An s-domain model of an HVDC converter

This paper describes a technique to model an HVDC power converter installation in the s-domain. A system equivalent is developed, utilising a frequency-domain model, allowing the closed loop frequency response to be expressed. A rational function approximation of the closed loop frequency response is found by writing an overdetermined equation set, solved directly using singular value decomposition. System poles and zeros in the s-domain are extracted through the solution of the rational function roots. Validation of the model at two power converter operating points is obtained via time-domain simulation and step response techniques for an inverter voltage perturbation