Co-ordinated three-phase hysteretic-control scheme for active power filtering

The authors examine a three-phase hysteretic-control algorithm, applicable to a voltage-source inverter for real-time implementation of power systems active power filtering. Special features of the proposed scheme are: co-ordinated hysteretic controller operating on the radial and tangential components of the busbar-voltage error, and the use of a microcontroller to implement the co-ordinate frame transformation, setting the switching parameters required by the hysteretic comparators, and monitoring the inverter-synthesised switching frequency. Provision for real-rime tailoring of the tangential hysteresis hand has been made to supplement the co-ordination scheme. The proposed algorithm is experimentally verified on a low-power prototype circuit. The experimental results have shown that the hysteretic controller can approach the generation of a fully optimised and uniform three-phase switching pattern with a corresponding reduction in residual harmonic distortion. The results also showed the desired regularity of the radial/tangential error trajectory with nearly constant average switching frequency