Commissioning of the second unit will be completed later this month, making the plant capable of generating up to 860MW.
Full commercial operation of all four units of the power station is expected by the end of this year.
RWE npower chief technical officer Kevin McCullough said that this new power station will play an important part in achieving the diverse mix of energy generation needed to reduce CO2 while maintaining affordable and secure supplies.
The company said it is undertaking a large scale building program of new generation infrastructure and is planning new-build investments over the next ten years to help UK meet the anticipated 15GW-25GW of new generating capacity by 2020.
RWE npower is an integrated energy business, generating electricity and supplying gas, electricity and related services to customers across the UK.
