Modeling and control design of hybrid - LCC and VSC based - HVDC systems

This paper reveals an approach for dynamic modeling and control design of hybrid High-Voltage Direct Current (HVDC) systems. In this case a hybrid system is supposed to be a connection of different converter topologies as Line Commutated (LCC) and Voltage Source Converters (VSC). Modeling will be based on the mathematical correlations of the respective topologies and therefore a model for each converter type is carried out. These models can be merged regarding the fact of balanced energy terms. A control strategy for the hybrid HVDC system is presented, where the LCC Converter controls the voltage of the DC link and the VSC Converter is in P/Q control mode and hence is responsible for DC current regulation. 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 and a comprehensive large signal model of a hybrid HVDC system which can be used for power system stability studies is revealed.