FCS - MPC with reduced switching frequency applied to a multi - cell AFE rectifier with improved transient behavior

To generate medium and high voltage with low Total Harmonic Distortion (THD) are used multilevel converters, through use of low voltage semiconductors devices, for applications as AC drives, PV farms and active power filters. This converter uses between the AC supply and the power cells a multipulse transformer, which is in charge of the harmonic cancellation of the input current harmonics generated by the three - phase rectifier. This transformer is expensive, heavy, bulky and must be designed according to the power, and the number of power cells. This work uses a THD minimization strategy based on a Finite Control Set - Model Predictive Control (FCS - MPC), which propose change the multipulse transformer by a simpler transformer, achieving a low THD in the input current of multi-cell AFE rectifier. The work is centered in the solution in one disadvantage of the FCS - MPC, high switching frequency. To solve this drawback, an additional objective function is used, which reduces the states changes of the power switches. Unfortunately, because of this the FCS - MPC loses an advantage, fast dynamic response to changes. In order to improve this issue, is necessary a modified control scheme, which detects the steady state and transient state to change the objectives of the FCS-MPC. Simulation results shows the feasibility of the proposed control.