An Approach to Electromagnetic Transient Modeling of Main Circuits of Line-Commutated HVDC Transmissions in Power System Stability Studies

To enhance representation of line-commutated HVDC transmissions in power system stability studies, this paper proposes an approach to the development of electromagnetic transient models of main circuits suitable for multirate simulations with positive-sequence root-mean-square dynamic programs. The paper describes the essential principles of model development. Discussed are differential equations of main circuit component models and model initialization. In converter models, the thyristor valve is represented by a variable resistor in parallel with a resistor-capacitor branch, which makes these models applicable for any combination of conducting and non-conducting valves. The full main circuit model is built from relevant components models. In summary, the proposed approach to model development ensures a modular structure and relatively small size of main circuit models, lacks algebraic systems to be solved at each internal time step by iteration and allows the use of the sufficiently accurate $4^{\text {th }}$ order Runge-Kutta method.