A double-band hysteresis control approach for three-phase four-switch active filters with switching frequency mitigation

A double-band hysteresis current-control (DBHCC) approach for three-phase four-switch shunt active power filters is introduced. The four-switch topology employs four switching devices and two capacitors connected in series. The phase C is connected to the midpoint of these capacitors. This topology with the DBHCC strategy has the advantages of reduced cost and switching frequency and increased reliability. It is shown that the imbalance existing in the capacitor voltages can be successfully eliminated. Also, the DBHCC strategy eliminates the unwanted load current harmonics and achieves sinusoidal supply currents having no phase difference with the supply voltages. The effectiveness of the DBHCC strategy has been simulated under a nonlinear load which draws non-sinusoidal currents from mains supply.