Control strategy for 2-terminal high power LCL DC-DC converter

This paper proposes a control strategy for 2-terminal LCL DC-DC converter. Cascaded control consists of outer loop power control, with inner loop current control in order limit converter currents. Three coordinate frames are used in order to satisfy zero reactive current at each bridge and power balance. The control strategy enables the 2-terminal LCL DC-DC converter operating in the whole range of the designed power rating and current limitation during faults. Operating principles of the LCL DC-DC converter and procedures for design the control strategy are presented. Effectiveness of the control strategy during step power orders and DC faults is verified by simulation of a detailed PSCAD model for a 200kV/640kV, 500MW 2-terminal LCL DC-DC converter.