An s-domain model of an HVdc converter

This paper describes a technique to model an HVdc 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 converter operating points is obtained via time domain simulation and step response techniques for an inverter voltage perturbation.