HVDC Light System Modulation Strategy Research Based On MMC

HVDC was paied more and more attention in the field of contemporary transmisssion system,when the evolving of power electronics technology in the field of contemporary transmission system. The voltage levels demand is rising, the large-capacity inverter as the core component of transmission system also need to be increased. The modular multilevel converter showed good performance succh as low harmonicand system expansion conveniently. As the theory proposed, the attention were focus on it. With the deeping of study, variet of control srategied were appropriate at MMC controller. Paper compared three common modulation strategies and sub-module capacitor voltage control methods, given reference when selecting the HVDC control strategy in actual.This paper introduces the modular multilevel converter topology and sub-module operating principle, maked a brief introduction about Four-quadrant. After the system-level control strategy of the HVDC gived, detailed analysis of three basic principles of the modular multilevel converter modulation method and the sub-module capacitor voltage regulator control method, and mathematical analysied the output of the system mainly about deuced the harmonic content.This paper simulation passive inverter and DC transmission model by software, System output performance of various control strategies were compared with theoretical studies, validation theoretical analysis and control methods. And gives the comparison of three different modulation strategy on modular multilevel converter performance, referenced for the actual projet modulation strategy.