Active power filter with sigma-delta modulator in control section

The work presents concept of 1-phase shunt Active Power Filter (APF) based on the modified sigma-delta modulator (SDM) in the control section. The modification depends on including in SDM the dynamic hysteresis comparator. Thank to this feature the resolution of SDM output bit stream is, theoretically, unlimited. As a result it is possible to more precise mapping of an APF input (power grid) current in a reference signal, compared to a PWM based inverter. Due to high switching frequency of power devices in an output stage of APF the GaN E-HEMTs are included. In the work basics of APF operation and results of its simulation model studies are presented.