A frequency locked loop grid synchronization method of single-phase grid-connected PV inverter under weak grid

作者：Liu Guihua; Cao Xiaojiao; Wang Wei

来源：Proceedings of the CSEE, 2015, 35(19): 5022-5029.

DOI：10.13334/j.0258-8013.pcsee.2015.19.021

• Distorted grid voltage
• Electrical characteristic
• Frequency lock loop (FLL)
• Grid-connected PV inverters
• PV inverter
• Second-order generalized integrators
• Synchronization method
• Weak grid

One of the main electrical characteristics of weak grid is the high grid impedance, which will easily lead to grid voltage waveform distortion. Distorted grid voltage can resultin deviation or failure of the phase-locked loop of photovoltaic (PV) inverter, and power quality will deteriorate. In order to tackle this problem, targeting on the LC-type PV inverter, a synchronization method is proposed based on the second order generalized integrator frequency locked loop (SOGI-FLL). Initially, the impact of various grid states, especially the weak grid, on the inverter is analyzed. Then the operation principle of SOGI-FLL and its implementation method are set forth in detail. Simulation and experimental results demonstrate the validity of this synchronization method in grid voltage disturbance and zero-crossing oscillation. This synchronization method has strong robustness and adaptability for grid voltage changes. Compared with the conventional zero-crossing synchronization method, the SOGI-FLL synchronization method can improve the reliability of grid-connected PV inverters under weak grid.

• 出版日期2015