Free vibration analysis of FG porous spherical cap reinforced by graphene platelet resting on Winkler foundation

Xiangqian Shen,Tong Li,Lei Xu,Faraz Kiarasi,Masoud Babaei,Kamran Asemi Techno-Press 2024 Advances in nano research Vol.16 No.1

In this study, free vibration analysis of FG porous spherical cap reinforced by graphene platelets resting on Winkler-type elastic foundation has been surveyed for the first time. Three different types of porosity patterns are considered for the spherical cap whose two types of porosity patterns in the metal matrix are symmetric and the other one is uniform. Besides, five GPL patterns are assumed for dispersing of GPLs in the metal matrix. Tsai-Halpin and extended rule of the mixture are used to determine the Young modulus and mass density of the shell, respectively. Employing 3D FEM elasticity in conjunction with Hamilton's Principle, the governing motion equations of the structure are obtained and solved. The impact of various parameters including porosity coefficient, various porosity distributions in conjunction with different GPL patterns, the weight fraction of graphene Nano fillers, polar angles and stiffness coefficient of elastic foundation on natural frequencies of FG porous spherical cap reinforced by GPLs have been reported for the first time.

Voltage Feedforward Control with Time-Delay Compensation for Grid-Connected Converters

Shude Yang,Xiangqian Tong 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5

In grid-connected converter control, grid voltage feedforward is usually introduced to suppress the influence of grid voltage distortion on the converter’s grid-side AC current. However, owing to the time-delay in control systems, the suppression effect of the grid voltage distortion is seriously affected. In this paper, the positive effects of the grid voltage feedforward control are analyzed in detail, and the time-delay caused by the low-pass filter (LPF) in the voltage filtering circuits and digital control are summarized. In order to reduce the time-delay effect on the performance of the feedforward control, a voltage feedforward control strategy with time-delay compensation is proposed, in which, a leading correction of the feedforward voltage is used. The optimal leading step used in this strategy is derived from analyzing the phase-frequency characteristics of a LPF and the implementation of digital control. By using the optimal leading step, the delay in the feedforward path can be further counteracted so that the performance of the feedforward control in terms of suppressing the influence of grid voltage distortion on the converter output current can be improved. The validity of the proposed method is verified through simulation and experiment results.

BPF-based Grid Voltage Feedforward Control of Grid-connected Converters for Improving Robust Stability

Shude Yang,Xiangqian Tong,Jun Yin,Haiyan Wang,Yaping Deng,Le Liu 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.2

Grid voltage feedforward is extensively used for controlling grid-connected converters. However, the conventional voltage feedforward control reduces the stability margins of the converter connected to a high-impedance grid. The effect mechanism of voltage feedforward on the grid-connected converter control under high-inductive conditions of the grid impedance is clearly explained in this study using the equivalent transformations of control block diagrams. Results show that the delay produced by the digital control is the root cause of this effect. An improved voltage feedforward strategy, in which a bandpass filter (BPF) is introduced into the feedforward path, is proposed to strengthen the converter’s robust stability against grid impedance variations. The selection method of the BPF’s bandwidth is also provided considering the tradeoff between the response speed to the grid voltage sag and the system’s robust stability. The converter can work stably over a wide range of the grid impedance through the proposed approach. Simulation and experimental results fully verify the effectiveness of the BPF-based voltage feedforward strategy.

Voltage Feedforward Control with Time-Delay Compensation for Grid-Connected Converters

Yang, Shude,Tong, Xiangqian The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5

In grid-connected converter control, grid voltage feedforward is usually introduced to suppress the influence of grid voltage distortion on the converter's grid-side AC current. However, owing to the time-delay in control systems, the suppression effect of the grid voltage distortion is seriously affected. In this paper, the positive effects of the grid voltage feedforward control are analyzed in detail, and the time-delay caused by the low-pass filter (LPF) in the voltage filtering circuits and digital control are summarized. In order to reduce the time-delay effect on the performance of the feedforward control, a voltage feedforward control strategy with time-delay compensation is proposed, in which, a leading correction of the feedforward voltage is used. The optimal leading step used in this strategy is derived from analyzing the phase-frequency characteristics of a LPF and the implementation of digital control. By using the optimal leading step, the delay in the feedforward path can be further counteracted so that the performance of the feedforward control in terms of suppressing the influence of grid voltage distortion on the converter output current can be improved. The validity of the proposed method is verified through simulation and experiment results.

BPF-based Grid Voltage Feedforward Control of Grid-connected Converters for Improving Robust Stability

Yang, Shude,Tong, Xiangqian,Yin, Jun,Wang, Haiyan,Deng, Yaping,Liu, Le The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.2

Grid voltage feedforward is extensively used for controlling grid-connected converters. However, the conventional voltage feedforward control reduces the stability margins of the converter connected to a high-impedance grid. The effect mechanism of voltage feedforward on the grid-connected converter control under high-inductive conditions of the grid impedance is clearly explained in this study using the equivalent transformations of control block diagrams. Results show that the delay produced by the digital control is the root cause of this effect. An improved voltage feedforward strategy, in which a bandpass filter (BPF) is introduced into the feedforward path, is proposed to strengthen the converter's robust stability against grid impedance variations. The selection method of the BPF's bandwidth is also provided considering the tradeoff between the response speed to the grid voltage sag and the system's robust stability. The converter can work stably over a wide range of the grid impedance through the proposed approach. Simulation and experimental results fully verify the effectiveness of the BPF-based voltage feedforward strategy.

An Efficient Reactive Power Regulation based DPC Method for AC/DC Converters

Huang Jingjing,Sun Yuangang,Tong Xiangqian,Li Ning 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

To eliminate the cyclical fluctuation problems of the reactive power existing in the traditional direct power control (DPC), a novel method is proposed for the threephase voltage source AC/DC converter. It employs two switching tables to select the proper switching states according to the instantaneous reactive power deviations. The design principle of the switching tables is provided to ensure the efficient reactive power regulation. Moreover, it should guarantee the steady characteristic of the converter system. The simulation model established under the MATLAB/Simulink environment and the experiment were presented to compare the characteristics obtained by the proposed strategy with that obtained by the traditional DPC strategy. The results show that the ac current obtained by the proposed strategy has the much lower total harmonic distortion rate (THD), and the fluctuation range of the reactive power has the more than two times reduction.

Design and Implementation of an Adaptive Sliding-Mode Observer for Sensorless Vector Controlled Induction Machine Drives

Zhang, Yanqing,Yin, Zhonggang,Liu, Jing,Tong, Xiangqian The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.3

An adaptive sliding-mode observer for speed estimation in sensorless vector controlled induction machine drives is proposed in this paper to balance the dilemma between the requirement of fast reaching transient and the chattering phenomenon reduction on the sliding-mode surface. It is well known that the sliding-mode observer (SMO) suffers from the chattering phenomenon. However, the reduction of the chattering phenomenon will lead to a slow transient process. In order to balance this dilemma, an adaptive exponential reaching law is introduced into SMO by optimizing the reaching way to the sliding-mode surface. The adaptive exponential reaching law is based on the options of an exponential term that adapts to the variations of the sliding-mode surface and system states. Moreover, the proposed sliding-mode observer considering adaptive exponential reaching law, which is called adaptive sliding-mode observer (ASMO), is capable for reducing the chattering phenomenon and decreasing the reaching time simultaneously. The stability analysis for ASMO is achieved based on Lyapunov stability theory. Simulation and experimental results both demonstrate the correctness and the effectiveness of the proposed method.

Design and Implementation of an Adaptive Sliding-Mode Observer for Sensorless Vector Controlled Induction Machine Drives

Yanqing Zhang,Zhonggang Yin,Jing Liu,Xiangqian Tong 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.3

An adaptive sliding-mode observer for speed estimation in sensorless vector controlled induction machine drives is proposed in this paper to balance the dilemma between the requirement of fast reaching transient and the chattering phenomenon reduction on the sliding-mode surface. It is well known that the sliding-mode observer (SMO) suffers from the chattering phenomenon. However, the reduction of the chattering phenomenon will lead to a slow transient process. In order to balance this dilemma, an adaptive exponential reaching law is introduced into SMO by optimizing the reaching way to the sliding-mode surface. The adaptive exponential reaching law is based on the options of an exponential term that adapts to the variations of the sliding-mode surface and system states. Moreover, the proposed sliding-mode observer considering adaptive exponential reaching law, which is called adaptive sliding-mode observer (ASMO), is capable for reducing the chattering phenomenon and decreasing the reaching time simultaneously. The stability analysis for ASMO is achieved based on Lyapunov stability theory. Simulation and experimental results both demonstrate the correctness and the effectiveness of the proposed method.

A Novel Speed Estimation Method of Induction Motors Using Real-Time Adaptive Extended Kalman Filter

Yanqing Zhang,Zhonggang Yin,Guoyin Li,Jing Liu,Xiangqian Tong 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.1

To improve the performance of sensorless induction motor (IM) drives, a novel speed estimation method based on the real-time adaptive extended Kalman filter (RAEKF) is proposed in this paper. In this algorithm, the fuzzy factor is introduced to tune the measurement covariance matrix online by the degree of mismatch between the actual innovation and the theoretical. Simultaneously, the fuzzy factor can be continuously self-tuned tuned by the fuzzy logic reasoning system based on Takagi–Sugeno (T-S) model. Therefore, the proposed method improves the model adaptability to the actual systems and the environmental variations, and reduces the speed estimation error. Furthermore, a simple exponential function based on the fuzzy theory is used to reduce the computational burden, and the real-time performance of the system is improved. The correctness and the effectiveness of the proposed method are verified by the simulation and experimental results.

A Novel Speed Estimation Method of Induction Motors Using Real-Time Adaptive Extended Kalman Filter

Zhang, Yanqing,Yin, Zhonggang,Li, Guoyin,Liu, Jing,Tong, Xiangqian The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.1

To improve the performance of sensorless induction motor (IM) drives, a novel speed estimation method based on the real-time adaptive extended Kalman filter (RAEKF) is proposed in this paper. In this algorithm, the fuzzy factor is introduced to tune the measurement covariance matrix online by the degree of mismatch between the actual innovation and the theoretical. Simultaneously, the fuzzy factor can be continuously self-tuned tuned by the fuzzy logic reasoning system based on Takagi-Sugeno (T-S) model. Therefore, the proposed method improves the model adaptability to the actual systems and the environmental variations, and reduces the speed estimation error. Furthermore, a simple exponential function based on the fuzzy theory is used to reduce the computational burden, and the real-time performance of the system is improved. The correctness and the effectiveness of the proposed method are verified by the simulation and experimental results.