A protection control method, system, device and medium under single-pole blocking fault

Abstract

The application discloses a protection control method, system, device and medium under single-pole blocking fault, the protection control method under single-pole blocking fault adopts two part strategies of main protection and backup protection, wherein the main protection control is a protection control strategy based on a communication system, the backup protection control is a protection control strategy based on a frequency signal, extreme conditions such as communication system failure can be fully considered, double protection of single-pole blocking fault of a sending end converter station is realized, and the reliability of protection is greatly improved. Thus, the problem that the current control strategy often does not consider backup control when the communication system fails, resulting in poor reliability of the sending end system after single-pole blocking fault when the communication system has problems is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy direct transmission engineering, and in particular to a protection control method, system, device and medium under single-pole blocking fault. BACKGROUND

[0002] At present, most new energy units (wind power, photovoltaic) adopt grid-following control, which requires strong supporting power to operate. The geographical location of desert, gobi and desert areas is remote, and the local conventional power supply of new energy bases is small, and the power grid is weak, and the system is in an unsupported or weakly supported state. The flexible direct current transmission technology based on modular multilevel converter (MMC) can provide voltage and frequency support for new energy, and is widely used in offshore wind power and land new energy island transmission scenarios. Therefore, the large-scale new energy base through the flexible direct current transmission system (hereinafter referred to as "new energy flexible direct current transmission system") will become a typical form of new energy development in desert, gobi and desert areas.

[0003] For high-voltage direct current transmission systems, single-pole blocking is one of the common faults. DC line fault, converter station fault and AC system fault may cause single-pole blocking of the DC system. Since the sending end new energy base is not interconnected with the large power grid, the fault pole power sending is blocked after single-pole blocking, and the sending end power grid will have a power surplus of several gigawatts in a short time. Research shows that if no measures are taken after single-pole blocking, a large amount of surplus power will flow into the MMC healthy pole converter station, causing serious overvoltage of the DC system, and thus threatening the safety and stability of the entire sending end power grid.

[0004] However, there are still many problems in the current single-pole blocking fault handling strategy of new energy through photovoltaic flexible direct current transmission system. On the one hand, improper control strategy during single-pole blocking fault will cause low voltage or overvoltage problems in the sending end new energy power grid; on the other hand, the current control strategy often does not consider the backup control when the communication system fails. Since the new energy sending end power grid is mostly located in remote areas, the communication infrastructure is not perfect, and the reliability of communication is insufficient. When the communication system fails, the reliability of the sending end system after single-pole blocking fault will face great risks, seriously threatening the safe and stable operation of the system. SUMMARY

[0005] The present application provides a protection control method, system, device and medium under single-pole blocking fault, which is used to solve the problem that the current control strategy often does not consider the backup control when the communication system fails, resulting in poor reliability of the sending end system after single-pole blocking fault.

[0006] Therefore, the first aspect of the present application provides a protection control method under monopolar blocking failure, applied to a new energy through flexible DC transmission system, the new energy through flexible DC transmission system comprising: a sending end flexible DC converter station, a communication system, a new energy station and a plurality of groups of energy dissipation resistors;

[0007] The method comprises:

[0008] When the monopolar blocking failure is detected, the energy dissipation resistors are put into operation, and a power reduction instruction is issued to each new energy station through the communication system;

[0009] After the monopolar blocking failure occurs and a time delay of , the frequency instruction value of the sending end flexible DC system is corrected to a frequency signal with specific characteristics;

[0010] According to whether the new energy station receives the power reduction instruction from the communication system, and in combination with the frequency signal, the enabling state of the main protection control strategy and the backup protection control strategy for power reduction is determined.

[0011] Optionally, after the enabling state of the main protection control strategy and the backup protection control strategy for power reduction is determined according to whether the new energy station receives the power reduction instruction from the communication system and in combination with the frequency signal, the method further comprises:

[0012] The power injected into the sending end flexible DC converter station is monitored in real time to obtain the speed of power reduction of the new energy station, and the energy dissipation resistors are grouped out of operation according to the speed of power reduction of the new energy station.

[0013] Optionally, the enabling state of the main protection control strategy and the backup protection control strategy for power reduction is determined according to whether the new energy station receives the power reduction instruction from the communication system and in combination with the frequency signal, comprising:

[0014] When the new energy station cannot receive the power reduction instruction from the communication system, but can determine that the DC system has a monopolar blocking failure according to the frequency signal, the backup protection control strategy is enabled; the backup protection control strategy is to control the unit of the new energy station to reduce to a preset power value according to the received frequency signal.

[0015] Optionally, the enabling state of the main protection control strategy and the backup protection control strategy for power reduction is determined according to whether the new energy station receives the power reduction instruction from the communication system and in combination with the frequency signal, further comprising:

[0016] When the new energy station receives the power reduction instruction from the communication system, a preset main protection control strategy is enabled, and a backup protection control strategy is closed; the main protection control strategy is to control the new energy station to reduce power according to the power reduction instruction.

[0017] Optionally, the number of groups of the energy dissipation resistor is determined according to a relationship between the pre-fault bipolar power and the maximum power that can be transmitted by the healthy pole.

[0018] Optionally, the number of groups of the energy dissipation resistor is determined according to a relationship between the pre-fault bipolar power and the maximum power that can be transmitted by the healthy pole, including:

[0019] When the pre-fault bipolar power is greater than the maximum power that can be transmitted by the healthy pole, the number N of groups of the energy dissipation resistor is:

[0020] ;

[0021] In the formula, is the pre-fault bipolar power, is the maximum power that can be transmitted by the healthy pole, is a rounding up symbol, is the power consumed by a single group of the energy dissipation resistor.

[0022] Optionally, the number of groups of the energy dissipation resistor is determined according to a relationship between the pre-fault bipolar power and the maximum power that can be transmitted by the healthy pole, and further including:

[0023] When the pre-fault bipolar power is not greater than the maximum power that can be transmitted by the healthy pole, no energy dissipation resistor is put into operation, and fault ride-through is realized through healthy pole power transfer.

[0024] Optionally, the generation process of the power reduction instruction includes:

[0025] According to the initial operating power of each new energy station, the relationship between the pre-fault bipolar power and the maximum power that can be transmitted by the healthy pole, the expression is:

[0026] ;

[0027] In the formula, is the power reduction size allocated to the i th new energy station, is the initial operating power of the i th new energy station, is the pre-fault bipolar power, is the maximum power that can be transmitted by the healthy pole.

[0028] Optionally, the frequency signal includes:

[0029] The duration is a frequency square wave signal with a frequency higher than the rated value , wherein the expression of the frequency signal f is

[0030] ;

[0031] In the formula, is the initial frequency of the new energy sending end power grid.

[0032] Optionally, the main protection control strategy comprises:

[0033] After the time , the new energy station is controlled to reduce power according to the power reduction instruction;

[0034] In the formula, ;

[0035] In the formula, is the time delay of the measuring instrument when measuring power, is the capacity of a single set of the energy dissipation resistor, is the pre-fault bipolar power, is the maximum power that the healthy pole can transmit.

[0036] Optionally, The size is and the maximum value of the action delay time of the sending end flexible DC converter station sending information to the new energy station receiving information.

[0037] Optionally, it further comprises:

[0038] The new energy station monitors the frequency of the new energy through flexible DC transmission system in real time, when a short-term frequency rise occurs, and then a frequency square wave signal with a duration of milliseconds is monitored after the time , it is determined that the sending end monopolar blocking fault occurs.

[0039] The second aspect of the application provides a monopolar blocking fault protection control device, which is applied to a new energy through flexible DC transmission system, and the new energy through flexible DC transmission system comprises a sending end flexible DC converter station, a communication system, a new energy station and a plurality of groups of energy dissipation resistors.

[0040] The device comprises:

[0041] A first control module is configured to put into the energy dissipation resistor when detecting the monopolar blocking fault, and issue a power reduction instruction to each new energy station through the communication system;

[0042] A second control module is configured to, when the monopolar blocking fault occurs and after the time after a time delay, the frequency instruction value of the sending-end HVDC system is corrected to a frequency signal with specific characteristics;

[0043] a third control module, configured to determine the enabling state of the main protection control strategy and the backup protection control strategy for power reduction according to whether the new energy station receives the power reduction instruction from the communication system and in combination with the frequency signal.

[0044] Optionally, the method further comprises a fourth control module.

[0045] The fourth control module is configured to monitor the power injected into the sending-end HVDC converter station in real time to obtain the speed of power reduction of the new energy station, and control the grouping exit of the energy dissipation resistor according to the speed of power reduction of the new energy station.

[0046] The third aspect of the present application provides a protection control device under monopolar blocking fault, the device comprising a processor and a memory:

[0047] The memory is configured to store program code and transmit the program code to the processor.

[0048] The processor is configured to execute the steps of the protection control method under monopolar blocking fault according to the instructions in the program code.

[0049] The fourth aspect of the present application provides a computer readable storage medium for storing program code, the program code being used to execute the protection control method under monopolar blocking fault.

[0050] From the above technical solutions, the present application has the following advantages:

[0051] The present application provides a protection control method under monopolar blocking fault, which adopts two strategies of main protection and backup protection. The main protection control is a protection control strategy based on a communication system, and the backup protection control is a protection control strategy based on a frequency signal. The method can fully consider extreme conditions such as communication system failure, realize double protection of the sending-end converter station under monopolar blocking fault, and greatly improve the reliability of protection. Thus, the problem that the current control strategy often does not consider backup control when the communication system fails, resulting in poor reliability of the sending-end system after monopolar blocking fault, is solved. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 FIG. 1 is a flowchart of a protection control method under monopolar blocking fault provided in an embodiment of the present application;

[0053] Figure 2A schematic diagram of a new energy through flexible DC transmission system provided in the embodiments of the present application;

[0054] Figure 3 A schematic diagram of a frequency signal reference value of a sending-end HVDC converter station provided in the embodiments of the present application;

[0055] Figure 4 A control system timing logic diagram under a sending-end power grid single-pole blocking fault in the first case provided in the embodiments of the present application;

[0056] FIG. 5(a) is a waveform diagram of a voltage instantaneous value under a sending-end power grid single-pole blocking fault in the first case provided in the embodiments of the present application;

[0057] FIG. 5(b) is a waveform diagram of total active power injected into a sending-end HVDC converter station and active power consumed by a discharge resistor in the first case provided in the embodiments of the present application;

[0058] FIG. 5(c) is a waveform diagram of switching of the discharge resistor in the first case provided in the embodiments of the present application;

[0059] Figure 6 A control system timing logic diagram under a sending-end power grid single-pole blocking fault in the second case provided in the embodiments of the present application;

[0060] FIG. 7(a) is a waveform diagram of a voltage instantaneous value under a sending-end power grid single-pole blocking fault in the second case provided in the embodiments of the present application;

[0061] FIG. 7(b) is a waveform diagram of total active power injected into a sending-end HVDC converter station and active power consumed by a discharge resistor in the second case provided in the embodiments of the present application;

[0062] FIG. 7(c) is a waveform diagram of switching of the discharge resistor in the second case provided in the embodiments of the present application;

[0063] Figure 8 A structural schematic diagram of a protection control system under a single-pole blocking fault provided in the embodiments of the present application. DETAILED DESCRIPTION

[0064] In order to enable persons skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by persons skilled in the art without creative work fall within the protection scope of the present application.

[0065] Please refer to Figure 1The single-pole blocking fault protection control method provided in the embodiments of the present application is applied to a new energy through flexible DC transmission system, such as Figure 2 As shown in the figure, the new energy through flexible DC transmission system comprises a sending-end flexible DC converter station, a communication system, a new energy station and a plurality of groups of energy dissipation resistors.

[0066] The method comprises the following steps.

[0067] Step 101: When a single-pole blocking fault is detected, the energy dissipation resistors are put into operation, and a power reduction instruction is issued to each new energy station through the communication system.

[0068] It should be noted that, as shown in the figure Figure 2 As shown in the figure Figure 2 After the sending-end flexible DC converter station detects that the new energy through flexible DC transmission system has a single-pole blocking fault, the sending-end flexible DC converter station puts into operation energy dissipation resistors with a given capacity, and issues a power reduction instruction to each new energy station through the communication system.

[0069] In one embodiment, before step 101, the method further comprises the following steps.

[0070] The frequency of the new energy through flexible DC transmission system is monitored in real time by the new energy station, and when a short-term frequency rise occurs, and then a frequency square wave signal with a duration of milliseconds is monitored after a time of milliseconds, it is determined that a sending-end single-pole blocking fault has occurred.

[0071] In one embodiment, the number of groups of energy dissipation resistors put into operation is determined according to the relationship between the pre-fault bipolar power and the maximum power that the healthy pole can transmit, and specifically comprises the following steps.

[0072] When the pre-fault bipolar power is not greater than the maximum power that the healthy pole can transmit, the energy dissipation resistors are not put into operation, and fault ride-through is realized by healthy pole power transfer;

[0073] When the pre-fault bipolar power is greater than the maximum power that the healthy pole can transmit, the number N of groups of energy dissipation resistors put into operation is:

[0074] ;

[0075] In the formula, P is the pre-fault bipolar power, P is the maximum power that the healthy pole can transmit, is a rounding up symbol, is the power consumed by a single group of energy dissipation resistors.

[0076] In one embodiment, the generation process of the power reduction instruction specifically comprises the following steps.

[0077] ​According to the relationship between the initial operation power of each new energy station, the bipolar power before the fault and the maximum power that the healthy pole can transmit, the distribution is performed, and the expression is:

[0078]

[0079] In the formula, is the power reduction size allocated to the i th new energy station, is the initial operation power of the i th new energy station, is the bipolar power before the fault, is the maximum power that the healthy pole can transmit.

[0080] Step 102, after the monopolar lockout fault occurs and a time delay of passes, the frequency instruction value of the sending-end flexible DC system is corrected to a frequency signal with specific characteristics.

[0081] It should be noted that, as shown in Figure 2 , after the sending-end flexible DC converter station detects that the monopolar lockout fault of the new energy through the flexible DC transmission system occurs and a time delay of passes, the sending-end flexible DC converter station corrects the frequency instruction value of the new energy sending-end flexible DC system to a frequency signal with specific characteristics.

[0082] In one embodiment, the frequency signal with specific characteristics specifically includes: a frequency square wave signal with a duration of and a frequency higher than the rated value , wherein the expression of the frequency signal f is:

[0083]

[0084] In the formula, is the maximum value of and the action delay time of the sending-end flexible DC converter station sending information to the new energy station receiving information. For example, when the action delay time of the sending-end flexible DC converter station sending information to the new energy station receiving information is 150 ms, the expression is:

[0085]

[0086] In the formula, is the initial frequency of the new energy sending-end power grid.

[0087] It should be noted that the action delay time of the sending-end flexible DC converter station sending information to the new energy station receiving information is related to the actual communication distance and the performance of the communication equipment. Its example range can be 50-300 ms, and its example value can be 150 ms. ​​​

[0088] It should be noted that the frequency signal of the specific feature of the present application refers to a frequency signal designed to be different from the original frequency, and this feature is that the new energy station and the converter station have advance and unified cognition, when the new energy station detects the frequency feature, it can be judged that it is a signal sent by the sending end flexible HVDC converter station for prompting monopolar blocking fault, and then the corresponding subsequent operation is performed, for example, the backup protection control strategy is executed, and the new energy station unit is controlled to reduce to a preset power value, that is, the description of the following step 1032. It should be further pointed out that in actual application, the new energy station measures through the frequency measuring device equipped by itself, so that when the communication system fails, the new energy station can monitor the specific feature frequency signal through the frequency measuring device equipped by itself to judge the operation state of the new energy flexible HVDC transmission system.

[0089] Step 103, according to whether the new energy station receives the power reduction instruction from the communication system, and in combination with the frequency signal, the enable state of the main protection control strategy and the backup protection control strategy for power reduction is determined.

[0090] In one embodiment, step 103 comprises:

[0091] Step 1031, when the new energy station receives the power reduction instruction from the communication system, the main protection control strategy is enabled, and the backup protection control strategy is closed, and the main protection control strategy is to control the new energy station to reduce power according to the power reduction instruction.

[0092] In one embodiment, the main protection control strategy is specifically:

[0093] After the time of , the new energy station is controlled to reduce power according to the power reduction instruction;

[0094] Wherein, ;

[0095] In the formula, is the time delay of the measuring instrument when measuring power, is the capacity of a single group of energy dissipation resistance, is the pre-fault bipolar power, is the maximum power that the healthy pole can transmit.

[0096] Step 1032, when the new energy station cannot receive the power reduction instruction from the communication system, but can determine that the DC system has a monopolar blocking fault according to the frequency signal, the backup protection control strategy is enabled, and the backup protection control strategy is to control the unit of the new energy station to reduce to a preset power value according to the received frequency signal.

[0097] It should be noted that the step 1032 controls the unit of the new energy station to reduce to the preset power value, specifically, it can be to control the unit of the new energy station to reduce half power, and it can be understood that the application considers full load of the new energy station, and when reducing by half, the power sent to the sending end converter station becomes the power of monopole. But no matter whether the new energy station is full load or not, reducing to 50% of the initial value can pass through the fault.

[0098] Further, in one embodiment, the step 103 further includes:

[0099] Real-time monitoring of the power injected into the sending end flexible HVDC converter station to obtain the speed of the new energy station reducing power, and controlling the grouping exit of the energy dissipation resistor according to the speed of the new energy station reducing power.

[0100] In one embodiment, in the step 103, the grouping exit of the energy dissipation resistor is controlled according to the speed of the new energy station reducing power, specifically including:

[0101] Real-time monitoring of the active power injected into the AC bus of the converter station, and controlling a group of energy dissipation resistors to exit whenever the power consumed by the group of energy dissipation resistors is reduced.

[0102] The following is a specific example of the protection control method under monopole blocking fault provided in the embodiment of the application:

[0103] The first case: as shown in Figure 4 , the communication system is intact, the main protection control strategy works, and the backup protection control strategy does not work:

[0104] At 1.0s, the sending end converter station is monopole blocked. According to the bipolar power of 10000MW before the fault and the maximum power of 5000MW transmitted by the MMC monopole, the number of groups of energy dissipation resistors to be input is calculated to be 10 groups. The total power to be reduced in the sending end new energy grid is 5000MW, and the power reduction share of each new energy station is calculated to be 50% of the initial power of each new energy station. Then, according to the capacity of a single group of energy dissipation resistors, the measurement time delay, the speed of the new energy reducing power is calculated to be 200ms, i.e. the new energy reduces the power to 50% in 200ms. At 1.002s, the sending end converter station inputs 5000MW AC energy dissipation resistor. At 1.030s, the sending end flexible HVDC station sets the frequency signal reference value (such as Figure 3The frequency (as shown) is modified to 50.35Hz, generating a 50.35Hz square wave signal with a duration of 170 milliseconds. This frequency signal is then modified back to 50Hz at 1.200s. At 1.15s, the stabilization control device on the renewable energy power plant side receives a single-pole blocking signal, and all photovoltaic power plants begin to reduce power while simultaneously shutting down the single-pole blocking backup protection control for each renewable energy power plant. At 1.17s, the total power of the photovoltaic power plants decreases by 500MW, and one set of leakage resistors is deactivated. Thereafter, for every 500MW decrease in the total power of the sending-end photovoltaic power plants, one set of leakage resistors is deactivated.

[0105] Figures 5(a)-5(c) The diagram shows the instantaneous voltage value, the total active power injected into the sending-end converter station and the active power consumed by the leakage resistor under the first case of a single-pole blocking fault in the sending-end power grid, as well as the switching status of the leakage resistor.

[0106] The second scenario: Figure 6 As shown, in the case of a communication system failure, the primary protection control strategy is ineffective, while the backup protection control strategy is effective.

[0107] At 1.0s, the sending-end converter station is single-pole blocked. Based on the pre-fault bipolar power of 10000MW and the maximum power of MMC single-pole transmission of 5000MW, the number of sets of leakage resistors is calculated to be 10. The total power reduction required by the sending-end renewable energy grid is 5000MW, and the power reduction share allocated to each renewable energy station is calculated to be 50% of its initial power. Then, based on the capacity of a single leakage resistor and the measurement time delay, the renewable energy power reduction rate is calculated. The timeframe is 200ms, meaning the new energy source reduces its power to 50% within 200ms. At 1.002s, the sending-end converter station activates a 5000MW AC power leakage resistor. At 1.030s, the sending-end flexible DC station sets the frequency signal reference value (e.g., Figure 3 The frequency (as shown) is modified to 50.35Hz, generating a 50.35Hz square wave signal with a duration of 170 milliseconds. This frequency signal is then modified back to 50Hz at 1.200s. At 1.270s, the new energy power plant's side stability control device still has not received the single-pole blocking signal from the communication system, but it has detected two frequency pulses, completing the fault judgment for single-pole blocking through the frequency signal. Once the new energy power plant completes the fault judgment for single-pole blocking, it issues a power reduction signal. The control system determines that the communication system is faulty, the main protection fails, and the new energy power plant activates backup protection control. All photovoltaic power plants reduce their respective power by half within 200ms. Subsequently, for every 500MW reduction in the total power of the sending-end photovoltaic power plants, one set of leakage resistors is deactivated.

[0108] Figures 7(a)-7(c)The voltage instantaneous value under the sending end power grid single-pole closed-loop fault, the total active power injected into the sending end converter station, the active power consumed by the energy dissipation resistor, and the switching of the energy dissipation resistor in the second case are shown.

[0109] The above is a protection control method under single-pole closed-loop fault provided in the embodiments of the present application, and the following is a protection control device under single-pole closed-loop fault provided in the embodiments of the present application.

[0110] Please refer to Figure 8 The protection control device under single-pole closed-loop fault provided in the embodiments of the present application is applied to a new energy through flexible DC transmission system, and the new energy through flexible DC transmission system includes a sending end flexible DC converter station, a communication system, a new energy station, and a plurality of groups of energy dissipation resistors.

[0111] The device includes:

[0112] The first control module 201 is configured to, after detecting the single-pole closed-loop fault, put in the energy dissipation resistor and issue a power reduction instruction to each new energy station through the communication system.

[0113] The second control module 202 is configured to, after the single-pole closed-loop fault occurs and a time delay of , correct the frequency instruction value of the sending end flexible DC system to a frequency signal with a specific feature

[0114] The third control module 203 is configured to, according to whether the new energy station receives the power reduction instruction from the communication system and in combination with the frequency signal, determine the activation state of the main protection control strategy and the backup protection control strategy for power reduction.

[0115] Further, in an embodiment, the protection control device under single-pole closed-loop fault of the present application further includes:

[0116] The fourth control module is configured to monitor the power injected into the sending end flexible DC converter station in real time to obtain the speed of power reduction of the new energy station, and control the energy dissipation resistor to be grouped out according to the speed of power reduction of the new energy station.

[0117] Further, the embodiments of the present application further provide a protection control device under single-pole closed-loop fault, which includes a processor and a memory:

[0118] The memory is configured to store program code and transmit the program code to the processor;

[0119] The processor is configured to execute the steps of the protection control method under single-pole closed-loop fault according to the instructions in the program code.

[0120] Further, the embodiment of the present application further provides a computer readable storage medium for storing program codes, the program codes being used for executing the single-pole blocking fault protection control method described in the above method embodiment.

[0121] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described system and unit can refer to the corresponding processes in the foregoing method embodiments, which will not be described here.

[0122] The terms "first", "second", "third", "fourth" and the like in the description of the present application and in the claims of the foregoing drawings, if any, are used for the purpose of distinction like objects and do not have to be described in a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to the clearly listed steps or units, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0123] It should be understood that in the present application, "at least one" refers to one or more, and "multiple" refers to two or more. "And / or" is used to describe the association between the associated objects, which means that there can be three relationships, for example, "A and / or B" can represent three cases: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally represents that the associated objects before and after are in an "or" relationship. "At least one of the following" or similar expressions means any combination of these items, including any combination of single item or multiple items. For example, at least one of a, b or c, can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0124] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other manners. For example, the described device embodiments are merely schematic. The division of the units is merely a logical function division. There can be another division manner for the actual implementation, for example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections can be indirect couplings or communication connections through some interfaces, devices or units, and can be electrical, mechanical or other forms.

[0125] The units described as separated components can or can not be physically separated, and the components displayed as units can or can not be physical units, i.e., can be located in one place, or can be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purposes of the embodiments of the present application.

[0126] In addition, each functional unit in the embodiments of the present application can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be implemented in the form of hardware, or in the form of software functional units.

[0127] When the integrated unit is implemented in the form of software functional units and sold or used as an independent product, it can be stored in a computer readable storage medium. Based on such an understanding, the technical solutions of the present application essentially, or the part that contributes to the prior art, or all or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the embodiments of the present application. The foregoing storage medium includes: U disk, mobile hard disk, read-only memory (English full name: Read-Only Memory, English abbreviation: ROM), random access memory (English full name: Random Access Memory, English abbreviation: RAM), magnetic disk or optical disk, and various program codes that can be stored in the medium.

[0128] The above-described embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A protection control method under a single-pole blocking fault, characterized in that, It is applied to a new energy transmission system via flexible DC transmission, which includes: a sending-end flexible DC converter station, a communication system, a new energy power station, and several sets of energy leakage resistors; The methods include: When a single-pole blocking fault is detected, the energy leakage resistor is activated, and a power reduction command is issued to each of the new energy power stations through the communication system. After a single-stage interlocking fault occurs and... After a time delay, the frequency command value of the sending-end flexible DC system is corrected to a frequency signal with specific characteristics; Based on whether the new energy power station receives the power reduction command from the communication system, and in conjunction with the frequency signal, determine the activation status of the main protection control strategy and the backup protection control strategy for power reduction; The step of determining the activation status of the main protection control strategy and the backup protection control strategy for power reduction based on whether the renewable energy power station receives the power reduction command from the communication system, and in conjunction with the frequency signal, includes: When the renewable energy power station cannot receive the power reduction command from the communication system, but can determine from the frequency signal that a single-pole blocking fault has occurred in the renewable energy through the flexible DC transmission system, the backup protection control strategy is activated; the backup protection control strategy is to control the generators of the renewable energy power station to reduce to a preset power value according to the received frequency signal. When the new energy power station receives the power reduction command from the communication system, it activates the preset main protection control strategy and simultaneously disables the backup protection control strategy; the main protection control strategy is to control the new energy power station to reduce power according to the power reduction command.

2. The protection control method under single-pole blocking fault according to claim 1, characterized in that, The step of determining the activation status of the main protection control strategy and backup protection control strategy for power reduction based on whether the new energy power station receives the power reduction command from the communication system, and in conjunction with the frequency signal, further includes: The power injected into the sending-end flexible DC converter station is monitored in real time to obtain the rate at which the power of the new energy power station is reduced. At the same time, the leakage resistors are controlled to be disconnected in groups according to the rate at which the power of the new energy power station is reduced.

3. The protection control method under single-pole blocking fault according to claim 1, characterized in that, The number of groups of leakage resistors is determined based on the relationship between the bipolar power before the fault and the maximum power that the healthy pole can transmit.

4. The protection control method under single-pole blocking fault according to claim 3, characterized in that, The number of groups of leakage resistors is determined based on the relationship between the bipolar power before the fault and the maximum power that the healthy pole can transmit, including: When the bipolar power before the fault exceeds the maximum power that the healthy pole can transmit, the number N of leakage resistors should be: ； In the formula, The bipolar power prior to the fault, The maximum power that the healthy pole can transmit. The rounding up symbol, This refers to the power consumed by a single set of leakage resistors.

5. The protection control method under single-pole blocking fault according to claim 3, characterized in that, The number of sets of leakage resistors is determined based on the relationship between the bipolar power before the fault and the maximum power that the healthy pole can transmit, and also includes: When the bipolar power before the fault is not greater than the maximum power that the healthy electrode can transmit, the leakage resistor is not applied, and the fault ride-through is achieved by transferring power from the healthy electrode.

6. The protection control method under a single-pole blocking fault according to claim 1, characterized in that, The process of generating the power reduction command includes: The allocation is based on the relationship between the initial operating power of each renewable energy power station, the power of the bipolar poles before the fault, and the maximum power that the healthy poles can transmit. The expression is as follows: ； In the formula, The amount of power reduction allocated to the i-th renewable energy power station. The initial operating power of the i-th renewable energy power station is... The bipolar power prior to the fault, The maximum power that the healthy pole can transmit.

7. The protection control method under a single-pole blocking fault according to claim 1, characterized in that, The frequency signal includes: Duration is The frequency is higher than the rated value. A square wave signal with frequency f, where the expression for the frequency signal f is: ； In the formula, This is the initial frequency of the power grid at the source of new energy.

8. The protection control method under a single-pole blocking fault according to claim 6, characterized in that, The main protection control strategy includes: go through After a certain period of time, the power reduction command is used to control the new energy power station to reduce its power. in, ; In the formula, This refers to the time delay of the measuring instrument when measuring power. The capacitance of a single set of the discharge resistors is given. The bipolar power prior to the fault, The maximum power that a perfect electrode can transmit.

9. The protection control method under a single-pole blocking fault according to claim 8, characterized in that, The size is The maximum of the two: the time delay between the sending-end flexible DC converter station sending information and the new energy power station receiving information.

10. The protection control method under a single-pole blocking fault according to any one of claims 1 to 9, characterized in that, Also includes: The frequency of the new energy transmitted through the flexible DC transmission system is monitored in real time at the new energy power station. When a brief frequency increase occurs, followed by a decrease... The time monitoring showed a duration of A square wave signal with a frequency of milliseconds is used to determine if a single-pole blocking fault has occurred at the sending end.

11. A protection and control device under a single-pole blocking fault, characterized in that, It is applied to a new energy transmission system via flexible DC transmission, which includes: a sending-end flexible DC converter station, a communication system, a new energy power station, and several sets of energy leakage resistors; The device includes: The first control module is used to activate the energy leakage resistor when a single-pole blocking fault is detected, and to issue a power reduction command to each of the new energy power stations through the communication system. The second control module is used to handle single-stage interlocking faults and after... After a time delay, the frequency command value of the sending-end flexible DC system is corrected to a frequency signal with specific characteristics; The third control module is used to determine the activation status of the main protection control strategy and the backup protection control strategy for power reduction based on whether the new energy power station receives the power reduction command from the communication system and in conjunction with the frequency signal. The third control module is specifically used for: The step of determining the activation status of the main protection control strategy and the backup protection control strategy for power reduction based on whether the renewable energy power station receives the power reduction command from the communication system, and in conjunction with the frequency signal, includes: When the renewable energy power station cannot receive the power reduction command from the communication system, but can determine from the frequency signal that a single-pole blocking fault has occurred in the renewable energy through the flexible DC transmission system, the backup protection control strategy is activated; the backup protection control strategy is to control the generators of the renewable energy power station to reduce to a preset power value according to the received frequency signal. When the new energy power station receives the power reduction command from the communication system, it activates the preset main protection control strategy and simultaneously disables the backup protection control strategy; the main protection control strategy is to control the new energy power station to reduce power according to the power reduction command.

12. The protection and control device under single-pole lockout fault according to claim 11, characterized in that, Also includes: Fourth control module; The fourth control module is used to monitor the power injected into the sending-end flexible DC converter station in real time to obtain the rate at which the power of the new energy power station is reduced, and at the same time control the energy leakage resistor to exit in groups according to the rate at which the power of the new energy power station is reduced.

13. A protection and control device under a single-pole blocking fault, characterized in that, The device includes a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the protection control method under single-pole blocking fault as described in any one of claims 1-10 according to the instructions in the program code.

14. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store program code for executing the protection control method under a single-pole blocking fault as described in any one of claims 1-10.

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