Multiterminal voltage-sourced converter-based HVDC models for power flow analysis

Two mathematical models for multiterminal voltage-sourced converter (VSC)-based HVDC are proposed in this paper. The first model assumes that all the converters are co-located in the same substation while the second model is a general one, in which DC network can be explicitly represented. For both models proposed, primary converters basically have the ability to independently control either active and reactive power or active power and voltage of the terminals while the secondary converter of the multiterminal VSC HVDC can be used to control terminal bus voltage and balance power exchange among the VSC converters. In addition, theoretic and numerical comparisons between the multiterminal VSC HVDC and the VSC FACTS controller-the Generalized Unified Power Flow Controller are also presented. Numerical examples are given on the IEEE 30-bus system, IEEE 118-bus system and IEEE 300-bus system.