Deadbeat and Hierarchical Predictive Control with Space-Vector Modulation for Three-Phase Five-Level Nested Neutral Point Piloted Converters

Li, Junjie,Chang, Xiangyu,Yang, Dirui,Liu, Yunlong,Jiang, Jianguo The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.6

To achieve a fast dynamic response and to solve the multi-objective control problems of the output currents, capacitor voltages and system constraints, this paper proposes a deadbeat and hierarchical predictive control with space-vector modulation (DB-HPC-SVM) for five-level nested neutral point piloted (NNPP) converters. First, deadbeat control (DBC) is adopted to track the reference currents by calculating the deadbeat reference voltage vector (DB-RVV). After that, all of the candidate switching sequences that synthesize the DB-RVV are obtained by using the fast SVM principle. Furthermore, according to the redundancies of the switch combination and switching sequence, a hierarchical model predictive control (MPC) is presented to select the optimal switch combination (OSC) and optimal switching sequence (OSS). The proposed DB-HPC-SVM maintains the advantages of DBC and SVM, such as fast dynamic response, zero steady-state error and fixed switching frequency, and combines the characteristics of MPC, such as multi-objective control and simple inclusion of constraints. Finally, comparative simulation and experimental results of a five-level NNPP converter verify the correctness of the proposed DB-HPC-SVM.

Differentially expressed serum proteins associated with calcium regulation and hypocalcemia in dairy cows

Shi Shu,Yunlong Bai,Gang Wang,Xinhuan Xiao,Ziling Fan,Jiang Zhang,Chang Zhao,Yang Zhao,Cheng Xia,Hongyou Zhang 아세아·태평양축산학회 2017 Animal Bioscience Vol.30 No.6

Objective: Hypocalcemia is an important metabolic disease of dairy cows during the transition period, although the effect of hypocalcemia on biological function in dairy cows remains unknown. Methods: In this study, proteomic, mass spectrum, bioinformatics and western blotting were employed to identify differentially expressed proteins related to serum Ca concentration. Serum samples from dairy cows were collected at three time points: 3rd days before calving (day –3), the day of calving (day 0), and 3rd days after calving (day +3). According to the Ca concentration on day 0, a total of 27 dairy cows were assigned to one of three groups (clinical, subclinical, and healthy). Samples collected on day –3 were used for discovery of differentially expressed proteins, which were separated and identified via proteomic analysis and mass spectrometry. Bioinformatics analysis was performed to determine the function of the identified proteins (gene ontology and pathway analysis). The differentially expressed proteins were verified by western blot analysis. Results: There were 57 differential spots separated and eight different proteins were identified. Vitamin D-binding protein precursor (group-specific component, GC), alpha-2-macroglobulin (A2M) protein, and apolipoprotein A-IV were related to hypocalcemia by bioinformatics analysis. Due to its specific expression (up-regulated in clinical hypocalcemia and down-regulated in subclinical hypocalcemia), A2M was selected for validation. The results were consistent with those of proteomic analysis. Conclusion: A2M was as an early detection index for distinguishing clinical and subclinical hypocalcemia. The possible pathogenesis of clinical hypocalcemia caused by GC and apolipoprotein A-IV was speculated. The down-regulated expression of GC was a probable cause of the decrease in calcium concentration.

Deadbeat and Hierarchical Predictive Control with Space-Vector Modulation for Three-Phase Five-Level Nested Neutral Point Piloted Converters

Junjie Li,Xiangyu Chang,Dirui Yang,Yunlong Liu,Jianguo Jiang 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.6

To achieve a fast dynamic response and to solve the multi-objective control problems of the output currents, capacitor voltages and system constraints, this paper proposes a deadbeat and hierarchical predictive control with space-vector modulation (DB-HPC-SVM) for five-level nested neutral point piloted (NNPP) converters. First, deadbeat control (DBC) is adopted to track the reference currents by calculating the deadbeat reference voltage vector (DB-RVV). After that, all of the candidate switching sequences that synthesize the DB-RVV are obtained by using the fast SVM principle. Furthermore, according to the redundancies of the switch combination and switching sequence, a hierarchical model predictive control (MPC) is presented to select the optimal switch combination (OSC) and optimal switching sequence (OSS). The proposed DB-HPC-SVM maintains the advantages of DBC and SVM, such as fast dynamic response, zero steady-state error and fixed switching frequency, and combines the characteristics of MPC, such as multi-objective control and simple inclusion of constraints. Finally, comparative simulation and experimental results of a five-level NNPP converter verify the correctness of the proposed DB-HPC-SVM.

Toward the multiscale nature of stress corrosion cracking

Xiaolong Liu,황웅기,박재웅,반동현,Yunlong Chang,이승환,김성엽,한상수,이보영 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.1

This article reviews the multiscale nature of stress corrosion cracking (SCC) observed by high-resolutioncharacterizations in austenite stainless steels and Ni-base superalloys in light water reactors (includingboiling water reactors, pressurized water reactors, and supercritical water reactors) with related opinions. A new statistical summary and comparison of observed degradation phenomena at different lengthscales is included. The intrinsic causes of this multiscale nature of SCC are discussed based on existingevidence and related opinions, ranging from materials theory to practical processing technologies. Questions of interest are then discussed to improve bottom-up understanding of the intrinsic causes. Last, a multiscale modeling and simulation methodology is proposed as a promising interdisciplinarysolution to understand the intrinsic causes of the multiscale nature of SCC in light water reactors, basedon a review of related supporting application evidence

Heat transfer enhancement in gas tungsten arc welding using azimuthal magnetic fields generated by external current

Kim, Yiseul,Lee, Jaewook,Liu, Xiaolong,Lee, Boyoung,Chang, Yunlong Techno-Press 2017 Coupled systems mechanics Vol.6 No.2

This paper proposes the idea to enhance the heat transfer in Gas Tungsten Arc Welding (GTAW) by using the azimuthal magnetic field. The azimuthal magnetic field generated by the external currents makes the Lorentz force stronger, and consequently improves the heat transfer by the faster flow movement. The enhanced heat transfer might improve the welding performance by increasing the temperature at the workpiece. To validate the proposed idea, a two-dimensional axi-symmetric model of GTAW is built, and the multiphysics simulation of GTAW is carried out. As the analysis result, the distributions of electric current, electromagnetic fields, arc flow velocity, and temperature are investigated. Then, the proposed idea for heat transfer enhancement is validated by comparing the Lorentz force, flow velocity, and temperature distribution with and without azimuthal magnetic fields.

Heat transfer enhancement in gas tungsten arc welding using azimuthal magnetic fields generated by external current

Kim, Yiseul,Lee, Jaewook,Liu, Xiaolong,Lee, Boyoung,Chang, Yunlong 테크노프레스 2016 Multiscale and multiphysics mechanics Vol.1 No.1

This paper proposes the idea to enhance the heat transfer in Gas Tungsten Arc Welding (GTAW) by using the azimuthal magnetic field. The azimuthal magnetic field generated by the external currents makes the Lorentz force stronger, and consequently improves the heat transfer by the faster flow movement. The enhanced heat transfer might improve the welding performance by increasing the temperature at the workpiece. To validate the proposed idea, a two-dimensional axi-symmetric model of GTAW is built, and the multiphysics simulation of GTAW is carried out. As the analysis result, the distributions of electric current, electromagnetic fields, arc flow velocity, and temperature are investigated. Then, the proposed idea for heat transfer enhancement is validated by comparing the Lorentz force, flow velocity, and temperature distribution with and without azimuthal magnetic fields.