A mode switching based transient ride-through phase-locked loop

In the case of grid voltage quality problems, the traditional phase-locked loop (PLL) is hard to detect the accurate grid frequency and phase during the transient response, which will be detrimental to the transient synchronous stability of grid-connected inverters. This paper proposes a mode switching based transient ride-through PLL (TRT-PLL), aiming to improve the transient phase-locking performance through detection technique and mode switching. The TRT-PLL incorporates a hybrid filter (HF), a dual-speed detection module, and a state switch into the traditional synchronous reference frame PLL (SRF-PLL) structure. The theoretical analysis and paradigm design of TRT-PLL is presented in detail. Digital simulations and physical experiments are carried out for the comparisons with other existed PLL techniques. The results demonstrate that the satisfied transient performance of the TRT-PLL has significant advantages, especially in the event of phase jumps.