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Yanjun Shi

Bio: Yanjun Shi is an academic researcher from Florida State University. The author has contributed to research in topics: Inverter & Transformer. The author has an hindex of 16, co-authored 47 publications receiving 702 citations. Previous affiliations of Yanjun Shi include Huazhong University of Science and Technology & Medical University of South Carolina.

Papers
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Journal ArticleDOI
Yanjun Shi1, Lu Wang1, Ren Xie1, Yuxiang Shi, Hui Li1 
TL;DR: A five-level T-type (5LT2) photovoltaic (PV) inverter that achieves better utilization of SiC devices than the traditional three- level T- type LCL topology at higher switching frequency is presented.
Abstract: A silicon carbide (SiC) T-type LCL inverter can achieve smaller device loss than two-level topology, however, its improvement on power density is limited by current ripple loss on magnetic components as switching frequency increases. This paper presents a five-level T-type (5LT2) photovoltaic (PV) inverter that achieves better utilization of SiC devices than the traditional three-level T-type LCL topology at higher switching frequency. The operation principle of the SiC 5LT2 PV inverter has been presented. The key design aspects including magnetic balancing, short-circuit protection, and digital controller computation time have been discussed and methods are developed. A 60-kW PV converter including boost stage and inverter stage has been built in the laboratory, which achieves a power density of 27 W/in3 and 3 kW/kg, and measured peak efficiency of 99.2%.

89 citations

Journal ArticleDOI
Yuxiang Shi, Ren Xie1, Lu Wang1, Yanjun Shi1, Hui Li1 
TL;DR: Experimental results show the superior performance of the T-type module-based PV inverter and demonstrate the effectiveness of the protection scheme.
Abstract: In this paper, a 1200 V, 100 A T-type full SiC power module is evaluated in a five-level T-type photovoltaic (PV) inverter. The T-type module is characterized with double pulse test, and based on the results, loss evaluation of the PV inverter is performed. The high power density of 27 W/in3 and 3 kW/kg, and the peak efficiency of 99.2% are achieved for the lab prototype. A de-sat based short-circuit protection scheme using commercial driver chip ACPL339J is presented and experimentally verified on the PV inverter prototype. With the presented circuit, less than 600 ns response time is realized, and a two-stage soft turn-off circuit with gate voltage clamping is implemented. A gate voltage stabilizer circuit without affecting the switching loss is also proposed to prevent false trigger. Experimental results show the superior performance of the T-type module-based PV inverter and demonstrate the effectiveness of the protection scheme.

79 citations

Journal ArticleDOI
Lu Wang1, Yanjun Shi1, Yuxiang Shi, Ren Xie1, Hui Li1 
TL;DR: In this article, ground leakage current suppression in a 60kW 5-level T-type (5LT2) transformerless SiC photovoltaic (PV) inverter has been presented.
Abstract: In this paper, ground leakage current suppression in a 60-kW 5-level T-type (5LT2) transformerless SiC photovoltaic (PV) inverter has been presented. The common mode (CM) equivalent circuit is analyzed based on a high frequency (HF) CM loop and a low frequency (LF) CM loop, respectively. In the 5LT2 inverter, the derived HF CM voltage (CMV) is found to have 86% reduction compared to that of a 3-level T-type (3LT2) inverter. The simulation and experiment results are provided to demonstrate the advantages of 5LT2 inverter on HF leakage current suppression. In addition, LF CMV caused by neutral point (NP) voltage oscillation has been analyzed in this paper. It is shown that the LF CMV is nearly proportional to the NP voltage oscillation. Furthermore, an LF CMV compensation method is proposed to suppress the LF CMV by 64%, which is verified by simulation and experiment results. Finally, the leakage current shows 79% reduction in the 5LT2 inverter compared to the conventional 3LT2 inverter in the experiment. A further 52% leakage current reduction is achieved by the LF CMV compensation in the 5LT2 inverter.

56 citations

Journal ArticleDOI
TL;DR: SK2 plays an important role in mitochondrial dysfunction, inflammation responses, hepatocyte death, and survival after hepatic IR and represents a new target for the treatment of IR injury.

52 citations

Journal ArticleDOI
TL;DR: In this paper, a phase-shifted square wave modulation strategy is proposed for modular multilevel converters (MMCs) as well as dc transformers for medium-voltage applications.
Abstract: In this letter, a phase-shifted square wave modulation strategy is proposed for modular multilevel converters (MMCs) as well as dc transformers for medium-voltage applications. The proposed technique can achieve a smaller cell capacitor size without increasing the total device rating (TDR) and degrading the dc current control capability. The operation principle of the proposed method is presented on an isolated modular multilevel dc–dc converter, which consists of an MMC stage and applied as a dc transformer for medium-voltage dc grid. The TDR and passive components sizing are derived and compared with those using other modulation methods. Finally a downscaled hardware prototype has been built and tested to verify the proposed modulation method.

51 citations


Cited by
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Journal ArticleDOI
TL;DR: The cellular and molecular mechanisms that account for the most deleterious effect of hepatic inflammation at the cellular level are discussed, that is, the initiation of a massive cell death response among hepatocytes.

696 citations

Journal Article
TL;DR: The adenine nucleotide translocase (ANT) may provide a molecular link between physiopathological mechanisms of infection and the regulation of MPTP function and so represents a potential therapeutic target.
Abstract: In addition to its normal function, the adenine nucleotide translocase (ANT) forms the inner membrane channel of the mitochondrial permeability transition pore (MPTP). Binding of cyclophilin-D (CyP-D) to its matrix surface (probably on Pro 61 on loop 1) facilitates a calcium-triggered conformational change converting it from a specific transporter to a non-specific pore. The voltage dependent anion channel (VDAC) binds to the outer face of the ANT, at contact sites between the inner and outer membranes, and together VDAC, ANT and CyP-D probably represent the minimum MPTP configuration. The evidence for this is critically reviewed as is the structure and molecular mechanism of the carrier in its normal physiological mode. This provides helpful insights into MPTP regulation by adenine nucleotides, membrane potential and ANT ligands such as carboxyatractyloside and bongkrekic acid. Oxidative stress activates the MPTP by glutathione-mediated cross-linking of Cys 159 and Cys 256 on matrix-facing loops of the ANT that inhibits ADP binding and enhances CyP-D binding. Molecular modeling of the loop containing the ADP binding site suggests an arrangement of aspartate and glutamate residues that may provide a calcium binding site. There are other proteins that may bind to the ANT, modulating MPTP opening and hence cell death. These included members of the Bax/Bcl-2 family (both oncoproteins and tumor suppressors) and viral proteins. Vpr from HIV-1 can bind to ANT and convert it into a pro-apoptotic pore, whereas vMIA from cytomegalovirus interacts to inhibit opening. Thus the ANT may provide a molecular link between physiopathological mechanisms of infection and the regulation of MPTP function and so represents a potential therapeutic target.

448 citations

Journal ArticleDOI
TL;DR: The present review aims at summarizing the current knowledge in liver ischemia-reperfusion, but specifically focusing on liver cell phenotype and paracrine interaction deregulations, as well as some of the scientific controversies in the field.

428 citations

Journal ArticleDOI
TL;DR: The ways in which S1P might be therapeutically targeted are discussed — for example, via the development of chemical inhibitors that target the generation, transport and degradation of S 1P and via thedevelopment of specific S1p receptor agonists.
Abstract: The bioactive lipid sphingosine-1-phosphate (S1P) is involved in multiple cellular signalling systems and has a pivotal role in the control of immune cell trafficking. As such, S1P has been implicated in disorders such as cancer and inflammatory diseases. This Review discusses the ways in which S1P might be therapeutically targeted — for example, via the development of chemical inhibitors that target the generation, transport and degradation of S1P and via the development of specific S1P receptor agonists. We also highlight recent conflicting results observed in preclinical studies targeting S1P and discuss ongoing clinical trials in this field.

390 citations

Journal ArticleDOI
TL;DR: The importance of Ca(2+)-dependent cell death is analyzed in light of new observations of reperfusion-induced cardiomyocyte death, which appears to play an important role in cell death during the initial minutes of reperFusion, particularly after brief periods of ischaemia.
Abstract: Reperfusion may induce additional cell death in patients with acute myocardial infarction receiving primary angioplasty or thrombolysis. Altered intracellular Ca 2+ handling was initially considered an essential mechanism of reperfusion-induced cardiomyocyte death. However, more recent studies have demonstrated the importance of Ca 2+ -independent mechanisms that converge on mitochondrial permeability transition (MPT) and are shared by cardiomyocytes and other cell types. This article analyses the importance of Ca 2+ -dependent cell death in light of these new observations. Altered Ca 2+ handling includes increased cytosolic Ca 2+ levels, leading to activation of calpainmediated proteolysis and sarcoplasmic reticulum-driven oscillations; this can induce hypercontracture, but also MPT due to the privileged Ca 2+ transfer between sarcoplasmic reticulum and mitochondria through cytosolic Ca 2+ microdomains. In the opposite direction, permeability transition can worsen altered Ca 2+ handling and favour hypercontracture. Ca 2+ appears to play an important role in cell death during the initial minutes of reperfusion, particularly after brief periods of ischaemia. Developing effective and safe treatments to prevent Ca 2+ -mediated cardiomyocyte death in patients with transient ischaemia, by targeting Ca 2+ influx, intracellular Ca 2+ handling, or Ca 2+ -induced cell death effectors, is an unmet challenge with important therapeutic implications and large potential clinical impact.

262 citations