Hierarchical control of a small wind turbine system for active integration in LV distribution network

Reactive power handling capability is requested to distributed power generation systems by the new national grid codes. The reactive power exchange should be maintained inside a triangular/rectangular reactive power capability curve. Among distributed power generation systems based on renewable sources, small wind turbines systems are becoming an increasingly attractive structure for the proposal of an active low voltage (LV) distribution network. A hierarchical control applied to a small wind turbine system, and enabling a real integration into the distribution network, is proposed in this paper. It consists of: a local control system (primary and secondary level) performed on the back-to-back converter and a remote control system providing the set-points for the local control. The local control system is based on a coordinated active/reactive power control strategy carried out by means of three-levels cascade loops. Simulation results and some selected experimental results validate the effectiveness of the proposed solution.