Study of Maximum Power Delivery to Movable Device in Omnidirectional Wireless Power Transfer System

More mobile devices are now being charged wirelessly due to the convenience, ease of use, and competitive power efficiency of wireless power transfer. However, traditional wireless power transfer systems are not applicable if the mobile devices need to be charged while moving. This paper focused on an omnidirectional wireless power transfer system, which has the potential to transfer power to a movable device. And two different maximum power delivery methods are proposed for applications with intermittently and frequently moving devices. By analyzing the relationship between the input power of the system and the load power, the communication link between the transmitter and the receiver is eliminated. Both methods satisfied the need of dynamic charging for the movable device. The parameter identification method is more suitable for the device which moves intermittently, while the gradient descent method aims at charging the frequently moving devices. Based on the circuit model of the omnidirectional WPT system, the two methods have been mathematically modeled, and the corresponding algorithms for maximum power transfer are proposed. Then, a prototype is implemented to validate the proposed methods. Experimental results have shown that both the methods can be used to achieve maximum output power during the movement of power pickups. At steady-state, a maximum power of 37.08W at 70.39% efficiency has been achieved using the parameter identification method; while 36.48W at 69.90% has been achieved using the gradient descent method.