Analysis of a Space Vector Modulated Five-Level Converter

The phenomenon of DC-capacitor voltages drift is the main technical drawback of a passive front ends, diode- clamped multi-level converter (DCMC). This paper develops a mathematical model and an equivalent circuit for a passive front ends, five-level DCMC. Based on the developed model, the DC-capacitor voltage drift phenomenon of a sinusoidal PWM (SPWM) switched five-level DCMC is analyzed. The analysis shows dependency of the voltage drift phenomenon on the modulation index and the AC-side power factor of the DCMC. This paper also proposes a SVM-based switching strategy that takes advantage of redundant switching vectors of the SVM method to counteract the voltage drift phenomenon. The limit to the range of operation of the DCMC that utilizes the proposed SVM strategy and can prevent the voltage drift phenomenon, is deduced. Performance of a DCMC under various operating conditions, based on time-domain simulation studies in the MATLAB/SIMULINK environment, is evaluated. The studies demonstrate capability of the proposed SVM strategy to control and maintain voltage balance of the DC capacitors within a viable range.