Air-conditioning apparatus

Abstract

A control unit configured to control a manipulated variable of an operational object so that a current value of a controlled object, which is one measurement obtained by the measurement unit configured to measure an operating state variable of the refrigerant circuit, reaches a target value of the controlled object determined based on measurements other than the one measurement. The control unit determines, while the current value is lower than a lower limit value of an upper limit value and the lower limit value of a settling range in which the target value is centered, the manipulated variable by using the upper limit value as a target value, determines the manipulated variable by using the lower limit value as a target value, and determines, after the current value falls within the settling range, the manipulated variable based on a reference allowable overshoot ratio Xb, which is a preset overshoot ratio.

1 . An air-conditioning apparatus comprising:
 a compressor, a condenser, an expansion valve, and an evaporator, included in a refrigerant circuit through which refrigerant circulates;   a condenser fan;   an evaporator fan;   a measurement unit configured to measure an operating state variable of the refrigerant circuit; and   a control unit configured to control a manipulated variable of an operational object, which is at least one of frequency of the compressor, an opening degree of the expansion valve, a rotation speed of the condenser fan, and a rotation speed of the evaporator fan, so that a current value of a controlled object, which is one measurement of measurements obtained by the measurement unit, reaches a target value of the controlled object determined based on measurements other than the one measurement,   wherein the control unit   controls the manipulated variable of the operational object by changing a control gain.   
     
     
         2 . The air-conditioning apparatus of  claim 6 ,
 wherein the control unit   calculates, when determining the manipulated variable while the current value is outside the settling range, a variable allowable overshoot ratio by dividing the settling range by a difference between the current value and the target value, calculates the control gain for determining the manipulated variable based on the variable allowable overshoot ratio, and determines the manipulated variable based on the control gain, and   calculates, when determining the manipulated variable after the current value falls within the settling range, the control gain for determining the manipulated variable based on the reference allowable overshoot ratio, and determines the manipulated variable based on the control gain.   
     
     
         3 . The air-conditioning apparatus of  claim 1 ,
 wherein the control unit,   when the current value of the controlled object approaches the target value, increases a maximum limit value of the target value of the controlled object above a present level, or reduces a minimum limit value of the target value of the controlled object below a present level.   
     
     
         4 . The air-conditioning apparatus of  claim 1 ,
 wherein the control unit   predicts a subsequent value by using a past value and a current value of the operational object at control intervals, and reduces the control gain if the subsequent value exceeds an allowable overshoot amount.   
     
     
         5 . The air-conditioning apparatus of  claim 1 ,
 wherein the control unit further uses a control interval, an expansion valve opening degree, and compressor frequency when calculating the control gain.   
     
     
         6 . The air-conditioning apparatus of  claim 1 , wherein
 the control unit allows the control gain to be variable in a case the current value falls within a settling range in which the target value is centered, and fixes the control gain in a case the current value falls within the settling range.   
     
     
         7 . The air-conditioning apparatus of  claim 6 , wherein the control unit
 determines, while the current value is lower than a lower limit value of an upper limit value and the lower limit value of the settling range, the manipulated variable by using the upper limit value as a target value,   determines, while the current value is higher than the upper limit value, the manipulated variable by using the lower limit value as a target value, and   determines, after the current value falls within the settling range, the manipulated variable based on a reference allowable overshoot ratio, which is a preset overshoot ratio.   
     
     
         8 . An air-conditioning apparatus comprising:
 a compressor, a condenser, an expansion valve, and an evaporator, included in a refrigerant circuit through which refrigerant circulates;   a condenser fan;   an evaporator fan;   a measurement unit configured to measure an operating state variable of the refrigerant circuit; and   a control unit configured to control a manipulated variable of an operational object, which is at least one of frequency of the compressor, an opening degree of the expansion valve, a rotation speed of the condenser fan, or a rotation speed of the evaporator fan, so that a current value of a controlled object, which is one measurement of measurements obtained by the measurement unit, reaches a target value of the controlled object determined based on measurements other than the one measurement,   wherein the control unit   determines, while the current value is lower than a lower limit value of an upper limit value and the lower limit value of a settling range in which the target value is centered, the manipulated variable by using the upper limit value as a target value,   determines, while the current value is higher than the upper limit value, the manipulated variable by using the lower limit value as a target value, and   determines, after the current value falls within the settling range, the manipulated variable based on a reference allowable overshoot ratio, which is a preset overshoot ratio.