Cascaded Symmetrical Hybrid Multilevel Dc-Ac converter

Abstract

This paper proposes the cascading of Symmetrical Hybrid Multilevel Inverters based on the three-levels cell (TC). The inverter operates with dc power sources of equal value and two distinct switching frequencies. The presented inverter presents high modularity as an advantage, which makes it very reliable since it can be designed with redundancy in the number of cascaded modules. The modulation strategy for driving the switches is based on the sinusoidal PWM technique known as Phase-Shifted Disposition (PSD). The output voltages for N cascaded cells are represented by means of its Fourier series. A single-phase low power prototype has been built, operating at 1.5 kHz for the fast switches and 50 Hz for the slow switches in order to validate the operating principle.