Electromagnetic Model Automatic Initialization Method for HVDC Transmission System

Along with the development of UHV technology, an extra-large-scaled AC / DC hybrid power grid has been accomplished in China, the characteristics of the power system is facing profound changes, the techs of simulations are needed to be improved as well to meet the new requirements. The electromagnetic transient simulation is often used to model DC system to obtain more accurate dynamic characteristics. However, the operation status adjustment and initialization process of the EMT model of DC systems seriously affect the efficiency in simulation of AC/DC power grids. In this paper, a method of auto-initializing the electromagnetic model of DC transmission is proposed. Using the AC/DC large-scale network power flow as the boundary condition, the internal power flow solution of the DC electromagnetic model is quickly calculated, and the initial on-valves, the position of converter transformer's tap, the AC filters' switching scheme, and the control instructions are accurately determined. This solution enables the automatic initialization of the UHVDC electromagnetic model so that it can reach a predetermined steady state during the 0.5 s simulation. The method proposed in this paper realizes the fast and smooth start-up of the electromechanical-electromagnetic transient hybrid simulation with a large number of electromagnetic UHVDC models, and solves the application problems of the electromechanical-electromagnetic transient hybrid simulation in operation mode calculation and online simulation of power grid.