An Improved Predictive Control for T-Type 3L Active-Front-Ends with LCL Filters: a Full State-Variable Feedback Solution

T-type three-level power converters have been widely used in distributed power generation systems (DPGSs), particularly for medium-voltage applications. In order to restrain grid-tied current harmonics, LCL filters are usually installed at the converter output side, due to their effectiveness to eliminate high-frequency harmonic. However, the LCL filter is a typical three-order system that includes a potential resonance frequency and may render the system into an unstable situation. To tackle this problem, we propose an improved Finite-Control-Set Model Predictive Control (FCS-MPC), using a full state-variable feedback mechanism and the exact discretization method. The proposed solution, different from its classical counterparts, takes the full state variables into account that realizes active damping control and harmonic elimination. Finally, simulation verifies that: (i) the exact discretization method improves control accuracy effectively; (ii) the full state-variables feedback FCS-MPC method shows good steady-state and dynamic performance than existed control methods.