Generalized power flow models for VSC based multi-terminal HVDC systems

• Power flow algorithms for M-VSC HVDC systems.
• BTB and PTP VSC HVDC systems.
• IEEE 118.

This paper presents a generalized Newton Raphson (NR) power flow model for voltage source converter (VSC) based multi-terminal HVDC (M-VSC-HVDC) systems. This model is applicable to both the back to back (BTB) and the point to point (PTP) M-VSC-HVDC configurations. The amplitude modulation indices of the PWM scheme and the converter DC voltage(s) appear as unknowns in the generalized model, which is developed from first principles. While the master converter controls the voltage magnitude at its AC terminal bus and maintains the converters’ active power balance, the slave converters operate their terminal buses in the PV or PQ control modes. This model offers the flexibility of controlling either the DC voltage or the modulation index for the master converter. Numerous case studies carried out by applying different control strategies to various topologies of MTDC networks incorporated in the IEEE-118 bus test system validate the model.