A novel adaptive hysteresis band current control method for three-level based active power filter

A novel adaptive hysteresis band (HB) current control strategy is used in active power filter (APF) based on three-level inverter in this paper. The hysteresis bandwidth is changed according to modulation frequency, supply voltage, dc-link voltage and slope of the reference compensator current in this method. Compared with the conventional HB control with unfixed switching frequency, the method proposed in this paper can keep the switching frequency constant so that the switching losses will be reduced and the design for filter inductor will be easier. An improved d-q method based on vector projection principle is applied to determine the reference current. In view of the HB control strategy used, a matched method which adjusts the switching combinations is used to maintain the balance of the midpoint potential. Finally, results of the simulation using the MATLAB Simulink show the validity of the control strategy presented.