Efficiency Evaluation of Receiving Current Control Using Pulse Density Modulation for Dynamic Wireless Power Transfer

Dynamic wireless power transfer (DWPT) for electric vehicles (EVs) is an innovative technique that enables the EVs to enhance the driving range and reduce the capacity of the battery. The receiving current control is important to prevent the battery from overcharging. In this paper, the receiving current control using an active rectifier is focused on. Pulse density modulation (PDM) is effective in terms of the switching loss in the rectifier compared with pulse width modulation. In the previous papers regarding to the PDM, the operation is evaluated in stationary WPT systems. In this paper, the transmission energy efficiency of the receiving current control with the PDM is evaluated using a high-speed rotational testbench for the DWPT. In addition, centralized PDM (CPDM) and distributed PDM (DPDM) are experimentally compared. As a result, it was confirmed that the current control performances using the CPDM and DPDM are the same in spite of the mutual inductance dynamic change at 40 km/h. The energy efficiency of the DPDM was 3.3-7.9% higher compared with one of the CPDM because it can reduce the filter current and loss in the filter inductance. Therefore, the DPDM is effective for the receiving current control of the DWPT system.