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Cai, Xinjian,Wu, Zhenxing,Li, Quanfeng,Wang, Shuxiu The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.2
Cascaded H-bridge multilevel (CHBML) inverters usually include a large number of isolated dc-voltage sources. Some faults in the dc-voltage sources result in unequal cell dc voltages. Unfortunately, the conventional phase-shifted carrier (PSC) PWM method that is widely used for CHBML inverters cannot eliminate low frequency sideband harmonics when the cell dc voltages are not equal. This paper analyzes the principle of sideband harmonic elimination, and proposes an improved PSCPWM that can eliminate low frequency sideband harmonics under the condition of unequal dc voltages. In order to calculate the carrier phases, it is necessary to solve transcendental equations for low frequency sideband harmonic elimination. Therefore, an approach based on the artificial bee colony (ABC) algorithm is presented in this paper. The proposed PSCPWM method enhances the reliability of CHBML inverters. The proposed PSCPWM is not limited to CHBML inverters. It can also be applied to other types of multilevel inverters. Simulation and experimental result obtained from a prototype CHBML inverter verify the theoretical analysis and the achievements made in this paper.
Xinjian Cai,Zhenxing Wu,Quanfeng Li,Shuxiu Wang 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.2
Cascaded H-bridge multilevel (CHBML) inverters usually include a large number of isolated dc-voltage sources. Some faults in the dc-voltage sources result in unequal cell dc voltages. Unfortunately, the conventional phase-shifted carrier (PSC) PWM method that is widely used for CHBML inverters cannot eliminate low frequency sideband harmonics when the cell dc voltages are not equal. This paper analyzes the principle of sideband harmonic elimination, and proposes an improved PSCPWM that can eliminate low frequency sideband harmonics under the condition of unequal dc voltages. In order to calculate the carrier phases, it is necessary to solve transcendental equations for low frequency sideband harmonic elimination. Therefore, an approach based on the artificial bee colony (ABC) algorithm is presented in this paper. The proposed PSCPWM method enhances the reliability of CHBML inverters. The proposed PSCPWM is not limited to CHBML inverters. It can also be applied to other types of multilevel inverters. Simulation and experimental result obtained from a prototype CHBML inverter verify the theoretical analysis and the achievements made in this paper.
Shi, Xinjian,Cai, Lili,Choi, Il Yong,Ma, Ming,Zhang, Kan,Zhao, Jiheng,Kim, Jung Kyu,Kim, Jong Kyu,Zheng, Xiaolin,Park, Jong Hyeok The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.40
<P>Charge carrier dynamics and light harvesting ability are most important for the performance of a photoanode in photoelectrochemical (PEC) systems. In this work, through a facile flame surface treatment process in a reducing atmosphere, oriented WO3 nanoneedles are grown on pre-formed vertically aligned nanohelices. Nanohelices have excellent light harvesting abilities on their own; however, the addition of nanoneedles to the top of nanohelices increases the light harvesting abilities even further. More importantly, the reducing atmosphere for the post-treatment process enhances the metallic properties of WO3, changes the band position to facilitate hole transport, and modifies the flat band potential, all of which contribute to an improved performance in terms of photocurrent density and onset. The as-fabricated WO3 nanohelices/nanoneedles with a metallic interface have also been used for heterojunction photoanode fabrication for water oxidation through two- and four-electron pathways for H2O2 and O2 production, respectively.</P>
General Characterization Methods for Photoelectrochemical Cells for Solar Water Splitting.
Shi, Xinjian,Cai, Lili,Ma, Ming,Zheng, Xiaolin,Park, Jong Hyeok Wiley-VCH 2015 ChemSusChem Vol.8 No.19
<P>Photoelectrochemical (PEC) water splitting is a very promising technology that converts water into clean hydrogen fuel and oxygen by using solar light. However, the characterization methods for PEC cells are diverse and a systematic introduction to characterization methods for PEC cells has rarely been attempted. Unlike most other review articles that focus mainly on the material used for the working electrodes of PEC cells, this review introduces general characterization methods for PEC cells, including their basic configurations and methods for characterizing their performance under various conditions, regardless of the materials used. Detailed experimental operation procedures with theoretical information are provided for each characterization method. The PEC research area is rapidly expanding and more researchers are beginning to devote themselves to related work. Therefore, the content of this Minireview can provide entry-level knowledge to beginners in the area of PEC, which might accelerate progress in this area.</P>