A Technical Assessment of Artificial Commutation of HVDC Converters with Series Capacitors

Artificial commutation with series capacitors, to extend the operation of mercury tube or solid-state converters beyond the normally attainable control angles, is analyzed in detail, and performance assessed for application to HVDC transmission. Operating characteristics are presented, including details of tube voltage stress and attainable range of control for particular capacitor values and system quantities. The repercussions of arc-back and commutation failure are discussed, and control requirements outlined.