Coal-fired power station operator Drax said that commodity market trading has improved in the year-to-date and the numbers remain on target for 2011."We have taken advantage of better dark green spreads to strengthen our contracted position. This, together with continued good operating performance, currently underpins expectations for the full year," the statement said.The group - which supplies 7% of the UK's electricity needs - sought to reassure investors after it warned in February that volatile commodity markets were putting pressures on coal generation margins.Drax also confirmed the release of £180m cash tax relief for the business - announced on 5 April - in relation to its Eurobond financing structure.---BC