Master‐slave control strategy of the cascaded multi‐terminal ultra‐high voltage direct current transmission system

Abstract

AbstractIn the case of dispersed load consumption, Ultra‐high Voltage Direct Current (UHVDC) system in cascaded connection mode can significantly reduce the cost by building DC lines between different ends, but the communication delay caused by it brings challenges to the original control strategy. Therefore, the control strategy suitable for cascaded multi‐terminal UHVDC (CMT‐UHVDC) system is developed. In this paper, first of all, the operation characteristics, mathematical model, and adaptability of the original control strategy are discussed. Next, an autonomous master‐slave control strategy is proposed to maintain voltage balance without real‐time communication between high‐end and low‐end valves. Finally, based on the planning parameters of an actual project, the electromagnetic transient simulation model of the CMT‐UHVDC transmission system is established. Several working conditions and the practical influence of sampling deviation on the control performance are discussed and analyzed, which verifies the proposed control strategy's effectiveness.