Over-current protection method, system and equipment of starting resistor and medium

Abstract

The invention discloses an overcurrent protection method, system and device for a starting resistor, and a medium, which are suitable for a flexible direct-current power transmission system comprising a converter valve. The overcurrent protection method comprises the following steps: determining the working state of a starting resistor according to the charging state of the converter valve; acquiring real-time resistance values of two ends of the starting resistor based on the working state, and performing fault diagnosis on the starting resistor based on the real-time resistance values; when it is determined that the starting resistor does not have the fault, whether the starting resistor has an overcurrent risk or not is judged according to the real-time resistance value; and when it is determined that the starting resistor has the overcurrent risk, controlling the converter valve to exit the charging state so as to carry out overcurrent protection on the starting resistor, thereby preventing equipment damage caused by overcurrent of the starting resistor.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible direct current power transmission, and in particular to an overcurrent protection method, system, device and medium for a starting resistor. Background Art

[0002] When starting the flexible direct current transmission system to perform AC-DC conversion, the capacitors in the submodules in the converter valves in the flexible direct current transmission system need to undergo uncontrolled charging before operation. In order to reduce the charging current in the uncontrolled charging, the impact current voltage is reduced, and the risk of damage to the submodule due to overcurrent is reduced. The prior art often connects a starting resistor in series before the charging circuit in the transmission system to reduce the charging current through the starting resistor, and then when the submodule voltage reaches a certain value, the starting resistor is cut off through a bypass to reduce the loss during normal operation of the flexible direct current system.

[0003] However, in the process of limiting the current by the starting resistor, the existing technology lacks protection measures for the starting resistor, which results in excessive current passing through the starting resistor when the residual magnetism of the transformer is too large, the excitation inrush current is too large, and the starting resistor is easily overheated, and even the current limiting resistor equipment is damaged. At the same time, since the starting resistor will be repeatedly switched on and off during normal operation, the resistor sheet and the end of the resistor edge may be burned at high temperature, which will cause a large deviation between the actual resistance value of the resistor and the design value, and finally reduce the limiting effect of the resistor on the charging current, thereby increasing the risk of the submodule being damaged due to overcurrent. Summary of the invention

[0004] In order to solve the above technical problems, the present invention discloses an overcurrent protection method, system, device and medium for a starting resistor, which are used to prevent equipment damage caused by overcurrent of the starting resistor.

[0005] In order to achieve the above-mentioned object, in a first aspect, the present invention discloses an overcurrent protection method for a starting resistor, which is applicable to a flexible direct current transmission system including a converter valve; wherein the overcurrent protection method comprises:

[0006] Determining the working state of the starting resistor according to the charging state of the converter valve;

[0007] Acquire the real-time resistance value at both ends of the starting resistor based on the working state, and perform fault diagnosis on the starting resistor based on the real-time resistance value;

[0008] When it is determined that the starting resistor does not have a fault, judging whether the starting resistor has an overcurrent risk according to the real-time resistance value;

[0009] When it is determined that the starting resistor has an overcurrent risk, the converter valve is controlled to exit the charging state to perform overcurrent protection on the starting resistor.

[0010] The present invention discloses a method for overcurrent protection of a starting resistor. First, the working state of the starting resistor is identified according to the charging state of the converter valve, so as to timely perform overcurrent protection judgment on the starting resistor. After identifying the working state of the starting resistor, the real-time resistance value of the resistor is first obtained for fault diagnosis to avoid the inability to effectively limit the charging current due to the fault of the resistor itself, thereby improving the safety of charging protection. Furthermore, when it is identified that the starting resistor is not faulty, the real-time resistance value is used to determine whether to perform overcurrent protection on the starting resistor, and when it is determined that the starting resistor is in an overcurrent state, the converter valve is promptly controlled to exit the charging state to perform overcurrent protection on the starting resistor, thereby avoiding equipment damage caused by overcurrent of the starting resistor.

[0011] As a preferred example, the determining the working state of the starting resistor according to the charging state of the converter valve includes:

[0012] Acquire a charging circuit when the AC grid in the flexible DC power transmission system charges the converter valve;

[0013] When it is determined that the starting resistor is in the charging circuit and the AC power grid charges the converter valve through the starting resistor, it is determined that the starting resistor is in a working state.

[0014] The present invention is based on the fact that the function of the starting resistor is to limit the current in the initial charging stage, and thus when it is identified that the AC power grid is charging the converter valve through the starting resistor, the starting resistor can be protected from overcurrent in time.

[0015] As a preferred example, the step of obtaining the real-time resistance value at both ends of the starting resistor based on the working state includes:

[0016] When it is determined that the starting resistor is in a working state, obtaining a real-time current flowing into the starting resistor and a real-time voltage difference across the starting resistor;

[0017] The real-time resistance value at both ends of the starting resistor is obtained according to the real-time voltage difference and the real-time current.

[0018] The present invention utilizes the voltage value across the starting resistor and the real-time current flowing through the starting resistor to obtain the actual resistance value of the starting resistor during the current charging process, so as to determine the actual situation of the starting resistor, avoid the failure to limit the charging current due to damage to the resistor itself, and thus improve the safety of charging.

[0019] As a preferred example, the performing fault diagnosis on the starting resistor based on the real-time resistance value includes:

[0020] Obtaining a deviation between a factory designed resistance value of the startup resistor and the real-time resistance value, and comparing the deviation with a preset deviation threshold;

[0021] When the deviation is greater than or equal to the deviation threshold, it is determined that the starting resistor is faulty.

[0022] The present invention controls the damage of the resistor within an acceptable range by setting the deviation threshold, thereby avoiding the failure to effectively limit the charging current due to excessive resistance deviation, thereby reducing the risk of equipment damage, and avoiding the cost increase due to frequent replacement.

[0023] As a preferred example, judging whether the startup resistor has an overcurrent risk according to the real-time resistance value includes:

[0024] Obtaining the factory design voltage of the starting resistor to determine the protection setting current of the starting resistor according to the factory design voltage and the real-time resistance value;

[0025] When the real-time current is greater than the protection setting current, it is determined that the starting resistor has an overcurrent risk.

[0026] After the present invention identifies that there is no problem with the resistor itself, because the resistor may overheat and cause damage to itself due to excessive current, when it is identified that the real-time current flowing through the resistor is too large, it is determined that the current state of the starting resistor needs overcurrent protection, and the resistor is protected in time.

[0027] As a preferred example, the executing a corresponding protection action to end the charging process of the converter valve includes:

[0028] Controlling the grid-side circuit breaker connected in series between the AC grid and the starting resistor to disconnect;

[0029] The valve-side circuit breaker connected in series at one end of the converter valve is controlled to be disconnected; wherein the other end of the converter valve is connected in series with the starting resistor.

[0030] When the present invention identifies that there is an overcurrent risk in the starting resistor, the circuit breakers at both ends of the starting resistor are promptly tripped, thereby isolating the starting resistor, which not only avoids damage to the starting resistor, but also avoids the converter valve side from receiving excessive charging current, and can effectively prevent equipment damage caused by overcurrent of the starting resistor.

[0031] In a second aspect, the present invention discloses an overcurrent protection system for a starting resistor, which is applicable to a flexible direct current transmission system including a converter valve; wherein the overcurrent protection system comprises a state recognition module, a fault diagnosis module, an overcurrent recognition module and an overcurrent protection module;

[0032] The state identification module is used to determine the working state of the starting resistor according to the charging state of the converter valve;

[0033] The fault diagnosis module is used to obtain the real-time resistance value of the two ends of the starting resistor based on the working state, and perform fault diagnosis on the starting resistor based on the real-time resistance value;

[0034] The overcurrent identification module is used to determine whether there is an overcurrent risk of the starting resistor according to the real-time resistance value when it is determined that the starting resistor does not have a fault;

[0035] The overcurrent protection module is used to execute a corresponding protection action and end the charging process of the converter valve when it is determined that the starting resistor has an overcurrent risk.

[0036] The present invention discloses an overcurrent protection system for a starting resistor, which first identifies the working state of the starting resistor according to the charging state of the converter valve, and timely performs overcurrent protection judgment on the starting resistor. After identifying the working state of the starting resistor, the real-time resistance value of the resistor is first obtained for fault diagnosis to avoid the inability to effectively limit the charging current due to the fault of the resistor itself, thereby improving the safety of charging protection. Furthermore, when it is identified that the starting resistor is not faulty, the real-time resistance value is used to determine whether to perform overcurrent protection on the starting resistor, and when it is determined that the starting resistor is in an overcurrent state, the converter valve is promptly controlled to exit the charging state to perform overcurrent protection on the starting resistor, thereby avoiding equipment damage caused by overcurrent of the starting resistor.

[0037] As a preferred example, the fault diagnosis module includes a resistance value identification unit and a fault determination unit;

[0038] The resistance identification unit is used to obtain the real-time current flowing into the starting resistor and the real-time voltage difference across the starting resistor when it is determined that the starting resistor is in a working state; and obtain the real-time resistance value across the starting resistor according to the real-time voltage difference and the real-time current;

[0039] The fault determination unit is used to obtain the deviation between the factory designed resistance value of the starting resistor and the real-time resistance value, and compare the deviation with a preset deviation threshold; when the deviation is greater than or equal to the deviation threshold, it is determined that the starting resistor is faulty.

[0040] The present invention utilizes the voltage value across the starting resistor and the real-time current flowing through the starting resistor to obtain the actual resistance value of the starting resistor in the current charging process, so as to determine the actual situation of the starting resistor, thereby avoiding the inability to limit the charging current due to damage to the resistor itself, thereby improving the safety of charging, and by setting the deviation threshold to control the damage of the resistor within an acceptable range, it is avoided that the resistance value deviation is too large to cause the inability to effectively limit the charging current, thereby reducing the risk of equipment damage, and avoiding the cost increased due to frequent replacement.

[0041] In a third aspect, the present invention discloses a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the overcurrent protection method for a starting resistor as described in the first aspect is implemented.

[0042] In a fourth aspect, the present invention discloses a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the method for overcurrent protection of a starting resistor as described in any one of the first aspects is implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 : A flow chart of an overcurrent protection method for a starting resistor provided by an embodiment of the present invention;

[0044] Figure 2 : A schematic structural diagram of an overcurrent protection system for a starting resistor provided by another embodiment of the present invention;

[0045] Figure 3 : A schematic flow chart of an overcurrent protection method for a starting resistor provided by another embodiment of the present invention;

[0046] Figure 4 : A schematic diagram of a charging circuit including a starting resistor provided by another embodiment of the present invention;

[0047] Figure 5 : A flow chart of an overcurrent protection method for a starting resistor provided in another embodiment of the present invention. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. The singular forms of "a", "said" and "the" used in this disclosure and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0050] It should be understood that although the terms first, second, third, etc. may be used in the present disclosure to describe various information, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present disclosure, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0051] Embodiment 1

[0052] When starting the flexible DC transmission system, the capacitors in the submodules within the converter valves in the transmission system need to undergo a period of uncontrollable charging. To avoid damage to the submodules due to excessive charging current during uncontrollable charging, a starting resistor needs to be connected in series in the charging circuit of the submodule to limit the charging current. In summary, under the premise that a starting resistor is connected in series in the flexible DC transmission system to limit charging, this embodiment discloses a method for overcurrent protection of a starting resistor, which is suitable for a flexible DC transmission system including a converter valve to prevent equipment damage caused by overcurrent in the starting resistor. Specifically, the implementation process of the overcurrent protection method can be referred to. Figure 1 , mainly including the following steps:

[0053] Step 101: Determine the working state of the starting resistor according to the charging state of the converter valve.

[0054] In the disclosed embodiment, the flexible DC power transmission system is composed of a converter station and a DC transmission line. When the flexible DC power transmission system is started to supply power, the power supply end connected to the flexible DC power transmission system will first uncontrollably charge the capacitor in the submodule of the converter valve in the converter station in the DC power transmission system. The converter valve is used to connect the three-phase AC voltage provided by the power supply end to the DC end to obtain the desired DC voltage. The converter valve enters the corresponding charging state according to the start-up time of the flexible DC power transmission system, that is, it is in a state where it can receive the AC voltage provided by the power supply end. The starting resistor is connected in series between the power supply end and the converter valve to limit the charging current from the power supply end to the converter valve.

[0055] Step 102: acquiring real-time resistance values ​​at both ends of the starting resistor based on the working state, and performing fault diagnosis on the starting resistor based on the real-time resistance values.

[0056] In the disclosed embodiment, the startup resistor must be in a working state to detect faults. The working state refers to a state when a current flows through the startup resistor and the startup resistor is used to control the magnitude of the current. The resistance value of the resistor can be determined by obtaining the ratio of the voltage difference across the resistor and the current flowing through the resistor itself, which can be expressed as the ability of the resistor to limit current. The failure of the resistor refers to the inability of the resistor to effectively limit the current due to internal damage.

[0057] Step 103: When it is determined that the starting resistor has no fault, judging whether the starting resistor has an overcurrent risk according to the real-time resistance value.

[0058] In the embodiment of the present disclosure, the overcurrent risk refers to the situation that when the current flowing through the starting resistor exceeds the rated current that the starting resistor can allow to pass, there will be damage to the inside of the resistor.

[0059] Step 104: When it is determined that the starting resistor has an overcurrent risk, the converter valve is controlled to exit the charging state to perform overcurrent protection on the starting resistor.

[0060] In the embodiment of the present disclosure, when it is determined that the starting resistor has an overcurrent risk, the converter valve is controlled to exit the charging state, that is, the power supply end is controlled to stop charging the capacitor in the submodule of the converter valve through the starting resistor. At this time, since the current no longer flows through the starting resistor, the starting resistor can avoid the overcurrent risk.

[0061] on the other hand, Figure 2 A starting resistor overcurrent protection system is presented for a flexible DC transmission system including a converter valve to perform Figure 1 The overcurrent protection method shown in the figure. The specific structure of the overcurrent protection system includes a state recognition module 201, a fault diagnosis module 202, an overcurrent recognition module 203 and an overcurrent protection module 204.

[0062] The state identification module 201 is used to determine the working state of the starting resistor according to the charging state of the converter valve;

[0063] The fault diagnosis module 202 is used to obtain the real-time resistance value of the two ends of the starting resistor based on the working state, and perform fault diagnosis on the starting resistor based on the real-time resistance value;

[0064] The overcurrent identification module 203 is used to determine whether there is an overcurrent risk of the starting resistor according to the real-time resistance value when it is determined that the starting resistor does not have a fault;

[0065] The overcurrent protection module 204 is used to control the converter valve to exit the charging state to perform overcurrent protection on the starting resistor when it is determined that the starting resistor has an overcurrent risk.

[0066] In this embodiment, the fault diagnosis module 202 includes a resistance value identification unit and a fault determination unit;

[0067] The resistance identification unit is used to obtain the real-time current flowing into the starting resistor and the real-time voltage difference across the starting resistor when it is determined that the starting resistor is in a working state; and obtain the real-time resistance value across the starting resistor according to the real-time voltage difference and the real-time current;

[0068] The fault determination unit is used to obtain the deviation between the factory designed resistance value of the starting resistor and the real-time resistance value, and compare the deviation with a preset deviation threshold; when the deviation is greater than or equal to the deviation threshold, it is determined that the starting resistor is faulty.

[0069] In other implementations disclosed in this embodiment, according to Figure 1 The present embodiment provides an electronic device, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the following when executing the computer program: Figure 1The overcurrent protection method of the starting resistor shown in the figure. The processor can be a central processing unit (CPU), or other general processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. The general processor can be a microprocessor or the processor can also be any conventional processor, etc. The processor is the control center of the terminal, and various interfaces and lines are used to connect various parts of the entire terminal. The memory can be used to store the computer program, and the processor realizes various functions of the terminal by running or executing the computer program stored in the memory and calling the data stored in the memory. The memory may mainly include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function (such as a sound playback function, an image playback function, etc.), etc.; the data storage area may store data created according to the use of the mobile phone (such as audio data, a phone book, etc.), etc. In addition, the memory may include a high-speed random access memory, and may also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Med ia Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (FlashCard), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0070] Furthermore, this embodiment also provides a computer-readable storage medium, wherein the computer-readable storage medium includes a stored computer program, wherein when the computer program is executed, the device where the computer-readable storage medium is located is controlled to execute the following Figure 1 A method of overcurrent protection of a starting resistor is shown.

[0071] Among them, Figure 2If the overcurrent protection system of the starting resistor shown is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above-mentioned embodiment method can also be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned various method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electrical carrier signal, telecommunication signal and software distribution medium, etc.

[0072] Compared with the prior art, the overcurrent protection method, system, device and medium of the starting resistor provided in this embodiment have the following beneficial effects:

[0073] The present embodiment discloses a method, system, device and medium for overcurrent protection of a starting resistor, which first identifies the working state of the starting resistor according to the charging state of the converter valve, and timely performs overcurrent protection judgment on the starting resistor. After identifying the working state of the starting resistor, the real-time resistance value of the resistor is first obtained for fault diagnosis to avoid the inability to effectively limit the charging current due to the failure of the resistor itself, thereby improving the safety of charging protection. Furthermore, when it is identified that the starting resistor is not faulty, the real-time resistance value is used to determine whether to perform overcurrent protection on the starting resistor, and when it is determined that the starting resistor is in an overcurrent state, the converter valve is promptly controlled to exit the charging state to perform overcurrent protection on the starting resistor, thereby avoiding equipment damage caused by overcurrent of the starting resistor.

[0074] Embodiment 2

[0075] like Figure 3 As shown, a method for overcurrent protection of a starting resistor is provided in a specific implementation of this embodiment. In this embodiment, the working state of the starting resistor is first determined by the size of the charging current charged into the converter valve. Then, when the starting resistor is in the working state, the real-time resistance value of the starting resistor is calculated using the voltage difference across the starting resistor and the real-time current flowing through the starting resistor, so as to perform fault diagnosis on the starting resistor based on the real-time resistance value, and after the fault diagnosis, the real-time current is used to determine the overcurrent risk of the resistor, so as to perform the corresponding protection action. Figure 3As shown, the method for implementing resistance protection in this embodiment includes the following steps:

[0076] Step 301: when it is determined that the charging current flows into the converter valve through the starting resistor, it is determined that the starting resistor is in a working state.

[0077] Specifically, in this embodiment, since the starting resistor is used to limit the size of the charging current flowing into the converter valve, when the charging current actually enters the converter valve through the starting resistor and the charging current exceeds the current threshold of the converter valve, the starting resistor enters the working state.

[0078] Preferably, this embodiment can obtain a charging circuit when the AC power grid in the flexible DC transmission system charges the converter valve; when it is determined that the starting resistor is in the charging circuit and the AC power grid charges the converter valve through the starting resistor, it is determined that the starting resistor is in a working state.

[0079] Step 302: Obtain a real-time voltage difference across the starting resistor and a real-time current value flowing through the starting resistor to obtain a fault diagnosis result of the starting resistor.

[0080] Specifically, in this embodiment, the degree of limitation of the charging current by the starting resistor depends on the resistance value of the resistor itself. When the resistance value of the resistor itself changes, the magnitude of the charging current flowing into the converter valve is also different from the preset value. On the other hand, when making an overcurrent judgment on the starting resistor, the overcurrent judgment needs to be made based on the magnitude of the current that the starting resistor itself can allow to pass, and the magnitude of the current that the starting resistor itself can allow to pass also depends on the resistance value of the starting resistor itself. Therefore, this embodiment can first perform preliminary fault diagnosis based on the actual resistance value of the starting resistor.

[0081] Preferably, in some implementations of this embodiment, when it is determined that the starting resistor is in a working state, the real-time current flowing into the starting resistor and the real-time voltage difference across the starting resistor are obtained; the real-time resistance value across the starting resistor is obtained according to the real-time voltage difference and the real-time current. Then, the deviation between the factory design resistance value of the starting resistor and the real-time resistance value is obtained, and the deviation is compared with a preset deviation threshold; when the deviation is greater than or equal to the deviation threshold, it is determined that the starting resistor is faulty.

[0082] Step 303: When it is determined that the starting resistor is not faulty, determine whether the starting resistor has an overcurrent risk according to the real-time current value and the real-time resistance value of the starting resistor.

[0083] Specifically, in this embodiment, when it is determined based on the actual resistance value that the resistor itself has no fault, in order to determine the overcurrent risk, the factory design voltage of the starting resistor can be obtained to determine the protection setting current of the starting resistor based on the factory design voltage and the real-time resistance value; and when the real-time current is greater than the protection setting current, it is determined that the starting resistor has an overcurrent risk.

[0084] Step 304: When it is determined that the starting resistor has an overcurrent risk, the converter valve is controlled to exit the charging state to perform overcurrent protection on the starting resistor.

[0085] Specifically, in this embodiment, the grid-side circuit breaker connected in series between the AC power grid and the starting resistor is controlled to be disconnected; the valve-side circuit breaker connected in series at one end of the converter valve is controlled to be disconnected; wherein the other end of the converter valve is connected in series with the starting resistor.

[0086] The present embodiment provides a method for overcurrent protection of a starting resistor. First, when it is identified that the AC power grid charges the converter valve through the starting resistor, the starting resistor is promptly protected from overcurrent. Furthermore, the actual resistance value of the starting resistor in the current charging process is obtained by using the voltage value at both ends of the starting resistor and the real-time current flowing through the starting resistor to determine the actual situation of the starting resistor, so as to avoid the failure to limit the charging current due to damage to the resistor itself, thereby improving the safety of charging. After it is identified that there is no problem with the resistor itself, because the resistor may overheat due to excessive current and other self-damaging behaviors, and the charging circuit of the power transmission system is often provided with a protection delay time for delayed charging, therefore, when it is identified that the real-time current flowing through the resistor is too large and the charging state of the converter valve exceeds the protection delay time for delayed charging set in the power transmission system, it is determined that the current state of the starting resistor needs to be protected from overcurrent, and the resistor is protected in a timely manner. Finally, when it is identified that there is an overcurrent risk in the starting resistor, the circuit breakers at both ends of the starting resistor are promptly tripped, thereby isolating the starting resistor, which not only avoids damage to the starting resistor, but also prevents the converter valve side from receiving excessive charging current, which can effectively prevent equipment damage caused by overcurrent of the starting resistor.

[0087] Embodiment 3

[0088] In the process of charging protection of the flexible DC transmission system, the starting resistor used for charging current limitation is generally composed of several boxes connected in series, several resistor banks connected in series inside the boxes, and several resistor sheets connected end to end inside the resistor banks. The starting resistor will be repeatedly switched on and off during normal operation, and the resistor sheets and the ends of the resistor wrapping may be ablated at high temperature, and the internal insulating mica sheet will be damaged, resulting in insulation failure, leakage heating, and finally changing the resistance value of the resistor. The existing overcurrent protection technology lacks overcurrent protection for the starting resistor, and thus the charging protection cannot be effectively performed due to the change in the resistance value of the starting resistor.

[0089] In this regard, this embodiment provides an overcurrent protection method for a starting resistor in a flexible DC power transmission system to prevent equipment damage caused by overcurrent of the starting resistor. The connection structure between the starting resistor and the charging circuit of the flexible DC power transmission system is as follows: Figure 4 shown.

[0090] Reference Figure 4 , the input end of the starting resistor R is connected to the grid-side circuit breaker Q0 through the busbar, and the output end of the starting resistor R is respectively connected to the upper bridge arm Q3 of the converter valve and the lower bridge arm Q4 of the converter valve in the flexible DC power transmission system. The output end of the upper bridge arm Q3 of the converter valve is connected in series with the DC circuit breaker Q1, and the output end of the lower bridge arm Q4 of the converter valve is connected in series with the DC circuit breaker Q2. Furthermore, the flexible DC power transmission system needs to withdraw the starting resistor R from the charging circuit after the uncontrolled charging is completed. To this end, a bypass switch Q5 can be connected in parallel at both ends of the starting resistor R to close the bypass switch Q5, thereby withdrawing the starting resistor R from the charging circuit.

[0091] Furthermore, in order to perform overcurrent protection of the resistor, voltage sensors PT1 and PT2 and a current sensor CT may be arranged between the grid-side circuit breaker Q0 and the starting resistor R, so as to obtain the voltage across the starting resistor R through the voltage sensors PT1 and PT2 and obtain the real-time current flowing through the starting resistor through the current sensor CT.

[0092] Reference Figure 4 The circuit structure shown in FIG. 1 and the method for overcurrent protection of the starting resistor R can be referred to Figure 5 ,like Figure 5 As shown, the overcurrent protection method includes steps 501 to 504, and the steps are:

[0093] Step 501: Determine whether the starting resistor is in working state.

[0094] Specifically, in this embodiment, the sensor information fed back by the voltage sensors PT1 and PT2 or the current sensor CT can be obtained to determine whether the starting resistor is in a working state. When the sensor signals fed back by the voltage sensors PT1 and PT2 change from 0 or a very small value to a large value or the sensor signal fed back by the current sensor CT changes from 0 or a very small value to a large value, it is determined that the starting resistor is in a working state.

[0095] Step 502: When it is determined that the starting resistor is in a working state, a fault diagnosis is performed on the starting resistor according to a voltage difference across the starting resistor and a real-time current flowing through the starting resistor.

[0096] Specifically, firstly, the first voltage Uvc fed back by the voltage sensor PT1 and the second voltage Uvr fed back by the voltage sensor PT2 are obtained to calculate the difference between the Uvr and the Uvc, and the difference is determined as the voltage difference across the starting resistor. Then, the real-time current Ivr fed back by the current sensor CT is obtained to determine the real-time resistance value R′ of the starting resistor according to the ratio of the difference to the Ivr.

[0097] Obtain the standard resistance value R set by the starting resistor when it leaves the factory, calculate the deviation between the R and the R′, and determine whether the starting resistor is faulty according to the deviation. The specific process of fault diagnosis is as follows:

[0098] R′=abs(Uvr-Uvc) / Ivr

[0099] abs(RR′) / R≥Rmax

[0100] The Rmax is a set deviation threshold value, which can be set according to charging control requirements, such as 2%, 4%, 10%, etc.

[0101] When the deviation between the real-time resistance value of the starting resistor and the standard resistance value is too large and does not meet the specification requirements, a signal can be sent to the control system to warn. The warning resistance value deviation is too large, there is a risk of malfunction, and it reminds you to repair and replace the starting resistor. If the resistance value deviation meets the specification requirements, the overcurrent risk is determined.

[0102] Step 503: determining an overcurrent risk of the starting resistor according to the real-time current and the real-time resistance value of the starting resistor.

[0103] Specifically, in this embodiment, the effective value of the current measured by the current sensor CT connected in series with the starting resistor circuit is used as the real-time current of the starting resistor, and then the protection setting current corresponding to the starting resistor is calculated using the standard voltage set when the starting resistor leaves the factory and the measured real-time resistance of the starting resistor, so as to compare the real-time current with the protection setting current to determine whether the starting resistor has an overcurrent risk. Specifically, the overcurrent risk determination process is as follows:

[0104] Iset=U / (2*R′) / A

[0105] Ivr>Iset

[0106] Wherein, Iset is the protection setting current; A is the sensitivity coefficient, which can be set in the overcurrent protection module according to specification requirements and actual engineering needs, such as 1.1, 1.2, 1.3, etc.

[0107] When the real-time current exceeds the protection setting current, it is determined that the starting resistor has an overcurrent risk.

[0108] Step 504: When it is determined that the starting resistor has an overcurrent risk, disconnect the grid-side circuit breaker and the valve-side circuit breaker.

[0109] Specifically, when it is determined that the starting resistor has an overcurrent risk, the starting resistor is isolated to perform overcurrent protection. Specifically, when the protection action is executed, the converter is locked, the grid-side circuit breaker Q0 is tripped, the DC circuit breaker Q1 and the DC circuit breaker Q2 are tripped, and the starting grid-side circuit breaker fails.

[0110] The present embodiment provides a method for overcurrent protection of a starting resistor. The criterion of the actual resistance value is added to the overcurrent protection criterion of the starting resistor. The deviation between the actual resistance value and the design value is first judged. When it is determined that the actual resistance value of the resistor does not meet the specification requirements, a signal can be sent to the extreme control alarm. Then, an alarm is issued that the resistance value deviation is too large and there is a risk of false operation, and the starting resistor is reminded to repair and replace. If the resistance value deviation meets the specification requirements, the protection logic judgment is performed according to the protection criterion during operation to determine the overcurrent risk, reduce the number of manual setting times, and prevent the problem of false protection caused by changes in the starting resistor value due to long-term operation and other fault conditions.

[0111] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for overcurrent protection of a starting resistor, characterized in that: Applicable to a flexible direct current transmission system including a converter valve; wherein the overcurrent protection method comprises: Determining the working state of the starting resistor according to the charging state of the converter valve; Acquire the real-time resistance value at both ends of the starting resistor based on the working state, and perform fault diagnosis on the starting resistor based on the real-time resistance value; When it is determined that the starting resistor does not have a fault, judging whether the starting resistor has an overcurrent risk according to the real-time resistance value; When it is determined that the starting resistor has an overcurrent risk, the converter valve is controlled to exit the charging state to perform overcurrent protection on the starting resistor.

2. The overcurrent protection method of a starting resistor according to claim 1, characterized in that: Determining the working state of the starting resistor according to the charging state of the converter valve includes: Acquire a charging circuit when the AC grid in the flexible DC power transmission system charges the converter valve; When it is determined that the starting resistor is in the charging circuit and the AC power grid charges the converter valve through the starting resistor, it is determined that the starting resistor is in a working state.

3. The overcurrent protection method of a starting resistor according to claim 2, characterized in that: The acquiring the real-time resistance value of both ends of the starting resistor based on the working state includes: When it is determined that the starting resistor is in a working state, obtaining a real-time current flowing into the starting resistor and a real-time voltage difference across the starting resistor; The real-time resistance value at both ends of the starting resistor is obtained according to the real-time voltage difference and the real-time current.

4. The overcurrent protection method of a starting resistor according to claim 3, characterized in that: The performing fault diagnosis on the starting resistor based on the real-time resistance value includes: Obtaining a deviation between a factory designed resistance value of the startup resistor and the real-time resistance value, and comparing the deviation with a preset deviation threshold; When the deviation is greater than or equal to the deviation threshold, it is determined that the starting resistor is faulty.

5. The overcurrent protection method of a starting resistor according to claim 3, characterized in that: Judging whether the starting resistor has an overcurrent risk according to the real-time resistance value includes: Obtaining the factory design voltage of the starting resistor to determine the protection setting current of the starting resistor according to the factory design voltage and the real-time resistance value; When the real-time current is greater than the protection setting current, it is determined that the starting resistor has an overcurrent risk.

6. The overcurrent protection method of a starting resistor according to claim 2, characterized in that: The controlling the converter valve to exit the charging state to perform overcurrent protection on the starting resistor includes: Controlling the grid-side circuit breaker connected in series between the AC grid and the starting resistor to disconnect; The valve-side circuit breaker connected in series at one end of the converter valve is controlled to be disconnected; wherein the other end of the converter valve is connected in series with the starting resistor.

7. An overcurrent protection system for a starting resistor, characterized in that: Applicable to a flexible direct current transmission system including a converter valve; wherein the overcurrent protection system comprises a state recognition module, a fault diagnosis module, an overcurrent recognition module and an overcurrent protection module; The state identification module is used to determine the working state of the starting resistor according to the charging state of the converter valve; The fault diagnosis module is used to obtain the real-time resistance value of the two ends of the starting resistor based on the working state, and perform fault diagnosis on the starting resistor based on the real-time resistance value; The overcurrent identification module is used to determine whether there is an overcurrent risk of the starting resistor according to the real-time resistance value when it is determined that the starting resistor does not have a fault; The overcurrent protection module is used to control the converter valve to exit the charging state to perform overcurrent protection on the starting resistor when it is determined that the starting resistor has an overcurrent risk.

8. The overcurrent protection system of a starting resistor according to claim 7, characterized in that: The fault diagnosis module includes a resistance value identification unit and a fault determination unit; The resistance identification unit is used to obtain the real-time current flowing into the starting resistor and the real-time voltage difference across the starting resistor when it is determined that the starting resistor is in a working state; and obtain the real-time resistance value across the starting resistor according to the real-time voltage difference and the real-time current; The fault determination unit is used to obtain the deviation between the factory design resistance value of the starting resistor and the real-time resistance value, and compare the deviation with a preset deviation threshold; When the deviation is greater than or equal to the deviation threshold, it is determined that the starting resistor is faulty.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, an overcurrent protection method for a starting resistor according to any one of claims 1 to 6 is implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, an overcurrent protection method for a starting resistor according to any one of claims 1 to 6 is implemented.

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