Simulation Study for a Hybrid Multi-terminal HVDC System

Abstract

A digital simulation model for a hybrid three terminal HVDC system is developed. In the hybrid three terminal HVDC system, both a VSC and a CSC are used. Based on the developed HVDC system, a control scheme is proposed, in which a DC constant current control is used for the CSC type rectifier, a constant extinction angle control is used for the CSC type inverter, and a DC constant current control for the VSC type inverter. The performance of the HVDC system is studied by simulation under the following conditions: system startup, system normal operations, and system faults in the DC links as well as the AC systems. Simulation results show that the control scheme proposed is effective for the hybrid multi-terminal HVDC (MTDC) system. The simulation results also show that the DC breaker is indispensable to effectively control and protect the hybrid MTDC system