A method for validating the operation of a compressor, the method comprising: receiving by a processor operating parameter data Z of the compressor from a plurality of sensors; making a determination whether the compressor is operating in (i) a transient speed state or (ii) a steady speed state; and adjusting, based on the determination, a portion of a variable flow area downstream of discharge of the compressor by adjusting one or more valves to achieve a desired compressor pressure ratio comprising: (i) dynamic control when the compressor is operating in the transient speed state or (ii) steady state control when the compressor is operating in the steady speed state, wherein dynamic control comprises: determining whether the compressor is operating in the transient speed state under (i) open loop control or (ii) closed loop control; and adjusting the one or more valves based at least in part on: (i) a compressor schedule correlated to the compressor shaft speed when the compressor is operating in the transient speed state under open loop control, wherein the open loop is regulated by a startup/shutdown algorithm, or (ii) a pressure ratio of the compressor calculated using pressure measurements when the compressor is operating in the transient speed state under closed loop control, thereby realising a closed loop control of the compressor pressure ratio, and wherein steady state control comprises: determining whether the compressor is not being manually controlled; and if the compressor is not being manually controlled, adjusting the one or more valves based at least in part on said calculated compressor pressure ratio, thereby also realising a closed loop control of the compressor pressure ratio. receiving by a processor operating parameter data Z of the compressor from a plurality of sensors; making a determination whether the compressor is operating in (i) a transient speed state or (ii) a steady speed state; and adjusting, based on the determination, a portion of a variable flow area downstream of discharge of the compressor by adjusting one or more valves to achieve a desired compressor pressure ratio comprising: (i) dynamic control when the compressor is operating in the transient speed state or (ii) steady state control when the compressor is operating in the steady speed state, wherein dynamic control comprises: determining whether the compressor is operating in the transient speed state under (i) open loop control or (ii) closed loop control; and adjusting the one or more valves based at least in part on: (i) a compressor schedule correlated to the compressor shaft speed when the compressor is operating in the transient speed state under open loop control, wherein the open loop is regulated by a startup/shutdown algorithm, or (ii) a pressure ratio of the compressor calculated using pressure measurements when the compressor is operating in the transient speed state under closed loop control, thereby realising a closed loop control of the compressor pressure ratio, determining whether the compressor is operating in the transient speed state under (i) open loop control or (ii) closed loop control; and adjusting the one or more valves based at least in part on: (i) a compressor schedule correlated to the compressor shaft speed when the compressor is operating in the transient speed state under open loop control, wherein the open loop is regulated by a startup/shutdown algorithm, or (ii) a pressure ratio of the compressor calculated using pressure measurements when the compressor is operating in the transient speed state under closed loop control, thereby realising a closed loop control of the compressor pressure ratio, and wherein steady state control comprises: determining whether the compressor is not being manually controlled; and if the compressor is not being manually controlled, adjusting the one or more valves based at least in part on said calculated compressor pressure ratio, thereby also realising a closed loop control of the compressor pressure ratio.