Multi-pulse transformer rectifier diode open-circuit fault on-line detection method

Abstract

The invention relates to a track-based online detection method for open-circuit faults of rectifier bridge diodes in a multi-pulse transformer rectifier. On-line detection is carried out on open circuits of a single diode or multiple diodes of a rectifier bridge in the multi-pulse transformer rectifier according to the approximate circle rate of a track of primary side current of the transformer rectifier and the center offset of a normalized track. And carrying out average processing after carrying out full-period phase alignment window cutting on the three-phase primary steady-state current of the phase-shifting transformer, and calculating a current amplitude and a phase in a coordinate system to obtain a trajectory diagram. According to the trajectory diagram, calculating a near-circle rate and a normalized trajectory center offset for judging whether a diode in the multi-pulse transformer rectifier has an open-circuit fault or not; and comparing with a predefined criterion threshold, and further judging whether the plurality of diode open circuits occur in the same rectifier bridge or different rectifier bridges. According to the detection method, online monitoring can be achieved, engineering is easy to achieve, and an additional detection circuit does not need to be installed.

Description

Technical Field

[0001] This invention belongs to the field of power electronic system testing, specifically relating to an online detection method for open-circuit faults in diodes of multi-pulse transformer rectifiers. Background Technology

[0002] Multi-pulse transformer rectifiers are key energy conversion devices in aviation power systems, rail transit traction power supply, marine power systems, and industrial DC buses. Their operational reliability directly affects the safety and availability of the system. In these applications, they typically operate under high current, high temperature, frequent load fluctuations, and complex electromagnetic environments for extended periods, inevitably subjecting the diodes to significant thermal and electrical stresses. In practical engineering operations, diode failure is one of the most common and insidious failure modes in multi-pulse transformer rectifiers. Unlike short-circuit faults, diode open circuits often do not immediately trigger protection actions or system shutdowns, but rather evolve gradually in the form of "performance degradation," making them more insidious and difficult to detect quickly.

[0003] Extensive engineering experience shows that a single open-circuit diode is usually not the final failure mode, but rather the initial stage of a multi-diode open-circuit fault. When a single diode becomes open-circuited, the current in its corresponding conduction region is rapidly redistributed to other diodes in the same or adjacent bridge arms. This causes these devices to withstand larger transient peak currents and thermal loads, eventually evolving into multiple open-circuit diodes, resulting in severe DC voltage drops, increased electromagnetic interference, and safety hazards such as overheating of upstream transformers. Therefore, from an engineering safety and maintenance perspective, focusing solely on a single open-circuit diode is far from sufficient; a detection method that can cover multiple open-circuit diodes and provides practical guidance for later maintenance and replacement is urgently needed.

[0004] Existing literature on open-circuit diodes in multi-pulse transformer rectifiers mostly focuses on single-diode open-circuit cases and primarily relies on DC component and harmonic analysis. While the DC component can directly reflect faults, it is not suitable for interference-prone environments. For example, the characteristics of industrial DC buses—high load and rapid changes in operating conditions—can lead to misjudgments in diode open-circuit detection based on DC components. Furthermore, harmonic characteristics of different fault modes often overlap, making fault differentiation impossible. Therefore, research based on… The spatial domain detection method maps one-dimensional fault features to two-dimensional space, deriving more geometric features. These features not only intuitively reflect various symmetrical faults in multi-pulse transformer rectifiers, but also possess stronger robustness and are more suitable for applications under complex and dynamic operating conditions. Therefore, from the perspective of detecting multiple open-circuit faults and engineering versatility, this patent utilizes... Tracing the open circuit diagnosis of diodes in transformer rectifiers not only has significant advantages, but is also of practical necessity in high-risk applications with multiple open circuits. Summary of the Invention

[0005] The purpose of this invention is to provide an online detection method for open-circuit faults in diodes of multi-pulse transformer rectifiers, comprising the following steps:

[0006] Step 1: Calculation Current sequence in coordinate system and plot trajectory:

[0007] Steady-state current of the three-phase primary side of the phase-shifting transformer , , Perform full-cycle phase alignment windowing and averaging to obtain... , , Its value is obtained through Clark transformation. Current sequence in coordinate system and ,in ,draw Trajectory.

[0008] Step 2: Calculation The characteristic quantities of the trajectory include the coordinates of the trajectory center and the distance from the trajectory to the origin:

[0009] Calculate the trajectory center angle sequence ,in ;

[0010] Calculate the distance sequence from the trajectory to the origin. ,in ;

[0011] Calculate the coordinates of the trajectory center .

[0012] Step 3: Calculation Trajectory circularity and normalized trajectory center offset:

[0013] Calculate the near-circularity ratio based on the current sequence. ;

[0014] Where P is the perimeter of the trajectory, obtained by accumulating the side lengths, and the specific formula is as follows: ;

[0015] A is the area of ​​the trajectory, which is obtained using the triangulation method. The specific formula is as follows: .

[0016] Calculate the average value of the characteristic quantity and The normalized trajectory center offset was calculated. .

[0017] All of the above calculations can be performed by importing code into the registers.

[0018] Step 4: Given a threshold , , and ,and and The system compares and determines whether a fault has occurred. If two or more diodes fail, the faulty diodes are identified as being located in the same rectifier bridge or different rectifier bridges. The specific determination process is as follows:

[0019] If the near-circularity ratio And the normalized trajectory center offset If the diodes in the multi-pulse transformer rectifier are open-circuited, then no diodes in the multi-pulse transformer rectifier will have an open-circuit fault; otherwise, a diode will have an open-circuit fault.

[0020] Furthermore, if and and If this occurs, a single diode in the multi-pulse transformer rectifier will experience an open-circuit fault.

[0021] like but and If either of the two conditions is not met or neither of them is met, then two or more diodes in the same rectifier bridge but different phases will simultaneously experience an open-circuit fault.

[0022] Furthermore, if It is not true, and If two or more diodes in the same phase as the rectifier bridge in a multi-pulse rectifier bridge simultaneously experience an open-circuit fault;

[0023] like It is not true, and If this condition is not met, then two or more diodes in different rectifier bridges in a multi-pulse rectifier bridge will simultaneously experience open-circuit faults.

[0024] Furthermore, the threshold mentioned in step 4 , , The value range of the threshold is adjusted according to the actual application object. The value range is 0.01 to 0.05.

[0025] This invention proposes an online detection method for diode open-circuit faults in multi-pulse transformer rectifiers, which calculates the primary current of the transformer rectifier under different fault modes. The near-circularity of the trajectory and the normalized trajectory center offset are compared with thresholds to determine whether single or multiple diodes in a multi-pulse transformer rectifier have open circuits, and to preliminarily determine whether the open circuits occur in the same rectifier bridge or different rectifier bridges. The proposed method maps traditional one-dimensional fault features to the spatial domain, enabling not only intuitive online detection of various diode open-circuit fault modes in transformer rectifiers, but also stronger robustness, making it more suitable for applications under complex and dynamic operating conditions. Attached Figure Description

[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.

[0027] Figure 1 This is a general block diagram of an online detection method for open-circuit faults in diodes of a multi-pulse transformer rectifier;

[0028] Figure 2 This is a schematic diagram showing the diode markings in a typical 12-pulse transformer rectifier.

[0029] Figure 3 A flowchart for diagnosing open-circuit faults in diodes of a multi-pulse transformer rectifier;

[0030] Figure 4 For the primary steady-state current under different fault modes Components in coordinate system and ;

[0031] Figure 5 For the phase-shifting transformer current sequence in a healthy state trajectory map

[0032] Figure 6 For the phase-shifting transformer current sequence when D11 is open trajectory map

[0033] Figure 7 For the phase-shifting transformer current sequence when D11 and D13 are open trajectory map

[0034] Figure 8 For the phase-shifting transformer current sequence when D11 and D14 are open trajectory map

[0035] Figure 9 For the phase-shifting transformer current sequence when D11 and D21 are open trajectory map Detailed Implementation

[0036] The exemplary embodiments of this application are described below with reference to the accompanying drawings, including various details of the embodiments to aid understanding. Therefore, those skilled in the art will recognize that modifications can be made to the embodiments described herein without departing from the scope and spirit of this application. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0037] like Figure 1 As shown, an online detection method for open-circuit faults in diodes of a multi-pulse transformer rectifier includes the following steps:

[0038] Step 1: Calculation Current sequence in coordinate system and plot trajectory:

[0039] Steady-state current of the three-phase primary side of the phase-shifting transformer , , Perform full-cycle phase alignment windowing and averaging to obtain... , , Its value is obtained through Clark transformation. Current sequence in coordinate system and ,in ,draw Trajectory.

[0040] Step 2: Calculation The characteristic quantities of the trajectory include the coordinates of the trajectory center and the distance from the trajectory to the origin:

[0041] Calculate the trajectory center angle sequence ,in ;

[0042] Calculate the distance sequence from the trajectory to the origin. ,in ;

[0043] Calculate the coordinates of the trajectory center .

[0044] Step 3: Calculation Trajectory circularity and normalized trajectory center offset:

[0045] Calculate the near-circularity ratio based on the current sequence. ;

[0046] Where P is the perimeter of the trajectory, obtained by accumulating the side lengths, and the specific formula is as follows: ;

[0047] A is the area of ​​the trajectory, which is obtained using the triangulation method. The specific formula is as follows: .

[0048] Calculate the average value of the characteristic quantity and The normalized trajectory center offset was calculated. .

[0049] All of the above calculations can be performed by importing code into the registers.

[0050] Step 4: Given a threshold , , and ,and and The comparison determines whether a fault has occurred. If two or more diodes fail, it is determined whether the faulty diodes are located in the same rectifier bridge or different rectifier bridges.

[0051] like Figure 2 As shown, the present invention will be further explained using a typical 12-pulse transformer rectifier as an example.

[0052] Figure 2 In rectifier bridge I, the upper arm diode for phase a1 is D11, and the lower arm diode is D14; the upper arm diode for phase b1 is D13, and the lower arm diode is D16; the upper arm diode for phase c1 is D15, and the lower arm diode is D12. The corresponding diodes in rectifier bridge II are distributed as D21~D26. The input voltage of phase a on the primary side of the phase-shifting transformer is expressed as... The initial phase is , effective value , , The voltages of phases b and c lag behind and lead phase a by 120°, respectively.

[0053] The online detection method for diode open-circuit faults in multi-pulse transformer rectifiers is explained using five fault modes as examples: healthy condition, single diode D11 open circuit, two diodes D11 and D13 open circuit (different phases in the same bridge), two diodes D11 and D14 open circuit (same phase in the same bridge), and two diodes D11 and D21 open circuit (different phases in the same bridge). Details are as follows:

[0054] Under different fault modes, sensors are used to detect the primary current of the phase-shifting transformer. , , The data sampling rate is 100k, and the data within 0.02s (8 cycles) is averaged to obtain the results. , , Each phase has 2000 data points, which are obtained after Clark transformation. and The Clark coordinate transformation formula is:

[0055]

[0056] Different fault modes correspond to and Waveforms that change over time, such as Figure 4 As shown, they are respectively composed of sequences and sequence Composition, in which .

[0057] by As the x-axis, with Using the vertical axis, we obtain the corresponding values ​​for different failure modes. trajectory diagram, such as Figures 5-9 As shown. Calculate each separately. Trajectory center angle sequence ,in Calculate the distance sequence from the trajectory to the origin. ,in Therefore, the trajectory center sequence is calculated. The distance from the trajectory to the origin is obtained using the average value. Average coordinates of the trajectory center .

[0058] Then calculate the different fault modes separately. The perimeter and area of ​​the trajectory are calculated using the following formulas:

[0059]

[0060]

[0061] Therefore, using the formula The near-circularity ratio under different failure modes was obtained.

[0062] Further calculate the normalized trajectory center offset .

[0063] The values ​​of the above characteristic quantities are summarized in the following table:

[0064]

[0065] In this embodiment, the threshold is customized based on experience. , .

[0066] Figure 3 Here is a flowchart for troubleshooting open-circuit faults in diodes of a multi-pulse transformer rectifier, specifically:

[0067] The R and C values ​​for different failure modes are compared according to the above procedure to obtain the test results. When healthy, and The test result was "healthy"; when D11 was open, but ,and The test result was "single diode open circuit"; when D11 and D13 are open circuit, but ,and The test result was "two diodes open circuit (different phases in the same bridge)"; when D11 and D14 are open circuit, and ,and The test result was "two diodes open circuit (in phase and on the same bridge)"; when D11 and D21 are open circuit, and ,and The test result was "two diodes in different bridges are open". Therefore, the fault detection result obtained in this embodiment is completely consistent with the actual diode state.

[0068] It should be noted that this method is also applicable to embodiments with inductive / capacitive loads under different operating conditions. Furthermore, different variations of this invention exist in other structural transformer rectifiers, all of which remain within the scope of this invention.

[0069] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An online detection method for open-circuit faults in diodes of a multi-pulse transformer rectifier, characterized by comprising the following steps: Step 1: Calculation Current sequence in coordinate system and plot trajectory: Steady-state current of the three-phase primary side of the phase-shifting transformer , , Perform full-cycle phase alignment windowing and averaging to obtain , , Its value is obtained through Clark transformation. Current sequence in coordinate system and ,in ,draw Trajectory; Step 2: Calculation The characteristic quantities of the trajectory include the coordinates of the trajectory center and the distance from the trajectory to the origin: Calculate the trajectory center angle sequence ,in ; Calculate the distance sequence from the trajectory to the origin. ,in ; Calculate the coordinates of the trajectory center ; Step 3: Calculation Trajectory circularity and normalized trajectory center offset: Calculate the near-circularity ratio based on the current sequence. , Where P is the perimeter of the trajectory, which is obtained by accumulating the side lengths, and the specific formula is as follows: ; A is the area of ​​the trajectory, which is obtained using the triangulation method. The specific formula is as follows: ; Calculate the average value of the characteristic quantity and The normalized trajectory center offset was calculated. ; Step 4: Given a threshold and ,and and The comparison determines whether a fault has occurred. If two or more diodes fail, the faulty diodes are located in the same rectifier bridge or different rectifier bridges.

2. The online detection method for open-circuit faults of diodes in a multi-pulse transformer rectifier according to claim 1, characterized in that, The calculations in step 3 are all implemented by importing code from the registers.

3. The online detection method for open-circuit faults of diodes in a multi-pulse transformer rectifier according to claim 1, characterized in that, The fault diagnosis process in step 4 is as follows: If the near-circularity ratio And the normalized trajectory center offset If the diodes in the multi-pulse transformer rectifier are open-circuited, then no diodes in the multi-pulse transformer rectifier will have an open-circuit fault; otherwise, a diode will have an open-circuit fault. Furthermore, if and and If this occurs, a single diode in the multi-pulse transformer rectifier will experience an open-circuit fault. like but and If either of the two conditions is not met or neither of them is met, then two or more diodes in the same rectifier bridge but different phases will simultaneously experience an open-circuit fault. Furthermore, if It is not true, and If two or more diodes in the same phase as the rectifier bridge in a multi-pulse rectifier bridge simultaneously experience an open-circuit fault; like It is not true, and If this condition is not met, then two or more diodes in different rectifier bridges in a multi-pulse rectifier bridge will simultaneously experience open-circuit faults.

4. The online detection method for open-circuit faults of diodes in a multi-pulse transformer rectifier according to claim 3, characterized in that, The The range of values ​​is adjusted according to the actual application object. The value range is 0.01 to 0.05.

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