Active filter for compensation of specific harmonics

An example of a specific harmonic is the third harmonic. In several types of equipment such as power supplies for electronic equipment, high power rectifiers and HVDC systems a relatively large third harmonic current is generated. A new method to compensate the third harmonic in a supply phase of the grid is introduced [J.B. Woudstra, et al., 1997]. A controllable filter consisting of a LC-circuit and an electronic switch will produce a third harmonic current with about the same amplitude as the third harmonic load current in the grid phase and with about 180° phase shift. Several methods of control of the newly proposed circuit have been investigated. The relations between design parameters and the control range have been identified. Results of both simulations and experiments will be shown. The same method can be used to compensate other harmonics.