Autotransformer Rectifier Units Research Articles

Open-Circuit Fault Research on Asymmetric Delta-Polygon 18-Pulse Autotransformer Rectifier Unit for More Electric Aircraft

In aviation aircraft, autotransformer rectifier units (ATRUs) have been widely used as front-end rectifiers. The comprehensive analysis of its operating characteristics under the fault is beneficial to assessing the hazards of the faults and developing a fault diagnosis scheme. This article investigates two types of open-circuit (OC) faults in delta-polygon 18-pulse ATRU, namely, diode OC fault and input OC fault. First, the effects of the diode OC fault on five aspects are quantitatively analyzed: diode conduction angle, output voltage ripple, winding current, input current harmonics, and diode and transformer winding losses. Next, the operating characteristics of ATRU are investigated under input OC fault, and the quantitative effects of the five aspects above are also calculated. Then, based on the affected intervals of dc output voltage, a fault diagnosis idea dealing with two types of OC faults is discussed. Meanwhile, the predictive maintenance objects after the fault location are also summarized. Finally, the simulation and experimental results validate the theoretical analysis and discussion. This work is very significant for guiding the fault detection, fault location, and predictive maintenance of ATRUs.

Two-level fault diagnosis RBF networks for auto-transformer rectifier units using multi-source features

The auto-transformer rectifier unit (ATRU) is one of the most widely used avionic secondary power supplies. Timely fault identification and location of the ATRU is significant in terms of system reliability. A two-level fault diagnosis method for the ATRU using multi-source features (MSF) is proposed in this paper. Based on the topology of the ATRU, three key electrical signals are selected and analyzed to extract appropriate features for fault diagnosis. Mathematic expressions and simulation results of the feature signals under different fault modes are presented in the paper. Therefore, a unique MSF system is developed and a two-level fault diagnosis method based on radial basis function network groups is proposed. On the first level, the overall fault set is classified into three subsets and then on the second level, three radial basis function neural networks are constructed and trained to realize accurate fault localization. To verify the diagnosis performance of the proposed method, several comparative tests are implemented on a 12-pulse ATRU system, which shows that this method has a lower computational cost, better diagnostic accuracy and increased stability when compared with alternative methods.

Investigation on the Selection and Design of Step-Up/Down 18-Pulse ATRUs for More Electric Aircrafts

Multi-pulse autotransformer rectifier units (ATRUs) have been widely used in aviation applications due to their rugged structure, cost-effectiveness, and high-reliability features. In this paper, up to six types of autotransformers for an 18-pulse ATRU are investigated, aiming to provide an optimal selection guideline for a proper structure. By conducting a thorough comparative study on the kilovoltampere (kVA) rating of the autotransformers and the current harmonic characteristics over a wide voltage step-up or step-down range, the asymmetric delta–polygon (DP) structure is considered as the most promising choice. Subsequently, an example 18-pulse ATRU with such structure is adopted as the front end of an alternative current (ac)/ac converter powering an onboard hydraulic pump. After analyzing the operational principle, accurate mathematical expressions among the overall voltage gain $K$ , the total harmonic distortion (THD) of the line current, and the kVA rating of the autotransformer were carefully deduced. Before conclusions, the theoretical analyses were verified by simulations and experiments. It is shown that the THD of the input line current of the designed 10-kW ATRU is 6.74%, the rated efficiency reaches 98.5%, and the autotransformer’s weight is merely 3.3 kg.

Design and Implementation of 12 Pulse AC to DC Converter in Aircraft for Aerospace Applications

Aircraft applications like landing gears, flaps, rudder systems and etc. use actuator systems which includes combination of motor, actuators and auto transformer rectifier units (ATRU). These systems work at a frequency of 400Hz. These are AC to DC converters used in aircraft's system to supply constant DC power to the motors which in turn operates actuators. These converters varies with the pulses like 12 pulse, 24 pulse etc. For the systems like this harmonics too play a major role. Less the harmonics more efficient and reliable the system will be. In this paper, a 12 pulse AC to DC converter was designed for 400Hz and 50Hz and the actual model was built for 50Hz of 1KW power. The design of 400Hz and 50Hz was done in MATLAB/Simulink and the prototype was built for 50Hz. Total harmonic distortion (THD) was obtained and compared for the two systems. All the results the simulation and the prototype are shown in this paper.

Progressive Improved Convolutional Neural Network for Avionics Fault Diagnosis

Among deep learning methods, convolutional neural networks (CNNs) are able to extract features automatically and have increasingly been used in intelligent fault diagnosis studies. However, studies seldomly concentrate on the weakness associated with a highly imbalanced distribution of fault types due to different failure rates and when multiple faults are easily confused with single faults. To solve these problems, this paper developed a stochastic discrete-time series deep convolutional neural network (SDCNN) method based on random oversampling along with a progressive method with multiple SDCNNs to improve the diagnosis performance. To assess the developed method, datasets from three avionics 24-pulse auto-transformer rectifier units (ATRUs), which are secondary electric power supplies in aircraft, were analyzed and compared with other CNN methods.

Comparative Analysis of 18-Pulse Autotransformer Rectifier Unit Topologies with Intrinsic Harmonic Current Cancellation

With the evolution of the More Electric Aircraft (MEA) concept, high pulse converters have gained the attention of researchers due to their higher power quality. Among the high pulse converters, 18-pulse autotransformer rectifier unit (ATRU) offers better power quality level with small size, weight and medium complexity. The conventional topologies of autotransformers that require the use of extra elements such as Inter Phase Transformers (IPT) or Zero Sequence Blocking Transformers (ZSBT), adding to the complexity, weight and size of the overall system, are not considered in the analysis. For 18-pulse rectification, only those topologies of autotransformers which have the intrinsic current harmonic cancellation capabilities are presented here for comparison. These topologies offer current harmonic levels within limits specified by IEEE 519 with reduced weight and size as compared to the conventional multi-pulse converters. A comparison of different differential delta/fork configured 18-pulse autotransformer rectifier units is presented so as to come up with the best among available topologies with respect to weight, size and power quality. Experimental prototypes of each topology were designed and their results are displayed along with the simulation results for comparison.

Generic functional modelling of multi-pulse auto-transformer rectifier units for more-electric aircraft applications

The Auto-Transformer Rectifier Unit (ATRU) is one preferred solution for high-power AC/DC power conversion in aircraft. This is mainly due to its simple structure, high reliability and reduced kVA ratings. Indeed, the ATRU has become a preferred AC/DC solution to supply power to the electric environment control system on-board future aircraft. In this paper, a general modelling method for ATRUs is introduced. The developed model is based on the fact that the DC voltage and current are strongly related to the voltage and current vectors at the AC terminals of ATRUs. In this paper, we carry on our research in modelling symmetric 18-pulse ATRUs and develop a generic modelling technique. The developed generic model can study not only symmetric but also asymmetric ATRUs. An 18-pulse asymmetric ATRU is used to demonstrate the accuracy and efficiency of the developed model by comparing with corresponding detailed switching SABER models provided by our industrial partner. The functional models also allow accelerated and accurate simulations and thus enable whole-scale more-electric aircraft electrical power system studies in the future.

Methods for building ATRU real‐time model based on different application scenarios

This study introduces three methods for building an auto-transformer rectifier units (ATRU) real-time model based on different application scenarios. Real-time models run on an advanced real-time simulator that has the capability to leverage central processing units and field programming gate arrays. In the first section, the disadvantages of the off-line simulation are explained and the solution is offered through real-time simulation. In the second section, applications of real-time simulation in a more electric aircraft (MEA) electric power system will be presented. In the third section, methods to build the ATRU real-time model are illustrated based on requirements and different scenarios. Simulations are conducted to demonstrate the agreement between the results and analysis.

Functional Modeling of Symmetrical Multipulse Autotransformer Rectifier Units for Aerospace Applications

This paper aims to develop a functional model of symmetrical multipulse autotransformer rectifier units (ATRUs) for more-electric aircraft (MEA) applications. The ATRU is seen as the most reliable way readily to be applied in the MEA. Interestingly, there is no model of ATRUs suitable for unbalanced or faulty conditions at the moment. This paper is aimed to fill this gap and develop functional models suitable for both balanced and unbalanced conditions. Using the fact that the dc voltage and current are strongly related to the voltage and current vectors at the ac terminals of ATRUs, a functional model has been developed for the asymmetric ATRUs. The developed functional models are validated through simulation and experiment. The efficiency of the developed model is also demonstrated by comparing with corresponding detailed switching models. The developed functional model shows significant improvement of simulation efficiency, especially under balanced conditions.