Dynamic Wireless Power Transfer System With an Extensible Charging Area Suitable for Moving Objects

Extensible magnetic resonance coupling-based wireless power transfer (WPT) systems are presented in this article. A transmitter (Tx) containing an 8-shape loop and two resonators is proposed to construct a bipolar Tx array. A unipolar receiver (Rx) is placed above the Tx perpendicularly to overcome the power null phenomenon. The proposed structure ensures that magnetic flux lines are confined in the vicinity of the Rx, leading to a high power transfer efficiency (PTE) over a wide range of lateral misalignment distances. Experiments demonstrated that the proposed WPT system can achieve an efficiency of 87% under perfectly aligned operating conditions, and maintain over 70% efficiency from 0 to 30 mm lateral misalignment distances. Based on the proposed Tx module, a single-feed Tx array is constructed to further increase the charging area. The PTE of a 1 \times 2 array system is between 57.5% and 71.6% without the power null phenomenon. Meanwhile, the concern of heating due to magnetic field leakage can be significantly mitigated. These designs are proved to be very good candidates for dynamic WPT (DWPT) applications

Precise Analysis on Mutual Inductance Variation in DynamicWireless Charging of Electric Vehicle

Wireless power transfer provides an opportunity to charge electric vehicles (EVs) without electrical cables. Two categories of this technique are distinguished: Stationary Wireless Charging (SWC) and DynamicWireless Charging (DWC) systems. Implementation of DWC is more desirable than SWC as it can potentially eliminate challenges associated with heavy weight batteries and time-consuming charging processes. However, power transfer efficiency and range, lateral misalignment of coils as well as implementation cost are issues affecting DWC. These issues need to be addressed through developing coil architectures and topologies as well as operating novel semiconductor switches at higher frequencies. This study presents a small-scale dynamic wireless power transfer system for EV. It specifically concentrates on analyzing the dynamic mutual inductance between the coils due to the misalignment as it has significant influence on the EV charging process, particularly, over the output power and overall efficiency. A simulation study is carried out to explore dynamic mutual inductance profile between the transmitter and receiver coils. Mutual inductance simulation results are then verified through practical measurements on fabricated coils. Integrating the practical results into the model, an EV DWC power transfer simulation is conducted and the relation between dynamic mutual inductance and output power are discussed technically

Control of wireless power transfer system for dynamic charging of electric vehicles

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Multiphase wireless dynamic charging systems for electric vehicles

PhD ThesisElectric vehicles (EVs) have been intensively developed as an attempt to reduce carbon-dioxide emissions caused by fossil-fuel vehicles. EVs require expensive batteries and power electronics for charging and discharging the battery. Unfortunately, battery technology, such as lithium-ion batteries requires substantial improvements to effectively compete with fossil-fuel cars in price. Also, batteries are usually heavy, take up large space and still have range limitation. Wireless Dynamic Charging (WDC), while the vehicles are in motion, is seen as an alternative to overcome the drawbacks associated with batteries. Due to the continues charging when driving, batteries can become smaller as most of the traction energy comes from the grid directly. WDC is fundamentally developed based on inductive power transfer (IPT) technology, where a time-varying magnetic field is generated by transmitter coils, which are installed underneath the road surface, to wirelessly power receiver coils, that charge the EV’s battery continuously. Presently, there are several technical challenges associated with WDC, which hinders commercialization. The output power fluctuation along the driving direction is one of the most serious problems. These fluctuations cause reduction in constant energy transfer thus requiring larger batteries. Also, batteries lifetime is significantly reduced as a result of increasing internal heating. Several studies attempted to realise constant output power for WDC. However, proposed methods so far, have disadvantages such as high cost, complexity or unable to sustain constant output power throughout the charging process. The work in this thesis proposes a multiphase WDC system to simultaneously achieve constant and high output power for EV applications. The proposed WDC system utilizes multiple primary windings that guarantee a homogeneous mutual magnetic flux for the receiver along the driving direction. This results in a constant induced voltage across the receiver and hence constant output power to charge the EV battery. High output power capability is attained by using multiple transmitter windings arranged in a novel winding method. The effectiveness of the proposed system is analytically described, simulated and demonstrated experimentally using a 3-kW laboratory prototype with the three-phase transmitter. The proposed system requires only simple control, eliminates communications between the primary and secondary sides and delivers 125% higher power transfer capability compared to conventional single-phase WDC systems