A multi-split air conditioning system and a control method thereof

Abstract

This invention discloses a multi-split air conditioning system and its control method. The control method includes: collecting the current indoor ambient temperature of the room where the indoor unit is located; constructing a temperature prediction model and predicting the future indoor ambient temperature based on the temperature prediction model and the current indoor ambient temperature; calculating the total cooling capacity demand of the multi-split air conditioning system based on the future indoor ambient temperature; and switching the variable frequency / variable capacity compressor to operate in single-cylinder mode or dual-cylinder mode according to the total cooling capacity demand, as well as adjusting the operating frequency of the variable frequency / variable capacity compressor. Compared with the prior art, this invention, by collecting the current indoor ambient temperature and combining it with the constructed temperature prediction model, can predict the future indoor ambient temperature, thereby coordinating the control of the operating frequency and cylinder state of the variable frequency / variable capacity compressor, reducing the number of state switching times of the variable frequency / variable capacity compressor, reducing the losses caused by dual-cylinder operation and frequent start-stop, and belonging to the field of energy-saving air conditioning.

Description

Technical Field

[0001] This invention relates to the field of air conditioning technology, and in particular to a multi-split air conditioning system and its control method. Background Technology

[0002] Variable frequency and variable capacity compressors are widely used in multi-split air conditioning systems. By connecting or disconnecting the second cylinder, they can switch between single-cylinder small displacement and dual-cylinder large displacement to adapt to different loads. Currently, the control method for variable frequency and variable capacity compressors is generally based on comparing the current room temperature with a fixed temperature threshold, and then switching between single-cylinder and dual-cylinder modes according to the temperature difference. However, rooms have thermal inertia. After the variable frequency and variable capacity compressor stops or disconnects a cylinder, the room temperature will still change in the original direction for a period of time, which will cause the variable frequency and variable capacity compressor to repeatedly disconnect cylinders, causing room temperature overshoot.

[0003] Existing technology provides a control method for a multi-split air conditioning system. This method compares the indoor ambient temperature with a preset temperature threshold. If the indoor ambient temperature is lower than the preset threshold, the variable frequency / variable capacity compressor operates in single-cylinder mode; otherwise, it operates in dual-cylinder mode. During operation, if the single-cylinder operation time exceeds a first target time and the room temperature has not reached the set temperature, it switches to dual-cylinder operation. When the temperature difference between the room temperature and the set temperature is less than a first temperature difference value, it switches to single-cylinder operation. When the difference is less than a second temperature difference value, the variable frequency / variable capacity compressor and outdoor fan are shut down. When the difference is greater than a third temperature threshold, it resumes single-cylinder operation. However, this scheme does not consider room thermal inertia, which can easily lead to temperature overshoot and frequent cylinder switching, and it cannot adapt to the different thermal characteristics of multiple rooms.

[0004] Therefore, how to design a multi-split air conditioning system and its control method to avoid repeated cylinder cut-off caused by room thermal inertia of variable frequency and variable capacity compressors is a technical problem that the industry urgently needs to solve. Summary of the Invention

[0005] In response to the problem in existing technologies where the presence of room thermal inertia easily leads to repeated cylinder switching of variable frequency and variable capacity compressors, this invention proposes a multi-split air conditioning system and its control method.

[0006] The technical solution of this invention is to propose a control method for a multi-split air conditioning system. The multi-split air conditioning system includes one outdoor unit and multiple indoor units. The outdoor unit is equipped with a variable frequency, variable capacity compressor capable of switching between single-cylinder and dual-cylinder operation. The control method for the multi-split air conditioning system includes:

[0007] Collect the current indoor ambient temperature of the room where the indoor unit is located;

[0008] Construct a temperature prediction model, and predict the future indoor ambient temperature based on the temperature prediction model and the current indoor ambient temperature;

[0009] The total cooling capacity requirement of the multi-split air conditioning system is calculated based on the future indoor ambient temperature, and the variable frequency and variable capacity compressor is switched to single-cylinder mode or dual-cylinder mode and the operating frequency of the variable frequency and variable capacity compressor is adjusted according to the total cooling capacity requirement.

[0010] Based on the above-mentioned solution, this invention can collect the current indoor ambient temperature, construct a temperature prediction model, and thus predict the future indoor ambient temperature. This model can be used to coordinate the control of the operating frequency and cylinder state of the variable frequency and variable capacity compressor, thereby reducing the number of cylinder state switching times of the variable frequency and variable capacity compressor. This allows the variable frequency and variable capacity compressor to operate in the single-cylinder high-efficiency range and favorable frequency range most of the time, reducing the losses caused by dual-cylinder operation and frequency start-stop.

[0011] Furthermore, the temperature prediction model described in this invention is as follows:

[0012]

[0013] Where T(k) is the current indoor ambient temperature at the kth sampling time, u(kd) is the cooling input variable d sampling periods ago, d is the lag step, and a and b are model parameters.

[0014] Based on the above-mentioned solution, this invention provides a temperature prediction model that can be used to predict the future indoor ambient temperature and predict the room temperature trend in the near future, providing a basis for the control of the operating frequency and cylinder state of the variable frequency and variable capacity compressor.

[0015] Furthermore, the model parameters described in this invention are estimated using recursive least squares with a forgetting factor.

[0016] Based on the above scheme, this invention enables the temperature prediction model to capture the slow changes in room thermal inertia without being disturbed by random fluctuations in temperature data over a short period of time by setting an appropriate forgetting factor.

[0017] Furthermore, the number of lag steps described in this invention is estimated based on the room area.

[0018] Based on the above solution, this invention can set an appropriate lag step according to the relevant parameters of the room where the indoor unit is located, so that the future indoor ambient temperature predicted by the temperature prediction model is close to the actual future indoor ambient temperature, thus ensuring the accuracy of the prediction of the future indoor ambient temperature.

[0019] Furthermore, the total cooling capacity requirement mentioned in this invention is the sum of the cooling capacity requirements of the rooms in which the multiple indoor units are located, and the cooling capacity requirement of the room in which each indoor unit is located satisfies:

[0020]

[0021] Among them, K c,i T is the cooling load factor of the room where the indoor unit is located. set,i The temperature setpoint for the room where the indoor unit is located, max(T̂) i ) represents the maximum predicted future indoor ambient temperature of the room where the indoor unit is located, and δ is a constant.

[0022] Based on the above scheme, this invention can calculate the cooling demand of each room by predicting the future indoor ambient temperature, thereby realizing the rational allocation of cooling capacity in each room. At the same time, by combining the maximum cooling capacity of the variable frequency and variable capacity compressor in single-cylinder and dual-cylinder modes, it can select and switch the variable frequency and variable capacity compressor to operate in the corresponding cylinder state, so that the variable frequency and variable capacity compressor operates in the single-cylinder effective range and favorable frequency range most of the time.

[0023] Furthermore, in this invention, switching the variable frequency and variable capacity compressor to operate in single-cylinder mode or dual-cylinder mode according to the total cooling capacity requirement, and adjusting the operating frequency of the variable frequency and variable capacity compressor include:

[0024] Obtain the highest operating frequency and maximum cooling capacity of the variable frequency and variable capacity compressor in single-cylinder mode;

[0025] When the variable frequency and variable capacity compressor is in single-cylinder mode, determine whether the total cooling capacity demand is less than the maximum cooling capacity of the variable frequency and variable capacity compressor in single-cylinder mode.

[0026] If so, the variable frequency and variable capacity compressor is kept in single-cylinder mode, and the variable frequency and variable capacity compressor is controlled to operate at a frequency corresponding to the total cooling capacity requirement, based on the correspondence between the operating frequency and cooling capacity of the variable frequency and variable capacity compressor.

[0027] If not, the variable frequency and variable capacity compressor is switched to dual-cylinder mode, and the variable frequency and variable capacity compressor is controlled to operate at a frequency corresponding to the total cooling capacity requirement, based on the correspondence between the operating frequency and cooling capacity of the variable frequency and variable capacity compressor.

[0028] Based on the above-mentioned solution, this invention can reasonably switch the variable frequency and variable capacity compressor in single-cylinder mode according to the total cooling capacity demand. When the single-cylinder mode can meet the demand, the maximum operating frequency of the variable frequency and variable capacity compressor in single-cylinder mode is increased first. Only when the maximum operating frequency of the variable frequency and variable capacity compressor in single-cylinder mode can no longer meet the cooling capacity demand will it switch to dual-cylinder mode. This ensures that the variable frequency and variable capacity compressor operates in the effective range and favorable frequency range of single-cylinder mode most of the time, reducing the losses caused by dual-cylinder operation and frequency start-stop.

[0029] Furthermore, the present invention further includes switching the variable frequency and variable capacity compressor to operate in single-cylinder mode or dual-cylinder mode according to the total cooling capacity requirement, and adjusting the operating frequency of the variable frequency and variable capacity compressor.

[0030] When the variable frequency and variable capacity compressor is in dual-cylinder mode, determine whether the total cooling capacity demand is less than the maximum cooling capacity of the variable frequency and variable capacity compressor in single-cylinder mode.

[0031] If so, when the future indoor ambient temperature does not rise, the variable frequency and variable capacity compressor is controlled to operate at the highest operating frequency in single-cylinder mode. After a preset time, the variable frequency and variable capacity compressor is switched to single-cylinder mode, and according to the correspondence between the operating frequency of the variable frequency and variable capacity compressor and the cooling capacity, the variable frequency and variable capacity compressor is controlled to operate at the operating frequency corresponding to the total cooling capacity requirement.

[0032] If not, the variable frequency and variable capacity compressor is kept in dual-cylinder mode, and the compressor is controlled to operate at a frequency corresponding to the total cooling capacity requirement, based on the relationship between the operating frequency and cooling capacity of the variable frequency and variable capacity compressor.

[0033] Based on the above solution, this invention can reasonably switch the variable frequency and variable capacity compressor in dual-cylinder mode according to the total cooling capacity demand. When switching to single-cylinder mode, the operating frequency of the variable frequency and variable capacity compressor is first switched to the highest operating frequency in single-cylinder mode. After a stabilization delay of a preset time, the variable frequency and variable capacity compressor is controlled to enter single-cylinder mode. Then, the total cooling capacity demand is finely adjusted to match the total cooling capacity demand. This can avoid frequent switching when the load is just below the boundary.

[0034] Furthermore, when allocating cooling capacity to the indoor unit, the control method of the multi-split air conditioning system further includes setting an urgency coefficient for the room where the indoor unit is located, and setting a priority for allocating cooling capacity to different rooms according to the urgency coefficient.

[0035] The calculation model for the urgency coefficient is as follows:

[0036]

[0037] Among them, E i Let T be the urgency coefficient. set,i The temperature setpoint for the room where the indoor unit is located, max(T̂) i The value of the predicted future indoor temperature of the room where the indoor unit is located is the maximum value.

[0038] Based on the above solution, this invention can set different urgency coefficients for each room, allowing rooms with higher urgency coefficients to obtain more cooling capacity, enabling the temperature in each room to approach the set value more quickly, and making the overall temperature control more stable.

[0039] Furthermore, when predicting the future indoor ambient temperature, if the root mean square error between the predicted future indoor ambient temperature and the actual future indoor ambient temperature exceeds a preset threshold, the control method of the multi-split air conditioning system further includes:

[0040] The forgetting factor is lowered to accelerate the convergence of the temperature prediction model.

[0041] When the root mean square error between the predicted future indoor temperature and the actual future indoor temperature is less than a preset threshold, the forgetting factor is called back.

[0042] Based on the above scheme, this invention can, through the design of the forgetting factor, enable the temperature prediction model to capture the slow changes in room thermal inertia without being disturbed by random fluctuations in short-term temperature data.

[0043] The present invention also proposes a multi-split air conditioning control system, which includes an outdoor unit and multiple indoor units, wherein the outdoor unit is equipped with a variable frequency and variable capacity compressor that can switch between single-cylinder and dual-cylinder operation.

[0044] The multi-split air conditioning control system also includes a controller, which has a computer storage medium containing a computer program. When the computer program is executed by the controller, the multi-split air conditioning control system implements the control method of the multi-split air conditioning system described above.

[0045] This invention belongs to the field of energy-saving air conditioning. Compared with the prior art, this invention has at least the following beneficial effects:

[0046] This invention constructs a temperature prediction model by collecting the current indoor ambient temperature to predict the short-term temperature trend in the future, and then coordinates the control of the operating frequency and cylinder state of the variable frequency variable capacity compressor, which can reduce the number of cylinder state switching times of the variable frequency variable capacity compressor.

[0047] Before the variable frequency / variable capacity compressor reaches the boundary for cylinder state switching, this invention adjusts the operating frequency of the compressor in advance based on the predicted future indoor ambient temperature, ensuring that the cylinder state switching occurs only when truly necessary. When single-cylinder mode can meet the cooling demand, the compressor is prioritized to operate at its highest frequency in single-cylinder mode, ensuring it only switches to dual-cylinder mode when the frequency limit is reached. This allows the compressor to operate in the high-efficiency range and favorable frequency range of single-cylinder operation most of the time, reducing losses caused by dual-cylinder mode and frequency start-stop.

[0048] At the same time, the flow rate is allocated based on the cooling demand and urgency coefficient of each room, so that rooms with a large temperature difference from the set temperature receive more refrigerant, thus avoiding over- or under-adjustment of the temperature in a single room. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the overall flow of the control method for the multi-split air conditioning system in this invention;

[0051] Figure 2 This is a schematic diagram of the outdoor unit in this invention;

[0052] Figure 3 This is a schematic diagram of the indoor unit in this invention;

[0053] Figure 4 This is a schematic diagram of the overall structure of a multi-split air conditioning system according to one embodiment of the present invention;

[0054] Figure 5 This is a schematic diagram of the overall structure of a multi-split air conditioning system according to another embodiment of the present invention;

[0055] Figure 6 This is a schematic diagram of the cylinder switching process of the present invention when the current cylinder block state of the compressor is single-cylinder mode;

[0056] Figure 7 This is a schematic diagram of the cylinder switching process of the present invention when the compressor is currently in dual-cylinder mode;

[0057] Figure 8 This is the overall control flow of the control method for the multi-split air conditioning system in this invention;

[0058] Figure 9 This is the process for predicting future indoor ambient temperature in this invention;

[0059] Figure 10 This is the control flow of the control method for the multi-split air conditioning system in a specific embodiment of the present invention;

[0060] Figure 11 This is a schematic diagram of the data acquisition process in the control method of the multi-split air conditioning system provided by the present invention;

[0061] Figure 12This is a schematic diagram illustrating the process of correcting the temperature prediction model in the control method of the multi-split air conditioning system provided by the present invention. Detailed Implementation

[0062] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0063] Therefore, a feature pointed out in this specification is used to describe one feature of one embodiment of the invention, and does not imply that every embodiment of the invention must have the described feature. Furthermore, it should be noted that this specification describes many features. Although certain features may be combined to illustrate possible system designs, these features may also be used in other combinations not explicitly stated. Therefore, unless otherwise stated, the described combinations are not intended to be limiting.

[0064] The principles and structure of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0065] Currently, the control method for variable frequency and variable capacity compressors is generally based on comparing the current room temperature with a fixed temperature threshold, and then switching between single-cylinder mode and dual-cylinder mode according to the size of the temperature difference. However, the room has thermal inertia. After the variable frequency and variable capacity compressor stops or switches cylinders, the room temperature will still change in the original direction for a period of time, which will cause the variable frequency and variable capacity compressor to switch cylinders repeatedly, causing room temperature overshoot.

[0066] To address the aforementioned issues, this invention proposes a control method for a multi-split air conditioning system. The method aims to construct a temperature prediction model by collecting the current indoor ambient temperature, thereby predicting short-term temperature change trends in the future. This model is then used to coordinate the control of the operating frequency and cylinder state of the variable frequency and variable capacity compressor, thereby reducing the number of cylinder state switching operations of the variable frequency and variable capacity compressor.

[0067] Please see the appendix Figure 1 Based on the above design objectives, the control method for a multi-split air conditioning system proposed in this invention specifically includes the following steps:

[0068] Collect the current indoor ambient temperature of the room where the indoor unit is located;

[0069] Construct a temperature prediction model and predict the future indoor temperature based on the temperature prediction model and the current indoor temperature;

[0070] The total cooling capacity requirement of the multi-split air conditioning system is calculated based on the future indoor ambient temperature. The variable frequency and variable capacity compressor is then switched to single-cylinder or dual-cylinder mode and its operating frequency is adjusted according to the total cooling capacity requirement.

[0071] First, the main application scenario for this invention is multi-split air conditioners, which generally consist of one outdoor unit and multiple indoor units. Please refer to the appendix. Figure 2 For the outdoor unit, it is equipped with a variable frequency variable capacity compressor, an outdoor unit controller, and a drive.

[0072] The outdoor unit controller and driver are mainly used to control the working status of the outdoor unit.

[0073] The variable frequency and variable capacity compressor has a first cylinder and a second cylinder. The first cylinder is always in the engaged state, and the second cylinder is controlled by a solenoid valve. When the solenoid valve is closed, the second cylinder is in the engaged state, and the variable frequency and variable capacity compressor is in dual-cylinder mode.

[0074] When the solenoid valve is disconnected, the second cylinder is in an unconnected state, and the variable frequency and variable capacity compressor is in single-cylinder mode.

[0075] Generally speaking, the maximum cooling capacity and highest operating frequency of a variable frequency variable capacity compressor in dual-cylinder mode are higher than those in single-cylinder mode, but this also results in higher energy consumption. Therefore, under normal circumstances, the variable frequency variable capacity compressor will be operated in single-cylinder mode first, and it will only be switched to dual-cylinder mode when the single-cylinder mode cannot meet the total cooling capacity requirements of the variable frequency variable capacity compressor.

[0076] Please see the appendix Figure 3 For the indoor unit, it is installed in the room and has an electronic expansion valve, temperature sensor, indoor unit controller, and driver, etc.

[0077] The indoor unit controller and driver are mainly used to control the working status of the indoor unit.

[0078] The electronic expansion valve can be continuously adjusted to distribute the refrigerant flow into the indoor unit, which is the corresponding cooling capacity.

[0079] The temperature sensor is used to monitor the current indoor ambient temperature in the room where the indoor unit is located. The data detected by the temperature sensor will also be used in the control method of the multi-split air conditioning system described above, as the basis for subsequent related control.

[0080] Please see the appendix Figure 4 and appendix Figure 5 These are two different implementations of a multi-split air conditioning system, attached. Figure 4 The document provides a solution for connecting two indoor units to form a multi-split air conditioning system, with attached... Figure 5 A solution is provided for connecting three indoor units to form a multi-split air conditioner. The control scheme for the multi-split air conditioner system provided by this invention can adapt to the above-mentioned scenario and scenarios with more indoor units.

[0081] In the above embodiments, each indoor unit is installed in a room, and each indoor unit is equipped with a temperature sensor. Based on this, the present invention can detect the current indoor ambient temperature of each room. At the same time, the outdoor unit and all indoor units are connected through a communication bus, enabling bidirectional exchange of data and commands. The outdoor unit controller can obtain the current indoor ambient temperature data of all rooms accordingly.

[0082] Under this design, the present invention provides a corresponding temperature data acquisition scheme for the step "collecting the current indoor ambient temperature of the room where the indoor unit is located" in the control method of the above-mentioned multi-split air conditioning system. Please refer to the appendix. Figure 11 The steps are as follows:

[0083] Multi-split air conditioning systems operate in a 30-second cycle. This time can be adjusted according to actual conditions. If the time is too short, the outdoor unit controller will have a large workload and will not be able to obtain data on significant changes in the current indoor temperature. If the time is too long, the prediction accuracy of the future indoor temperature will be insufficient.

[0084] During each cycle, each indoor unit collects the current indoor ambient temperature of the room it is in through its own temperature sensor, and then uploads it to the outdoor unit controller via the communication bus after adding the corresponding time stamp.

[0085] The outdoor unit controller creates a circular buffer of length 40 for each room to store the temperature time series of the most recent 20 minutes. This environmental buffer is a fixed-capacity, first-in-first-out (FIFO) data result, enabling efficient data access through a circular pointer mechanism.

[0086] After completing the data collection for this cycle, the subsequent identification and prediction steps will proceed to predict the future indoor ambient temperature. This corresponds to the step of "constructing a temperature prediction model and predicting the future indoor ambient temperature based on the temperature prediction model and the current indoor ambient temperature" in the control method of the aforementioned multi-split air conditioning system. In this step, the temperature prediction model constructed by this invention is as follows:

[0087]

[0088] Where T(k) is the current indoor ambient temperature at the kth sampling time, u(kd) is the cooling input variable d sampling periods ago, d is the lag step, and a and b are model parameters.

[0089] Please see the appendix Figure 9Based on this temperature prediction model, the process of predicting future indoor ambient temperature in this invention is mainly divided into the following steps: S21, model construction; S22, online identification method; S23, determination of lag steps; S24, extraction of thermal time constant; S25, prediction of future indoor ambient temperature.

[0090] Each step will be explained in detail below:

[0091] Step S21 is mainly used to construct the temperature prediction model mentioned above. For each room, a first-order inertial plus pure time delay discrete-time model is used to describe the change law of ambient temperature over time, and the expression is:

[0092]

[0093] Where T(k) is the current indoor ambient temperature at the k-th sampling time;

[0094] u(kd) is the cooling input variable d sampling periods ago, which is calculated by the opening of the electronic expansion valve of the indoor unit and the current actual cooling output of the variable frequency and variable capacity compressor.

[0095] d represents the lag step, which is the number of sampling cycles that occur from the adjustment of the cooling capacity to the start of a corresponding response in the room temperature.

[0096] a and b are the model parameters to be identified, where a directly reflects the magnitude of the room's thermal inertia;

[0097] Step S22 is mainly used to identify the model parameters to be identified. In this invention, the model parameters are estimated using a recursive least squares method with a forgetting factor. The parameter vector and observation vector are defined as follows:

[0098]

[0099]

[0100] Here, the parameter vector represents the set of unknown parameters in the temperature prediction model above, such as model parameters a and b; the observation vector is a linear combination of known historical input / output data, such as T(k) and u(kd).

[0101] By recursively applying the above parameter vector and observation vector, we can obtain:

[0102]

[0103]

[0104]

[0105] in, It is the parameter estimate at the k-th sampling time, K k Let P be the gain matrix. k Let be the covariance matrix, and λ be the forgetting factor, with an initial value of 0.98.

[0106] A forgetting factor λ close to 1 indicates slow forgetting; λ close to 0 indicates fast forgetting. This invention sets λ to 0.98, enabling the temperature prediction model to capture both the slow changes in room thermal inertia and to avoid interference from random fluctuations in short-term temperature data.

[0107] For step S23, the initial value of the lag step d in the temperature prediction model is estimated in advance based on the room area (e.g., 3 steps for 20 square meters). After each identification period, the residual sum of squares is checked. If the residual sum of squares shows an obvious increasing trend, the lag step d is adjusted by a certain step size. The lag step d with the smallest residual is selected as the current optimal lag step.

[0108] Here, the residual is the difference between the predicted future indoor temperature and the actual future indoor temperature, which is used to reflect the prediction accuracy. The smaller the residual, the higher the accuracy of the temperature prediction model. In this case, the lag step d is optimal. In the above steps, the initial value of the lag step d does not need to be given accurately. The optimal lag step can be obtained after optimization by the sum of squared residuals.

[0109] Regarding step S24, there is a direct relationship between the model parameter a and the thermal time constant τ:

[0110]

[0111] Among them, T s As mentioned earlier, the sampling period is set to 30 seconds in this invention. The thermal time constant reflects how quickly the room temperature reaches a new equilibrium after a step change in cooling capacity. A larger change in the thermal time constant indicates a slower change in indoor ambient temperature and stronger thermal inertia; a smaller change in the thermal time constant indicates a more sensitive change in indoor ambient temperature. The outdoor unit controller can store the thermal time constants of each room for use as a basis for subsequent prediction and decision-making.

[0112] Regarding step S25, after identifying the model parameters a and b, a forward recursion can be performed using the temperature prediction model. Assuming that the cooling input u of each room remains unchanged in the near future, the calculations are performed sequentially starting from the currently known T(k) and u(kd):

[0113]

[0114]

[0115] Following this pattern, a total of 10 steps are recursively applied to obtain the predicted temperature sequence for the next 5 minutes:

[0116]

[0117] This sequence represents the future temperature change trend based on the room's thermal inertia, which is the future indoor ambient temperature mentioned earlier. Different rooms will have different predicted temperature curves due to variations in model parameters a, b, and d. The entire identification and prediction process is executed every 30 seconds to ensure real-time updates to the temperature change trend.

[0118] After predicting the future indoor temperature, the total cooling capacity requirement can be calculated, which is the calculation of the total cooling capacity requirement of the multi-split air conditioning system based on the future indoor temperature, as mentioned earlier. The multi-split air conditioning system has multiple indoor units, each installed in one room. The total cooling capacity requirement set in this invention is the sum of the cooling capacity requirements of all rooms containing the indoor units. For each room, the cooling capacity requirement is:

[0119]

[0120] Here, i represents the number of rooms, and max(T̂) i K represents the maximum value in the predicted temperature sequence for room i within the next 5 minutes obtained through the preceding temperature prediction model. c,i The cooling load factor of room i is denoted by the room area and the static gain of the model, T. set,i The temperature setpoint for room i is given by δ, which is a constant and is set to 0.2℃ in this invention to suppress minor oscillations at the adjustment boundary.

[0121] Taking a room with 3 rooms as an example, after obtaining the cooling capacity requirement of each room through the above calculation model, the total cooling capacity requirement of the multi-split air conditioner can be obtained:

[0122]

[0123] As mentioned above, variable frequency and variable capacity compressors have a maximum cooling capacity in single-cylinder and dual-cylinder modes, and the maximum cooling capacity in single-cylinder mode is lower than that in dual-cylinder mode. If the maximum cooling capacity in single-cylinder mode cannot meet the total cooling capacity requirement, it is necessary to switch to dual-cylinder mode. At the same time, in order to avoid increased energy consumption, it is generally necessary to adjust the operating frequency of the compressor so that the cooling capacity provided by the outdoor unit corresponds exactly to the total cooling capacity requirement. Therefore, this invention provides corresponding control methods for variable frequency and variable capacity compressors currently in single-cylinder and dual-cylinder modes respectively.

[0124] Please see the appendix Figure 6When the compressor is currently in single-cylinder mode, the steps above, including switching the variable frequency / variable capacity compressor to single-cylinder or dual-cylinder mode according to the total cooling capacity requirement, and adjusting the operating frequency of the variable frequency / variable capacity compressor, include:

[0125] Obtain the highest operating frequency and maximum cooling capacity of the variable frequency and variable capacity compressor in single-cylinder mode;

[0126] When the variable frequency and variable capacity compressor is in single-cylinder mode, determine whether the total cooling capacity demand is less than the maximum cooling capacity of the variable frequency and variable capacity compressor in single-cylinder mode.

[0127] If so, the variable frequency and variable capacity compressor will be kept in single-cylinder mode, and the variable frequency and variable capacity compressor will be controlled to operate at a frequency corresponding to the total cooling capacity requirement, based on the relationship between the operating frequency of the variable frequency and variable capacity compressor and the cooling capacity.

[0128] If not, the variable frequency and variable capacity compressor will be switched to dual-cylinder mode, and the compressor will be controlled to operate at a frequency corresponding to the total cooling capacity requirement, based on the relationship between the operating frequency and cooling capacity of the variable frequency and variable capacity compressor.

[0129] Generally, the outdoor unit controller contains a characteristic curve showing the relationship between the operating frequency and cooling capacity of the variable frequency, variable capacity compressor. This curve calibrates the highest operating frequency F of the variable frequency, variable capacity compressor in single-cylinder mode. max,s and the corresponding maximum cooling capacity Q max,s And the highest operating frequency F of the variable frequency variable capacity compressor in dual-cylinder mode max,d and the corresponding maximum cooling capacity Q max,d ;

[0130] Based on the above scheme, the present invention first determines the total cooling capacity requirement Q of the multi-split air conditioning system. total Is it less than the maximum cooling capacity Q in single-cylinder mode? max,s If so, it means that the cooling demand of the multi-split air conditioning system can be met by the single-cylinder mode. In this case, the variable frequency and variable capacity compressor is kept in the single-cylinder mode first. Then, the corresponding operating frequency is obtained according to the characteristic curve of the operating frequency and cooling capacity. This ensures that the energy provided by the variable frequency and variable capacity compressor corresponds to the total cooling capacity demand of the multi-split air conditioning system, with a certain margin reserved. The corresponding frequency command is then sent to the driver of the variable frequency and variable capacity compressor.

[0131] If not, it means that the cooling demand of the multi-split air conditioning system cannot be met by the single-cylinder mode. In this case, it is necessary to control the solenoid valve to switch the variable frequency and variable capacity compressor to dual-cylinder mode. Then, according to the characteristic curve of the operating frequency and cooling capacity, the corresponding operating frequency is obtained so that the energy provided by the variable frequency and variable capacity compressor corresponds to the total cooling capacity demand of the multi-split air conditioning system.

[0132] Based on this part of the solution, the present invention can reasonably switch the current cylinder state of the variable frequency and variable capacity compressor in single-cylinder mode according to the total cooling capacity demand. When the single-cylinder mode can meet the demand, the maximum operating frequency of the variable frequency and variable capacity compressor in single-cylinder mode is increased first. Only when the maximum operating frequency of the variable frequency and variable capacity compressor in single-cylinder mode can no longer meet the cooling capacity demand will it switch to dual-cylinder mode. This allows the variable frequency and variable capacity compressor to operate in the effective range and favorable frequency range of single-cylinder mode most of the time, reducing the losses caused by dual-cylinder operation and frequency start-stop.

[0133] Please see the appendix Figure 7 When the compressor is currently in dual-cylinder mode, the steps above, including switching the variable frequency / variable capacity compressor to single-cylinder or dual-cylinder mode according to the total cooling capacity demand and adjusting the operating frequency of the variable frequency / variable capacity compressor, include:

[0134] When the variable frequency and variable capacity compressor is in dual-cylinder mode, determine whether the total cooling capacity demand is less than the maximum cooling capacity of the variable frequency and variable capacity compressor in single-cylinder mode.

[0135] If so, when the indoor ambient temperature does not rise in the future, control the variable frequency and variable capacity compressor to operate at the highest operating frequency in single-cylinder mode. After a preset time, switch the variable frequency and variable capacity compressor to operate in single-cylinder mode, and control the variable frequency and variable capacity compressor to operate at the operating frequency corresponding to the total cooling capacity requirement according to the correspondence between the operating frequency and cooling capacity of the variable frequency and variable capacity compressor.

[0136] If not, the variable frequency and variable capacity compressor will remain in dual-cylinder mode, and the compressor will be controlled to operate at a frequency corresponding to the total cooling capacity requirement, based on the relationship between the compressor's operating frequency and cooling capacity.

[0137] Based on the above scheme, the present invention first determines the total cooling demand Q over five consecutive forecast periods. total Are they all below Q? max,s If the predicted indoor ambient temperature shows no upward trend, first control the variable frequency variable capacity compressor to operate at its highest operating frequency F in single-cylinder mode. max,s Then, after a preset time (30 seconds in this invention), the variable frequency and variable capacity compressor is switched to single-cylinder mode. Then, the operating frequency of the variable frequency and variable capacity compressor is finely adjusted according to the characteristic curve of the operating frequency and cooling capacity, so that the cooling capacity provided by the outdoor unit can meet the total cooling capacity requirement.

[0138] Based on the above solution, this invention can reasonably switch the variable frequency and variable capacity compressor in dual-cylinder mode according to the total cooling capacity demand. When switching to single-cylinder mode, the operating frequency of the variable frequency and variable capacity compressor is first switched to the highest operating frequency in single-cylinder mode. After a stabilization delay of a preset time, the variable frequency and variable capacity compressor is controlled to enter single-cylinder mode. Then, the total cooling capacity demand is finely adjusted to match the total cooling capacity demand. This can avoid frequent switching when the load is just below the boundary.

[0139] After the present invention completes the control of the operating frequency and cylinder state of the variable frequency and variable capacity compressor through the above scheme, it is necessary to allocate cooling capacity to each indoor unit to meet the cooling needs of different rooms. Based on this, the control method of the multi-split air conditioning system provided by the present invention further includes: setting an emergency coefficient for the room where each indoor unit is located, and setting the priority of cooling capacity allocation for different rooms according to the emergency coefficient. Generally speaking, the higher the emergency coefficient, the higher the priority of cooling capacity allocation.

[0140] The urgency coefficient calculation model provided by this invention is as follows:

[0141]

[0142] Among them, E i T is the urgency coefficient. set,i The temperature setpoint for the room where the indoor unit is located, max(T̂) i The value of the predicted future indoor temperature of the room where the indoor unit is located is the maximum value.

[0143] This urgency coefficient is related to the cooling demand in each room. The higher the urgency coefficient, the greater the corresponding cooling demand. Based on this urgency coefficient, this invention can set the allocation ratio for each room.

[0144]

[0145] The outdoor unit controller sends the electronic expansion valve targets for each room to the corresponding indoor unit controller via the communication bus, so that rooms with higher urgency coefficients can receive more cooling capacity, enabling the temperature of each room to approach the set value more quickly and making the overall temperature control more stable.

[0146] Please see the appendix Figure 12 After completing the cooling capacity distribution to different rooms, this invention also provides a method for adaptively correcting the temperature prediction model. This invention calculates the root mean square error between the predicted and measured values ​​of the future indoor ambient temperature of each room every 5 minutes using the outdoor unit controller.

[0147] If the root mean square error of a room exceeds 0.5℃ (i.e., the preset threshold) in three consecutive calculations, it indicates that its thermal inertia has changed significantly, and the identification forgetting factor of the room needs to be temporarily lowered to 0.9 to accelerate model convergence.

[0148] When the error falls below 0.5℃ (i.e., the preset threshold), the forgetting factor is restored to 0.98 to prevent the system from being too sensitive to noise.

[0149] Based on the above scheme, this invention can, through the design of the forgetting factor, enable the temperature prediction model to capture the slow changes in room thermal inertia without being disturbed by random fluctuations in short-term temperature data.

[0150] The above is a specific scheme for the multi-split air conditioning control system in this invention. Through the above scheme, this invention can collect the current indoor ambient temperature, construct a temperature prediction model, and thus predict the future indoor ambient temperature. This model is then used to coordinate the control of the operating frequency and cylinder state of the variable frequency and variable capacity compressor. This reduces the number of cylinder state switching times of the variable frequency and variable capacity compressor, allowing the compressor to operate in the single-cylinder high-efficiency range and favorable frequency range most of the time, thus reducing the losses caused by dual-cylinder operation and frequency start-stop.

[0151] Appendix Figure 8 and attached Figure 10 The specific steps are given, including:

[0152] Step S1: Temperature Data Acquisition; This corresponds to the solution mentioned earlier regarding "collecting the current indoor ambient temperature of the room where the indoor unit is located," as detailed in the attached document. Figure 11 The relevant statements are contained within this text;

[0153] Step S2: Online identification and temperature prediction of the room's thermal inertia model, specifically including step S21: model construction; step S22: online identification method; step S23: determination of the lag step number; step S24: extraction of the thermal time constant; step S25: prediction of future indoor ambient temperature, which corresponds to "constructing a temperature prediction model and predicting the future indoor ambient temperature based on the temperature prediction model and the current indoor ambient temperature" mentioned earlier. (See attached text.) Figure 9 The relevant statements are contained within this text;

[0154] Step S3: Calculate total cooling capacity requirement; this corresponds to the previous step of "calculating the total cooling capacity requirement of the multi-split air conditioning system based on the future indoor ambient temperature";

[0155] Step S4: Decision-making based on compressor frequency and cylinder status; corresponding to the previous statement "switching the variable frequency and variable capacity compressor to single-cylinder or dual-cylinder mode according to the total cooling capacity requirement, and adjusting the operating frequency of the variable frequency and variable capacity compressor";

[0156] Step S5: Dynamic allocation of cooling capacity to each room; corresponding to the relevant scheme for setting the urgency coefficient mentioned above;

[0157] Step S6: Model adaptive correction; corresponding to the above, when the root mean square error between the future indoor ambient temperature and the actual future indoor ambient temperature exceeds the preset threshold, the adjustment scheme for the forgetting factor is implemented.

[0158] Based on the above solution, the present invention also proposes a multi-split air conditioning control system, which belongs to the field of energy-saving air conditioning. The multi-split air conditioning control system includes an outdoor unit and multiple indoor units. The outdoor unit is equipped with a variable frequency variable capacity compressor that can switch between single cylinder and dual cylinder.

[0159] The multi-split air conditioning control system also has a controller, which contains a computer storage medium with a built-in computer program. When the computer program is executed by the controller, the multi-split air conditioning control system implements the control method of the multi-split air conditioning system described above.

[0160] Compared with the prior art, the present invention has at least the following beneficial effects:

[0161] This invention constructs a temperature prediction model by collecting the current indoor ambient temperature to predict the short-term temperature trend in the future, and then coordinates the control of the operating frequency and cylinder state of the variable frequency variable capacity compressor, which can reduce the number of cylinder state switching times of the variable frequency variable capacity compressor.

[0162] Before the variable frequency / variable capacity compressor reaches the boundary for cylinder state switching, this invention adjusts the operating frequency of the compressor in advance based on the predicted future indoor ambient temperature, ensuring that the cylinder state switching occurs only when truly necessary. When single-cylinder mode can meet the cooling demand, the compressor is prioritized to operate at its highest frequency in single-cylinder mode, ensuring it only switches to dual-cylinder mode when the frequency limit is reached. This allows the compressor to operate in the high-efficiency range and favorable frequency range of single-cylinder operation most of the time, reducing losses caused by dual-cylinder mode and frequency start-stop.

[0163] At the same time, the flow rate is allocated based on the cooling demand and urgency coefficient of each room, so that rooms with a large temperature difference from the set temperature receive more refrigerant, thus avoiding over- or under-adjustment of the temperature in a single room.

[0164] It should be noted that the terminology used above is for describing specific embodiments only and is not intended to limit the exemplary embodiments of the present invention. When the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. The order of execution of actions, steps, etc., in the apparatus and methods described in the specification and drawings can be implemented in any order unless a specific order is expressly specified, and as long as the output of the preceding process is not used in the subsequent process. Similar sequential terms used for ease of description do not imply that such an order must be followed.

[0165] Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as constraints. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0166] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A control method for a multi-split air conditioning system, the multi-split air conditioning system comprising one outdoor unit and multiple indoor units, wherein the outdoor unit is equipped with a variable frequency variable capacity compressor capable of switching between single-cylinder and dual-cylinder operation, characterized in that, The control method for the multi-split air conditioning system includes: Collect the current indoor ambient temperature of the room where the indoor unit is located; Construct a temperature prediction model, and predict the future indoor ambient temperature based on the temperature prediction model and the current indoor ambient temperature; The total cooling capacity requirement of the multi-split air conditioning system is calculated based on the future indoor ambient temperature, and the variable frequency and variable capacity compressor is switched to single-cylinder mode or dual-cylinder mode and the operating frequency of the variable frequency and variable capacity compressor is adjusted according to the total cooling capacity requirement.

2. The control method for a multi-split air conditioning system according to claim 1, characterized in that, The temperature prediction model is as follows: ； Where T(k) is the current indoor ambient temperature at the kth sampling time, u(kd) is the cooling input variable d sampling periods ago, d is the lag step, and a and b are model parameters.

3. The control method for a multi-split air conditioning system according to claim 2, characterized in that, The model parameters are estimated using recursive least squares with a forgetting factor.

4. The control method for a multi-split air conditioning system according to claim 2, characterized in that, The number of lag steps is estimated based on the room area.

5. The control method for a multi-split air conditioning system according to claim 1, characterized in that, The total cooling capacity requirement is the sum of the cooling capacity requirements of the rooms where the multiple indoor units are located, and the cooling capacity requirement of each room where the indoor unit is located satisfies: ； Among them, K c,i T is the cooling load factor of the room where the indoor unit is located. set,i The temperature setpoint for the room where the indoor unit is located, max(T̂) i ) represents the maximum predicted future indoor ambient temperature of the room where the indoor unit is located, and δ is a constant.

6. The control method for a multi-split air conditioning system according to claim 1, characterized in that, Switching the variable frequency and variable capacity compressor to operate in single-cylinder or dual-cylinder mode according to the total cooling capacity requirement, and adjusting the operating frequency of the variable frequency and variable capacity compressor include: Obtain the highest operating frequency and maximum cooling capacity of the variable frequency and variable capacity compressor in single-cylinder mode; When the variable frequency and variable capacity compressor is in single-cylinder mode, determine whether the total cooling capacity demand is less than the maximum cooling capacity of the variable frequency and variable capacity compressor in single-cylinder mode. If so, the variable frequency and variable capacity compressor is kept in single-cylinder mode, and the variable frequency and variable capacity compressor is controlled to operate at a frequency corresponding to the total cooling capacity requirement, based on the correspondence between the operating frequency and cooling capacity of the variable frequency and variable capacity compressor. If not, the variable frequency and variable capacity compressor is switched to dual-cylinder mode, and the variable frequency and variable capacity compressor is controlled to operate at a frequency corresponding to the total cooling capacity requirement, based on the correspondence between the operating frequency and cooling capacity of the variable frequency and variable capacity compressor.

7. The control method for a multi-split air conditioning system according to claim 6, characterized in that, Switching the variable frequency and variable capacity compressor to single-cylinder or dual-cylinder mode according to the total cooling capacity requirement, and adjusting the operating frequency of the variable frequency and variable capacity compressor also include: When the variable frequency and variable capacity compressor is in dual-cylinder mode, determine whether the total cooling capacity demand is less than the maximum cooling capacity of the variable frequency and variable capacity compressor in single-cylinder mode. If so, when the future indoor ambient temperature does not rise, the variable frequency and variable capacity compressor is controlled to operate at the highest operating frequency in single-cylinder mode. After a preset time, the variable frequency and variable capacity compressor is switched to single-cylinder mode, and according to the correspondence between the operating frequency of the variable frequency and variable capacity compressor and the cooling capacity, the variable frequency and variable capacity compressor is controlled to operate at the operating frequency corresponding to the total cooling capacity requirement. If not, the variable frequency and variable capacity compressor is kept in dual-cylinder mode, and the compressor is controlled to operate at a frequency corresponding to the total cooling capacity requirement, based on the relationship between the operating frequency and cooling capacity of the variable frequency and variable capacity compressor.

8. The control method for a multi-split air conditioning system according to claim 1, characterized in that, When allocating cooling capacity to the indoor unit, the control method of the multi-split air conditioning system further includes setting an urgency coefficient for the room where the indoor unit is located, and setting the priority of cooling capacity allocation for different rooms according to the urgency coefficient; The calculation model for the urgency coefficient is as follows: ； Among them, E i Let T be the urgency coefficient. set,i The temperature setpoint for the room where the indoor unit is located, max(T̂) i The value of the predicted future indoor ambient temperature of the room where the indoor unit is located is the maximum value.

9. The control method for a multi-split air conditioning system according to claim 4, characterized in that, When predicting the future indoor ambient temperature, if the root mean square error between the predicted future indoor ambient temperature and the actual future indoor ambient temperature exceeds a preset threshold, the control method of the multi-split air conditioning system further includes: The forgetting factor is lowered to accelerate the convergence of the temperature prediction model. When the root mean square error between the predicted future indoor temperature and the actual future indoor temperature is less than a preset threshold, the forgetting factor is called back.

10. A multi-split air conditioning system, characterized in that, The multi-split air conditioning system includes one outdoor unit and multiple indoor units. The outdoor unit is equipped with a variable frequency and variable capacity compressor that can switch between single-cylinder and dual-cylinder operation. The multi-split air conditioning system also includes a controller, which has a computer storage medium and a built-in computer program. When the computer program is executed by the controller, the multi-split air conditioning system implements the control method of the multi-split air conditioning system as described in any one of claims 1 to 9.

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