Shares of NRG Energy Inc. NRG rose 1.5% toward a 6-week high in premarket trading Thursday, after the home-services energy company authorized an additional $650 million in stock repurchases. The new authorization will follow the closing of the deal to sell 44% of its interest in South Texas Project Electric Generating Station (STP) to Constellation Energy Corp. CEG for $1.75 billion, which is expected to occur by the end of 2023. With $350 million remaining in NRG’s existing share buyback program, the total repurchase authorization will increase to $1 billion, which represents 12.9% of the company’s market capitalization…