Doubly-fed Induction Generator Drives for Wind Power Plants

Abstract

The basics of electrical drives in rotating dq-coordinate system was introduced as well as the classical definition of active and reactive powers leading to the complex power. Electrical power generation, specifically the induction generator and later the doubly-fed induction machine and the power flow were discussed. The simplified analysis showed the possible operating ranges of the doubly-fed induction generator drive for production of active and reactive powers. The drive system topology allows for an independent control of the reactive power in the generator and mains side as well as the decoupling from the active power due to the mains voltage or flux orientation. The suggested optimisation is based on the controlled distribution of the reactive power flow in the drive components. The reactive power can be defined the rate of magnetic and electrical energy exchange between the generator, the mains supply and the inverters. It is a function of the reactive current and of the voltage amplitude and, therefore, closely related to process losses. For this reason, it proves to be a very suitable optimization variable.