Analysis and suppression of DC oscillation caused by DC capacitors in VSC‐based offshore island power supply system.

Voltage source converter‐high‐voltage direct current (VSC‐HVDC) is an effective way to ensure the reliable supply of offshore island power. However, it is easily liable to direct current (DC) oscillation or even instability due to the interaction between the rectifier and inverter stations. In order to solve this problem, this paper analyzes the stability of the VSC‐HVDC system caused by DC capacitors based on VSC impedance modeling and impedance stability criterion. Besides, an adaptive virtual impedance control strategy to suppress the DC oscillation is proposed. The impedance models of the VSC in the rectifier and inverter stations are constructed and verified. Then, the influence of the DC capacitors on the system stability is analyzed based on impedance stability criteria. The analysis shows that the decrease of DC capacitors will cause DC oscillation, and the DC virtual impedance is used to damping the oscillation. Finally, this paper presents a simple but effective adaptive fuzzy segmented virtual impedance control strategy to suppress the oscillation. Electromagnetic transient simulation and hardware‐in‐the‐loop (HIL) test results show that the proposed adaptive virtual impedance is more effective and has better robustness than the conventional virtual impedance. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]