This disclosure relates to a control system and method for the centrifugal compressor. The system, for example, includes a controller configured command an adjustment of at least one of (1) a flow regulator and (2) a speed of a shaft in order to provide safe, efficient compressor operation. Centrifugal compressors are used to circulate refrigerant in a chiller via a refrigerant loop. Centrifugal compressors operate efficiently before reaching a condition known as surge.