Multi-wind-field offshore wind power collecting and sending-out system and method

Abstract

The invention relates to a multi-wind-field offshore wind power collecting and sending-out system and method, and the system comprises a high-voltage interconnecting transformer module, at least one offshore flexible DC conversion module, a high-voltage AC connecting cable, and a high-voltage DC sending-out cable. The high-voltage interconnecting transformer module is used for collecting and boosting offshore wind power of a plurality of different wind fields with the current distance larger than a preset distance value to obtain high-voltage alternating current, and the high-voltage alternating current is connected to the offshore flexible direct current conversion module through the high-voltage alternating current connecting cable. The offshore flexible direct current conversion module is used for converting high-voltage alternating current collected by alternating current in a plurality of different wind fields into high-voltage direct current, and the high-voltage direct current is transmitted to an onshore converter station through a high-voltage direct current sending-out cable. Therefore, the problems that when a plurality of dispersed wind fields need to adopt the same offshore flexible direct current converter station for sending out, the investment of boosting equipment of the dispersed wind fields is large, the two-stage boosting efficiency is low, and the construction difficulty is large are solved.

Description

Technical Field

[0001] The present application relates to the field of electric power technology, and in particular to a system and method for collecting and transmitting offshore wind power from multiple wind farms. Background Art

[0002] Renewable energy sources such as photovoltaics and wind power have been developed and connected to the grid on a large scale, and have gradually replaced traditional fossil energy as the main source of electricity supply for mankind. On this basis, offshore wind power has been developed on a large scale in my country's coastal areas. In recent years, with the increase in development efforts, the development of offshore wind power resources in the nearshore area has approached saturation, and the acquisition and development of deep-sea wind resources has become the focus of competition among major investors.

[0003] Deep sea offshore wind power resources are far from the shore, and their transmission is generally carried out by flexible direct current. Flexible direct current transmission of offshore wind has the advantages of large single-circuit transmission capacity, small sea area for engineering, and no need to add reactive power compensation devices. Due to its large single-circuit transmission capacity, it is often necessary to gather wind energy from multiple dispersed wind farms into an offshore flexible direct current converter station before transmission.

[0004] like Figure 1 As shown, in order to gather wind farms that are far apart from each other to the flexible DC converter station, the relevant technology first increases the voltage at different decentralized wind farm AC booster stations, and then gathers it to the offshore flexible DC converter station through high-voltage submarine cables. It is then transformed by multiple flexible DC interconnecting transformers and connected to the converter valve for conversion into DC for transmission.

[0005] This method requires the construction of booster stations in dispersed wind farms. After boosting, the power is transmitted to the flexible DC converter station through high-voltage cables, and then connected to the converter valve after boosting through the interconnecting transformer. The relevant technology treats the AC booster station and the flexible DC converter station as two independent functional units through the AC boosting collection and the flexible DC converter station delivery. The AC boosting is first collected, and then the flexible DC is delivered. The advantage of this method is that the structure is clear and the principle is simple and clear. However, for wind power far away from the wind farm where the flexible DC converter station is located, two-stage boosting is carried out. The investment in boosting equipment is large, and the efficiency of two-stage boosting is low. There are many AC submarine cables, the sea area is increased, and there are many submarine cross-spans, which not only increases the project investment, but also increases the difficulty of construction. Especially in some complex sea areas, where there are large restrictions on submarine optical cables and cable cross-spans, this method may make the project completely impossible to implement. Summary of the invention

[0006] The present application provides a multi-wind farm offshore wind power collection and transmission system and method to solve the problems of large investment in boosting equipment for dispersed wind farms far away from offshore flexible direct current converter stations, low two-stage boosting efficiency, and great construction difficulty. It reduces the number of high-voltage AC cables collected, improves the efficiency of collecting and transmitting offshore wind power at multiple sites in the deep sea, and reduces the installation difficulty and construction cost of the transmission system.

[0007] The first aspect of the present application provides a multi-wind farm offshore wind power collection and transmission system, comprising: multiple high-voltage interconnecting transformer modules, at least one offshore flexible direct current converter module, a high-voltage AC connecting cable and a high-voltage DC transmission cable, wherein the high-voltage interconnecting transformer module is used to collect and boost the offshore wind power of multiple different wind farms whose current distance is greater than a preset distance value to obtain high-voltage AC power, and connect the high-voltage AC power to the offshore flexible direct current converter module through the high-voltage AC connecting cable; the offshore flexible direct current converter module is used to convert the high-voltage AC power collected from the multiple different wind farms into high-voltage DC power, so as to transmit the high-voltage DC power to an onshore converter station through the high-voltage DC transmission cable.

[0008] Optionally, in some embodiments, the high-voltage interconnecting transformer module includes: a first high-voltage interconnecting transformer, a first low-voltage AC switch device, a first high-voltage AC switch device, a first low-voltage AC bus, and a first high-voltage AC bus, wherein the first high-voltage interconnecting transformer is used to boost the low-voltage AC power at the outlet of each wind farm to obtain the high-voltage AC power; the first low-voltage AC switch device is used to control the outlet of each wind farm collection line to be connected to the first low-voltage AC bus, and control the connection and disconnection between the first low-voltage AC bus and the first high-voltage interconnecting transformer; the first high-voltage AC switch device is used to control the high-voltage AC power to be connected to the first high-voltage AC bus, and control the connection and disconnection between the first high-voltage AC bus and the offshore flexible DC converter module; the first low-voltage AC bus is used to connect the multiple offshore wind power collection lines to the first high-voltage interconnecting transformer; the first high-voltage AC bus is used to collect the high-voltage AC power boosted by at least one high-voltage interconnecting transformer and connect it to the offshore flexible DC converter module through the high-voltage AC cable.

[0009] Optionally, in some embodiments, the offshore flexible DC converter module includes: a converter valve, a second high-voltage interconnecting transformer, a DC switch device, a second low-voltage AC switch device, a second high-voltage AC switch device, a second low-voltage AC bus, and a second high-voltage AC bus, wherein the converter valve is used to convert the high-voltage AC power boosted by the high-voltage interconnecting transformer into the high-voltage DC power; the second high-voltage interconnecting transformer is used to boost the low-voltage AC power of the multiple offshore wind power collection lines located in the wind farm to obtain the high-voltage AC power; the DC switch device is used to control the connection between the high-voltage DC transmission cable and the converter valve; the second low-voltage AC switch device Used to control the multiple offshore wind power collection lines located in this wind farm to access the second low-voltage AC bus, and control the connection between the second low-voltage AC bus and the second high-voltage interconnecting transformer located in this wind farm; the second high-voltage AC switch device is used to control the high-voltage AC power located in this wind farm to access the second high-voltage AC bus, and control the connection between the second high-voltage AC bus and the converter valve located in this wind farm; the second low-voltage AC bus is used to collect the low-voltage AC power sent by the multiple offshore wind power collection lines located in this wind farm; the second high-voltage AC bus is used to collect the high-voltage AC power boosted by the first high-voltage interconnecting transformer and the second high-voltage interconnecting transformer.

[0010] Optionally, in some embodiments, when there are multiple wind farms of different capacities, the offshore flexible DC converter station modules are distributed in the center of a larger wind farm among the multiple wind farms, and the multiple high-voltage interconnection transformer modules are distributed in other wind farms at different locations. The low-voltage side of the first high-voltage interconnection transformer in the high-voltage interconnection transformer module is a first preset voltage, and the low-voltage side voltage of the second high-voltage interconnection transformer in the offshore flexible DC converter station module is a second preset voltage, and the voltage level of the high-voltage side of the first high-voltage interconnection transformer is the same as the voltage level of the high-voltage side of the second high-voltage interconnection transformer.

[0011] Optionally, in some embodiments, the rated voltage of the first high-voltage interconnecting transformer is calculated according to the wind farm distribution location and the length and electrical parameters of the high-voltage AC cable.

[0012] Optionally, in some embodiments, the high-voltage AC connection cable between the first high-voltage interconnecting transformer and the offshore flexible DC converter module includes an integrated communication optical cable.

[0013] The second aspect of the present application provides a method for collecting and transmitting offshore wind power from multiple wind farms, using the multiple wind farm offshore wind power collection and transmission system as described above, wherein the method includes the following steps: collecting the offshore wind power from the multiple different wind farms through the high-voltage interconnecting transformer module, and boosting the offshore wind power from the multiple different wind farms to obtain the high-voltage alternating current; collecting the high-voltage alternating current through the offshore flexible direct current converter module, and converting the high-voltage alternating current using the converter valve to obtain the high-voltage direct current; transmitting the high-voltage direct current to the onshore converter station through the high-voltage direct current transmission cable.

[0014] Optionally, the current wind farm position, current wind farm capacity and current wind farm operation mode of the high-voltage interconnecting transformer module and the offshore flexible DC converter module are obtained; and the technical parameters of different equipment and the control system operation mode of the offshore flexible DC converter module are simulated and calculated based on the current wind farm position, current wind farm capacity and current wind farm operation mode of the high-voltage interconnecting transformer module and the offshore flexible DC converter station module.

[0015] Therefore, according to the multi-wind-field offshore wind power collection and transmission system of the present application, the offshore wind power of multiple different wind fields is collected and boosted through the high-voltage interconnection transformer module to obtain high-voltage AC power, and the high-voltage AC power is connected to the offshore flexible DC converter module through the high-voltage AC connecting cable, and the offshore flexible DC converter module is used to convert the high-voltage AC power collected from multiple different wind fields into high-voltage DC power, so as to transmit the high-voltage DC power to the onshore converter station through the high-voltage DC transmission cable. Therefore, for each dispersed wind field far away from the wind field, its AC power is only boosted once, which solves the problems of large investment in boosting equipment far away from the offshore flexible DC converter station, low two-stage boosting efficiency, and high construction difficulty, reduces the number of AC cables collected, improves the efficiency of collecting and transmitting offshore wind power in multiple sites and deep seas, and reduces the installation difficulty and construction cost of the transmission system.

[0016] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0018] Figure 1 A schematic diagram of a multi-wind farm offshore wind power collection and transmission system in the related art;

[0019] Figure 2 A schematic diagram of a multi-wind farm offshore wind power collection and transmission system provided according to an embodiment of the present application;

[0020] Figure 3 A schematic diagram of a multi-wind farm offshore wind power collection and transmission system according to a specific embodiment of the present application;

[0021] Figure 4 This is a flow chart of a method for collecting and transmitting offshore wind power from multiple wind farms provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0022] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0023] The following describes the multi-wind field offshore wind power collection and transmission system and method of the embodiment of the present application with reference to the accompanying drawings. In view of the problems mentioned in the above background technology that the boosting equipment far away from the wind field where the offshore flexible direct current converter station is located has a large investment, a low two-stage boosting efficiency, and a high construction difficulty, the present application provides a multi-wind field offshore wind power collection and transmission system, in which a high-voltage interconnection transformer module is used to collect and boost the offshore wind power of multiple different dispersed wind fields to obtain high-voltage alternating current, and connect the high-voltage alternating current to the offshore flexible direct current converter module through a high-voltage alternating current connecting cable; the offshore flexible direct current converter module is used to convert the high-voltage alternating current collected by the alternating current in multiple different wind fields into high-voltage direct current, so as to transmit the high-voltage direct current to the onshore converter station through a high-voltage direct current transmission cable. Thus, for each dispersed wind field far away from the wind field, its alternating current is only boosted once, which solves the problems of large investment in boosting equipment far away from the wind field where the offshore flexible direct current converter station is located, low two-stage boosting efficiency, and high construction difficulty, reduces the number of AC cables collected, improves the efficiency of collecting and transmitting offshore wind power in multiple sites and deep seas, and reduces the installation difficulty and construction cost of the transmission system.

[0024] Specifically, Figure 2 Schematic diagram of the multi-wind farm offshore wind power collection and transmission system provided in an embodiment of the present application.

[0025] like Figure 2 As shown, the multi-wind farm offshore wind power collection and transmission system includes: multiple high-voltage interconnecting transformer modules, at least one offshore flexible DC converter module, high-voltage AC connecting cables and high-voltage DC transmission cables.

[0026] Among them, the high-voltage interconnecting transformer module is used to collect and boost the offshore wind power of multiple different wind farms whose current distance is greater than the preset distance value to obtain high-voltage AC power, and connect the high-voltage AC power to the offshore flexible DC converter module through the high-voltage AC connecting cable; the offshore flexible DC converter module is used to convert the high-voltage AC power collected from multiple different wind farms into high-voltage DC power, so as to transmit the high-voltage DC power to the onshore converter station through the high-voltage DC transmission cable.

[0027] Specifically, Figure 2 As shown, in the embodiment of the present application, multiple high-voltage interconnection transformers of the offshore flexible DC converter module are arranged in parallel in different wind farm areas, and the offshore wind of each wind farm is collected and boosted to obtain high-voltage AC power of the corresponding wind farm. Therefore, the embodiment of the present application uses distributed high-voltage interconnection transformers to achieve on-site boosting of wind farms in different regions, and then collects them through high-voltage AC submarine cables.

[0028] It can be understood that the offshore flexible DC conversion module is an offshore power facility built based on flexible DC transmission technology. The multi-wind farm offshore wind power collection and transmission system of the embodiment of the present application is equipped with at least one offshore flexible DC conversion module, which is connected to the grid through DC. There is no need for the wind farm to keep in sync with the connected AC power grid. The high-voltage AC power collected from multiple different wind farms is converted into high-voltage DC power, and the transmission efficiency of wind power energy is effectively improved, the operation of the power grid is stabilized, and the environmental impact is reduced.

[0029] Furthermore, the high-voltage AC connecting cable of the embodiment of the present application is used to transmit high-voltage AC power in different wind farm areas to the high-voltage AC bus of the offshore flexible DC converter station; the high-voltage DC transmission cable of the embodiment of the present application is used to transmit the high-voltage DC power converted by the offshore flexible DC converter station to the converter station built on land.

[0030] Therefore, this application designs the interconnecting transformer of the traditional large-capacity flexible DC converter station into a high-voltage interconnecting transformer module, which is dispersed with the offshore flexible DC converter station. It can locally collect and boost the offshore wind power in different wind farm areas, and then connect it to the valve-side AC busbar of the offshore flexible DC converter station through a high-voltage AC connecting cable, thereby realizing the high-voltage AC collection of offshore wind power in different areas, which is then converted into DC by the flexible DC converter station and then sent out.

[0031] Compared to Figure 1The multi-wind farm offshore wind power collection and transmission system in the related art shown in the figure, and the multi-wind farm offshore wind power collection and transmission system in the embodiment of the present application can save a lot of AC collection cable engineering, reduce the crossing of AC submarine cables and other submarine facilities, and avoid the multi-stage boosting of the AC side of the offshore flexible DC converter station, which greatly saves engineering investment. It also reduces the operation and maintenance interface after the centralized transmission of offshore wind power of different owners in different regions, and avoids economic and safety disputes between different owners due to too many centralized transmission management interfaces.

[0032] Next, the specific structure and principle of the multi-wind farm offshore wind power collection and transmission system of the embodiment of the present application will be introduced.

[0033] Optionally, in some embodiments, the high-voltage interconnecting transformer module includes: a first high-voltage interconnecting transformer, a first low-voltage AC switch device, a first high-voltage AC switch device, a first low-voltage AC bus, and a first high-voltage AC bus, wherein the first high-voltage interconnecting transformer is used to boost the low-voltage AC power at the outlet of each wind farm to obtain high-voltage AC power; the first low-voltage AC switch device is used to control the access of each wind farm collection line outlet to the first low-voltage AC bus, and control the connection and disconnection between the first low-voltage AC bus and the first high-voltage interconnecting transformer; the first high-voltage AC switch device is used to control the access of high-voltage AC power to the first high-voltage AC bus, and control the connection and disconnection between the first high-voltage AC bus and the offshore flexible DC converter module; the first low-voltage AC bus is used to connect multiple offshore wind power collection lines to the first high-voltage interconnecting transformer; the first high-voltage AC bus is used to collect the high-voltage AC power boosted by at least one high-voltage interconnecting transformer and connect it to the offshore flexible DC converter module via a high-voltage AC cable.

[0034] The high-voltage interconnecting transformer modules arranged in different areas in the embodiment of the present application at least include a high-voltage interconnecting transformer, a low-voltage AC switch device, a high-voltage AC switch device, a low-voltage AC bus, and a high-voltage AC bus.

[0035] Among them, the low-voltage AC switch device of the high-voltage interconnecting transformer module, that is, the first low-voltage AC switch device of the embodiment of the present application is located on the low-voltage side of the first high-voltage interconnecting transformer, and is used to control the connection of the offshore wind turbine outlet circuit of the corresponding wind farm area to the first low-voltage AC bus, and control the connection between the first low-voltage AC bus and the first high-voltage interconnecting transformer.

[0036] The high-voltage AC switch device of the high-voltage interconnecting transformer module, that is, the first high-voltage AC switch device of the embodiment of the present application is located on the high-voltage side of the first high-voltage interconnecting transformer, and is used to control the high-voltage AC power after boosting in the corresponding wind farm area to be connected to the first high-voltage AC bus, and to control the connection between the first high-voltage AC bus in the corresponding wind farm area and the first high-voltage AC bus of the offshore flexible DC converter station.

[0037] The low-voltage AC busbar of the high-voltage interconnecting transformer module, that is, the first low-voltage AC busbar in the embodiment of the present application, is located in the corresponding wind farm area, and is used to collect the outlet circuits of offshore wind turbines, so as to realize the collection of energy generated by multiple wind turbines and then connect it to the first high-voltage interconnecting transformer in the corresponding wind farm area.

[0038] The high-voltage AC busbar of the high-voltage interconnecting transformer module, that is, the first high-voltage AC busbar in the embodiment of the present application, is used to collect high-voltage AC power that has been boosted by multiple high-voltage interconnecting transformers in the corresponding wind farm area, so as to realize the high-voltage AC busbar of the offshore flexible DC converter station after the high-voltage side energy of multiple different high-voltage interconnecting transformers is collected.

[0039] Therefore, the present application disperses the interconnecting transformers in the flexible DC converter station to various wind farms to replace the AC step-up transformers in other wind farms, thereby avoiding two-stage step-up, reducing the number of transformers, and reducing investment. After the multiple interconnecting transformers in the flexible DC converter station are arranged separately, the weight of the entire flexible DC converter station equipment can be reduced by about 15%, and the volume and weight of the converter station platform can be reduced by about 20%, reducing the difficulty of platform manufacturing and installation.

[0040] Optionally, in some embodiments, the offshore flexible DC converter module includes: a converter valve, a second high-voltage interconnecting transformer, a DC switch device, a second low-voltage AC switch device, a second high-voltage AC switch device, a second low-voltage AC bus, and a second high-voltage AC bus, wherein the converter valve is used to convert the high-voltage AC power boosted by the high-voltage interconnecting transformer into high-voltage DC power; the second high-voltage interconnecting transformer is used to boost the low-voltage AC power of multiple offshore wind power collection lines located in the wind farm to obtain high-voltage AC power; the DC switch device is used to control the connection between the high-voltage DC transmission cable and the converter valve; the second low-voltage AC switch device The equipment is used to control the access of multiple offshore wind power collection lines located in this wind farm to the second low-voltage AC bus, and to control the connection between the second low-voltage AC bus and the second high-voltage interconnecting transformer located in this wind farm; the second high-voltage AC switchgear is used to control the access of the high-voltage AC power located in this wind farm to the second high-voltage AC bus, and to control the connection between the second high-voltage AC bus and the converter valve located in this wind farm; the second low-voltage AC bus is used to collect the low-voltage AC power sent by multiple offshore wind power collection lines located in this wind farm; the second high-voltage AC bus is used to collect the high-voltage AC power boosted by the first high-voltage interconnecting transformer and the second high-voltage interconnecting transformer.

[0041] The offshore flexible DC converter station of the embodiment of the present application includes a converter valve, a high-voltage interconnecting transformer, a DC switchgear, a low-voltage AC switchgear, a high-voltage AC switchgear, a low-voltage AC busbar, a high-voltage AC busbar, etc. The offshore flexible DC converter station of the embodiment of the present application can be one or more.

[0042] Among them, the converter valve of the offshore flexible DC converter station is used to convert high-voltage AC power into high-voltage DC power; the high-voltage interconnecting transformer of the offshore flexible DC converter station, that is, the second high-voltage interconnecting transformer of the embodiment of the present application is used to boost the low-voltage electricity at the outlet of the offshore wind turbine into high-voltage electricity suitable for long-distance transmission.

[0043] The DC switchgear of the offshore flexible DC converter station is used to control the connection between the high-voltage DC transmission cable and the converter valve; the low-voltage AC switchgear of the offshore flexible DC converter station, that is, the second low-voltage AC switchgear of the embodiment of the present application is located on the low-voltage side of the second high-voltage interconnecting transformer, and is used to control the offshore wind turbine outlet circuit to access the second low-voltage AC bus, and control the connection between the second low-voltage AC bus and the second high-voltage interconnecting transformer.

[0044] The high-voltage AC switchgear of the offshore flexible DC converter station, that is, the second high-voltage AC switchgear of the embodiment of the present application is located on the high-voltage side of the second high-voltage interconnecting transformer, and is used to control the access of the boosted high-voltage AC power to the second high-voltage AC bus, and to control the connection between the second high-voltage AC bus and the converter valve.

[0045] The low-voltage AC busbar of the offshore flexible DC converter station, that is, the second low-voltage AC busbar in the embodiment of the present application, is used to collect the outlet circuits of the offshore wind turbines in the wind farm, so as to collect the energy generated by multiple wind turbines and then connect them to the second high-voltage interconnecting transformer.

[0046] The high-voltage AC busbar of the offshore flexible DC converter station, that is, the second high-voltage AC busbar in the embodiment of the present application, is used to collect high-voltage AC power after being boosted by different high-voltage interconnecting transformers, so as to realize the connection of the converter valve after the high-voltage side energy of multiple different high-voltage interconnecting transformers is collected.

[0047] When a short-circuit fault occurs, the bridge arm inductor increases the impedance of the circuit through its inductance characteristics, thereby limiting the size of the short-circuit current, preventing the short-circuit fault from causing excessive impact on the system, effectively reducing the risk of damage to power equipment, and maintaining stable operation of the system.

[0048] Optionally, in some embodiments, when there are multiple wind farms of different capacities, the offshore flexible DC converter station modules are distributed in the center of a larger wind farm among the multiple wind farms, and multiple high-voltage interconnection transformer modules are distributed in other wind farms at different locations. The low-voltage side of the first high-voltage interconnection transformer in the high-voltage interconnection transformer module is a first preset voltage, and the low-voltage side voltage of the second high-voltage interconnection transformer in the offshore flexible DC converter station module is a second preset voltage, and the voltage level of the high-voltage side of the first high-voltage interconnection transformer is the same as the voltage level of the high-voltage side of the second high-voltage interconnection transformer.

[0049] It is understandable that when there are multiple wind farms with different capacities, the number of offshore flexible DC converter station modules is generally one, which is arranged in the center of the larger wind farm among the multiple wind farms, and the number of high-voltage interconnection transformer modules is generally multiple (determined according to the number of different wind farms), which are distributed in other wind farms with different locations. The low-voltage side of the first high-voltage interconnection transformer can select different voltages, such as 35kV or 66kV, and the low-voltage side voltage of the second high-voltage interconnection transformer can be 35kV, 66kV or 110kV. The voltage level of the high-voltage side of the first high-voltage interconnection transformer and the second high-voltage interconnection transformer must be the same, which can generally be 500kV, 400kV or 320kV.

[0050] Therefore, the multi-wind farm offshore wind power collection and transmission system of the present application reduces the amount of AC current collection to a certain extent, reduces the number of seabed crossings and the sea area used, and reduces the difficulty of project implementation.

[0051] Specifically, the high-voltage AC circuit breaker of the embodiment of the present application is configured at both ends of the high-voltage AC connecting cable.

[0052] It can be understood that a high-voltage AC circuit breaker is an important electrical appliance used to open and close current under abnormal circuit conditions. In the embodiment of the present application, multiple high-voltage AC circuit breakers are arranged in a multi-wind farm offshore wind power collection and transmission system to disconnect the circuit current when a high-voltage AC connecting cable fails, so as to protect the safety of the circuit and electrical equipment.

[0053] Specifically, the high-voltage side of the dispersedly arranged high-voltage interconnecting transformer in the embodiment of the present application should adopt neutral point wiring via a lightning arrester to reduce the insulation level of the interconnecting transformer body and the high-voltage AC submarine cable.

[0054] Specifically, three-phase voltage transformers should be configured at both ends of the high-voltage AC connecting cable in the embodiment of the present application. When a single-phase grounding fault occurs in the high-voltage AC cable, the transformer detects the grounding fault and triggers the guarantee device to trip.

[0055] Therefore, the embodiment of the present application sets high-voltage AC circuit breakers, lightning arresters and three-phase voltage transformers in the multi-wind farm offshore wind power collection and transmission system, which effectively protects the safe operation of each equipment in the system and ensures the reliability and safety of offshore wind power collection and transmission.

[0056] In some embodiments, Figure 3 This is a schematic diagram of a multi-wind farm offshore wind power collection and transmission system according to a specific embodiment of the present application. Figure 3As shown, the multi-wind farm offshore wind power collection and transmission system of the embodiment of the present application includes: at least one flexible DC converter station, switch equipment, high-voltage interconnection transformer module, high-voltage AC connecting submarine cable, and high-voltage DC transmission submarine cable. Among them, the valve group of the flexible DC converter station is used to convert the AC collected offshore wind power into high-voltage DC; the dispersed high-voltage interconnection transformer modules are used to collect and boost the offshore wind power in different areas; the high-voltage AC connecting submarine cable is used to transmit the boosted offshore wind power energy in different areas to the AC busbar on the valve side of the flexible DC converter station; the high-voltage DC transmission submarine cable transmits the converted DC offshore wind power energy to the onshore converter station.

[0057] Therefore, the multi-wind farm offshore wind power collection and transmission system according to the embodiment of the present application solves the problems of high investment and multiple cross-overs in the two-stage voltage boosting. In addition, the multi-wind farm offshore wind power collection and transmission system according to the embodiment of the present application is equipped with high-voltage AC circuit breakers and other equipment, which effectively protects the safety of each equipment in the system while improving the system efficiency.

[0058] Optionally, in some embodiments, the rated voltage of the first high-voltage interconnection transformer is calculated based on the wind farm distribution location and the length and electrical parameters of the high-voltage AC cable. Generally speaking, the rated voltage of the high-voltage side of the first high-voltage interconnection transformer varies with the length of the AC submarine cable. For a 500kV system, its voltage can be 500-530kV; for a 400kV system, its voltage can be 400-420kV; for a 320kV system, its voltage can be 320-335kV.

[0059] In some embodiments, the high-voltage AC connecting cable between the first high-voltage interconnecting transformer and the offshore flexible DC converter module includes an integrated communication optical cable.

[0060] According to the multi-wind farm offshore wind power collection and transmission system proposed in the embodiment of the present application, the offshore wind power of multiple different wind farms is collected and boosted through a high-voltage interconnection transformer module to obtain high-voltage AC power, and the high-voltage AC power is connected to the offshore flexible DC converter module through a high-voltage AC connecting cable. The offshore flexible DC converter module is used to convert the high-voltage AC power collected from multiple different wind farms into high-voltage DC power, so as to transmit the high-voltage DC power to the onshore converter station through a high-voltage DC transmission cable. In this way, the problems of large investment in boosting equipment far away from the offshore flexible DC converter station, low two-stage boosting efficiency, and high construction difficulty are solved, the number of AC cables collected is reduced, the efficiency of collecting and transmitting offshore wind power in multiple sites and deep sea is improved, and the installation difficulty and construction cost of the transmission system are reduced.

[0061] Next, a method for collecting and transmitting offshore wind power from multiple wind farms is described with reference to the accompanying drawings according to an embodiment of the present application. The method adopts the above-mentioned system for collecting and transmitting offshore wind power from multiple wind farms.

[0062] Figure 4 It is a flow chart of a method for collecting and transmitting offshore wind power from multiple wind farms according to an embodiment of the present application.

[0063] like Figure 4 As shown, the method for collecting and transmitting offshore wind power from multiple wind farms includes the following steps:

[0064] In step S401, offshore wind power from multiple wind farms is collected through a high-voltage interconnection transformer module, and the offshore wind power from multiple wind farms is boosted to obtain high-voltage alternating current.

[0065] In step S402, high-voltage alternating current is collected by an offshore flexible direct current converter module, and the high-voltage alternating current is converted by a converter valve to obtain high-voltage direct current.

[0066] In step S403, the high voltage direct current is transmitted to an onshore converter station via a high voltage direct current transmission cable.

[0067] Optionally, in some embodiments, the current wind farm position, current wind farm capacity and current wind farm operation mode of the high-voltage interconnecting transformer module and the offshore flexible DC converter module are obtained; and the technical parameters of different equipment and the control system operation mode of the offshore flexible DC converter module are simulated and calculated based on the current wind farm position, current wind farm capacity and current wind farm operation mode of the high-voltage interconnecting transformer module and the offshore flexible DC converter station module.

[0068] Therefore, the present application utilizes a multi-wind farm offshore wind power collection and transmission system, collects and boosts the offshore wind power in different wind farm areas through a high-voltage interconnecting transformer module, converts the collected and boosted high-voltage AC power into high-voltage DC power through a valve group of an offshore flexible DC converter module, and transmits the boosted offshore wind power in different wind farm areas to the AC bus on the valve side of the flexible DC converter station through a high-voltage AC connecting cable, and finally transmits the offshore wind power to the onshore converter station through a high-voltage DC transmission cable.

[0069] It is understandable that when the wind turbine is fully powered, the converter station may need to provide more reactive power to support the stable operation of the system, or adjust the system voltage through reactive power control strategies. In addition, the active power generated by the wind turbine will also increase the power flow on the DC side of the converter station, and the operating parameters of the converter valve may need to be adjusted to adapt to this change. When the wind turbine is fully stopped, the reactive power demand of the converter station may be relatively low, but a certain reactive power reserve still needs to be maintained to cope with transient disturbances and voltage fluctuations in the system. In addition, due to the shutdown of the wind turbine, the active power balance of the system may also change, and the converter station may need to adjust its active and reactive output to maintain the stable operation of the system.

[0070] Therefore, the embodiment of the present application needs to calculate the changes in the reactive power demand on the AC side of the converter valve of the flexible DC converter station under different operating conditions. Generally speaking, each high-voltage AC submarine cable collection circuit should consider two operating conditions: full power generation of the wind turbine and complete shutdown of the wind turbine, and calculate the operating conditions formed by the combination of different power generation states of multiple collection circuits, and consider the changes in its reactive power demand accordingly.

[0071] Specifically, the preset control method of the embodiment of the present application is a v / f (Volt & Frequency Control, voltage-frequency conversion control) control method, which can ensure that the output voltage is proportional to the frequency, and is used to maintain the magnetic flux of the motor constant and avoid the occurrence of weak magnetic field and magnetic saturation. In the context of v / f control, the converter valve needs to be able to accurately adjust the frequency of its output voltage to meet the needs of the motor or other loads.

[0072] That is to say, the method proposed in this application will lead to an increase in reactive power demand on the AC side of the flexible DC converter station valve, and this increase in reactive power should be balanced by adjusting the operation mode of the flexible DC converter station valve. Generally speaking, the flexible DC converter station valve can be used for v / f control, and the wind turbine grid-side converter adopts a fixed DC voltage and reactive power control, so that the reactive power on the flexible DC converter station valve side is balanced by the wind turbine converter and the converter valve.

[0073] It should be noted that the aforementioned explanation of the embodiment of the multi-wind farm offshore wind power collection and transmission system is also applicable to the multi-wind farm offshore wind power collection and transmission method of this embodiment, and will not be repeated here.

[0074] According to the multi-wind farm offshore wind power collection and transmission method proposed in the embodiment of the present application, offshore wind power from multiple different wind farms is collected through a high-voltage interconnection transformer module, and the offshore wind power from multiple different wind farms is boosted to obtain high-voltage AC power. The high-voltage AC power is collected through an offshore flexible direct current converter module, and the high-voltage AC power is converted using a converter valve to obtain high-voltage DC power. The high-voltage DC power is transmitted to the onshore converter station through a high-voltage DC transmission cable. Thus, the problems of large investment in boosting equipment far away from the offshore flexible direct current converter station, low two-stage boosting efficiency, and high construction difficulty are solved, the number of AC cables collected is reduced, the efficiency of collecting and transmitting offshore wind power from multiple sites in the deep sea is improved, and the installation difficulty and construction cost of the transmission system are reduced.

[0075] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0076] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0077] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or N executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0078] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above embodiment, the N steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one or a combination of multiple of the following technologies known in the art: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array, a field programmable gate array, etc.

[0079] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0080] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A multi-wind farm offshore wind power collection and transmission system, characterized in that: include: A plurality of high-voltage interconnection transformer modules, at least one offshore flexible DC converter module, a high-voltage AC connection cable and a high-voltage DC transmission cable, wherein: The high-voltage interconnection transformer module is used to collect and boost the offshore wind power of multiple different wind farms whose current distance is greater than a preset distance value to obtain high-voltage alternating current, and connect the high-voltage alternating current to the offshore flexible direct current converter module through the high-voltage alternating current connecting cable; The offshore flexible DC converter module is used to convert the high-voltage AC power collected from the multiple different wind farms into high-voltage DC power, so as to transmit the high-voltage DC power to the onshore converter station through the high-voltage DC transmission cable.

2. The multi-wind farm offshore wind power collection and transmission system according to claim 1 is characterized in that: The high-voltage interconnection transformer module comprises: a first high-voltage interconnection transformer, a first low-voltage AC switch device, a first high-voltage AC switch device, a first low-voltage AC bus, and a first high-voltage AC bus, wherein the first high-voltage interconnection transformer is used to boost the low-voltage AC power at the outlet of each wind farm to obtain the high-voltage AC power; The first low-voltage AC switch device is used to control the connection of each wind farm collection line outlet to the first low-voltage AC bus, and to control the connection and disconnection between the first low-voltage AC bus and the first high-voltage interconnection transformer; The first high-voltage AC switchgear is used to control the high-voltage AC power to be connected to the first high-voltage AC bus, and to control the connection and disconnection between the first high-voltage AC bus and the offshore flexible DC converter module; The first low-voltage AC bus is used to connect multiple offshore wind power collection lines to the first high-voltage interconnection transformer; The first high-voltage AC bus is used to collect high-voltage AC power that has been boosted by at least one high-voltage interconnecting transformer and then connect it to the offshore flexible DC converter module via the high-voltage AC cable.

3. The multi-wind farm offshore wind power collection and transmission system according to claim 2 is characterized in that: The offshore flexible DC converter module includes: a converter valve, a second high-voltage interconnecting transformer, a DC switch device, a second low-voltage AC switch device, a second high-voltage AC switch device, a second low-voltage AC bus, and a second high-voltage AC bus, wherein: The converter valve is used to convert the high-voltage alternating current that has been boosted by the high-voltage interconnecting transformer into the high-voltage direct current; The second high-voltage interconnecting transformer is used to step up the low-voltage alternating current of multiple offshore wind power collection lines in the wind farm to obtain the high-voltage alternating current; The DC switch device is used to control the connection between the high-voltage DC transmission cable and the converter valve; The second low-voltage AC switchgear is used to control the connection of multiple offshore wind power collection lines in the wind farm to the second low-voltage AC busbar, and to control the connection between the second low-voltage AC busbar and the second high-voltage interconnection transformer in the wind farm; The second high-voltage AC switchgear is used to control the high-voltage AC power in the wind farm to be connected to the second high-voltage AC busbar, and to control the connection between the second high-voltage AC busbar in the wind farm and the converter valve; The second low-voltage AC bus is used to collect low-voltage AC power sent by multiple offshore wind power collection lines in the wind farm; The second high-voltage AC bus is used to collect the high-voltage AC power boosted by the first high-voltage interconnecting transformer and the second high-voltage interconnecting transformer.

4. The multi-wind farm offshore wind power collection and transmission system according to claim 3 is characterized in that: When there are multiple wind farms with different capacities, the offshore flexible DC converter station modules are distributed in the center of a larger wind farm among the multiple wind farms, and the multiple high-voltage interconnection transformer modules are distributed in other wind farms at different locations. The low-voltage side of the first high-voltage interconnection transformer in the high-voltage interconnection transformer module is a first preset voltage, and the low-voltage side voltage of the second high-voltage interconnection transformer in the offshore flexible DC converter station module is a second preset voltage. The voltage level of the high-voltage side of the first high-voltage interconnection transformer is the same as the voltage level of the high-voltage side of the second high-voltage interconnection transformer.

5. The multi-wind farm offshore wind power collection and transmission system according to claim 3 is characterized in that: The rated voltage of the first high-voltage interconnecting transformer is calculated based on the wind farm distribution location and the length and electrical parameters of the high-voltage AC cable.

6. The multi-wind farm offshore wind power collection and transmission system according to claim 3 is characterized in that: The high-voltage AC connecting cable between the first high-voltage interconnecting transformer and the offshore flexible DC converter module includes an integrated communication optical cable.

7. A method for collecting and transmitting offshore wind power from multiple wind farms, characterized in that: The multi-wind farm offshore wind power collection and transmission system according to any one of claims 1 to 6 is used, wherein the method comprises the following steps: The offshore wind power of the plurality of different wind farms is collected by the high-voltage interconnection transformer module, and the offshore wind power of the plurality of different wind farms is boosted to obtain the high-voltage alternating current; The high-voltage alternating current is collected by the offshore flexible direct current power exchange station, and the high-voltage alternating current is converted by the converter valve to obtain the high-voltage direct current; The high voltage direct current is transmitted to an onshore converter station via the high voltage direct current transmission cable.

8. The method for collecting and transmitting offshore wind power from multiple wind farms according to claim 7, characterized in that: include: Obtain the current wind farm location, current wind farm capacity and current wind farm operation mode of the high-voltage interconnection transformer module and the offshore flexible DC converter module; According to the current wind farm position, current wind farm capacity and current wind farm operation mode of the high-voltage interconnecting transformer module and the offshore flexible DC converter station module, the technical parameters of different equipment and the control system operation mode of the offshore flexible DC converter module are simulated and calculated.

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