Comparison of Dynamic Behaviour between Average Model and Switch Function Based Model VSC-HVDC Converters

One of the qualities of a good high voltage direct current (HVDC) system is robustness. The system should produce the output with very minimum harmonics distortion, and it should be stable against both small and large disturbances. In this paper, to determine the better model configuration of voltage source converter (VSC) that has both minimum harmonic distortion at the output and strong resistance to disturbances, the average model (AVM) and Switch Function based model were compared using dynamic behaviour validation. For analysis purposes, two point-to-point VSC-HVDC systems connecting two asynchronous high voltage alternate current (HVAC) systems which include two VSC terminals and the dc-link were developed base on the selected models. And two-level-VSC topology was used for simplifying calculations. The Vector control technique was proposed to control active and reactive power flow on the rectifier (sending end) and to control the dc voltage and reactive power flow at the inverter (receiving end). Using MATLAB SIMULINK the systems were simulated and the result was obtained and discussed. The results were good and accurate for both models but the only difference is that the high-frequency harmonics generated by the switching pulse cannot be presented by AVM since it can only present the fundamental component of ac currents and voltages.