Reversed polarity voltage suppression method for offshore wind power direct current submarine cable and related device

Abstract

The invention discloses an offshore wind power direct current submarine cable reversed polarity voltage suppression method and a related device, and the method comprises the steps: optimizing the locking logic of a full-bridge sub-module after the overcurrent locking of an offshore sending end converter station when an inter-pole fault occurs in an overhead line or a port of an onshore receiving end converter station; one part of full-bridge sub-modules of the same bridge arm of the converter of the offshore sending end converter station are controlled to output negative voltage, and the other part of full-bridge sub-modules output voltage to be zero, so that the reverse polarity voltage of a submarine cable port is inhibited; the technical problem that in the prior art, an effective method for restraining the reverse polarity voltage of the direct-current submarine cable caused by the direct-current inter-electrode fault of the offshore wind power submarine cable and overhead line hybrid power transmission system is lacked is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible direct current systems, and in particular to a method for suppressing reverse polarity voltage of an offshore wind power direct current submarine cable and a related device. Background Art

[0002] Offshore wind energy resources are abundant and stable, and offshore wind power development is moving towards a trend of larger capacity and farther from the coast. In order to further reduce transmission costs and compress transmission corridors, the hybrid line of sea-land integrated submarine cable + overhead line directly delivering to the load center will become the main solution for the future intensive development of ultra-large-scale offshore wind power.

[0003] For long-distance submarine cable + overhead line hybrid transmission systems, when an inter-pole fault occurs at the overhead line or the receiving end converter station port, if the sending and receiving end converter station is closed due to valve overcurrent, the energy stored in the line inductance and stray capacitance before the fault and the energy fed into the offshore converter station will oscillate in the line, resulting in a large reverse polarity voltage at the submarine cable port, exceeding the reverse polarity voltage tolerance standard of the DC submarine cable, and even causing the submarine cable insulation to break down, endangering the safe operation of the system. At present, there is no effective method for suppressing the reverse polarity voltage of the DC submarine cable caused by the DC inter-pole fault in the submarine cable + overhead line hybrid transmission system. Summary of the invention

[0004] The present invention provides a method and related device for suppressing reverse polarity voltage of offshore wind power DC submarine cable, which is used to solve the technical problem that the prior art lacks an effective method for suppressing reverse polarity voltage of DC submarine cable caused by DC inter-pole fault in a hybrid power transmission system of offshore wind power submarine cable and overhead line.

[0005] In view of this, a first aspect of the present invention provides a method for suppressing reverse polarity voltage of an offshore wind power DC submarine cable, comprising:

[0006] When an inter-pole fault occurs at the port of the overhead line or the onshore receiving converter station, the offshore sending converter station triggers overcurrent blocking;

[0007] After the offshore sending-end converter station is overcurrent locked, a part of the full-bridge submodules in the same bridge arm of the converter of the offshore sending-end converter station are controlled to output negative voltage, and the output voltage of another part of the full-bridge submodules is zero.

[0008] Optionally, it also includes:

[0009] When an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station, the negative pressure output capacity of the DC side of the offshore sending-end converter station is increased before the offshore sending-end converter station is overcurrent-locked.

[0010] Optionally, the step of improving the negative pressure output capacity of the DC side of the offshore sending-end converter station includes:

[0011] Under the condition that the safety margin of the offshore sending-end converter station is met, the DC side negative pressure output capacity of the offshore sending-end converter station is improved by reducing the minimum output limit value of the outer loop PI controller of the DC bias control of the offshore sending-end converter station.

[0012] Optionally, the mapping relationship between the minimum value of the output limit of the outer loop PI controller and the negative pressure output capacity of the DC side of the offshore sending-end converter station is:

[0013]

[0014] in, is the minimum value of the output limit of the outer loop PI controller, It is the negative pressure output capacity of the DC side of the offshore sending-end converter station.

[0015] A second aspect of the present invention provides an offshore wind power DC submarine cable reverse polarity voltage suppression device, comprising:

[0016] A trigger module is used to trigger overcurrent blocking at the offshore sending-end converter station when an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station;

[0017] The full-bridge locking logic optimization module is used to control a part of the full-bridge sub-modules in the same bridge arm of the converter of the offshore sending-end converter station to output negative voltage and another part of the full-bridge sub-modules to output zero voltage after the offshore sending-end converter station is overcurrent locked.

[0018] Optionally, it also includes:

[0019] The DC bias control module is used to improve the negative pressure output capacity of the DC side of the offshore sending-end converter station before the offshore sending-end converter station is overcurrent locked when an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station.

[0020] Optionally, the DC bias control module is specifically used to:

[0021] When an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station, before the overcurrent locking of the offshore sending-end converter station, the DC side negative pressure output capacity of the offshore sending-end converter station is improved by reducing the minimum output limit value of the outer loop PI controller of the DC bias control of the offshore sending-end converter station, provided that the safety margin of the offshore sending-end converter station is met.

[0022] Optionally, in the DC bias control module, the mapping relationship between the minimum value of the output limit of the outer loop PI controller and the DC side negative pressure output capability of the offshore sending-end converter station is:

[0023]

[0024] in, is the minimum value of the output limit of the outer loop PI controller, It is the negative pressure output capacity of the DC side of the offshore sending-end converter station.

[0025] A third aspect of the present invention provides an offshore wind power DC submarine cable reverse polarity voltage suppression device, the device comprising a processor and a memory:

[0026] The memory is used to store program codes and transmit the program codes to the processor;

[0027] The processor is used to execute the method for suppressing reverse polarity voltage of an offshore wind power DC cable according to any one of the first aspects according to the instructions in the program code.

[0028] 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 method for suppressing reverse polarity voltage of an offshore wind power DC cable as described in any one of the first aspects.

[0029] It can be seen from the above technical solutions that the method for suppressing reverse polarity voltage of offshore wind power DC submarine cables provided by the present invention has the following advantages:

[0030] The method for suppressing reverse polarity voltage of offshore wind power DC submarine cable provided by the present invention optimizes the locking logic of the full-bridge submodule after the overcurrent locking of the offshore sending-end converter station when an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station, controls a part of the full-bridge submodules in the same bridge arm of the converter of the offshore sending-end converter station to output negative voltage, and controls the output voltage of the other part of the full-bridge submodules to be zero, thereby suppressing the reverse polarity voltage at the submarine cable port, and solving the technical problem that the prior art lacks an effective method for suppressing reverse polarity voltage of DC submarine cable caused by DC inter-pole fault in the hybrid transmission system of offshore wind power submarine cable and overhead line.

[0031] At the same time, the method for suppressing reverse polarity voltage of offshore wind power DC submarine cable provided by the present invention improves the negative pressure output capacity of the DC side of the offshore converter station before the offshore converter station is locked when an inter-pole fault occurs at the overhead line or the onshore receiving end converter station port, thereby further suppressing the reverse polarity voltage at the submarine cable port. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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.

[0033] Figure 1A schematic flow chart of a method for suppressing reverse polarity voltage of an offshore wind power DC submarine cable provided in an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of the traditional locking logic of an offshore sending-end converter station when an inter-pole fault occurs in a DC line provided in an embodiment of the present invention;

[0035] Figure 3 A schematic diagram of a zero-voltage locking mode of a method for suppressing reverse polarity voltage of an offshore wind power DC submarine cable provided in an embodiment of the present invention;

[0036] Figure 4 A schematic diagram of another zero-voltage locking mode of the method for suppressing reverse polarity voltage of an offshore wind power DC submarine cable provided in an embodiment of the present invention;

[0037] Figure 5 A comparison diagram of the voltage waveform at the submarine cable port when all full-bridge submodules adopt the negative pressure locking mode and the voltage waveform when some full-bridge submodules adopt the negative pressure locking mode and some adopt the zero pressure locking mode provided in an embodiment of the present invention;

[0038] Figure 6 Another schematic diagram of a flow chart of a method for suppressing reverse polarity voltage of an offshore wind power DC submarine cable provided in an embodiment of the present invention;

[0039] Figure 7 This is the DC bias control block diagram of the offshore sending-end converter station;

[0040] Figure 8 This is a diagram showing the effect of improving the negative voltage output capacity of the DC side of the offshore sending-end converter station on the reverse polarity voltage suppression of the submarine cable provided in an embodiment of the present invention;

[0041] Fig. 9 A schematic diagram of the overall effect of a method for suppressing reverse polarity voltage of an offshore wind power DC submarine cable provided in an embodiment of the present invention;

[0042] Fig.10 It is a structural schematic diagram of a reverse polarity voltage suppression device for an offshore wind power DC submarine cable provided in an embodiment of the present invention;

[0043] Fig.11 The present invention is a schematic structural diagram of a reverse polarity voltage suppression device for an offshore wind power DC submarine cable provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] 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.

[0045] For easier understanding, see Figure 1 The present invention provides an embodiment of a method for suppressing reverse polarity voltage of an offshore wind power DC submarine cable, comprising:

[0046] Step 101: When an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station, the offshore sending-end converter station triggers an overcurrent lockout.

[0047] It should be noted that when an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station, the offshore sending-end converter station will trigger the overcurrent lock for overcurrent protection.

[0048] Step 102: After the overcurrent blocking of the offshore sending-end converter station, control a part of the full-bridge submodules in the same bridge arm of the converter of the offshore sending-end converter station to output negative voltage, and control the output voltage of the other part of the full-bridge submodules to be zero.

[0049] It should be noted that in the traditional overcurrent blocking logic, all IGBTs of all full-bridge submodules in the offshore sending-end converter station are turned off. Figure 2 As shown, at this time, the full-bridge submodule outputs negative pressure, that is, negative pressure locking. In the present invention, in order to suppress the reverse polarity voltage of the submarine cable, the locking logic of the full-bridge submodule is optimized. After the overcurrent locking at the offshore sending-end converter station, a part of the full-bridge submodules in the same bridge arm of the converter adopts the negative pressure locking mode, and the other part of the full-bridge submodules adopts the zero-pressure locking mode (that is, the output voltage of the full-bridge submodule is zero). There are two types of zero-pressure locking modes for the full-bridge submodule, namely Figure 3 and Figure 4 As shown, Figure 3 The zero-voltage locking mode in the full-bridge submodule is to keep the No. 1 IGBT tube turned on and the other IGBTs turned off. At this time, the output voltage of the full-bridge submodule is zero; Figure 4 The zero-voltage locking mode in the circuit keeps the No. 4 IGBT on and the other IGBTs off. At this time, the output voltage of the full-bridge submodule is zero.

[0050] In order to verify the effectiveness of the suppression method proposed in the present invention, the present invention takes the offshore sending-end converter station of full-half-bridge hybrid (60% full-bridge submodule + 40% half-bridge submodule) MMC (Modular Multilevel Converter) as an example, and compares the submarine cable port voltage waveform under the negative pressure locking logic of all full-bridge submodules and the submarine cable port voltage waveform under the locking logic of a part of the full-bridge submodules using the negative pressure locking method and the other part of the full-bridge submodules using the zero pressure locking method, as shown in FIG. Figure 5 As shown, Figure 5 In the figure, the solid line is the voltage waveform at the submarine cable port when 60% of the full-bridge submodules adopt negative pressure locking, and the dotted line is the voltage waveform at the submarine cable port when 45% of the full-bridge submodules adopt negative pressure locking and 15% of the full-bridge submodules adopt zero pressure locking. Figure 5 It can be found that by modifying the locking mode of a part of the full-bridge sub-modules to zero-voltage locking and optimizing the locking logic of the full-bridge sub-modules in the bridge arm, the reverse polarity voltage at the submarine cable port can be suppressed. The simulation results prove the effectiveness of the suppression method proposed in the present invention.

[0051] The method for suppressing reverse polarity voltage of offshore wind power DC submarine cable provided by the present invention optimizes the locking logic of the full-bridge submodule after the overcurrent locking of the offshore sending-end converter station when an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station, controls a part of the full-bridge submodules in the same bridge arm of the converter of the offshore sending-end converter station to output negative voltage, and controls the output voltage of another part of the full-bridge submodules to be zero, thereby suppressing the reverse polarity voltage at the submarine cable port, and solving the technical problem that the prior art lacks an effective method for suppressing reverse polarity voltage of DC submarine cable caused by DC inter-pole fault in a hybrid power transmission system of offshore wind power submarine cable and overhead line.

[0052] In one embodiment, Figure 6 As shown, before step 102, it also includes:

[0053] Step 100: When an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station, before the overcurrent locking of the offshore sending-end converter station, the negative pressure output capacity of the DC side of the offshore sending-end converter station is increased.

[0054] It should be noted that the theoretical minimum output negative pressure on the DC side of the offshore sending-end converter station including the full-bridge submodule is ) by the full bridge ratio ( ) and the full-bridge submodule capacitor voltage rating ( ) is determined and expressed as:

[0055]

[0056] in, is the DC rated voltage, is the negative pressure output capacity of the DC side of the offshore sending-end converter station, and N is the number of all bridge arm submodules including full-bridge submodules and half-bridge submodules.

[0057] The actual output voltage of the DC side of the offshore converter station is determined by the DC bias per unit value. Determine, generally speaking, the DC bias per unit value It is controlled by the capacitor voltage outer loop and the DC current inner loop, such as Figure 7 As shown, Represents the average value of the submodule capacitor voltage, Indicates the rated DC current, represents the direct current, and They represent the maximum value of the output limit of the outer loop PI controller and the minimum value of the output limit of the outer loop PI controller respectively. The actual output voltage of the DC side ( ) can be determined by Indicates that:

[0058]

[0059] If the full-bridge submodule capacitor voltage is considered equal to the submodule rated capacitor voltage, then , if the full-bridge submodule capacitor voltage is considered to be appropriately higher than the submodule rated capacitor voltage, the DC side negative voltage output range can be further increased, that is, Therefore, in order to suppress the reverse polarity voltage at the submarine cable port, the output limit minimum value of the outer loop PI controller is reduced under the premise of considering the safety margin of the offshore converter station. , to improve the negative pressure output capacity of the DC side of the offshore sending-end converter station. Figure 8 The negative voltage output capacity of the DC side of the offshore converter station is 10% (that is, the negative voltage of the DC side can output 10% of the rated voltage at the lowest, which is regarded as the original working condition, corresponding to ) and 30% (that is, the DC side negative pressure can output 30% of the rated voltage at the lowest, which is regarded as improving the DC side negative pressure output capacity, corresponding to ) when the voltage waveform of the submarine cable port is compared, it can be seen that the reverse polarity voltage at the submarine cable port can be suppressed by improving the negative voltage output capacity of the DC side of the offshore sending-end converter station, which verifies the effectiveness of the suppression method provided by the present invention. Fig. 9 A comparison diagram of the cable port voltage waveform under the original working condition (10% negative pressure output capacity + 60% full-bridge submodule negative pressure lock) and the suppression method provided by the present invention (30% negative pressure output capacity + 45% full-bridge submodule negative pressure lock + 15% full-bridge submodule zero pressure lock) is given. Fig. 9It can be found that when an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station, before the offshore sending-end converter station is overcurrent locked, the negative voltage output capacity of the DC side of the offshore sending-end converter station is improved. After the offshore sending-end converter station is overcurrent locked, a part of the full-bridge sub-modules in the same bridge arm of the converter of the offshore sending-end converter station are controlled to output negative voltage, and the output voltage of the other part of the full-bridge sub-modules is zero, which can further suppress the reverse polarity voltage of the submarine cable and achieve better suppression effect.

[0060] For easier understanding, please participate Fig.10 The present invention provides an embodiment of a reverse polarity voltage suppression device for an offshore wind power DC submarine cable, comprising:

[0061] A trigger module is used to trigger overcurrent blocking at the offshore sending-end converter station when an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station;

[0062] The full-bridge interlocking logic optimization module is used to control a part of the full-bridge sub-modules of the same bridge arm of the converter of the offshore sending-end converter station to output negative voltage and another part of the full-bridge sub-modules to output zero voltage after the overcurrent interlocking of the offshore sending-end converter station.

[0063] In one embodiment, it further includes:

[0064] The DC bias control module is used to increase the negative pressure output capacity of the DC side of the offshore sending-end converter station before the offshore sending-end converter station is overcurrent locked when an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station.

[0065] In one embodiment, the DC bias control module is specifically used to:

[0066] When an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station, before the overcurrent lockout of the offshore sending-end converter station, and subject to the safety margin condition of the offshore sending-end converter station, the DC side negative pressure output capacity of the offshore sending-end converter station is improved by reducing the minimum output limit value of the outer loop PI controller of the DC bias control of the offshore sending-end converter station.

[0067] In one embodiment, in the DC bias control module, the mapping relationship between the minimum output limit value of the outer loop PI controller and the DC side negative voltage output capability of the offshore sending-end converter station is:

[0068]

[0069] in, is the minimum value of the output limit of the outer loop PI controller, It is the negative pressure output capacity of the DC side of the offshore sending-end converter station.

[0070] For easier understanding, see Fig.11The present invention also provides an embodiment of an offshore wind power DC submarine cable reverse polarity voltage suppression device, the device comprising a processor and a memory:

[0071] The memory is used to store the program code and transmit the program code to the processor;

[0072] The processor is used to execute any one of the aforementioned embodiments of the method for suppressing reverse polarity voltage of offshore wind power DC cables according to the instructions in the program code.

[0073] The present invention also provides an embodiment of a computer-readable storage medium, which is used to store program code, and the program code is used to execute any one of the aforementioned embodiments of the method for suppressing reverse polarity voltage of offshore wind power DC submarine cables.

[0074] The present invention also provides an embodiment of a computer program product including instructions, which, when executed on a computer, enables the computer to execute any one of the aforementioned embodiments of the method for suppressing reverse polarity voltage of a direct current submarine cable of offshore wind power.

[0075] The offshore wind power DC cable reverse polarity voltage suppression device, equipment, computer-readable storage medium and computer program product including instructions provided in the present invention are all used to execute the offshore wind power DC cable reverse polarity voltage suppression method provided in the present invention. The principle and technical effects achieved are the same as those of the offshore wind power DC cable reverse polarity voltage suppression method provided in the present invention, and will not be repeated here.

[0076] 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. A method for suppressing reverse polarity voltage of an offshore wind power DC cable, characterized in that: include: When an inter-pole fault occurs at the port of the overhead line or the onshore receiving converter station, the offshore sending converter station triggers overcurrent blocking; After the offshore sending-end converter station is overcurrent locked, a part of the full-bridge submodules in the same bridge arm of the converter of the offshore sending-end converter station are controlled to output negative voltage, and the output voltage of another part of the full-bridge submodules is zero.

2. The method for suppressing reverse polarity voltage of offshore wind power DC submarine cable according to claim 1 is characterized in that: Also includes: When an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station, the negative pressure output capacity of the DC side of the offshore sending-end converter station is increased before the offshore sending-end converter station is overcurrent-locked.

3. The method for suppressing reverse polarity voltage of offshore wind power DC submarine cable according to claim 2 is characterized in that: The method of improving the negative pressure output capacity of the DC side of the offshore sending-end converter station includes: Under the condition that the safety margin of the offshore sending-end converter station is met, the DC side negative pressure output capacity of the offshore sending-end converter station is improved by reducing the minimum output limit value of the outer loop PI controller of the DC bias control of the offshore sending-end converter station.

4. The method for suppressing reverse polarity voltage of offshore wind power DC submarine cable according to claim 3 is characterized in that: The mapping relationship between the minimum output limit value of the outer loop PI controller and the negative voltage output capacity of the DC side of the offshore sending-end converter station is: in, is the minimum value of the output limit of the outer loop PI controller, It is the negative pressure output capacity of the DC side of the offshore sending-end converter station.

5. A reverse polarity voltage suppression device for offshore wind power DC submarine cable, characterized in that: include: A trigger module is used to trigger overcurrent blocking at the offshore sending-end converter station when an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station; The full-bridge locking logic optimization module is used to control a part of the full-bridge sub-modules in the same bridge arm of the converter of the offshore sending-end converter station to output negative voltage and another part of the full-bridge sub-modules to output zero voltage after the offshore sending-end converter station is overcurrent locked.

6. The reverse polarity voltage suppression device for offshore wind power DC submarine cable according to claim 5 is characterized in that: Also includes: The DC bias control module is used to improve the negative pressure output capacity of the DC side of the offshore sending-end converter station before the offshore sending-end converter station is overcurrent locked when an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station.

7. The reverse polarity voltage suppression device for offshore wind power DC submarine cable according to claim 6 is characterized in that: The DC bias control module is specifically used for: When an inter-pole fault occurs at the port of the overhead line or the onshore receiving-end converter station, before the overcurrent locking of the offshore sending-end converter station, the DC side negative pressure output capacity of the offshore sending-end converter station is improved by reducing the minimum output limit value of the outer loop PI controller of the DC bias control of the offshore sending-end converter station, provided that the safety margin of the offshore sending-end converter station is met.

8. The reverse polarity voltage suppression device for offshore wind power DC submarine cable according to claim 7 is characterized in that: In the DC bias control module, the mapping relationship between the minimum output limit value of the outer loop PI controller and the DC side negative pressure output capability of the offshore sending-end converter station is: in, is the minimum value of the output limit of the outer loop PI controller, It is the negative pressure output capacity of the DC side of the offshore sending-end converter station.

9. An offshore wind power DC cable reverse polarity voltage suppression device, characterized in that: The device comprises 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 method for suppressing reverse polarity voltage of an offshore wind power DC cable according to any one of claims 1 to 4 according to the instructions in the program code.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium is used to store program code, and the program code is used to execute the method for suppressing reverse polarity voltage of an offshore wind power DC submarine cable as described in any one of claims 1-4.

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