The vector PWM for two-section frequency converter

The paper deals with analysis of operating modes of two-section frequency converter (TSFC) based on two series-connected voltage inverters. The author considers implementation of the vector pulse-width modulation for analyzed converter. The schemes of converter powering and the vector diagram of the output voltage states are presented. It is shown that the vector state diagram corresponds to the diagram of the traditional three-level converter. The proposed algorithm of vector PWM provides a doubled frequency of phase voltage switching with respect to the switching frequency of the power switches. The presented algorithm of the vector PWM eliminates the necessity to compensate the 2nd and 4th harmonics that occur when using a traditional sinusoidal PWM with asymmetric reference signal. Also this technique slightly improves harmonic composition of the output voltage of the convertor. However additional switching of the zero vector increases the load on the power switches. To implement the presented algorithm it is useful to apply FPGA module. The paper presents the plot of the phase output voltage of the converter and its spectral composition.