Harmonic filters for industrial power systems

The authors present a brief review of the various conventional passive harmonic filters that are used in many industrial power systems. They then discuss the fundamental principles of some recently proposed filters, often referred to as active filters. Two particular types of active filters, one based on analog signal and the other on pulse width modulation (PWM) control, have been recently implemented by the authors. Results from laboratory investigations are presented. Potentials for the use of these filters in other areas of power systems are also described. Finally, advantages and disadvantages of these filters are discussed