Methods and systems for detecting and recovering from control instability caused by impeller stall
AssigneeTrane International Inc.
InventorsThomas J. Clanin, Lee L. Sibik
Life of this patent
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Abstract
Methods and systems for detecting and recovering from control instability caused by impeller stall in a chiller system are provided. In one embodiment, an impeller stall detection and recovery component of a chiller control unit calculates a control error signal frequency spectrum for an evaporator leaving water temperature, determines whether a high frequency signal content of the control error signal frequency spectrum exceeds acceptable limits, and adjusts a surge boundary control curve downward by a predetermined incremental value in order to resolve instability caused by impeller stall.
Claims14
A method for detecting and recovering from control instability caused by impeller stall in a chiller system that includes a centrifugal compressor, a chiller control unit and one or more inlet guide vanes, the method comprising:
- calculating a chiller control error signal based on a chilled water set point temperature signal, an evaporator leaving water temperature signal, a design delta temperature signal that is indicative of a design delta temperature across an evaporator of the chiller system and a lift compensation signal, wherein calculating the chiller control error signal includes using a leaving water temperature control algorithm;
- determining a frequency spectrum of the chiller control error signal to obtain a controller error signal frequency spectrum signal, wherein the frequency spectrum of the chiller control error signal is determined using a fast Fourier transform algorithm;
- detecting, via the chiller control unit, whether an impeller stall event has occurred based on the controller error signal frequency spectrum signal;
- restoring stable operation of the centrifugal compressor when an impeller stall event is detected.
A chiller system comprising:
- a centrifugal compressor;
- one or more inlet guide vanes;
- and
- a chiller control unit that includes an impeller stall detection and recovery component, the impeller stall detection and recovery component includes:
- a control error signal module configured to calculate a chiller control error signal based on a chilled water set point temperature signal, an evaporator leaving water temperature signal, a design delta temperature signal and a lift compensation signal,
- a control error signal frequency spectrum module configured to determine a frequency spectrum of the chiller control error signal to obtain a controller error signal frequency spectrum signal, wherein the control error signal frequency spectrum module is configured to determine the frequency spectrum of the chiller control error signal using a fast Fourier transform algorithm,
- an impeller stall detection module configured to detect whether an impeller stall event has occurred based on the controller error signal frequency spectrum signal, and
- an impeller stall recovery module configured to restore stable operation of the centrifugal compressor when an impeller stall event is detected.
Dependencies are inferred from the claim text.