Duluth-based Allete Clean Energy has purchased a wind farm in Oklahoma with plans to build, own and operate a 303-megawatt facility, its largest so far.

In a news release Friday, Allete Clean Energy said it bought 100 percent interest in Diamond Spring from Apex Clean Energy, the project’s developer. A purchase price was not disclosed.

The sale included 15-year power sale agreements to “two large Fortune 500 companies” that Apex had negotiated, but the companies were not named. In a separate release, Apex said the two companies would be announced at a later date.

The Diamond Spring wind project in Johnston and Pontotoc Counties in Oklahoma would bring Allete Clean Energy’s overall wind production to 1,000 megawatts.

Allete Clean Energy, founded by Duluth-based Allete in 2011, has grown rapidly and can currently provide 540 megawatts of wind generation to its customers. The company expects that to jump to 720 megawatts when its next two wind farms are operational later this year and to over 1000 megawatts when Diamond Spring is online.

Construction at Diamond Spring is set to begin this year with wind energy production expected in 2020, Allete said.