Integrated detection and communication method for collection line transient permanent fault using iidg active energy injection

Abstract

The application relates to a detection and communication integrated identification method for instantaneous permanent fault of a power collection line by means of IIDG active energy injection, and belongs to the technical field of power system relay protection and automation. The method comprises the following steps: after a fault occurs in a power collection line, starting an IIDG with network construction capability, realizing zero starting voltage rise through VF control, establishing a characteristic voltage, judging whether a composite voltage criterion is met, if yes, the fault is permanent, and the injection source exits after maintaining a constant frequency transmission; if not, the fault is instantaneous, and the injection source sends a frequency shift information after a time delay. Voltage is continuously monitored during the injection, and whether a complete frequency shift signal is received is determined through a frequency variance criterion and data segment correlation. If the voltage does not meet the composite voltage criterion during the detection process and the complete frequency shift signal is received, reclosing is allowed after power loss again, otherwise, reclosing is locked. The method aims to solve the technical problem that the fault nature of the power collection line under a voltage loss condition is difficult to identify in the prior art.

Description

Technical Field

[0001] This invention relates to an integrated identification method for detecting and communicating transient permanent faults in collector lines using IIDG active energy injection, belonging to the field of power system relay protection and automation technology. Background Technology

[0002] In recent years, with the continuous increase in installed capacity of new energy sources such as wind power and photovoltaics, the scale of new energy power plants has been expanding. As a key channel connecting various power generation units and substations, the operational reliability of the collector lines directly affects the power generation efficiency of the power plants and the stability of the power grid. Since collector lines are often located in complex environments, transient faults occur frequently. Therefore, rapid reconnection to the grid after a fault is of great significance for improving the utilization rate of the power plants.

[0003] However, currently, when a fault occurs at a renewable energy power station causing the collection lines to disconnect from the grid, restoring power requires permission from the grid dispatch center. The main reason for this is to avoid blindly reconnecting to a fault and impacting grid operation. Blindly reconnecting to a permanent fault would not only damage the collection line equipment but could also cause voltage drops and large-scale cascading grid disconnections in adjacent collection lines, seriously threatening system safety. Summary of the Invention

[0004] The purpose of this invention is to provide an integrated detection and communication method for instantaneous permanent faults in collector lines using IIDG active energy injection, aiming to solve the technical problem that it is difficult to identify the nature of faults in collector lines under undervoltage conditions, thereby avoiding blind closing of circuits.

[0005] To achieve the above objectives, the technical solution of the present invention is: an integrated method for detecting and communicating transient permanent faults in collector wires using IIDG active energy injection, comprising the following steps: S1: When the collector line trips due to a fault, after a delay until the line is completely de-energized, an IIDG with grid-building capability is started. The voltage is boosted from zero through VF control, and energy is injected into the line in the form of a constant current source through current limiting control to establish a characteristic voltage in the line. S2: Determine whether the composite voltage criterion is met by establishing the characteristic voltage at the high-voltage side outlet of the injection source: If the composite voltage criterion is met, it is determined to be a permanent fault, and the fixed-frequency power transmission is maintained and exited after a preset exit time; if the composite voltage criterion is not met, it is determined to be a transient fault, and the frequency-shifting characteristic voltage is emitted after a preset delay time. S3: During the injection of the injection source, the protection device at the closing point continuously detects the characteristic voltage established in the line. If the composite voltage criterion is met, the blocking is maintained. If the composite voltage criterion is not met, the frequency of the characteristic voltage is extracted by short-time Fourier transform, and the frequency variance based on the power frequency is calculated. If the frequency exceeds the preset variance threshold, the abnormal frequency fluctuation is determined and frequency shift confirmation is initiated. Otherwise, the detection continues. S4: If the abnormal frequency fluctuation is determined, frequency shift confirmation is initiated. The frequency of the characteristic voltage emitted by the injection source is extracted from the line. The original frequency data segment is extracted according to the time window of an integer multiple of the frequency shift period. After half a period shift, the shifted frequency data segment is obtained. The original frequency data segment and the shifted frequency data segment are subjected to correlation analysis to obtain the correlation coefficient. Multiple window data segments are processed within the preset processing time. If all correlation coefficients meet the threshold, the complete frequency shift signal is confirmed to be received; otherwise, the signal is determined to be interrupted. S5: If the characteristic voltage detected by the protection device at the closing point does not meet the composite voltage criterion throughout the entire detection process, and after frequency correlation analysis of the frequency shift characteristic voltage, it is determined that a complete frequency shift signal has been received, then reclosing is allowed after power failure; otherwise, reclosing is blocked.

[0006] Optionally, S2 specifically includes: The characteristic voltage established at the high-voltage side outlet by the injection source is used to calculate the voltage imbalance, expressed as follows:

[0007] in, For voltage imbalance, It is the negative sequence component of voltage. It is the positive sequence component of voltage; The expression for determining whether the composite voltage criterion is met is:

[0008]

[0009] in, For the tuned imbalance, Establish per-unit values ​​for the inverter voltage set at the rated voltage. The voltage threshold used as the criterion; If the composite voltage criterion is met, it is determined that a permanent fault has occurred, and the fixed-frequency power transmission is maintained. The injection source exits after a preset exit time t1 seconds. If the composite voltage criterion is not met, it is determined that a transient fault has occurred. The IIDG emits a frequency-shifting characteristic voltage after a preset delay time t2 seconds, the expression of which is:

[0010] in, Let be the reference frequency at time t. For power frequency, , For frequency shift 1 and frequency shift 2, This is the frequency shift start time. This is the frequency shifting interval. Injection end time, T This is the start time of the frequency shift sequence. n This represents the total number of frequency shifting handovers.

[0011] Optionally, S3 specifically includes: The frequency of the characteristic voltage is extracted using short-time Fourier transform, and the frequency variance based on the power frequency is calculated. The expression is as follows:

[0012] in, Let be the frequency variance at time t. The starting time for summation, for Frequency of time, For data points in a sliding time window, For power frequency; The expression for determining whether variance is out of the ordinary is:

[0013] in, This is a preset variance threshold value; like If the variance exceeds the preset threshold, it is determined to be an abnormal frequency fluctuation and frequency shift confirmation is initiated; otherwise, the detection continues.

[0014] Optionally, S4 specifically includes: Define the raw frequency data segment extracted according to a time window that is an integer multiple of the frequency shift period as The frequency data segment obtained after half-cycle shift is The original frequency data segment and the translated frequency data segment are subjected to correlation analysis, which is Spearman rank correlation analysis, to obtain the correlation coefficient, which is expressed as:

[0015] in, Original frequency data segment F and the shifted frequency data segment F shift The correlation coefficient of Spearman's rank correlation. for F The Middle i Each frequency sample value, forF shift Zhongyu The corresponding number i Each frequency sample value, for exist rank in for exist In the rank analysis, k represents the total number of sampling points within the data window participating in the rank correlation analysis; Process multiple window data segments within a preset processing time t3 seconds, if all correlation coefficients meet the requirements. , If the threshold value of the correlation coefficient is set, then the complete frequency shift signal is confirmed to be received; otherwise, it is determined that the signal is interrupted.

[0016] The beneficial effects of this invention are: This invention makes full use of the controllability of IIDG energy injection and the local connectivity of the collector line, and can determine whether there is a fault in the collector line based on the steady-state characteristic voltage established by the injection. The injection impact is small, the characteristic duration is long, the reliability is high, and the judgment result can be transmitted to each node along the line without relying on external communication. Sensing and communication are integrated. The system can still work when conventional communication fails due to long-term power loss, which helps to reduce blind reclosing and reduce downtime losses. Attached Figure Description

[0017] Figure 1 This is a flowchart of the steps of the present invention; Figure 2 This is a schematic diagram of the 35kV collector line topology of the present invention; Figure 3 This is a full-process voltage diagram of the closing device under symmetrical permanent fault conditions according to the present invention; Figure 4 This is a full-process voltage diagram of the closing device under the BC phase asymmetrical short-circuit grounding permanent fault condition of the present invention; Figure 5 This is a full-process voltage diagram of the closing device under instantaneous fault conditions according to the present invention; Figure 6 This is a frequency diagram of characteristic voltage extraction for the instantaneous fault condition closing device of the present invention. Detailed Implementation

[0018] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0019] Example 1: As Figure 1 As shown, an integrated method for detecting and communicating transient permanent faults in collector lines using IIDG active energy injection includes the following steps: S1: When the collector line trips due to a fault, after a delay until the line is completely de-energized, an IIDG with grid-building capability is started. The voltage is boosted from zero through voltage-frequency (VF) control, and energy is injected in the form of a constant current source through current limiting control to establish a characteristic voltage in the line. Optionally, when a fault occurs in the collector line, the system-side circuit breaker trips. After a delay until the line is completely de-energized, an inverter-interfaced distributed generation (IIDG) with grid-connecting capability is started. To avoid the characteristic voltage being established when the line fault has disappeared by the time the injection source is put into operation, which would cause the line unloaded transformer to generate inrush current, a zero-start voltage boost and current limiting control strategy is adopted. Finally, energy is injected in the form of a constant current source to establish the characteristic voltage.

[0020] S2: Determine whether the composite voltage criterion is met by establishing the characteristic voltage at the high-voltage side outlet of the injection source: If the composite voltage criterion is met, it is determined to be a permanent fault, and the fixed-frequency power transmission is maintained and exited after a preset exit time; if the composite voltage criterion is not met, it is determined to be a transient fault, and the frequency-shifting characteristic voltage is emitted after a preset delay time. Optionally, under current source excitation, if it is a transient fault, a symmetrical high-amplitude voltage is established throughout the line; if it is a permanent asymmetrical short-circuit fault, a negative-sequence voltage is established throughout the line due to the fault disrupting the system symmetry; if it is a permanent symmetrical short-circuit fault, the fault will cause the entire line to have a low voltage. Therefore, by detecting the characteristic voltage established at the high-voltage side outlet through the injection source, the voltage imbalance is calculated, and the expression is:

[0021] in, For voltage imbalance, It is the negative sequence component of voltage. It is the positive sequence component of voltage; The expression for determining whether the composite voltage criterion is met is:

[0022]

[0023] in, For the tuned imbalance, Establish per-unit values ​​for the inverter voltage set at the rated voltage. In this embodiment, the voltage threshold used as the criterion is... Take 0.3, Take 0.5 pu; If the composite voltage criterion is met, it is determined that a permanent fault has occurred, and the fixed-frequency power transmission is maintained. The injection source exits after a preset exit time t1 seconds. If the composite voltage criterion is not met, it is determined that a transient fault has occurred. The IIDG emits a frequency-shifting characteristic voltage after a preset delay time t2 seconds, the expression of which is:

[0024] in, Let be the reference frequency at time t. For power frequency, , For frequency shift 1 and frequency shift 2, This is the frequency shift start time. This is the frequency shifting interval. Injection end time, T This is the start time of the frequency shift sequence. n This represents the total number of frequency shifting handovers.

[0025] Optionally, in this embodiment, the preset exit time t1 is 0.5 seconds and the preset delay time t2 is 3 seconds.

[0026] S3: During the injection of the injection source, the protection device at the closing point continuously detects the characteristic voltage established in the line. If the composite voltage criterion is met, the blocking is maintained. If the composite voltage criterion is not met, the frequency of the characteristic voltage is extracted by short-time Fourier transform, and the frequency variance based on the power frequency is calculated. If the frequency exceeds the preset variance threshold, the abnormal frequency fluctuation is determined and frequency shift confirmation is initiated. Otherwise, the detection continues. Optionally, the frequency of the characteristic voltage is extracted using short-time Fourier transform, and the frequency variance based on the power frequency is calculated, as expressed by:

[0027] in, Let be the frequency variance at time t. The starting time for summation, for Frequency of time, For data points in a sliding time window, For power frequency; The expression for determining whether variance is out of the ordinary is:

[0028] in, To preset the variance threshold, taking frequency shifts of 45Hz and 55Hz as examples, It can be set to 8; like If the variance exceeds the preset threshold, it is determined to be an abnormal frequency fluctuation and frequency shift confirmation is initiated; otherwise, the detection continues.

[0029] It is understood that in this embodiment, S2 and S3 are performed synchronously. The injection source establishes a characteristic voltage on the undervoltage line. The injection source determines whether the composite voltage criterion is met based on the established characteristic voltage, and then performs subsequent operations. At the same time, the closing device detects the characteristic voltage established by the injection source in the line and performs subsequent operations based on its own criteria.

[0030] S4: If the abnormal frequency fluctuation is determined, frequency shift confirmation is initiated. The frequency of the characteristic voltage emitted by the injection source is extracted from the line. The original frequency data segment is extracted according to the time window of an integer multiple of the frequency shift period. After half a period shift, the shifted frequency data segment is obtained. The original frequency data segment and the shifted frequency data segment are subjected to correlation analysis to obtain the correlation coefficient. Multiple window data segments are processed within the preset processing time. If all correlation coefficients meet the threshold, the complete frequency shift signal is confirmed to be received; otherwise, the signal is determined to be interrupted. Optionally, the raw frequency data segment extracted by time windows that are integer multiples of the frequency shift period is defined as... The frequency data segment obtained after half-cycle shift is The original frequency data segment and the translated frequency data segment are subjected to correlation analysis, which is Spearman rank correlation analysis, to obtain the correlation coefficient, which is expressed as:

[0031] in, Original frequency data segment F and the shifted frequency data segment F shift The correlation coefficient of Spearman's rank correlation. for F The Middle i Each frequency sample value, for F shift Zhongyu The corresponding number i Each frequency sample value, for exist rank in for exist In the rank analysis, k represents the total number of sampling points within the data window participating in the rank correlation analysis; Process multiple window data segments within a preset processing time t3 seconds, if all correlation coefficients meet the requirements. , If the threshold value of the preset correlation coefficient is met, then a complete frequency-shifted signal is confirmed to have been received; otherwise, it is determined to be a signal interruption. In this embodiment, the preset processing time t3 seconds is taken as 2 seconds. Take -0.8.

[0032] S5: If the characteristic voltage detected by the protection device at the closing point does not meet the composite voltage criterion throughout the entire detection process, and after frequency correlation analysis of the frequency shift characteristic voltage, it is determined that a complete frequency shift signal has been received, then reclosing is allowed after power failure; otherwise, reclosing is blocked.

[0033] It is understandable that this embodiment achieves integrated detection and communication identification of transient and permanent faults in power lines through S1-S5. That is, signal interaction is achieved through electrical quantities. After the injection source injects energy into the system, a characteristic voltage is established. If it is determined to be a transient fault, a specific frequency shift signal will be sent through frequency control. When the closing device detects voltage information, it must not only meet the voltage criteria, but also fully identify the frequency shift signal before allowing the closing action. In this way, the transmission of electrical signals in the power grid can realize the coordinated communication and logic interlocking between the two devices.

[0034] The technical solution of the present invention will be further illustrated below through a specific implementation example.

[0035] Specifically, taking a certain new energy power distribution line as an example, a system is built in PSCAD / EMTDC as follows: Figure 2 The simulation model of the 35kV collector line shown is configured with a sampling rate of 100kHz. The specific model of the overhead line is JL / G1A-240 / 40, and the lengths of each section are: L1=5km, L2=6km, L3=7km, L4=4km, L5=L6=L7=L8=3km. The main transformer is 115kV / 35kV, the box-type transformer is 35kV / 0.38kV, and the single-unit capacity of the injection source inverter is 300kW. The specific implementation steps are as follows: Step 1: When the collector line trips due to a fault, after a delay until the line is completely de-energized, an IIDG with grid-building capability is started. The voltage is boosted from zero through VF control, and energy is injected into the line in the form of a constant current source through current limiting control to establish a characteristic voltage in the line. Specifically, taking a transient / permanent fault occurring 3km along the L2 overhead line as an example, the voltage measurement point is set at... Figure 2 The observation points are m1 at the closing point and m2 at the high-voltage outlet of the inverter power supply. When this fault occurs in the collector line, the voltage drops sharply, the line protection activates, the collector line trips, the inverter is locked, and only the unloaded transformer connected to the inverter remains in the line. The entire line enters a de-energized state, and the injected power starts working in 3.1 seconds, boosting the voltage from zero in VF mode. Once the current reaches the limit, it outputs in constant current form.

[0036] Step 2: Determine whether the composite voltage criterion is met by establishing the characteristic voltage at the high-voltage side outlet of the injection source. If the composite voltage criterion is met, it is determined to be a permanent fault, and the fixed-frequency power transmission is maintained and exited after a preset exit time. If the composite voltage criterion is not met, it is determined to be a transient fault, and the frequency-shifting characteristic voltage is emitted after a preset delay time. Specifically, such as Figure 3 As shown, when the fault is a three-phase permanent fault with a transition resistance of 5Ω, the effective value per unit of the voltage established in the collector line under the injected source excitation is much less than 0.5pu, and its voltage imbalance is 0.001, which is judged as a permanent symmetrical fault. The inverter exits in 3.6 seconds.

[0037] like Figure 4 As shown, when the fault is a permanent two-phase ground fault with a transition resistance of 10Ω, the voltage with a per-unit effective value of 0.4pu established at each point of the collector line under the excitation of the injected source is lower than the set threshold value. Based on the established voltage, the unbalance is calculated to be 0.997, which is greater than the set threshold value of 0.5. Therefore, it is determined to be an asymmetrical permanent fault.

[0038] like Figure 5 As shown, when the fault is a transient fault lasting 1 second, under the excitation of the injection source, the collector line establishes a high amplitude voltage of 23kV, with a per-unit value greater than 0.5pu and the voltage imbalance at each measuring point is calculated to be 0.0054. It is determined to be a transient fault. The injection source continues to inject and continuously probes for 5 seconds. At 6 seconds, it starts frequency shift transmission. After 8 seconds, the injection source withdraws.

[0039] Step 3: During the injection of the injection source, the protection device at the closing point continuously detects the characteristic voltage established in the line. If the composite voltage criterion is met, the blocking is maintained. If the composite voltage criterion is not met, the frequency of the characteristic voltage is extracted by short-time Fourier transform, and the frequency variance based on the power frequency is calculated. If the frequency exceeds the preset variance threshold, abnormal frequency fluctuation is determined and frequency shift confirmation is initiated. Otherwise, the detection continues. Specifically, after the closing protection device trips, it enters the detection window period after a delay. For three-phase permanent faults with a transition resistance of 5Ω and two-phase grounding permanent faults of phases B and C with a transition resistance of 10Ω, if the detected voltage meets the composite voltage criterion, that is, the effective voltage per unit value is less than 0.5pu, or the unbalance is greater than 0.2, the closing protection device directly blocks the closing.

[0040] For a transient fault lasting 1 second, the voltage established by the excitation at the closing point does not meet the criteria for composite voltage within 6-8 seconds during the detection process. Furthermore, the frequency characteristics are extracted by short-time Fourier transform, and the frequency variance is calculated based on the power frequency. At 6 seconds, the variance is 11, which is greater than the threshold value of 8, triggering a frequency shift signal for confirmation.

[0041] Step 4: If the abnormal frequency fluctuation is determined, frequency shift confirmation is initiated. The frequency of the characteristic voltage emitted by the injection source is extracted from the line. The original frequency data segment is extracted according to the time window of an integer multiple of the frequency shift period. After half a period shift, the shifted frequency data segment is obtained. Correlation analysis is performed on the original frequency data segment and the shifted frequency data segment to obtain the correlation coefficient. Multiple window data segments are processed within the preset processing time. If all correlation coefficients meet the threshold, the complete frequency shift signal is confirmed to be received; otherwise, the signal is determined to be interrupted. Specifically, such as Figure 6 As shown, for a transient fault lasting 1 second, the closing device triggers a frequency shift signal for confirmation every 6 seconds. Starting from the trigger moment, data segments with a length that is an integer multiple of the frequency shift signal period are extracted. These data segments are then shifted by half a period. Correlation analysis is performed between the original data segments and the processed data segments to obtain the corresponding correlation coefficients. For closing devices operating within the 6-8 second range, the obtained correlation coefficients... If both are -1, it is determined that a specific complete frequency shift signal has been received.

[0042] Step 5: If the characteristic voltage detected by the protection device at the closing point does not meet the composite voltage criterion throughout the entire detection process, and the complete frequency shift signal is determined to be received after frequency correlation analysis of the frequency shift characteristic voltage, then reclosing is allowed after power failure; otherwise, reclosing is blocked.

[0043] Specifically, when the closing protection device enters the detection window period after tripping, for three-phase permanent faults with a transition resistance of 5Ω and two-phase grounding permanent faults of phases B and C with a transition resistance of 10Ω, if the detected voltage meets the composite voltage criterion, that is, the effective voltage per unit value is less than 0.5pu, or the unbalance is greater than 0.2, the closing protection device directly blocks the closing.

[0044] Furthermore, for a transient fault lasting 1 second, the voltage established by the excitation at the closing point does not meet the criteria for composite voltage within 6-8 seconds during the detection process, and it is determined that a specific complete frequency shift signal has been received. Therefore, reclosing is allowed, thus realizing information confirmation and expressing the pre-signal of reclosing permission.

[0045] In summary, this invention applies an excitation to the faulty line using the naturally existing IIDG in the collector line to establish a characteristic voltage and identify the nature of the fault. The controllability of the IIDG enables the transmission of the identification results and pre-notification of closing. This allows for real-time judgment of the fault nature before reclosing, thus deciding whether to reclose. This better solves the problem of blind reclosing after a collector network fault. It can also serve as a basis for restoring grid connection to the collector line after a momentary fault disconnection at a new energy power station. Therefore, this invention can accurately distinguish between momentary and permanent faults, avoid reclosing to permanent faults, and reduce downtime losses due to momentary faults. It is of great significance for improving the intelligent operation level of collector lines in new energy power stations.

[0046] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for integrated detection and communication identification of transient permanent faults in collector wires using IIDG active energy injection, characterized in that, The method includes the following steps: S1: When the collector line trips due to a fault, after a delay until the line is completely de-energized, an IIDG with grid-building capability is started. The voltage is boosted from zero through VF control, and energy is injected into the line in the form of a constant current source through current limiting control to establish a characteristic voltage in the line. S2: Determine whether the composite voltage criterion is met by establishing the characteristic voltage at the high-voltage side outlet of the injection source: If the composite voltage criterion is met, it is determined to be a permanent fault, and the fixed-frequency power transmission is maintained and exited after a preset exit time; if the composite voltage criterion is not met, it is determined to be a transient fault, and the frequency-shifting characteristic voltage is emitted after a preset delay time. S3: During the injection of the injection source, the protection device at the closing point continuously detects the characteristic voltage established in the line. If the composite voltage criterion is met, the blocking is maintained. If the composite voltage criterion is not met, the frequency of the characteristic voltage is extracted by short-time Fourier transform, and the frequency variance based on the power frequency is calculated. If the frequency exceeds the preset variance threshold, the abnormal frequency fluctuation is determined and frequency shift confirmation is initiated. Otherwise, the detection continues. S4: If the abnormal frequency fluctuation is determined, frequency shift confirmation is initiated. The frequency of the characteristic voltage emitted by the injection source is extracted from the line. The original frequency data segment is extracted according to the time window of an integer multiple of the frequency shift period. After half a period shift, the shifted frequency data segment is obtained. The original frequency data segment and the shifted frequency data segment are subjected to correlation analysis to obtain the correlation coefficient. Multiple window data segments are processed within the preset processing time. If all correlation coefficients meet the threshold, the complete frequency shift signal is confirmed to be received; otherwise, the signal is determined to be interrupted. S5: If the characteristic voltage detected by the protection device at the closing point does not meet the composite voltage criterion throughout the entire detection process, and after frequency correlation analysis of the frequency shift characteristic voltage, it is determined that a complete frequency shift signal has been received, then reclosing is allowed after power failure; otherwise, reclosing is blocked.

2. The integrated detection and communication identification method for transient permanent faults in collector lines using IIDG active energy injection as described in claim 1, characterized in that, Specifically, S2 is: The characteristic voltage established at the high-voltage side outlet by the injection source is used to calculate the voltage imbalance, expressed as follows: ； in, For voltage imbalance, It is the negative sequence component of voltage. It is the positive sequence component of voltage; The expression for determining whether the composite voltage criterion is met is: ； ； in, For the tuned imbalance, Establish per-unit values ​​for the inverter voltage set at the rated voltage. The voltage threshold used as the criterion; If the composite voltage criterion is met, it is determined that a permanent fault has occurred, and the fixed-frequency power transmission is maintained. The injection source exits after a preset exit time t1 seconds. If the composite voltage criterion is not met, it is determined that a transient fault has occurred. The IIDG emits a frequency-shifting characteristic voltage after a preset delay time t2 seconds, the expression of which is: ； in, Let be the reference frequency at time t. For power frequency, , For frequency shift 1 and frequency shift 2, This is the frequency shift start time. This is the frequency shifting interval. Injection end time, T This is the start time of the frequency shift sequence. n This represents the total number of frequency shifting handovers.

3. The integrated detection and communication identification method for transient permanent faults in collector lines using IIDG active energy injection as described in claim 1, characterized in that, Specifically, S3 is: The frequency of the characteristic voltage is extracted using short-time Fourier transform, and the frequency variance based on the power frequency is calculated. The expression is as follows: ； in, Let be the frequency variance at time t. The starting time for summation, for Frequency of time, For data points in a sliding time window, For power frequency; The expression for determining whether variance is out of the ordinary is: ； in, This is a preset variance threshold value; like If the variance exceeds the preset threshold, it is determined to be an abnormal frequency fluctuation and frequency shift confirmation is initiated; otherwise, the detection continues.

4. The integrated detection and communication identification method for transient permanent faults in collector lines using IIDG active energy injection as described in claim 1, characterized in that, Specifically, S4 is: Define the raw frequency data segment extracted according to a time window that is an integer multiple of the frequency shift period as The frequency data segment obtained after half-cycle shift is The original frequency data segment and the translated frequency data segment are subjected to correlation analysis, which is Spearman rank correlation analysis, to obtain the correlation coefficient, which is expressed as: ； in, Original frequency data segment F and the shifted frequency data segment F shift The correlation coefficient of Spearman's rank correlation. for F The Middle i Each frequency sample value, for F shift Zhongyu The corresponding number i Each frequency sample value, for exist rank in for exist In the rank analysis, k represents the total number of sampling points within the data window participating in the rank correlation analysis; Process multiple window data segments within a preset processing time t3 seconds, if all correlation coefficients meet the requirements. , If the threshold value of the correlation coefficient is set, then the complete frequency shift signal is confirmed to be received; otherwise, it is determined that the signal is interrupted.

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