Current Error Based Compensations for VSC Current Control in Weak Grids for Wind Farm Applications

A novel current control strategy is proposed for voltage source converters connected to weak grids using conventional current vector control with additional current error based voltage angle and magnitude compensations. For connecting to very weak ac network, the combination of vector control and grid synchronization with a conventional phase-locked loop is proved to be unstable, whereas the proposed current error based compensations can significantly improve system stability. In this way, the proposed control can still benefit from the presence of closed-loop current control without the need for control switching during large ac voltage variations. A comprehensive frequency domain model is established to analyze stability performance. Comprehensive time domain simulations are further carried out to validate its effectiveness and robustness by demonstrating its current control performance during a three-phase fault, multiple-converter situation, and various grid strength conditions.