1. A method for optimizing operation of a refrigeration system having an evaporator, comprising: defining an inner control loop for optimizing a supply of liquid refrigerant to the evaporator; and defining an outer control loop for optimizing a level of refrigerant in the evaporator, said outer control loop defining a supply rate for said inner control loop based on an optimization including measurement of evaporator performance, said inner control loop optimizing liquid refrigerant supply based on said defined supply rate.