Novel MTDC droop scheme with decoupled power control for enhancing frequency stabilities of weak AC systems. Issue 11 (21st July 2020)

• Record Type: Journal Article
• Authors: Li, Yujun; Liu, Sining; Zhu, Jiebei; Yuan, Xiaotian; Xu, Zhao; Jia, Ke
• Is Part Of: IET renewable power generation. Volume 14:Issue 11(2020)
• Page Start: 2007
• Page End: 2016
• Publication Date: 2020-07-21
• Subjects: frequency control -- power generation control -- distributed power generation -- load flow -- voltage control -- power system interconnection -- power transmission control -- HVDC power transmission -- frequency stability -- power control -- HVDC power convertors -- power grids; frequency support -- MTDC system -- connected weak AC systems -- standard power‐sharing droop control -- weak grid -- asynchronous AC systems -- connected AC system -- multiterminal DC grid -- low inertia AC systems -- isolated weak inertia AC systems -- decoupled power control -- novel MTDC droop scheme -- main AC grid -- independent frequency regulation characteristic -- weak AC system -- frequency instability -- traditional droop‐based frequency control -- frequency coupling properties -- MTDC power flow equations -- integrated weak AC systems -- frequency stability -- decoupled frequency control scheme -- broader frequency disturbance propagations; Renewable energy sources -- Periodicals; 333.79405
• DOI: 10.1049/iet-rpg.2019.1503
• Languages: English
• ISSNs: 1752-1416

Abstract

Abstract : Traditional way to enable frequency support provided by MTDC system for the connected weak AC systems is to modify the power reference of each converter under standard power‐sharing droop control based on the weak grid's frequency deviations. However, this scheme artificially couples all asynchronous AC systems to tackle with the frequency disturbances of any connected AC systems, which might result in broader frequency disturbance propagations. To overcome this, this study proposes a decoupled frequency control (DFC) scheme to improve weak AC systems frequency stabilities. First, the relationship between the active power and power set points of each converter is derived by the linearization of MTDC power flow equations. Then, the frequency coupling properties of each AC system with traditional frequency control are derived, and it shows that the frequency disturbance will be propagated to all the connected AC systems with traditional control. Furthermore, the control law of each converter in the proposed DFC is developed through the defined decoupled matrix, and the independent frequency regulation characteristic of each converter can be obtained. Finally, numerical simulations have demonstrated the effectiveness of the proposed DFC scheme in events of load changes and converter loss in the main and weak AC grid.