Active filter for eliminating current harmonicscaused by nonlinearcircuit elements

In recent years there has been an increasing concern over the introduction of current harmonics in power supply systems owing to the use of nonlinear loads such as television receivers, personal computers and thyristors for controlling electric motors, lamps and heaters. Conventional filtering techniques which use passive filters are inflexible because they cannot cope with variations in the filtering requirements as the load and system conditions vary. The development of an active filter that can be connected across a nonlinear load, is capable of self-tuning and overcomes the disadvantages of the conventional passive filters, is presented.