SAMPLING-DATA APPROACH FOR HVDC DYNAMIC MODELING

Conventional quasi-steady model of HVDC is not able to describe the dynamic switching behavior of HVDC converters. By means of the sampling-data modeling approach, a linear time-invariant (LTI) small-signal dynamic model is developed for HVDC main circuit in the synchronous rotating d-q reference frame: taking one sample per 1/6 cycle of fundamental frequency, deriving the function between the sampled points by integrating, and linearizing the function, then the small-signal model can be obtained. In contrast to conventionally used quasi-steady model, the developed model represents the dynamic response of converter switching circuit to nominal changes in operating point. The linearized model is validated by a set of time-domain simulation and the derived suitable frequency range is 0-3 times fundamental frequency. The model is applied in SSO analysis and the results are compared with those that utilize quasi-steady model. It is proved that the quasi-steady model of HVDC is valid for normal SSO analysis.