Modelling and validation of a squirrel cage induction generator wind turbine during connection to the local grid

The increasing penetration of wind turbine generators (WTGs) into power systems can affect many network operational aspects such as stability and power quality. The accurate, validated representation of these generators and their components for studying particular operational events, such as cut-in and soft-starting, short-circuit faults and generator switching, remains a challenge. Accurate simulation is particularly important for investigating stability interactions within weak grids or localised networks (e.g. micro-grids or islanded networks). One of the events producing major transient interaction between a WTG and a local grid is the grid connection itself. A simulation model of the use of a soft-starter during the grid connection of a wind turbine equipped with a squirrel cage induction generator and thyristor-based soft-start module is presented. This model has been validated using experimental measurements taken from a wind turbine generator in an operational wind farm site. The analysis focuses on verifying the transients produced during the short-time after the connection to the local grid. Existing literature presents insufficient details about this particular process as well as the practical performance of the soft-starter. It is further demonstrated that ambiguities in this subject may lead to mistaken conclusions in technical assessments carried out by wind farm operators and distribution network operators (DNOs).