Deepening Research on State Space Analytical Model of HVDC Transmission System

The state-space analytical model can reflect the high voltage direct current (HVDC) transmission system's transient characteristics quickly and accurately. In order to overcome the problems of the traditional state-space model. For example, the inaccuracy of the DC current when the sudden change of current in the snubber circuit. Therefore a state-space analytical algorithm considering the thyristor snubber circuit is proposed. In this paper, the snubber current is added as the state variable to the state equation of the converter. And the coefficient matrix is used to represent the initial value of the state variable under different working conditions. Besides, the implicit trapezoid method is used for calculation, which effectively improves the calculation accuracy of the differential equation of the primary equipment. According to the data exchange between the control system and primary equipment, a complete HVDC analytical model consists of the converter, DC line, and control system is established using the state-space theory and solved by the backward Euler method. Furthermore, the simulation results in PSCAD/EMTDC proved the accuracy and validity of the proposed model.