Co-ordination of parallel multiterminal HVDC systems

This paper considers methods for co-ordinating the converters of parallel multiterminal HVDC systems. The principle is based on balancing the converter current orders and two different balancing methods are described. The first uses a centralized current reference balancer and therefore requires some means of communication. The second method is slower but it is decentralized. The decentralized current reference balancer may be used to back-up the first when communication links are not operational. These current reference balancers and a telecommunication delay simulator are described. The performances of both controls are evaluated on the IREQ dc simulation of a parallel multiterminal HVDC system with two rectifiers and two inverters.