Variable Speed Wind Turbines using Induction Generators

Abstract

In this paper, the performance of two variable speed wind turbine concepts with induction generators connected to the grid is investigated. Variable-speed wind turbine generator systems have been modelled and simulated to study their steady state and dynamic behaviour. A doubly-fed induction generator of 11 kW fed by a vector controlled back-to-back PWM-VSI inverter on the rotor side and a cage rotor induction generator of 11 kW rating with a vector controlled back-to-back PWM-VSI inverter on the stator side have been tested and the results compared with digital simulations. It is shown by both modelling and laboratory tests that a doubly-fed induction machine can be used as a variable speed wind generator over a large speed range (±40 %). The cage rotor induction machine also allows good speed range and it should be used in low-power variable-speed systems, replacing the classical direct grid connected fixed speed wind generator systems. Its capacity to deliver reactive power is remarkable.