Protected control strategies for voltage-source-converter (VSC) under grid faults in AC/DC hybrid grid

In AC/DC hybrid grid, the individual AC and DC grids exist. The power converters are the key interfaces between these two kinds of individual grids. Under unbalance AC grid, the grid voltage is distorted and the harmonics is involved. Therefore, the active power and reactive power also give rise to the uncontrolled oscillations, which will damage the interface converters. In order to ensure the safety of the converters and the facilities in the grids, the proper control strategy is crucial in AC/DC hybrid grids. In this paper an improved Flexible Positive- and Negative- Sequence Control method (FPNSC) used in d-q axis is proposed. From the simulating and experimental results, this new method shows its advantages compared to other classical methods such as Positive- and Negative-Sequence Control, Average Active-Reactive Control, and Balanced Positive-Sequence Control.