Patent ID: 9746228
Date: 2017-08-29
CPC Classifications: F04B,F04D,F25B,Y02B

Claim:
1. A method for controlling a chiller system that includes a centrifugal compressor with a variable speed drive, a chiller control unit and one or more inlet guide vanes, the method comprising: the chiller control unit receiving first measurement data and second measurement data, wherein the second measurement data includes a condenser entering water temperature data and a condenser refrigerant pressure data; a capacity control component of the chiller control unit determining a desired chiller capacity based on the first measurement data, wherein the desired chiller capacity is indicative of a load demanded on the chiller system; and a multi-actuator control component of the chiller control unit determining a centrifugal compressor speed and an inlet guide vane position based on the second measurement data; determining a normalized chiller capacity based on the desired chiller capacity; determining a normalized centrifugal compressor speed based on the centrifugal compressor speed; determining a pressure coefficient that represents a static pressure and a kinetic energy of the centrifugal compressor; determining an inflection point based on the normalized chiller capacity, the normalized centrifugal compressor speed, and the pressure coefficient; determining an adjusted centrifugal compressor speed and an adjusted inlet guide vane position based on the normalized chiller capacity, the normalized centrifugal compressor speed and the pressure coefficient; wherein the chiller control unit generates a compressor speed command and an inlet guide vane command based on the adjusted centrifugal compressor speed and the adjusted inlet guide vane position; and sends the compressor speed command to the variable speed drive of the centrifugal compressor and the inlet guide vane command to the centrifugal compressor to control the one or more inlet guide vanes; and wherein determining the adjusted centrifugal compressor speed and the adjusted inlet guide vane position includes: determining whether the desired chiller capacity is greater than the inflection point; adjusting the centrifugal compressor speed to achieve the desired chiller capacity and setting the inlet guide vane position to a fully open inlet guide vane position when the desired chiller capacity is greater than the inflection point; and adjusting both the inlet guide vane position and the centrifugal compressor speed to obtain the desired chiller capacity when the desired chiller capacity is not greater than the inflection point.