Abstract:

With growing capacity of wind power generator, the grid-connection technology increasingly attracts attention. Traditional methods can produce high impact current therefore threaten safety of generators and the power system. In recent years, variable speed, constant frequency and doubly fed wind power generation system gradually becomes the mainstream technology. Based on the system’s characteristics, two methods of soft gridconnection with doubly-fed generator are analyzed and compared. The mathematical model for prior gridconnection is established. A strategy for gridconnection control is proposed based on the grid voltage orientation. Simulation and experiments show that both methods can realize non-impact grid-connection and smoothly transition in the maximum power point tracking (MPPT) control, even under changeable wind speeds. Both are ideal for doubly-fed wind power generation.

Key words: doubly fed; variable speed constant frequency; soft grid connection; grid voltage orientation