The project is estimated to cost around EUR13.5 million.
Lukoil secured the construction license for the project at the end of 2013.
Lukoil officials said last year they were considering building solar power parks on land near the refinery in Ploiesti. At that time, they said they were aiming for an installed power of up to 12 MW.
Apart from the refinery in Ploiesti, Lukoil operates a network of 300 gas stations in Romania.
Solar power projects under construction in Romania currently add up to around 1,000 MW.