A novel multi-resolution network for the open-circuit faults diagnosis of automatic ramming drive system

The open-circuit fault is one of the most common faults of the automatic ramming drive system(ARDS),and it can be categorized into the open-phase faults of Permanent Magnet Synchronous Motor(PMSM)and the open-circuit faults of Voltage Source Inverter(VSI). The stator current serves as a common indicator for detecting open-circuit faults. Due to the identical changes of the stator current between the open-phase faults in the PMSM and failures of double switches within the same leg of the VSI, this paper utilizes the zero-sequence voltage component as an additional diagnostic criterion to differentiate them.Considering the variable conditions and substantial noise of the ARDS, a novel Multi-resolution Network(Mr Net) is proposed, which can extract multi-resolution perceptual information and enhance robustness to the noise. Meanwhile, a feature weighted layer is introduced to allocate higher weights to characteristics situated near the feature frequency. Both simulation and experiment results validate that the proposed fault diagnosis method can diagnose 25 types of open-circuit faults and achieve more than98.28% diagnostic accuracy. In addition, the experiment results also demonstrate that Mr Net has the capability of diagnosing the fault types accurately under the interference of noise signals(Laplace noise and Gaussian noise).

Deep neural network-enabled battery open-circuit voltage estimation based on partial charging data

Battery management systems(BMSs) play a vital role in ensuring efficient and reliable operations of lithium-ion batteries.The main function of the BMSs is to estimate battery states and diagnose battery health using battery open-circuit voltage(OCV).However,acquiring the complete OCV data online can be a challenging endeavor due to the time-consuming measurement process or the need for specific operating conditions required by OCV estimation models.In addressing these concerns,this study introduces a deep neural network-combined framework for accurate and robust OCV estimation,utilizing partial daily charging data.We incorporate a generative deep learning model to extract aging-related features from data and generate high-fidelity OCV curves.Correlation analysis is employed to identify the optimal partial charging data,optimizing the OCV estimation precision while preserving exceptional flexibility.The validation results,using data from nickel-cobalt-magnesium(NCM) batteries,illustrate the accurate estimation of the complete OCV-capacity curve,with an average root mean square errors(RMSE) of less than 3 mAh.Achieving this level of precision for OCV estimation requires only around 50 s collection of partial charging data.Further validations on diverse battery types operating under various conditions confirm the effectiveness of our proposed method.Additional cases of precise health diagnosis based on OCV highlight the significance of conducting online OCV estimation.Our method provides a flexible approach to achieve complete OCV estimation and holds promise for generalization to other tasks in BMSs.

A Hybrid Diagnosis Method for Inverter Open-circuit Faults in PMSM Drives

In order to improve the evaluation process of inverter open-circuit faults diagnosis in permanent magnet synchronous motor(PMSM)drives,this paper presents a diagnosis method based on current residuals and machine learning models.The machine learning models are introduced to make a comprehensive evaluation for the current residuals obtained from a state observer,instead of evaluating the residuals by comparing with thresholds.Meanwhile,fault diagnosis and location are conducted simultaneously by the machine learning models,which simplifies the diagnosis process.Besides,a sampling strategy is designed to implement the proposed scheme online.Experiments are carried out on a DSP based PMSM drive,and the effectiveness of the proposed method is verified.

Open-circuit Fault-tolerant Control Strategy Based on Five-level Power Converter for SRM System

Switched reluctance motor power converters are prone to open-circuit faults because it need to withstand large voltages and currents.Due to the small number of traditional asymmetrical half bridge topology switches,it is difficult to carry out fault tolerant control when power converters has an open-circuit fault,resulting in larger output torque ripple.This paper presents a five-level power converter based on the traditional asymmetric half-bridge power converter.The five-level topology has more switching states and can work in multi-level mode.Based on the topology,different excitation and demagnetization voltages can be choose at different speeds.A fault-tolerance strategy is developed to decrease the influence of the open-circuit fault.The five-level power converter has four switches per phase,and two of them will be used in one of the operating mode.So the remaining two of the switches can be used for safe backup,enabling fault-tolerant control when an open-circuit occur.Since each phase of the five-level power converter proposed in this paper is independent of each other,a reasonable control strategy can be used to avoid the unbalance of the midpoint potential.Finally,the topology and fault-tolerant strategy proposed in this paper are verified by simulation and experiment.

Open-circuit voltage analysis of p-i-n type amorphous silicon solar cells deposited at low temperature

This paper identifies the contributions of p-a-SiC：H layers and i-a-Si：H layers to the open circuit voltage of p-i-n type a-Si：H solar cells deposited at a low temperature of 125℃. We find that poor quality p-a-SiC：H films under regular conditions lead to a restriction of open circuit voltage although the band gap of the i-layer varies widely. A significant improvement in open circuit voltage has been obtained by using high quality p-~SiC：H films optimized at the ＂low-power regime＂ under low silane flow rates and high hydrogen dilution conditions.

An analytical model to explore open-circuit voltage of a-Si:H/c-Si heterojunction solar cells

The effect of the parameters on the open-circuit voltage, V_(OC) of a-Si:H/c-Si heterojunction solar cells was explored by an analytical model. The analytical results show that V_(OC) increases linearly with the logarithm of illumination intensity under usual illumination. There are two critical values of the interface state density(D_(it)) for the open-circuit voltage(V_(OC)), D_(it)^(crit,1) and D_(it)crit,2(a few 1010 cm^(-2)·e V^(-1)). V_(OC) decreases remarkably when D_(it) is higher than D_(it)^(crit,1). To achieve high V_(OC), the interface states should reduce down to a few 1010 cm^(-2)·e V^(-1). Due to the difference between the effective density of states in the conduction and valence band edges of c-Si, the open-circuit voltage of a-Si:H/c-Si heterojunction cells fabricated on n-type c-Si wafers is about 22 mV higher than that fabricated on p-type c-Si wafers at the same case. V_(OC) decreases with decreasing the a-Si:H doping concentration at low doping level since the electric field over the c-Si depletion region is reduced at low doping level. Therefore, the a-Si:H layer should be doped higher than a critical value of 5×10^(18) cm^(-3) to achieve high V_(OC).

Perovskite Self-Passivation with PCBM for Small Open-Circuit Voltage Loss

It is well known that [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is a common n-type passivation material in PSCs, usually used as an interface modification layer. However, PCBM is extremely expensive and is not suitable for future industrialization. Herein, the various concentrations of PCBM as an additive are adopted for PSCs. It not only avoids the routine process of spin coating the multi-layer films, but also reduces the PCBM material and cost. Meanwhile, PCBM can passivate the grain surface and modulate morphology of perovskite films. Furthermore, the most important optical parameters of solar cells, the current density (Jsc), fill factor (FF), open-circuit voltage (Voc) and power conversion efficiencies (PCE) were improved. Especially, when the PCBM doping ratio in CH3NH3PbI3 (MAPbI3) precursor solution was 1 wt%, the device obtained the smallest Voc decay (less than 1%) in the p-i-n type PSCs with poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) as hole transport layer (HTL) and fullerene (C60) as electron transport layer (ETL). The PSCs Voc stability improvement is attributed to enhanced crystallinity of photoactive layer and decreased non-radiative recombination by PCBM doping in the perovskites.

Open-Circuit Faults Diagnosis in Direct-Drive PMSG Wind Turbine Converter

The condition monitoring and fault diagnosis have been identified as the key to achieving higher availabilities of wind turbines.Numerous studies show that the open-circuit fault is a significant contributor to the failures of wind turbine converter.However,the multiple faults combinations and the influence of wind speed changes abruptly,grid voltage sags and noise interference have brought great challenges to fault diagnosis.Accordingly,concerning the open-circuit fault of converters in direct-driven PMSG wind turbine,a diagnostic method for multiple open-circuit faults is proposed in this paper,which is divided into two tasks:The first one is the fault detection and the second one is the fault localization.The detection method is based on the relative current residuals after exponential transformation and on an adaptive threshold,and the localization method is based on the average values of fault phase currents.The scheduled diagnosis method is available to both the generator-side converter and the grid-side converter,allowing to detect and locate single and double open-circuit faults.For validating this,robustness test and multiple open-circuit faults diagnosis are presented in a 2-MW direct-driven PMSG wind turbine system,the results validate the reliability and effectiveness of the proposed method.

Improvement of Open-Circuit Voltage in Organic Photovoltaic Cells with Chemically Modified Indium-Tin Oxide

The possibility of the increase in open-circuit voltage of organic photovoltaic cells based primarily indium-tin oxide (ITO)/rubrene/fullerene/Al structure by changing the work function of ITO anodes and Al cathodes was described in this work. To change built-in potential preferably in order to increase the open-circuit voltage, the work function of ITO should be increased and work function of Al should be decreased. The correlation between the change in work functions of electrodes and performance of the organic photovoltaic cells before and after surface modifications was examined in detail. The enhancement of open-circuit voltage depends on a function of work function change of both ITO and Al electrode. We could show that the built-in potential in the cells played an important role in open-circuit voltage.

Efficient wide-bandgap perovskite solar cells with open-circuit voltage deficit below 0.4 V via hole-selective interface engineering

Wide-bandgap mixed-halide perovskite solar cells(WBG-PSCs)are promising top cells for efficient tandem photovoltaics to achieve high power conversion efficiency(PCE)at low cost.However,the open-circuit voltage(V_(OC))of WBG-PSCs is still unsatisfactory as the V_(OC)-deficit is generally larger than 0.45 V.Herein,we report a buried interface engineering strategy that substantially improves the V_(OC)of WBG-PSCs by inserting amphiphilic molecular hole-selective materials featuring with a cyanovinyl phosphonic acid(CPA)anchoring group between the perovskite and substrate.The assembly and redistribution of CPA-based amphiphilic molecules at the perovskite-substrate buried interface not only promotes the growth of a low-defect crystalline perovskite thin film,but also suppresses the photo-induced halide phase separation.The energy level alignment between wide-bandgap perovskite and the hole-selective layer is further improved by modulating the substituents on the triphenylamine donor moiety(methoxyls for MPA-CPA,methyls for Me PA-CPA,and bare TPA-CPA).Using a 1.68 e V bandgap perovskite,the Me PA-CPA-based devices achieved an unprecedentedly high V_(OC)of 1.29 V and PCE of 22.3%under standard AM 1.5 sunlight.The V_(OC)-deficit(<0.40 V)is the lowest value reported for WBG-PSCs.This work not only provides an effective approach to decreasing the V_(OC)-deficit of WBG-PSCs,but also confirms the importance of energy level alignment at the charge-selective layers in PSCs.

Currentless Multiple Switch Open-Circuit Faults Diagnosis for Modular Multilevel Converters with Nearest Level Modulation in HVDC Systems

Due to the large number of submodules(SMs),and modular multilevel converters(MMCs)in high-voltage applications,they are usually regulated by the nearest level modulation(NLM).Moreover,the large number of SMs causes a challenge for the fault diagnosis strategy(FDS).This paper proposes a currentless FDS for MMC with NLM.In FDS,the voltage sensor is relocated to measure the output voltage of the SM.To acquire the capacitor voltage and avoid increasing extra sensors,a capacitor voltage calculation method is proposed.Based on the measurement of output voltages,the faults can be detected and the number of different-type switch open-circuit faults can be confirmed from the numerous SMs in an arm,which narrows the scope of fault localization.Then,the faulty SMs and faulty switches in these SMs are further located without arm current according to the sorting of capacitor voltages in the voltage balancing algorithm.The FDS is independent of the arm current,which can reduce the communication cost in the hierarchical control system of MMC.Furthermore,the proposed FDS not only simplifies the identification of switch open-circuit faults by confirming the scope of faults,but also detects and locates multiple different-type faults in an arm.The effectiveness of the proposed strategy is verified by the simulation results.

充电桩充电模块功率器件故障诊断研究综述

大功率直流充电桩是未来电动汽车充电设施的发展方向,充电模块是直流充电桩最重要以及故障率最高的部件,其中功率器件开路故障较为常见。为保证充电模块安全可靠运行,需要对充电模块功率器件开路故障进行准确识别和定位。文中首先对充电模块拓扑结构和故障类型进行分析,然后分别对基于解析模型、基于信号处理和基于知识的功率器件开路故障诊断方法进行总结,分别介绍了各类方法的基本思想、研究进展和优缺点,最后总结并展望充电模块功率器件开路故障诊断方法未来的研究和发展方向。

基于短时傅里叶变换和深度网络的模块化多电平换流器子模块IGBT开路故障诊断

针对现有模块化多电平换流器(MMC)子模块故障诊断过程中所需传感器较多、测量干扰较大等问题,提出一种基于深度学习的MMC子模块IGBT开路故障诊断方法。在对MMC子模块开路故障特征进行分析的基础上,利用短时傅里叶变换(STFT)提取桥臂电压信号的谐波分量信息作为故障诊断所需的特征参数。将所得到的特征参数进行处理后构建故障诊断样本,在通过深度置信网络实现故障类型快速检测的基础上,依据不同故障类型,构建多个基于卷积神经网络的故障定位网络,进而实现开路故障的检测与定位。通过129电平的MMC系统仿真模型和降功率的MMC实验系统搭建,对该文所提方法进行了验证。仿真和实验结果表明,所提故障诊断方法可以在减少传感器数量的基础上实现子模块开路故障的诊断,提高系统的可靠性。

面向光伏能量收集应用的实时MPPT预估算法研究

对于环境中存在的各种类型能量源,其往往具有不同的阻抗特性以及输出功率范围。为了提高能量收集系统的能量萃取能力,合理的接口电路设计是关键。基于此,通过对环境中光伏(Photovoltaic,PV)能量源微弱直流特性以及高效率收集和转化的研究,在传统开路电压法(Open-Circuit Voltage,OCV)的基础上,结合输入电压纹波控制,提出了一种可实时最大功率点追踪(Maximum Power Point Tracking,MPPT)的预估算法。该预估算法根据能量源的输出特性,采用了分数开路电压法(Fractional Open-Circuit Voltage,FOCV),并根据纹波大小动态调节变换器的工作模式,实现阻抗匹配。为了尽可能减小因采样带来的能量损失,采用可片上全集成的较小的采样电容,并逐周期的进行开路电压采样和计算,实现了对源功率变化的高精度追踪。仿真结果表明,所提出的追踪算法能够实时监测能量源的状态,具有高的追踪速度和追踪精度,且采样时间仅需100 ns。能量源功率在1μW~10 mW范围内变化时,最短的追踪时间仅需4.37μs,追踪精度可达99.7%。

基于扰动观测器的五相永磁同步电机开路和短路容错矢量控制

针对反电动势含有3次谐波的五相永磁同步电机(PMSM)开路和短路故障导致转矩脉动大的问题,该文提出一种基于扰动观测器的矢量控制(DOB-FOC)策略。该策略基于降阶正交变换矩阵在同步旋转坐标系上建立PMSM开路故障情况下的基波模型,将3次谐波反电动势、短路电流等作为扰动信号。在此基础上,设计扰动观测器,观测出以上扰动导致的转矩脉动,将其转化为q轴补偿电流前馈到q轴电流指令中,有效地抑制了故障导致的转矩脉动,并且实现了PMSM在开路和短路故障情况下的平稳无扰运行。仿真和实验结果验证了所提容错策略的有效性。

无刷励磁机旋转整流器二极管开路故障的轴电压特征研究

内转子式三相无刷励磁机旋转整流器二极管单管开路故障发生频率较高且不易直接监测,可能诱发多个二极管故障的连锁效应,严重影响发电机组的安全可靠运行,根据故障在轴电压中形成的特征谐波进行在线监测是一种新型检测方法。首先分析了旋转整流器二极管单管开路故障时励磁机电枢磁动势特征,利用气隙磁导法得到交链电枢转轴交变磁通表达式,进而预测二极管开路故障后,励磁机轴电压中将出现Pωr/2π整数倍频率的谐波。最后以一台5.8 MW的三相无刷励磁机为例进行有限元仿真,结果与理论预期相符,证明了轴电压信号可用于内转子式无刷励磁机的旋转整流桥二极管开路故障在线监测。

单相脉冲整流器故障在线智能诊断实验设计

针对高速列车电力牵引系统中单相脉冲整流器的功率器件开路故障和传感器故障,设计了基于数据驱动的故障在线智能诊断实验。首先,对单相脉冲整流器系统进行数学建模,分析功率器件开路故障的故障拓扑和传感器故障的故障机理;然后,基于极限学习机算法和非线性自回归结构设计智能诊断模型,并将故障在线智能诊断实验分为离线训练和在线验证2个阶段;最后,基于RT Box半实物仿真器搭建快速原型控制实验平台,对故障模型和诊断模型进行实验验证。实验结果表明,构建的单相脉冲整流器故障在线智能诊断模型可以在1/4个基波周期内检测到故障的发生,并在3/4个基波周期内识别出具体故障类型。

锂离子电池自放电K值检测系统设计

锂离子电池自放电检测对评估单体锂离子电池或电池组的容量、循环特性和使用寿命具有重要作用。快速检测开路状态下锂离子电池存储电量自发消耗是目前该领域的研究热点。采用开路电压法,通过测量单位时间内锂离子电池的电压降,即自放电K值,表征其自放电程度,设计了锂离子电池自放电K值检测系统。该系统由上、下位机组成,两者之间采用Type-C方式连接,可对锂离子电池进行自放电率检测。以三元锂离子电池为测试对象,对其进行14 d的静置实验,检测静置过程中的自放电K值。测试结果表明该系统不仅缩短了锂离子电池自放电检测时间,而且可准确检测锂离子电池的自放电率。在锂离子电池20%、40%、60%、80%、100%5种荷电状态,20、50、-20、-40℃4种温度条件下对锂离子电池进行自放电K值检测。依据K值测试结果,可分析荷电状态和自放电环境温度对锂离子电池自放电率的影响。

基于自然容错开关表的五相永磁同步电机直接转矩控制

五相永磁同步电机(permanent-magnetsynchronous motor,PMSM)传统直接转矩控制(direct torque control,DTC)存在相电流畸变严重、共模电压(common-modevoltage,CMV)高、转矩和磁链脉动大等问题,且无法实现相开路故障情况下的无扰运行。为解决上述问题,提出一种基于自然容错开关表的DTC策略。该策略根据PMSM开路故障前后基电压矢量的特点以及三次平面合成电压矢量为零的原则,构建虚拟矢量(virtual vector,VV),设计故障前后同一套自然容错开关表,进而不但抑制了故障导致的转矩脉动,而且在故障前后均能降低三次谐波电流、减小转矩和磁链脉动、抑制CMV。实验结果验证所提策略的可行性。

Buried interface management via bifunctional NH_(4)BF_(4)towards efficient CsPbI_(2)Br solar cells with a V_(oc)over 1.4 V

CsPbI_(2)Br perovskite solar cells(PSCs)have drawn tremendous attention due to their suitable bandgap,excellent photothermal stability,and great potential as an ideal candidate for top cells in tandem solar cells.However,the abundant defects at the buried interface and perovskite layer induce severe charge recombination,resulting in the open-circuit voltage(V_(oc))output and stability much lower than anticipated.Herein,a novel buried interface management strategy is developed to regulate interfacial carrier dynamics and CsPbI_(2)Br defects by introducing ammonium tetrafluoroborate(NH_(4)BF_(4)),thereby resulting in both high CsPbI_(2)Br crystallization and minimized interfacial energy losses.Specifically,NH_(4)^(+)ions could preferentially heal hydroxyl groups on the SnO_(2)surface and balance energy level alignment between SnO_(2)and CsPbI_(2)Br,enhancing charge transport efficiency,while BF_(4)^(-)anions as a quasi-halogen regulate crystal growth of CsPbI_(2)Br,thus reducing perovskite defects.Additionally,it is proved that eliminating hydroxyl groups at the buried interface enhances the iodide migration activation energy of CsPbI_(2)Br for strengthening the phase stability.As a result,the optimized CsPbI_(2)Br PSCs realize a remarkable efficiency of 17.09%and an ultrahigh V_(oc)output of 1.43 V,which is one of the highest values for CsPbI_(2)Br PSCs.