Analytical modelling of hvdc transmission system converter using matlab/simulink

Deeper insight into the functioning of complex HVDC transmission system converter can be obtained by analytical modelling. Further easy to comprehend analytical model in universally available software like Matlab/Simulink can help in fast spread of complex HVDC system knowledge also to those who are responsible for operation and maintenance of these systems thus bringing large benefits. With this in view, a simple analytical model using Matlab/Simulink has been developed in this work to investigate the steady state operation of the 6 pulse single bridge HVDC transmission system converter. The model is based on dividing each cycle of the 60 Hz system into twelve intervals out of which six intervals are commutation intervals with three valves conducting. The system performance for each of the 12 interval has been captured using differential equations applicable for particular interval. These equations have then been converted into integral form followed by Laplace representation to develop the 6 pulse HVDC model in Matlab/Simulink. Steady state operation of the system has been investigated by observing the DC circuit current, commutation process, current and voltage in transformer windings, and source current in time domain. Further the performance of tuned filters for 5
^th
, 7
^th
, 11
^th
and, 13
^th
harmonics and high-pass filters has been observed in time domain. Determination of commutation overlap angle by iterative process using the model has been demonstrated. This contribution can be very useful particularly for the operation and maintenance personnel who can perform better with greater insight into the functioning of the complex system obtained through the model as developed