Direct-current transformer fault protection method and device, computer device and storage medium

Abstract

The present application relates to the technical field of flexible direct current transmission, and discloses a DC transformer fault protection method and device, computer equipment and a storage medium, wherein the DC transformer comprises at least one unit; each unit comprises a high-voltage bridge arm, a low-voltage bridge arm and a common bridge arm; the protection method comprises: obtaining low-voltage bridge arm parameters, high-voltage bridge arm parameters and common bridge arm parameters; determining the type of short-circuit fault occurring according to the relationship between the low-voltage bridge arm parameters, the high-voltage bridge arm parameters and the common bridge arm parameters and preset protection setting values; generating a corresponding protection action signal according to the type of short-circuit fault; generating a corresponding lockout control instruction according to the protection action signal, and locking the corresponding bridge arm according to the lockout control instruction. The present application solves the problem that the existing technology causes harm to the DC transformer and the DC system when a short-circuit fault occurs in the DC transformer.

Description

Technical Field

[0001] This invention relates to the field of flexible DC power transmission technology, specifically to a DC transformer fault protection method, device, computer equipment, and storage medium. Background Technology

[0002] Due to the intermittent and random nature of renewable energy generation such as wind and solar power, as well as the limitations of traditional AC grid-connected technologies in terms of absorption capacity, there is an urgent need to accelerate research on new collection and transmission technologies. Compared with AC grid-connected technologies, DC grid-connected technologies based on flexible DC transmission have advantages such as high transmission efficiency, saving transmission corridors, fast and reliable regulation, and no stability issues. They are considered the most effective option for large-scale renewable energy grid connection and transmission, and represent an important direction for future power grid development.

[0003] DC transformers are core equipment in building DC power grids, enabling the interconnection of DC lines of different voltage levels and types to form a DC grid. DC transformers used for DC grid interconnection possess functions such as DC voltage transformation, bidirectional power transfer, controllable power flow, and fault isolation. DC power grids involve large investments and have a wide range of fault impacts, placing extremely high reliability requirements on DC transformers. However, current research on high-voltage, high-capacity DC transformers is still in the stage of circuit topology design, simulation analysis, and prototype verification.

[0004] When a short-circuit fault occurs in a DC transformer, its rapid detection and protection are directly related to the stability and reliability of the DC transformer itself and even the entire system. If left uncontrolled, it will cause significant overvoltage and overcurrent surges to the DC transformer, potentially damaging it and affecting the stable operation of the system. Therefore, to prevent DC transformer faults from harming the equipment and the DC system and to ensure equipment and system safety, a DC transformer fault protection technology solution is urgently needed. Summary of the Invention

[0005] In view of this, the present invention provides a method, device, computer equipment and storage medium for DC transformer fault protection, in order to solve the problem that the DC transformer and DC system are harmed when a short circuit fault occurs in the prior art.

[0006] In a first aspect, the present invention provides a fault protection method for a DC transformer, wherein the DC transformer includes at least one unit; each unit includes a high-voltage bridge arm, a low-voltage bridge arm, and a common bridge arm; one end of the high-voltage bridge arm is connected to one end of the low-voltage bridge arm and one end of the common bridge arm to form a common point, the other end of the low-voltage bridge arm and the other end of the common bridge arm form a low-voltage side port, and the other end of the high-voltage bridge arm and the other end of the common bridge arm form a high-voltage side port; the method includes:

[0007] Obtain the parameters of the low-voltage bridge arm, the high-voltage bridge arm, and the common bridge arm;

[0008] The type of short-circuit fault is determined based on the relationship between the low-voltage bridge arm parameters, the high-voltage bridge arm parameters, and the common bridge arm parameters and the preset protection settings.

[0009] Generate corresponding protection action signals based on the type of short-circuit fault;

[0010] The corresponding interlocking control command is generated based on the protection action signal, and the corresponding bridge arm is interlocked according to the interlocking control command.

[0011] The DC transformer fault protection method provided in this invention acquires low-voltage bridge arm parameters, high-voltage bridge arm parameters, and common bridge arm parameters. Based on the relationship between these parameters and preset protection settings, it determines the type of short-circuit fault. A corresponding protection action signal is generated based on the short-circuit fault type. A corresponding blocking control command is generated based on the protection action signal. The corresponding bridge arm is blocked according to the blocking control command, achieving rapid detection of short-circuit faults in the DC transformer. By blocking the corresponding bridge arm through the blocking control command, the faulty bridge arm is blocked, quickly cutting off the short-circuit fault current and protecting the entire DC transformer from the impact of short-circuit faults. This solves the problem in the prior art where short-circuit faults in DC transformers cause harm to the DC transformer and DC system.

[0012] In one alternative implementation, the high-voltage arm, the low-voltage arm, and the common arm each include multiple sub-modules connected in series.

[0013] The low-voltage bridge arm parameters include any one or more of the following: low-voltage bridge arm current, low-voltage bridge arm submodule capacitor voltage, low-voltage side DC voltage, and low-voltage side DC pole current.

[0014] The high-voltage bridge arm parameters include any one or more of the following: high-voltage bridge arm current, high-voltage bridge arm submodule capacitor voltage, and high-voltage side DC voltage.

[0015] The common arm parameters include the common arm current.

[0016] In one alternative implementation, when the DC transformer includes a single unit, the low-voltage side DC pole current is the difference between the fault pole DC current and the non-fault pole DC current.

[0017] When a DC transformer includes two symmetrically arranged units, the DC pole current on the low-voltage side is the difference between the DC current of the fault pole on the low-voltage side, the DC current of the neutral line, and the current of the common arm.

[0018] When a DC transformer includes two or more low-voltage side ports, the low-voltage bridge arm parameters also include the difference current between the DC current at the faulty low-voltage side port and the DC current at the non-faulty low-voltage side port.

[0019] The DC transformer fault protection method provided in this invention includes key fault electrical quantities of the DC transformer in its low-voltage arm parameters, high-voltage arm parameters, and common arm parameters. The parameters are comprehensively collected. Based on the slow development of faults on the low-voltage side of the DC transformer, the method further sets the low-voltage side DC pole current and clarifies the calculation method of the low-voltage side DC pole current. When the DC transformer has two or more low-voltage side ports, the low-voltage arm parameters also include the difference current between the DC current of the faulty port and the DC current of the non-faulty port on the low-voltage side, which improves the sensitivity of low-voltage side fault detection and provides a basis for subsequent judgment of short-circuit faults based on the relationship between the low-voltage arm parameters, high-voltage arm parameters, common arm parameters, and preset protection settings.

[0020] In one optional implementation, determining the type of short-circuit fault based on the relationship between the low-voltage bridge arm parameters, high-voltage bridge arm parameters, and common bridge arm parameters and preset protection settings includes:

[0021] When any one or more of the following conditions are met—the low-voltage bridge arm parameter being greater than or equal to the first bridge arm overcurrent protection setting, the low-voltage bridge arm submodule capacitor voltage being greater than or equal to the first submodule overvoltage protection setting, the low-voltage side DC voltage being greater than or equal to the first DC overvoltage protection setting, and the low-voltage side DC pole current being greater than or equal to the first DC current differential protection setting—and the duration exceeds the first preset time, a low-voltage side short-circuit fault is determined to have occurred.

[0022] When any one or more of the following conditions are met—the high-voltage bridge arm parameter being greater than or equal to the second bridge arm overcurrent protection setting, the high-voltage bridge arm submodule capacitor voltage being greater than or equal to the second submodule overvoltage protection setting, and the high-voltage side DC voltage being greater than or equal to the second DC overvoltage protection setting—and the duration exceeds the second preset time, a first high-voltage side short-circuit fault is determined to have occurred.

[0023] When the common arm current is greater than or equal to the third preset overcurrent protection setting, and the high-voltage arm parameter is greater than or equal to the second arm overcurrent protection action setting, the high-voltage arm submodule capacitor voltage is greater than or equal to the second submodule overvoltage protection action setting, and the high-voltage side DC voltage is greater than or equal to the second DC overvoltage protection action setting, and the duration exceeds the third preset time, a second high-voltage side short circuit fault is determined to have occurred.

[0024] The DC transformer fault protection method provided in this invention accurately determines whether a low-voltage side short-circuit fault or a high-voltage side short-circuit fault has occurred by comparing the low-voltage arm parameters, high-voltage arm parameters, and common arm current with specific preset protection settings. This enables rapid identification of DC transformer short-circuit faults and provides a basis for generating corresponding protection action signals based on the type of short-circuit fault.

[0025] In one optional implementation, generating a corresponding protection action signal based on the short-circuit fault type includes:

[0026] When a low-voltage side short-circuit fault occurs, a first low-voltage bridge arm protection action signal and a first high-voltage bridge arm protection action signal are generated.

[0027] When a short-circuit fault occurs on the first high-voltage side, a second low-voltage bridge arm protection action signal, a second high-voltage bridge arm protection action signal, and a first common bridge arm protection signal are generated.

[0028] When a short-circuit fault occurs on the second high-voltage side, a third low-voltage bridge arm protection action signal, a third high-voltage bridge arm protection action signal, and a second common bridge arm protection action signal are generated. The second low-voltage bridge arm protection action signal and the third low-voltage bridge arm protection action signal are the same, but different from the first low-voltage bridge arm protection action signal. The second high-voltage bridge arm protection action signal and the third high-voltage bridge arm protection action signal are the same, but different from the first high-voltage bridge arm protection action signal. The first common bridge arm protection action signal and the second common bridge arm protection action signal are different.

[0029] The DC transformer fault protection method provided in this invention generates a first low-voltage bridge arm protection action signal and a first high-voltage bridge arm protection action signal when a low-voltage side short-circuit fault occurs; generates a second low-voltage bridge arm protection action signal, a second high-voltage bridge arm protection action signal, and a first common bridge arm protection signal when a first high-voltage side short-circuit fault occurs; and generates a third low-voltage bridge arm protection action signal, a third high-voltage bridge arm protection action signal, and a second common bridge arm protection action signal when a second high-voltage side short-circuit fault occurs. The second and third low-voltage bridge arm protection action signals are the same but different from the first low-voltage bridge arm protection action signal, the second and third high-voltage bridge arm protection action signals are the same but different from the first high-voltage bridge arm protection action signal, and the first and second common bridge arm protection action signals are different. This achieves the goal of quickly generating corresponding protection action signals based on the occurrence of a low-voltage side short-circuit fault or a high-voltage side short-circuit fault, providing a basis for subsequently generating corresponding blocking control commands based on the protection action signals.

[0030] In one optional implementation, generating a corresponding interlocking control command based on the protection action signal includes:

[0031] When a low-voltage side short-circuit fault occurs, an AND logic gate is used to combine the first low-voltage bridge arm protection action signal and the first high-voltage bridge arm protection action signal to generate a first low-voltage bridge arm blocking control command.

[0032] When a short-circuit fault occurs on the first high-voltage side, an AND logic gate is used to combine the second low-voltage bridge arm protection action signal and the second high-voltage bridge arm protection action signal to generate a second low-voltage bridge arm blocking control command; an AND logic gate is used to combine the second high-voltage bridge arm protection action signal and the first common bridge arm protection action signal to generate a first high-voltage bridge arm blocking control command and a first common bridge arm blocking control command.

[0033] When a short-circuit fault occurs on the second high-voltage side, an AND logic gate is used to combine the third low-voltage bridge arm protection action signal and the third high-voltage bridge arm protection action signal to generate a third low-voltage bridge arm blocking control command; an AND logic gate is also used to combine the third high-voltage bridge arm protection action signal and the second common bridge arm protection action signal to generate a second high-voltage bridge arm blocking control command and a second common bridge arm blocking control command.

[0034] In one optional implementation, locking the corresponding bridge arm according to the locking control command includes:

[0035] When a low-voltage side short-circuit fault occurs, the low-voltage bridge arm where the fault is located is locked according to the first low-voltage bridge arm locking control command.

[0036] When a short circuit fault occurs on the first high-voltage side, the low-voltage bridge arm is locked according to the second low-voltage bridge arm locking control command; the high-voltage bridge arm is locked according to the first high-voltage bridge arm locking control command; and the common bridge arm is locked according to the first common bridge arm locking control command.

[0037] When a short-circuit fault occurs on the second high-voltage side, the low-voltage bridge arm is locked according to the third low-voltage bridge arm locking control command, the high-voltage bridge arm is locked according to the second high-voltage bridge arm locking control command, and the common bridge arm is locked according to the second common bridge arm locking control command.

[0038] The DC transformer fault protection method provided in this invention locks out the low-voltage bridge arm where the fault occurs when a low-voltage side short-circuit fault occurs, and locks out all low-voltage bridge arms, high-voltage bridge arms and common bridge arms when a high-voltage side short-circuit fault occurs, that is, locks out the entire DC transformer and quickly cuts off the fault current, ensuring that the DC transformer and DC system are not harmed when a short-circuit fault occurs in the DC transformer.

[0039] Secondly, the present invention provides a DC transformer fault protection device, wherein the DC transformer includes at least one unit; each unit includes a high-voltage bridge arm, a low-voltage bridge arm, and a common bridge arm; one end of the high-voltage bridge arm is connected to one end of the low-voltage bridge arm and one end of the common bridge arm to form a common point, the other end of the low-voltage bridge arm and the other end of the common bridge arm form a low-voltage side port, and the other end of the high-voltage bridge arm and the other end of the common bridge arm form a high-voltage side port; the device includes:

[0040] The acquisition module is used for low-voltage arm parameters, high-voltage arm parameters, and common arm parameters;

[0041] The judgment module is used to determine the type of short-circuit fault based on the relationship between the low-voltage bridge arm parameters, high-voltage bridge arm parameters, and common bridge arm parameters and the preset protection settings.

[0042] The generation module is used to generate corresponding protection action signals based on the type of short-circuit fault.

[0043] The interlocking module is used to generate corresponding interlocking control commands based on protection action signals, and to interlock the corresponding bridge arm according to the interlocking control commands.

[0044] Thirdly, the present invention provides a computer device, comprising: a memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the computer instructions to perform the DC transformer fault protection method of the first aspect or any corresponding embodiment described above.

[0045] Fourthly, the present invention provides a computer-readable storage medium storing computer instructions for causing a computer to execute the DC transformer fault protection method of the first aspect or any corresponding embodiment described above. Attached Figure Description

[0046] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0047] Figure 1 This is a flowchart illustrating a DC transformer fault protection method according to an embodiment of the present invention;

[0048] Figure 2 This is a flowchart illustrating another DC transformer fault protection method according to an embodiment of the present invention;

[0049] Figure 3This is a flowchart illustrating another DC transformer fault protection method according to an embodiment of the present invention;

[0050] Figure 4 This is a schematic diagram of a DC transformer unipolar circuit topology according to an embodiment of the present invention;

[0051] Figure 5 This is a schematic diagram of a symmetrical bipolar circuit topology of a DC transformer according to an embodiment of the present invention;

[0052] Figure 6 This is a schematic diagram of a multi-port topology on the low-voltage side of a DC transformer according to an embodiment of the present invention;

[0053] Figure 7 This is a schematic diagram of the topology of a half-bridge submodule in a DC transformer according to an embodiment of the present invention;

[0054] Figure 8 This is a schematic diagram of the full-bridge submodule topology in a DC transformer according to an embodiment of the present invention;

[0055] Figure 9 This is a schematic diagram of the hybrid submodule topology in a DC transformer according to an embodiment of the present invention;

[0056] Figure 10 This is a schematic diagram of the asymmetric submodule topology in a DC transformer according to an embodiment of the present invention;

[0057] Figure 11 This is a schematic diagram of an interleaved submodule topology in a DC transformer according to an embodiment of the present invention;

[0058] Figure 12 This is a schematic diagram of another interleaved submodule topology in a DC transformer according to an embodiment of the present invention;

[0059] Figure 13 This is a schematic diagram of the clamped twin-module topology in a DC transformer according to an embodiment of the present invention;

[0060] Figure 14 This is a schematic diagram of the topology of a flying capacitor type submodule in a DC transformer according to an embodiment of the present invention;

[0061] Figure 15 This is a schematic diagram of a three-level sub-module topology in a DC transformer according to an embodiment of the present invention;

[0062] Figure 16 This is a schematic diagram of another three-level sub-module topology in a DC transformer according to an embodiment of the present invention;

[0063] Figure 17This is a schematic diagram of the neutral line DC current in a DC transformer unipolar circuit topology according to an embodiment of the present invention;

[0064] Figure 18 This is a schematic diagram of the neutral line DC current in a symmetrical bipolar circuit topology of a DC transformer according to an embodiment of the present invention;

[0065] Figure 19 This is a schematic diagram of the overcurrent protection action criterion for the bridge arm according to an embodiment of the present invention;

[0066] Figure 20 This is a schematic diagram of the overvoltage protection action criterion of a submodule according to an embodiment of the present invention;

[0067] Figure 21 This is a schematic diagram of the DC overvoltage protection action criterion according to an embodiment of the present invention;

[0068] Figure 22 This is a schematic diagram of the DC pole current differential protection operation criteria according to an embodiment of the present invention;

[0069] Figure 23 This is a schematic diagram of the action criteria for DC port current differential protection according to an embodiment of the present invention;

[0070] Figure 24 This is a schematic diagram of the protection action criteria of the neutral point grounding device according to an embodiment of the present invention;

[0071] Figure 25 This is a schematic diagram of the blocking logic for the low-voltage bridge arm protection of a DC transformer according to an embodiment of the present invention;

[0072] Figure 26 This is a schematic diagram of the DC transformer high-voltage bridge arm protection blocking logic according to an embodiment of the present invention;

[0073] Figure 27 This is a schematic diagram of the DC transformer common arm protection blocking logic according to an embodiment of the present invention;

[0074] Figure 28 This is a structural block diagram of a DC transformer fault protection device according to an embodiment of the present invention;

[0075] Figure 29 This is a schematic diagram of the hardware structure of a computer device according to an embodiment of the present invention. Detailed Implementation

[0076] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0077] According to an embodiment of the present invention, a method for fault protection of a DC transformer is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0078] This embodiment provides a DC transformer fault protection method, and the topology diagram of the DC transformer is shown below. Figure 4 and Figure 5 As shown, the topology of a DC transformer can be a unipolar circuit or a symmetrical bipolar circuit. Figure 4 This is a topology diagram of a single-pole DC transformer circuit. Figure 5 This is a symmetrical bipolar circuit topology diagram of a DC transformer. The DC transformer includes at least one unit; each unit includes a high-voltage bridge arm, a low-voltage bridge arm, and a common bridge arm; one end of the high-voltage bridge arm connects to one end of the low-voltage bridge arm and one end of the common bridge arm to form a common point, the other end of the low-voltage bridge arm and the other end of the common bridge arm form a low-voltage side port, and the other end of the high-voltage bridge arm and the other end of the common bridge arm form a high-voltage side port, where L represents the low-voltage bridge arm and H represents the high-voltage bridge arm; Figure 1 This is a flowchart of a DC transformer fault protection method according to an embodiment of the present invention, such as... Figure 1 As shown, the process includes the following steps:

[0079] Step S101: Obtain the low-voltage bridge arm parameters, high-voltage bridge arm parameters, and common bridge arm parameters. Specifically, when the DC transformer is working, the parameters used for DC transformer fault diagnosis may include DC current, low-voltage bridge arm current, high-voltage bridge arm current, common bridge arm current, DC voltage on the low-voltage side of the DC transformer, and DC voltage on the high-voltage side of the DC transformer. These parameters can all be used as fault diagnosis parameters.

[0080] Step S102: Determine the type of short-circuit fault based on the relationship between the low-voltage arm parameters, high-voltage arm parameters, and common arm parameters and the preset protection settings. Specifically, the preset protection settings can be pre-set overvoltage protection settings, overcurrent protection settings, and differential protection settings, which can be determined based on the selection and withstand levels of each component in the DC transformer. The preset protection settings are used as the criteria for determining the type of short-circuit fault in the DC transformer. The type of short-circuit fault in the DC transformer is determined by comparing the low-voltage arm parameters (DC current, low-voltage arm current, high-voltage arm current, common arm current, DC voltage on the low-voltage side of the DC transformer, and DC voltage on the high-voltage side of the DC transformer) with the overvoltage protection settings, overcurrent protection settings, and differential protection settings, respectively.

[0081] Step S103: Generate a corresponding protection action signal based on the fault type. Specifically, generate a protection action signal corresponding to the short-circuit fault type. The short-circuit fault type and the corresponding protection action signal can be preset.

[0082] Step S104: Generate a corresponding interlocking control command based on the protection action signal, and interlock the corresponding bridge arm according to the interlocking control command.

[0083] The DC transformer fault protection method provided in this invention acquires low-voltage bridge arm parameters, high-voltage bridge arm parameters, and common bridge arm parameters. Based on the relationship between these parameters and preset protection settings, it determines the type of short-circuit fault. A corresponding protection action signal is generated based on the fault type. A corresponding blocking control command is generated based on the protection action signal. The corresponding bridge arm is blocked according to the blocking control command, achieving rapid detection of short-circuit faults in the DC transformer. By blocking the corresponding bridge arm through the blocking control command, the faulty bridge arm is blocked, quickly cutting off the short-circuit fault current and protecting the entire DC transformer from the impact of short-circuit faults. This solves the problem in the prior art where short-circuit faults in DC transformers cause harm to the DC transformer and DC system.

[0084] This embodiment provides a DC transformer fault protection method, and the topology diagram of the DC transformer is shown below. Figure 4 and Figure 5 As shown, the topology of a DC transformer can be a unipolar circuit or a symmetrical bipolar circuit. Figure 4 This is a topology diagram of a single-pole DC transformer circuit. Figure 5This is a symmetrical bipolar circuit topology diagram of a DC transformer. The DC transformer includes at least one unit; each unit includes a high-voltage bridge arm, a low-voltage bridge arm, and a common bridge arm; one end of the high-voltage bridge arm connects to one end of the low-voltage bridge arm and one end of the common bridge arm to form a common point, the other end of the low-voltage bridge arm and the other end of the common bridge arm form the low-voltage side port, and the other end of the high-voltage bridge arm and the other end of the common bridge arm form the high-voltage side port, where L represents low voltage and H represents high voltage; Figure 2 This is a flowchart of a DC transformer fault protection method according to an embodiment of the present invention, such as... Figure 2 As shown, the process includes the following steps:

[0085] Step S201: Obtain the parameters of the low-voltage bridge arm, the high-voltage bridge arm, and the common bridge arm. Specifically, the high-voltage bridge arm, the low-voltage bridge arm, and the common bridge arm each include multiple sub-modules connected in series; the sub-modules can be configured as half-bridge sub-modules, full-bridge sub-modules, hybrid sub-modules, asymmetric sub-modules, interleaved connection sub-modules, clamped dual sub-modules, flying capacitor sub-modules, or three-level sub-modules. For example... Figure 7 As shown, this is a half-bridge submodule structure. A half-bridge submodule includes at least one protection unit and a DC support capacitor. The protection unit is connected in series and then in parallel with the DC support capacitor. The specific structures of the full-bridge submodule, hybrid submodule, asymmetric submodule, two types of interleaved connection submodules, clamped dual submodule, flying capacitor submodule, and two types of three-level submodules are respectively shown below. Figure 8 , Figure 9 , Figure 10 , Figure 11 , Figure 12 , Figure 13 , Figure 14 , Figure 15 and Figure 16 As shown.

[0086] The low-voltage bridge arm parameters include any one or more of the following: low-voltage bridge arm current, low-voltage bridge arm submodule capacitor voltage, low-voltage side DC voltage, and low-voltage side DC pole current; the high-voltage bridge arm parameters include any one or more of the following: high-voltage bridge arm current, high-voltage bridge arm submodule capacitor voltage, and high-voltage side DC voltage; the common bridge arm parameters include the common bridge arm current.

[0087] The specific method for setting the DC pole current difference on the low-voltage side, based on the characteristics of DC fault current in DC transformers, is as follows:

[0088] When a DC transformer comprises a single unit, the low-voltage side DC pole current is the difference between the faulty pole DC current and the non-faulty pole DC current. Specifically, for example... Figure 4 As shown, when a DC transformer includes a single unit, i.e., a unipolar circuit, as... Figure 17 As shown, the DC pole current on the low-voltage side is the difference between the DC current of the faulty pole and the DC current of the non-faulty pole.

[0089] When a DC transformer comprises two symmetrically arranged units, the low-voltage side DC pole current is the difference between the low-voltage side fault pole DC current, the neutral line DC current, and the common arm current. Specifically, when a DC transformer comprises two symmetrically arranged units, i.e., a symmetrical bipolar circuit, such as... Figure 5 As shown in the figure, the low-voltage side DC pole current is the difference between the low-voltage side fault pole DC current, the neutral line DC current, and the common arm current. Figure 18 As shown, that is, |i dcline1 -i ground _ centrl1 -i dcW |or|i dcline2 -i ground _ centrl1 -i dcW |>I set1 .

[0090] Figure 17 and Figure 18 in,i dcline1 Indicates the DC current of the faulty electrode or the DC current of the non-faulty electrode, i dcline2 Indicates i dcline1 The corresponding non-faulty pole DC current or faulty pole DC current, i ground _ centrl1 For the neutral line DC current, i dcW For the common arm current.

[0091] When a DC transformer includes two or more low-voltage side ports, the low-voltage bridge arm parameters also include the difference current between the DC current at the faulty low-voltage side port and the DC current at the non-faulty low-voltage side port. Specifically, a schematic diagram of a multi-port low-voltage side DC transformer is shown below. Figure 6 As shown, when a DC transformer includes two or more low-voltage side ports, the number of low-voltage bridge arms is two or more. The other end of each low-voltage bridge arm and the other end of the common bridge arm can form a low-voltage side port, that is, two or more low-voltage side ports are formed. At this time, the low-voltage bridge arm parameters also include the difference current between the DC current of the low-voltage side fault port and the DC current of the low-voltage side non-fault port.

[0092] Step S202: Determine the type of short-circuit fault based on the relationship between the low-voltage bridge arm parameters, high-voltage bridge arm parameters, and common bridge arm parameters and the preset protection settings.

[0093] Specifically, step S202 includes:

[0094] Step S2021: When any one or more of the following conditions are met—the low-voltage bridge arm parameter being greater than or equal to the first bridge arm overcurrent protection setting, the low-voltage bridge arm submodule capacitor voltage being greater than or equal to the first submodule overvoltage protection setting, the low-voltage side DC voltage being greater than or equal to the first DC overvoltage protection setting, and the low-voltage side DC pole current being greater than or equal to the first DC current differential protection setting—and the duration exceeds a first preset time, a low-voltage side short-circuit fault is determined to have occurred. Specifically, a low-voltage side short-circuit fault is determined to have occurred when any one or more of the following conditions are met:

[0095] In the low-voltage bridge arm parameters of the DC transformer, the low-voltage bridge arm current is greater than or equal to the overcurrent protection setting value of the first bridge arm, and the duration exceeds the first preset time. The overcurrent protection setting value of the first bridge arm is determined based on the selection and withstand level of each component in the DC transformer. The first preset time can be set to a first detection time setting, which is within 1 ms (ms represents milliseconds). The bridge arm overcurrent protection action criteria are as follows: Figure 19 As shown.

[0096] In the low-voltage bridge arm parameters of the DC transformer, the capacitor voltage of the low-voltage bridge arm submodule is greater than or equal to the overvoltage protection action setting value of the first submodule, and the duration exceeds the first preset time. Specifically, the overvoltage protection action setting value of the first submodule is determined based on the selection and withstand level of each component in the DC transformer, and the first preset time can be set as the second detection time setting value, approximately 1 ms. The overvoltage protection action criterion for the bridge arm submodule is as follows: Figure 20 As shown.

[0097] In the low-voltage bridge arm parameters of the DC transformer, the DC voltage on the low-voltage side is greater than or equal to the first DC overvoltage protection action setting value, and the duration exceeds the first preset time. Specifically, the first DC overvoltage protection action setting value can be set to approximately 1.3 pu to 1.4 pu, where pu is a per-unit value, and the first preset time can be set to the third detection time setting value, approximately 30 ms. The DC overvoltage protection action criteria are as follows: Figure 21 As shown.

[0098] In the low-voltage bridge arm parameters of the DC transformer, the DC pole current difference on the low-voltage side is greater than or equal to the first DC current differential protection operating setting value, and the duration exceeds the first preset time. Specifically, the first DC current differential protection operating setting value can be set to approximately 0.2 pu to 0.5 pu, and the first preset time can be set to the eighth detection time setting value, approximately 10 ms. The low-voltage side DC pole current difference protection operating criteria are as follows: Figure 22 As shown.

[0099] In the low-voltage bridge arm parameters of the DC transformer, the difference between the DC current at the fault port and the DC current at the non-fault port on the low-voltage side is greater than or equal to the second DC current differential protection operating setting, and the duration exceeds the first preset time. Specifically, the second DC current differential protection operating setting is determined based on the selection and withstand level of each component in the DC transformer, and the first preset time can be set to the ninth detection time setting, approximately 10ms. The operating criteria for the differential protection operating between the DC current at the fault port and the non-fault port on the low-voltage side are as follows: Figure 23 As shown, I dcport1 I represents the DC current at the low-voltage side fault port. dcport2 | indicates the DC current at the non-faulty port.

[0100] like Figure 24 As shown, considering a DC transformer comprising two symmetrically arranged units, forming a symmetrical bipolar circuit, a neutral point grounding device is required. Therefore, neutral point grounding overcurrent protection is implemented to protect the neutral point grounding device in the event of a DC transformer fault. ground_centrl1 i ground_centrl2 All are neutral point grounding currents. When the neutral point grounding current i ground_centrl1 or i ground_centrl2 The absolute value of the value is greater than or equal to the neutral point grounding overcurrent protection setting I. set3 If the time exceeds the set fourth preset time, the neutral point grounding overcurrent protection setting is adjusted according to the overcurrent capacity of the grounding electrode. The fourth preset time can be set to the tenth detection time setting, which is set according to actual needs. The neutral point grounding overcurrent protection operates as a backup protection. When the neutral point grounding current i ground_centrl1 or i ground_centrl2 The absolute value of the value is greater than or equal to the neutral point grounding overcurrent protection setting I. set3 When the condition is met, the neutral point grounding overcurrent protection will trip, protecting the neutral point grounding device. Conversely, when the condition is not met, the neutral point grounding overcurrent protection will not trip.

[0101] Step S2022: When any one or more of the following conditions are met—the high-voltage bridge arm parameter being greater than or equal to the second bridge arm overcurrent protection setting, the high-voltage bridge arm submodule capacitor voltage being greater than or equal to the second submodule overvoltage protection setting, and the high-voltage side DC voltage being greater than or equal to the second DC overvoltage protection setting—and the duration exceeds a second preset time, a first high-voltage side short-circuit fault is determined to have occurred. Specifically, a first high-voltage side short-circuit fault is determined to have occurred when any one or more of the following conditions are met:

[0102] In the parameters of the high-voltage bridge arm of the DC transformer, the high-voltage bridge arm current is greater than or equal to the overcurrent protection setting value of the second bridge arm, and the duration exceeds the second preset time. Specifically, the overcurrent protection setting value of the second bridge arm is determined based on the selection and withstand level of each component in the DC transformer, and the second preset time can be set to the fourth detection time setting value, which is within 1 ms.

[0103] In the parameters of the high-voltage bridge arm of the DC transformer, the capacitor voltage of the high-voltage bridge arm submodule is greater than or equal to the overvoltage protection action setting of the second submodule, and the duration exceeds the second preset time. Specifically, the overvoltage protection action setting of the second submodule is determined based on the selection and withstand level of each component in the DC transformer, and the second preset time can be set to the fifth detection time setting, which is approximately 1 ms.

[0104] In the parameters of the high-voltage bridge arm of the DC transformer, the DC voltage on the high-voltage side is greater than or equal to the second DC overvoltage protection action setting value, and the duration exceeds the second preset time. Specifically, the second DC overvoltage protection action setting value can be set to approximately 1.3 pu to 1.4 pu, and the second preset time can be set to the sixth detection time setting value, which is approximately 30 ms.

[0105] Step S2023: When the common arm current is greater than or equal to the third preset overcurrent protection setting, and the following conditions are met: the high-voltage arm parameter is greater than or equal to the second arm overcurrent protection action setting, the high-voltage arm submodule capacitor voltage is greater than or equal to the second submodule overvoltage protection action setting, and the high-voltage side DC voltage is greater than or equal to the second DC overvoltage protection action setting, and the duration exceeds the third preset time, a second high-voltage side short-circuit fault is determined. Wherein: the third arm overcurrent protection action setting is determined based on the selection and withstand level of each component in the DC transformer, and the third preset time can be set to the seventh detection time setting, which is within 1 ms.

[0106] Figure 19 in,|I arm | represents the absolute value of the arm current in the low-voltage arm, high-voltage arm, or common arm. set This indicates the overcurrent protection setting value for the low-voltage or high-voltage bridge arm. Figure 20 in, |U sm | represents the absolute value of the capacitor voltage in the submodule of the low-voltage or high-voltage bridge arm, U set This indicates the overvoltage protection setting value for the submodule in the low-voltage or high-voltage bridge arm. Figure 21 in, |U dc | Represents the absolute value of the DC voltage of the low-voltage bridge arm or the DC voltage of the high-voltage bridge arm, U set1 This indicates the DC overvoltage protection setting value for the low-voltage or high-voltage bridge arm. Figure 22In a DC transformer, when the transformer comprises a single unit, the low-voltage DC limiting current difference is the absolute value of the difference between the fault pole DC current and the non-fault pole DC current |I dcline1 -I dcline2 When a DC transformer comprises two symmetrically arranged units, the low-voltage side DC pole current is the absolute value of the difference between the low-voltage side fault pole DC current, the neutral line DC current, and the common arm current, i.e., |I dcline1 -I ground _ centrl1 -I dcW |or|I dcline2 -I ground _ centrl1 -I dcW |,I dcline1 I represents the DC current of the faulty electrode or the DC current of the non-faulty electrode. dcline2 Indicates i dcline1 The corresponding non-faulty pole DC current or faulty pole DC current, I ground _ centrl1 For the neutral line DC current, I dcW For the common arm current, I set1 This indicates the operating setting value of the DC pole current differential protection, i.e., the operating setting value of the first DC current differential protection. Figure 23 In this context, the low-voltage DC port current difference is the absolute value of the difference between the DC current at the faulty port on the low-voltage side and the DC current at the non-faulty port on the low-voltage side |I dcport1 -I dcport2 |,I set2 This indicates the DC port current differential protection setting, i.e., the second DC current differential protection operating setting. Figures 19 to 24 In this case, the values ​​of both the A and B terminals of the size comparator are absolute values.

[0107] Step S203: Generate the corresponding protection action signal based on the fault type. For details, please refer to [link to relevant documentation]. Figure 1 Step S103 of the illustrated embodiment will not be described again here.

[0108] Step S204: Generate a corresponding interlocking control command based on the protection action signal, and interlock the corresponding bridge arm according to the interlocking control command. For details, please refer to [link to relevant documentation]. Figure 1 Step S104 of the illustrated embodiment will not be described again here.

[0109] The DC transformer fault protection method provided in this invention includes key fault electrical quantities of the DC transformer in its low-voltage arm parameters, high-voltage arm parameters, and common arm parameters. The parameter acquisition is comprehensive. Considering the slow development of faults on the low-voltage side of a DC transformer, a low-voltage side DC pole current is further defined, and its calculation method is clarified. When the DC transformer has two or more low-voltage side ports, the low-voltage arm parameters also include the difference current between the DC current at the faulty low-voltage side port and the DC current at the non-faulty low-voltage side port, improving the sensitivity of low-voltage side fault detection. This provides a foundation for subsequently judging short-circuit faults based on the relationship between the low-voltage arm parameters, high-voltage arm parameters, and common arm parameters and preset protection settings. By comparing the magnitudes of the low-voltage arm parameters, high-voltage arm parameters, and common arm parameters with specific preset protection settings, it accurately determines whether a low-voltage side short-circuit fault or a high-voltage side short-circuit fault has occurred, achieving rapid identification of DC transformer short-circuit faults and providing a basis for generating corresponding protection action signals based on the short-circuit fault type.

[0110] This embodiment provides a DC transformer fault protection method, and the topology diagram of the DC transformer is shown below. Figure 4 and Figure 5 As shown, the topology of a DC transformer can be a unipolar circuit or a symmetrical bipolar circuit. Figure 4 This is a topology diagram of a single-pole DC transformer circuit. Figure 5 This is a symmetrical bipolar circuit topology diagram of a DC transformer. The DC transformer includes at least one unit; each unit includes a high-voltage bridge arm, a low-voltage bridge arm, and a common bridge arm; one end of the high-voltage bridge arm connects to one end of the low-voltage bridge arm and one end of the common bridge arm to form a common point, the other end of the low-voltage bridge arm and the other end of the common bridge arm form the low-voltage side port, and the other end of the high-voltage bridge arm and the other end of the common bridge arm form the high-voltage side port, where L represents low voltage and H represents high voltage; Figure 3 This is a flowchart of a DC transformer fault protection method according to an embodiment of the present invention, such as... Figure 3 As shown, the process includes the following steps:

[0111] Step S301: Obtain the low-voltage arm parameters, high-voltage arm parameters, and common arm parameters. For details, please refer to [link to relevant documentation]. Figure 2 Step S201 of the illustrated embodiment will not be described again here.

[0112] Step S302: Determine the type of short-circuit fault based on the relationship between the low-voltage bridge arm parameters, high-voltage bridge arm parameters, and common bridge arm parameters and the preset protection settings. For details, please refer to [link to relevant documentation]. Figure 2 Step S202 of the illustrated embodiment will not be described again here.

[0113] Step S303: Generate the corresponding protection action signal according to the short circuit fault type.

[0114] Specifically, step S303 includes:

[0115] Step S3031: When a low-voltage side short-circuit fault occurs, a first low-voltage bridge arm protection action signal and a first high-voltage bridge arm protection action signal are generated. Specifically, as follows... Figure 25 As shown, when a voltage-side short-circuit fault occurs because the low-voltage bridge arm current is greater than or equal to the overcurrent protection setting value of the first bridge arm, a corresponding low-voltage bridge arm overcurrent protection action signal is generated.

[0116] When a low-voltage side short-circuit fault occurs when the capacitor voltage of the low-voltage bridge arm submodule is greater than or equal to the overvoltage protection action setting value of the first submodule, a corresponding overvoltage protection action signal for the first submodule is generated.

[0117] When a short-circuit fault occurs on the low-voltage side, the DC voltage on the low-voltage side is greater than or equal to the first DC overvoltage protection action setting value. A corresponding first DC overvoltage protection action signal is generated.

[0118] When a short-circuit fault occurs on the low-voltage side, the difference in DC pole current on the low-voltage side is greater than or equal to the first DC current differential protection action setting value. The corresponding first DC current differential protection action signal is generated.

[0119] When a short-circuit fault occurs on the low-voltage side, the difference between the DC current at the fault port and the DC current at the non-fault port is greater than or equal to the operating setting of the second DC current differential protection. A corresponding second DC current differential protection operating signal is generated.

[0120] The above-mentioned low-voltage bridge arm overcurrent protection action signal, first submodule overvoltage protection action signal, first DC overvoltage protection action signal, first DC current differential protection action signal and second DC current differential protection action signal are combined with logic gates to generate the first low-voltage bridge arm protection action signal.

[0121] Specifically, all protection action signals are represented by logic values ​​"1" and "0". A logic value "1" represents that the protection does not operate, and a logic value "0" represents that the protection operates.

[0122] (1) In the initial state, all protection action signals on the high-voltage side and the low-voltage side are "1", that is, the protection does not operate.

[0123] (2) When a low-voltage side short-circuit fault occurs, such as Figure 25 As shown, at least one of the following protection mechanisms on the low-voltage side—low-voltage bridge arm overcurrent protection, first submodule overvoltage protection, first DC overvoltage protection, first DC current differential protection, and second DC current differential protection—will activate. The protection action signal corresponding to the protection action will become "0", thereby making the first low-voltage bridge arm protection action signal generated by merging with the logic gate "0".

[0124] (3) When a short-circuit fault occurs on the low-voltage side, all protections on the high-voltage side will not operate, such as Figure 26 As shown, the first high-voltage bridge arm protection action signal is "1" at this time.

[0125] Step S3032: When a first high-voltage side short-circuit fault occurs, a second low-voltage bridge arm protection action signal, a second high-voltage bridge arm protection action signal, and a first common bridge arm protection signal are generated. Specifically, as follows... Figure 26 As shown:

[0126] When a short-circuit fault occurs on the first high-voltage side, the overcurrent protection action signal of the second bridge arm is generated when the high-voltage arm current is greater than or equal to the overcurrent protection action setting of the second bridge arm.

[0127] When a short-circuit fault occurs on the first high-voltage side due to a capacitor voltage greater than or equal to the overvoltage protection setting value of the second submodule, a corresponding overvoltage protection signal for the second submodule is generated.

[0128] When a short-circuit fault occurs on the first high-voltage side, the DC voltage on the high-voltage side is greater than or equal to the second DC overvoltage protection setting value. A corresponding second DC overvoltage protection signal is generated.

[0129] The aforementioned second bridge arm overcurrent protection action signal, second submodule overvoltage protection signal, and second DC overvoltage protection signal are combined with logic gates to generate the second high-voltage bridge arm protection action signal.

[0130] Specifically, all protection action signals are represented by logic values ​​"1" and "0". A logic value "1" represents that the protection does not operate, and a logic value "0" represents that the protection operates.

[0131] (1) In the initial state, all protection action signals on the high-voltage side and the low-voltage side are "1", that is, the protection does not operate.

[0132] (2) When a short circuit fault occurs on the first high-voltage side, such as Figure 26 As shown, at least one of the following protection actions will be performed: the overcurrent protection of the second bridge arm on the high-voltage side, the overvoltage protection of the second submodule, and the second DC overvoltage protection. The protection action signal corresponding to the protection action will become "0", thereby the second high-voltage bridge arm protection action signal generated by merging with the logic gate will also become "0".

[0133] (3) When a short-circuit fault occurs on the first high-voltage side, the low-voltage bridge arm overcurrent protection, the first submodule overvoltage protection, the first DC overvoltage protection, the first DC current differential protection, and the second DC current differential protection on the low-voltage side will all fail to operate. Figure 25 As shown, the second low-voltage bridge arm protection action signal generated by merging with the logic gate is "1".

[0134] (4) When a short circuit fault occurs on the first high-voltage side, the common arm does not operate, and the first common arm protection signal generated is "1".

[0135] Step S3033: When a short-circuit fault occurs on the second high-voltage side, a third low-voltage bridge arm protection action signal, a third high-voltage bridge arm protection action signal, and a second common bridge arm protection action signal are generated. The second low-voltage bridge arm protection action signal and the third low-voltage bridge arm protection action signal are the same and different from the first low-voltage bridge arm protection action signal. The second high-voltage bridge arm protection action signal and the third high-voltage bridge arm protection action signal are the same and different from the first high-voltage bridge arm protection action signal. The first common bridge arm protection action signal and the second common bridge arm protection action signal are different.

[0136] Specifically, all protection action signals are represented by logic values ​​"1" and "0". A logic value "1" represents that the protection does not operate, and a logic value "0" represents that the protection operates.

[0137] (1) In the initial state, all protection action signals on the high-voltage side and the low-voltage side are "1", that is, the protection does not operate.

[0138] (2) When a short circuit fault occurs on the second high-voltage side, such as Figure 26 As shown, at least one of the following protection actions will be activated: the overcurrent protection of the second bridge arm on the high-voltage side, the overvoltage protection of the second submodule, and the second DC overvoltage protection. The protection action signal corresponding to the protection action will become "0", thereby the third high-voltage bridge arm protection action signal generated by merging with the logic gate will also become "0".

[0139] (3) When a second high-voltage side short-circuit fault occurs, the low-voltage side low-voltage bridge arm overcurrent protection, the first submodule overvoltage protection, the first DC overvoltage protection, the first DC current differential protection, and the second DC current differential protection will all fail to operate. Figure 25 As shown, the third low-voltage bridge arm protection action signal generated by merging with the logic gate is "1".

[0140] (4) When a short circuit fault occurs on the second high voltage side, the common bridge arm will operate, and the generated second common bridge arm protection signal will be “0”.

[0141] Step S304: Generate a corresponding interlocking control command based on the protection action signal, and interlock the corresponding bridge arm according to the interlocking control command.

[0142] Specifically, step S304 includes:

[0143] Step S3041: When a low-voltage side short-circuit fault occurs, an AND logic gate is used to combine the first low-voltage bridge arm protection action signal and the first high-voltage bridge arm protection action signal to generate a first low-voltage bridge arm blocking control command.

[0144] For example, all protection action signals are represented by logic values ​​"1" and "0". A logic value "1" represents that the protection does not operate, and a logic value "0" represents that the protection operates. The working status of each bridge arm is also represented by logic values ​​"1" and "0". A logic value "1" represents that the bridge arm is unlocked, and a logic value "0" represents that the bridge arm is locked.

[0145] Step a1, as follows Figure 25 As shown, in the initial state, all protection action signals on both the high-voltage and low-voltage sides are "1", meaning the protection does not operate. The first low-voltage bridge arm blocking control command, generated by merging the first low-voltage bridge arm protection action signal and the first high-voltage bridge arm protection action signal using an AND logic gate, is also "1", meaning the high-voltage bridge arm, low-voltage bridge arm, and common bridge arm of the DC transformer are unlocked.

[0146] Step a2, when a low-voltage side short-circuit fault occurs, such as Figure 25 As shown, at least one of the following protections on the low-voltage side—the low-voltage bridge arm overcurrent protection, the first submodule overvoltage protection, the first DC overvoltage protection, the first DC current differential protection, and the second DC current differential protection—will activate. The protection activation signal corresponding to this activation will become "0," thus the first low-voltage bridge arm protection activation signal, generated by combining it with the logic gate, will also become "0." All protections on the high-voltage side will not activate. Figure 26 As shown, the first high-voltage bridge arm protection action signal is "1" at this time. An AND logic gate is used to combine the first low-voltage bridge arm protection action signal and the first high-voltage bridge arm protection action signal to generate the first low-voltage bridge arm interlocking control command, which becomes "0" and is then sent to the external valve control system of the low-voltage bridge arm.

[0147] Step a3, as follows Figure 26 and Figure 27 As shown, since the first high-voltage bridge arm protection action signal "1" and the common bridge arm protection action signal are both "1", the high-voltage bridge arm unlocking control command generated by combining the "AND" logic gates is also "1", and the common bridge arm unlocking control command generated by combining the "AND" logic gates is also "1", that is, neither the high-voltage bridge arm nor the common bridge arm is locked.

[0148] Step S3042: When a first high-voltage side short-circuit fault occurs, an AND gate is used to combine the second low-voltage bridge arm protection action signal and the second high-voltage bridge arm protection action signal to generate a second low-voltage bridge arm blocking control command; an AND gate is used to combine the second high-voltage bridge arm protection action signal and the first common bridge arm protection action signal to generate a first high-voltage bridge arm blocking control command and a first common bridge arm blocking control command. Specifically:

[0149] Step b1, as follows Figure 25As shown, in the initial state, all protection action signals on both the high-voltage and low-voltage sides are "1", meaning the protection does not operate. The second low-voltage bridge arm blocking control command generated by merging the second low-voltage bridge arm protection action signal and the second high-voltage bridge arm protection action signal using an AND logic gate is also "1", meaning the high-voltage bridge arm, low-voltage bridge arm, and common bridge arm of the DC transformer are unlocked.

[0150] Step b2, when a first high-voltage side short-circuit fault occurs, such as Figure 26 As shown, at least one of the following protection actions will be performed: the overcurrent protection of the second bridge arm on the high-voltage side, the overvoltage protection of the second submodule, and the second DC overvoltage protection. The protection action signal corresponding to the protection action will become "0", thereby the second high-voltage bridge arm protection action signal generated by merging with the logic gate will also become "0".

[0151] Step b3: When a first high-voltage side short-circuit fault occurs, regardless of whether the low-voltage side protection operates, if... Figure 25 As shown, the second low-voltage bridge arm protection action signal and the second high-voltage bridge arm protection action signal "0" are combined with logic gates to generate a second low-voltage bridge arm interlocking control command, which will both become "0" and be sent to the external valve control system of the low-voltage bridge arm.

[0152] Step b4: When a short circuit fault occurs on the first high-voltage side, regardless of whether the common arm protection operates, the first common arm protection operation signal and the second high-voltage arm protection operation signal "0" are combined with the logic gate to generate the first common arm blocking control command, which will both become "0" and be sent to the external valve control system of the common arm.

[0153] Step b5, as follows Figure 26 As shown, the second high-voltage bridge arm protection action signal "0" and the first common bridge arm protection action signal are combined with the logic gate to generate the first high-voltage bridge arm interlocking control command, which is then changed to "0" and sent to the external valve control system of the high-voltage bridge arm.

[0154] Step S3043: When a short circuit fault occurs on the second high-voltage side, the low-voltage bridge arm is locked according to the third low-voltage bridge arm locking control command, the high-voltage bridge arm is locked according to the second high-voltage bridge arm locking control command, and the common bridge arm is locked according to the second common bridge arm locking control command.

[0155] Specifically:

[0156] Step c1, as follows Figure 25 As shown, in the initial state, all protection action signals on both the high-voltage and low-voltage sides are "1", meaning the protection does not operate. The third low-voltage bridge arm blocking control command, generated by combining the third low-voltage bridge arm protection action signal and the third high-voltage bridge arm protection action signal using an AND logic gate, is also "1", meaning the high-voltage bridge arm, low-voltage bridge arm, and common bridge arm of the DC transformer are unlocked.

[0157] Step c2, when a second high-voltage side short-circuit fault occurs, such as Figure 26 As shown, at least one of the following protection actions will be activated: the overcurrent protection of the second bridge arm on the high-voltage side, the overvoltage protection of the second submodule, and the second DC overvoltage protection. The protection action signal corresponding to the protection action will become "0", thereby the third high-voltage bridge arm protection action signal generated by merging with the logic gate will also become "0".

[0158] Step c3: When a second high-voltage side short-circuit fault occurs, regardless of whether the low-voltage side protection operates, if... Figure 25 As shown, the third low-voltage bridge arm protection action signal and the third high-voltage bridge arm protection action signal "0" are combined with logic gates to generate the third low-voltage bridge arm interlocking control command, which will both become "0" and be sent to the external valve control system of the low-voltage bridge arm.

[0159] Step c4: When a short circuit fault occurs on the second high-voltage side, the common arm operates. The second common arm protection action signal "0" and the third high-voltage arm protection action signal "0" are combined with logic gates to generate a second common arm interlocking control command, which will both become "0" and be sent to the external valve control system of the common arm.

[0160] Step c5, as follows Figure 27 As shown, the third high-voltage bridge arm protection action signal "0" and the second common bridge arm protection action signal "0" are combined with the logic gate to generate the second high-voltage bridge arm interlocking control command, which is then sent to the external valve control system of the high-voltage bridge arm.

[0161] Step S3044: When a low-voltage side short-circuit fault occurs, the low-voltage bridge arm where the fault is located is locked according to the first low-voltage bridge arm locking control command.

[0162] Step S3045: When a first high-voltage side short-circuit fault occurs, the low-voltage bridge arm is locked according to the second low-voltage bridge arm locking control command; the high-voltage bridge arm is locked according to the first high-voltage bridge arm locking control command; and the common bridge arm is locked according to the first common bridge arm locking control command.

[0163] Step S3046: When a short circuit fault occurs on the second high-voltage side, the low-voltage bridge arm is locked according to the third low-voltage bridge arm locking control command, the high-voltage bridge arm is locked according to the second high-voltage bridge arm locking control command, and the common bridge arm is locked according to the second common bridge arm locking control command.

[0164] Specifically, when a low-voltage side short-circuit fault occurs, the low-voltage bridge arm where the fault is located is locked according to the first low-voltage bridge arm locking control command "0". However, the high-voltage bridge arm and the common bridge arm are not locked according to the high-voltage bridge arm unlocking control command "1" and the common bridge arm unlocking control command "1". In other words, when a low-voltage side short-circuit fault occurs, only the low-voltage bridge arm where the fault is located is locked.

[0165] When a short circuit fault occurs on the first high-voltage side, the low-voltage bridge arm is locked according to the second low-voltage bridge arm unlocking control command "0", the high-voltage bridge arm is locked according to the first high-voltage bridge arm locking control command "0", and the common bridge arm is locked according to the first common bridge arm locking control command "0".

[0166] When a short circuit fault occurs on the second high-voltage side, the low-voltage bridge arm is locked according to the third low-voltage bridge arm unlocking control command "0", the high-voltage bridge arm is locked according to the second high-voltage bridge arm locking control command "0", and the common bridge arm is locked according to the second common bridge arm locking control command "0".

[0167] When a high-voltage side short-circuit fault occurs, all low-voltage bridge arms, high-voltage bridge arms, and common bridge arms of the DC transformer are locked to quickly cut off the fault current.

[0168] The DC transformer fault protection method provided in this invention generates a first low-voltage bridge arm protection action signal and a first high-voltage bridge arm protection action signal when a low-voltage side short-circuit fault occurs; generates a second low-voltage bridge arm protection action signal, a second high-voltage bridge arm protection action signal, and a first common bridge arm protection signal when a first high-voltage side short-circuit fault occurs; and generates a third low-voltage bridge arm protection action signal, a third high-voltage bridge arm protection action signal, and a second common bridge arm protection action signal when a second high-voltage side short-circuit fault occurs. This achieves the goal of quickly generating corresponding protection action signals based on the occurrence of a low-voltage side short-circuit fault or a high-voltage side short-circuit fault, providing a basis for subsequently generating corresponding blocking control commands based on the protection action signals. When a low-voltage side short-circuit fault occurs, the low-voltage bridge arm where the fault occurs is blocked. When a high-voltage side short-circuit fault occurs, all low-voltage bridge arms, high-voltage bridge arms, and common bridge arms are blocked, that is, the entire DC transformer is blocked, and the fault current is quickly cut off, ensuring that when a short-circuit fault occurs in the DC transformer, it will not cause harm to the DC transformer and DC system.

[0169] This embodiment also provides a DC transformer fault protection device, which is used to implement the above embodiments and preferred embodiments; details already described will not be repeated. As used below, the term "module" can refer to a combination of software and / or hardware that performs a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0170] This embodiment provides a DC transformer fault protection device, such as... Figure 28As shown, the DC transformer includes at least one unit; each unit includes a high-voltage bridge arm, a low-voltage bridge arm, and a common bridge arm; one end of the high-voltage bridge arm connects to one end of the low-voltage bridge arm and one end of the common bridge arm to form a common point; the other end of the low-voltage bridge arm and the other end of the common bridge arm form a low-voltage side port; the other end of the high-voltage bridge arm and the other end of the common bridge arm form a high-voltage side port; the DC transformer fault protection device includes:

[0171] Module 2801 is used to obtain low-voltage bridge arm parameters, high-voltage bridge arm parameters, and common bridge arm parameters;

[0172] The judgment module 2802 is used to determine the type of short circuit fault based on the relationship between the low-voltage bridge arm parameters, the high-voltage bridge arm parameters and the common bridge arm parameters and the preset protection settings.

[0173] The generation module 2803 is used to generate corresponding protection action signals according to the short-circuit fault type;

[0174] The interlocking module 2804 is used to generate a corresponding interlocking control command based on the protection action signal, and to interlock the corresponding bridge arm according to the interlocking control command.

[0175] In some optional implementations, the determination module 2802 includes:

[0176] The first judgment unit is used to determine that a low-voltage side short-circuit fault has occurred when any one or more of the following conditions are met: the low-voltage bridge arm parameter is greater than or equal to the first bridge arm overcurrent protection action setting value, the low-voltage bridge arm submodule capacitor voltage is greater than or equal to the first submodule overvoltage protection action setting value, the low-voltage side DC voltage is greater than or equal to the first DC overvoltage protection action setting value, and the low-voltage side DC pole current is greater than or equal to the first DC current differential protection action setting value, and the duration exceeds a first preset time.

[0177] The second judgment unit is used to determine that a first high-voltage side short circuit fault has occurred when any one or more of the following conditions are met: the high-voltage bridge arm parameter is greater than or equal to the second bridge arm overcurrent protection action setting value, the high-voltage bridge arm submodule capacitor voltage is greater than or equal to the second submodule overvoltage protection action setting value, and the high-voltage side DC voltage is greater than or equal to the second DC overvoltage protection action setting value, and the duration exceeds the second preset time.

[0178] The third judgment unit is used to determine that a second high-voltage side short circuit fault has occurred when the common arm current is greater than or equal to the third preset overcurrent protection setting value, and the high-voltage arm parameter is greater than or equal to the second arm overcurrent protection action setting value, the high-voltage arm submodule capacitor voltage is greater than or equal to the second submodule overvoltage protection action setting value, and the high-voltage side DC voltage is greater than or equal to the second DC overvoltage protection action setting value, and the duration exceeds the third preset time.

[0179] In some alternative implementations, the generation module 2803 includes:

[0180] The first generation unit is used to generate a first low-voltage bridge arm protection action signal and a first high-voltage bridge arm protection action signal when a low-voltage side short-circuit fault occurs.

[0181] The second generation unit is used to generate a second low-voltage bridge arm protection action signal, a second high-voltage bridge arm protection action signal, and a first common bridge arm protection signal when a first high-voltage side short-circuit fault occurs.

[0182] The third generation unit is used to generate a third low-voltage bridge arm protection action signal, a third high-voltage bridge arm protection action signal, and a second common bridge arm protection action signal when a second high-voltage side short-circuit fault occurs. The second low-voltage bridge arm protection action signal and the third low-voltage bridge arm protection action signal are the same and different from the first low-voltage bridge arm protection action signal. The second high-voltage bridge arm protection action signal and the third high-voltage bridge arm protection action signal are the same and different from the first high-voltage bridge arm protection action signal. The first common bridge arm protection action signal and the second common bridge arm protection action signal are different.

[0183] In some alternative implementations, the locking module 2804 includes:

[0184] The first merging generation unit is used to generate a first low-voltage bridge arm blocking control command by merging the first low-voltage bridge arm protection action signal and the first high-voltage bridge arm protection action signal with an AND logic gate when a low-voltage side short-circuit fault occurs.

[0185] The second merging generation unit is used to, when a first high-voltage side short-circuit fault occurs, use an AND logic gate to merge the second low-voltage bridge arm protection action signal and the second high-voltage bridge arm protection action signal to generate a second low-voltage bridge arm blocking control command; and use an AND logic gate to merge the second high-voltage bridge arm protection action signal and the first common bridge arm protection action signal to generate a first high-voltage bridge arm blocking control command and a first common bridge arm blocking control command.

[0186] The third merging generation unit is used to, when a short-circuit fault occurs on the second high-voltage side, use AND logic gates to merge the third low-voltage bridge arm protection action signal and the third high-voltage bridge arm protection action signal to generate a third low-voltage bridge arm blocking control command; and use AND logic gates to merge the third high-voltage bridge arm protection action signal and the second common bridge arm protection action signal to generate a second high-voltage bridge arm blocking control command and a second common bridge arm blocking control command.

[0187] The first locking unit is used to lock the low-voltage bridge arm where the fault occurs according to the first low-voltage bridge arm locking control command when a low-voltage side short-circuit fault occurs.

[0188] The second interlocking unit is used to lock the low-voltage bridge arm according to the second low-voltage bridge arm interlocking control command when a first high-voltage side short-circuit fault occurs; lock the high-voltage bridge arm according to the first high-voltage bridge arm interlocking control command; and lock the common bridge arm according to the first common bridge arm interlocking control command.

[0189] The third interlocking unit is used to lock the low-voltage bridge arm according to the third low-voltage bridge arm interlocking control command, lock the high-voltage bridge arm according to the second high-voltage bridge arm interlocking control command, and lock the common bridge arm according to the second common bridge arm interlocking control command when a second high-voltage side short-circuit fault occurs.

[0190] Further functional descriptions of the above modules and units are the same as those in the corresponding embodiments described above, and will not be repeated here.

[0191] In this embodiment, the DC transformer fault protection device is presented in the form of a functional unit. Here, a unit refers to an ASIC (Application Specific Integrated Circuit) circuit, a processor and memory that execute one or more software or fixed programs, and / or other devices that can provide the above functions.

[0192] This invention also provides a computer device having the above-described features. Figure 28 The DC transformer fault protection device shown is shown.

[0193] Please see Figure 29 , Figure 29 This is a schematic diagram of the structure of a computer device provided in an optional embodiment of the present invention, such as... Figure 29 As shown, the computer device includes one or more processors 10, memory 20, and interfaces for connecting the components, including high-speed interfaces and low-speed interfaces. The components communicate with each other via different buses and can be mounted on a common motherboard or otherwise installed as needed. The processors can process instructions executed within the computer device, including instructions stored in or on memory to display graphical information of a GUI on external input / output devices (such as display devices coupled to the interfaces). In some alternative implementations, multiple processors and / or multiple buses can be used with multiple memories and multiple memory modules, if desired. Similarly, multiple computer devices can be connected, each providing some of the necessary operations (e.g., as a server array, a group of blade servers, or a multiprocessor system). Figure 29 Take a processor 10 as an example.

[0194] Processor 10 may be a central processing unit, a network processor, or a combination thereof. Processor 10 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The programmable logic device may be a complex programmable logic device (CAMP), a field-programmable gate array (FPGA), a general-purpose array logic (GDA), or any combination thereof.

[0195] The memory 20 stores instructions executable by at least one processor 10 to cause the at least one processor 10 to perform the method shown in the above embodiments.

[0196] The memory 20 may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created based on the use of the computer device. Furthermore, the memory 20 may include high-speed random access memory and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some alternative embodiments, the memory 20 may optionally include memory remotely located relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0197] The memory 20 may include volatile memory, such as random access memory; the memory may also include non-volatile memory, such as flash memory, hard disk or solid-state drive; the memory 20 may also include a combination of the above types of memory.

[0198] The computer device also includes an input device 30 and an output device 40. The processor 10, memory 20, input device 30, and output device 40 can be connected via a bus or other means. Figure 29 Taking the example of a connection between China and Israel via a bus.

[0199] Input device 30 can receive input numerical or character information, and generate key signal inputs related to user settings and function control of the computer device, such as a touchscreen, keypad, mouse, trackpad, touchpad, joystick, one or more mouse buttons, trackball, joystick, etc. Output device 40 may include display devices, auxiliary lighting devices (e.g., LEDs), and haptic feedback devices (e.g., vibration motors). The aforementioned display devices include, but are not limited to, liquid crystal displays, light-emitting diodes, displays, and plasma displays. In some alternative embodiments, the display device may be a touchscreen.

[0200] This invention also provides a computer-readable storage medium. The methods described above according to embodiments of the invention can be implemented in hardware or firmware, or implemented as computer code that can be recorded on a storage medium, or implemented as computer code downloaded via a network and originally stored on a remote storage medium or a non-transitory machine-readable storage medium and then stored on a local storage medium. Thus, the methods described herein can be processed by software stored on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; further, the storage medium can also include combinations of the above types of memory. It is understood that computers, processors, microprocessor controllers, or programmable hardware include storage components capable of storing or receiving software or computer code, which, when accessed and executed by the computer, processor, or hardware, implements the methods shown in the above embodiments.

[0201] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method for fault protection of a DC transformer, characterized in that, The DC transformer includes at least one unit; each unit includes a high-voltage bridge arm, a low-voltage bridge arm, and a common bridge arm; one end of the high-voltage bridge arm is connected to one end of the low-voltage bridge arm and one end of the common bridge arm to form a common point, the other end of the low-voltage bridge arm and the other end of the common bridge arm form a low-voltage side port, and the other end of the high-voltage bridge arm and the other end of the common bridge arm form a high-voltage side port; the method includes: Obtain the parameters of the low-voltage bridge arm, the high-voltage bridge arm, and the common bridge arm; The type of short-circuit fault is determined based on the relationship between the low-voltage bridge arm parameters, the high-voltage bridge arm parameters, and the common bridge arm parameters and the preset protection settings. Generate a corresponding protection action signal based on the short-circuit fault type; Generate a corresponding interlocking control command based on the protection action signal, and interlock the corresponding bridge arm according to the interlocking control command; The high-voltage bridge arm, low-voltage bridge arm, and common bridge arm each include multiple sub-modules connected in series; The low-voltage bridge arm parameters include any one or more of the following: low-voltage bridge arm current, low-voltage bridge arm submodule capacitor voltage, low-voltage side DC voltage, and low-voltage side DC pole current. The high-voltage bridge arm parameters include any one or more of the high-voltage bridge arm current, the submodule capacitor voltage of the high-voltage bridge arm, and the DC voltage on the high-voltage side. The common arm parameters include the common arm current; When a DC transformer comprises a single unit, the low-voltage side DC pole current is the difference between the fault pole DC current and the non-fault pole DC current. When a DC transformer includes two symmetrically arranged units, the low-voltage side DC pole current is the difference between the low-voltage side fault pole DC current, the neutral line DC current, and the common arm current. When a DC transformer includes two or more low-voltage side ports, the low-voltage bridge arm parameters also include the difference current between the DC current at the faulty low-voltage side port and the DC current at the non-faulty low-voltage side port. The type of short-circuit fault determined based on the relationship between the low-voltage bridge arm parameters, the high-voltage bridge arm parameters, and the common bridge arm parameters and the preset protection settings includes: When any one or more of the following conditions are met—that the low-voltage bridge arm parameter is greater than or equal to the first bridge arm overcurrent protection setting, the low-voltage bridge arm submodule capacitor voltage is greater than or equal to the first submodule overvoltage protection setting, the low-voltage side DC voltage is greater than or equal to the first DC overvoltage protection setting, and the low-voltage side DC pole current is greater than or equal to the first DC current differential protection setting—and the duration exceeds the first preset time, a low-voltage side short-circuit fault is determined to have occurred. When any one or more of the following conditions are met: the high-voltage bridge arm parameter is greater than or equal to the second bridge arm overcurrent protection action setting value, the high-voltage bridge arm submodule capacitor voltage is greater than or equal to the second submodule overvoltage protection action setting value, and the high-voltage side DC voltage is greater than or equal to the second DC overvoltage protection action setting value, and the duration exceeds the second preset time, a first high-voltage side short circuit fault is determined to have occurred. When the current of the common bridge arm is greater than or equal to the third preset overcurrent protection setting, and the high-voltage bridge arm parameter is greater than or equal to the second bridge arm overcurrent protection action setting, the high-voltage bridge arm sub-module capacitor voltage is greater than or equal to the second sub-module overvoltage protection action setting, and the high-voltage side DC voltage is greater than or equal to the second DC overvoltage protection action setting, and the duration exceeds the third preset time, it is determined that a second high-voltage side short circuit fault has occurred. The step of generating the corresponding protection action signal based on the short-circuit fault type includes: When a low-voltage side short-circuit fault occurs, a first low-voltage bridge arm protection action signal and a first high-voltage bridge arm protection action signal are generated. When a short-circuit fault occurs on the first high-voltage side, a second low-voltage bridge arm protection action signal, a second high-voltage bridge arm protection action signal, and a first common bridge arm protection action signal are generated. When a second high-voltage side short-circuit fault occurs, a third low-voltage bridge arm protection action signal, a third high-voltage bridge arm protection action signal, and a second common bridge arm protection action signal are generated. The second low-voltage bridge arm protection action signal is the same as the third low-voltage bridge arm protection action signal and is different from the first low-voltage bridge arm protection action signal. The second high-voltage bridge arm protection action signal is the same as the third high-voltage bridge arm protection action signal and is different from the first high-voltage bridge arm protection action signal. The first common bridge arm protection action signal and the second common bridge arm protection action signal are different.

2. The method according to claim 1, characterized in that, The corresponding interlocking control command generated based on the protection action signal includes: When a low-voltage side short-circuit fault occurs, an AND logic gate is used to combine the first low-voltage bridge arm protection action signal and the first high-voltage bridge arm protection action signal to generate a first low-voltage bridge arm blocking control command. When a short-circuit fault occurs on the first high-voltage side, an AND logic gate is used to combine the second low-voltage bridge arm protection action signal and the second high-voltage bridge arm protection action signal to generate a second low-voltage bridge arm blocking control command; an AND logic gate is used to combine the second high-voltage bridge arm protection action signal and the first common bridge arm protection action signal to generate a first high-voltage bridge arm blocking control command and a first common bridge arm blocking control command. When a short-circuit fault occurs on the second high-voltage side, an AND logic gate is used to combine the third low-voltage bridge arm protection action signal and the third high-voltage bridge arm protection action signal to generate a third low-voltage bridge arm blocking control command; an AND logic gate is also used to combine the third high-voltage bridge arm protection action signal and the second common bridge arm protection action signal to generate a second high-voltage bridge arm blocking control command and a second common bridge arm blocking control command.

3. The method according to claim 2, characterized in that, According to the locking control command, the corresponding bridge arm is locked, including: When a low-voltage side short-circuit fault occurs, the low-voltage bridge arm where the fault is located is locked according to the first low-voltage bridge arm locking control command. When a first high-voltage side short-circuit fault occurs, the low-voltage bridge arm is locked according to the second low-voltage bridge arm locking control command; the high-voltage bridge arm is locked according to the first high-voltage bridge arm locking control command; and the common bridge arm is locked according to the first common bridge arm locking control command. When a second high-voltage side short-circuit fault occurs, the low-voltage bridge arm is locked according to the third low-voltage bridge arm locking control command, the high-voltage bridge arm is locked according to the second high-voltage bridge arm locking control command, and the common bridge arm is locked according to the second common bridge arm locking control command.

4. A DC transformer fault protection device, characterized in that, The fault protection method for a DC transformer according to any one of claims 1 to 3, wherein the DC transformer comprises at least one unit; each unit comprises a high-voltage bridge arm, a low-voltage bridge arm, and a common bridge arm; one end of the high-voltage bridge arm is connected to one end of the low-voltage bridge arm and one end of the common bridge arm to form a common point, the other end of the low-voltage bridge arm and the other end of the common bridge arm form a low-voltage side port, and the other end of the high-voltage bridge arm and the other end of the common bridge arm form a high-voltage side port; the device comprises: The acquisition module is used to acquire low-voltage bridge arm parameters, high-voltage bridge arm parameters, and common bridge arm parameters; The judgment module is used to determine the type of short-circuit fault based on the relationship between the low-voltage bridge arm parameters, the high-voltage bridge arm parameters, and the common bridge arm parameters and the preset protection settings. The generation module is used to generate corresponding protection action signals based on the type of short-circuit fault. The interlocking module is used to generate a corresponding interlocking control command based on the protection action signal, and to interlock the corresponding bridge arm according to the interlocking control command.

5. A computer device, characterized in that, include: The system includes a memory and a processor, which are interconnected. The memory stores computer instructions, and the processor executes the computer instructions to perform the DC transformer fault protection method according to any one of claims 1 to 3.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing a computer to execute the DC transformer fault protection method according to any one of claims 1 to 3.

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