A new dual series-connected Nine-Switch Converter topology for a twelve-phase induction machine wind energy system

摘要

This paper introduces a new transformerless converter topology for Multiphase-Based Wind Energy Conversion Systems (WECSs). In this topology, a twelve-phase induction generator is integrated to the grid using dual Nine-Switch Converters (NSCs) connected in series forming a high voltage cascaded dc-link. For this generator phase number, this topology reduces the total number of semiconductor devices in the machine side converter by 25% than conventional topologies, where four three-phase two-level voltage source converters are typically needed. Moreover, it offers a high ac-dc boosting capability, which facilities a transformerless system operation. The twelve-phase induction generator can be regarded as dual symmetrical six-phase windings with a spatial displacement of 30°. Therefore, each NSC controls each six-phase winding set. The dc-link midpoint balancing is achieved based on controlling the (x?y) current components of the two winding groups. The proposed topology and its control system are analyzed and simulated under different operating cases using MATLAB/SIMULINK.