Boost-type PWM HVDC transmission system

By combining pulse width modulation (PWM) techniques with the boost type bridge topology, an alternate system of HVDC transmission is developed. Each boost type PWM HVDC converter is presented as a black box. It is shown how the black boxes can tie several independent AC utility systems, together through a multiterminal DC grid which facilitates power exchanges. On the AC side, the converter station has active controls over: (1) the voltage amplitude, (2) the voltage angle, and (3) the frequency. On the DC side, parallel connections facilitate multiterminal load sharing by simple local controls so that redundant communication channels are not required. Bidirectional power through each station is accomplished by the reversal of the direction of DC current flow. These claims have been substantiated by experimental results from laboratory size multiterminal models