(Adds quotes in paragraphs 5-6; clarifies in last paragraph that performance is of Citadel's flagship fund)

TOKYO, June 28 (Reuters) - Citadel will buy Japanese power firm Energy Grid in its first acquisition in Japan and the first major U.S. investment in Japan's wholesale energy market in recent years, billionaire investor Kenneth Griffin's hedge fund said in a statement.

The privately held Energy Grid provides power price risk management services to Japanese companies and the deal will give Citadel direct access to the Japanese power market.

Since Energy Grid's establishment in 2021, the power market in resource-poor Japan has been volatile due to Russia's invasion of Ukraine, which precipitated a global energy crisis.

Japan, which imports most of its energy resources, was already in a precarious position following the March 2011 earthquake and Fukushima nuclear disaster, when many of its major nuclear power stations were shut down.

The deal will "broaden the delivery of hedging solutions to Japanese energy producers and consumers", Sebastian Barrack, head of commodities at Citadel, said.

Energy Grid will expand trading volumes and "offer longer-term risk management opportunities to more market participants", said Yohei Jozaki, chief executive officer of Energy Grid.

The transaction is expected to close in the third quarter of 2024, subject to conditions. The deal size has not been disclosed.

Miami, Florida-based Citadel manages approximately $63 billion in assets and its flagship fund has gained more than 7.5% so far in 2024, according to a person familiar with the matter. (Reporting by Anton Bridge in Tokyo; Editing by Matthew Lewis and Muralikumar Anantharaman)