Reduced DC voltage source flying capacitor multicell multilevel inverter: analysis and implementation

Voltage source multicell multilevel converters (VSMMCs) have been extensively exploited in medium-voltage highpower fed industrial applications. One of the typical breeds of the VSMMCs is flying-capacitor multicell converter (FCMC). This study presents an improved configuration for FCMCs, accompanied by its analysis, modelling and implementation. The main advantage of the proposed converter, in comparison with the conventional one, is that the number and voltage rating of the required dc voltage sources are halved in the improved topology which results in reducing the cost, size, installation area and weight of the FCMCs effectively. This amelioration is attained by adding four power switches to the conventional topology of an FCMC without making any amendments to the number and voltage rating of high-frequency power-switches and flying capacitors (FCs). The proposed switching and control methodology for the adopted FCMC is based on the phase-shifted carrier pulse width modulation technique with applying some amendments; therefore the natural balancing phenomenon of the FC voltages, one of the critical advantages of the FCMCs, is preserved in the proposed VSMMC. Experimental measurements taken from the 3-cell-four-level and 4-cell-five-level laboratory prototype systems of the proposed converter are presented in order to validate and corroborate the effectiveness and advantages of the proposed topology, its switching and suggested control strategy. Furthermore, experimental studies are accomplished on an 8-cell-nine-level prototype system of the proposed FCMC to peruse its feasibility and viability for higher number of cells and voltage levels. In addition, comparison of the proposed converter with the other types of multilevel converters is carried out to underline the advantages of the proposed structure profoundly.