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Your search keyword '"Zou, Xudong"' showing total 427 results
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427 results on '"Zou, Xudong"'

57. Characterization of a Temperature-Sensitive Nano Piezoelectric Mechanical Resonator With a 20nm Free-Standing Hf0.5Zr0.5O2 Membrane

Author

Zhang, Jingyi, Lyu, Haoqi, Yang, Wuhao, Zhong, Hai, Liu, Zhuohui, Bie, Xiaorui, Xiong, Xingyin, Wang, Zheng, Ge, Chen, and Zou, Xudong

Abstract

We studied the temperature effects on the resonant frequency of nano piezoelectric mechanical resonators based on Hf0.5Zr0.5O2 thin films. Two square-shaped resonators of 30 $\mu$ m and 50 $\mu$ m in length were fabricated and tested, having a resonant frequency of 225.8 kHz and 98.5 kHz, respectively. The temperature coefficient of frequency (TCF) of the devices was characterized in the range from −20 °C to 147 °C. Both devices exhibited a positive TCF around 83.6 ppm/°C to 105 ppm/°C in the range from 30 °C to 147 °C, which may result from the combined effect of thermal expansion mismatch between the materials and the temperature coefficient of Young’s modulus of the HZO material. Moreover, the 50 $\mu$ m device shows a negative TCF around −110 ppm/°C to −99.9 ppm/°C within the range from −20 °C to 30 °C, which may be due to stress relaxation during the heating process. These results underscore the significance of HZO material in nanoscale piezoelectric resonator applications and lay the foundation for our future work aimed at developing nanoscale piezoelectric devices based on HZO. [2024-0040]

Published
2024
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62. Rethinking Fault Ride-Through Control of DFIG-Based Wind Turbines From New Perspective of Rotor-Port Impedance Characteristics

Author

Zhu, Donghai, Wang, Zhen, Hu, Jiabing, Zou, Xudong, Kang, Yong, and Guerrero, Josep M.

Abstract

To achieve the fault ride through (FRT) operation of DFIG-based wind turbines, various improved control methods have been proposed. However, it is difficult to reveal their essential relations and quantitatively evaluate their performance differences, due to the wide assortment of solving ideas and control structures. To cope with this issue, this paper revisits the FRT control from a new perspective of rotor-port impedance characteristics (RPIC). First, a unified RPIC model of nine typical FRT controls is established and it is found that their RPIC are manifested as the pure inductance, but the inductance values are different in the phase sequence. Subsequently, the influence of RPIC on FRT performance is analyzed and some practical design guidelines for FRT control are given. On this basis, nine typical FRT control methods are quantitatively evaluated and compared in terms of six key performance dimensions. Moreover, the study contributes to the understanding, analysis and redesign of FRT control, and the RPIC perspective features the definite physical meaning and simple. Finally, the analysis is validated by the experiments.

Published
2024
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63. Reduced-Order Modeling and Transient Stability Analysis of Grid-Connected VSC in DC-Link Voltage Control Timescale

Author

Ma, Yumei, Zhu, Donghai, Hu, Jiabing, Liu, Dan, Ji, Xiaotong, Zou, Xudong, and Kang, Yong

Abstract

For grid-connected voltage source converters (VSCs), the transient instability in dc-link voltage control (DVC) timescale threatens the dc capacitor safety and grid stable operation. However, the transient stability analysis presents great challenges, due to the high-order and nonlinear coupling characteristics of VSC. Existing studies mainly consider single control loop to reduce order and simplify analysis, failing to fully reveal the transient instability mechanism. To cope with it, this article develops a reduced-order model based on singular perturbation, and the fourth-order full model of VSC is decomposed into a second-order nonlinear slow subsystem and a third-order linearized fast subsystem. Subsequently, the transient stability of slow and fast subsystem is analyzed by Lyapunov’s direct method and eigenvalue method, respectively. Meanwhile, a set of sufficient conditions for transient stability are derived, and the influence of several factors (e.g., grid impedance and multiple control loop parameters) on stability are revealed. Furthermore, some guidelines for transient stability enhancement are proposed. Finally, the analysis is validated by the experiments.

Published
2024
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65. Dynamic Temperature Compensation of Pressure Sensors in Migratory Bird Biologging Applications.

Author

Xie, Jinlu, Li, Zhitian, and Zou, Xudong

Subjects
PRESSURE sensors, MIGRATORY birds, RADIAL basis functions, PARTICLE swarm optimization, TEMPERATURE
Abstract

This article proposes an improved dynamic quantum particle swarm optimization (DQPSO) algorithm to optimize a radial basis function (RBF) neural network for temperature compensation of pressure sensors used in tracking and monitoring wild migratory birds. The algorithm incorporates a temperature-pressure fitting model that includes temperature rate of change and gradient reference terms. It also includes a loss function that considers fitting accuracy and complexity, thereby improving the robustness of the sensor for complex temperature variations. The calibration experiments revealed that after implementation, the average absolute error of the pressure sensor output during dynamic temperature changes was reduced from 145.3 Pa to 20.2 Pa. This reduction represents an 86% improvement over the commercial polynomial compensation method, and the DQPSO approach significantly outperformed traditional feedforward network models. Finally, the algorithm was deployed and verified in an embedded environment for low-power, high-precision, real-time pressure compensation during the tracking and monitoring of wild migratory birds. [ABSTRACT FROM AUTHOR]

Published
2023
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76. A Scale Factor Calibration Method for MEMS Resonant Accelerometers Based on Virtual Accelerations.

Author

Zhai, Zhaoyang, Xiong, Xingyin, Ma, Liangbo, Wang, Zheng, Wang, Kunfeng, Wang, Bowen, Zhang, Mingjiang, and Zou, Xudong

Subjects
GRAVITATIONAL fields
Abstract

This paper presents a scale factor calibration method based on virtual accelerations generated by electrostatic force. This method uses a series of voltage signals to simulate the inertial forces caused by the acceleration input, rather than frequent and laborious calibrations with high-precision instruments. The error transfer model of this method is systematically analyzed, and the geometrical parameters of this novel micromachined resonant accelerometer (MRA) are optimized. The experimental results demonstrate that, referring to the traditional earth's gravitational field tumble calibration method, the error of the scale factor calibration is 0.46% within ±1 g by using our method. Moreover, the scale factor is compensated by virtual accelerations. After compensation, the maximum temperature drift of the scale factor decreases from 2.46 Hz/g to 1.02 Hz/g, with a temperature range from 40 °C to 80 °C. [ABSTRACT FROM AUTHOR]

Published
2023
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77. The introduction of the disconnection approach into polymer synthesis.

Author

Lu, Dawei, Zou, Xudong, and Ye, Liqin

Subjects
POLYMERIZATION, ORGANIC chemistry, COVALENT bonds, POLYMER structure, RATE coefficients (Chemistry), POLYMERS
Abstract

The disconnection approach, a widely utilized method of design synthesis route, has played crucial roles in contemporary organic chemistry for decades. Here, we provide an introduction to the construction of polymer main chains. The implementation of the strategy hinges on determining where to disconnect based on the successful polymerization reaction in order to infer a suitable monomer. By investigating specific covalent bonds and structures in polymers, several specific linkers are highlighted to demonstrate how to design and synthesize polymer main chains using reverse thinking, thus inspiring those in polymer synthesis. [ABSTRACT FROM AUTHOR]

Published
2023
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93. Advances in the application of named reactions in polymer synthesis.

Author

Lu, Dawei, Zou, Xudong, and Li, Chaofan

Subjects
*POLYMERIZATION, *FREE radical reactions, *PERICYCLIC reactions, *REARRANGEMENTS (Chemistry), *NUCLEOPHILIC reactions, *POLYMERS
Abstract

With the development of polymer science, more and more named reactions have been applied to synthesizing polymers. Introducing new reactions into polymer synthesis is undoubtedly an excellent expansion for monomer and polymer libraries. In this review, the named reactions employed in polymer-chain synthesis were divided into seven types: electrophilic reactions, nucleophilic reactions, transition metal-mediated cross-coupling reactions, free radical reactions, pericyclic reactions, multi-component reactions and rearrangement reactions. The discussion was mainly focused on the progress in the utilization of these named reactions in polymer synthesis, which could be a valuable reference for researchers in the polymer field. [ABSTRACT FROM AUTHOR]

Published
2023
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94. Hybrid-Type Dual Active Bridge DC–DC Converter for Ultrawide Input-Voltage Range

Author

Liu, Caifeng, Liu, Shuang, Chen, Yu, Zou, Xudong, and Kang, Yong

Abstract

This article proposes a hybrid-type dual active bridge (H-DAB) topology and extended gain (EG) control method applied to the ultrawide input-voltage range. The H-DAB is obtained by adding an auxiliary half-bridge to the conventional current-fed dual active bridge (CF-DAB) topology. The auxiliary half-bridge can assist the CF-DAB to achieve zero voltage switching (ZVS) on the one hand and further expand the voltage gain range on the other. The proposed EG control expands the input-voltage range of ZVS for all switches by calculating the optimal intermediate bus voltage. In addition, the backflow power has also been drastically reduced. The proposed piecewise control strategy simplifies the complexity of control. The proposed topology and the control method are verified by the experimental results of a 500 W prototype. The input-voltage range is 27–240 V and the output voltage is 375 V. The experimental results proved that the proposed scheme achieves ZVS of all switches in a wide input-voltage range and power range, and the efficiency is improved.

Published
2023
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95. Modeling and Transient Stability Analysis for Type-3 Wind Turbines Using Singular Perturbation and Lyapunov Methods

Author

Ma, Yumei, Zhu, Donghai, Zhang, Ziqin, Zou, Xudong, Hu, Jiabing, and Kang, Yong

Abstract

Wind turbines (WTs) are prone to transient instability during weak grid faults, which is caused by their complex interactions. However, it is a challenge to analyze the transient stability, due to high-order and strong nonlinearity. Moreover, the existing works mainly focus on a phase-locked loop (PLL) system while ignoring current control, which cannot fully reflect the transient instability mechanism. To fill this gap, this article studies the transient stability of type-3 WT considering both PLL and current control. First, to simplify the full model of type-3 WT, a slow–fast subsystem is established using the singular perturbation. Then, the sixth-order full model is simplified as a second-order slow subsystem and its small disturbance (i.e., fast subsystem). Based on it, Lyapunov's direct and indirect methods are adopted to analyze the stability of slow and fast subsystems, respectively. Meanwhile, the influence of various factors (e.g., the fault degree, grid inductance, current references, current controller, and PLL controller) on transient stability of type-3 WT is revealed. In addition, the proposed analytical method combining singular perturbation and Lyapunov methods is a new approach to studying transient stability, which can also be applied to other renewable energy resources. Finally, the analysis is validated by experiments.

Published
2023
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