Search

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]

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]

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]

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]