Variable hysteresis current control applied in a shunt active filter with constant switching frequency

Presence of harmonics in power networks makes it inevitable to use power filters. Shunt active power filters (APF) are widely used in power systems to eliminate the current harmonics and to compensate reactive power due to their accurate and fast operation. In this paper the instantaneous power theory is used to extract the harmonic components of system current. Then fixed-band hysteresis current control is explained. Because of fixed-band variable frequency disadvantages, the adaptive hysteresis current control (AHCC) is introduced that leads to fix the switching frequency and reduce the high frequency components in source current waveform. Some simulations are done in Matlab/Simulink. The Fourier Transform and THD results of source and load currents are discussed to prove the validity of this method.