Power Converter Resonant Control for an Unbalanced and Non-Constant Frequency Supply

Area of Science:

• Electrical Engineering
• Power Systems
• Control Theory

Background:

• Weak grids like microgrids and islanded systems are susceptible to distorted voltage, including unbalance and frequency variations.
• Such conditions are exacerbated by load changes, particularly large single-phase loads causing voltage unbalance and high-current loads causing frequency fluctuations.

Purpose of the Study:

• To propose a resonant control algorithm for power converters that effectively manages distorted power supplies with voltage amplitude and frequency variations.
• To address the challenges posed by frequency variations in resonant control by employing a variable sampling frequency.
• To enhance grid stability under unbalanced voltage conditions by adjusting power draw from different phases.

Main Methods:

• Development of a resonant control algorithm tailored for distorted power supplies.
• Implementation of a variable sampling frequency to adapt to grid frequency variations without controller re-tuning.
• A strategy to manage unbalanced voltage by redistributing power across phases.

Main Results:

• The proposed resonant control algorithm effectively handles variations in voltage amplitude and grid frequency.
• The variable sampling frequency successfully overcomes the tuning limitations of traditional resonant controllers.
• The method improves grid supply stability under unbalanced voltage conditions by intelligently managing power flow.

Conclusions:

• The resonant control algorithm provides a robust solution for power converter control in weak grids with distorted voltage.
• The adaptive sampling frequency and phase power redistribution strategies are key to maintaining stability.
• The study's findings are validated through mathematical analysis, experimental, and simulated results.