MMC-HVDC Operation Under Unbalanced Grid Conditions and Its Protection Control

doi:10.3969/j.issn.1000-7229.2017.08.018

Abstract

Abstract: ABSTRACT： AC system imbalance will cause the fluctuation on output power and the imbalance of output current in modular multilevel converter （MMC）, and also lead the bridge arm current and sub module voltage to be greater volatility in modular multilevel converter-high voltage direct current transmission （MMC-HVDC）, which may endanger the security operation of the converter. This paper analyzes the influence of AC system unbalance and control parameters on the bridge arm current of MMC and sub module voltage, and constructs a 3-D function among unbalance component, control parameters, bridge arm current and sub module voltage. Then, through the first fitting method, we obtain the control parameter that makes the bridge arm current minimum in different situation and ensures the safety and stability of MMC at utmost. Finally, we establish the control system of MMC on stationary coordinate and verify the correctness of the theoretical analysis through simulation.

Key words: modular multilevel converter-high voltage direct current transmission （MMC-HVDC）, AC system imbalance, bridge arm current, sub-module voltage, protection control, first fit

CLC Number:

TM 46

DONG Wei1，HUANG Jingsheng1，SHI Enze2，WU Xuezhi2，JING Long3. MMC-HVDC Operation Under Unbalanced Grid Conditions and Its Protection Control

[J]. Electric Power Construction, 2017, 38(8): 129-.

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