By using Voltage source inverter (VSI) for non linear loads like Adjustable speed drives, three phase ac source would be connected for HVDC transmission, non sinusoidal current and voltage waveforms would be generated. To overcome this, current reference generation is used

There are several ways to mitigate the harmonics on the HVDC converter station. However, the most common methods are:

1. Using AC harmonic filters. They create low-impedance paths to ground for specific harmonic frequencies which should be mitigated, and

2. Canceling out harmonics by using different converter configurations. Typically, 12 or 24 pulse bridges are deployed. 12 pulse bridge, for example, consists of two six-pulse bridges connected in series or parallel, with their AC connections supplied from a converter transformer that produces a 30° phase shift between the bridges.