A systematic controller design approach for neutral-point-clamped three-level inverters

This paper proposes a simple linear control technique that is able to keep zero neutral point potential in three level inverters. The technique works even under dynamic operating conditions and enables the decoupled control of the direct and in quadrature motor currents based on the relative gain array approach. This strategy allows the use of outer control loops to set the direct and in quadrature motor currents references as required, for instance, by field oriented and/or direct torque control strategies. Experimental results prove the theoretical considerations and show the simplicity of the proposed control scheme.