Variable Transmission Voltage for Loss Minimization in Long Offshore Wind Farm AC Export Cables

TL;DR

This paper demonstrates that dynamically adjusting the transmission voltage in long offshore wind farm cables significantly reduces power losses, with potential savings up to 21%, using existing technology and simple tap changer regulation.

Contribution

It introduces a method for loss reduction in offshore wind farm cables by variable voltage regulation, achievable without new technology development.

Findings

Up to 21% loss reduction with variable voltage control.

A 15% tap changer regulation achieves 9% loss reduction.

Further loss reduction possible with wider voltage regulation range.

Abstract

Connection of offshore wind farms to shore requires the use of submarine cables. In the case of long HVAC connections, the capacitive charging currents limit the transfer capability and lead to high losses. This paper shows that the losses can be substantially reduced by continuously adjusting the cable operating voltage according to the instantaneous wind farm power production.Calculations for a 320 MW windfarm connected to shore via a 200 km cable at 220 kV nominal voltage shows that an annual loss reduction of 9 percent is achievable by simply using a 15 percent tap changer voltage regulation on the two transformers. Allowing a larger voltage regulation range leads to further loss reduction (13 percent for 0.4-1.0 p.u. voltage range). If the windfarm has a low utilization factor, the loss reduction potential is demonstrated to be as high as 21 percent . The methodology can be applied without introducing new technology that needs to be developed or qualified.