Improved control method for variable volume ratio valve

Abstract

This application relates to improved control methods for variable displacement ratio valves. A variable displacement ratio compressor can be controlled using a switching parameter based on compressor speed and suction density to improve the match of the compressor displacement ratio to desired discharge conditions. A delay period can be implemented in determining when to change the displacement ratio to control the frequency of changing the displacement ratio. The switching parameter can be the product of the compressor speed and suction density. The displacement ratio of the compressor can be controlled by a switching valve that directs pressure to pistons of a variable displacement ratio system of the compressor.

Description

[0001] This application is a divisional application of Chinese patent application No. 201911325276.6, filed on December 20, 2019, entitled "Improved Control Method for Variable Volume Ratio Valve". Technical Field

[0002] This disclosure relates to a method and system for controlling a control valve for controlling the volume ratio of a variable volume ratio compressor. Specifically, this disclosure relates to controlling the volume ratio of a compressor based on the compressor mass flow rate, which is determined by inputs (e.g., suction density and compressor speed). Background Technology

[0003] The compressor may include hardware that allows adjustment of the compressor's volumetric ratio. Changing the compressor's volumetric ratio affects the compressor's discharge conditions. Changes in the volumetric ratio affect the compressor's performance under partial load conditions, thereby increasing or decreasing the compressor's efficiency at both partial and full load, depending on whether the volumetric ratio was correctly selected for the compressor's set of operating conditions. Summary of the Invention

[0004] This disclosure relates to a method and system for controlling a control valve for controlling the volume ratio of a variable volume ratio compressor. Specifically, this disclosure relates to controlling the volume ratio of a compressor based on the compressor mass flow rate, which is determined by inputs (e.g., suction density and compressor speed).

[0005] Variable volume ratio compressors allow the volume ratio to be changed between at least two settings, which can improve the matching of compressor discharge conditions with pressure conditions at the condenser of the refrigerant circuit that includes the compressor, thereby increasing efficiency.

[0006] In certain situations, such as when the compressor is operating near switching conditions, automatic volume ratio switching may occur frequently. This high-frequency switching can cause additional wear on components of a variable volume ratio system. Delay periods can be incorporated into determining and implementing changes to the volume ratio, thereby providing more consistent operation over time and reducing potential excessive variations in the compressor's volume ratio.

[0007] In one embodiment, the compressor system includes a variable volume ratio compressor configured to operate at one of a plurality of different volume ratios and having a suction inlet. The compressor system also includes a controller. The controller is configured to obtain the operating speed of the variable volume ratio compressor and the refrigerant density at the suction inlet of the variable volume ratio compressor. The controller is also configured to determine switching parameters based on the operating speed and refrigerant density. The controller is further configured to determine whether to change the volume ratio of the variable volume ratio compressor based on switching conditions and the switching parameters. When the controller determines that a change in volume ratio is to be made, the controller guides the change in volume ratio during the operation of the variable volume ratio compressor.

[0008] In this embodiment, the multiple different volume ratios are two different volume ratios.

[0009] In one embodiment, the compressor system includes one or more sensors located at the suction inlet of the variable volume ratio compressor, and the controller obtains the refrigerant density based on the output of the one or more sensors.

[0010] In an embodiment, the output of the one or more sensors includes inhalation pressure and inhalation temperature.

[0011] In this embodiment, the switching parameter determined by the controller is the product of the operating speed and the refrigerant density.

[0012] In this embodiment, the switching condition is a linear function of the operating speed and the refrigerant density.

[0013] In one embodiment, the compressor system includes a piston, a first valve, and a second valve. The first valve is configured to communicate with a first pressure, and the second valve is configured to communicate with the piston with a second pressure different from the first pressure, and the piston is configured to be positioned by the received pressure. In one embodiment, the first pressure is the pressure at the inlet of the variable volume ratio compressor, and the second pressure is the pressure at the midpoint of the variable volume ratio compressor. In one embodiment, a controller guides changes in the volume ratio during operation of the variable volume ratio compressor by guiding changes in the position of each of the first and second valves.

[0014] An embodiment of a method for controlling a variable volume ratio compressor includes: obtaining the suction density and operating speed of the variable volume ratio compressor. The method further includes: determining a switching parameter based on the suction density and operating speed. The method also includes: determining whether to change the volume ratio of the variable volume ratio compressor; and when it is determined that the volume ratio of the variable volume ratio compressor should be changed, changing the volume ratio of the variable volume ratio compressor. In this embodiment, the switching parameter is a function of the suction density of the variable volume ratio compressor and the operating speed of the compressor.

[0015] In this embodiment, determining the switching parameters includes: first determining the switching parameters; waiting for a delay period for the switching parameters; and second determining the switching parameters; and based on the second determined switching parameters, determining whether to change the volume ratio of the variable volume ratio compressor. In this embodiment, the delay period for the switching parameters is approximately five (5) minutes.

[0016] In one embodiment, the method includes waiting for a volume ratio change delay period after changing the compressor's volume ratio. In another embodiment, this volume ratio change delay period is approximately fifteen (15) minutes.

[0017] In this embodiment, the switching parameter is the product of the suction density of the variable volume ratio compressor and its operating speed.

[0018] In this embodiment, the switching condition is a linear function of the product of the suction density of the variable volume ratio compressor and its operating speed.

[0019] In one embodiment, changing the volume ratio of the variable volume ratio compressor includes switching the compressor from a first volume ratio to a second volume ratio by changing the position of each of a first valve and a second valve, wherein the first valve is in fluid communication with a first pressure source, and the second valve is in fluid communication with a second pressure source different from the first pressure. In another embodiment, the first pressure is the suction pressure of the variable volume ratio compressor, and the second pressure is an intermediate pressure within the compressor. In yet another embodiment, the first and second valves are configured to supply either the first or the second pressure to a piston within the compressor. Attached Figure Description

[0020] Figure 1 A compressor system and refrigerant circuit according to an embodiment are shown.

[0021] Figure 2 A flowchart of a method for controlling a compressor system according to an embodiment is shown.

[0022] Figure 3 A flowchart illustrating an embodiment of a compressor control system is shown. Detailed Implementation

[0023] This disclosure relates to a method and system for controlling a control valve of a variable volume ratio compressor. Specifically, this disclosure relates to controlling the volume ratio of a compressor based on the compressor's suction density and velocity.

[0024] Figure 1A compressor system 100 according to an embodiment is shown. The compressor system 100 includes a variable volume ratio compressor 102, one or more sensors 104 at or near the suction port 108 of the compressor 102, and a controller 106. The compressor 102 is incorporated into a refrigerant circuit including a condenser 110, an expansion device 112, and an evaporator 114. In an embodiment, the controller 106 is operably connected to solenoid valves 116, 118, which control whether pressure from the compressor suction port 108 or intermediate point 120 acts on the piston 122 of the compressor 102 to adjust the volume ratio of the compressor 102.

[0025] Compressor 102 is a variable volume ratio compressor configured to operate at multiple different volume ratios. The variable volume ratio compressor 102 operates at a volume ratio that can be determined by controller 106. This volume ratio can be changed by a variable volume ratio system. In an embodiment, compressor 102 is configured to operate at two different volume ratios. In an embodiment, compressor 102 switches between these two volume ratios by the movement of piston 122. In an embodiment, piston 122 is controlled by changing the pressure applied to piston 122 between the compressor's suction pressure at suction inlet 108 and the intermediate oil pressure at midpoint 120 within the compressor. Although Figure 1 The illustrated embodiment relates to a piston 122 controlled by applying suction or intermediate pressure; however, it should be understood that other variable volume ratio systems for compressors can be used. In one embodiment, the compressor 102 is configured to vary between different volume ratios via the operation of a slide valve. In another embodiment, the volume ratio of the compressor 102 is changed by the operation of a stepper motor. In yet another embodiment, the volume ratio of the compressor 102 can vary continuously within a range of volume ratio states.

[0026] One or more sensors 104 are configured to obtain the refrigerant density at the suction inlet 108 of the compressor 102, either individually or in combination with the controller 106. The one or more sensors 104 may be located at or near the suction inlet 108 of the compressor 102.

[0027] Controller 106 is configured to determine switching parameters based on the refrigerant density at suction inlet 108 and the operating speed of compressor 102. Controller 106 may obtain the refrigerant density, for example, from one or more sensors 104, or by determining the suction density from values ​​reported by one or more sensors 104. Suction density is the refrigerant density at suction inlet 108 of compressor 102. Controller 106 may obtain the compressor speed from sensors included in compressor 102, or from a controller that directs the operation of compressor 102. Controller 106 may be configured to: determine the switching parameters multiple times; implement a delay between determining the switching parameters; implement a delay between changing the compressor's volume ratio and determining the switching parameters; or perform other such operations that affect the frequency of volume ratio changes. The switching parameters may be the product of the suction density and the speed of compressor 102.

[0028] The controller 106 is also configured to determine whether to change the volume ratio of the compressor 102 based on switching parameters and switching conditions. The switching conditions may be, for example, a pressure ratio criterion. The pressure ratio criterion can provide a threshold for determining whether to switch the volume ratio of the compressor 102. The pressure ratio criterion may be specific to a component of the compressor system 100 (e.g., the compressor 102) and the refrigerant used in the refrigeration circuit of the compressor system 100. In an embodiment, the pressure ratio criterion is a linear function of the product of the suction density and the compressor speed. The switching parameters can be compared with the switching conditions at the controller 106, and this comparison can be used to determine whether to change the volume ratio of the compressor 102.

[0029] The controller 106 is also configured to direct the compressor 102 to change its volume ratio. The controller 106 can be configured to direct the compressor 102 to change its volume ratio based on switching parameters and switching conditions. In an embodiment, the controller 106 is operatively connected to a first solenoid valve 116 and a second solenoid valve 118 and is configured to direct their operation. The first solenoid valve 116 may be a valve in fluid communication with the compressor's suction inlet and is capable of applying pressure at the suction inlet 108 of the compressor 102 to the piston 122 of the compressor 102. The second solenoid valve 118 may be a valve in fluid communication with a midpoint 120 within the compressor 102 and is capable of providing pressure to the piston 122 at that midpoint 120. The pressure at the suction inlet 108 or the midpoint 118 drives the piston to a specific position, thereby changing the volume ratio of the compressor 102. The controller 106 can switch the first solenoid valve 116 to a closed position and the second solenoid valve 118 to an open position, and vice versa, to switch the compressor 102 between two different volume ratios.

[0030] Compressor 102 may be included in a refrigerant circuit comprising a condenser 110, an expansion device 112, and an evaporator 114. Refrigerant compressed and discharged by compressor 102 may be directed to condenser 110 and then from condenser 110 to expansion device 112. Expansion device 112 is a device configured to expand and reduce the pressure of the fluid, such as an expansion valve, orifice, etc. The refrigerant expanded at expansion device 112 is passed to evaporator 114 and then returned to compressor 102 at compressor suction port 108. Any refrigerant may be used in the refrigerant circuit, such as refrigerant R134(a), refrigerant R1234ze(E), or any other suitable refrigerant.

[0031] Figure 2 A flowchart of a method 200 for determining when to switch the volume ratio of a compressor according to an embodiment is shown. Method 200 includes: obtaining suction density and compressor speed 202; determining switching parameters based on compressor speed and suction density in 204; determining whether to switch the volume ratio of the compressor based on the switching parameters and switching conditions 206; and changing the volume ratio of the compressor when it is determined that the volume ratio of the compressor should be switched 208.

[0032] At 202, the suction density and compressor speed are obtained. Suction density is the refrigerant density at the compressor's suction inlet. Suction density can be obtained from one or more sensors located at or near the compressor's suction inlet. Suction density can be measured directly or calculated from the output of these sensors. In an embodiment, the suction density is calculated based on the suction pressure and suction temperature measured by the sensors and the specific refrigerant used with the compressor. For each refrigerant, the suction pressure and temperature are related to the suction density through refrigerant-specific features, for example, due to the properties of the refrigerant and its behavior as a gas. The compressor speed can be obtained from the compressor's controller, the compressor's drive (e.g., a variable frequency drive), or measured at the compressor.

[0033] In step 204, the switching parameters are determined based on compressor speed and suction density. The switching parameters are functions of compressor speed and suction density. In one embodiment, the switching parameters are the product of compressor speed and suction density. In another embodiment, the switching parameters are mass flow rates. The mass flow rate can be determined based on the compressor's volumetric flow rate and suction density.

[0034] At 206, it is determined whether to change the compressor's volumetric ratio based on switching parameters and switching conditions. Switching conditions may be, for example, a pressure ratio criterion. The pressure ratio criterion can provide a threshold for determining whether to switch the compressor's volumetric ratio. The pressure ratio criterion may be specific to the compressor and the refrigerant used in the refrigeration circuit, which includes the compressor. The pressure ratio criterion may be a function of the compressor's mass flow rate. In one embodiment, the pressure ratio criterion is a linear function of the product of the suction density and the compressor speed. In another embodiment, the pressure ratio criterion is a linear function of the mass flow rate. In yet another embodiment, the mass flow rate is the product of the suction density and the compressor speed. In yet another embodiment, the mass flow rate is the product of the suction density and the volumetric flow rate. Switching parameters can be compared with switching conditions to determine at 206 whether to change the compressor's volumetric ratio. Method 200 can be used with various refrigerants in a variable volumetric ratio compressor system. In one embodiment, the refrigerant is refrigerant 134a (R134a). In another embodiment, the refrigerant is refrigerant 513A (R513A). In this embodiment, the refrigerant is refrigerant 1234ze (R1234ze). The parameters of the function (e.g., constants) can be determined by testing the compressor efficiency under the variable volume ratio setting on the operating chart of a particular compressor.

[0035] When it is determined in step 206 that the volume ratio needs to be changed, the compressor's volume ratio is changed in step 208. The volume ratio can be changed from a first volume ratio to a second volume ratio. In an embodiment, the first and second volume ratios are two of a plurality of volume ratios. In an embodiment, the compressor switches from one of the two volume ratios to the other of the two volume ratios. In an embodiment, the switching of the compressor's volume ratio is performed by operating one or more valves to change a pressure source applied to the piston of a variable volume ratio system included in the compressor. In an embodiment, the pressure source can be switched between the compressor's intermediate oil pressure and the compressor's suction pressure. In an embodiment, in step 208, the compressor's volume ratio is changed, for example, by operating a stepper motor or by operating a slide valve.

[0036] During compressor operation, method 200 may also include, for example, a delay to avoid constant switching and to confirm when to switch the volume ratio. Figure 3 Examples of such compressor operation are provided in the document.

[0037] Figure 3 A flowchart of an example method 300 for controlling a compressor system according to an embodiment is shown. Figure 3In method 300, the switching parameters are determined for the first time (302). A delay period (304) is allowed. The switching parameters are determined for the second time (306). The switching parameters determined in 306 are used to determine whether to change the compressor's volume ratio (308). When it is determined in 308 that the compressor's volume ratio should be changed, the compressor's volume ratio is changed (310). After changing the compressor's volume ratio in 310, a second delay period (312) is allowed before returning to 302 or 304 and iterating through method 300.

[0038] The switching parameters are determined in section 302. These switching parameters can be functions of the compressor intake density and compressor speed. The intake density and compressor speed can be determined according to the above-mentioned sections 202 and 302. Figure 2 As shown. It can be obtained according to the above and Figure 2 The 204 shown indicates the switching parameters.

[0039] After the switching parameters are determined in 302, a switching parameter delay period 304 is allowed. The switching parameter delay period is the time interval between the first determination of the switching parameters in 302 and the second determination of the switching parameters in 306. The switching parameter delay period in 304 can be used to prevent excessive switching frequency, for example, by reducing the number of switching events triggered by abnormal results or transient conditions (e.g., erroneous sensor readings, temperature or pressure peaks, etc.). In an embodiment, the switching parameter delay in 304 is the time interval during which a cumulative value reaches a target, for example, by integrating the compressor speed and suction density over time and ending the switching parameter delay period in 304 when that value meets a threshold. In an embodiment, the switching parameter delay period in 304 is approximately five (5) minutes.

[0040] Once the switching parameter delay period 304 has elapsed, the switching parameters are determined a second time 306. The switching parameters are determined in the same manner as in 302, including based on the intake density and compressor speed obtained in 202, and based on the switching parameters determined in 204.

[0041] The second determination of the switching parameters in 306 can be used to determine whether the compressor's volume ratio 308 should be changed. This is done by comparing the switching parameters obtained in 306 with the switching conditions, according to the above and Figure 2 As shown in 206, the determination in 308 whether to change the volume ratio of the compressor can be performed.

[0042] When it is determined in step 308 that the compressor's volume ratio needs to be changed, the compressor's volume ratio is changed in step 310. The compressor's volume ratio can be determined according to the above and Figure 2 The 208 shown is changed in 310.

[0043] After changing the volume ratio in 310, method 300 includes allowing a volume ratio change delay period 312 to pass. In an embodiment, the volume ratio change delay period in 312 is the time interval between the change of the volume ratio in 310 and the first determination of the switching parameters in 302 during subsequent iterations of method 300 (e.g., when compressor speed and suction density values ​​are continuously obtained). In an embodiment, for example, the volume ratio change delay period may be varied based on the number of times the volume ratio is changed according to 310 within a predetermined time interval. In an embodiment, the volume ratio change delay period is in the range of one (1) minute or about one (1) minute to one (1) hour or about one (1) hour. In an embodiment, the volume ratio change delay period in 312 is about fifteen (15) minutes.

[0044] All aspects:

[0045] It should be understood that any aspect of aspects 1-9 can be combined with any aspect of aspects 10-19.

[0046] Aspect 1, a compressor system, comprising:

[0047] A variable volume ratio compressor, configured to operate at one of several different volume ratios and having a suction inlet; and

[0048] The controller is configured as follows:

[0049] The operating speed of the variable volume ratio compressor and the refrigerant density at the suction inlet of the variable volume ratio compressor are obtained;

[0050] The switching parameters are determined based on the operating speed and the refrigerant density;

[0051] Based on the switching conditions and the switching parameters, determine whether to change the volume ratio of the variable volume ratio compressor; and

[0052] When it is determined that the volume ratio will be changed, the volume ratio change is guided during the operation of the variable volume ratio compressor.

[0053] Aspect 2, the compressor system according to aspect 1, wherein the plurality of different volume ratios are two different volume ratios.

[0054] Aspect 3, the compressor system according to any one of Aspects 1-2, further includes one or more sensors located at the suction inlet of the variable volume ratio compressor, and wherein the controller obtains the refrigerant density based on the output of the one or more sensors.

[0055] Aspect 4, the compressor system according to aspect 3, wherein the outputs of the one or more sensors include inhalation pressure and inhalation temperature.

[0056] Aspect 5, the compressor system according to any one of Aspects 1-4, wherein the switching parameter determined by the controller is the product of the operating speed and the refrigerant density.

[0057] Aspect 6, the compressor system according to any one of Aspects 1-5, wherein the switching condition is a linear function of the operating speed and the refrigerant density.

[0058] Aspect 7, the compressor system according to any one of Aspects 1-6, further includes a piston, a first valve and a second valve, wherein the first valve is configured to control fluid communication between the piston and a first pressure source, the second valve is configured to control fluid communication between the piston and a second pressure source other than the first pressure source, and the piston is configured to be positioned by the received pressure.

[0059] Aspect 8, the compressor system according to aspect 7, wherein the first pressure source is the suction port of the variable volume ratio compressor, and the second pressure source is the midpoint of the variable volume ratio compressor.

[0060] Aspect 9, the compressor system according to any one of Aspects 7-8, wherein the controller guides the change in the volume ratio of the variable volume ratio compressor by guiding a change in the position of each of the first valve and the second valve.

[0061] Aspect 10, a method for controlling a variable volume ratio compressor, comprising:

[0062] Obtain the suction density and operating speed of the variable volume ratio compressor;

[0063] The switching parameters are determined based on the inhalation density and the operating speed;

[0064] Based on the switching parameters and switching conditions, determine whether to change the volume ratio of the variable volume ratio compressor; and

[0065] When it is determined that the volume ratio of the variable volume ratio compressor will subsequently be changed, the volume ratio of the variable volume ratio compressor will be changed.

[0066] The switching parameter is a function of the suction density of the variable volume ratio compressor and the operating speed of the compressor.

[0067] Aspect 11, according to the method of aspect 10, wherein determining the switching parameters includes:

[0068] The switching parameters are determined for the first time;

[0069] Waiting for the parameter switching delay period; and

[0070] The switching parameters are determined a second time, and

[0071] The determination of whether to change the volume ratio of the variable volume ratio compressor is based on the switching parameters determined in the second step.

[0072] Aspect 12, according to the method of aspect 11, wherein the switching parameter delay period is approximately five (5) minutes.

[0073] Aspect 13, the method according to any one of aspects 10-12, further includes waiting for a volume ratio change delay period after changing the volume ratio of the compressor.

[0074] Aspect 14, according to the method of aspect 13, wherein the volume ratio change delay period is approximately fifteen (15) minutes.

[0075] Aspect 15, the method according to any one of Aspects 10-14, wherein the switching parameter is the product of the suction density and the operating speed of the variable volume ratio compressor.

[0076] Aspect 16, the method according to any one of Aspects 10-15, wherein the switching condition is a linear function of the product of the suction density and the operating speed of the variable volume ratio compressor.

[0077] Aspect 17, the method according to any one of Aspects 10-16, wherein changing the volume ratio of the variable volume ratio compressor comprises: switching the variable volume ratio compressor from a first volume ratio to a second volume ratio by changing the position of each of the first valve and the second valve, wherein the first valve is in fluid communication with a first pressure source and the second valve is in fluid communication with a second pressure source different from the first pressure.

[0078] Aspect 18, according to the method of aspect 17, wherein the first pressure is the suction pressure of the variable volume ratio compressor, and the second pressure is the intermediate pressure within the variable volume ratio compressor.

[0079] Aspect 19, the method according to any one of Aspects 17-18, wherein the first valve and the second valve are configured to provide one of the first pressure or the second pressure to a piston within the variable volume ratio compressor.

[0080] In all respects, the examples disclosed in this application are to be considered illustrative rather than restrictive. The scope of the invention is indicated by the appended claims rather than the foregoing description; and all modifications within the meaning and scope of equivalents of the claims should be included therein.

Claims

1. A compressor system, comprising: A variable volume ratio compressor is configured to operate at one of a number of different volume ratios and has a suction inlet; and The controller is configured as follows: The switching parameters are determined for the first time, wherein the switching parameters are the mass flow rate of the refrigerant through the compressor; After the switching parameters are determined for the first time, wait for a delay period. The switching parameters are determined a second time after the aforementioned delay period. Based on the switching parameters and switching conditions determined in the second step, it is determined whether to change the volume ratio of the variable volume ratio compressor, wherein the switching condition is a pressure ratio standard, and the pressure ratio standard provides a threshold for determining whether to switch the compressor volume ratio; and When it is determined that the volume ratio needs to be changed, the volume ratio of the variable volume ratio compressor is changed from a first volume ratio to a second volume ratio; and The compressor system further includes a piston, a first valve, and a second valve, wherein the first valve is configured to control fluid communication between the piston and a first pressure source, the second valve is configured to control fluid communication between the piston and a second pressure source other than the first pressure source, and the piston is configured to be positioned by the received pressure.

2. The compressor system according to claim 1, wherein, The first pressure source is the suction port of the variable volume ratio compressor, and the second pressure source is the midpoint of the variable volume ratio compressor.

3. The compressor system according to claim 1, wherein, The controller guides the change in the volume ratio of the variable volume ratio compressor by guiding a change in the position of each of the first and second valves.

4. The compressor system according to claim 1, wherein, The switching parameter is a function of the refrigerant density and the operating speed of the variable volume ratio compressor.

5. The compressor system according to claim 1, wherein, The pressure ratio standard is a linear function of the product of the refrigerant density and the operating speed of the variable volume ratio compressor.

6. The compressor system according to claim 1, wherein, The refrigerant is one of R134a, R513a, and R1234ze.

7. A method for controlling a variable volume ratio compressor, comprising: The first acquisition of the refrigerant mass flow rate through the compressor; Wait for a delay period after the first acquisition of the quality flow rate; The quality flow rate is acquired a second time after the aforementioned delay period; Set the second obtained mass flow rate as the switching parameter; The decision to change the volume ratio of the variable volume ratio compressor is based on the switching parameters and switching conditions, wherein the switching condition is a pressure ratio standard, and the pressure ratio standard provides a threshold for determining whether to switch the compressor volume ratio; and When it is determined that the volume ratio of the variable volume ratio compressor needs to be changed, the volume ratio of the variable volume ratio compressor is changed from the first volume ratio to the second volume ratio; The method further includes: controlling fluid communication between the piston and a first pressure source; controlling fluid communication between the piston and a second pressure source different from the first pressure source; and positioning the piston by the received pressure.

8. The method according to claim 7, wherein, The switching parameter is a function of the suction density and operating speed of the variable volume ratio compressor.

9. The method according to claim 7, wherein, The pressure ratio standard is a linear function of the product of the suction density and the operating speed of the variable volume ratio compressor.

10. The method according to claim 7, wherein, The refrigerant is one of R134a, R513a, and R1234ze.

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