State Estimation Based Foreign Object Detection in Wireless Power Transfer Systems

Foreign objects detection (FOD) is of great importance for wireless power transfer (WPT) systems to ensure safety operation. This paper proposes a state estimation based FOD method. The method first systematically builds the model of WPT systems to describe the physical laws during normal operation. When there exist foreign objects on the transmitting coils, the new model of the system no longer satisfies the physical laws during normal operation. Based on this principle, the detection method gives a foreign object indicator by monitoring the consistency between the measurements and the system model. For the system model during normal operation, the mutual inductances and loads are introduced as unknown states to avoid false detection of foreign object caused by coils misalignments or loads variations. Compared to the existing FOD methods, the proposed method has the advantages such as: (1) it is only based on the transmitter side information; (2) no additional detection coils or sensors are required; (3) it can avoid false detection of foreign object caused by coils misalignments or loads variations, by introducing the mutual inductances and loads as additional unknown states. An example experiment on 2TX-1RX WPT system has been conducted to verify the effectiveness of the FOD method.