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Keke Hu,Huajun Wang,Yihua Liu,Chao Yang 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.28 No.-
Various heterogeneous KNO3/CaO catalysts with different KNO3 loadings are prepared and used for thesynthesis of glycerol carbonate from glycerol and dimethyl carbonate. It is found that the basicity ofKNO3/CaO catalyst depends on the KNO3 loading and calcination temperature. Under the dimethylcarbonate/glycerol molar ratio of 3.0, reaction temperature of 70 8C, and reaction time of 2 h, the glycerolconversion for the fresh KNO3/CaO(15%, 700) catalyst can reach 99.23%. Recycling experiments revealthat 94.95% of glycerol conversion can be obtained at the fifth reuse for the recovered KNO3/CaO(15%,700), which is much higher than that of unmodified CaO.
Coupled inductor based zero‑voltage‑switching buck/boost converter
Shanshan Wang,Yihua Hu,Ming Gao,Jianjiang Shi,Tao Liu 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.7
This paper proposes a zero-voltage-switching (ZVS) Buck/Boost converter (BBC). In addition, an auxiliary circuit based on a coupled inductor is introduced to realize ZVS for the main MOSFETs. The magnetic coupling inductor plays the role of filtering and provides ZVS conditions for the main MOSFETs. Since all of the switches can achieve soft switching conditions, and the conduction loss of the auxiliary circuit is small, the conversion efficiency for the overall system is improved. When compared with the traditional ZVS implementation methods based on magnetic coupling inductors used in Buck, Boost, and Buck/Boost converters, the proposed topology can prevent current notches on the current waveform of the input source. Since there are no notches on the input source current, when the proposed ZVS implementation method is applied to an interleaved parallel BBC structure, it has a smaller current ripple of the input source. Finally, experimental results are given and analyzed. Based on these results, both the ZVS conditions and efficiency improvement are verified.
Lu, Jiadong,Liu, Jinglin,Hu, Yihua,Zhang, Xiaokang,Ni, Kai,Si, Jikai The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.5
High frequency signal injection (HFI) is an alternative method for estimating rotor position of interior permanent magnet synchronous motor (IPMSM). The general method of frequency and amplitude selection is based on error tolerance and experiments, and is usually set with only one group of HF parameters, which is not efficient for different working modes. This paper proposes a novel rotor position estimation scheme by HFI with optimized frequency and amplitude, based on the mathematic model of IPMSM. The requirements for standstill and low-speed operational modes are met by applying this novel scheme. Additionally, the effects of the frequency and amplitude of the injected HF signal on the position estimation results under different operating conditions are analyzed. Furthermore, an optimization method for HF parameter selection is proposed to make the estimation process more efficient under different working conditions according to error tolerance. The effectiveness of the propose scheme is verified by the experiments on an IPMSM motor prototype.
SYNTHESIS OF ULTRAFINE $Si_3N_4$ PARTICLES BY RF PLASMA CHEMICAL VAPOR DEPOSITION
Hongjie, Zhu,Zhu, Yihua,Han, Jinyi,Li, Chunzhong,Hu, Liming 한국재료학회 1995 Fabrication and Characterization of Advanced Mater Vol.1 No.2
Processing of synthesis $Si_3N_4$ UFP in the RFCVD reactor, using $SiCl_4$ and $NH_3$ as precursors, were experimentally researched. The influence of some operation parameters on the properties of products was investigaed. The nanostructured material made of such $Si_3N_4$ particles was fabricated under highpressure. The results of experiments indicated that it differed from the materials made of coarse $Si_3N_4$ powder on some electric properties.
Jiadong Lu,Jinglin Liu,Yihua Hu,Xiaokang Zhang,Kai Ni,Jikai Si 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.5
High frequency signal injection (HFI) is an alternative method for estimating rotor position of interior permanent magnet synchronous motor (IPMSM). The general method of frequency and amplitude selection is based on error tolerance and experiments, and is usually set with only one group of HF parameters, which is not efficient for different working modes. This paper proposes a novel rotor position estimation scheme by HFI with optimized frequency and amplitude, based on the mathematic model of IPMSM. The requirements for standstill and low-speed operational modes are met by applying this novel scheme. Additionally, the effects of the frequency and amplitude of the injected HF signal on the position estimation results under different operating conditions are analyzed. Furthermore, an optimization method for HF parameter selection is proposed to make the estimation process more efficient under different working conditions according to error tolerance. The effectiveness of the propose scheme is verified by the experiments on an IPMSM motor prototype.
NUCLEATION AND GRAIN-GROWTH MODEL FOR REDUCTION OF ACICULATE ULTRAFINE ${alpha}$-$Fe_2O_3$ PARTICLES
Li, Chunzhong,Hong, Zhifu,Zhu, Yihua,Hu, Liming 한국재료학회 1995 Fabrication and Characterization of Advanced Mater Vol.2 No.4
By use of temperature programmed reduction technology, the kinetics of aciculate ultrafine ${alpha}$-F${e_2}{O_3}$</T powder are studied and the optimum conditions of the reduction process are investigated. From this study the kinetic equation can be written as $rac{d{alpha}}{d1}$=9.003${ imes}{10^3}$ exp($rac{-72.66{ imes}{10^3}}{RT}$)(1-${alpha}$)${alpha}^{0.54}$ this equation fits well with experiment results at 570-720K, and the reduction rate of oxide at the surface of the particles increases and the reduction rate of oxide inner the particles decreases with increasing the degree of ${alpha}$-F${e_2}{O_3}$</T eduction. The optimum temperature for magnetic powder preparation is 630-670K.
Sen Song,Kai Ni,Guipeng Chen,Yihua Hu,Dongsheng Yu 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.1
This study presents a new portable eight-output light emitting diode (LED) driver. The eight output-channels are divided intotwo equal groups, and their output powers can be controlled individually by three active switches. In addition, a simplecapacitor-based passive current balancing circuit (CBC) is employed in each port to guarantee that the currents of the four LEDsare the same. When compared with the conventionally used separate two-output isolated converters, the proposed one uses oneless active switch. Moreover, zero-voltage-switching (ZVS) is achieved, which improves the power efficiency of the driver. Finally, a highly compact prototype is built, which can reach an efficiency of 94.6%.
Hybrid Control and Protection Scheme for Inverter Dominated Microgrids
Xiaotong Xu,Huiqing Wen,Lin Jiang,Yihua Hu 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3
With the high penetration of various sustainable energy sources, the control and protection of Microgrids has become a challenging problem considering the inherent current limitation feature of inverter-based Distributed Generators (DGs) and the bidirectional power flow in Microgrids. In this paper, a hybrid control and protection scheme is proposed, which combines the traditional inverse-time overcurrent protection with the biased differential protection for different feeders with different kinds of loads. It naturally accommodates various control strategies such as P-Q control and V-f control. The parameter settings of the protection scheme are analyzed and calculated through a fast Fourier transform algorithm, and the stability of the control strategy is discussed by building a small signal model in MATLAB. Different operation modes such as the grid-connected mode, the islanding mode, and the transitions between these two modes are ensured. A Microgrid model is established in PSCAD and the analysis results show that a Microgrid system can be effectively protected against different faults such as the single phase to ground and the three phase faults in both the grid-connected and islanded operation modes.
Song, Sen,Ni, Kai,Chen, Guipeng,Hu, Yihua,Yu, Dongsheng The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.1
This study presents a new portable eight-output light emitting diode (LED) driver. The eight output-channels are divided into two equal groups, and their output powers can be controlled individually by three active switches. In addition, a simple capacitor-based passive current balancing circuit (CBC) is employed in each port to guarantee that the currents of the four LEDs are the same. When compared with the conventionally used separate two-output isolated converters, the proposed one uses one less active switch. Moreover, zero-voltage-switching (ZVS) is achieved, which improves the power efficiency of the driver. Finally, a highly compact prototype is built, which can reach an efficiency of 94.6%.
Hybrid Control and Protection Scheme for Inverter Dominated Microgrids
Xu, Xiaotong,Wen, Huiqing,Jiang, Lin,Hu, Yihua The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3
With the high penetration of various sustainable energy sources, the control and protection of Microgrids has become a challenging problem considering the inherent current limitation feature of inverter-based Distributed Generators (DGs) and the bidirectional power flow in Microgrids. In this paper, a hybrid control and protection scheme is proposed, which combines the traditional inverse-time overcurrent protection with the biased differential protection for different feeders with different kinds of loads. It naturally accommodates various control strategies such as P-Q control and V-f control. The parameter settings of the protection scheme are analyzed and calculated through a fast Fourier transform algorithm, and the stability of the control strategy is discussed by building a small signal model in MATLAB. Different operation modes such as the grid-connected mode, the islanding mode, and the transitions between these two modes are ensured. A Microgrid model is established in PSCAD and the analysis results show that a Microgrid system can be effectively protected against different faults such as the single phase to ground and the three phase faults in both the grid-connected and islanded operation modes.