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- 2019
- cascaded H-bridge (CHB) multilevel converters
- PWM clamping strategy
- solar PhotoVoltaic (PV)
- fault tolerance
- reactive power
- Ancillary services
- Electrical Engineering and Automation
- Indian Institute of Technology
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Dicyanovinyl substituted push–pull chromophores: effect of the central C=C/phenyl spacers, crystal structures and application in hydrazine sensing
摘要： To discern the distinctive effect of C=C bond and phenyl bridge on the photophysical and chemical properties of D?π?A molecular systems, three new dicyanovinyl substituted push–pull chromophores 1-3 containing either a C=C bond or a phenyl ring as the central π?linker, were synthesized by Suzuki-Miyaura and Knoevenagel reactions. Together with the counterpart of 1 developed by Zhang’s group (TPE-z), their optical properties and single crystal structures were systematically and comparatively investigated. Notably, the simple π–extension of a C=C linker to a phenyl ring between electron-donor and -acceptor moieties could greatly affect the photophysical properties of chromophores, particularly leading to significant hypsochromic shifts in both absorption and emission spectra. Meanwhile, as a node of twisted sections in chromophores, the C=C bond was demonstrated to play an important role in the nonradiative relaxation of excited states, as compared to the rigid phenyl spacer. Moreover, the three chromophores were found to display spectral responses to hydrazine with slightly different sensitivities and visual detection of hydrazine in gaseous state was achieved via using readily fabricated paper test strips.
关键词： C=C bond,hydrazine sensing,phenyl bridge,push-pull chromophores,photophysical properties,Dicyanovinyl
更新于2025-09-19 17:15:36
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An iminodibenzyl–quinoxaline–iminodibenzyl scaffold as a mechanochromic and dual emitter: donor and bridge effects on optical properties
摘要： The influence of phenyl linkage and donor strength on the photophysical properties of new derivatives of quinoxaline-containing iminodibenzyl and iminostilbene moieties is studied. The donor–acceptor derivatives showed dual thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) despite a large energy gap between the excited singlet and triplet states (ca. 0.5 eV). This extremely rare observation is explained by the twisted and rigidified structure of the iminodibenzyl moiety.
关键词： dual emitter,quinoxaline,room temperature phosphorescence,iminodibenzyl,optical properties,mechanochromic,bridge effects,thermally activated delayed fluorescence,donor
更新于2025-09-19 17:15:36
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Molecular design for novel sensing materials with self-screening interference effect (SSIE): Reversible recognizing Cu2+ in aqueous and biologic samples
摘要： In the work, self-screening interference effect (SSIE) was proposed for sensing trace Cu2+ by simply thermodynamic control reactions, using dipyridine as self-screening interference group, rhodamine as mother chromophore and cyanuric chloride as connecting bridge. After its UV-vis and fluorescent spectral properties were optimized in detail, it was noted to find that the present sensing material (RACD) could selectively and reversibly react Cu2+ with obvious colorimetric or fluorescent spectral and color changes from colorless to pink or orange-red. Some other concomitant ions, even trivalent Fe3+ or Al3+, had no interferences on it. Under the optimized conditions, RACD could multiple-mode sense trace Cu2+ in aqueous with a detection limit as low as 11.0 nmol/L. Especially with low toxicity, RACD was successfully applied for quantitatively monitoring Cu2+ and evaluating its toxicity in living cells and bio-tissues. RACD-functionalized paper-strips were also prepared to visibly recognize Cu2+ more conveniently. The selective action mechanism for RACD to Cu2+ was to form some stable 5-membered and 5-membered condensed rings between Cu2+ and O or N atoms.
关键词： Self-screening interference effect (SSIE),Tumor-bearing mice,Recognition mechanism,Trace Cu2+,Cyanuric-bridge multi-chelate,Reversibly sensing
更新于2025-09-19 17:15:36
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Effect of double bond conjugation on hole mobility of thiophene-based hole transport materials in perovskite solar cells
摘要： It is of great significance to fully explore the relationship between π-bridge size and intermolecular packing for improving the hole mobility of hole transport materials in perovskite solar cells. We performed the density functional theory (DFT) computations of a series of Z26 derivatives (Z26-2, Z26-3, and Z26-4) and investigated the effect of the size of π-bridge and intermolecular packing on hole mobility of hole transport materials. The calculated results show that Z26-2 (7.7 ? 10?4 cm2 V?1 s?1) and Z26-3 (1.3 ? 10?3 cm2 V?1 s?1) have larger hole mobility than Z26 (5.60 ? 10?4 cm2 V?1 s?1) due to their appropriate conjugated length leading to effective face to face packing. The smallest hole mobility of Z26-4 (4.20 ? 10?5 cm2 V?1 s?1) is attributed to its overlong conjugation with four double bonds on each side, which produces a long centroid-to-centroid distance and small electronic coupling. The present theoretical study on the relationship between the size of π-bridge and intermolecular packing provides insight for the future design of thiophene-based hole transport materials.
关键词： Intermolecular packing,Hole transport materials,Density functional theory,Perovskite solar cells,π-bridge size
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Gravitational Physics with Atomic Quantum Sensors
摘要： This paper proposes a practical solution of high-frequency-link dc transformer based on switched capacitor (SCDCT) for medium-voltage dc (MVDC) power distribution application. Compared to the traditional dc transformer scheme, the proposed SCDCT can disconnect from MVDC distribution grid effectively as a dc breaker when a short fault occurs in the distribution, can enhance power transfer capacity, and always ensures high-frequency-link voltage match to improve current impact and ef?ciency performances, and the redundancy design can be achieved when some submodules fail to improve the reliability. In the paper, the topology, voltage and power characterization, control strategy, startup, and fault solution of SCDCT are presented and analyzed comprehensively. At last, an SCDCT prototype is built and the experimental results verify the correctness and effectively of the proposed solution.
关键词： switched capacitor,dc transformer,dc–dc converter,solid-state transformer (SST),DC distribution,high-frequency-link,dual active bridge (DAB)
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Thinking Beyond Limiting Efficiencies Of Advanced Concepts: Design Rules And Material Requirements For Realistic Devices
摘要： The current-fed dual active bridge (CF-DAB) dc–dc converter gains growing applications in photovoltaic (PV) and energy storage systems due to its advantages, e.g., a wide input voltage range, a high step-up ratio, a low input current ripple, and a multiport interface capability. In addition, the direct input current controllability and extra control freedom of the CF-DAB converter make it possible to buffer the double-line-frequency energy in grid-interactive PV systems without using electrolytic capacitors in the dc link. Therefore, a PV system achieves high reliability and highly ef?cient maximum power point tracking. This paper studies the optimized operation of a CF-DAB converter for a PV application in order to improve the system ef?ciency. The operating principle and soft-switching conditions over the wide operating range are thoroughly analyzed with phase-shift control and duty-cycle control, and an optimized operating mode is proposed to achieve the minimum root-mean-square transformer current. The proposed operating mode can extend the soft-switching region and reduce the power loss, particularly under a heavy load and a high input voltage. Moreover, the ef?ciency can be further improved with a higher dc-link voltage. A 5-kW hardware prototype was built in the laboratory, and experimental results are provided for veri?cation. This paper provides a design guideline for the CF-DAB converter applied to PV systems, as well as other applications with a wide input voltage variation.
关键词： root-mean-square (RMS) current,photovoltaic (PV),soft switching,optimized operation,Current-fed dual active bridge (CF-DAB)
更新于2025-09-19 17:13:59
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Ultrasensitive MoS2 photodetector by serial nano-bridge multi-heterojunction
摘要： The recent reports of various photodetectors based on molybdenum disulfide (MoS2) field effect transistors showed that it was difficult to obtain optoelectronic performances in the broad detection range [visible–infrared (IR)] applicable to various fields. Here, by forming a mono-/multi-layer nano-bridge multi-heterojunction structure (more than > 300 junctions with 25 nm intervals) through the selective layer control of multi-layer MoS2, a photodetector with ultrasensitive optoelectronic performances in a broad spectral range (photoresponsivity of 2.67 × 106 A/W at λ = 520 nm and 1.65 × 104 A/W at λ = 1064 nm) superior to the previously reported MoS2-based photodetectors could be successfully fabricated. The nano-bridge multi-heterojunction is believed to be an important device technology that can be applied to broadband light sensing, highly sensitive fluorescence imaging, ultrasensitive biomedical diagnostics, and ultrafast optoelectronic integrated circuits through the formation of a nanoscale serial multi-heterojunction, just by adding a selective layer control process.
关键词： photodetector,nano-bridge,multi-heterojunction,MoS2,optoelectronic performances
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 8th International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP) - Le gosier, Guadeloupe (2019.12.15-2019.12.18)] 2019 IEEE 8th International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP) - Hyperspectral Super-Resolution: A Coupled Nonnegative Block-Term Tensor Decomposition Approach
摘要： This paper proposes a grid-tied photovoltaic (PV) system consisting of modular current-fed dual-active-bridge (CF-DAB) dc–dc converter with cascaded multilevel inverter. The proposed converter allows a small dc-link capacitor in the three-phase wye-connected PV system; therefore, the system reliability can be improved by replacing electrolytic capacitors with ?lm capacitors. The low-frequency ripple-free maximum power point tracking (MPPT) is also realized in the proposed converter. First of all, to minimize the in?uence resulting from reduced capacitance, a dc-link voltage synchronizing control is developed. Then, a detailed design of power mitigation control based on CF-DAB dynamic model is presented to prevent the large low-frequency voltage variation propagating from the dc-link to PV side. Finally, a novel variable step-size MPPT algorithm is proposed to ensure not only high MPPT ef?ciency, but also fast maximum power extraction under rapid irradiation change. A downscaled 5-kW PV converter module with a small dc-link capacitor was built in the laboratory with the proposed control and MPPT algorithm, and experimental results are given to validate the converter performance.
关键词： Current-fed dual-active-bridge (CF-DAB),low-frequency ripple,maximum power point tracking (MPPT),small dc-link capacitor,high-frequency link (HFL)
更新于2025-09-19 17:13:59
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Elevated Photovoltaic Performance in Medium Bandgap Copolymers Composed of Indacenodi-thieno[3,2-b]thiophene and Benzothiadiazole Subunits by Modulating the ??-Bridge
摘要： Two random conjugated polymers (CPs), namely, PIDTT‐TBT and PIDTT‐TFBT, in which indacenodithieno[3,2‐b]thiophene (IDTT), 3‐octylthiophene, and benzothiadiazole (BT) were in turn utilized as electron‐donor (D), π‐bridge, and electron‐acceptor (A) units, were synthesized to comprehensively analyze the impact of reducing thiophene π‐bridge and further fluorination on photostability and photovoltaic performance. Meanwhile, the control polymer PIDTT‐DTBT with alternating structure was also prepared for comparison. The broadened and enhanced absorption, down‐shifted highest occupied molecular orbital energy level (EHOMO), more planar molecular geometry thus enhanced the aggregation in the film state, but insignificant impact on aggregation in solution and photostability were found after both reducing thiophene π‐bridge in PIDTT‐TBT and further fluorination in PIDTT‐TFBT. Consequently, PIDTT‐TBT‐based device showed 185% increased PCE of 5.84% profited by synergistically elevated VOC, JSC, and FF than those of its counterpart PIDTT‐DTBT, and this improvement was chiefly ascribed to the improved absorption, deepened EHOMO, raised μh and more balanced μh/μe, and optimized morphology of photoactive layer. However, the dropped PCE was observed after further fluorination in PIDTT‐TFBT, which was mainly restricted by undesired morphology for photoactive layer as a result of strong aggregation even if in the condition of the upshifted VOC. Our preliminary results can demonstrate that modulating the π‐bridge in polymer backbone was an effective method with the aim to enhance the performance for solar cell.
关键词： 2‐b]thiophene,random conjugated polymer,modulating π‐bridge,indacenodithieno[3,photovoltaic property
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Validation of Advanced Photovoltaic Module Materials and Processes by Combined-Accelerated Stress Testing (C-AST)
摘要： The current-fed dual active bridge (CF-DAB) dc–dc converter gains growing applications in photovoltaic (PV) and energy storage systems due to its advantages, e.g., a wide input voltage range, a high step-up ratio, a low input current ripple, and a multiport interface capability. In addition, the direct input current controllability and extra control freedom of the CF-DAB converter make it possible to buffer the double-line-frequency energy in grid-interactive PV systems without using electrolytic capacitors in the dc link. Therefore, a PV system achieves high reliability and highly ef?cient maximum power point tracking. This paper studies the optimized operation of a CF-DAB converter for a PV application in order to improve the system ef?ciency. The operating principle and soft-switching conditions over the wide operating range are thoroughly analyzed with phase-shift control and duty-cycle control, and an optimized operating mode is proposed to achieve the minimum root-mean-square transformer current. The proposed operating mode can extend the soft-switching region and reduce the power loss, particularly under a heavy load and a high input voltage. Moreover, the ef?ciency can be further improved with a higher dc-link voltage. A 5-kW hardware prototype was built in the laboratory, and experimental results are provided for veri?cation. This paper provides a design guideline for the CF-DAB converter applied to PV systems, as well as other applications with a wide input voltage variation.
关键词： soft switching,optimized operation,Current-fed dual active bridge (CF-DAB),photovoltaic (PV),root-mean-square (RMS) current
更新于2025-09-19 17:13:59