PROJECT TITLE :

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

ABSTRACT:

This paper presents an enhanced independent pole management theme for hybrid modular multilevel converter based on a full-bridge submodule and [*fr1]-bridge submodule. A detailed analysis of the power distribution between higher and lower arms beneath asymmetrical dc pole voltages is presented. It's found that the elemental ac currents within the upper and lower arms are asymmetrical. To enable operation beneath asymmetrical dc pole voltages, an enhanced freelance pole management scheme is proposed. The controller is composed of 2 dc management loops, two ac management loops, and circulating current suppression management based on current injection. Six modulation indices are presented to independently management the higher and lower arms. With this controller, the dc voltage operating region is significantly extended. To ride through a pole-to-ground dc fault while not 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 control scheme are verified by simulation results using PSCAD/EMTDC.