Health condition monitoring is critical to secure the availability and reliability of the power semiconductor devices in power converter. Massive efforts have been devoted to the development of condition monitoring methods in the past decade. However, most of them are limited to simplifying laboratory testing conditions, without considering the dynamic operational and environmental conditions in real applications, or field implementation aspects such as the inconvenient terminal connecting of real converter products. To facilitate the implementation of condition monitoring in field applications, first, this article creatively proposes a bipolar self-power circuit. It can provide the power supply to the chips in the health indicator sensing unit, including the isolation chip, operational amplifier, and analog-to-digital (AD) converter, enabling a plug-and-play edge condition monitoring module. Second, an effective data processing procedure is proposed to suppress the effects caused by the dynamic conditions of the converter, avoiding the complex data calibration conducted in conventional studies. Then, based on the creations, an Internet of Things (IoT)-aimed systematic health monitoring scheme is presented, consisting of the edge health indicator monitoring unit, a wireless data communication, and a user-friendly software embedded with a data processing algorithm. The proposed scheme is demonstrated by a three-phase inverter-based motor drive mission-profile emulator. The final results give that the proposed indicator is increased by about 25 times for the degraded devices and is up to 30% only for new devices.

Power loss estimation is an indispensable procedure to conduct lifetime prediction for power semiconductor device. The previous studies successfully perform steady-state power loss estimation for different applications, but which may be limited for the electric vehicles (EVs) with high dynamics. Based on two EV standard driving cycle profiles, this paper gives a comparative study of power loss estimation models with two different time resolutions, i.e., the output period average and the switching period average. The correspondingly estimated power losses, thermal profiles, and lifetime clearly pointed out that the widely applied power loss model with the output period average is limited for EV applications, in particular for the highly dynamic driving cycle. The difference in the predicted lifetime can be up to 300 times due to the unreasonable choice the loss model, which calls for the industry attention on the differences of the EVs and the importance of loss model selection in lifetime prediction.

The electrification of the transportation sector is moving on at a fast pace. All car manufacturers have strong programs to electrify their car fleet to fulfill the demands of society and customers by offering carbon-neutral technologies to bring goods and persons from one location to another. Power electronics technology is, in this evolution, essential and also in a rapid development technology-wise. Some of the introduced technologies are quite mature, and the systems designed must have high reliability as they can be quite complicated from an electrical perspective. Therefore, this article focuses on the reliability of the used power electronic systems applied in electric vehicles (EVs) and hybrid EVs (HEVs). It introduces the reliability requirements and challenges given for the power electronics applied in EV/HEV applications. Then, the advances in power electronic components to address the reliability challenges are introduced as they individually contribute to the overall system reliability. The reliability-oriented design methodology is also discussed, including two examples: an EV onboard charger and the drive train inverter. Finally, an outlook in terms of research opportunities in power electronics reliability related to EV/HEVs is provided. It can be concluded that many topics are already well handled in terms of reliability, but issues related to complete new technology introduction are important to keep the focus on.

In order to prevent catastrophic failures in power electronic systems, multiple failure precursors have been identified to characterize the degradation of power devices. However, there are some practical challenges in determining the suitable failure precursor, which supports the high-accuracy prediction of remaining useful life (RUL). This article proposes a method to formulate a composite failure precursor (CFP) by taking full advantage of potential failure precursors (PFPs), where CFP is directly optimized in terms of the degradation model to improve the prediction performance. The RUL estimations of the degradation model are explicitly derived to facilitate the precursor quality calculation. For CFP formulation, a genetic programming method is applied to integrate the PFPs in a nonlinear way. As a result, a framework that can formulate a superior failure precursor for the given RUL prediction model is elaborated. The proposed method is validated with the power cycling testing results of SiC MOSFETs.

This paper proposes an analytical approach for modeling low frequency Differential Model (DM) Electromagnetic Interference (EMI) noise of single-phase Power Factor Correction (PFC) converters within 9-150 kHz frequency range. In order to develop analytical model of the DM EMI noise, the switching function model of the converter is calculated utilizing double Fourier analysis including its input closed-loop impedance model. Notably, the analytical modeling includes Line Impedance Stabilization Network (LISN) circuit and EMI receiver. A 1 kW single-phase boost PFC converter prototype is used for validation of the proposed EMI modeling technique.

This paper discusses reliability issues of three different types of capacitors (ceramic, electrolytic and film) applied in the input side of an impedance-source photovoltaic (PV) microconverter having an ultra-wide dc gain range. The study considers a wear-out failure analysis based on a daily PV mission profile. The general operation and control principle are first described. Then the selection criteria of the capacitors are analyzed. Experimental measurements of capacitors temperature are translated into accumulated damage using their corresponding lifetime models. Finally, conclusions are drawn regarding the applicability of different capacitor technologies in impedance-source PV microconverters, where the film capacitor has the lowest damage.

This paper advocates a novel conceptual formulation of the fractional-order spatial steganography (FSS) and blind steganalysis for printed matter, which can be efficiently employed in the anti-counterfeiting for product external packing in Internet-of-Things (IoT). Traditional digital steganography is not printable. Within the limits of our knowledge, until now, there are not a well-established steganography and a corresponding steganalysis for printed matter in IoT, which should receive desired attention. Fractional calculus has potentially received prominence in applications in the domain of image processing mainly because of its strengths like long-term memory, nonlocality, and weak singularity. Therefore, in an attempt to overcome the aforementioned technical limitation of traditional digital steganography, this paper has studied here, as an interesting theoretical problem, would it be possible to apply the capability of preserving the edges and textural details of fractional calculus to the achievement of the steganography and steganalysis for printed matter in IoT. Motivated by this inspiration, in this work, this paper introduces a novel conceptual formulation of an FSS and a fractional-order blind steganalysis (FBS) for printed matter. At first, according to the opponent process theory of color vision, to better achieve the imperceptibility of the hidden secret information, this paper uses both the self-similar complex textures in a neighborhood and the opponent channel of blue versus yellow to implement FSS for printed matter. Second, without requiring a priori knowledge regarding the characteristics of the original carrier image, hidden secret image, and steganography, an FBS, a fractional-order multimodal function optimization algorithm, is proposed. Finally, the efficient capability of hiding secret information of FSS and that of detecting secret information of FBS are analyzed in detail experimentally, respectively. These two important advantages lead to the superiority of the proposed approach for defending against statistics attack, rotation and distortion attack, cropping attack, scaling attack, noise attack, and color copy attack. The main contribution of this paper is the first preliminary attempt of a feasible achievement of a spatial steganography and a blind steganalysis for printed matter.

This paper proposes a unity power factor (PF) bridgeless buck-boost power factor correction (PFC) converter to minimize conduction losses caused by the diode bridge. Moreover, compared to the conventional buck-boost PFC converter, the proposed converter has lower voltage stresses across switches, which further improves the overall efficiency of the proposed converter, especially when it operates in the light load conditions. Operation modes with inductors working in the discontinuous conduction mode (DCM) are given in detail, and comparative analysis is conducted to show the proposed converter performance regarding the PF, component stresses, and output ripple. The proposed and conventional converter prototypes with load range of 20~100 W are built and tested. The obtained results verify merits and theoretical predictions of the proposed.

The lifetime prediction of LED lighting system is important to guide the designers to fulfill the design specifications and to benchmark the cost-competitiveness of different lighting technologies. Currently, the lifetime of LED system is usually predicted from the source part and the driver part separately, and then the thermal design is also optimized independently. In practice, the LED source and driver are usually compacted in a single fixture. The heat dissipated from LED source and driver will be coupled together and affect the heat transfer performance, which may degrade the whole system and accelerate the failure. In this paper, a new thermal model concerning the thermal coupling is proposed with Finite Element Method (FEM) simulation for parameter acquirement. The proposed model has a better estimation of the thermal stresses of key components in the LED lamps and therefore an improved lifetime prediction of the LED systems. Moreover, with a given lifetime requirements, this method can be used to guide the thermal design of the LED system. A case study of an outdoor lighting application is then demonstrated by both FEM simulations and experimental verifications in this digest.

Indirect rotor field oriented control (IRFOC) plays an important role in the high performance induction machine drives. In the indirect rotor field oriented control - based induction machine adjustable speed control system, the rotor field angle is usually obtained by the rotor angular velocity and the slip angular velocity. The rotor angular velocity can be sensed by an encoder with sufficient accuracy. However, the slip angular velocity is affected by the rotor parameters variations and the current control performance degradation especially in the field-weakening region. Therefore, the field angle used in the indirect rotor field oriented control may have considerable error. In the paper, the angle error caused by rotor resistance variation is analyzed and the impact on the output torque and the rotor field intensity of the induction machine is studied. Simulations and experimental verification in base-speed region and field-weakening region are presented.

A novel switching power loss estimation method for modular multilevel converters (MMCs) with the nearest level modulation (NLM) is introduced in this paper. It focuses on the switching actions caused only by change of the inserted submodule (SM) number per arm, named as the essential switching transitions. Every essential switching action can be identified under the assumption of ideal sinusoidal arm voltage reference. The corresponding arm current value determining the switching energy can be obtained with the exclusive use of the exact time of the switching action. Effects of the modulation index and the power factor on the power loss are also taken into account. Simulations have been performed on a 30-MVA three-phase grid-connected MMC system with 20 SMs per arm. The results have confirmed the effectiveness of the proposed method, where high estimation accuracy can be achieved under a range of operating conditions.

Capacitive DC links provide the only low-impedance current path connected with an input source during the start-up of many voltage source converters. A soft-start circuit is usually implemented to limit the inrush current. A two-terminal active capacitor is recently proposed which can directly replace conventional passive capacitors in DC links, with reduced cost or size for a given application. The active capacitor has the same level of convenience with two power terminals only as a passive capacitor. This paper proposes two start-up schemes for the active capacitor to overcome the drawbacks of existing methods previously widely used for passive capacitors. One scheme is based on a trade-off design between the start-up performance and the component sizing of the active capacitor. The other scheme is based on either an additional bypass switch together with the existing soft-start circuit in the DC bus or a start-up circuit fully integrated in the active capacitor. The theoretical analyses and experiments are presented. A case study on a single-phase full-bridge rectifier demonstrates the effectiveness of the implemented start-up schemes.

The reliability aspect study of Modular Multilevel Converter (MMC) is of great interest in industry applications, such as offshore wind. Lifetime prediction of key components is an important tool to design MMC with fulfilled reliability specifications. While many efforts have been made to the lifetime prediction of IGBT modules in renewable energy applications by considering long-term varying operation conditions (i.e., mission profile), the justifications of using the associated mission profiles are still missed. This paper investigates the impact of mission profile data resolutions and electrical power modeling methods on the estimated lifetime of IGBT modules in an MMC for offshore wind power application. In a 30 MW MMC case study, an annual wind speed profile with a resolution of 1 s/data, 10 minute/data, and 1 hour/data are considered, respectively. A method to re-generate higher resolution wind speed data from lower resolution data is introduced as well. Based on the wind speed data, IEC 61400-12-1 power curve model and a wind speed-power stochastic model are compared as well. Five mission profile modeling scenarios are compared in terms of the predicted lifetime of the IGBT modules used in the MMC, resulting in significant differences. The study serves as a first step to quantify the impact of mission profile modeling on lifetime prediction, and to provide a guideline on mission profile collection for the presented application.

In single-phase inverters, DC-link capacitors are installed at the DC-link to buffer the ripple power between the AC side and DC side. Active decoupling methods introduce additional circuits at the DC side or AC side to partially or fully supply the ripple power. So that the demanded DC-link capacitor capacitance can be decreased. However, few research is about the effect of DC side and AC side decoupling on the DC-link capacitor reliability considering its electro-thermal stresses. This paper presents a quantitative analysis on the lifetime of capacitors with power decoupling circuits at the DC side and AC side, respectively. The ripple current spectrum of the capacitors is obtained by double Fourier analysis of a H-bridge inverter with natural sampling PWM modulation. A study case is demonstrated by a 2,000 W H-bridge inverter with 400 V DC-link voltage.

The basic Zero-Voltage Switching (ZVS) three-level DC-DC converter has one clamping capacitor to realize the ZVS of the switches, and two clamping diodes to clamp the voltage of the clamping capacitor. In order to reduce the reverse recovery loss of the diode as well as its cost, this paper proposes to remove one of the clamping diodes in basic ZVS three-level DC-DC converter. With less components, the proposed converter can still have a stable clamping capacitor voltage, which is clamped at half of the dc link voltage. Moreover, the ZVS performance will be influenced by removing the clamping diode. But as long as the clamping capacitor is properly selected, the degradation of the ZVS performance can be neglected. The impact of the clamping capacitor on the ZVS performance is mathematically analyzed as well.

Various power decoupling methods have been proposed recently to replace the DC-link Electrolytic Capacitors (E-caps) in single-phase conversion system, in order to extend the lifetime and improve the reliability of the DC-link. However, it is still an open question whether the converter level reliability becomes better or not, since additional components are introduced and the loading of the existing components may be changed. This paper aims to study the converter level reliability of a single-phase full-bridge inverter with two kinds of active power decoupling module and to compare it with the traditional passive DC-link solution. The converter level reliability is obtained by component level electro-thermal stress modeling, lifetime model, Weibull distribution, and Reliability Block Diagram (RBD) method. The results are demonstrated by a 2 kW single-phase inverter application.

This paper presents a new soft-switched, current-driven full-bridge converter. A simple snubber is used in order to get ZVS for all the main switches. The soft-switching realization is independent of the load. The snubber is placed in parallel with the bridge. All the resonant circuit energy is recycled by the load in each half cycle. No additional current stresses appear on the main switches. A design-oriented steady-state analysis leads to the expressions of the dc voltage conversion ratio and ZVS analytical conditions, allowing for a trade-off design of the resonant inductor. A prototype has been built with a high energy transfer efficiency. The simulation and experiment results confirm the detailed theoretical analysis.

DC power systems connecting to single-phase DC/AC inverters with nonlinear loads will have their DC sources being injected with AC ripple currents containing a low-frequency component at twice the output voltage frequency of the inverter and also other current harmonics. Such a current may create instability in the DC power system, lower its efficiency, and shorten the lifetime of the DC source. This paper presents a general waveform control method that can mitigate the injection of the low-frequency ripple current by the single-phase DC/AC inverter into the DC source. It also discusses the inhibiting ability of the waveform control method on other coexisting harmonics, while the DC source delivers AC power to a nonlinear load. With the application of the waveform control, the average DC output power is supplied by the DC source, while the other harmonics pulsation power can be confined to the AC side (between the capacitors and the AC load). Theoretical analyses and experiment results are provided to explain the operation and the inhibiting ability, and to showcase the performance of the approach in tackling the harmonics. Results validate that the proposed solution can achieve significant mitigation of harmonic component at DC side with nonlinear load as well as a high quality output voltage without the need for extra large capacitive energy storage element implementation.

This paper describes the design and development of a 6 kA/1.1 kV non-destructive testing system, which aims for short circuit testing of high-power IGBT modules. An ultra-low stray inductance of 37 nH is achieved in the implementation of the tester. An 100 MHz FPGA supervising unit enables 10 ns level control accuracy of the short-circuit duration, protection triggering, and acquisition of the electrical waveforms. Moreover, a protection circuit avoids explosions in case of failure, making the post-failure analysis possible. A case study has been carried out on an aged 1.7 kV IGBT power module. The case study shows the current and voltage waveforms during short-circuit, as well as the current mismatch among six inner sections, which demonstrate the capability and the effectiveness of the proposed setup in the short-circuit aspect reliability studies of MW-scale power modules.

Context-aware pervasive software is responsive to various contexts and their changes. A faulty implementation of the context-aware features may lead to unpredictable behavior with adverse effects. In software testing, one of the most important research issues is to determine the sufficiency of a test suite to verify the software under test. Existing adequacy criteria for testing traditional software, however, have not explored the dimension of serial test inputs and have not considered context changes when constructing test suites. In this article, we define the concept of context diversity to capture the extent of context changes in serial inputs and propose three strategies to study how context diversity may improve the effectiveness of the data-flow testing criteria. Our case study shows that the strategy that uses test cases with higher context diversity can significantly improve the effectiveness of existing data-flow testing criteria for context-aware pervasive software. In addition, test suites with higher context diversity are found to execute significantly longer paths, which may provide a clue that reveals why context diversity can contribute to the improvement of effectiveness of test suites.

Wind speed variations make the power of wind turbine system to fluctuate, which could increase the thermal stress of the power converter and reduce its lifetime. In order to relieve this problem, short-term energy storage technologies are applied to improve the thermal performance of a 3 MW grid side wind power converter. The cost, weight and cycle life of the energy storage technologies are evaluated based on a typical low speed high turbulence wind profile. In detail, a wind turbine system model is established and its control strategy is illustrated, which is followed by the power control method of the energy storage system. Then the conventional thermal evaluation approach is simplified for evaluation with long term wind profile. The case studies are done to address the optimal power size and capacity of the energy storage system by comparing the improvement of the thermal performance. Also, the two promising candidates, ultracapacitors and batteries, are compared.

This paper deals with the design, control, efficiency and thermal cycling estimation of associated Si and SiC based three-phase PV-inverters. A novel Electro-Thermal Model able to consider the thermal coupling within the Transistor and Diode integrated on the same package is proposed. For each topology, three different cases study are simulated, according to the heatsink repartition: one-leg heatsink, shared heatsink and individual heatsink. Based on the model, it has been determined the minimum required heatsink thermal impedance in order not to overpass the device physically thermal limitations. Finally, simulation results are analyzed in order to decide which topology has a higher efficiency and a better thermal loading distribution within the devices.

Reliability is one of the key issues for the application of Insulated Gate Bipolar Transistors (IGBTs) in power electronic converters. Many efforts have been devoted to the reduction of IGBT wear out failure induced by accumulated degradation and catastrophic failure triggered by single-event overstress. The wear out failure under field operation could be mitigated by scheduled maintenances based on lifetime prediction and condition monitoring. However, the catastrophic failure is difficult to be predicted and thus may lead to serious consequence of power electronic converters. To obtain a better understanding of catastrophic failure of IGBTs, the state-of-the-art research on their failure behaviors and failure mechanisms is presented in this paper. Moreover, various fault-tolerant design methods, to prevent converter level malfunctions in the event of IGBT failure, are also reviewed.

Advances in power electronics enable efficient and flexible processing of electric power in the application of renewable energy sources, electric vehicles, adjustable-speed drives, etc. More and more efforts are devoted to better power electronic systems in terms of reliability to ensure high availability, long lifetime, sufficient robustness, low maintenance cost and low cost of energy. However, the reliability predictions are still dominantly according to outdated models and terms, such as MIL-HDBK-217H handbook models, Mean-Time-To-Failure (MTTF), and Mean-Time-Between-Failures (MTBF). A collection of methodologies based on Physics-of-Failure (PoF) approach and mission profile analysis are presented in this paper to perform reliability-oriented design of power electronic systems. The corresponding design procedures and reliability prediction models are provided. Further on, a case study on a 2.3 MW wind power converter is discussed with emphasis on the reliability critical components IGBTs. Different aspects of improving the reliability of the power converter are mapped. Finally, the challenges and opportunities to achieve more reliable power electronic systems are addressed.

Context-aware applications capture environmental changes as contexts and self-adapt their behaviors dynamically. Existing testing research has not explored context evolutions or their patterns inherent to individual test cases when constructing test suites. We propose the notation of context diversity as a metric to measure how many changes in contextual values of individual test cases. In this paper, we discuss how this notion can be incorporated in a test case generation process by pairing it with coverage-based test data selection criteria.

Advances in data collection and storage technologies have resulted in large and dynamically growing data sets at many organizations. Database and data mining researchers often use sampling with great effect to scale up performance on these data sets with small cost to accuracy. However, existing techniques often ignore the cost of computing a sample. This cost is often linear in the size of the data set, not the sample, which is expensive. Furthermore, for data mining applications that leverage progressive sampling or bootstrapping-based techniques, this cost can be prohibitive, since they require the generation of multiple samples.To address this problem, we present a solution in the context of a state-of-the-art data analysis center. Specifically, we propose a scalable service that supports sample generation with cost linear in the size of the sample. We then present an efficient parallelization of this service. Our solution leverages high speed interconnects (e.g. Myrinet, Infini-band) for parallel I/O operations with pipelined data transfers. We export an interface that supports both ad-hoc SQL-like querying for database applications, as well as a stand-alone service for data mining applications. We then evaluate our work using queries abstracted from a network monitoring and analysis application, which uses both database and progressive sampling queries. We demonstrate that our implementation achieves good load balance and realizes up to an order of magnitude speedup when compared with extant approaches.