A multi-connected air conditioner system

Abstract

The present invention discloses a multi-connected air conditioner system, comprising: an indoor unit; an outdoor unit, wherein a compressor is connected to heat exchangers of respective indoor units through pipes; a control module configured to: when the operating mode is a heating mode, include: respectively obtaining a first reference frequency and a second reference frequency of the system; determining a reference frequency; controlling the operating frequency of the compressor; an up-frequency judgment step, including controlling the compressor to increase the operating frequency when a set up-frequency condition is satisfied. In the multi-connected air conditioner system of the present invention, the influence of the capacity of the turned-on indoor units and the capacity of the unturned-on indoor units on the operating frequency is comprehensively considered to determine the reference frequency of the compressor, and after controlling the compressor to start running, up-frequency control is carried out in stages, which can effectively prevent a series of problems caused by over-opening of an electronic expansion valve due to too fast up-frequency in the prior art. In addition, by reasonably controlling the proportion of the capacity of the turned-on indoor units, the heat exchange requirements of the turned-on indoor units can be satisfied simultaneously, achieving the purpose of rapid temperature rise.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioners, and particularly to a multi-connected unit system. Background Art

[0002] A multi-connected unit system is a type of central air conditioner. Specifically, it refers to an outdoor unit connected to two or more indoor units through pipes. This structure has currently been widely used in central air conditioning systems, central heating systems, and ventilation and purification systems to purify (or purify), cool (or heat), humidify (or dehumidify), etc. the air in multiple rooms in the same building or multiple buildings in the same building complex, and to achieve transportation and distribution. The multi-connected unit air conditioning system aims to create an indoor air environment with standard temperature, standard humidity, standard cleanliness, and freshness to meet the air conditioning requirements for living comfort or production processes.

[0003] When the existing multi-connected unit system is in heating mode, in order to quickly increase the indoor temperature, it controls the compressor to quickly run at a high frequency.

[0004] The main problems existing in the small-load heating operation of the multi-connected unit system are as follows: 1. When starting and transitioning to the normal stage in small-load heating, the frequency increases too quickly, or when starting and transitioning to the normal stage after defrosting, the frequency increases too quickly, resulting in the over-opening of the EVO (electronic expansion valve). The over-opening of the EVO leads to the risk of liquid return in the system. 2. In the long-pipe system of the multi-connected unit, due to the certain hysteresis of the high-pressure pressure relative to the compressor frequency, when the small-load heating reaches the highest frequency, the pressure has not yet reached the target pressure. After running at the highest frequency for a period of time, the pressure suddenly rises, and finally the high-pressure protection reduces the frequency, and the frequency drops to the lowest frequency. At this time, the opening of the EVO is relatively large and the system pressure is relatively high, and a large amount of incompletely evaporated liquid refrigerant floods into the gas separator, resulting in a relatively high liquid level or full-liquid operation in the large gas separator, and finally leading to liquid return in the system, affecting the reliability of the compressor operation. 3. When operating in small-load heating, when the EVO is at a large opening and the frequency drops too much, the outdoor fan speed does not increase, resulting in liquid return in the system and affecting the reliability of the compressor. Summary of the Invention

[0005] In order to solve the problems in the prior art that the electronic expansion valve is over-opened due to too fast frequency increase during the small-load heating start of the multi-connected unit system and a series of problems brought about by the over-opening of the electronic expansion valve, the present invention provides a multi-connected unit system that can solve the above problems.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a multi-connected unit system, including:

[0008] Indoor units, and there are multiple of them;

[0009] Outdoor unit, which is provided with a compressor inside, and the compressor is respectively connected to the heat exchangers of each indoor unit through pipes;

[0010] Control module, which is configured as follows: when the operating mode is the heating mode, it includes:

[0011] Respectively obtain the first reference frequency and the second reference frequency of the system. The first reference frequency is the contribution value of the capacity of the turned-on indoor unit to the reference frequency, and the second reference frequency is the contribution value of the capacity of the standby indoor unit and the capacity of the turned-off indoor unit to the reference frequency;

[0012] Determine the reference frequency, which is the sum of the first reference frequency and the second reference frequency;

[0013] Control and adjust the operating frequency of the compressor, including:

[0014] Control the compressor to operate at the initial frequency for the first preset time;

[0015] Control the compressor to operate at the reference frequency;

[0016] Frequency increase judgment step, including when the set frequency increase condition is met, controlling the compressor to increase the operating frequency.

[0017] In some embodiments of the present invention, the calculation method of the first reference frequency includes:

[0018] Obtain the capacity of the turned-on indoor unit and e;

[0019] Respectively obtain the target pressure Pdo of the system operation, the maximum high-pressure pressure Pdmax during system operation, the set temperature of the turned-on indoor unit, the indoor air temperature of the turned-on indoor unit, and the air duct of the turned-on indoor unit, and determine the first reference coefficient;

[0020] The product of the capacity of the turned-on indoor unit and e and the first reference coefficient is the first reference frequency.

[0021] In some embodiments of the present invention, the first reference coefficient includes a first coefficient c, a second coefficient h, and a third coefficient k, where:

[0022] The determination method of the first coefficient c is:

[0023] c = -2.04×(Pdmax - Pdo) + 1.0 (1.0 ≤ c ≤ 4.0);

[0024] The determination method of the second coefficient h is:

[0025] Calculate the difference ⊿h between the set temperature and the indoor air temperature of the turned-on indoor unit, and determine h by looking up the preset ⊿h-h lookup table;

[0026] The method for determining the third coefficient k is as follows:

[0027] Search for a preset wind speed - k lookup table, and determine k according to the wind speed of the indoor unit when it is turned on;

[0028] The first reference frequency F1 = a1×c×e×h×k, where a1 is a constant coefficient.

[0029] In some embodiments of the present invention, the calculation method of the second reference frequency includes:

[0030] Obtain the capacity sum g of the indoor unit when it is turned off and the capacity sum f of the indoor unit in standby;

[0031] Respectively obtain the target pressure Pdo of the system operation and the maximum high - pressure pressure Pdmax during the system operation, and determine the second reference coefficient;

[0032] The sum of the products of the capacity sum g of the indoor unit when it is turned off and the capacity sum f of the indoor unit in standby and the second reference coefficient respectively obtains the second reference frequency.

[0033] In some embodiments of the present invention, the method for determining the second reference coefficient d is as follows:

[0034] d = 1.0 - (Pdmax - Pdo)×1.2;

[0035] The second reference frequency F2 = (a2×f + a3×g)×d, where a2 and a3 are constant coefficients, and a2 > a3.

[0036] In some embodiments of the present invention, when controlling the compressor to increase the operating frequency, the reference frequency is doubled each time.

[0037] In some embodiments of the present invention, after the frequency - increasing judgment step, there is also a step of correcting the operating frequency of the compressor, including:

[0038] Calculate the correction value ⊿F: ⊿F = m×(Pdo - Pdmax)-n×(Pd(n) - Pd(n - 1));

[0039] Where Pd(n) is the current maximum high - pressure pressure, Pd(n - 1) is the maximum high - pressure pressure at the previous moment, and m and n are determined according to the current maximum high - pressure pressure and the target pressure.

[0040] In some embodiments of the present invention, after the frequency - increasing judgment step, there is also a step of monitoring and controlling the compressor to decrease the frequency. When the operating frequency of the compressor drops by more than the set threshold, the opening degree of the electronic expansion valve is reduced and / or the gear of the outdoor unit fan is increased.

[0041] In some embodiments of the present invention, when the operating frequency of the compressor drops by more than a set threshold, the control method for reducing the opening degree of the electronic expansion valve includes:

[0042] Determine the adjustment amount of the electronic expansion valve according to the interval where the drop value of the operating frequency of the compressor is located. The larger the drop value interval, the larger the adjustment amount of the electronic expansion valve corresponding to it.

[0043] In some embodiments of the present invention, when the operating frequency of the compressor drops by more than a set threshold, the control method for increasing the gear of the outdoor unit fan includes:

[0044] Determine the adjustment amount of the gear of the outdoor unit fan according to the interval where the drop value of the operating frequency of the compressor is located. The larger the drop value interval, the larger the adjustment amount of the gear of the outdoor unit fan corresponding to it.

[0045] The technical solution of the present invention has the following technical effects compared with the prior art:

[0046] The multi-connected air-conditioning system of the present invention comprehensively considers the influence of the capacity of the turned-on indoor units and the capacity of the unturned-on indoor units on the operating frequency, determines the reference frequency of the compressor, and performs frequency increase control in stages after controlling the compressor to start running, which can effectively prevent a series of problems caused by the over-opening of the electronic expansion valve due to too fast frequency increase in the prior art. In addition, by reasonably controlling the proportion of the capacity of the turned-on indoor units, the heat exchange requirements of the turned-on indoor units can be satisfied simultaneously, achieving the purpose of rapid temperature rise. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0048] Figure 1 It is the system schematic diagram of an embodiment of the multi-connected air-conditioning system proposed by the present invention;

[0049] Figure 2 It is the control flowchart in an embodiment of the multi-connected air-conditioning system proposed by the present invention;

[0050] Figure 3 It is the compressor frequency control flowchart in an embodiment of the multi-connected air-conditioning system proposed by the present invention;

[0051] Figure 4 It is the frequency increase control schematic diagram in an embodiment of the multi-connected air-conditioning system proposed by the present invention;

[0052] Figure 5It is a schematic diagram of frequency increase control in another embodiment of the multi-link system proposed by the present invention;

[0053] Figure 6 It is a schematic diagram of ⊿hh search representation in one embodiment of the multi-connection system proposed by the present invention;

[0054] Figure 7 It is a schematic diagram of the windshield-k search in one embodiment of the multi-connection system proposed by the present invention;

[0055] Figure 8 1 is a schematic diagram of the range of m, n and ⊿F in one embodiment of the multi-connection system proposed by the present invention;

[0056] Figure 9 It is a schematic diagram of EVO following change adjustment when frequency drops too much in one embodiment of the multi-link system proposed by the present invention;

[0057] Figure 10 This is a schematic diagram of EVO following changes when the frequency drops excessively in an embodiment of the multi-connected system proposed by the present invention. DETAILED DESCRIPTION

[0058] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0060] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0061] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0062] Embodiment 1

[0063] [Basic Principle of Multi-Split Air Conditioner]

[0064] The air conditioning system performs the refrigeration or heating cycle of the air conditioner by using a compressor, a condenser, an expansion valve, and an evaporator. The refrigeration or heating cycle includes a series of processes involving compression, condensation, expansion, and evaporation, and supplies refrigerant to the air that has been conditioned and heat-exchanged.

[0065] The compressor compresses the refrigerant gas in a low-temperature and low-pressure state and discharges the compressed refrigerant gas. The discharged refrigerant gas flows into the condenser. The condenser condenses the compressed refrigerant into a liquid phase, and heat is released to the surrounding environment through the condensation process.

[0066] The expansion valve expands the liquid-phase refrigerant in a high-temperature and high-pressure state condensed in the condenser into a low-pressure liquid-phase refrigerant. The evaporator evaporates the refrigerant expanded in the expansion valve and returns the refrigerant gas in a low-temperature and low-pressure state to the compressor. The evaporator can achieve a refrigeration effect by using the latent heat of evaporation of the refrigerant for heat exchange with the material to be cooled. Throughout the cycle, the air conditioner can adjust the temperature of the indoor space.

[0067] The outdoor unit of the air conditioner refers to the part of the refrigeration cycle including the compressor and the outdoor heat exchanger. The indoor unit of the air conditioner includes the indoor heat exchanger, and the expansion valve can be provided in the indoor unit or the outdoor unit.

[0068] The indoor heat exchanger and the outdoor heat exchanger serve as condensers or evaporators. When the indoor heat exchanger serves as a condenser, the air conditioner serves as a heater in the heating mode. When the indoor heat exchanger serves as an evaporator, the air conditioner serves as a cooler in the refrigeration mode.

[0069] In this embodiment, the compressor should be a variable-frequency compressor that can receive the control of the control module to adjust the operating frequency.

[0070] There are multiple indoor units. Generally, the compressor is installed in the outdoor unit, and the compressor is connected to the heat exchangers of each indoor unit through pipes;

[0071] The flow direction of the refrigerant and the outdoor unit, etc. are controlled by the control module.

[0072] In the existing multi-connected air-conditioning system during heating, the outdoor unit may be connected to multiple indoor units simultaneously. To rapidly increase the indoor temperature, a control method is adopted to quickly raise the compressor to high-frequency operation. However, the indoor units may not be turned on simultaneously. When only one indoor unit is operating, if the compressor still needs to quickly reach high-frequency operation at this time, there will be a series of problems such as the electronic expansion valve being over-opened due to too rapid frequency increase during the start-up to normal stage of small-load heating or too rapid frequency increase during the start-up to normal stage after defrosting. The over-opening of the electronic expansion valve may lead to the risk of liquid return in the system. Based on this, the multi-connected air-conditioning system proposed by the present invention aims to solve the above problems.

[0073] In one embodiment of the present invention, as Figure 1 shown, the multi-connected air-conditioning system includes multiple indoor units, an outdoor unit, a compressor 11, and a control module (not shown in the figure). The compressor 11 is disposed in the outdoor unit, and the compressor 11 connects the heat exchangers 12 of each indoor unit to the outdoor heat exchanger 13 through pipes respectively.

[0074] The multi-connected air-conditioning system further includes a gas-liquid separator 14.

[0075] The control module is configured to: when the operating mode is the heating mode, include:

[0076] Respectively obtain the first reference frequency and the second reference frequency of the system. The first reference frequency is the contribution value of the capacity of the turned-on indoor units to the reference frequency, and the second reference frequency is the contribution value of the capacity of the standby indoor units and the capacity of the turned-off indoor units to the reference frequency.

[0077] Determine the reference frequency, and the reference frequency is the sum of the first reference frequency and the second reference frequency.

[0078] Control and adjust the operating frequency of the compressor, including:

[0079] Control the compressor to operate at the initial frequency for the first preset time;

[0080] Control the compressor to operate at the reference frequency;

[0081] The frequency increase judgment step includes controlling the compressor to increase the operating frequency when the set frequency increase condition is satisfied.

[0082] In the solution of this embodiment, the reference frequency is restricted by both the capacity of the turned-on indoor units and the capacity of the unturned-on indoor units. By comprehensively considering the influence of the capacity of the turned-on indoor units and the capacity of the unturned-on indoor units on the operating frequency, the reference frequency of the compressor is determined, and frequency increase control is performed in stages after controlling the compressor to start running, which can effectively prevent a series of problems caused by over-opening of the electronic expansion valve due to too rapid frequency increase in the prior art. In addition, by reasonably controlling the proportion of the capacity of the turned-on indoor units, the heat exchange requirements of the turned-on indoor units can be satisfied simultaneously, achieving the purpose of rapid temperature rise.

[0083] As shown Figure 2 in the figure, it is a schematic diagram of the operating frequency adjustment of the compressor in an embodiment of the multi-connected unit system of the invention. When the compressor starts initially, it is controlled to operate at the initial frequency f0 for the first preset time. After the first preset time is satisfied, the compressor is controlled to operate at the reference frequency F.

[0084] As shown Figure 3 , Figure 4 in the figure, in some embodiments of the present invention, the initial frequency f0 is less than the reference frequency, that is, when the compressor changes from operating at the initial frequency f0 to operating at the reference frequency, the operating frequency is increased.

[0085] Since the reference frequency is obtained by comprehensively considering the influence of the capacity of the turned-on indoor units and the capacity of the unturned-on indoor units on the operating frequency, especially during small-load heating operation, that is, when the number of turned-on indoor units is small, the operating frequency of the compressor will not be increased to a relatively high value in a short time, thereby avoiding a series of problems caused by an overly high opening degree of the corresponding electronic expansion valve due to a relatively high operating frequency of the compressor.

[0086] In addition, since the energy demand during small-load heating operation is relatively small, this solution can also meet the needs of small-load heating and achieve the purpose of rapid temperature rise by means of frequency increase control in a certain stage.

[0087] In the frequency increase judgment step, when the set frequency increase condition is satisfied, the compressor is controlled to increase the operating frequency. Multiple frequency increase stages can be set in this step. If the current operating frequency can ensure system safety but cannot meet any one of the heating requirements, frequency increase control is performed.

[0088] In this embodiment, it is described by taking three frequency increase stages as an example.

[0089] As shown Figure 5 in the figure, the compressor is controlled to operate at the initial frequency f0 for the first preset time. After the first preset time is satisfied, the first frequency increase stage is entered, and the compressor is controlled to operate at the reference frequency.

[0090] During the operation in the first frequency increase stage, when the set frequency increase condition is satisfied, the operating frequency is increased, and the second frequency increase stage is entered, that is, the operating frequency in the second frequency increase stage is greater than the operating frequency in the first frequency increase stage.

[0091] Similarly, during the operation in the second frequency increase stage, when the set frequency increase condition is satisfied, the operating frequency is increased, and the third frequency increase stage is entered, that is, the operating frequency in the third frequency increase stage is greater than the operating frequency in the second frequency increase stage.

[0092] For the convenience of control, reduce the computational amount, and at the same time achieve the purpose of quickly improving the heating effect, the operating frequencies corresponding to the second frequency increase stage and the third frequency increase stage are integer multiples or non-integer multiples of the reference frequency.

[0093] In some embodiments of the present invention, when controlling the compressor to increase the operating frequency, the reference frequency is doubled each time.

[0094] For example, the operating frequency in the second frequency increase stage is 2 times the reference frequency, and the operating frequency in the third frequency increase stage is 3 times the reference frequency.

[0095] In some embodiments of the present invention, the set frequency increase conditions include:

[0096] ① Pdmax>Pdo;

[0097] ② Compressor protection control;

[0098] ③ Operate for a / 3 minutes in this stage.

[0099] When any of the above conditions is met, the current frequency control is exited.

[0100] Wherein, a is a set time parameter, and the entire frequency increase stage is controlled within a time.

[0101] The compressor protection control can be based on the existing protection control mechanism, and no specific limitation is made in this embodiment.

[0102] After the entire frequency increase stage is executed, the system enters the normal control stage, that is, the frequency is adjusted according to the actual operating state of the system, which can be frequency increase, frequency decrease, or maintaining the current operating frequency.

[0103] In summary, within the first a / 3 minutes after the compressor starts and turns to normal operation, based on the actual startup capacity of the user and the target pressure to be achieved by the system, according to the reference frequency F, and operate for a / 3 minutes. If the exit condition of the first frequency increase stage is met during this period, the first frequency increase stage can be exited at any time and enter the next frequency increase stage; when entering the second frequency increase stage, the compressor continues to operate at 2*F for a / 3 minutes. If the exit condition of the second frequency increase stage is met during this period, the second frequency increase stage can be exited at any time and enter the next frequency increase stage for operation; when entering the third frequency increase stage, the compressor continues to operate at 3*F for a / 3 minutes. If the exit condition of the third frequency increase stage is met during this period, the third frequency increase stage can be exited at any time and enter the normal operation after a minutes.

[0104] This solution automatically identifies the actual requirements of the indoor units in a multi-connected air-conditioning system and stepwise regulates the operating frequency of the compressor to match the operating frequency of the compressor with the system pressure to achieve stable operation of the whole machine, effectively solving the problem that the system cannot operate stably caused by the over-opening of the electronic expansion valve and the over-increase of the compressor frequency during small-load heating. At the same time, it can also avoid the liquid return problem caused by the failure of the electronic expansion valve to close in time and the failure of the outdoor fan to increase in time when the frequency drops too much.

[0105] In some embodiments of the present invention, the calculation method of the first reference frequency includes:

[0106] Obtain the capacity sum e of the turned-on indoor units. The capacity sum e of the turned-on indoor units is also the sum of the capacities of all turned-on indoor units. The capacity of each indoor unit is fixed and known. Therefore, the control module can easily calculate the capacity sum e of the turned-on indoor units by obtaining all the turned-on indoor units.

[0107] Respectively obtain the target pressure Pdo of the system operation, the maximum high-pressure pressure Pdmax during system operation, the set temperature of the turned-on indoor units, the indoor air temperature of the turned-on indoor units, and the air volume of the turned-on indoor units, and determine the first reference coefficient.

[0108] The target pressure Pdo can be calculated based on parameters such as the set temperature of the turned-on indoor units and the indoor air temperature of the turned-on indoor units. The calculation method can adopt the existing algorithm.

[0109] The maximum high-pressure pressure Pdmax during system operation can be measured by setting a pressure sensor or calculated from other temperature parameters and pressure parameters of the system. The calculation method can adopt the existing algorithm.

[0110] Multiply the capacity sum e of the turned-on indoor units by the first reference coefficient to obtain the first reference frequency.

[0111] In this embodiment, the unit of the first reference coefficient should be such that the unit obtained by multiplying it with the unit of the capacity is the frequency unit.

[0112] The set temperature of the turned-on indoor units and the indoor air temperature of the turned-on indoor units reflect the actual load demand of the system. The target pressure Pdo of the system operation and the maximum high-pressure pressure Pdmax during system operation reflect the safe state of the system operation. The air volume of the turned-on indoor units reflects the heat exchange efficiency of the indoor units from one aspect. Therefore, this solution determines the first reference frequency by comprehensively considering the load demand, the system safe state, and the heat exchange efficiency, achieving the improvement of the heat exchange efficiency of the system while ensuring the safe operation of the system.

[0113] In some embodiments of the present invention, the first reference coefficient includes a first coefficient c, a second coefficient h, and a third coefficient k, where:

[0114] The method for determining the first coefficient c is as follows:

[0115] c = -2.04×(Pdmax - Pdo) + 1.0.

[0116] Where, 1.0 ≤ c ≤ 4.0.

[0117] The first coefficient c reflects the pressure safety state of the system. When the system is operating in any frequency increasing stage, the maximum high - pressure pressure Pdmax should not be greater than the target pressure Pdo. Otherwise, the condition for exiting the current operating stage is met. Therefore, the difference between the maximum high - pressure pressure Pdmax and the target pressure Pdo is negative. After multiplying by the negative number -2.04, it becomes positive. Therefore, the larger the absolute value of the difference between the maximum high - pressure pressure Pdmax and the target pressure Pdo, the larger the first coefficient c. The absolute value of the difference between the maximum high - pressure pressure Pdmax and the target pressure Pdo reflects the gap between the maximum high - pressure pressure during the current operation and the actual required pressure. Therefore, the larger the gap, the larger the corresponding first coefficient c, and then the larger the first reference frequency and the final reference frequency.

[0118] In some embodiments of the present invention, the method for determining the second coefficient h is as follows:

[0119] Calculate the difference ⊿h between the set temperature of the indoor unit at startup and the indoor air temperature, and determine h by looking up the preset ⊿h - h look - up table.

[0120] The second coefficient h reflects the heating demand of the system. In some embodiments of the present invention, as Figure 6 shown, it is a schematic diagram of one kind of ⊿h - h look - up table. The larger the temperature difference ⊿h, the greater the heating demand, the larger the second coefficient h. Then, when other coefficients are the same, the finally calculated first reference frequency is larger, which can meet the demand for rapid temperature rise.

[0121] In some embodiments of the present invention, the method for determining the third coefficient k is as follows:

[0122] Look up the preset wind speed - k look - up table and determine k according to the wind speed of the indoor unit at startup;

[0123] The first reference frequency F1 = a1×c×e×h×k, where a1 is a constant coefficient.

[0124] The third coefficient k reflects the heat exchange capacity of the indoor unit at startup. As Figure 7 shown, it is a schematic diagram of one kind of wind speed - k look - up table. In the state where the fan is turned on, the higher the wind speed gear, the better the heat exchange capacity of the indoor unit at startup, the larger the third coefficient k. Then, when other coefficients are the same, the finally calculated first reference frequency is larger, which can meet the demand for rapid temperature rise.

[0125] In some embodiments of the present invention, the calculation method of the second reference frequency F2 includes:

[0126] Obtain the capacity sum g of the shutdown indoor units and the capacity sum f of the standby indoor units;

[0127] Respectively obtain the target pressure Pdo of the system operation and the maximum high-pressure pressure Pdmax during the system operation, and determine the second reference coefficient.

[0128] The sum of the products of the capacity sum g of the shutdown indoor units and the capacity sum f of the standby indoor units and the second reference coefficient respectively obtains the second reference frequency.

[0129] The common point of the shutdown indoor units and the standby indoor units is that they are both unstarted indoor units, that is, there is no heat exchange requirement currently. Since the started indoor units and the unstarted indoor units together are both part of the multi-connected air-conditioning system and have a proportion of the total capacity of the multi-connected air-conditioning system, therefore, in this solution, by considering the capacity of the unstarted indoor units at the same time, the reference frequency is comprehensively calculated.

[0130] In some embodiments of the present invention, the method for determining the second reference coefficient d is:

[0131] d = 1.0 - (Pdmax - Pdo) × 1.2.

[0132] Where, 0.1 ≤ d ≤ 1.0.

[0133] The second reference frequency F2 = (a2 × f + a3 × g) × d, where a2 and a3 are constant coefficients, and a2 > a3.

[0134] The reference frequency F = F1 + F2.

[0135] The reference frequency F is calculated based on the startup load rate of the actual user and the target pressure to be achieved by the system for the compressor frequency requirement.

[0136] Although both the shutdown indoor units and the standby indoor units are unstarted indoor units, in this solution, different weight coefficients are further assigned to the shutdown indoor units and the standby indoor units, and the coefficient a2 of the capacity sum f of the standby indoor units is greater than the coefficient of the capacity sum g of the shutdown indoor units. The capacity of the standby indoor units reflects the potential power consumption demand, so the assigned weight coefficient is larger, so that once the standby indoor units are converted into started indoor units, the system can make timely responses and quickly reach the compressor frequency required due to the newly added started indoor units.

[0137] In some embodiments of the present invention, after the frequency increase judgment step, it further includes a step of correcting the operating frequency of the compressor, including:

[0138] Calculate the correction value ΔF: ΔF = m×(Pdo - Pdmax) - n×(Pd(n) - Pd(n - 1));

[0139] Where Pd(n) is the current maximum high-pressure pressure, Pd(n - 1) is the maximum high-pressure pressure at the previous moment, and m and n are determined according to the current maximum high-pressure pressure and the target pressure.

[0140] The ranges of m, n, and ΔF are as Figure 8 shown. When the system operating pressure is much lower than the target pressure Pdo, ΔF is positive and the change amount is also large, and the frequency can be quickly increased to meet the system operating target pressure; when the system is already near the target pressure at this time, the frequency of the compressor can be finely adjusted according to the difference between the current maximum high-pressure pressure Pd(n) and the maximum high-pressure pressure Pd(n - 1) at the previous moment; when the pressure in the system is higher than the system operating target pressure, ΔF is negative and the change amount is slightly large to prevent over-high high-pressure pressure protection.

[0141] Specifically, when Pdmax < Pdo - 0.25, 0 ≤ ΔF ≤ 5.

[0142] When Pdo - 0.25 ≤ Pdmax ≤ Pdo + 0.25, further judge the difference between Pd(n) and Pd(n - 1). That is, when 0.1 ≤ Pd(n) - Pd(n - 1) < 0.2, -4 ≤ ΔF ≤ 4.

[0143] Pd(n) - Pd(n - 1) ≥ 0.2, -6 ≤ ΔF ≤ 6.

[0144] When the difference between Pd(n) and Pd(n - 1) is other than the above cases, -2 ≤ ΔF ≤ 2.

[0145] When Pdo + 0.25 < Pdmax < Pdo + 0.5, -15 ≤ ΔF ≤ 0.

[0146] When Pdmax ≥ Pdo + 0.5, -25 ≤ ΔF ≤ -6.

[0147] The multi-connected system of this embodiment should also include an exhaust pressure sensor 15 for detecting the exhaust pressure Pd of the compressor.

[0148] Based on the above control, when the system still shows a situation of excessive reduction in the compressor frequency, to prevent the problem that when the compressor frequency drops excessively, the opening degree of the electronic expansion valve is too large, resulting in liquid accumulation or full liquid in the gas-liquid separator, affecting the reliability of the compressor, the present invention, when the frequency drops excessively, adopts the electronic expansion valve to close in time to reduce the liquid refrigerant returning to the gas-liquid separator, and the outdoor unit fan increases the gear in time to increase the evaporation capacity of the outdoor heat exchanger, thereby reducing the liquid refrigerant returning to the gas-liquid separator, and finally avoiding the phenomenon of liquid accumulation or full liquid in the gas-liquid separator, and solving the problem of damage to the compressor due to liquid return operation caused by excessive frequency drop.

[0149] In some embodiments of the present invention, after the up - frequency judgment step, it further includes a step of monitoring and controlling the down - frequency of the compressor. When the operating frequency of the compressor drops by more than a set threshold, the opening degree of the electronic expansion valve is reduced and / or the gear of the outdoor unit fan is increased.

[0150] In some embodiments of the present invention, as Figure 9 shown, when the operating frequency of the compressor drops by more than a set threshold, the control method for reducing the opening degree of the electronic expansion valve includes:

[0151] Determine the adjustment amount of the electronic expansion valve according to the interval where the drop value of the operating frequency of the compressor is located. The larger the drop value interval, the larger the adjustment amount of the electronic expansion valve corresponding to it.

[0152] Where p is a correction coefficient; Tdmax is the maximum exhaust temperature of the compressor during operation. ⊿EVO is the adjustment amount of the electronic expansion valve; EVO(n - 1) is the opening degree of the electronic expansion valve at the previous moment; F(n) is the operating frequency of the compressor at the current moment; F(n - 1) is the operating frequency of the compressor at the previous moment; Ta is the outdoor ambient temperature.

[0153] In some embodiments of the present invention, as Figure 10 shown, when the operating frequency of the compressor drops by more than a set threshold, the control method for increasing the gear of the outdoor unit fan includes:

[0154] Determine the adjustment amount of the gear of the outdoor unit fan according to the interval where the drop value of the operating frequency of the compressor is located. The larger the drop value interval, the larger the adjustment amount of the gear of the outdoor unit fan corresponding to it.

[0155] It can be seen from Figure 10 that when - 30 < F(n) - F(n - 1) ≤ - 20, the electronic expansion valve needs to close the valve, and the valve - closing amount is p×{F(n) - F(n - 1)} (-EVO(n - 1) / 6 ≤ ⊿EVO ≤ 0), and at the same time, the gear of the outdoor fan also needs to rise by 1 gear on the original basis; when - 40 < F(n) - F(n - 1) ≤ - 30, the electronic expansion valve needs to close the valve, and the valve - closing amount is p×{F(n) - F(n - 1)} (-EVO(n - 1) / 4 ≤ ⊿EVO ≤ 0), and at the same time, the gear of the outdoor fan also needs to rise by 2 gears on the original basis; when F(n) - F(n - 1) ≤ - 40, the electronic expansion valve needs to close the valve, and the valve - closing amount is p×{F(n) - F(n - 1)} (-EVO(n - 1) / 2 ≤ ⊿EVO ≤ 0), and at the same time, the gear of the outdoor fan also needs to rise by 3 gears on the original basis.

[0156] In the description of the above - mentioned embodiments, specific features, structures, materials or characteristics can be combined in a suitable manner in any one or more embodiments or examples.

[0157] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A multi-connected air-conditioning system, characterized in that, Including: An indoor unit, which has multiple ones; An outdoor unit, in which a compressor is provided, and the compressor is connected to the heat exchangers of each indoor unit through pipes respectively; A control module, which is configured to: when the operation mode is the heating mode, include: Obtain the first reference frequency and the second reference frequency of the system respectively. The first reference frequency is the contribution value of the capacity of the turned-on indoor unit to the reference frequency, and the second reference frequency is the contribution value of the capacity of the standby indoor unit and the capacity of the turned-off indoor unit to the reference frequency; Determine the reference frequency, and the reference frequency is the sum of the first reference frequency and the second reference frequency; Adjust the operating frequency of the compressor, including: Control the compressor to operate at the initial frequency for a first preset time; Control the compressor to operate at the reference frequency; A frequency increase judgment step, including when the set frequency increase condition is met, controlling the compressor to increase the operating frequency; The calculation method of the second reference frequency includes: Obtain the sum of the capacities g of the turned-off indoor units and the sum of the capacities f of the standby indoor units; Obtain the target pressure Pdo of the system operation, the maximum high pressure Pdmax during the system operation respectively, and determine the second reference coefficient; The sum of the products of the sum of the capacities g of the turned-off indoor units and the sum of the capacities f of the standby indoor units and the second reference coefficient respectively obtains the second reference frequency.

2. The multi-connected air conditioner system according to claim 1, wherein The calculation method of the first reference frequency includes: Obtain the sum of the capacities e of the turned-on indoor units; Obtain the target pressure Pdo of the system operation, the maximum high pressure Pdmax during the system operation, the set temperature of the turned-on indoor unit, the indoor air temperature of the turned-on indoor unit, and the air duct of the turned-on indoor unit respectively, and determine the first reference coefficient; The product of the sum of the capacities e of the turned-on indoor units and the first reference coefficient obtains the first reference frequency.

3. The multi-connected air conditioner system according to claim 2, characterized in that, The first reference coefficient includes a first coefficient c, a second coefficient h, and a third coefficient k, where: The determination method of the first coefficient c is: c = -2.04×(Pdmax - Pdo) + 1.0 (1.0 ≤ c ≤ 4.0); The determination method of the second coefficient h is: Calculate the difference ⊿h between the set temperature and the indoor air temperature of the turned-on indoor unit, and determine h by looking up the preset ⊿h-h lookup table; The determination method of the third coefficient k is: Look up the preset air duct-k lookup table, and determine k according to the air duct of the turned-on indoor unit; The first reference frequency F1 = a1×c×e×h×k, where a1 is a constant coefficient.

4. The multi-connected air conditioner system according to claim 1, wherein The determination method of the second reference coefficient d is: d = 1.0 - (Pdmax - Pdo)×1.2; The second reference frequency F2 = (a2×f + a3×g)×d, where a2 and a3 are constant coefficients, and a2 > a3.

5. The multi-connected air conditioner system according to any one of claims 1 to 4, characterized in that When controlling the compressor to increase the operating frequency, the reference frequency is doubled each time.

6. The multi-connected air conditioner system according to any one of claims 1-4, characterized in that After the frequency increase judgment step, there is also a step of correcting the operating frequency of the compressor, including: Calculate the correction value ⊿F: ⊿F = m×(Pdo - Pdmax) - n×(Pd(n) - Pd(n - 1)); Where Pd(n) is the current maximum high-pressure, Pd(n - 1) is the maximum high-pressure at the previous moment, and m and n are determined according to the current maximum high-pressure and the target pressure.

7. The multi-connected air conditioner system according to any one of claims 1-4, characterized in that, After the frequency increase determination step, it further includes a step of monitoring and controlling the frequency decrease of the compressor. When the operating frequency of the compressor drops by more than the set threshold, the opening degree of the electronic expansion valve is reduced and / or the gear of the outdoor unit fan is increased.

8. The multi-connected air conditioner system according to claim 7, characterized in that, When the operating frequency of the compressor drops by more than the set threshold, the control method for reducing the opening degree of the electronic expansion valve includes: Determining the adjustment amount of the electronic expansion valve according to the interval where the drop value of the operating frequency of the compressor is located. The larger the interval of the drop value, the larger the adjustment amount of the electronic expansion valve corresponding to it.

9. The multi-connected air conditioner system according to claim 7, wherein, When the operating frequency of the compressor drops by more than the set threshold, the control method for increasing the gear of the outdoor unit fan includes: Determining the adjustment amount of the gear of the outdoor unit fan according to the interval where the drop value of the operating frequency of the compressor is located. The larger the interval of the drop value, the larger the adjustment amount of the gear of the outdoor unit fan corresponding to it.

Images