A converter station integrating an oil-immersed converter valve and a transformer

Abstract

This application provides a converter station integrating an oil-immersed converter valve and a transformer, which may include an oil-immersed converter valve, a transformer, and an isolation bushing. The oil-immersed converter valve is electrically connected to the transformer through the isolation bushing. The oil-immersed converter valve includes a first housing and a converter located inside the first housing. The transformer includes a second housing and windings located inside the second housing. The first housing contains a first insulating oil, and the second housing contains a second insulating oil. The first insulating oil and the second insulating oil are physically isolated from each other through the first and second housings. It can be seen that the converter station in this application achieves physical isolation between the oil-immersed converter valve and the transformer through the first and second insulating oils. Compared with converter stations arranged in a valve hall in related technologies, this application not only significantly reduces the cost of the converter station but also reduces its footprint.

Description

Technical Field

[0001] This application relates to the field of DC power transmission technology, specifically to a converter station integrating an oil-immersed converter valve and a transformer. Background Technology

[0002] With the rapid development of new energy technologies, converter stations have been widely used in the field of DC power transmission. A converter station typically includes converter valves and transformers. The converter valve can be a six-pulse converter valve with thyristors as the core semiconductor component, characterized by simple control logic, high thyristor withstand voltage, and large conduction current. Alternatively, the converter valve can be a flexible DC converter valve with insulated-gate bipolar transistors (IGBTs) as the core semiconductor component, characterized by controllable semiconductor components and minimal influence from source voltage.

[0003] In converter stations provided by related technologies, the converter valves (i.e., six-pulse converter valves or flexible DC converter valves) and transformers are usually located inside the valve hall, resulting in higher costs for the converter stations. Moreover, the converter valves typically require air insulation, leading to a large footprint for the valves and consequently, a large footprint for the converter station. Summary of the Invention

[0004] To address the issues of high cost and large footprint in existing technologies, this application provides a converter station integrating an oil-immersed converter valve and a transformer, which may include an oil-immersed converter valve, a transformer, and an isolation bushing. The oil-immersed converter valve is electrically connected to the transformer through the isolation bushing.

[0005] The oil-immersed converter valve includes a first housing and a converter located inside the first housing. The transformer includes a second housing and windings located inside the second housing. The first housing contains a first insulating oil, and the second housing contains a second insulating oil. The first insulating oil and the second insulating oil are physically isolated from each other through the first and second housings.

[0006] Optionally, both the first and second enclosures may be made of metal materials with anti-corrosion coatings or composite materials with insulating properties.

[0007] In one possible implementation, the converter station may also include a first circulating pump, a second circulating pump, and a first cooling device.

[0008] The first circulating pump is located outside the first housing and is connected to the first housing via a first pipe. The second circulating pump is located outside the second housing and is connected to the second housing via a second pipe. The first circulating pump is also connected to the first cooling device via a third pipe, and the second circulating pump is also connected to the first cooling device via a fourth pipe.

[0009] The first circulation pump is used to accelerate the circulation speed of the first insulating oil.

[0010] The second circulation pump is used to accelerate the circulation speed of the second insulating oil.

[0011] The first cooling device is used to reduce the temperature of the first and second insulating oils, thereby achieving heat dissipation for the oil-immersed converter valve and transformer.

[0012] Optionally, the first cooling device can be an air-cooled device or a water-cooled device.

[0013] In another possible implementation, the converter station also includes a first circulating pump, a second circulating pump, a second cooling device, and a third cooling device.

[0014] The first circulating pump and the second cooling device are both located outside the first housing. The first circulating pump is connected to the first housing through a first pipe, and the first circulating pump is also connected to the second cooling device through a third pipe.

[0015] The second circulating pump and the third cooling device are both located outside the second housing. The second circulating pump is connected to the second housing through the second pipe, and the second circulating pump is also connected to the third cooling device through the fourth pipe.

[0016] The first circulation pump is used to accelerate the circulation speed of the first insulating oil.

[0017] The second cooling device is used to reduce the temperature of the first insulating oil and to dissipate heat from the oil-immersed converter valve.

[0018] The second circulation pump is used to accelerate the circulation speed of the second insulating oil.

[0019] The third cooling device is used to reduce the temperature of the second insulating oil, thereby dissipating heat from the transformer.

[0020] Optionally, both the second and third cooling devices can be air-cooled or water-cooled.

[0021] In another possible implementation, the isolation sealing sleeve includes a first flange sleeve and a second flange sleeve.

[0022] The first end of the first flange sleeve and the first end of the second flange sleeve are connected by flanges. The second end of the first flange sleeve is connected to the first housing, and the second end of the second flange sleeve is connected to the second housing.

[0023] For example, the converter includes multiple diodes, multiple heat sinks, a first housing, a first insulator, a first end plate, and a second end plate.

[0024] Multiple diodes and multiple heat sinks are arranged alternately to form a crimping assembly. A first end plate and a second end plate are located at opposite ends of the crimping assembly. The first end of the first insulator is connected to either the first end plate or the second end plate, and the second end of the first insulator is connected to the first housing.

[0025] Optionally, the radiator includes a heat sink and fins, with the fins connected to the heat sink.

[0026] In one example, the converter also includes a resilient component. The resilient component is located between the first end plate and the crimping assembly, or alternatively, the resilient component is located between the second end plate and the crimping assembly.

[0027] In another example, the converter also includes a first insulating tie rod and a second insulating tie rod.

[0028] The first insulating rod and the second insulating rod are arranged in parallel, and the first end of each of the first insulating rod and the second insulating rod is fixed to the first end plate, and the second end of each of the first insulating rod and the second insulating rod is fixed to the second end plate.

[0029] In another example, the converter also includes multiple damping capacitors, multiple damping resistors, and multiple voltage-equalizing resistors. Each of the multiple damping capacitors, multiple damping resistors, and multiple voltage-equalizing resistors corresponds one-to-one with a multiple diode.

[0030] The damping capacitor and damping resistor are connected in series to form an RC branch. The RC branch and the voltage equalizing resistor are both connected in parallel with the diode.

[0031] Furthermore, multiple damping capacitors are arranged in parallel with the crimping assembly, and multiple damping resistors and multiple equalizing resistors are correspondingly fixed on multiple heat sinks.

[0032] In yet another example, the converter also includes multiple equalizing rings.

[0033] Multiple equalizing rings are evenly fitted onto the crimping assembly along its axial direction.

[0034] In one possible implementation, both the first and second enclosures are made of metal materials with anti-corrosion coatings or composite materials with insulating properties.

[0035] In another possible implementation, the converter station also includes a first bushing, a second bushing, a third bushing, a fourth bushing, a fifth bushing, and a sixth bushing.

[0036] The first end of each of the first, second, and third bushings is connected to the AC incoming line of phase A, phase B, and phase C in a one-to-one correspondence. The second end of each of the first, second, and third bushings serves as the first, second, and third AC terminals of the converter station.

[0037] The first end of the fourth bushing is connected to the positive DC bus, and the second end of the fourth bushing serves as the first DC terminal of the converter station, used for connection to the DC grid. The first end of the fifth bushing is connected to the negative DC bus, and the second end of the fifth bushing serves as the second DC terminal of the converter station, used for connection to the DC grid. The first end of the sixth bushing is connected to the neutral point, and the second end of the sixth bushing serves as the neutral terminal of the converter station.

[0038] Compared with the prior art, the beneficial effects of this application are as follows:

[0039] The converter station provided in this application may include an oil-immersed converter valve, a transformer, and an isolation bushing. The oil-immersed converter valve is electrically connected to the transformer via the isolation bushing. The oil-immersed converter valve includes a first housing and a converter located inside the first housing. The transformer includes a second housing and windings located inside the second housing. The first housing contains a first insulating oil, and the second housing contains a second insulating oil. The first insulating oil and the second insulating oil are physically isolated from each other through the first and second housings. It can be seen that the converter station in this application achieves physical isolation between the oil-immersed converter valve and the transformer through the first and second insulating oils. Compared with converter stations arranged in valve halls in related technologies, this application not only significantly reduces the cost of the converter station but also reduces its footprint.

[0040] In this application, the first and second enclosures can be made of metal materials with anti-corrosion coatings or composite materials with insulating functions, so that the entire converter station can be corrosion-resistant and also has dustproof and waterproof capabilities, which further improves the protection level of the converter station.

[0041] In this application, the oil-immersed converter valve achieves commutation through multiple diodes, eliminating the need for a control section. Compared to control via a circuit board, this application can improve the protection level of the oil-immersed converter valve.

[0042] This application utilizes a first insulating oil to achieve not only insulation but also cooling of the oil-immersed converter valve. Compared with related technologies that use water-cooling equipment, this application can improve the cooling speed of the oil-immersed converter valve and further reduce its footprint.

[0043] In this application, multiple damping capacitors, multiple damping resistors, and multiple voltage-equalizing resistors correspond one-to-one with multiple diodes. The damping capacitors and damping resistors are connected in series to form an RC branch. The RC branch and the voltage-equalizing resistors are all connected in parallel with the diodes, which can meet the pulse voltage at the moment of diode turn-off. The voltage-equalizing resistors can improve the voltage equalization of the multi-stage circuit.

[0044] This application makes the entire crimping assembly more stable by using a first end plate, a second end plate, a first insulating tie rod, and a second insulating tie rod, thereby improving the stability and reliability of the oil-immersed converter valve structure. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a schematic structural diagram of a converter station in an embodiment of this application.

[0047] Figure 2 This is a schematic structural diagram of an oil-immersed converter valve in an embodiment of this application.

[0048] Figure 3 This is a schematic structural diagram of a heat sink in an embodiment of this application.

[0049] In the diagram, 10000 - Converter station, 100 - Oil-immersed converter valve, 200 - Transformer, 300 - First bushing, 400 - Second bushing, 500 - Third bushing, 600 - Fourth bushing, 700 - Fifth bushing, 800 - Sixth bushing, 900 - Isolation and sealing bushing, 1000 - First circulating pump, 1100 - Second circulating pump, 1200 - Second cooling equipment, 1300 - Third cooling equipment, 1401 - First pipeline (first insulating oil flows from the first housing to the first circulating pump), 1402 - First pipeline (first insulating oil flows from the first circulating pump to the... 1-Box), 1501-Second Pipeline (Second insulating oil flows from the second box to the second circulating pump), 1502-Second Pipeline (First insulating oil flows from the first box to the first circulating pump), 101-First box, 102-Converter, 201-Second box, 1-Diode, 2-Radiator, 4-First insulator, 5-First end plate, 6-Second end plate, 7-First insulating tie rod, 8-Second insulating tie rod, 9-Elastic component, 10-Damping capacitor, 12-Crimping component, 900-Isolation sealing sleeve, 901-First flange sleeve, 902-Second flange sleeve. Detailed Implementation

[0050] The technical solutions in this application will now be described with reference to the accompanying drawings.

[0051] The terms "first," "second," etc., used in the specification, embodiments, claims, and drawings of this application are for distinguishing purposes only and should not be construed as indicating or implying relative importance or order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as including a series of steps or units. A method, system, product, or apparatus is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses.

[0052] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0053] This application provides a converter station integrating an oil-immersed converter valve and a transformer, such as... Figure 1 As shown. The converter station 10000 may include an oil-immersed converter valve 100, a transformer 200, and an isolation sealing sleeve 900. The oil-immersed converter valve 100 is electrically connected to the transformer 200 through the isolation sealing sleeve 900.

[0054] The oil-immersed converter valve 100 includes a first housing 101 and a converter 102 located inside the first housing 100. The transformer 200 includes a second housing 201 and windings located inside the second housing 201. Figure 1 (Not shown in the image). The first housing 101 contains the first insulating oil, and the second housing 201 contains the second insulating oil. The first insulating oil and the second insulating oil are physically isolated from each other through the first housing 101 and the second housing 201.

[0055] In one possible implementation, such as Figure 1 As shown, the converter station 1000 also includes a first circulating pump 1000, a second circulating pump 1100, a second cooling device 1200, and a third cooling device 1300.

[0056] The first circulation pump 1000 and the second cooling device 1200 are both located outside the first housing 101. The first circulation pump 1000 is connected to the first housing 101 through the first pipe 1401 and the first pipe 1402. The first circulation pump 1000 is also connected to the second cooling device 1200 through the third pipe.

[0057] The second circulation pump 1100 and the third cooling device 1300 are both located outside the second housing 201. The second circulation pump 1100 is connected to the second housing 201 through the second pipe 1501 and the first pipe 1502. The second circulation pump 1100 is also connected to the third cooling device 1300 through the fourth pipe.

[0058] The first circulation pump 1000 is used to accelerate the circulation speed of the first insulating oil.

[0059] The second cooling device 1200 is used to reduce the temperature of the first insulating oil and to dissipate heat from the oil-immersed converter valve 100.

[0060] The second circulation pump 1100 is used to accelerate the circulation speed of the second insulating oil.

[0061] The third cooling device 1300 is used to reduce the temperature of the second insulating oil and to dissipate heat from the transformer 200.

[0062] Optionally, both the second cooling device 1200 and the third cooling device 1300 may be air-cooled or water-cooled, etc., and this application embodiment does not limit the scope.

[0063] In another possible implementation, the converter station may further include a first circulating pump, a second circulating pump, and a first cooling device. The first circulating pump is located outside the first housing and is connected to the first housing via a first pipe and a second pipe. The second circulating pump is located outside the second housing and is connected to the second housing via a second pipe and a first pipe. The first circulating pump is also connected to the first cooling device via a third pipe, and the second circulating pump is also connected to the first cooling device via a fourth pipe.

[0064] The first circulating pump is used to accelerate the circulation speed of the first insulating oil. The second circulating pump is used to accelerate the circulation speed of the second insulating oil. The first cooling device is used to reduce the temperature of the first and second insulating oils, thereby achieving heat dissipation for the oil-immersed converter valve and transformer. Optionally, the first cooling device can be an air-cooled device or a water-cooled device, etc., and this application embodiment is not limited thereto.

[0065] Optionally, the first enclosure 101 and the second enclosure 201 are made of metal materials with anti-corrosion coating or composite materials with insulating function, so that the entire converter station 10000 can be corrosion-resistant and also has dustproof and waterproof capabilities, which further improves the protection level of the converter station 10000.

[0066] In another possible implementation, such as Figure 1 As shown, the isolation sealing sleeve 900 includes a first flange sleeve 901 and a second flange sleeve 902.

[0067] The first end of the first flange sleeve 901 is connected to the first end of the second flange sleeve 902. The second end of the first flange sleeve 901 is connected to the first housing 101, and the second end of the second flange sleeve 902 is connected to the second housing 201.

[0068] For example, the converter 102 includes a plurality of diodes 1, a plurality of heat sinks 2, a first insulator 4, a first end plate 5, and a second end plate 6.

[0069] Optionally, multiple diodes 1 and multiple heat sinks 2 are arranged alternately to form a crimping assembly 12. A first end plate 5 and a second end plate 6 are located at opposite ends of the crimping assembly 12. The first end of the first insulator 4 is connected to either the first end plate 5 or the second end plate 6, and the second end of the first insulator 4 can be connected to the first housing 101. (Reference) Figure 1 The crimping assembly 12 can be connected in series in a spiral pattern.

[0070] It can be seen that the first and second end plates make the entire crimping assembly more stable, thereby improving the stability and reliability of the converter valve structure.

[0071] In some possible implementations, such as Figure 2 and Figure 3 As shown, the heat sink 2 includes a heat sink 21 and fins 22, with the fins 22 connected to the heat sink 21. To improve heat dissipation, there can be multiple fins 22, but this embodiment does not limit the number of fins.

[0072] In some other possible implementations, the converter 102 further includes a resilient component 9. The resilient component 9 is located between the first end plate 5 and the crimping component 12, or the resilient component 9 is located between the second end plate 6 and the crimping component 12. In embodiments of this application, such as... Figure 2 The elastic component 9 is located between the first end plate 5 and the crimping component 12.

[0073] In another possible implementation, such as Figure 2 The converter 102 also includes a first insulating rod 7 and a second insulating rod 8. The first insulating rod 7 and the second insulating rod 8 are arranged in parallel, and the first end of each of the first insulating rod 7 and the second insulating rod 8 is fixed to the first end plate 5, and the second end of each of the first insulating rod 7 and the second insulating rod 8 is fixed to the second end plate 6. Of course, more insulating rods can be provided to enhance the stability of the entire converter valve.

[0074] In some possible implementations, such as Figure 2 As shown, the converter 102 also includes multiple damping capacitors 10 and multiple damping resistors ( Figure 2 (not shown in the image) and multiple voltage equalizing resistors ( Figure 2 (Not shown in the image). Multiple damping capacitors 10, multiple damping resistors, and multiple voltage equalizing resistors correspond one-to-one with multiple diodes.

[0075] Damping capacitor 10 and damping resistor connected in series can form an RC branch. The RC branch and the voltage equalizing resistor are both connected in parallel with the diode.

[0076] Furthermore, multiple damping capacitors 10 can be arranged in parallel with the crimping assembly 12, and multiple damping resistors and multiple equalizing resistors are correspondingly fixed on multiple heat sinks 2.

[0077] In some other possible implementations, the converter 102 also includes multiple equalizing rings ( Figure 2 (Not shown in the image). Multiple equalizing rings are uniformly fitted onto the crimping assembly 12 along the axial direction of the crimping assembly 12.

[0078] In another possible implementation, such as Figure 1 As shown, converter station 10000 also includes first bushing 300, second bushing 400, third bushing 500, fourth bushing 600, fifth bushing 700 and sixth bushing 800.

[0079] The first end of each of the first bushing 300, the second bushing 400, and the third bushing 500 is connected to the AC incoming line of phase A, phase B, and phase C in a one-to-one correspondence. The second end of each of the first bushing 300, the second bushing 400, and the third bushing 500 serves as the first AC end, the second AC end, and the third AC end of the converter station 10000.

[0080] The first end of the fourth bushing 600 is connected to the positive DC bus, and the second end of the fourth bushing 600 serves as the first DC terminal of the converter station, used for connection to the DC grid. The first end of the fifth bushing 700 is connected to the negative DC bus, and the second end of the fifth bushing 700 serves as the second DC terminal of the converter station 10000, used for connection to the DC grid. The first end of the sixth bushing 800 is connected to the neutral point, and the second end of the sixth bushing 800 serves as the neutral terminal of the converter station.

[0081] In summary, the converter station provided in this application achieves physical isolation between the oil-immersed converter valve and the transformer through a first insulating oil and a second insulating oil. Compared with converter stations arranged in the valve hall in related technologies, this application not only greatly reduces the cost of the converter station, but also reduces the footprint of the converter station.

[0082] The above are merely embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application shall be included within the scope of the claims of this application pending approval.

Claims

1. A converter station integrating an oil-immersed converter valve and a transformer, characterized in that, It includes an oil-immersed converter valve, a transformer, and an isolation sealing bushing; the oil-immersed converter valve is electrically connected to the transformer through the isolation sealing bushing; The oil-immersed converter valve includes a first housing and a converter located inside the first housing; the transformer includes a second housing and windings located inside the second housing. The first box contains a first insulating oil, and the second box contains a second insulating oil. The first insulating oil and the second insulating oil are physically isolated from each other through the first box and the second box. The converter includes multiple diodes, multiple heat sinks, a first insulator, a first end plate, and a second end plate; The plurality of diodes and the plurality of heat sinks are arranged alternately to form a crimping assembly; the first end plate and the second end plate are respectively located at both ends of the crimping assembly; the first end of the first insulator is connected to the first end plate or the second end plate, and the second end of the first insulator is connected to the first housing. The converter also includes multiple damping capacitors, multiple damping resistors, and multiple voltage-equalizing resistors; each of the multiple damping capacitors, multiple damping resistors, and multiple voltage-equalizing resistors corresponds one-to-one with the multiple diodes; The damping capacitor and the damping resistor are connected in series to form an RC branch; the RC branch and the voltage equalizing resistor are both connected in parallel with the diode. The converter also includes multiple equalizing rings; The plurality of equalizing rings are uniformly fitted onto the crimping assembly along the axial direction of the crimping assembly.

2. The converter station according to claim 1, characterized in that, The converter station also includes a first circulating pump, a second circulating pump, and a first cooling device; The first circulating pump is located outside the first housing and is connected to the first housing via a first pipe; the second circulating pump is located outside the second housing and is connected to the second housing via a second pipe; the first circulating pump is also connected to the first cooling device via a third pipe, and the second circulating pump is also connected to the first cooling device via a fourth pipe; The first circulating pump is used to: accelerate the circulation speed of the first insulating oil; The second circulating pump is used to: accelerate the circulation speed of the second insulating oil; The first cooling device is used to reduce the temperature of the first insulating oil and the second insulating oil, thereby achieving heat dissipation of the oil-immersed converter valve and the transformer.

3. The converter station according to claim 1, characterized in that, The converter station also includes a first circulating pump, a second circulating pump, a second cooling device, and a third cooling device; Both the first circulating pump and the second cooling device are located outside the first housing. The first circulating pump is connected to the first housing through a first pipe, and the first circulating pump is also connected to the second cooling device through a third pipe. The second circulating pump and the third cooling device are both located outside the second housing. The second circulating pump is connected to the second housing through a second pipe, and the second circulating pump is also connected to the third cooling device through a fourth pipe. The first circulating pump is used to: accelerate the circulation speed of the first insulating oil; The second cooling device is used to: reduce the temperature of the first insulating oil, thereby dissipating heat from the oil-immersed converter valve; The second circulating pump is used to: accelerate the circulation speed of the second insulating oil; The third cooling device is used to reduce the temperature of the second insulating oil, thereby dissipating heat from the transformer.

4. The converter station according to claim 1, characterized in that, The isolation sealing sleeve includes a first flange sleeve and a second flange sleeve; The first end of the first flange sleeve is flange-connected to the first end of the second flange sleeve, the second end of the first flange sleeve is connected to the first housing, and the second end of the second flange sleeve is connected to the second housing.

5. The converter station according to claim 1, characterized in that: The radiator includes a heat sink and fins, with the fins connected to the heat sink.

6. The converter station according to claim 1, characterized in that: The converter also includes a resilient component; The elastic component is located between the first end plate and the crimping component, or the elastic component is located between the second end plate and the crimping component.

7. The converter station according to claim 1, characterized in that: The converter also includes a first insulating tie rod and a second insulating tie rod; The first insulating rod and the second insulating rod are arranged in parallel, and the first end of each of the first insulating rod and the second insulating rod is fixed to the first end plate, and the second end of each of the first insulating rod and the second insulating rod is fixed to the second end plate.

8. The converter station according to claim 1, characterized in that, The plurality of damping capacitors are arranged in parallel with the crimping assembly, and the plurality of damping resistors and the plurality of voltage equalizing resistors are correspondingly fixed on the plurality of heat sinks.

9. The converter station according to claim 1, characterized in that: Both the first and second enclosures are made of metal materials with anti-corrosion coatings or composite materials with insulating properties.

10. The converter station according to claim 3, characterized in that: Both the second and third cooling devices are air-cooled or water-cooled.

11. The converter station according to claim 1, characterized in that, The converter station also includes a first sleeve, a second sleeve, a third sleeve, a fourth sleeve, a fifth sleeve, and a sixth sleeve; The first end of each of the first bushing, the second bushing, and the third bushing is connected to the A-phase AC incoming line, the B-phase AC incoming line, and the C-phase AC incoming line in a one-to-one correspondence. The second end of each of the first bushing, the second bushing, and the third bushing serves as the first AC terminal, the second AC terminal, and the third AC terminal of the converter station. The first end of the fourth bushing is connected to the positive DC bus, and the second end of the fourth bushing serves as the first DC terminal of the converter station for connection to the DC grid; the first end of the fifth bushing is connected to the negative DC bus, and the second end of the fifth bushing serves as the second DC terminal of the converter station for connection to the DC grid; the first end of the sixth bushing is connected to the neutral point, and the second end of the sixth bushing serves as the neutral terminal of the converter station.

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