Modeling of Nine-Switch-Converter Based on Virtual Leg and Its Application in DFIG Wind Generation System

This article proposes a doubly fed induction generator (DFIG) wind energy conversion system (WECS) based on nine-switch converter. In this article, a new concept of virtual-leg is proposed, and the equivalent mechanism between the nine-switch converter and the dual six-switch converter is first proposed. Furthermore, a mathematical model of the nine-switch converter based on the unipolar binary logic switching function is established. In order to simplify the mathematical model of the nine-switch-converter-based DFIG-WECS, the parameter mapping relationship between the nine-switch converter with loads and the nine-switch-converter-based DFIG-WECS under dq coordinate system is given. Meanwhile, the adaptive resonant proportional integral (PI) (AR-PI) current controller based on the resonant controller, the PI controller, and the adaptive genetic algorithm is applied for the DFIG wind generation system. As a result, harmonic current content, overshoot, and dynamic response speed of the nine-switch-converter-based DFIG-WECS have been significantly improved. Finally, the simulations and experimental results verify the validity and reliability of the proposed mathematical model and control algorithm.