Essentially, there are many options for handling harmonics, including reduction, cancellation, and diversion.
By adding inductance, you can achieve minor harmonic reduction. Drives with active front end (AFE) technology further reduce harmonics to meet IEEE-519 requirements. Reduction can also be accomplished by using closed loop active filters that inject an ‘anti-harmonic’ current spectrum that sums to zero (or client specific values) with the load harmonic currents. This is an engineered solution that can allow you to manage harmonics throughout the facility. What remains is a ‘clean’ current on the mains supply.
Multi-pulse drives (or harmonic filters) provide an antiquated technology for cancellation of harmonics. Diversion technology involves a standard 6-pulse rectifier with a passive harmonic filter. Currently, multi-pulse drives tend to be used if the required transformers are already on-site.
The most basic technique for harmonics management is to use line reactors, sometimes known as chokes, fitted inside or outside a drive. This is called reduction, because with correctly sized AC/DC impedance in a standard 6-pulse drive, harmonics levels can be reduced to where they cause fewer problems. Another approach to reduction is to use an active rectifier. This has an inverter working “backwards” onto the mains supply, treating the mains as it would treat an electric motor and controlling the current flow more effectively, resulting in essentially no harmonic contribution.