Multi-channel inductive power transfer system based on ISOP topology

Qijun Deng,Lixian Wang,Peng Luo,Dariusz Czarkowski,Wenshan Hu 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.3

With the expansion of mid-voltage DC distribution, inductive power transfer (IPT) systems supplied directly by DC distribution with a high input voltage become a possibility. A high input voltage leads to an enhanced power transfer level and low losses with the DC bus under a certain power transmission. However, the ultra-high input voltage of single-channel IPT is impossible because of the limits on the voltage/current ratings of converter components. Thus, a multi-channel IPT system based on an input-series output-parallel (ISOP) topology is proposed. Parameter differences among various channels result in an unbalanced input voltage for series inverters, which affects the system's operation stability and life. A leader–follower control strategy is proposed to implement input voltage sharing and output load voltage tracking for the proposed ISOP-based IPT system. One of the inverters serves as the lead control unit to keep the output voltage constant, while the remaining inverters function as followers that trace the input DC voltage of the main channel to implement voltage sharing among the inverters. A three-channel ISOP-based IPT prototype is constructed to verify the eff ectiveness of the control strategy. Experimental results show that the input voltage sharing and constant output voltage are both achieved under the designed controller.

Effects of back pressure fluctuation on pseudo-shock waves in a rectangular duct

Ruoyu Deng,Heuy Dong Kim,Qijun Chen 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.11

Pseudo-shock waves in a scramjet isolator are worth studying. These waves are generally subjected to back pressure fluctuation induced by combustion. The characteristics and unsteadiness mechanism of pseudo-shock waves are investigated using a numerical method. A second nozzle with a movable pintle is utilized to simulate the back pressure fluctuation of a combustion chamber in the numerical model. A 2D numerical method with the kωshear stress transport turbulence model is adopted to investigate the behavior of pseudo-shock waves. Validation of the numerical model is performed by comparing its results with existing experimental results. The accuracy of the numerical model is proven. The present study aims to investigate the unsteady characteristics of pseudo-shock waves in a scramjet isolator. As indicated by the results, the amplitude of pseudo-shock wave motion can be reduced by increasing the exciting frequency of back pressure fluctuation. The influence mechanism of exciting frequency is the phase difference caused by time delay.

Effects of isolator length on pseudoshock wave in a rectangular duct

Ruoyu Deng,Ke Xin Wu,Heuy Dong Kim,Qijun Chen 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.1

The scramjet isolator length is a very important influence factor on the stability of scramjet engines. The effects of the isolator length on the pseudo-shock wave (PSW) were studied through a numerical method. The steady and unsteady PSW characteristics were analyzed to explore the influence mechanism of the isolator length. The numerical model was validated with the existing experimental results, and the validation results show that the numerical model has high accuracy. The effects of the structural variation of the PSW on self-excited oscillation were explored at different isolator lengths. Result shows that increasing the isolator length increases the length of the PSW. The leading shock becomes stable with the increasing of PSW length, and the following shocks become unstable. This phenomenon indicates that the unsteady characteristics of self-excited oscillation are closely related to the PSW structure. The influence mechanism of isolator length is represented by the amplitude difference of the leading and following shocks caused by the PSW structure variation.

Analysis and validation of novel inverter and LCC‑S topology‑based WPT system

Hong Zhou,Haitang Liu,Qijun Deng,Li Fang 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.3

Wireless power transfer (WPT) technology has been widely researched and employed due to its advantages when compared with conventional cable-connected power transmission in terms of convenience, flexibility, security, and so on. In common wireless power transfer systems, DC sources, such as batteries and AC–DC modules, are frequently utilized in the front end of the inverters to generate a relatively high frequency circuit driving voltage. The strategy of directly arranging inverters behind AC sources is feasible by replacing a single NMOS with a pair of back-to-back placed switches that can tolerate both forward and reverse voltage. This novel inverter structure is systematically explored from the perspectives of the time domain and the frequency domain, which demonstrates the convenience and feasibility of the proposed structure. Due to the canceling of the front-end rectifier, the complexity of the system hardware is significantly reduced. In addition, when taking the constant current output feature into account, the LCC-S topology is comprehensively investigated and properly applied. Finally, a laboratory platform is constructed and experiments are conducted to verify the effectiveness of the proposed structure. Furthermore, experiment results show that there is only a slight transfer efficiency decrease when compared with the commonly adopted scheme containing an extra diode rectifier at the transmitting side.

Evaluation of AC Resistance in Litz Wire Planar Spiral Coils for Wireless Power Transfer

Xiaona Wang,Pan Sun,Qijun Deng,Wengbin Wang 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.4

A relatively high operating frequency is required for efficient wireless power transfer (WPT). However, the alternating current (AC) resistance of coils increases sharply with operating frequency, which possibly degrades overall efficiency. Hence, the evaluation of coil AC resistance is critical in selecting operating frequency to achieve good efficiency. For a Litz wire coil, AC resistance is attributed to the magnetic field, which leads to the skin effect, the proximity effect, and the corresponding conductive resistance and inductive resistance in the coil. A numerical calculation method based on the Biot–Savart law is proposed to calculate magnetic field strength over strands in Litz wire planar spiral coils to evaluate their AC resistance. An optimized frequency can be found to achieve the maximum efficiency of a WPT system based on the predicted resistance. Sample coils are manufactured to verify the resistance analysis method. A prototype WPT system is set up to conduct the experiments. The experiments show that the proposed method can accurately predict the AC resistance of Litz wire planar spiral coils and the optimized operating frequency for maximum efficiency.

Modeling and Design of Zero-Voltage-Switching Controller for Wireless Power Transfer Systems Based on Closed-Loop Dominant Pole

Chen, Cheng,Zhou, Hong,Deng, Qijun,Hu, Wenshan,Yu, Yanjuan,Lu, Xiaoqing,Lai, Jingang The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.5

Zero-Voltage-Switching (ZVS) operation for a Wireless Power Transfer (WPT) system can be achieved by designing a ZVS controller. However, the performance of the controller in some industrial applications needs to be designed tightly. This paper introduces a ZVS controller design method for WPT systems. The parameters of the controller are designed according to the desired performance based on the closed loop dominant pole placement method. To describe the dynamic characteristics of the system ZVS angle, a nonlinear dynamic model is deduced and linearized using the small signal linearization method. By analyzing the zero-pole distribution, a low-order equivalent model that facilitates the controller design is obtained. The parameters of the controller are designed by calculating the time constant of the closed-loop dominant poles. A prototype of a WPT system with the designed controller and a five-stage multistage series variable capacitor (MSVC) is built and tested to verify the performance of the controller. The recorded response curves and waveforms show that the designed controller can maintain the ZVS angle at the reference angle with satisfactory control performance.

Modeling and Design of Zero-Voltage-Switching Controller for Wireless Power Transfer Systems Based on Closed-Loop Dominant Pole

Cheng Chen,Hong Zhou,Qijun Deng,Wenshan Hu,Yanjuan Yu,Xiaoqing Lu,Jingang Lai 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.5

Zero-Voltage-Switching (ZVS) operation for a Wireless Power Transfer (WPT) system can be achieved by designing a ZVS controller. However, the performance of the controller in some industrial applications needs to be designed tightly. This paper introduces a ZVS controller design method for WPT systems. The parameters of the controller are designed according to the desired performance based on the closed loop dominant pole placement method. To describe the dynamic characteristics of the system ZVS angle, a nonlinear dynamic model is deduced and linearized using the small signal linearization method. By analyzing the zero-pole distribution, a low-order equivalent model that facilitates the controller design is obtained. The parameters of the controller are designed by calculating the time constant of the closed-loop dominant poles. A prototype of a WPT system with the designed controller and a five-stage multistage series variable capacitor (MSVC) is built and tested to verify the performance of the controller. The recorded response curves and waveforms show that the designed controller can maintain the ZVS angle at the reference angle with satisfactory control performance.

Evaluation of AC Resistance in Litz Wire Planar Spiral Coils for Wireless Power Transfer

Wang, Xiaona,Sun, Pan,Deng, Qijun,Wang, Wengbin The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.4

A relatively high operating frequency is required for efficient wireless power transfer (WPT). However, the alternating current (AC) resistance of coils increases sharply with operating frequency, which possibly degrades overall efficiency. Hence, the evaluation of coil AC resistance is critical in selecting operating frequency to achieve good efficiency. For a Litz wire coil, AC resistance is attributed to the magnetic field, which leads to the skin effect, the proximity effect, and the corresponding conductive resistance and inductive resistance in the coil. A numerical calculation method based on the Biot-Savart law is proposed to calculate magnetic field strength over strands in Litz wire planar spiral coils to evaluate their AC resistance. An optimized frequency can be found to achieve the maximum efficiency of a WPT system based on the predicted resistance. Sample coils are manufactured to verify the resistance analysis method. A prototype WPT system is set up to conduct the experiments. The experiments show that the proposed method can accurately predict the AC resistance of Litz wire planar spiral coils and the optimized operating frequency for maximum efficiency.