A ZPE Based Frequency Control Approach to Realize Soft Switching in Contactless Power Transfer of Energy Storage System Applications

Abstract

This paper proposes a zero phase angle error (ZPE) based frequency control approach to realize soft switching in inductive power transfer (IPT) charging of energy storage system applications. IPT is influenced by many parameters, such as the coupling coefficient between the transmitting and receiving coils and the load power requirement. This introduces new challenges, such as hard switching of the power converters in the system, which increases the power losses and degrades the power conversion efficiency. Furthermore, the switching devices need to be selected with higher ratings which increases the cost of the converters. To address these issues, an optimal frequency operation of the converter is proposed to achieve soft switching and transmit the maximum power to the load. The optimal frequency control is developed by minimizing the ZPE between the excitation voltage and current from the transmitting side. This makes the controller not require information on the IPT system's receiver side voltages and currents to achieve the aforementioned goals. Furthermore, the performance of the proposed control algorithm is validated using digital simulations. Finally, the IPT system is developed and tested for a maximum power of $1.7\text{kW}$ under open loop conditions, with experimental results presented in this paper.