Multiple load control for variable frequency drive harmonic mitigation

Abstract

Apparatuses, methods, and systems of multiple load control for variable frequency drive harmonic mitigation are disclosed. An exemplary embodiment includes a system including a plurality of loads including at least one compressor configured to compress refrigerant. The plurality of loads are driven by a plurality of electric motors. The plurality of electric motors are driven by a plurality of variable frequency drives. The plurality of variable frequency drives are electrically coupled to an AC source. In operation a desired cooling capacity of the system is determined, a harmonic mitigation control parameter is determined, and output of one or more of the variable frequency drives is activated, deactivated, adjusted or modulated to reduce the input harmonics and provide the desired cooling capacity.

1 . A method comprising:
 operating an HVACR system including a plurality of loads including at least one compressor configured to compress refrigerant, the plurality of loads being driven by a plurality of electric motors, the plurality of electric motors being driven by a plurality of variable frequency drives, the plurality of variable frequency drives being electrically coupled to an AC source;   determining a desired cooling capacity of the system;   measuring input information associated with the variable frequency drives; and   adjusting output of one or more of the variable frequency drives to reduce input harmonics to the variable frequency drives and provide the desired system cooling capacity.   
     
     
         2 . A method according to  claim 1  wherein the plurality of loads include a plurality of compressors configured to compress refrigerant. 
     
     
         3 .- 7 . (canceled) 
     
     
         8 . A method according to  claim 1  wherein the plurality of loads include the compressor configured to compress refrigerant and a condenser fan drive. 
     
     
         9 . A method according to  claim 1  further comprising determining input current TDD from the measured input information. 
     
     
         10 . A method according to  claim 9  further comprising determining a terminal voltage THD and comparing the determined terminal voltage THD to a measured terminal voltage THD to evaluate efficacy of harmonic mitigation. 
     
     
         12 - 15 . (canceled) 
     
     
         16 . A system comprising:
 a plurality of electric motors configured to drive a respective plurality of loads including at least one refrigerant compressor;   a plurality of variable frequency drives configured to drive the plurality of electric motors; and   a controller configured to control output of the variable frequency drives;   wherein the controller is configured to:   determine a target cooling capacity of the system,   measure input current harmonics associated with the variable frequency drives, and   adjust output of one or more of the variable frequency drives to mitigate the input current harmonics while providing the target cooling capacity.   
     
     
         17 . A system according to  claim 16  wherein the variable frequency drives each include a rectifier electrically coupled to an AC source, a DC link electrically coupled to the rectifier and an inverter electrically coupled to the DC link. 
     
     
         18 .- 24 . (canceled) 
     
     
         25 . A system according to  claim 16  wherein the controller is configured to determine input current TDD and input voltage THD. 
     
     
         26 . A system according to  claim 25  wherein the controller is configured to determine contributions of load imbalance and other sources of distortion to net harmonic distortion utilizing the input current TDD and the input voltage THD. 
     
     
         27 . A system according to  claim 16  wherein the controller is configured to adjust the variable frequency drives collectively in response to an increase or decrease in the target cooling capacity. 
     
     
         28 . A system according to  claim 16  wherein the controller is configured to adjust a particular one of the variable frequency drives selected to optimize harmonic mitigation in response to an increase or decrease in the target cooling capacity. 
     
     
         29 . A system according to  claim 16  wherein the controller is configured to operate capacity control logic to determine a capacity increase or decrease and operate load balancing logic to determine one or more loads to adjust to provide the increase or decrease while mitigating system input harmonics. 
     
     
         30 . A system according to  claim 29  wherein the balancing logic is configured to calculate balance results based on a stored matrix of machine configuration for the system design designating phase balance alignment and capacity influence on balancing. 
     
     
         31 . A system according to  claim 29  wherein the balancing logic is configured to utilize a fixed sequencing matrix, pre-calculated using a balancing algorithm. 
     
     
         32 . A system according to  claim 16  wherein the controller is configured to determine whether to turn on or off one or more of the electric motors to meet the target cooling capacity and to select at least one specific machine and determine its initial capacity and optimize the harmonic mitigation. 
     
     
         33 . A system according to  claim 16  wherein the controller is configured to determine whether to change capacity of one or more of the electric motors which are operating and to select at least one specific electric motor and at least one capacity magnitude change to meet the target cooling capacity and optimize the harmonic mitigation. 
     
     
         34 .- 43 . (canceled) 
     
     
         44 . A method comprising:
 operating an HVACR system including a plurality of loads including at least one compressor configured to compress refrigerant, the plurality of loads being driven by a plurality of electric motors, the plurality of electric motors being driven by a plurality of variable frequency drives, the plurality of variable frequency drives being electrically coupled to an AC source;   determining a desired cooling capacity of the system;   determining an operating configuration of the variable frequency drives configured to provide desired input harmonic mitigation; and   controlling one or more of the variable frequency drives provide the desired input harmonic mitigation and provide the desired system cooling capacity.   
     
     
         45 .- 51 . (canceled) 
     
     
         52 . A method according to  claim 44  further comprising determining input current TDD from the measured input information. 
     
     
         53 . A method according to  claim 52  further comprising determining a terminal voltage THD and comparing the determined terminal voltage THD to a measured terminal voltage THD to evaluate efficacy of harmonic mitigation. 
     
     
         54 .- 62 . (canceled) 
     
     
         63 . A method according to  claim 44  wherein the controlling comprises one of: adjusting output to the plurality of loads collective to increase or decrease overall capacity; adjusting output to a subset of the plurality of loads to increase or decrease overall capacity; increasing or decreasing capacity of at least one of the plurality of loads which is operating; and turning on or off at least one of the plurality of loads.