Indirect Torque Control of a Cascaded Brushless Doubly-Fed Induction Generator Operating With Unbalanced Power Grid

This article describes an indirect torque control algorithm for a cascaded brushless doubly-fed generator (CBDFIG). The control algorithm presented in the article provides a possibility for CBDFIG to work with an unbalanced power grid applying different strategies: electromagnetic torque oscillations reduction, generated active power oscillation reduction, generated phase currents balancing, sinusoidal control currents under grid imbalance. The proposed control method is based on a cascaded brushless doubly-fed induction generator equivalent model and requires fewer tuning-demanding elements in comparison to classic control methods. The control algorithm presented in the paper was implemented and tested on a CBDFIG machine model in a simulation environment PSIM and on a real physical stand with a cascaded brushless doubly-fed generator.