Hector R. Robles-Campos, Fernando Mancilla-David
Within the last two decades modular multilevel converters topologies have received plenty of research attention given their possibilities to be used in medium and high power levels.
The main advantages of multilevel converters against the very famous two-level power converter are:
- reduced requirements for series connection of semiconductor devices for the same voltage level,
- improved quality of the processed power, and
- relatively low switching frequency.
On any modular multilevel topology, it is required to determine n number of submodules (SMs) to be inserted at any given time, so that, the process of transferring power from source to load, at minimum losses, can be achieved. In addition, a key objective is to be compliant with international standards, such as the IEEE 519 and the IEC 61000-3-2, regarding the quality of the power being supplied to the load.
Different modulation techniques such as: nearest level control (NLC) and phase disposition-sinusoidal pulse width modulation (PD-SPWM,) have been already implemented for some multilevel topologies. Nonetheless, there is a lack of a detailed assessment regarding multilevel modulation strategies applied for the direct AC-AC modular multilevel topology “Hexverter” that in turn is depicted in Fig. 1
Fig.1 Hexverter Topology
The aim of the proposed work is to assess NLC and PD-SPWM modulation techniques applied to the Hexverter. In addition, a voltage balancing algorithms (VBA) integrated along each modulation strategy is evaluated. Furthermore, spectrum and total harmonic distortion (THD) content of synthesized systems voltages, shown below in Fig. 2, are compared and assessed.
Fig. 2: Spectrum of 𝑣asw, 𝑣1sw as well as THD results of (a) NLC and (b) PD-SPWM.
2019 IEEE International Conference on Industrial Technology (ICIT) – Student best paper award
Check full paper at: https://ieeexplore.ieee.org/document/8755144