Patent Publication Number: US-9835346-B2

Title: Air conditioner and method for controlling the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed on Mar. 18, 2014 in the Korean Intellectual Property Office and assigned Serial No. 10-2014-0031423, the entire disclosure of which is incorporated hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an air conditioner and method for controlling the same. 
     BACKGROUND 
     A/C is an abbreviation for Air Conditioner, meaning a device used for cooling or heating indoor space. Refrigerant fluid absorbs surrounding heat during evaporation, and this property is used for cooling. On the contrary, the property that refrigerant gas discharges heat during liquefaction is used for heating. 
     It is common for an A/C to have a single indoor unit connected to a single outdoor unit, but recently, the demand for a system A/C with a single outdoor unit connected to multiple indoor units having various forms and capacities has been increasing. The system A/C with an outdoor unit connected to multiple indoor units may be optimally designed to fit for building types and characteristics of respective rooms and may efficiently use indoor and/or outdoor space, thereby being installed in schools, government offices, hospitals, commercial buildings, studio apartments, apartment houses, shopping malls, offices, etc. 
     Multi split A/C systems having capacity-variable compressors mounted thereon are becoming more common, and Variable Refrigerant Flow (VRF) systems having functions varying with indoor loads are also increasingly used. Such systems have an advantage of enabling rapid cooling and/or heating by increasing capacity as required. 
     In the meantime, a need exists for a technology for the A/C to actively deal with a change in load state for a compressor in a high temperature region. 
     SUMMARY 
     The present disclosure provides an air conditioner and method for controlling the same to adjust overall refrigerant flow rate by regulating set air flow of an indoor unit based on a pressure range of a compressor during protection control of the compressor. 
     In accordance with an aspect of the present disclosure, an air conditioner is provided. The air conditioner includes a compressor; a sensor for measuring the compressor&#39;s state configured to detect compressor state information that includes at least one of a pressure value and a saturation temperature of the compressor; and a controller configured to control air flow on the side of an indoor unit by comparing the compressor state information measured from the sensor and a threshold. 
     The controller may control subcooling control mode according to a result of comparing the compressor state information and the threshold. 
     If a pressure value of the compressor is detected by the sensor measuring suction pressure and discharge pressure of the compressor, the controller may control air flow on the side of an indoor unit by comparing the pressure value of the compressor measured from the sensor with a pressure threshold. 
     The controller may adjust the air flow on the side of the indoor unit to a necessary air flow for now and turn off the subcooling control mode, if the pressure value of the compressor has exceeded a first pressure threshold in a dangerous range for a predetermined time. 
     If the pressure value of the compressor has been less than a second pressure threshold in the maintenance range for a predetermined time since the controller adjusted the air flow on the side of the indoor unit to a necessary air flow for now and turned off the subcooling control mode, the controller may adjust the air flow on the side of the indoor unit to a set air flow and keep on turning off the subcooling control mode. 
     If the pressure value of the compressor has been less than a third pressure threshold in a normal range for a predetermined time since the controller adjusted the air flow on the side of the indoor unit to a set air flow and kept on turning off the subcooling control mode, the controller  130  may turn on the subcooling control mode. 
     If the sensor measures a saturation temperature, the controller may control air flow on the side of an indoor unit by comparing the saturation temperature measured from the sensor with a temperature threshold. 
     The controller may adjust the air flow on the side of the indoor unit to a necessary air flow for now and turn off the subcooling control mode, if the saturation temperature has exceeded a first temperature threshold in a dangerous range for a predetermined time. 
     The controller may adjust the air flow on the side of the indoor unit to a set air flow and keep on turning off the subcooling control mode, if the saturation temperature has been less than a second temperature threshold in a maintenance range for a predetermined time since the air flow on the side of the indoor unit was adjusted to the necessary air flow for now and the subcooling control mode was turned off. 
     The controller may turn on the subcooling control mode, if the saturation temperature has been less than a third temperature threshold in a normal range for a predetermined time since the air flow on the side of the indoor unit was adjusted to the set air flow and the subcooling control mode was kept being turned off. 
     The air flow on the side of the indoor unit may comprise a user-set air flow manipulated by a user and an initially-set air flow set in initially setting the indoor unit, and the controller may control at least one of the user-set air flow and initially-set air flow in regulating the air flow on the side of the indoor unit. 
     In accordance with another aspect of the present disclosure, a method of controlling an air conditioner is provided. The method includes operating compressor protection mode; detecting compressor state information that includes at least one of a pressure value and a saturation temperature of a compressor; and controlling air flow on the side of an indoor unit by comparing the compressor state information with a threshold. 
     Controlling air flow on the side of an indoor unit may include controlling subcooling control mode according to a result of comparing the compressor state information and the threshold. 
     If the compressor state information is a pressure value of the compressor obtained by measuring suction pressure and discharge pressure of the compressor, controlling air flow on the side of an indoor unit may include determining whether the pressure value of the compressor has exceeded a first pressure threshold in a dangerous range for a predetermined time; and adjusting the air flow on the side of the indoor unit to a necessary air flow for now and turning off the subcooling control mode, if it is determined that the pressure value of the compressor has exceeded the first pressure threshold for the predetermined time. 
     The method further includes, after adjusting the air flow on the side of the indoor unit to a necessary air flow for now and turning off the subcooling control mode, determining whether the pressure value of the compressor has been less than a second pressure threshold in a maintenance range for a predetermined time; and adjusting the air flow on the side of the indoor unit to a set air flow and keeping on turning off the subcooling control mode, if it is determined that the pressure value of the compressor has been less than the second pressure threshold for the predetermined time. 
     The method further includes, after adjusting the air flow on the side of the indoor unit to the set air flow and keeping on turning off the subcooling control mode, determining whether the pressure value of the compressor has been less than a third pressure threshold in a normal range for a predetermined time; and turning on the subcooling control mode, if it is determined that the pressure value of the compressor has been less than the third pressure threshold for the predetermined time. 
     If the compressor state information is a saturation temperature, controlling air flow on the side of an indoor unit may include determining whether the saturation temperature has exceeded a first temperature threshold in a dangerous range for a predetermined time; and adjusting the air flow on the side of the indoor unit to a necessary air flow for now and turning off the subcooling control mode, if it is determined that the saturation temperature has exceeded the first temperature threshold for the predetermined time. 
     The method further includes, after adjusting the air flow on the side of the indoor unit to a necessary air flow for now and turning off the subcooling control mode, determining whether the saturation temperature has been less than a second temperature threshold in a maintenance range for a predetermined time; and adjusting the air flow on the side of the indoor unit to a set air flow and keeping on turning off the subcooling control mode, if it is determined that the saturation temperature has been less than the second temperature threshold for the predetermined time. 
     The method further includes, after adjusting the air flow on the side of the indoor unit to the set air flow and keeping on turning off the subcooling control mode, determining whether the saturation temperature has been less than a third temperature threshold in a normal range for a predetermined time; and turning on the subcooling control mode, if it is determined that the saturation temperature has been less than the third temperature threshold for the predetermined time. 
     The air flow on the side of the indoor unit may include a user-set air flow manipulated by a user and an initially-set air flow set in initially setting the indoor unit, and controlling air flow on the side of an indoor unit may include control at least one of the user-set air flow and initially-set air flow in regulating the air flow on the side of the indoor unit. 
     Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the disclosure 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present disclosure will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  is a block diagram of an air conditioner; 
         FIG. 2  is a control bock diagram of an air conditioner; 
         FIG. 3  is a flowchart illustrating a method for controlling an air conditioner, according to an embodiment of the present disclosure; 
         FIG. 4  is a flowchart illustrating a method for controlling an air conditioner, according to another embodiment of the present disclosure; and 
         FIG. 5  is a graph representing a range of suction and discharge pressures for compressor protection control. 
     
    
    
     Throughout the drawings, like reference numerals will be understood to refer to like parts, components, and structures. 
     DETAILED DESCRIPTION 
     The present disclosure will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the disclosure are shown. The disclosure may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the disclosure to those skilled in the art. Like reference numerals in the drawings denote like elements, and thus their description will be omitted. In the description of the present disclosure, if it is determined that a detailed description of commonly-used technologies or structures related to the embodiments of the present disclosure may unnecessarily obscure the subject matter of the invention, the detailed description will be omitted. It will be understood that, although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. 
     Embodiments of the present disclosure will now be described with reference to accompanying drawings. 
     As an example of an air conditioner of the present disclosure, a system air conditioner including a single outdoor unit and multiple indoor units will be described below, but embodiments of the present disclosure are not limited thereto. 
       FIG. 1  is a block diagram of an air conditioner. 
     As shown in  FIG. 1 , an air conditioner  100  may include a single outdoor unit  110  and multiple indoor units  120   a ,  120   b ,  120   c , and  120   d . Although shown as having the single outdoor unit  110 , it is possible for the air conditioner  100  to have multiple outdoor units. 
     The outdoor unit  110  may include a compressor  111 , a four-way valve  112 , an outdoor heat exchanger  113 , an outdoor fan  114 , an electronic expansion valve for heating control  115 , an accumulator  116 , a sensor for measuring the compressors state  117 , a heat exchanger for subcooling control  118 , and an electronic expansion valve for subcooling control  119 . 
     The indoor units  120   a ,  120   b ,  120   c , and  120   d  may include indoor heat exchangers  121   a ,  121   b ,  121   c , and  121   d , indoor fans  122   a ,  122   b ,  122   c , and  122   d , indoor temperature sensors  123   a ,  123   b ,  123   c , and  123   d , and indoor electronic expansion valves  124   a ,  124   b ,  124   c , and  124   d , respectively. 
     The compressor  111  may be, but not exclusively, an inverter-type compressor  111  for compressing a low-temperature low pressure refrigerant fluid and discharging it as hot-temperature high pressure refrigerant gas. 
     The four-way valve  112  may be operated to be turned on/off to change the refrigerant flow according to whether the operation mode selected by the user is cooling operation mode or heating operation mode. Specifically, the four-way valve  112  may have two separate paths, which enable high temperature and high pressure refrigerant gas discharged from the compressor  111  to be transferred to the indoor heat exchangers  121   a ,  121   b ,  121   c , and  121   d  in the heating operation mode and to the outdoor heat exchanger  113  in the cooling operation mode. 
     The outdoor heat exchanger  113  may serve as a condenser for condensing a high pressure high temperature refrigerant gas into a high pressure room temperature fluid in the cooling operation mode, and as an evaporator for evaporating a low pressure low temperature refrigerant fluid into a gas in the heating operation mode, thereby acting to cause heat exchange with the surrounding air in response to a change in enthalpy of the refrigerant. In this regard, the outdoor heat exchanger  113  may be a main heat exchanger distinguished from the heat exchanger for subcooling control  118 . 
     The outdoor fan  114  may play the role of catalyst for facilitating the heat exchange action between the air and the refrigerant flowing in the outdoor heat exchanger  113 , thereby increasing the heat exchange ability of the outdoor unit  110 . 
     The electronic expansion valve for subcooling control  119  may enable some of the refrigerant having passed through the heat exchanger for subcooling control  118  to be sent back to the heat exchanger for subcooling control  118  and then transferred to the accumulator  116 . In this regard, the high temperature refrigerant that has passed through the outdoor heat exchanger  113  may undergo a drop in temperature while passing through the heat exchanger for subcooling control  118 , and the resultant refrigerant may be transferred to the heat exchanger for subcooling control  118  through the electronic expansion valve for subcooling control  119 . The heat exchanger  118  for subcooling control  118  may be a plate-type heat exchanger, but is not limited thereto. 
     The electronic expansion valve  119  for subcooling control  119  may be switched to various modes (e.g., On mode, Off mode, etc.) according to a control signal sent from a controller  130  as will be discussed in connection with  FIG. 2 . 
     The accumulator  116  may be installed on the suction side of the compressor  111  for changing the phase of the refrigerant inhaled to the compressor  111  into a complete form of gas. 
     The sensor for measuring the compressors state  117  may include a first pressure sensor  117   a  for measuring suction pressure and a second pressure sensor  117   b  for measuring discharge pressure, which are arranged on either side (i.e., on the suction side and discharge side) of the compressor  111 . The suction pressure means a pressure on the suction side of the compressor  111  and the discharge pressure means a pressure of the gas discharged from the compressor  111 . 
     The sensor for measuring the compressors state  117  may further include an outdoor temperature sensor  117   c  for measuring a saturation temperature during condensation in the outdoor heat exchange  113  and indoor temperature sensors  123   a ,  123   b ,  123   c , and  123   d  for measuring respective saturation pressures temperatures during evaporation in respective indoor heat exchangers  121   a ,  121   b ,  121   c , and  121   d . A saturation temperature measured by the outdoor temperature sensor  117   c  is a temperature at a high pressure, and respective saturation temperatures of pressures measured by the respective indoor temperature sensors  123   a ,  123   b ,  123   c , and  123   d  are temperatures at low pressures. 
     As opposed to the outdoor heat exchanger  113 , the indoor heat exchangers  121   a ,  121   b ,  121   c , and  121   d  may serve as evaporators during the cooling operation and as condensers during the heating operation, exchanging heat with the surrounding air. 
     The indoor fans  122   a ,  122   b ,  122   c , and  122   d  may facilitate heat exchanges between the refrigerant flowing in the indoor heat exchangers  121   a ,  121   b ,  121   c , and  121   d , and the air and generate a cool current of air or warm current of air for indoor rooms. 
     The indoor temperature sensors  123   a ,  123   b ,  123   c , and  123   d  may measure respective saturation temperatures of pressures during the evaporation operation of the respective indoor units  120   a ,  120   b ,  120   c , and  120   d.    
     The indoor electronic expansion valve  124   a ,  124   b ,  124   c , and  124   d  may be arranged in the four indoor units  120   a ,  120   b ,  120   c , and  120   d , respectively. 
     The air conditioner  100  may change the flow of the refrigerant by switching the four-way valve  112  according to whether the operating mode selected by the user is the cooling operation mode or heating operation mode. 
       FIG. 2  is a control block diagram of an air conditioner, which will be described with reference to  FIG. 5  showing a graph representing a range of protection control values comprised of suction and discharge pressures for compressor protection control. 
     The air conditioner  100  will be described by focusing on the configuration for protection control for a compressor while omitting the description of the other configurations. 
     As shown in  FIG. 2 , the air conditioner  100  may include the compressor  111 , the sensor for measuring the compressors state  117 , the electronic expansion valve (EEV) for subcooling control  119 , the indoor unit  120 , and the controller  130 . 
     The sensor for measuring the compressors state  117  may detect compressor state information that includes at least one of a pressure value and a saturation temperature of the compressor  111 . 
     In this regard, the sensor for measuring the compressors state  117  may detect the pressure value by measuring a suction pressure and discharge pressure of the compressor  111 . 
     More specifically, the sensor for measuring the compressors state  117  may include the first pressure sensor  117   a  for measuring suction pressure and the second pressure sensor  117   b  for measuring discharge pressure, which are arranged on either side (i.e., on the suction side and discharge side) of the compressor  111 . The suction pressure is a low pressure, and the discharge pressure is a high pressure. 
     The sensor for measuring the compressors state  117  may further include an outdoor temperature sensor  117   c  for measuring a saturation temperature during condensation in the outdoor heat exchange  113  and indoor temperature sensors  123   a ,  123   b ,  123   c , and  123   d  for measuring respective saturation temperatures of pressures during evaporation in respective indoor heat exchangers  121   a ,  121   b ,  121   c , and  121   d , to detect respective saturation temperatures of pressures. A saturation temperature measured by the outdoor temperature sensor  117   c  is a temperature at a high pressure, and respective saturation temperatures of pressures measured by the respective indoor temperature sensors  123   a ,  123   b ,  123   c , and  123   d  are temperatures at low pressures. The saturation temperature means a temperature corresponding to a pressure value of the compressor  111 . It is possible for the saturation temperature to be set in advance by being matched per pressure values. In this case, if a pressure value of the compressor  111  is detected, the saturation temperature may be obtained by reading out a temperature stored to match the detected pressure value. On the contrary, once the saturation temperature is detected, a pressure value stored to correspond to the detected saturation temperature may be obtained. Accordingly, it may be possible to omit any of the pressure sensors (i.e., the first pressure sensor  117   a  and the second pressure sensor  117   b ) and temperature sensors (i.e., the outdoor temperature sensor  117   c  and the indoor temperature sensors  123   a ,  123   b ,  123   c , and  123   d ). 
     The controller  130  may compare the compressor state information measured from the sensor for measuring the compressors state  117  with a threshold, and accordingly control the air flow on the side of the indoor unit. 
     More specifically, the controller  130  may compare the pressure value of the compressor measured from the sensor for measuring the compressors state  117  with a pressure threshold, and accordingly control the air flow on the side of the indoor unit. The air flow on the side of the indoor unit may include a user-set air flow manipulated by the user and an initially-set air flow set in initially setting the indoor unit. The initially-set air flow may refer to not only the air flow set in initially setting the indoor unit  120  but also air flow set for safety of the indoor unit  120 , and may be distinguished from the user-set air flow set by the user manipulating an input button. 
     The controller  130  may control at least one of the user-set air flow and initially-set air flow in regulating the air flow on the side of the indoor unit. In other words, the controller  130  may only control the user-set air flow set by manipulation of the user for the air conditioner  100 , may only control the initially-set air flow set for the air conditioner  100  by an operator, or may control both the user-set air flow and the initially-set air flow, in regulating the air flow on the side of the indoor unit. 
     The pressure threshold is set based on a range of protection control values for protecting the compressors  111  performance, and the range of protected control values may be represented by an area encircled by a solid or dashed line, as shown in  FIG. 5 . The range of the protection control values may be defined as a range of pressure values that may protect the compressors performance in good state. 
     For example, the pressure threshold may be set to be in a dangerous range if exceeding 1.5 MPa, g with respect to the suction pressure, and 1.4 MPa, g of the pressure threshold with respect to the suction pressure may be set to be in a normal but maintenance range to further check the state of the compressor  111  in a phase of entering the normal range from the dangerous range. However, the pressure threshold is not limited thereto, but may vary by an operator. 
     The controller  130  may be further configured to control not only the air flow on the side of the indoor unit but also the subcooling control mode based on a result of comparing the compressor state information (e.g., a pressure value or saturation temperature of the compressor  111 ) and the threshold (e.g., pressure threshold or temperature threshold). The subcooling control means to control a subcooling degree by controlling the electronic expansion valve for subcooling control  119  and an Enhanced Vapor Injection (EVI) bypass (not shown). 
     More specifically, the controller  130  may adjust the air flow on the side of the indoor unit to a necessary air flow for now and turn off the subcooling control mode, if the pressure value of the compressor  111  has exceeded a first pressure threshold in the dangerous range for a predetermined time. The necessary air flow may be defined as air flow required for the pressure value of the compressor  111  to reach the normal range. Turning off the subcooling control mode means to regulate the electronic expansion valve for subcooling control  119  to 0 step and control the subcooling degree by opening the EVI bypass, during operation. 
     Referring to  FIG. 5 , the pressure value of the compressor  111  may be a value comprised of a suction pressure value and a discharge pressure value. The dangerous range may refer to a pressure range that may affect degradation of the compressor&#39;s  111  performance. 
     For example, if a pressure value of the compressor  111  is in overvoltage state of 58 degrees, as shown as point “B” in  FIG. 5 , the controller  130  may determine that the compressor  111  is in the dangerous state, send the indoor unit  120  a control signal to control the air flow on the side of the indoor unit  120  to be low, and turn off the subcooling control mode. In this regard, the air flow on the side of the indoor unit is not exclusively regulated to the low level but to any level for the pressure value of the compressor  111  to enter the normal range. 
     If the pressure value of the compressor  111  has been less than a second pressure threshold in the maintenance range for a predetermined time since the controller  130  controlled the air flow on the side of the indoor unit to be the necessary air flow for now and turned off the subcooling control mode, the controller  130  may control the air flow on the side of the indoor unit to be the set air flow and keep on turning off the subcooling control mode (that is, maintain the subcooling control mode to be off). The maintenance range may refer to a mid range between the normal range and the dangerous range that may affect degradation of the compressor&#39;s  111  performance, in which it is determined that the pressure value of the compressor  111  deviates from the normal range but has not fully entered the normal range. Controlling the air flow on the side of the indoor unit to the set air flow means to return to the user-set air flow before the compressor protection mode was operated and the initially-set air flow set during initial setting of the indoor unit  120 . For example, it may mean to control the air flow on the indoor side to be higher than the current air flow. 
     If the pressure value of the compressor  111  has been less than a third pressure threshold in the normal range for a predetermined time since the controller  130  controlled the air flow on the side of the indoor unit to be the set air flow and kept on turning off the subcooling control mode, the controller  130  may turn on the subcooling control mode. The normal range may refer to a range of pressure values that may maintain the compressors performance in good state. Turning on the subcooling control mode means to control the subcooling degree by opening the electronic expansion valve for subcooling control  119  and EVI bypass during operation. 
       FIG. 5  is a graph representing a range of protection control values for compressor envelope protection control, in which ‘A’ represents a range of protection control values including a high temperature region. If the pressure value of the compressor  111  exceeds a pressure threshold and deviates from the range of protection control values, as represented by point B (58-degree overvoltage), the controller  130  may enable the compressor  111  to be operated within the range of protection control values by changing the air flow on the side of the indoor unit and mode of the electronic expansion valve for subcooling control  119 . 
     In the meantime, the controller  130  may compare the saturation temperature measured from the sensor for measuring the compressors state  117  with a temperature threshold, and accordingly control the air flow on the side of the indoor unit. The temperature threshold may be a value of a saturation temperature corresponding to a pressure value with respect to the range of protection control values for protecting the compressors  111  performance. 
     The controller  130  may be further configured to control not only the air flow on the side of the indoor unit but also the subcooling control mode according to a result of comparing the saturation temperature with the temperature threshold. The subcooling control means to control a subcooling degree by controlling the electronic expansion valve for subcooling control  115  and an EVI bypass (not shown). 
     More specifically, the controller  130  may adjust the air flow on the side of the indoor unit to necessary air flow for now and turn off the subcooling control mode, if the saturation temperature of the compressor  111  has exceeded a first temperature threshold in the dangerous range for a predetermined time. The necessary air flow may be defined as air flow required for the pressure value of the compressor  111  corresponding to the saturation temperature to reach the normal range. Turning off the subcooling control mode means to regulate the electronic expansion valve for subcooling control  119  to 0 step and control the subcooling degree by opening the EVI bypass, during operation. The dangerous range refers to a pressure range that may affect degradation of the compressors  111  performance, and the first temperature threshold may refer to a temperature value corresponding to a pressure in the dangerous range. 
     If the saturation temperature has been less than a second temperature threshold in the maintenance range for a predetermined time since the controller  130  controlled the air flow on the side of the indoor unit to be the necessary air flow for now and turned off the subcooling control mode, the controller  130  may control the air flow on the side of the indoor unit to be the set air flow and keep on turning off the subcooling control mode. 
     The maintenance range may refer to a mid range between the normal range and the dangerous range that may affect degradation of the compressors  111  performance, in which it is determined that the saturation temperature deviates from the dangerous pressure range but has not fully entered the normal range. 
     Controlling the air flow on the side of the indoor unit to the set air flow means to return to the user-set air flow before the compressor protection mode was operated and the initially-set air flow set during initial setting of the indoor unit  120 . For example, it may mean to control the air flow on the indoor side to be higher than the current air flow. 
     If the saturation temperature has been less than a third temperature threshold in the normal range for a predetermined time since the controller  130  controlled the air flow on the side of the indoor unit to be the set air flow and kept on turning off the subcooling control mode, the controller  130  may turn on the subcooling control mode. The normal range may refer to a range of pressure values that may maintain the compressor&#39;s performance in good state. Turning on the subcooling control mode means to control the subcooling degree by opening the electronic expansion valve for subcooling control  119  and EVI bypass during operation. 
     The controller  130  may be included on the side of the outdoor unit, but is not limited thereto. Of course, the controller  130  may include functions to control the air flow on the side of the indoor unit. The controller  130  may switch the mode of indoor fans  122   a ,  122   b ,  122   c , and  122   d  on the side of the indoor unit  120  by sending the indoor unit  120  a signal to control the air flow on the side of the indoor unit  120 . 
       FIG. 3  is a flowchart illustrating a method for controlling an air conditioner, according to an embodiment of the present disclosure, which will be described with reference to  FIG. 5  showing a graph representing a range of suction pressure and discharge pressure for compressor protection control. 
     First, in operation S 101 , the air conditioner  100  operates compressor protection mode. The compressor protection mode may be manually selected by the user selecting a separate button, or may be automatically selected by being matched to a particular condition set for the air conditioner  100 . 
     In operation S 103 , the air conditioner  100  may detect a pressure value by measuring suction pressure and discharge pressure of the compressor  111 . 
     The air conditioner  100  may then compare the pressure value of the compressor  111  with a pressure threshold and accordingly control air flow on the side of the indoor unit. The air flow on the side of the indoor unit may include a user-set air flow manipulated by the user and an initially-set air flow set in initially setting the indoor unit. The initially-set air flow may refer to not only the air flow set in initially setting the indoor unit  120  but also air flow set for safety of the indoor unit  120 , and may be distinguished from the user-set air flow set by the user manipulating an input button. The controller  130  of the air conditioner  100  may control at least one of the user-set air flow and initially-set air flow in regulating the air flow on the side of the indoor unit. In other words, the controller  130  may only control the user-set air flow set by manipulation of the user for the air conditioner  100 , may only control the initially-set air flow set for the air conditioner  100  by an operator, or may control both the user-set air flow and the initially-set air flow, in regulating the air flow on the side of the indoor unit. 
     The pressure threshold is set based on the range of protection control values for protecting the compressors  111  performance, and the range of protected control values may be represented by an area encircled by a solid or dashed line, as shown in  FIG. 5 . The range of the protection control values may be defined as a range of pressure values that may protect the compressors performance in good state. 
     For example, the pressure threshold may be set to be in a dangerous range if exceeding 1.5 MPa, g with respect to the suction pressure, and 1.4 MPa, g of the pressure threshold with respect to the suction pressure may be set to be in a normal but maintenance range to further check the state of the compressor  111  in a phase of entering the normal range from the dangerous range. However, the pressure threshold is not limited thereto, but may vary by an operator. 
     In the meantime, the air conditioner  100  may also control subcooling mode according to a result of comparing the pressure value of the compressor and the pressure threshold while controlling the air flow on the side of the indoor unit. 
     The subcooling control means to control a subcooling degree by controlling the electronic expansion valve for subcooling control  119  and an EVI bypass (not shown). 
     More specifically, in operation S 105 , the air conditioner  100  may determine whether the pressure value of the compressor  111  has exceeded the first pressure threshold in the dangerous range for a predetermined time. 
     If it is determined that the pressure value of the compressor  111  has exceeded the first pressure threshold for the predetermined time, the air conditioner  100  may adjust the air flow on the side of the indoor unit to a necessary air flow for now and turn off the subcooling control mode, in operation S 107 . At this time, it may be possible for the air conditioner  100  to adjust only the air flow on the side of the indoor unit. 
     The necessary air flow may be defined as air flow required for the pressure value of the compressor  111  to reach the normal range. Turning off the subcooling control mode means to regulate the electronic expansion valve for subcooling control  119  to 0 step and control the subcooling degree by opening the EVI bypass during operation. 
     In operation S 109 , the air conditioner  100  may determine whether the pressure value of the compressor  111  has been less than a second pressure threshold in a maintenance range for a predetermined time. The maintenance range may refer to a mid range between the dangerous range that may affect degradation of the compressor&#39;s  111  performance and the normal range, in which it is determined that the pressure value of the compressor  111  deviates from the normal range but has not fully entered the normal range. 
     If it is determined that the pressure value of the compressor  111  has been less than the second pressure threshold for the predetermined time, the air conditioner  100  may adjust the air flow on the side of the indoor unit to a set air flow and keep on turning off the subcooling control mode, in operation S 111 . Controlling the air flow on the side of the indoor unit to the set air flow means to return to the user-set air flow before the compressor protection mode was operated and the initially-set air flow set during initial setting of the indoor unit  120 . For example, it may mean to control the air flow on the indoor side to be higher than the current air flow. 
     In operation S 113 , the air conditioner  100  may determine whether the pressure value of the compressor  111  has been less than a third pressure threshold in a normal range for a predetermined time. 
     If it is determined that the pressure value of the compressor  111  has been less than the third pressure threshold for the predetermined time, the air conditioner  100  may turn on the subcooling control mode and release the compressor protection mode in operations S 115  and S 117 . Turning on the subcooling control mode means to control the subcooling degree by opening the electronic expansion valve for subcooling control  119  and EVI bypass during operation. 
       FIG. 4  is a flowchart illustrating a method for controlling an air conditioner, according to another embodiment of the present disclosure. 
     First, in operation S 201 , the air conditioner  100  operates compressor protection mode. The compressor protection mode may be manually selected by the user selecting a separate button, or may be automatically selected by being matched to a particular condition set for the air conditioner  100 . 
     In operation S 203 , the air conditioner  100  may detect a saturation temperature. 
     The saturation temperature may refer to one measured from the outdoor temperature sensor  140  during condensation or others measured from indoor temperature sensors  123   a ,  123   b ,  123   c , and  123   d  during evaporation, which corresponds to the pressure value of the compressor  111 . 
     The air conditioner  100  may then compare the saturation temperature with a saturation temperature threshold and accordingly control air flow on the side of the indoor unit. The air flow on the side of the indoor unit may include a user-set air flow manipulated by the user and an initially-set air flow set in initially setting the indoor unit. The initially-set air flow may refer to not only the air flow set in initially setting the indoor unit  120  but also air flow set for safety of the indoor unit  120 , and may be distinguished from the user-set air flow set by the user manipulating an input button. The controller  130  of the air conditioner  100  may control at least one of the user-set air flow and initially-set air flow in regulating the air flow on the side of the indoor unit. In other words, the controller  130  may only control the user-set air flow set by manipulation of the user for the air conditioner  100 , may only control the initially-set air flow set for the air conditioner  100  by an operator, or may control both the user-set air flow and the initially-set air flow, in regulating the air flow on the side of the indoor unit. 
     Furthermore, the saturation temperature threshold may be set based on a saturation temperature corresponding to a pressure value in a range of protection control values for protecting the compressors  111  performance. The range of the protection control values may be defined as a range of pressure values that may protect the compressors performance in good state. 
     In the meantime, the air conditioner  100  may also control subcooling mode according to a result of comparing the saturation temperature and the saturation temperature threshold in controlling the air flow on the side of the indoor unit. The subcooling control means to control a subcooling degree by controlling the electronic expansion valve for subcooling control  119  and an EVI bypass (not shown). 
     More specifically, in operation S 205 , the air conditioner  100  may determine whether the saturation temperature has exceeded a first temperature threshold in a dangerous range for a predetermined time. 
     If it is determined that the saturation temperature has exceeded the first temperature threshold for the predetermined time, the air conditioner  100  may adjust the air flow on the side of the indoor unit to necessary air flow for now and turn off the subcooling control mode, in operation S 207 . At this time, it may be possible for the air conditioner  100  to adjust only the air flow on the side of the indoor unit. 
     The necessary air flow may be defined as air flow required for the pressure value of the compressor  111  corresponding to the saturation temperature to reach the normal range. 
     Turning off the subcooling control mode means to regulate the electronic expansion valve for subcooling control  119  to 0 step and control the subcooling degree by opening the EVI bypass during operation. 
     In operation S 209 , the air conditioner  100  may determine whether the saturation temperature has been less than a second temperature threshold in a maintenance range for a predetermined time. The maintenance range may refer to a mid range between the normal range and the dangerous range that may affect degradation of the compressor&#39;s  111  performance, in which it is determined that the saturation temperature deviates from the dangerous pressure range but has not fully entered the normal range. 
     If it is determined that the saturation temperature has been less than the second temperature threshold for the predetermined time, the air conditioner  100  may adjust the air flow on the side of the indoor unit to a set air flow and keep on turning off the subcooling control mode, in operation S 211 . Controlling the air flow on the side of the indoor unit to the set air flow means to return to the user-set air flow before the compressor protection mode was operated and the initially-set air flow set during initial setting of the indoor unit  120 . For example, it may mean to control the air flow on the indoor side to be higher than the current air flow. 
     In operation S 213 , the air conditioner  100  may determine whether the saturation temperature has been less than a third temperature threshold in a normal range for a predetermined time. 
     If it is determined that the saturation temperature has been less than the third temperature threshold for the predetermined time, the air conditioner  100  may turn on the subcooling control mode and release the compressor protection mode in operations S 215  and S 217 . Turning on the subcooling control mode means to control the subcooling degree by opening the electronic expansion valve for subcooling control  119  and EVI bypass during operation. 
     In typical compressor control, frequency or varying capacity of the compressor may be controlled to be reduced without controlling other factors. Especially, under high temperature conditions, an air conditioner like a system air conditioner is operated such that frequency or capacity of the compressor may be reduced to its minimum since the saturation temperature is high due to the surrounding temperature. However, as the compressor reaches the hardware limit, the compressor may be operated out of a range of protection control values, thereby reducing the reliability of the compressor. 
     In accordance with embodiments of the present disclosure, adjusting the air flow on the side of an indoor unit based on the range of protection control values for the compressor in the compressor protection control mode may increase the reliability of the compressor and a customers satisfaction in the product in a high temperature region. Since measurements of the compressors low pressure range depend on installation rate of indoor unit, an air conditioner in accordance with embodiments of the present disclosure may have an advantage of controlling the compressors performance according to the installation rate of indoor rate. In other words, in accordance with embodiments of the present disclosure, in operation of the compressor under high temperature conditions, having the compressor operate in a range of protection control values may increase the reliability of the compressor. Furthermore, in accordance with embodiments of the present disclosure, adjusting the air flow of an indoor unit based on an operation range may enable the operation range to be expanded and enable continuous operation. 
     Various operations are described herein as being performed by the controller  130 . The controller  130  may include, for example, a memory storing computer-executable instructions, and a computer processor to execute the instructions stored in the memory, to thereby perform the operations. However, the controller  130  is not limited to including any specific components, or to any specific structure or configuration. 
     According to the embodiments of the present disclosure, regulating air flow on the side of an indoor unit by taking into account a pressure range of a compressor during protection control of the compressor may increase reliability of the compressor and controlling the air conditioner actively may expand its operating range, thereby increasing the users feeling of satisfaction with the air conditioner. 
     Several embodiments have been described, but a person of ordinary skill in the art will understand and appreciate that various modifications can be made without departing the scope of the present disclosure. Thus, it will be apparent to those ordinary skilled in the art that the disclosure is not limited to the embodiments described, which have been provided only for illustrative purposes.