Modeling and control of extended multiterminal high voltage direct current systems with three-wire bipole structure

Abstract

Summary In order to improve the transmission capability of power grids and mitigate the congestion of power flow, an idea on converting existing alternating current lines to an extended multiterminal high voltage direct current (MTDC) system is presented in this paper, and a three-wire bipole structure (TWBS) suitable for MTDC systems is proposed. The topology of an extended MTDC system with the TWBS is described, and the operating principle of the TWBS and its transmission capability expansion mechanism are explained. The operating characteristic of the TWBS and its key equipment, the current regulation controller, are elaborated. The further application of the TWBS in DC grids is also proposed and analyzed in this paper. A test extended three-terminal high voltage direct current system based on the TWBS is simulated with PSCAD/EMTDC. The simulation results verify the feasibility of the application of the TWBS in MTDC systems and demonstrate the effectiveness of the corresponding control strategies as well as the validity of the current regulation controller, with the full bridge modular multilevel converter. Copyright © 2014 John Wiley & Sons, Ltd.