*4.1.4.6 Startup of DRU*

After starting the two 150-kV submarine cables, the DRU is switched on at 18.5 s. **Figure 16** shows the current and the voltage of on the DRU. Both the voltage and current are in the nominal range. Since the AC filters on the DRU are deactivated, the

**Figure 15.** *Voltage of the OWF transformer.*

*Offshore Wind Farm Grid Connection with Diode Rectifier Unit HVDC and Phase Shifting… DOI: http://dx.doi.org/10.5772/intechopen.103111*

**Figure 16.** *Current and voltage on the DRU.*

**Figure 17.** *FFT analysis of the DRU current.*

DRU current contains 5th, 7th, 11th, and 13th harmonics as the fast fourier transformation (FFT) analysis shown in **Figure 17**.

After starting DRU, the whole OWF and DRU-HVDC link are in normal operation.
