Control method and system of air source heat pump unit

Abstract

The application discloses a control method and system of an air source heat pump unit, the air source heat pump unit comprising at least one variable frequency system, at least one fixed frequency system and an outdoor heat exchanger, the variable frequency system and the fixed frequency system being respectively connected with the outdoor heat exchanger independently, the variable frequency system comprising a plurality of variable frequency compressors arranged in parallel, the fixed frequency system comprising a fixed frequency compressor, and the outdoor heat exchanger being connected with a water pump. The control method comprises the following steps: monitoring a first state parameter of the air source heat pump unit, judging whether the first state parameter meets a first preset condition, if not, controlling the air source heat pump unit to be on standby, if yes, calculating the energy demand of the air source heat pump unit, and controlling the operation of the variable frequency compressors in the variable frequency system and the fixed frequency compressors in the fixed frequency system based on the energy demand of the air source heat pump unit until the first state parameter meets a second preset condition. Based on the control method, the water temperature stability of the air source heat pump unit is high, the energy efficiency of the unit is high, and the noise is low.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of control of air source heat pump equipment, and particularly relates to a control method and system of an air source heat pump unit. BACKGROUND

[0002] The air source heat pump unit is a heat pump system using outdoor air as a heat source. The heat pump system absorbs heat from the air environment through a heat exchanger, so that the heat transfer working medium evaporates, thereby realizing heat energy transfer and utilization.

[0003] The selection of the type of compressor and the combination of compressors are crucial for building an air source heat pump unit with high energy efficiency, flexible regulation and economy. In theory, the frequency conversion technology of the variable frequency turbine compressor is conducive to realizing flexible regulation of the unit load, but compared with a single machine, the output capacity of the fixed frequency turbine compressor is stronger. A single variable frequency turbine compressor cannot directly meet the demand for large capacity, and multiple variable frequency turbine compressors are often used in parallel to achieve this. However, if more than double the number of variable frequency turbine compressors are used to build an air source heat pump unit, the number of electrical components in the unit will significantly increase. The increased number of components not only increases the stability and maintenance cost of the unit, but also may have a potential impact on the stability and reliability of the system.

[0004] The fixed frequency turbine compressor and the variable frequency turbine compressor are often combined to form a large-capacity air source heat pump unit in the existing market. In the control process of such a unit, the problem that cannot be avoided is that the fixed frequency turbine compressor can only adjust the load by constantly starting and stopping. The constant start-stop operation will cause the water temperature in the air source heat pump unit to fluctuate greatly, thereby affecting the heating and cooling effect. In terms of flexible regulation, the use of variable frequency compressors has advantages, but the problem is that the high-efficiency operating frequency of the variable frequency compressor is in the medium-high frequency band. When the variable frequency compressor operates at an ultra-high frequency, the noise it produces is relatively large, and the energy efficiency is relatively low.

[0005] Therefore, how to coordinate the operation inside the unit has become a problem to be solved. SUMMARY

[0006] The purpose of the present application is to provide a control method and system of an air source heat pump unit, which monitors the state parameters of the operation process of the air source heat pump unit to adjust the operation of the unit, thereby ensuring the stability of the water temperature of the unit, improving the energy efficiency of the unit, and reducing noise.

[0007] To achieve the above object, the application discloses a control method and system of an air source heat pump unit, wherein the air source heat pump unit comprises at least one variable frequency system, at least one fixed frequency system and an outdoor heat exchanger; the variable frequency system comprises a plurality of variable frequency compressors arranged in parallel; the fixed frequency system comprises a fixed frequency compressor; the variable frequency system and the fixed frequency system are respectively connected to the outdoor heat exchanger independently; and the outdoor heat exchanger is connected to a water pump.

[0008] The control method comprises the following steps.

[0009] The first state parameter of the air source heat pump unit is monitored, and it is determined whether the first state parameter meets a first preset condition; if not, the air source heat pump unit is controlled to be on standby; if yes, the following steps are performed.

[0010] The energy demand of the air source heat pump unit is calculated, and the operation of the variable frequency compressors in the variable frequency system and the fixed frequency compressors in the fixed frequency system is controlled based on the energy demand of the air source heat pump unit until the first state parameter meets a second preset condition.

[0011] Specifically, when the first state parameter meets the first preset condition, the control method further comprises the following steps.

[0012] The initial energy demand of the air source heat pump unit is calculated based on the first state parameter and a set temperature.

[0013] Within a first preset time length, the operation of the variable frequency compressors in the variable frequency system and the fixed frequency compressors in the fixed frequency system is controlled based on the initial energy demand.

[0014] Specifically, the initial energy demand N1 is calculated based on the following formula.

[0015]

[0016] Wherein, T1 is the first state parameter, T2 is the set temperature, N max is the maximum energy demand of the air source heat pump unit, T max is the maximum temperature difference of the first state parameter and the set temperature, and at the maximum temperature difference, all the variable frequency compressors in the variable frequency system and the fixed frequency compressors in the fixed frequency system of the air source heat pump unit are fully opened.

[0017] Furthermore, when the running time of the air source heat pump unit reaches the first preset time length and the first state parameter still does not meet the second preset condition, the control method further comprises the following steps.

[0018] The energy demand of the air source heat pump unit is calculated, and the operation of the variable frequency compressor in the variable frequency system and the fixed frequency compressor in the fixed frequency system is controlled based on the energy demand of the air source heat pump unit until the first state parameter meets a second preset condition.

[0019] Further, an energy demand calculation period is further included, and a length of the energy demand calculation period is less than the first preset length.

[0020] The energy demand of the air source heat pump unit is recalculated every energy demand calculation period.

[0021] Further, the calculation method of the air source heat pump unit includes:

[0022] The difference between the first state parameter and the set temperature in the last energy demand calculation period is calculated to obtain a first difference value.

[0023] The difference between the current first state parameter and the set temperature is calculated to obtain a second difference value.

[0024] Based on the first difference value and the second difference value, a difference value change rate is obtained.

[0025] Based on the second difference value, the difference value change rate, and the energy demand of the air source heat pump unit in the last energy demand calculation period, the energy demand of the air source heat pump unit is obtained.

[0026] Specifically, the first state parameter is the ratio of the water inlet quantity of the air source heat pump unit to the total water outlet quantity of the water pump.

[0027] The working mode of the air source heat pump unit includes a heating mode and a cooling mode.

[0028] When the air source heat pump unit works in the heating mode, the first preset condition is that the first state parameter is less than or equal to the difference between the set temperature and a preset start-up temperature difference, and the second preset condition is that the first state parameter is greater than or equal to the sum of the set temperature and a preset shutdown temperature difference.

[0029] When the air source heat pump unit works in the cooling mode, the first preset condition is that the first state parameter is greater than or equal to the sum of the set temperature and the start-up temperature difference, and the second preset condition is that the first state parameter is less than or equal to the difference between the set temperature and the shutdown temperature difference.

[0030] Further, first and second threshold values representing the size of the energy demand that the variable frequency system and the fixed frequency system can output are included, the first threshold value being smaller than the second threshold value; the control method controls the operation of the variable frequency compressors in the variable frequency system and the fixed frequency compressors in the fixed frequency system based on the following rules:

[0031] When the energy demand of the air source heat pump unit is smaller than the first threshold value, all the variable frequency system and the fixed frequency system are controlled to standby;

[0032] When the energy demand of the air source heat pump unit is greater than or equal to the first threshold value and smaller than or equal to the second threshold value, the variable frequency compressors in the variable frequency system are controlled to operate based on the energy demand of the air source heat pump unit, and the fixed frequency system is controlled to standby;

[0033] When the energy demand of the air source heat pump unit is greater than the second threshold value, the operation of the variable frequency compressors in the variable frequency system and the fixed frequency compressors in the fixed frequency system is controlled based on the energy demand of the air source heat pump unit.

[0034] Further, when the energy demand of the air source heat pump unit is equal to the second threshold value, the variable frequency compressors in all the variable frequency system are controlled to operate at a preset optimal operating frequency.

[0035] Further, third and fourth threshold values representing the size of the energy demand that the variable frequency system and the fixed frequency system can output are included, the third and fourth threshold values being greater than the first and second threshold values, the third threshold value being smaller than the fourth threshold value;

[0036] When the energy demand of the air source heat pump unit is greater than the second threshold value and smaller than the third threshold value, the variable frequency compressors in all the variable frequency system are controlled to operate at the optimal operating frequency, and the operation of the fixed frequency compressors in the fixed frequency system is controlled based on the energy demand of the air source heat pump unit;

[0037] When the energy demand of the air source heat pump unit is equal to the third threshold value, the variable frequency compressors in all the variable frequency system are controlled to operate at the optimal operating frequency, and the fixed frequency compressors in all the fixed frequency system are controlled to be fully on;

[0038] When the energy demand of the air source heat pump unit is greater than the third threshold value and smaller than the fourth threshold value, the fixed frequency compressors in all the fixed frequency system are controlled to be fully on, and the operation of the variable frequency compressors in all the variable frequency system is controlled based on the energy demand of the air source heat pump unit;

[0039] When the energy demand of the air source heat pump unit is equal to the fourth threshold, control all variable frequency compressors in the variable frequency system and all fixed frequency compressors in the fixed frequency system to be fully operational.

[0040] The present invention also discloses an air source heat pump system, the air source heat pump system including a control system and at least one air source heat pump unit as described above, the control system controlling the air source heat pump unit based on the control method described above.

[0041] The present invention also discloses a control system for an air source heat pump unit, the control system comprising:

[0042] One or more processors;

[0043] Memory;

[0044] and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the programs including instructions for performing the control methods as described above.

[0045] The present invention also discloses a computer-readable storage medium including a computer program, which is executed by a processor to perform the control method described above.

[0046] Compared with existing technologies, the control method provided by the present invention, by monitoring the current relevant status parameters of the air source heat pump unit, can promptly control the unit's operating status and adjust its operating status in real time according to the current energy demand of the air source heat pump unit, thereby ensuring that the air source heat pump unit operates under optimal conditions. The control method of the present invention can improve the operating efficiency of the air source heat pump unit, maintain stable water temperature during operation, and avoid the excessive noise generated by the variable frequency compressor in the variable frequency system operating at high speed for extended periods, ensuring a quieter working environment. Furthermore, adjusting the operating scheme according to real-time status parameters further reduces energy loss caused by excessive work. Attached Figure Description

[0047] Figure 1 This is a system structure diagram of the air source heat pump unit in an embodiment of the present invention.

[0048] Figure 2 This is a flowchart of the control method for an air source heat pump unit in an embodiment of the present invention.

[0049] Figure 3 This is a flowchart of a control method for an air source heat pump unit according to another embodiment of the present invention.

[0050] Figure 4This is a control schematic diagram of the variable frequency compressor / fixed frequency compressor of the air source heat pump system in another embodiment of the present invention. Detailed Implementation

[0051] To illustrate the technical content, structural features, objectives, and effects of the present invention in detail, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0052] See Figure 1 As shown, this embodiment discloses a large-capacity air source heat pump unit with adjustable load. The air source heat pump unit includes at least one variable frequency system 1, one fixed frequency system 2, and an outdoor heat exchanger 3. The variable frequency system 1 includes several variable frequency compressors 11 arranged in parallel. The fixed frequency system 2 includes a fixed frequency compressor 21. The variable frequency system 1 and the fixed frequency system 2 are independently connected to the outdoor heat exchanger 3. The outdoor heat exchanger 3 is connected to a water pump.

[0053] This invention also provides a control method for the above-mentioned air source heat pump unit, which adjusts the operating scheme of the air source heat pump unit according to the operating state parameters of the air source heat pump unit, thereby improving energy efficiency and reducing noise. See also Figure 2 As shown, the control method includes:

[0054] S1: Control the air source heat pump unit to standby mode and monitor the first state parameter T1 of the air source heat pump unit.

[0055] S2: Determine whether the first state parameter T1 meets the first preset condition. If yes, proceed to step S3; otherwise, return to step S1.

[0056] S3: Calculate the energy demand of the air source heat pump unit, and control the operation of the variable frequency compressor 11 in the variable frequency system 1 and the fixed frequency compressor 21 in the fixed frequency system 2 based on the energy demand of the air source heat pump unit.

[0057] S4: Determine whether the first state parameter T1 meets the second preset condition. If yes, proceed to step S41; otherwise, proceed to step S3.

[0058] S41: Clear the energy requirement and jump to step S1.

[0059] During the operation of the air source heat pump unit, the operation schemes of the variable frequency compressor 11 in the variable frequency system 1 and the fixed frequency compressor 21 in the fixed frequency system 2 can be controlled and adjusted based on the changes in the first state parameter T1. Specifically, the operating frequency of each variable frequency compressor 11 can be changed or the start / standby of the fixed frequency compressor 21 can be controlled.

[0060] Specifically, the first state parameter T1 is the ratio of the inlet water flow of the air source heat pump unit to the total outlet water flow of the water pump. The operating modes of the air source heat pump unit include heating mode and cooling mode.

[0061] When the air source heat pump unit is operating in heating mode, the first preset condition is: the first state parameter T1 is less than or equal to the difference between the set temperature T2 and the preset start-up temperature difference T3, and the second preset condition is: the first state parameter is greater than or equal to the sum of the set temperature T2 and the preset shutdown temperature difference T4.

[0062] When the air source heat pump unit is operating in cooling mode, the first preset condition is: the first state parameter T1 is greater than or equal to the sum of the set temperature T2 and the start-up temperature difference T3, and the second preset condition is: the first state parameter T1 is less than or equal to the difference between the set temperature T2 and the stop temperature difference T4.

[0063] Here, the set temperature T2 is the temperature set by the user and the desired output temperature when the air source heat pump unit is operating. The start-up temperature difference T3 and the stop temperature difference T4 both represent the differences between the control temperature and the set temperature. When the absolute value of the difference between the first state parameter T1 and the set temperature T2 reaches the start-up temperature difference T3, the air source heat pump unit starts operating. When the absolute value of the difference between the first state parameter T1 and the set temperature T2 is less than or equal to the stop temperature difference T4, the air source heat pump unit needs to be reset to zero, the compressor inside the unit stops, and the air source heat pump unit enters standby mode. The start-up temperature difference T3 ranges from 1 to 5℃, with a preferred value of 3℃. The stop temperature difference T4 also ranges from 1 to 5℃, with a preferred value of 1℃. It is important to note that the set value of the start-up temperature difference T3 must be greater than the stop temperature difference T4.

[0064] See Figure 3 As shown, specifically, when the first state parameter T1 satisfies the aforementioned first preset condition, step S3 further includes:

[0065] S31: Determine whether the running time of the air source heat pump unit has reached the first preset time. If not, proceed to step S32; if yes, proceed to step S33.

[0066] It should be noted in advance that this embodiment includes an energy demand calculation period T, the value of which ranges from 10 to 90 seconds, with a preferred value of 50 seconds. In this embodiment, the preferred value of the first preset duration is 2Ts.

[0067] S32: Calculate the initial energy demand of the air source heat pump unit based on the first state parameter T1 and the set temperature T2, and control the operation of the variable frequency compressor 11 in the variable frequency system 1 and the fixed frequency compressor 21 in the fixed frequency system 2 based on the initial energy demand, and jump to step S4.

[0068] S33: Calculate the current energy demand of the air source heat pump unit, control the operation of the variable frequency compressor 11 in the variable frequency system 1 and the fixed frequency compressor 21 in the fixed frequency system 2 based on the current energy demand of the air source heat pump unit, and jump to step S4.

[0069] It should be noted that in this embodiment, if the result of step S4 is negative, the process returns to step S31.

[0070] Specifically, the initial energy requirement of the air source heat pump unit is calculated based on the following formula:

[0071]

[0072] Where N1 is the initial energy requirement, T1 is the first state parameter, T2 is the set temperature, and N max The maximum energy demand of the air source heat pump unit is the sum of the maximum energy demand output by all variable frequency systems 1 and all fixed frequency systems 2 within the air source heat pump unit. max The value of T varies with the number of variable frequency systems 1 and fixed frequency systems 2 in the air source heat pump unit. max Given the maximum temperature difference between the preset first state parameter T1 and the set temperature T2, at this maximum temperature difference value, all variable frequency compressors 11 in the variable frequency system 1 and the fixed frequency compressors 21 in the fixed frequency system 2 within the air source heat pump unit are fully operational. max The value range is 5–30℃, with a preferred value of 20℃. Furthermore, when the air source heat pump unit is in heating mode, |T1-T2|=(T2-T1), and when the air source heat pump unit is in cooling mode, |T1-T2|=(T1-T2). The calculated initial energy needs to be rounded to the nearest integer.

[0073] Specifically, in this embodiment, after the air source heat pump unit runs for a first preset time according to the initial energy demand, the energy demand of the air source heat pump unit will be recalculated every time the air source heat pump unit runs for another energy demand calculation cycle T, thereby adjusting the operation mode of the air source heat pump unit.

[0074] Specifically, in this embodiment, the method for calculating the energy requirement of the current air source heat pump unit includes:

[0075] Calculate the difference between the first state parameter T1 and the set temperature T2 within the previous energy calculation cycle to obtain the first difference dt1;

[0076] Calculate the difference between the current first state parameter T1 and the set temperature T2 to obtain the second difference dt2;

[0077] Based on the first difference dt1 and the second difference dt2, the rate of change of the difference ddt is obtained;

[0078] Based on the second difference dt2, the rate of change of the difference ddt, and the energy demand N(k-1) of the air source heat pump unit in the previous energy demand calculation cycle, the current energy demand N(k) of the air source heat pump unit can be obtained. Here, k represents the k-th energy demand calculation cycle in which the air source heat pump unit operates, and k-1 represents the previous energy demand cycle. In this embodiment, the rate of change of the difference ddt is the difference between the first difference dt1 and the second difference dt2.

[0079] Current methods for calculating the energy requirement N(k) of air source heat pump units include:

[0080] The energy demand deviation ΔN(k) of the current air source heat pump unit is obtained based on the second difference dt2 and the rate of change of the difference ddt; the energy demand N(k) of the current air source heat pump unit is calculated based on the energy demand N(k-1) of the air source heat pump unit in the previous energy demand calculation period and the energy demand deviation ΔN(k) of the current air source heat pump unit.

[0081] Specifically, the energy requirement N(k) of the current air source heat pump unit is calculated based on the following formula:

[0082] N(k) = N(k-1) + ΔN(k)

[0083] Specifically, in this embodiment, the energy demand deviation ΔN(k) of the current air source heat pump unit is determined based on the membership of the second difference dt2 and the rate of change of the difference ddt, as shown in Table 1 below:

[0084] Table 1. Membership table of the second difference dt2 and the rate of change of the difference ddt.

[0085]

[0086] It should be noted that when the air source heat pump unit is operating in cooling mode, the first difference dt1 or the second difference dt2 = set temperature T2 - first state parameter T1; when the air source heat pump unit is operating in heating mode, the first difference dt1 or the second difference dt2 = first state parameter T1 - set temperature T2.

[0087] The required deviation ΔN(k) is determined as shown in the table below:

[0088] Table 2 Energy Demand Deviation △N(k)

[0089]

[0090] The following is an example:

[0091] Assume that the energy demand of the air source heat pump unit in the previous energy demand calculation cycle is 10HP, the first difference dt1 between the first state parameter T1 and the set temperature T2 in the previous energy demand calculation cycle is -2℃, and the second difference dt2 between the current first state parameter T1 and the set temperature T2 is -1.5℃.

[0092] Based on the first difference dt1 and the second difference dt2, the rate of change of the difference ddt is -0.5℃. As shown in Table 1, the second difference dt2 is within the range of NL, and the rate of change of the difference ddt is within the range of NM.

[0093] Based on Tables 1 and 2, the energy demand deviation ΔN(k) is -2. Therefore, the energy demand of the current air source heat pump unit is calculated to be 10 + (-2) = 8HP.

[0094] On the other hand, in this embodiment, the control method first starts the variable frequency compressor 11 in the variable frequency system 1 to meet the energy demand of the air source heat pump unit. When all the variable frequency compressors 11 in the variable frequency system 1 are operating at their optimal operating state but still cannot meet the energy demand of the air source heat pump unit, the fixed frequency compressor 21 in the fixed frequency system 2 is then started. Here, "optimal" refers to the operating frequency of the variable frequency compressor 11 when it operates at its highest energy efficiency state. This setting is based on the actual situation of the compressor and is not specifically limited here.

[0095] Specifically, this control method includes a first threshold, a second threshold, a third threshold, and a fourth threshold representing the energy demand output by the variable frequency system 1 and the fixed frequency system 2. The first threshold is less than the second threshold, the third and fourth thresholds are greater than the first and second thresholds, and the third threshold is less than the fourth threshold. Specifically, the first threshold represents the energy demand that can be met when all variable frequency compressors 11 in a variable frequency system 1 operate at their lowest operating frequency; the second threshold represents the energy demand that can be met when all variable frequency compressors 11 in the variable frequency system 1 of the air source heat pump unit operate at their optimal operating frequency; the third threshold represents the energy demand that can be met when all variable frequency compressors 11 in the variable frequency system 1 of the air source heat pump unit operate at their optimal operating frequency and all fixed frequency compressors 21 in the fixed frequency system 2 are fully operational; and the fourth threshold represents the energy demand that can be met when all compressors in both the variable frequency system 1 and the fixed frequency system 2 are fully operational.

[0096] In this embodiment, when the energy demand of the air source heat pump unit is equal to the first threshold, the variable frequency compressor 11 in a variable frequency system 1 is controlled to operate at the lowest operating frequency first.

[0097] When the energy demand of the air source heat pump unit is greater than the first threshold and less than the second threshold, the operating frequency of the variable frequency compressor 11 in the variable frequency system 1 is increased from the lowest operating frequency to meet the energy demand. If there are multiple variable frequency systems 1 in the air source heat pump unit, the variable frequency compressor 11 in the variable frequency system 1 is turned on in sequence, and its operating frequency is increased in sequence until the optimal operating frequency is reached.

[0098] When the energy demand of the air source heat pump unit is equal to the second threshold, control all variable frequency compressors 11 in the variable frequency system 1 to operate at the preset optimal operating frequency.

[0099] When the energy demand of the air source heat pump unit is greater than the second threshold and less than the third threshold, under the premise that the variable frequency compressor 11 in the variable frequency system 1 is controlled to be at the optimal operating frequency, the fixed frequency compressor 21 in the fixed frequency system 2 is controlled to start to meet the energy demand of the air source heat pump unit.

[0100] When the energy demand of the air source heat pump unit is equal to the third threshold, control all variable frequency compressors 11 in the variable frequency system 1 to operate at the optimal operating frequency, and control all fixed frequency compressors 21 in the fixed frequency system 2 to be fully open.

[0101] When the energy demand of the air source heat pump unit is greater than the third threshold and less than the fourth threshold, the operating frequency of the variable frequency compressor 11 in the variable frequency control system 1 increases.

[0102] When the energy demand of the air source heat pump unit is greater than or equal to the fourth threshold, control all variable frequency compressors 11 in variable frequency system 1 and fixed frequency compressors 21 in fixed frequency system 2 to be fully turned on.

[0103] The first threshold, the second threshold, the third threshold, and the fourth threshold vary depending on the number of variable frequency compressors 11 in the variable frequency system 1, the number of fixed frequency compressors 21 in the fixed frequency system 2, and the output capacity of each compressor. No specific restrictions are imposed here.

[0104] The following specific embodiment will be used as an example to illustrate the control method of the air source heat pump unit, so as to better understand the control method in the embodiment of the present invention.

[0105] Please see Figure 1 Taking an air source heat pump unit A, which includes two variable frequency systems 1 and two fixed frequency systems 2 as an example, each of the two variable frequency systems 1 is equipped with a pair of variable frequency compressors 11 connected in parallel, namely C1 and C2. Each of the two fixed frequency systems 2 is equipped with a fixed frequency compressor 21. The two variable frequency systems 1 are named SYS1 and SYS2, respectively, and the two fixed frequency systems 2 are named SYS3 and SYS4, respectively. The four systems SYS1, SYS2, SYS3 and SYS4 are independent of each other.

[0106] In SYS1 and SYS2, the two variable frequency compressors 11 connected in parallel adopt the same frequency control, specifically: (1) when both C1 and C2 are normal, C1 and C2 are loaded and unloaded synchronously; (2) when either of the compressors C1 and C2 is restricted from loading (such as when loading is restricted due to exhaust, current, drive temperature, etc.), neither C1 nor C2 is loaded; (3) when either of the compressors C1 and C2 needs to unload or shut down due to failure, both C1 and C2 unload or shut down; (4) when either of the compressors C1 and C2 fails and cannot start, neither C1 nor C2 can start.

[0107] In SYS3 and SYS4, when two fixed-frequency compressors 21 need to start / stop simultaneously, the fixed-frequency compressor 21 performs the start / stop operation every 10 seconds.

[0108] In this embodiment, the relationship between the energy demand range and frequency of the compressors in the variable frequency system 1 and the fixed frequency system 2 of the air source heat pump unit A is shown in the following table:

[0109] Table 3 Relationship between the output energy demand range and frequency of each compressor

[0110]

[0111] As shown in Table 3, in this embodiment, the energy required to output by a single inverter system 1 at its lowest operating frequency is 5 HP, therefore the first threshold is 5 HP. The energy required to output by a single inverter system 1 at its optimal operating frequency is 10 HP, the second threshold is 20 HP, the third threshold is 44 HP, and the fourth threshold is 52 HP. (See Table 3 for details.) Figure 4 As shown, the control process of air source heat pump unit A is as follows, depending on different energy demand conditions:

[0112] (1) When the energy demand of A is less than 5HP (first threshold), control A to standby;

[0113] (2) When the energy demand of A is greater than 5HP (first threshold) and less than or equal to 10HP, the operating frequency of the variable frequency compressor 11 of SYS1 is controlled to increase based on the energy demand, and SYS2, SYS3 and SYS4 are controlled to be in standby mode.

[0114] (3) When the energy requirement of A is equal to 10HP, the variable frequency compressor 11 of SYS1 is controlled to operate at the optimal operating frequency;

[0115] (4) When the energy demand of A is greater than 10HP and less than 15HP, control SYS1 to maintain operation at the optimal operating frequency. The energy demand that A fails to meet is 15HP-10HP=5HP, which is less than the energy demand that the single frequency converter system 1 can output when it is at the lowest operating frequency. Control SYS2, SYS3 and SYS4 to be in standby mode.

[0116] (5) When the energy requirement of A is equal to 15HP, control SYS1 to maintain operation at the optimal operating frequency, control SYS2 to start at the minimum operating frequency, and control SYS3 and SYS4 to standby.

[0117] (6) When the energy demand of A is greater than 15HP and less than 20HP (second threshold), control SYS1 to maintain operation at the optimal operating frequency, and control the operating frequency of the variable frequency compressor 11 of SYS2 to be loaded based on the energy demand, and control SYS2, SYS3 and SYS4 to be in standby mode.

[0118] (7) When the energy demand of A is equal to 20HP (second threshold), control the variable frequency compressor 11 in SYS1 and SYS2 to run at the optimal operating frequency, and control SYS3 and SYS4 to standby.

[0119] (8) When the energy demand of A is greater than 20HP (second threshold) and less than or equal to 44HP (third threshold), control the variable frequency compressor 11 in SYS1 and SYS2 to maintain the optimal frequency operation. When the energy demand of A reaches 32HP, control the fixed frequency compressor 21 in SYS3 to start. When the energy demand of A reaches 44HP, control the fixed frequency compressor 21 in SYS4 to start.

[0120] (9) When the energy demand of A is greater than 44HP (third threshold) and less than 52HP (fourth threshold), control the operating frequency of the variable frequency compressor 11 in SYS1 and SYS2 to be loaded based on the energy demand, and control the fixed frequency compressor 21 in SYS3 and SYS4 to start.

[0121] (10) When the energy demand of A is greater than or equal to 52HP (fourth threshold), control the compressors in SYS1 to SYS4 to be fully open.

[0122] It is worth noting that in SYS1 / SYS2 of the variable frequency system 1, when the variable frequency compressor 11 starts and its operating frequency is loaded to the minimum operating frequency, it will maintain this minimum operating frequency for a stable period of Hmin. After Hmin, the variable frequency system 1 will control the variable frequency compressor 11 to enter the normal operating frequency loading and unloading phase according to the energy demand of the air source heat pump unit. The preferred value of H is 1.

[0123] On the other hand, the loading speed of the variable frequency compressor 11 is as follows: when the operating frequency of the variable frequency compressor 11 is less than 70Hz, the variable frequency compressor 11 is controlled to load at a speed of 3Hz / 10s; when the operating frequency of the variable frequency compressor 11 is greater than or equal to 70Hz and less than or equal to 95Hz, the variable frequency compressor 11 is controlled to load at a speed of 3Hz / 20s; when the operating frequency of the variable frequency compressor 11 is greater than 95Hz, the variable frequency compressor 11 is controlled to load at a speed of 2Hz / 20s.

[0124] On the other hand, please refer to [further details]. Figure 1 As shown, the variable frequency system 1 also includes a first four-way valve 12 and a first heat exchanger 13. The first four-way valve 12 is provided with a first valve port 121, a second valve port 122, a third valve port 123 and a fourth valve port 124. The first exhaust ports 111 of a plurality of variable frequency compressors 11 connected in parallel are respectively connected to the first valve port 121. The first air inlets 112 of the plurality of variable frequency compressors 11 connected in parallel are respectively connected to the second valve port 122. The third valve port 123 is connected to the first heat exchanger 13. The fourth valve port 124 is connected to the outdoor heat exchanger 3 through the first gas supply pipeline 14. The first heat exchanger 13 is connected to the outdoor heat exchanger 3 through the first liquid supply pipeline 15.

[0125] Specifically, the fixed-frequency system 2 also includes a second four-way valve 22 and a second heat exchanger 23. The second four-way valve 22 is provided with a fifth valve port 221, a sixth valve port 222, a seventh valve port 223 and an eighth valve port 224. The second exhaust port 211 of the fixed-frequency compressor 21 is connected to the fifth valve port 221, the second air inlet port 212 of the fixed-frequency compressor 21 is connected to the sixth valve port 222, the seventh valve port 223 is connected to the second heat exchanger 23, the eighth valve port 224 is connected to the outdoor heat exchanger 3 through the second gas supply pipeline 24, and the second heat exchanger 23 is connected to the outdoor heat exchanger 3 through the second liquid supply pipeline 25.

[0126] Specifically, the variable frequency system 1 also includes a first fan 16, and the fixed frequency system also includes a second fan 26. The first fan 16 and the second fan 26 are respectively connected to the first heat exchanger 13 and the second heat exchanger 23 to realize the heat exchange of the working fluid of the air source heat pump unit.

[0127] Optionally, the frequency conversion system 1 is also equipped with an oil-gas separation device 17 for separating refrigerant gas and lubricating oil.

[0128] Optionally, the variable frequency system 1 and the fixed frequency system 2 are respectively provided with a first liquid storage tank 18 and a second liquid storage tank 27 for balancing the refrigerant flow.

[0129] Optionally, the variable frequency system 1 and the fixed frequency system 2 are also respectively provided with a first gas-liquid separation device 19 and a second gas-liquid separation device 28 for separating liquid refrigerant and gaseous refrigerant.

[0130] Optionally, the variable frequency system 1 and the fixed frequency system 2 are also equipped with several one-way valves a for guiding the flow of refrigerant.

[0131] Optionally, the variable frequency compressor 11 also includes a first air supply port 113, and the variable frequency system 1 is also provided with a first economizer 10. The first economizer 10 is connected to the first heat exchanger 13, the first air supply ports 113 of several variable frequency compressors 11 arranged in parallel, and the outdoor heat exchanger 3. The first economizer 10 is also provided with a first throttling filter device 101 connected thereto.

[0132] Optionally, the fixed-frequency compressor 21 also includes a second air inlet 213, and the fixed-frequency system 2 is also provided with a second economizer 29. The second economizer 29 is connected to the second heat exchanger 23, the second air inlet 213 of the fixed-frequency compressor 21 and the outdoor heat exchanger 3 respectively. The second economizer 29 is also provided with a second throttling filter device 291 connected thereto.

[0133] In another preferred embodiment of the present invention, an air source heat pump system is also disclosed, which includes a control system and at least one air source heat pump unit as described in the above embodiments. The control system controls the operation of the air source heat pump unit based on the control method described above.

[0134] Specifically, when an air source heat pump system includes more than one of the aforementioned air source heat pump units, the N in the initial energy requirement calculation... max This is the maximum energy demand of the air source heat pump system, which is the sum of the maximum energy demand that all air source heat pump units can output.

[0135] On the other hand, when an air source heat pump system comprises multiple air source heat pump units, when these units are loaded according to energy demand, each unit operates sequentially based on energy demand until it reaches 44HP (the third threshold). Then, the next unit is loaded sequentially. Energy demand is preferentially allocated to units with no faults and short start-up times until all units have reached 44HP (the third threshold), after which it is evenly distributed among all units. When air source heat pump units are unloaded according to energy demand, the required unloaded energy is evenly distributed to units with energy demand > 44HP (the third threshold) until all operating units have energy demand ≤ 44HP (the third threshold). Then, units are unloaded sequentially, with unloaded energy preferentially allocated to units with longer start-up times.

[0136] On the other hand, when the first state parameter T1 meets the second preset condition, every 10 seconds, the air source heat pump system sequentially forces unloads one air source heat pump unit (i.e. controls the air source heat pump unit to standby) until all air source heat pump units in the air source heat pump system are unloaded or the second preset condition is no longer met, at which point the forced unloading stops.

[0137] This invention also discloses a control system for an air source heat pump unit, comprising one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the programs including instructions for performing the control method described above. The processor may be a general-purpose central processing unit (CPU), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits, used to execute the relevant programs to perform the control method of the embodiments of this application.

[0138] The present invention also discloses a computer-readable storage medium comprising a computer program executable by a processor to perform the control method described above. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center integrating one or more available media. The available medium can be read-only memory (ROM), random access memory (RAM), or magnetic media, such as floppy disks, hard disks, magnetic tapes, magnetic disks, or optical media, such as digital versatile discs (DVDs), or semiconductor media, such as solid-state drives (SSDs).

[0139] This application also discloses a computer program product or computer program, which includes computer instructions stored in a computer-readable storage medium. A processor of an electronic device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the electronic device to perform the aforementioned control method.

[0140] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A control method for an air source heat pump unit, characterized in that, The air source heat pump unit includes at least one variable frequency system, at least one fixed frequency system and an outdoor heat exchanger. The variable frequency system includes several variable frequency compressors arranged in parallel. The fixed frequency system includes a fixed frequency compressor. The variable frequency system and the fixed frequency system are independently connected to the outdoor heat exchanger. The outdoor heat exchanger is connected to a water pump. The control method includes: Monitor the first state parameter of the air source heat pump unit, and determine whether the first state parameter meets the first preset condition. If not, control the air source heat pump unit to standby mode; if yes, then: Within a first preset time period, the initial energy requirement of the air source heat pump unit is calculated based on the first state parameters and the set temperature. Based on this initial energy requirement, the operation of the variable frequency compressor in the variable frequency system and the fixed frequency compressor in the fixed frequency system is controlled. Simultaneously, it is determined whether the first state parameters meet a second preset condition. If, within the first preset time period, the first state parameters cannot meet the second preset condition, then: Calculate the energy requirement of the current air source heat pump unit, and control the operation of the variable frequency compressor in the variable frequency system and the fixed frequency compressor in the fixed frequency system based on the energy requirement of the current air source heat pump unit until the first state parameter meets the second preset condition; The first state parameter is the ratio of the inlet water volume of the air source heat pump unit to the total outlet water volume of the water pump. The operating modes of the air source heat pump unit include heating mode and cooling mode. When the air source heat pump unit is operating in the heating mode, the first preset condition is: the first state parameter is less than or equal to the difference between the set temperature and the preset start-up temperature difference, and the second preset condition is: the first state parameter is greater than or equal to the sum of the set temperature and the preset shutdown temperature difference. When the air source heat pump unit operates in the cooling mode, the first preset condition is: the first state parameter is greater than or equal to the sum of the set temperature and the start-up temperature difference, and the second preset condition is: the first state parameter is less than or equal to the difference between the set temperature and the stop temperature difference.

2. The control method for an air source heat pump unit according to claim 1, characterized in that, The initial energy requirement is calculated based on the following formula. ; in, The first state parameter, Set the temperature. The maximum energy requirement of the air source heat pump unit is preset. Given the maximum temperature difference between the preset first state parameter and the set temperature, under this maximum temperature difference value, all variable frequency compressors in the variable frequency system and the fixed frequency compressors in the fixed frequency system within the air source heat pump unit are fully operational.

3. The control method for an air source heat pump unit according to claim 1, characterized in that, It also includes an energy demand calculation cycle, the duration of which is less than the first preset duration; After each energy demand calculation cycle, the energy demand of the current air source heat pump unit is recalculated.

4. The control method for an air source heat pump unit according to claim 1, characterized in that, The current method for calculating the energy requirement of air source heat pump units includes: Calculate the difference between the first state parameter and the set temperature within the energy calculation cycle described above to obtain the first difference; Calculate the difference between the current first state parameter and the set temperature to obtain a second difference; Based on the first difference and the second difference, the rate of change of the difference is obtained; Based on the second difference, the rate of change of the difference, and the energy demand of the air source heat pump unit in the previous energy demand calculation period, the current energy demand of the air source heat pump unit is obtained.

5. The control method for an air source heat pump unit according to claim 1, characterized in that, It also includes a first threshold and a second threshold representing the energy demand that the variable frequency system and the fixed frequency system can output, wherein the first threshold is less than the second threshold; the control method controls the operation of the variable frequency compressor in the variable frequency system and the fixed frequency compressor in the fixed frequency system based on the following rules: When the energy demand of the air source heat pump unit is less than the first threshold, all the variable frequency systems and the fixed frequency systems are put into standby mode. When the energy demand of the air source heat pump unit is greater than or equal to the preset first threshold and less than or equal to the second threshold, the variable frequency compressor in the variable frequency system is controlled to operate based on the energy demand of the air source heat pump unit, and the fixed frequency system is controlled to standby. When the energy demand of the air source heat pump unit is greater than the second threshold, the operation of the variable frequency compressor in the variable frequency system and the fixed frequency compressor in the fixed frequency system is controlled based on the energy demand of the air source heat pump unit.

6. The control method for an air source heat pump unit according to claim 5, characterized in that, When the energy demand of the air source heat pump unit is equal to the second threshold, all the variable frequency compressors in the variable frequency system are controlled to operate at a preset optimal operating frequency.

7. The control method for an air source heat pump unit according to claim 6, characterized in that, It also includes a third threshold and a fourth threshold representing the energy demand that the variable frequency system and the fixed frequency system can output, wherein the third threshold and the fourth threshold are greater than the first threshold and the second threshold, and the third threshold is less than the fourth threshold; When the energy demand of the air source heat pump unit is greater than the second threshold and less than the third threshold, control all the variable frequency compressors in the variable frequency system to operate at the optimal operating frequency, and control the operation of the fixed frequency compressors in the fixed frequency system based on the energy demand of the air source heat pump unit. When the energy demand of the air source heat pump unit is equal to the third threshold, control all the variable frequency compressors in the variable frequency system to operate at the optimal operating frequency, and control all the fixed frequency compressors in the fixed frequency system to be fully open. When the energy demand of the air source heat pump unit is greater than the third threshold and less than the fourth threshold, control all fixed-frequency compressors in the fixed-frequency system to be fully turned on, and control the operation of the variable-frequency compressors in the variable-frequency system based on the energy demand of the air source heat pump unit. When the energy demand of the air source heat pump unit is equal to the fourth threshold, control all variable frequency compressors in the variable frequency system and all fixed frequency compressors in the fixed frequency system to be fully operational.

8. An air source heat pump system, characterized in that, The air source heat pump system includes a control system and at least one air source heat pump unit, wherein the control system controls the air source heat pump unit based on the control method according to any one of claims 1 to 7.

9. A control system for an air source heat pump unit, characterized in that, include: One or more processors; Memory; And one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the programs including instructions for performing the control method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, Includes a computer program, which is executed by a processor to perform the control method as described in any one of claims 1 to 7.

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