Sliding Mode Control with Fixed Switching Frequency for Four-wire Shunt Active Filter

Abstract

The present paper proposes a sliding mode control
with fixed switching frequency for three-phase three-leg voltage
source inverter based four-wire shunt active power filter, to
improve phase current waveform, neutral current mitigation
and reactive power compensation in electric power distribution
system. The performed sliding mode for active filter current
control is formulated using elementary differential geometry, and
the discrete control vector is deduced from the sliding surface
accessibility using the Lyapunov stability. The problematic of
the switching frequency has been treated considering hysteresis
comparators for the switched signals generating. In this way, a
variable hysteresis band has been established as a function of
the sliding mode equivalent control and a predefined switching
frequency in order to keep this one always constant. The
proposed control has been verified with computer simulation
which showed satisfactory results for the above objectives.