Modelling and Control of Multiterminal LCC HVDC

Recent advances in the development and availability of multiple manufacturer for power electronics industries have made multiterminal-High Voltage Direct Current (HVDC) links possible and feasible. The multiterminal HVDC (MTDC) configuration is commonly referred to as `HVDC Grids'. The power flow into, or out of, each converter can be dynamically changed without any reconfiguration of the HVDC grid. This configuration can pose a threat on the stability of the system if channeled ineffectively. Another factor that also determines the stability margin of conventional thyristor HVDC converter is the Effective Short Circuit Ratio (ESCR) of the AC grid. This paper investigates the fault current contribution of each converter of three terminal system in respect to the interconnected AC grid. Line Commutated Converter technology was used to model a three terminal HVDC network on PSCAD. The dynamic modelling and fault contribution on MTDC network with consideration to AC grid strength was also considered. The results show that disturbances on the AC side of inverter would cause the system to experience large transient overcurrent and non-severe commutation failures.