Transient Model and Load Voltage Identification Control of Buck–WPT Systems for Wireless-Powered Buses to Achieve Stable Output Voltage Under Wide-Load-Range Conditions

Magnetically coupled resonant wireless power transfer technology provides a contactless power supply solution for permanent magnet synchronous motors in urban electric buses. By utilizing road-embedded transmitting coils, energy can be harvested in real time during vehicle operation, thereby avoiding the excessive weight of battery-powered schemes and the wear and arcing issues of trolley-pole contact charging. Nevertheless, frequent start–stop, acceleration and hill-climbing of buses produce wide-range step variations in motor equivalent load, triggering severe output-voltage fluctuations. Existing regulation approaches fail to simultaneously meet demands for wide-load adaptability, fast dynamics and communication-free reliability. This work studies modeling and control for cascaded Buck-WPT systems. A dual closed-loop PI controller adjusts the Buck duty cycle to suppress large voltage disturbances. A primary-side-only output-voltage identification method is further proposed, removing secondary-side sensors and wireless communication. The open-loop transfer function is derived by combining the Buck small-signal model and the generalized state-space averaging model of the WPT network. Prototype experiments verify the performance: under load step-down from 50 Ω to 10 Ω, voltage recovers to 20 V within 0.3 s; for step-up from 10 Ω to 50 Ω, recovery takes 0.28 s with acceptable overshoot and negligible steady-state error. The presented solution supports lightweight wireless bus power systems.