On the Design and Analysis of a Weighting Factor Free-Based Predictive Flux Control Strategy for Three-Level NPC Inverter-Fed IM Drives

The model predictive torque control (MPTC) schemes of three-level neutral point clamped (3L-NPC) inverters have multiobjective cost functions, including three weighting factors (WFs). With the lack of theoretical approaches that make rapid the WFs online-tuning, the paper proposes a predictive flux control strategy with weighting factor free cost function (WFFPFC) for 3L-NPC inverter fed induction motor (IM) drives. It consists in discarding the following: 1) the flux WF through a generation of the reference stator flux vector; 2) the NP voltage WF by introducing a comparative condition of the dc-bus capacitors voltages at the beginning of each sector; and 3) the switching number WF by selecting a group of seven voltage vectors per sector that enables the clamping of the stator phase voltages at low or high level of the dc-bus voltage. The proposed approach is then applied to a case study, considering a comparison among the performance of the proposed WFF-PFC, the model predictive flux control (MPFC), and the MPTC strategies, considering both steady-state and transient behaviors of the 3L-NPC inverter-fed IM drive. It is found that the elimination of the WFs leads to an improvement of drive features except a slight increase of the NP voltage. Simulation results are validated by experiments.