A new hybrid filter for power quality improvement in unbalanced load conditions

This paper presents the design of a new hybrid filter for quality improvement of power systems in unbalanced conditions. This filter includes a variable passive filter in parallel with an active filter. The passive part is designed with a varying inductance to reduce the rating of the active part. By using this proposed filter it is possible to compensate for the current harmonics and unbalanced loads with a lower rating active filter compared with conventional ones. Also a simple and accurate method is used to generate the harmonic reference current in the active part of this filter which makes it efficient in unbalanced load conditions. Furthermore, an intelligent hysteresis band current controller is utilized to generate inverter pulses owing to its quick current controllability and easy implementation. Simulation results using the MATLAB Simulink Power System Toolbox show the efficiency and effectiveness of the proposed hybrid filter in elimination of harmonics and balance of the utility current with a desired level of load balancing.