Katsuhiro Hata

Maximum efficiency control of wireless power transfer via magnetic resonant coupling considering dynamics of DC-DC converter for moving electric vehicles

Wireless charging for moving electric vehicles could extend their cruising distance. Wireless power transfer via magnetic resonant coupling is suitable for this application. The transmitting efficiency can be maximized by using a DC-DC converter on the secondary side. The control system, however, must be designed properly to satisfy the response requirements depending on motion of the vehicle. Previous controllers were designed without considering the dynamics of the DC-DC converter for wireless power transfer via magnetic resonant coupling. This paper proposes the design method of secondary voltage control with a feedback controller using a novel DC-DC converter model based on the analysis of wireless power transfer system. Experiments show that the proposed model is effective and that the secondary voltage control improves not only the transmitting efficiency but also the charging power at any transmitting distance.

Dynamic wireless power transfer system for electric vehicles to simplify ground facilities - power control and efficiency maximization on the secondary side

A dynamic wireless power transfer (WPT) system for electric vehicles can extend their cruising distance and reduce the size of their energy storage system. Power control and efficiency maximization of WPT are preferable to be controlled on the secondary side because ground facilities of the dynamic charging system have to be simplified. Although previous research has proposed a secondary-side simultaneous control of the maximum efficiency and the desired power, the battery charging current cannot be controlled directly. In this paper, a novel secondary-side control method for power control and efficiency maximization is proposed. The battery charging power is controlled by the DC-DC converter and the transmitting efficiency is maximized by Half Active Rectifier. These control strategies and the controller design are proposed based on the WPT circuit analysis and the power converter model. The effectiveness of the proposed method is verified by simulation and experiment.

Simultaneous estimation of primary voltage and mutual inductance based on secondary-side information in wireless power transfer systems

A dynamic wireless power transfer (WPT) system for electric vehicles (EVs) has gathered attention and been expected to extend the limited driving range of EVs. Previous research has proposed secondary-side-only power and efficiency control to simplify the road-side facilities, which are installed over long distances. Although the primary voltage and the mutual inductance between the transmitter and receiver have to be given or estimated in the control, multi-parameter estimation from the secondary side without signal communication remains unrealized. This paper proposes a simultaneous estimation method of the primary voltage and the mutual inductance using only secondary-side information. The simulations and the experiments show that the proposed method is effective for secondary-side control.

Efficiency maximization of wireless power transfer based on simultaneous estimation of generalized two parameters

A dynamic wireless power transfer (WPT) system for electric vehicles has to simplify its road-side facilities, which are installed over long distances. Although previous research has proposed secondary-side efficiency control, design constraints of the WPT system have to be imposed to obtain the reference value of the control. In this paper, an efficiency maximization method based on simultaneous estimation of the generalized two parameters, which determine the reference value of the control, is proposed. Since the generalized two parameters are estimated using secondary-side information, the design constraints of the WPT system can be eliminated. Simulations and experiments demonstrated that the estimation strategy achieved sufficient accuracy for maximum efficiency control and the proposed method drastically improved the transmitting efficiency.

Power flow control of magnetic resonance wireless charing for hybrid energy storage system of electric vehicles application

Battery and supercapacitor (SC) hybrid energy storage system (HESS) has been widely known for solving a power density problem of a conventional battery storage system for electric vehicles (EVs). Wireless power transfer (WPT) is a promising solution for the EV charging. In this paper, the frame of wireless charging is given for EV applications and a charging power control method for the HESS to achieve the constant current charging of the main battery is proposed. A small power test equipment is implemented and the effectiveness of the charging power control is verified by the experiment. This result shows the importance of the SC bank for the WPT charging system and the need for optimized power coordination control of the HESS.

Analysis and experiment on harmonic current distortion in wireless power transfer system using a diode rectifier

Wireless power transfer (WPT) via magnetic resonance coupling provides highly efficient mid-range transmission. Its transmitting power can be controlled using a diode rectifier and a DC-DC converter on the secondary side. Previous research replaces the load and the rectifier circuit with an equivalent load resistance or a fundamental harmonic sine wave voltage source to analyze the charging power of WPT. In such a case however, the effect caused by the rectifier circuit becomes unclear because the harmonic components are neglected. As a result, the theoretical charging power and its true value have an error due to the harmonic current distortion. In this paper, a novel WPT circuit model is proposed for the analysis of the harmonic current distortion on the secondary side. The proposed model uses the secondary voltage as the input variable of transfer functions and makes clear the effect caused by the rectifier circuit. Experiments demonstrate that the harmonic current distortion is increased with the increase in the secondary voltage. These results accord with the analysis using the proposed model and verify the effectiveness of the proposed model.

Maximum efficiency control of wireless power transfer systems with Half Active Rectifier based on primary current measurement

Applying wireless power transfer (WPT) to transportation applications is one of the best solutions to overcome drawbacks of a limited energy souse in electric vehicles (EVs). Although dynamic charging of EVs can extend their driving distance, control techniques have to be further developed to maintain maximum transmitting efficiency because of parameters variation, e.g. distance change and load change. This paper proposes an efficiency maximization method based on the primary current change with power control on the secondary side using Half Active Rectifier (HAR). The reference value of the primary voltage is calculated based on the measured primary current. The simulation and experiment results demonstrate that the reference voltage can be obtained with satisfactory accuracy and the transmitting efficiency can be maximized by primary voltage control without communication between the primary side and the secondary side of the system.

Efficiency maximization of wireless power transfer based on simultaneous estimation of primary voltage and mutual inductance using secondary-side information

A dynamic wireless charging system for electric vehicles (EVs) is expected to extend the limited driving distance of EVs. As the transmitting efficiency changes according to motion of the vehicle in dynamic charging, an efficiency maximization method is important. Previous research has proposed secondary-side efficiency control based on mutual inductance estimation to simplify the ground facilities, which would be installed over long distances. However, the ground facilities have to regulate the primary voltage to achieve maximum efficiency control on the secondary side without signal communication. In this paper, a calculation method of the reference value for maximum efficiency control is proposed using simultaneous estimation of the primary voltage and the mutual inductance on the secondary side to eliminate the need for the primary voltage regulation. Simulations and experiments demonstrate that the proposed method is available for maximum efficiency control on the secondary side.