Controlling vapor compression cooling in a thermal system

Abstract

A method of controlling vapor compression cooling in a thermal system comprises: changing, using a controller and according to a first function, a first operating parameter of a first actuator of the thermal system, the first function defined by performing fitting to data, the first actuator controlling one of a speed of a fan of a condenser or a speed of a compressor; and changing, using the controller, a second operating parameter of a second actuator of the thermal system, the second actuator controlling another of the speed of the fan of the condenser or the speed of the compressor, the second operating parameter changed according to a second function that at least in part depends on a capacity request for the vapor compression cooling.

What is claimed is: 
     
         1 . A method of controlling vapor compression cooling in a thermal system, the method comprising:
 changing, using a controller and according to a first function, a first operating parameter of a first actuator of the thermal system, the first function defined by performing fitting to data, the first actuator controlling one of a speed of a fan of a condenser or a speed of a compressor; and   changing, using the controller, a second operating parameter of a second actuator of the thermal system, the second actuator controlling another of the speed of the fan of the condenser or the speed of the compressor, the second operating parameter changed according to a second function that at least in part depends on a capacity request for the vapor compression cooling.   
     
     
         2 . The method of  claim 1 , wherein the first actuator controls the speed of the fan of the condenser, wherein changing the first operating parameter increases or decreases the speed of the fan of the condenser, wherein the second actuator controls the speed of the compressor, and wherein changing the second operating parameter increases or decreases the speed of the compressor. 
     
     
         3 . The method of  claim 2 , wherein changing the speed of the compressor according to the second function comprises taking into account a requested mass flow derived from the capacity request. 
     
     
         4 . The method of  claim 1 , wherein the first actuator controls the speed of the compressor, wherein changing the first operating parameter increases or decreases the speed of the compressor, wherein the second actuator controls the fan speed of the condenser, and wherein changing the second operating parameter increases or decreases the speed of the fan of the condenser. 
     
     
         5 . The method of  claim 1 , wherein controlling the vapor compression cooling comprises minimizing a cost function regarding power consumption by the compressor and the power consumption by the fan. 
     
     
         6 . The method of  claim 5 , wherein the cost function comprises a sum of the power consumption by the compressor and the power consumption by the fan. 
     
     
         7 . The method of  claim 5 , wherein the cost function is minimized using (i) a first partial derivative of the power consumption by the compressor, and (ii) a second partial derivative of the power consumption by the fan. 
     
     
         8 . The method of  claim 7 , wherein the first and second functions represent the first and second partial derivatives, respectively. 
     
     
         9 . The method of  claim 7 , wherein the first partial derivative is decomposed into a first relative partial derivative, wherein the second partial derivative is decomposed into a second relative partial derivative. 
     
     
         10 . The method of  claim 9 , wherein the first actuator controls the speed of the fan of the condenser, wherein changing the first operating parameter increases or decreases the speed of the fan of the condenser, the method further comprising decomposing the first relative partial derivative into a third partial derivative and a fourth partial derivative multiplied with each other. 
     
     
         11 . The method of  claim 10 , wherein the third partial derivative corresponds to a change in relative compressor power with respect to a change in saturated discharge temperature, and wherein the fourth partial derivative corresponds to the change in saturated discharge temperature with respect to a change in the speed of the fan of the condenser. 
     
     
         12 . The method of  claim 11 , wherein the first function defined by performing fitting to the data comprises: (i) a first model fitted to data reflecting the third partial derivative, (ii) a second model data reflecting the fourth partial derivative, and (iii) a third model fitted to data reflecting the second relative partial derivative. 
     
     
         13 . The method of  claim 9 , wherein the changing of the first operating parameter is done based on multiplying the first and second relative partial derivatives with a gain. 
     
     
         14 . The method of  claim 1 , wherein the data comprises simulated data. 
     
     
         15 . The method of  claim 1 , wherein the thermal system includes a non-electronic expansion device, and wherein the first and second operating parameters are changed without changing the non-electronic expansion device. 
     
     
         16 . The method of  claim 15 , wherein the non-electronic expansion device comprises a passive expansion device or a mechanically adjusted expansion device. 
     
     
         17 . The method of  claim 1 , further comprising changing, using the controller, a third operating parameter of an expansion device of the thermal system, the third operating parameter changed to obtain a predefined value in the thermal system. 
     
     
         18 . The method of  claim 17 , wherein changing the third operating parameter comprises using a feedback loop. 
     
     
         19 . The method of  claim 17 , wherein the predefined value is at least one of a superheat value a subcooling value, a mass flow rate, a suction pressure, a capacity of the thermal system, a discharge air temperature for an evaporator of the thermal system, or a coolant temperature for a chiller of the thermal system. 
     
     
         20 . The method of  claim 1 , wherein the thermal system is part of a vehicle. 
     
     
         21 . The method of  claim 1 , wherein the thermal system is part of a stationary energy storage. 
     
     
         22 . A method of controlling vapor compression cooling in a thermal system, the method comprising:
 setting (i) a first operating parameter of a first actuator of the thermal system and (ii) a second operating parameter of a second actuator of the thermal system;   performing realtime optimization of the first and second operating parameters during operation of the thermal system based on minimization of a cost function taking into account at least the first and second actuators; and   adjusting the first and second operating parameters based on the realtime optimization.   
     
     
         23 . The method of  claim 22 , wherein the first actuator controls one of a speed of a fan of a condenser or a speed of a compressor, and wherein the second actuator controls another of the speed of the fan of the condenser or the speed of the compressor. 
     
     
         24 . The method of  claim 22 , wherein the realtime optimization is performed using a function fitted to data reflecting relative partial derivatives. 
     
     
         25 . The method of  claim 22 , further comprising setting (iii) a third operating parameter of an expansion device of the thermal system, wherein the performing realtime optimization is performed also of the third operating parameter, and wherein the third operating parameter is also adjusted based on the realtime optimization.