Investigations of new control paradigm for the next-generation wireless power transfer systems

• Main Author: Zeng, Junming
• Other Authors: Yun Yang
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2025
• Subjects: Engineering; Wireless power transfer
• Online Access: https://hdl.handle.net/10356/182571
• Institution: Nanyang Technological University

Since the world’s first wireless charging standard “Qi” was launched by the Wireless Power Consortium (WPC) in 2010, the first generation of commercialized wireless power transfer (WPT) technologies mainly focuses on the compatibility between transmitter devices and receiver devices over the last decade. In the new era, the primary concern of compatibility in the existing wireless charging standards is suggested to be shifted to both compatibility and optimization. The optimization refers to the maximum power transfer efficiency, minimum charging time, longer lifespan of components and loads, etc. To do that, a promising way is to develop a more compatible wireless charging system that is compliant with diverse products from different brands. Therefore, in such a universal wireless charging system, a simple and reliable receiver circuit is required, and most control schemes are implemented on the transmitter side. This thesis presents a series of novel technologies to address the following critical issues in developing universal wireless charging systems: (i) compatibility between transmitters and receivers with different parameters, (ii) maximum efficiency point tracking and minimum charging time, and (iii) primary-side monitoring and control. For compatibility, receiver parameters should be estimated on the transmitter side without any communication feedback. The estimated parameters include the compensation types, resonant frequency, self-inductance of the coil, compensated capacitance, load condition, and the mutual coupling (mutual inductance or coupling coefficient) before the charging. During the charging process, the mutual inductance and load conditions are supposed to be monitored in real time over a wide range of frequency spectrums. On this basis, the output charging current and charging voltage can be calculated and regulated on the primary side, and the state-of-charge (SOC) and charging power of battery loads can be observed on the primary side. For the optimization of charging efficiency, conventional maximum efficiency tracking schemes are upgraded by including the simplified circuit with the new control paradigm, which is performed on the primary side. For charging time optimization, fast charging is also implemented based on the primary-side control schemes. Regarding the safety issue, the thermal limits of battery loads are fully considered for the proposed primary-side fast charging control. Overall, the new control paradigm for the next-generation WPT in this thesis is conducted in an integrated manner considering both the compatibility and optimization. The first work package addresses the compatibility issue of the universal wireless charging system based on a series of front-end estimation methods, which sets the foundation for the second work package. Based on the estimated information, the optimal charging for the battery loads is conducted on the transmitter side without any external communication feedback in the second work package. In each work package, the tasks are also highly relevant. All the proposed methods in this thesis are validated by practical results.