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581 results on '"Li, Wuhua"'

66. Dissipativity Enhancement for Multisampled LCL-Type Inverter Using a Low-Delay Ripple-Removal Method

Author

Wang, Tingkang, Yao, Wenxi, Yang, Huan, Li, Wuhua, and Ou, Zhujian

Abstract

Multisampling is considered as a direct path toward inherent admittance passivity because it can directly reduce the control delay. However, the phase lag caused by the switching ripple suppression filter weakens the advantage of multisampling, making it difficult to extend the dissipativity of the high-frequency band. In this article, to address the challenge of phase lag limiting the dissipativity enhancement, a low-delay ripple-removal method based on sliding discrete Fourier transform (SDFT) is proposed. The application of this method in eliminating switching ripples is analyzed theoretically. It also explains why there is a low delay in the control loop. Accordingly, based on the proposed method and multisampling, the dissipativity of the high-frequency band is enhanced greatly with the single-loop control of inverter-side current feedback. When combining voltage proportional feedforward of the point of common coupling (PCC), the dissipative region can be extended to switching frequency. Finally, the experimental results verify the effectiveness of the proposed method and its application effect in enhancing dissipativity.

Published
2023
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67. High-Efficient Operation for Modular Multilevel Resonant DC–DC Converters in Medium Voltage Applications With Wide Input Range and Wide Load Condition

Author

Sheng, Jing, Xiang, Xin, Li, Boliang, Lu, Rui, Li, Chushan, Zhang, Xiaotian, Li, Wuhua, and He, Xiangning

Abstract

The modular multilevel resonant dc–dc converters (MMRDCs) are becoming one of the most attractive candidates in medium voltage applications, but they would usually face technical challenges in high-efficient operation with wide input range and wide load condition. First, this article provides an elaborate review of the voltage control dimensions in MMRDC, and their corresponding operation principles, regulation capabilities, and efficiency influences for MMRDC are also analyzed respectively. Then for the wide input range, a tailored voltage regulation method combining both phase shift angle control and inserted submodule number control is proposed, and the optimal regulation principles of these two control dimensions are further investigated to realize high-efficient operation for MMRDC with wide load condition. Finally, the effectiveness of the proposed strategy is demonstrated through a simulation model and a full-scale MMRDC prototype with 9–18 kV input and 60 kW power rating.

Published
2023
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98. The Analysis and Calculation of Power Angle Dynamics in Grid Forming Converter Under Large Disturbances Based on KBM Asymptotic Method.

Author

Lei, Jintao, Xiang, Xin, Li, Wuhua, and He, Xiangning

Abstract

Grid forming (GFM) control strategy has been increasingly used in grid-connected converters to regulate system frequency and mimic the inertia of synchronous generator. However, the description of its power angle dynamics under large disturbances is still lacking up to date, which may pose great challenges to stable operation and economic configuration of grid-connected converters in the future power system. To overcome the aforementioned obstacle, a Krylov–Bogoliubov–Mitropolsky (KBM) asymptotic method with the perturbation theory is presented first in this article to derive an analytical solution for power angle trajectory under large disturbances. Considering that the antiderivative problem is usually unsolvable due to the complicated perturbation function, a tailored integral method is further proposed to address this problem and simplify the final result, which facilitates the KBM asymptotic method to the analysis and calculation of power angle trajectory. As a result, an explicit and accurate time-domain expression is obtained, and it reveals the quantitative relationships between control parameters and dynamic characteristics, which may provide a good potential for system transient stability analysis and GFM converter design. In the end, the effectiveness and accuracy of the proposed method are verified by both simulations and control-hardware-in-loop experiments. [ABSTRACT FROM AUTHOR]

Published
2023
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99. Buck-Boost Type High Step-Down Low Power Modular Converter for Medium Voltage DC Systems.

Author

Zhu, Lin, Li, Chushan, Yang, Huan, Ren, Shengdao, Zhang, Shilei, Li, Wuhua, and He, Xiangning

Abstract

The medium-voltage dc (MVDC) system are intensely investigated by both industry and academy. However, how to realize a lower power circuit directly fed by MVDC is an important but easily neglected problem, which seriously affects the reliability of the dc system. The current high step-down circuits are mostly suitable for high-power applications, while the circuits for low-power applications are designed case by case. To address the obstacle, a generalized buck-boost type high step-down converter (BHSC) structure is proposed in this article. The submodules of BHSC are derived from basic dc–dc converter. As a result, the features of high modularity, simple structure, and low cost can be obtained, and each submodule operates independently without communication and synchronization to achieve voltage balance. Furthermore, a submodule strategy with Bang-Bang control, instead of hardware modification, is proposed to overcome the limitation of BHSC generality in medium-voltage (MV) and high-voltage (HV) applications, due to the operating current difference in different submodules of the cascaded structure. Therefore, BHSC can be easily extended to MV or HV by increasing the number of submodules. Finally, an experimental evaluation of a 1 kV/80 W prototype converter is presented, which can be applied as auxiliary power supply for high-power converter. [ABSTRACT FROM AUTHOR]

Published
2023
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