Development of phase lock loop system for synchronisation of a hybrid system with the grid

Abstract

Phase locked loop (PLL) is an important part of the control unit of the grid connected power converter. The method of zero crossing detection (ZCD) does not produce accurate phase information when grid is non-ideal. In this work, a synchronous reference frame (SRF) PLL method to obtain accurate phase information when the grid voltages are unbalanced is proposed. The performances of the PLL have been verified for ideal and abnormal grid conditions such as unbalance, voltage sag, faults condition etc. Based on the results obtained, the developed PLL gives better fault ride when unbalances in the three phase input signals are overall handled well by the PLL system as it locks the two signal back within the first cycle. It also overcomes a phase jump after 5 milliseconds from the time the fault was introduced and performs better tracking of the grid voltage and that of the renewable energy source.

Investigation of voltage regulation in grid–connected PV system

“…SRF-PLL can capable of execute quick and exact synchronization details with respect to the large amount of protection also sensitivity to any kind problem associated with the power system. Another advantage of SRF-PLL over conventional PLL [24] is that it is mostly used for the three-phase application. General representation of PLL is given below in Figure 5.…”