Numerical-based frequency domain controller design for stand-alone brushless doubly fed induction generator power system

Brushless doubly fed induction generator (BDFIG) shows high reliability in either grid-connected or stand-alone applications due to its brushless structure. However, the brushless structure results in a complicated electromagnetic feature. The BDFIG controller design is thus challenged. The recent controller design either ignores the usefully model information or requires the complicated feedforward terms. Besides, the bandwidth restriction exists if the dual-loop control is applied. To overcome these problems, this study proposes a numerical-based frequency domain design method and applies it to a CW-current-oriented stand-alone BDFIG system with dual-loop control. The control objects are developed as transfer function forms and derived from the complete BDFIG model. Then the PI controllers for inner current loops and outer voltage loop are designed step by step, and the previous design result is considered in the recent step. In this way, more model and controller information are considered, and the bandwidth limitation can be eliminated. The design steps are presented in this study. The results show that the good steady and dynamic performances of the voltage regulation can be obtained compared with the traditional methods, which is practically important for a stand-alone BDFIG system.