Analytical Determination of Operating Conditions and Control Laws of a Doubly Fed Induction Generator

Abstract

This paper explores steady-state characteristics of a grid-connected Doubly Fed Induction Generator (DFIG) in case of unity power factor operation. Based on the synchronized mathematical model, analytic determination of the electrical and mechanical variables is presented and illustrated by various figures in order to understand the effect of the applied rotor voltage on the machine’s behavior. Moreover, unlike previous works where the stator resistance was neglected, in this paper stator resistance is included such that the equations can be applied to small wind turbine generators, which are becoming more popular. Finally, analytical expressions are used to drive the converter control laws in terms of rotor voltage. Experimental results in open loop control are given to demonstrate the effectiveness of the theoretical analysis. The proposed method confers a remarkable simplicity of implementation compared to the previous methods.