Three-Phase Grid-Connected WECS With Mechanical Power Control

Abstract

This paper presents a grid-connected wind energy conversion system (WECS) based on a permanent magnet synchronous generator (PMSG) operating with variable speed. Considering that the wind has intrinsic intermittent nature, it is desirable to maximize the extracted energy, as a maximum power point tracking (MPPT) strategy is described for this purpose. Otherwise, the MPPT algorithm is disabled to maintain the rated power condition and avoid damage to the PMSG, as an external mechanical power control loop associated to active stall is introduced in this work, whose power extraction characteristic is similar to that obtained with pitch control. The WECS employs a bridgeless boost rectifier, which provides power factor correction using self-control strategy, with the advantages of reduced conduction losses, simplified drive circuitry for the active switches, and high input power factor without the need to use multipliers in the control system and impose a sinusoidal reference to the input current unlike average current mode control. Connection with the power grid occurs through a three-phase full-bridge inverter, as experimental results on a 6-kW prototype are presented and discussed in detail in order to validate the proposed approach.