Model Predictive Direct Torque Control of a Five-Level ANPC Converter Drive System

The five-level active neutral-point-clamped converter is a recently introduced topology that offers low harmonic distortion and a high output voltage. In addition to a neutral point potential in the dc link, this topology features, in each phase, a flying phase capacitor. Balancing these four internal converter voltages around their references while providing fast torque and/or current control for the machine is an intrinsically challenging control problem. Model predictive direct torque control (DTC) (MPDTC) is an ideal control methodology to address this problem. It is shown, in this paper, how MPDTC, originally developed for three-level inverters, can be adapted to this new five-level topology. Compared to DTC, the performance results of MPDTC are very promising-for the same switching frequency, the harmonic distortions of the stator currents and the torque can be more than halved. At the same time, the very fast torque response of DTC is maintained.