A new control method for multiterminal DC transmission

A new control scheme for parallel multiterminal dc systems is proposed. The scheme is divided into two separate functions: (1) a supervisory control called the System Monitor-State Predictor (SMSP), which determines the steady state operating point of the system from ac voltage measurements, power requirements at the converters, and the dc network configuration; and (2) the feedback controllers which drive the system to the desired operating point supplied by the SMSP. A systematic method is presented for calculating local feedback gains based on optimal control theory, and it is shown that use of feedback measurements is possible with negligible loss of dynamic performance. A detailed hybrid computer simulation of a four-terminal dc system was used to demonstrate the excellent performance of the new control scheme during steady state operation and for large system disturbances.