Power based Single-phase PLL with in-loop Fix Delay Filter under Distortion

Precise voltage phase information is of great importance for grid-connected converter control. For single-phase system, product-type based Power Phase-Locked Loop (pPLL) has high order disturbs in phase detector when the grid voltage is distorted. To obtain zero steady state phase detected error, this paper presents a cascade fix delay filter applied in loop of pPLL. The configuration of cascade filter unit is analyzed, also the parameter design guidelines and digital implementation of the methods are provided. The simulation and experimental tests are carried out to verify the correctness and effectiveness of the filter.