A method and system for detecting AC section power failure in a converter

Abstract

This invention provides a method and system for determining AC section power failure in a converter, belonging to the field of power technology. The method includes: determining the voltage equations of the admittance matrix at the converter station, the intermediate station, and the system station based on the network topology of the DC converter station, the opposite substation, and the downstream substation; then, using the node injection current method, determining the connectivity between the upstream and downstream components of the DC converter station, the opposite substation, and the downstream substation's upstream component and the AC system; and finally, determining the power failure state of the converter and the AC system based on these connectivity states. This invention improves the determination efficiency while ensuring safety and reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric power, in particular to a method and system for judging loss of AC connection of AC section of converter. BACKGROUND

[0002] With the rapid development of DC power transmission technology, DC power transmission has gradually become an important means of power transmission. However, when the DC receiving end converter station has no AC channel for sending out, the converter station equipment (such as converter valve and lightning arrester) is damaged due to overvoltage. When the DC receiving end has few AC outgoing lines (generally no more than two), an AC section loss of power discrimination system is usually configured to send AC section loss of power state information to the DC control protection system to lock the DC when the running converter station loses connection with the AC system.

[0003] At present, the loss of connection between the DC converter station side and the AC section is generally judged by the last circuit breaker in the DC control protection system, and the loss of connection between the opposite side of the converter station or the next level substation side and the AC system is generally judged by the AC section loss of power discrimination device. The existing AC section loss of power discrimination mainly has the following deficiencies:

[0004] Firstly, in some schemes, the DC control protection system and the AC section loss of power discrimination device on the opposite side of the converter station only consider the loss of connection between the AC section and the system on the side, and do not consider the case that each line of the two-line AC section is disconnected; secondly, in some projects, the AC section loss of power discrimination system only considers the switch of the AC outgoing line (using 3 / 2 wiring), and does not consider the operating state of the same string element, which cannot adapt to some situations; thirdly, some projects use the bus regression method to avoid the problem described in the second item, but this method still needs to judge the connection relationship between the AC line and the two buses and the connection relationship between the two buses, which is still complicated and cannot form a complete and unified logical expression relationship; fourthly, for the AC section discrimination of the multi-level station site series long chain structure, some schemes propose a distributed architecture, but there is a centralized master station, the connection relationship of the lines on both sides of each substation is judged by the substation and sent to the master station, and then the master station comprehensively considers the information of each substation to finally judge whether the converter station loses connection with the AC section. This way is not conducive to the standardization and unification of the program because the master station and the substation programs are inconsistent; fifthly, the existing AC section loss of power discrimination scheme considers the outgoing line of the converter station as a total AC section, and cannot prevent the loss of connection between the converter and the AC system. SUMMARY

[0005] The purpose of the present application is to provide a method and system for judging loss of AC connection of AC section of converter, which can improve the discrimination efficiency under the premise of ensuring safety and reliability.

[0006] To achieve the above-mentioned purpose, the present application provides the following scheme:

[0007] A method for determining AC section power failure of a converter is provided for identifying the power failure status of the AC section at the DC converter station side in a DC transmission system. The DC transmission system includes a DC converter station, a corresponding substation, a downstream substation, and an AC system connected in sequence. The method for determining AC section power failure of the converter includes:

[0008] Obtain the network topology of the DC converter station, the opposite substation, and the downstream substation;

[0009] The voltage equations of the admittance matrix of the converter station side nodes are determined based on the network topology of the DC converter station.

[0010] Determine the voltage equation of the admittance matrix of the intermediate station side node based on the network topology of the opposite substation.

[0011] Determine the system station-side node admittance matrix and voltage equation based on the network topology of the lower-level substation.

[0012] Based on the voltage equation of the admittance matrix of the converter station side node, the connection state of the upper-level component and the lower-level component of the DC converter station is determined by the node injection current method; the upper-level component of the DC converter station is the converter, and the lower-level component of the DC converter station is the AC line between the DC converter station and the substation on the opposite side.

[0013] Based on the voltage equation of the admittance matrix of the intermediate station side node, the connection state of the upper-level component and the lower-level component of the opposite substation is determined by the node injection current method; the upper-level component of the opposite substation is the lower-level component of the DC converter station, and the lower-level component of the opposite substation is the AC line between the opposite substation and the lower-level substation.

[0014] Based on the voltage equation of the admittance matrix of the station-side nodes of the system, the connection status between the upstream components of the lower-level substation and the AC system is determined by the node injection current method; the upstream components of the lower-level substation are the downstream components of the opposite substation.

[0015] The de-energization status of the converter and the AC system is determined based on the connection status between the upstream and downstream components of the DC converter station, the connection status between the upstream and downstream components of the opposite substation, and the connection status between the upstream components of the downstream substation and the AC system.

[0016] To achieve the above objectives, the present invention also provides the following solution:

[0017] A converter AC section power failure detection system includes:

[0018] The system substation-side discrimination device is used to determine the voltage equation of the system substation-side node admittance matrix based on the network topology of the lower-level substation, and to determine the connection status between the upper-level components of the lower-level substation and the AC system based on the voltage equation of the system substation-side node admittance matrix using the node injection current method; the upper-level components of the lower-level substation are the lower-level components of the opposite substation.

[0019] The intermediate station-side discrimination device, connected to the system station-side discrimination device, is used to determine the intermediate station-side node admittance matrix voltage equation based on the network topology of the opposite substation, and, based on the intermediate station-side node admittance matrix voltage equation, to determine the connectivity status of the upstream components and downstream components of the opposite substation using the node injection current method; the upstream components of the opposite substation are downstream components of the DC converter station, and the downstream components of the opposite substation are the AC lines between the opposite substation and the downstream substation.

[0020] A converter station-side discrimination device, connected to the intermediate station-side discrimination device, is used to determine the voltage equation of the converter station-side node admittance matrix based on the network topology of the DC converter station, and, based on the voltage equation of the converter station-side node admittance matrix, to determine the connection state of the upstream and downstream components of the DC converter station using the node injection current method, so as to determine the de-energization state of the converter and the AC system; the upstream component of the DC converter station is the converter, and the downstream component of the DC converter station is the AC line between the DC converter station and the opposite substation.

[0021] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0022] This invention determines the voltage equations of the admittance matrix at the converter station, intermediate station, and system station based on the network topology of the DC converter station, the opposite substation, and the downstream substation. Then, using the node injection current method, it determines the connectivity between upstream and downstream components of the DC converter station, the upstream and downstream components of the opposite substation, and the connectivity between the upstream components of the downstream substation and the AC system. Finally, it determines the de-energization state of the converter and the AC system. The injection current method based on the node admittance matrix voltage equations is used to determine the connectivity between upstream and downstream components within the station. The physical meaning is clear, the admittance matrix establishment process is simple, and the calculation is convenient. Furthermore, the decentralized distributed architecture improves the efficiency of AC section de-energization detection of the converter while ensuring safety and reliability. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This diagram shows the connection between one side of a DC converter station and the AC system, as well as the wiring diagram within the AC station.

[0025] Figure 2 This is a schematic diagram illustrating the structure and communication of an AC section power failure detection system.

[0026] Figure 3 This is a flowchart of the AC section power failure detection method for converters according to the present invention;

[0027] Figure 4 This is a schematic diagram of the AC section power failure detection system for the converter of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The purpose of this invention is to provide a converter AC section power failure detection method and system based on node admittance matrix and decentralized distributed architecture. At the same time, the injection current method based on node admittance matrix is ​​used to determine the connection relationship between upstream and downstream components in the station. The physical meaning is clear, the admittance matrix is ​​simple to form and easy to calculate. The decentralized distributed architecture allows the programs of each station device to be standardized and unified, which greatly improves the efficiency of system construction and testing while ensuring safety and reliability.

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Example 1

[0032] like Figure 1 The diagram shows an AC substation opposite the AC outgoing line of a converter station (inverter station). All wiring within the station is in 3 / 2 configuration. Substation A (converter station) is connected to substation B via lines L1 and L2. Substation B is then connected to substation C via lines L3 and L4. Substation C has multiple lines connected to the system (except for the two lines shown in the diagram, the other lines are not drawn).

[0033] In this embodiment, substation A is the DC converter station, substation B is the opposite substation, and substation C is the downstream substation. AC section power failure detection devices are configured at the converter station, the opposite substation, and the downstream substation requiring detection. Each station's AC section power failure detection device has two upstream components (the one closer to the converter station side is the upstream component) and two downstream components (the one closer to the AC system side is the downstream component). The AC section power failure detection devices at each station are connected in series via a 2M multiplexed optical fiber. All AC section power failure detection devices use the same software version. Based on the topology relationships of each station, substation A is defined as the converter station side, substation B as the intermediate station side, and substation C as the system station side, as follows. Figure 2 As shown.

[0034] In one example, the converter station (substation A) is connected to substation B via only two AC lines, substation B is connected to substation C via only two AC lines, and substation C is connected to the AC system via multiple AC lines.

[0035] like Figure 3 As shown, this embodiment provides a method for determining AC section power failure in a converter, including:

[0036] S1: Obtain the network topology of the DC converter station, the opposite substation, and the downstream substation.

[0037] In this embodiment, the upstream components of the converter station side (DC converter station) are two DC converters, denoted as the first converter H1 and the second converter H2, respectively. The downstream components are the AC outgoing lines of the converter station, denoted as L1 and L2, respectively. The upstream components of the intermediate station side (opposite substation) are the AC lines connected to the converter station direction, i.e., the downstream components of the converter station side, namely L1 and L2. The downstream components are the AC lines connected to the AC system direction, denoted as L3 and L4, respectively. The upstream components of the system station side (lower-level substation) are the AC lines connected to the converter station direction, i.e., the downstream components of the intermediate station, namely L3 and L4. The downstream components are set to none.

[0038] S2: Determine the voltage equation of the admittance matrix of the converter station side node based on the network topology of the DC converter station.

[0039] S3: Determine the voltage equation of the admittance matrix of the intermediate station side node based on the network topology of the opposite substation.

[0040] S4: Determine the voltage equation of the system station-side node admittance matrix based on the network topology of the lower-level substation.

[0041] Specifically, the initial node admittance matrix of the station is formed based on the station topology and the switch position status signals of the AC lines in the accessed AC sections. The values ​​of each element in the node admittance matrix are updated in real time based on the protection trip signals of the AC lines in the accessed AC sections and the switch position status after the switch position trip signals, thus forming the node admittance matrix after the trip.

[0042] In this embodiment, each switch in the station is considered as a branch, and each upstream and downstream component of each station is also considered as a branch. The busbar and the connection point between two switches are all considered as nodes. For the system station side, only the switches in the bay where the relevant upstream line is located need to be considered. The busbar is considered to be directly connected to the system, so an equivalent system-to-ground branch is added to the busbar. Components (lines or main transformers) in the same string as the relevant upstream line are also considered to be directly connected to the system (manual value assignment can be made according to the actual situation), and are also regarded as an equivalent system-to-ground branch. After the above processing, it is ensured that the initial and modified node admittance matrices are invertible.

[0043] Based on the topological connections, the node admittance matrix and voltage equations can be directly constructed:

[0044]

[0045] Where n is the number of nodes in the DC converter station (or the opposite substation or the downstream substation), and V n Let I be the voltage at node n. n Y is the injected current at node n. nn The elements of the node admittance matrix on the converter station side (or the opposite substation or the downstream substation), with diagonal elements Y ii Let Y be the self-admittance of node i, whose value is equal to the sum of the admittances of all branches connected to node i, and the off-diagonal element Y. ij Y is the mutual admittance between node i and node j, and its value is equal to the negative of the admittance of the branch directly connecting node i and node j. If there is no direct branch between node i and node j, then Y ij =0. In the network topology of the DC converter station, switches, upstream components, and downstream components are all branches, and the connection points between buses and switches are nodes.

[0046] The elements of the admittance matrix can be easily obtained intuitively from the network diagram and branch parameters, making the program for forming the nodal admittance matrix relatively simple. The admittance matrix is ​​a sparse matrix, with most elements being 0. Therefore, excluding the storage and calculation of zero elements in the program design can significantly save storage units and improve computation speed.

[0047] Based on the above method and the initial network topology and the states of each switch, the initial admittance matrix Y of the system station side is constructed respectively.系统侧 Initial admittance matrix Y of intermediate station side 中间侧 and the initial admittance matrix Y on the converter station side 换流站侧 Then, construct the admittance matrix after the switch trips: if a switch trips, it is considered to be in the open state, so the admittance of that switch branch is set to 0, and the values ​​of the elements of the corresponding nodes of that branch in the initial admittance matrix are modified to form the modified admittance matrix, denoted as Y'. 系统侧 Y' 中间站侧 Y' 换流站侧 .

[0048] Based on the physical meaning of the nodal admittance matrix, to determine whether two nodes are connected, a current can be injected into one node. If the other node generates a voltage, then they are connected; otherwise, they are disconnected. In the voltage equation of the nodal admittance matrix, let the injected current at a certain node be 1, i.e., let I... i =1=1 The injected current at all other nodes is 0, i.e., I j =0, j≠i. Find the target node voltage V. j,j≠i If we get V j,j≠i >ε, where ε is a set voltage threshold. A small value indicates that node i and node j are connected.

[0049] S5: Based on the voltage equation of the admittance matrix of the converter station side node, the connection state of the upper-level components and lower-level components of the DC converter station is determined using the node injection current method. The upper-level component of the DC converter station is the converter, and the lower-level component is the AC line between the DC converter station and the opposite substation. The DC converter station includes a first upper-level component node, a first lower-level component node, and nodes within the converter station. The first upper-level component node is the node of the converter within the DC converter station, and the first lower-level component node is the node of the lower-level component within the DC converter station.

[0050] S5 specifically includes:

[0051] For any first-level upper-level component node, the injection current of the first-level upper-level component node is set to 1, and the injection current of the remaining first-level upper-level component nodes, each first-level lower-level component node, and nodes within the converter station is set to 0.

[0052] Based on the voltage equation of the admittance matrix of the converter station side node, the voltage of each first lower-level component node is determined according to the injection current of each first upper-level component node, the injection current of each first lower-level component node, and the injection current of each node within the converter station.

[0053] Based on the voltage of each first lower-level component node, the connection status between the first upper-level component node and each first lower-level component node is determined, thereby determining the connection status between the upper-level components and lower-level components of the DC converter station. In this embodiment, for any first lower-level component node, it is determined whether the voltage of the first lower-level component node is greater than a set voltage threshold. If so, the first upper-level component node is connected to the first lower-level component node; otherwise, the first upper-level component node is disconnected from the first lower-level component node.

[0054] Furthermore, determine the connectivity relationships between two nodes of the upstream components H1 and H2 within the DC converter station and two nodes of the downstream components L1 and L2 within the station, respectively, denoted as H1×L1, H1×L2, H2×L1, and H2×L2. If H1 is connected to L1, set H1×L1 = 1; if disconnected, set H1×L1 = 0. If H1 is connected to L2, set H1×L2 = 1; if disconnected, set H1×L2 = 0. If H2 is connected to L1, set H2×L1 = 1; if disconnected, set H2×L1 = 0. If H2 is connected to L2, set H2×L2 = 1; if disconnected, set H2×L2 = 0.

[0055] S6: Based on the voltage equation of the admittance matrix of the intermediate station side node, the connection state of the upstream component and the downstream component of the opposite substation is determined using the node injection current method. The upstream component of the opposite substation is the downstream component of the DC converter station, and the downstream component of the opposite substation is the AC line between the opposite substation and the downstream substation. The opposite substation includes a second upstream component node, a second downstream component node, and nodes within the opposite substation. The second upstream component node is the node of the upstream component of the opposite substation within the opposite substation, and the second downstream component node is the node of the downstream component of the opposite substation within the opposite substation.

[0056] S6 specifically includes:

[0057] For any second-level upper-level component node, the injection current of the second-level upper-level component node is set to 1, and the injection current of the remaining second-level upper-level component nodes, each second-level lower-level component node, and each node in the substation on the opposite side is set to 0.

[0058] Based on the voltage equation of the admittance matrix of the intermediate station side node, the voltage of each second lower-level element node is determined according to the injection current of each second upper-level element node, the injection current of each second lower-level element node, and the injection current of each node in the opposite substation.

[0059] Based on the voltage of each second lower-level component node, the connection status between the second upper-level component node and each second lower-level component node is determined, thereby determining the connection status between the upper-level component and the lower-level component of the opposite substation.

[0060] Furthermore, determine the connectivity relationships between two nodes of the upper-level components L1 and L2 within the intermediate station and two nodes of the lower-level components L3 and L4 within the station, respectively, denoted as L1×L3, L1×L4, L2×L3, and L2×L4. If L1 is connected to L3, set L1×L3 = 1; if they are disconnected, set L1×L3 = 0. Similarly, if L1 is connected to L4, set L1×L4 = 1; if they are disconnected, set L1×L4 = 0. If L2 is connected to L3, set L2×L3 = 1; if they are disconnected, set L2×L3 = 0. If L2 is connected to L4, set L2×L4 = 1; if they are disconnected, set L2×L4 = 0.

[0061] S7: Based on the voltage equation of the admittance matrix of the system station-side nodes, the connection status between the upstream element of the lower-level substation and the AC system is determined using the node injection current method. The upstream element of the lower-level substation is the downstream element of the opposite substation. The lower-level substation includes a third upstream element node and a system node. The third upstream element node is the node of the upstream element of the lower-level substation within the lower-level substation, and the system node is the node connecting the lower-level substation to the AC system.

[0062] S7 specifically includes:

[0063] For any third-level upper-level component node, the injection current of the third-level upper-level component node is set to 1, and the injection current of the remaining third-level upper-level component nodes and each system node is set to 0.

[0064] Based on the voltage equation of the admittance matrix of the system station-side node, the voltage of each system node is determined according to the injection current of each third upper-level component node and the injection current of each system node.

[0065] Based on the voltage of each system node, the connection status between the third upper-level component node and each system node is determined, thereby determining the connection status between the upper-level component of the lower-level substation and the AC system.

[0066] Furthermore, the connectivity relationships between the two nodes of the upper-level components L3 and L4 within the station and the system nodes (i.e., bus nodes and line nodes in the same string directly connected to the system) are determined and denoted as L3×B. 系统 L4×B 系统 If L3 is connected to the AC system, then let L3 × B 系统 =1, otherwise disconnect from the AC system, then let L3×B 系统 =0, similarly, if L4 is connected to the AC system, then let L4 × B 系统 =1, otherwise disconnect from the AC system, then let L4×B 系统 =0.

[0067] S8: Determine the de-energization status of the converter and the AC system based on the connection status between the upstream and downstream components of the DC converter station, the connection status between the upstream and downstream components of the opposite substation, and the connection status between the upstream components of the downstream substation and the AC system.

[0068] Specifically, each station determines the connectivity between its upstream components and the AC system based on the connectivity relationships between its internal nodes and the connection relationships with the AC system sent from the next level. It then sends the connectivity relationships between its upstream components and the AC system to the upstream station, and so on, until the AC section de-energization device in the converter station determines the connectivity status of each converter with the AC system.

[0069] (1) System station side: L3×B 系统 L4×B 系统 The results are sent to the intermediate station side device at the next higher level.

[0070] (2) Intermediate station side: Based on the connection status of the upper-level components of the opposite substation and the lower-level components of the opposite substation, as well as the connection status of the upper-level components of the lower-level substation and the AC system, determine the connection status of the upper-level components of the opposite substation and the AC system.

[0071] Based on the connectivity relationships between upstream and downstream components in the opposite substation, and the connection relationships between downstream components and the AC system sent from the next-level station, the connectivity relationships between upstream components L1 and L2 in the opposite substation and the AC system are determined and denoted as L1×B. 系统 L2×B 系统 That is, L1×B 系统 =L1×L3×L3×B 系统 +L1×L4×L4×B 系统 L2×B 系统 =L2×L3×L3×B 系统 +L2×L4×L4×B 系统 If L1×B 系统 If ≥1, it indicates that L1 is connected to the AC system, L1×B 系统 =0, which means L1 is disconnected from the AC system; if L2×B 系统 If L1 × B is greater than or equal to 1, it means that L2 is connected to the AC system. 系统 =0 indicates that L2 is disconnected from the AC system. This result information is then sent to the next higher-level station device.

[0072] (3) Converter station side: Based on the connection status of the upper-level components of the DC converter station and the lower-level components of the DC converter station, as well as the connection status of the upper-level components of the opposite substation and the AC system, determine the connection status of the upper-level components of the DC converter station and the AC system, so as to determine the power outage status of the converter and the AC system.

[0073] Based on the connectivity between the converters and downstream components within the DC converter station, and the connection relationships between the downstream components from the next-level station and the AC system, the connectivity relationships between converter components H1 and H2 within this station and the AC system are determined and denoted as H1×B. 系统 H2×B 系统 That is, H1×B 系统 =H1×L1×L1×B 系统 +H1×L2×L2×B 系统 H2×B 系统 =H2×L1×L1×B 系统 +H2×L2×L2×B 系统 If H1×B 系统 If ≥1, it indicates that H1 is connected to the AC system. If H1×B 系统 =0, which means H1 is disconnected from the AC system, and a lockout command for the first converter is sent to the DC control and protection system; if H2×B 系统 If ≥1, it indicates that H2 is connected to the AC system. If H2 × B 系统 If the value is 0, it indicates that H2 is disconnected from the AC system, and a lockout command for the second converter is sent to the DC control and protection system. In other words, if the converter is disconnected from the AC system, the converter is locked out.

[0074] In summary, this invention sets up two upstream components (the one closer to the converter station) and two downstream components (the one closer to the AC system) in the AC section power failure detection device at each station. Based on the station's topology and the switch position status signals of the relevant AC sections involving the AC lines, an initial node admittance matrix is ​​formed for the station. The values ​​of each element in the node admittance matrix are updated in real time based on the protection trip signals of the relevant AC sections involving the AC lines and the switch position status after the trip signals. The connection relationship between the upstream and downstream components on the AC section is determined using the injection current method, thereby obtaining the connection relationship between the upstream component and the AC system. This connection relationship is then sent to the upstream AC section power failure device (i.e., the AC section power failure device closer to the converter station), and so on upwards until the AC section power failure device within the converter station determines the connection status of each converter with the AC system and sends it to the control and protection system. Finally, the control and protection system issues a command to block the converters that have lost contact with the AC system, preventing overvoltage risks.

[0075] To better understand the solution of the present invention, further explanation is provided below with reference to specific embodiments.

[0076] Step 1: Set the hierarchical relationship of the access elements of the AC section mains power discrimination device at each station.

[0077] The upstream components of substation A on the converter station side are two DC converters, H1 and H2, and the downstream components are the AC outgoing lines connecting substation A to substation B on the system side, L1 and L2. The upstream components of substation B on the intermediate station side are AC lines connecting to the converter station direction, L1 and L2, and the downstream components are AC lines connecting to the system direction, L3 and L4. The upstream components of substation C on the system station side are AC lines connecting to the converter station direction, L3 and L4, and there are no downstream components.

[0078] Step 2: Construct the initial admittance matrix for each station.

[0079] Construct the initial admittance matrices for three substations: substation A, substation B, and substation C. Assume... Figure 1 The admittance value of each upstream and downstream component branch in the system is 1, and the admittance value of the system to ground equivalent branch is also 1. In the initial state, all switches are in the closed state.

[0080] For substation C on the system station side, there are a total of 6 nodes, including U c1 U c2 The node is a busbar, and each needs to have an equivalent branch to ground, such as... Figure 1 The first and second system equivalent branches, and lines in the same series as the related superior lines L3 and L4, are also considered as a system-to-ground equivalent branch, such as... Figure 1 The third system equivalent branch and the fourth system equivalent branch are in the middle. Each switch is a branch, and the upper-level components L3 and L4 are branches respectively.

[0081] The admittance matrix Y of substation C can be directly constructed based on the substation's internal topology. 系统侧 ,Right now

[0082]

[0083] For substation B, there are 8 nodes, none of which are directly connected to the AC system. Each switch is a branch, and the upstream and downstream lines L1, L2, L3, and L4 are each branches. Based on the substation topology, the admittance matrix Y of substation B can be directly constructed. 中间侧 ,Right now

[0084]

[0085] For substation A, there are 6 nodes, none of which are directly connected to the AC system. Each switch is a branch, and the upstream and downstream components H1, H2, L1, and L2 are each a branch.

[0086] The admittance matrix Y of substation A can be directly constructed based on the substation topology. 换流站侧 ,Right now

[0087]

[0088] Step 3: Construct the admittance matrix after the switch trips.

[0089] Assume switch U in substation B b1 -U b7 U b7 -U b8 Tripping, switch U in substation C c5 -U c6 U c2 -U c6 If a trip occurs, the admittance value of the corresponding switch branch is set to 0, and the initial admittance matrices of substations B and C are modified as follows:

[0090] For substation B, switch U b1 -U b7 The branch admittance becomes 0, and the switch U b7 -U b8 The branch admittance becomes 0, affecting the node and causing matrix Y to... 中间侧 Middle Y 11 Y 17 Y 71 Y 77 Y 78 Y 87 Y 88 The values ​​are changed from 3, -1, -1, 3, -1, -1, 2 to 2, 0, 0, 1, 0, 0, 1 respectively, while the rest remain unchanged. The modified admittance matrix Y' 中间站侧 as follows:

[0091]

[0092] For substation C, switch U c5 -U c6 U c2 -U c6 The branch admittances all become 0, affecting the nodes and causing matrix Y to... 系统侧 Middle Y 55 Y 56 Y 65 Y 66 Y 26 Y 62 Y 22 The values ​​are changed from 3, -1, -1, 3, -1, -1, 3 to 2, 0, 0, 1, 0, 0, 2 respectively, while the rest remain unchanged. The modified admittance matrix Y' 系统侧 as follows:

[0093]

[0094] Step 4: Use the node injection current method to determine the connectivity between the nodes of this station.

[0095] (1) System station side: There is a circuit breaker tripping in substation C on the system station side, so it is necessary to refer to the modified admittance matrix Y' 系统侧 Determine the connectivity relationships. For substation C, upstream components L3 and L4 have nodes 3 and 6 within the substation, respectively. The system nodes are 1, 2, 4, and 5. Therefore, inject a current of 1 at nodes 3 and 6, and inject a current of 0 at the remaining nodes. Calculate the voltages generated by nodes 1, 2, 4, and 5. This involves solving the following two matrix equations:

[0096] and

[0097] Using mature algorithms such as matrix inversion and matrix multiplication, the following can be obtained respectively:

[0098] and

[0099] From the above results, it can be seen that after injecting current 1 into node 3, the voltage values ​​of nodes 1, 2, 4, and 5 are all greater than 0. Therefore, it can be determined that node 3 is connected to nodes 1, 2, 4, and 5, that is, node 3 is connected to the AC system. Therefore, let L3 × B 系统 =1; Similarly, after injecting 1 into the circuit at node 6, the voltage values ​​of nodes 1, 2, 4, and 5 are all equal to 0. Therefore, it can be determined that node 6 is disconnected from nodes 1, 2, 4, and 5. Thus, let L4×B 系统 =0.

[0100] (2) Intermediate station side: There is a circuit breaker tripping in substation B on the intermediate station side, therefore it is necessary to refer to the modified admittance matrix Y' 中间侧 Determine the connectivity relationships. For substation B, upstream components L1 and L2 are located at nodes 5 and 4 within the substation, respectively. Downstream components L3 and L4 are located at nodes 7 and 6 within the substation, respectively. Therefore, inject a current of 1 at nodes 5 and 4, and inject a current of 0 at the remaining nodes. Calculate the voltages generated at nodes 7 and 6 of the system. That is, solve the following two matrix equations:

[0101] and

[0102] Using mature algorithms such as matrix inversion and matrix multiplication, the following can be obtained respectively:

[0103] and

[0104] From the above results, we know that after injecting a unit current of 1 into node 5, the voltage value of node 6 is greater than 0. Therefore, we can determine that nodes 5 and 6 are connected. So let L1×L4=1. The voltage of node 7 is equal to 0. Therefore, we can determine that nodes 5 and 7 are disconnected. So let L1×L3=0. Similarly, after injecting a unit current of 1 into node 4, the voltage value of node 6 is greater than 0. Therefore, we can determine that nodes 4 and 6 are connected. So let L2×L4=1. The voltage of node 7 is equal to 0. Therefore, we can determine that nodes 4 and 7 are disconnected. So let L2×L3=0.

[0105] (3) Converter station side: There are no circuit breakers tripped in substation A on the converter station side, therefore, according to the initial admittance matrix Y 换流站侧 Determine the connectivity relationships. For substation A, upstream components H1 and H2 are located at nodes 3 and 6 within the substation, respectively. Downstream components L1 and L2 are located at nodes 5 and 4 within the substation, respectively. Therefore, inject a unit current of 1 at nodes 3 and 6, and inject zero current at the remaining nodes. Calculate the voltages generated at nodes 5 and 4 of the system. That is, solve the following two matrix equations:

[0106] and

[0107] Using mature algorithms such as matrix inversion and matrix multiplication, the following can be obtained respectively:

[0108] and

[0109] From the above results, it can be seen that after injecting a unit current of 1 into nodes 3 and 6 respectively, the voltage values ​​of nodes 5 and 4 are both greater than 0. Therefore, it can be determined that nodes 3 are connected to nodes 5 and 4. Thus, let H1×L1=1 and H1×L2=1; nodes 6 are connected to nodes 5 and 4. Thus, let H2×L1=1 and H2×L2=1.

[0110] Step 5: De-energization of AC section of converter and output.

[0111] (1) System station side: Based on the connectivity obtained in step 5, connect L3×B 系统 =1, L4×B 系统 The result information of 0 is sent to the device of substation B on the intermediate station side.

[0112] (2) Intermediate station side: Based on the connectivity obtained in step 5, and the L3×B signal received from substation C on the system station side. 系统 =1, L4×B系统 The result information = 0 allows us to derive L1×B 系统 =L1×L3×L3×B 系统 +L1×L4×L4×B 系统 =0×1+1×0=0,L2×B 系统 =L2×L3×L3×B 系统 +L2×L4×L4×B 系统 =0×1+1×0=0, and simultaneously set L1×B 系统 =0, L2×B 系统 The result information of =0 is sent to substation A on the upper-level converter station side.

[0113] (3) Converter station side: Based on the connectivity obtained in step 5, and the L1×B signal received from intermediate station B substation. 系统 =0, L2×B 系统 =0 result information, from which H1×B can be obtained. 系统 =H1×L1×L1×B 系统 +H1×L2×L2×B 系统 =1×0+1×0=0、H2×B 系统 =H2×L1×L1×B 系统 +H2×L2×L2×B 系统 =1×0+1×0=0.

[0114] As can be seen from the above results, H1 and H2 are both disconnected from the AC system. Therefore, a command is sent to the DC control and protection system of substation A to disconnect the first and second converters from the AC system. After receiving the command, the DC control and protection system immediately blocks the first and second converters to prevent the risk of overvoltage.

[0115] Meanwhile, the injection current method based on the node admittance matrix is ​​used to determine the connectivity between the upper and lower level components within the station. The physical meaning is clear, the admittance matrix is ​​simple to form and easy to calculate. Furthermore, the decentralized distributed architecture allows for the standardization and unification of the programs for each station device, which significantly improves the efficiency of system construction and testing while ensuring safety and reliability.

[0116] Example 2

[0117] In order to implement the method corresponding to Embodiment 1 above and achieve the corresponding functions and technical effects, a converter AC section power failure detection system is provided below.

[0118] like Figure 4 As shown, the converter AC section power failure detection system provided in this embodiment includes: converter station side detection device 21, intermediate station side detection device 22 and system station side detection device 23.

[0119] The system substation-side discrimination device 23 is used to determine the voltage equation of the system substation-side node admittance matrix based on the network topology of the lower-level substation, and based on the voltage equation of the system substation-side node admittance matrix, to determine the connection status between the upper-level components of the lower-level substation and the AC system using the node injection current method; the upper-level components of the lower-level substation are the lower-level components of the opposite substation.

[0120] The intermediate station side discrimination device 22 is connected to the system station side discrimination device 23. The intermediate station side discrimination device 22 is used to determine the intermediate station side node admittance matrix voltage equation according to the network topology of the opposite substation, and based on the intermediate station side node admittance matrix voltage equation, the node injection current method is used to determine the connection status between the upper-level components and the lower-level components of the opposite substation. The upper-level components of the opposite substation are the lower-level components of the DC converter station, and the lower-level components of the opposite substation are the AC lines between the opposite substation and the lower-level substation.

[0121] The converter station-side discrimination device 21 is connected to the intermediate station-side discrimination device 22. The converter station-side discrimination device 21 is used to determine the voltage equation of the node admittance matrix of the converter station according to the network topology of the DC converter station, and based on the voltage equation of the node admittance matrix of the converter station, it uses the node injection current method to determine the connection state of the upstream component and the downstream component of the DC converter station, so as to determine the power failure state of the converter and the AC system. The upstream component of the DC converter station is the converter, and the downstream component of the DC converter station is the AC line between the DC converter station and the opposite substation.

[0122] Compared with the prior art, the converter AC section power failure detection system provided in this embodiment has the same beneficial effects as the converter AC section power failure detection method provided in Embodiment 1, and will not be repeated here.

[0123] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0124] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for determining the power loss status of an AC section of a converter, used to determine the power loss status of the AC section at the DC converter station side in a DC transmission system, wherein the DC transmission system includes a DC converter station, a corresponding substation, a downstream substation, and an AC system connected in sequence, characterized in that... The converter AC section power failure detection method includes: Obtain the network topology of the DC converter station, the opposite substation, and the downstream substation; The voltage equations of the admittance matrix of the converter station side nodes are determined based on the network topology of the DC converter station. Determine the voltage equation of the admittance matrix of the intermediate station side node based on the network topology of the opposite substation. Determine the system station-side node admittance matrix and voltage equation based on the network topology of the lower-level substation. Based on the voltage equation of the admittance matrix of the converter station side node, the connection state of the upper-level component and the lower-level component of the DC converter station is determined by the node injection current method; the upper-level component of the DC converter station is the converter, and the lower-level component of the DC converter station is the AC line between the DC converter station and the substation on the opposite side. Based on the voltage equation of the admittance matrix of the intermediate station side node, the connection state of the upper-level component and the lower-level component of the opposite substation is determined by the node injection current method; the upper-level component of the opposite substation is the lower-level component of the DC converter station, and the lower-level component of the opposite substation is the AC line between the opposite substation and the lower-level substation. Based on the voltage equation of the admittance matrix of the station-side nodes of the system, the connection status between the upstream components of the lower-level substation and the AC system is determined by the node injection current method; the upstream components of the lower-level substation are the downstream components of the opposite substation. The de-energization status of the converter and the AC system is determined based on the connection status between the upstream and downstream components of the DC converter station, the connection status between the upstream and downstream components of the opposite substation, and the connection status between the upstream components of the downstream substation and the AC system.

2. The converter AC section power failure determination method according to claim 1, characterized in that, The voltage equation for the admittance matrix of the converter station side node is: Where n is the number of nodes in the DC converter station, V n Let I be the voltage at node n. n Y is the injected current at node n. nn The elements of the converter station side node admittance matrix, the diagonal elements Y ii Let Y be the self-admittance of node i, and the off-diagonal element Y. ij Let Y be the mutual admittance between node i and node j. If there is no direct branch between node i and node j, then Y... ij =0; In the network topology of the DC converter station, switches, upstream components and downstream components are all branches, and the connection points between buses and switches are nodes.

3. The converter AC section power failure detection method according to claim 1, characterized in that, The DC converter station includes a first upper-level component node, a first lower-level component node, and nodes within the converter station; the first upper-level component node is a node of the converter within the DC converter station, and the first lower-level component node is a node of the lower-level component of the DC converter station within the DC converter station. Based on the voltage equation of the admittance matrix of the converter station side node, the connection state of the upstream and downstream components of the DC converter station is determined using the node injection current method, specifically including: For any first upper-level component node, the injection current of the first upper-level component node is set to 1, and the injection current of the remaining first upper-level component nodes, each first lower-level component node, and each node within the converter station is set to 0. Based on the voltage equation of the admittance matrix of the converter station side node, the voltage of each first lower-level element node is determined according to the injection current of each first upper-level element node, the injection current of each first lower-level element node and the injection current of each node in the converter station. Based on the voltage of each first lower-level component node, the connection status between the first upper-level component node and each first lower-level component node is determined, thereby determining the connection status between the upper-level components and the lower-level components of the DC converter station.

4. The converter AC section power failure detection method according to claim 3, characterized in that, Based on the voltage of each first lower-level component node, the connection state between the first upper-level component node and each first lower-level component node is determined, specifically including: For any first lower-level component node, determine whether the voltage of the first lower-level component node is greater than a set voltage threshold. If so, the first upper-level component node is connected to the first lower-level component node; otherwise, the first upper-level component node is disconnected from the first lower-level component node.

5. The converter AC section power failure detection method according to claim 1, characterized in that, The opposite substation includes a second upper-level component node, a second lower-level component node, and nodes within the opposite substation; the second upper-level component node is a node of the upper-level component of the opposite substation within the opposite substation, and the second lower-level component node is a node of the lower-level component of the opposite substation within the opposite substation. Based on the voltage equation of the admittance matrix of the intermediate station side node, the connection state between the upstream component and the downstream component of the opposite substation is determined using the node injection current method, specifically including: For any second-level upper-level component node, the injection current of the second-level upper-level component node is set to 1, and the injection current of the remaining second-level upper-level component nodes, each second-level lower-level component node, and each node in the substation on the opposite side is set to 0. Based on the voltage equation of the admittance matrix of the intermediate station side node, the voltage of each second lower-level element node is determined according to the injection current of each second upper-level element node, the injection current of each second lower-level element node and the injection current of each node in the opposite substation. Based on the voltage of each second lower-level component node, the connection status between the second upper-level component node and each second lower-level component node is determined, thereby determining the connection status between the upper-level component and the lower-level component of the opposite substation.

6. The converter AC section power failure determination method according to claim 1, characterized in that, The lower-level substation includes a third-level upper-level component node and a system node; the third-level upper-level component node is the node of the upper-level component of the lower-level substation within the lower-level substation, and the system node is the node connecting the lower-level substation to the AC system; Based on the voltage equation of the station-side admittance matrix, the connection state between the upstream components of the lower-level substation and the AC system is determined using the nodal injection current method, specifically including: For any third-level upper-level component node, the injection current of the third-level upper-level component node is set to 1, and the injection current of the remaining third-level upper-level component nodes and each system node is set to 0. Based on the admittance matrix of the system station-side nodes, the voltage of each system node is determined according to the injection current of each third upper-level component node and the injection current of each system node. Based on the voltage of each system node, the connection status between the third upper-level component node and each system node is determined, thereby determining the connection status between the upper-level component of the lower-level substation and the AC system.

7. The converter AC section power failure detection method according to claim 1, characterized in that, Based on the connectivity status between the upstream and downstream components of the DC converter station, the connectivity status between the upstream and downstream components of the opposite substation, and the connectivity status between the upstream components of the downstream substation and the AC system, the de-energization status of the converter and the AC system is determined, specifically including: The connection status between the upstream components of the opposite substation and the downstream components of the opposite substation, as well as the connection status between the upstream components of the downstream substation and the AC system, is determined. Based on the connection status of the upstream components and downstream components of the DC converter station, as well as the connection status of the upstream components of the opposite substation and the AC system, the connection status of the upstream components and the AC system of the DC converter station is determined, so as to determine the de-energization status of the converter and the AC system.

8. The converter AC section power failure detection method according to claim 1, characterized in that, The converter AC section power failure detection method also includes: If the converter is disconnected from the AC system, the converter is locked.

9. A converter AC section power failure detection system, characterized in that, The converter AC section power failure detection system includes: The system substation-side discrimination device is used to determine the voltage equation of the system substation-side node admittance matrix based on the network topology of the lower-level substation, and to determine the connection status between the upper-level components of the lower-level substation and the AC system based on the voltage equation of the system substation-side node admittance matrix using the node injection current method; the upper-level components of the lower-level substation are the lower-level components of the opposite substation. The intermediate station-side discrimination device, connected to the system station-side discrimination device, is used to determine the intermediate station-side node admittance matrix voltage equation based on the network topology of the opposite substation, and, based on the intermediate station-side node admittance matrix voltage equation, to determine the connectivity status of the upstream components and downstream components of the opposite substation using the node injection current method; the upstream components of the opposite substation are downstream components of the DC converter station, and the downstream components of the opposite substation are the AC lines between the opposite substation and the downstream substation. A converter station-side discrimination device, connected to the intermediate station-side discrimination device, is used to determine the voltage equation of the converter station-side node admittance matrix based on the network topology of the DC converter station, and, based on the voltage equation of the converter station-side node admittance matrix, to determine the connection state of the upstream and downstream components of the DC converter station using the node injection current method, so as to determine the de-energization state of the converter and the AC system; the upstream component of the DC converter station is the converter, and the downstream component of the DC converter station is the AC line between the DC converter station and the opposite substation.

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