Method and device for protecting the ground of a third harmonic zero voltage stator of a distributed phase modifier

Abstract

The application provides a method and device for distributed phase modifier third harmonic zero voltage stator grounding protection, the method comprising: collecting the closing position information of the circuit breaker and static var compensator at the generator end and the analog quantity information at the generator end; calculating the third harmonic components of the zero sequence voltage at the generator end and the neutral point zero sequence voltage, the reactive power and the frequency based on the analog quantity information; forming the operating condition with the adjustment criterion, and automatically switching the third harmonic voltage ratio fixed value before and after the grid connection based on the operating condition with the adjustment criterion; forming the power with the adjustment criterion, and determining the third harmonic voltage ratio calculation fixed value based on the power with the adjustment criterion; forming the grounding protection criterion, and judging whether the third harmonic zero voltage stator grounding protection action condition is met based on the grounding protection criterion. The application can quickly identify the operating condition of the unit, and automatically switch the corresponding protection fixed value, thereby improving the flexibility of the protection. The power with the adjustment criterion is braked by the reactive power unit value, thereby further improving the protection reliability under different operating conditions.

Description

Technical Field

[0001] This invention relates to the field of power system relay protection technology, and in particular to a method and device for third harmonic zero-voltage stator grounding protection of distributed synchronous condensers. Background Technology

[0002] Large synchronous condensers have fixed wiring configurations for salient-pole units and transformer groups, as well as fixed neutral grounding methods, and do not have terminal circuit breakers. Distributed synchronous condensers, on the other hand, exist in both salient-pole and non-salient-pole configurations. Their main wiring configurations and neutral grounding methods are not fixed and differ from those of large synchronous condensers. They have terminal circuit breakers. When the terminal circuit breaker is open, the calculation of the third harmonic voltage ratio only considers the influence of the distributed capacitance at the terminal and neutral point. When the terminal circuit breaker is closed, the calculation of the third harmonic voltage ratio also considers the influence of system-side capacitances such as those of the main transformer, excitation transformer, and busbar. Furthermore, most terminal circuit breakers are equipped with parallel capacitors on both sides to prevent overvoltage. Therefore, the difference in the third harmonic voltage ratio before and after grid connection is significant, requiring the setting of corresponding protection settings according to different operating conditions.

[0003] The magnetomotive force of the rotor winding and the magnetomotive force of the stator winding work together to generate the third harmonic flux of the air gap magnetic field of the distributed synchronous condenser. Before grid connection, there is no armature reaction, and the third harmonic at the generator terminal is the third harmonic component of the generator terminal voltage. After grid connection and load, the armature reaction saturates the magnetic circuit, generating a third harmonic potential. The flux generated by the armature reaction of active power is located in the q-axis direction of the synchronous condenser, while the flux generated by the armature reaction of reactive power is located in the d-axis direction. For salient-pole distributed synchronous condensers, the air gap in the d-axis direction is smaller and more prone to saturation. Therefore, reactive power has a significant impact on the third harmonic potential of salient-pole distributed synchronous condensers. The third harmonic voltage ratio varies with different reactive power levels, leading to a decrease in the reliability of conventional third harmonic voltage ratio criteria. Therefore, a third harmonic zero-voltage stator grounding protection method applicable to both salient-pole and non-salient-pole distributed synchronous condensers should be specifically researched. Summary of the Invention

[0004] In view of this, the present invention provides a method and apparatus for protecting the third harmonic zero-voltage stator grounding of a distributed synchronous condenser, in order to solve at least one of the problems mentioned above.

[0005] To achieve the above objectives, the present invention adopts the following solution:

[0006] According to a first aspect of the present invention, a method for third harmonic zero-voltage stator grounding protection of a distributed synchronous condenser is provided. The method includes: acquiring the closing position information of the circuit breaker at the generator terminal of the distributed synchronous condenser, the closing position information of the static var compensator, and the analog quantity information at the generator terminal; based on the analog quantity information at the generator terminal, acquiring the third harmonic component of the zero-sequence voltage at the generator terminal and the zero-sequence voltage at the neutral point, the generator reactive power, and the generator frequency; constructing a condition-based adjustment criterion based on the closing position information of the circuit breaker at the generator terminal, the closing position information of the static var compensator, and the generator frequency, and automatically switching the third harmonic before and after grid connection based on the condition-based adjustment criterion. Voltage ratio setpoint; obtain the per-unit value of reactive power based on the unit's reactive power; construct a power adjustment criterion based on the per-unit value of reactive power, the third harmonic voltage ratio setpoint, a preset reliability coefficient, and a preset power adjustment control word, and determine the third harmonic voltage ratio calculation setpoint based on the power adjustment criterion; construct a grounding protection criterion based on the third harmonic voltage ratio calculation setpoint, the amplitude of the third harmonic component of the neutral point zero-sequence voltage, the PT ratio of the neutral point zero-sequence voltage, and the PT ratio of the generator terminal zero-sequence voltage, and determine whether the third harmonic zero-voltage stator grounding protection operation condition is met based on the grounding protection criterion.

[0007] As an embodiment of the present invention, the analog quantity information at the generator terminal in the above method includes: sampled values ​​of generator terminal three-phase voltage, generator terminal three-phase current, generator terminal zero-sequence voltage and neutral point zero-sequence voltage.

[0008] As an embodiment of the present invention, the method described above, based on the analog quantity information at the generator terminal, includes obtaining the third harmonic components of the zero-sequence voltage at the generator terminal and the neutral point zero-sequence voltage, the generator reactive power, and the generator frequency. This includes: using the sampled values ​​of the zero-sequence voltage at the generator terminal and the zero-sequence voltage at the neutral point, calculating the third harmonic components of the zero-sequence voltage at the generator terminal and the neutral point zero-sequence voltage using a Fourier algorithm and a digital filter algorithm; using the sampled values ​​of the three-phase voltage and the three-phase current at the generator terminal, obtaining the generator reactive power using a Fourier algorithm and a reactive power algorithm; and using the sampled values ​​of the three-phase voltage at the generator terminal, obtaining the generator frequency using a hardware frequency measurement algorithm or a software frequency measurement algorithm.

[0009] As an embodiment of the present invention, the above method uses the closing position information of the generator-terminal circuit breaker, the closing position information of the static var compensator, and the generator frequency to form a condition-based adjustment criterion, and automatically switches the third harmonic voltage ratio setting before and after grid connection based on the condition-based adjustment criterion. This includes: when the closing position information of the generator-terminal circuit breaker is 1, the closing position information of the static var compensator is 0, and the generator frequency is greater than the set frequency, the generator grid connection status is determined to be 1. A closing position information of 1 for the generator-terminal circuit breaker indicates that there is a generator-terminal circuit breaker. When the closing position is entered, a static reactive power compensator closing position information of 0 indicates that no static reactive power compensator closing position has been entered, and the unit grid connection status of 1 indicates that the unit is in grid connection status; when the unit-end circuit breaker closing position is 0 or the static reactive power compensator closing position is 1, the unit grid connection status is determined to be 0 after a delay. A unit-end circuit breaker closing position of 0 indicates that no unit-end circuit breaker closing position has been entered, a static reactive power compensator closing position of 1 indicates that a static reactive power compensator closing position has been entered, and the unit grid connection status of 0 indicates that the unit is not in grid connection status.

[0010] Construct the following operating condition adjustment criterion:

[0011]

[0012] In the above formula, K Set K is the set value for the third harmonic voltage ratio. BeforeSet K is the setpoint for the third harmonic voltage ratio before grid connection. AfterSet After grid connection, the third harmonic voltage ratio is set. The operating condition adjustment control word is an adjustable control word. When the difference between the measured third harmonic voltage ratio before and after grid connection of the distributed synchronous condenser exceeds the set threshold, the operating condition adjustment control word is set to 1; otherwise, the operating condition adjustment control word is set to 0.

[0013] Based on the aforementioned operating condition adjustment criterion, the output setpoint K is automatically switched. Set value.

[0014] As an embodiment of the present invention, obtaining the per-unit value of reactive power based on the reactive power of the unit in the above method includes:

[0015] Based on the reactive power of the aforementioned unit, the per-unit value of reactive power is obtained using the following formula:

[0016]

[0017] In the above formula, Q * Q is the per-unit value of reactive power. N Q represents the rated capacity of the distributed synchronous condenser, and Q represents the reactive power of the unit.

[0018] As an embodiment of the present invention, the above method comprises constructing a power adjustment criterion based on the per-unit value of reactive power, the third harmonic voltage ratio setpoint, a preset reliability coefficient, and a preset power adjustment control word, and determining the third harmonic voltage ratio calculation setpoint based on the power adjustment criterion, including:

[0019] Based on the per-unit value of reactive power, the third harmonic voltage ratio setting, the preset reliability coefficient, and the preset power adjustment control word, the power adjustment criterion is constructed as follows:

[0020]

[0021] In the above formula: K jsSet It is the calculated constant value for the third harmonic voltage ratio, k r k is the reliability coefficient. r The adjustable range is 0.01 to 0.2. The power follow-up control word is an adjustable control word. When the distributed synchronous condenser is a salient pole machine, the power follow-up control word is set to 1. When it is a non-salient pole machine, the power follow-up control word is set to 0.

[0022] As an embodiment of the present invention, the above method uses the third harmonic voltage ratio to calculate the set value, the amplitude of the third harmonic component of the neutral point zero-sequence voltage, the PT ratio of the neutral point zero-sequence voltage, and the PT ratio of the generator terminal zero-sequence voltage to form a grounding protection criterion, and determines whether the third harmonic zero-voltage stator grounding protection operation condition is met based on the grounding protection criterion, including:

[0023] Based on the calculated setpoint of the third harmonic voltage ratio, the amplitude of the third harmonic component of the neutral point zero-sequence voltage, the PT ratio of the neutral point zero-sequence voltage, and the PT ratio of the generator terminal zero-sequence voltage, the grounding protection criterion is constructed as shown in the following formula:

[0024]

[0025] In the above formula: U is the third harmonic component of the zero-sequence voltage at the machine terminal. n3 n represents the amplitude of the third harmonic component of the neutral point zero-sequence voltage; TV3 The PT turns ratio is the zero-sequence voltage at the neutral point; n TV1 The PT turns ratio is the zero-sequence voltage at the machine terminal.

[0026] When the grounding protection criterion meets the operating conditions, after a delay T set The system was determined to be activated by the third harmonic zero-voltage stator grounding protection.

[0027] According to a second aspect of the present invention, a distributed synchronous condenser third harmonic zero-voltage stator grounding protection device is provided. The device includes: an information acquisition unit for acquiring the closing position information of the distributed synchronous condenser terminal circuit breaker, the closing position information of the static var compensator, and the terminal analog quantity information; a data calculation unit for calculating the third harmonic component of the terminal zero-sequence voltage and the neutral point zero-sequence voltage, the unit reactive power, and the unit frequency based on the terminal analog quantity information; and an operating condition adjustment unit for constructing an operating condition adjustment criterion based on the terminal circuit breaker closing position information, the static var compensator closing position information, and the unit frequency, and automatically switching the third harmonic voltage before and after grid connection based on the operating condition adjustment criterion. The system includes: a per-unit value acquisition unit for obtaining the per-unit value of reactive power based on the unit's reactive power; a calculation setpoint determination unit for constructing a power adjustment criterion based on the per-unit value of reactive power, the third harmonic voltage ratio setpoint, a preset reliability coefficient, and a preset power adjustment control word, and determining the third harmonic voltage ratio calculation setpoint based on the power adjustment criterion; and a grounding protection judgment unit for constructing a grounding protection criterion based on the third harmonic voltage ratio calculation setpoint, the amplitude of the third harmonic component of the neutral point zero-sequence voltage, the PT ratio of the neutral point zero-sequence voltage, and the PT ratio of the generator terminal zero-sequence voltage, and determining whether the conditions for the third harmonic zero-voltage stator grounding protection are met based on the grounding protection criterion.

[0028] As an embodiment of the present invention, the above-mentioned analog quantity information at the generator terminal includes: sampled values ​​of generator terminal three-phase voltage, generator terminal three-phase current, generator terminal zero-sequence voltage and neutral point zero-sequence voltage.

[0029] As an embodiment of the present invention, the above-mentioned data calculation unit includes: a harmonic component calculation module, used to calculate the third harmonic component of the zero-sequence voltage at the generator terminals and the third harmonic component of the zero-sequence voltage at the neutral point using the sampled values ​​of the zero-sequence voltage at the generator terminals and the zero-sequence voltage at the neutral point through Fourier algorithm and digital filter algorithm; a reactive power calculation module, used to calculate the reactive power of the generator unit using the sampled values ​​of the three-phase voltage at the generator terminals and the three-phase current at the generator terminals through Fourier algorithm and reactive power algorithm; and a frequency calculation module, used to calculate the frequency of the generator unit using the sampled values ​​of the three-phase voltage at the generator terminals through hardware frequency measurement algorithm or software frequency measurement algorithm.

[0030] As an embodiment of the present invention, the above-mentioned operating condition adjustment unit is specifically used for: when the closing position information of the generator-end circuit breaker is 1, the closing position information of the static reactive power compensator is 0, and the generator frequency is greater than the set frequency, determining that the generator grid connection status is 1, the closing position information of the generator-end circuit breaker being 1 indicates that the closing position of the generator-end circuit breaker is activated, the closing position information of the static reactive power compensator being 0 indicates that the closing position of the static reactive power compensator is not activated, and the generator grid connection status being 1 indicates that the generator is in grid connection status; when the closing position of the generator-end circuit breaker is 0 or the closing position of the static reactive power compensator is 1, after a delay, determining that the generator grid connection status is 0, the closing position of the generator-end circuit breaker being 0 indicates that the closing position of the generator-end circuit breaker is not activated, the closing position of the static reactive power compensator being 1 indicates that the closing position of the static reactive power compensator is activated, and the generator grid connection status being 0 indicates that the generator is not in grid connection status.

[0031] Construct the following operating condition adjustment criterion:

[0032]

[0033] In the above formula, K Set K is the set value for the third harmonic voltage ratio. BeforeSet K is the setpoint for the third harmonic voltage ratio before grid connection. AfterSet After grid connection, the third harmonic voltage ratio is set. The operating condition adjustment control word is an adjustable control word. When the difference between the measured third harmonic voltage ratio before and after grid connection of the distributed synchronous condenser exceeds the set threshold, the operating condition adjustment control word is set to 1; otherwise, the operating condition adjustment control word is set to 0.

[0034] Based on the aforementioned operating condition adjustment criterion, the output setpoint K is automatically switched. Set value.

[0035] As an embodiment of the present invention, the per-unit value acquisition unit is specifically used to: obtain the per-unit value of reactive power based on the reactive power of the unit using the following formula:

[0036]

[0037] In the above formula, Q * Q is the per-unit value of reactive power. N Q represents the rated capacity of the distributed synchronous condenser, and Q represents the reactive power of the unit.

[0038] As an embodiment of the present invention, the above-mentioned calculation setpoint determination unit is specifically used to: construct a power adjustment criterion as follows based on the per-unit value of reactive power, the setpoint of the third harmonic voltage ratio, the preset reliability coefficient, and the preset power adjustment control word:

[0039]

[0040] In the above formula: K jsSetIt is the calculated constant value for the third harmonic voltage ratio, k r k is the reliability coefficient. r The adjustable range is 0.01 to 0.2. The power follow-up control word is an adjustable control word. When the distributed synchronous condenser is a salient pole machine, the power follow-up control word is set to 1. When it is a non-salient pole machine, the power follow-up control word is set to 0.

[0041] As an embodiment of the present invention, the above-mentioned grounding protection judgment unit is specifically used to: calculate the set value based on the third harmonic voltage ratio, the amplitude of the third harmonic component of the neutral point zero-sequence voltage, the PT ratio of the neutral point zero-sequence voltage, and the PT ratio of the generator terminal zero-sequence voltage to form the grounding protection criterion as shown in the following formula:

[0042]

[0043] In the above formula: U is the third harmonic component of the zero-sequence voltage at the machine terminal. n3 n represents the amplitude of the third harmonic component of the neutral point zero-sequence voltage; TV3 The PT turns ratio is the zero-sequence voltage at the neutral point; n TV1 The PT turns ratio is the zero-sequence voltage at the machine terminal.

[0044] When the grounding protection criterion meets the operating conditions, after a delay T set The system was determined to be activated by the third harmonic zero-voltage stator grounding protection.

[0045] According to a third aspect of the present invention, an electronic device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described method.

[0046] According to a fourth aspect of the present invention, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0047] The distributed synchronous condenser third harmonic zero-voltage stator grounding protection method and device proposed in this invention can quickly identify the unit's operating condition (before or after grid connection) through operating condition-based adjustment criteria, and automatically switch the corresponding protection settings, avoiding protection maloperation or failure to operate due to changes in operating conditions, and improving protection flexibility. The power-based adjustment criteria further improves protection reliability under different operating conditions through reactive power per-unit braking. In addition, this application is applicable to both salient-pole and non-salient-pole distributed synchronous condensers, as well as various situations involving organic and inorganic-terminal circuit breakers, with a wide range of applications and suitable for widespread application. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0049] Figure 1 This is a schematic flowchart of a distributed synchronous condenser third harmonic zero-voltage stator grounding protection method provided in an embodiment of this application;

[0050] Figure 2 This is a flowchart illustrating the calculation of relevant information based on analog quantity information on the machine side, provided in an embodiment of this application.

[0051] Figure 3 This is a flowchart illustrating the automatic switching of setpoints based on operating condition adjustment criteria provided in an embodiment of the present invention.

[0052] Figure 4 This is a schematic diagram of the structure of a distributed synchronous condenser third harmonic zero-voltage stator grounding protection device provided in an embodiment of this application;

[0053] Figure 5 This is a schematic diagram of the structure of the data calculation unit provided in the embodiments of this application;

[0054] Figure 6 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0056] like Figure 1 The diagram shown is a schematic flowchart of a distributed synchronous condenser third harmonic zero-voltage stator grounding protection method provided in an embodiment of this application. This embodiment describes the application from the perspective of the grounding protection device. The method includes the following steps:

[0057] Step S101: Collect the closing position information of the circuit breaker at the distributed synchronous condenser, the closing position information of the static var compensator (SFC), and the analog quantity information at the condenser.

[0058] In this embodiment, the closing position information can be obtained through the auxiliary contacts of the circuit breaker and the static var compensator (SFC). The closing position information here refers to the switching state of the disconnector. Specifically, the position information in this embodiment can be represented by "0" and "1", where "1" indicates that the circuit breaker is closed and the SFC is closed, and "0" indicates that the circuit breaker is open and the SFC is open.

[0059] Preferably, the analog quantity information collected in this step includes: sampled values ​​of the generator terminal three-phase voltage, generator terminal three-phase current, generator terminal zero-sequence voltage, and neutral point zero-sequence voltage. The generator terminal three-phase voltage refers to the three-phase voltage at the connection point of the distributed synchronous condenser; the generator terminal three-phase current refers to the three-phase current flowing through the connection point of the distributed synchronous condenser; the generator terminal zero-sequence voltage refers to the zero-sequence component of the generator terminal three-phase voltage; and the neutral point zero-sequence voltage refers to the zero-sequence voltage at the neutral point of the power system. The neutral point is the common point of the three-phase power supply.

[0060] Specifically, the electrical quantities of devices such as ordinary voltage transformers, current transformers, and neutral point voltage transformers at the distributed synchronous condenser terminals can be collected and then connected to the grounding protection device via cables to obtain the aforementioned analog quantity information at the terminals.

[0061] Step S102: Based on the analog quantity information at the generator terminal, the third harmonic component of the zero-sequence voltage at the computer terminal and the zero-sequence voltage at the neutral point, the reactive power of the generator unit, and the generator unit frequency.

[0062] Preferred, such as Figure 2 As shown, this step may further include the following sub-steps:

[0063] Step S1021: Using the sampled values ​​of the terminal zero-sequence voltage and the neutral point zero-sequence voltage, the third harmonic component of the terminal zero-sequence voltage and the third harmonic component of the neutral point zero-sequence voltage are obtained by using the Fourier algorithm and the digital filter algorithm.

[0064] First, the collected zero-sequence voltage sample values ​​and neutral point zero-sequence voltage sample values ​​can be preprocessed, such as removing DC components and filtering high-frequency noise. This can improve the accuracy of the subsequent Fourier transform. Commonly used preprocessing methods include averaging filtering and median filtering.

[0065] Then, the Fast Fourier Transform (FFT) algorithm is used to convert the zero-sequence voltage sample value in the time domain into frequency domain data. The FFT algorithm can efficiently calculate the Discrete Fourier Transform, decomposing the signal into sinusoidal components of different frequencies.

[0066] Since the FFT result contains various frequency components, this embodiment continues to use a digital filter (e.g., a bandpass filter) to extract the third harmonic component (the frequency is three times the fundamental frequency). Here, it is necessary to set appropriate filter parameters to accurately separate the third harmonic and suppress other frequency components.

[0067] Finally, the third harmonic component of the zero-sequence voltage at the generator terminal and the third harmonic component of the zero-sequence voltage at the neutral point are extracted from the filtered results.

[0068] Step S1022: Using the sampled values ​​of the three-phase voltage and the three-phase current at the generator terminals, the reactive power of the generator unit is obtained through the Fourier algorithm and the reactive power algorithm.

[0069] Similarly, as in step S1021, the sampled values ​​of the three-phase voltage and three-phase current at the generator terminals can be preprocessed to remove DC components and noise.

[0070] Then, the FFT algorithm is used to convert the time-domain three-phase voltage and current sample values ​​into frequency-domain data.

[0071] Next, based on the frequency domain data, the reactive power of the unit is calculated using the reactive power calculation formula. Commonly used formulas include instantaneous power theory or calculation methods based on phasor methods. Specifically, the amplitude and phase relationship of voltage and current need to be considered.

[0072] Finally, the calculated reactive power value of the unit is output.

[0073] Step S1023: Using the sampled values ​​of the three-phase voltage at the generator terminals, the generator frequency is obtained through a hardware frequency measurement algorithm or a software frequency measurement algorithm.

[0074] The goal of this step is to calculate the generator frequency from the sampled values ​​of the three-phase voltage at the generator terminals. Hardware frequency measurement algorithms refer to the use of dedicated hardware, such as a frequency meter, to directly measure the frequency. This method typically offers high accuracy and speed. Software frequency measurement algorithms, on the other hand, are usually based on FFT or other signal processing techniques. For example, the FFT algorithm can be used to calculate the dominant frequency component of the voltage signal, and the frequency of this component is the generator frequency. Other algorithms, such as zero-crossing detection, can also be used for frequency measurement. It should be noted that the accuracy and speed of software frequency measurement algorithms depend on the algorithm itself and the sampling frequency.

[0075] The three sub-steps S1021-S1023 described above together complete the process from raw sampled data to key parameter extraction, providing the necessary data foundation for subsequent protection criterion calculations. Each sub-step relies on precise signal processing techniques and algorithms to ensure the accuracy and reliability of the calculation results.

[0076] Step S103: Based on the closing position information of the circuit breaker at the generator terminal, the closing position information of the static reactive power compensator, and the generator frequency, a condition adjustment criterion is constructed, and the third harmonic voltage ratio setting value before and after grid connection is automatically switched based on the condition adjustment criterion.

[0077] Preferred, such as Figure 3 As shown, this step may specifically include:

[0078] Step S1031: First, determine the grid connection status of the generator unit based on the closing position information of the generator terminal circuit breaker, the closing position information of the static reactive power compensator, and the generator unit frequency.

[0079] When the circuit breaker closing position information is 1, the static var compensator closing position information is 0, and the unit frequency is greater than the set frequency, the unit grid connection status is determined to be 1. A circuit breaker closing position information of 1 indicates that the circuit breaker closing position is open (closed), and a static var compensator closing position information of 0 indicates that the static var compensator closing position is not open (opened). A unit grid connection status of 1 indicates that the unit is in grid connection status.

[0080] When the circuit breaker at the generator terminal is in position 0 or the static var compensator is in position 1, the delay determines that the generator's grid connection status is 0. A circuit breaker at the generator terminal being in position 0 indicates that no circuit breaker is in position 0, while a static var compensator being in position 1 indicates that a static var compensator is in position 1. A generator's grid connection status of 0 indicates that the generator is not in grid connection status.

[0081] Step S1032: Construct a condition-based adjustment criterion based on the unit's grid connection status. This condition-based adjustment criterion is shown in the following formula:

[0082]

[0083] In the above formula, K Set K is the set value for the third harmonic voltage ratio. BeforeSet K is the setpoint for the third harmonic voltage ratio before grid connection. AfterSet After grid connection, the third harmonic voltage ratio is set. The operating condition adjustment control word is an adjustable control word. When the difference between the measured third harmonic voltage ratio before and after grid connection of the distributed synchronous condenser exceeds the set threshold, the operating condition adjustment control word is set to 1. Otherwise, the operating condition adjustment control word is set to 0. At the same time, for the case of no machine terminal circuit breaker, the machine terminal circuit breaker closing position information is not collected, and the operating condition adjustment control word is set to 0.

[0084] Step S1033: Based on the aforementioned operating condition adjustment criterion, output the third harmonic voltage ratio setpoint (K) after automatic switching. Set value).

[0085] As can be seen, the above steps S1031-S1033 realize the function of dynamically adjusting the protection setting value according to the grid connection status of the unit and the difference in the ratio of the third harmonic voltage before and after grid connection, thereby improving the adaptability and reliability of grounding protection.

[0086] Step S104: Obtain the per-unit value of reactive power based on the reactive power of the unit.

[0087] Preferably, this step can specifically obtain the per-unit value of reactive power based on the unit's reactive power using the following formula:

[0088]

[0089] In the above formula, Q * Q is the per-unit value of reactive power. N Q represents the rated capacity of the distributed synchronous condenser, and Q represents the reactive power of the unit.

[0090] Step S105: Construct a power adjustment criterion based on the per-unit value of reactive power, the set value of the third harmonic voltage ratio, the preset reliability coefficient, and the preset power adjustment control word, and determine the set value of the third harmonic voltage ratio calculation based on the power adjustment criterion.

[0091] Preferably, this step may specifically include: constructing a power adjustment criterion based on the per-unit reactive power value, the third harmonic voltage ratio setting, a preset reliability coefficient, and a preset power adjustment control word, as follows:

[0092]

[0093] In the above formula: K jsSet It is the calculated constant value for the third harmonic voltage ratio, k r k is the reliability coefficient. r The adjustable range is 0.01 to 0.2. The power follow-up control word is an adjustable control word. When the distributed synchronous condenser is a salient pole machine, the power follow-up control word is set to 1. When it is a non-salient pole machine, the power follow-up control word is set to 0.

[0094] The core idea of ​​the aforementioned power-following criterion is to dynamically adjust the power output based on the unit type and operating status. By introducing a reliability coefficient and a power-following control word, flexible adjustments can be made according to different unit types and operating conditions. Salient-pole and non-salient-pole turbines have different operating characteristics, thus requiring different control strategies. The reliability coefficient allows for adjustments to the conservatism of the control strategy based on actual conditions. This enables this application to adapt to different operating environments and unit types.

[0095] Step S106: Based on the third harmonic voltage ratio, calculate the set value, the amplitude of the third harmonic component of the neutral point zero-sequence voltage, the PT ratio of the neutral point zero-sequence voltage, and the PT ratio of the generator terminal zero-sequence voltage to form a grounding protection criterion, and determine whether the third harmonic zero-voltage stator grounding protection operation condition is met based on the grounding protection criterion.

[0096] Preferably, this step may specifically include: calculating the set value based on the third harmonic voltage ratio, the amplitude of the third harmonic component of the neutral point zero-sequence voltage, the PT ratio of the neutral point zero-sequence voltage, and the PT ratio of the generator terminal zero-sequence voltage to form the grounding protection criterion as shown in the following formula:

[0097]

[0098] In the above formula: U is the third harmonic component of the zero-sequence voltage at the machine terminal. n3 n represents the amplitude of the third harmonic component of the neutral point zero-sequence voltage; TV3 The PT turns ratio is the zero-sequence voltage at the neutral point; n TV1 The PT turns ratio is the zero-sequence voltage at the machine terminal.

[0099] When the grounding protection criterion meets the operating conditions, after a delay T set The circuit is identified as a third harmonic zero-voltage stator grounding protection operation, and tripping or signaling can be selected via control words.

[0100] As can be seen from the above technical solution, the distributed synchronous condenser third harmonic zero-voltage stator grounding protection method proposed in this invention can quickly identify the operating conditions of the unit (before or after grid connection) through the operating condition-based adjustment criterion, and automatically switch the corresponding protection settings, avoiding protection maloperation or failure to operate due to changes in operating conditions, and improving the flexibility of protection. The power-based adjustment criterion further improves the protection reliability under different operating conditions by using reactive power per-unit value braking. In addition, this application is applicable to both salient-pole and non-salient-pole distributed synchronous condensers, as well as various situations involving organic and inorganic-terminal circuit breakers, with a wide range of applications and suitable for widespread application.

[0101] like Figure 4 The diagram shown is a structural schematic of a distributed synchronous condenser third harmonic zero-voltage stator grounding protection device according to an embodiment of this application. The device includes: an information acquisition unit 410, a data calculation unit 420, an operating condition adjustment unit 430, a per-unit value acquisition unit 440, a setpoint determination unit 450, and a grounding protection judgment unit 460, which are connected sequentially.

[0102] Information acquisition unit 410 is used to acquire the closing position information of the circuit breaker at the distributed synchronous condenser, the closing position information of the static reactive power compensator, and the analog quantity information at the condenser.

[0103] The data calculation unit 420 is used to calculate the third harmonic component of the zero-sequence voltage at the computer terminal and the zero-sequence voltage at the neutral point, the reactive power of the unit, and the unit frequency based on the analog quantity information at the generator terminal.

[0104] The operating condition adjustment unit 430 is used to construct an operating condition adjustment criterion based on the closing position information of the generator circuit breaker, the closing position information of the static reactive power compensator, and the generator frequency, and to automatically switch the third harmonic voltage ratio setting value before and after grid connection based on the operating condition adjustment criterion.

[0105] The per-unit value acquisition unit 440 is used to obtain the per-unit value of reactive power based on the reactive power of the unit.

[0106] The setpoint determination unit 450 is used to construct a power adjustment criterion based on the per-unit value of reactive power, the setpoint of the third harmonic voltage ratio, the preset reliability coefficient and the preset power adjustment control word, and to determine the setpoint of the third harmonic voltage ratio based on the power adjustment criterion.

[0107] The grounding protection judgment unit 460 is used to calculate the set value based on the third harmonic voltage ratio, the amplitude of the third harmonic component of the neutral point zero-sequence voltage, the PT ratio of the neutral point zero-sequence voltage, and the PT ratio of the generator terminal zero-sequence voltage to form a grounding protection criterion, and to determine whether the third harmonic zero-voltage stator grounding protection operation condition is met based on the grounding protection criterion.

[0108] Preferably, the aforementioned analog terminal information includes: sampled values ​​of the three-phase voltage at the terminal, the three-phase current at the terminal, the zero-sequence voltage at the terminal, and the zero-sequence voltage at the neutral point.

[0109] Preferred, such as Figure 5 As shown, the data calculation unit 420 may further include:

[0110] The harmonic component calculation module 421 is used to calculate the third harmonic component of the terminal zero-sequence voltage and the third harmonic component of the neutral point zero-sequence voltage by using the sampled values ​​of the terminal zero-sequence voltage and the neutral point zero-sequence voltage through Fourier algorithm and digital filter algorithm.

[0111] The reactive power calculation module 422 is used to calculate the reactive power of the generator unit by using the sampled values ​​of the three-phase voltage and the three-phase current at the generator terminals, through the Fourier algorithm and the reactive power algorithm.

[0112] The frequency calculation module 423 is used to obtain the unit frequency by using the sampled values ​​of the three-phase voltage at the generator terminal through a hardware frequency measurement algorithm or a software frequency measurement algorithm.

[0113] Preferably, the above-mentioned operating condition adjustment unit 430 is specifically used for: when the generator-end circuit breaker closing position information is 1, the static reactive power compensator closing position information is 0, and the unit frequency is greater than the set frequency, determining the unit grid connection status as 1. The generator-end circuit breaker closing position information being 1 indicates that the generator-end circuit breaker closing position is activated, and the static reactive power compensator closing position information being 0 indicates that no static reactive power compensator closing position is activated. The unit grid connection status being 1 indicates that the unit is in grid connection status; when the generator-end circuit breaker closing position is 0 or the static reactive power compensator closing position is 1, after a delay, determining the unit grid connection status as 0. The generator-end circuit breaker closing position being 0 indicates that no generator-end circuit breaker closing position is activated, and the static reactive power compensator closing position being 1 indicates that a static reactive power compensator closing position is activated. The unit grid connection status being 0 indicates that the unit is not in grid connection status.

[0114] Construct the following operating condition adjustment criterion:

[0115]

[0116] In the above formula, K Set K is the set value for the third harmonic voltage ratio. BeforeSet K is the setpoint for the third harmonic voltage ratio before grid connection. AfterSet After grid connection, the third harmonic voltage ratio is set. The operating condition adjustment control word is an adjustable control word. When the difference between the measured third harmonic voltage ratio before and after grid connection of the distributed synchronous condenser exceeds the set threshold, the operating condition adjustment control word is set to 1; otherwise, the operating condition adjustment control word is set to 0.

[0117] Based on the aforementioned operating condition adjustment criterion, the output setpoint K is automatically switched. Set value.

[0118] Preferably, the per-unit value acquisition unit 440 is specifically used to: obtain the per-unit value of reactive power based on the reactive power of the unit using the following formula:

[0119]

[0120] In the above formula, Q * Q is the per-unit value of reactive power. N Q represents the rated capacity of the distributed synchronous condenser, and Q represents the reactive power of the unit.

[0121] Preferably, the aforementioned calculation setpoint determination unit 450 is specifically used to: construct a power adjustment criterion as follows based on the per-unit value of reactive power, the setpoint of the third harmonic voltage ratio, the preset reliability coefficient, and the preset power adjustment control word:

[0122]

[0123] In the above formula: K jsSet It is the calculated constant value for the third harmonic voltage ratio, kr k is the reliability coefficient. r The adjustable range is 0.01 to 0.2. The power follow-up control word is an adjustable control word. When the distributed synchronous condenser is a salient pole machine, the power follow-up control word is set to 1. When it is a non-salient pole machine, the power follow-up control word is set to 0.

[0124] Preferably, the aforementioned grounding protection judgment unit 460 is specifically used to: calculate the set value based on the third harmonic voltage ratio, the amplitude of the third harmonic component of the neutral point zero-sequence voltage, the PT ratio of the neutral point zero-sequence voltage, and the PT ratio of the generator terminal zero-sequence voltage to form the grounding protection criterion as shown in the following formula:

[0125]

[0126] In the above formula: U is the third harmonic component of the zero-sequence voltage at the machine terminal. n3 n represents the amplitude of the third harmonic component of the neutral point zero-sequence voltage; TV3 The PT turns ratio is the zero-sequence voltage at the neutral point; n TV1 The PT turns ratio is the zero-sequence voltage at the machine terminal.

[0127] When the grounding protection criterion meets the operating conditions, after a delay T set The system was determined to be activated by the third harmonic zero-voltage stator grounding protection.

[0128] For detailed descriptions of the above-mentioned units and modules, please refer to the corresponding descriptions in the foregoing method embodiments, which will not be repeated here.

[0129] As can be seen from the above technical solution, the distributed synchronous condenser third harmonic zero-voltage stator grounding protection device proposed in this invention can quickly identify the operating conditions of the unit (before or after grid connection) through the operating condition-based adjustment criterion, and automatically switch the corresponding protection settings, avoiding protection maloperation or failure to operate due to changes in operating conditions, and improving the flexibility of protection. The power-based adjustment criterion further improves the protection reliability under different operating conditions by using reactive power per-unit value braking. In addition, this application is applicable to both salient-pole and non-salient-pole distributed synchronous condensers, as well as various situations involving organic and inorganic-terminal circuit breakers, with a wide range of applications and suitable for widespread application.

[0130] Figure 6 This is a schematic diagram of an electronic device provided in an embodiment of the present invention. Figure 6The illustrated electronic device is a general-purpose data processing apparatus, comprising a general-purpose computer hardware structure, including at least a processor 801 and a memory 802. The processor 801 and memory 802 are connected via a bus 803. The memory 802 is adapted to store one or more instructions or programs executable by the processor 801. These instructions or programs are executed by the processor 801 to implement the steps in the aforementioned distributed synchronous condenser third harmonic zero-voltage stator grounding protection method.

[0131] The processor 801 described above can be a standalone microprocessor or a collection of one or more microprocessors. Thus, the processor 801 executes commands stored in the memory 802, thereby performing the method flow of the embodiments of the present invention as described above to process data and control other devices. The bus 803 connects the aforementioned components together, and also connects these components to the display controller 804, the display device, and the input / output (I / O) device 805. The input / output (I / O) device 805 can be a mouse, keyboard, modem, network interface, touch input device, motion-sensing input device, printer, and other devices known in the art. Typically, the input / output (I / O) device 805 is connected to the system via an input / output (I / O) controller 806.

[0132] The memory 802 can store software components, such as an operating system, a communication module, an interaction module, and application programs. Each of the modules and application programs described above corresponds to a set of executable program instructions that perform one or more functions and the methods described in the embodiments of the invention.

[0133] This invention also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the above-described distributed synchronous condenser third harmonic zero-voltage stator grounding protection method.

[0134] As described above, the distributed synchronous condenser third harmonic zero-voltage stator grounding protection method and device proposed in this invention can quickly identify the unit's operating conditions (before or after grid connection) through the operating condition-based adjustment criterion, and automatically switch the corresponding protection settings, avoiding protection maloperation or failure to operate due to changes in operating conditions, and improving the flexibility of protection. The power-based adjustment criterion further improves the protection reliability under different operating conditions by using reactive power per-unit value braking. In addition, this application is applicable to both salient-pole and non-salient-pole distributed synchronous condensers, as well as various situations involving organic and inorganic-terminal circuit breakers, with a wide range of applications and suitable for widespread application.

[0135] Preferred embodiments of the invention have been described above with reference to the accompanying drawings. Many features and advantages of these embodiments are apparent from this detailed description, and therefore the claims are intended to cover all such features and advantages of these embodiments that fall within their true spirit and scope. Furthermore, since many modifications and alterations will readily occur to those skilled in the art, the embodiments of the invention are not intended to be limited to the precise structures and operations illustrated and described, but rather to encompass all suitable modifications and equivalents falling within their scope.

[0136] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0137] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0138] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0139] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0140] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for third harmonic zero-voltage stator grounding protection of distributed synchronous condensers, characterized in that, The method includes: Collect the closing position information of the circuit breaker at the distributed synchronous condenser, the closing position information of the static reactive power compensator, and the analog quantity information at the condenser terminal; Based on the analog quantity information at the generator terminal, the third harmonic component of the zero-sequence voltage at the computer terminal and the zero-sequence voltage at the neutral point, the reactive power of the generator unit, and the generator unit frequency; The operating condition adjustment criteria are constructed based on the closing position information of the circuit breaker at the generator terminal, the closing position information of the static reactive power compensator, and the generator frequency. The third harmonic voltage ratio setting value before and after grid connection is automatically switched based on the operating condition adjustment criteria. The per-unit value of reactive power is obtained based on the reactive power of the unit. The power adjustment criterion is constructed based on the per-unit value of reactive power, the set value of the third harmonic voltage ratio, the preset reliability coefficient, and the preset power adjustment control word, and the set value of the third harmonic voltage ratio is determined based on the power adjustment criterion. The grounding protection criterion is constructed based on the set value of the third harmonic voltage ratio, the amplitude of the third harmonic component of the neutral point zero-sequence voltage, the PT ratio of the neutral point zero-sequence voltage, and the PT ratio of the generator terminal zero-sequence voltage. The grounding protection criterion is used to determine whether the conditions for the third harmonic zero-voltage stator grounding protection are met. The step of constructing a condition-based adjustment criterion based on the closing position information of the generator-terminal circuit breaker, the closing position information of the static var compensator, and the generator frequency, and automatically switching the third harmonic voltage ratio setting value before and after grid connection based on the condition-based adjustment criterion, includes: When the circuit breaker closing position information is 1, the static var compensator closing position information is 0, and the unit frequency is greater than the set frequency, the unit grid connection status is determined to be 1. The circuit breaker closing position information of 1 indicates that the circuit breaker closing position is activated, the static var compensator closing position information of 0 indicates that the static var compensator closing position is not activated, and the unit grid connection status of 1 indicates that the unit is in grid connection status. When the closing position of the generator-end circuit breaker is 0 or the closing position of the static reactive power compensator is 1, the delay judgment is that the grid connection status of the unit is 0. The closing position of the generator-end circuit breaker is 0, which means that no closing position of the generator-end circuit breaker is entered. The closing position of the static reactive power compensator is 1, which means that the closing position of the static reactive power compensator is entered. The grid connection status of the unit is 0, which means that the unit is not in grid connection status. Construct the following operating condition adjustment criterion: ； In the above formula, The third harmonic voltage ratio is a fixed value. The third harmonic voltage ratio is the set value before grid connection. After grid connection, the third harmonic voltage ratio is set. The operating condition adjustment control word is an adjustable control word. When the difference between the measured third harmonic voltage ratio before and after grid connection of the distributed synchronous condenser exceeds the set threshold, the operating condition adjustment control word is set to 1; otherwise, the operating condition adjustment control word is set to 0. Based on the aforementioned operating condition adjustment criteria, the output setpoint is automatically switched. value.

2. The distributed synchronous condenser third harmonic zero-voltage stator grounding protection method as described in claim 1, characterized in that, The analog information at the generator terminal includes: sampled values ​​of the generator terminal three-phase voltage, generator terminal three-phase current, generator terminal zero-sequence voltage, and neutral point zero-sequence voltage.

3. The distributed synchronous condenser third harmonic zero-voltage stator grounding protection method as described in claim 2, characterized in that, Based on the analog quantity information at the generator terminal, the third harmonic component of the zero-sequence voltage at the computer terminal and the zero-sequence voltage at the neutral point, the reactive power of the generator unit, and the generator unit frequency include: Using the sampled values ​​of the terminal zero-sequence voltage and the neutral point zero-sequence voltage, the third harmonic component of the terminal zero-sequence voltage and the third harmonic component of the neutral point zero-sequence voltage are obtained through Fourier algorithm and digital filter algorithm. The reactive power of the generator unit is obtained by using the sampled values ​​of the three-phase voltage and the three-phase current at the generator terminals through the Fourier algorithm and the reactive power algorithm. The generator frequency is obtained by using the sampled values ​​of the three-phase voltage at the generator terminals through a hardware frequency measurement algorithm or a software frequency measurement algorithm.

4. The method for third harmonic zero-voltage stator grounding protection of distributed synchronous condensers as described in claim 1, characterized in that, The process of obtaining the per-unit value of reactive power based on the unit's reactive power includes: Based on the reactive power of the aforementioned unit, the per-unit value of reactive power is obtained using the following formula: ； In the above formula, This is the per-unit value for reactive power. Q represents the rated capacity of the distributed synchronous condenser, and Q represents the reactive power of the unit.

5. The distributed synchronous condenser third harmonic zero-voltage stator grounding protection method as described in claim 4, characterized in that, The power adjustment criterion is constructed based on the per-unit value of reactive power, the setpoint of the third harmonic voltage ratio, the preset reliability coefficient, and the preset power adjustment control word. The calculation of the setpoint for the third harmonic voltage ratio is then determined based on the power adjustment criterion, including: Based on the per-unit value of reactive power, the third harmonic voltage ratio setting, the preset reliability coefficient, and the preset power adjustment control word, the power adjustment criterion is constructed as follows: ； In the above formula: It is the calculated constant value for the third harmonic voltage ratio. The third harmonic voltage ratio is a fixed value. For reliability coefficient, The adjustable range is 0.01~0.

2. The power follow-up control word is an adjustable control word. When the distributed synchronous condenser is a salient pole machine, the power follow-up control word is set to 1. When it is a non-salient pole machine, the power follow-up control word is set to 0.

6. The method for third harmonic zero-voltage stator grounding protection of distributed synchronous condensers as described in claim 1, characterized in that, The grounding protection criterion is constructed based on the calculated setpoint of the third harmonic voltage ratio, the amplitude of the third harmonic component of the neutral point zero-sequence voltage, the PT ratio of the neutral point zero-sequence voltage, and the PT ratio of the generator terminal zero-sequence voltage. The determination of whether the third harmonic zero-voltage stator grounding protection operation condition is met based on the grounding protection criterion includes: Based on the calculated setpoint of the third harmonic voltage ratio, the amplitude of the third harmonic component of the neutral point zero-sequence voltage, the PT ratio of the neutral point zero-sequence voltage, and the PT ratio of the generator terminal zero-sequence voltage, the grounding protection criterion is constructed as shown in the following formula: ； In the above formula: The third harmonic component of the zero-sequence voltage at the machine terminal. The amplitude of the third harmonic component of the neutral point zero-sequence voltage; The PT turns ratio represents the zero-sequence voltage at the neutral point. The PT turns ratio is the zero-sequence voltage at the generator terminals. It is the calculated value of the third harmonic voltage ratio; When the grounding protection criterion meets the operating conditions, after a delay... The system was determined to be activated by the third harmonic zero-voltage stator grounding protection.

7. A distributed synchronous condenser third harmonic zero-voltage stator grounding protection device, characterized in that, For implementing the distributed synchronous condenser third harmonic zero-voltage stator grounding protection method as described in claim 1, the apparatus comprises: The information acquisition unit is used to collect the closing position information of the circuit breaker at the distributed synchronous condenser, the closing position information of the static reactive power compensator, and the analog quantity information at the condenser. The data calculation unit is used to calculate the third harmonic component of the zero-sequence voltage at the computer terminal and the zero-sequence voltage at the neutral point, the reactive power of the unit, and the unit frequency based on the analog quantity information at the generator terminal. The operating condition adjustment unit is used to construct the operating condition adjustment criteria based on the closing position information of the circuit breaker at the generator terminal, the closing position information of the static reactive power compensator, and the generator frequency, and to automatically switch the third harmonic voltage ratio setting value before and after grid connection based on the operating condition adjustment criteria. The per-unit value acquisition unit is used to obtain the per-unit value of reactive power based on the reactive power of the unit. The setpoint determination unit is used to construct a power adjustment criterion based on the per-unit value of reactive power, the setpoint of the third harmonic voltage ratio, a preset reliability coefficient, and a preset power adjustment control word, and to determine the setpoint of the third harmonic voltage ratio based on the power adjustment criterion. The grounding protection judgment unit is used to calculate the set value based on the third harmonic voltage ratio, the amplitude of the third harmonic component of the neutral point zero-sequence voltage, the PT ratio of the neutral point zero-sequence voltage, and the PT ratio of the generator terminal zero-sequence voltage to form a grounding protection criterion, and to determine whether the third harmonic zero-voltage stator grounding protection operation condition is met based on the grounding protection criterion.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

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