Auto-normalizing Phase-Locked Loop for Grid-connected Converters

A proper synchronization algorithm is a key issue for modern grid-connected power electronic devices, especially in case of weak networks. This paper deals with a novel Phase-Locked Loop (PLL) algorithm for power electronic devices. The proposed algorithm, here named Auto-normalizing PLL (AN-PLL), is able to deal with both amplitude and phase-angle changes in the measured grid voltage. Thus, the proposed concept provides a PLL control performance that is independent on the control signal amplitude. Advantages of the AN-PLL over the conventional PLL approach are highlighted. Experimental results are used to validate the dynamic performance of the proposed synchronization system.