Modeling and Control of a New Five-Level Converter for Medium-Voltage Drive Systems

Multilevel inverters (MLIs) with medium-voltage (MV) capacity have become a promising solution to handle the increase in power demand for MV drives in electrified transportation systems. This article proposes a new five-level dc/ac converter (inverter) with a reduced component count for MV drive systems. Also, the proposed converter is designed without a split dc-bus structure and isolated dc sources. Furthermore, it has few flying capacitors (FCs) and only requires its voltage regulation mechanism. Hence, its overall control complexity is relatively low. Moreover, the proposed converter operates at a low switching frequency, leading to low switching losses and improved efficiency in comparison to the existing MLIs. To achieve a fast transient response, a predictive current control (PCC) method is presented for this converter. The discrete-time models of a new five-level converter are developed to implement the PCC method. The steady-state and transient performance of the proposed five-level converter with the PCC method is demonstrated through experimental studies on a dSPACE-controlled laboratory prototype. The performance comparison of the proposed and the existing MLIs with the PCC method is further assessed in terms of inverter average switching frequency, current harmonic distortion, switching power losses, and efficiency at different operating conditions.