Air conditioning compressor start-stop control method and system

Abstract

The present invention relates to the technical field of air conditioning control, and specifically to a start-stop control method and system for an air conditioning compressor, including: obtaining a downward shift amplitude of a minimum frequency according to a second process of a compressor; obtaining a frequency error interference amount according to the difference in start-stop frequencies between historical frequency curves of different first processes of the compressor, and the difference in temperature rise between temperature recovery curves in different second processes; fusing the historical frequency curve of the first process into the simulated frequency change curve according to the difference in temperature rise between the temperature recovery curves in the second process to obtain a fused frequency curve; constructing a frequency interval using the downward shift amplitude and the frequency error interference amount; obtaining a mean value F1 of all frequencies within the frequency interval for all frequencies on the fused frequency curve and within the frequency stability interval; and re-obtaining the minimum frequency using the frequency stability duration and the mean value F1. The present invention avoids the inefficiency problem when the compressor is running at a low frequency.

Description

Technical Field

[0001] The present invention relates to the technical field of air-conditioning control, and in particular to a start-stop control method and system for an air-conditioning compressor. Background Art

[0002] During the operation of variable frequency air conditioners, the frequency regulation of the compressor is a key factor in achieving efficient energy saving and comfortable temperature control. However, when the compressor operating frequency is too low (i.e., below a certain threshold), a series of problems may occur, such as insufficient refrigerant flow, reduced refrigerant circulation efficiency, and abnormal compressor operation. These problems may cause the air conditioner performance to decline and fail to meet the indoor cooling or heating requirements. In addition, when the system tries to save energy by further reducing the frequency, the compressor may enter a nonlinear working area, affecting the overall operating stability.

[0003] To avoid the above problems, some design solutions set a fixed minimum frequency for the variable frequency air conditioner compressor to ensure that the system can maintain a normal cooling or heating cycle under low load. However, this fixed minimum frequency strategy may cause new problems: when the indoor load demand is low (for example, the ambient temperature is close to the set temperature), the compressor may start and stop frequently because the frequency cannot be further reduced. Frequent starting and stopping will not only increase the mechanical wear of the compressor, but may also lead to a series of negative effects such as increased energy consumption and unstable operation. Summary of the invention

[0004] In order to solve the above problems, the present invention provides an air-conditioning compressor start-stop control method and system.

[0005] The air-conditioning compressor start-stop control method and system of the present invention adopts the following technical solutions:

[0006] An embodiment of the present invention provides a method for starting and stopping an air conditioner compressor, the method comprising the following steps:

[0007] The compressor stops working when the frequency is lower than the minimum frequency after starting; it starts again when the indoor temperature is higher than the starting threshold;

[0008] The process from each start to stop of the compressor is recorded as the first process, and the process from each stop to start is recorded as the second process; in the second process, the temperature recovery curve of the indoor temperature is recorded, and the temperature recovery efficiency is obtained using the temperature recovery curve; the frequency recorded in the first process constitutes a historical frequency curve;

[0009] After the compressor is started again, the frequency change curve of the compressor is simulated to obtain the frequency stability interval and frequency stability duration on the frequency change curve;

[0010] The downward shift amplitude of the minimum frequency is obtained according to the time interval of the second process and the temperature recovery efficiency during the historical start-stop process of the compressor; the downward shift amplitude is negatively correlated with the time interval and the temperature recovery efficiency respectively;

[0011] The frequency error interference amount is obtained according to the start-stop frequency difference between the historical frequency curves of different first processes in the historical start-stop process of the compressor, and the temperature rise difference between the temperature recovery curves of different second processes; the correlation between the start-stop frequency difference and the temperature rise difference is negatively correlated with the frequency error interference amount;

[0012] According to the temperature rise difference between the temperature recovery curves, the historical frequency curve of the first process is integrated into the simulated frequency change curve to obtain a fused frequency curve;

[0013] The frequency interval is constructed using the downshift amplitude and the frequency error interference amount;

[0014] For all frequencies on the fusion frequency curve and within the frequency stability interval, obtain the mean value F1 of all frequencies within the frequency interval; use the frequency stability duration and the mean value F1 to regain the minimum frequency, the minimum frequency maximizes the frequency stability duration and the mean value F1;

[0015] When the compressor is restarted and the frequency is within the frequency stability range and is less than the minimum frequency, it stops working again.

[0016] Preferably, the method of obtaining the temperature recovery efficiency by using the temperature recovery curve includes the following specific steps:

[0017] The temperature recovery curve has a horizontal axis of time and a vertical axis of temperature.

[0018] The temperature value at the next moment on the temperature recovery curve minus the temperature value at the previous moment is recorded as the temperature change at adjacent moments, and the ratio of the average of all temperature changes at adjacent moments to the maximum temperature value on the temperature recovery curve is recorded as the temperature recovery efficiency.

[0019] Preferably, the obtaining of the frequency stability interval and the frequency stability duration on the frequency change curve comprises the following specific steps:

[0020] The horizontal axis of the frequency change curve is time, and the vertical axis is frequency;

[0021] For any horizontal coordinate x on the frequency change curve, obtain the average value of the frequencies at N1 moments before x, record it as the average frequency at the moment corresponding to the horizontal coordinate x, and record the difference between the maximum and minimum values ​​of the frequencies at N1 moments as D2;

[0022] The average frequencies of N2 moments before x form an average frequency sequence. In the average frequency sequence, the difference between two adjacent average frequencies is obtained. The average value D3 of the differences of all adjacent average frequencies in the average frequency sequence is calculated. When D2 and D3 are respectively less than the preset thresholds, the moment corresponding to the horizontal coordinate x is recorded as the frequency stable duration, and the time interval formed by the N1 moments before x is recorded as the frequency stable interval;

[0023] Wherein N1 and N2 are preset values.

[0024] Preferably, the step of obtaining the downward shift amplitude of the minimum frequency according to the time interval of the second process in the historical start-stop process of the compressor and the temperature recovery efficiency includes the following specific steps:

[0025] During the historical start-stop process, the temperature recovery efficiency in all second processes is normalized to obtain the delayed attention degree in each second process. The time intervals of all second processes are weighted and summed with the delayed attention degree in each second process as the weight. The result is recorded as G1. The downward shift amplitude of the minimum frequency is negatively correlated with G1.

[0026] Preferably, the frequency error interference amount is obtained according to the start-stop frequency difference between the historical frequency curves of different first processes in the historical start-stop process of the compressor, and the temperature rise difference between the temperature recovery curves of different second processes, and the specific steps include the following:

[0027] The difference between any two historical frequency curves in the first process is recorded as the start-stop frequency difference, and the difference between any two temperature recovery curves in the second process is recorded as the temperature rise difference;

[0028] In the historical start-stop process, the start-stop frequency differences of all adjacent first processes constitute the first sequence; the temperature rise differences of all adjacent second processes constitute the second sequence. The absolute value of the Pearson correlation coefficient between the first sequence and the second sequence is denoted as q, and the frequency error interference amount Q=exp(-q), where exp() represents an exponential function with a natural constant as the base.

[0029] Preferably, the step of fusing the historical frequency curve of the first process into the simulated frequency change curve according to the temperature rise difference between the temperature recovery curves to obtain the fused frequency curve includes the following specific steps:

[0030] Clustering all the historical frequency curves of the first process according to the temperature rise difference between any two second processes to obtain all categories, and taking the historical frequency curve included in the category with the largest mean value of the temperature rise difference as the reference historical frequency curve;

[0031] Any one of the reference historical frequency curve and the simulated frequency change curve is recorded as a target curve, the target curve corresponds to a frequency stability interval, and the curve segments within the frequency stability interval on all target curves are recorded as sub-curves. The sub-curves of all target curves are averaged, and the obtained average sub-curve is recorded as a fused frequency curve.

[0032] Preferably, the step of constructing the frequency interval by using the downshift amplitude and the frequency error interference amount includes the following specific steps:

[0033] Get the mean F2 of all frequencies in the fusion frequency curve, and take [F2-g×mm, F2-g×m+m] as the frequency interval, where g represents the downward shift amplitude, and m is used to describe the range of the frequency interval, and m is positively correlated with the frequency error interference.

[0034] Preferably, the method of re-obtaining the minimum frequency by using the frequency stabilization time and the mean value F1 includes the following specific steps:

[0035] The simulated frequency change curve means that when the compressor is restarted, any frequency is recorded as the target frequency, and the frequency change curve when the PID control algorithm starts to control the frequency change from the target frequency as the initial value is simulated;

[0036] k×L+(1-k)×F1 is recorded as the startup efficiency of the target frequency, k represents the recovery efficiency of the most recent second process, and L represents the frequency stabilization time;

[0037] The target frequency with the largest starting frequency is recorded as the starting frequency, and the frequency change curve when the PID control algorithm starts to control the frequency change from the starting frequency as the initial value is simulated, which is recorded as curve C;

[0038] According to the temperature rise difference between the temperature recovery curves in the second process, the historical frequency curve of the first process is merged into the curve C to obtain the fused frequency curve C1;

[0039] For all frequencies on the fused frequency curve C1 and within the frequency stability interval, the average value of all frequencies within the frequency interval is obtained as the minimum frequency.

[0040] Preferably, the historical start-stop process refers to: the working process of the compressor from the most recent setting T0 to the current moment; T0 is the set temperature value, and when the air conditioner is working, the indoor temperature is stabilized at T0.

[0041] Another embodiment of the present invention provides an air-conditioning compressor start-stop control system, the system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, the processor implementing the steps of the above-mentioned air-conditioning compressor start-stop control method when executing the computer program.

[0042] The beneficial effects of the technical solution of the present invention are:

[0043] The present invention integrates the historical frequency curve of the first process into the simulated frequency change curve based on the temperature rise difference between the temperature recovery curves in the second process to obtain a fused frequency curve; for all frequencies on the fused frequency curve and within the frequency stability interval, obtain the mean F1 of all frequencies within the frequency interval; and use the frequency stability time and mean F1 to regain the minimum frequency. This process integrates the frequency change behavior during the historical start-stop process into the simulated frequency change curve. On this basis, the minimum frequency maximizes the frequency stability time and mean F1, so that the compressor frequency can slowly decrease, avoiding the situation where the compressor frequency reaches the minimum frequency too early and shuts down too early, or avoiding the compressor frequency quickly reaching the minimum frequency and then running at a lower frequency for a long time, which causes the compressor to be inefficient; at the same time, it enables the compressor to work at a higher frequency, avoiding the situation where the compressor frequency does not stop working when it is too low, and avoiding the compressor inefficiency problem.

[0044] Furthermore, the present invention obtains the downward shift amplitude of the minimum frequency according to the time interval of the second process in the historical start and stop process of the compressor and the temperature recovery efficiency. The frequency error interference amount is obtained according to the start and stop frequency difference between the historical frequency curves of different first processes in the historical start and stop process of the compressor, and the temperature rise difference between the temperature recovery curves in different second processes. The frequency interval is constructed using the downward shift amplitude and the frequency error interference amount. This process selects a frequency interval based on the downward shift amplitude, obtains or selects a frequency as the minimum frequency from the frequency interval, and at the same time, the frequency error interference amount is used to ensure that the minimum frequency obtained in the frequency interval can avoid the error introduced by the mechanical movement of the compressor, and finally avoid the problem of too small time interval when starting again later.

[0045] In summary, the present invention continuously updates the minimum frequency, so that the compressor can avoid the inefficiency problem caused by long-term low-frequency operation and avoid the problem of frequent startup of the compressor as much as possible, thereby improving the efficiency of the compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 A flowchart of a method for starting and stopping an air-conditioning compressor provided in Embodiment 1 of the present invention;

[0048] Figure 2 A flow chart of the steps included in a method for starting and stopping an air-conditioning compressor provided in Embodiment 2 of the present invention;

[0049] Figure 3 This is a flow chart of the steps included in a method for starting and stopping an air-conditioning compressor provided in Embodiment 3 of the present invention. DETAILED DESCRIPTION

[0050] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of the air-conditioning compressor start-stop control method and system proposed by the present invention, its specific implementation, structure, features and effects, in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0051] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0052] All embodiments of the present invention add an energy-saving mode based on the existing air-conditioning working mode, which is a cooling mode. In this mode, the compressor can avoid running for a long time at a low frequency. When the frequency of the compressor is lower than a certain frequency (i.e., the minimum frequency), it can stop working. On the one hand, it saves energy consumption, and on the other hand, it solves the following problems (referred to as compressor inefficiency problems) as much as possible: (1) Running at an excessively low frequency may cause the mechanical parts of the compressor to not be properly lubricated, thereby increasing wear or causing failures; (2) The compressor needs to be at a certain frequency to ensure the effective circulation of the refrigerant to maintain the normal cooling or heating effect of the system; (3) Too low a frequency may cause the compressor efficiency to decrease, affecting the overall performance and energy efficiency ratio (COP) of the air-conditioning system; (4) The motor may not be able to generate sufficient torque to drive the compressor at a low frequency, affecting normal operation.

[0053] In this energy-saving mode, in order to avoid starting and stopping the compressor too frequently, the minimum frequency needs to be set to be dynamically updated to avoid the current shock, high energy consumption and rapid wear caused by frequent starting and stopping of the compressor.

[0054] The existing air-conditioning working modes mentioned above include a constant temperature mode (for example, the indoor temperature is precisely controlled at a set temperature value). The energy-saving mode of the present invention takes into account that in most air-conditioning application scenarios or user habits, it is not necessary to precisely control the indoor temperature at a certain temperature, but rather to allow certain temperature fluctuations. In the energy-saving mode of the present invention, the efficient operation of the compressor is ensured (that is, the above-mentioned problem is further solved) by the feature of precise control of loss temperature (that is, the present application does not pursue precise temperature control).

[0055] The specific scheme of the air-conditioning compressor start-stop control method and system provided by the present invention is described in detail below with reference to the accompanying drawings.

[0056] See also Figure 1 , which shows a flowchart of a method for starting and stopping an air-conditioning compressor provided by an embodiment of the present invention, the method comprising the following steps:

[0057] Step S001: Start the air conditioning compressor, and stop the compressor when the compressor frequency is lower than the minimum frequency.

[0058] After turning on the air conditioner, a preset temperature is first set on the air conditioner panel, recorded as T0, and then the air conditioner starts the compressor to start cooling, so that the indoor temperature gradually becomes T0. The compressor in this embodiment is a variable frequency compressor. As the ambient temperature gradually changes to T0, the frequency of the compressor gradually changes from high to low.

[0059] As an example, the air conditioner starts the compressor to start cooling so that the ambient temperature gradually becomes TO, including the following methods:

[0060] The PID control algorithm is used to control the frequency of the compressor so that the indoor temperature approaches T0.

[0061] It should be noted that three control parameters are required in the PID control algorithm, namely the proportional coefficient, the integral coefficient and the differential gain coefficient. The three control coefficients in this embodiment are set in advance by the implementers. The setting methods of the above three control parameters are well known and will not be described in detail in this embodiment.

[0062] In other embodiments, for other working modes of the air conditioner, such as the working mode in which the room temperature is precisely kept constant at the set temperature value during cooling of the air conditioner (i.e., the constant temperature mode), when the working mode is also controlled by the PID algorithm, the proportional coefficient, integral coefficient, and differential gain coefficient used by the PID control algorithm in the mode are recorded as kp, ki, and kd, respectively; then the proportional coefficient, integral coefficient, and differential gain coefficient of the PID algorithm in the above process of this embodiment are set to: kp, 1.2×ki, and 0.9×kd, respectively; wherein the integral coefficient in the above process of this embodiment is larger than the integral coefficient ki in other working modes of the air conditioner, and can change more slowly while ensuring the stable operation of the compressor, avoiding the situation where the compressor quickly reaches a lower frequency and then runs at a lower frequency for a long time, thereby avoiding the problem of compressor inefficiency to a certain extent; the differential gain coefficient in the above process of this embodiment is larger than the differential gain coefficient kd in other working modes of the air conditioner, and can also avoid the situation where the compressor quickly reaches a lower frequency and then runs at a lower frequency for a long time, thereby avoiding the problem of compressor inefficiency to a certain extent. In other embodiments, the above two proportional coefficients of 1.2 and 0.9 may be replaced by other values, which are not specifically limited in this embodiment.

[0063] Furthermore, the compressor frequency when approaching TO is recorded as F0, and 85% of F0 is taken as the initial value of the minimum frequency F.

[0064] It should be noted that when the indoor temperature approaches TO, the indoor temperature may not be completely constant to T0, but fluctuates around TO, and the frequency of the compressor also fluctuates around F0. The reasons are many, such as indoor temperature changes (such as temperature changes caused by sunlight, electrical heat dissipation, human activities, etc.), fluctuations caused by the mechanical motion error of the compressor itself, and the process of PID adjustment by the control algorithm is a dynamic process, which determines that the temperature and frequency are a dynamic balance process. For example, in this embodiment, F0 is 30Hz and the fluctuation amplitude is 6Hz.

[0065] When the frequency of the compressor is less than F, stop starting the compressor.

[0066] Step S002: After stopping the compressor, record the temperature recovery curve, and when the temperature is greater than the start threshold, start the compressor again.

[0067] When the compressor is stopped, the indoor temperature at each moment is recorded in real time. The recorded indoor temperature constitutes a temperature recovery curve (the horizontal axis is time, and the vertical axis is temperature). When the indoor temperature is greater than the start threshold T1, the compressor is started again, where T1=T0+t. In this embodiment, t is greater than 0. This embodiment is described by taking t equal to 3 degrees as an example. In other embodiments, t can be set to other values, which is not specifically limited in this embodiment.

[0068] Step S003: re-obtain the minimum frequency of the compressor according to the temperature recovery curve.

[0069] (1) Record any frequency as the target frequency and simulate the frequency change curve when the PID control algorithm starts to control the frequency change from the target frequency as the initial value. The frequency change curve describes: assuming that the compressor is started at the target frequency, the frequency change curve of the compressor is predicted during the process of temperature recovery to TO.

[0070] It is a known technology to simulate the frequency change curve when the PID control algorithm starts to control the frequency change from the target frequency as the initial value. This embodiment will not be described in detail. The frequency change curve can be simulated using tools such as MATLAB, Simulink or Python. The horizontal axis of the frequency change curve is time, and the vertical axis is frequency.

[0071] The arbitrary frequency refers to any frequency within the range of 10 Hz, 12 Hz, 14 Hz, ..., P, where P is 120% of the rated operating frequency of the compressor (P needs to be rounded down, the unit is Hz). In other embodiments, any frequency within other frequency ranges can also be set as the target frequency, which is not specifically limited in this embodiment.

[0072] (2) Obtain the frequency stability interval and the duration L when the frequency reaches stability (abbreviated as frequency stability duration L) on the frequency change curve.

[0073] As an optional example, a method of obtaining a frequency stability interval and a frequency stability duration L on a frequency change curve includes:

[0074] For any horizontal coordinate x on the frequency change curve, obtain the N1 moments before x (including the moment corresponding to the horizontal coordinate x), obtain the mean of the frequencies in these moments, record it as the average frequency D1 at the moment corresponding to the horizontal coordinate x, record the difference between the maximum and minimum frequencies in these moments as D2, when D2 is less than 0.2×D1, it means that the frequency corresponding to the horizontal coordinate x has reached a smaller value, at this time it is determined that the frequency has reached stability at the moment corresponding to the horizontal coordinate x, and record the moment corresponding to the horizontal coordinate x as the frequency stability duration L. The time interval formed by the N1 moments before x is recorded as the frequency stability interval. The mean of all frequencies in the frequency stability interval is recorded as F1, indicating that under the control of the PID algorithm, the average frequency when the compressor frequency is stable is F1.

[0075] In this embodiment, every 0.5 seconds is a moment. In addition, this embodiment is described by taking N1=20 as an example. In other embodiments, N1 may be set to other values, which are not specifically limited in this embodiment.

[0076] As a preferred example, the frequency stability interval and the frequency stability duration L are obtained on the frequency change curve, including the following method:

[0077] First of all, it should be noted that it is feasible to obtain the average frequency F1 and the duration L for the simulated frequency change curve in the above optional example. However, when the frequency change curve is not simulated but acquired in real time, the frequency change curve will be interfered by noise, resulting in the inability to accurately judge whether the frequency has reached stability based only on the size of D2.

[0078] This preferred example is based on the above optional example. The average frequencies of the N2 moments before x (including the moment corresponding to the horizontal coordinate x) constitute an average frequency sequence. In the average frequency sequence, the absolute value of the difference between two adjacent average frequencies is obtained (recorded as the difference between the two adjacent average frequencies). The difference between all adjacent average frequencies in the average frequency sequence is averaged to obtain D3. The smaller the average value D3 is, the more dynamically stable the frequency change curve is in the local time. When D2 is less than 0.2×D1, and D3 is less than 0.05×D1, it is determined that the frequency at the moment corresponding to the horizontal coordinate x has reached stability, and the moment corresponding to the horizontal coordinate x is recorded as the frequency stability duration L, and the time interval composed of the N1 moments before x is recorded as the frequency stability interval, and the average value of all frequencies in the frequency stability interval is recorded as F1. This embodiment is described using N2=5 as an example. In other embodiments, N2 can be set to other values, which are not specifically limited in this embodiment.

[0079] (3) Use the temperature recovery curve to obtain the temperature recovery efficiency k, and record k×L+(1-k)×F1 as the starting efficiency of the target frequency. The target frequency with the largest starting frequency is recorded as the starting frequency, and the average frequency F1 obtained under this starting frequency is taken as the minimum frequency F.

[0080] The average frequency F1 obtained at the starting frequency is used as the minimum frequency F, including: simulating a frequency change curve when the PID control algorithm controls the frequency change from the starting frequency as the initial value, and taking the average value F1 of all frequencies in the frequency stability range on the frequency change curve as the minimum frequency F.

[0081] After the compressor is started, it starts to run at the starting frequency. Under the control of the PID control algorithm, the indoor temperature gradually changes to TO. During this process, the frequency of the compressor is recorded at each moment, and the recorded frequency also constitutes a frequency change curve (that is, the frequency change curve obtained by real-time acquisition as described above, recorded as the historical frequency curve). When the frequency of the compressor is in the frequency stability range (the frequency stability range is obtained by the historical frequency curve, and the acquisition method has been described above), and the frequency is less than the minimum frequency F, the compressor stops working again; if the frequency of the compressor is not yet in the frequency stability range, but the frequency is less than the minimum frequency F, the compressor continues to work because the compressor is not yet in a stable state and needs to work to ensure that the air conditioner can continue to cool down; when the frequency of the compressor is already in the frequency stability range, but the frequency is not less than the minimum frequency F, the compressor continues to work, and stops working when the frequency of the compressor is less than the minimum frequency F again.

[0082] In the above process, the larger the L, the slower the compressor frequency can be reduced, avoiding the situation where the compressor frequency reaches the minimum frequency F too early and shuts down too early, or avoiding the problem of compressor inefficiency caused by the compressor frequency quickly reaching the minimum frequency F and then running at a lower frequency for a long time. The larger the F1, the faster the compressor can work at a higher frequency, avoiding the situation where the compressor frequency does not stop working when it is too low, and avoiding the problem of compressor inefficiency.

[0083] Compressor inefficiency issues include: (1) Operating at too low a frequency may cause the mechanical parts of the compressor to not be properly lubricated, thereby increasing wear or causing failure; (2) The compressor needs to operate at a certain frequency to ensure effective circulation of the refrigerant to maintain the normal cooling or heating effect of the system; (3) Too low a frequency may cause the compressor efficiency to decrease, affecting the overall performance and energy efficiency ratio (COP) of the air-conditioning system; (4) The motor may not be able to generate sufficient torque to drive the compressor at low frequency, affecting normal operation.

[0084] The temperature recovery efficiency k is used to describe the rise in indoor temperature. The larger k is, the faster the temperature recovers. At this time, we pay more attention to the stable time L instead of the minimum frequency. The reason is that when the temperature recovers quickly, the larger minimum frequency F will cause the temperature to reach the starting threshold T1 in a short time after the compressor stops, causing the compressor to start prematurely. In addition, when the temperature recovers faster (that is, the larger k is), we pay more attention to the stable time L, which can avoid the problem of the compressor frequency stabilizing at the minimum value too early, which may lead to easy shutdown.

[0085] As an example, the temperature recovery efficiency k is obtained using the temperature recovery curve, including the following method:

[0086] The temperature value at the next moment on the temperature recovery curve minus the temperature value at the previous moment is recorded as the temperature change at adjacent moments. The ratio of the mean of the temperature changes at all adjacent moments to the maximum temperature value on the temperature recovery curve is recorded as the temperature recovery efficiency k.

[0087] In some embodiments, the target frequency with the largest startup frequency is recorded as the startup frequency, the average frequency obtained at the startup frequency is recorded as F1, th1×F1 is taken as the minimum frequency F, th1 is the preset first threshold, and the purpose of introducing th1 is: during implementation, the minimum frequency F can be further adjusted by artificially setting the size of th1, for example, th1=0.9.

[0088] In some other embodiments, when the frequency of the compressor is within the frequency stability interval and the frequency is less than the minimum frequency F, further considering that the frequency of the compressor is dynamically changing (that is, the frequency fluctuates around the above F1), when there is error interference (such as errors caused by the mechanical movement of the compressor, errors caused by accidental and violent fluctuations in ambient temperature, etc.), if such error interference causes the frequency to be less than the minimum frequency F, then it is not expected that the compressor will stop working. Therefore, in some embodiments, when the frequency of the compressor is within the frequency stability interval and the frequency is less than the minimum frequency F, the compressor is not stopped temporarily, but the number of times the compressor frequency is less than the minimum frequency F in the next several moments (for example, the next 5 moments) is continuously obtained, and the compressor is stopped when the number is greater than a preset threshold (for example, greater than 3 times). If the number is not greater than the preset threshold, the compressor continues to work, and then the number of times the compressor frequency is less than the minimum frequency F in the next several moments is continuously obtained, and the compressor is stopped when the number is greater than the preset threshold.

[0089] In summary, the above process from starting to stopping again ensures that the compressor avoids starting immediately after starting as much as possible when working, and avoids the inefficiency of the compressor caused by running the compressor at a lower frequency for a long time.

[0090] Step S004: When the compressor is restarted and the frequency is less than the minimum frequency, it stops working again.

[0091] The above step S003 describes the method of obtaining the starting frequency and the minimum frequency F, and the method of stopping the compressor according to the minimum frequency F. After the compressor is stopped according to the method in step S003, the compressor is restarted again according to the method in step S002, and then the compressor is stopped again according to the method in step S003, and so on, until the air conditioner is turned off or switched to other modes.

[0092] The above process avoids the inefficiency of the compressor caused by the low-frequency movement of the compressor to a certain extent, and also avoids frequent start and stop, especially at night when the indoor temperature does not fluctuate much. It should be noted that although this process cannot accurately stabilize the indoor temperature at T0, in many cases the indoor temperature does not need to be accurately stabilized at T0, such as in some offices, shopping malls, or under some user preferences, the indoor temperature does not need to be strictly stabilized at T0. At this time, the air-conditioning working mode described in this embodiment (that is, the control process of the compressor described above) is more efficient than other air-conditioning working modes.

[0093] In some other embodiments, during the operation of the compressor described in step S004, when TO does not change, it means that the initial conditions of the PID control algorithm of the compressor remain unchanged. At this time, after the compressor is started again, the starting frequency is set to the starting frequency of the last start, that is, when T0 remains unchanged, the starting frequency of the compressor when it is started again also remains unchanged. This can reduce the amount of calculation. However, it should be noted that although the starting frequency remains unchanged, after the compressor is started again, the minimum frequency F needs to be recalculated according to the method in S003. The reason is that after the compressor is started again, the indoor temperature, the working status of the compressor, etc. may change. Therefore, the minimum frequency F needs to be updated in real time to ensure that the compressor inefficiency problem is solved as much as possible.

[0094] When T0 changes, for example, the air conditioner user resets the value of T0, then the start-up frequency needs to be recalculated according to the method in step S003.

[0095] Embodiment 2:

[0096] For step S004 in the first embodiment, the process from each start to stop of the compressor is recorded as the first process, and the process from each stop to start is recorded as the second process. In the second process, the temperature recovery curve of the indoor temperature is recorded, and the temperature recovery efficiency is obtained using the temperature recovery curve; the frequency recorded in the first process constitutes a historical frequency curve;

[0097] The difference between this embodiment and the first embodiment is that after the compressor is started and stopped several times according to the method in the first embodiment (for example, after being started and stopped 5 times), the minimum frequency F is recalculated in this embodiment.

[0098] Specifically, if Figure 2 As shown, this embodiment obtains the downward shift amplitude of the minimum frequency according to the time interval of the second process in the historical start-stop process of the compressor and the temperature recovery efficiency, and uses the downward shift amplitude of the minimum frequency to update the minimum frequency F, thereby further avoiding the situation where the start-stop frequency is too frequent.

[0099] As an example, the downward shift amplitude of the minimum frequency is obtained according to the time interval of the second process in the historical start-stop process of the compressor and the temperature recovery efficiency, including the following method:

[0100] Assume that the compressor is started at the current moment;

[0101] The historical start-stop process described in this embodiment refers to the working process of the compressor from the most recent setting T0 to the current moment.

[0102] The second process (the process from stopping to starting) includes the recorded temperature recovery curve and the temperature recovery efficiency k obtained according to the temperature recovery curve. The second process also includes a time interval from stopping to starting.

[0103] During the historical start-stop process, the temperature recovery efficiency k in all the second processes is normalized. This embodiment uses the softmax algorithm for normalization. The normalized temperature recovery efficiency k is recorded as the delayed attention degree in each second process; the time intervals of all the second processes are weighted and summed with the delayed attention degree in each second process as the weight, and the result is recorded as G1, and the time interval from the most recent setting of T0 to the current moment is recorded as G0. The ratio of G1 to G0 is G, and exp(-G) is recorded as the downward shift amplitude g of the minimum frequency F. The smaller G is, the larger g is when the temperature rises quickly during the historical start-stop process, resulting in a more serious situation where the compressor is started again after a short time interval; exp() represents an exponential function with a natural constant as the base.

[0104] As an example, the minimum frequency F is updated using the downward shift amplitude of the minimum frequency. The included methods are:

[0105] Similar to step S003 in the first embodiment, a frequency change curve when the PID control algorithm starts to control the frequency change from the target frequency as the initial value is simulated, and a frequency stability interval is obtained on the frequency change curve;

[0106] On the frequency change curve, the mean value F2 of all frequencies in the frequency stability interval is obtained. For all frequencies belonging to the frequency interval [F2-g×mm, F2-g×m+m], the mean value of these frequencies is taken as F1, and then the startup efficiency of the target frequency is obtained according to the method described in Example 1, that is, k×L+(1-k)×F1 is recorded as the startup efficiency of the target frequency, and the target frequency with the maximum startup efficiency is recorded as the startup frequency. The F1 obtained corresponding to the startup frequency is taken as the value of the minimum frequency F.

[0107] The above m is used to describe the range of the frequency interval, or the range of the above frequency interval is equal to 2m. This implementation is described by taking m=F2×5% as an example. In other embodiments, m can be set to other values. For example, in some embodiments, the method for obtaining m also includes:

[0108] Obtain the difference between the maximum and minimum values ​​of all frequencies within the frequency stability interval, and use 30% of the difference as the size of m.

[0109] The above process selects a frequency interval according to the downward shift amplitude g of the minimum frequency F, and obtains or selects a frequency from the frequency interval as the minimum frequency F, wherein the larger the downward shift amplitude g, the smaller the frequency interval from which the minimum frequency F needs to be obtained (the frequency interval [F2-g×mm, F2-g×m+m] is equivalent to shifting a frequency interval centered on F2 and having an interval range of 2m to the left by an amplitude of g×m), thereby avoiding the problem of too short a time interval of the second process when restarting later, especially when the temperature rises quickly during the historical start-stop process, resulting in a more serious situation in which the compressor is restarted after a short time interval (that is, when g is larger). This embodiment updates the current compressor startup process based on the temperature rise and time interval at different stages from stop to start during the historical start-stop process, further avoiding the situation in which the compressor is frequently started.

[0110] Embodiment three:

[0111] This embodiment further considers the following on the basis of Embodiment 1 and Embodiment 2: the minimum frequency F in Embodiment 1 and Embodiment 2 is obtained based on the simulated frequency change curve, but when the compressor works under the control of the PID algorithm, the curve composed of the frequencies actually collected has errors compared with the simulated frequency change curve, wherein some of the errors are caused by errors in the mechanical movement of the compressor (such as aging and wear of mechanical parts, failure of lubricating fluid, abnormal heating and vibration of the compressor, errors contained in the control signal output by the controller (such as errors in the PWM signal), etc.), which makes the obtained minimum frequency F unreliable and may cause the compressor to stop prematurely.

[0112] like Figure 3 As shown, in this embodiment, for the historical start and stop process under the same TO, the frequency error interference amount is obtained according to the start and stop frequency difference between the historical frequency curves of different first processes in the historical start and stop process of the compressor, and the temperature rise difference between the temperature recovery curves in different second processes; the historical frequency curve of the first process is integrated into the simulated frequency change curve according to the temperature rise difference between the temperature recovery curves in the second process to obtain the integrated frequency curve.

[0113] As an example, the frequency error interference amount is obtained according to the start-stop frequency difference between the historical frequency curves of different first processes in the historical start-stop process of the compressor, and the temperature rise difference between the temperature recovery curves of different second processes, including the following method:

[0114] As described in the second embodiment, the process from each start to stop of the compressor is recorded as the first process, and the process from each stop to start is recorded as the second process. In the second process, the temperature recovery curve of the indoor temperature is recorded, and the temperature recovery efficiency is obtained using the temperature recovery curve; the frequency recorded in the first process constitutes a historical frequency curve.

[0115] The historical frequency curve describes the change of the compressor frequency over time in the first process of each historical start-stop process. Compared with the simulated frequency change curve, the historical frequency curve contains error interference.

[0116] The difference between any two historical frequency curves in the first process is obtained, which is recorded as the start-stop frequency difference, and the difference between the temperature recovery curves in the two second processes is obtained, which is recorded as the temperature rise difference.

[0117] As an example, the start-stop frequency difference is equal to the DTW distance between any two historical frequency curves in the first process, and the larger the DTW distance, the larger the start-stop frequency difference. The DTW distance is obtained by the DTW algorithm, which belongs to the known technology and is not specifically described in this embodiment. In other embodiments, the DTW distance can also be replaced by the cosine distance.

[0118] As an example, the temperature rise difference is equal to the DTW distance between the temperature recovery curves in the two second processes. The greater the DTW distance, the greater the temperature rise difference.

[0119] Furthermore, in all historical start-stop processes, the sequence consisting of the start-stop frequency differences of all adjacent first processes is recorded as the first sequence; in all historical start-stop processes, the sequence consisting of the temperature rise differences of all adjacent second processes is recorded as the second sequence, and the absolute value of the Pearson correlation coefficient between the first sequence and the second sequence is recorded as q, and the frequency error interference amount Q=exp(-q). The smaller the absolute value q of the Pearson correlation coefficient, the smaller the correlation between the first sequence and the second sequence, which further indicates that the start-stop frequency differences of the historical start-stop process are not only caused by the temperature rise difference, but may also be caused by the error in the mechanical movement of the compressor. At this time, the frequency error interference amount Q is larger, which further indicates that the interference caused by the error in the mechanical movement of the compressor is greater.

[0120] As an example, the historical frequency curve of the first process is integrated into the simulated frequency change curve according to the temperature rise difference between the temperature recovery curves in the second process to obtain a fused frequency curve.

[0121] According to the temperature rise difference between any two second processes, all the historical frequency curves of the first process are clustered to obtain all categories, each category has the same or similar temperature rise difference, and the mean of the temperature rise difference corresponding to all historical frequency curves is obtained in each category, and the historical frequency curve included in the category with the largest mean is used as the reference historical frequency curve of the current startup process. The reference historical frequency curve of the current startup process describes the frequency curve that is not disturbed by errors as much as possible during the restart of the current compressor.

[0122] Get the simulated frequency change curve when the current compressor is started again, and record any one of the historical frequency curve and the simulated frequency change curve as the target curve. The target curve corresponds to a frequency stability interval, and all curve segments in the frequency stability interval on the target curve are recorded as sub-curves. The average sub-curves of all target curves are averaged to obtain an average sub-curve, which is recorded as a fused frequency curve. The fused frequency curve allows the simulated frequency change curve to incorporate the frequency change behavior during the historical start-stop process.

[0123] Furthermore, the minimum frequency is recovered by using the frequency error interference amount on the fusion frequency curve, including:

[0124] Using the same method as in Example 2, the mean F2 of all frequencies in the fusion frequency curve is obtained. For all frequencies belonging to the frequency interval [F2-g×mm, F2-g×m+m], the mean of these frequencies is taken as F1. Then, the startup efficiency of the target frequency is obtained according to the method described in Example 1, that is, k×L+(1-k)×F1 is recorded as the startup efficiency of the target frequency, the target frequency with the maximum startup efficiency is recorded as the startup frequency, and the F1 obtained corresponding to the startup frequency is taken as the value of the minimum frequency F.

[0125] It should be noted that, in this embodiment, different from the first and second embodiments, the F1 obtained corresponding to the starting frequency is used as the value of the minimum frequency F, and the specific process included is:

[0126] The frequency change curve of the PID control algorithm when the frequency change is controlled from the starting frequency as the initial value is re-simulated, which is recorded as curve C; the historical frequency curve of the first process is integrated into curve C according to the temperature rise difference between the temperature recovery curves in the second process to obtain the fused frequency curve C1; similarly, the mean F2 of all frequencies in the fused frequency curve C1 is re-obtained, and for all frequencies belonging to the frequency interval [F2-g×mm, F2-g×m+m], the mean F1 of these frequencies is taken as the minimum frequency.

[0127] Wherein, m is positively correlated with the frequency error interference amount Q, so that when the frequency error interference amount Q is larger, the value of the minimum frequency F is obtained from a larger frequency interval to ensure the reliability of the minimum frequency F.

[0128] As an example, clustering the historical frequency curves of all first processes according to the temperature rise difference between any two second processes includes: taking the temperature rise difference between any two second processes as a metric distance, and performing mean shift clustering on the historical frequency curves of all first processes according to the metric distance.

[0129] As an example, m=F2×Q.

[0130] Embodiment 4:

[0131] This embodiment solves the following problems that may exist in the third embodiment:

[0132] When the noise interference in Example 3 is more serious (for example, the compressor is severely worn, the indoor temperature environment changes suddenly, and the controller is affected by high temperature and a circuit failure occurs), the frequency in the fused frequency curve cannot reflect the frequency change. At this time, the appropriate minimum frequency F cannot be screened out in the fused frequency curve (for example, the frequency in the fused frequency curve has no obvious convergence trend, or no obvious change trend).

[0133] The method for obtaining the minimum frequency F given in this implementation is:

[0134] The attention coefficient w of the minimum frequency F is obtained according to the fusion frequency curve.

[0135] (1-w)×k×L+w×(1-k)×F1 is recorded as the startup efficiency of the target frequency, and the target frequency with the highest startup efficiency is recorded as the startup frequency. Then, the value of the minimum frequency F is obtained again according to the method in Example 3. That is, the historical frequency curve of the first process is integrated into the curve C according to the temperature rise difference between the temperature recovery curves in the second process to obtain the fused frequency curve C1, and the mean F2 of all frequencies in the fused frequency curve C1 is obtained again. For all frequencies belonging to the frequency interval [F2-g×mm, F2-g×m+m], the mean F1 of these frequencies is taken as the minimum frequency.

[0136] The larger the attention coefficient w is, the more the frequency in the fused frequency curve can reflect the frequency change, and the appropriate minimum frequency F can be screened out in the fused frequency curve. At this time, more attention should be paid to the size of F1; the smaller the attention coefficient w is, the more the frequency in the fused frequency curve cannot reflect the frequency change, and the appropriate minimum frequency F cannot be screened out in the fused frequency curve. At this time, you should not pay too much attention to the size of F1.

[0137] As an example, the method for obtaining the attention coefficient w includes:

[0138] When the compressor is currently started at the target frequency, a frequency change curve is simulated, and a section of the frequency change curve in the frequency stability range is recorded as the first curve, and the Pirelli coefficient of the first curve and the fusion frequency curve is used as the focus coefficient w. The larger w is, the more likely the fusion frequency curve is to tend to the simulated frequency change curve, which further indicates that the frequency in the fusion frequency curve can reflect the frequency change.

[0139] Embodiment five:

[0140] This embodiment provides an air-conditioning compressor start-stop control system, the system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the steps of an air-conditioning compressor start-stop control method in all the above embodiments when executing the computer program.

[0141] 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, improvements, etc. made within the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling the start and stop of an air-conditioning compressor, characterized in that: The method includes: The compressor stops working when the frequency is lower than the minimum frequency after starting; it starts again when the indoor temperature is higher than the starting threshold; The process from each start to stop of the compressor is recorded as the first process, and the process from each stop to start is recorded as the second process; in the second process, the temperature recovery curve of the indoor temperature is recorded, and the temperature recovery efficiency is obtained using the temperature recovery curve; the frequency recorded in the first process constitutes a historical frequency curve; After the compressor is started again, the frequency change curve of the compressor is simulated to obtain the frequency stability interval and frequency stability duration on the frequency change curve; The downward shift amplitude of the minimum frequency is obtained according to the time interval of the second process and the temperature recovery efficiency during the historical start-stop process of the compressor; the downward shift amplitude is negatively correlated with the time interval and the temperature recovery efficiency respectively; The frequency error interference amount is obtained according to the start-stop frequency difference between the historical frequency curves of different first processes in the historical start-stop process of the compressor, and the temperature rise difference between the temperature recovery curves of different second processes; the correlation between the start-stop frequency difference and the temperature rise difference is negatively correlated with the frequency error interference amount; According to the temperature rise difference between the temperature recovery curves, the historical frequency curve of the first process is integrated into the simulated frequency change curve to obtain a fused frequency curve; The frequency interval is constructed using the downshift amplitude and the frequency error interference amount; For all frequencies on the fusion frequency curve and within the frequency stability interval, obtain the mean value F1 of all frequencies within the frequency interval; use the frequency stability duration and the mean value F1 to regain the minimum frequency, the minimum frequency maximizes the frequency stability duration and the mean value F1; When the compressor is restarted and the frequency is within the frequency stability range and is less than the minimum frequency, it stops working again.

2. The air conditioner compressor start-stop control method according to claim 1, characterized in that: The specific steps of obtaining the temperature recovery efficiency by using the temperature recovery curve are as follows: The temperature recovery curve has a horizontal axis of time and a vertical axis of temperature. The temperature value at the next moment on the temperature recovery curve minus the temperature value at the previous moment is recorded as the temperature change between adjacent moments, and the ratio of the average of all temperature changes at adjacent moments to the maximum temperature value on the temperature recovery curve is recorded as the temperature recovery efficiency.

3. The air-conditioning compressor start-stop control method according to claim 1, characterized in that: The specific steps of obtaining the frequency stability interval and the frequency stability duration on the frequency change curve are as follows: The horizontal axis of the frequency change curve is time, and the vertical axis is frequency; For any horizontal coordinate x on the frequency change curve, obtain the average value of the frequencies at N1 moments before x, record it as the average frequency at the moment corresponding to the horizontal coordinate x, and record the difference between the maximum and minimum values ​​of the frequencies at N1 moments as D2; The average frequencies of N2 moments before x form an average frequency sequence. In the average frequency sequence, the difference between two adjacent average frequencies is obtained. The average value D3 of the differences of all adjacent average frequencies in the average frequency sequence is calculated. When D2 and D3 are respectively less than the preset thresholds, the moment corresponding to the horizontal coordinate x is recorded as the frequency stable duration, and the time interval formed by the N1 moments before x is recorded as the frequency stable interval; Where N1 and N2 are preset values.

4. The air-conditioning compressor start-stop control method according to claim 1, characterized in that: The step of obtaining the minimum frequency downward shift amplitude according to the time interval of the second process in the compressor history start-stop process and the temperature recovery efficiency includes the following specific steps: During the historical start-stop process, the temperature recovery efficiency in all second processes is normalized to obtain the delayed attention degree in each second process. The time intervals of all second processes are weighted and summed with the delayed attention degree in each second process as the weight. The result is recorded as G1. The downward shift amplitude of the minimum frequency is negatively correlated with G1.

5. The air-conditioning compressor start-stop control method according to claim 1, characterized in that: The specific steps of obtaining the frequency error interference amount according to the start-stop frequency difference between the historical frequency curves of different first processes in the historical start-stop process of the compressor and the temperature rise difference between the temperature recovery curves of different second processes are as follows: The difference between any two historical frequency curves in the first process is recorded as the start-stop frequency difference, and the difference between any two temperature recovery curves in the second process is recorded as the temperature rise difference; In the historical start-stop process, the start-stop frequency differences of all adjacent first processes constitute the first sequence; the temperature rise differences of all adjacent second processes constitute the second sequence. The absolute value of the Pearson correlation coefficient between the first sequence and the second sequence is denoted as q, and the frequency error interference amount Q=exp(-q), where exp() represents an exponential function with a natural constant as the base.

6. The air-conditioning compressor start-stop control method according to claim 1, characterized in that: The specific steps of fusing the historical frequency curve of the first process into the simulated frequency change curve according to the temperature rise difference between the temperature recovery curves to obtain the fused frequency curve are as follows: Clustering all the historical frequency curves of the first process according to the temperature rise difference between any two second processes to obtain all categories, and taking the historical frequency curve included in the category with the largest mean value of the temperature rise difference as the reference historical frequency curve; Any one of the reference historical frequency curve and the simulated frequency change curve is recorded as a target curve, the target curve corresponds to a frequency stability interval, and the curve segments within the frequency stability interval on all target curves are recorded as sub-curves. The sub-curves of all target curves are averaged, and the obtained average sub-curve is recorded as a fused frequency curve.

7. The air-conditioning compressor start-stop control method according to claim 1, characterized in that: The specific steps of constructing the frequency interval by using the downshift amplitude and the frequency error interference amount are as follows: Get the mean F2 of all frequencies in the fusion frequency curve, and take [F2-g×mm, F2-g×m+m] as the frequency interval, where g represents the downward shift amplitude, and m is used to describe the range of the frequency interval, and m is positively correlated with the frequency error interference.

8. The air-conditioning compressor start-stop control method according to claim 1, characterized in that: The specific steps of re-obtaining the minimum frequency by using the frequency stabilization time and the mean value F1 are as follows: The simulated frequency change curve means that when the compressor is restarted, any frequency is recorded as the target frequency, and the frequency change curve when the PID control algorithm starts to control the frequency change from the target frequency as the initial value is simulated; k×L+(1-k)×F1 is recorded as the startup efficiency of the target frequency, k represents the recovery efficiency of the most recent second process, and L represents the frequency stabilization time; The target frequency with the largest starting frequency is recorded as the starting frequency, and the frequency change curve when the PID control algorithm starts to control the frequency change from the starting frequency as the initial value is simulated, which is recorded as curve C; According to the temperature rise difference between the temperature recovery curves in the second process, the historical frequency curve of the first process is merged into the curve C to obtain the fused frequency curve C1; For all frequencies on the fused frequency curve C1 and within the frequency stability interval, the average value of all frequencies within the frequency interval is obtained as the minimum frequency.

9. The air-conditioning compressor start-stop control method according to claim 1, 4 or 5, characterized in that: The historical start-stop process refers to: the working process of the compressor from the most recent setting T0 to the current moment; T0 is the set temperature value, and when the air conditioner is working, the indoor temperature is stabilized at T0.

10. An air-conditioning compressor start-stop control system, the system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the air-conditioning compressor start-stop control method as described in any one of claims 1 to 9 are implemented.

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