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Improved Grid Voltage Control Strategy for Wind Farms with DFIGs Connected to Distribution Networks
Zhang, Xueguang,Pan, Weiming,Liu, Yicheng,Xu, Dianguo The Korean Institute of Power Electronics 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.3
This paper presents an improved grid voltage control strategy for wind farms with doubly-fed induction generators (DFIGs) connected to distribution networks based on an analysis of the operation limits of DFIG systems. A modified reactive power limit calculation method in different operation states is proposed and a reactive power control strategy during grid voltage dips/rises is further discussed. A control strategy for compensating unbalanced grid voltage, based on DFIG systems, by injecting negative sequence current into the grid through the grid side converter (GSC) is proposed. In addition, the negative current limit of the GSC is discussed. The distribution principle of the negative sequence current among the different DFIG systems in a wind farm is also introduced. The validity of the proposed voltage control strategy is demonstrated by Matlab/Simulink simulations. It is shown that the stability of a wind farm and the power grid can be improved with the proposed strategy.
Self-collision Avoidance Trajectory Planning and Robust Control of a Dual-arm Space Robot
Yicheng Liu,Chunxiao Yu,Jingyuan Sheng,Tao Zhang 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.6
This paper addresses robust trajectory tracking for a dual-arm 6-DOF (degree of freedom) space robot with self-collision avoidance. A trajectory planning method for self-collision avoidance is presented with the information of danger field between the manipulators. On this basis, the kinematics and dynamics models of the whole system are considered together to realize the tracking of the end effectors. Thus a robust decentralized control strategy is proposed based on signal compensation and back-stepping. In contrast to the existing researches, the proposed scheme ensures that the space robotic system can automatically avoid self-collision and displays good robust performance. The simulation results verify the effectiveness of the proposed approach.
Improved Grid Voltage Control Strategy for Wind Farms with DFIGs Connected to Distribution Networks
Xueguang Zhang,Weiming Pan,Yicheng Liu,Dianguo Xu 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.3
This paper presents an improved grid voltage control strategy for wind farms with doubly-fed induction generators (DFIGs) connected to distribution networks based on an analysis of the operation limits of DFIG systems. A modified reactive power limit calculation method in different operation states is proposed and a reactive power control strategy during grid voltage dips/rises is further discussed. A control strategy for compensating unbalanced grid voltage, based on DFIG systems, by injecting negative sequence current into the grid through the grid side converter (GSC) is proposed. In addition, the negative current limit of the GSC is discussed. The distribution principle of the negative sequence current among the different DFIG systems in a wind farm is also introduced. The validity of the proposed voltage control strategy is demonstrated by Matlab/Simulink simulations. It is shown that the stability of a wind farm and the power grid can be improved with the proposed strategy.
78 fs SWCNT-SA mode-locked Tm:CLNGG disordered garnet crystal laser at 2017 nm
Wang, Yicheng,Zhao, Yongguang,Pan, Zhongben,Bae, Ji Eun,Choi, Sun Young,Rotermund, Fabian,Loiko, Pavel,Serres, Josep Maria,Mateos, Xavier,Yu, Haohai,Zhang, Huaijin,Mero, Mark,Griebner, Uwe,Petrov, Val The Optical Society 2018 Optics letters Vol.43 No.17
Imbalance phenomenon caused by CPS-PWM strategy for MMC systems
Wang, Chuyang,Zhang, Li,Zhang, Zitao,Tao, Yicheng The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.1
The carrier phase-shift PWM strategy is widely used in modular multilevel converters to satisfy the driver demands of the numerous switches in submodules. However, the traditional carrier phase-shift PWM strategy can cause an imbalance phenomenon in the submodule capacitor voltages, which deteriorates the system working performance. This study develops a mathematical model of an MMC system, which is the basis of a quantitative analysis of the relations between the PWM strategy and the imbalance phenomenon. A novel method is then proposed to provide an accurate description of the cause of the imbalance phenomenon in relation to the PWM strategy. Based on the above analysis, a quantitative analysis of the imbalance phenomenon in the capacitor voltages is used to further measure the magnitudes of the imbalance phenomenon. The effect of the PWM strategy on the capacitor voltages is finally demonstrated via experiments.
Shenshun Ying,Yicheng Sun,Chentai Fu,Lvgao Lin,Shunqi Zhang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.12
Broaching tool condition monitoring is the basis of intelligent manufacturing of high-end broaching equipment. There are still technical bottlenecks in tool wear recognition accuracy and response speed. Aiming at the characteristics of complex cutter tooth shape and variable spatial distribution of turbine disc fir-tree slot broaching tool, a method of wear state recognition for broaching tool based on maximum relevance and minimum redundancy and gray wolf optimization algorithm is proposed. In the process of broaching, the broach vibration signals are collected in real time. The signal characteristics in time domain, frequency domain and time-frequency domain are extracted by signal processing technology, and the support vector machine (SVM) recognition model of broach wear state is established. The maximum relevance and minimum redundancy (mRMR) method is used to reduce the dimension of data, grey wolf optimization algorithm (GWO) is used to optimize parameters to improve the recognition accuracy of SVM. The experimental results show that the model can accurately recognize the wear state of fir-tree slot broach at different stages. In addition, grey wolf optimizationsupport vector machine (GWO-SVM) model shows higher accu-racy in classification than particle swarm optimization based support vector machine (PSO-SVM) and genetic algorithm based support vector machine (GA-SVM) models. Compared with PSO-SVM and GA-SVM models, the computational time of GWO-SVM is reduced by 54.2 % and 60.5 % respectively.
Liu, Shuai,Wei, Li,Zhang, Yicheng,Yao, Yongtao The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.2
The application of soft-switching techniques is increasing in the DC/DC converter area. It is important to design soft-switching parameters to ensure the converter operates properly and efficiently. An optimized design method is presented in this paper. The objective function is the total power loss of a converter, while the variables are soft-switching parameters and the constraints are the electrical requirements for soft-switching. Firstly, a response surface methodology (RSM) model with a high precision is built, and the rough optimized parameters can be obtained with the help of a genetic algorithm (GA) in the solution space determined by the constraints. Secondly, a re-optimization is conducted with a SPICE model and a GA, and accurate optimized parameters can be obtained. Simulation and experiment results show that the proposed method performs well in terms of a wide adaptability, efficiency, and global optimization.
67-fs pulse generation from a mode-locked Tm,Ho:CLNGG laser at 2083 nm
Zhao, Yongguang,Wang, Yicheng,Chen, Weidong,Pan, Zhongben,Wang, Li,Dai, Xiaojun,Yuan, Hualei,Zhang, Yan,Cai, Huaqiang,Bae, Ji Eun,Choi, Sun Young,Rotermund, Fabian,Loiko, Pavel,Serres, Josep Maria,Mat The Optical Society 2019 Optics express Vol.27 No.3