Impacts of electric vehicle charging on distribution networks in Denmark

2011-2012 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Self-generated magnetic flux in YBa2_2Cu3_3O7−x_{7-x} grain boundaries

Grain boundaries in YBa$_2$Cu$_3$O$_{7-x}$ superconducting films are considered as Josephson junctions with a critical current density $j_c(x)$ alternating along the junction. A self-generated magnetic flux is treated both analytically and numerically for an almost periodic distribution of $j_c(x)$. We obtained a magnetic flux-pattern similar to the one which was recently observed experimentally.Comment: 7 pages, 3 figure

Frequency markets and the problem of pre-dictability

Ancillary services markets (ASMs) are gaining higher importance in renewable-based power systems. They, however, remain less explored than the energy markets (EMs) of different regions. For limited energy units, such as battery energy storage systems (BESSs), it is vital to investigate the relative predictability of the two markets as suitable bidding hours of a less predictable product are more challenging to identify, thus entailing less certain revenues. This paper develops forecast models of the two markets of three Nordic countries – Denmark, Finland, and Norway – to quantify the difference in their predictability. Frequency containment normal reserves (FCR-N) are considered as a case of the Nordic ancillary service product. The dataset of 315648 datapoints contains three years (2019 – 2021) of their hourly FCR-N, and spot market revenues. Generalized additive models (GAMs) are used to develop week-ahead forecasts using smooth curves of hourly and daily patterns. The forecast allows both inter country – between same markets of different countries – and intra country – between different markets of the same country – comparison. The results show that the FCR-N markets of the Nordic countries are less predictable than their respective spot markets except for the case of Denmark due to its fixed hourly volumes. Moreover, the smoothing curves of FCR-N forecast models differ for each Nordic country despite their similar market requirements. This is in contrast to the Nordic spot markets where the smoothing curves indicate similarity in inter-country mar-ket behaviors. Considering market predictability differences in addition to their hourly prices is thus vital for BESS units performing multi-market bidding

Multi-timescale coordinated operation of a CHP plant-wind farm portfolio considering multiple uncertainties

This paper proposes a multi-timescale coordinated operation approach which coordinates the combined heat and power (CHP) plant and wind farm operation in a deregulated day-ahead heat market and a real-time balancing electricity market. This approach aims to optimize profits of the CHP-wind farm portfolio by considering energy sale in the day-ahead heat market and penalty in the real-time two-price balancing market. Multiple uncertainties of heat load, wind power generation, day-ahead electricity price, up- and down-regulation prices are taken into account for the optimal operation. A stochastic optimization method is applied to solve the proposed coordinated operation problem. The proposed multi-timescale coordinated operation approach is simulated on a real-life system in Copenhagen Denmark where an energy company owns both a CHP plant and a wind farm. The simulation results verify that the proposed method can achieve a profitable operation in the markets and a highly robust operation against the multiple uncertainties