Journal Article

Reduction of low-frequency harmonics in modular multilevel converters (MMCs) by harmonic function analysis

Ooi, Boon-Teck, Hao, Quanrui, Wang, Can

2014

Overview

Modular multilevel converter (MMC) is troubled by the inherent second harmonic of single-phase ac power. By adding feedforward to the modulation signal, low-frequency harmonic voltages are significantly reduced thus overcoming an important weakness of MMC. Capacitors of sub-modules do not have to be over-sized. If desired for protection, transformers can be wye-connected with grounded neutral. The reduction method is based on harmonic function analysis. In addition to deriving algebraic formulae of harmonic voltage components of ‘open loop’ control, this study makes original contributions by deriving formulae which include feedforward control. Analytical insights from the formulae have shown the way to design feedforward methods to reduce low-frequency harmonics. Validation is by simulations using SIMULINK/MATLAB.

• Publisher: The Institution of Engineering and Technology,Institution of Engineering and Technology,The Institution of Engineering & Technology
• Subject: Applied sciences / Control theory / Electric potential / Electrical engineering. Electrical power engineering / Electrical power engineering / Exact sciences and technology / Feedforward / feedforward control / grounded neutral / harmonic analysis / harmonic function analysis / harmonic voltage components / Harmonics / low‐frequency harmonic reduction / low‐frequency harmonic voltage / mathematics computing / Matlab / Metal matrix composites / MMC / Modular / modular multilevel converter / open loop control / power convertors / Power electronics, power supplies / Power networks and lines / power system control / power system harmonics / power transformers / Reduction / signal modulation / Simulink‐Matlab / single‐phase AC power / Theory. Simulation / transformers / Transformers and inductors / voltage control