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In medium-voltage (MV) drives, the switching frequency is limited to a few hundred Hz, for which high-performance control and modulation schemes are necessary to maintain acceptable current and torque distortion. Forced machine current control (FMCC) is a predictive control strategy for MV drives which was proposed in the early 1980s, which can be formulated for either torque or current control. Recently, model predictive direct torque control (MPDTC) and model predictive direct current control (MPDCC) have been developed, sharing with FMCC the use of hysteresis bounds, switching and prediction horizons. However, the relative performances of these schemes are yet to be compared. Through simulation, this paper compares the schemes across a range of operating points. It is shown that the steady-state performance of MPDxC and FMCC is similar when the switching horizon of MPDxC is limited. However, when the switching horizon is extended, the performance of MPDxC is shown to be superior to FMCC, the horizon of which is inherently restricted.
Date of Publication: May 2013