Mitigating the Voltage Fluctuation of DC Capacitor and Coupling Point Using Capacitor Current Control Method in DFIG System

Abstract

When symmetric or asymmetric fault occurs, the voltage become unbalanced at the grid point of common coupling (PCC) in Doubly Fed Induction Generator (DFIG) wind turbine system. This unbalanced voltage creates a serious current and power oscillation at grid PCC. In addition to that, it also creates the DC link capacitor voltage fluctuation in DFIG system. The fluctuated DC capacitor voltage can cause leakage current through it which will reduce the reliability and Lifespan of it. On the other hand, severe current oscillation at grid PCC can create a hazardous situation in the whole system. It is found that the conventional vector control method in DFIG system cannot encounter these problems. In this paper, a proportional resonant controller is connected to the conventional control system which will control the capacitor current and alleviate the aforementioned problems. It is to be mentioned that the controller is connected to the Grid Side Converter part of the DFIG system. A transient simulation using simpower system in MATLAB/SIMULINK is accomplished to validate the effectiveness of the control method. Conventional method is compared with the new control method and we got promising results.