Analysis of chinese photovoltaic generation system low voltage ride through characters

Distributed power generation systems (DPGS) such as wind and photovoltaic power got more and more widely utilized. However with the DPGS installation capacities increasing, it also introduced more and more grid unsteady problems. New Wind and PV installation codes required these renewable energy power sources are able to provide more stiff power and over-ride particular grid faults. As part of the general fault ride through requirements this paper first introduced a new Chinese PV station code, then analyzed this code requirements and the phenomenon during photovoltaic system low voltage ride through (LVRT) period, especially focused on unbalanced grid faults condition. Through the analysis, it´s necessary to improve the traditional D-Q frame control strategy by additional methods such as positive (PS), negative (NS) and zero sequence (ZS) separation, stable phase-locked-loop (PLL) due to the 2nd order power harmonics and synchronization reasons during unbalanced grid faults.