A method, system, and medium for detecting a fault in a rectifier thyristor of an excitation system

Abstract

The application provides a kind of excitation system rectifier thyristor fault detection method, system and medium, belongs to synchronous machine excitation system power cabinet fault detection technical field of generator, phase modifier etc.;The following technical solutions are realized: the three-phase alternating current input current of the to-be-detected rectifier in the excitation system is collected;The effective value of the three-phase current of the rectifier is calculated according to the collected current, and the current effective value difference coefficient is calculated according to the current effective value;The current effective value difference coefficient is compared with the difference coefficient threshold value, if the current effective value difference coefficient is greater than the difference coefficient threshold value, the to-be-tested rectifier exists thyristor degradation, otherwise the to-be-tested rectifier does not exist thyristor degradation;Adjust the excitation system, and the degraded rectifier or thyristor is withdrawn from the excitation system.The application avoids the further degradation of thyristor to cause the short-circuit fault of rectifier, and has good application prospect.

Description

Technical Field

[0001] This invention relates to a method, system, and medium for detecting faults in thyristors of excitation system rectifiers, belonging to the technical field of power cabinet fault detection in excitation systems of synchronous motors such as generators and synchronous condensers. Background Technology

[0002] The excitation system is a general term for the power supply and auxiliary equipment that supplies the excitation current to the synchronous generator. Excitation systems can be divided into three main categories: DC exciter systems, AC exciter systems, and static excitation systems. Among static excitation systems, the self-excited excitation system has a simple structure and fast voltage response speed, and is currently the main application form.

[0003] The self-excited excitation system consists of two parts: power and control. The power part comprises an excitation transformer and a rectifier. The high-voltage side of the excitation transformer is connected to the generator terminals, reducing the terminal voltage. The rectifier converts AC to DC, supplying the rotor windings with excitation energy. The control part is implemented by an excitation regulator, which collects the generator terminal voltage as a synchronization signal for pulse generation. Based on the target voltage command, it changes the firing angle of the thyristors in the rectifier bridge in real time to regulate the generator terminal voltage. The rectifier bridge is a three-phase controllable rectifier bridge composed of thyristors, and the excitation transformer is a dry-type transformer. The power part model of the excitation system is consistent across different manufacturers, as shown in the figure. In this model, Tex represents the excitation transformer, V11~V26 represent thyristors, and XL represents the rotor coil.

[0004] When a rectifier is in continuous operation, the thyristors deteriorate under voltage and current stress, potentially losing their reverse cutoff capability and causing a short circuit. Currently, thyristors connected in series with fast-acting fuses are mainly used for short-circuit protection. After a short circuit occurs, the large current will melt the fast-acting fuse, interrupting the short-circuit current. However, there are problems such as damage to various components caused by the short-circuit current, and the fast-acting fuse failing to blow properly, leading to the expansion of the short circuit. Therefore, how to detect thyristor faults and stop the rectifier from operating before a short circuit occurs is an urgent problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a method, system, and medium for detecting thyristor faults in an excitation system rectifier, which can prevent further deterioration of the thyristor from causing short-circuit faults in the rectifier and has good application prospects.

[0006] To achieve the above objectives, the present invention employs the following technical solution: Collect the three-phase AC input current of the rectifier under test in the excitation system; The effective value of the three-phase current of the rectifier is calculated based on the collected current, and the effective value difference coefficient is calculated based on the effective value of the current. Compare the current effective value difference coefficient with the difference coefficient threshold. If the current effective value difference coefficient is greater than the difference coefficient threshold, the rectifier under test has thyristor degradation; otherwise, the rectifier under test does not have thyristor degradation. Adjusting the excitation system will cause degraded rectifiers or thyristors to be removed from the excitation system.

[0007] Preferably, the difference coefficient threshold is 0.05.

[0008] Preferably, the formula for calculating the effective value of the three-phase current is as follows: , , ; in, This indicates the input current of phase A of the rectifier under test. This indicates the input current of phase B of the rectifier under test. This indicates the C-phase input current of the rectifier under test. Indicates time, This represents the effective value of the A-phase current of the rectifier under test. This represents the effective value of the B-phase current of the rectifier under test. This represents the effective value of the C-phase current of the rectifier under test.

[0009] Preferably, the specific formula for calculating the effective value difference coefficient of the current is as follows: ; in, This represents the average value of the effective value of the three-phase current.

[0010] Preferably, the formula for calculating the average value of the three-phase current effective value is as follows: .

[0011] Preferably, the specific method for removing a deteriorated rectifier from the excitation system is as follows: the rectifier number with deteriorated thyristors is transmitted to the excitation regulator, and the excitation regulator stops the triggering of all thyristors of that rectifier, thus removing the rectifier from operation.

[0012] Preferably, the method also includes determining the location of the degraded thyristor in the degraded rectifier under test, as follows: Obtain the degraded three-phase current waveforms on the input side of the rectifier under test and compare them with the normal waveforms. If, in the obtained three-phase current waveform, the current of a certain phase should be 0 for a certain period of time, but the actual value of the current during that period is negative, then the thyristor below the connection point in the excitation system to which that phase current is connected has deteriorated. If, in the acquired three-phase current waveform, the current of a certain phase should be 0 for a certain period of time, but the actual value of the current during that period is positive, then the thyristor above the connection point in the excitation system to which that phase current is connected has deteriorated.

[0013] A fault detection system for rectifier thyristors in an excitation system includes: Data acquisition module: Acquires the three-phase AC input current of the rectifier under test in the excitation system; Coefficient calculation module: Calculates the effective value of the three-phase current of the rectifier based on the collected current, and calculates the current effective value difference coefficient based on the current effective value; Comparison module: Compares the difference coefficient of the current effective value with the difference coefficient threshold. If the difference coefficient of the current effective value is greater than the difference coefficient threshold, the rectifier under test has thyristor degradation; otherwise, the rectifier under test does not have thyristor degradation. Fault adjustment module: The rectifier serial number with deteriorated thyristors is transmitted to the excitation regulator. The excitation regulator stops the triggering of all thyristors of the rectifier, causing the rectifier to take off.

[0014] Preferably, the comparison module can also analyze the three-phase current waveform on the input side of the rectifier, obtain the degraded three-phase current waveform on the input side of the rectifier under test, and compare it with the normal waveform. If, in the obtained three-phase current waveform, the current of a certain phase should be 0 for a certain period of time, but the actual value of the current during that period is negative, then the thyristor below the connection point in the excitation system to which that phase current is connected has deteriorated. If, in the acquired three-phase current waveform, the current of a certain phase should be 0 for a certain period of time, but the actual value of the current during that period is positive, then the thyristor above the connection point in the excitation system to which that phase current is connected has deteriorated.

[0015] The advantages of this invention are: it can detect the early deterioration of the rectifier thyristor, which loses its forward cutoff capability but retains its reverse cutoff capability, and promptly remove the faulty thyristor or rectifier from operation, preventing further deterioration and complete failure of the thyristor that could lead to a short circuit in the rectifier. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0017] Figure 1 This is the circuit schematic of the excitation system.

[0018] Figure 2 This is the current waveform on the AC input side of the rectifier of the excitation system under normal conditions.

[0019] Figure 3The current waveform on the AC input side of the rectifier is shown when the C-phase negative bridge arm thyristor has initially deteriorated and lost its forward cutoff capability.

[0020] Figure 4 This is a circuit schematic to simulate the initial degradation of the C-phase negative bridge arm thyristor.

[0021] Figure 5 It is the correspondence between the triggering time of the thyristor and the current waveform.

[0022] Figure 6 This is a schematic diagram of the process structure of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1 A method for detecting thyristor faults in an excitation system rectifier is achieved through the following technical solution: Collect the three-phase AC input current of the rectifier under test in the excitation system; The effective values ​​of the three-phase currents of the rectifier are calculated based on the collected current data, and the effective value difference coefficient is calculated based on the effective current values. The formula for calculating the effective value of the three-phase current is as follows: , , ; in, This indicates the input current of phase A of the rectifier under test. This indicates the input current of phase B of the rectifier under test. This indicates the C-phase input current of the rectifier under test. Indicates time, This represents the effective value of the A-phase current of the rectifier under test. This represents the effective value of the B-phase current of the rectifier under test. This represents the effective value of the C-phase current of the rectifier under test.

[0025] The specific formula for calculating the difference coefficient of the effective value of the current is as follows: ; in, This represents the average value of the effective value of the three-phase current.

[0026] The formula for calculating the average value of the three-phase current RMS is as follows: .

[0027] The difference coefficient of the effective current value is compared with the difference coefficient threshold, which is 0.05. If the difference coefficient of the effective current value is greater than the difference coefficient threshold, the rectifier under test has thyristor degradation; otherwise, the rectifier under test does not have thyristor degradation. Adjusting the excitation system will remove any degraded rectifiers or thyristors from the system. Specifically, the rectifier number with degraded thyristors is transmitted to the excitation regulator, which then stops the triggering of all thyristors in that rectifier, thus taking it out of operation.

[0028] Example 2 This also includes determining the location of the degraded thyristors in the degraded rectifier under test, as detailed below: Obtain the degraded three-phase current waveforms on the input side of the rectifier under test and compare them with the normal waveforms. If, in the obtained three-phase current waveform, the current of a certain phase should be 0 for a certain period of time, but the actual value of the current during that period is negative, then the thyristor below the connection point in the excitation system to which that phase current is connected has deteriorated. If, in the acquired three-phase current waveform, the current of a certain phase should be 0 for a certain period of time, but the actual value of the current during that period is positive, then the thyristor above the connection point in the excitation system to which that phase current is connected has deteriorated.

[0029] Example 3 A fault detection system for rectifier thyristors in an excitation system includes: Data acquisition module: Acquires the three-phase AC input current of the rectifier under test in the excitation system; Coefficient calculation module: Calculates the effective value of the three-phase current of the rectifier based on the collected current, and calculates the current effective value difference coefficient based on the current effective value; Comparison module: Compares the difference coefficient of the current effective value with the difference coefficient threshold. If the difference coefficient of the current effective value is greater than the difference coefficient threshold, the rectifier under test has thyristor degradation; otherwise, the rectifier under test does not have thyristor degradation. Fault adjustment module: The rectifier serial number with deteriorated thyristors is transmitted to the excitation regulator. The excitation regulator stops the triggering of all thyristors of the rectifier, causing the rectifier to take off.

[0030] The comparison module can also analyze the three-phase current waveform on the input side of the rectifier, obtain the degraded three-phase current waveform on the input side of the rectifier under test, and compare it with the normal waveform. If, in the obtained three-phase current waveform, the current of a certain phase should be 0 for a certain period of time, but the actual value of the current during that period is negative, then the thyristor below the connection point in the excitation system to which that phase current is connected has deteriorated. If, in the acquired three-phase current waveform, the current of a certain phase should be 0 for a certain period of time, but the actual value of the current during that period is positive, then the thyristor above the connection point in the excitation system to which that phase current is connected has deteriorated.

[0031] Figure 1 The diagram shown is a schematic of the excitation system, where Tex represents the excitation transformer, XL represents the rotor coil, V11~V16 represent rectifier 1, and V21~V26 represent rectifier 2. Rectifier 1 and rectifier 2 are connected in parallel. Figure 2 The figure shows the AC input current waveform under normal conditions. One power frequency cycle can be divided into 6 stages: I, II, III, IV, V, and VI, with 6 thyristor commutations occurring. The thyristors that are turned on in each stage are shown in Table 1. The DC current of the rotor winding is considered to be constant within one power frequency cycle, and its magnitude is Id.

[0032] Table 1. Thyristors in each conduction stage Figure 4 The diagram shows the state in rectifier 2 where thyristor V22 has undergone initial degradation and lost its forward cutoff capability. V22 is represented by a diode in the diagram. Assume the thyristor's trigger angle is 70 degrees. Figure 5 At time t0, the voltage of phase B equals the voltage of phase C. Under normal operating conditions, V26 commutates to V22 at time t1. However, under initial thyristor degradation, the voltage of phase B is higher than the voltage of phase C after time t0. Between t0 and t6, V25, XL, V26, and the excitation transformer form a complete circuit. At time t6, V25 commutates to V21, and V21, XL, V22, and the low-voltage side of the excitation transformer form a complete circuit. During the time interval between t6 and t1, V22 replaces V26 for conduction. Therefore, the AC current waveform at this time is as follows: Figure 3 As shown.

[0033] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for detecting thyristor faults in an excitation system rectifier, characterized in that, include: Collect the three-phase AC input current of the rectifier under test in the excitation system; The effective value of the three-phase current of the rectifier is calculated based on the collected current, and the effective value difference coefficient is calculated based on the effective value of the current. Compare the current effective value difference coefficient with the difference coefficient threshold. If the current effective value difference coefficient is greater than the difference coefficient threshold, the rectifier under test has thyristor degradation; otherwise, the rectifier under test does not have thyristor degradation. Adjusting the excitation system will cause degraded rectifiers or thyristors to be removed from the excitation system.

2. The method for detecting thyristor faults in an excitation system rectifier according to claim 1, characterized in that, The threshold for the difference coefficient is 0.

05.

3. The method for detecting thyristor faults in an excitation system rectifier according to claim 2, characterized in that, The formula for calculating the effective value of the three-phase current is as follows: ， ， ； in, This indicates the input current of phase A of the rectifier under test. This indicates the input current of phase B of the rectifier under test. This indicates the C-phase input current of the rectifier under test. Indicates time, This represents the effective value of the A-phase current of the rectifier under test. This represents the effective value of the B-phase current of the rectifier under test. This represents the effective value of the C-phase current of the rectifier under test.

4. The method for detecting thyristor faults in an excitation system rectifier according to claim 3, characterized in that, The specific formula for calculating the difference coefficient of the effective value of the current is as follows: ； in, This represents the average value of the effective value of the three-phase current.

5. The method for detecting thyristor faults in an excitation system rectifier according to claim 4, characterized in that, The formula for calculating the average value of the three-phase current RMS is as follows: 。 6. The method for detecting thyristor faults in an excitation system rectifier according to claim 5, characterized in that, The specific method for removing a deteriorated rectifier from the excitation system is as follows: The rectifier number with deteriorated thyristors is transmitted to the excitation regulator, which then stops the triggering of all thyristors of that rectifier, thus removing the rectifier from operation.

7. The method for detecting thyristor faults in an excitation system rectifier according to claim 5, characterized in that, This also includes determining the location of the degraded thyristors in the degraded rectifier under test, as detailed below: Obtain the degraded three-phase current waveforms on the input side of the rectifier under test and compare them with the normal waveforms. If, in the obtained three-phase current waveform, the current of a certain phase should be 0 for a certain period of time, but the actual value of the current during that period is negative, then the thyristor below the connection point in the excitation system to which that phase current is connected has deteriorated. If, in the obtained three-phase current waveform, the current of a certain phase should be 0 for a certain period of time, but the actual value of the current during that period is positive, then the thyristor above the connection point in the excitation system to which that phase current is connected has deteriorated.

8. A thyristor fault detection system for an excitation system rectifier, characterized in that, include: Data acquisition module: Acquires the three-phase AC input current of the rectifier under test in the excitation system; Coefficient calculation module: Calculates the effective value of the three-phase current of the rectifier based on the collected current, and calculates the current effective value difference coefficient based on the current effective value; Comparison module: Compares the difference coefficient of the current effective value with the difference coefficient threshold. If the difference coefficient of the current effective value is greater than the difference coefficient threshold, the rectifier under test has thyristor degradation; otherwise, the rectifier under test does not have thyristor degradation. Fault adjustment module: The rectifier serial number with deteriorated thyristors is transmitted to the excitation regulator. The excitation regulator stops the triggering of all thyristors of the rectifier, causing the rectifier to take off.

9. The excitation system rectifier thyristor fault detection system according to claim 8, characterized in that, The comparison module can also analyze the three-phase current waveform on the input side of the rectifier, obtain the degraded three-phase current waveform on the input side of the rectifier under test, and compare it with the normal waveform. If, in the obtained three-phase current waveform, the current of a certain phase should be 0 for a certain period of time, but the actual value of the current during that period is negative, then the thyristor below the connection point in the excitation system to which that phase current is connected has deteriorated. If, in the obtained three-phase current waveform, the current of a certain phase should be 0 for a certain period of time, but the actual value of the current during that period is positive, then the thyristor above the connection point in the excitation system to which that phase current is connected has deteriorated.

10. A storage medium storing program instructions, characterized in that, When the program instructions are executed, they perform the excitation system rectifier thyristor fault detection method as described in any one of claims 1 to 7.

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