Generic Modeling of a Self-Commutated Multilevel VSC HVDC System for Power System Stability Studies

This paper provides a generic stability model of a self-commutated multilevel VSC (Voltage Source Converter) HVDC (High Voltage Direct Current) and its appropriate control. At first the approach of modeling depicts the independence of the AC and DC quantities and therefore two separate models - one for the AC and one for the DC side - can be figured out. The AC side model is developed in the dq frame out of the according differential equations. For the DC side no further transformation is required. Regarding the fact of balanced energy terms the two models can be merged. The consolidation of both models reveals a comprehensive large signal model of a multilevel based HVDC system which can be used for detailed analyses in power system stability studies. Due to the comparison of the generic stability model with an EMT (Electro-Magnetic Transient) HVDC model the consistence of the dynamic behavior is shown.