- - - Department of Electrical Engineering, Iran University of Science and Technology, Tehran, Iran
- - - Department of Electrical Engineering, Iran University of Science and Technology Tehran, Iran

Abstract—The starting-up strategy is an important issue for voltage source convert-high voltage direct current (VSC-HVDC) system. If a VSC-HVDC system starts up without any auxiliary system or improved control system, overvoltage and inrush current will occur. This large overvoltage can cause serious damage on the DC capacitors and this large inrush current at turn-on may destroy the switches in converter. Starting-up VSC-HVDC has two steps. In this paper, starting-up steps in a three-phase two-level VSC-HVDC system is studied with details. The effect of capacitor and inductor sizes and also circuit breaker closing time on overvoltage and inrush current in first step are investigated attentively. Possible methods for control overvoltage and inrush currents during this step are presented, and a comparison has been made between them in terms of power dissipation and cost. Eventually, the best auxiliary starting-up system is selected in terms of costs. In addition, the second step of starting-up is also examined and the circuit performance for increasing the DC link voltage is described in this step. Also, a simple control method is proposed for controlling the inrush current in second step. This method controls the inrush current without imposing additional costs and losses on the system. Substantial simulations conducted on PSCAD/EMTDC platform. It is worth mentioning this paper is an extended version of the paper accepted at the 34th Power System Conference (PSC 2019).

VSC-HVDC, Starting-up, Inrush Current, Diode bridge rectifier, PWM-Rctifier