A Reconstructed Nearest Level Modulation Method With ABC Coordinate-Based Deadbeat Predictive Control for the Four-Level Single Flying Capacitor Converter

This article presents a new modulation method based on nearest level modulation (NLM) and phase voltage level reconstruction for the four-level single flying capacitor (4L-SFC) converter. The reconstruction procedure addresses the voltage balancing issues of the 4L-SFC converter and performs the per-phase modification of the phase voltages. In the proposed reconstructed NLM (R-NLM) method, the modulation procedure is carried out in the abc reference frame to eliminate the complexities associated with the space vector modulation (SVM). It is also compatible with the per-phase implementation of the reconstruction, making the whole process more straightforward. The required computations in the NLM-based reconstruction are also reduced when compared to the SVM-based reconstruction technique. The current control task is carried out using deadbeat predictive control (DBPC) by defining the system model in the abc coordinate. Also, a new approach for estimating the common-mode voltage (CMV) value, required in the abc frame-based system model, is presented. Simulation results demonstrate that the proposed R-NLM simplifies the modulator while retaining the performance of the SVM-based modulation technique for the 4L-SFC converter. The R-NLM alongside DBPC in the abc coordinate is implemented on a laboratory scale setup of the 4L-SFC converter to validate the feasibility of the proposed modulation scheme.