Influences of Virtual Inertia Control on the Mechanical Drive Train of Wind Turbines

With the increasing share of renewable energy sources (RES) within the electric power supply and the decreased share of conventional power plants, considerable challenges arise to further ensure a stable and reliable power supply. As a result, the requirements for a grid connection of RES defined by distribution operators are extended steadily. Especially wind turbines are in the focus of research to provide inertial power to the grid since the inertial masses of their drive train comprise a mechanical acceleration time constant comparable with the one of conventional power plants. The present work focuses on the df/dt- virtual inertia control and its effects on the mechanical drive train of a wind turbine. Specifically, the design of the PLL and of the filter as components of the control structure are investigated in detail. Based on a mathematical analysis, simulation results clarify the influence of the controller parameters on the drive train with resulting torque oscillations at the wind turbine's drive shaft.