A flexible DC converter valve series module electrical voltage balancing device

Abstract

The present invention discloses a flexible DC converter valve series module electrical voltage balancing device, including a valve tower waterway and a submodule, the valve tower waterway including a valve tower interlayer horizontal water pipe, a valve tower interlayer vertical water pipe and a valve tower ground vertical water pipe; the submodule's inlet and return water branch pipe is connected in parallel to the valve tower interlayer horizontal water pipe, the valve tower interlayer horizontal water pipe is connected in parallel to the valve tower interlayer vertical water pipe, and the valve tower interlayer vertical water pipe is connected to the valve tower ground vertical water pipe; the valve tower interlayer horizontal water pipe has n layers, the length of the valve tower interlayer vertical water pipe connected in parallel to the first and nth valve tower interlayer horizontal water pipes is L, and the length of the valve tower interlayer vertical water pipe connected in parallel to the 2nd to (n-1)th valve tower interlayer horizontal water pipes is 2L. The flexible DC converter valve series module electrical voltage balancing device provided by the present invention uses the valve tower waterway as a voltage balancing resistor, and further optimizes the electrical voltage balancing characteristics of the valve tower as a whole by controlling the length of the valve tower interlayer vertical water pipe.

Description

Technical Field

[0001] The present invention belongs to the technical field of converter valve voltage balancing, and in particular relates to an electrical voltage balancing device for series-connected modules of flexible direct current converter valves. Background Art

[0002] Flexible DC converter valve is the core equipment of DC transmission project. Traditional electrical voltage equalization technology uses the voltage equalization resistor inside the sub-module for natural voltage equalization. Since the water conductivity of the valve tower is relatively high and the equivalent resistance cannot be ignored, the traditional valve tower sub-module only relies on the voltage equalization resistor inside the module to achieve electrical voltage equalization, which is not ideal. As the voltage level of DC transmission projects becomes higher and higher, during the valve lock waiting stage, the sub-module voltage dispersion caused by uneven voltage, sub-module power failure and sub-module overvoltage problems become more and more prominent. Summary of the invention

[0003] The present invention provides an electrical voltage balancing device for a flexible DC converter valve series module, which utilizes the equivalent resistance of a valve tower water channel to balance the equivalent impedance of each submodule, thereby achieving a voltage balancing effect for the entire valve tower submodule.

[0004] The present invention is achieved through the following technical solutions:

[0005] A flexible DC converter valve series module electrical voltage balancing device, comprising a valve tower water path and a submodule, wherein the valve tower water path comprises a valve tower interlayer horizontal water pipe, a valve tower interlayer vertical water pipe and a valve tower to ground vertical water pipe;

[0006] The water inlet and return branches of the submodules are connected in parallel to the horizontal water pipes between the valve tower layers, the horizontal water pipes between the valve tower layers are connected in parallel to the vertical water pipes between the valve tower layers, and the vertical water pipes between the valve tower layers are connected to the vertical water pipes on the ground of the valve tower;

[0007] The valve tower interlayer horizontal water pipes have n layers, the valve tower interlayer vertical water pipes connected in parallel on the first and nth valve tower interlayer horizontal water pipes are all L in length, and the valve tower interlayer vertical water pipes connected in parallel on the 2nd to nth valve tower interlayer horizontal water pipes are all 2L in length.

[0008] Furthermore, equipotential needles are provided at both ends of the horizontal water pipes between the valve tower layers.

[0009] Furthermore, the length of the vertical water pipes between the valve tower layers can be adjusted during design.

[0010] Furthermore, the electrical circuits of the submodules are connected in spiral series.

[0011] Furthermore, there are one group of valve tower interlayer vertical water pipes connected in parallel to the first and nth valve tower interlayer horizontal water pipes.

[0012] Furthermore, there are two groups of vertical water pipes between valve tower layers connected in parallel to the horizontal water pipes between the 2nd to (n-1)th valve tower layers.

[0013] Furthermore, all the submodules connected in series in the same valve layer are equivalent to resistors and capacitors connected in parallel.

[0014] Furthermore, the resistors and capacitors connected in parallel in the same valve layer are connected in series with the resistors and capacitors connected in parallel in another adjacent valve layer to form a spiral series electrical structure.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The flexible DC converter valve series module electrical voltage balancing device provided by the embodiment of the present invention has the following features: the inlet and return water branches of the submodules are connected in parallel to the horizontal water pipes between valve tower layers; the horizontal water pipes between valve tower layers are connected in parallel to the vertical water pipes between valve tower layers; the valve tower water channel is used as a voltage balancing resistor; and the electrical voltage balancing characteristics of the valve tower as a whole can be further optimized by controlling the length of the vertical water pipes between valve tower layers; the design is simple and the process is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0018] Figure 1 It is a schematic diagram of the physical model of the valve tower water channel of an embodiment of the present invention.

[0019] Figure 2 1 is an electrical equivalent diagram of the converter valve according to an embodiment of the present invention.

[0020] In the figure: 1 is a submodule; 2 is a vertical water pipe between valve tower layers; 3 is a horizontal water pipe between valve tower layers; 4 is a vertical water pipe between the valve tower and the ground; 5 is an equipotential needle; 6 is the equivalent resistance and capacitance of the valve layer submodule. DETAILED DESCRIPTION

[0021] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0022] The following detailed description is an exemplary description, which is intended to provide further detailed description of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used in the present invention are only for describing specific embodiments, and are not intended to limit exemplary embodiments according to the present invention.

[0023] The present invention provides an electrical voltage balancing device for a series connection module of a flexible DC converter valve, which adopts a water circuit electrical clamping method to evenly distribute the water circuit equivalent impedance on the valve tower to each layer of the valve tower, so that the equivalent resistance of the series connection submodules 1 on each layer of the valve tower is consistent, thereby having better electrical voltage balancing characteristics;

[0024] like Figure 1 As shown, the electrical voltage balancing device of the flexible DC converter valve series module includes a valve tower water circuit and a submodule 1. The valve tower water circuit adopts a double-row multi-layer arrangement, and the electrical circuit of each submodule 1 is spirally connected in series. The valve tower water circuit includes a horizontal water pipe 3 between valve tower layers, a vertical water pipe 2 between valve tower layers, and a vertical water pipe 4 between valve towers and the ground; the inlet and return water branch pipes of the submodule 1 are connected in parallel to the horizontal water pipe 3 between valve tower layers, the horizontal water pipe 3 between valve tower layers is connected in parallel with the vertical water pipe 2 between valve tower layers, the vertical water pipe 2 between valve tower layers is connected with the vertical water pipe 4 between valve tower layers, and equipotential needles 5 are arranged at both ends of the horizontal water pipe 3 between valve tower layers.

[0025] like Figure 1 As shown, the valve layers are arranged in order from bottom to top as layer 1, layer 2, ... layer n; there are n layers of horizontal water pipes 3 between valve tower layers, one group of vertical water pipes 2 between valve tower layers are connected in parallel to the horizontal water pipes 3 between the first and nth layers of valve tower layers, and two groups of vertical water pipes 2 between valve tower layers are connected in parallel to the horizontal water pipes 3 between the 2nd to n-1st layers of valve tower layers; each group of vertical water pipes 2 between valve tower layers can include one or more. Its equivalent principle diagram is shown in Figure 2 As shown in the figure, the valve layer sub-module equivalent resistor and capacitor 6 is an overall equivalent schematic diagram of the sub-modules 1 of the same valve layer connected in series. The sub-modules in the same valve layer are equivalent to parallel resistors and capacitors after being connected in series. Then the parallel resistors and capacitors in the valve layer are connected in series with the parallel resistors and capacitors in another adjacent valve layer, and so on, to form a spiral series electrical structure.

[0026] In order to make the resistance of the parallel vertical water pipes 2 between valve tower layers of each valve layer equal, according to the water resistance formula R=ρ*L / S; ρ is the electrical conductivity, L is the water pipe length, S is the water pipe cross-sectional area, the length of the vertical water pipes 2 between valve tower layers connected in parallel on the horizontal water pipes 3 between valve tower layers of the first and nth layers is L, and the length of the vertical water pipes 2 between valve tower layers connected in parallel on the horizontal water pipes 3 between valve tower layers of the 2nd to (n-1)th layers is 2L.

[0027] In this embodiment, when calculating the impedance of each part of the water channel of the valve tower, the horizontal water pipe 3 between the valve tower layers and the inlet and return water branches of the sub-module 1 have no effect on the overall uneven pressure characteristics of the valve tower. Therefore, the dimensions of the horizontal water pipe 3 between the valve tower layers and the inlet and return water branches of the sub-module 1 are confirmed according to the structural layout and thermal design; the length of the vertical water pipe 4 of the valve tower to the ground is usually longer, and the water resistance is at the level of hundreds of megohms, and the influence of the electrical uneven pressure on the valve tower can be ignored; therefore, it is only necessary to calculate the length of the vertical water pipe 2 between the valve tower layers in detail to achieve the purpose of controlling the overall uneven pressure of the valve tower.

[0028] The calculation method is: 1) According to the valve tower water channel physical model and equivalent circuit, confirm the number of vertical water pipes 2 connected in parallel between valve tower layers on each valve layer; 2) According to the equivalent circuit diagram, make the equivalent resistance of the vertical water pipes 2 connected in parallel between valve tower layers on each valve layer equal; 3) According to the equivalent resistance formula R=ρ*L / S; ρ is the conductivity, L is the water pipe length, S is the water pipe cross-sectional area, and the water pipe length L is inferred.

[0029] It is known from common technical knowledge that the present invention can be implemented by other embodiments that do not deviate from its spirit or essential features. Therefore, the above disclosed embodiments are only illustrative in all respects and are not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are included in the present invention.

Claims

1. An electrical voltage balancing device for series-connected modules of flexible DC converter valves, characterized in that: It comprises a valve tower water circuit and a submodule (1), wherein the valve tower water circuit comprises a horizontal water pipe (3) between valve tower layers, a vertical water pipe (2) between valve tower layers, and a vertical water pipe (4) between the valve tower and the ground; The water inlet and return branches of the submodule (1) are connected in parallel to the horizontal water pipe (3) between valve tower layers, the horizontal water pipe (3) between valve tower layers is connected in parallel to the vertical water pipe (2) between valve tower layers, and the vertical water pipe (2) between valve tower layers is connected to the vertical water pipe (4) between valve tower layers; The valve tower interlayer horizontal water pipe (3) has n layers, the valve tower interlayer vertical water pipes (2) connected in parallel to the first and nth valve tower interlayer horizontal water pipes (3) are both L in length, and the valve tower interlayer vertical water pipes (2) connected in parallel to the 2nd to (n-1)th valve tower interlayer horizontal water pipes (3) are both 2L in length; There are one group of valve tower interlayer vertical water pipes (2) connected in parallel to the first and nth valve tower interlayer horizontal water pipes (3); There are two groups of valve tower interlayer vertical water pipes (2) connected in parallel to the 2nd to (n-1)th valve tower interlayer horizontal water pipes (3).

2. The electrical voltage balancing device for series-connected flexible DC converter valve modules according to claim 1, characterized in that: Equipotential needles (5) are provided at both ends of the valve tower interlayer transverse water pipe (3).

3. The electrical voltage balancing device for series-connected flexible DC converter valve modules according to claim 1, characterized in that: The length of the vertical water pipe (2) between the valve tower layers can be adjusted during design.

4. The electrical voltage balancing device for series-connected flexible DC converter valve modules according to claim 1, characterized in that: The electrical circuits of the submodules (1) are spirally connected in series.

5. The electrical voltage balancing device for series-connected flexible DC converter valve modules according to claim 4, characterized in that: All the submodules (1) connected in series in the same valve layer are equivalent to resistors and capacitors connected in parallel.

6. The electrical voltage balancing device for series-connected flexible DC converter valve modules according to claim 5, characterized in that: The resistors and capacitors connected in parallel in the same valve layer are connected in series with the resistors and capacitors connected in parallel in another adjacent valve layer to form a spiral series electrical structure.

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