Methods for detecting and locating open-circuit faults in diodes of aircraft transformer rectifiers

Abstract

This invention discloses a method for detecting and locating open-circuit faults in the diodes (TRU) of aircraft transformer rectifiers. It effectively solves the problem that open-circuit faults are prone to occur in aircraft transformer rectifier diodes due to long-term stress, and that timely and effective detection and location are difficult. First, the working principle of the TRU is analyzed to obtain the corresponding phase relationship between the diode's conduction interval and the transient output voltage. The transient output voltage is collected within one electrical cycle under healthy conditions. This voltage is divided into p equal intervals according to the diode's conduction interval, and the minimum value of each interval is calculated. The average minimum value is then calculated, and its ratio to the global maximum value is used as the health baseline value R. ref For a TRU in an unknown state, calculate the ratio of the interval minimum to the global maximum within one electrical cycle, and compare it with R. ref The method compares the diodes to determine if an open-circuit fault has occurred. If a fault is found, the location of the faulty diode is determined based on the corresponding phase relationship between the diode's conduction range and the transient output voltage of the TRU. The method proposed in this invention is simple to implement, requires few signals, and has good real-time detection performance. It helps to detect and quickly decide on open-circuit faults in transformer rectifier diodes as early as possible, thus maintaining the safe operation of the aviation secondary power supply system.

Description

Technical Field

[0001] This invention belongs to the field of fault diagnosis technology for aviation secondary power supply systems, specifically involving a method for judging and locating open-circuit faults in aviation transformer rectifiers. It is a method that uses transient analysis of the output voltage of the transformer rectifier, combined with input phase information and the winding configuration of the phase-shifting transformer, to judge the type of diode fault and locate it. Background Technology

[0002] Transformer rectifier units (TRUs) are key components of aircraft secondary power systems due to their simple structure, high power factor, good stability, and strong overload capacity. They convert 115V / 360-800Hz AC power into 28V low-voltage DC power to supply power to airborne equipment. For example... Figure 1 As shown, the TRU consists of a phase-shifting transformer, m parallel three-phase uncontrolled rectifier bridges, and a filter circuit. To enable the TRU output voltage to pulsate p times in one electrical cycle, the primary and secondary windings of the phase-shifting transformer are configured with different connections, so that the voltage phases of the m secondary windings are staggered by 2π / p.

[0003] As a key component of the transformer rectifier (TRU), diodes are susceptible to open-circuit (OC) or short-circuit (SC) faults due to factors such as temperature, mechanical stress, and electrical stress. These faults can lead to degraded power quality and even abnormal shutdowns. SC faults cause overcurrent and are easily detected and isolated by fuses. OC faults, however, do not reach significant overvoltage or overcurrent amplitudes, making early and effective diagnosis difficult, especially when only a few diodes are open-circuited, allowing the system to continue operating with the fault. In such cases, healthy diodes will bear greater electrical stress, further exacerbating the open-circuit risk and posing a potentially significant threat to system safety. Therefore, accurate, efficient, and timely diagnosis of diode OC faults in aerospace transformer rectifiers is of paramount importance.

[0004] For open-circuit diodes in transformer rectifiers, the industry typically employs periodic replacement or individual inspection. This method is resource-intensive, costly, and unreliable, making it unsuitable for transformer rectifiers with high pulse counts. Considering that open-circuit diodes in the rectifier bridge directly affect the output voltage, academic research often uses frequency domain and time-frequency domain methods combined with intelligent algorithms for fault diagnosis. However, these methods can only determine whether a transformer rectifier diode is faulty, not its location. Furthermore, efficient intelligent algorithms require sufficient historical fault data and significant computer resources for training, necessitating at least one data processing cycle before making a decision, which cannot adequately meet the real-time requirements of transformer rectifier fault diagnosis in the aviation field. A simple, efficient fault diagnosis method that does not overly rely on historical data and intelligent algorithms still needs to address the fault mechanism itself, enabling rapid diagnosis and autonomous maintenance of open-circuit diodes in transformer rectifiers, thus improving aircraft operational safety. Therefore, this patent proposes a simple, theoretically interpretable, and real-time-compliant method for detecting and locating open-circuit diode faults in aviation transformer rectifiers. Summary of the Invention

[0005] The purpose of this invention is to achieve rapid diagnosis and accurate location of open-circuit faults in the diodes (TRUs) of aircraft transformer rectifiers. This invention proposes a diode open-circuit fault diagnosis method based on the transient characteristics of the transformer rectifier output voltage, and can combine the input voltage phase and the phase-shifting transformer winding configuration to achieve fault diode location.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a strategy for detecting and locating open-circuit faults in the diode (TRU) of an aviation transformer rectifier, the specific contents of which are as follows:

[0008] Step 1: Determine the TRU electrical parameters, including pulse number p and sampling frequency f. s Input voltage frequency f AC The phase information of input voltage phase A is used to analyze the correspondence between diode conduction and the transient output voltage waveform of the TRU, as detailed below:

[0009] 1a. In the TRU structure, one three-phase uncontrolled rectifier bridge corresponds to 6 pulses, and M three-phase uncontrolled rectifier bridges are connected in parallel to form a p=6M pulse TRU;

[0010] 1b.TRU's f AC =360~800Hz, according to the Nyquist–Shannon sampling theorem, determine the sampling frequency f. s ≥2·p·f AC ;

[0011] 1c. A single-phase phase-locked loop circuit obtains the initial phase information θ0 of the input voltage phase a;

[0012] 1d. For a given TRU, adhering to the principle that conduction occurs when the diode terminal voltage difference is at its maximum, that is, the transient output voltage of the m-th three-phase uncontrolled rectifier bridge is...

[0013] v DCm (t)=max{v am (t),v bm (t),v cm (t)}-min{v am (t),v bm (t),v cm (t)},

[0014] Where 1≤m≤M, v am (t),v bm (t),v cm (t) represents the three-phase voltage, and max and min represent the maximum and minimum values, respectively. For a p-pulse TRU, its transient output voltage is v. DC (t)=max{v DC1 (t),v DC2 (t),…,v DCm (t),…,v DCM (t)}; Divide the output voltage into p intervals according to the pulse wave to obtain the corresponding phase relationship between the conduction diode interval and the TRU output voltage waveform;

[0015] Step 2: Obtain the average minimum value of the TRU output voltage over one electrical cycle when the system is in a healthy state. and global maximum value Calculate the ratio R between the two. ref As a benchmark for health, the specific values ​​are as follows:

[0016] 2a. Determine the electrical period The sampling start position is selected as (θ0+2nπ), where n=0,1,2,…;

[0017] 2b. Sample the pulsating DC voltage output by the TRU to obtain a sampling sequence;

[0018] v DC ={v DC (1),v DC (2),…,v DC (N)}

[0019] Where N is the number of waveform sampling points in one electrical cycle, v DC (·) represents the value corresponding to each sampling point, thus obtaining the number of sampling points for each interval. The k-th interval sequence is represented as:

[0020]

[0021] 2c. Compare each value in the k-th interval sequence pairwise to obtain the minimum value of the interval. and global maximum value

[0022] 2d. Minimum values ​​for these p intervals Find the average and obtain the minimum average value.

[0023]

[0024] 2f. Calculate the ratio of the average minimum to the global maximum. As a benchmark for health;

[0025] Step 3: For the TRU in an unknown state, follow steps 2a to 2d to obtain the average minimum value of the output voltage over p intervals in the unknown state. and global maximum value

[0026] Step 4: Calculate separately and ratio With R ref By comparison, we obtain the Boolean function S. k Specifically, if R' k <R ref ±R th S k =1; otherwise, S k =0; Considering sampling error and calculation error, assume R = 0; th The preset value is near zero;

[0027] Step 5: According to S k The value determines whether a diode open-circuit fault has occurred in the TRU, and there are three cases:

[0028] (1) If S k If all values ​​are 0, then the TRU is fault-free;

[0029] (2) If S k and S k+M or S k and S k-M If both are 1, then the TRU experiences a diode open-circuit fault;

[0030] (3) If any of the above conditions are not met, collect the transient output voltage of TRU within one cycle starting at the next moment (θ0+(2n+1)π), and repeat steps 3 and 4 until any of the above conditions (1) and (2) are met.

[0031] Step 6: Based on the phase relationship between the conduction diode interval obtained in Step 1 and the TRU output voltage waveform, and S in Step 5... k The value of determines the location of the faulty diode.

[0032] Furthermore, the electrical parameters of the TRU mentioned in step 1, as well as the corresponding phase relationship between the diode conduction interval and the TRU output voltage determined by the working principle, are set according to the actual application.

[0033] Furthermore, the health benchmark value R mentioned in step 4 ref The theoretical value is sin75°≈0.966, with a preset near-zero value R. th The value ranges from 0.005 to 0.01, and should be set according to the actual application.

[0034] Furthermore, in step 5, if there is no fault, the fault location in step 6 is not performed; if there is a fault, step 6 is performed to locate the fault.

[0035] The beneficial effects of this invention are as follows: To effectively address the problem of open-circuit faults in aircraft transformer rectifier diodes due to long-term stress and the difficulty in timely and effective diagnosis, this invention proposes a method for detecting and locating open-circuit faults in aircraft transformer rectifier diodes. By analyzing the impact of diode open-circuit faults on the transient output voltage of the TRU, a correspondence between diode conduction and the minimum value of the output voltage range is established. By comparing the ratio of the minimum to the average maximum value of the TRU output voltage range in the unknown state with the ratio of the average minimum to the average maximum value in the healthy state, it is determined whether an open-circuit fault has occurred in the diode and the location of the faulty diode is accurately determined. Compared with existing aircraft transformer rectifier fault diagnosis methods, the method proposed in this invention requires only two sensors: one to measure the TRU output voltage and the other to measure the phase a voltage of the primary winding of the phase-shifting transformer to ensure phase synchronization. Furthermore, this method has good real-time performance, capable of detecting and accurately locating diode open-circuit faults within one electrical cycle, meeting the needs of aircraft secondary power systems for simple, easy, and rapid fault diagnosis. Attached Figure Description

[0036] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of a parallel structure of a transformer rectifier.

[0038] Figure 2This is a schematic diagram of a typical 12-pulse transformer rectifier.

[0039] Figure 3 This is the voltage phasor diagram of the phase-shifting transformer in a typical 12-pulse transformer-rectifier.

[0040] Figure 4 A schematic diagram of the transient waveform of the TRU output voltage when it is in a healthy state.

[0041] Figure 5 This is a schematic diagram of the instantaneous waveform of the TRU output voltage when D11 in rectifier bridge 1 is open.

[0042] Figure 6 This is a schematic diagram of the instantaneous waveform of the TRU output voltage when D21 in rectifier bridge 2 is open.

[0043] Figure 7 S caused by the fault k The relationship between the range of change and the location of the faulty diode. Detailed Implementation

[0044] The following description, in conjunction with the accompanying drawings, illustrates exemplary embodiments of this application, including various details to aid understanding. These should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and 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.

[0045] Considering the size, weight, cost, and stability of magnetic components in aerospace transformer rectifiers, 12-pulse transformer rectifiers are more widely used in the aerospace field. Therefore, this embodiment uses a 12-pulse transformer rectifier as an example, and further explains the invention with reference to the accompanying drawings.

[0046] In this embodiment, as Figure 2 As shown, the 12-pulse transformer rectifier rectifies the three-phase 115V / 400Hz AC power into 28V DC power. The input voltage of phase a is expressed as... The initial phase is θ0 = 0°, and the effective value is V. rms =115V, ω=2πf AC f AC =400Hz. The voltages of phases b and c lag and lead phase a by 120° respectively, expressed as: The phase-shifting transformer windings adopt the Yy0d11 connection method, meaning the primary winding is connected in a star configuration, and the secondary windings are connected to rectifier bridges 1 and 2 using both star and delta connections. The voltage phasor v of the secondary star connection... a1 v b1 v c1 With the primary voltage phasor va v b v c In phase, voltage phasors v with secondary side delta connection a2 v b2 v c2 The phasor is 30° ahead of the primary phasor, and the phasor relationship diagram is as follows. Figure 3 As shown. Therefore, the secondary voltage phasor of the phase-shifting transformer is expressed as:

[0047]

[0048]

[0049] Where n1, n2, and n3 are the number of turns in the primary and secondary windings of the phase-shifting transformer, respectively. To ensure that the output voltage amplitudes of rectifier bridges 1 and 2 are equal, the following conditions must be met: When analyzing the health status of the TRU, the transient output voltages of rectifier bridges 1 and 2 are expressed as follows:

[0050]

[0051] At this time, the TRU output voltage v DC (t)=max{v DC1 (t),v DC2 (t)}. The TRU output voltage waveform within one cycle is as follows: Figure 4 As shown, it is divided into 12 intervals, and the correspondence between the TRU output waveform and the conducting diode is analyzed.

[0052] The sampling frequency is set to 1MHz, the sampling start position is determined by a single-phase PLL, the number of sampling points N = 2500 within one cycle (2.5ms), and the number of sampling points in each interval is N. int ≈208. In a healthy state, the average of the unique minimum values ​​in each interval is taken, and this average is compared to the global maximum value to obtain the health baseline value R. ref =sin75°≈0.966. When a diode has an open-circuit fault, the conduction time of the diode that was conducting in the previous moment will increase until the next diode conducts, which will cause a change in the minimum value of the TRU output voltage range. Taking D11 in rectifier bridge 1 and D21 in rectifier bridge 2 as examples, the corresponding TRU transient output voltages are as follows: Figure 5 and Figure 6 As shown. When D11 is open, the minimum values ​​of intervals 3 and 5 decrease compared to the healthy state, and the ratio of this minimum value to the global maximum value is R'3 = R'5 = sin60° ≈ 0.866. <R ref The value is less than the healthy baseline. When D21 is open, the minimum values ​​of intervals 2 and 4 decrease compared to the healthy state, and the ratio of this minimum value to the global maximum value is R'2 = R'4 = sin60° ≈ 0.866. <R refIt is lower than the health benchmark value.

[0053] Conversely, for a 12-pulse transformer-rectifier in an unknown state, similarly, the ratio of the minimum value to the global maximum value of the TRU output voltage in each interval is obtained, along with R. ref By comparison, we obtain the Boolean function S. k If R' k <R ref ±R th S k =1; otherwise, S k =0; where R th To preset near-zero values, the range here is 0.005 to 0.01. This yields the Boolean sequence {S1, S2, S3, S4, S5, S6, S7, S8, S9, S...}. 10 S 11 S 12},Depend on Figure 6 The interval Boolean function value shown is related to S k The corresponding relationship is used to realize the fault diode.

[0054] If S k If all values ​​are 0, then the TRU is fault-free;

[0055] If S k and S k+M If both values ​​are 1, then there are 12 possible scenarios for an open-circuit fault in a single diode in the TRU rectifier bridge, such as... Figure 6 As shown. If any two cases are combined, the corresponding two diodes will be open simultaneously; if any three cases are combined, the corresponding three diodes will be open simultaneously, and so on.

[0056] It should be noted that this method can provide correct diagnostic and positioning results in embodiments with different loads and operating conditions, but it is necessary to ensure that the rectifier bridge operates in continuous conduction mode. Furthermore, this invention has different variations in other aviation transformer rectifiers, all of which do not depart from the scope of this invention.

[0057] 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. A method for detecting and locating open-circuit faults in the TRU diode of an aircraft transformer rectifier, characterized in that... The steps are as follows: Step 1: Determine the TRU electrical parameters, including pulse number p and sampling frequency f. s Input voltage frequency f AC The phase information of input voltage phase A is used to analyze the correspondence between diode conduction and the transient output voltage waveform of the TRU, as detailed below: 1a. In the TRU structure, one three-phase uncontrolled rectifier bridge corresponds to 6 pulses, and M three-phase uncontrolled rectifier bridges are connected in parallel to form a p=6M pulse TRU; 1b.TRU's f AC =360~800Hz, according to the Nyquist–Shannon sampling theorem, determine the sampling frequency f. s ≥2·p·f AC ; 1c. A single-phase phase-locked loop circuit obtains the initial phase information θ0 of the input voltage phase A; 1d. For a given TRU, adhering to the principle that conduction occurs when the diode terminal voltage difference is at its maximum, that is, the transient output voltage of the m-th three-phase uncontrolled rectifier bridge is... v DCm (t)=max{v am (t),v bm (t),v cm (t)}-min{v am (t),v bm (t),v cm (t)}, Where 1≤m≤M, v am (t),v bm (t),v cm (t) represents the three-phase voltage, and max and min represent the maximum and minimum values, respectively. For a p-pulse TRU, its transient output voltage is v. DC (t)=max{v DC1 (t),v DC2 (t),…,v DCm (t),…,v DCM (t)}; Divide the output voltage into p equal intervals according to the pulse wave to obtain the corresponding phase relationship between the conduction diode interval and the transient output voltage waveform of TRU; Step 2: Obtain the average minimum value of the TRU output voltage over one electrical cycle when the system is in a healthy state. and global maximum value Calculate the ratio R between the two. ref As a benchmark for health, the specific values ​​are as follows: 2a. Determine the electrical period The sampling start position is selected as (θ0+2nπ), where n=0,1,2,…; 2b. Sample the pulsating DC voltage output by the TRU to obtain a sampling sequence; v DC ={v DC (1),v DC (2),…,v DC (N)} Where N is the number of waveform sampling points in one electrical cycle, v DC (·) represents the value corresponding to each sampling point, thus obtaining the number of sampling points for each interval. The k-th interval sequence is represented as: 2c. Compare each value in the k-th interval sequence pairwise to obtain the minimum value of the interval. and global maximum value 2d. Minimum values ​​for these p intervals Find the average and obtain the minimum average value. 2e. Calculate the ratio of the average minimum to the global maximum. As a benchmark for health; Step 3: For the TRU in an unknown state, follow steps 2a to 2d to obtain the average minimum value of the output voltage over p intervals in the unknown state. and global maximum value Step 4: Calculate separately and ratio With R ref By comparison, we obtain the Boolean function S. k Specifically, if R ′ k <R ref ±R th S k =1; otherwise, S k =0; Considering sampling error and calculation error, assume R = 0; th The preset value is near zero; Step 5: According to S k The value determines whether a diode open-circuit fault has occurred in the TRU, and there are three cases: (1) If S k If all values ​​are 0, then the TRU is fault-free; (2) If S k and S k+M or S k and S k-M If both are 1, then the TRU experiences a diode open-circuit fault; (3) If any of the above conditions are not met, collect the transient output voltage of TRU within one cycle starting at the next moment (θ0+(2n+1)π), and repeat steps 3 and 4 until any of the above conditions (1) and (2) are met. Step 6: Based on the phase relationship between the conduction diode interval obtained in Step 1 and the transient output voltage waveform of the TRU, and S in Step 5... k The value of determines the location of the faulty diode.

2. The method for detecting and locating open-circuit faults in the TRU diode of an aviation transformer rectifier according to claim 1, characterized in that, The electrical parameters of the TRU mentioned in step 1, as well as the corresponding phase relationship between the conduction diode interval determined by the working principle and the transient output voltage waveform of the TRU, are set according to the actual application.

3. The method for detecting and locating open-circuit faults in the TRU diode of an aviation transformer rectifier according to claim 1, characterized in that, The health baseline value R mentioned in step 4 ref The theoretical value is sin75°≈0.966, with a preset near-zero value R. th The value ranges from 0.005 to 0.01, and should be set according to the actual application.

4. The method for detecting and locating open-circuit faults in the TRU diode of an aviation transformer rectifier according to claim 1, characterized in that, If there is no fault in step 5, then the fault location in step 6 will not be performed; if there is a fault, then step 6 will be performed to locate the fault.

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