Modeling And Stability Analysis Of A Three Phase DC-AC Converter Based On Sequence Impedance

Large-scale and centralization is the development trend of the smart grid, but with improvement of the development of distributed generation system and new energy technology, micro grid, which is a special form of electricity as grid complementary coexistence of a part, began to become more and more important. As distributed power, the power supply mode and dynamic characteristics of the power grid is becoming increasingly complex. The grid connected between each distributed power supply and power grid, the problem is particularly critical, and this problem can be used impedance between distributed power supply and power grid, to reflect the situation. Therefore, based on the stability criterion of impedance, the impedance modeling and stability analysis of grid connected inverter is of some significance to ensure the stability of the grid connected system.In this paper, the impedance of the grid connected inverter is modeled, and the output impedance of the inverter is obtained by using the harmonic linearization and small signal model. The impedance model with phase locked loop (PLL) and non phase locked loop (PLL) is verified in the simulation analysis. And on this basis to determine factors affecting on the stability of the system in the impedance model, the use of inverter output impedance model and the grid impedance model and the analysis method based on impedance respectively analysis the influence of inverter and grid impedance on the stability of the grid connected system. According to the analysis results, combined with the adaptive rules of the corresponding optimization of impedance inverter.Subsequent grid impedance online measurement and lay the foundation for the research and the measured grid impedance can be used to implement adaptive control strategy, in the face of large grid impedance variation to keep the inverter control is stable and the development of the impedance model and the proposed control method can validation and certification in the follow-up of the distributed power generation experiment platform of experiment.