A Comparison of Control and Modulation Schemes for Medium-Voltage Drives: Emerging Predictive Control Concepts versus Field Oriented Control

Control and modulation schemes for electrical drives synthesize switched three-phase voltage waveforms that control the electrical machine. Particularly in medium-voltage applications, the aim is to minimize both the switching losses in the inverter as well as the harmonic distortions of the stator currents and the torque. For a given modulation scheme, lower switching losses usually imply higher distortion factors and vice versa. As shown in this paper, for pulse width modulation, this trade-off can be described by a hyperbolic function. Predictive control concepts are rapidly emerging. Their characteristic hyperbolic trade-off functions are derived and compared with each other and with the one of pulse width modulation. It is shown that predictive schemes with long prediction horizons shift the trade-off point towards the origin thus lowering both the switching losses and the harmonic distortions.