A PLL-Based Controller for Three-Phase Grid-Connected Power Converters

The current control of three-phase grid-connected converters is typically carried out by using a proportional-resonant controller or synchronous reference frame (SRF) proportional-integral regulator. The implementation of these controllers often requires knowledge of the grid voltage frequency/phase angle, which is typically provided by a synchronization unit. It implies that dynamics and possible inaccuracies of the synchronization unit have a considerable impact on the current controller performance. The aim of this letter is to design an adaptive current controller by using a conventional SRF phase-locked loop. In this way, the current controller and synchronization part are merged into a single unit, which results in a simpler and more compact structure. The effectiveness of the proposed controller is verified using experimental results.