Constant Power Output Wireless Charging System for Automatic Guided Vehicle Using the Primary Side Controllable Magnetic Flux Capacitor

This article proposes a novel primary side controllable magnetic flux capacitor (CMFC) for a wireless charging system (WCS) in automated guided vehicles (AGVs). It aims to address two challenges: zero-voltage switching (ZVS) for the full-bridge inverter and constant power (CP) charging for the battery, which are affected by variations in the transmitter coil's self-inductance and the magnetic coupler's mutual inductance, as well as the battery's equivalent load resistance. The CMFC also replaces the resonant capacitor on the primary side. First, the circuit structure of the designed WCS for AGVs and the two problems existing in it are analyzed. Therefore, the CMFC is proposed to address the drawbacks of similar existing methods in resolving these problems. Second, from the hardware aspects, the concept of “controllable magnetic flux principle” and parameter design method for the CMFC is given. From the software aspects, the closed-loop control strategy for the WCS with CMFC is given. Finally, an engineering prototype is constructed. It verifies that the designed WCS can achieve 350 W CP charging and 92.7% efficiency with equivalent load resistance from 2.57 Ω to 8.33 Ω and misalignment up to 40% or 10% of the transmitter coil's width in x- or y-direction.