (11) and stored in the gas tank (12), part of the hydrogen in the gas tank is used for power generation in the fuel cell (10), and part of the hydrogen is liquefied into liquid hydrogen in the hydrogen liquefaction equipment (13) and stored in the liquid tank (14), part of the liquid hydrogen in the liquid tank is used to cool the superconducting magnet in the superconducting energy storage device (9), and part of the liquid hydrogen is used in the liquid hydrogen-superconducting hybrid submarine AC and DC cable; wherein, The hydrogen source of the fuel cell (10) is the hydrogen stored in the gas tank (12) after water electrolysis hydrogen production, and the hydrogen inlet amount and the first DC chopper (15) in the battery are controlled according to the load and the electrical characteristics detected by the main power grid (8), so as to adjust the power generated; The superconducting energy storage magnet (902) in the superconducting energy storage device (9) is in a superconducting state in the Dewar (901) filled with liquid hydrogen, and is charged and discharged through the second DC chopper (16).

2. The hybrid superconducting microgrid system for smoothing offshore wind power fluctuation according to claim 1, wherein, The superconducting energy storage device (9) and the fuel cell (10) control their respective choppers to charge or discharge according to the electrical characteristics on the DC bus (17), so as to smooth the power fluctuation of the offshore wind power generation device.

3. The hybrid superconducting microgrid system for smoothing offshore wind power fluctuation according to claim 1, wherein, The liquid tank (14) is connected to the liquid hydrogen transmission pipeline in the liquid hydrogen-superconducting hybrid submarine AC and DC cable through the liquid hydrogen pump (21), and is finally connected to the superconducting step-up transformer (2), and the controller on the liquid hydrogen relay booster station (4) judges whether the liquid hydrogen pump (21) is needed to supplement the insufficient liquid hydrogen in the pipeline by monitoring the flow rate of the liquid hydrogen in the liquid hydrogen transmission pipeline.

4. The hybrid superconducting microgrid system for smoothing offshore wind power fluctuation according to claim 1, wherein, The liquid hydrogen in the liquid tank (14) enters the Dewar (901) through the liquid inlet pipe (19) to cool the superconducting energy storage device, and the superconducting energy storage magnet (902) in the superconducting energy storage device generates heat during operation to gasify the liquid hydrogen in the Dewar to produce hydrogen gas, which enters the gas tank (12) through the exhaust pipe (20).

5. The hybrid superconducting microgrid system for smoothing offshore wind power fluctuation according to claim 4, wherein, The liquid level in the Dewar (901) of the superconducting energy storage device changes during the operation of the superconducting energy storage device (9), and the intelligent control switch (903) on the liquid inlet pipe (19) controls the opening and closing of the liquid inlet pipe according to the signal sensed by the liquid level sensor in the Dewar, and the intelligent control switch (904) on the exhaust pipe (20) controls the opening and closing of the exhaust pipe according to the gas pressure sensed by the pressure sensor in the Dewar, so that the liquid level in the Dewar is always above the superconducting energy storage magnet (902).

6. The composite superconducting microgrid system for smoothing offshore wind power fluctuation according to any one of claims 1-5, characterized in that, It comprises the following steps: S1, power generation, the offshore superconducting generator set (1) converts wind energy into electrical energy, and the electrical energy is boosted by the superconducting booster transformer (2) and then transmitted to the offshore converter station (5) by the liquid hydrogen-superconducting hybrid submarine AC cable (3), realizing the conversion of offshore wind energy and electrical energy; S2, current conversion, the offshore converter station (5) converts three-phase AC power into DC power using flexible DC power transmission, and the DC power is transmitted to the onshore converter station (7) through the liquid hydrogen-superconducting hybrid submarine DC cable (6), and the onshore converter station (7) converts the DC power into AC power, which is used to meet the electricity demand of the water electrolysis hydrogen production equipment (11) and the superconducting energy storage device (9) in priority, and the surplus electrical energy is transmitted to the main power grid (8), realizing the rational distribution of electrical energy; S3, hydrogen production and storage, the water electrolysis hydrogen production equipment (11) receives the electrical energy sent by the onshore converter (7) to perform water electrolysis, and the hydrogen gas is stored in the gas tank (12), and the hydrogen gas liquefaction equipment (13) converts the hydrogen gas in the gas tank into liquid hydrogen, which is stored in the liquid tank (14), realizing the conversion of electrical energy, hydrogen energy, hydrogen gas and liquid hydrogen; S4, power smoothing, the hydrogen gas in the gas tank (12) is used as raw material for the fuel cell (10), and the liquid hydrogen enters the Dewar of the superconducting energy storage device (9) along the liquid inlet pipe (19), and the liquid hydrogen flows over the superconducting energy storage magnet (902) to realize immersion cooling, and the fuel cell (10) and the superconducting energy storage device (9) control their respective DC choppers by judging the electrical characteristics of the connected DC bus (17), thereby realizing the power fluctuation smoothing of offshore wind power generation; In S2, due to the long transmission distance of the liquid hydrogen-superconducting hybrid submarine DC cable (6), a liquid hydrogen relay booster station (4) is added, and when the flow rate of the liquid hydrogen in the liquid hydrogen transmission pipeline is detected to be lower than the lower threshold value, the liquid hydrogen pump on the liquid hydrogen relay booster station is started to supplement the insufficient liquid hydrogen in the pipeline; In S2, when it is detected that the liquid level of the Dewar (203) in the superconducting booster transformer (2) cooling machine drops to the lowest set value, the liquid inlet valve (202) is opened to supplement the liquid hydrogen in the liquid tank (201), and when the liquid hydrogen in the liquid tank (201) is insufficient, the liquid hydrogen pump on the liquid hydrogen relay booster station (4) supplements the liquid hydrogen; In S3, hydrogen in the gas tank (12) meets the needs of the hydrogen liquefaction device (13) first, the surplus hydrogen can be used for fuel cell (10), liquid hydrogen in the liquid tank (14) meets the needs of superconducting energy storage device (9), liquid hydrogen-superconducting hybrid submarine AC / DC cable (6) and superconducting booster transformer (2) first, to ensure that they are in low temperature environment for a long time; In S4, when the liquid level of liquid hydrogen in the Dewar (901) is lower than the minimum threshold, the liquid level sensor will open the intelligent control switch (903) on the inlet pipe (19) to let the liquid hydrogen into the superconducting energy storage device (9), the liquid hydrogen is easy to be gasified by the heat generated by the operation of the superconducting energy storage device (9), when the hydrogen pressure in the Dewar is higher than the maximum threshold, the exhaust pipe (20) opens the intelligent switch (904) according to the gas pressure sensor to let the hydrogen into the gas tank; In S4, when controlling the direct current chopper of the superconducting energy storage device (9) and the fuel cell (10) respectively, the filter is used, the high frequency component of power fluctuation is borne by the superconducting energy storage device (9), and the low frequency component is borne by the fuel cell (10).

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