BOOST TYPE PWM HVDC TRANSMISSION-SYSTEM

Conventional HVdc is built around the mercury arc rectifier or the thyristor which requires line commutation. The advances of fast, high power GTO's and future devices such as MCT's with "turn off" capabilities, are bringing PWM techniques within the range of HVdc applications. By combining PWM techniques to the boost type bridge topology, one has an alternate system of HVdc Transmission. 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 multi-terminal 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 multi-terminal models.