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Zhao, Fangzhou,Xiao, Guochun,Liu, Min,Yang, Daoshu The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.2
The Modular Multilevel Converter (MMC) is particularly attractive for medium and high power applications such as High-Voltage Direct Current (HVDC) systems. In order to reach a high voltage, the number of cascaded submodules (SMs) is generally very large. Thus, in the applications with hundreds or even thousands of SMs such as MMC-HVDCs, the sorting algorithm of the conventional voltage balancing strategy is extremely slow. This complicates the controller design and increases the hardware cost tremendously. This paper presents a Two-Way Merge Sort (TWMS) strategy based on the prediction of the capacitor voltages under ideal conditions. It also proposes an innovative Insertion Sort Correction for the TWMS (ISC-TWMS) to solve issues in practical engineering under non-ideal conditions. The proposed sorting methods are combined with the features of the MMC-HVDC control strategy, which significantly accelerates the sorting process and reduces the implementation efforts. In comparison with the commonly used quicksort algorithm, it saves at least two-thirds of the sorting execution time in one arm with 100 SMs, and saves more with a higher number of SMs. A 501-level MMC-HVDC simulation model in PSCAD/EMTDC has been built to verify the validity of the proposed strategies. The fast speed and high efficiency of the algorithms are demonstrated by experiments with a DSP controller (TMS320F28335).
Fangzhou Zhao,Guochun Xiao,Min Liu,Daoshu Yang 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.2
The Modular Multilevel Converter (MMC) is particularly attractive for medium and high power applications such as High-Voltage Direct Current (HVDC) systems. In order to reach a high voltage, the number of cascaded submodules (SMs) is generally very large. Thus, in the applications with hundreds or even thousands of SMs such as MMC-HVDCs, the sorting algorithm of the conventional voltage balancing strategy is extremely slow. This complicates the controller design and increases the hardware cost tremendously. This paper presents a Two-Way Merge Sort (TWMS) strategy based on the prediction of the capacitor voltages under ideal conditions. It also proposes an innovative Insertion Sort Correction for the TWMS (ISC-TWMS) to solve issues in practical engineering under non-ideal conditions. The proposed sorting methods are combined with the features of the MMC-HVDC control strategy, which significantly accelerates the sorting process and reduces the implementation efforts. In comparison with the commonly used quicksort algorithm, it saves at least two-thirds of the sorting execution time in one arm with 100 SMs, and saves more with a higher number of SMs. A 501-level MMC-HVDC simulation model in PSCAD/EMTDC has been built to verify the validity of the proposed strategies. The fast speed and high efficiency of the algorithms are demonstrated by experiments with a DSP controller (TMS320F28335).
Gaowen Zhao,Yiqi Hu,Shaomin Li,Zhuo Wang,Mengzhen Guo,Fangzhou Han,Haoran Wang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.2
Cast-in-situ concrete suffers complicated working conditions in sulfate-rich saline soil areas. Sulfate-magnesium combined attack can be encountered in heavy saline or salty lake areas. This study investigated the degradation process and corresponding mechanisms of cast-in-situconcrete, contaminated by chlorides, partially exposed to sulfate-magnesium combined corrosiveenvironments. Concrete samples were cast and partially immersed in the pre-prepareddistilled water, sulfate or sulfate-magnesium mixed solutions for 12 months. Physical andmechanical properties of concrete samples were continuously measured and recorded duringthe immersion. Sulfate concentration in different depths were measured by chemical titration. SEM, XRD, TG/DTG tests were conducted to analyze the microstructural and mineral propertychanges after corrosion for concrete suffered different corrosion conditions. Results show thatpartially immersed concrete encounters both chemical and physical degradation induced bycorrosive sources. Concrete contaminated by chlorides obviously shows weaker resistanceagainst sulfate attack and the strength development is also negatively affected. Magnesium inthe environments reduces the early strength of partially immersed cast-in-situ concrete whileenhancing the sulfate resistance ability in the later corrosion stage. Magnesium limits thenegative effect of contaminated chlorides on the partially immersed cast-in-situ concrete. Performance of cast-in-situ concrete is different from precast concrete when encounteringdifferent corrosive sources, and thus more attention should be paid on the degradation ofcast-in-situ concrete structures induce by aggressive environments.
Wang, Dandan,Zhao, Gong-Bo,Wang, Yuting,Percival, Will J,Ruggeri, Rossana,Zhu, Fangzhou,Tojeiro, Rita,Myers, Adam D,Chuang, Chia-Hsun,Baumgarten, Falk,Zhao, Cheng,Gil-Marí,n, Hé,ctor,Ross, Oxford University Press 2018 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.477 No.2
<B>Abstract</B><P>We present a measurement of the anisotropic and isotropic Baryon Acoustic Oscillations (BAO) from the extended Baryon Oscillation Spectroscopic Survey Data Release 14 quasar sample with optimal redshift weights. Applying the redshift weights improves the constraint on the BAO dilation parameter α(zeff) by 17 per cent. We reconstruct the evolution history of the BAO distance indicators in the redshift range of 0.8 < z < 2.2. This paper is part of a set that analyses the eBOSS DR14 quasar sample.</P>
Tuoya Wulan,Peijun Wang,Chengxin Xia,Xinyu Liu,Mei Liu,Fangzhou Liu,Ou Zhao,Lulu Zhang 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.42 No.1
This paper presents a study on the behavior of a bolted T-stub to square tube connection using Thread-fixed Oneside Bolts (TOBs) through tests and numerical simulations. It outlines a research work of four connections with focus on the failure modes and strengths of the connection under tensile load. It was observed that the thread anchor failure caused by shear failure of hole threads controlled the final failure of the connection in the tests. Meanwhile, the out-of-plane deformation of tube wall resulted in the contact separation between hole threads and bolt threads, which in turn reduced the shear strength of hole threads. Finite element models (FEMs) allowing for the configuration details of the TOBs fixed connection are then developed and compared with the test results. Subsequently, the failure mechanism of hole threads and stress distribution of each component are analyzed based on FEM results. It was concluded that the ultimate strength of connection was not only concerned with the shear strength of hole threads, but also was influenced by the plastic out-of-plane deformation of tube wall. These studies lay a foundation for the establishment of suitable design methods of this type of connection.