Sources and mitigation of interharmonics in back-to-back controllable drives

The theme here is to identify the sources of interharmonics that can affect back-to-back controllable drives and make non-characteristic interharmonic components in the grid side currents when the motor currents are unbalanced. A new control methodology then is formulated and proposed to compensate for the sources, leading to undistorted grid currents, which are growingly important as more drives are tied to the grid. It is shown that in the case of back-to-back controllable drives it is possible to reduce the input current interharmonic distortion caused by motor current imbalance.