Unfortunately, there is limited availability in larger 208 string inverters. Fronius has a 15kw that does 1kv strings. Chint has a 14Kw but it only does 600v strings. Solectria also has a 208V 14Kw but it also only does 600V strings. In fact, the fronius is the only three phase 208 inverter I could find doing a quick and dirty search that does 1kv strings. It seems many that are faced with this dilemma are using transformers. Other options to weigh are using more of the smaller 208 inverters, bring in a 480 service, or possibly investigate central inverter options.
Edit: Just wanted to add, that I worked on system where they had 480 inverters and a 208 service and used transformers. It was horrible. So much time, hassle and money to for all the extra equipment and connections. I would strongly lean toward getting the correct voltage inverters, even if they are smaller than you might otherwise want.
