Improved Interoperability Evaluation Method for Wireless Charging Systems Based on Interface Impedance
Artikel i vetenskaplig tidskrift, 2021

The interoperability between the vehicle assembly (VA) and ground assembly (GA) of wireless charging systems has been specified in international standards. SAE J2954 first proposed an interoperability evaluation method based on interface impedance. However, the impedance measurement is challenging at high frequency since the phase difference between the voltage and current is not easy to measure accurately, especially when it is close to 90. Small errors in phase angle measurement are amplified in impedance calculation due to the sine/cosine function. This letter proposes an impedance measurement method using the power decomposition algorithm. By decomposing the input power into two orthogonal components, the impedance angle can be calculated without directly measuring the phase difference between the voltage and current. Thus, the measurement results of the impedance angle do not introduce errors. With the proposal, the high-cost probe or complex high-precision phase difference measurement circuit is not needed. The experimental results show that the conventional methods maximum relative error reaches 80%, making interoperability hard to determine. Reversely, with the proposed method, the relative error of impedance measurement is reduced to less than 10%.

impedance measurement

interface impedance

Power measurement


wireless charging

Voltage measurement

Current measurement

Impedance measurement

Phase measurement



power decomposition


Guang Yang

Harbin Institute of Technology

Kai Song

Harbin Institute of Technology

Xiaoliang Huang

Chalmers, Elektroteknik, Elkraftteknik, Elmaskiner och kraftelektronik

Chao Wang

Harbin Institute of Technology

Xiaohua Huang

China Electric Power Research Institute

Jin Li

State Grid Xiongan New Area Electric Power Supply Company

Chunbo Zhu

Harbin Institute of Technology

IEEE Transactions on Power Electronics

0885-8993 (ISSN)

Vol. In Press


Medicinsk laboratorie- och mätteknik


Annan elektroteknik och elektronik



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