Constant Switching Frequency Virtual Vector Based Predictive Control of a Three-Level Flying Capacitor Active Front End Converter

In this paper, a constant switching frequency predictive control method for a three-level flying capacitor active front end converter is presented for the first time. This predictive control scheme results in reduced switching frequency operation of the converter with reduced computation burden compared to conventional predictive control methods. For the predictive controller, the cost function is defined in terms of grid current error vector in synchronously rotating d - q frame and the condition for optimal converter voltage vector is derived. The optimal converter voltage vector is then synthesized using level shifted carrier based space vector modulation. Thus the proposed method overcomes the disadvantage of variable switching frequency in predictive based control methods. The controller ensures very low harmonic distortion of line currents with minimum computational requirement of the predictive controller. The performance of the proposed predictive controller is analysed using MATLAB/SIMULINK and the results are compared with that of a conventional PI based control. It can be observed that the proposed controller results in similar performance in terms of harmonic spectrum, better performance in response time and decoupled control compared to a classical PI based controller and can be readily used for grid connected power conversion applications and distributed generation systems.