Hysteresis current control of hybrid active power filters

This article presents a hysteresis pulse width modulation study for a inductor-capacitor (LC)-coupling hybrid active power filter (HAPF). As the coupling LC impedance yields a non-linear inverter current slope, this can affect the controllability of using the conventional hysteresis control method and generate unexpected trigger signals to the switching devices. This results in deteriorating the system operating performances. On the basis of the proposed modelling, the linearisation of the hysteresis control for the HAPF is firstly studied, investigated and compared with the linear active power filter. Two limits are proposed in this study that divides the HAPF into non-linear, quasi-linear and linear operation regions. The design criteria of hysteresis band and sampling time can then be derived. Single-phase simulation and experimental results are given to verify the hysteresis control study of HAPF compared with active power filter. Finally, representative simulation and experimental results of a three-phase four-wire centre-split HAPF for power quality compensation are presented to demonstrate the validity of the hysteresis linearisation study.