Study on fault ride-through control of islanded wind farm connected to VSC-HVDC grid based on the VSC converter AC-side bus forced short circuit

• Main Authors: Yan Li, Chao Liu, Xinshou Tian, Zhibing Wang
• Format: Article
• Language: English
• Published: Wiley 2019-02-01
• Series: The Journal of Engineering
• Subjects: power grids; wind power plants; power generation faults; HVDC power convertors; offshore installations; power generation control; HVDC power transmission; voltage-source convertors; VSC; short-circuit resistance; protection equipment; grid fault conditions; fault responding feature; fault ride-through; VSC-HVDC system; voltage source converter-based high-voltage direct current system; HVDC fault; VSC station; wind farm collection network; wind farm side converter; VSC converter; AC-side bus; forced short circuit; islanded wind farms
• Online Access: https://digital-library.theiet.org/content/journals/10.1049/joe.2018.8421

Wind farms integrated to an AC power system through a voltage source converter-based high-voltage direct current system (VSC-HVDC) are viewed as islanded wind farms. The wind farm side converter of VSC-HVDC maintains a constant frequency of the wind farm collection network and also controls its voltage. However, the transient responding time of VSC-HVDC is very short, and its fault responding feature is at the millisecond (ms) level. As a result, under grid fault conditions, the VSC station could be overloaded and even operation could be quitted because of blocking if islanded wind farms fail to limit their power generation in time. This study proposes a fault ride through control method for VSC-HVDC connected with islanded wind farms based on the forced short circuit of the AC-side bus of the VSC station. When there is a fault in the VSC-HVDC and the protection equipment is not able to cut off the excessive power at the ms level, the short-circuit resistance installed on the AC side of the VSC station would be switched to make a forced short circuit. That would activate the low-voltage ride through mode of islanded wind farms, and therefore reduce the power flowing into the VSC quickly. The HVDC fault and short circuit on the AC side would be cleared at the same time. The VSC-HVDC system accomplishes fault ride through.