Modified Scheme of Predictive Torque Control for Three-Phase Four-Switch Inverter-Fed Motor Drive with Adaptive DC-Link Voltage Imbalance Suppression

Classical voltage space vector modulation techniques cannot be efficiently applied in four-switch three-phase voltage inverter-fed electrical drives due to a voltage offset in DC-link capacitors. The capacitor voltages imbalance is a result of a bidirectional current which flows in a phase of an electric motor that is connected to a DC-link capacitor midpoint. To overcome this problem which leads to an incorrect inverter voltage modulation or even can affect the DC-link capacitors, predictive control algorithms considering the voltage offset in DC-link capacitors have been developed. Despite the predictive methods are highly effective, they require to adjust the cost function weighting factors which is normally an inexplicit task. In this paper, an on-line tuning method of the weighting factor related to the capacitor voltages imbalance incorporated in the cost function of the predictive algorithm has been proposed. According to the proposed approach, the weighting factor is self-adjusted so that the DC-link capacitor voltages are stabilized as well as a high quality of the drive control is remained simultaneously, regardless of its operating point. The proposed strategy has been validated by using simulation model of the induction motor drive system.