The VSC-HVDC control system adopts layer control
structure for reducing the damage caused by control system’s
faults. Considering the speed demands and the traditional
HVDC control structure [15], it is necessary to divide the
VSC-HVDC into five layers, namely, DC system control layer,
pole control layer, converters control layer, valves control
layer and separate control layer. The structure is shown as the
Fig.1