Method for correcting pump model

Abstract

A method for correcting pump model includes: obtaining a pump model for a pump, the pump model including a Q-P curve and a Q-H curve at each of a plurality of frequencies; at each frequency, determining a power error based on a zero-flow-rate power or an actual operating point of the pump under one of the frequencies; and determining a corrected pump model based on the pump model and the power error. The determination of the corrected pump model includes: at each frequency, determining a corrected Q-P curve to be the Q-P curve shifted by the power error; determining a Q-H-P surface based on the corrected Q-P curves and the Q-H curves at all the frequencies; at each frequency, determining a head error based on the surface and the power error; and at each frequency, determining a corrected Q-H curve to be the Q-H curve shifted by the head error.

What is claimed is: 
     
         1 . A method for correcting pump model, comprising:
 obtaining a pump model for a pump, the pump model comprising a Q-P curve and a Q-H curve at each of a plurality of frequencies for the pump;   at each of the plurality of frequencies, determining a power error based on a zero-flow-rate power or an actual operating point of the pump at a first frequency of the plurality of frequencies; and   determining a corrected pump model based on the pump model and the power error, comprising:
 at each of the plurality of frequencies, determining a corrected Q-P curve to be the Q-P curve shifted by the power error; 
 determining a Q-H-P surface based on the corrected Q-P curves and the Q-H curves at the plurality of frequencies; 
 at each of the plurality of frequencies, determining a head error based on the Q-H-P surface and the power error; and 
 at each of the plurality of frequencies, determining a corrected Q-H curve to be the Q-H curve shifted by the head error. 
   
     
     
         2 . The method of  claim 1 , further comprising:
 at each of the plurality of frequencies, determining an estimated operating point based on the corrected Q-H curve;   determining a fitted demand curve based on the estimated operating points at the plurality of frequencies;   determining a residual sum of squares between the estimated operating points at the plurality of frequencies and the fitted demand curve; and   if the residual sum of squares is less than or equal to an error threshold, then the corrected pump model is set.   
     
     
         3 . The method of  claim 2 , further comprising:
 if the residual sum of squares is greater than the error threshold, then:
 at each of the plurality of frequencies, updating the power error based on the estimated operating point and the fitted demand curve; 
 at each of the plurality of frequencies, updating the Q-P curve of the pump model to the corrected Q-P curve and updating the Q-H curve of the pump model to the corrected Q-H curve; and 
 after updating the power error and the pump model, performing the step of determining the corrected pump model based on the pump model and the power error. 
   
     
     
         4 . The method of  claim 3 , wherein the step of updating the power error based on the estimated operating point and the fitted demand curve comprises:
 determining a head residual between the fitted demand curve and the estimated operating point;   determining a flow rate correction amount based on the head residual and a differential of a function corresponding to the fitted demand curve; and   updating the power error to be a product of the flow rate correction amount and a slope of the corrected Q-P curve.   
     
     
         5 . The method of  claim 1 , wherein the step of determining the power error comprises:
 determining a first estimated flow rate of the pump based on the Q-P curve at the first frequency;   determining a flow rate error ratio to be a difference of the zero-flow-rate power and a P-intercept of the Q-P curve at the first frequency, divided by a slope of the Q-P curve at the first frequency, and further divided by the first estimated flow rate;   determining a second estimated flow rate of the pump based on the Q-P curve at a second frequency of the plurality of frequencies; and   determining the power error at the second frequency to be a product of the flow rate error ratio, the second estimated flow rate and a slope of the Q-P curve at the second frequency.   
     
     
         6 . The method of  claim 1 , wherein the step of determining the head error comprises:
 at each of the plurality of frequencies, iteratively calculating the head error based on the Q-H-P surface and the power error.   
     
     
         7 . The method of  claim 6 , wherein the step of iteratively calculating the head error based on the Q-H-P surface and the power error comprises:
 determining a second head error based on a derivative of the Q-H-P surface and the power error;   determining a second estimated operating point based on a second Q-H curve, wherein the second Q-H curve is the Q-H curve shifted by the second head error;   determining a power difference to be a difference of an estimated power at the second estimated operating point and an input power of the pump at corresponding frequency; and   determining the head error to be the second head error if the power difference is within an allowable range, or else updating the second head error based on the power difference and returning to the step of determining the second estimated operating point.   
     
     
         8 . The method of  claim 7 , further comprising:
 determining a second Q-H-P surface based on the second Q-H curve; and   determining the estimated power based on the second Q-H-P surface and the second estimated operating point.   
     
     
         9 . The method of  claim 1 , wherein the step of determining the Q-H-P surface comprises:
 determining the Q-H-P surface based on the corrected Q-P curves and the Q-H curves at the plurality of frequencies by means of surface fitting;   wherein the Q-H-P surface is expressed as P=f(Q,H), in which f has highest degree of 3 in flow rate Q and has highest degree of 2 in head H.   
     
     
         10 . The method of  claim 1 , wherein the step of determining the power error comprises:
 determining a first estimated flow rate of the pump based on the Q-P curve at the first frequency;   determining a flow rate error ratio to be a difference of a flow rate at the actual operating point and the first estimated flow rate, divided by the first estimated flow rate;   determining a second estimated flow rate of the pump based on the Q-P curve at a second frequency of the plurality of frequencies; and   determining the power error at the second frequency to be a product of the flow rate error ratio, the second estimated flow rate and a slope of the Q-P curve at the second frequency.