Novel control method for reducing EMI in shunt active filters with level shifted random modulation

This paper presents a modulation scheme for H-bridge shunt active filter. Random pulse width modulation (RPWM) technique along with level shifted pulse width modulation (LSPWM) which is called level shifted random pulse width modulation (LSRPWM) are applied in order to distribute high frequency harmonics over a wide range; thus, the proposed method reduces electromagnetic interference problems. The effect of this modulation technique along with the proportional multi resonant current control on a system supplying linear and nonlinear loads are analyzed and presented. Simulation results confirm the validity of the proposed control scheme in reducing harmonic level below the limits specified by international standards.