Performance Analysis with Power Factor Compensation of a 75 kW Brushless Doubly Fed Induction Generator Prototype

This paper presents an analysis of a 75 kW brushless doubly fed induction generator (BDFIG) prototype. Experimental results are presented for the prototype in the cascade mode that enables a comparison in terms of efficiency and power factor with an equivalent wound-rotor doubly fed induction generator. The generator's control system is based on vector control principles which enable to decouple active and reactive power control. The power flow in the two stator windings (power and control windings) and in the grid is analyzed with and without the reactive compensation capacitor bank in the grid using a MatLab/Simulink simulation model. Four cases were studied: (a) the reactive power compensation of the machine is realized only by the control-side converter; (b) the reactive power compensation is realized by both converters (control-side and grid-side converters); (c) the reactive power compensation of the machine is performed only by the control- side converter and a capacitor bank connected at the grid terminals and (d) the reactive power compensation is performed by both converters and a capacitor bank is connected at the grid terminals. The main advantage is obtained with the last case resulting in a significant improvement of the overall system efficiency.