Output Feedback Control of a WPT Charger based on Sliding Mode and High Gain Observer

This paper focuses on the regulation of the output voltage of a Wireless Power Transfer (WPT) charger feeding an Electric Vehicle (EV) battery through an On-Board Charger (OBC) with a DC input voltage. To achieve optimal OBC performance, maintaining a well-regulated voltage is crucial. However, direct control of the WPT charger's output voltage is challenging due to the non-minimum phase nature of the WPT circuit. To address this, the paper proposes an indirect control technique where the output voltage is regulated by controlling the current in the ground side coil. After establishing an accurate model of the WPT charger, a nonlinear controller has been designed using the sliding mode control technique. Although effective in simulation scenarios, the main limitation of the controller is the need to measure all signals involved, increasing cost and complexity. To overcome this, a high-gain observer is introduced, requiring only two measured signals. This reduces the complexity and cost of the proposed control technique while maintaining effectiveness, as validated through simulation scenarios.