The control layer has the responsible for receiving the
instruction from DC system control layer and the operation
information from the converters control layer, and then judging
whether meet the requirement of the DC system control layer
and itself besides adjusting real-time the instruction which
send to the next layer. For pole control layer, it must consider
the master control station and the subordinate station,
dominant right exercises anytime only in main control station.
Choose the main/subordinate control between the rectifier and
inverter stations, the master control station completes the
control task of the VSC-HVDC system. The main control
include pole starting and off-streaming control, fault disposal
control, power transmission of HVDC control, DC open test
control, sequence control of the converters opening or closing.
It uses instruction forms to coordinate the operation of the
bipolar for bipolar system. It is be used to realize the control
for power balance between two poles, power transmission
direction, reactive power and AC bus voltage of the converters
station etc.