Control method of heat pump unit

Abstract

The invention relates to the technical field of heat pump units, particularly provides a control method of a heat pump unit, and aims to solve the problem that the heat pump unit cannot run stably due to voltage fluctuation. In order to achieve the purpose, the control method of the heat pump unit comprises the steps that the actual operation voltage and the rated voltage of the heat pump unit are obtained; determining a voltage fluctuation ratio according to the actual operation voltage and the rated voltage; comparing the voltage fluctuation ratio with a preset fluctuation ratio; an operating frequency of the at least one compressor is selectively reduced based on a result of the comparison. The voltage fluctuation ratio is determined according to the actual operation voltage and the rated voltage, and then the operation frequency of the compressor is adjusted in time according to the voltage fluctuation ratio and the preset fluctuation ratio, so that stable operation of the unit is ensured, potential damage to key components such as the compressor due to voltage fluctuation is reduced, and the service life of the unit is prolonged.

Description

Technical Field

[0001] The present invention relates to the field of heat pump units, and specifically provides a control method for a heat pump unit. Background Art

[0002] A heat pump unit is an energy-saving device that uses high-level energy to make heat flow from a low-level heat source (such as air, water, etc.) to a high-level heat source. It can effectively utilize low-grade heat energy that is difficult to apply and has the beneficial effect of energy saving, so it is widely used in production and life. However, in remote areas and during the peak electricity consumption seasons of winter and summer, the power supply grid is prone to voltage fluctuations, which will pose challenges to the stable operation of the heat pump unit and even cause compressor damage.

[0003] Therefore, a new technical solution is needed in this field to solve the above problems. Summary of the Invention

[0004] To solve at least one problem in the prior art, that is, to solve the problem that the heat pump unit cannot operate stably due to voltage fluctuations, the present application provides a control method for a heat pump unit. The heat pump unit includes n compressors, where n≥1. The control method includes:

[0005] Obtain the actual operating voltage and the rated voltage of the heat pump unit respectively;

[0006] Determine the voltage fluctuation rate according to the actual operating voltage and the rated voltage;

[0007] Compare the size of the voltage fluctuation rate with the preset fluctuation rate;

[0008] Based on the comparison result, selectively reduce the operating frequency of at least one of the compressors.

[0009] In a preferred technical solution of the above control method, the step of "based on the comparison result, selectively reduce the operating frequency of at least one of the compressors" further includes:

[0010] When the voltage fluctuation rate is greater than or equal to the preset fluctuation rate, reduce the operating frequency of at least one of the compressors.

[0011] In a preferred technical solution of the above control method, after the step of "reduce the operating frequency of at least one of the compressors", the following steps are further included:

[0012] Obtain the actual operating voltage again;

[0013] Determine the voltage fluctuation rate according to the actual operating voltage and the rated voltage;

[0014] Compare the size of the voltage fluctuation rate with the preset fluctuation rate;

[0015] When the voltage volatility is greater than or equal to the preset volatility, the compressor that controls the reduction of the operating frequency stops operating.

[0016] In a preferred technical solution of the above control method, when the heat pump unit further includes the compressor in an operating state, after the step of "reducing the operating frequency of at least one of the compressors", the following steps are further included:

[0017] Repeat the steps of reducing the compressor frequency and stopping the operation until the voltage volatility is less than the preset volatility or all n compressors are in a stopped operating state.

[0018] In a preferred technical solution of the above control method, when the heat pump unit further includes a water circulation loop and a water pump is provided on the water circulation loop, before the step of "selectively reducing the operating frequency of at least one of the compressors", the following steps are further included:

[0019] When the voltage volatility is greater than or equal to the preset volatility, control the water pump to stop working or reduce the operating frequency of the water pump;

[0020] Continue to obtain the actual operating voltage;

[0021] Determine the voltage volatility according to the actual operating voltage and the rated voltage;

[0022] Compare the magnitude of the voltage volatility with the preset volatility;

[0023] When the voltage volatility is greater than or equal to the preset volatility, reduce the operating frequency of at least one of the compressors.

[0024] In a preferred technical solution of the above control method, when the heat pump unit further includes an auxiliary heating device, before the step of "selectively reducing the operating frequency of at least one of the compressors", the following steps are further included:

[0025] When the voltage volatility is greater than or equal to the preset volatility, control the auxiliary heating device to stop working;

[0026] Continue to obtain the actual operating voltage and the rated voltage;

[0027] Determine the voltage volatility according to the actual operating voltage and the rated voltage;

[0028] Compare the magnitude of the voltage volatility with the preset volatility;

[0029] When the voltage volatility is greater than or equal to the preset volatility, selectively reduce the operating frequency of at least one of the compressors.

[0030] In the preferred technical solution of the above control method, before, after or at the same time as the step of "selectively reducing the operating frequency of at least one of the compressors based on the comparison result", the following steps are further included:

[0031] Obtain the three-phase currents of each of the compressors respectively;

[0032] Compare the magnitudes of the three-phase currents with a preset current;

[0033] When at least one of the three-phase currents of at least one of the compressors is greater than the preset current, control the corresponding compressor to stop working; or

[0034] Obtain the three-phase currents of each of the compressors respectively;

[0035] Based on the three-phase currents, determine the maximum phase current of the compressor;

[0036] Compare the magnitude of the maximum phase current with the preset current;

[0037] When the maximum phase current of at least one of the compressors is greater than the preset current, control the corresponding compressor to stop working.

[0038] In the preferred technical solution of the above control method, before, after or at the same time as the step of "selectively reducing the operating frequency of at least one of the compressors based on the comparison result", the following steps are further included:

[0039] Obtain the three-phase currents of each of the compressors respectively;

[0040] Determine the three-phase current unbalance degree of each of the compressors according to the three-phase currents;

[0041] Compare the magnitudes of the three-phase current unbalance degree and the preset three-phase current unbalance degree;

[0042] When the three-phase current unbalance degree is greater than the preset unbalance degree, control the corresponding compressor to stop working.

[0043] In the preferred technical solution of the above control method, the three-phase current unbalance degree is determined according to the following formula:

[0044] The three-phase current unbalance degree is determined based on the following formula:

[0045]

[0046] where L is the three-phase current unbalance degree, I1, I2, and I3 are the three-phase currents, is the average value of the three-phase currents.

[0047] where L is the three-phase current unbalance degree, is the average value of the three-phase currents.

[0048] In the preferred technical solution of the above control method, the voltage fluctuation rate is determined based on the following formula:

[0049] m = (U - Un) / Un

[0050] Where m is the voltage fluctuation rate, U is the actual operating voltage, and Un is the rated voltage.

[0051] Those skilled in the art can understand that the control method of the heat pump unit in this application determines the voltage fluctuation rate according to the actual operating voltage and the rated voltage, and then adjusts the operating frequency of the compressor in a timely manner according to the magnitude of the voltage fluctuation rate and the preset fluctuation rate, so as to ensure the stable operation of the unit, reduce the potential damage to key components such as the compressor caused by voltage fluctuations, and thus extend the service life of the unit.

[0052] Furthermore, when the voltage fluctuation rate is greater than the preset fluctuation rate, the voltage fluctuation rate is reduced by reducing the operating frequency of at least one compressor, ensuring the stable operation of the unit, reducing the potential damage to key components such as the compressor caused by voltage fluctuations, and thus extending the service life of the unit.

[0053] Furthermore, after reducing the operating frequency of the compressor, the voltage fluctuation rate is re-determined, and when the voltage fluctuation rate is higher than the preset value, the compressor whose operating frequency is reduced is controlled to stop running, so that the voltage fluctuation rate is further reduced, ensuring the stable operation of the unit and improving the reliability of the unit.

[0054] Furthermore, by repeating the steps of reducing the compressor frequency and stopping the operation until the voltage fluctuation rate is continuously less than the preset fluctuation rate or all compressors are in the stopped state when the voltage fluctuation rate is continuously higher than the preset fluctuation rate, key components such as the compressor can be protected from damage, which helps to extend the service life of the unit and reduce the maintenance and replacement costs.

[0055] Furthermore, before reducing the operating frequency of the compressor, the voltage fluctuation rate is reduced by reducing the operating frequency of the water pump or controlling the water pump to stop running, ensuring the stable operation of the unit, reducing the potential damage to key components such as the compressor caused by voltage fluctuations, and thus extending the service life of the unit.

[0056] Furthermore, before reducing the operating frequency of the compressor, the voltage fluctuation rate is reduced by controlling the auxiliary heating equipment to stop working, ensuring the stable operation of the unit, reducing the potential damage to key components such as the compressor caused by voltage fluctuations, and thus extending the service life of the unit.

[0057] Further, by obtaining the three-phase current of each compressor, when at least one of the three-phase currents exceeds a preset current, the corresponding compressor is controlled to stop working, thereby protecting the compressor and preventing the compressor's service life from being affected by abnormal current.

[0058] Further, by calculating the three-phase current unbalance degree of each compressor and controlling the corresponding compressor to stop working when the three-phase current unbalance degree exceeds a preset value of the current unbalance degree, it is possible to avoid problems such as the overall or partial overheating of the compressor caused by the three-phase current unbalance, increased energy consumption, and further affect the service life of the compressor. Brief Description of the Drawings

[0059] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings, in which:

[0060] Figure 1 is a flowchart of the control method of the heat pump unit of the present application;

[0061] Figure 2 is a system diagram of the heat pump unit of the present application;

[0062] Figure 3 is the logic of a possible implementation manner of the control method of the heat pump unit of the present application Figure 1 ;

[0063] Figure 4 is the logic of a possible implementation manner of the control method of the heat pump unit of the present application Figure 2 .

[0064] Description of the reference numerals:

[0065] 1. Compressor; 11. Heating belt; 2. Indoor heat exchanger; 21. Water inlet side; 22. Water outlet side; 3. Water pump; 4. Water circulation loop. Detailed Embodiments

[0066] The preferred embodiments of the present application will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are only used to explain the technical principle of the present application and are not intended to limit the protection scope of the present application.

[0067] It should be noted that in the description of the present application, terms such as "upper", "lower", "inner", "bottom", "end" and other terms indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present application.

[0068] In addition, it should be noted that in the description of this application, unless otherwise clearly specified and limited, the terms "set", "connected", and "communicated" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0069] First, in combination with Figure 1-2 , the control method of the heat pump unit of this application will be introduced. Among them, Figure 1 is the flowchart of the control method of the heat pump unit of this application, Figure 2 is the system diagram of the heat pump unit of this application.

[0070] As Figure 1-2 shown, in order to solve the problem that the heat pump unit cannot operate stably due to voltage fluctuations, the heat pump unit of this application includes n compressors 1, where n≥1. Among them, the n compressors 1 are arranged in parallel.

[0071] On the premise of the above setting method, the control method of the heat pump unit of this application includes:

[0072] S101. Respectively obtain the actual operating voltage and the rated voltage of the heat pump unit; for example, the heat pump unit can be configured with a circuit or component for obtaining voltage, and the actual operating voltage of the heat pump unit is detected through this circuit or component. The rated voltage of the heat pump unit can be stored in the memory of the heat pump unit before leaving the factory for convenient retrieval during use. Of course, it can also be obtained from the cloud database through networking or other means.

[0073] S102. Determine the voltage fluctuation rate according to the actual operating voltage and the rated voltage; for example, the voltage fluctuation rate can be determined based on the comparison relationship between the actual operating voltage and the rated voltage, such as a comparison table, an empirical formula, or a fitting formula.

[0074] S103. Compare the size of the voltage fluctuation rate with the preset fluctuation rate. For example, after determining the voltage fluctuation rate, the size of the two is compared by comparing whether the difference between the voltage fluctuation rate and the preset fluctuation rate is greater than 0, or whether the ratio between the two is greater than 1.

[0075] S104. Based on the comparison result, selectively reduce the operating frequency of at least one compressor 1. After determining the size of the voltage fluctuation rate and the preset fluctuation rate, the operating frequency of one compressor 1 or the operating frequencies of n compressors 1 can be reduced. On the one hand, it can balance the impact of voltage fluctuations on the entire unit, and on the other hand, it can avoid damage to the compressor 1 caused by voltage fluctuations.

[0076] Based on the actual operating voltage and the rated voltage, this application determines the voltage fluctuation rate, and then adjusts the operating frequency of the compressor 1 in a timely manner according to the magnitude of the voltage fluctuation rate and the preset fluctuation rate, so as to ensure the stable operation of the unit, reduce the potential damage to key components such as the compressor 1 caused by voltage fluctuations, and thus extend the service life of the unit.

[0077] It should be noted that the unit mentioned in this application refers to a heat pump unit.

[0078] It should be noted that the power grid fluctuation includes two situations. One is that the power grid voltage is lower than the municipal standard voltage, and the other is that the power grid voltage exceeds the municipal standard voltage. Among them, when the power grid voltage is lower than the indoor standard voltage, it will cause the operating voltage of the unit to decrease. When the power grid voltage exceeds the indoor voltage, it will cause the operating voltage of the unit to be too high, and then the operating current will increase. Therefore, these two fluctuation methods enable the heat pump unit to have two control methods. The following takes the power grid voltage being lower than the municipal standard voltage as an example to introduce the preferred implementation manner of the control method of the heat pump unit of this application.

[0079] In one implementation manner, the voltage fluctuation rate is determined based on the following formula (Ⅰ):

[0080] m = (U - Un) / Un (Ⅰ)

[0081] Wherein, m is the voltage fluctuation rate, U is the actual operating voltage, and Un is the rated voltage.

[0082] By using the comparison formula between the voltage fluctuation rate and the preset fluctuation rate to determine the voltage fluctuation rate, the accuracy of the voltage fluctuation rate can be improved, the precise control of the unit can be realized, and the stability and reliability of the unit can be improved.

[0083] In one implementation manner, when the heat pump unit includes a water circulation loop 4 and a water pump 3 is provided on the water circulation loop 4, before the step of "selectively reducing the operating frequency of at least one of the compressors 1", it further includes:

[0084] When the voltage fluctuation rate is greater than or equal to the preset fluctuation rate, control the water pump 3 to stop working or reduce the operating frequency of the water pump 3;

[0085] Continue to obtain the actual operating voltage;

[0086] Determine the voltage fluctuation rate according to the actual operating voltage and the rated voltage;

[0087] Compare the magnitude of the voltage fluctuation rate and the preset fluctuation rate;

[0088] Based on the comparison result, selectively reduce the operating frequency of at least one of the compressors 1.

[0089] Among them, the water pump 3 can be arranged on the water inlet side of the water circulation loop 4, that is, the water inlet side 21 of the indoor heat exchanger 2.

[0090] For example, taking the voltage fluctuation rate as m and the preset fluctuation rate K as 0.1 for illustration. When m≥0.1, it indicates that the power grid fluctuates greatly, resulting in a relatively large voltage fluctuation rate of the unit, exceeding the range allowed for the normal operation of the unit, and directly affecting the stability and reliability of the unit. Therefore, when m≥0.1, by controlling the water pump 3 to stop working or reducing the operating frequency of the water pump 3, the voltage fluctuation rate can be reduced to solve the impact caused by voltage fluctuation on the unit. When m<0.1, it indicates that the power grid fluctuates relatively little, resulting in a relatively small voltage fluctuation of the heat pump unit, which is within the range allowed for the normal operation of the unit, and the heat pump unit can operate normally within this range.

[0091] Also, for example, taking the voltage fluctuation rate as m, the preset fluctuation rate K as 0.1, and n as 1 for illustration. When m≥0.1, reduce the operating frequency of the water pump 3. Then continue to obtain the actual operating voltage of the unit and calculate the voltage fluctuation rate again. If m≥0.1, the water pump 3 can be controlled to stop working to reduce the voltage fluctuation rate. After stopping the water pump 3 from working, the actual operating voltage of the unit can be obtained again, the voltage fluctuation rate can be calculated, and based on the comparison result, the operating frequency of the compressor 1 can be selectively reduced.

[0092] Also, for example, taking the voltage fluctuation rate as m, the preset fluctuation rate K as 0.1, and n as 2 for illustration. After controlling the water pump 3 to stop working or reducing the operating frequency, since the stop or reduction of the operating frequency of the water pump 3 will affect the actual operating voltage of the unit. Therefore, it is necessary to continue to obtain the actual operating voltage of the unit, calculate the voltage fluctuation rate, and based on the comparison result, selectively reduce the operating frequency of one or two compressors 1.

[0093] In one implementation, when the heat pump unit further includes an auxiliary heating device, before the step of "selectively reducing the operating frequency of at least one of the compressors 1", it further includes:

[0094] When the voltage fluctuation rate is greater than or equal to the preset fluctuation rate, control the auxiliary heating device to stop working;

[0095] Continue to obtain the actual operating voltage and the rated voltage;

[0096] Determine the voltage fluctuation rate according to the actual operating voltage and the rated voltage;

[0097] Compare the size of the voltage fluctuation rate and the preset fluctuation rate;

[0098] When the voltage fluctuation rate is greater than or equal to the preset fluctuation rate, selectively reduce the operating frequency of at least one of the compressors 1.

[0099] Among them, the auxiliary heating device includes a heating tape 11 provided on the compressor 1 and / or an electric heating device provided on the water outlet side of the water circulation loop 4 (i.e., the water outlet side 22 of the indoor heat exchanger). In addition, when the auxiliary heating device includes the heating tape 11, the same heating tape 11 can be provided on n compressors 1, or the heating tape 11 can be provided on each compressor 1 separately. When the heating tape 11 is provided on each compressor 1 separately, all the heating tapes 11 can be controlled to stop working simultaneously, or the heating tapes 11 can be controlled to stop working in sequence until the voltage fluctuation rate is less than the preset fluctuation rate. If, after controlling all the heating tapes 11 to stop working, the voltage fluctuation rate is still greater than or equal to the preset fluctuation rate, the operating frequency of the compressor 1 can be reduced.

[0100] For example, taking the auxiliary heating device as an electric heating device, the voltage fluctuation rate is m, and the preset fluctuation rate K is 0.1 for illustration. When m≥0.1, it indicates that the power grid fluctuates greatly, resulting in a relatively large voltage fluctuation rate of the unit, exceeding the range allowed for the normal operation of the unit. Therefore, m≥0.1 will directly affect the stability and reliability of the unit. So, when m≥0.1, by controlling the heating device to stop working, the voltage fluctuation rate can be reduced to solve the impact on the unit caused by voltage fluctuations. When m<0.1, it indicates that the power grid fluctuates relatively little, resulting in a relatively small voltage fluctuation of the heat pump unit, which is within the range allowed for the normal operation of the unit, and the heat pump unit can operate normally. Therefore, when m<0.1, the original working mode of the heat pump unit can be maintained.

[0101] Again, for example, taking the auxiliary heating device as the heating tape 11, the voltage fluctuation rate is m, the preset fluctuation rate K is 0.1, and the number of compressors 1 is 1 for illustration. After controlling the heating tape 11 heating device to stop working, since the stop of the heating tape 11 will affect the actual operating voltage of the unit. Therefore, it is necessary to continue to obtain the actual operating voltage of the unit, calculate the voltage fluctuation rate, and then selectively reduce the operating frequency of one or two compressors 1 based on the comparison result.

[0102] Again, for example, taking the voltage fluctuation rate as m, the preset fluctuation rate K is 0.1, the number of compressors 1 is 2, and the heating tape 11 is provided on each compressor 1 for illustration. When m≥0.1, the heating tape 11 can be controlled to stop working in sequence. Specifically, as follows, the heating tape 11 on one compressor 1 can be controlled to stop working first, and then it is necessary to obtain the actual operating voltage of the unit again and calculate the voltage fluctuation rate. If the voltage fluctuation rate is still greater than or equal to 0.1, the heating tape 11 on the other compressor 1 can be controlled to stop working. After all the heating tapes 11 stop working, by re-obtaining the actual operating voltage, calculating the voltage fluctuation rate, and then selectively reducing the operating frequency of one or two compressors 1 based on the comparison result.

[0103] Again, for example, taking the voltage fluctuation rate as m, the preset fluctuation rate K as 0.1, and the number of compressors 1 as 2, heating tapes 11 are provided on each compressor 1 for illustration. When m ≥ 0.1, all the heating tapes 11 can be controlled to stop working in sequence. Specifically, the heating tapes 11 on the two compressors 1 can be controlled to stop working simultaneously. After all the heating tapes 11 stop working, by re-acquiring the actual operating voltage and then based on the comparison result, the operating frequency of one or two compressors 1 can be selectively reduced.

[0104] In one implementation manner, the step of "selectively reducing the operating frequency of at least one of the compressors 1 based on the comparison result" further includes:

[0105] When the voltage fluctuation rate is greater than or equal to the preset fluctuation rate, reduce the operating frequency of at least one of the compressors 1.

[0106] For example, taking the voltage fluctuation rate as m, the preset fluctuation rate K as 0.1, and the number of compressors 1 as 1 for illustration. When m ≥ 0.1, it indicates that the power grid fluctuates greatly, resulting in a relatively large voltage fluctuation rate of the unit, exceeding the range allowed for the normal operation of the unit. Therefore, m ≥ 0.1 will directly affect the stability and reliability of the unit. At this time, it is necessary to reduce the voltage fluctuation rate by reducing the operating frequency of the compressor 1 to solve the impact on the unit caused by the voltage fluctuation. When m < 0.1, it means that the voltage fluctuation rate is within the range allowed for the normal operation of the unit, and the heat pump unit can operate normally. At this time, maintaining the working mode of the heat pump unit is sufficient.

[0107] Again, for example, taking the voltage fluctuation rate as m, the preset fluctuation rate K as 0.1, and the number of compressors 1 as 2 for illustration. When m ≥ 0.1, the voltage fluctuation rate can be reduced by reducing the operating frequency of one or two compressors 1 to solve the impact on the unit caused by the voltage fluctuation.

[0108] Further, after the step of "reducing the operating frequency of at least one of the compressors 1", it further includes:

[0109] Acquire the actual operating voltage again;

[0110] Determine the voltage fluctuation rate according to the actual operating voltage and the rated voltage;

[0111] Compare the size of the voltage fluctuation rate and the preset fluctuation rate;

[0112] When the voltage fluctuation rate is greater than or equal to the preset fluctuation rate, control the compressor 1 with the reduced operating frequency to stop running.

[0113] For example, let the voltage volatility be m, the preset volatility K be 0.1, and the number of compressors 1 be 1 for illustration. After reducing the operating frequency of compressor 1, since the reduction in the frequency of compressor 1 will affect the actual operating voltage of the unit. Therefore, it is necessary to obtain the actual operating voltage of the unit again and calculate the voltage volatility again. If m≥0.1, it means that the voltage fluctuation of the unit is still relatively large. At this time, it is necessary to control compressor 1 to stop working to further reduce the voltage volatility to solve the impact caused by voltage fluctuation on the unit. And since there is only 1 compressor 1 in the unit, controlling this compressor 1 to stop working means that it is necessary to control the entire unit to stop working. When m<0.1, it means that by reducing the operating frequency of compressor 1, the voltage volatility is within the range allowed for the normal operation of the unit, and the unit can work normally. At this time, the working mode of the heat pump unit can be maintained.

[0114] Again, for example, let the preset volatility K be 0.1 and the number of compressors 1 be 2 for illustration. After reducing the operating frequency of one compressor 1, since the reduction in the frequency of compressor 1 will affect the actual operating voltage of the unit. Therefore, it is necessary to obtain the actual operating voltage U of the unit again and calculate the voltage volatility again. If m≥0.1, it means that the voltage fluctuation of the unit is still relatively large. At this time, it is necessary to control the compressor 1 with the reduced operating frequency to stop working to further reduce the voltage volatility to solve the impact caused by voltage fluctuation on the unit. And since there are two compressors 1 in the unit, controlling one compressor 1 to stop working will not affect the operation of the unit. When m<0.1, it means that by reducing the operating frequency of 1 compressor 1, the voltage volatility is within the range allowed for the normal operation of the unit, and the unit can work normally. At this time, the working mode of the heat pump unit can be maintained.

[0115] Again, for example, let the preset volatility K be 0.1 and the number of compressors 1 be 2 for illustration. After reducing the operating frequencies of two compressors 1, since the reduction in the frequencies of compressors 1 will affect the actual operating voltage of the unit. Therefore, it is necessary to obtain the actual operating voltage of the unit again and calculate the voltage volatility again. If m≥0.1, it means that the voltage fluctuation of the unit is still relatively large. At this time, it is possible to control one or two compressors 1 to stop working to further reduce the voltage volatility to solve the impact caused by voltage fluctuation on the unit. When controlling one compressor 1 to stop working, since there are two compressors 1 in the unit, controlling one compressor 1 to stop working will not affect the operation of the unit. When controlling two compressors 1 to stop working, since there are only two compressors 1 in the unit, and both of these compressors 1 stop working, it means that the entire unit needs to stop working.

[0116] Next, in combination with Figure 3 , a possible operation process of the control method of the heat pump unit of the present application will be briefly described.Figure 3 It is a logic diagram of a possible implementation manner of the control method of the heat pump unit of the present application. Among them, it is described with the number of compressors 1 in the heat pump unit being 2.

[0117] S201. Respectively obtain the actual operating voltage U1 and the rated voltage U of the unit, n and then execute S202.

[0118] S202. Calculate the voltage fluctuation rate m1 according to formula (Ⅰ), and then execute S203.

[0119] S203. Determine whether m1≥0.1 holds? If it holds, execute S204; if it does not hold, execute S201.

[0120] S204. Control the water pump 3 to stop working, and then execute S205.

[0121] S205. Obtain the actual operating voltage U2 again, and then execute S206.

[0122] S206. Calculate the voltage fluctuation rate m2 according to formula (Ⅰ), and then execute S207.

[0123] S207. Determine whether m2≥0.1 holds? If it holds, execute S208; if it does not hold, execute S205.

[0124] S208. Control the heating belts 11 on the two compressors 1 and the electric heating devices on the water circulation loop 4 to stop working, and then execute S209.

[0125] S209. Obtain the actual operating voltage U3 again, and then execute S210.

[0126] S210. Calculate the voltage fluctuation rate m3 according to formula (Ⅰ), and then execute S211.

[0127] S211. Determine whether m3≥0.1 holds? If it holds, execute S212; if it does not hold, execute S209.

[0128] S212. Reduce the operating frequency of any one of the compressors 1, and then execute S213.

[0129] S213. Obtain the actual operating voltage U4 again, and then execute S214.

[0130] S214. Calculate the voltage fluctuation rate m4 according to formula (Ⅰ), and then execute S215.

[0131] S215. Determine whether m4≥0.1 holds? If it holds, execute S216; if it does not hold, execute S213.

[0132] S216. Stop the compressor 1 with the reduced operating frequency, and then execute S209.

[0133] The following is an introduction to the preferred implementation mode of the control method of the heat pump unit of the present application when the grid voltage exceeds the municipal standard voltage.

[0134] In one implementation mode, before, after, or at the same time as the step of "selectively reducing the operating frequency of at least one compressor 1 based on the comparison result", it further includes:

[0135] Obtain the three-phase currents of each of the compressors 1 respectively;

[0136] Compare the magnitudes of the three-phase currents with a preset current;

[0137] When at least one of the three-phase currents of at least one of the compressors 1 is greater than the preset current, control the corresponding compressor 1 to stop working; or

[0138] Obtain the three-phase currents of each of the compressors 1 respectively;

[0139] Based on the three-phase currents, determine the maximum phase current of the compressor 1;

[0140] Compare the magnitude of the maximum phase current with the preset current;

[0141] When the maximum phase current of at least one of the compressors 1 is greater than the preset current, control the corresponding compressor 1 to stop working.

[0142] It should be noted that due to the influence of grid fluctuations on the voltage fluctuations of the unit, the current of the compressor 1 in the unit will also be too large, which is likely to damage the compressor 1. Therefore, it is necessary to detect the three-phase currents of each compressor 1 to avoid damage to the compressor 1 due to excessive current.

[0143] For example, taking the preset current as 1.2 A and the number of compressors 1 as 1 for illustration. Obtain the three-phase currents of the compressor 1 respectively, that is, I1, I2, and I3. Compare the three-phase currents I1, I2, and I3 of the compressor 1 with the preset current b respectively. When at least one of I1, I2, and I3 is greater than 1.2 A, it indicates that the compressor 1 is abnormal. Therefore, control the compressor 1 to stop working. And since there is only one compressor 1 in the unit, when the compressor 1 stops working due to abnormal current, it means that the entire unit stops working. Therefore, there is no need to further perform the step of adjusting the working mode of the compressor 1 due to voltage fluctuations.

[0144] Also, for example, it is described with a preset current of 1.2 A and the number of compressors 1 being 2. The three-phase currents of each compressor 1 are obtained respectively, namely I1, I2, and I3. The three-phase currents I1, I2, and I3 of each compressor 1 are compared with the preset current b respectively. When the phase current of one compressor 1 is abnormal, that is, at least one of I1, I2, and I3 of this compressor 1 is greater than 1.2 A, it indicates that the compressor 1 is abnormal. Therefore, the compressor 1 is controlled to stop working. And since there are two compressors 1 in the unit, when one compressor 1 stops working due to abnormal current, it does not affect the operation of the other compressor 1. Therefore, the step of adjusting the working mode of the compressor 1 due to voltage fluctuation can be continued.

[0145] Also, for example, it is described with a preset current of 1.2 A and the number of compressors 1 being 2. The three-phase currents of each compressor 1 are obtained respectively, namely I1, I2, and I3. The three-phase currents I1, I2, and I3 of each compressor 1 are compared with the preset current b respectively. When the phase currents of the two compressors 1 are abnormal, the two compressors 1 are controlled to stop working. And since there are two compressors 1 in the unit, when the two compressors 1 stop working due to abnormal current, it means that the entire unit stops working. Therefore, there is no need to perform the step of adjusting the working mode of the compressor 1 due to voltage fluctuation.

[0146] Also, for example, it is described with the maximum phase current being Imax, the preset current being 1.2 A, and the number of compressors 1 being 1. The three-phase currents of the compressor 1 are obtained respectively, namely I1, I2, and I3. The magnitudes of I1, I2, and I3 are compared to determine the maximum value of the three-phase currents, and the maximum phase current Imax is obtained. The maximum phase current Imax of the compressor 1 is compared with the preset current. When Imax > 1.2 A, it indicates that the compressor 1 is abnormal, and then the compressor 1 is controlled to stop working. And since there is only one compressor 1 in the unit, when the compressor 1 stops working due to abnormal current, it means that the entire unit stops working. Therefore, there is no need to perform the step of adjusting the working mode of the compressor 1 due to voltage fluctuation.

[0147] Also, for example, it is described with the maximum phase current being Imax, the preset current being 1.2 A, and the number of compressors 1 being 2. The three-phase currents of each compressor 1 are obtained respectively, namely I1, I2, and I3. The magnitudes of I1, I2, and I3 are compared to determine the maximum value of the three-phase currents, and the maximum phase currents Imax of the two compressors 1 are obtained. The two maximum phase currents Imax are compared with the preset current b respectively. When the maximum phase current Imax of one compressor 1 is greater than 1.2 A, it indicates that this compressor 1 is abnormal. Therefore, the compressor 1 with the maximum phase current Imax greater than 1.2 A is controlled to stop working. And since there are two compressors 1 in the unit, when this compressor 1 stops working due to abnormal current, it does not affect the operation of the two compressors 1. Therefore, the step of adjusting the working mode of the compressor 1 due to voltage fluctuation can be continued.

[0148] Also, for example, taking the maximum phase current as Imax, the preset current as 1.2 A, and the number of compressors 1 as 2 for illustration. The three-phase currents of each compressor 1 are obtained respectively, namely I1, I2, and I3. Compare the magnitudes of I1, I2, and I3 to determine the maximum value among the three phase currents, and obtain the maximum phase current Imax of the two compressors 1. Compare the two maximum phase currents Imax with the preset current b respectively. When the maximum phase currents Imax of the two compressors 1 are both greater than 1.2 A, it indicates that there is an abnormality in the two compressors 1. Therefore, control these two compressors 1 to stop working. And since there are two compressors 1 in the unit, when the two compressors 1 stop working due to current abnormality, it means that the entire unit stops working. Therefore, there is no need to perform the step of adjusting the working mode of the compressor 1 due to voltage fluctuation anymore.

[0149] In one implementation, before, after, or at the same time as the step of "selectively reducing the operating frequency of at least one of the compressors 1 based on the comparison result", it further includes:

[0150] Obtain the three-phase currents of each compressor 1 respectively;

[0151] Determine the three-phase current unbalance degree of each compressor 1 according to the three-phase currents;

[0152] Compare the magnitudes of the three-phase current unbalance degree and the preset current unbalance degree;

[0153] When the three-phase current unbalance degree is greater than the preset unbalance degree, control the corresponding compressor 1 to stop working.

[0154] Specifically, the three-phase current unbalance degree is determined based on the following formula (Ⅱ):

[0155]

[0156] where L is the three-phase current unbalance degree, I1, I2, I3 are the three-phase currents, is the average value of the three-phase currents.

[0157] It should be noted that due to the influence of power grid fluctuations on the voltage fluctuations of the unit, it will also cause the three-phase currents of the compressors 1 in the unit to be unbalanced. The three-phase current unbalance not only affects the normal operation of the compressors 1, but also reduces the power utilization efficiency and increases the line loss. It may even have an adverse impact on other equipment in the unit. Therefore, it is necessary to make adjustments according to the three-phase current unbalance degree of each compressor 1. Among them, the three-phase current unbalance degree can be determined by formula (Ⅱ).

[0158] For example, taking the three-phase current unbalance degree as L, the preset three-phase current unbalance degree b as 0.05, and the number of compressors 1 as 1 for illustration. The three-phase currents of the compressor 1 are obtained respectively, namely I1, I2, and I3. According to Calculate the average value of the three-phase currents of the compressor 1 Then according to the formula Calculate the three-phase current unbalance degree of the compressor 1. When L > 0.5, it indicates that the three-phase current unbalance degree of the compressor 1 exceeds the normal operating range of the compressor 1. At this time, it is necessary to control the compressor 1 to stop working to avoid the adverse effects on the compressor 1 caused by the excessive three-phase current unbalance degree. Since there is only one compressor 1 in the unit, when the compressor 1 stops working due to abnormal current, it means that the entire unit stops working. Therefore, there is no need to perform the step of adjusting the working mode of the compressor 1 due to voltage fluctuations. When L ≤ 0.5, it indicates that the three-phase current unbalance degree of the compressor 1 does not exceed the normal operating range of the compressor 1. At this time, the compressor 1 can operate normally, and the working mode of this part of the compressor 1 can be maintained.

[0159] Again, for example, taking the three-phase current unbalance degree as L, the preset three-phase current unbalance degree b as 0.05, and the number of compressors 1 as 2 for illustration. After calculating the three-phase current unbalance degrees of the two compressors 1, when the L of one compressor 1 > 0.5, it indicates that the three-phase current unbalance degree of this compressor 1 exceeds the normal operating range. At this time, it is necessary to control this compressor 1 to stop working to avoid the adverse effects on the compressor 1 caused by the excessive three-phase current unbalance degree. When the L of the other compressor 1 ≤ 0.5, it indicates that the three-phase current unbalance degree of this compressor 1 does not exceed the normal operating range of the compressor 1. At this time, the compressor 1 can operate normally. Since there are two compressors 1 in the unit, when one compressor 1 stops working due to abnormal current, it does not affect the operation of the other compressor 1. Therefore, the step of adjusting the working mode of the compressor 1 due to voltage fluctuations can be continued.

[0160] Again, for example, taking the three-phase current unbalance degree as L, the preset three-phase current unbalance degree b as 0.05, and the number of compressors 1 as 2 for illustration. After calculating the three-phase current unbalance degrees of the two compressors 1, when the L of both compressors 1 > 0.5, it indicates that the three-phase current unbalance degrees of these two compressors 1 exceed the normal operating range. At this time, it is necessary to control these two compressors 1 to stop working. Since there are two compressors 1 in the unit, when the two compressors 1 stop working due to abnormal current, it means that the entire unit stops working. Therefore, there is no need to perform the step of adjusting the working mode of the compressor 1 due to voltage fluctuations.

[0161] Next, in combination with Figure 4 , a possible operation process of the control method of the heat pump unit of the present application will be briefly described. Figure 4Logic of a possible implementation manner of the control method for the heat pump unit of the present application Figure 2 。

[0162] S301. Obtain the three-phase currents I1, I2, and I3 of each compressor 1, and then execute S302 and S305.

[0163] S302. Calculate the three-phase current unbalance degree L according to formula (Ⅱ), and then execute S303.

[0164] S303. Determine whether L>0.05 holds; if it holds, execute S304; if not, execute S301.

[0165] S304. Control the compressor 1 with L>0.05 to stop working, and then execute S301.

[0166] S305. Determine the maximum phase current Imax in each compressor 1, and then execute S306.

[0167] S306. Determine whether Imax>1.2A exists; if it exists, execute S307; otherwise, execute S301.

[0168] S307. Control the compressor 1 with Imax>1.2A to stop working, and then execute S301.

[0169] Those skilled in the art can understand that although some of the embodiments described herein include certain features included in other embodiments rather than other features, the combination of the features of different embodiments means that it is within the scope of the present application and forms different embodiments. For example, in the claims of the present application, any one of the claimed embodiments can be used in any combination.

[0170] So far, the technical solutions of the present application have been described in conjunction with the preferred implementation manners shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present application is obviously not limited to these specific implementation manners. Without departing from the principle of the present application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present application.

Claims

1. A control method for a heat pump unit, characterized in that The heat pump unit includes n compressors, where n≥1, and the control method includes: Obtaining the actual operating voltage and the rated voltage of the heat pump unit respectively; Determining the voltage fluctuation rate based on the actual operating voltage and the rated voltage; Comparing the size of the voltage fluctuation rate with the preset fluctuation rate; Based on the comparison result, selectively reducing the operating frequency of at least one of the compressors.

2. The control method according to claim 1, characterized in that The step of "Based on the comparison result, selectively reducing the operating frequency of at least one of the compressors" further includes: When the voltage fluctuation rate is greater than or equal to the preset fluctuation rate, reducing the operating frequency of at least one of the compressors.

3. The control method according to claim 2, characterized in that After the step of "reducing the operating frequency of at least one of the compressors", the following steps are further included: Obtaining the actual operating voltage again; Determining the voltage fluctuation rate based on the actual operating voltage and the rated voltage; Comparing the size of the voltage fluctuation rate with the preset fluctuation rate; When the voltage fluctuation rate is greater than or equal to the preset fluctuation rate, controlling the compressor whose operating frequency is reduced to stop operating.

4. The control method according to claim 3, wherein When there are still compressors in the running state in the heat pump unit, after the step of "reducing the operating frequency of at least one of the compressors", the following steps are further included: Repeating the steps of reducing the compressor frequency and stopping the operation until the voltage fluctuation rate is less than the preset fluctuation rate or all n compressors are in the stopped operating state.

5. The control method according to claim 1, characterized in that When the heat pump unit further includes a water circulation loop and a water pump is provided on the water circulation loop, before the step of "selectively reducing the operating frequency of at least one of the compressors", the following steps are further included: When the voltage fluctuation rate is greater than or equal to the preset fluctuation rate, controlling the water pump to stop working or reducing the operating frequency of the water pump; Continuing to obtain the actual operating voltage; Determining the voltage fluctuation rate based on the actual operating voltage and the rated voltage; Comparing the size of the voltage fluctuation rate with the preset fluctuation rate; Based on the comparison result, selectively reducing the operating frequency of at least one of the compressors.

6. The control method according to claim 1, characterized in that When the heat pump unit further includes an auxiliary heating device, before the step of "selectively reducing the operating frequency of at least one of the compressors", the following steps are further included: When the voltage fluctuation rate is greater than or equal to the preset fluctuation rate, controlling the auxiliary heating device to stop working; Continuing to obtain the actual operating voltage and the rated voltage; Determining the voltage fluctuation rate based on the actual operating voltage and the rated voltage; Comparing the size of the voltage fluctuation rate with the preset fluctuation rate; Based on the comparison result, selectively reducing the operating frequency of at least one of the compressors.

7. The control method according to claim 1, characterized in that, Before, after or simultaneously with the step of "Based on the comparison result, selectively reducing the operating frequency of at least one of the compressors", the following steps are further included: Obtaining the three-phase current of each of the compressors respectively; Comparing the size of the three-phase current with the preset current; When at least one of the three-phase currents of at least one of the compressors is greater than the preset current, controlling the corresponding compressor to stop working; or Obtaining the three-phase current of each of the compressors respectively; Determining the maximum phase current of the compressor based on the three-phase current; Comparing the size of the maximum phase current with the preset current; When the maximum phase current of at least one of the compressors is greater than the preset current, controlling the corresponding compressor to stop working.

8. The control method according to claim 1, characterized in that Before, after or at the same time as the step of "selectively reducing the operating frequency of at least one of the compressors based on the comparison result", the following steps are further included: Obtain the three-phase currents of each of the compressors respectively; Determine the three-phase current unbalance degree of each of the compressors according to the three-phase currents; Compare the magnitude of the three-phase current unbalance degree with a preset current unbalance degree; When the three-phase current unbalance degree is greater than the preset unbalance degree, control the corresponding compressor to stop working.

9. The control method according to claim 8, wherein The three-phase current unbalance degree is determined based on the following formula: Among them, L is the three-phase current unbalance degree, I1, I2, and I3 are the three-phase currents, and is the average value of the three-phase currents.

10. The control method according to claim 1, characterized in that The voltage fluctuation rate is determined based on the following formula: m = (U - Un) / Un where m is the voltage fluctuation rate, U is the actual operating voltage, and Un is the rated voltage.

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