Method for controlling EEV and EVI electronic expansion valves of ultralow-temperature heat pump unit

Abstract

The invention relates to an ultralow-temperature heat pump unit EEV and EVI electronic expansion valve control method which is characterized in that data are collected, and a main valve EEV control method comprises the steps of main valve EEV initial opening, main valve EEV opening automatic adjustment and main valve EEV electronic expansion valve final opening; the auxiliary valve EVI control method comprises auxiliary valve EVI starting conditions, EVI initial opening PEVI, auxiliary valve EVI opening automatic adjustment and auxiliary valve EVI final opening; the method has the advantages that the opening degrees of the EEV and EVI electronic expansion valves are accurately controlled, so that the enhanced vapor injection refrigerant flow of the compressor is controlled, the efficiency of the compressor is improved, the energy efficiency is improved, the exhaust temperature of a compressor system is reduced, and the service life of the machine is prolonged.

Description

Technical Field

[0001] The invention relates to an EEV and EVI electronic expansion valve control method for an ultra-low temperature heat pump unit. Background Art

[0002] The jet reheat technology is an ultra-low temperature heat pump system composed of a jet reheat compressor, a high-efficiency heat exchanger and an electronic expansion valve. These components together form an efficient and energy-saving jet system. The jet reheat compressor inhales a portion of the intermediate pressure gas through the intermediate pressure suction hole, mixes it with the partially compressed refrigerant and then compresses it, thereby achieving "two-stage compression". This technology not only improves the efficiency of the compressor, but also solves the problem of insufficient heating capacity of a single-stage compressor under low temperature conditions; however, the problems with the above technical solution are that the electronic expansion valve is easily too large or too small, the system stability is poor, the compressor exhaust temperature is high, and the life of the electronic expansion valve is short. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an EEV, EVI electronic expansion valve control method for an ultra-low temperature heat pump unit, accurately control the opening of the EEV, EVI electronic expansion valve, thereby controlling the compressor jet enthalpy increase refrigerant flow rate, improving the efficiency of the compressor, improving energy efficiency, reducing the exhaust temperature of the compressor system, and extending the life of the machine.

[0004] In order to achieve the above object, the present invention is implemented as follows: it is a control method for an EEV or EVI electronic expansion valve of an ultra-low temperature heat pump unit, wherein the heat pump factory parameters are:

[0005] Parameter P100: Main valve EEV initial opening constant, parameter P101: Main valve EEV initial opening coefficient A, parameter P102: Main valve EEV initial opening coefficient B, parameter P103: Heating target superheat correction value, parameter P1: Ambient temperature that allows auxiliary valve EVI and enthalpy increase valve to open, parameter P2: Compressor frequency that allows auxiliary valve EVI and enthalpy increase valve to open, parameter P3: Compressor travel time that allows auxiliary valve EVI and enthalpy increase valve to open, parameter P4: Ambient temperature that allows auxiliary valve EVI and enthalpy increase valve to open The compressor exhaust temperature when the enthalpy valve is opened, parameter P5: the temperature difference that allows the auxiliary valve EVI and the enthalpy increasing valve to be opened, parameter P6: the exhaust superheat degree when the auxiliary valve EVI is opened, parameter P7: the shortest interval between the opening and closing of the auxiliary valve EVI and the enthalpy increasing valve, parameter P8: the initial opening constant of the auxiliary valve EVI, parameter P8: the initial opening constant of the auxiliary valve EVI, parameter P9: the initial opening coefficient A of the auxiliary valve EVI, parameter P10: the initial opening coefficient B of the auxiliary valve EVI, parameter P16: the compressor frequency limit value when the exhaust temperature is too high;

[0006] The control method is as follows:

[0007] Collect data:

[0008] Step 1: Collect the operating frequency F of the compressor of the heat pump unit, the heat pump inlet water temperature T1, the compressor exhaust temperature T2, the high-pressure saturation temperature T3, the economizer inlet temperature T4, the economizer outlet temperature T5, the suction temperature T6, the low-pressure saturation temperature T7, the regenerator temperature T8, the external environment temperature T9 and the compressor return air temperature T 10 ;

[0009] Main valve EEV control method:

[0010] Step 1: Initial opening of the main valve EEV;

[0011] (1) When the compressor starts, the main valve EEV is first reset to its initial opening. The initial opening of the main valve EEV is P EEV The calculation is as follows:

[0012] P EEV = parameter P100 + (parameter P101*T9 + parameter P102*T1) / 10

[0013] (2) The main valve EEV maintains the initial opening for 5 minutes and enters automatic regulation;

[0014] Step 2: Automatically adjust the opening of the main valve EEV;

[0015] (1) Calculate superheat deviation EEV_ESH

[0016] S1. Obtain target superheat T according to T2 11 , T 11 The calculation of is as follows:

[0017] T 11 =T2 / 30+2

[0018] The normal value range of T2 is 2≤T 11 ≤5, T 11 If it is greater than 5, then take 5, T 11 If it is less than 2, take 2;

[0019] S2. Calculate the target superheat compensation value T 12 ,as follows:

[0020] T 12 =(T9+25) / 10

[0021] S3. Final target superheat EEV_SHT: EEV_SHT = T 11 -T 12 + Parameter P103

[0022] S4. Calculate the actual superheat EEV_SH = T 10 -T7

[0023] S5. Calculate superheat deviation: EEV_ESH = EEV_SH - EEV_SHT;

[0024] (2) Calculate the main valve EEV opening change:

[0025] S1, 0≤EEV_ESH≤1, then there is no need to adjust the EEV opening △P EEV =0, otherwise go to the next step;

[0026] S2. If the EVI opening is not 0, and 3≤T5-T4≤15, then EEV_ESH>1, the difference opening △P EEV =1, when EV_ESH<0, the difference opening △P EEV =-1; otherwise go to the next step;

[0027] S3. Set a KP value. When EEV_ESH>5, KP=2; when 5≥EEV_ESH>3, KP=1.0; when EEV_ESH≤3, KP=0.8;

[0028] Differential opening △P EEV =KP*EEV_ESH;

[0029] △P EEV The normal value range of is [-3,3]. EEV When it is greater than 3, then △P EEV The value is 3; when △P EEV When it is less than -3, △P EEV The value is -3;

[0030] Step 3: Final opening of the main valve EEV electronic expansion valve;

[0031] P EEV终 =P EEV +△P EEV ;

[0032] Auxiliary valve EVI control method:

[0033] After starting the heat pump unit

[0034] Step 1: Auxiliary valve EVI starting conditions;

[0035] After the EVI electronic expansion valve is opened, the timing starts, which is t1;

[0036] After the EVI electronic expansion valve is closed, the timing starts, which is t2;

[0037] After the compressor is started and the EVI electronic expansion valve is in the closed state, the EVI electronic expansion valve is opened when the following conditions are met:

[0038] 1. T9 ≤ parameter P1;

[0039] 2. F> parameter P2, and the compressor continuous operation time> parameter P3;

[0040] 3. T2> parameter P4;

[0041] 4. T1-T9> parameter P5;

[0042] 5. T2-T3 ≥ parameter P6;

[0043] 6. t2 ≥ parameter P7;

[0044] When any of the following conditions are met, the EVI electronic expansion valve is closed.

[0045] 1. T9> parameter P1+5℃;

[0046] 2. T1-T9≤0℃;

[0047] 3. T2-T3 ≤ parameter P8 and lasts for 5 minutes;

[0048] 4. The compressor is turned off;

[0049] 5. The compressor operating frequency is ≤40Hz and lasts for 5 minutes;

[0050] When the EVI electronic expansion valve is closed due to the above condition 3, the opening time t1 is recorded as t3;

[0051] Step 2: When the auxiliary valve EVI is started, calculate the initial opening degree P of EVI according to the ambient temperature and the inlet water temperature. EVI , P EVI The calculation formula is:

[0052] P EVI = parameter P8 + (parameter P9*T9 + parameter P10*T1) / 10

[0053] When t3 < 10 minutes, the initial opening needs to be corrected to prevent the EVI electronic expansion valve from starting frequently due to exhaust superheat. The initial opening of EVI is P EVI初 ;

[0054] When t3<3 minutes: P EVI初 =P EVI *30%;

[0055] When t3<5 minutes: P EVI初 =P EVI *50%;

[0056] When t3<10 minutes: P EVI初 =P EVI *70%;

[0057] Step 3: Automatically adjust the opening of the auxiliary valve EVI;

[0058] After the EVI electronic expansion valve is started, it needs to maintain the actual initial opening for 3 minutes, and then enter normal adjustment. The adjustment cycle is 40 seconds, as follows:

[0059] 1. T9> parameter P1, EVI electronic expansion valve fixed opening 100P;

[0060] 2. When T9≤parameter P1, the opening of the EVI electronic expansion valve is controlled as follows:

[0061] First, determine the target superheat, the calculation formula is:

[0062] Target superheat SHT = parameter P11 + T9 / 5;

[0063] The target superheat SHT value range is [3,10];

[0064] The actual superheat SH calculation formula is:

[0065] Actual superheat SH = T5-T4

[0066] The superheat deviation calculation formula is:

[0067] Superheat deviation ESH = SH-SHT;

[0068] When the superheat deviation ESH value is: 0≤ESH≤2, the EVI electronic expansion valve maintains the initial opening P EVI or P EVI初 ;

[0069] Otherwise, the EVI electronic expansion valve changes △P EVI =KP*ESH / 2, KP value is 1;

[0070] Calculated value △P EVI The value range is [-3,3]. When △P EVI When it is greater than 3, then △P EVI The value is 3;

[0071] When △P EVI When it is less than -3, △P EVI The value is -3;

[0072] Step 4: Final opening of auxiliary valve EVI;

[0073] P EVI终 =P EVI初 +△P EVI or P EVI终 =P EVI +△P EVI .

[0074] In this technical solution, the control method is as follows:

[0075] In the EEV control method, when T2-T3 < minimum exhaust superheat, △P EEV Re-assign the value; the minimum exhaust superheat is calculated as follows:

[0076] When T9≤0℃: minimum exhaust superheat = 10-T9 / 3;

[0077] When T9>0℃: minimum exhaust superheat = 5-(F-20) / 8;

[0078] When T2-T3<minimum exhaust superheat, the electronic expansion valve is closed by 3%, that is, △P EEV =P EEV *3 / 100.

[0079] In this embodiment, the control method is as follows:

[0080] In the main valve EEV control method, if the regenerator condition is met, then △P EEV Reassignment;

[0081] T9≥0℃, the regenerator superheat value is 0;

[0082] T9<0℃, the regenerator superheat value is T9;

[0083] (1)T8-T 10 ≥5-regenerator superheat / 5, the main valve EEV opening is not allowed to be closed down, when △P EEV <0,△P EEV =0; △P EEV ≥0, then △P EEV Remain unchanged.

[0085] (2)T8-T 10 ≥8-regenerator superheat / 5, when △P EEV <1,△P EEV =1; △P EEV ≥1, then △P EEV Remain unchanged.

[0086] In this technical solution, the control method is as follows:

[0087] In the main valve EEV control method, if the compressor exhaust temperature condition is met and the auxiliary valve EVI is not opened, then △P EEV Reassignment;

[0088] When T2≥P16+10, △P EEV =5;

[0089] When T2≥P16+5, △P EEV =2;

[0090] When T2>P16, △P EEV =1;

[0091] When T2≥P16-5, △P EEV <0, then △P EEV =0.

[0092] In this technical solution, the control method is as follows:

[0093] In the EVI control method, if the compressor exhaust temperature condition is met, then △P EVI Reassignment;

[0094] T2≥P16-2, EVI electronic expansion valve needs special correction to prevent the compressor exhaust temperature from continuing to rise. The correction is as follows:

[0095] When T2≥P16+10, △P EVI =5;

[0096] When T2≥P16+5, △P EVI =2;

[0097] When T2>P16, △P EVI =1;

[0098] When T2≥P16-5, △P EVI <0, then △P EVI =0;

[0099] When the exhaust superheat (T2-T3) ≤ P13, the EVI electronic expansion valve needs to be gradually closed to prevent the EVI electronic expansion valve from closing due to the reduction of exhaust superheat;

[0100] When the exhaust superheat is ≤12℃, close the current opening by 5% in each cycle. That is: △P EVI =P EVI / 20.

[0101] The advantages of the present invention compared with the prior art are: accurately controlling the opening of the EEV and EVI electronic expansion valves, thereby controlling the compressor jet enthalpy increase refrigerant flow rate, improving the efficiency of the compressor, improving energy efficiency, reducing the exhaust temperature of the compressor system, and extending the life of the machine. DETAILED DESCRIPTION

[0102] It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as there is no conflict between them.

[0103] In the description of the present invention, the terms "upper", "lower", "top" and "bottom" etc. indicating directions or positional relationships are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific direction. Therefore, they should not be understood as limitations on the present invention.

[0104] In the present invention, unless otherwise clearly specified and limited, the terms "set", "connected", "located" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or a detachable arrangement or integration; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, which can enable the internal connectivity of two elements or the interaction relationship between the two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0105] It is a control method for the EEV and EVI electronic expansion valves of ultra-low temperature heat pump units, in which the heat pump factory parameters are:

[0106] Parameter P100: Main valve EEV initial opening constant, parameter P101: Main valve EEV initial opening coefficient A, parameter P102: Main valve EEV initial opening coefficient B, parameter P103: Heating target superheat correction value, parameter P1: Ambient temperature that allows auxiliary valve EVI and enthalpy increase valve to open, parameter P2: Compressor frequency that allows auxiliary valve EVI and enthalpy increase valve to open, parameter P3: Compressor travel time that allows auxiliary valve EVI and enthalpy increase valve to open, parameter P4: Ambient temperature that allows auxiliary valve EVI and enthalpy increase valve to open The compressor exhaust temperature when the enthalpy valve is opened, parameter P5: the temperature difference that allows the auxiliary valve EVI and the enthalpy increasing valve to be opened, parameter P6: the exhaust superheat degree when the auxiliary valve EVI is opened, parameter P7: the shortest interval between the opening and closing of the auxiliary valve EVI and the enthalpy increasing valve, parameter P8: the initial opening constant of the auxiliary valve EVI, parameter P8: the initial opening constant of the auxiliary valve EVI, parameter P9: the initial opening coefficient A of the auxiliary valve EVI, parameter P10: the initial opening coefficient B of the auxiliary valve EVI, parameter P16: the compressor frequency limit value when the exhaust temperature is too high;

[0107] The control method is as follows:

[0108] Collect data:

[0109] Step 1: Collect the operating frequency F of the compressor of the heat pump unit, the heat pump inlet water temperature T1, the compressor exhaust temperature T2, the high-pressure saturation temperature T3, the economizer inlet temperature T4, the economizer outlet temperature T5, the suction temperature T6, the low-pressure saturation temperature T7, the regenerator temperature T8, the external environment temperature T9 and the compressor return air temperature T 10 ;

[0110] Main valve EEV control method:

[0111] Step 1: Initial opening of the main valve EEV;

[0112] (1) When the compressor starts, the main valve EEV is first reset to its initial opening. The initial opening of the main valve EEV is P EEV The calculation is as follows:

[0113] P EEV = parameter P100 + (parameter P101*T9 + parameter P102*T1) / 10

[0114] (2) The main valve EEV maintains the initial opening for 5 minutes and enters automatic regulation;

[0115] Step 2: Automatically adjust the opening of the main valve EEV;

[0116] (1) Calculate superheat deviation EEV_ESH

[0117] S1. Obtain target superheat T according to T2 11 , T 11 The calculation of is as follows:

[0118] T 11 =T2 / 30+2

[0119] The normal value range of T2 is 2≤T 11 ≤5, T 11 If it is greater than 5, then take 5, T 11 If it is less than 2, take 2;

[0120] S2. Calculate the target superheat compensation value T 12 ,as follows:

[0121] T 12 =(T9+25) / 10

[0122] S3. Final target superheat EEV_SHT: EEV_SHT = T 11 -T 12 + Parameter P103

[0123] S4. Calculate the actual superheat EEV_SH = T 10 -T7

[0124] S5. Calculate superheat deviation: EEV_ESH = EEV_SH - EEV_SHT;

[0125] (2) Calculate the main valve EEV opening change:

[0126] S1, 0≤EEV_ESH≤1, then there is no need to adjust the EEV opening △P EEV =0, otherwise go to the next step;

[0127] S2. If the EVI opening is not 0, and 3≤T5-T4≤15, then EEV_ESH>1, the difference opening △P EEV =1, when EV_ESH<0, the difference opening △P EEV =-1; otherwise go to the next step;

[0128] S3. Set a KP value. When EEV_ESH>5, KP=2; when 5≥EEV_ESH>3, KP=1.0; when EEV_ESH≤3, KP=0.8;

[0129] Differential opening △P EEV =KP*EEV_ESH;

[0130] △P EEV The normal value range of is [-3,3]. EEV When it is greater than 3, then △P EEV The value is 3; when △P EEV When it is less than -3, △P EEV The value is -3;

[0131] Step 3: Final opening of the main valve EEV electronic expansion valve;

[0132] P EEV终 =P EEV +△P EEV ;

[0133] Auxiliary valve EVI control method:

[0134] After starting the heat pump unit

[0135] Step 1: Auxiliary valve EVI starting conditions;

[0136] After the EVI electronic expansion valve is opened, the timing starts, which is t1;

[0137] After the EVI electronic expansion valve is closed, the timing starts, which is t2;

[0138] After the compressor is started and the EVI electronic expansion valve is in the closed state, the EVI electronic expansion valve is opened when the following conditions are met:

[0139] 1. T9 ≤ parameter P1;

[0140] 2. F> parameter P2, and the compressor continuous operation time> parameter P3;

[0141] 3. T2> parameter P4;

[0142] 4. T1-T9> parameter P5;

[0143] 5. T2-T3 ≥ parameter P6;

[0144] 6. t2 ≥ parameter P7;

[0145] When any of the following conditions are met, the EVI electronic expansion valve is closed.

[0146] 1. T9> parameter P1+5℃;

[0147] 2. T1-T9≤0℃;

[0148] 3. T2-T3 ≤ parameter P8 and lasts for 5 minutes;

[0149] 4. The compressor is turned off;

[0150] 5. The compressor operating frequency is ≤40Hz and lasts for 5 minutes;

[0151] When the EVI electronic expansion valve is closed due to the above condition 3, the opening time t1 is recorded as t3;

[0152] Step 2: When the auxiliary valve EVI is started, calculate the initial opening degree P of EVI according to the ambient temperature and the inlet water temperature. EVI , P EVI The calculation formula is:

[0153] P EVI = parameter P8 + (parameter P9*T9 + parameter P10*T1) / 10

[0154] When t3 < 10 minutes, the initial opening needs to be corrected to prevent the EVI electronic expansion valve from starting frequently due to exhaust superheat. The initial opening of EVI is P EVI初 ;

[0155] When t3<3 minutes: P EVI初 =P EVI *30%;

[0156] When t3<5 minutes: P EVI初 =P EVI *50%;

[0157] When t3<10 minutes: P EVI初 =P EVI *70%;

[0158] Step 3: Automatically adjust the opening of the auxiliary valve EVI;

[0159] After the EVI electronic expansion valve is started, it needs to maintain the actual initial opening for 3 minutes, and then enter normal adjustment. The adjustment cycle is 40 seconds, as follows:

[0160] 1. T9> parameter P1, EVI electronic expansion valve fixed opening 100P;

[0161] 2. When T9≤parameter P1, the opening of the EVI electronic expansion valve is controlled as follows:

[0162] First, determine the target superheat, the calculation formula is:

[0163] Target superheat SHT = parameter P11 + T9 / 5;

[0164] The target superheat SHT value range is [3,10];

[0165] The actual superheat SH calculation formula is:

[0166] Actual superheat SH = T5-T4

[0167] The superheat deviation calculation formula is:

[0168] Superheat deviation ESH = SH-SHT;

[0169] When the superheat deviation ESH value is: 0≤ESH≤2, the EVI electronic expansion valve maintains the initial opening P EVI or P EVI初 ;

[0170] Otherwise, the EVI electronic expansion valve changes △P EVI =KP*ESH / 2, KP value is 1;

[0171] Calculated value △P EVI The value range is [-3,3]. When △P EVI When it is greater than 3, then △P EVI The value is 3;

[0172] When △P EVI When it is less than -3, △P EVI The value is -3;

[0173] Step 4: Final opening of auxiliary valve EVI;

[0174] P EVI终 =P EVI初 +△P EVI or P EVI终 =P EVI +△P EVI .

[0175] Accurately control the opening of EEV and EVI electronic expansion valves, thereby controlling the compressor jet enthalpy increase refrigerant flow rate, improving the efficiency of the compressor, improving energy efficiency, reducing the exhaust temperature of the compressor system, and extending the life of the machine.

[0176] In this embodiment, the control method is as follows:

[0177] In the EEV control method, when T2-T3 < minimum exhaust superheat, △PEEV Reassignment;

[0178] The minimum exhaust superheat is calculated as follows:

[0179] When T9≤0℃: minimum exhaust superheat = 10-T9 / 3;

[0180] When T9>0℃: minimum exhaust superheat = 5-(F-20) / 8;

[0181] When T2-T3<minimum exhaust superheat, the electronic expansion valve is closed by 3%, that is, △P EEV =P EEV *3 / 100.

[0182] In this embodiment, the control method is as follows:

[0183] In the main valve EEV control method, if the regenerator condition is met, then △P EEV Reassignment;

[0184] T9≥0℃, the regenerator superheat value is 0;

[0185] T9<0℃, the regenerator superheat value is T9;

[0186] (1)T8-T 10 ≥5-regenerator superheat / 5, the main valve EEV opening is not allowed to be closed down, when △P EEV <0,△P EEV =0; △P EEV ≥0, then △P EEV Remain unchanged.

[0188] (2)T8-T 10 ≥8-regenerator superheat / 5, when △P EEV <1,△P EEV =1; △P EEV ≥1, then △P EEV Remain unchanged.

[0189] In this embodiment, the control method is as follows:

[0190] In the main valve EEV control method, if the compressor exhaust temperature condition is met and the auxiliary valve EVI is not opened, then △P EEV Reassignment;

[0191] When T2≥P16+10, △P EEV =5;

[0192] When T2≥P16+5, △P EEV =2;

[0193] When T2>P16, △P EEV =1;

[0194] When T2≥P16-5, △P EEV <0, then △P EEV =0.

[0195] In this embodiment, the control method is as follows:

[0196] In the EVI control method, if the compressor exhaust temperature condition is met, then △P EVI Reassignment;

[0197] T2≥P16-2, EVI electronic expansion valve needs special correction to prevent the compressor exhaust temperature from continuing to rise. The correction is as follows:

[0198] When T2≥P16+10, △P EVI =5;

[0199] When T2≥P16+5, △P EVI =2;

[0200] When T2>P16, △P EVI =1;

[0201] When T2≥P16-5, △P EVI <0, then △P EVI =0;

[0202] When the exhaust superheat (T2-T3) ≤ P13, the EVI electronic expansion valve needs to be gradually closed to prevent the EVI electronic expansion valve from closing due to the reduction of exhaust superheat;

[0203] When the exhaust superheat is ≤12℃, close the current opening by 5% in each cycle. That is: △P EVI =P EVI / 20.

[0204] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and deformations of these embodiments without departing from the principles and purpose of the present invention still fall within the protection scope of the present invention.

Claims

1. A control method for an EEV or EVI electronic expansion valve of an ultra-low temperature heat pump unit, wherein the heat pump factory parameters are: Parameter P100: Main valve EEV initial opening constant, parameter P101: Main valve EEV initial opening coefficient A, parameter P102: Main valve EEV initial opening coefficient B, parameter P103: Heating target superheat correction value, parameter P1: Ambient temperature that allows auxiliary valve EVI and enthalpy increasing valve to open, parameter P2: Compressor frequency that allows auxiliary valve EVI and enthalpy increasing valve to open, parameter P3: Compressor travel time that allows auxiliary valve EVI and enthalpy increasing valve to open, parameter P4: Compressor exhaust temperature that allows auxiliary valve EVI and enthalpy increasing valve to open, parameter P5: Temperature difference that allows auxiliary valve EVI and enthalpy increasing valve to open, parameter P6: Auxiliary valve EVI opening exhaust superheat, parameter P7: The shortest interval between auxiliary valve EVI and enthalpy increasing valve opening and closing, parameter P8: Auxiliary valve EVI initial opening constant, parameter P8: Auxiliary valve EVI initial opening constant, parameter P9: Auxiliary valve EVI initial opening coefficient A, parameter P10: Auxiliary valve EVI initial opening coefficient B, parameter P16: Exhaust temperature is too high compressor frequency limit value; Features The control method is as follows: Collect data: Step 1: Collect the operating frequency F of the compressor of the heat pump unit, the heat pump inlet water temperature T1, the compressor exhaust temperature T2, the high-pressure saturation temperature T3, the economizer inlet temperature T4, the economizer outlet temperature T5, the suction temperature T6, the low-pressure saturation temperature T7, the regenerator temperature T8, the external environment temperature T9 and the compressor return air temperature T10; Main valve EEV control method: Step 1: Initial opening of the main valve EEV; (1) When the compressor starts, the main valve EEV is first reset to the initial opening. The initial opening PEEV of the main valve EEV is calculated as follows: PEEV=parameter P100+(parameter P101*T9 + parameter P102*T1) / 10 (2) The main valve EEV maintains the initial opening for 5 minutes and enters automatic regulation; Step 2: Automatically adjust the opening of the main valve EEV; (1) Calculate superheat deviation EEV_ESH S1. Obtain the target superheat T11 based on T2. ​​The calculation of T11 is as follows: T11=T2 / 30+2 The normal value range of T2 is 2≤T11≤5. When T11 is greater than 5, it is 5, and when T11 is less than 2, it is 2. S2. Calculate the target superheat compensation value T12 as follows: T12=(T9+25) / 10 S3, the final target superheat EEV_SHT: EEV_SHT = T11-T12 + parameter P103 S4. Calculate the actual superheat EEV_SH = T10-T7 S5. Calculate superheat deviation: EEV_ESH = EEV_SH - EEV_SHT; (2) Calculate the main valve EEV opening change: S1, 0≤EEV_ESH≤1, then there is no need to adjust the EEV opening △PEEV=0, otherwise proceed to the next step; S2. If the EVI opening is not 0, and 3≤T5-T4≤15, then EEV_ESH>1, the difference opening △PEEV=1, when EV_ESH<0, the difference opening △PEEV=-1; otherwise, go to the next step; S3. Set a KP value. When EEV_ESH>5, KP=2; when 5≥EEV_ESH>3, KP=1.0; when EEV_ESH≤3, KP=0.8; Differential opening △PEEV=KP*EEV_ESH; The normal value range of △PEEV is [-3,3]. When △PEEV is greater than 3, the value of △PEEV is 3; When △PEEV is less than -3, the value of △PEEV is -3; Step 3: Final opening of the main valve EEV electronic expansion valve; PEEV = PEEV + △PEEV; Auxiliary valve EVI control method: After starting the heat pump unit Step 1: Auxiliary valve EVI starting conditions; After the EVI electronic expansion valve is opened, the timing starts, which is t1; After the EVI electronic expansion valve is closed, the timing starts, which is t2; After the compressor is started and the EVI electronic expansion valve is in the closed state, the EVI electronic expansion valve is opened when the following conditions are met:

1. T9 ≤ parameter P1; 2. F> parameter P2, and the compressor continuous operation time> parameter P3; 3. T2> parameter P4; 4. T1-T9> parameter P5; 5. T2-T3 ≥ parameter P6; 6. t2 ≥ parameter P7; When any of the following conditions are met, the EVI electronic expansion valve is closed.

1. T9> parameter P1+5℃; 2. T1-T9≤0℃; 3. T2-T3 ≤ parameter P8 and lasts for 5 minutes; 4. The compressor is turned off; 5. The compressor operating frequency is ≤40Hz and lasts for 5 minutes; When the EVI electronic expansion valve is closed due to the above condition 3, the opening time t1 is recorded as t3; Step 2: When the auxiliary valve EVI is started, the initial opening PEVI of EVI is calculated according to the ambient temperature and the inlet water temperature. The PEVI calculation formula is: PEVI = parameter P8 + (parameter P9*T9+parameter P10*T1) / 10 When t3 < 10 minutes, the above initial opening needs to be corrected to prevent the EVI electronic expansion valve from starting frequently due to exhaust superheat. The initial opening of EVI is PEVI initial; When t3 < 3 minutes: PEVI initial = PEVI*30%; When t3 < 5 minutes: PEVI initial = PEVI*50%; When t3 < 10 minutes: PEVI initial = PEVI*70%; Step 3: Automatically adjust the opening of the auxiliary valve EVI; After the EVI electronic expansion valve is started, it needs to maintain the actual initial opening for 3 minutes, and then enter normal adjustment. The adjustment cycle is 40 seconds, as follows:

1. T9> parameter P1, EVI electronic expansion valve fixed opening 100P; 2. When T9≤parameter P1, the opening of the EVI electronic expansion valve is controlled as follows: First, determine the target superheat, the calculation formula is: Target superheat SHT = parameter P11 + T9 / 5; The target superheat SHT value range is [3,10]; The actual superheat SH calculation formula is: Actual superheat SH = T5-T4 The superheat deviation calculation formula is: Superheat deviation ESH = SH-SHT; When the superheat deviation ESH is: 0≤ESH≤2, the EVI electronic expansion valve maintains the initial opening PEVI or PEVI initial; Otherwise, the change of EVI electronic expansion valve △PEVI=KP*ESH / 2, and KP takes the value of 1; The calculated value △PEVI has a range of [-3,3]. When △PEVI is greater than 3, the value of △PEVI is 3. When △PEVI is less than -3, the value of △PEVI is -3; Step 4: Final opening of auxiliary valve EVI; PEVI final = PEVI initial + △PEVI or PEVI final = PEVI + △PEVI.

2. The method for controlling the electronic expansion valve of the ultra-low temperature heat pump unit EEV and EVI according to claim 1, characterized in that The control method is as follows: In the EEV control method, when T2-T3 < minimum exhaust superheat, △PEEV is reassigned; The minimum exhaust superheat is calculated as follows: When T9≤ 0 ℃: minimum exhaust superheat = 10-T9 / 3; When T9>0℃: minimum exhaust superheat = 5-(F-20) / 8; When T2-T3 < minimum exhaust superheat, the electronic expansion valve is closed by 3%, that is, △PEEV = PEEV*3 / 100.

3. The control method of the electronic expansion valve of the ultra-low temperature heat pump unit EEV and EVI according to claim 1 is characterized in that The control method is as follows: In the main valve EEV control method, if the regenerator condition is met, △PEEV is reassigned; T9≥0℃, the regenerator superheat value is 0; T9 <0℃, the superheat value of the regenerator is T9; (1) T8-T10≥5-regenerator superheat / 5, the main valve EEV opening is not allowed to be reduced. When △PEEV<0, △PEEV=0; △PEEV≥0, △PEEV remains unchanged; (2) T8-T10≥8-regenerator superheat / 5, when △PEEV<1, △PEEV=1; △PEEV≥1, △PEEV remains unchanged.

4. The method for controlling the electronic expansion valve of the ultra-low temperature heat pump unit EEV and EVI according to claim 1, characterized in that The control method is as follows: In the main valve EEV control method, if the condition of the compressor exhaust temperature is met and the auxiliary valve EVI is not open, △PEEV is reassigned; When T2 ≥ P16 + 10, △PEEV = 5; When T2 ≥ P16 + 5, △PEEV = 2; When T2 > P16, △PEEV = 1; When T2 ≥ P16 -5, △PEEV<0, then △PEEV = 0.

5. The method for controlling the electronic expansion valve of the ultra-low temperature heat pump unit EEV and EVI according to claim 1, characterized in that The control method is as follows: In the EVI control method, if the condition of the compressor exhaust temperature is met, △PEVI is reassigned; T2 ≥ P16 - 2, the EVI electronic expansion valve needs special correction to prevent the compressor exhaust temperature from continuing to rise. The correction is as follows: When T2 ≥ P16 + 10, △PEVI = 5; When T2 ≥ P16 + 5, △PEVI = 2; When T2 > P16, △PEVI = 1; When T2 ≥ P16 -5, △PEVI <0, then △PEVI = 0; When the exhaust superheat (T2-T3) ≤ P13, the EVI electronic expansion valve needs to be gradually closed to prevent the EVI electronic expansion valve from closing due to the reduction of exhaust superheat; When the exhaust superheat is ≤ 12℃, close the current opening by 5% in each cycle. That is: △PEVI = PEVI / 20.