Unidirectional DC/DC modular multilevel converter for offshore windfarm with the control strategy based on stationary frame

Abstract

This paper presents the design and control of an advanced unidirectional DC/DC modular multilevel converter (MMC) that facilitate the integration of off-shore windfarms with the high-voltage direct current (HVDC) transmission system. The proposed converter deploys a single-phase MMC inverter coupled with series-connected rectifier modules through multiple medium frequency transformers. Unlike the conventional dq control method, which involves multiple transformations, this paper also proposes a simple control strategy that directly acts on the AC output of the MMC, under the stationary reference frame.

Keywords

• offshore installations
• wind power plants
• power generation control
• invertors
• DC-DC power convertors
• HVDC power transmission
• control system synthesis
• rectifiers
• power transformers
• offshore windfarm
• advanced unidirectional DC/DC modular multilevel converter
• high-voltage direct current transmission system
• single-phase MMC
• series-connected rectifier modules
• multiple medium frequency transformers
• conventional dq control method
• stationary reference frame