Method, system and apparatus relating to reheat combustion turbine engines with exhaust gas recirculation

A method of controlling a power plant (9) that includes a working fluid and a recirculation loop (10), wherein the power plant (9) includes a combustion system having an upstream combustor (22) operably connected to a high-pressure turbine (30) and a downstream combustor (24) operably connected to a low-pressure turbine (32). The method may include the steps of: recirculating the working fluid through the recirculation loop (10); controlling a compressed oxidant amount supplied to each of the upstream combustor (22) and the downstream combustor (24); controlling a fuel amount supplied to each of the upstream combustor (22) and the downstream combustor (24); controlling the power plant (9) such that each of the upstream combustor (22) and the downstream combustor (24) periodically operates at a preferred stoichiometric ratio; and selectively extracting the working fluid from a first extraction point (75) associated with the upstream combustor (22) and a second extraction point (76) associated with the downstream combustor (24) based upon which of the upstream and the downstream combustors (22,24) operates at the preferred stoichiometric ratio.