DC-offset elimination method for grid synchronisation

For three-phase power system, the synchronous reference frame (SRF) phase-locked loop (PLL) is probably the most widely used synchronisation technique under ideal grid condition. However, the presence of dc-offset causes fundamental frequency oscillations errors in estimated phase. To deal with this problem, delay signal cancellation (DSC) operator is utilised in SRF-PLL in recent published literature at the cost of slowing down the dynamic behaviour. The aim is to propose a rapid dc-offset rejection method in three-phase PLL for grid synchronisation. With the employment of modified DSC operator, the dynamic performance of the conventional DSC-based PLL is improved. The effectiveness of the proposed method is confirmed through simulation results.