Offshore wind power black start method, device and equipment based on diode rectifier

Abstract

The invention discloses a method, device and equipment for black start of offshore wind power based on diode rectifiers, based on an offshore wind power DC transmission system including a first offshore wind farm, a second offshore wind farm, four first inverters, two second inverters, back-to-back AC / DC / AC modules, a first diode rectifier, a second diode rectifier, an onshore converter valve, an onshore transformer and an onshore power grid, and configures corresponding first switches, second switches, third switches, fourth switches, fifth switches, sixth switches and seventh switches, and adopts a small-capacity inverter in combination with a certain switching sequence to achieve black start at the sending end and power balance. The method solves the technical problems that the existing offshore wind power black start method based on diode rectifiers has high construction investment costs for offshore wind turbines and reduces the technical advantages of the diode solution of small volume and low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of offshore wind power, and in particular to an offshore wind power black start method, device and equipment based on a diode rectifier. Background Art

[0002] At present, offshore wind power mainly adopts the transmission mode of nearshore-AC and offshore-DC, and the capacity of a single project is about one million kilowatts. With the exhaustion of offshore wind power development, deep-sea offshore wind power has become the focus of future offshore wind power development. The AC transmission scheme cannot meet the needs of large-scale deep-sea offshore wind power development, and the traditional DC transmission scheme is costly and difficult to meet the needs of large-scale offshore wind power economic development. It is necessary to explore low-cost new transmission schemes to provide new technical options for deep-sea offshore wind power development. Large-scale offshore wind power has AC transmission and multiple DC transmission conversion schemes. At present, the mainstream DC transmission scheme in practical applications is the flexible DC transmission technology based on MMC topology, but its platform is large in size and weight, and the cost is high, so the large-scale offshore wind power transmission scheme needs to be further optimized. In order to adapt to various application scenarios and reduce the cost of transmission projects, a variety of transmission schemes with their own characteristics have been proposed at home and abroad, including the use of unidirectional current-type uncontrolled rectifier converters based on diode elements at the sending end, DC wind turbines aggregate boost transmission, low-frequency transmission and other transmission schemes.

[0003] The use of a unidirectional current-type uncontrolled rectifier converter based on diode elements at the sending end helps to achieve lightweight offshore platforms, but the existing solutions still have shortcomings. The black start problem is the most difficult problem to solve in the existing diode solutions. At present, it is necessary to set up a special onshore power supply to access the offshore converter platform, and the solution of on-site diesel generators is usually adopted, but this solution requires the installation of many diesel generators, and the construction investment for offshore wind turbines is relatively high. There are also proposals to use hybrid converters such as VSC converters in series and parallel to assist in starting, but this solution uses a certain proportion of VSC structure, which reduces the technical advantages of the diode solution in small size and low cost. Therefore, with regard to the problem of black start of offshore wind power based on diode rectifiers, how to reduce the construction investment cost of offshore wind turbines and maintain the technical advantages of the diode solution in small size and low cost is a technical problem that needs to be solved urgently by technical personnel in this field. Summary of the invention

[0004] The present invention provides a method, device and equipment for offshore wind power black start based on a diode rectifier, which is used to solve the technical problems that the existing offshore wind power black start method based on a diode rectifier has high construction investment cost for offshore wind turbines and reduces the technical advantages of the diode solution of small volume and low cost.

[0005] In view of this, a first aspect of the present invention provides an offshore wind power black start method based on a diode rectifier, which is applied to an offshore wind power DC transmission system, wherein the offshore wind power DC transmission system comprises: a first offshore wind farm, a second offshore wind farm, four first inverters, two second inverters, a back-to-back AC / DC / AC module, a first diode rectifier, a second diode rectifier, an onshore converter valve, an onshore transformer and an onshore power grid;

[0006] The first offshore wind farm is respectively connected to two first inverters and one second inverter through a first busbar, one first inverter connected to the first busbar is connected to one end of a first diode rectifier, the other end of the first diode rectifier is connected to the second inverter connected to the first busbar, another first inverter connected to the first busbar is connected to one end of a back-to-back AC / DC / AC module, and two AC / DC modules of the back-to-back AC / DC / AC module are connected through a first switch;

[0007] The second offshore wind farm is respectively connected to two first inverters and one second inverter through the second busbar, one first inverter connected to the second busbar is connected to one end of the second diode rectifier, the other end of the second diode rectifier is connected to the second inverter connected to the second busbar, and the other first inverter connected to the second busbar is connected to the other end of the back-to-back AC / DC / AC module;

[0008] The positive terminal of the first diode rectifier is connected to one end of the first switch connecting the two AC / DC modules through a second switch, the negative terminal of the second diode rectifier is connected to the other end of the first switch connecting the two AC / DC modules through another second switch, the positive terminal of the first diode rectifier is connected to the negative terminal of the second diode rectifier through another first switch, the positive terminal of the first diode rectifier is connected to the input end of the first DC line through a third switch, the output end of the first DC line is connected to the input end of the onshore converter valve, the negative terminal of the second diode rectifier is connected to the input end of the second DC line through another third switch, the output end of the second DC line is connected to the input end of the onshore converter valve, the negative terminal of the first diode rectifier is connected to the input end of the first DC line through a fifth switch, the positive terminal of the second diode rectifier is connected to the input end of the second DC line through another fifth switch, one output end of the onshore converter valve is connected to the low voltage winding of the onshore transformer through a sixth switch, the other output end of the onshore converter valve is connected to the high voltage winding of the onshore transformer through a seventh switch, and the output end of the onshore transformer is connected to the onshore power grid;

[0009] The capacity of the onshore converter valve is at least 20% of the total capacity of the first diode rectifier and the second diode rectifier;

[0010] The offshore wind power black start method based on diode rectifier includes the following steps:

[0011] T1, control all the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch and the seventh switch to be in an open state;

[0012] T2, close all the second switches and the third switches, and then close the sixth switch, so that voltage is established between the first DC line and the second DC line;

[0013] T3. After the voltage is established on the first DC line and the second DC line, the voltage is established on the DC side of the back-to-back AC / DC / AC module, and the rated AC voltage is established on the first bus and the second bus;

[0014] T4. One of the first offshore wind farm and the second offshore wind farm unlocks a wind turbine. After the unlocked wind turbine outputs stable power, the other of the first offshore wind farm and the second offshore wind farm unlocks a wind turbine. This process is repeated to unlock the wind turbines in the first offshore wind farm and the second offshore wind farm, respectively. The total capacity of the unlocked wind turbines is lower than the total capacity of the back-to-back AC / DC / AC modules.

[0015] T5, turn on all third switches and close all fifth switches at the same time, and after the entire system runs stably, the first offshore wind farm and the second offshore wind farm supply low voltage power to the onshore power grid through the back-to-back AC / DC / AC module and the first diode rectifier and the second diode rectifier;

[0016] T6, turn on the sixth switch, and close the seventh switch and all the fourth switches at the same time, the first diode rectifier and the second diode rectifier normally establish voltage and transmit power, and the DC side output voltage is controlled to be 0 through the back-to-back AC / DC / AC module;

[0017] T7. Close all the first switches, remove the back-to-back AC / DC / AC modules, and complete the black start.

[0018] Optionally, the first diode rectifier and the second diode rectifier are diode commutation valves with a six-pulse full-bridge structure.

[0019] Optionally, the first inverter is a YY-type transformer, and the second inverter is a YD-type transformer.

[0020] Optionally, in step T2, after the voltages of the first DC line and the second DC line are established, the low voltage winding voltage of the onshore transformer and the DC side voltage of the back-to-back AC / DC / AC module follow preset constraints, which are:

[0021]

[0022] Where m is the modulation ratio, U dc is the DC side voltage of the back-to-back AC / DC / AC module, U ac It is the low voltage winding voltage of the onshore transformer.

[0023] Optionally, in step T6, the time interval error between opening the sixth switch and closing the seventh switch does not exceed 60 ms.

[0024] A second aspect of the present invention provides an offshore wind power black start device based on a diode rectifier, which is applied to an offshore wind power DC transmission system, wherein the offshore wind power DC transmission system comprises: a first offshore wind farm, a second offshore wind farm, four first inverters, two second inverters, a back-to-back AC / DC / AC module, a first diode rectifier, a second diode rectifier, an onshore converter valve, an onshore transformer and an onshore power grid;

[0025] The first offshore wind farm is respectively connected to two first inverters and one second inverter through a first busbar, one first inverter connected to the first busbar is connected to one end of a first diode rectifier, the other end of the first diode rectifier is connected to the second inverter connected to the first busbar, another first inverter connected to the first busbar is connected to one end of a back-to-back AC / DC / AC module, and two AC / DC modules of the back-to-back AC / DC / AC module are connected through a first switch;

[0026] The second offshore wind farm is respectively connected to two first inverters and one second inverter through the second busbar, one first inverter connected to the second busbar is connected to one end of the second diode rectifier, the other end of the second diode rectifier is connected to the second inverter connected to the second busbar, and the other first inverter connected to the second busbar is connected to the other end of the back-to-back AC / DC / AC module;

[0027] The positive terminal of the first diode rectifier is connected to one end of the first switch connecting the two AC / DC modules through a second switch, the negative terminal of the second diode rectifier is connected to the other end of the first switch connecting the two AC / DC modules through another second switch, the positive terminal of the first diode rectifier is connected to the negative terminal of the second diode rectifier through another first switch, the positive terminal of the first diode rectifier is connected to the input end of the first DC line through a third switch, the output end of the first DC line is connected to the input end of the onshore converter valve, the negative terminal of the second diode rectifier is connected to the input end of the second DC line through another third switch, the output end of the second DC line is connected to the input end of the onshore converter valve, the negative terminal of the first diode rectifier is connected to the input end of the first DC line through a fifth switch, the positive terminal of the second diode rectifier is connected to the input end of the second DC line through another fifth switch, one output end of the onshore converter valve is connected to the low voltage winding of the onshore transformer through a sixth switch, the other output end of the onshore converter valve is connected to the high voltage winding of the onshore transformer through a seventh switch, and the output end of the onshore transformer is connected to the onshore power grid;

[0028] The capacity of the onshore converter valve is at least 20% of the total capacity of the first diode rectifier and the second diode rectifier;

[0029] The offshore wind power black start device based on diode rectifier is used to perform the following steps:

[0030] T1, control all the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch and the seventh switch to be in an open state;

[0031] T2, close all the second switches and the third switches, and then close the sixth switch, so that voltage is established between the first DC line and the second DC line;

[0032] T3. After the voltage is established on the first DC line and the second DC line, the voltage is established on the DC side of the back-to-back AC / DC / AC module, and the rated AC voltage is established on the first bus and the second bus;

[0033] T4. One of the first offshore wind farm and the second offshore wind farm unlocks a wind turbine. After the unlocked wind turbine outputs stable power, the other of the first offshore wind farm and the second offshore wind farm unlocks a wind turbine. This process is repeated to unlock the wind turbines in the first offshore wind farm and the second offshore wind farm, respectively. The total capacity of the unlocked wind turbines is lower than the total capacity of the back-to-back AC / DC / AC modules.

[0034] T5, turn on all third switches and close all fifth switches at the same time, and after the entire system runs stably, the first offshore wind farm and the second offshore wind farm supply low voltage power to the onshore power grid through the back-to-back AC / DC / AC module and the first diode rectifier and the second diode rectifier;

[0035] T6, turn on the sixth switch, and close the seventh switch and all the fourth switches at the same time, the first diode rectifier and the second diode rectifier normally establish voltage and transmit power, and the DC side output voltage is controlled to be 0 through the back-to-back AC / DC / AC module;

[0036] T7. Close all the first switches, remove the back-to-back AC / DC / AC modules, and complete the black start.

[0037] Optionally, the first diode rectifier and the second diode rectifier are diode commutation valves with a six-pulse full-bridge structure, the first inverter is a YY-type transformer, and the second inverter is a YD-type transformer.

[0038] Optionally, in step T2, after the voltages of the first DC line and the second DC line are established, the low voltage winding voltage of the onshore transformer and the DC side voltage of the back-to-back AC / DC / AC module follow preset constraints, which are:

[0039]

[0040] Where m is the modulation ratio, U dc is the DC side voltage of the back-to-back AC / DC / AC module, U ac It is the low voltage winding voltage of the onshore transformer.

[0041] Optionally, in step T6, the time interval error between opening the sixth switch and closing the seventh switch does not exceed 60 ms.

[0042] A third aspect of the present invention provides an offshore wind power black start device based on a diode rectifier, the device comprising a processor and a memory:

[0043] The memory is used to store program code and transmit the program code to the processor;

[0044] The processor is used to execute the offshore wind power black start method based on a diode rectifier as described in any one of the first aspects according to the instructions in the program code.

[0045] A fourth aspect of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium is used to store program code, and the program code is used to execute the offshore wind power black start method based on a diode rectifier as described in any one of the first aspects.

[0046] It can be seen from the above technical solutions that the offshore wind power black start method based on diode rectifier provided by the present invention has the following advantages:

[0047] The offshore wind power black start method based on a diode rectifier provided by the present invention is based on an offshore wind power DC transmission system comprising a first offshore wind farm, a second offshore wind farm, four first inverters, two second inverters, a back-to-back AC / DC / AC module, a first diode rectifier, a second diode rectifier, an onshore converter valve, an onshore transformer and an onshore power grid, and is configured with corresponding first switches, second switches, third switches, fourth switches, fifth switches, sixth switches and seventh switches. A small-capacity inverter is used in conjunction with a certain switching sequence to achieve a sending-end black start and power balance, thereby maintaining the technical advantages of a diode solution in terms of low cost and small size, without relying on a diesel generator, and reducing the construction investment cost. The technical problems of the existing offshore wind power black start method based on a diode rectifier, namely, high construction investment cost of offshore wind turbines and reduced technical advantages of a diode solution in terms of small size and low cost, are solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0049] Figure 1 A schematic flow chart of a method for black start of offshore wind power based on a diode rectifier provided in an embodiment of the present invention;

[0050] Figure 2 This is a topological wiring diagram of an offshore wind power direct current transmission system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] For easier understanding, see Figure 1 and Figure 2The present invention provides an embodiment of an offshore wind power black start method based on a diode rectifier, the method is applied to an offshore wind power DC transmission system, the offshore wind power DC transmission system comprising: a first offshore wind farm F1, a second offshore wind farm F2, four first inverters TB1, two second inverters TB2, a back-to-back AC / DC / AC module, a first diode rectifier V1, a second diode rectifier V2, an onshore converter valve G, an onshore transformer T and an onshore power grid;

[0053] The first offshore wind farm F1 is connected to two first inverters TB1 and one second inverter TB2 through a first bus A, one first inverter TB1 connected to the first bus A is connected to one end of a first diode rectifier V1, the other end of the first diode rectifier V1 is connected to the second inverter TB2 connected to the first bus A, another first inverter TB1 connected to the first bus A is connected to one end of a back-to-back AC / DC / AC module, and two AC / DC modules of the back-to-back AC / DC / AC module are connected through a first switch S1;

[0054] The second offshore wind farm F2 is respectively connected to two first inverters TB1 and one second inverter TB2 through the second busbar B, one first inverter TB1 connected to the second busbar B is connected to one end of the second diode rectifier V2, the other end of the second diode rectifier V2 is connected to the second inverter TB2 connected to the second busbar B, and another first inverter TB1 connected to the second busbar B is connected to the other end of the back-to-back AC / DC / AC module;

[0055] The first inverter TB1 may adopt a YY-type transformer, and the second inverter TB2 may adopt a YD-type transformer.

[0056] The positive terminal of the first diode rectifier V1 is connected to one end of the first switch S1 connecting the two AC / DC modules through a second switch S2, the negative terminal of the second diode rectifier V2 is connected to the other end of the first switch connecting the two AC / DC modules through another second switch S2, the positive terminal of the first diode rectifier V1 is connected to the negative terminal of the second diode rectifier V2 through another first switch S1, the positive terminal of the first diode rectifier V1 is connected to the input end of the first DC line L1 through a third switch S3, the output end of the first DC line L1 is connected to the input end of the onshore converter valve G, and the negative terminal of the second diode rectifier V2 is connected to the onshore converter valve G through a third switch S3. Another third switch S3 is connected to the input end of the second DC line L2, the output end of the second DC line L2 is connected to the input end of the onshore converter valve G, the negative terminal of the first diode rectifier V1 is connected to the input end of the first DC line L1 through a fifth switch S5, the positive terminal of the second diode rectifier V2 is connected to the input end of the second DC line L2 through another fifth switch S5, one output end of the onshore converter valve G is connected to the low-voltage winding of the onshore transformer T through a sixth switch S6, the other output end of the onshore converter valve G is connected to the high-voltage winding of the onshore transformer T through a seventh switch S7, and the output end of the onshore transformer T is connected to the onshore power grid;

[0057] The first diode rectifier V1 and the second diode rectifier V2 are diode commutation valves with a six-pulse full-bridge structure.

[0058] The capacity of the onshore converter valve G is at least 20% of the total capacity of the first diode rectifier V1 and the second diode rectifier V2;

[0059] The offshore wind power black start method based on diode rectifier includes the following steps:

[0060] Step T1, control all the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6 and the seventh switch S7 to be in an open state.

[0061] Step T2, close all the second switches S2 and the third switches S3, and then close the sixth switch S6, and the voltage is established between the first DC line L1 and the second DC line L2. At this time, the low-voltage winding is used, so the voltage of the first DC line L1 and the second DC line L2 does not reach the rated voltage, and the low-voltage winding voltage of the onshore transformer G and the DC side voltage of the back-to-back AC / DC / AC module must comply with the preset constraints, which are:

[0062]

[0063] Where m is the modulation ratio, U dc is the DC side voltage of the back-to-back AC / DC / AC module, Uac It is the low voltage winding voltage of the onshore transformer.

[0064] Step T3: After the voltage is established on the first DC line L1 and the second DC line L2, the voltage is established on the DC side of the back-to-back AC / DC / AC module, and the first bus A and the second bus B establish the rated AC voltage.

[0065] Step T4, one of the first offshore wind farm F1 and the second offshore wind farm F2 unlocks a wind turbine, and after the unlocked wind turbine outputs stable power, the other offshore wind farm in the first offshore wind farm F1 and the second offshore wind farm F2 unlocks a wind turbine, and this is performed back and forth to unlock the wind turbines in the first offshore wind farm F1 and the second offshore wind farm F2, respectively, wherein the total capacity of the unlocked wind turbines is lower than the total capacity of the back-to-back AC / DC / AC modules. After the first offshore wind farm F1 and the second offshore wind farm F2 are in stable operation, low-voltage power supply is realized to the onshore side through AC / DC / AC.

[0066] Step T5, open all third switches S3, and close all fifth switches S5 at the same time. After the entire system runs stably, the first offshore wind farm F1 and the second offshore wind farm F2 provide low voltage power supply to the onshore power grid through the back-to-back AC / DC / AC module and the first diode rectifier V1 and the second diode rectifier V2.

[0067] Step T6, open the sixth switch S6, and close the seventh switch S7 and all the fourth switches S4 at the same time when the sixth switch S6 is opened. The first diode rectifier V1 and the second diode rectifier V2 establish voltage and power transmission normally, and the DC side output voltage is controlled to be 0 through the back-to-back AC / DC / AC module. In the process of opening the sixth switch S6 and closing the seventh switch S7, a short-term power imbalance occurs in the sending end system. When the short-term power imbalance causes an overvoltage in the sending end system, the crowbar resistor of the wind turbine needs to be put into use to absorb the energy sent by the sending end, but the time interval between opening and closing the two switches should be completed within 60ms. When the seventh switch S7 is closed, the fourth switch D4 is closed, and the first diode rectifier V1 and the second diode rectifier V2 establish voltage and power transmission normally. According to the natural voltage division of the onshore converter valve G and the back-to-back AC / DC / AC module, the back-to-back AC / DC / AC module is adjusted at the same time so that the DC side output voltage of the onshore back-to-back AC / DC / AC module is 0.

[0068] Step T7: Close all first switches S1 to cut off the back-to-back AC / DC / AC modules to complete the black start.

[0069] The offshore wind power black start method based on a diode rectifier provided by the present invention is based on an offshore wind power DC transmission system comprising a first offshore wind farm, a second offshore wind farm, four first inverters, two second inverters, a back-to-back AC / DC / AC module, a first diode rectifier, a second diode rectifier, an onshore converter valve, an onshore transformer and an onshore power grid, and is configured with corresponding first switches, second switches, third switches, fourth switches, fifth switches, sixth switches and seventh switches. A small-capacity inverter is used in conjunction with a certain switching sequence to achieve a sending-end black start and power balance, thereby maintaining the technical advantages of a diode solution in terms of low cost and small size, without relying on a diesel generator, and reducing the construction investment cost. The technical problems of the existing offshore wind power black start method based on a diode rectifier, namely, high construction investment cost of offshore wind turbines and reduced technical advantages of a diode solution in terms of small size and low cost, are solved.

[0070] The present invention provides an embodiment of an offshore wind power black start device based on a diode rectifier, and the device is applied to an offshore wind power DC transmission system, and the offshore wind power DC transmission system comprises: a first offshore wind farm F1, a second offshore wind farm F2, four first inverters TB1, two second inverters TB2, a back-to-back AC / DC / AC module, a first diode rectifier V1, a second diode rectifier V2, an onshore converter valve G, an onshore transformer T and an onshore power grid;

[0071] The first offshore wind farm F1 is connected to two first inverters TB1 and one second inverter TB2 through a first bus A, one first inverter TB1 connected to the first bus A is connected to one end of a first diode rectifier V1, the other end of the first diode rectifier V1 is connected to the second inverter TB2 connected to the first bus A, another first inverter TB1 connected to the first bus A is connected to one end of a back-to-back AC / DC / AC module, and two AC / DC modules of the back-to-back AC / DC / AC module are connected through a first switch S1;

[0072] The second offshore wind farm F2 is respectively connected to two first inverters TB1 and one second inverter TB2 through the second busbar B, one first inverter TB1 connected to the second busbar B is connected to one end of the second diode rectifier V2, the other end of the second diode rectifier V2 is connected to the second inverter TB2 connected to the second busbar B, and another first inverter TB1 connected to the second busbar B is connected to the other end of the back-to-back AC / DC / AC module;

[0073] The first inverter TB1 may adopt a YY-type transformer, and the second inverter TB2 may adopt a YD-type transformer.

[0074] The positive terminal of the first diode rectifier V1 is connected to one end of the first switch S1 connecting the two AC / DC modules through a second switch S2, the negative terminal of the second diode rectifier V2 is connected to the other end of the first switch connecting the two AC / DC modules through another second switch S2, the positive terminal of the first diode rectifier V1 is connected to the negative terminal of the second diode rectifier V2 through another first switch S1, the positive terminal of the first diode rectifier V1 is connected to the input end of the first DC line L1 through a third switch S3, the output end of the first DC line L1 is connected to the input end of the onshore converter valve G, and the negative terminal of the second diode rectifier V2 is connected to the onshore converter valve G through a third switch S3. Another third switch S3 is connected to the input end of the second DC line L2, the output end of the second DC line L2 is connected to the input end of the onshore converter valve G, the negative terminal of the first diode rectifier V1 is connected to the input end of the first DC line L1 through a fifth switch S5, the positive terminal of the second diode rectifier V2 is connected to the input end of the second DC line L2 through another fifth switch S5, one output end of the onshore converter valve G is connected to the low-voltage winding of the onshore transformer T through a sixth switch S6, the other output end of the onshore converter valve G is connected to the high-voltage winding of the onshore transformer T through a seventh switch S7, and the output end of the onshore transformer T is connected to the onshore power grid;

[0075] The first diode rectifier V1 and the second diode rectifier V2 are diode commutation valves with a six-pulse full-bridge structure.

[0076] The capacity of the onshore converter valve G is at least 20% of the total capacity of the first diode rectifier V1 and the second diode rectifier V2;

[0077] The offshore wind power black start device based on diode rectifier is used to perform the following steps:

[0078] Step T1, control all the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6 and the seventh switch S7 to be in an open state.

[0079] Step T2, close all the second switches S2 and the third switches S3, and then close the sixth switch S6, and the voltage is established between the first DC line L1 and the second DC line L2. At this time, the low-voltage winding is used, so the voltage of the first DC line L1 and the second DC line L2 does not reach the rated voltage, and the low-voltage winding voltage of the onshore transformer G and the DC side voltage of the back-to-back AC / DC / AC module must comply with the preset constraints, which are:

[0080]

[0081] Where m is the modulation ratio, U dc is the DC side voltage of the back-to-back AC / DC / AC module, Uac It is the low voltage winding voltage of the onshore transformer.

[0082] Step T3: After the voltage is established on the first DC line L1 and the second DC line L2, the voltage is established on the DC side of the back-to-back AC / DC / AC module, and the first bus A and the second bus B establish the rated AC voltage.

[0083] Step T4, one of the first offshore wind farm F1 and the second offshore wind farm F2 unlocks a wind turbine, and after the unlocked wind turbine outputs stable power, the other offshore wind farm in the first offshore wind farm F1 and the second offshore wind farm F2 unlocks a wind turbine, and this is performed back and forth to unlock the wind turbines in the first offshore wind farm F1 and the second offshore wind farm F2, respectively, wherein the total capacity of the unlocked wind turbines is lower than the total capacity of the back-to-back AC / DC / AC modules. After the first offshore wind farm F1 and the second offshore wind farm F2 are in stable operation, low-voltage power supply is realized to the onshore side through AC / DC / AC.

[0084] Step T5, open all third switches S3, and close all fifth switches S5 at the same time. After the entire system runs stably, the first offshore wind farm F1 and the second offshore wind farm F2 provide low voltage power supply to the onshore power grid through the back-to-back AC / DC / AC module and the first diode rectifier V1 and the second diode rectifier V2.

[0085] Step T6, open the sixth switch S6, and close the seventh switch S7 and all the fourth switches S4 at the same time when the sixth switch S6 is opened. The first diode rectifier V1 and the second diode rectifier V2 establish voltage and power transmission normally, and the DC side output voltage is controlled to be 0 through the back-to-back AC / DC / AC module. In the process of opening the sixth switch S6 and closing the seventh switch S7, a short-term power imbalance occurs in the sending end system. When the short-term power imbalance causes an overvoltage in the sending end system, the crowbar resistor of the wind turbine needs to be put into use to absorb the energy sent by the sending end, but the time interval between opening and closing the two switches should be completed within 60ms. When the seventh switch S7 is closed, the fourth switch D4 is closed, and the first diode rectifier V1 and the second diode rectifier V2 establish voltage and power transmission normally. According to the natural voltage division of the onshore converter valve G and the back-to-back AC / DC / AC module, the back-to-back AC / DC / AC module is adjusted at the same time so that the DC side output voltage of the onshore back-to-back AC / DC / AC module is 0.

[0086] Step T7: Close all first switches S1 to cut off the back-to-back AC / DC / AC modules to complete the black start.

[0087] The present invention also provides an embodiment of an offshore wind power black start device based on a diode rectifier, the device comprising a processor and a memory:

[0088] The memory is used to store program code and transmit the program code to the processor;

[0089] The processor is used to execute the offshore wind power black start method based on a diode rectifier in the present invention according to the instructions in the program code.

[0090] The present invention also provides a computer-readable storage medium, which is used to store program codes, and the program codes are used to execute the offshore wind power black start method based on a diode rectifier in the present invention.

[0091] The offshore wind power black start device, equipment and computer-readable storage medium based on diode rectifier provided in the present invention are used to execute the offshore wind power black start method based on diode rectifier provided in the present invention. The principle and technical effects achieved are the same as those of the offshore wind power black start based on diode rectifier provided in the present invention, and will not be repeated here.

[0092] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An offshore wind power black start device based on a diode rectifier, characterized in that: Applied to an offshore wind power DC transmission system, the offshore wind power DC transmission system includes an offshore wind power black start device and an onshore power grid, the offshore wind power black start device includes a first offshore wind farm, a second offshore wind farm, four first inverters, two second inverters, a back-to-back AC / DC / AC module, a first diode rectifier, a second diode rectifier, an onshore converter valve and an onshore transformer; The first offshore wind farm is respectively connected to two first inverters and one second inverter through a first busbar, one first inverter connected to the first busbar is connected to one end of a first diode rectifier, the other end of the first diode rectifier is connected to the second inverter connected to the first busbar, another first inverter connected to the first busbar is connected to one end of a back-to-back AC / DC / AC module, and two AC / DC modules of the back-to-back AC / DC / AC module are connected through a first switch; The second offshore wind farm is respectively connected to two first inverters and one second inverter through the second busbar, one first inverter connected to the second busbar is connected to one end of the second diode rectifier, the other end of the second diode rectifier is connected to the second inverter connected to the second busbar, and the other first inverter connected to the second busbar is connected to the other end of the back-to-back AC / DC / AC module; The positive terminal of the first diode rectifier is connected to one end of the first switch connecting the two AC / DC modules through a second switch, the negative terminal of the second diode rectifier is connected to the other end of the first switch connecting the two AC / DC modules through another second switch, the positive terminal of the first diode rectifier is connected to the negative terminal of the second diode rectifier through another first switch, the positive terminal of the first diode rectifier is connected to the input end of the first DC line through a third switch, the output end of the first DC line is connected to the input end of the onshore converter valve, the negative terminal of the second diode rectifier is connected to the input end of the second DC line through another third switch, the output end of the second DC line is connected to the input end of the onshore converter valve, the negative terminal of the first diode rectifier is connected to the input end of the first DC line through a fifth switch, the positive terminal of the second diode rectifier is connected to the input end of the second DC line through another fifth switch, one output end of the onshore converter valve is connected to the low voltage winding of the onshore transformer through a sixth switch, the other output end of the onshore converter valve is connected to the high voltage winding of the onshore transformer through a seventh switch, and the output end of the onshore transformer is connected to the onshore power grid; The capacity of the onshore converter valve is at least 20% of the total capacity of the first diode rectifier and the second diode rectifier.

2. The offshore wind power black start device based on a diode rectifier according to claim 1, characterized in that: The first diode rectifier and the second diode rectifier are diode commutation valves with a six-pulse full-bridge structure.

3. The offshore wind power black start device based on a diode rectifier according to claim 1, characterized in that: The first inverter is a YY type transformer, and the second inverter is a YD type transformer.

4. The offshore wind power black start device based on a diode rectifier according to claim 1, characterized in that: After the voltage of the first DC line and the second DC line is established, the low voltage winding voltage of the onshore transformer and the DC side voltage of the back-to-back AC / DC / AC module follow the preset constraints, which are: Where m is the modulation ratio, U dc is the DC side voltage of the back-to-back AC / DC / AC module, U ac It is the low voltage winding voltage of the onshore transformer.

5. The offshore wind power black start device based on a diode rectifier according to claim 1, characterized in that: The time interval error between opening the sixth switch and closing the seventh switch does not exceed 60ms.

6. A method for applying a diode rectifier-based offshore wind power black start device as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: T1, control all the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch and the seventh switch to be in an open state; T2, close all the second switches and the third switches, and then close the sixth switch, so that voltage is established between the first DC line and the second DC line; T3. After the voltage is established on the first DC line and the second DC line, the voltage is established on the DC side of the back-to-back AC / DC / AC module, and the rated AC voltage is established on the first bus and the second bus; T4. One of the first offshore wind farm and the second offshore wind farm unlocks a wind turbine. After the unlocked wind turbine outputs stable power, the other of the first offshore wind farm and the second offshore wind farm unlocks a wind turbine. This process is repeated to unlock the wind turbines in the first offshore wind farm and the second offshore wind farm, respectively. The total capacity of the unlocked wind turbines is lower than the total capacity of the back-to-back AC / DC / AC modules. T5, turn on all third switches and close all fifth switches at the same time, and after the entire system runs stably, the first offshore wind farm and the second offshore wind farm supply low voltage power to the onshore power grid through the back-to-back AC / DC / AC module and the first diode rectifier and the second diode rectifier; T6, turn on the sixth switch, and close the seventh switch and all the fourth switches at the same time, the first diode rectifier and the second diode rectifier normally establish voltage and transmit power, and the DC side output voltage is controlled to be 0 through the back-to-back AC / DC / AC module; T7. Close all the first switches, remove the back-to-back AC / DC / AC modules, and complete the black start.

7. The black start method of the offshore wind power black start device based on a diode rectifier according to claim 6, characterized in that: In step T2, after the voltages of the first DC line and the second DC line are established, the low voltage winding voltage of the onshore transformer and the DC side voltage of the back-to-back AC / DC / AC module follow preset constraints, which are: Where m is the modulation ratio, U dc is the DC side voltage of the back-to-back AC / DC / AC module, U ac It is the low voltage winding voltage of the onshore transformer.

8. The black start method of the offshore wind power black start device based on a diode rectifier according to claim 6, characterized in that: In step T6, the time interval error between opening the sixth switch and closing the seventh switch does not exceed 60 ms.

9. An offshore wind power black start device based on a diode rectifier, the device comprising a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the black start method of the offshore wind power black start device based on a diode rectifier according to any one of claims 6-8 according to the instructions in the program code.

Images