Aviation transformer rectifier diode open-circuit fault detection and positioning method

Abstract

The invention discloses an aviation transformer rectifier diode (TRU) open-circuit fault detection and positioning method, which can effectively solve the problems that an aviation transformer rectifier diode is easily subjected to open-circuit fault due to long-term stress influence and is difficult to timely and effectively detect and position. The method comprises the following steps: firstly, analyzing a TRU working principle to obtain a corresponding phase relation between a diode conduction interval and transient output voltage; the method comprises the following steps: acquiring transient output voltage in a next electric period in a healthy state, equally dividing the transient output voltage into p intervals according to a diode conduction interval, calculating an interval minimum value, averaging to obtain an average minimum value, and taking a ratio of the average minimum value to a global maximum value as a healthy reference value Rref; and for the TRU in an unknown state, calculating the ratio of the interval minimum value to the global maximum value in an electric period, comparing the ratio with the Rref, and judging whether the diode has an open-circuit fault or not. And if so, determining the position of the fault diode according to the corresponding phase relation between the diode conduction interval and the TRU transient output voltage. The method provided by the invention is simple and easy to implement, needs few signals, has good detection real-time performance, and is beneficial to finding and quickly deciding the open-circuit fault of the transformer rectifier diode as early as possible and maintaining the safe operation of an aviation secondary power supply system.

Description

Technical Field

[0001] The present invention belongs to the technical field of fault diagnosis of aviation secondary power supply systems, and specifically relates to a method for judging and locating the type of diode open circuit fault in an aviation transformer rectifier. The present invention is a method for performing transient analysis on the output voltage of the transformer rectifier, combining input electrical phase information and the winding configuration of a phase-shifting transformer, to judge the type of diode fault and achieve positioning. Background Art

[0002] The Transformer Rectifier Unit (TRU) is one of the main components of the current aircraft secondary power system due to its simple structure, high power factor, good stability, and strong overload capacity. It converts 115V / 360-800Hz AC power into 28V low-voltage DC power to power onboard equipment. Figure 1 As shown, the TRU consists of a phase-shifting transformer, m groups of three-phase uncontrolled rectifier bridges connected in parallel, and a filter link. In order to achieve that the TRU output voltage can pulsate p times in one electrical cycle, different connection methods are configured for the primary / secondary windings of the phase-shifting transformer so that the voltage phases of the m groups of secondary windings are staggered by 2π / p.

[0003] As the main component of TRU, diodes are susceptible to factors such as temperature, mechanical and electrical stress, resulting in open circuit (OC) or short circuit (SC) failures, which can reduce the power quality of TRU or even cause abnormal shutdown. Among them, SC failures can cause overcurrent, which is easy to detect and isolate through fuses. OC failures are difficult to diagnose in an early and timely manner because they do not reach a large overvoltage or overcurrent amplitude. In particular, when a small number of diodes are open, the system will still run "with the disease". In this case, healthy diodes will be subjected to greater electrical stress, further exacerbating the risk of open circuits, posing a potential huge threat to system safety. Therefore, accurate, efficient and timely diagnosis of diode OC failures in aviation transformer rectifiers is of great significance.

[0004] For the diode open circuit in the transformer rectifier, the industry mostly adopts the method of regular replacement or one-by-one inspection. This method consumes huge manpower and material resources, is high in cost and low in reliability, and is no longer suitable for transformer rectifiers with a large number of pulses. Considering that the diode open circuit in the rectifier bridge directly affects its output voltage, the academic community mostly uses frequency domain and time-frequency domain methods combined with intelligent algorithms for fault diagnosis, but this type of method can only determine whether the transformer rectifier diode is faulty or not, and cannot determine the location of the faulty diode. In addition, efficient intelligent algorithms require sufficient historical fault data and a large amount of computer resources for algorithm training, and at least one cycle is required to process the data and then make decisions, which cannot well meet the real-time requirements of transformer rectifier fault diagnosis in the aviation field. Simple and efficient fault diagnosis methods that do not rely too much on historical data and intelligent algorithms still need to start from the fault mechanism itself, realize the rapid diagnosis and autonomous maintenance of the transformer rectifier diode open circuit, and have practical value for improving the safety of aircraft operation. Therefore, this patent proposes a method for detecting and locating the open circuit fault of the aviation transformer rectifier diode, which is simple to implement, has strong theoretical explainability, and has high real-time performance. Summary of the invention

[0005] The purpose of the present invention is to realize rapid diagnosis and accurate positioning of aviation transformer rectifier diode (TRU) open-circuit faults. The present invention proposes a diode open-circuit fault diagnosis method based on the transient characteristics of the transformer rectifier output voltage, and can realize the positioning of the faulty diode in combination with the input voltage phase and the phase-shifting transformer winding configuration.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides an aviation transformer rectifier diode (TRU) open circuit fault detection and location strategy, and the specific invention content is as follows:

[0008] Step 1: Determine the TRU electrical parameters, including the pulse number p and sampling frequency f s , input voltage frequency f AC , input voltage A phase information, analyze the corresponding relationship between diode conduction and TRU transient output voltage waveform, as follows:

[0009] 1a. In the TRU structure, a 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 f AC =360~800Hz, according to Nyquist–Shannon sampling theorem, determine the sampling frequency f s ≥2·p·f AC ;

[0011] 1c. Single-phase phase-locked loop circuit obtains the initial phase information of input voltage phase a θ 0 ;

[0012] 1d. For a certain TRU, adhering to the principle of conducting when the voltage difference between the diode terminals is the largest, the transient output voltage of the mth 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) corresponds to the three-phase voltage, max and min are the maximum and minimum values ​​respectively. For 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, and obtain the corresponding phase relationship between the diode conduction interval and the TRU output voltage waveform;

[0015] Step 2: Obtain the average minimum value of the TRU output voltage within one electrical cycle when in a healthy state and the global maximum Calculate the ratio R of the two ref The health benchmark values ​​are as follows:

[0016] 2a. Determine the electrical cycle Select the sampling starting position as (θ 0 +2nπ), where n=0,1,2,…;

[0017] 2b. Sampling 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 (·) is the value corresponding to each sampling point, so the number of sampling points in each interval is The kth interval sequence is expressed as:

[0020]

[0021] 2c. Compare the values ​​in the kth interval sequence pairwise to obtain the minimum value of the interval and the global maximum

[0022] 2d. Minimum value of these p intervals Find the average and get the average minimum value

[0023]

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

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

[0026] Step 4: Calculate separately and Ratio With R ref By comparison, we get 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, assuming R th To preset near zero value;

[0027] Step 5: According to S k The value of determines whether the TRU has a diode open circuit fault, which is divided into three cases:

[0028] (1) If S k If both are 0, the TRU has no fault;

[0029] (2) If S k and S k+M or S k and S k-M If both are 1 at the same time, a diode open circuit fault occurs in the TRU;

[0030] (3) If none of the above conditions are met, collect the next moment (θ 0+(2n+1)π), 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 TRU electrical parameters in step 1, and the corresponding phase relationship between the diode conduction interval determined by the working principle and the TRU output voltage are set according to the actual application object.

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

[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 achieve fault location.

[0035] Beneficial effects of the present invention: In order to effectively solve the problem that the aviation transformer rectifier diode is prone to open circuit failure due to long-term stress and is difficult to diagnose in a timely and effective manner, the present invention proposes a method for detecting and locating the open circuit failure of the aviation transformer rectifier diode. By analyzing the impact of the diode open circuit failure on the transient output voltage of the TRU, the corresponding relationship between the diode conduction and the minimum value of the output voltage interval is constructed, and the ratio of the minimum value to the average maximum value of the TRU output voltage interval in the unknown state is compared with the ratio of the average minimum value to the average maximum value in the healthy state, to determine whether the diode has an open circuit failure and accurately locate the location of the faulty diode. Compared with the existing aviation transformer rectifier fault diagnosis method, the method proposed by the present invention only requires 2 sensors, one to measure the TRU output voltage, and the other to measure the a-phase voltage of the primary winding of the phase-shifting transformer to ensure phase synchronization. At the same time, the method has good real-time performance and can detect whether a diode open circuit failure occurs and accurately locate it within one electrical cycle, meeting the requirements of the aircraft secondary power supply system for simple and easy fault diagnosis and quick decision-making. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 Schematic diagram of the transformer-rectifier parallel structure.

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

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

[0040] Figure 4 Schematic diagram of the transient waveform of TRU output voltage when in healthy state.

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

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

[0043] Figure 7 S caused by the fault k The change interval corresponds to the position of the faulty diode. DETAILED DESCRIPTION

[0044] The following is a description of exemplary embodiments of the present application in conjunction with the accompanying drawings, including various details of the embodiments of the present application to facilitate understanding, which should be considered as merely exemplary. Therefore, it should be recognized by those of ordinary skill in the art that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. Similarly, for the sake of clarity and conciseness, the description of well-known functions and structures is omitted in the following description.

[0045] Considering the size, weight, cost and stability of magnetic components in aviation transformer rectifiers, 12-pulse transformer rectifiers are more widely used in the aviation field. Therefore, this embodiment takes the 12-pulse transformer rectifier as an example and further describes the present invention in conjunction with the accompanying drawings.

[0046] In this embodiment, Figure 2 As shown in the figure, the 12-pulse transformer rectifier rectifies the three-phase 115V / 400Hz AC into 28V DC. The a-phase input voltage is expressed as The initial phase is θ 0 =0°, effective value 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 winding adopts the Yy0d11 connection method, that is, the primary winding adopts star connection, and the secondary winding adopts star and triangle connection methods to connect to rectifier bridges 1 and 2 respectively. The voltage phasor v of the secondary star connection a1 、v b1 、v c1 The primary voltage phasor v a 、v b 、v c In phase, secondary triangle connected voltage phasor v a2 、v b2 、v c2 Leading the primary phase by 30°, the phase relationship diagram is as follows Figure 3 Therefore, the secondary voltage phasor of the phase-shifting transformer is expressed as:

[0047]

[0048]

[0049] Among them, n 1 、n 2 、n 3 are the turns of the primary and secondary windings of the phase-shifting transformer respectively. In order to make the output voltage amplitudes of rectifier bridges 1 and 2 equal, it is necessary to satisfy When analyzing the health status of the TRU, the transient output voltage of rectifier bridges 1 and 2 is expressed as:

[0050]

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

[0052] The sampling frequency is set to 1MHz, the sampling start position is determined by the single-phase PLL, the number of sampling points in one cycle (2.5ms) is N=2500, and the number of sampling points in each interval is N int ≈208. In the healthy state, the unique minimum values ​​of each interval are averaged and compared with the global maximum value to obtain the health benchmark value R ref = sin75°≈0.966. When a diode fails to open, the conduction time of the diode that was turned on at the last moment will increase until the next diode turns on, which will cause the minimum value of the TRU output voltage interval to change. Taking D11 in rectifier bridge 1 and D21 in rectifier bridge 2 as an example, the corresponding TRU transient output voltage is as follows: Figure 5 and Figure 6 When D11 is open, the minimum values ​​of intervals 3 and 5 decrease compared to the healthy state, and the ratio to the global maximum value is R' 3 =R' 5 =sin60°≈0.866 <R ref , which is less than the healthy reference value. When D21 is open, the minimum values ​​of intervals 2 and 4 decrease compared with the healthy state, and the ratio to the global maximum value is R' 2 =R' 4 =sin60°≈0.866 <R ref , which is lower than the health benchmark value.

[0053] Conversely, for the 12-pulse transformer-rectifier in an unknown state, similarly, the ratio of the minimum value of each interval of TRU output voltage to the global maximum value is obtained, and R ref By comparison, we get the Boolean function S k If R' k <R ref ±R th , S k =1; otherwise, S k =0; where R th To preset a near-zero value, the value range here is 0.005 to 0.01. Thus, the Boolean sequence {S 1 , S 2 , S 3 , S 4 , S 5 , S 6 , S 7 , S 8 , S 9 , S 10 , S 11 , S 12},Depend on Figure 6 The interval Boolean function value shown is related to S k The corresponding relationship realizes the faulty diode.

[0054] If S k If both are 0, the TRU has no fault;

[0055] If S k and S k+M If both are 1 at the same time, a single diode in the TRU rectifier bridge is open-circuited. There are 12 situations, such as Figure 6 If any two situations are combined, the corresponding two diodes are open at the same time. If any three situations are combined, the corresponding three diodes are open at the same time, and so on.

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

[0057] The above specific implementations do not constitute a limitation on the protection scope of this application. It should be understood by those skilled in the art 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 in the protection scope of this application.

Claims

1. Aviation transformer rectifier (TRU) diode open circuit fault detection and location method, characterized in that Here are the steps: Step 1: Determine the TRU electrical parameters, including the pulse number p and sampling frequency f s , input voltage frequency f AC , input voltage A phase information, analyze the corresponding relationship between diode conduction and TRU transient output voltage waveform, as follows: 1a. In the TRU structure, a 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 f AC =360~800Hz, according to Nyquist-Shannon sampling theorem, determine the sampling frequency f s ≥2·p·f AC ; 1c. The single-phase phase-locked loop circuit obtains the initial phase information θ0 of the input voltage phase a; 1d. For a certain TRU, adhering to the principle of conducting when the voltage difference between the diode terminals is the largest, that is, the transient output voltage of the mth 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) corresponds to the three-phase voltage, max and min are the maximum and minimum values ​​respectively. For 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, and obtain the corresponding phase relationship between the diode conduction interval and the TRU output voltage waveform; Step 2: Obtain the average minimum value of the TRU output voltage within one electrical cycle when in a healthy state and the global maximum Calculate the ratio R of the two ref The health benchmark values ​​are as follows: 2a. Determine the electrical cycle The sampling starting position is selected as (θ0+2nπ), where n=0, 1, 2, ...; 2b. Sampling 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 (·) is the value corresponding to each sampling point, so the number of sampling points in each interval is The kth interval sequence is expressed as: 2c. Compare the values ​​in the kth interval sequence pairwise to obtain the minimum value of the interval and the global maximum 2d. Minimum value of these p intervals Find the average and get the average minimum value 2f. Calculate the ratio of the average minimum value to the global maximum value As a health benchmark value; Step 3: For the TRU in the unknown state, follow steps 2a to 2d to obtain the average minimum value of the output voltage in p intervals in the unknown state. and the global maximum Step 4: Calculate separately and Ratio Compared with Rref, we get 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, assuming R th To preset near zero value; Step 5: According to S k The value of determines whether the TRU has a diode open circuit fault, which can be divided into three cases: (1) If S k If both are 0, the TRU has no fault; (2) If S k and S k+M or S k and S k-M If both are 1 at the same time, a diode open circuit fault occurs in the TRU; (3) If none of the above conditions are met, collect the TRU transient output voltage within a period starting from 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 TRU output voltage waveform and S in step 5 k The value of determines the location of the faulty diode.

2. The method for detecting and locating an open-circuit fault of a diode in an aviation transformer rectifier (TRU) according to claim 1, characterized in that: The TRU electrical parameters described in step 1, and the corresponding phase relationship between the diode conduction interval determined by the working principle and the TRU output voltage are set according to the actual application object.

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

4. The method for detecting and locating an open-circuit fault of a diode in an aviation transformer rectifier (TRU) according to claim 1, characterized in that: 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 achieve fault location.

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