Robustification of Proportional-Resonant Control Against Frequency Variations

Replacing traditional power generation with distributed sources leads to a grid frequency that is more vulnerable to fluctuations. This can impact the efficiency and function of power converters, which are essential for integrating renewable energies into the electrical network. Instead of estimating and tracking the grid’s frequency to counter these changes, this paper proposes a robust proportional-resonant (PR) controller that maintains reference tracking in the presence of a varying frequency. Unlike other approaches, the proposed controller does not require precise knowledge of the frequency. This is made possible by integrating into the PR controller a second-order bi-homogeneous differentiator, significantly improving the controller’s tracking performance. The performance of the proposed approach is demonstrated through numerical simulations involving the operation of a grid-connected inverter during a frequency variation event.