Control of Nine-Phase Machine with Strongly Coupled Winding Sets

In this paper, a decoupling matrix for a nine-phase permanent magnet machine with strongly magnetically coupled winding sets is proposed. The machine consists of three three-phase winding sets without phase shift, which share a common neutral point. This winding arrangement combined with strong magnetic coupling prevents the implementation of the well-known decoupling matrices such as vector space decomposition (VSD) method and the multi-stator (MS) method. The proposed decoupling matrix is derived from VSD where only the first subspace relates to the torque generation. Other degrees of freedom are used for control of the zero-sequence component and for balancing the machine variables (currents) in the phases which are aligned in space. The decoupling matrix can be used in the control of nine-phase machines with a single neutral point and is validated using a simulation model.