Software developer LHP Inc. today said it plans to invest $1 million and add 320 workers by 2011 at its Columbus, Ind., headquarters. LHP, which employs 130 in Columbus, does work for the military, automotive and medical industries globally. LHP will begin hiring technology specialists, engineers and administrative workers next year. The company will receive up to $2.1 million in tax credits and another $50,000 in training grants from the state. The city of Columbus also will provide LHP with property-tax abatement.