| Title |
PLL Control Strategy for ZVRT(Zero Voltage Ride Through) of a Grid-connected Single-phase Inverter |
| Authors |
Tae-Il Lee and Kyung-Soo Lee ; |
| DOI |
https://doi.org/10.6113/TKPE/2019.24.3.169 |
| Keywords |
LVRT(Low Voltage Ride Through) ; ZVRT(Zero Voltage Ride Through ; ) Grid-connected inverter ; PLL(Phase Locked Loop) |
| Abstract |
Grid codes for grid-connected inverters are essential considerations for bulk grid systems. In particular, a low-voltage ride-through (LVRT) function, which can contribute to the grid system’s stabilization with the occurrence of voltage sag, is required by such inverters. However, when the grid voltage is under zero-voltage condition due to a grid accident, a zero-voltage ride-through (ZVRT) function is required. Grid-connected inverters typically have phase-locked loop (PLL) control to synchronize the phase of the grid voltage with that of the inverter output. In this study, the LVRT regulations of Germany, the United States, and Japan are analyzed. Then, three major PLL methods of grid-connected single-phase inverters, namely, notch filter-PLL, dq-PLL using an active power filter, and second-order generalized integrator-PLL, are reviewed. The proposed PLL method, which controls inverter output under ZVRT condition, is suggested. The proposed PLL operates better than the three major PLL methods under ZVRT condition in the simulation and experimental tests. |