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M. Uno,A. Kukita 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
Differential power processing converters or voltage equalizers have been proposed and used for photovoltaic (PV) string comprising multiple modules/substrings connected in series in order to preclude negative influences of partial shading. The single-switch voltage equalizer using multi-stacked buck-boost converters can significantly reduce the necessary switch count compared to that of conventional topologies, achieving simplified circuitry. However, multiple current sensors are necessary for this single-switch equalizer to effectively perform equalization. In this paper, a current sensorless equalization technique, ΔV-controlled equalization, is presented. An equalization strategy using the ΔV-controlled equalization is explained and discussed on the basis of comparison with other equalization strategies. Experimental equalization tests emulating partial-shading conditions were performed using the single-switch equalizer employing the ΔV-controlled equalization. Negative impacts of partialshading were successfully precluded, demonstrating the efficacy of the proposed ΔV-controlled equalization strategy.
M. Uno,K. Hasegawa 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This paper proposes a modular equalization system integrating module- and cell-level voltage equalizers for energy storage systems consisting of series-connected multiple energy storage modules, each comprising multiple cells connected in series. Phase-shift switched capacitor converters (PS-SCCs) and tapped-inductor-based resonant voltage multiplier (TI-RVM) are employed as module- and cell-level equalizers, respectively. Since two kinds of equalizers are integrated with sharing active switches, the proposed system can halve the switch count compared to conventional modular systems, hence achieving the reduced circuit complexity and cost. In addition, equalization currents of both the PS-SCC and TI-RVM can be constant, regardless of voltage imbalance conditions, offering intrinsic current protection capability at both the module and cell levels. An experimental equalization test was performed using the prototype for three electric double-layer capacitor (EDLC) modules, each containing six cells connected in series. Module and cell voltages were equalized at different rates, demonstrating the equalization performance.
M. Uno,A. Kukita 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
In recent photovoltaic (PV) systems, an energy storage source is often installed for power leveling and/or night-time power supply. However, such PV systems require multiple converters, including a voltage equalizer for series-connected PV modules to preclude negative impacts of partial shading, central converter for PV string control, and equalizer for series-connected energy storage cells to ensure years of safe operation, and therefore, PV systems are prone to complexity. To realize the system-level simplification, a PWM converter integrating voltage equalizers for PV modules and energy storage cells is proposed in this paper. The proposed integrated converter comprises a switched capacitor converter (SCC), PWM buck converter, and series-resonant voltage multiplier (SRVM) that perform PV equalization, string control, and cell equalization, respectively. The derivation procedure of the integrated converter is explained and discussed, followed by operation analysis. An experimental test was performed using series-connected supercapacitor (SC) modules and solar array simulators to emulate a partial-shading condition. With the integrated converter, the extractable maximum power from the PV modules was significantly improved while voltage imbalance of SC modules was adequately eliminated, demonstrating the integrated performance of the proposed converter.
hajime Arimoto,F. Sano,G. Motojima,H. Yamazaki,H. Nakamura,H. Yabutani,H. Kitagawa,H. Okada,J. Arakawa,K. Kondo,K. Ohashi,K. Nagasaki,M. Yamada,M. Uno,M. Kikutake,M. Kaneko,N. Watanabe,N. Nishino,N. S 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III
The measurement of D, CII and CIII line spectral profiles and the CD band spectrum from the vicinity of a test limiter surface is performed in Heliotron J test limiter experiments. With deep insertion of the limiter, there is a localized intense region of the D, CII and CIII line intensity in the limiter surface, and the CD band spectrum is observed at this region. It is considered that the deuterium ion flux and heat load concentrate at this region and enhance carbon impurity generation.r_che
Bendable Differential Power Processing Converter for Curved Photovoltaic Panels
K. Aikawa,H. Sato,M. Uno 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
Electrical characteristic mismatches of seriesconnected photovoltaic (PV) substrings is well known for triggering various negative influences, such as a significant reduction in power generation and occurrence of multiple maximum power points (MPPs). Recently, curved PV panels have been developed. Uneven solar irradiance due to the curved surface results in mismatched substring characteristics. Although various kinds of differential power processing (DPP) converters have been proposed to address the mismatch issues, the conventional converters equipping with bulky magnetic components, such as inductors and transformers, are difficult to be employed for curved PV panels. This paper proposes an LLC resonant voltage multiplier (VM)-based bendable DPP converter using a flexible transformer. The proposed DPP converter can flexibly be applied to curved surfaces thanks to the flexible transformer and lack of bulky magnetic components. Experiments under mismatched irradiance conditions were performed, and the results demonstrated the proposed DPP converter could preclude the mismatch issues.
Fukushima, H.,Schmidt, M.,Sohn, B. J.,Toratani, M.,Uno, I. 대한원격탐사학회 1999 International Symposium on Remote Sensing Vol.15 No.1
The paper first proposes an empirical algorithm for detecting dust-loaded airmass observed by Sea Wide Field-of-view Scanner (SeaWiFS). The proposed dust index formula is based on the curvature of the spectral reflectance estimated from the SeaWiFS band 4 (510 nm band) through band 8 (865 nm band) data, assuming $quot;clear ocean water$quot; reflectance. Evaluation of the algorithm is made over several typical Asian dust images including the ones over the Pacific in April, 1998, when a major dust event was reported. The study analyzes the performance and the characteristics of the algorithm by comparing the satellite-derived dust index images with contemporaneous columnar concentration of dust particles predicted by a numerical dust transport model. The comparison reveals several small-scale differences although their dust distribution patterns show good agreement generally.
Configuration Dependence of Toroidal Current in Heliotron J
gen Motojima,F. Sano,H. Yabutani,H. Okada,H. Nakamura,H. Arimoto,H. Kitagawa,H. Yamazaki,K. Kondo,K. Nagasaki,K. Hanatani,K.Y. Watanabe,M. Kaneko,M. Uno,S. Fujikawa,S. Watanabe,S. Yamamoto,S. Kobayash 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III
A change of toroidal current by controlling the magnetic configuration has been observed in Heliotron J. The effect of the magnetic configuration on the neoclassical bootstrap current has been theoretically investigated for Heliotron J. It is found that the bumpy field component (B04) plays an important role in changing both the value and the direction of the bootstrap current in Heliotron J. The bootstrap current density is reversed at the small minor radius first, and then the net bootstrap current changes its direction from a positive value to a negative value as B04 decreases.