Small signal modelling of HVDC transmission systems

An exact small signal linear model of the HVDC converter has been published, and this paper describes two applications of the model. The first application is the calculation of steady state harmonic levels in the presence of unbalanced AC systems. The method presented is general, and can be applied to asynchronous links of different operating frequencies, with different sources of waveform distortion. The second application is the calculation of the dynamics of HVDC systems, particularly within the frequency range from 2 to 200 Hz. All interactions relevant to the dynamics and control of HVdc systems are accurately represented in the s-domain. Both applications are in excellent agreement with time domain simulations using PSCAD/EMTDC.