1. A vapor compression refrigeration cycle system, comprising: a compressor having first and second refrigerant ports; an electronic expansion valve connected between said first and second refrigerant ports; and an expansion valve controller configured to control a flow of refrigerant through said expansion valve in response to a superheat temperature of said refrigerant, wherein said controller is configured to execute a startup control algorithm, after receiving a signal indicating that said compressor is running, that instructs said expansion valve to open thereby to increase a flow rate of said refrigerant as a function of said superheat temperature, said controller is configured to determine an occurrence of a local maximum of said superheat temperature when a first derivative of said superheat temperature changes from positive to negative and a current iteration time is greater than a predetermined startup time detected by said controller, said controller continues to execute a steady-state control algorithm, after said execution of said startup control algorithm, that controls said expansion valve such that said superheat temperature remains within predetermined control band limits.