A series LC filter for harmonic compensation of AC drives

This paper characterizes typical nonlinear loads into two types of harmonic sources-harmonic current source and harmonic voltage source-which produce inherent current and voltage distortion, respectively. The conventional approach of harmonic compensation has been the parallel (or shunt) LC filter in which shunt low impedance branches traditionally consisting of 5^th and 7^th tuned LC series resonant and high-pass circuitry are connected in parallel to a nonlinear load. It is shown in this paper that the parallel LC filter is effective only for harmonic current source type of nonlinear loads but not for harmonic voltage source type of nonlinear loads such as adjustable speed AC drives with a diode rectifier at front end. This paper presents a series LC filter that is very effective in harmonic compensation for harmonic voltage source type of nonlinear loads such as AC drives. General compensation characteristics and comparison of parallel LC filters and series LC filters are given analytically. The effectiveness of series LC filters is demonstrated experimentally