Modeling and Simulation of Tri-Pole HVDC Transmission System

With the increase of the power demand and reduction of land resources, it is imperative to increase AC transmission line capacity. Tri-pole HVDC is proposed as a new technique to solve this problem. This paper presents the basic principle of tri-pole HVDC, including its schematic and current modulation strategy. Based on the platform of PSCAD/EMTDC a tri-pole simulation model is built to carry out the simulation on deblock startup and block shun down. Besides, a cooperation mode of the controller with the protection under emergency outage of single converter station or under fault occurred in DC transmission line is put forward, and simulation results show that the proposed control and protection strategies are effective.