Efficient Sequential Switching Hybrid-Modulation Techniques for Cascaded Multilevel Inverters

This paper presents four different sequential switching hybrid-modulation strategies and compared for cascaded multilevel inverters. Hybrid-modulation strategies represent combinations of fundamental-frequency modulation and multilevel sinusoidal-modulation (MSPWM) strategies, and are designed for performance of the well-known alternative phase opposition disposition, phase-shifted carrier, carrier-based space-vector modulation, and single-carrier sinusoidal-modulations. The main characteristic of these modulations are the reduction of switching losses with good harmonic performance, balanced power loss dissipation among the devices with in a cell, and among the series-connected cells. MSPWM and its base modulator design are implemented on a TMS320F2407 digital signal processor (DSP). Complex programmable logic device realizes hybrid-modulation algorithm with base pulsewidth modulation (PWM) circulation, and is integrated with DSP for sequential switching hybrid PWM generation. The proposed modulations can be easily extended to three phase, and higher level inverters, operates with same physical structure of the power module. The feasibility of these hybrid modulations are verified through spectral analysis, power loss analysis, simulation, and experimental results.