Design and optimization of the basic unit of modular multilevel converter

 

XIE Rui1, ZHOU Zhichao1, QIAN Feng1, GAO Zhiling1,

LV Zibo2, WANG Ying2, LI Guangdi2, DENG Yan2

(1. Zhejiang Electric Power Design Institute, Hangzhou 310027, China;

2. College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China)

 

Abstract: For the problems that the existing design schemes of the basic unit of modular multilevel converter (MMC) are too complex and unreliable, the research on structural design, communication design and their optimization were studied. A novel design scheme of submodule and the corresponding communication protocols between it and the upper controller were proposed. In the scheme, two optical fibers were used to complete the communication work. The voltage and states of the submodule were uploaded to the upper controller by serial communication interface (SCI). At the same time, the switch signal and protection order generated by the upper controller were sent to submodule by the time division multiplexing technology, and then analyzed by the submodule controller to execute the corresponding task. The results indicate that the proposed design scheme can accomplish the communication between the upper controller and submodule reliably. The usage of optical fiber is reduced to two, which simplify the communication mechanism and enhance the reliability of the overall system of MMC.

Key words: modular multilevel converter(MMC); VSCHVDC; design of submodule; time division multiplexing technology