Design of a Dual-Loop Controller with Two Voltage-Dependent Current Compensators for an LLC-Based Charger

Area of Science:

• Electrical Engineering
• Power Electronics
• Control Systems

Background:

• Power Mobility Devices (PMDs) require reliable charging solutions.
• Traditional chargers face challenges maintaining stability under varying loads.
• Two-stage charger topologies, specifically PFC+LLC, offer advantages like Zero Voltage Switching (ZVS).

Purpose of the Study:

• To address the design challenges of dual-loop controllers for LLC-based chargers in PMD applications.
• To propose a modified inner current loop control strategy for enhanced operational stability.
• To ensure stable charger performance across a wide input and output voltage range.

Main Methods:

• Development of a two-stage charger (PFC+LLC) for PMD applications.
• Design and implementation of a novel dual-loop controller with an adaptive inner current loop.
• Intelligent switching between two current controllers based on output voltage levels.
• Prototyping a 300-W charger and testing with a resistive load.

Main Results:

• The proposed controller successfully maintains stable operation over a wide input and output range.
• Simulation and experimental results confirm the controller's robustness and stability.
• The LLC topology demonstrated effective ZVS operation under diverse load conditions.

Conclusions:

• The modified dual-loop controller effectively enhances the stability and robustness of LLC-based chargers for PMDs.
• The intelligent current control strategy is crucial for wide-range operation.
• This design offers a reliable charging solution for power wheelchairs and similar devices.