Communication-Less Frequency Support from Offshore Wind Farms Connected
to HVdc via Diode Rectifiers
Abstract
Before diode rectifier (DR) technology for connecting offshore wind
farms (OWFs) to HVdc is deployed, in-depth studies are needed to assess
the actual capabilities of DR-connected OWFs to contribute to the secure
operation of the networks linked to them. This study assesses the
capability of such an OWF to provide communication-less frequency
support (CLFS) to an onshore ac network. It is shown that the HVdc
link’s offshore terminal direct voltage can be estimated from
measurements at the OWF’s point of connection with the DR platform. Two
different methods are proposed for implementing CLFS in the OWF active
power controls. In Method 1, the estimated offshore terminal direct
voltage is used for estimating the onshore frequency deviation. In
Method 2, the actual offshore terminal direct voltage measurement is
used instead. Unique features of the provision of CLFS from OWFs
connected to HVdc via DRs are highlighted, and the dynamic and static
performance of the CLFS control scheme is compared to that of the
communication-based frequency support scheme. To assess the impact of
parameter estimation errors on the provision of CLFS, a parametric
sensitivity study is presented as well, and recommendations are given to
increase accuracy.
The manuscript has been accepted for
publication in IEEE Transactions on Sustainable Energy.