Air conditioning system and control method therefor

Abstract

A control method for an air conditioning system, wherein the air conditioning system comprises an indoor unit and an outdoor unit. The method comprises: determining load parameters of an indoor unit; determining a desired indoor temperature at each moment; on the basis of the load parameters, an indoor temperature at the current moment, an outdoor temperature, the desired indoor temperature and a control period, determining a real-time required load of the indoor unit; and on the basis of the real-time required load, controlling an air conditioning system.

Description

Air conditioning system and control method thereof

[0001] This application claims priority to Chinese Patent Application No. 202411073832.6, filed on August 6, 2024, and Chinese Patent Application No. 202411074143.7, filed on August 6, 2024, the contents of which are incorporated herein by reference in their entirety. TECHNICAL FIELD

[0002] The present application relates to the field of air conditioning technology, in particular to an air conditioning system and a control method thereof. BACKGROUND

[0003] The system control target of the current multi-split central air conditioner is usually the difference between the set temperature and the return air temperature, which will be used as a reference for the control of the compressor frequency, evaporating temperature, superheat, condensing temperature, subcooling, and other key parameters in the system. However, since the temperature difference only reflects the target room temperature state, the actual output control target of the multi-split central air conditioner system is the building load, and the temperature difference is only an important parameter in the air heat load item of the building load, which fails to fully reflect the state of this item and lacks the description of the quantity in this item. In addition, in the building load, heat leakage load, solar radiation load, and internal disturbance load are also important factors. Therefore, using the temperature difference as the control target alone can easily cause problems such as small temperature difference with large load under-regulation, large temperature difference with small load over-regulation, and room temperature fluctuation of medium load, which also leads to frequent start and stop of the unit, low energy efficiency, and poor user experience.

[0004] The above information disclosed in this BACKGROUND section is only for increasing the understanding of the background of the present application, therefore, it can include information known by those of ordinary skill in the art. SUMMARY

[0005] In one aspect, the present application provides a control method of an air conditioning system, the air conditioning system comprising an indoor unit and an outdoor unit, the method comprising: determining a load parameter of the indoor unit; determining a desired indoor temperature at each time; determining a real-time demand load of the indoor unit based on the load parameter, an indoor temperature at a current time, an outdoor temperature, the desired indoor temperature, and a control period; and controlling the air conditioning system according to the real-time demand load.

[0006] In some embodiments, the determining the real-time demand load of the indoor unit comprises determining the real-time demand load based on a load characteristic model, the load characteristic model comprising:

[0007] Model for heating mode: Q n = a × (T i - T s ) + b × (T a - T i)xt + cxt

[0008] or the model for cooling mode: Q n = a x (T s -T i ) + b x (T a -T i )xt - cxt

[0009] wherein Qn is the building load, kW; a, b, c are load parameters, dimensionless; Ti is the indoor temperature, ℃; Ts is the set temperature, ℃; Ta is the outdoor temperature, ℃; t is the time step, min.

[0010] In some embodiments, the determining the load parameters of the indoor unit comprises: obtaining the real-time capacity of the indoor unit as the building load, and solving the load parameters based on the load characteristic model.

[0011] In some embodiments, the obtaining the real-time capacity of the indoor unit as the building load, and solving the load parameters based on the load characteristic model comprises: when one operation period meets that the operation time is longer than the set time, the initial indoor temperature and the outdoor temperature difference is lower than the set temperature difference, the indoor temperature change in a certain time is higher than the first set difference, and the final indoor temperature and the set temperature difference is lower than the second set difference, obtaining the real-time capacity, the set temperature, the indoor temperature and the outdoor temperature at least three time points in the operation period, and solving the load characteristic parameters based on the equation group established based on the load characteristic model.

[0012] In some embodiments, the determining the expected indoor temperature at each time point comprises: determining the expected indoor temperature at each time point according to the difference between the indoor temperature and the set temperature, the equipment capacity characteristics and the time of the executed cooling or heating process.

[0013] In some embodiments, the determining the load parameters of the indoor unit comprises: obtaining the built-in parameters of the air conditioning system as the load parameters.

[0014] In some embodiments, the controlling the air conditioning system according to the real-time demand load comprises: in the cooling mode, determining the target evaporation temperature of the air conditioning system according to the real-time demand load, and determining the compressor frequency according to the target evaporation temperature.

[0015] In some embodiments, the determining the target evaporation temperature of the air conditioning system according to the real-time demand load comprises: calculating the target evaporation temperature T e_i according to the following formula:

[0016] wherein Q r_n is the real-time demand load; f sh , f sca superheat degree characteristic parameter of the indoor unit; m cs , n cs a sensible heat capacity characteristic parameter of the indoor unit for refrigeration; cl , n cl a latent heat capacity characteristic parameter of the indoor unit for refrigeration; T i an indoor temperature corresponding to the indoor unit; T ld a dew point temperature corresponding to the return air temperature of the indoor unit.

[0017] In some embodiments, the air conditioning system includes a plurality of indoor units, and the determining the target evaporating temperature of the air conditioning system according to the real-time demand load includes: calculating a corresponding target evaporating temperature for each of the plurality of indoor units, and taking an average or a minimum of the target evaporating temperatures as the target evaporating temperature of the air conditioning system.

[0018] In some embodiments, the determining the compressor frequency according to the target evaporating temperature includes: determining the compressor frequency according to the compressor parameter, the capacities of all indoor units, and the target evaporating temperature.

[0019] In some embodiments, the controlling the air conditioning system according to the real-time demand load includes: in a heating mode, determining a target condensing temperature of the air conditioning system according to the real-time demand load, and determining the compressor frequency according to the target condensing temperature.

[0020] In some embodiments, the determining the target condensing temperature of the air conditioning system according to the real-time demand load includes: calculating the target condensing temperature T c_i according to the following formula:

[0021] wherein Q r_n is the real-time demand load; f sh , f sc a superheat degree characteristic parameter of the indoor unit; m cs , n cs a sensible heat capacity characteristic parameter of the indoor unit for heating; i an indoor temperature of the indoor unit.

[0022] In some embodiments, the air conditioning system includes a plurality of indoor units, and the determining the target condensing temperature of the air conditioning system according to the real-time demand load includes: calculating a corresponding target condensing temperature for each of the plurality of indoor units, and taking an average or a maximum of the target condensing temperatures as the target condensing temperature of the air conditioning system.

[0023] In some embodiments, the determining the compressor frequency according to the target condensing temperature includes: determining the compressor frequency according to the compressor parameter, the capacities of all indoor units, and the target condensing temperature.

[0024] In some embodiments, the controlling the air conditioning system according to the real-time demand load comprises: determining the rotating speed of the indoor fan according to the maximum rotating speed of the indoor fan, the real-time demand load and the capacity characteristic coefficient of the indoor unit.

[0025] In some embodiments, the air conditioning system comprises a plurality of indoor units, and each of the indoor units comprises an indoor expansion valve, and the method further comprises: determining the superheat value of the current indoor unit; when the superheat value is lower than a set value, keeping the opening degree of the indoor expansion valve unchanged; and when the superheat value is higher than the set value, increasing the opening degree of the indoor expansion valve.

[0026] In some embodiments, the increasing the opening degree of the indoor expansion valve comprises: determining the increasing amount of the opening degree of the indoor expansion valve according to the superheat difference value, the difference between the superheat difference values of two continuous time points and a superheat correction coefficient.

[0027] In some embodiments, the air conditioning system comprises a plurality of indoor units, and the outdoor unit comprises an outdoor expansion valve, and the method further comprises: determining the subcooling degree of the indoor unit; when the subcooling degree is lower than a target condensing temperature, decreasing the opening degree of the outdoor expansion valve; when the subcooling degree is equal to the target condensing temperature, keeping the opening degree of the indoor expansion valve unchanged; and when the subcooling degree is higher than the target condensing temperature, increasing the opening degree of the outdoor expansion valve.

[0028] In some embodiments, the decreasing or increasing the opening degree of the outdoor expansion valve comprises: determining the changing amount of the opening degree of the outdoor expansion valve according to the subcooling difference value, the difference between the subcooling difference values of two continuous time points and a subcooling correction coefficient.

[0029] Another aspect of the present application comprises an air conditioning system comprising an indoor unit, an outdoor unit and a controller, wherein the controller is configured to perform the method of controlling the air conditioning system according to any one of the above embodiments.

[0030] Other characteristics and advantages of the present application will become more apparent after reading the specific embodiments of the present application in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative labor.

[0032] FIG. 1 is a refrigerant circulation schematic diagram of a multi-split system in a refrigeration mode according to an embodiment;

[0033] Fig. 2 is a flow chart of determining a refrigeration load parameter in a refrigeration mode of a multi-connected system according to an embodiment;

[0034] Fig. 3 is a flow chart of obtaining historical operation data of indoor units available for model learning in a refrigeration mode of a multi-connected system according to an embodiment;

[0035] Fig. 4 is a control flow chart in a refrigeration mode of a multi-connected system according to an embodiment;

[0036] Fig. 5 is a flow chart of compressor frequency, indoor fan speed, and indoor expansion valve adjustment in a refrigeration mode of a multi-connected system according to an embodiment;

[0037] Fig. 6 is a refrigerant circulation schematic diagram in a heating mode of a multi-connected system according to an embodiment;

[0038] Fig. 7 is a flow chart of determining a refrigeration load parameter in a heating mode of a multi-connected system according to an embodiment;

[0039] Fig. 8 is a flow chart of self-learning of a refrigeration load parameter in a heating mode of a multi-connected system according to an embodiment;

[0040] Fig. 9 is a control flow chart in a heating mode of a multi-connected system according to an embodiment;

[0041] Fig. 10 is a flow chart of compressor frequency, indoor fan speed, and indoor expansion valve adjustment in a heating mode of a multi-connected system according to an embodiment. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0043] In the description of the present application, it should be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0044] The terms "first", "second", etc. are used only for the purpose of description and do not imply or indicate relative importance or imply the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specified.

[0045] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0046] In the present application, unless otherwise explicitly specified and limited, the "upper" or "lower" of the first feature to the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the "upper", "above" and "on" of the first feature to the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The "under", "below" and "under" of the first feature to the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0047] The following disclosure provides many different embodiments or examples for implementing different structures of the present application. In order to simplify the disclosure of the present application, the components and arrangements of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeatedly refer to numbers and / or letters in different examples, and such repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or arrangements discussed. In addition, the present application provides examples of various specific processes and materials, but those skilled in the art can realize the application of other processes and / or the use of other materials.

[0048] The present application discloses a control method of an air conditioning system. The air conditioning system includes an indoor unit and an outdoor unit. When including multiple indoor units, the air conditioning system is also called a multi-split air conditioning system or simply a multi-split system.

[0049] The following focuses on the multi-split system to introduce the control method of the air conditioning system of the present application in the cooling and heating modes.

[0050] The multi-split system presented in this application performs a refrigeration cycle of an air conditioner by using a compressor, a condenser, a throttling device and an evaporator. The refrigeration cycle includes a series of processes involving compression, condensation, expansion and evaporation to cool or heat an indoor space.

[0051] The low-temperature and low-pressure refrigerant enters the compressor, which compresses the refrigerant gas into a high-temperature and high-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.

[0052] The throttling device expands the high-temperature and high-pressure liquid-phase refrigerant formed in the condenser into low-pressure liquid-phase refrigerant. The evaporator evaporates the refrigerant expanded in the throttling device and returns the refrigerant gas in a low-temperature and low-pressure state to the compressor. The evaporator can achieve a refrigeration effect by exchanging heat with the material to be cooled using the latent heat of evaporation of the refrigerant. Throughout the cycle, the air conditioner can adjust the temperature of the indoor space.

[0053] The outdoor unit of the multi-split system refers to the part of the refrigeration cycle that includes the compressor and the outdoor heat exchanger, and the throttling device is located in the outdoor unit.

[0054] The indoor unit of the multi-split system includes an indoor heat exchanger, the multi-split system includes at least two indoor units, and each indoor unit is provided with an indoor expansion valve, and the capacity of the indoor unit is adjusted by adjusting the opening degree of the indoor expansion valve.

[0055] The indoor heat exchanger and the outdoor heat exchanger are used as a condenser or an evaporator. When the indoor heat exchanger is used as a condenser, the air conditioner is used as a heater in a heating state, and when the indoor heat exchanger is used as an evaporator, the air conditioner is used as a cooler in a cooling state.

[0056] The multi-split system includes an outdoor unit and at least two indoor units, the outdoor unit includes a compressor and an outdoor heat exchanger, and each indoor unit includes an indoor heat exchanger and an indoor expansion valve.

[0057] Figure 1 is a schematic diagram of the refrigerant cycle of the multi-split system in cooling mode. In the example of Figure 1, the multi-split system includes an outdoor unit and a first indoor unit, a second indoor unit and a third indoor unit, and the outdoor unit is connected to the first indoor unit, the second indoor unit and the third indoor unit through a split pipe to form a multi-split system.

[0058] The outdoor unit is provided with a compressor 1, an outdoor heat exchanger 5, an outdoor expansion valve 6 and a four-way valve 4, and the operating capacity of the indoor unit can be adjusted by adjusting the operating frequency of the compressor 1.

[0059] In some embodiments, the outdoor unit is also provided with an outdoor temperature detection module for detecting the outdoor temperature T aIn other embodiments, the outdoor temperature Ta can also be obtained in other ways, such as independently of the outdoor unit, by providing a temperature detection device to detect the outdoor temperature, or by the multi-split system directly obtaining the outdoor temperature through a network.

[0060] The first indoor unit is provided with a first indoor heat exchanger 18-1, a first indoor expansion valve 19-1, and a first indoor fan (not shown in the figure), and the operating capacity of the first indoor unit can be adjusted by adjusting the opening degree of the first indoor expansion valve 19-1 and / or the rotating speed of the first indoor fan.

[0061] The first indoor unit includes a first indoor environment temperature detection module d1, a first indoor unit liquid pipe temperature detection module c1, and a first indoor unit gas pipe temperature detection module b1.

[0062] The second indoor unit is provided with a second indoor heat exchanger 18-2, a second indoor expansion valve 19-2, and a second indoor fan (not shown in the figure), and the operating capacity of the second indoor unit can be adjusted by adjusting the opening degree of the second indoor expansion valve 19-2 and / or the rotating speed of the second indoor fan.

[0063] The second indoor unit includes a second indoor environment temperature detection module d2, a second indoor unit liquid pipe temperature detection module c2, and a second indoor unit gas pipe temperature detection module b2.

[0064] The third indoor unit is provided with a third indoor heat exchanger 18-3, a third indoor expansion valve 19-3, and a third indoor fan (not shown in the figure), and the operating capacity of the third indoor unit can be adjusted by adjusting the opening degree of the third indoor expansion valve 19-3 and / or the rotating speed of the third indoor fan.

[0065] The third indoor unit includes a third indoor environment temperature detection module d3, a third indoor unit liquid pipe temperature detection module c3, and a third indoor unit gas pipe temperature detection module b3.

[0066] The indoor environment temperature detection module is used to detect the indoor temperature T i .

[0067] All indoor units include a set temperature acquisition module.

[0068] The set temperature acquisition module is used to acquire the indoor set temperature T s .

[0069] When the multi-split system operates in the cooling mode of the indoor unit:

[0070] Determine the cooling load parameters a, b, and c of the room corresponding to the indoor unit;

[0071] Determine the expected indoor temperature T exp_n at each moment;

[0072] According to the refrigeration load parameter and the indoor temperature T at the current moment i(n) , the expected indoor temperature T exp_n , the outdoor temperature T a(n) , the control cycle determines the real-time demand load Q r_n ;

[0073] According to the real-time demand load Q r_n , the target evaporation temperature is determined, and the compressor frequency H is determined according to the target evaporation temperature.

[0074] In some embodiments, the speed F of the indoor fan is determined according to the real-time demand load Q r_n .

[0075] In some embodiments, the initial opening of the indoor expansion valve is determined, the superheat degree of the indoor unit is determined, and the opening of the indoor expansion valve is adjusted according to the superheat degree.

[0076] The load characteristics of the given target building are learned using a capacity estimation algorithm, for example, using a capacity estimation algorithm that can be run in the indoor unit to take the building demand load as the control target of the control system.

[0077] After obtaining the load characteristic parameters of the target building, a load model is established, and the target evaporation temperature and the superheat degree of the multi-split system are directly calculated according to the demand load, so as to control the compressor frequency and the speed of the indoor fan, and the indoor unit electronic expansion valve is used as a control supplement.

[0078] Through the control of the multi-split system according to the real-time demand load, the under-regulation problem of large load and small temperature difference scenes and the over-regulation problem of small load and large temperature difference scenes are solved, so that the air conditioning capacity is matched with the building load, the room temperature fluctuation is reduced when the load is small, and the power consumption caused by frequent start and stop is avoided, the indoor unit capacity is improved when the load is large, and the room temperature change speed is improved to improve user comfort. Under the condition of load following technology, various energy-saving controls can be realized according to user demand, while the system operation reliability is improved, energy saving and efficiency improvement are realized, and user comfort is improved.

[0079] First, determine the refrigeration load parameters of the indoor unit corresponding room:

[0080] In some embodiments, the method for determining the refrigeration load parameters a, b, and c of the indoor unit corresponding room is that the refrigeration load parameters are built-in parameters of the multi-split system, which can be directly read.

[0081] In some embodiments, the method for determining the refrigeration load parameters a, b, and c of the indoor unit corresponding room is that the refrigeration load parameters of the room are determined more accurately through self-learning of historical data.

[0082] In some embodiments, it is judged whether the multi-connected system is started for the first time. If so, the built-in refrigeration load parameters a0, b0 and c0 of the multi-connected system are read and the multi-connected system is controlled by the refrigeration load parameters a0, b0 and c0. If not, it is judged whether self-learning is needed for the current operation. When the refrigeration self-learning condition is met, self-learning is performed to determine the refrigeration load parameters, and the multi-connected system is controlled by the learned refrigeration load parameters. In the subsequent start-up process, it is judged whether self-learning is needed for the current operation. If not, the refrigeration load parameters determined by the last self-learning are used for control. If so, self-learning is performed to determine the refrigeration load parameters, and the multi-connected system is controlled by the learned refrigeration load parameters.

[0083] In the example of FIG. 2, the flow of determining the refrigeration load parameters in the refrigeration mode is as follows:

[0084] S21, start.

[0085] S22, judge whether it is started for the first time. If so, go to step S23, otherwise, go to step S24.

[0086] S23, read the built-in refrigeration load parameters a0, b0 and c0 of the multi-connected system as the refrigeration load parameters.

[0087] S24, judge whether the refrigeration self-learning condition is met. If not, go to step S25, if so, go to step S26.

[0088] S25, obtain the refrigeration load parameters of the last start-up.

[0089] S26, perform self-learning to determine the learned refrigeration load parameters.

[0090] Determination of the indoor unit capacity Q in the multi-connected system e The real-time capacity Q of the indoor unit in the balanced state is regarded as the room load Q e The real-time capacity Q of the indoor unit in the balanced state is regarded as the room load Q n The building load characteristic learning is performed. The building load characteristic model at least contains three parts of the indoor air heat storage load, the wall and window heat leakage load and the equipment and personnel internal disturbance load.

[0091] The air heat storage load is related to the room space size, the difference between the set temperature and the initial temperature, the wall and window heat leakage load is mainly related to the building thermal insulation and the indoor and outdoor temperature difference, and the equipment and personnel internal disturbance load is related to the use scenario. According to the actual composition of the building load, the numerical model of the load can be established, and the real-time capacity Q of the indoor unit is obtained. eThe building load characteristics are learned as the actual building load. The learning of the model needs to be selected in a complete cooling process, and the building load characteristic parameters in the load model are determined through the operation data in the process, and finally the load characteristic model of the target model building is formed.

[0092] After the establishment of the load characteristic model, the future outdoor environment temperature, indoor temperature and set temperature can be input into the model to determine the future room demand load, and the system operation parameters are adjusted according to the demand load and the expected control target.

[0093] The self-learning process of the refrigeration load parameter is as follows:

[0094] The data of the total cooling time in the complete cooling process being greater than the set time Ymin, the temperature difference between the initial indoor temperature and the outdoor temperature being lower than the set temperature difference, the indoor temperature change in a certain time being higher than the first set difference value, and the final indoor temperature and the set temperature difference being lower than the set difference value are obtained as the learning data.

[0095] The real-time capacity Q of the indoor unit is obtained. e ;

[0096] The refrigeration load parameters a, b and c are determined by solving the load characteristic model according to the real-time capacity of the indoor unit and the learning data, and the load characteristic model is Q e =Q n =a×(indoor temperature-set temperature) + b×(outdoor temperature-indoor temperature)×time step+c×time step.

[0097] The load characteristic model is: Q n =a×(T i -T s )+b×(T a -T i )×t+c×t

[0098] In the above formula: Q n : building load, kW; a, b, c: refrigeration load parameter, dimensionless unit; T i : indoor temperature, ℃; T s : set temperature, ℃; T a : outdoor temperature, ℃; t: time step, min.

[0099] In some embodiments, the self-learning of the refrigeration load parameter is only performed when the following three conditions are met:

[0100] Condition 1: No learning has been performed since the indoor unit was started this time;

[0101] Condition 2: The time length from the last learning end time point is greater than m hours;

[0102] Condition 3: Obtain the historical operation data of the indoor unit that can be used for model learning. That is, the quality of the historical data of the indoor unit is screened. When the historical process to be learned is a complete cooling process, only when the data meets the following conditions: the total data length is greater than Ymin, the initial room temperature is close to the outdoor environment temperature, the indoor temperature changes by more than a first set difference value within a specific time, and the final indoor temperature is less than a second set difference value from the set temperature, the model learning step is performed.

[0103] In the example of FIG. 3, the method for obtaining the historical operation data of the indoor unit that can be used for model learning is as follows:

[0104] S31, start.

[0105] S32, select the indoor unit cooling operation period to be used for learning, and obtain the operation parameters in this period: operation time tn, indoor temperature T i , outdoor temperature T a , and set temperature T s .

[0106] S33, judge whether the operation time tn is greater than the set time Ymin. If yes, go to step S34, otherwise go to step S32.

[0107] S34, the absolute value of the difference between the initial indoor temperature and the outdoor temperature is less than the set temperature difference, i.e., |T i0 -T a0 |≤k℃, if yes, go to step S35, otherwise go to step S32.

[0108] S35, within a specific time, the indoor temperature changes by more than a first set difference value. If yes, go to step S36, otherwise go to step S32. The first set difference value is, for example, 0.5℃.

[0109] S36, the final indoor temperature is the same as the set temperature, if yes, go to step S37, otherwise go to step S32.

[0110] S37, obtain the real-time performance capability Q e of the indoor unit in this operation period, the indoor temperature T i , the outdoor temperature T a , the set temperature T s , and the time step t.

[0111] The real-time performance capability Q e of the indoor unit is a function related to the structure parameters of the indoor unit heat exchanger, the heat exchange coefficient, the superheat degree, the subcooling degree, and the evaporation temperature, which can be calculated by existing technology: Q e =f(S str ,K i ,SH i ,SC i ,Te )

[0112] In the formula: S str : indoor heat exchanger structure parameters; K i : heat transfer coefficient of the indoor heat exchanger under the current working condition; SH i : outlet superheat of the indoor heat exchanger, ℃; SC i : inlet subcooling of the indoor heat exchanger, ℃; T e : evaporation temperature of the indoor heat exchanger, ℃.

[0113] The real-time capacity Q e of the indoor unit in this period is taken as the actual load Q n of the room.

[0114] At least three time points in the historical operation period of the indoor unit for model learning are selected, and the indoor unit equipment operation data at the above-mentioned time points are substituted into the building load characteristic model to establish an equation group to solve the building load characteristic parameters a, b and c.

[0115] Second step: real-time target temperature setting

[0116] The expected indoor temperature at each time point is taken as the real-time target temperature, and the expected indoor temperature at each time point is determined according to the indoor temperature, the set temperature, the equipment capacity characteristics and the time of the executed cooling process.

[0117] The expected indoor temperature T exp_n at each time point is determined according to the temperature drop curve.

[0118] The optimal temperature drop curve of the cooling process is calculated and set from the start of the multi-split system operation, and the temperature drop curve includes the expected indoor temperature T exp_n at each time point, which is used to calculate the required load of the target room, and the calculation formula of the curve is as follows:

[0119] In the formula, α, β, γ and θ are temperature characteristic constant terms; τ n is the current time value since the start of the cooling process, h; T i(n-1) is the indoor temperature at the n-1 time point, ℃; T i0 is the initial indoor temperature, ℃; T s is the set temperature, ℃.

[0120] The optimal temperature drop curve controls the indoor temperature to achieve rapid temperature drop from the start to the first half, quickly reach the comfortable temperature, and slowly drop in the second half to avoid over-regulation.

[0121] In the optimal temperature drop curve, the target temperature value T exp_0 at the initial time point is taken as the initial indoor temperature T i0the value of the actual indoor temperature T i the first time the indoor temperature T s equals the set temperature T i . s .

[0122] The optimal temperature drop curve gradually reaches the set temperature in a gentle approximation, and the expected temperature change at each step is related to the temperature difference between the indoor temperature and the set temperature at the initial time, and the temperature difference between the indoor temperature and the set stable temperature at the current time.

[0123] Thirdly, determine the real-time demand load Q r_n .

[0124] According to the refrigeration load parameters and the indoor temperature T i(n) , the expected indoor temperature T exp_n , the outdoor temperature T a(n) , and the control period, determine the real-time demand load Q r_n .

[0125] The real-time demand load Q r_n = a × (the difference between the indoor temperature at the nth time and the expected indoor temperature) + b × (the difference between the outdoor temperature at the nth time and the indoor temperature) × the control period + c × the control period.

[0126] After confirming the refrigeration load parameters a, b, and c, and the real-time expected indoor temperature, the real-time demand load Q r_n of the target indoor unit needs to be calculated, and the calculation formula is as follows: Q r_n = a × (T i(n) -T exp_n ) + b × (T a(n) -T i(n) ) × t + c × t

[0127] In the above formula: Q r_n : real-time demand load, kW; a, b, c: refrigeration load parameters, dimensionless unit; T i(n) : indoor temperature at the nth time, ℃; T exp_n : expected indoor temperature at the nth time, ℃; T a(n) : outdoor environment temperature, ℃; t: control period, h.

[0128] Fourthly, load following control.

[0129] After determining the real-time demand load, control the multi-split system according to the real-time demand load. For example, control the control target of the multi-split system to achieve load following control.

[0130] In the example of FIG. 4, the process of load following control is as follows:

[0131] S41, start up.

[0132] S42, obtain refrigeration load parameters.

[0133] S43, real-time target temperature setting: obtain indoor temperature, outdoor temperature, set temperature, calculate expected indoor temperature T at each moment according to optimal temperature drop curve exp_n .

[0134] S44, input indoor temperature T i(n) , expected indoor temperature T exp_n , outdoor temperature T a(n) , refrigeration load parameters into load characteristic model, calculate real-time demand load Q r_n .

[0135] S45, calculate and control the control target of the multi-split system according to the real-time demand load.

[0136] S46, whether to shut down, if yes, go to step S47, otherwise go to step S43.

[0137] S47, shut down.

[0138] The multi-split system building load following control mainly includes evaporating temperature control and air volume control, and the above control targets are mainly realized by compressor frequency control, indoor unit electronic expansion valve opening control, and indoor unit air damper control.

[0139] The main logic of load following control is to make the real-time load demand value directly equal to the real-time generation capacity value of the indoor unit, that is, to realize load following control. For example, after obtaining the real-time load demand value in the third step, the target evaporating temperature is determined, and the compressor operating frequency is determined according to the target evaporating temperature, the indoor fan speed is determined according to the real-time load demand, the initial opening of the indoor expansion valve is determined, the opening of the indoor expansion valve is adjusted according to the superheat degree, and the compressor frequency, indoor fan speed and indoor expansion valve opening are precisely adjusted.

[0140] Obtain the real-time demand load Q r_n of each indoor unit, and calculate the target evaporating temperature T e_i of each indoor unit:

[0141] Wherein, f sh , f sc are the supercooling degree and superheat degree characteristic parameters of each indoor unit; m cs , n cs are the sensible heat capacity characteristic parameters of the indoor unit; m cl , n cl are the latent heat capacity characteristic parameters of the indoor unit; Ti T is the indoor temperature of each indoor unit, ℃; T ld T is the dew point temperature corresponding to the return air temperature of each indoor unit, ℃.

[0142] The above calculation method considers the evaporation temperature corresponding to the sensible heat capacity and latent heat capacity of the indoor unit heat exchanger in the refrigeration working condition.

[0143] The target evaporation temperature of the multi-split system is the minimum or average value of the target evaporation temperatures of all indoor units.

[0144] It can be understood that when the air conditioning system only includes one indoor unit, the target evaporation temperature of the indoor unit is the target evaporation temperature of the multi-split system.

[0145] In some embodiments, when the user selects a high comfort scene, the target evaporation temperature T e0_i is the minimum value of the target evaporation temperatures of all indoor units in the system.

[0146] In some embodiments, when the user selects a high performance scene, the target evaporation temperature T e0_i is the average value of the target evaporation temperatures of all indoor units in the system.

[0147] The target evaporation temperature T e0_i of the multi-split system is determined. i .

[0148] In some embodiments, the compressor frequency is determined according to the compressor parameters, the capacities of all indoor units, and the target evaporation temperature.

[0149] The compressor frequency at the i-th moment is calculated by the following formula:

[0150] In the above formula, S1 is a compressor characteristic parameter, a constant, related to the compressor specification; S2 is a compressor frequency correction coefficient, a constant, related to the indoor unit specification; V HP_j is the capacity characteristic coefficient of the j-th indoor unit in the system, a constant, related to the capacity and specification of the indoor unit.

[0151] The speed of the indoor fan is determined according to the real-time demand load. In some embodiments, the speed of the indoor fan is determined according to the maximum speed of the indoor fan, the real-time demand load, and the capacity characteristic coefficient of the indoor unit.

[0152] In further embodiments, the speed of the indoor fan is determined by the following formula:

[0153] In the above formula: F i is the speed of the indoor fan at the i-th moment; Qr_n : the required load of each indoor unit, kWh; F max : the maximum rotating speed of the fan, rpm; Fo sh : the overheat correction parameter of the rotating speed of the fan; Fo Te : the evaporation temperature correction parameter of the rotating speed of the fan; V HP_j : the capacity characteristic coefficient of the jth indoor unit in the system, constant, related to the capacity and specification of the indoor unit; a is a constant, for example: a = 28.

[0154] The fan is set to be stepless variable speed type, the rotating speed of the fan is related to the proportion of the real-time required load to the capacity characteristic coefficient of the indoor unit, in addition, the overheat and evaporation temperature correction terms are added.

[0155] The indoor unit includes an indoor expansion valve, the initial opening degree of the indoor expansion valve is determined according to the maximum opening degree of the indoor expansion valve, the ratio of the capacity value of the current indoor unit to the sum of the capacities of all the indoor units.

[0156] The initial opening degree value of the electronic expansion valve of each indoor unit is determined by the following formula:

[0157] In the above formula: EVX0: the initial opening degree of the electronic expansion valve of the indoor unit; EXV max : the maximum opening degree value of the electronic expansion valve of the indoor unit; VO j : the capacity value of the jth indoor unit, HP; : the sum of the capacities of the indoor units in the system, HP. C b : the mode correction parameter, dimensionless parameter, related to the specific function selection term.

[0158] The overheat value SH of the indoor unit is calculated i When the overheat value is lower than the set value, the opening degree of the indoor expansion valve is unchanged, and when the overheat value is higher than the set value, the opening degree of the indoor expansion valve is increased.

[0159] The increase amount of the opening degree of the indoor expansion valve is determined according to the overheat difference value, the difference between the overheat difference values of two continuous time points and the overheat correction coefficient.

[0160] In some embodiments, the set value is 0.

[0161] The overheat value SH of the ith indoor unit is determined i If the overheat value SH is ≤0, the opening degree value EXV of the indoor expansion valve is unchanged; if the overheat value SH is >0, the opening degree EXV of the electronic expansion valve of the indoor unit is increased i i i i , then the opening degree value EXV of the electronic expansion valve at the next time is​​​i(n+1) The calculation method is as follows: ΔSH i(n) = SH i(n) - SH i(n-1)

[0162] In the above formula: r1, r2, C SH : superheat iterative correction coefficient, constant, related to the indoor unit specification; EXV i(n) : the n-th moment indoor expansion valve opening value; EXV i(n+1) : the n+1-th moment indoor expansion valve opening value; SH i(n) : the superheat at the n-th moment at the indoor unit outlet; SH i(n-1) : the superheat at the n-1-th moment at the indoor unit outlet.

[0163] In the example of FIG. 5, the process of controlling the multi-split system is as follows:

[0164] S51, start.

[0165] S52, obtain system operating state parameters.

[0166] S53, calculate the real-time demand load Q r_n of each indoor unit.

[0167] S54, calculate the target evaporation temperature T e_i of each indoor unit according to the real-time demand load.

[0168] S55, calculate the target evaporation temperature T eo_i of the multi-split system.

[0169] S56, calculate the initial opening of the indoor expansion valve, calculate the compressor frequency and the indoor fan speed according to the target evaporation temperature T eo_i . Control the compressor frequency, the indoor expansion valve opening and the indoor fan speed.

[0170] S57, judge whether the indoor superheat value SH i ≤ 0, if yes, go to step S59, otherwise go to step S58.

[0171] S58, increase the indoor expansion valve opening. Go to step S510.

[0172] S59, keep the indoor expansion valve opening unchanged. Go to step S510.

[0173] S510, whether to shut down, if yes, go to step S511, otherwise, go to step S52.

[0174] S511, shut down.

[0175] Fig. 6 is a schematic diagram of a refrigerant circulation in a heating mode of a multi-connected system. In the example of Fig. 6, the multi-connected system includes an outdoor unit and a first indoor unit, a second indoor unit, and a third indoor unit. The outdoor unit is connected to the first indoor unit, the second indoor unit, and the third indoor unit through connected pipes, forming a multi-connected system.

[0176] The outdoor unit is provided with a compressor 1, an outdoor heat exchanger 5, an outdoor expansion valve 6, and a four-way valve 4. The operating capacity of the indoor unit can be adjusted by adjusting the operating frequency of the compressor 1.

[0177] In some embodiments, the outdoor unit is further provided with an outdoor temperature detection module for detecting the outdoor temperature T a In other embodiments, the outdoor temperature Ta can also be obtained in other ways, such as providing a temperature detection device independent of the outdoor unit to detect the outdoor temperature, or the multi-connected system directly obtaining the outdoor temperature through a network.

[0178] The first indoor unit is provided with a first indoor heat exchanger 18-1, a first outdoor expansion valve 19-1, and a first indoor fan (not shown in the figure). The operating capacity of the first indoor unit can be adjusted by adjusting the opening degree of the first outdoor expansion valve 19-1 and / or the rotating speed of the first indoor fan.

[0179] The first indoor unit includes a first indoor ambient temperature detection module d1, a first indoor unit liquid pipe temperature detection module c1, and a first indoor unit gas pipe temperature detection module b1.

[0180] The second indoor unit is provided with a second indoor heat exchanger 18-2, a second outdoor expansion valve 19-2, and a second indoor fan (not shown in the figure). The operating capacity of the second indoor unit can be adjusted by adjusting the opening degree of the second outdoor expansion valve 19-2 and / or the rotating speed of the second indoor fan.

[0181] The second indoor unit includes a second indoor ambient temperature detection module d2, a second indoor unit liquid pipe temperature detection module c2, and a second indoor unit gas pipe temperature detection module b2.

[0182] The third indoor unit is provided with a third indoor heat exchanger 18-3, a third outdoor expansion valve 19-3, and a third indoor fan (not shown in the figure). The operating capacity of the third indoor unit can be adjusted by adjusting the opening degree of the third outdoor expansion valve 19-3 and / or the rotating speed of the third indoor fan.

[0183] The third indoor unit includes a third indoor ambient temperature detection module d3, a third indoor unit liquid pipe temperature detection module c3, and a third indoor unit gas pipe temperature detection module b3.

[0184] The indoor ambient temperature detection module is used to detect the indoor temperature T i .

[0185] All indoor units include a set temperature acquisition module.

[0186] The set temperature acquisition module is used to acquire the indoor set temperature T s .

[0187] When the multi-split system is running in the heating mode at the indoor unit:

[0188] Determine the heating load parameters a, b, and c of the indoor unit corresponding to the room;

[0189] Determine the expected indoor temperature T exp_n at each moment;

[0190] According to the heating load parameters and the expected indoor temperature T exp_n , the indoor temperature T i(n) , the outdoor temperature T a(n) , and the control period, determine the real-time demand load Q r_n ;

[0191] Determine the target condensing temperature according to the real-time demand load Q r_n , and determine the compressor frequency H according to the target condensing temperature.

[0192] In some embodiments, the speed F of the indoor fan is determined according to the real-time demand load Q r_n .

[0193] In some embodiments, the initial opening of the outdoor expansion valve is determined, the supercooling degree of the indoor unit is determined, and the opening of the outdoor expansion valve is adjusted according to the supercooling degree.

[0194] Use the capacity estimation algorithm, for example, the capacity estimation algorithm running in the multi-split indoor unit, to learn the load characteristics of the target building, and take the building demand load as the control target of the control system.

[0195] After obtaining the load characteristic parameters of the target building, establish a load model, and directly calculate the target condensing temperature and supercooling degree of the multi-split system in the heating condition according to the demand load, so as to control the compressor frequency and the speed of the indoor fan, and the outdoor electronic expansion valve as a control supplement.

[0196] Through the control of the multi-split system according to the real-time demand load, the under-adjustment problem of large load and small temperature difference scenes and the over-adjustment problem of small load and large temperature difference scenes are solved, so that the air conditioning capacity is matched with the building load, the room temperature fluctuation is reduced when the load is small, and the power consumption caused by frequent start and stop is avoided, the indoor unit capacity is increased when the load is large, the room temperature change speed is increased, and the user comfort is improved. Under the condition of load following technology, various energy-saving controls can be realized according to user demand, while the system operation reliability is improved, energy saving and efficiency improvement are realized, and user comfort is improved.

[0197] First step, determine the heating load parameters of the room corresponding to the indoor unit:

[0198] In some embodiments, the method for determining the heating load parameters a, b, c of the room corresponding to the indoor unit is that the heating load parameters are built-in parameters of the multi-split system, which can be directly read.

[0199] In some embodiments, the method for determining the heating load parameters a, b, c of the room corresponding to the indoor unit is that the heating load parameters are determined by self-learning based on historical data.

[0200] In some embodiments, it is judged whether the multi-split system is started for the first time. If it is started for the first time, the built-in heating load parameters a0, b0, c0 of the multi-split system are read, and the multi-split system is controlled by the heating load parameters a0, b0, c0. If it is not started for the first time, it is necessary to judge whether self-learning is needed for the current operation. When the heating self-learning condition is met, self-learning is performed to determine the heating load parameters, and the multi-split system is controlled by the learned heating load parameters. In the subsequent start-up process, it is judged whether self-learning is needed for the current operation. If not, the heating load parameters determined by the last self-learning are used for control. If so, self-learning is performed to determine the heating load parameters, and the multi-split system is controlled by the learned heating load parameters.

[0201] In the example of FIG. 7, the flow of determining the heating load parameters in the heating mode is as follows:

[0202] S71, start.

[0203] S72, judge whether it is started for the first time. If yes, go to step S73, otherwise go to step S74.

[0204] S73, read the built-in heating load parameters a0, b0, c0 of the multi-split system as the heating load parameters.

[0205] S74, judge whether the heating self-learning condition is met. If not, go to step S75, if yes, go to step S76.

[0206] S75, obtain the heating load parameters of the last start-up.

[0207] S76, perform self-learning to determine the learned heating load parameters.

[0208] Based on the capacity Q of the indoor unit in the multi-split system e , the real-time capacity Q of the indoor unit in the balanced state is regarded as the room load Q e . n The building load characteristic learning is performed. The building load characteristic model at least includes three parts of indoor air heat storage load, wall and window heat leakage load, and equipment and personnel internal disturbance load.

[0209] Wherein, the air storage load is related to the room space size, the difference between the set temperature and the initial temperature, the wall and window heat loss load is mainly related to the building insulation and the indoor and outdoor temperature difference, the equipment and personnel internal disturbance load is related to the use scene. According to the actual composition of the building load, the numerical model of the load can be established, and the real-time capacity Q e is regarded as the actual load of the building to learn the load characteristics of the building. The learning of the model needs to be selected in a complete heating process, and the load characteristics parameters in the load model are determined through the operation data in the process, and finally the load characteristics model of the target model building is formed.

[0210] After the establishment of the load characteristics model, the future outdoor environment temperature, the room indoor temperature and the set temperature can be input into the model to determine the future room demand load, and the system operation parameters are adjusted according to the demand load and the expected control target.

[0211] The self-learning process of the heating load parameters is as follows:

[0212] The data that the total length of the heating process is greater than the set length Ymin, the temperature difference between the initial indoor temperature and the outdoor temperature is lower than the set temperature difference, the indoor temperature change in a certain time is higher than the first set difference value, and the difference between the final indoor temperature and the set temperature is lower than the set difference value are obtained as the learning data;

[0213] The real-time capacity Q e of the indoor unit is obtained;

[0214] According to the real-time capacity of the indoor unit and the learning data, the heating load parameters a, b and c are determined by solving the load characteristics model, and the load characteristics model is Q e = Q n =a×(set temperature-indoor temperature)+b×(indoor temperature-outdoor temperature)×time step-c×time step.

[0215] The load characteristics model is: Q n =a×(T s -T i )+b×(T a -T i )×t-c×t

[0216] In the formula, Q n : building load, kW; a, b, c: heating load parameters, dimensionless unit; T i : indoor temperature, ℃; T s : set temperature, ℃; T a : outdoor temperature, ℃; t: time step, min.

[0217] In some embodiments, self-learning of the heating load parameter is only performed when the following three conditions are met:

[0218] Condition 1: No learning has been performed since the last time the indoor unit was turned on.

[0219] Condition 2: The time length from the last learning end time point is greater than m hours.

[0220] Condition 3: The indoor unit historical operation data available for model learning is obtained: that is, the indoor unit historical data quality is screened, and when the historical process to be learned is a complete heating process, only when the data meets the following conditions, the model learning step is performed: the total length of the data is greater than Ymin, the initial room temperature is close to the outdoor environment temperature, the indoor temperature changes by more than a first set difference value within a specific time, and the final set temperature is lower than a second set difference value from the indoor temperature.

[0221] In the example of FIG. 8, the method for obtaining the indoor unit historical operation data available for model learning is as follows:

[0222] S81, start.

[0223] S82, select the indoor unit heating operation period to be used for learning, and obtain the operation parameters in this period: operation length tn, indoor temperature T i , outdoor temperature T a , and set temperature T s .

[0224] S83, determine whether the operation length tn is greater than the set length Ymin. If yes, go to step S84, otherwise go to step S82.

[0225] S84, the absolute value of the difference between the initial indoor temperature and the outdoor temperature is lower than the set temperature difference, that is, |T i0 -T a0 |≤k℃, if yes, go to step S85, otherwise go to step S82.

[0226] S85, the indoor temperature changes by more than a first set difference value within a specific time. If yes, go to step S86, otherwise go to step S82. The first set difference value is, for example, 0.7℃.

[0227] S86, the final indoor temperature is the same as the set temperature, if yes, go to step S87, otherwise go to step S82.

[0228] S87, obtain the indoor unit real-time capacity Q e , indoor temperature T i , outdoor temperature T a , set temperature T s , and time step t of this operation period.

[0229] Real-time capacity of indoor unit Q e is a function related to the structure parameters of the indoor unit heat exchanger, heat exchange coefficient, superheat, subcooling, and condensing temperature, which can be calculated by existing technology: Q e = f(S str ,K i ,SH i ,SC i ,T c )

[0230] In the above formula: S str : structure parameters of the indoor heat exchanger; K i : heat exchange coefficient of the indoor heat exchanger under the current working condition; SH i : superheat of the indoor heat exchanger inlet, ℃; SC i : subcooling of the indoor heat exchanger outlet, ℃; T c : condensing temperature of the indoor heat exchanger, ℃.

[0231] The real-time capacity of the indoor unit Q e in this period is taken as the actual load Q n of the target room.

[0232] At least three time points in the historical running period of the indoor unit for model learning are selected, and the indoor unit equipment running data at the above time points is substituted into the building load characteristic model to establish an equation group to solve the building load characteristic parameters a, b, and c.

[0233] Second step: real-time target temperature setting

[0234] The expected indoor temperature at each time point is taken as the real-time target temperature, and the expected indoor temperature at each time point is determined according to the set temperature, indoor temperature, equipment capacity characteristics, and the time of the executed temperature rising process.

[0235] The expected indoor temperature T exp_n at each time point is determined according to the temperature rising curve.

[0236] The optimal temperature rising curve of the heating process is calculated and set from the start of the multi-split system operation, and the temperature rising curve includes the expected indoor temperature T exp_n at each time point, which is used to calculate the required load of the target room, and the calculation formula of the curve is as follows:

[0237] In the above formula, α, β, γ, and θ are temperature characteristic constant terms; τ n is the current time value since the start of the heating process, h; T i(n-1) is the indoor temperature at the n-1 time point, ℃; T i0 is the initial indoor temperature, ℃; T s is the set temperature, ℃.

[0238] The optimal temperature rising curve controls the indoor temperature to achieve a rapid temperature drop in the beginning and the first half, quickly reaches the comfortable temperature, and slowly drops in the second half to avoid over-regulation.

[0239] In the optimal temperature rising curve, the target temperature value T exp_0 at the initial time is the value of the initial indoor temperature T i0 ; when the actual indoor temperature T i first reaches the set temperature T s since the start of the heating process, T i is always equal to T s .

[0240] The optimal temperature rising curve gradually reaches the set temperature in a gentle approximation form, and the expected temperature change at each step is related to the temperature difference between the initial indoor temperature and the set temperature, and the temperature difference between the current indoor temperature and the set temperature.

[0241] Step 3, determine the real-time demand load Q r_n .

[0242] According to the heating load parameters and the expected indoor temperature T exp_n at the current time, the indoor temperature T i(n) , the outdoor temperature T a(n) , and the control period, the real-time demand load Q r_n is determined.

[0243] Real-time demand load Q r_n = a × (difference between the expected indoor temperature at the nth time and the indoor temperature) + b × (difference between the indoor temperature at the nth time and the outdoor temperature) × control period - c × control period.

[0244] After confirming the heating load parameters a, b, and c and the real-time expected indoor temperature, the real-time demand load Q r_n of the target indoor unit needs to be calculated, and the calculation formula is as follows: Q r_n = a × (T exp_n - T i(n) ) + b × (T i(n) - T a(n) ) × t - c × t

[0245] In the above formula: Q r_n : real-time demand load, kW; a, b, c: heating load parameters, dimensionless unit; T i(n) : indoor temperature at the nth time, ℃; T exp_n : expected indoor temperature at the nth time, ℃; T a(n) : outdoor environment temperature, ℃; t: control period, h.

[0246] Step 4: Load following control.

[0247] After determining the real-time demand load, the multi-connected system is controlled according to the real-time demand load, for example, the target of the multi-connected system is controlled to realize load following control.

[0248] In the example of FIG. 9, the process of load following control is as follows:

[0249] S91, start.

[0250] S92, obtain heating load parameters.

[0251] S93, real-time target temperature setting: obtain indoor temperature, outdoor temperature, set temperature, calculate expected indoor temperature T exp_n at each moment according to the optimal temperature rise curve.

[0252] S94, input indoor temperature T i(n) , expected indoor temperature T exp_n , outdoor temperature T a(n) , and heating load parameters into the load characteristic model to calculate real-time demand load Q r_n .

[0253] S95, calculate and control the control target of the multi-connected system according to the real-time demand load.

[0254] S96, whether to shut down, if yes, go to step S97, otherwise go to step S93.

[0255] S97, shut down.

[0256] The load following control of the multi-connected system building mainly includes condensing temperature control and air volume control, and the above control targets are mainly realized by compressor frequency control, outdoor expansion valve opening control, and indoor unit air damper control.

[0257] The main logic of load following control is to make the real-time load demand value directly equal to the real-time capacity value of the indoor unit, that is, to realize load following control. For example, after obtaining the real-time load demand value from the third step, the target condensing temperature is determined, and the compressor operating frequency is determined according to the target condensing temperature, and the indoor fan speed is determined according to the real-time load demand. The compressor frequency and indoor fan speed are precisely adjusted. The initial opening of the outdoor expansion valve is determined, and the opening of the outdoor expansion valve is adjusted according to the supercooling degree, and the multi-connected system is finely adjusted.

[0258] Obtain the real-time demand load Q r_n of each indoor unit, and calculate the target condensing temperature T c_i of each indoor unit:

[0259] Wherein, fsh , f sc is the supercooling degree of each indoor unit; m cs , n cs is the sensible heat capacity characteristic parameter of the indoor unit; T i is the indoor temperature of each indoor unit.

[0260] The above calculation method considers the corresponding condensing temperature when the indoor unit heat exchanger may exert sensible heat capacity in the heating operating mode.

[0261] The target condensing temperature of the multi-split system is the maximum or average of the target condensing temperatures of all indoor units.

[0262] It can be understood that when the air conditioning system only includes one indoor unit, the target evaporating temperature of the indoor unit is the target evaporating temperature of the multi-split system.

[0263] In some embodiments, when the user selects a high comfort scene, the target condensing temperature T c0_i is the maximum of the target condensing temperatures of all indoor units in the system.

[0264] In some embodiments, when the user selects a high performance scene, the target condensing temperature T c0_i is the average of the target condensing temperatures of all indoor units in the system.

[0265] The actual operating frequency H i of the compressor is determined by the target condensing temperature T c0_i of the multi-split system.

[0266] In some embodiments, the compressor frequency is determined according to the compressor parameters, the capacities of all indoor units, and the target condensing temperature.

[0267] The compressor frequency at the i-th moment is calculated by the following formula:

[0268] In the above formula, S1 is a compressor characteristic parameter, a constant, related to the compressor specification; S2 is a compressor frequency correction coefficient, a constant, related to the indoor unit specification; V HP_j is the capacity characteristic coefficient of the j-th indoor unit in the system, a constant, related to the capacity and specification of the indoor unit.

[0269] The speed of the indoor fan is determined according to the real-time demand load. In some embodiments, the speed of the indoor fan is determined according to the maximum speed of the indoor fan, the real-time demand load, and the capacity characteristic coefficient of the indoor unit.

[0270] In further embodiments, the speed of the indoor fan is determined by the following formula:

[0271] In the above formula: F i : the rotational speed of the indoor fan at the i th moment; Q r_n : the required load corresponding to each indoor unit, kWh; F max : the maximum rotational speed of the fan, rpm; Fo sh : the supercooling degree correction parameter of the fan rotational speed; Fo Tc : the condensation temperature correction parameter of the fan rotational speed; V HP_j : the capacity characteristic coefficient of the j th indoor unit in the system, constant, related to the capacity and size of the indoor unit; a is a constant, for example: a = 28.

[0272] The fan is set to a stepless speed form as the main component of auxiliary adjustment, and the rotational speed of the fan is related to the proportion of the real-time required load to the capacity characteristic coefficient of the indoor unit. In addition, correction terms of supercooling degree and condensation temperature are added.

[0273] The outdoor unit includes an outdoor expansion valve 6, and the initial opening degree of the outdoor expansion valve 6 is determined according to the maximum opening degree of the outdoor expansion valve 6, the capacity of the running indoor unit, and the ratio of the sum of the capacities of all indoor units.

[0274] The initial opening degree value of each outdoor electronic expansion valve is calculated by the following formula:

[0275] In the above formula: EVO0: the initial opening degree value of the outdoor expansion valve; EVO max : the maximum opening degree value of the outdoor expansion valve; : the sum of the capacities of the running indoor units in the system, HP; : the sum of the capacities of the indoor units in the system, HP; C b : mode correction parameter, dimensionless parameter, related to a specific function selection item.

[0276] The supercooling degree Tsc sc_i of the indoor unit is calculated.

[0277] When the supercooling degree is lower than the target condensation temperature, the opening degree of the outdoor expansion valve is reduced, when the supercooling degree is equal to the target condensation temperature, the opening degree of the indoor expansion valve is unchanged, and when the supercooling degree is higher than the target condensation temperature, the opening degree of the outdoor expansion valve is increased.

[0278] The supercooling degree Tsc i of the indoor unit is determined. sco The relationship between the target condensation temperature T i and the supercooling degree Tsc sco is determined. i If the supercooling degree Tsc sco is equal to the target condensation temperature T , the opening degree value EVO of the outdoor expansion valve is not changed., then keep the outdoor expansion valve opening degree value EVO unchanged; if Tsc i > T sco , then increase the outdoor expansion valve opening degree value EVO.

[0279] T sco The value range is [8, 15]℃.

[0280] The electronic expansion valve opening degree value EVO i(n+1) The calculation method is as follows: ΔSC i(n) = SC i(n) - SC i(n-1)

[0281] In the above formula: r1, r2, C SH : subcooling iterative correction coefficient, constant, related to the indoor unit specification; EVO i(n) : outdoor expansion valve opening degree value at the n th moment; EVO i(n+1) : outdoor expansion valve opening degree value at the n+1 th moment; SC i(n) : subcooling degree at the n th moment; SC i(n-1) : subcooling degree at the n-1 th moment.

[0282] In the example of FIG. 10, the process of controlling the multi-split system is as follows:

[0283] S101, start.

[0284] S102, obtain system running state parameters.

[0285] S103, calculate the real-time demand load Q r_n corresponding to each indoor unit.

[0286] S104, calculate the target condensing temperature T c_i of each indoor unit according to the real-time demand load.

[0287] S105, calculate the target condensing temperature T co_i of the multi-split system.

[0288] S106, calculate the initial opening degree of the outdoor expansion valve, calculate the compressor frequency and indoor fan speed according to the target condensing temperature T co_i . Control the compressor frequency, outdoor expansion valve opening degree and indoor fan speed.

[0289] S107, judge the relationship between the indoor subcooling degree value Tsc i and the target condensing temperature T sco . When Tsc i > T sco , go to step S108, when Tsci = T sco When Tsc i < T sco , go to step S1010.

[0290] S108, increase the opening degree of the outdoor expansion valve. Go to step S1011.

[0291] S109, keep the opening degree of the outdoor expansion valve unchanged. Go to step S1011.

[0292] S1010, decrease the opening degree of the outdoor expansion valve unchanged. Go to step S1011.

[0293] S1011, whether to shut down, if yes, go to step S1012, otherwise, go to step S102.

[0294] S1012, shut down.

[0295] In combination with the above described embodiments, the present application provides a control method of an air conditioning system, the air conditioning system comprising an indoor unit and an outdoor unit, the method comprising: determining a load parameter of the indoor unit; determining a desired indoor temperature at each moment; determining a real-time required load of the indoor unit based on the load parameter, an indoor temperature at a current moment, an outdoor temperature, the desired indoor temperature and a control period; and controlling the air conditioning system according to the real-time required load.

[0296] The features of each embodiment of the control method of the air conditioning system can refer to the above described embodiments for the cooling mode and the heating mode, and will not be described in detail herein.

[0297] The above describes in detail the method of the present application for controlling the air conditioning system in the cooling mode and the heating mode. It should be noted that the "difference between A and B" described in the present application refers to the absolute value of the difference between A and B. For example, for the expression "difference between the indoor temperature and the set temperature", when the indoor temperature is higher than the set temperature, it means that the indoor temperature is subtracted from the set temperature, and when the indoor temperature is lower than the set temperature, it means that the set temperature is subtracted from the indoor temperature.

[0298] In combination with the above described control method of the air conditioning system, the present application also provides an air conditioning system comprising an indoor unit, an outdoor unit and a controller. It can be understood that the controller can be one or multiple, and can be arranged in the indoor unit or the outdoor unit, or can be arranged independently of the indoor unit and the outdoor unit. The controller can be, but is not limited to, a CPU, a single-chip microcomputer, a DSP, an FPGA, etc., or can be a component formed by these operation devices and other devices. The controller is used to execute the control method of the air conditioning system described in the above embodiments.

[0299] Based on the above-described partial embodiments, the advantages and positive effects of the present application include:

[0300] In the cooling mode of the indoor unit: determining the cooling load parameter of the room corresponding to the indoor unit; determining the expected indoor temperature at each time; determining the real-time demand load according to the cooling load parameter, the difference between the indoor temperature and the expected indoor temperature at the current time, the difference between the outdoor temperature and the indoor temperature, and the control period; determining the target evaporation temperature according to the real-time demand load, and determining the compressor frequency according to the target evaporation temperature. Thus, the real-time demand load of the room is taken as a control element of the air conditioning system, so that the operating state of the air conditioning system can be matched with the real-time demand load, solving the under-adjustment problem in the large load small temperature difference scene and the over-adjustment problem in the small load large temperature difference scene, matching the air conditioning capacity with the building load, reducing the room temperature fluctuation in the medium and small load, avoiding the increase of power consumption caused by frequent start and stop, improving the indoor unit capacity in the large load, accelerating the room temperature change speed and improving the user comfort. Under the condition of load following technology, various energy-saving controls can be realized according to the user demand, the system operation reliability is improved, energy saving and efficiency improvement are realized, and the user comfort is improved.

[0301] In the heating mode of the indoor unit: determining the heating load parameter of the room corresponding to the indoor unit; determining the expected indoor temperature at each time; determining the real-time demand load according to the heating load parameter, the difference between the indoor temperature and the expected indoor temperature at the current time, the difference between the indoor temperature and the outdoor temperature, and the control period; determining the target condensation temperature according to the real-time demand load, and determining the compressor frequency according to the target condensation temperature. Thus, the real-time demand load of the room is taken as a control element of the air conditioning system, so that the operating state of the air conditioning system can be matched with the real-time demand load, solving the under-adjustment problem in the large load small temperature difference scene and the over-adjustment problem in the small load large temperature difference scene, matching the air conditioning capacity with the building load, reducing the room temperature fluctuation in the medium and small load, avoiding the increase of power consumption caused by frequent start and stop, improving the indoor unit capacity in the large load, accelerating the room temperature change speed and improving the user comfort. Under the condition of load following technology, various energy-saving controls can be realized according to the user demand, the system operation reliability is improved, energy saving and efficiency improvement are realized, and the user comfort is improved. In the embodiments of the present application, the control method of the compressor and the expansion valve is adjusted based on the actual demand load of the building, which can match the air conditioning capacity with the actual load of the building, solving the problems of overplay and underplay of the indoor unit capacity.

[0302] It can be understood that the summary of the technical effects above is only for understanding the partial embodiments of the application, and is not an explanation or limitation of the protection scope of the present application.

[0303] 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.

[0304] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A control method of an air conditioning system, the air conditioning system comprising an indoor unit and an outdoor unit, the method comprising: determining a load parameter of the indoor unit; determining a desired indoor temperature at each time instant; determining a real-time demand load of the indoor unit based on the load parameter, an indoor temperature at a current time instant, an outdoor temperature, the desired indoor temperature, and a control period; and controlling the air conditioning system according to the real-time demand load. The determining of the real-time demand load of the indoor unit comprises determining the real-time demand load based on a load characteristic model, the load characteristic model comprising: a model for a heating mode: or a model for a cooling mode: wherein Qn is a building load, kW; a, b, c are load parameters, dimensionless; Ti is an indoor temperature, ℃; Ts is a set temperature, ℃; Ta is an outdoor temperature, ℃; t is a time step, min. The determining of the load parameter of the indoor unit comprises: obtaining a real-time capacity of the indoor unit as a building load, and solving the load parameter based on the load characteristic model. The obtaining of the real-time capacity of the indoor unit as a building load, and the solving of the load parameter based on the load characteristic model comprises: when a running period meets a running time longer than a set time, an initial indoor temperature and an outdoor temperature difference lower than a set difference, an indoor temperature change within a specific time higher than a first set difference, and a final indoor temperature and a set temperature difference lower than a second set difference, obtaining real-time capacities at at least three time instants in the running period, a set temperature, an indoor temperature, and an outdoor temperature, and solving the load characteristic parameters based on an equation group established based on the load characteristic model.

2. The control method of an air conditioning system according to claim 1, wherein, The determining of the desired indoor temperature at each time instant comprises: determining the desired indoor temperature at each time instant according to a difference between the indoor temperature and the set temperature, a device capacity characteristic, and a time of a cooling or heating process performed. The determining of the load parameter of the indoor unit comprises: obtaining an air conditioning system built-in parameter as the load parameter. Q n = a x (T i - T s ) + b x (T a - T i ) x t + c x t The controlling of the air conditioning system according to the real-time demand load comprises: in the cooling mode, determining a target evaporating temperature of the air conditioning system according to the real-time demand load, and determining a compressor frequency according to the target evaporating temperature. Q n = a x (T s - T i ) + b x (T a - T i ) x t - c x t The determining of the target evaporating temperature of the air conditioning system according to the real-time demand load comprises: the air conditioning system comprises a plurality of indoor units, and the determining of the target evaporating temperature of the air conditioning system according to the real-time demand load comprises: calculating corresponding target evaporating temperatures for the plurality of indoor units respectively, and taking an average value or a minimum value of the corresponding target evaporating temperatures as the target evaporating temperature of the air conditioning system.

3. The control method of an air conditioning system according to claim 2, wherein, The determining of the compressor frequency according to the target evaporating temperature comprises: determining the compressor frequency according to a compressor parameter, capacities of all indoor units, and the target evaporating temperature. The controlling of the air conditioning system according to the real-time demand load comprises: in the heating mode, determining a target condensing temperature of the air conditioning system according to the real-time demand load, and determining a compressor frequency according to the target condensing temperature.

4. The control method of an air conditioning system according to claim 3, wherein, The determining of the target condensing temperature of the air conditioning system according to the real-time demand load comprises: the air conditioning system comprises a plurality of indoor units, and the determining of the target condensing temperature of the air conditioning system according to the real-time demand load comprises: ​ ​ 5. The control method of an air conditioning system according to claim 1, wherein, ​ ​ 6. The control method of an air conditioning system according to claim 1, wherein, ​ ​ 7. The control method of an air conditioning system according to claim 1, wherein, ​ ​ 8. The control method of an air conditioning system according to claim 7, wherein, ​ The target evaporation temperature T is calculated based on the following formula e_i : wherein Q r_n is the real-time demand load; f sh , f sc are the overheat degree characteristic parameter and the subcooling degree characteristic parameter of the indoor unit; m cs , n cs are the indoor unit sensible heat capacity characteristic parameter; m cl , n cl are the indoor unit latent heat capacity characteristic parameter; T i is the indoor temperature corresponding to the indoor unit; T ld is the dew point temperature corresponding to the return air temperature of the indoor unit.

9. The control method of an air conditioning system according to claim 8, wherein, ​ ​ 10.The control method of an air conditioning system according to claim 7, wherein, ​ ​ 11. The control method of an air conditioning system according to claim 1, wherein, ​ ​ 12.The control method of an air conditioning system according to claim 11, wherein, ​ The target condensing temperature T is calculated based on the following formula c_i : wherein Q r_n is the real-time demand load; f sh , f sc are the overheat degree characteristic parameter and the subcooling degree characteristic parameter of the indoor unit; m cs , n cs are the heating sensible heat capacity characteristic parameters of the indoor unit; T i is the indoor temperature of the indoor unit. 13.The control method of an air conditioning system according to claim 12, wherein, ​ The target condensing temperature of the air conditioning system is calculated according to the target condensing temperature of each indoor unit, and the average or maximum value of the target condensing temperature of each indoor unit is taken as the target condensing temperature of the air conditioning system. 14.The control method of an air conditioning system according to claim 11, wherein, The method further comprises: The frequency of the compressor is determined according to the target condensing temperature.

15. The control method of an air conditioning system according to any one of claims 1-14, wherein, The frequency of the compressor is determined according to the target condensing temperature, the capacity of each indoor unit and the parameters of the compressor. The method further comprises:

16. The control method of an air conditioning system according to any one of claims 1-14, wherein, The speed of the indoor fan is determined according to the maximum speed of the indoor fan, the real-time demand load and the capacity characteristic coefficient of the indoor unit. The air conditioning system comprises a plurality of indoor units, and each indoor unit comprises an indoor expansion valve. The superheat value of the current indoor unit is determined. 17.The control method of the air conditioning system according to claim 16, wherein, When the superheat value is lower than a set value, the opening degree of the indoor expansion valve is kept unchanged, and when the superheat value is higher than the set value, the opening degree of the indoor expansion valve is increased. The method further comprises:

18. The control method of an air conditioning system according to any one of claims 1-14, wherein, The amount of increase of the opening degree of the indoor expansion valve is determined according to the superheat difference value, the difference between the superheat difference values of two continuous time points and the superheat correction coefficient. The air conditioning system comprises a plurality of indoor units, and the outdoor unit comprises an outdoor expansion valve. The supercooling degree of the indoor unit is determined.

19. The control method of an air conditioning system according to claim 18, wherein, When the supercooling degree is lower than the target condensing temperature, the opening degree of the outdoor expansion valve is decreased, when the supercooling degree is equal to the target condensing temperature, the opening degree of the indoor expansion valve is kept unchanged, and when the supercooling degree is higher than the target condensing temperature, the opening degree of the outdoor expansion valve is increased. The method further comprises: The change amount of the opening degree of the outdoor expansion valve is determined according to the supercooling difference value, the difference between the supercooling difference values of two continuous time points and the supercooling correction coefficient.

20. An air conditioning system comprising an indoor unit, an outdoor unit and a controller, wherein the controller is configured to perform the control method of the air conditioning system according to any one of claims 1-19.

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