Laboratory demonstration of inertial response from VSC-HVDC connected wind farms

In this paper a communication-less method for obtaining inertial response from a VSC-HVDC connected wind farm is proposed and verified experimentally in a scaled laboratory model with ratings in the range of 20 kVA. A two-terminal HVDC grid, connecting a wind farm with variable speed wind turbines and a weak AC grid, is used to analyse the possibility of inertial support during load imbalances. The objective of the work is to enhance the frequency control in the weak grid by emulating an inertial response from the VSC-HVDC connected wind farm. This is done by implementing additional controls on the VSC converter terminals. The results show that the inertial response from the wind farm has a beneficial impact on the frequency response in the weak grid during the transient event following a power imbalance. The wind farm equivalent is able to modify the frequency low-point and the time at which it occurs. In the best case, the first frequency dip is reduced from 3.7 Hz to 2.5 Hz. The first dip is also shifted in time with approximately 1.3 seconds compared to base case.(19 refs)