Effects of Voltage Unbalance and System Harmonics on the Performance of Doubly Fed Induction Wind Generators

Renewable energy harvesting is of prime interest in lieu of increasing demand for energy and high price of fossil fuels. Albeit the diminishing resources of petroleum and natural gas has given a renewed attention to the topic. Wind energy is by far the most accessible and efficient form of renewable energy forms given the state of technology in other renewable resources i.e., solar, fuel cells, etc. Over the past decade there have been significant advances on capturing wind energy using doubly fed induction generators (DFIG). The versatility of the DFIG in providing a controllable flow of active and reactive power to the system as well as its inherent low cost and minimum size power electronic converters has been the driving force in superior adequacy of this family of generators. However, as it has been noted in the literature, voltage unbalance and system harmonics can deteriorate the performance of DFIG by introducing unwanted torque harmonics and inaccuracy in generation of commanded active/reactive power. The present article will address this phenomenon from an electromagnetic and system analysis points of view. Simulation results are given to validate the claims.