Search

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.

The uncertainty arising from high levels of solar photovoltaic (PV) penetration can have a substantial impact on power system operation. Therefore, there is a need to develop models capable of representing PV generation in a rigorous manner. This paper introduces a novel transformation-based methodology to generate stochastic solar area power forecast scenarios; easy to apply to new locations. We present a simulation study comparing day-ahead solar forecast errors covering regions with different geographical sizes, total installed capacities, and climatic characteristics. The results show that our model can capture the spatio-temporal properties and match the long-term statistical properties of actual data. Hence, it can be used to characterize the PV input uncertainty in power system studies.

Diode rectifiers (DRs) have been recently suggested as a viable alternative for connecting offshore wind farms (OWFs) to HVdc, eliciting growing interest from both industry and academia. However, energisation of DR-connected OWFs is not straightforward. The present study constitutes a proof of concept of a novel energisation method for DR-connected OWFs, in which auxiliary power is provided from the shore through the HVdc link and the dc bus bar of one or more WTs. The proposed method provides an alternative with minimal additional hardware, which can be easily extended to more WTs in the OWF, increasing reliability by providing redundancy. The study includes coinciding auxiliary loads with active and reactive power components and a semi-aggregated OWF model, in which every WT is individually represented in the string containing the energising WT. Two additional sequences of simulation events are considered following the initial energisation sequence. Such sequences comprise wind power taking over the provision of the auxiliary power and the run-up to maximum (available) power production. The simulation results indicate that the proposed method is a suitable alternative for energising OWFs connected to HVdc via DRs.The manuscript has been submitted to IEEE Transactions on Power Delivery.

Recently put forward as a feasible alternative for connecting OWFs to HVdc networks, diode rectifiers (DRs) have elicited growing interest from both academia and industry. Energisation of such OWFs is, however, not straightforward. The present study constitutes a proof of concept for the application of a novel energisation method to the case of an OWF connected to HVdc via DRs. The proposed method provides a robust and reliable alternative with minimal additional hardware, i.e. short additional dc cables connecting the dc bus bar of the energising WT to the HVdc link, and corresponding dc disconnectors at the cable terminals and at the DR dc terminals. This can be easily extended to more WTs in the OWF, increasing reliability by providing redundancy. The simulation results indicate that the proposed method is a suitable alternative for energising OWFs connected to HVdc via DRs.The manuscript has been accepted for presentation in the 45th Annual Conference of the IEEE Industrial Electronics Society (IECON 2019).

This work presents two large-scale regional models used for the evaluation of normalized power output from wind turbines and photovoltaic power plants on a European regional scale. The models give an estimate of renewable production on a regional scale with 1 h resolution, starting from a mesoscale mete- orological data input and taking in account the characteristics of different plants technologies and spatial distribution. An evalu- ation of the hourly forecasted energy production on a regional scale would be very valuable for the transmission system operators when making the long-term planning of the transmission system, especially regarding the cross-border power flows. The tuning of these regional models is done using historical meteorological data acquired on a per-country basis and using publicly available data of installed capacity.

This paper deals with power fluctuations from wind farms. The time range in focus is between one minute and up to a couple of hours. In this time range, substantial power fluctuations have been observed during unstable weather conditions. A wind power fluctuation model is described, and measured time series from the first large offshore wind farm, Horns Rev in Denmark, are compared to simulated time series. The comparison between measured and simulated time series focuses on the ramping characteristics of the wind farm at different power levels and on the need for system generation reserves due to the fluctuations. The comparison shows a reasonable agreement between simulations and measurements, although there is still room for improvement of the simulation model.