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Accurate measurement of the junction temperature Tj is crucial for ensuring safe operation and evaluating the performance of silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors (MOSFETs). In this paper, the junction temperature of a half-bridge is monitored by combining transient voltage and current peaks across the lower device. Both theoretical analysis and switch tests validate that the peak induced voltage and peak reversed current during the commutation transient exhibit a linear relationship with the temperature of the corresponding devices. The impact of load current and bus voltage on the measurement results is also investigated. Moreover, the effectiveness of the proposed method is confirmed by carrying out tests at different temperatures, and the feasibility of online implementation is discussed. The experimental results show that the proposed method has high linearity and sensitivity and can simultaneously provide temperature information for both devices of a half-bridge. [ABSTRACT FROM AUTHOR]

This letter proposes an indirect power dissipation level short circuit protection (IPDL-SCP) method for silicon carbide (SiC) metal-oxide semiconductor field-effect transistors (mosfets). Due to differences between normal conducting and short-circuit (SC) conditions, this method is triggered by the voltage oscillation vss at the parasitic inductance (Lss) of the source and directly monitoring vds of SiC mosfet. For verification, the short circuit protection circuit is tested and proved functional on the SC test bench. Experimental results show that the protection circuit can respond to both hard switching fault (HSF) and fault under load (FUL), while the fastest response delays are 75 ns for HSF and 170 ns for FUL. Comparisons with other commonly used SC protection methods have also been made, which show that the proposed IPDL-SCP method has better performance in shorter protection delays. [ABSTRACT FROM AUTHOR]

Gate-oxide degradation has been one of the critical reliability concerns of silicon carbide (SiC) metal–oxide–semiconductor-field-effect transistors (mosfets), which could be monitored through aging-sensitive parameters. In this article, an online gate-oxide degradation monitoring method for planar SiC mosfets is proposed by extracting gate charge time at a specific range of gate voltage. It is based on the findings that the input capacitances of planar SiC mosfets change significantly over gate-oxide degradation, which is theoretically analyzed and experimentally verified. The capacitance variations are converted into the gate charge time as the new aging-sensitive parameter. The new parameter measurement circuit is proposed and integrated into the gate driver module. The article results indicate that the new parameter varies noticeably with gate-oxide degradation and the difference of this parameter caused by junction temperature is much smaller than that caused by degradation. Besides, the parameter is immune to package degradation and load current. The condition monitoring method can be implemented online since the parameter is extracted during the off-state of SiC mosfet devices, which does not affect normal operation. The confirmatory experiment is carried out to verify the correctness of the proposed method. [ABSTRACT FROM AUTHOR]

• This paper presents an effective approach for coupling relationship analysis in multiple differently parameterized inverters. • All system resonance cases and phenomena are presented. • The proposed method is suitable for all multi-inverter parallel structures. This study investigates the coupling problem between different types of resonances in the system of multiple differently parameterized inverters. The coupling between the inverters and the grid, as well as between differently parameterized inverters, can lead to different types of resonances, which have different resonance characteristics. Due to the absence of resonance coupling relationship analysis, it is difficult to form a unified and complete understanding of the system resonances that are formed by the superposition of different types of resonances. In this paper, the system model is established, and the expressionsof the interactive current circulating between the parallel inverters and input-grid current injecting the power grid can be obtained. Stability analysis of the interactive current and input-grid current reveal characteristics of different types of resonances, and thus the resonance coupling relationship is obtained. It helps to form a complete understanding of system resonance characteristics, and then obtain all system resonance cases. The effects of system parameters on the resonance characteristics and harmonic interaction are analyzed. Finally, the correctness of the theoretical analysis is validated through simulations and experiments. [ABSTRACT FROM AUTHOR]

In this article, an online condition monitoring (CM) method is proposed for the bond wire degradation of insulated-gate bipolar transistor (IGBT) modules in a single-phase or three-phase three-level neutral-point-clamped (3LNPC) dc–ac, ac–dc converter. The proposed method has the ability to detect the whole IGBTs in a 3LNPC converter, based on finding the idle on-state IGBTs under the specific load current direction and switching sequence of a leg. The detection time is short (0.2 ms) and the influence of online CM on load current can be completely neglected as long as the insertion areas for CM test are chosen reasonably. Meanwhile, an advanced bond wire CM module is designed to conduct the CM test. This module can generate and inject the current pulse trains into IGBT modules, with the high current for CM test and low current for temperature-sensitive electrical parameter measurement, and sample the collector–emitter on-state voltage (VCE ON) stably and precisely. Finally, the experimental work was carried out to verify the effectiveness of the proposed method and the practicality of the developed CM module. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) is a vital gas signaling molecule that performs crucial physiological functions in biological systems, and it can also cause food safety problems. In this study, we developed a cyanine derivative-based mitochondrial-targeted near-infrared fluorescent probe PC-H 2 S for detecting H 2 S. When PC-H 2 S reacted with H 2 S, it reached maximum fluorescence intensity at 656 nm and detection limit as low as 34 nM, and exhibited strong chromogenic response from green to red for H 2 S. Moreover, PC-H 2 S could be utilized to identify H 2 S generated during food spoilage and thus monitored the process of food spoilage. More significantly, PC-H 2 S showed excellent mitochondrial targeting capabilities and endogenous/exogenous H 2 S imaging of living cells and zebrafish could be performed. As a result, this research provides an attractive method for detecting H 2 S in food and biological systems and has potential value in physiopathological research. [Display omitted] • A cyanine derivative-based mitochondrial-targeted NIR fluorescent probe PC-H 2 S for detecting H 2 S was developed. • PC-H 2 S had a low detection limit and exhibited strong chromogenic response from green to red for H 2 S in naked eyes and UV light. • PC-H 2 S test strips was capable of monitoring H 2 S produced by food spoilage. • PC-H 2 S could be used for living cells and zebrafish imaging. [ABSTRACT FROM AUTHOR]

Grid-connected current quality is seriously affected by the low-order background harmonics in the gird-inverter dynamic system. The point of common coupling voltage feedforward impedance reshaping method of the grid-connected inverter is generally applied to solve this problem, however about 90° phase lag of the inverter output impedance is brought in, which would deteriorate the adaptability of the inverter to the weak grid. To solve this problem, this article proposes a novel frequency-division virtual impedance shaping method, which shapes the output impedance of the grid-connected inverter with different coefficients in different frequency bands, respectively. The basic principles, parameters design, and application analysis are studied in detail. With the proposed scheme, the grid-connected inverter can be equipped with strong adaptability to a wide range of grid impedance and suppression ability to the background voltage harmonics simultaneously. Theoretical analysis and experimental results confirm the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

A series of compounds similar to Pracinostat that contained benzimidazole ring and N‐hydroxyacrylamide attached at 5‐ or 6‐position were designed, synthesized, and evaluated as HDAC inhibitors. It was interesting to find that the corresponding derivative 1 with N‐hydroxyacrylamide attached at 5‐position was a potent HDAC inhibitor while the others at 6‐position were not. This is the first time to demonstrate the position difference plays important role in the HDAC inhibitory activities of the cinnamic hydroxamates. [ABSTRACT FROM AUTHOR]

An efficient and stereoselective procedure of oxidizing disulfide to thiosulfinate 2a using CHP as the oxidant and economically available Ti(O-i-Pr)4/L-DET/H2O as catalysts were developed. The reaction went smoothly under mild conditions with synthetic useful yield and the workup for obtaining the final product is quite convenient. [ABSTRACT FROM AUTHOR]

Insulated-gate bipolar transistor (IGBT) modules and dc-link capacitors are important parts in the majority of power electronic converters which contribute to cost, size, and failure rate on a considerable scale. This paper presents an online condition monitoring method for both IGBT modules and dc-link capacitors of power converters based on short-circuit current of an IGBT module, which is a good condition indicator according to the theory analysis. The failure prediction of dc-Link capacitor is realized by equivalent series resistance, which can be calculated by short-circuit current and a step voltage, and the bond wires fatigue can also be identified by the short-circuit current. The proposed method is capable for detecting small changes in the failure indicators of IGBT modules and electrolytic capacitors, and its effectiveness is validated by a confirmatory experiment. The novelty of the proposed method is that the degradations of IGBT modules and capacitors can be identified simultaneously, and has the merits of low cost and circuit simplicity [ABSTRACT FROM PUBLISHER]

Finding and replacing the defective insulated-gate bipolar transistor (IGBT) module timely by monitoring the ageing state of IGBT can improve the reliability of a power converter and reduce the loss caused by IGBT failure. A method for detecting the condition of bond wires in IGBT module by identifying the short-circuit current of IGBT module is presented in this paper. It is based on the fact that parasitic parameters of IGBT module are affected by the local damage induced by ageing over time, and these changes can be easily detected by monitoring the difference of short-circuit current. The study results indicate that short-circuit current of IGBT module decreases with module ageing over time, and the difference of short-circuit current caused by junction temperature is much smaller than that caused by bond wires fatigue on a specific gate driving voltage. Therefore, the IGBT module in the power converter can be diagnosed by detecting the difference of short-circuit current without considering the effects of junction temperature. Finally, a confirmatory experiment is carried out, and the correctness of the method proposed in this paper is verified. [ABSTRACT FROM AUTHOR]

Background: The discovery of the glymphatic system and meningeal lymphatic vessels challenged the traditional view regarding the lack of a lymphatic system in the central nervous system. It is now known that the intracranial lymphatic system plays an important role in fluid transport, macromolecule uptake, and immune cell trafficking. Studies have also shown that the function of the intracranial lymphatic system is significantly associated with neurological diseases; for example, an impaired intracranial lymphatic system can lead to Tau deposition and an increased lymphocyte count in the brain tissue of mice with subarachnoid hemorrhage. Methods: In this study, we assessed the changes in the intracranial lymphatic system after intracerebral hemorrhage and the regulatory effects of repeated transcranial magnetic stimulation on the glymphatic system and meningeal lymphatic vessels in an intracerebral hemorrhage (ICH) model of male mice. Experimental mice were divided into three groups: Sham, ICH, and ICH + repeated transcranial magnetic stimulation (rTMS). Three days after ICH, mice in the ICH+rTMS group were subjected to rTMS daily for 7 days. Thereafter, the function of the intracranial lymphatic system, clearance of RITC‐dextran and FITC‐dextran, and neurological functions were evaluated. Results: Compared with the Sham group, the ICH group had an impaired glymphatic system. Importantly, rTMS treatment could improve intracranial lymphatic system function as well as behavioral functions and enhance the clearance of parenchymal RITC‐dextran and FITC‐dextran after ICH. Conclusion: Our results indicate that rTMS can abrogate ICH‐induced brain parenchymal metabolite clearance dysfunction by regulating intracranial lymphatic drainage. [ABSTRACT FROM AUTHOR]

As the core component of wearable electronic devices, flexible energy storage materials play an irreplaceable role. At present, it is still a challenge to prepare flexible electrode materials with high energy density. In this paper, a polyaniline‐based composite flexible conductive hydrogel (PPG‐P) with a two‐level conductive network is successfully prepared by a secondary induced assembly in situ polymerization method. The special conductive structure greatly promotes the efficiency of charge transfer and the utilization of electroactive substances, so that PPG‐P exhibits excellent electrochemical performance. In a three‐electrode system, PPG‐P has a mass‐specific capacitance as high as 989 F g−1 (0.5 A g−1). After 1000 charge and discharge cycles, the capacitance retention is 87%. Symmetrical flexible supercapacitors based on PPG‐P have high specific capacitance (176 F g−1/0.5 A g−1) and high energy density (15.6 Wh kg−1). After 1000 cycles of constant current charge and discharge, the capacitance maintains 78.1%. The preparation of PPG‐P with a hierarchical structure demonstrates the possibility of achieving high energy density in flexible electrode materials, which has great application potential in the development of energy storage elements in wearable devices. [ABSTRACT FROM AUTHOR]

An experimental study on the emissions of a diesel car fueled with national II diesel fuel, Shanghai IV diesel fuel and mixed fuels B10, G10 and C10 is conducted, in which its modal emission characteristics of HC, CO, NOx and CO2 with I-type test cycle in GB 18352.3-2005 are analyzed. The results show that compared to national II diesel fuel, the engine fueled with Shanghai II diesel fuel, B10, C10 and G10 has lower emissions of HC, CO, NOx and CO2. With I-type test cycle in GB 18352. 3-2005, the major HC emissions are in urban driving cycles, while CO emissions in urban cold cycle and NOx and CO2 in suburban cycles. In acceleration phase, all HC, NOx and CO2 emissions increase. [ABSTRACT FROM AUTHOR]

This paper presents a reconfigurable structure dc–dc converter with wide output range and constant peak power (RS-WOCP). This converter is an extension of the traditional isolated dc–dc converter with two output channels by adding an active switch and two diodes. Theoretical analysis indicates that the proposed RS-WOCP converter is able to smoothly reconfigure the output channels in parallel or series to realize wide output voltage range. With this approach, the output voltage is shared equally in the series operating mode and so is the output current in the parallel operating mode. Therefore, the power rating of devices is significantly reduced and the output rectifiers and filters can distribute power losses and thermal stresses. Operating principle, control strategy, modeling, and stability analysis are illustrated in this paper. An experimental prototype of a 200-W DSP-based RS-WOCP converter was built. The experimental results have verified the steady-state performance and fast dynamic response in the whole output voltage range. Comparisons with two close relatives of wide output converters show that the proposed RS-WOCP converter is advantageous for wide output range constant peak power applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • The structure and biological functions of LDs and their mode of interaction with other organelles are briefly described. • Fluorescent probes that focus on the network of interactions between LDs and other organelles were summarized. • Fluorescent probes reviewed are divided into dual-targeted and multi-targeted based on the number of organelles targeted. • Challenges and directions for developing multi-organelle LDs-associated fluorescent probes are discussed. Lipid droplets, as the centre of lipid metabolism, interact with the endoplasmic reticulum, mitochondria, lysosome, nucleus and other organelles to maintain the body's energy balance through vesicle transport or membrane contact. Disruption of the interaction process will lead to the development of lipid metabolism-related diseases. In recent years, many fluorescent probes have been developed to visually follow the dynamic interaction process visually between lipid droplets and other organelles. Existing reviews on lipid droplets fluorescent probes are mainly categorised and reviewed in terms of the emission band of probes, mother fluorophores and design strategies. However, probes that focus on the interactions between lipid droplets and other organelles can provide further insight into the whole process from lipid droplets formation to transformation as well as the mechanisms of diseases related to lipid metabolism. This paper mainly reviews the progress of fluorescent probes targeting lipid droplets interactions with other organelles in the last five years and is divided into dual-targeted and multi-targeted sections based on the number of targeted organelles. The focus is on the biological contacts and dynamic interaction processes between lipid droplet-centred organelles observed by fluorescence imaging with dual-targeted and multi-targeted probes in the article. The targeting groups and reaction sites of the probes are marked in the figure. Moreover, the paper briefly describes the structure and biological functions of lipid droplets and their connections with other organelles. Perhaps in addition to the imaging performance of the probes, we believe that the use of precision instruments to provide high spatio-temporal resolution and reliable results is also a key factor in observational studies. Finally, we summarize the development prospect of multi-color multi-targeted fluorescent probes related to lipid droplets. We expect to bring novel thinking to the design of lipid droplet fluorescent probes and provide new ideas for exploring diagnostic and therapeutic options for lipid droplet-related diseases. [ABSTRACT FROM AUTHOR]

Condition monitoring is a cost-effective means to reduce the unscheduled maintenance cost of insulated gate bipolar transistor (IGBT) modules. The junction to case thermal resistance $R_{\mathrm {thjc}}$ is considered as a critical health indicator of IGBT module solder layer. However, thermal interface materials’ (TIMs) deterioration will not only reduce the heat dissipation performance but also affects the accuracy of $R_{\mathrm {thjc}}$ monitoring of IGBT modules. This article investigates the effect of thermal grease deterioration on $R_{\mathrm {thjc}}$ monitoring of IGBT module. First, it is found that the thermal grease deterioration will lead to the decrease of monitored $R_{\mathrm {thjc}}$ of IGBT module under the same health status of IGBT solder layer, despite that the thermal resistance of TIM increasing as deterioration of the TIM takes place. That is, the same monitored increment ratio of $R_{\mathrm {thjc}}$ caused by the solder fatigue may correspond to different health status of the IGBT module, which cannot accurately reflect its actual health status. Then, a compensation strategy for thermal resistance monitoring based on the TIM aging rate is proposed, which uses the established mapping relationship to decouple the negative coupling part of TIM degradation. The compensated thermal resistance can better reflect the actual health status of the IGBT module and approximately eliminate the negative impact. Finally, the feasibility of the proposed compensation strategy is verified by finite element model (FEM) analysis and experiments. [ABSTRACT FROM AUTHOR]

• Studied the distribution characteristics of six heavy metals in four anaerobic digestion system. • Effects of substrate types on the transformation of heavy metal speciation was investigated. • The mechanism leading to the transformation of heavy metal speciation was hypothesized. Chemical speciation can fundamentally affect the potential toxicity and bioavailability of heavy metals. The transformation of heavy metal speciation and change of bioavailability were investigated in an anaerobic digestion (AD) system using four different substrates (pig manure (PM), cattle manure (CAM), chicken manure (CHM) and rice straw (RS)). The results obtained indicated that the total contents of heavy metals in PM, CHM and CAM were higher than in RS and decreased in the order Zn > Cu > Ni > Pb > As > Cd in all substrates. Moreover, the speciation with the largest proportion for each heavy metal was the same both in the different substrates and the biogas residues. Among them, Zn, Ni, Cd and As were mainly in the reducible fraction (F2), while Cu was mainly in the oxidizable fraction (F3) and Pb occurred predominantly in the residual fraction (F4). Our results further indicated that the AD process had a greater effect on the speciation of heavy metals in CHM and PM, but less on CAM and RS. The rates of change in bioavailability followed the order PM > CHM > CAM > RS. Changes in organic matter, humic acid or local metal ion environment as a result of AD were inferred as likely mechanisms leading to the transformation of heavy metal speciation. These results enhanced our understanding of the behavior of heavy metals in AD and provided a new perspective for the treatment and disposal of the substrates. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Monitoring the defective multichip insulated gate bipolar transistor (IGBT) module is a cost-effective approach to improve the quality of customer service. A method using time duration of the gate charge is proposed to monitor bond wires fatigue of the multichip IGBT modules when the modules are in the off-state. It is based on the fact that failure of the chip branch due to bond wires fatigue changes the gate input capacitance of the multichip IGBT module. The health state of bond wires can be converted into the change of time duration of gate charge under the constant gate current. A driver containing the constant current source is proposed. The study results indicate that the time duration of the gate charge decreases significantly when the failure of the chip branch occurs, and the effect of junction temperature can be ignored within the special range of gate voltage. Condition monitoring can be implemented during the off-state of the multichip module and without considering the effects of junction temperature. The confirmatory experiment is carried out to verify the correctness of the proposed method. [ABSTRACT FROM AUTHOR]

Stability studies of voltage-source converter HVDC (VSC-HVDC) systems are mainly based on small-signal linearization techniques. However, when VSC-HVDC systems become unstable due to large-signal disturbances, the small-signal analysis method would be no longer available. In this paper, the large signal stability of VSC-HVDC system is studied based on mixed potential theory. A simplified state-space averaging model of VSC-HVDC system is established under the synchronous rotating reference frame. Based on this model, the stability prediction criteria for VSC-HVDC system under large-signal disturbances is obtained through Brayton-Moser's nonlinear potential method. On this foundation, the influence of system parameters on the large-signal stability is studied and the boundaries of stability are located as well. Time-domain simulations conducted in Matlab/Simulink are used to test the stability of the working points next to the stable boundary, which aim to prove the correctness of the obtained stability criterion. Aiming at the unstable situation, the time-domain simulation results prove the feasibility of the method of adjusting the system parameters according to the stability criterion to make the system stable, which further verifies the correctness of the stability criterion. [ABSTRACT FROM AUTHOR]

The existing research on voltage-source converter HVDC (VSC-HVDC) system stability mostly focuses on small-signal stability analysis methods. However, when large-signal disturbances occur, the intrinsic nonlinearity of the VSC-HVDC system becomes inevitable so that the small-signal studies are no longer valid. In this paper, a large-signal stability analysis method of the VSC-HVDC system is proposed based on the estimation of domain of attraction (DOA). This method can not only analyze the asymptotic stability of the operating point, but also answer the question of how large deviations from the operating point can be tolerated by the system. By using Takagi-Sugeno (T-S) fuzzy model and Lyapunov stability theorem, the DOA of the VSC-HVDC System at the operating point is estimated, and the large-signal stability of VSC-HVDC System is analyzed. On this foundation, the influence of system parameters on the large-signal stability is studied. The results can be used to guide the adjustment of system parameters to solve the problem of system instability. The time-domain simulations conducted in Matlab/Simulink are used to test the stability of the system under large-signal disturbance in the range of DOA. The simulation results verify the feasibility and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

With the widespread application of lithium-ion battery packs, it calls for efficient balancing methods to improve the performance of these battery systems. The relevant research has focused on the design of equalization circuits and control strategies while neglecting quantitative analysis and comparison of battery active equalization structures from the systematic level. In this paper, we propose an improved system-theoretic modeling approach for active equalization structures that takes into account the battery's constraints, including equalization current rate and SOC operation range. Accordingly, the mathematical models of various active equalization structures are derived that can describe their equalization dynamic behavior. Then, the analytical algorithms are developed to estimate the balancing time of active equalization structures online. Finally, extensive numerical simulations are conducted to evaluate and compare the average performance of these equalization systems in term of equalization time. It then comes up with a comprehensive comparison among them. Consequently, the Multicell-to-Multicell (MC2MC) balancing structure benefits the fast balancing speed and the lowest sensitive to initial batteries’ SOCs. The global structure has the lowest implementation cost and the series structure benefits the simplest control. Moreover, the module-based structures have faster balancing speed when each module contains about 4–6 batteries. [ABSTRACT FROM AUTHOR]

IGBT power module is the key component of the power electronic converter, but it has the lowest reliability. The junction temperature is the crucial factor which affects power module’s reliability. To some extent, the power handling capability of the converter depends on the thermal stress of the power module. Thermal management is an effective method to improve the reliability of power device, as well as enhance the power capability. For this purpose, this paper introduces the reliability design to the power converter’s traditional compensation controller design for the first time. A new concept of generalized dual-loop controller, which includes temperature control loop and electric power control loop, is proposed. The reliability and stability of the system are both considered, with the help of the hybrid controller, the power converter can operate steadily with higher reliability. The novelty of this paper is to improve the thermal control method of carrier frequency adjustment through experimental implementation during the full life cycle of the converter. The target is to control the temperature variation to be almost a constant value as well as extend the lifetime of the converter. IR sensor is used to measure the chip temperature of the unpackaged IGBT module. The temperature variation and the average temperature are all considered in thermal management, from the reliability improvement point of view. At last, the idea is digital implemented based on a varying load of power inverter system with real-time measurement of the chip’s surface temperature. [ABSTRACT FROM AUTHOR]

In order to further improve the efficiency of dual-active-bridge (DAB) converter, a hybrid five-variable modulation scheme with minimal root mean square (rms) current is proposed in this article, which combines the traditional phase-shift and pulsewidth modulation schemes. By adopting the proposed optimal scheme, a wider zero-voltage switching (ZVS) operation range and lower rms current level are achieved simultaneously when compared with other modulation schemes, which significantly improves the efficiency of the DAB converter. Moreover, for the complexity of the proposed modulation scheme with five variables, the Fourier decomposition based analytical expressions are derived for the converter and a generalized performance analysis results are presented. Besides, in order to avoid the analysis error, especially at light-load condition, the optimization strategy takes the rms current as the optimal objective, which includes the eight harmonic component of the inductor current rather than just considers the fundamental component. And an offline particle swarm optimization algorithm is introduced to acquire the optimal operating points for the whole power range. To substantiate the effectiveness of the proposed modulation scheme, a comprehensive comparison among related works in terms of the rms value and ZVS range were carried out under various operation condition. Finally, a 1.2 kW experimental platform was built and the highest experimental efficiency under the proposed modulation scheme reaches 96.8%. [ABSTRACT FROM AUTHOR]

Light-emitting diodes (LEDs) are widely used in street lighting, landscape lighting, liquid crystal display (LCD) backlighting, healthcare, etc. As an important part of LED lighting products, LED driver plays a vital role in maintenance costs reduction, energy saving and lifetime prolongation. In this paper, a single-stage LED driver is proposed, which is integrated by a totem-pole bridgeless power factor correction (PFC) unit and several modular LCL-T resonant rectifiers. The totem-pole bridgeless PFC unit and the LCL-T resonant rectifiers are integrated by sharing switches, which can simplify the circuit and reduce the system cost. The output current can be regulated by applying the variable inductor control. Constant duty cycle and fixed switching frequency operation can be achieved as well. The operating principle and the performance of the proposed converter are analyzed in this paper. In addition, a precise parameter design method is proposed by considering the high-order harmonics. At last, an experimental prototype is established to validate the proposed parameter design and variable inductor control method. [ABSTRACT FROM AUTHOR]

Potential defects inside an insulated gate bipolar transistor (IGBT) module can be seen as precursors of being about to wear out, and are important for health monitoring of the IGBT module which is used to enhance reliability. A method for detecting defects in the IGBT module by identifying dynamic changes of the gate current is presented in this paper. It is based on the fact that parasitic elements inside the IGBT module are affected by local damage induced by aging over time, and subsequently, these influences are easily distinguished by dynamic changes of the gate current. The proposed prognostic approach is based on relevance vector machine framework, which can give accurate predictions and allow operators to observe unhealthy IGBT modules inside a power converter, and then take appropriate measures timely to avoid breakdown. The parasitic elements involved in the gate circuit are extracted, and their contributions to dynamic changes of the gate current are also discussed. Finally, a confirmatory experiment is carried out, and the correctness of the proposed method is verified. [ABSTRACT FROM AUTHOR]

In this article, an efficiency-oriented hybrid duty modulation (HDM) scheme is proposed for the dual active bridge (DAB) converter that can reduce the inductor root-mean-square (rms) current and extend the switch soft-switching range. First, a complete description of the combination forms of different modulation schemes is presented considering the allocation of the zero-voltage portion. A unified description for these combination forms is obtained in the frequency domain. Second, the symmetric–symmetric duty modulation (SSDM) scheme and asymmetric–symmetric duty modulation (A2SDM) scheme are established to minimize the inductor rms current by considering its fundamental component. Third, the characteristics of SSDM, A2SDM, and the traditional phase shift modulation schemes are compared from several aspects, mainly including the inductor rms current and the soft-switching performance. Furthermore, the loss breakdown analysis results for the three modulation schemes are presented and compared. According to these results, the HDM scheme is proposed to improve the overall efficiency of the DAB converter. Finally, an experimental prototype was built with a peak efficiency of 97%, which validates the effectiveness of the proposed modulation scheme. [ABSTRACT FROM AUTHOR]

Wide bandgap (WBG) devices offer the advantages of high frequency, high efficiency, and high power density to power converters due to their excellent performance. However, their low parasitic capacitance and fast switching speed also make them more susceptible to switching oscillations. The switching oscillations can cause voltage and current overshoots, shoot-through, electromagnetic interference, additional power loss, and even device damage, which can seriously affect the performance of power converters and systems. However, a comprehensive and in-depth overview is lacking on this topic. This article reviews the types, the causes and negative effects, the effects of parasitic parameters and suppression methods of these switching oscillations, which is helpful for practical engineering. First, the switching oscillations are divided into different types, and their causes and negative effects are reviewed. Then, the effects of different parasitic parameters on the switching oscillations are overviewed. It is found that due to the different physical structures of silicon carbide metal-oxide-semiconductor field-effect transistors, enhancement-mode gallium nitride high-electron mobility transistors (eGaN HEMTs), and cascode GaN HEMTs, the effects are also different. Finally, the main methods of suppressing the switching oscillations are summarized, and the advantages and disadvantages of these methods are presented. Furthermore, future research works on this topic and the conclusion of this paper are drawn, which will help readers deepen their understanding of the switching oscillations of WBG devices, and inspire readers to better use WBG devices for high-frequency and high-efficient power conversion. [ABSTRACT FROM AUTHOR]

In order to realize power flow control among photovoltaic (PV) panel port, battery port, and load port in the distributed photovoltaic power generation system, integrated three-port dc–dc converters (TPCs) are widely adopted. The objective of this article is to provide a comprehensive, comparative, and insightful analysis and overview of these TPCs. First, based on the power transmission and control requirements of the system, five topological structures of three-port dc–dc conversion system (TPCS) composed of two or three two-port dc–dc converters are presented. And the five structures are comparatively analyzed. Second, based on these topological structures, and combing with the basic two-port dc–dc converters, three groups of typical TPCs with different galvanic isolation requirements are derived, respectively, by sharing switches, combining branches, etc., And comprehensive analysis, comparisons, and reviews of these TPCs with different structures of each isolation type are presented with tables and figures. Finally, the comparison results of the three isolation groups are summarized, which leads to a guidance for the selection of TPCs in different applications, and then some suggestions for the future research on TPCs are given. [ABSTRACT FROM AUTHOR]

Multiple output LED drivers are necessary to achieve better performance and higher reliability in street lighting, tunnel lighting and LCD background lighting applications. Based on LCL-T constant-current characteristics, a modular multiple output LED driver is proposed in this paper. The LCL-T rectifiers are connected to the same voltage bus and work like current sources. However, since there are much higher voltage harmonics in the AC square bus voltage, it is very important to quantitatively analyze how these harmonics influence the precision of the output currents. In addition, all of the switches can achieve Zero Voltage Switching (ZVS) by proper design of the LCL-T network. Finally, a 200-W prototype with five channels is established with an efficiency of 92.25%. [ABSTRACT FROM AUTHOR]

Wide bandgap devices such as gallium nitride (GaN) devices are being widely used due to their low on-resistance and parasitic parameters that can improve system performance compared to Si mosfets. However, these advantages mentioned above can sometimes lead to unexpected behavior in practical systems, such as false triggering oscillation. False triggering oscillation may cause overshoot, electromagnetic interference, shoot-through, and even device damage, which seriously affects the performance of the system. In this paper, an RC snubber circuit is proposed to suppress false triggering oscillation in a half-bridge circuit, and the design method of the RC parameters is proposed. The proposed oscillation suppression method is simpler, easier to implement, and more effective than the active gate driver. In addition, it can provide guidance for oscillation suppression design in high-order systems. First, the double pulse circuit is used as an example to analyze false triggering oscillation and its high-frequency equivalent circuit is obtained. Then, the RC region is established by scrutinizing the characteristic equations via a root locus method. The RC snubber circuit has better oscillation suppression effect when the RC parameters are within the region rather than outside the region. Finally, the RC region designed by the proposed method is verified by simulation and experiment results, and the proposed method indicates a substantial improvement of the switching characteristics of the controlled device at turn-off. [ABSTRACT FROM AUTHOR]

High step-up boost converters with coupled inductor have attracted much attention in the fuel cell or photovoltaic grid-connected generation system, however, there are few literatures elaborated on the construction ideas and derivation methods of them. Accordingly, in order to obtain a clear roadmap on the derivation and inner connection of these converters, a comprehensive review and analysis are presented in this paper. First, the basic boost converter with coupled inductor is regarded as the basic topology, and its merits and demerits are analyzed in detail. Then, in order to address these demerits, various step-up techniques are introduced, such as the rectifier circuit, the active-clamped circuit, the multi-winding coupled inductor, and the voltage doubler rectifier; and numerous new topologies are continuously proposed by combinations and equivalent simplifications. In addition to a detailed synthesis of each topology, a comparative and quantitative analysis among some important converters is presented, and the optimal one is chosen to build a 250 W prototype. Finally, based on comparisons and analysis, the main characteristics and inner connections of these high step-up boost converters with coupled inductor are identified and clarified. [ABSTRACT FROM AUTHOR]

In this paper, we propose to monitor the thermal parameters of insulated gate bipolar transistor (IGBT) module using the case temperature. This method works during the shutoff period of IGBT module where the case temperature is in the cooling phase By establishing the relationship between the Cauer-type thermal RC parameters and the time constants of case temperature cooling curves, thermal parameters of the IGBT module can be identified. The proposed method is able to eliminate the influence of thermal interface material (TIM) degradation on the monitored results, which is quite challenging for the current case temperature monitoring methods. Moreover, it enables the detection of thermal resistance and thermal capacitance of the TIM and that of the IGBT module at the same time. Experimental tests are performed to validate the accuracy and feasibility of the proposed method. Moreover, impacts of the junction temperature, case temperature sensing position, and thermal coupling on the monitored results are analyzed. [ABSTRACT FROM AUTHOR]

A single-stage high-frequency resonant ac/ac converter converts the ac-line input voltage into the high-frequency sinusoidal output voltage, which consists of two power conversion units, i.e., a power factor correction (PFC) unit and a high-frequency resonant dc/ac unit, and it can be used to derive a modular multichannel constant current LED driver. By adopting a totem-pole bridgeless PFC boost rectifier to reduce conduction losses, a single-stage bridgeless high-frequency resonant ac/ac converter is proposed in this paper. The operating principle is described, and the performance analysis is presented in detail. Moreover, the quantitative parameter design method of the main circuit is presented, which is suitable for other single-stage ac input converters, such as a single-stage PFC rectifier. Finally, a 130-W prototype has been built and tested to verify the correction of related theoretical analysis and parameter design. [ABSTRACT FROM AUTHOR]

The junction temperature fluctuation of an insulated-gate bipolar transistor (IGBT) is the most important factor of its aging failure, and smoothing the fluctuation is an effective way to improve the life of an IGBT. The existing methods for smoothing the fluctuation by active junction temperature control are not yet ready wide application, and exploring the different approaches to active junction temperature control is a hot topic. This paper presents a method of active junction temperature control that shifts the turn-off trajectory of an IGBT to adjust the IGBT turn-off loss for smoothing the junction temperature. The relationship between parameters of the adjusting circuit and turn-off loss is analyzed. On the basis of this analysis, a method of estimating the smoothing ability for the proposed active junction temperature control is deduced. Using an IGBT installed in a 1.2-MW direct-drive wind power converter as an example, the evaluation result shows that the proposed method can completely smooth the junction temperature fluctuation caused by a 40% rated load fluctuation. Finally, a low-power experiment is carried out. [ABSTRACT FROM PUBLISHER]

A series of spiro [fluorene-9,7′-dibenzo[c,h]acridine]-5′-one (SFDBAO) derivatives have been concisely and cleanly obtained by exposure to sunlight without external photosensitizers in the higher yields than that when using a UV lamp. An interesting autocatalyst and self-sensitive procedure have been proposed to explain the effective photooxygenation. SFDBAO derivatives exhibit the continuous π-stacks in single-crystal and electron-withdraw properties with red light-emitting and photovoltaic properties. [ABSTRACT FROM AUTHOR]

Objective To study the curative effect and prognosis of patients with basal ganglia cerebral hemorrhages treated using a transcortical-sulcus approach and compare with results obtained using the traditional cerebral cortex approach. Methods Clinical data were collected from 106 patients with hypertensive hemorrhage in the basal ganglia who were treated using either a transcortical-sulcus approach or traditional cerebral cortex approach. The rate of rehemorrhage, incidence of epilepsy, and 3-month efficacy (defined by an activities of daily living score) rate between the 2 groups were compared. Results The 3-month efficacy rates of patients treated using the transcortical-sulcus and traditional cerebral cortex surgical approaches were 78.4% and 60%, respectively ( P < 0.05). The incidence of epilepsy was lower in the transcortical-sulcus approach group compared with the traditional approach group, and significant differences were detected between the 2 groups ( P < 0.05). Conclusions The transcortical-sulcus approach can significantly improve the prognosis of patients with intracerebral hemorrhages in the basal ganglia and reduce the incidence of postoperative seizures. [ABSTRACT FROM AUTHOR]

Power semiconductors in the wind turbine power converter system suffer from two-scale thermal loadings, the fundamental frequency thermal cycling caused by the output frequency of converter and the low frequency thermal cycling due to the variation of long-term wind speed. These two-scale thermal loadings introduce different consumed lifetimes. Accurate lifetime estimation in the wind power application is desired for reliability prediction and health management. This paper adopts the Bayerer lifetime model to evaluate the consumed lifetime of power semiconductors in wind power converter systems based on a numerical junction temperature calculation method. Lifetime estimation can be improved by taking into account the ambient temperature. Studies show that fluctuations of the ambient temperature increase the consumed lifetime due to the low frequency thermal cycling, but have little effect on the consumed lifetime due to the fundamental frequency thermal cycling. Our results also show that the consumed lifetime due to fundamental frequency thermal cycling mainly falls on the high wind speed area, whereas the consumed lifetime due to low frequency thermal cycling is clustered in the area due to large low frequency junction temperature fluctuations. The resulting distribution characteristics can be used in the thermal management for reliability improvement. [ABSTRACT FROM AUTHOR]

Chip fatigue inside an insulated gate bipolar transistor (IGBT) module is a kind of incipient defect. It can be considered as an indication of the impending failure, and is utmost important for the safe operation of IGBT modules. Therefore, monitoring the chip fatigue is one of crucial measures to enhance the operating reliability of IGBT modules. This paper presents a prognostic approach for the chip fatigue based on grey relational analysis (GRA), which uses dynamic change of the gate voltage as precursor parameter. This dynamic change is caused by aging of the intrinsic parasitic elements involved in gate drive circuit, which reflect the advent of chip fatigue. Grey relational grade is employed in this proposed prognostic approach to quantify the extent of those dynamic changes by little data, and find out potential chip fatigue. Then the operator would have a chance to schedule the maintenance and replace defective IGBT modules timely to avoid wear out. So it can be seen as a prefault diagnostic method. Finally, a confirmatory experiment is also carried out, and the correctness of the proposed approach is verified. [ABSTRACT FROM AUTHOR]

Synchronization with the grid voltage is critical in the control of grid-connected power converters. Under unbalanced grid condition, the conventional synchronous reference frame phase-locked loop (SRF-PLL) does not work well due to the effect of the fundamental negative sequence component. This paper proposes a new synchronization method, the sinusoidal amplitude integrator based phase locked loop (SAI-based PLL), to efficiently eradicate the effect of the fundamental negative sequence component. As a result, it can accurately and quickly estimate the amplitude and phase angle of the fundamental components of grid voltages in unbalanced grid conditions. In addition, when dc offset and harmonics are contained in the grid voltage, a multi-SAI-based PLL method is developed to extract the synchronization signal. The proposed SAI-based PLL incorporates the sinusoidal amplitude integrator into the conventional SRF-PLL. Its operation is analyzed using the complex-vector notation. Simulation and experimental results on the performance of the proposed SAI-based PLL and comparison with other synchronization methods are presented. [ABSTRACT FROM AUTHOR]