A Method of Capacitor Voltage Ripple Reduction by Controlling Modulation Index Together with 2nd Order Current Injection for Modular Multilevel Converter

In this invention, a method of capacitor voltage ripple reduction for modular multilevel converter is proposed. In conventional control of MMC, capacitor voltage ripples consist of fundamental component and 2nd order component. That is because the module input power contains fundamental power and 2nd order power. With power flow analysis, the physical meaning is that this fundamental power is swapping between upper arm and lower arm, but the 2nd order power is delivered to the load. With this proposed method, both fundamental power and 2nd order power of module have been reduced dramatically. As a result, the capacitor voltage ripple can be reduce about 80%.
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For Information, Contact:
Li Chen
Licensing Associate
Virginia Tech Intellectual Properties, Inc.
(540) 443-9217
Yadong Lyu
Yi-Hsun Hsieh
Fred Lee
Qiang Li