Efficiency Analysis of Predictive Current Control in Multiphase Drives: A Comparison of Weighting Factor Elimination and Scheduling Methods

Multiphase drives are of interest in transportation applications such as electric propulsion, where energy efficiency has a direct impact on range and on the feasibility of extended missions. Efficiency can be improved during the design phase, but for a given hardware platform, further gains must come from the control of the electrical drive. In this context, this paper addresses the issue of weighting factor elimination versus weighting factor selection in predictive stator current control of multiphase drives, where three cost function designs are compared. The first is a conventional formulation with a single weighting factor selected offline and held constant at all operating points. The second is a ranking-based scheme inspired by the Technique for Order of Preference by Similarity to Ideal Solution, in which the cost function terms are treated as separate targets and the candidate control action is selected from the aggregated classification, so that no weighting factor is required. The third retains the structure of the first, but this factor is programmed with the operating point using values obtained offline from the minimization of a meta cost function that combines multiple objectives. Experimental tests are conducted on a five-phase induction motor to assess and compare the performance of the three methods. The results show that no constant weighting factor performs well over the entire operating range, and that the ranking-based scheme, although it removes the weighting factor, still yields a fixed compromise. Scheduling the weighting factor with the operating point instead reduces the tracking error and the switching frequency simultaneously over most of the tested range, and hence the switching losses, which no constant value can achieve.