Communication-Less Reactance Compensation Using PWM-Controlled Switched Capacitors for Wireless Power Transfer

• Published in: IEEE transactions on power electronics pp. 1 - 13
• Main Authors: Matsumoto, Ryo, Fujita, Toshiyuki, Fujimoto, Hiroshi
• Format: Journal Article
• Language: English
• Published: IEEE 11.07.2023
• Subjects: Capacitors; Coils; Component tolerance; Control systems; Inverters; resonant frequency; RLC circuits; self-tuning; switched capacitor; Switches; Wireless communication; wireless power transfer (WPT)
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2023.3294487

Self-inductance variations caused by component tolerance and aging decrease the efficiency of wireless power transfer (WPT) systems. This paper deals with this issue by compensating for the self-inductance variations using pulsewidth modulation controlled switched capacitors. Previous methods relied on wireless communication between the transmitter (Tx) and receiver (Rx) to control the variable capacitors, which is not a feasible approach when considering practical constraints. This paper proposes a control scheme in which the switched capacitors are controlled simultaneously by separate closed-loops on the Tx and Rx sides, thus eliminating wireless communication. The control scheme is based on a unique condition for perfect resonance derived by focusing on the output power of the WPT circuit. This paper also points out the necessity to compensate for the self-inductance variations of both the Tx and Rx coils to achieve maximum AC/AC efficiency in battery charging applications. Furthermore, the proposed control scheme incorporates the soft switching condition of the inverter to improve the DC/DC efficiency. Experimental results of a 1-kW prototype show that the switched capacitors can flexibly adapt to the self-inductance variations and improve the AC/AC efficiency and DC/DC efficiency by up to 3.04% and 8.63%, respectively.