A Ground Fault Protection Method and System for a Static Var Generator

Abstract

The present invention discloses a grounding fault protection method and system for a static var generator. After it is determined that a fault exists in the static var generator, by judging the instantaneous current values of each bridge arm sub-module, if the instantaneous current value is greater than the first protection setting value, the corresponding bridge arm sub-module will be temporarily blocked after the first preset time, and the instantaneous current value of the corresponding bridge arm will continue to be obtained. If the instantaneous current value of the corresponding bridge arm sub-module is less than the return protection value, the corresponding bridge arm sub-module will be restarted, otherwise the corresponding bridge arm sub-module will continue to be blocked. If the instantaneous current value is greater than the second protection setting value, the corresponding bridge arm sub-module will be permanently blocked after the first preset time, so that the current of the corresponding bridge arm sub-module flows to other bridge arm sub-modules. The above method solves the problem of overvoltage due to continuous current during uncontrolled charging of sub-modules after all bridge arm sub-modules are blocked simultaneously in the prior art through bridge arm-by-bridge arm blocking protection.

Description

Technical Field

[0001] The present invention relates to the technical field of DC power transmission in power systems, and particularly to a grounding fault protection method and system for a static var generator. Background Art

[0002] With the rapid growth of the access scale of new energy and DC power electronic equipment, the proportion of traditional synchronous units has decreased, and the weak synchronous voltage support characteristics of local power grids in the power system have gradually emerged. The static var generator (SVG) uses power electronic devices to achieve reactive power compensation for the system, has the advantages of dynamic compensation and fast response, can effectively support the system voltage and improve the stability of the power system, and is another important device to support the construction of a new power system. With the gradual increase of the voltage support demand, the existing SVG devices are gradually developing towards high voltage and large capacity, and the interaction with DC and other power electronic equipment is closer, and the fault forms are more diverse.

[0003] The multi-source commutation technology is a new commutation technology that combines a voltage-source SVG device with a current-source conventional DC. By connecting the SVG in parallel on the valve side of the commutation transformer, the dynamic compensation of conventional DC harmonics and reactive power is realized, and the network adaptability performance of the conventional DC is improved. However, due to the close coupling between the SVG device and the conventional DC, the fault forms are more complex. In the case of some SVG valve area faults, the traditional direct blocking strategy will cause the conventional DC to form a continuous current path to the SVG through diodes, resulting in continuous overcharging of the sub-modules and the risk of large-scale bypass of the sub-modules, threatening the safety of the equipment. Summary of the Invention

[0004] To solve the above technical problems, an embodiment of the present invention provides a grounding fault protection method and system for a static var generator, so as to solve the problem of overvoltage of sub-modules caused by DC current charging the capacitor through diodes after a grounding fault occurs in a high-voltage and large-capacity static var generator combined with a multi-source adaptive commutation converter in the prior art.

[0005] A first aspect of an embodiment of the present invention provides a grounding fault protection method for a static var generator, the method including:

[0006] Determine whether the static var generator has a fault. If so, obtain the instantaneous current values of each bridge arm sub-module of the static var generator in the operating state;

[0007] Judge the instantaneous current value of each arm sub-module. If the instantaneous current value is greater than the first protection setting value, lock the corresponding arm sub-module for a second preset time after the first preset time, continue to obtain the instantaneous current value of the corresponding arm sub-module, get the updated instantaneous current value, and judge whether the updated instantaneous current value is less than the return protection value. If it is less, restart the corresponding arm sub-module. If it is greater, continue to lock the corresponding arm sub-module;

[0008] If the instantaneous current value is greater than the second protection setting value, permanently lock the corresponding arm sub-module after the first preset time, so that the current of the corresponding arm sub-module flows to other arm sub-modules.

[0009] In a possible implementation manner of the first aspect, judging whether the static var generator has a fault includes:

[0010] Obtain the three-phase current data or three-phase voltage data of the access point of the static var generator;

[0011] Calculate the zero-sequence component based on the three-phase current data or three-phase voltage data to obtain the zero-sequence current component or zero-sequence voltage component;

[0012] Judge whether the zero-sequence current component or zero-sequence voltage component is greater than a preset threshold. If it is greater, determine that the static var generator has a fault.

[0013] In a possible implementation manner of the first aspect, after judging that the static var generator has a fault, it further includes:

[0014] Increase the trigger angle of the multi-source adaptive phase-shifting converter to the first trigger angle, and obtain the DC current output by the multi-source adaptive phase-shifting converter;

[0015] If the DC current is less than the preset current value, lock the trigger pulse after the third preset time, and increase the trigger angle of the multi-source adaptive phase-shifting converter to the second trigger angle, where the first trigger angle is less than the second trigger angle.

[0016] In a possible implementation manner of the first aspect, after locking the corresponding arm sub-module for the second preset time after the first preset time, it further includes:

[0017] When the corresponding arm sub-module operates for a preset time period, count the number of times the corresponding arm sub-module is locked for the second preset time;

[0018] When the number of times is greater than the preset number of times, permanently lock the corresponding arm sub-module.

[0019] In a possible implementation manner of the first aspect, if the DC current is less than the preset current value, it further includes:

[0020] If the DC current is less than the preset current value, the multi-source adaptive commutation converter is made to send a blocking instruction to the static var generator, so that the static var generator permanently blocks all the arm sub-modules.

[0021] In a possible implementation manner of the first aspect, the first protection setting value is less than the second protection setting value, and the returned protection value is less than the first protection setting value.

[0022] To solve the same technical problem, a second aspect of the embodiments of the present invention provides a static var generator ground fault protection system, and the system includes:

[0023] An acquisition module, configured to determine whether a static var generator has a fault. If so, acquire the instantaneous current values of each arm sub-module of the static var generator in the operating state;

[0024] A first execution module, configured to judge the instantaneous current values of each arm sub-module. If the instantaneous current value is greater than the first protection setting value, block the corresponding arm sub-module for a second preset time after a first preset time, continue to acquire the instantaneous current value of the corresponding arm sub-module, obtain the updated instantaneous current value, and judge whether the updated instantaneous current value is less than the returned protection value. If it is less, restart the corresponding arm sub-module. If it is greater, continue to block the corresponding arm sub-module;

[0025] A second execution module, configured to if the instantaneous current value is greater than the second protection setting value, permanently block the corresponding arm sub-module after a first preset time, so that the current of the corresponding arm sub-module flows to other arm sub-modules.

[0026] In a possible implementation manner of the second aspect, the acquisition module includes a current and voltage acquisition unit, a zero-sequence component calculation unit, and a zero-sequence component judgment unit, where

[0027] The current and voltage acquisition unit is configured to acquire three-phase current data or three-phase voltage data of the access point of the static var generator;

[0028] The zero-sequence component calculation unit is configured to calculate a zero-sequence component based on the three-phase current data or the three-phase voltage data to obtain a zero-sequence current component or a zero-sequence voltage component;

[0029] The zero-sequence component judgment unit is configured to judge whether the zero-sequence current component or the zero-sequence voltage component is greater than a preset threshold. If it is greater, determine that the static var generator has a fault.

[0030] In a possible implementation manner of the second aspect, the acquisition module further includes a first trigger angle adjustment unit and a second trigger angle adjustment unit, where

[0031] The first trigger angle adjustment unit is used to increase the trigger angle of the multi-source adaptive commutation converter to the first trigger angle and obtain the DC current output by the multi-source adaptive commutation converter;

[0032] The second trigger angle adjustment unit is used to block the trigger pulse after a third preset time if the DC current is less than the preset current value, and increase the trigger angle of the multi-source adaptive commutation converter to the second trigger angle, where the first trigger angle is less than the second trigger angle.

[0033] In a possible implementation manner of the second aspect, the first execution module includes a statistics unit and a blocking execution unit, where

[0034] The statistics unit is used to count the number of times the corresponding arm sub-module is blocked for a second preset time after the corresponding arm sub-module operates for a preset time period;

[0035] The blocking execution unit is used to permanently block the corresponding arm sub-module when the number of times is greater than the preset number of times.

[0036] The technical solution of the present invention has the following advantages:

[0037] The static var generator grounding fault protection method provided by the embodiment of the present invention, after determining that the static var generator has a fault, judges the instantaneous current value of each arm sub-module. If the instantaneous current value is greater than the first protection setting value, the corresponding arm sub-module is temporarily blocked after a first preset time, and the instantaneous current value of the corresponding arm is continuously obtained. If the instantaneous current value of the corresponding arm sub-module is less than the return protection value, the corresponding arm sub-module is restarted, otherwise the corresponding arm sub-module is continuously blocked. If the instantaneous current value is greater than the second protection setting value, the corresponding arm sub-module is permanently blocked after a first preset time, so that the current of the corresponding arm sub-module flows to other arm sub-modules. The above method uses branch-arm blocking protection and utilizes the shunt effect of the unlocked state of the remaining phase arm sub-modules to reduce the charging current flowing through the blocked arm sub-module, and solves the problem of overvoltage due to continuous current of uncontrolled charging of sub-modules after all arm sub-modules are blocked simultaneously in the prior art without increasing the hardware cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0039] Figure 1It is a flowchart of the grounding fault protection method for the static var generator in the embodiment of the present invention;

[0040] Figure 2 It is a schematic diagram of the topology structure of the static var generator for the grounding fault protection method in the embodiment of the present invention;

[0041] Figure 3 It is a schematic diagram of the typical fault path of the interaction between the static var generator and the conventional DC for the grounding fault protection method in the embodiment of the present invention;

[0042] Figure 4 It is a schematic diagram of the electromagnetic transient simulation waveform of the SVG grounding fault in the common technology of the grounding fault protection method for the static var generator in the embodiment of the present invention;

[0043] Figure 5 It is a timing diagram of the operation of the static var generator and the multi-source adaptive phase-shifting converter for the grounding fault protection method in the embodiment of the present invention;

[0044] Figure 6 It is a schematic diagram of the split-bridge-arm blocking protection method for the static var generator in the grounding fault protection method in the embodiment of the present invention;

[0045] Figure 7 It is a single-phase timing diagram of the split-bridge-arm blocking protection for the static var generator in the grounding fault protection method in the embodiment of the present invention;

[0046] Figure 8 It is an electromagnetic transient simulation waveform diagram of the SVG grounding fault under the split-phase blocking protection method in the grounding fault protection method for the static var generator in the embodiment of the present invention;

[0047] Figure 9 It is a block diagram of the grounding fault protection system for the static var generator in the embodiment of the present invention. Detailed implementation manners

[0048] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] In the description of the present invention, it should be noted that the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0050] The grounding fault protection method for a static var generator provided by an embodiment of the present invention is as follows Figure 1 as shown Figure 1 in the grounding fault protection flow chart of the static var generator, which includes steps S101 to S103, and the specific steps are as follows:

[0051] S101: Determine whether there is a fault in the static var generator. If there is, obtain the instantaneous current values of each arm sub-module of the static var generator in the operating state.

[0052] In this embodiment, as Figure 2 shown, the static var generator (SVG) is connected to the valve side of a conventional DC converter station, and includes a starting resistor, a connecting reactor, a bushing, and an SVG valve. The SVG valve adopts a star connection method. The connecting reactor is connected in series with the SVG valve through the bushing. The SVG valve includes a number of series-connected full-bridge sub-modules.

[0053] When a grounding fault occurs in the SVG, the DC voltage built by the series valve group injects current into the fault point through the lower arm thyristor. Generally, after detecting the zero-sequence component, each arm sub-module of the SVG is quickly blocked, that is, the IGBT changes from conduction to blocking under the gate control, and the arm sub-module is in an uncontrolled charging state. The fault current charges the capacitor through the diode. With the alternating commutation of the multi-source adaptive commutation converter (LCC) arm, the voltage of a certain arm sub-module of the SVG rises rapidly. Figure 3 is a schematic diagram of a typical fault path for the interaction between the static var generator and the conventional DC.

[0054] Figure 4 is the electromagnetic transient waveform of the main electrical quantities under the grounding fault of the SVG when using the existing technology. The sending end of the model uses SLCC, and the receiving end uses VSC. It can be seen from Figure 4 that after the SVG has a grounding fault, all arm sub-modules are quickly blocked. Due to the uncontrollable charging stage, the peak voltage of the sub-module reaches 3.9 kV, and there is a risk of overvoltage in the sub-module. Therefore, by setting overcurrent blocking protection for each arm respectively, when the current of a single arm reaches the protection setting value, the arm is blocked with a time delay, and the other arms continue to operate, so as to reduce the risk of overvoltage of the sub-module. The specific steps are as follows: First, judge whether there is a grounding fault in the static var generator according to the three-phase current data or three-phase voltage data at the access point of the static var generator. If there is, detect the instantaneous current values of each arm sub-module, and perform three-phase arm-by-arm blocking protection on each arm sub-module according to the instantaneous current values, that is, when the current of a single arm sub-module reaches the protection setting value, the arm is blocked with a time delay, and the other arm sub-modules continue to operate.

[0055] It should be noted that the static var generator refers to SVG. The static var generator includes but is not limited to high-voltage large-capacity SVG. "High voltage" means it can be directly connected to a power grid with a relatively high voltage level, such as 10 kV, 35 kV, 110 kV or even higher voltage levels. "Large capacity" means it has a large reactive power compensation ability and can provide or absorb a large amount of reactive power. Generally, its capacity can reach the megavar (Mvar) level.

[0056] In one embodiment, determining whether there is a fault in the static var generator includes:

[0057] Obtaining three-phase current data or three-phase voltage data of the access point of the static var generator;

[0058] Calculating the zero-sequence component based on the three-phase current data or three-phase voltage data to obtain the zero-sequence current component or zero-sequence voltage component;

[0059] Determining whether the zero-sequence current component or zero-sequence voltage component is greater than a preset threshold. If it is greater, it is determined that there is a fault in the static var generator.

[0060] In this embodiment, the grounding fault of SVG is detected by the zero-sequence component. Specifically, the zero-sequence component is calculated according to the three-phase current data or three-phase voltage data of the access point of the static var generator to obtain the zero-sequence current component or zero-sequence voltage component, and it is determined whether the zero-sequence current component or zero-sequence voltage component is greater than a preset threshold. If it is greater, it is determined that there is a fault in the static var generator.

[0061] In one embodiment, after determining that there is a fault in the static var generator, it further includes:

[0062] Increasing the trigger angle of the multi-source adaptive phase-shifting converter to the first trigger angle and obtaining the DC current output by the multi-source adaptive phase-shifting converter;

[0063] If the DC current is less than a preset current value, lock the trigger pulse after a third preset time and increase the trigger angle of the multi-source adaptive phase-shifting converter to the second trigger angle, where the first trigger angle is less than the second trigger angle.

[0064] In this embodiment, as Figure 5 shown, after detecting the grounding fault of SVG by the zero-sequence component, the action timing of the multi-source adaptive phase-shifting converter (LCC) is as follows: increasing the LCC trigger angle to the first trigger angle , when the DC current is less than the preset current value, locking the trigger pulse after a set time delay; then controlling the trigger angle of the sending-end LCC to increase to the second trigger angle . Among them, the first trigger angle is less than the second trigger angle .

[0065] Regarding the description of the value, the first trigger angle is preferably 120°, and the second trigger angle is preferably 160°, and the preset current value is preferably 0.03 p.u.

[0066] In this embodiment, under the three-phase split-bridge-arm locking protection strategy, by utilizing the shunt effect of the unlocking state of the remaining phase bridge arms and cooperating with the phase-shifting strategy of the LCC, the charging current flowing through the locked bridge-arm submodules is effectively reduced. Without increasing the hardware cost, the problem of continuous overvoltage caused by uncontrolled charging of submodules after all bridge arms are locked simultaneously in the prior art is solved, the large-scale bypass of SVG submodules and the long-time maintenance after the bypass switch operates are avoided, and the engineering investment cost is greatly reduced.

[0067] S102: Judge the instantaneous current values of each bridge-arm submodule. If the instantaneous current value is greater than the first protection setting value, lock the corresponding bridge-arm submodule for a second preset time after a first preset time, continue to obtain the instantaneous current value of the corresponding bridge-arm submodule to get the updated instantaneous current value, and judge whether the updated instantaneous current value is less than the return protection value. If it is less, restart the corresponding bridge-arm submodule. If it is greater, continue to lock the corresponding bridge-arm submodule.

[0068] In this embodiment, as Figure 6 shown, Figure 6 is a schematic diagram of the split-bridge-arm locking protection method for a static var generator. After detecting the SVG grounding fault through zero-sequence component detection, the action timing of the SVG is as follows: after the instantaneous current value of the bridge-arm submodule reaches the protection setting value, the split-bridge-arm locking protection is executed. According to the current of the bridge-arm submodule after the fault, the bridge-arm submodule enters the temporary locking, locking reset, or permanent locking state. Specifically, as Figure 7 shown, the single-phase action timing of the split-bridge-arm locking protection is: detect the instantaneous bridge-arm current. When the instantaneous current value of any one or more bridge-arm submodules exceeds the first protection setting value , the bridge-arm submodule of this phase is temporarily locked after a set delay time, and the number of temporary lockings is recorded. If the instantaneous current value of this bridge-arm submodule drops to the return protection value , unlock this phase of the bridge-arm submodule again.

[0069] It should be noted that the first preset time refers to the set delay time, which can be understood as when the instantaneous current value exceeds the first protection setting value , wait for a period of time and then temporarily lock the bridge-arm submodule of this phase. The second preset time is the time of temporary locking. The first preset time and the second preset time can be set according to actual needs.

[0070] In one embodiment, after locking the corresponding arm sub-module for a second preset time after a first preset time, it further includes:

[0071] When the corresponding arm sub-module operates for a preset time period, count the number of times the corresponding arm sub-module is locked for the second preset time;

[0072] When the number of times is greater than a preset number, permanently lock the corresponding arm sub-module.

[0073] In this embodiment, if any one or more phase arm sub-modules are temporarily locked and the number of temporary locks is recorded, after the SVG operates for a period of time, count the number of temporary locks of the arm sub-modules. If the number of temporary locks exceeds the preset number , then permanently lock the phase arm sub-module.

[0074] It should be noted that the preset number is preferably 12 times.

[0075] In one embodiment, if the DC current is less than a preset current value, it further includes:

[0076] If the DC current is less than the preset current value, then make the multi-source adaptive commutation converter send a locking instruction to the static var generator, so that the static var generator permanently locks all arm sub-modules.

[0077] In this embodiment, after the DC current is less than the DC current threshold, the multi-source adaptive commutation converter (LCC) sends a locking signal to the SVG, and all arm sub-modules of the SVG are permanently locked. The preset current value is preferably 0.03 p.u.

[0078] S103: If the instantaneous current is greater than the second protection setting value, then permanently lock the corresponding arm sub-module after a first preset time, so that the current of the corresponding arm sub-module flows to other arm sub-modules.

[0079] In this embodiment, when the arm current exceeds the second protection setting value , after a delay of a set time, the phase arm sub-module is permanently locked. In the currently commonly used technology, after judging arm overcurrent, the three-phase arm sub-modules are directly locked. This method effectively utilizes the current sharing characteristic of the parallel arms in the controllable state through the arm-by-arm locking strategy. As Figure 8 shown, Figure 8 is the electromagnetic transient waveform of the main electrical quantities under the grounding fault of the SVG adopting the arm-by-arm locking strategy. From Figure 8It can be seen that after a ground fault occurs in the SVG, due to the use of the phase-separated locking strategy, the fault current is shunted through the remaining phase sub-modules. Compared with the currently commonly used technologies, the peak value of the highest sub-module voltage is reduced to 2.6 kV, which is within the overvoltage protection setting value range.

[0080] In one embodiment, the first protection setting value is less than the second protection setting value, and the returned protection value is less than the first protection setting value.

[0081] In this embodiment, the first protection setting value is less than the second protection setting value , and the returned protection value is less than the first protection setting value

[0082] It should be noted that the first protection setting value is preferably 4.5 kA, the second protection setting value is preferably 5.3 kA, and the returned protection value is 4.2 kA.

[0083] Through the split-bridge-arm locking protection, the present invention utilizes the shunting effect of the remaining phase bridge arms in the unlocked state, and cooperates with the phase-shifting strategy of the multi-source adaptive commutation converter (LCC) to reduce the charging current flowing through the sub-modules of the locked bridge arm. Without increasing the hardware cost, the problem of continuous overvoltage caused by uncontrolled charging of sub-modules after all bridge arms are locked simultaneously in the prior art is solved, and large-scale bypass of SVG sub-modules and long-time maintenance after the bypass switch operates are avoided, greatly reducing the engineering investment cost.

[0084] The present invention also achieves the remarkable effect of avoiding reducing the sub-module overvoltage by paralleling high-energy lightning arresters or increasing the number of converter valve modules, effectively solves the technical problems faced by the project, reduces the engineering investment, improves the economy and adaptability of the static var generator (SVG) in more scenarios, and has broad application prospects.

[0085] The static var generator ground fault protection system provided by the embodiment of the present invention, as Figure 9 shown, Figure 9 is the block diagram 900 of the static var generator ground fault protection system, including:

[0086] An acquisition module 901, configured to determine whether a fault exists in the static var generator. If so, acquire the instantaneous current values of each bridge arm sub-module when the static var generator is in the operating state;

[0087] The first execution module 902 is configured to judge the instantaneous current values of each arm sub-module. If the instantaneous current value is greater than the first protection setting value, the corresponding arm sub-module is blocked for a second preset time after a first preset time, and the instantaneous current value of the corresponding arm sub-module is continuously obtained to get the updated instantaneous current value. Then, it is judged whether the updated instantaneous current value is less than the return protection value. If it is less, the corresponding arm sub-module is restarted; if it is greater, the corresponding arm sub-module continues to be blocked.

[0088] The second execution module 903 is configured to, if the instantaneous current value is greater than the second protection setting value, permanently block the corresponding arm sub-module after a first preset time, so that the current of the corresponding arm sub-module flows to other arm sub-modules.

[0089] In one embodiment, the acquisition module 901 includes a current and voltage acquisition unit, a zero-sequence component calculation unit, and a zero-sequence component judgment unit, where

[0090] The current and voltage acquisition unit is configured to acquire three-phase current data or three-phase voltage data of the access point of the static var generator.

[0091] The zero-sequence component calculation unit is configured to calculate the zero-sequence component based on the three-phase current data or three-phase voltage data to obtain the zero-sequence current component or zero-sequence voltage component.

[0092] The zero-sequence component judgment unit is configured to judge whether the zero-sequence current component or zero-sequence voltage component is greater than a preset threshold. If it is greater, it is determined that the static var generator has a fault.

[0093] In one embodiment, the acquisition module 901 further includes a first trigger angle adjustment unit and a second trigger angle adjustment unit, where

[0094] The first trigger angle adjustment unit is configured to increase the trigger angle of the multi-source adaptive commutation converter to the first trigger angle and acquire the DC current output by the multi-source adaptive commutation converter.

[0095] The second trigger angle adjustment unit is configured to, if the DC current is less than a preset current value, block the trigger pulse after a third preset time and increase the trigger angle of the multi-source adaptive commutation converter to the second trigger angle, where the first trigger angle is less than the second trigger angle.

[0096] In one embodiment, the first execution module 902 includes a statistics unit and a blocking execution unit, where

[0097] The statistics unit is configured to, after the corresponding arm sub-module runs for a preset time period, count the number of times the corresponding arm sub-module is blocked for the second preset time.

[0098] The blocking execution unit is used to permanently block the corresponding arm sub-module when the number of times is greater than the preset number of times.

[0099] In one embodiment, if the DC current is less than the preset current value, it further includes:

[0100] If the DC current is less than the preset current value, the multi-source adaptive commutation converter is made to send a blocking instruction to the static var generator, so that the static var generator permanently blocks all the arm sub-modules.

[0101] In one embodiment, the first protection setting value is less than the second protection setting value, and the returned protection value is less than the first protection setting value.

[0102] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0103] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. It is particularly pointed out that for those skilled in the art, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A grounding fault protection method for a static var generator, characterized in that, Including: Determine whether the static var generator has a fault. If so, obtain the instantaneous current values of each arm sub-module of the static var generator in the operating state; Judge the instantaneous current values of each of the arm sub-modules. If the instantaneous current value is greater than the first protection setting value, lock the corresponding arm sub-module for a second preset time after a first preset time, continue to obtain the instantaneous current value of the corresponding arm sub-module, obtain the updated instantaneous current value, and judge whether the updated instantaneous current value is less than the return protection value. If it is less, restart the corresponding arm sub-module. If it is greater, continue to lock the corresponding arm sub-module; If the instantaneous current value is greater than the second protection setting value, permanently lock the corresponding arm sub-module after a first preset time, so that the current of the corresponding arm sub-module flows to other arm sub-modules; After it is determined that the static var generator has a fault, it further includes: Increase the trigger angle of the multi-source adaptive phase-shifting converter to a first trigger angle, and obtain the DC current output by the multi-source adaptive phase-shifting converter; If the DC current is less than a preset current value, lock the trigger pulse after a third preset time, and increase the trigger angle of the multi-source adaptive phase-shifting converter to a second trigger angle, where the first trigger angle is less than the second trigger angle.

2. The grounding fault protection method of the static var generator according to claim 1, characterized in that, The determination of whether the static var generator has a fault includes: Obtain the three-phase current data or three-phase voltage data of the access point of the static var generator; Calculate the zero-sequence component based on the three-phase current data or the three-phase voltage data to obtain the zero-sequence current component or zero-sequence voltage component; Judge whether the zero-sequence current component or the zero-sequence voltage component is greater than a preset threshold. If it is greater, determine that the static var generator has a fault.

3. The grounding fault protection method of the static var generator according to claim 1, characterized in that After locking the corresponding arm sub-module for a second preset time after a first preset time, it further includes: When the corresponding arm sub-module operates for a preset time period, count the number of times the corresponding arm sub-module is locked for the second preset time; When the number is greater than a preset number, permanently lock the corresponding arm sub-module.

4. The grounding fault protection method for a static var generator according to claim 1, characterized in that, When it is said that if the DC current is less than the preset current value, it further includes: If the DC current is less than the preset current value, the multi-source adaptive phase-shifting converter sends a locking instruction to the static var generator, so that the static var generator permanently locks all arm sub-modules.

5. The static var generator ground fault protection method according to claim 1, characterized in that, The first protection setting value is less than the second protection setting value, and the return protection value is less than the first protection setting value.

6. A grounding fault protection system for a static var generator, characterized in that, Including: An acquisition module, configured to determine whether the static var generator has a fault. If so, obtain the instantaneous current values of each arm sub-module of the static var generator in the operating state; The first execution module is used to judge the instantaneous current values of each of the arm sub-modules. If the instantaneous current value is greater than the first protection setting value, the corresponding arm sub-module is blocked for a second preset time after a first preset time, and the instantaneous current value of the corresponding arm sub-module is continuously obtained to get an updated instantaneous current value. Then it judges whether the updated instantaneous current value is less than the return protection value. If it is less, the corresponding arm sub-module is restarted. If it is greater, the corresponding arm sub-module continues to be blocked. The second execution module is used to permanently block the corresponding arm sub-module if the instantaneous current value is greater than the second protection setting value, so that the current of the corresponding arm sub-module flows to other arm sub-modules. The acquisition module further includes a first trigger angle adjustment unit and a second trigger angle adjustment unit, where the first trigger angle adjustment unit is used to increase the trigger angle of the multi-source adaptive commutation converter to a first trigger angle and obtain the DC current output by the multi-source adaptive commutation converter. The second trigger angle adjustment unit is used to block the trigger pulse after a third preset time and increase the trigger angle of the multi-source adaptive commutation converter to a second trigger angle if the DC current is less than a preset current value, where the first trigger angle is less than the second trigger angle.

7. The static var generator ground fault protection system according to claim 6, characterized in that, The acquisition module includes a current and voltage acquisition unit, a zero-sequence component calculation unit, and a zero-sequence component judgment unit, where the current and voltage acquisition unit is used to acquire three-phase current data or three-phase voltage data of the access point of the static var generator. the zero-sequence component calculation unit is used to calculate the zero-sequence component based on the three-phase current data or the three-phase voltage data to obtain a zero-sequence current component or a zero-sequence voltage component. the zero-sequence component judgment unit is used to judge whether the zero-sequence current component or the zero-sequence voltage component is greater than a preset threshold. If it is greater, it is determined that the static var generator has a fault.

8. The grounding fault protection system of the static var generator according to claim 6, characterized in that, The first execution module includes a statistics unit and a blocking execution unit, where the statistics unit is used to count the number of times the corresponding arm sub-module is blocked for the second preset time after the corresponding arm sub-module operates for a preset time period. the blocking execution unit is used to permanently block the corresponding arm sub-module if the number of times is greater than a preset number of times.

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