Application of Resonant Controllers for Current Harmonic Suppression and Rejection in Grid-Tied Modular Multilevel Converters

In this paper, a common current control structure in the stationary reference frame, comprising a proportional resonant (PR-)controller and additional resonant control units for harmonic suppression, is applied to a modular multilevel converter (MMC). Discretization of the controllers as well as different control targets in the context of distorted grid quantities are addressed. Current harmonic rejection is achieved applying a resonant band-pass unit to generate the according references for the current control. Simulations are performed to evaluate the designed control.