Static start control method of heat pump

Abstract

A standing start control method of a heat pump comprises the following steps that firstly, the heat pump is powered on to operate, and the second step is executed; 2, in the operation process, a central controller of the heat pump records the number of faults of current low-voltage over-low protection reporting, and the step 3 is executed; 3, the central controller judges whether the number of faults in the time period K is the third time or not, if yes, the step 4 is executed, and if not, the step 2 is executed, and the value range of K is 20-60 minutes; 4, after the fault is removed, the heat pump is restarted, the current running time T starts to be counted, and the step 5 is executed; step 5, the central controller judges whether T is smaller than or equal to 30 minutes or not, if yes, the step 6 is executed, and if not, the step 17 is executed; and 6, the central controller judges whether TS is smaller than P2 or not, if yes, the seventh step is executed, and if not, the fourteenth step is executed, TS is the current low-pressure pressure value, and P2 is the second preset pressure value. The device has the characteristic of stable operation.

Description

Technical Field

[0001] The invention relates to a heat pump, in particular to a static start-up control method of a heat pump. Background Art

[0002] During the heat pump heating process, as the operating ambient temperature of the heat pump becomes lower and lower, when it is started at ultra-low temperature or during startup, it is often easy to report low pressure protection. The main reason is that when the heat pump is stationary, the refrigerant and oil in the heat exchange tube and compressor are easy to deposit and have poor fluidity. At present, most of the solutions are to use multi-platform frequency startup, but there is still a risk of reporting low pressure protection.

[0003] In addition, when a new heat pump runs at high frequency at ultra-low temperatures, its heat exchange capacity is good because the fins on its evaporation side are not dirty or clogged, and the new heat pump can operate normally. However, after the heat pump has been running for a few years, the fins on its evaporation side may be dirty or clogged. At this time, when the heat pump runs at high frequency at ultra-low temperatures again, it is often easy to report low pressure protection.

[0004] Chinese patent document number CN 110701840 A disclosed a compressor startup low-pressure control method on January 17, 2020. The control method is applied before the normal operation of the compressor, including: step 1, when the controller on the compressor receives the start-up command of the heat pump system, the controller sends a corresponding power-on command to the contactor that controls the start and stop of the compressor; step 2, the contactor that controls the start and stop of the compressor is powered on, and after continuously running for a preset running time T1, it is powered off and continuously maintained for a preset power-off time T2 to realize the compressor jog operation, and the value range of the preset running time T1 is within the unit of seconds; step 3, the number of operations of the contactor being powered on and then powered off after the current operation is powered on is added by 1, and when the number of operations is less than the preset maximum opening and closing number Nmax, it is transferred to step 2, otherwise the contactor is powered on and closed again, so that the compressor enters the normal operation state. The value of the preset power-off time T2 is greater than the value of the preset running time T1. The actual use effect of this compressor startup low-pressure control method is not ideal and needs to be improved. Summary of the invention

[0005] The object of the present invention is to provide a static start-up control method for a heat pump with stable and reliable operation, so as to overcome the shortcomings of the prior art.

[0006] A static start-up control method for a heat pump designed for this purpose is characterized by comprising the following steps:

[0007] Step 1: The heat pump is powered on and starts running, and then proceeds to step 2;

[0008] Step 2: During operation, the central controller of the heat pump records the number of low voltage protection faults reported and enters step 3;

[0009] Step 3, the central controller determines whether the number of failures within the time period K is the third time. If it is true, it goes to step 4, otherwise it goes to step 2, where the value range of K is 20 to 60 minutes;

[0010] Step 4: After the fault is cleared, the heat pump restarts and starts timing the current running time T, and then goes to step 5;

[0011] Step 5: The central controller determines whether T≤30 minutes is established. If it is established, it proceeds to step 6; otherwise, it proceeds to step 17;

[0012] Step 6, the central controller determines whether TS<P2 is established. If it is established, it goes to step 7, otherwise it goes to step 14, where TS is the current low pressure value, P2 is the second preset pressure value, and the value range of P2 is 0 to 10 bar;

[0013] Step 7: The central controller directly reduces the current operating frequency N of the compressor to the frequency F1, and enters step 8, wherein the value range of F1 is 0 to 50 Hz;

[0014] Step 8, continue running and enter step 9;

[0015] Step 9, the central controller determines whether TS≥P1+X is established. If it is established, it goes to step 10, otherwise it goes to step 13, where P1 is the first preset pressure value, the value range of P1 is 0 to 10 bar, X is the hysteresis value, the value range of X is 0 to 10 bar, and P2<P1;

[0016] Step 10: The central controller controls the current operating frequency N of the compressor to increase by one level every 3 minutes, and then proceeds to step 11;

[0017] Step 11, continue running and enter step 12;

[0018] Step 12, the central controller determines whether N=M is ​​established. If it is established, it goes to step 2, otherwise it goes to step 10, where M is the target operating frequency of the compressor;

[0019] Step 13, continue running and enter step 5;

[0020] Step 14: The central controller determines whether TS<P1 is established. If it is established, it proceeds to step 15; otherwise, it proceeds to step 13.

[0021] Step 15: The central controller controls the current operating frequency N of the compressor to decrease by one level every 20 seconds, and then proceeds to step 8;

[0022] Step 16, continue running and enter step 5;

[0023] Step 17, the central controller determines whether TS<P3 is established. If it is established, it proceeds to step 21, otherwise it proceeds to step 16, wherein P3 is a third preset pressure value, and the value range of P3 is 0 to 10 bar;

[0024] Step 18, the central controller determines whether TS≥P3 or Z<Y is established. If either of them is established, it goes to step 10, otherwise it goes to step 16, where Z is the current exhaust superheat, Y is the preset exhaust superheat, and the value range of Y is 0-50°C;

[0025] Step 19, continue running and enter step 20;

[0026] Step 20, the central controller controls the electronic expansion valve of the heat pump to force open 6 steps per TM time period, and then enters step 21, wherein the value range of TM is 0 to 50 seconds;

[0027] Step 21, the central controller determines whether Z≥Y is established. If it is established, it goes to step 20, otherwise it goes to step 22;

[0028] Step 22: The central controller controls the current operating frequency N of the compressor to decrease by one level every 20 seconds, and then proceeds to step 23;

[0029] In step 23, the central controller determines whether TS≥P3 is established. If it is established, it goes to step 10, otherwise it goes to step 22.

[0030] After adopting the above technical solution, the present invention controls the current operating frequency of the compressor by combining the low-pressure value, so that the compressor can operate stably for a long time within a reliable range. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 FIG. 4 is a control flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0033] See also Figure 1 , a static start control method for a heat pump, characterized in that it comprises the following steps:

[0034] Step 1: The heat pump is powered on and starts running, and then proceeds to step 2;

[0035] Step 2: During operation, the central controller of the heat pump records the number of low voltage protection faults reported and enters step 3;

[0036] Step 3, the central controller determines whether the number of failures within the time period K is the third time. If it is true, it goes to step 4, otherwise it goes to step 2, where the value range of K is 20 to 60 minutes;

[0037] Step 4: After the fault is cleared, the heat pump restarts and starts timing the current running time T, and then goes to step 5;

[0038] Step 5: The central controller determines whether T≤30 minutes is established. If it is established, it proceeds to step 6; otherwise, it proceeds to step 17;

[0039] Step 6, the central controller determines whether TS<P2 is established. If it is established, it goes to step 7, otherwise it goes to step 14, where TS is the current low pressure value, P2 is the second preset pressure value, and the value range of P2 is 0 to 10 bar;

[0040] Step 7: The central controller directly reduces the current operating frequency N of the compressor to the frequency F1, and enters step 8, wherein the value range of F1 is 0 to 50 Hz;

[0041] Step 8, continue running and enter step 9;

[0042] Step 9, the central controller determines whether TS≥P1+X is established. If it is established, it goes to step 10, otherwise it goes to step 13, where P1 is the first preset pressure value, the value range of P1 is 0 to 10 bar, X is the hysteresis value, the value range of X is 0 to 10 bar, and P2<P1;

[0043] Step 10: The central controller controls the current operating frequency N of the compressor to increase by one level every 3 minutes, and then proceeds to step 11;

[0044] Step 11, continue running and enter step 12;

[0045] Step 12, the central controller determines whether N=M is ​​established. If it is established, it goes to step 2, otherwise it goes to step 10, where M is the target operating frequency of the compressor;

[0046] Step 13, continue running and enter step 5;

[0047] Step 14: The central controller determines whether TS<P1 is established. If it is established, it proceeds to step 15; otherwise, it proceeds to step 13.

[0048] Step 15: The central controller controls the current operating frequency N of the compressor to decrease by one level every 20 seconds, and then proceeds to step 8;

[0049] Step 16, continue running and enter step 5;

[0050] Step 17, the central controller determines whether TS<P3 is established. If it is established, it proceeds to step 21, otherwise it proceeds to step 16, wherein P3 is a third preset pressure value, and the value range of P3 is 0 to 10 bar;

[0051] Step 18, the central controller determines whether TS≥P3 or Z<Y is established. If either of them is established, it goes to step 10, otherwise it goes to step 16, where Z is the current exhaust superheat, Y is the preset exhaust superheat, and the value range of Y is 0-50°C;

[0052] Step 19, continue running and enter step 20;

[0053] Step 20, the central controller controls the electronic expansion valve of the heat pump to force open 6 steps per TM time period, and then enters step 21, wherein the value range of TM is 0 to 50 seconds;

[0054] Step 21, the central controller determines whether Z≥Y is established. If it is established, it goes to step 20, otherwise it goes to step 22;

[0055] Step 22: The central controller controls the current operating frequency N of the compressor to decrease by one level every 20 seconds, and then proceeds to step 23;

[0056] In step 23, the central controller determines whether TS≥P3 is established. If it is established, it goes to step 10, otherwise it goes to step 22.

[0057] Application Examples

[0058] The following example uses R290 as the refrigerant. The pressure values ​​of different refrigerants are different.

[0059] 1. During the startup of the heat pump, if the low pressure protection is reported three times in succession within 30 minutes, the following steps will be entered after the fault is cleared, where P1 = 0.8 bar, P2 = 0.5 bar, P3 = 0.6 bar, F1 = 30 Hz, X = 0.2 bar, Y = 10 ° C, TM = 5 seconds.

[0060] (1) Entry conditions: Within the first 30 minutes after the heat pump is restarted, if the current low pressure value TS = 0.7 bar during operation, TS < P2 = 0.5 bar does not hold, and TS < P1 = 0.8 bar holds, the central controller determines that there is a risk of low pressure protection. Therefore, the central controller reduces the current operating frequency of the heat pump by one gear every 20 seconds; the frequency is reduced immediately upon the first trigger, to a minimum of 30 Hz.

[0061] When the current low pressure value during operation is TS=0.4 bar, TS<P2=0.5 bar is established, so the central controller directly reduces the current operating frequency of the heat pump to 30 Hz.

[0062] (2) Exit condition: If the current low pressure value TS during operation is 1 bar, TS ≥ P1 + X = 0.8 bar + 0.2 bar is established. Then, the central controller allows the current operating frequency of the heat pump to increase by one level every 3 minutes. The frequency will be increased immediately upon the first trigger until the preset target frequency is reached.

[0063] Within the first 30 minutes after the heat pump is restarted, since the heat pump system has not yet warmed up, the frequency is controlled according to the low pressure TS to keep the heat pump running in the low frequency band. When the entire heat pump system is running, the refrigerant and oil deposited in the heat pump system also start to run. Therefore, when the machine heat pump is running, the frequency is increased or decreased according to the pressure.

[0064] 2. After the heat pump starts and runs normally for 30 minutes, if the current low pressure value TS during operation is 0.5 bar, TS = 0.5 bar < P3 = 0.6 bar is established, and the central controller of the heat pump operates according to the current exhaust superheat Z.

[0065] (1) Entry conditions: After the heat pump starts and operates normally for 30 minutes, if TS<P3=0.6bar and Z=12℃≥Y=10℃ are satisfied, the central controller will force the electronic expansion valve to open 6 steps every TM=5 seconds.

[0066] (2) Exit conditions: You can exit if any of the following conditions are met.

[0067] ① When the current low pressure value TS ≥ 0.6 bar or ② When the current exhaust superheat Z < 10 °C.

[0068] (3) Entry conditions.

[0069] When the heat pump starts running for 30 minutes, if TS<P3=0.6bar and Z=8℃≥Y=10℃ is not true, the central controller will reduce the current operating frequency of the compressor by one gear every 20 seconds, and will immediately downshift when it is triggered for the first time.

[0070] (4) Exit condition: when the current low pressure value TS ≥ P3 = 0.6 bar.

[0071] 3. 30 minutes after the heat pump is started, if the current low pressure value TS is too low, according to the current exhaust superheat Z, within the specified range of exhaust superheat, the electronic expansion valve is opened first to increase the refrigerant circulation volume of the entire heat pump system and improve the evaporation temperature.

[0072] If the current exhaust superheat Z is less than the preset exhaust superheat Y, and the current low pressure is too low, forcing the electronic expansion valve to open may cause the heat pump to have a risk of liquid return. Therefore, the heat pump can only be reduced in frequency to increase the evaporation temperature.

[0073] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.

[0074] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A static start-up control method for a heat pump, characterized in that The following steps are involved: Step 1: The heat pump is powered on and starts running, and then proceeds to step 2; Step 2: During operation, the central controller of the heat pump records the number of low voltage protection faults reported and enters step 3; Step 3, the central controller determines whether the number of failures within the time period K is the third time. If it is true, it goes to step 4, otherwise it goes to step 2, where the value range of K is 20 to 60 minutes; Step 4: After the fault is cleared, the heat pump restarts and starts timing the current running time T, and then goes to step 5; Step 5: The central controller determines whether T≤30 minutes is established. If it is established, it proceeds to step 6; otherwise, it proceeds to step 17; Step 6, the central controller determines whether TS<P2 is established. If it is established, it goes to step 7, otherwise it goes to step 14, where TS is the current low pressure value, P2 is the second preset pressure value, and the value range of P2 is 0 to 10 bar; Step 7: The central controller directly reduces the current operating frequency N of the compressor to the frequency F1, and enters step 8, wherein the value range of F1 is 0 to 50 Hz; Step 8, continue running and enter step 9; Step 9, the central controller determines whether TS≥P1+X is established. If it is established, it goes to step 10, otherwise it goes to step 13, where P1 is the first preset pressure value, the value range of P1 is 0 to 10 bar, X is the hysteresis value, the value range of X is 0 to 10 bar, and P2<P1; Step 10: The central controller controls the current operating frequency N of the compressor to increase by one level every 3 minutes, and then proceeds to step 11; Step 11, continue running and enter step 12; Step 12, the central controller determines whether N=M is ​​established. If it is established, it goes to step 2, otherwise it goes to step 10, where M is the target operating frequency of the compressor; Step 13, continue running and enter step 5; Step 14: The central controller determines whether TS<P1 is established. If it is established, it proceeds to step 15; otherwise, it proceeds to step 13. Step 15: The central controller controls the current operating frequency N of the compressor to decrease by one level every 20 seconds, and then proceeds to step 8; Step 16, continue running and enter step 5; Step 17, the central controller determines whether TS<P3 is established. If it is established, it proceeds to step 21, otherwise it proceeds to step 16, wherein P3 is a third preset pressure value, and the value range of P3 is 0 to 10 bar; Step 18, the central controller determines whether TS≥P3 or Z<Y is established. If either of them is established, it goes to step 10, otherwise it goes to step 16, where Z is the current exhaust superheat, Y is the preset exhaust superheat, and the value range of Y is 0-50°C; Step 19, continue running and enter step 20; Step 20, the central controller controls the electronic expansion valve of the heat pump to force open 6 steps per TM time period, and then enters step 21, wherein the value range of TM is 0 to 50 seconds; Step 21, the central controller determines whether Z≥Y is established. If it is established, it goes to step 20, otherwise it goes to step 22; Step 22: The central controller controls the current operating frequency N of the compressor to decrease by one level every 20 seconds, and then proceeds to step 23; In step 23, the central controller determines whether TS≥P3 is established. If it is established, it goes to step 10, otherwise it goes to step 22.

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