PROJECT TITLE :

Enhanced Independent Pole Control of Hybrid MMC-HVDC System - 2017

ABSTRACT:

This paper presents an enhanced freelance pole control scheme for hybrid modular multilevel converter primarily based on a full-bridge submodule and 0.5-bridge submodule. A detailed analysis of the facility distribution between higher and lower arms beneath asymmetrical dc pole voltages is presented. It is found that the fundamental ac currents in the higher and lower arms are asymmetrical. To enable operation beneath asymmetrical dc pole voltages, an enhanced freelance pole management theme is proposed. The controller consists of 2 dc management loops, two ac control loops, and circulating current suppression control based on current injection. Six modulation indices are presented to independently management the upper and lower arms. With this controller, the dc voltage operating region is considerably extended. To ride through a pole-to-ground dc fault without bringing dc bias at the neutral purpose of the interface transformer, a pole-to-ground dc fault ride through strategy is proposed. The feasibility and effectiveness of the proposed management scheme are verified by simulation results using PSCAD/EMTDC.