Discussion on filters when associated with drives can include  line reactors, matrix filters and sinus filters among others. The filters can be on the line side of the drive for harmonic mitigation or transient protection purposes. On the load side, reactors may be used for reflected wave mitigation( caused by long motor lead lengths for example) or sinus filtering which is to filter out higher frequency components of the output of the drive to the motor.

A reactor is essentially an inductor which acts to ‘smoothen’ out the voltage on the line/load . These are typically applied in variants of 3% or 5% of the line impedance, thus reducing the voltage by 3% or 5%. Going from a reactors, other forms  of harmonic mitigation may involve  combination of reactors and capacitors.

The following manufacturers of power quality and filtering equipment have useful resources on the various techniques of filtering and their application in improving power quality with drives:

MTE : http://www.mtecorp.com/

TCI: http://www.transcoil.com/Support/Documentlibrary.htm

UPDATE: Another one that I had heard of but never used.

MIRUS : http://www.mirusinternational.com

Some good technical papers in the Downloads section including an interesting paper comparing Active Front End’s(AFE’s) to a regular 6 pulse rectifier front end and a filter.