Phase locked-loop with decaying DC transient removal for three-phase grids

Frequency and phase of the power grid, which are critical for reliable control protection grid-tied devices, generally detected by closed-loop locked-loop (PLL). In highly inductive high-voltage transmission systems, decaying DC (DDC) components with large amplitude can be easily introduced load disturbances and/or grid abnormalities, leading to severe performance degradation PLL during transient. Focusing on this issue, in paper, modifications conventional synchronous reference frame (SRF)-PLL have been made address short-term including DDC component, system operation is divided into normal state DDC-transient state. The SRF-PLL only adopted where component negligible. presence a significant as well negative-/zero-sequence harmonics, weak effectiveness proved, an efficient extraction method, detection time 0.5 cycle, three-phase system. real-time positive-sequence efficiently extracted via proposed scheme, exploiting transient signal properties dq -frame assuming constant frequency short Finally, proper design switching logic has allow fast precise transition between state, thereby ensuring high steady-state accuracy immunity. Hardware-in-the-loop based experiments used verify technique. • Decaying lower traditional Proposed scheme detects components. criterion designed SNR. Proper measures increase speed/accuracy at start/end.