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Yonggyun Park,Daesu Han,Yongsug Suh,Wooyoung Choi 전력전자학회 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.6
This paper investigates control algorithms for a doubly fed induction generator with a back-to-back three-level neutral-point clamped voltage source converter in medium voltage wind power systems under unbalanced grid conditions. Three different control algorithms to compensate for unbalanced conditions have been investigated with respect to four performance factors; fault ride-through capability, instantaneous active power pulsation, harmonic distortions and torque pulsation. The control algorithm having a zero amplitude of torque ripple shows the most cost-effective performance concerning torque pulsation. The least active power pulsation is produced by the control algorithm that nullifies the oscillating component of the instantaneous stator active and reactive powers. A combination of these two control algorithms depending on the operating requirements and the depth of the grid unbalance presents the most optimized performance factors under generalized unbalanced operating conditions leading to high performance DFIG wind turbine systems.
Park, Yonggyun,Han, Daesu,Suh, Yongsug,Choi, Wooyoung The Korean Institute of Power Electronics 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.6
This paper investigates control algorithms for a doubly fed induction generator with a back-to-back three-level neutral-point clamped voltage source converter in medium voltage wind power systems under unbalanced grid conditions. Three different control algorithms to compensate for unbalanced conditions have been investigated with respect to four performance factors; fault ride-through capability, instantaneous active power pulsation, harmonic distortions and torque pulsation. The control algorithm having a zero amplitude of torque ripple shows the most cost-effective performance concerning torque pulsation. The least active power pulsation is produced by the control algorithm that nullifies the oscillating component of the instantaneous stator active and reactive powers. A combination of these two control algorithms depending on the operating requirements and the depth of the grid unbalance presents the most optimized performance factors under generalized unbalanced operating conditions leading to high performance DFIG wind turbine systems.
조소라,김대수,조유리,손신중,강형원,남산,한승호,Jo, Sora,Kim, Daesu,Cho, Yuri,Son, Sin Joong,Kang, Hyung-Won,Nahm, Sahn,Han, Seung Ho 한국전기전자재료학회 2018 전기전자재료학회논문지 Vol.31 No.4
The piezoelectric properties of $0.65Pb(Zr_{1-x}Ti_x)O_3-0.35Pb(Zn_{1/6}Ni_{1/6}Nb_{2/3})O_3$ ($PZT_x-PZNN$) ceramics with $0.530{\leq}x{\leq}0.555$ were investigated for application to piezoelectric energy harvesters. Although a morphotropic phase boundary (MPB) was found at approximately x = 0.545, the ceramic with the highest figure of merit (FOM) ($d_{33}{\times}g_{33}$) was observed at a composition of x = 0.540. Values of this figure of merit, $d_{33}{\times}g_{33}$, of $19.6pm^2/N$ and $20.2pm^2/N$ were obtained from $PZT_{0.540}-PZNN$ ceramics sintered at $920^{\circ}C$ and $950^{\circ}C$, respectively. A high output power of $937{\mu}W$ and a high power density of $3.3mW/cm^3$ were obtained from unimorph-type piezoelectric energy harvesters fabricated using $PZT_{0.540}-PZNN$ ceramic sintered at $920^{\circ}C$ for 4h.
Ferroelectrically tunable magnetic skyrmions in ultrathin oxide heterostructures
Wang, Lingfei,Feng, Qiyuan,Kim, Yoonkoo,Kim, Rokyeon,Lee, Ki Hoon,Pollard, Shawn D.,Shin, Yeong Jae,Zhou, Haibiao,Peng, Wei,Lee, Daesu,Meng, Wenjie,Yang, Hyunsoo,Han, Jung Hoon,Kim, Miyoung,Lu, Qingyo Springer Science and Business Media LLC 2018 NATURE MATERIALS Vol.17 No.12