Control strategies for maximum active power and minimum copper loss of doubly fed induction generator in wind turbine system

The doubly fed induction generator (DFIG) is one of the most widely used generator wind turbines. It can be controlled through rotor slip recovery with machine and line side converters (back-to-back converter). The active power and the reactive power flow can be controlled independently. A bi-level control objective is presented in this paper. The first level determines the maximum power from the wind. After the maximum active power is determined, the reactive power can be allocated between the stator and rotor to minimize the copper loss. The experiments in this paper are tested with a 7.5 kW DFIG coupled with an 11.2 kW wind turbine simulator. The normal control operation and copper loss minimization algorithm is implemented on the developed 7.5 kW back-to-back converter. The experimental results show the high-quality control performance during dynamic and steady state conditions. By the use of the copper loss minimization algorithm, the system control a d-axis rotor current through stator reactive power to give the copper loss minimization. The method can reduce the copper loss, thus improving the efficiency of energy production in the wind conversion system.