Offshore wind farm transmission connection structure compatible with power frequency and low frequency

Abstract

The application discloses a compatible offshore wind farm power transmission wiring structure of power frequency and low frequency, which comprises an offshore wind farm, an offshore booster station and a land frequency conversion station; the electric energy generated by a plurality of offshore wind turbine generators of the offshore wind farm is sent to a power frequency power grid after being boosted and converted; each offshore wind turbine generator is connected with the offshore booster station through a power collection line; the offshore booster station is connected with the land frequency conversion station through a high-voltage submarine cable; the offshore wind farm is provided with a third power frequency bypass; the offshore booster station is provided with a second power frequency bypass, a first power frequency parallel branch and a second power frequency high resistance; the land frequency conversion station is provided with a first power frequency bypass, a first power frequency high resistance and an SVG; when a frequency conversion valve fails, the electric energy is connected to the power frequency power grid through the first power frequency bypass, the second power frequency bypass, the third power frequency bypass, the first power frequency parallel branch, the first power frequency high resistance, the second power frequency high resistance and the SVG. The application can meet the demand of long-distance and large-capacity power transmission and greatly improve the overall reliability of the system.

Description

Technical Field

[0001] This invention relates to the field of power transmission technology, and in particular to a power transmission connection structure for offshore wind farms that is compatible with both power frequency and low frequency. Background Technology

[0002] Among existing technologies, power frequency AC transmission technology is the most important technology for grid connection of offshore wind farms. Its biggest advantage is that the structure of the power transmission connection type of offshore wind farms is simple and the system reliability is high. However, the capacitive current of the submarine cable will significantly reduce the active power transmission capacity of the cable. Therefore, it is generally used for short-distance and small-capacity power transmission.

[0003] In practical applications, flexible DC transmission schemes are used for long-distance, large-capacity offshore wind power transmission projects. However, converter stations and offshore converter platforms need to be installed at both ends of the DC line. In order to achieve a reliability close to that of conventional AC transmission connection type, a true bipolar system must be adopted, which will result in very high project investment and operation and maintenance costs.

[0004] Low-frequency power transmission technology, as a new type of high-efficiency power transmission technology, can increase the transmission distance of submarine cables by reducing the frequency of AC transmission lines, while eliminating the need to build offshore converter stations and converter platforms. It has technical and economic advantages in medium- and long-distance offshore wind power transmission scenarios.

[0005] However, the reliability of low-frequency power transmission still relies on valve modules composed of IGBTs or IGCTs and their cooling systems. The operation and maintenance work is much greater than that of static equipment, and it is difficult to avoid failures and shutdowns.

[0006] Therefore, how to meet the needs of long-distance, high-capacity power transmission without significantly increasing investment, while also improving the overall reliability of the system to the level of conventional power frequency AC transmission connection types, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of the above-mentioned deficiencies of the prior art, the present invention provides a power transmission connection structure for offshore wind farms that is compatible with both power frequency and low frequency transmission. The purpose of this invention is to be able to take into account both power frequency transmission and low frequency transmission modes, so as to meet the requirements of long-distance and high-capacity power transmission while greatly improving the overall reliability of the system.

[0008] To achieve the above objectives, the present invention discloses a power transmission connection structure for offshore wind farms that is compatible with both power frequency and low frequency, including an offshore wind farm, an offshore booster station, and an onshore frequency converter station; the electrical energy generated by several offshore wind turbines in the offshore wind farm is sequentially transmitted to the power frequency grid after being boosted and converted through the offshore booster station and the onshore frequency converter station.

[0009] Each of the offshore wind turbine units is connected to the offshore substation via a collection line that is compatible with both power frequency and low frequency.

[0010] The offshore booster station is connected to the onshore frequency converter station via a high-voltage submarine cable that is compatible with both the power frequency and low frequency.

[0011] The offshore wind farm is equipped with a third power frequency bypass;

[0012] The offshore booster station is equipped with a second power frequency bypass, a first power frequency parallel branch, and a second power frequency high-voltage reactor;

[0013] The land-based frequency converter station is equipped with a first power frequency bypass, a first power frequency high-resistance circuit, and an SVG.

[0014] When the frequency conversion valve in the onshore frequency conversion station malfunctions, the electrical energy is connected to the power grid through the first power frequency bypass, the second power frequency bypass, the third power frequency bypass, the first power frequency parallel branch, the first power frequency high-voltage reactor, the second power frequency high-voltage reactor, and the SVG.

[0015] Preferably, each of the offshore wind turbine units includes a converter that is compatible with the power frequency and low frequency, a third step-up transformer, a frequency converter for the wind turbine's own power consumption, and a corresponding third power frequency bypass.

[0016] The variable frequency power supply for the wind turbine's self-powered operation is only used at low frequencies.

[0017] More preferably, the rated capacity and size of each of the third step-up transformers, as well as the corresponding transformer leakage flux control, are matched with the power frequency low frequency.

[0018] Preferably, the offshore booster station includes a second booster transformer that is compatible with the power distribution equipment, power frequency and low frequency transformers, and a grounding station transformer that is compatible with power frequency and low frequency transformers;

[0019] The power distribution equipment includes high-voltage power distribution equipment applicable to both power frequency and low frequency, medium-voltage power distribution equipment applicable to both power frequency and low frequency, and low-voltage power distribution equipment for power frequency.

[0020] The power transmission circuit of the high-voltage power distribution device is connected to the second power frequency high-voltage reactor via the first power frequency parallel branch;

[0021] The low-voltage power distribution device is connected in series with a matching frequency converter and the second power frequency bypass on the low-voltage side of the transformer at the grounding station.

[0022] The variable frequency power supply is only used at low frequencies.

[0023] More preferably, the rated short-circuit breaking current of the circuit breaker of the power distribution device, the rated capacity and size of the second step-up transformer, and the corresponding transformer leakage flux control are all matched with the power frequency low frequency.

[0024] More preferably, the wiring configuration of the high-voltage power distribution device corresponds one-to-one with that of the low-frequency high-voltage power distribution device of the onshore frequency converter station;

[0025] The wiring types include line transformer group wiring, internal bridge wiring, single busbar wiring, and single busbar sectional wiring.

[0026] Preferably, the onshore frequency conversion station includes a first step-up transformer that is compatible with the power frequency and low frequency, the SVG, a power frequency station transformer, a first power frequency high-voltage reactor, a power frequency power distribution device, a power frequency valve-side power distribution device, a starting resistor, and a low-frequency high-voltage power distribution device, a low-frequency valve-side power distribution device, a low-frequency step-down transformer, an energy-consuming device, a current-limiting reactor, and a frequency conversion valve that are compatible with the power frequency and low frequency.

[0027] The power frequency distribution equipment includes a power frequency high voltage distribution equipment, a power frequency medium voltage distribution equipment, and a power frequency low voltage distribution equipment;

[0028] The first high-voltage transformer and the SVG are only used when operating at the power frequency.

[0029] The energy-consuming device, the current-limiting reactor, and the frequency-switching valve are only used at low frequencies.

[0030] Preferably, the number of the first power frequency high-voltage reactors corresponds to the number of outgoing circuits of the land-based frequency converter station;

[0031] The number of the second power frequency high-voltage reactor corresponds to the number of outgoing circuits of the offshore substation.

[0032] The beneficial effects of this invention are:

[0033] The application of this invention can take into account both power frequency transmission and low frequency transmission modes, which can greatly improve the overall reliability of the system while meeting the needs of long-distance and large-capacity power transmission.

[0034] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0035] Figure 1 A schematic diagram of an embodiment of the present invention is shown. Detailed Implementation

[0036] Example: Figure 1 As shown, the power transmission connection structure of an offshore wind farm compatible with both power frequency and low frequency includes an offshore wind farm 1, an offshore booster station 2, and an onshore frequency converter station 3. The electrical energy generated by several offshore wind turbine units 4 of the offshore wind farm 1 is transmitted to the power frequency grid after being boosted and converted through the offshore booster station 2 and the onshore frequency converter station 3.

[0037] Each offshore wind turbine 4 is connected to the offshore substation 2 via a collector line 5 that is compatible with both power frequency and low frequency.

[0038] The offshore booster station 2 is connected to the onshore frequency converter station 3 via a high-voltage submarine cable 6 that is compatible with both power frequency and low frequency.

[0039] Offshore wind farm 1 is equipped with a third power frequency bypass 7;

[0040] The offshore booster station 2 is equipped with a second power frequency bypass 8, a first power frequency parallel branch 35, and a second power frequency high-voltage reactor 9;

[0041] Land-based frequency converter station 3 is equipped with a first power frequency bypass 10, a first power frequency high-resistance circuit 11, and an SVG 12;

[0042] When the frequency conversion valve 34 in the onshore frequency conversion station 3 fails, the power is connected to the power frequency grid through the first power frequency bypass 10, the second power frequency bypass 8, the third power frequency bypass 7, the first power frequency parallel branch 35, the first power frequency high-voltage reactor 11, the second power frequency high-voltage reactor 9 and SVG12.

[0043] This invention transmits the electrical energy generated by each offshore wind turbine 4 to an offshore booster station 2 via a power frequency and low frequency common collection line 5. After being boosted by a second booster transformer 16 at the offshore booster station 2, the energy is transmitted to an onshore frequency converter station 3 via a power frequency and low frequency common submarine cable 6. After frequency conversion at the onshore frequency converter station 3, the energy is sent to the power frequency grid. When the frequency conversion equipment fails, all the first power frequency bypass 10, the second power frequency bypass 8, the third power frequency bypass 7, the first power frequency high-voltage reactor 11, the first power frequency parallel branch 35, the second power frequency high-voltage reactor 9, and the SVG 12 are activated and reconnected to the power frequency grid. This achieves both power frequency and low frequency transmission modes, greatly improving the overall reliability of the system while meeting the needs of long-distance, high-capacity power transmission.

[0044] In some embodiments, each offshore wind turbine 4 includes a converter 13 that is compatible with both power frequency and low frequency, a third step-up transformer 14, a frequency converter 15 for the turbine's own power consumption, and a corresponding third power frequency bypass 7.

[0045] The variable frequency power supply 15 used for the wind turbine's own power consumption is only put into use at low frequencies.

[0046] In some embodiments, the rated capacity and size of each third step-up transformer 14, as well as the corresponding transformer leakage flux control, are matched to the low-frequency power frequency.

[0047] Preferably, the offshore booster station 2 includes a second booster transformer 16 that is compatible with power distribution equipment and power frequency and low frequency transformers, and a grounding station transformer 17 that is compatible with power frequency and low frequency transformers;

[0048] The power distribution equipment includes a high-voltage power distribution device 18 that is used for both power frequency and low frequency, a medium-voltage power distribution device 19 that is used for both power frequency and low frequency, and a low-voltage power distribution device 20 used for power frequency.

[0049] The output circuit of the high-voltage power distribution device 18 is connected to the second high-frequency high-resistance device 9 via the first power frequency parallel branch 35;

[0050] The low-voltage power distribution device 20 is connected in series with a matching frequency converter 21 and a second power frequency bypass 8 on the low-voltage side of the grounding station transformer 17;

[0051] The frequency converter 21 is only used at low frequencies.

[0052] More preferably, the rated short-circuit breaking current of the circuit breaker of the power distribution device, the rated capacity and size of the second step-up transformer 16, and the corresponding transformer leakage flux control are all matched with the power frequency and low frequency.

[0053] More preferably, the wiring configurations of the high-voltage power distribution device 18 and the low-frequency high-voltage power distribution device 29 of the onshore frequency converter station 3 correspond one-to-one.

[0054] The wiring types include line transformer group wiring, internal bridge wiring, single busbar wiring, and single busbar sectional wiring.

[0055] Preferably, the onshore frequency conversion station 3 includes a first step-up transformer 22, SVG 12, a power frequency station transformer 23, a first power frequency high-voltage reactor 11, a power frequency power distribution device, a power frequency valve-side power distribution device 27, a starting resistor 28, and a low-frequency high-voltage power distribution device 29, a low-frequency valve-side power distribution device 30, a low-frequency step-down transformer 31, an energy-consuming device 32, a current-limiting reactor 33, and a frequency conversion valve 34 that are matched with the power frequency and low frequency.

[0056] The power frequency distribution equipment includes a power frequency high voltage distribution device 26, a power frequency medium voltage distribution device 25, and a power frequency low voltage distribution device 24;

[0057] The first high-frequency anti-tank 11 and SVG12 are only used when operating at the power frequency.

[0058] The energy-consuming device 32, the current-limiting reactor 33, and the frequency switching valve 34 are only used at low frequencies.

[0059] Preferably, the number of the first power frequency high-impact reactor 11 corresponds to the number of outgoing circuits of the land-based frequency converter station 3;

[0060] The number of the second high-frequency high-resistance reactor 9 corresponds to the number of outgoing circuits of the offshore substation 2.

[0061] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A power transmission connection structure compatible with power frequency and low frequency for offshore wind farm, comprising an offshore wind farm (1), an offshore booster station (2) and a land frequency conversion station (3); the electric energy generated by a plurality of offshore wind turbines (4) of the offshore wind farm (1) is transmitted through the offshore booster station (2) and the land frequency conversion station (3) in turn, and is sent to the power frequency power grid after being boosted and converted in frequency; characterized in that: each of the offshore wind turbines (4) is connected to the offshore booster station (2) through a power collection line (5); the power collection line (5) is compatible with power frequency and low frequency; the offshore booster station (2) is connected to the land frequency conversion station (3) through a high-voltage submarine cable (6); the high-voltage submarine cable (6) is compatible with power frequency and low frequency; the offshore wind farm (1) is provided with a third power frequency bypass (7); the offshore booster station (2) is provided with a second power frequency bypass (8), a first power frequency parallel branch (35) and a second power frequency high resistance (9); the land frequency conversion station (3) is provided with a first power frequency bypass (10), a first power frequency high resistance (11) and an SVG (12); when the frequency conversion valve (34) in the land frequency conversion station (3) fails, the electric energy is connected to the power frequency power grid through the first power frequency bypass (10), the second power frequency bypass (8), the third power frequency bypass (7), the first power frequency parallel branch (35), the first power frequency high resistance (11), the second power frequency high resistance (9) and the SVG (12); the frequency conversion power supply (15) for fan self-use power is only used in low frequency; the frequency conversion power supply (21) is only used in low frequency. Each of the offshore wind turbines (4) comprises a converter (13), a third step-up transformer (14), a frequency conversion power supply (15) for fan self-use power and a corresponding third power frequency bypass (7); the converter (13) is compatible with power frequency and low frequency. The rated capacity and size of each third step-up transformer (14) and the corresponding transformer leakage magnetic control are matched with power frequency and low frequency. The offshore booster station (2) comprises a second step-up transformer (16) and a grounding station transformer (17); the second step-up transformer (16) and the power distribution device are compatible with power frequency and low frequency; the grounding station transformer (17) is compatible with power frequency and low frequency; The power distribution device comprises a high-voltage power distribution device (18), a medium-voltage power distribution device (19) and a low-voltage power distribution device (20); the high-voltage power distribution device (18) is compatible with power frequency and low frequency; the medium-voltage power distribution device (19) is compatible with power frequency and low frequency; the low-voltage power distribution device (20) is used for power frequency; The outgoing circuit of the high-voltage power distribution device (18) is connected to the second power frequency high resistance (9) through the first power frequency parallel branch (35); The low-voltage power distribution device (20) is connected in series with a matched frequency conversion power supply (21) and the second power frequency bypass (8) on the low-voltage side of the grounding station transformer (17). The rated breaking short-circuit current of the circuit breaker of the power distribution device, the rated capacity and size of the second step-up transformer (16) and the corresponding transformer leakage magnetic control are matched with power frequency and low frequency. ​ 2. A marine wind farm power transmission arrangement compatible with power frequencies and low frequencies according to claim 1, characterized in that, ​ 3. A marine wind farm power transmission arrangement compatible with both power frequencies according to claim 2, characterized in that, ​ 4. A marine wind farm power transmission arrangement compatible with power frequencies and low frequencies according to claim 1, characterized in that, ​ ​ ​ ​ 5. A marine wind farm power transmission arrangement compatible with power frequencies and low frequencies according to claim 4, characterized in that, ​ 6. A marine wind farm power transmission arrangement compatible with power frequencies and low frequencies according to claim 4, characterized in that, The high-voltage power distribution device (18) corresponds to the wiring type of the low-frequency high-voltage power distribution device (29) of the land frequency conversion station (3) one by one. The wiring type includes line variable group wiring, inner bridge wiring, single bus wiring and single bus segment wiring.

7. A power transmission arrangement for an offshore wind farm according to claim 1, c h a r a c t e r i z e d i n that The land frequency conversion station (3) includes a first step-up transformer (22), the SVG (12), a power frequency station transformer (23), the first power frequency high resistance (11), a power frequency power distribution device, a power frequency valve side power distribution device (27), a starting resistance (28), a low-frequency high-voltage power distribution device (29), a low-frequency valve side power distribution device (30), a low-frequency step-down transformer (31), an energy consumption device (32), a current limiting reactor (33) and a frequency conversion valve (34); the first step-up transformer (22) is common to the power frequency low frequency; the low-frequency high-voltage power distribution device (29) matches the power frequency low frequency; The power frequency power distribution device includes a power frequency high-voltage power distribution device (26), a power frequency medium-voltage power distribution device (25) and a power frequency low-voltage power distribution device (24); The first power frequency high resistance (11) and the SVG (12) are only used when the power frequency is running; The energy consumption device (32), the current limiting reactor (33) and the frequency conversion valve (34) are only used at low frequency.

8. A marine wind farm power transmission arrangement compatible with power frequencies and low frequencies according to claim 1, characterized in that, The number of the first power frequency high resistance (11) corresponds to the number of loops of the outgoing line of the land frequency conversion station (3); The number of the second power frequency high resistance (9) corresponds to the number of loops of the outgoing line of the offshore booster station (2).

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