Harmonic reduction of grid-connected multilevel inverters using modulation of variable frequency carriers

Quang-Tho Tran

   Multilevel three-phase inverters are increasingly popular due to their ability to generate high-quality output voltage with harmonic distortion lower than traditional inverters. They are used in various applications, including grid-connected renewable energy systems, motor drives, and power transmission systems, to improve efficiency and reduce costs. The control quality of grid-connected multilevel inverters depends on various factors such as the modulation technique, switching frequency, and control strategy. A good control system can achieve a balance between output current harmonics and switching losses, improving the efficiency and performance of the inverter. This paper suggests a technique for reducing current harmonics of grid-connected multilevel three-phase inverters using variable frequency carriers, without any corresponding increase of the number of switching commutations. The effectiveness of the suggested method has been confirmed through simulation results, which were compared to those obtained from the method of phase opposite disposition modulation using fixed frequency carriers.

Keywords: grid-connected three-phase multilevel inverter, common mode voltage, modulation, number of switching commutations, total harmonic distortion

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