Direct current power transmission system configuration circuit, method and system

Abstract

The invention belongs to the technical field of high-voltage direct-current power transmission, and particularly relates to a direct-current power transmission system configuration circuit, method and system. The circuit comprises an HCC single-pole valve body, the HCC single-pole valve body comprises an HCC high-voltage valve group and an HCC low-voltage valve group, and the HCC high-voltage valve group and the HCC low-voltage valve group are connected in series; the HCC high-pressure valve group comprises at least two high-pressure valve sections, and each high-pressure valve section comprises three first branches which are connected in parallel; the HCC low-pressure valve set comprises at least two low-pressure valve sections, and each low-pressure valve section comprises three second branches which are connected in parallel. For a novel HCC type high-voltage direct-current power transmission system, due to the fact that a turn-off device IGCT is adopted and has a turn-off function, the extinction angle of the system can be much smaller than that of high-voltage direct-current power transmission based on a thyristor, and safety and reliability can be guaranteed; the method for configuring the AC filter and the reactive compensation group may be different from conventional high-voltage DC power transmission based on thyristors.

Description

Technical Field

[0001] The present invention belongs to the technical field of high voltage direct current transmission, and in particular relates to a direct current transmission system configuration circuit, method and system. Background Art

[0002] High-voltage direct current transmission converter stations consume a large amount of reactive power during operation, and the reactive power fluctuations of the converter stations will have a significant impact on the voltage stability of the AC system at the DC transmitting and receiving ends. DC converter stations need to be equipped with reactive power compensation devices to achieve steady-state reactive power balance of the system and dynamic reactive power support of the converter stations.

[0003] At present, there are three main types of reactive power compensation devices in converter stations in the world: mechanical switching capacitors and reactors, static reactive power compensation devices, and phase shifters. Among them, mechanical switching capacitors and reactors have the best economic performance and are the most commonly used reactive power compensation devices in conventional converter stations. At present, conventional converter stations use filter groups composed of capacitors and reactors to compensate for the steady-state reactive power demand of converter stations.

[0004] After searching, a Chinese patent discloses a method for optimizing near-field reactive power configuration of a UHV DC converter station, including the following steps: 1) determining the target UHV DC sending-end power grid and its network operation parameters, and determining the node range to be connected to the reactive power compensation equipment; 2) establishing a nonlinear optimization model with the AC bus voltage of the UHV converter station and the bus voltage of a key node of a power grid as the optimization target; 3) evaluating the change in voltage of each node when reactive power changes, calculating its sensitivity, and forming a preliminary set of reactive power configuration nodes according to the sensitivity; 4) performing reactive power compensation calculation on the preliminary set of reactive power configuration nodes to form a final node compensation configuration scheme. The method described in this patent is not applicable to the problem of reactive power optimization configuration of high-voltage DC converter stations based on HCC technology.

[0005] The Chinese patent also discloses a method for configuring synchronous condensers in a weak receiving-end UHV DC power grid, which includes: establishing an optimal configuration model for synchronous condensers, including taking into account the number of configurable condensers in the substation, the rotating reserve capacity of the condensers, and the transient voltage stability of the receiving-end power grid based on reducing the rotating reserve capacity of the generator sets reserved to maintain the transient voltage stability of the weak receiving-end power grid. According to the sensitivity relationship between the rotating reserve capacity of the generator sets and the dynamic reactive configuration capacity of the nodes, the optimal configuration node ranking of the condensers in the weak receiving-end power grid is determined; the optimal configuration number and capacity of the condensers in the weak receiving-end power grid are obtained by using the optimal configuration node ranking and the iteration method. The method described in the patent is specifically for the configuration method using synchronous condensers, and does not consider other reactive compensation methods. Summary of the invention

[0006] In view of the above problems, the present invention provides a DC power transmission system configuration circuit, the circuit comprising an HCC single-pole valve body,

[0007] The HCC unipolar valve body comprises an HCC high-pressure valve group and an HCC low-pressure valve group, and the HCC high-pressure valve group and the HCC low-pressure valve group are connected in series;

[0008] The HCC high-pressure valve group includes at least two high-pressure valve sections, and the high-pressure valve section includes three first branches connected in parallel; the HCC low-pressure valve group includes at least two low-pressure valve sections, and the low-pressure valve section includes three second branches connected in parallel; two IGCT devices connected in series are arranged on the first branch and the second branch; a high-pressure valve converter transformer is connected to the high-pressure valve section, and a low-pressure valve converter transformer is connected to the low-pressure valve section, and an AC filter and a reactive compensation group are connected to the AC busbars of the HCC high-pressure valve group and the HCC low-pressure valve group.

[0009] Preferably, the HCC high-pressure valve group includes a first bridge arm, a second bridge arm and a third bridge arm, and the two high-pressure valve sections share the second bridge arm.

[0010] Preferably, one of the high-pressure valve sections is arranged between the first bridge arm and the second bridge arm; and the other high-pressure valve section is arranged between the second bridge arm and the third bridge arm.

[0011] Preferably, the HCC low-pressure valve group includes a fourth bridge arm, a fifth bridge arm and a sixth bridge arm, and the two low-pressure valve sections share the fifth bridge arm.

[0012] Preferably, one of the low-pressure valve sections is arranged between the fourth bridge arm and the fifth bridge arm; the other low-pressure valve section is arranged between the fifth bridge arm and the sixth bridge arm.

[0013] Preferably, the AC busbars of the HCC high-pressure valve group and the HCC low-pressure valve group are also connected to a grid access point.

[0014] Preferably, the input ends of the high-voltage valve converter transformer are respectively connected to the corresponding first branches; the input ends of the low-voltage valve converter transformer are respectively connected to the corresponding second branches.

[0015] The present invention also provides a method for configuring a DC transmission system, the method comprising:

[0016] Control the HCC high pressure valve group and the HCC low pressure valve group to convert the DC voltage into AC voltage;

[0017] The harmonics in part of the AC voltage are offset by the high-voltage valve converter transformer and the low-voltage valve converter transformer;

[0018] The AC filter and reactive power compensation group are controlled to fully compensate the remaining harmonics in the AC voltage.

[0019] Preferably, the HCC high-pressure valve group and the HCC low-pressure valve group convert direct current into alternating current through IGCT devices.

[0020] The present invention also provides a DC power transmission system configuration system, the system comprising a conversion module, an offset module and a compensation module;

[0021] The conversion module is used to convert the DC voltage of the HCC high-pressure valve group and the HCC low-pressure valve group into AC voltage;

[0022] The offset module is used to offset the harmonics in part of the AC voltage through the high-voltage valve converter transformer and the low-voltage valve converter transformer;

[0023] The compensation module is used to completely compensate for the remaining harmonics in the AC voltage.

[0024] The present invention has the following beneficial effects:

[0025] The present invention is directed to a novel HCC type high-voltage direct current transmission system. Because it adopts a turn-off device IGCT and has a turn-off function, its arc extinction angle can be much smaller than that of a high-voltage direct current transmission system based on a thyristor, thereby ensuring safety and reliability. The configuration method of its AC filter and reactive power compensation group may be different from that of a conventional high-voltage direct current transmission system based on a thyristor.

[0026] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 A circuit diagram of a DC power transmission system configuration in an embodiment of the present invention is shown;

[0029] Figure 2 A diagram showing a method for configuring a DC power transmission system according to an embodiment of the present invention is shown;

[0030] Figure 3 A configuration system diagram of a DC power transmission system according to an embodiment of the present invention is shown;

[0031] In the figure: 1. HCC single-pole valve body; 2. HCC high-pressure valve group; 3. HCC low-pressure valve group; 4. High-pressure valve converter transformer; 5. Low-pressure valve converter transformer; 6. AC filter; 7. Grid access point. DETAILED DESCRIPTION

[0032] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as being limited to the examples set forth herein; on the contrary, these embodiments are provided so that the present disclosure will be more comprehensive and complete, and the concepts of the example embodiments are fully conveyed to those skilled in the art. The described features, structures, or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced while omitting one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known technical solutions are not shown or described in detail to avoid obscuring various aspects of the present disclosure.

[0033] In addition, the accompanying drawings are only schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or implemented in one or more hardware units or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices.

[0034] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the steps. For example, some steps may be decomposed, while some steps may be combined or partially combined, so the actual execution order may change according to the actual situation.

[0035] The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example.

[0036] In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or sub-modules is not necessarily limited to those steps or sub-modules explicitly listed, but may include other steps or sub-modules not explicitly listed or inherent to these processes, methods, products, or apparatuses.

[0037] like Figure 1 As shown, the present invention proposes a DC power transmission system configuration circuit, the circuit includes an HCC (Hybrid Commutated Converter) unipolar valve body 1, the HCC unipolar valve body 1 includes an HCC high-pressure valve group 2 and an HCC low-pressure valve group 3, the HCC high-pressure valve group 2 and the HCC low-pressure valve group 3 are connected in series, and the AC busbars of the HCC high-pressure valve group 2 and the HCC low-pressure valve group 3 are also connected to a grid access point 7. In this embodiment, the HCC high-pressure valve group 2 and the HCC low-pressure valve group 3 have self-shutoff capabilities, so when the system is running, the arc extinction angle can be greatly reduced compared to conventional valves, and it can also operate normally without causing commutation failure problems, so the demand for reactive power compensation and filters is greatly reduced. From the conventional thyristor-based gamma angle of about 17 degrees, it is reduced to a minimum of 5 degrees. The capacity of the reactive power compensation group and the AC filter 6 can be reduced by 20%, which can meet the requirements of relevant harmonic national standards.

[0038] The HCC high-pressure valve group 2 includes a first bridge arm, a second bridge arm and a third bridge arm, and the two high-pressure valve sections share the second bridge arm. The HCC high-pressure valve group 2 includes at least two high-pressure valve sections, and the high-pressure valve sections include three first branches connected in parallel with each other; one of the high-pressure valve sections is arranged between the first bridge arm and the second bridge arm; and the other high-pressure valve section is arranged between the second bridge arm and the third bridge arm. In this embodiment, the first bridge arm is connected to a voltage of +800KV, the second bridge arm is connected to a voltage of +600KV, and the third bridge arm is connected to a voltage of +400KV.

[0039] The HCC low-pressure valve group 3 includes a fourth bridge arm, a fifth bridge arm and a sixth bridge arm, and the two low-pressure valve sections share the fifth bridge arm. The HCC low-pressure valve group 3 includes at least two low-pressure valve sections, and the low-pressure valve sections include three second branches connected in parallel with each other, one of which is arranged between the fourth bridge arm and the fifth bridge arm; and the other low-pressure valve section is arranged between the fifth bridge arm and the sixth bridge arm. In this embodiment, the fourth bridge arm is connected to a voltage of +400KV, and the fifth bridge arm is connected to a voltage of +200KV.

[0040] In this embodiment, the first branch in one of the high-pressure valve sections includes a first first branch, a second first branch and a third first branch; the anode of one of the IGCT devices in the first first branch, the second first branch and the third first branch is connected to the first bridge arm, and the cathode of another IGCT device is connected to the second bridge arm; the first branch in another high-pressure valve section includes a fourth first branch, a fifth first branch and a sixth first branch, the anode of one of the IGCT devices in the fourth first branch, the fifth first branch and the sixth first branch is connected to the second bridge arm, and the cathode of another IGCT device is connected to the third bridge arm. In this embodiment, the second branch in one low-pressure valve section includes a first second branch, a second second branch and a third second branch; the anode of one of the IGCT devices in the first second branch, the second second branch and the third second branch is connected to the fourth bridge arm, and the cathode of another IGCT device is connected to the fifth bridge arm; the second branch in another low-pressure valve section includes a fourth second branch, a fifth second branch and a sixth second branch; the anode of one of the IGCT devices in the fourth second branch, the fifth second branch and the sixth second branch is connected to the fifth bridge arm, and the cathode of another IGCT device is connected to the sixth bridge arm; the fifth first branch is connected to the second second branch, and the fifth second branch is grounded.

[0041] The first branch located in the middle of the lower high-pressure valve section is connected to the second branch located in the middle of the upper low-pressure valve section, and the second branch located in the middle of the lower low-pressure valve section is grounded.

[0042] Two IGCT devices are provided in series on the first branch and the second branch; a high-pressure valve converter transformer 4 is connected to the high-pressure valve section, a low-pressure valve converter transformer 5 is connected to the low-pressure valve section, and an AC filter 6 and a reactive power compensation group are connected to the AC busbars of the HCC high-pressure valve group 2 and the HCC low-pressure valve group 3. The input end of the high-pressure valve converter transformer 4 is respectively connected to the corresponding first branch; the input end of the low-pressure valve converter transformer 5 is respectively connected to the corresponding second branch.

[0043] like Figure 2 As shown, the present invention also proposes a method for configuring a DC transmission system, the method comprising the following steps:

[0044] S1, control HCC high pressure valve group 2 and HCC low pressure valve group 3 to convert DC voltage into AC voltage; HCC high pressure valve group 2 and HCC low pressure valve group 3 convert DC power into AC power through IGCT devices;

[0045] S2, offsetting some harmonics in the AC voltage through the high-voltage valve converter transformer 4 and the low-voltage valve converter transformer 5;

[0046] S3, controlling the AC filter 6 and the reactive power compensation group to completely compensate for the remaining harmonics in the AC voltage.

[0047] like Figure 3 As shown, the present invention also proposes a DC power transmission system configuration system, the system comprising a conversion module 10, an offset module 20 and a compensation module 30;

[0048] The conversion module 10 is used to convert the DC voltage of the HCC high pressure valve group 2 and the HCC low pressure valve group 3 into AC voltage;

[0049] The offset module 20 is used to offset the harmonics in part of the AC voltage through the high-voltage valve converter transformer 4 and the low-voltage valve converter transformer 5;

[0050] The compensation module 30 is used to completely compensate for the remaining harmonics in the AC voltage.

[0051] Those skilled in the art should understand that although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible to modify the technical solutions described in the aforementioned embodiments, or to make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A DC power transmission system configuration circuit, the circuit comprising a HCC unipolar valve body (1), characterized in that: The HCC single-pole valve body (1) comprises an HCC high-pressure valve group (2) and an HCC low-pressure valve group (3), wherein the HCC high-pressure valve group (2) and the HCC low-pressure valve group (3) are connected in series; The HCC high-pressure valve group (2) comprises at least two high-pressure valve sections, each of which comprises three first branches connected in parallel; the HCC low-pressure valve group (3) comprises at least two low-pressure valve sections, each of which comprises three second branches connected in parallel; two IGCT devices connected in series are arranged on each of the first branch and the second branch; a high-pressure valve converter transformer (4) is connected to the high-pressure valve section, and a low-pressure valve converter transformer (5) is connected to the low-pressure valve section; and an AC filter (6) and a reactive power compensation group are connected to the AC busbars of the HCC high-pressure valve group (2) and the HCC low-pressure valve group (3).

2. The DC power transmission system configuration circuit according to claim 1, characterized in that: The HCC high-pressure valve group (2) comprises a first bridge arm, a second bridge arm and a third bridge arm, and the two high-pressure valve sections share the second bridge arm.

3. The DC power transmission system configuration circuit according to claim 2, characterized in that: One of the high-pressure valve sections is arranged between the first bridge arm and the second bridge arm; the other high-pressure valve section is arranged between the second bridge arm and the third bridge arm.

4. The DC power transmission system configuration circuit according to claim 2, characterized in that: The HCC low-pressure valve group (3) comprises a fourth bridge arm, a fifth bridge arm and a sixth bridge arm, and the two low-pressure valve sections share the fifth bridge arm.

5. The DC power transmission system configuration circuit according to claim 4, characterized in that: One of the low-pressure valve sections is arranged between the fourth bridge arm and the fifth bridge arm; the other low-pressure valve section is arranged between the fifth bridge arm and the sixth bridge arm.

6. The DC power transmission system configuration circuit according to claim 1, characterized in that: The AC busbars of the HCC high-pressure valve group (2) and the HCC low-pressure valve group (3) are also connected to a power grid access point (7).

7. The DC power transmission system configuration circuit according to claim 1, characterized in that: The input ends of the high-voltage valve converter transformer (4) are respectively connected to the corresponding first branches; the input ends of the low-voltage valve converter transformer (5) are respectively connected to the corresponding second branches.

8. A method for configuring a direct current transmission system, characterized in that: The method comprises: Controlling the HCC high pressure valve group (2) and the HCC low pressure valve group (3) to convert the DC voltage into AC voltage; The harmonics in a part of the AC voltage are offset by the high-voltage valve converter transformer (4) and the low-voltage valve converter transformer (5); The AC filter (6) and the reactive power compensation group are controlled to fully compensate for the remaining harmonics in the AC voltage.

9. The method for configuring a DC power transmission system according to claim 8, characterized in that: The HCC high-pressure valve group (2) and the HCC low-pressure valve group (3) convert direct current into alternating current through IGCT devices.

10. A DC transmission system configuration system, characterized in that: The system includes a conversion module, an offset module and a compensation module; The conversion module is used to convert the direct current voltage of the HCC high-pressure valve group (2) and the HCC low-pressure valve group (3) into alternating current voltage; The offset module is used to offset the harmonics in part of the AC voltage through a high-voltage valve converter transformer (4) and a low-voltage valve converter transformer (5); The compensation module is used to completely compensate for the remaining harmonics in the AC voltage.

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