A novel control method for restraining starting-up overcurrent in VSC-HVDC System

Abstract

Overcurrent and overvoltage can damage converter valves, DC capacitors and transformers in the VSC-HVDC systems. Therefore, a proper starting-up mechanism is needed to avoid overcurrent and overvoltage. Overcurrent occurs in the second stage of the starting-up procedure due to rapid response of controllers, high dVDC/dt and malfunction of PLL. Traditional methods reduce overcurrent, but they cause an increase in starting-up time duration. In this paper, a new control method is proposed to apply in the second stage of the starting-up procedure. Not only does the proposed method restrain overcurrent and overvoltage, but it also reduces time duration of starting-up. In addition, the proposed method reduces dVDC/dt and can limit the starting-up current to any desired value. Furthermore, the proposed method has a simple control system and does not need any extra elements, leading to a simple manufacturing. The operation and design principles of the proposed method are investigated in detail. Finally, the proposed control method is verified by simulation and experimental results of a bipolar two-level VSC-HVDC. © 2022 Elsevier B.V.