Hydro-generator excitation loss fault diagnosis method and device

Abstract

The invention discloses a hydro-generator excitation loss fault diagnosis method and device, and belongs to the technical field of power system relay protection, and the method comprises the following steps: collecting the phase current and line voltage of a hydro-generator terminal; the collected current and voltage data are stored in a register in sequence, and after the register is full, the last data is deleted when a new group of data is stored; calculating an instantaneous power integral according to m groups of current and voltage data in the register and solving a discrete form of the instantaneous power integral; normalizing the obtained instantaneous power integral to obtain an initial field loss fault index; eliminating average fluctuation of the initial field loss fault index to obtain a final field loss fault index; and judging the field loss fault by combining whether the final field loss fault index is smaller than a threshold value or not and a low-voltage criterion, and locking the field loss fault criterion by using a direct-current component criterion and a negative-sequence voltage criterion to avoid an external fault. The method does not depend on the operation state of the generator too much, has high sensitivity, and reduces the maloperation risk.

Description

Technical Field

[0001] This invention relates to the field of power system relay protection technology, and more specifically, to a method and device for diagnosing demagnetization faults in hydro-generators. Background Technology

[0002] Generator demagnetization is a common type of fault, and the risk of low excitation or demagnetization is particularly prominent in large units with complex excitation system structures. When a fault occurs, the stator current will increase significantly, while the terminal voltage will decrease accordingly, and the unit's state will change from outputting reactive power to absorbing reactive power. These are typical manifestations of demagnetization. If the situation is severe, it will endanger the stable operation of the power grid and pose a threat to the generator itself.

[0003] Currently, domestic and international relay protection devices generally use statically stable impedance circles or asynchronous impedance circles as the core criterion for loss of excitation faults. However, this approach has significant limitations: it is only effective under medium to high load conditions, and may fail to operate under light load or no-load conditions (such as loss of excitation events caused by malfunction of the demagnetizing switch). A typical case reported by the Xiluodu Power Plant fully illustrates this deficiency: when the turbine generator unexpectedly reconnected to the grid due to a broken GCB operating mechanism linkage during shutdown, although the shutdown demagnetizing process was triggered, the unit continued to absorb reactive power from the system (the terminal voltage dropped from 20 kV to 17.2 kV, and the current surged from no-load value to 20.5 kA / rated 24.69 kA), eventually stabilizing at an abnormal state of 75 MW reverse power and 609 Mvar reactive power absorption, but the loss of excitation protection failed to operate throughout the entire process. This technical problem urgently needs to be solved by those in the field. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and device for diagnosing demagnetization faults in hydro-generators. This method and device do not rely too much on the generator's operating status, have high sensitivity, and reduce the risk of malfunction.

[0005] The objective of this invention is achieved through the following solution: A method for diagnosing loss of excitation faults in hydro-generators includes the following steps: The phase current and corresponding line voltage measured at the generator terminals are used as input signals, and loss of excitation detection is achieved by comparing the phase-based loss of excitation index signal.

[0006] Furthermore, the step of using the phase current and corresponding line voltage measured at the generator terminals as input signals to achieve demagnetization detection by comparing them with phase-based demagnetization index signals specifically includes the following sub-steps: S1, collects the phase current and line voltage at the turbine generator terminals; S2 stores the collected current and voltage data in the register in sequence. When the register is full, the last bit of the data is deleted when a new set of data is stored. S3, based on the register contents m Instantaneous power integral calculated from group current and voltage data And find its discrete form; S4. The initial demagnetization fault index is obtained by normalizing the instantaneous power integral. ; S5, for the initial demagnetization fault index The final demagnetization fault index is obtained after eliminating the average fluctuation. ; S6 determines the demagnetization fault by combining the final demagnetization fault index with the low voltage criterion, and blocks the demagnetization fault criterion with the DC component criterion and the negative sequence voltage criterion to avoid external faults.

[0007] Further, in step S1, the acquisition of the phase current and line voltage at the turbine generator terminals specifically includes the sub-step: [the following is a separate, unrelated step:] [The text then abruptly shifts to a different topic:] ...the line voltage at the turbine generator terminals of the faulty turbine generator... , , Three-phase current at the generator terminals , , Data and waveforms are acquired.

[0008] Further, in step S2, the collected current and voltage data are stored sequentially in a register. When the register is full, the last bit of data is deleted after each new set of data is stored. This specifically includes the following sub-steps: The acquired terminal line voltage and phase current are used as signal inputs, denoted as: ; ; Among them, voltage and current The input signal samples are stored in voltage and current registers, with a length of [missing information]. m Whenever a new sample is collected, the register is updated according to the following rules: the oldest sample is removed, the remaining samples are shifted left by one bit, the index value is decremented by 1, and the new sample is filled into the last bit of the register and assigned an index value. m This process is executed after each sampling, by discarding historical data, shifting the existing samples to the left, and decrementing the index, finally writing the indexed data to the end of the register. m New samples are generated, thus forming a dynamically updated sliding window of data.

[0009] Further, in step S3, the data in the register... m Instantaneous power integral calculated from group current and voltage data And find its discrete form, specifically including the following sub-steps: Instantaneous power integral Calculated by the following formula: ; Its discrete form is: ; in, m For register length, Where is the sampling period, and T is the input signal period.

[0010] Furthermore, in step S4, the initial demagnetization fault index is obtained by normalizing the obtained instantaneous power integral. Specifically, it includes the following sub-steps: The instantaneous power integral value calculated over half a cycle of the input signal depends on the signal amplitude. The initial demagnetization fault index was obtained by normalization. Divide it by the instantaneous power integral value obtained when the input voltage and current signals are in phase, as follows: ; The root mean square methods for voltage and current are as follows: ; ; The initial demagnetization fault index is then calculated using the following formula: .

[0011] Furthermore, in step S5, the initial demagnetization fault index is... The final demagnetization fault index is obtained after eliminating the average fluctuation. The specific calculation is as follows: ; Where k is the number of samples.

[0012] Further, in step S6, the threshold value specifically includes: Threshold value and voltage threshold value These two parameters are set based on the capacity characteristic curve of the synchronous generator and the permissible range of underexcitation operation. and The value of should ensure that the operating range is between the steady-state stability limit and the minimum excitation limit. The operating range formed in this way can detect demagnetization faults in time before the generator becomes unstable.

[0013] Further, in step S6, the low voltage criterion is specifically as follows: ; in, , This is the secondary value of the generator's rated voltage. for; The criterion for the DC component is: ; in, for, for, The rated current of the generator; the criterion is that when the DC component is greater than the threshold value and the duration exceeds the set time, the DC component issues a blocking pulse signal; the set time includes 20ms.

[0014] A hydro-generator demagnetization fault diagnosis device includes a processor and a memory, wherein the memory stores a computer program that executes the method described in any of the preceding methods when the computer program is loaded by the processor.

[0015] The beneficial effects of this invention include: This invention employs a demagnetization fault diagnosis method for hydro-generators based on a digital phase comparator. Its advantages lie primarily in the following ways: compared to traditional protection methods which are prone to failure to operate under low-load conditions, this invention does not overly rely on the generator's operating state, and the physical meaning of the time-domain phase comparison input is clear. Furthermore, the integral polarity reverses during phase shift, thus exhibiting high sensitivity. In addition to comparing the demagnetization fault index, low-voltage criteria, DC component criteria, and negative-sequence voltage criteria are introduced to avoid external faults, reducing the risk of false tripping. Attached Figure Description

[0016] 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.

[0017] Figure 1 This is a flowchart of the steps in the method for diagnosing the demagnetization fault of a hydro-generator based on a digital phase comparator. Figure 2 This is a schematic diagram of the PQ plane action area in the method of this embodiment of the invention. Detailed Implementation

[0018] All features disclosed in all embodiments of this specification, or steps in all methods or processes implied in the disclosure, may be combined and / or extended or replaced in any way, except for mutually exclusive features and / or steps.

[0019] The specific implementation process of this invention is as follows: In view of the technical problems mentioned in the background, the inventors of this invention believe that it is necessary to design a loss-of-excitation fault diagnosis algorithm that is adaptable to all operating conditions of a hydro-generator. During normal operation of the generator, the phase current and phase voltage are at an angle... The phase voltage and line voltage are 90° out of phase. If... Let represent the angle between the phase current and the line voltage. Under underexcitation, the generator experiences the maximum angle. Limitations, i.e. Therefore, the change in the angle between the phase current and the line voltage can be considered as the basis for detecting loss of magnetism.

[0020] Specifically, addressing the issue that existing technologies fail to activate demagnetization fault protection for hydro-generators under certain operating conditions, this invention aims to diagnose demagnetization faults in hydro-generators by combining time-domain digital phase comparison principles. This solution utilizes a digital phase comparator to calculate the integral value of the instantaneous power of the input signal. The designed algorithm uses the phase current and corresponding line voltage measured at the generator terminals as input signals, and detects demagnetization by comparing them with phase-based demagnetization index values.

[0021] More specifically, as a first aspect of the present invention, a method for diagnosing demagnetization faults in hydro-generators is provided, such as... Figure 1 As shown, the method includes the following steps: S1, the terminal line voltage of the faulty hydro-generator. , , and the three-phase current at the generator terminals , , Data and waveforms are acquired; S2 stores the collected current and voltage data in a register. When the register is full, the last bit of the data is deleted after storing the latest current and voltage data. S3, Calculate the instantaneous power half-cycle integral. and its discrete form; S4, Integrating instantaneous power Divide by the integral of the instantaneous power obtained when the input voltage and current signals are in phase. The initial demagnetization fault index is obtained by normalization. ; S5, the initial demagnetization fault index The final demagnetization fault index is obtained by eliminating average fluctuations. ; S6, determine when a fault occurs. Is it less than the threshold value? ,when Less than the threshold value and the terminal voltage is less than the threshold value The fault is determined to be demagnetization. S7 uses negative sequence voltage criteria and DC component criteria to block out loss of excitation protection in order to avoid maloperation caused by external faults.

[0022] In this embodiment, step S2 involves recording the data register rules for the generator terminal line voltage and phase current. The specific processing flow is as follows: The acquired terminal line voltage and phase current are used as signal inputs, denoted as: ; ; Voltage and current The input signal samples are stored in voltage and current registers, with a length of [missing information]. m Whenever a new sample is collected, the register is updated according to the following rules: the oldest sample is removed, the remaining samples are shifted left by one bit, the index value is decremented by 1, and the new sample is filled into the last bit of the register and assigned an index value. m (Since the entire register length is m, the last data recorded is the m-th sample, with an index value of m). This process is executed after each sampling, by discarding historical data, shifting the existing samples left, and decrementing the index, finally writing the indexed value to the end of the register. m New samples are generated, thus forming a dynamically updated sliding window of data.

[0023] In this embodiment, step S3 involves integrating the instantaneous power. The calculation method and specific processing flow are as follows: ; Its discrete form is: ; in, m For register length, Where is the sampling period, and T is the input signal period.

[0024] In this embodiment, step S4 involves... The normalization method and specific processing flow are as follows: The instantaneous power integral calculated over half a cycle of the input signal depends on the signal amplitude, and it is difficult to assess the distance range from the action boundary based on the absolute value of this integral. Therefore, it is necessary to... The initial demagnetization fault index was obtained by normalization. That is, dividing it by the instantaneous power integral value obtained when the input voltage and current signals are in phase, as shown below: ; The root mean square methods for voltage and current are as follows: ; ; Therefore, the initial demagnetization fault index can be calculated using the following formula: ; In this embodiment, step S5 eliminates the average fluctuation of the initial demagnetization fault index, and the specific processing flow is as follows: eliminate The average fluctuation is calculated using the following formula: ; Where k is the number of samples.

[0025] In this embodiment, step S6 involves the demagnetization fault index threshold value. and voltage threshold value The definition and specific processing flow are as follows: S61 Let the phase angle between the phase current and the line voltage be... During under-excitation operation, this angle is limited by the maximum under-excitation operating angle, which is set as follows: So, during a demagnetization fault The range can be represented as: ; S62 in fact It can be defined as: ; in The minus sign indicates under-excitation.

[0026] The reactive power absorbed by the generator from the system when the generator loses its excitation can be expressed as: ; S63 and The settings need to be based on the capacity characteristic curve of the synchronous generator and the permissible range of underexcitation operation. and The value should ensure that the operating region is between the steady-state stability limit and the minimum excitation limit, such as... Figure 2 .in It is the generator's rated active power. It is the reverse reactive power boundary of the demagnetization fault. It is a low voltage boundary. At this point, through... Point B can also be determined by modification. The operating range is changed. This method of creating an operating range allows the algorithm to detect demagnetization faults in time, before the generator becomes unstable.

[0027] In this embodiment, step S7 involves the locking criterion and its set value range, and the specific processing flow is as follows: The negative sequence voltage criterion is: ; in, , This is the secondary value of the generator's rated voltage.

[0028] The criterion for DC component is: ; in, The rated current of the generator; when the DC component is greater than the threshold value and the duration exceeds 20ms, the DC component issues a blocking pulse signal.

[0029] The effectiveness of the proposed algorithm was tested by building a single-machine-infinite system model using the MATLAB / Simulink platform. In the simulation model, the signal sampling frequency was 2kHz. , , By setting different operating conditions, including rated load and light load, the response time of the algorithm to detect demagnetization faults was verified, as shown in Tables 1 and 2.

[0030] Table 1. Operation time of demagnetization protection (complete demagnetization)

[0031] Table 2. Operation time of demagnetization protection (partial demagnetization)

[0032] By comparing the action time of the algorithms for complete demagnetization and partial demagnetization under rated and light load conditions, the algorithm proposed in this specification has better speed of action than traditional protection methods. Furthermore, traditional solutions have the risk of failure to operate under certain conditions (such as partial demagnetization under light load), while the proposed algorithm can operate reliably under various operating conditions of hydro-generators.

[0033] It should be noted that, within the scope of protection defined in the claims of this invention, the following embodiments can be combined and / or extended or replaced in any logical manner from the above specific embodiments, such as the disclosed technical principles, disclosed technical features or implicitly disclosed technical features.

[0034] Example 1 A method for diagnosing loss of excitation faults in hydro-generators includes the following steps: The phase current and corresponding line voltage measured at the generator terminals are used as input signals, and loss of excitation detection is achieved by comparing the phase-based loss of excitation index signal.

[0035] Example 2 Based on Example 1, the step of using the phase current and corresponding line voltage measured at the generator terminals as input signals and comparing them with phase-based demagnetization index signals to achieve demagnetization detection specifically includes the following sub-steps: S1, collects the phase current and line voltage at the turbine generator terminals; S2 stores the collected current and voltage data in the register in sequence. When the register is full, the last bit of the data is deleted when a new set of data is stored. S3, based on the register contents m Instantaneous power integral calculated from group current and voltage data And find its discrete form; S4. The initial demagnetization fault index is obtained by normalizing the instantaneous power integral. ; S5, for the initial demagnetization fault index The final demagnetization fault index is obtained after eliminating the average fluctuation. ; S6 determines the demagnetization fault by combining the final demagnetization fault index with the low voltage criterion, and blocks the demagnetization fault criterion with the DC component criterion and the negative sequence voltage criterion to avoid external faults.

[0036] Example 3 Based on Example 2, in step S1, the acquisition of the phase current and line voltage at the turbine generator terminals specifically includes the sub-step: [The text abruptly ends here, so the translation stops.] , , Three-phase current at the generator terminals , , Data and waveforms are acquired.

[0037] Example 4 Based on Example 3, in step S2, the collected current and voltage data are stored sequentially in a register. When the register is full, the last bit of data is deleted after each new set of data is stored. This specifically includes the following sub-steps: The acquired terminal line voltage and phase current are used as signal inputs, denoted as: ; ; Among them, voltage and current The input signal samples are stored in voltage and current registers, with a length of [missing information]. m Whenever a new sample is collected, the register is updated according to the following rules: the oldest sample is removed, the remaining samples are shifted left by one bit, the index value is decremented by 1, and the new sample is filled into the last bit of the register and assigned an index value.m This process is executed after each sampling, by discarding historical data, shifting the existing samples to the left, and decrementing the index, finally writing the indexed data to the end of the register. m New samples are generated, thus forming a dynamically updated sliding window of data.

[0038] Example 5 Based on Example 2, in step S3, the reference register... m Instantaneous power integral calculated from group current and voltage data And find its discrete form, specifically including the following sub-steps: Instantaneous power integral Calculated by the following formula: ; Its discrete form is: ; in, m For register length, Where is the sampling period, and T is the input signal period.

[0039] Example 6 Based on Example 5, in step S4, the initial demagnetization fault index is obtained by normalizing the obtained instantaneous power integral. Specifically, it includes the following sub-steps: The instantaneous power integral value calculated over half a cycle of the input signal depends on the signal amplitude. The initial demagnetization fault index was obtained by normalization. Divide it by the instantaneous power integral value obtained when the input voltage and current signals are in phase, as follows: ; The root mean square methods for voltage and current are as follows: ; ; The initial demagnetization fault index is then calculated using the following formula: .

[0040] Example 7 Based on Example 6, in step S5, the initial demagnetization fault index is... The final demagnetization fault index is obtained after eliminating the average fluctuation. The specific calculation is as follows: ; Where k is the number of samples.

[0041] Example 8 Based on Example 2, in step S6, the threshold value specifically includes: Threshold value and voltage threshold value These two parameters are set based on the capacity characteristic curve of the synchronous generator and the permissible range of underexcitation operation. and The value of should ensure that the operating range is between the steady-state stability limit and the minimum excitation limit. The operating range formed in this way can detect demagnetization faults in time before the generator becomes unstable.

[0042] Example 9 Based on Example 2, in step S6, the low voltage criterion is specifically as follows: ; in, , This is the secondary value of the generator's rated voltage; The criterion for the DC component is: ; in, for, for, The rated current of the generator; the criterion is that when the DC component is greater than the threshold value and the duration exceeds the set time, the DC component issues a blocking pulse signal; the set time includes 20ms.

[0043] Example 10 A hydro-generator demagnetization fault diagnosis device includes a processor and a memory. The memory stores a computer program, which, when loaded by the processor, executes the method described in any one of Examples 1 to 9.

[0044] The units described in the embodiments of the present invention can be implemented in software or hardware, and the described units can also be located in a processor. The names of these units do not necessarily limit the specific unit itself.

[0045] According to one aspect of the present invention, a computer program product or computer program is provided, the computer program product or computer program including computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium, and executes the computer instructions, causing the computer device to perform the methods provided in the various optional implementations described above.

[0046] In another aspect, embodiments of the present invention also provide a computer-readable medium, which may be included in the electronic device described in the above embodiments; or it may exist independently and not assembled into the electronic device. The computer-readable medium carries one or more programs, which, when executed by the electronic device, cause the electronic device to perform the methods described in the above embodiments.

Claims

1. A method for diagnosing a loss-of-excitation fault of a hydroelectric generator, characterized by, It comprises the following steps: The phase current and corresponding line voltage obtained by generator terminal measurement are taken as input signals, and loss-of-excitation detection is realized by comparing the loss-of-excitation index value signals based on phase.

2. The method of claim 1, wherein, The phase current and corresponding line voltage obtained by generator terminal measurement are taken as input signals, and loss-of-excitation detection is realized by comparing the loss-of-excitation index value signals based on phase, and the specific steps include: S1, collecting phase current and line voltage of the generator terminal; S2, storing the collected current and voltage data in sequence in the register, and deleting the last data after storing a new set of data when the register is full; S3, in accordance with the register m Group current voltage data compute instantaneous power integral and find its discrete form; S4, the initial field failure index is obtained after the obtained instantaneous power is integrated and normalized ; S5, to the initial loss-of-field fault index after eliminating the average fluctuation to obtain the final loss-of-field fault index ; S6, judging the loss-of-excitation fault by combining whether the final loss-of-excitation fault index is less than the threshold value with the low voltage criterion, and locking the loss-of-excitation fault criterion by the DC component criterion and the negative sequence voltage criterion to avoid external faults.

3. The method of claim 2, wherein, In step S1, the generator end phase current and line voltage of the water turbine generator are collected, specifically including the following sub-steps: collecting data and waveforms of the line voltage and three-phase current at the generator end of the faulty water turbine generator. 、 、 and the three-phase current at the generator end. 、 、 of the water turbine generator are collected.

4. The method of claim 3, wherein, In step S2, the collected current and voltage data are stored in sequence in the register, and the last data is deleted after storing a new set of data when the register is full, and the specific steps include: The collected terminal line voltage and phase current are taken as signal input, denoted as: ； ； wherein the voltage and the current samples of the input signal are stored in the voltage and current registers, with a length of m ; each time a new sample is taken, the registers are updated according to the following rules: the oldest sample is removed, the remaining samples are shifted one position to the left, the index values are uniformly reduced by 1, and the new sample is filled in the last position of the register and given an index value of m ; this process is performed after each sampling, by discarding historical data, shifting the remaining samples to the left, and decrementing the indices, ultimately writing a new sample with an index m at the end of the register, thus forming a dynamically updated data sliding window.

5. The method of claim 2, wherein, In step S3, the register contents m Group current voltage data compute instantaneous power integral and its discrete form, in particular comprising the sub-steps: Instantaneous power integration is calculated from the equation: ； Its discrete form is: ； wherein, m is the register length, is the sampling period, T is the input signal period.

6. The hydro-generator open-circuit fault diagnostic method according to claim 5, characterized in that, In step S4, the resulting instantaneous power integral is normalized to obtain an initial field failure index comprising the sub-steps of: The instantaneous power integral value calculated over half a cycle of the input signal depends on the signal amplitude. The initial demagnetization fault index was obtained by normalization. Divide it by the instantaneous power integral value obtained when the input voltage and current signals are in phase, as follows: ； Wherein, the root mean square calculation method of voltage and current is: ； ； Then, the initial loss-of-excitation fault index is calculated according to the following formula: 。 7. The method of claim 6, wherein, In step S5, the initial loss-of-field failure index is determined The final loss-of-field failure index is obtained after eliminating the average fluctuation and is calculated according to the following formula: ； Wherein, k is the number of samples.

8. The method of claim 2, wherein, In step S6, the threshold value specifically includes: Threshold value And voltage threshold value ; the two parameters are set according to the capacity characteristic curve of the synchronous generator and the permissible range of under-excitation operation; And The values of the two parameters should ensure that the operation region is located between the steady-state stability limit and the minimum excitation limit, and in this way, the operation region formed can detect the loss of excitation fault in time before the generator loses stability.

9. The method of claim 2, wherein, In step S6, the low voltage criterion is specifically: ； wherein , is the generator rated voltage secondary value; The DC component criterion is: ； wherein, is, is, is the generator rated current; the criterion is that the DC component is greater than a threshold and the duration exceeds a set time; the set time comprises 20 ms.

10. A hydroelectric generator de-excitation fault diagnosis device characterized by comprising: It comprises a processor and a memory, and the memory stores a computer program, which, when loaded by the processor, executes the method of any one of claims 1-9.

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