Abstract:
A method for controlling a system comprising, receiving system demand data ( 402 ), processing the system demand data ( 404 ), defining a first system operating parameter ( 404 ), receiving system condition data ( 406 ), associating the system condition data with an operating map function ( 406 ), determining whether the system condition data exceeds a threshold of the operating map function ( 408 ), and changing the first system operating parameter responsive to determining that the system condition data exceeds the threshold of the operating map function ( 411 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to controlling heating and cooling systems and particularly to heating and cooling systems having subsystems that are dynamically adjustable such as a system described in U.S. Pat. No. 5,054,294. 
         [0002]    Heating and cooling systems that use vapor compression cycles typically include a variety of subsystems including, for example, a compressor, a condenser, an expansion valve, an evaporator, fans, a thermostat, and a system controller. Adjusting the operating parameters of a particular subsystem effects a change in operation of the other subsystems. 
         [0003]    A method and system that allows the operating parameters of subsystems to be effectively controlled allowing an increase in the efficiency of heating and cooling systems is desired. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    According to one aspect of the invention, a method for controlling a system comprises, receiving system demand data, processing the system demand data, defining a first value of a first system operating parameter, receiving system condition data, associating the first value of the first system operating parameter with a first operating map function, determining whether the system condition data exceeds a threshold of the first operating map function, determining whether the system condition data exceeds a threshold of a second operating map function responsive to determining that the system condition data exceeds the threshold of the first operating map function, and changing the first value of the first system operating parameter to a second value associated with the second operating map function responsive to determining that the system condition data does not exceed the threshold of the second operating map function. 
         [0005]    According to another aspect of the invention, a system comprises, a compressor, a sensor, a processor operative to receive system demand data, process the system demand data, define a first value of a first system operating parameter, receive system condition data from the sensor, associate the first value of the first system operating parameter with a first operating map function, determine whether the system condition data exceeds a threshold of the first operating map function, determine whether the system condition data exceeds a threshold of a second operating map function responsive to determining that the system condition data exceeds the threshold of the first operating map function, and change the first value of the first system operating parameter to a second value associated with the second operating map function responsive to determining that the system condition data exceeds the threshold of the second operating map function. 
         [0006]    According to yet another aspect of the invention, a method for controlling a system comprises, receiving system demand data, processing the system demand data, defining a first system operating parameter, receiving system condition data, associating the system condition data with an operating map function, determining whether the system condition data exceeds a threshold of the operating map function, changing the first system operating parameter responsive to determining that the system condition data exceeds the threshold of the operating map function. 
         [0007]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0008]    The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0009]      FIG. 1  is a block diagram of an exemplary embodiment of a heating and cooling system. 
           [0010]      FIG. 2  includes graphs of exemplary embodiments of functions for controlling the system of  FIG. 1 . 
           [0011]      FIG. 3  is a graph of an exemplary embodiment of a function for controlling the system of  FIG. 1 . 
           [0012]      FIG. 4  is a block diagram of an exemplary embodiment of control logic used to control the system of  FIG. 1 . 
       
    
    
       [0013]    The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0014]      FIG. 1  illustrates a block diagram of an exemplary embodiment of a heating and cooling system  100 . The system  100  includes a number of subsystems including, a compressor  102  having an inverter  112  and an inverter controller  114 , a condenser  104 , an expansion valve (EXV)  106 , an evaporator  108 , a fan  118 , a fan  116 , a thermostat  120 , a temperature sensor  122 , and a system controller  110 . The system controller  110  may include, for example, a processor and memory. 
         [0015]    Some embodiments of the system  100  may be optimized to either heat or cool a space, while other embodiment may be used for either function. A number of parameters effect the operation of the system  100 , for example, the desired temperature (i.e., user demand) and the outside temperature. The user demand may be input by a user via the thermostat  120 , while the outside temperature may be sensed by a temperature sensor  122 . In a cooling system, for example, an increase in user demand or an increase in outside temperature increases the work performed by the system  100 . A method and system that increases the efficiency of the system  100  is described below. 
         [0016]    Dynamically adjusting the operating parameters of the subsystems of the system  100  may increase the reliability, effectiveness of meeting operating goals, and efficiency of the system  100 . For example, the compressor subsystem  102  includes a variable speed compressor. The compressor  102  receives saturated vapor, compresses the saturated vapor, and discharges saturated vapor at a higher pressure. The compressor is electrically driven by the inverter  112  that is controlled by the inverter controller  114 . The inverter controller  114  controls the speed (revolutions per minute (RPMs)) of the compressor  102 . Varying the speed of the compressor  102  may offer an overall increase in the efficiency and a reduction of the energy consumption of the system  100 . The inverter controller  114  may determine and collect a number of types of operating condition data of the inverter  112  and the compressor  102 , for example, the inverter controller  114  may sense or calculate current used to drive the compressor  102 , torque output, the speed of the compressor  102 , evaporating temperature, condensing temperature, motor winding temperature, pump (scroll) temperature, and sump temperature. The design specifications of the compressor  102  define the thresholds of operating conditions for the compressor  102 . 
         [0017]    In operation, the inverter controller  114  may receive the motor winding temperature from a sensor. The inverter controller  114  may monitor the motor winding temperature and use logic to shutdown the compressor if the motor winding temperature exceeds a threshold of an operating condition. However, since shutting down the compressor  102  effectively shuts down the system  100 , adjusting the operating parameters of the compressor  102  or the other subsystems may reduce the motor winding temperature and offers an alternative to a shutdown of the system  100 . In the illustrated example of the system  100 , the compressor  102  is variable speed, thus, if the motor winding temperature increases, the motor winding temperature may be reduced by, for example, lowering the speed of the compressor  102 , or reducing the load on the compressor  102  by adjusting other parameters in the system  100 , such as adjusting the EXV  106  orifice. The inverter controller  114  typically operates at a low level of control, in that, the inverter controller  114  processes sensed data to run the compressor  102  at a directed speed without exceeding the design limits of the compressor  102 . 
         [0018]    The system controller  110  operates at a higher level of control and receives and processes sensed data from a number of the system  100  subsystems. For example, the system controller  110  may receive the user demand from the thermostat  120  and send a signal to the inverter controller  114  to run the compressor  102  at a particular speed. If the inverter controller  114  determines that the compressor  102  is approaching a threshold limit of a system condition (sensed data), the inverter controller  114  may send a signal to the system controller  110 . The system controller  110  may then adjust one or more operating parameters of the system  100 , such as, for example, reducing the speed of the compressor  102  and/or adjusting the EXV  106 . 
         [0019]    The variable speed compressor  102  operates over a range of speeds. As the speed of the compressor  102  varies, the operating condition thresholds of the compressor  102  may also vary.  FIG. 2  includes graphs of exemplary embodiments of functions for controlling the system  100 . The graphs  202  and  204  illustrate examples of functions of the operating envelopes for a compressor  102 . The graph  202  is a function of outdoor ambient temperature and compressor speed for a cooling compressor operating in a cooling mode, and the graph  204  is a function of outdoor ambient temperature and compressor speed for a heating compressor operating in a heating mode. The normal operation portions of the graphs  202  and  204  are defined by the maximum and minimum compressor speeds that vary as a function of the outdoor ambient temperature. In operation, the system controller  110  receives the outside temperature and determines whether the compressor  102  is operating within the normal operation envelope. If the compressor  102  is not operating in the normal operation envelope, the system controller  110  may vary the speed of the compressor  102  by sending a control signal to the inverter controller  114 . The functions illustrated in  FIG. 2  are examples of functions for an example compressor  102 . The functions may vary when a compressor  102  having different design specifications are used in the system  100 . By varying the commanded operating parameters of the compressor, undesirable shutdowns of the compressor may be avoided. 
         [0020]    Other system conditions may also be monitored by the system controller  110  to determine whether the compressor is operating within system condition thresholds.  FIG. 3  illustrates a function graph operating map having an acceptable operation envelope. The envelope is defined by a function of condensing temperature, evaporating temperature, and compressor current.  FIG. 3  illustrates an operating map at a particular compressor  102  operating speed. As the speed of the compressor  102  changes, the function may change—varying the operation envelope. In operation, for example, if the condensing temperature and evaporating temperature approach or fall outside the acceptable operation envelope, the system controller  110  may determine whether the condensing temperature and evaporating temperature may fall inside an acceptable operation envelope of the compressor  102  at a different compressor speed. Thus, the variable speed compressor  102  allows the system controller  110  to operate the compressor  102  within an acceptable operation envelope by changing the speed of the compressor  102 .  FIGS. 3 and 4  are examples of functions used to define operation envelopes. The system  100  may include a number of other functions of a variety of system conditions (such as, for example, compressor current, compressor torque, compressor scroll temperature, compressor sump temperature, inverter temperature, and motor temperature) that may be used to determine whether the system  100  is operating within specifications, and to adjust system parameters to maintain the operation of the system  100 . 
         [0021]      FIG. 4  illustrates a block diagram of an exemplary embodiment of control logic used to control the system  100 . The control logic may be implemented by the system controller  110  and the inverter controller  114 . In block  402  ambient condition and system demand data is received. Ambient condition may include, for example, the inside and outside temperatures, and system demand data may include, for example, a temperature desired by the user and input to the thermostat  120  (of  FIG. 1 ). The ambient condition and system demand data are processed in block  404  to determine desired system operating parameters, such as, for example, compressor speed, airflow (fan speed), and expansion valve orifice dimension. In block  406 , system condition data is received. The system condition data includes sensed system conditions. The received system condition data is compared to operating map functions. Block  408  determines whether any system condition data has met (or in alternate embodiments approaches) a threshold of the operating map function. In block  410 , the system controller  110  determines whether one or more operating parameters may be changed to move the system condition data away from the threshold of the operating map function—keeping the system condition data within the acceptable operation envelope. If yes, in block  413 , the operating parameter(s) are changed accordingly. If no, in block  415 , the system controller  110  identifies another operating map function (stored in memory) having an envelope threshold that includes the present system condition data. If the system condition will not exceed the threshold envelope of an identified operating map function, the system controller  110  may change an operating parameter associated with the identified operating map function—changing the threshold envelope so that the system condition value falls into an acceptable threshold envelope in block  411 . For example, the system controller  110  may apply the system condition data to operating map functions corresponding to a number of compressor  102  speeds. If the system controller  110  determines that the system condition data will be within the acceptable operation envelope of a different operating map function, the system controller  110  will direct the compressor  102  to change speed to the RPMs associated with the different operating map function. In block  412 , the system controller  110  determines whether the system is operating at desired operating parameters. If the system is not operating at desired operating parameters, the operating parameters are adjusted to meet the desired operating parameters in block  414 . 
         [0022]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.