Research of Decentralized Voltage Strategies and Farm-Level Fault-Tolerant Control for Wind Farms

Abstract

In recent years, the penetration of new energy generation represented by wind power in the grid has been increasing due to cleanliness and economy. However, the voltage control of wind farms has ushered in new technical challenges due to the expanding system scale and the mutual coupling characteristics between wind turbines. In this paper, the basic principles of wind farm voltage control are analyzed in detail and the mainstream control methods are introduced. Then, for the advantages of decentralized control methods in reducing communication costs and improving operational reliability, this paper presents in detail a decentralized voltage control method for wind farms based on variable coefficient gradient projection considering the dynamic model of wind turbines. As an example of this method, the paper analyzes the detrimental effects of off-grid events on the decentralized control method. Simulation results confirm the advantages of the decentralized approach in normal operation and its maladaptive nature in fault conditions. To solve this problem, a preliminary design of a fault-tolerant control method for wind farms under random off-grid events is presented based on a gradient correction approach. In which the aggregated form of the expression for the gradient deviation caused by the off-grid event is derived and integrated into the reactive power iterative optimization equation. Finally, we also propose some possible solutions to improve the fault-tolerance control performance in a decentralized manner.