Wind turbines with energy storage for power smoothing and FRT enhancement

The continued development of high power wind turbines raises the standards of operation requirement. This paper evaluates the ability of an energy storage device with a bidirectional dc-dc converter connected to the dc link of a direct driven wind turbine for output power smoothing and fault ride through enhancement. Method based on simple dc voltage measurement and coordinated dc voltage loops of the grid side dc-ac and the energy storage dc-dc converters are proposed to provide a versatile power smoothing control. Further studies on wind turbine fault ride through capability in the presence of energy storage and dc damping resistor are outlined. Simulation results based on a 3 MW wind turbine are presented to validate the effectiveness of the proposed power smoothing strategy. It also shows that with energy storage, the size of the dc damping resistor can be reduced.