Control method for electronic expansion valve of air conditioner of rail train

Abstract

The invention discloses a control method for an electronic expansion valve of an air conditioner of a rail train, and belongs to the technical field of refrigeration control of rail vehicles. The method comprises the following steps: S1, determining an actual superheat degree value according to the rotating speed of a compressor, the actual outlet pressure of an evaporator and the outlet temperature of the evaporator; s2, according to the actual air supply temperature and the target air outlet temperature in the vehicle, the valve element movement rate of the electronic expansion valve is calculated; s3, a superheat degree target value is determined according to the outdoor environment temperature, the in-vehicle target temperature and the in-vehicle return air temperature; and S4, according to the frequency of the compressor, the difference between the actual heat value and the target superheat value is compared, the superheat error is obtained, and the opening degree of the electronic expansion valve is controlled. According to the control method for the rail train air conditioner electronic expansion valve, errors are removed, the opening proportion of the electronic expansion valve is accurately calculated, the opening of the expansion valve can be accurately positioned, and the liquid supply amount control precision of an evaporator is improved.

Description

Technical Field

[0001] The invention relates to a control method for an electronic expansion valve of a rail train air conditioner, and belongs to the technical field of rail vehicle refrigeration control. Background Art

[0002] At present, as a key component in rail air-conditioning systems, the precise control of expansion valves is of great significance to the stable operation of the system, high efficiency and energy saving, and meeting user needs. With the continuous development of technology, expansion valves are becoming increasingly complex and diversified.

[0003] At present, rail air conditioning is controlled by electronic expansion valves, which are widely used in rail air conditioning units. It can control the liquid supply of the evaporator and throttle the saturated liquid refrigerant. The working principle of the thermal expansion valve is based on force balance. Figure 1 As shown, when working, the upper part of the elastic metal diaphragm of the electronic expansion valve 1 is acted by the pressure P3 of the working fluid in the temperature-sensing package, and the lower part is acted by the pressure P2 of the evaporator outlet and the spring force P1. Under the action of the three forces, the diaphragm bulges upward or sinks downward, thereby closing or opening the valve hole to adjust the liquid supply of the evaporator 2. When the amount of liquid entering the evaporator 2 is less than the heat load requirement of the evaporator 2, the superheat of the steam at the outlet of the evaporator 2 increases, and the pressure above the diaphragm is greater than the pressure below, which forces the diaphragm to bulge downward, compress the spring through the push rod, and push the valve needle open, so that the valve hole is opened, and the liquid supply increases. On the contrary, when the liquid supply is greater than the heat load requirement of the evaporator 2, the superheat of the steam at the outlet decreases, the pressure in the temperature-sensing system decreases, and the force above the diaphragm is less than the force below, so that the diaphragm bulges upward, the spring stretches, the push rod moves upward, and the valve hole is closed, and the liquid supply to the evaporator 2 is reduced accordingly.

[0004] The superheat of the electronic expansion valve consists of the opening superheat and the effective superheat. The opening superheat is related to the preload of the spring, and the effective superheat is related to the strength of the spring and the stroke of the valve needle. The spring of the expansion valve is designed according to standard working conditions. Under standard working conditions, the unit maintains a high refrigeration coefficient when it is fully loaded or variable load. However, under large pressure difference conditions, the evaporation pressure decreases, and the amount of liquid required by the evaporator load decreases, but the actual situation is the opposite. Under the condition of unchanged suction superheat, due to the decrease in evaporation pressure, the evaporator outlet pressure P2 decreases accordingly, and the pressure difference between the upper and lower parts of the diaphragm increases, so that the main valve opening increases and the liquid supply increases; but under small pressure difference conditions, the evaporation pressure increases, and the amount of liquid required by the evaporator load increases, but the actual situation is that under the condition of unchanged suction superheat, due to the increase in evaporation pressure, the evaporator outlet pressure P2 increases accordingly, and the pressure difference between the upper and lower parts of the diaphragm decreases, so that the main valve opening decreases and the liquid supply decreases; the same is true under variable load.

[0005] As a key component in refrigeration and air conditioning systems, the precise control of electronic expansion valves is of great significance to the stable operation of the system, high efficiency and energy saving, and meeting user needs. With the continuous development of technology, the control logic of electronic expansion valves has become increasingly complex and diversified.

[0006] However, the existing electronic expansion valve control has the following defects:

[0007] 1. Reaction lag: It responds relatively slowly to changes in evaporator load, resulting in unstable operation and reduced efficiency of the refrigeration system.

[0008] 2. Imprecise superheat control: It is difficult to achieve very precise superheat control, which may affect the performance and energy efficiency of the system.

[0009] 3. Limited adjustment range: In some applications where the working conditions vary greatly, the adjustment range may not be able to meet the needs.

[0010] 4. Affected by ambient temperature: Changes in ambient temperature may affect the working characteristics of the thermal expansion valve, resulting in inaccurate control.

[0011] 5. Complex installation and debugging: Professionals are required to carry out correct installation and debugging, otherwise the ideal control effect may not be achieved.

[0012] 6. Sensitive to refrigerant charge: Small changes in refrigerant charge may significantly affect the performance of the thermal expansion valve.

[0013] 7. Unsuitable for variable flow system: In variable flow refrigeration system, the control effect of thermal expansion valve is often poor. Summary of the invention

[0014] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a control method for an electronic expansion valve of a rail train air conditioner, eliminate errors, accurately calculate the opening ratio of the electronic expansion valve, accurately position the expansion valve opening, and improve the control accuracy of the evaporator liquid supply.

[0015] In order to solve the above technical problems, the technical solution of the present invention is:

[0016] A control method for an electronic expansion valve of a rail train air conditioner comprises the following steps:

[0017] Step S1, determining the actual value of superheat according to the compressor speed, the actual evaporator outlet pressure and the evaporator outlet temperature;

[0018] Step S2, calculating the valve core movement rate of the electronic expansion valve according to the actual air supply temperature and the target air outlet temperature in the vehicle;

[0019] Step S3, determining a superheat target value according to the outdoor ambient temperature, the target temperature in the vehicle, and the return air temperature in the vehicle;

[0020] Step S4: Compare the difference between the actual heat value and the superheat target value according to the compressor frequency, obtain the superheat error, and control the opening of the electronic expansion valve.

[0021] Furthermore, in step S1, the calculation formula of the actual superheat value SH_msm is:

[0022] SH_msm = T1-Y;

[0023] Among them, T1 is the evaporator outlet temperature, and Y is the saturation temperature corresponding to the actual pressure at the evaporator outlet;

[0024] The calculation formula of saturation temperature Y is:

[0025] Y=0.0006*X 5 -0.0215*X 4 +0.3312*X 3 -2.7118*X 2 +16.314*X-35.738;

[0026] Where X is the actual pressure at the evaporator outlet.

[0027] Further, in step S2, calculating the valve core movement rate of the electronic expansion valve specifically includes the following steps:

[0028] The valve port flow area A of the electronic expansion valve is expressed as:

[0029]

[0030] Where, h is the valve needle opening; β is the valve needle cone angle; d is the valve needle aperture;

[0031] Mass flow rate of electronic expansion valve m r The solution is obtained by using the basic hydraulic formula obtained by the Bernoulli equation considering the resistance loss. The mass flow rate m of the electronic expansion valve r That is, the valve core movement rate of the electronic expansion valve, the mass flow rate of the electronic expansion valve m r The calculation formula is:

[0032]

[0033] Among them, C D is the flow coefficient of the electronic expansion valve; ρ in P is the refrigerant density at the inlet of the electronic expansion valve; in is the refrigerant pressure at the inlet of the electronic expansion valve, P outis the refrigerant pressure at the outlet of the electronic expansion valve;

[0034] Flow coefficient C of electronic expansion valve D The calculation formula is:

[0035]

[0036] Among them, v out It is the specific volume of refrigerant at the outlet of the electronic expansion valve.

[0037] Further, in step S4, according to the compressor frequency, the difference between the actual heat value and the superheat target value is compared to obtain the superheat error, and the opening of the electronic expansion valve is controlled, which specifically includes the following steps:

[0038] Step S41, the electronic expansion valve is initialized and powered on, the electronic expansion valve is reset, and the opening of the electronic expansion valve is closed by 110%; when the power is turned on, the opening of the electronic expansion valve is closed by 10%*(1+T / 24), and then the opening of the electronic expansion valve is opened to the initial opening; wherein T is the time from the last reset action;

[0039] Step S42: Calculate the difference between the actual heat value SH_msm and the superheat target value SH_stp to obtain the superheat error err. The calculation formula of the superheat error err is:

[0040] err = SH_stp - SH_msm;

[0041] The deadband of the unsafe operating temperature range of the electronic expansion valve is ±0.5°C. The superheat error is judged based on the deadband of the unsafe operating temperature range of the electronic expansion valve, and the superheat error is redefined according to the judgment result.

[0042] Step S43, calculating the opening increment of the electronic expansion valve;

[0043] Step S44: Control the opening of the electronic expansion valve according to the electronic expansion valve opening increment ΔEXV_cmd.

[0044] Furthermore, in step S41, the calculation formula of the initial opening of the electronic expansion valve is as follows:

[0045] In cooling mode, the calculation formula for the initial opening of the electronic expansion valve EXV_opening is:

[0046] EXV_opening=0.1185986938+0.005613955683*CompSpd-0.003193849031*OAT+

[0047] 0.008823342804*RAT;

[0048] Among them, CompSpd is the compressor frequency, CompSpd = 16.67 ~ 71.67Hz, corresponding to the speed of 1000 ~ 4300RPM; OAT is the outdoor ambient temperature, OAT = 10 ~ 50℃; RAT is the return air temperature in the car, RAT = 8 ~ 20℃;

[0049] In heating mode, the calculation formula for the initial opening of the electronic expansion valve EXV_opening is:

[0050] EXV_opening=0.155533495+0.004424352*CompSpd+0.007261584*OAT-0.002312699*RAT;

[0051] Among them, CompSpd is the compressor frequency, CompSpd = 16.67 ~ 71.67Hz, corresponding to the speed of 1000 ~ 4300RPM; OAT is the outdoor ambient temperature, OAT = -15 ~ 20℃; RAT is the return air temperature in the car, RAT = 15 ~ -50℃.

[0052] Further, in step S42, the superheat error is redefined according to the judgment result, which specifically includes the following steps:

[0053] If -0.5℃≤err≤0.5℃, the redefined superheat error err'=0;

[0054] If err>0.5℃, the superheat error err'=err-0.5℃ is redefined;

[0055] If err<0.5℃, the superheat error err' is redefined as err+0.5℃.

[0056] Further, in step S43, the electronic expansion valve opening increment is calculated, which specifically includes the following steps:

[0057] Assume that the linear control parameter Kp = -0.15, the linear control parameter Ti = 16, and the sampling time Ts = 5s;

[0058] The linear control parameter Ti actually used is calculated based on the redefined superheat error err'. The calculation result TiOut of the linear control parameter Ti is as follows:

[0059] If err'<-8℃, then TiOut=Ti / 2;

[0060] If -8℃≤err'≤2℃, then TiOut=Ti;

[0061] If err'>2℃, then TiOut=Ti / 4;

[0062] Calculate the electronic expansion valve opening increment ΔEXV_cmd. The calculation formula of the electronic expansion valve opening increment ΔEXV_cmd is:

[0063]

[0064] Wherein, err'(k) is the k-th superheat error err', and err'(k-1) is the k-1-th superheat error err'.

[0065] By adopting the above technical scheme, the present invention obtains the compressor speed, the actual evaporator outlet pressure, and the evaporator outlet temperature to determine the actual superheat; determines the movement rate of the electronic expansion valve core according to the actual air supply temperature and the target air outlet temperature in the car; determines the target superheat according to the outdoor ambient temperature, the target temperature in the car, and the return air temperature in the car; and controls the opening of the electronic expansion valve by comparing the difference between the actual superheat and the target superheat according to the compressor frequency. Different electronic expansion valves can be selected in different situations to effectively control the target temperature in the car and improve the comfort of passengers in the car. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 It is a working schematic diagram of the electronic expansion valve and the evaporator of the present invention;

[0067] Figure 2 The present invention is a flow chart of a method for controlling an electronic expansion valve of a rail train air conditioner. DETAILED DESCRIPTION

[0068] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments in conjunction with the accompanying drawings.

[0069] like Figure 2 As shown, this embodiment provides a control method for an electronic expansion valve of a rail train air conditioner, which comprises the following steps:

[0070] Step S1, determining the actual value of superheat according to the compressor speed, the actual evaporator outlet pressure and the evaporator outlet temperature;

[0071] Step S2, calculating the valve core movement rate of the electronic expansion valve according to the actual air supply temperature and the target air outlet temperature in the vehicle;

[0072] Step S3, determining a superheat target value according to the outdoor ambient temperature, the target temperature in the vehicle, and the return air temperature in the vehicle;

[0073] Step S4: Compare the difference between the actual heat value and the superheat target value according to the compressor frequency, obtain the superheat error, and control the opening of the electronic expansion valve.

[0074] In step S1 of this embodiment, the calculation formula of the actual superheat value SH_msm is:

[0075] SH_msm = T1-Y;

[0076] Among them, T1 is the evaporator outlet temperature, and Y is the saturation temperature corresponding to the actual pressure at the evaporator outlet;

[0077] There are two methods to calculate the saturation temperature Y, one is the table lookup method, the other is the approximate formula calculation method. Let's take the formula method as an example. The calculation formula for the saturation temperature Y is:

[0078] Y=0.0006*X 5 -0.0215*X 4 +0.3312*X 3 -2.7118*X 2 +16.314*X-35.738;

[0079] Where X is the actual pressure at the evaporator outlet.

[0080] In step S2 of this embodiment, calculating the valve core movement rate of the electronic expansion valve specifically includes the following steps:

[0081] The valve port flow area A of the electronic expansion valve is expressed as:

[0082]

[0083] Where, h is the valve needle opening; β is the valve needle cone angle; d is the valve needle aperture;

[0084] Mass flow rate of electronic expansion valve m r The solution is obtained by using the basic hydraulic formula obtained by the Bernoulli equation considering the resistance loss. The mass flow rate m of the electronic expansion valve r That is, the valve core movement rate of the electronic expansion valve, the mass flow rate of the electronic expansion valve m r The calculation formula is:

[0085]

[0086] Among them, C D is the flow coefficient of the electronic expansion valve, which is related to the specific volume of the refrigerant; ρ in P is the refrigerant density at the inlet of the electronic expansion valve; in is the refrigerant pressure at the inlet of the electronic expansion valve, P out is the refrigerant pressure at the outlet of the electronic expansion valve;

[0087] Flow coefficient C of electronic expansion valve D The calculation formula is:

[0088]

[0089] Among them, v out It is the specific volume of refrigerant at the outlet of the electronic expansion valve.

[0090] In step S4 of this embodiment, based on the compressor frequency, the difference between the actual heat value and the superheat target value is compared to obtain the superheat error, and the opening of the electronic expansion valve is controlled, which specifically includes the following steps:

[0091] Step S41, the electronic expansion valve is initialized and powered on, the electronic expansion valve is reset, the opening of the electronic expansion valve is closed by 110%, and super-zero adjustment is performed. No matter what the opening of the electronic expansion valve is in the previous time period, it can be ensured that the electronic expansion valve can be closed to zero position; when starting up, the opening of the electronic expansion valve is closed by 10%*(1+T / 24), and then the opening of the electronic expansion valve is opened to the initial opening; wherein T is the time from the last reset action;

[0092] Step S42: Control the electronic expansion valve to adjust the superheat at the compressor inlet. Superheat control is necessary to ensure that liquid refrigerant does not enter the compressor. Calculate the difference between the actual heat value SH_msm and the superheat target value SH_stp to obtain the superheat error err. The calculation formula of the superheat error err is:

[0093] err = SH_stp - SH_msm;

[0094] The deadband of the unsafe operating temperature range of the electronic expansion valve is ±0.5°C. The superheat error is judged based on the deadband of the unsafe operating temperature range of the electronic expansion valve, and the superheat error is redefined according to the judgment result.

[0095] Step S43, calculating the opening increment of the electronic expansion valve;

[0096] Step S44: Control the opening of the electronic expansion valve according to the electronic expansion valve opening increment ΔEXV_cmd.

[0097] In step S41 of this embodiment, the calculation formula of the initial opening of the electronic expansion valve is as follows:

[0098] In cooling mode, the calculation formula for the initial opening of the electronic expansion valve EXV_opening is:

[0099] EXV_opening=0.1185986938+0.005613955683*CompSpd-0.003193849031*OAT+

[0100] 0.008823342804*RAT;

[0101] Among them, CompSpd is the compressor frequency, CompSpd = 16.67 ~ 71.67Hz, corresponding to the speed of 1000 ~ 4300RPM; OAT is the outdoor ambient temperature, OAT = 10 ~ 50℃ (over 50℃ is calculated as 50℃, below 10℃ is calculated as 10℃); RAT is the return air temperature in the car, RAT = 8 ~ 20℃ (over 20℃ is calculated as 20℃, below 8℃ is calculated as 8℃);

[0102] In heating mode, the calculation formula for the initial opening of the electronic expansion valve EXV_opening is:

[0103] EXV_opening=0.155533495+0.004424352*CompSpd+0.007261584*OAT-0.002312699*RAT;

[0104] Among them, CompSpd is the compressor frequency, CompSpd = 16.67 ~ 71.67Hz, corresponding to the speed of 1000 ~ 4300RPM; OAT is the outdoor ambient temperature, OAT = -15 ~ 20℃ (above 20℃, calculated as 20℃, below -5℃, calculated as -5℃); RAT is the return air temperature in the car, RAT = 15 ~ -50℃ (above 50℃, calculated as 50℃, below 15℃, calculated as 15℃).

[0105] In step S42 of this embodiment, the superheat error is redefined according to the judgment result, which specifically includes the following steps:

[0106] If -0.5℃≤err≤0.5℃, the redefined superheat error err'=0;

[0107] If err>0.5℃, the superheat error err'=err-0.5℃ is redefined;

[0108] If err<0.5℃, the superheat error err' is redefined as err+0.5℃.

[0109] In step S43 of this embodiment, the electronic expansion valve opening increment is calculated, which specifically includes the following steps:

[0110] Assume that the linear control parameter Kp = -0.15, the linear control parameter Ti = 16, and the sampling time Ts = 5s;

[0111] The linear control parameter Ti actually used is calculated based on the redefined superheat error err'. The calculation result TiOut of the linear control parameter Ti is as follows:

[0112] If err'<-8℃, then TiOut=Ti / 2;

[0113] If -8℃≤err'≤2℃, then TiOut=Ti;

[0114] If err'>2℃, then TiOut=Ti / 4;

[0115] Calculate the electronic expansion valve opening increment ΔEXV_cmd. The calculation formula of the electronic expansion valve opening increment ΔEXV_cmd is:

[0116]

[0117] Wherein, err'(k) is the k-th superheat error err', and err'(k-1) is the k-1-th superheat error err'.

[0118] The specific embodiments described above further illustrate the technical problems, technical solutions and beneficial effects solved by the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A control method for an electronic expansion valve of a rail train air conditioner, characterized in that: It includes the following steps: Step S1, determining the actual value of superheat according to the compressor speed, the actual evaporator outlet pressure and the evaporator outlet temperature; Step S2, calculating the valve core movement rate of the electronic expansion valve according to the actual air supply temperature and the target air outlet temperature in the vehicle; Step S3, determining a superheat target value according to the outdoor ambient temperature, the target temperature in the vehicle, and the return air temperature in the vehicle; Step S4: Compare the difference between the actual heat value and the superheat target value according to the compressor frequency, obtain the superheat error, and control the opening of the electronic expansion valve.

2. The control method of the electronic expansion valve of the rail train air conditioner according to claim 1, characterized in that: In step S1, the calculation formula of the actual superheat value SH_msm is: SH_msm = T1-Y; Among them, T1 is the evaporator outlet temperature, and Y is the saturation temperature corresponding to the actual pressure at the evaporator outlet; The calculation formula of saturation temperature Y is: Y=0.0006*X 5 -0.0215*X 4 +0.3312*X 3 -2.7118*X 2 +16.314*X-35.738; Where X is the actual pressure at the evaporator outlet.

3. The control method of the electronic expansion valve of the rail train air conditioner according to claim 1, characterized in that: In step S2, calculating the valve core movement rate of the electronic expansion valve specifically includes the following steps: The valve port flow area A of the electronic expansion valve is expressed as: Where, h is the valve needle opening; β is the valve needle cone angle; d is the valve needle aperture; Mass flow rate of electronic expansion valve m r The solution is obtained by using the basic hydraulic formula obtained by the Bernoulli equation considering the resistance loss. The mass flow rate m of the electronic expansion valve r That is, the valve core movement rate of the electronic expansion valve, the mass flow rate of the electronic expansion valve m r The calculation formula is: Among them, C D is the flow coefficient of the electronic expansion valve; ρ in P is the refrigerant density at the inlet of the electronic expansion valve; in is the refrigerant pressure at the inlet of the electronic expansion valve, P out is the refrigerant pressure at the outlet of the electronic expansion valve; Flow coefficient C of electronic expansion valve D The calculation formula is: Among them, v out It is the specific volume of refrigerant at the outlet of the electronic expansion valve.

4. The control method of the electronic expansion valve of the rail train air conditioner according to claim 1, characterized in that: In step S4, according to the compressor frequency, the difference between the actual heat value and the superheat target value is compared to obtain the superheat error, and the opening of the electronic expansion valve is controlled, which specifically includes the following steps: Step S41, the electronic expansion valve is initialized and powered on, the electronic expansion valve is reset, and the opening of the electronic expansion valve is closed by 110%; when the power is turned on, the opening of the electronic expansion valve is closed by 10%*(1+T / 24), and then the opening of the electronic expansion valve is opened to the initial opening; wherein T is the time from the last reset action; Step S42: Calculate the difference between the actual heat value SH_msm and the superheat target value SH_stp to obtain the superheat error err. The calculation formula of the superheat error err is: err = SH_stp - SH_msm; The deadband of the unsafe operating temperature range of the electronic expansion valve is ±0.5°C. The superheat error is judged based on the deadband of the unsafe operating temperature range of the electronic expansion valve, and the superheat error is redefined according to the judgment result. Step S43, calculating the opening increment of the electronic expansion valve; Step S44: Control the opening of the electronic expansion valve according to the electronic expansion valve opening increment ΔEXV_cmd.

5. The control method of the electronic expansion valve of the rail train air conditioner according to claim 1, characterized in that: In step S41, the calculation formula of the initial opening of the electronic expansion valve is as follows: In cooling mode, the calculation formula for the initial opening of the electronic expansion valve EXV_opening is: EXV_opening=0.1185986938+0.005613955683*CompSpd-0.003193849031*OAT+0.008823342804*RAT; Among them, CompSpd is the compressor frequency, CompSpd = 16.67 ~ 71.67Hz, corresponding to the speed of 1000 ~ 4300RPM; OAT is the outdoor ambient temperature, OAT = 10 ~ 50℃; RAT is the return air temperature in the car, RAT = 8 ~ 20℃; In heating mode, the calculation formula for the initial opening of the electronic expansion valve EXV_opening is: EXV_opening=0.155533495+0.004424352*CompSpd+0.007261584*OAT-0.002312699*RAT; Among them, CompSpd is the compressor frequency, CompSpd = 16.67 ~ 71.67Hz, corresponding to the speed of 1000 ~ 4300RPM; OAT is the outdoor ambient temperature, OAT = -15 ~ 20℃; RAT is the return air temperature in the car, RAT = 15 ~ -50℃.

6. The control method of the electronic expansion valve of the rail train air conditioner according to claim 5, characterized in that: In step S42, the superheat error is redefined according to the judgment result, which specifically includes the following steps: If -0.5℃≤err≤0.5℃, the redefined superheat error err'=0; If err>0.5℃, the superheat error err'=err-0.5℃ is redefined; If err<0.5℃, the superheat error err' is redefined as err+0.5℃.

7. The control method of the electronic expansion valve of the rail train air conditioner according to claim 6, characterized in that: In step S43, calculating the electronic expansion valve opening increment specifically includes the following steps: Assume that the linear control parameter Kp = -0.15, the linear control parameter Ti = 16, and the sampling time Ts = 5s; The linear control parameter Ti actually used is calculated based on the redefined superheat error err'. The calculation result TiOut of the linear control parameter Ti is as follows: If err'<-8℃, then TiOut=Ti / 2; If -8℃≤err'≤2℃, then TiOut=Ti; If err'>2℃, then TiOut=Ti / 4; Calculate the electronic expansion valve opening increment ΔEXV_cmd. The calculation formula of the electronic expansion valve opening increment ΔEXV_cmd is: Wherein, err'(k) is the k-th superheat error err', and err'(k-1) is the k-1-th superheat error err'.

Images