Effect of Wind-Energy Power Injection into Weak Grids

摘要

Frequency converter control can be challenging in regard to the connection of wind turbines to and the power injection into a weak grid due to uncertainty of grid parameters. This paper reviews the basic principles about weak grids in order to describe effects of power injection of wind turbines regarding the voltage level and grid stability. The occurrence of these effects differs significantly with variations of the grid parameters and can be influenced and partly controlled by the fed in power. The boundaries and requirements of this injection to realize a stable and controlled operation are investigated analytically and validated by means of simulations. A PI based control structure regulating the voltage at the point of common coupling is proposed. For weak grids an energy storage system is proposed to smooth the output power and to disburden the grid side converter while it needs to provide voltage regulation functionality.