Research On Grid-Connecting And Islanding Detection For Three-Phase Inverters

Many of the world's energy, electricity experts acknowledged that distributed power generation combined with the large power grids are the approach of saving investment, reducing energy consumption and improving the security of the system and flexibility in the 21st Century. Distributed power generation system to connect to the regional power grid interface caused a series of problems. One of the most important issues is the island detection. In this paper, the control methods of grid-connecting inverters and the island testing standards are analyzed.In connection with three phase grid-connecting inverters, research on the real timing track trigonal compare method, by three-phase Soft Phase Lock Loop, to transmit electricity at unity power factor. Presents adaptive frequency shift based on DQ transform to aim at three phase grid-connecting system, give the inverter's periodic perturbation, can decrease the grid obstruction effectively. By monitor the three phase unbalance condition to avoid mistaking action of islanding detection. Research on the grid impedance detection based on injecting a non-characteristic harmonic. Both of above methods are simulated.The three phase voltage inverter is controlled by output current. With TMS320LF2407A DSP, control system is designed. With C control algorithms, the digital Soft Phase Lock Loop is completed. Using active frequency drifting based on DQ transform method for islanding detection are verified by experiments.