Simple and robust multi-objective predictive control method for a single-phase three-level NPC converter based active power filter

A simple and robust multi-objective predictive control method that incorporates four main control objectives applied to a single-phase three-level neutral-point-clamped (NPC) converter operating as an active power filter (APF) is proposed in this paper. The four control objectives are: to self-support the dc-bus voltage under load variations, to compensate the reactive power and the current harmonics and to balance the dc capacitor voltages by using a predefined combination of the converter redundant switching states. The key benefit of the proposed method is that these objectives are accomplished without using weighting factors in the cost function which eliminates problems such as multi-objective optimization or additional empirical procedures for determination of these factors. As a result, the method is easy to implement and selects fast the optimal voltage to improve the dynamic-state performance. The well-known effect of model parameter errors issue, which is inherent in predictive control methods, is also tested to confirm that the method is robust even when the predictive model has a 25% error between actual and the theoretically estimated grid impedance values.