3‐Level cascaded voltage source converters controller with dispatcher droop feedback for direct current transmission grids. Issue 6 (1st April 2015)

• Record Type: Journal Article
• Authors: Jamshidifar, Ali Akbar; Jovcic, Dragan
• Is Part Of: IET generation, transmission & distribution. Volume 9:Issue 6(2015)
• Page Start: 571
• Page End: 579
• Publication Date: 2015-04-01
• Subjects: DC‐DC power convertors -- power grids -- PI control -- power system stability -- load flow -- feedback -- electric current control -- voltage control -- HVDC power transmission; 3‐level cascaded voltage source converter controller -- dispatcher droop feedback -- direct current transmission grids -- DC grids -- control functions -- VSC converters -- 3‐level cascaded control topology -- DC‐DC converters -- fast proportional integral feedback control -- local DC voltage control -- grid stability -- voltage droop power reference adjustment -- central dispatcher -- optimal power flow -- PSCAD‐EMTDC model -- CIGRE B4 DC grid test system -- steady‐state variables -- transient responses -- droop control method -- local current control -- converter overload -- control function; Electric power production -- Periodicals; Electric power transmission -- Periodicals; Electric power distribution -- Periodicals; 621.3105
• DOI: 10.1049/iet-gtd.2014.0348
• Languages: English
• ISSNs: 1751-8687

Abstract

Abstract : The future direct current (DC) grids will require additional control functions on voltage source converters (VSC) in order to ensure stability and integrity of DC grids under wide range of disturbances. This study proposes a 3‐level cascaded control topology for all the VSC and DC/DC converters in DC grids. The inner control level regulates local current which prevents converter overload. The middle control level uses fast proportional integral feedback control of local DC voltage on each terminal which is essential for the grid stability. The hard limits (suggested ±5%) on voltage reference will ensure that DC voltage at all terminals is kept within narrow band under all contingencies. At the highest level, each station follows power reference which is received from the dispatcher. It is proposed to locate voltage droop power reference adjustment at a central dispatcher, to maintain average DC voltage in the grid and to ensure optimal power flow in the grid. This slow control function has minimal impact on stability. Performance of the proposed control is tested on PSCAD/EMTDC model of the CIGRE B4 DC grid test system. A number of severe outages are simulated and both steady‐state variables and transient responses are observed and compared against conventional droop control method. The comparison verifies superior performance of the proposed control topology.