Control method and system for undervoltage of outdoor alternating current motor of variable frequency air conditioner

Abstract

The invention relates to the field of air conditioner control, and provides a control method and system for undervoltage of an outdoor alternating current motor of a variable frequency air conditioner, and the control method comprises the steps: obtaining the power supply voltage of the air conditioner, continuously monitoring the temperature of an outer coil when the power supply voltage is lower than a preset value, and recording the temperature change rate of the inner and outer coils in a first time period; first adjustment is conducted on the duty ratio of an outer fan driving motor according to the temperature change rate of the outer coil pipe, and first operation or second operation is executed in the second time period length equal to the first time period according to the change direction of the temperature change rate of the outer coil pipe; the second operation comprises the steps that when the temperature change rate of the outer coil pipe is a negative value, if the compressor frequency is lower than the preset working frequency, the compressor frequency is increased according to the temperature change rate of the outer coil pipe, the current compressor frequency and the preset working frequency, and if the compressor frequency is equal to the working frequency, the compressor frequency is increased. And second adjustment is conducted on the duty ratio of the outer fan according to the environment temperature and the current duty ratio of the outer fan.

Description

Technical Field

[0001] The invention relates to the field of air-conditioning control, and in particular to a method and system for controlling undervoltage of an outdoor AC motor of a variable frequency air-conditioning. Background Art

[0002] With the popularization of variable frequency air conditioning technology, the reliability of air conditioning operation and user experience have become the focus of industry attention. At present, the control scheme of outdoor AC motors of variable frequency air conditioners generally adopts a protection mechanism based on voltage fluctuation triggering. When the grid voltage fluctuates abnormally (especially when the voltage is too low), the speed of the outdoor fan decreases due to insufficient power supply, causing the temperature of the external coil to rise rapidly in a short period of time, thereby triggering the refrigeration overload protection shutdown. Although this type of protection mechanism can effectively prevent the air conditioner from being damaged by overload, under extreme conditions of frequent grid voltage fluctuations or continuous low voltage, the air conditioner will frequently shut down due to repeated entry into the protection state, seriously affecting the user's comfort experience and accelerating the loss of equipment components.

[0003] In the existing technology, the solutions to the voltage fluctuation problem are mostly focused on passive protection strategies, such as directly limiting the compressor frequency or external fan speed through a fixed threshold. The fixed frequency correction mode cannot adapt to the load changes under different ambient temperatures. The unreasonable setting of the upper frequency limit may aggravate the system load fluctuation and even cause the false triggering or overshoot of the protection mechanism. Therefore, how to reduce the number of unnecessary protection shutdowns through dynamic adjustment strategies while ensuring system reliability has become a technical problem that needs to be optimized in the field of variable frequency air conditioning control. Summary of the invention

[0004] In view of the above-mentioned defects, the purpose of the present invention is to propose a control method and system for undervoltage of the outdoor AC motor of a variable frequency air conditioner, aiming to prevent the air conditioner from frequently reaching the shutdown temperature when undervoltage occurs, reduce the number of unnecessary protection shutdowns to extend the service life of the air conditioner, and improve the comfort of user experience.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] A method for controlling undervoltage of an outdoor AC motor of a variable frequency air conditioner, the control method comprising:

[0007] Obtain the power supply voltage of the air conditioner. When the power supply voltage is lower than the preset value, continuously monitor the temperature of the external coil and record the temperature change rate of the internal and external coils in the first time period.

[0008] A first adjustment is performed on the duty cycle of the external fan drive motor according to the external coil temperature change rate, and a first operation or a second operation is performed according to the change direction of the external coil temperature change rate within a second time period equal to the first time period, wherein:

[0009] The first operation includes adjusting the compressor frequency according to the ambient temperature and the external coil temperature rise rate when the external coil temperature change rate is positive;

[0010] The second operation includes, when the rate of change of the external coil temperature is negative, if the compressor frequency is lower than the preset operating frequency, increasing the compressor frequency according to the rate of change of the external coil temperature, the current compressor frequency and the preset operating frequency; if the compressor frequency is equal to the operating frequency, performing a second adjustment on the duty cycle of the external fan drive motor according to the ambient temperature and the current duty cycle of the external fan drive motor.

[0011] Preferably, first adjusting the duty cycle of the external fan drive motor according to the external coil temperature change rate includes:

[0012] Get the current supply voltage;

[0013] Determine the maximum operating duty cycle of the external fan at the current voltage based on the current power supply voltage;

[0014] When the temperature change rate of the external coil exceeds the first temperature rise rate threshold, the adjustment level is divided based on the temperature change rate of the external coil, and the duty cycle of the external fan drive motor is increased based on the adjustment level until it is equal to the maximum working duty cycle;

[0015] When the external coil temperature change rate does not exceed the second temperature rise rate threshold, the current duty cycle of the external fan drive motor is maintained when the current external coil temperature value is less than the air conditioner shutdown temperature.

[0016] Furthermore, the regulation levels are divided based on the temperature change rate of the external coil, and the duty cycle of the external fan drive motor is increased based on the regulation level until it is equal to the maximum working duty cycle, satisfying the relationship:

[0017] D t+1 =min(D max ,D t +α·ΔD·(V t -V th )·V);

[0018] Among them, D t+1 represents the target duty cycle of the fan drive motor in the next time period, D t Indicates the current duty cycle of the external fan drive motor, D max Indicates the maximum duty cycle of the external fan drive motor under the current voltage, V t Indicates the current external coil temperature change rate, V th represents the first temperature rise rate threshold, α represents the adjustment coefficient, where α=k·(V nominal -V actual ), k is used to adjust the impact of voltage drop on duty cycle, V nominalIndicates the rated working voltage of the air conditioner, V actual represents the current supply voltage, ΔD represents the fixed increment selected according to the adjustment level, γ represents the ambient temperature compensation factor, γ=1+β(T env -T base1 ), T env Indicates the current ambient temperature, T base1 represents the first reference temperature, and β represents the temperature influence coefficient.

[0019] Preferably, adjusting the compressor frequency according to the ambient temperature and the external coil temperature rise rate includes:

[0020] A second reference temperature for adjusting the frequency of the compressor is set based on the ambient temperature, wherein the second reference temperature is used to distinguish between strong and weak working conditions of the heat dissipation efficiency of the external coil;

[0021] When the ambient temperature is higher than the second reference temperature, a frequency correction factor is generated which is positively correlated with the difference between the ambient temperature and the second reference temperature, and the frequency correction factor is used to quantify the inhibitory effect of the high temperature environment on the heat dissipation capacity of the external coil;

[0022] If the ambient temperature is higher than the second reference temperature and the current compressor frequency exceeds a preset proportional range of the rated frequency, the compressor frequency is adjusted by gradient attenuation based on the difference between the ambient temperature and the second reference temperature, and the amplitude of the gradient attenuation increases as the difference between the ambient temperature and the second reference temperature increases;

[0023] If the ambient temperature is lower than or equal to the reference temperature threshold, the current compressor frequency is maintained and the monitoring sensitivity of the external coil temperature rise rate is dynamically adjusted according to the frequency correction factor. When the growth acceleration of the external coil temperature rise rate is monitored to exceed the growth threshold associated with the frequency correction factor, the compressor frequency adjustment is re-triggered.

[0024] Furthermore, the gradient attenuation adjustment of the compressor frequency based on the difference between the ambient temperature and the second reference temperature satisfies the relationship:

[0025]

[0026] Among them, f new represents the compressor frequency after gradient attenuation adjustment, f current Indicates the current compressor frequency, T env -T base2 represents the difference between the ambient temperature and the second reference temperature, μ represents the attenuation coefficient for controlling the temperature difference on the frequency adjustment, n represents the influence of the difference between the ambient temperature and the second reference temperature on the frequency adjustment, τ represents the attenuation coefficient for adjusting the influence of the difference between the ambient temperature and the second reference temperature on the frequency, Indicates the rate of change of ambient temperature.

[0027] Preferably, the step of increasing the compressor frequency according to the external coil temperature change rate, the current compressor frequency and the preset operating frequency comprises:

[0028] Obtain the current compressor frequency, and calculate the frequency ratio between the current compressor frequency and the preset operating frequency;

[0029] If the product of the absolute value of the temperature change rate of the outer coil and the frequency ratio exceeds a preset dynamic response threshold, a frequency increase operation is performed;

[0030] The frequency increase operation includes:

[0031] The compressor frequency is gradually increased according to the graded proportional relationship between the absolute value of the rate of change of the temperature of the outer coil and the frequency ratio;

[0032] When executing the frequency increase operation, continuously monitor the absolute value of the temperature change rate of the external coil, and if the absolute value is lower than a preset negative maintenance threshold, terminate the frequency increase operation until the absolute value recovers to be above the negative maintenance threshold, and then re-execute the frequency increase operation until the compressor frequency reaches the preset operating frequency;

[0033] If the rate of change of the temperature of the outer coil turns to a positive value during the frequency increase operation, the operation is immediately terminated and the compressor frequency is adjusted by gradient attenuation based on the difference between the ambient temperature and the second reference temperature.

[0034] Furthermore, the compressor frequency is gradually increased according to the graded proportional relationship between the absolute value of the external coil temperature change rate and the frequency ratio, satisfying the relationship:

[0035]

[0036] Among them, f new Indicates the compressor frequency after the increase, f current Indicates the current compressor frequency. Δf is used to control the amplitude of the compressor frequency change. ratio Indicates the frequency ratio between the current compressor frequency and the preset operating frequency. represents the attenuation coefficient that controls the rate of gradual increase, and t represents the time variable.

[0037] Preferably, performing a second adjustment on the duty cycle of the external fan drive motor according to the ambient temperature and the current duty cycle of the external fan drive motor includes:

[0038] If the current ambient temperature is not higher than the external coil temperature, the current duty cycle of the external fan drive motor is set to the lowest value;

[0039] If the current ambient temperature is higher than the external coil temperature, the degree of increase in the external coil temperature caused by the current ambient temperature is calculated based on the difference between the current ambient temperature and the external coil temperature, and the degree of decrease in the external coil temperature caused by the current duty cycle of the external fan drive motor is calculated based on the current duty cycle of the external fan drive motor and the ambient temperature;

[0040] Based on the difference between the degree of temperature drop and the degree of temperature rise, the duty cycle of the external fan drive motor is reduced until the degree of temperature drop and the degree of temperature rise are balanced.

[0041] A control system for undervoltage of an outdoor AC motor of a variable frequency air conditioner, the control system is applied to the control method as described above, and the control system comprises:

[0042] The detection module is used to obtain the power supply voltage of the air conditioner. When the power supply voltage is lower than a preset value, the temperature of the external coil is continuously monitored and the rate of change of the temperature of the internal and external coils in the first time period is recorded;

[0043] The adjustment module is used to perform a first adjustment on the duty cycle of the external fan drive motor according to the external coil temperature change rate, and perform a first operation or a second operation according to the change direction of the external coil temperature change rate within a second time period equal to the first time period, wherein:

[0044] The first operation submodule is used to adjust the compressor frequency according to the ambient temperature and the temperature rise rate of the external coil when the temperature change rate of the external coil is positive;

[0045] The second operating submodule is used to increase the compressor frequency according to the external coil temperature change rate, the current compressor frequency and the preset operating frequency when the external coil temperature change rate is negative, if the compressor frequency is lower than the preset operating frequency; if the compressor frequency is equal to the operating frequency, the duty cycle of the external fan drive motor is adjusted for the second time according to the ambient temperature and the current duty cycle of the external fan drive motor.

[0046] One of the above technical solutions has the following advantages or beneficial effects:

[0047] The present invention continuously monitors the temperature of the external coil and records the temperature change rate, predicts the risk of refrigeration overload in advance, adjusts the duty cycle of the external fan drive motor in time according to the temperature change rate, and performs different operations according to the temperature change direction. When the temperature change rate of the external coil is positive, the compressor frequency is adjusted in combination with the ambient temperature and the temperature rise rate to avoid shutdown due to insufficient heat dissipation; when the temperature change rate is negative, if the compressor frequency is lower than the preset operating frequency, the frequency is increased; if the operating frequency has been reached, a secondary adjustment is performed based on the ambient temperature and the duty cycle to ensure stable operation of the system, which can effectively reduce the number of unnecessary protection shutdowns caused by voltage fluctuations and extend the service life. Equipment service life, improve user experience, improve the reliability and stability of air conditioners in complex voltage environments. In addition, it can monitor and predict risks in advance, and can timely capture potential undervoltage risks, providing a basis for subsequent corresponding adjustment measures; the external fan duty cycle can be accurately adjusted so that the operating status of the external fan can closely follow the changes in the system's heat dissipation requirements and improve the overall energy efficiency of the system; the compressor frequency can be flexibly adjusted to ensure the cooling effect and prevent the compressor from overloading due to excessive frequency; the secondary adjustment of the external fan duty cycle is optimized to further improve the refined control of the external fan operating status to ensure the stable operation of the system under complex working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] 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 embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0049] Figure 1 is a flow chart of a method for controlling undervoltage of an outdoor AC motor of a variable frequency air conditioner provided by an embodiment of the present invention;

[0050] Figure 2 It is a structural schematic diagram of a control system for undervoltage of an outdoor AC motor of a variable frequency air conditioner provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0051] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0052] In this application, the terms "comprises", "comprising" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0053] A control method for undervoltage of outdoor AC motor of variable frequency air conditioner, such as Figure 1 As shown, in a preferred embodiment of the present invention, the control method is applied to an air conditioning system (hereinafter referred to as the system), comprising the following steps:

[0054] S1: Obtain the power supply voltage of the air conditioner. When the power supply voltage is lower than a preset value, continuously monitor the temperature of the external coil and record the temperature change rate of the internal and external coils in the first time period.

[0055] During the operation of variable frequency air conditioners, the stability of the power supply voltage is crucial for the normal operation of components such as outdoor AC motors. When the power supply voltage is lower than the preset value, it means that undervoltage occurs. At this time, the speed of the external fan will decrease due to insufficient power supply. The speed of the external fan is closely related to the temperature of the external coil. When the speed decreases, the compressor works at the preset working frequency, which will cause the temperature of the external coil to rise rapidly. Therefore, continuous monitoring of the external coil temperature and recording its rate of change in the first time period can provide a key basis for the subsequent adjustment of parameters such as the duty cycle of the external fan drive motor, which helps to predict possible problems such as refrigeration overload in advance, so as to take corresponding measures to avoid the air conditioner frequently entering the protection shutdown state and ensure the stable operation of the air conditioning system.

[0056] Among them, the power supply voltage of the air conditioner is the power supply voltage that provides electrical energy to the various components of the air conditioner. Its normality is directly related to whether the air conditioner can work normally; the preset value is a voltage threshold set according to the design and operation requirements of the air conditioner, which is used to determine whether the power supply voltage is in the normal range; the external coil temperature reflects the working status of the outdoor heat exchanger. When the speed of the external fan drops due to undervoltage, the external coil temperature will change rapidly in a short time; the first time period is a set time period, which is used to determine the time range for monitoring the rate of change of the external coil temperature, so as to accurately obtain the temperature change trend and provide effective reference data for subsequent adjustment operations.

[0057] A high-precision voltage sensor can be used to obtain the power supply voltage of the air conditioner in real time, and compared with the preset value to determine whether it is lower than the preset value. When monitoring the temperature of the external coil, a temperature sensor such as a thermistor can be used to fit the external coil closely to measure the temperature value more accurately, and the data acquisition module can collect temperature data multiple times at a certain time interval within the first time period to calculate the temperature change rate. For example, the first time period can be set to 10 seconds, and the external coil temperature data is collected once per second within these 10 seconds, and then the change rate is calculated using the formula (temperature change rate = (last temperature value - initial temperature value) / time period).

[0058] S2: Perform a first adjustment on the duty cycle of the external fan drive motor according to the external coil temperature change rate. Within the second time period equal to the first time period, perform step S3 or step S4 according to the change direction of the external coil temperature change rate. In step S2, the external coil temperature change rate reflects the current comprehensive conditions of the outdoor heat exchange of the air conditioner and the operation of the external fan. According to this change rate, the duty cycle of the external fan drive motor is first adjusted. The adjustment of the duty cycle will affect the working power and speed of the external fan, and further affect the heat dissipation of the external coil. At the same time, considering that the external coil temperature change rate may change over time, within the second time period equal to the first time period, continue to monitor its change direction to determine whether to continue to execute the current adjustment strategy (execute step S3 or S4), so as to achieve dynamic adjustment of the air conditioning system, so that the system can maintain a relatively stable operating state under different working conditions, avoid frequent protection shutdowns caused by abnormal changes in the external coil temperature, and balance the system load and operation reliability.

[0059] The temperature change rate of the external coil reflects how fast the temperature of the external coil changes in unit time. A positive value indicates that the temperature is rising, and a negative value indicates that the temperature is falling. It directly reflects the degree of matching between the heat dissipation capacity of the external fan and the system load. The duty cycle refers to the proportion of the working time of the external fan drive motor in unit time. Adjusting the duty cycle can change the working power and speed of the motor, and then adjust the air volume of the external fan, affecting the heat dissipation effect of the external coil. The second time period is to ensure that the monitoring of the direction of the temperature change rate has the same time reference as the acquisition of the change rate, to ensure the consistency and accuracy of the adjustment strategy, so that the subsequent measures taken according to the direction of the temperature change rate are more reasonable and effective.

[0060] Specifically, the duty cycle can be adjusted through a pulse width modulation (PWM) controller, and the adjustment range of the duty cycle is determined according to the size and direction of the temperature change rate of the external coil. For example, if the temperature change rate is positive and large, it means that the temperature of the external coil rises rapidly, and the duty cycle needs to be reduced to reduce the speed of the external fan, reduce the air volume, and avoid excessive heat dissipation leading to excessive system load; conversely, if the temperature change rate is negative and the absolute value is large, the duty cycle can be appropriately increased. When monitoring the direction of the temperature change rate, the temperature data of the external coil can continue to be collected through the temperature sensor in the second time period, and the temperature change rate difference in adjacent time periods can be calculated, and the change direction can be determined based on the positive or negative value of the difference.

[0061] Wherein: S3: When the rate of change of the temperature of the external coil is positive, the compressor frequency is adjusted according to the ambient temperature and the rate of temperature rise of the external coil;

[0062] When the rate of change of the external coil temperature is positive, it means that the temperature of the external coil is still rising. At this time, it is necessary to consider adjusting the compressor frequency to balance the system load to prevent the external coil temperature from being too high and causing the refrigeration overload protection shutdown. Since the ambient temperature has an important impact on the heat dissipation of the external coil and the air conditioning refrigeration cycle, and the temperature rise rate of the external coil can also reflect the heat dissipation pressure of the current system, adjusting the compressor frequency based on these two factors can reasonably reduce the system load while ensuring the refrigeration effect, avoid system overload caused by excessive compressor frequency, and at the same time meet the actual refrigeration needs at different ambient temperatures, so that the air conditioner can maintain a relatively stable operation under adverse conditions such as undervoltage.

[0063] The ambient temperature is the temperature of the environment in which the air conditioner outdoor unit is located. It directly affects the heat exchange efficiency between the external coil and the outside world and the refrigeration cycle performance of the air conditioner. The external coil temperature rise rate is the speed at which the external coil temperature rises, which reflects the current heat dissipation pressure of the external coil and the load of the system refrigeration cycle. The compressor frequency determines the operating speed of the compressor. The higher the frequency, the greater the cooling capacity of the compressor, but it will also increase the system load and energy consumption.

[0064] S4: When the temperature change rate of the external coil is negative, if the compressor frequency is lower than the preset operating frequency, the compressor frequency is increased according to the temperature change rate of the external coil, the current compressor frequency and the preset operating frequency. If the compressor frequency is equal to the operating frequency, the duty cycle of the external fan drive motor is adjusted for the second time according to the ambient temperature and the current duty cycle of the external fan drive motor.

[0065] When the rate of change of the external coil temperature is negative, it means that the temperature of the external coil is decreasing, but the overall operation of the air conditioning system still needs to be considered at this time. If the compressor frequency is lower than the preset working frequency, it means that there is still a certain adjustment space to increase the compressor frequency to improve the cooling effect or balance the system load while ensuring the stable operation of the system. At this time, according to the rate of change of the external coil temperature (although it is negative, its absolute value also reflects the heat dissipation of the system) and the gap between the current compressor frequency and the preset working frequency, the compressor frequency can be increased to make the system better adapt to the current operation needs under undervoltage conditions, avoiding the cooling effect or unstable system operation caused by the compressor frequency being too low. If the compressor frequency is equal to the operating frequency, it means that the compressor frequency has reached the currently set upper limit. At this time, the system can no longer be further optimized by adjusting the compressor frequency. Therefore, it is necessary to perform a second adjustment on the duty cycle of the external fan drive motor according to the ambient temperature and the current duty cycle of the external fan drive motor to adjust the speed of the external fan and change the heat dissipation of the external coil. When the system provides sufficient heat dissipation for the external coil, the duty cycle of the external fan drive motor is reduced to reduce the speed of the external fan to save energy expenses, so that the system can maintain a good operating state under current conditions and avoid problems such as frequent shutdowns due to unreasonable parameters.

[0066] For the case of increasing the compressor frequency according to the external coil temperature change rate, the current compressor frequency and the preset working frequency, a frequency increase function can be pre-set, the input variables are the external coil temperature change rate (the larger the absolute value of the negative value, the better the heat dissipation effect, and the frequency can be appropriately increased), the difference between the current compressor frequency and the preset working frequency (the larger the difference, the larger the space for adjustment), the output is the adjustment amount of the compressor frequency, and the frequency increase is achieved through the variable frequency drive. When the second adjustment is required, a duty cycle adjustment mapping relationship can be established according to the ambient temperature and the current duty cycle. For example, when the ambient temperature is high, the duty cycle can be appropriately increased to enhance the heat dissipation capacity of the external fan; if the current duty cycle is already high, the duty cycle can be appropriately reduced according to the actual situation to avoid excessive heat dissipation affecting the system balance. At the same time, the duty cycle adjusted in combination with the ambient temperature can make the operation of the external fan more reasonable and meet the needs of the system under current conditions. This implementation method can flexibly adjust the compressor frequency or the external fan duty cycle under different conditions, give full play to the adjustment potential of each component, optimize the system operation parameters, and improve the adaptability and stability of the air conditioner under undervoltage conditions.

[0067] Preferably, first adjusting the duty cycle of the external fan drive motor according to the external coil temperature change rate includes:

[0068] Get the current supply voltage;

[0069] Determine the maximum operating duty cycle of the external fan at the current voltage based on the current power supply voltage;

[0070] During the operation of variable frequency air conditioners, the level of power supply voltage directly affects the working state of the external fan drive motor. After obtaining the current power supply voltage, the maximum working duty cycle of the external fan under the current voltage is determined based on this voltage to ensure that the external fan can exert the maximum heat dissipation capacity as much as possible according to actual needs without exceeding its allowable working range. Because the power supply voltage is different, the maximum duty cycle that the external fan motor can withstand will vary. Determining the maximum working duty cycle can provide a safe and effective upper limit for the subsequent duty cycle adjustment according to the temperature change rate of the external coil, ensuring that the external fan will not malfunction or be damaged due to excessive duty cycle during the adjustment process. At the same time, a clear boundary condition is established for the subsequent duty cycle increase operation according to the temperature change rate, so that the adjustment process is based on basis and safe and controllable, thereby achieving the purpose of optimizing the operation of the air conditioning system and reducing unnecessary shutdowns caused by voltage problems.

[0071] The current power supply voltage can be monitored and obtained in real time through a high-precision voltage sensor, and the measured voltage value can be transmitted to the air conditioner control system. The system pre-stores the data table or calculation formula of the maximum working duty cycle of the external fan corresponding to different power supply voltages. The maximum working duty cycle can be calculated based on the current power supply voltage by querying the data table or substituting it into the formula. For example, when the power supply voltage is 220V, the corresponding maximum working duty cycle is 80%; when the power supply voltage drops to 190V, the maximum working duty cycle is calculated to be 70% through the formula.

[0072] When the temperature change rate of the external coil exceeds the first temperature rise rate threshold, the adjustment level is divided based on the temperature change rate of the external coil, and the duty cycle of the external fan drive motor is increased based on the adjustment level until it is equal to the maximum working duty cycle;

[0073] When the temperature change rate of the external coil exceeds the first temperature rise rate threshold, it indicates that the temperature of the external coil rises rapidly and the heat dissipation pressure of the system is large. At this time, the heat dissipation capacity of the external fan needs to be increased to alleviate this situation. The temperature change rate of the external coil is divided into different adjustment levels, and the duty cycle of the external fan drive motor is gradually increased according to the adjustment level until the maximum working duty cycle is reached, so that the external fan speed can be accurately controlled. Through this hierarchical adjustment method, the heat dissipation capacity of the external fan is matched with the actual heat dissipation demand of the system, avoiding poor heat dissipation effect or excessive system load fluctuation due to excessive or small duty cycle adjustment. At the same time, gradually increasing the duty cycle to the maximum working duty cycle, while ensuring the heat dissipation effect, can take into account the stability of the system and the rational use of energy, prevent the sudden and substantial increase in the duty cycle from causing impact on the motor and other components, or prevent the inability to effectively reduce the temperature of the external coil due to insufficient duty cycle increase, thereby reducing the number of protection shutdowns triggered by excessive external coil temperature, and improving the operation continuity of the air conditioner under adverse conditions such as undervoltage.

[0074] Specifically, multiple adjustment levels are pre-set, and the corresponding duty cycle increase amplitude and time interval are determined for each level. For example, when the temperature change rate of the external coil exceeds 10%-20% of the first temperature rise rate threshold, it is the first-level adjustment, and the duty cycle is increased by 5%; when it exceeds 20%-30%, it is the second-level adjustment, and the duty cycle is increased by 10%; and so on, by real-time monitoring of the temperature change rate of the external coil, when it exceeds the first temperature rise rate threshold, the adjustment level is determined, and the duty cycle is gradually increased according to the set increase amplitude until the maximum working duty cycle is reached or the temperature change rate of the external coil returns to normal.

[0075] When the external coil temperature change rate does not exceed the second temperature rise rate threshold, the current duty cycle of the external fan drive motor is maintained when the current external coil temperature value is less than the air conditioner shutdown temperature.

[0076] Specifically, the second temperature rise rate threshold is lower than the first temperature rise rate threshold. When the temperature change rate of the external coil does not exceed the second temperature rise threshold, it means that the temperature rise rate of the external coil is within the range allowed by the system. At this time, the heat dissipation can basically meet the cooling demand, and the external fan does not need to further increase the heat dissipation capacity. Maintaining the current duty cycle of the external fan drive motor when the current external coil temperature value is less than the air conditioner shutdown temperature is to maintain the stability and economy of the system operation, avoid unstable operation or energy waste of the external fan due to unnecessary duty cycle adjustment, and ensure that the system can continue to operate stably under the current working conditions, and will not affect the cooling effect or cause other potential problems due to frequent changes in the duty cycle, such as compressor load fluctuations. By maintaining the current duty cycle, the system operates in a relatively stable state, and the operating parameters of each component are kept in a more reasonable range, thereby reducing the risk of system failures caused by parameter fluctuations and improving the reliability and service life of the air conditioner operation. For example, during system operation, if the monitored external coil temperature change rate is 0.5°C per minute, which does not exceed the second temperature rise threshold of 1°C / minute, and the current external coil temperature is 40°C, which is lower than the air conditioner shutdown temperature of 60°C, the external fan continues to operate at the current duty cycle.

[0077] Furthermore, the regulation levels are divided based on the temperature change rate of the external coil, and the duty cycle of the external fan drive motor is increased based on the regulation level until it is equal to the maximum working duty cycle, satisfying the relationship:

[0078] D t+1 =min(D max ,D t +α·ΔD·(V t -V th )·γ);

[0079] Among them, D t+1 represents the target duty cycle of the fan drive motor in the next time period, Dt Indicates the current duty cycle of the external fan drive motor, D max Indicates the maximum duty cycle of the external fan drive motor under the current voltage, V t Indicates the current external coil temperature change rate, V th represents the first temperature rise rate threshold, α represents the adjustment coefficient, where α=k·(V nominal -V actual ), k is used to adjust the impact of voltage drop on duty cycle, V nominal Indicates the rated working voltage of the air conditioner, V actual represents the current supply voltage, ΔD represents the fixed increment selected according to the adjustment level, γ represents the ambient temperature compensation factor, γ=1+β(T env -T base1 ), T env Indicates the current ambient temperature, T base1 represents the first reference temperature, and β represents the temperature influence coefficient.

[0080] Among them, the temperature change rate of the outer coil is V t Indicates the increase or decrease of the temperature of the inner and outer coils per unit time, reflecting the urgency of the system's heat dissipation needs; the first temperature rise rate threshold V th It is the reference value for judging whether the temperature rise of the external coil is too fast, and is used to trigger the duty cycle increase mechanism. The adjustment coefficient (α) is determined by the adjustment intensity k and the voltage drop effect. The adjustment intensity k is used to control the sensitivity of the duty cycle to voltage changes, and the voltage drop effect is determined by the rated voltage V nominal The actual voltage V actual The fixed increment (ΔD) is the duty cycle increase amplitude selected according to the adjustment level, which is used to achieve a step-by-step increase in the duty cycle. The ambient temperature compensation factor (γ) is determined by the ambient temperature T env , the first reference temperature T base1 Calculated together with the temperature influence coefficient β, it is used to compensate for the influence of ambient temperature changes on the heat dissipation effect; the maximum working duty cycle D max The maximum duty cycle of the external fan is determined based on the current power supply voltage to ensure that the external fan operates within a safe range. The current duty cycle D t is the actual working duty cycle of the external fan, which is used to calculate the next target duty cycle; the target duty cycle D t+1 It indicates the duty cycle that the fan drive motor is planned to achieve in the next time period. It is calculated by the formula and its value does not exceed the maximum working duty cycle.

[0081] During the operation of the variable frequency air conditioner, the duty cycle of the external fan drive motor is dynamically adjusted based on the above formula by real-time monitoring of the temperature change rate of the external coil, combined with factors such as the power supply voltage and ambient temperature. When the temperature of the external coil rises rapidly, the duty cycle is gradually increased to the maximum working duty cycle to enhance the heat dissipation capacity, alleviate the temperature rise trend, and avoid triggering the overload protection shutdown. If the power supply voltage drops, the adjustment coefficient (α) increases, and the duty cycle increase increases accordingly, further enhancing the heat dissipation effect and compensating for the decrease in heat dissipation capacity caused by insufficient voltage. At the same time, the ambient temperature compensation factor (γ) enables the duty cycle adjustment to automatically adapt to changes in ambient temperature, ensuring effective heat dissipation in high temperature environments.

[0082] Preferably, adjusting the compressor frequency according to the ambient temperature and the external coil temperature rise rate includes:

[0083] A second reference temperature for adjusting the frequency of the compressor is set based on the ambient temperature, wherein the second reference temperature is used to distinguish between strong and weak working conditions of the heat dissipation efficiency of the external coil;

[0084] When the ambient temperature is higher than the second reference temperature, a frequency correction factor is generated which is positively correlated with the difference between the ambient temperature and the second reference temperature, and the frequency correction factor is used to quantify the inhibitory effect of the high temperature environment on the heat dissipation capacity of the external coil;

[0085] If the ambient temperature is higher than the second reference temperature and the current compressor frequency exceeds a preset proportional range of the rated frequency, the compressor frequency is adjusted by gradient attenuation based on the difference between the ambient temperature and the second reference temperature, and the amplitude of the gradient attenuation increases as the difference between the ambient temperature and the second reference temperature increases;

[0086] If the ambient temperature is lower than or equal to the reference temperature threshold, the current compressor frequency is maintained and the monitoring sensitivity of the external coil temperature rise rate is dynamically adjusted according to the frequency correction factor. When the growth acceleration of the external coil temperature rise rate is monitored to exceed the growth threshold associated with the frequency correction factor, the compressor frequency adjustment is re-triggered.

[0087] Among them, the ambient temperature refers to the temperature of the outdoor environment where the air conditioner is located, which affects the heat dissipation efficiency and refrigeration cycle effect of the external coil; the second reference temperature is a temperature value pre-set according to the air conditioner design and the performance of the external coil, which is used to judge the strength of the heat dissipation condition of the external coil; the frequency correction factor reflects the degree of inhibition of the heat dissipation capacity of the external coil in the high temperature environment, which is positively correlated with the difference between the ambient temperature and the second reference temperature, and is used to adjust the compressor frequency; the preset proportional range of the rated frequency is the frequency fluctuation range allowed when the compressor is operating normally, and adjustment is required when it exceeds this range; gradient attenuation adjustment is a method of gradually adjusting the compressor frequency as the difference between the ambient temperature and the reference temperature changes, ensuring that the adjustment process is smooth and matches actual needs; monitoring sensitivity refers to the system's response to changes in the temperature rise rate of the external coil, which can be dynamically adjusted according to the frequency correction factor; the growth threshold is the critical value of the acceleration of the growth rate of the temperature rise rate of the external coil. When this value is exceeded, the compressor frequency adjustment needs to be re-triggered.

[0088] Specifically, when the ambient temperature and the temperature rise rate of the external coil change, the compressor frequency needs to be adjusted accordingly to balance the system load and heat dissipation capacity. First, the second reference temperature is set based on the ambient temperature to distinguish whether the external coil is in a strong heat dissipation or weak heat dissipation condition. When the ambient temperature is higher than the second reference temperature, the high temperature will inhibit the heat dissipation of the external coil. At this time, a frequency correction factor positively correlated with the difference between the ambient temperature and the reference temperature is generated to quantify this inhibition. If the compressor frequency is too high at this time, the compressor frequency is adjusted by gradient attenuation based on the difference between the two. The gradient attenuation amplitude increases as the difference increases to reduce the system load and prevent overload. If the ambient temperature is lower than or equal to the reference temperature, the current compressor frequency is maintained, and the monitoring sensitivity of the temperature rise rate of the external coil is dynamically adjusted according to the frequency correction factor. When the acceleration of the temperature rise rate growth exceeds the growth threshold associated with the frequency correction factor, the compressor frequency adjustment is re-triggered. This ensures that the system reasonably adjusts the compressor frequency under different ambient temperatures and external coil heat dissipation conditions to avoid overload shutdown due to poor heat dissipation or frequent adjustments that affect system stability, thereby ensuring the reliable operation of the air-conditioning system and reducing the number of unnecessary shutdowns.

[0089] For example, a second reference temperature value, such as 35°C, is pre-set in the air-conditioning control system. The ambient temperature is obtained in real time through the temperature sensor. When the ambient temperature is higher than 35°C, the difference between the two is calculated, and the frequency correction factor is generated according to the formula, for example, the frequency correction factor = 1 + 0.02 × (ambient temperature - 35°C). If the current compressor frequency exceeds 80% of the rated frequency, it is adjusted according to the gradient attenuation, and the frequency is attenuated by 5% for every 5°C difference until the frequency returns to a reasonable range. At the same time, when the ambient temperature is lower than or equal to 35°C, the monitoring sensitivity is adjusted according to the frequency correction factor. For example, when the frequency correction factor is 1.2, the monitoring sensitivity is increased by 20%, so as to more accurately monitor the changes in the temperature rise rate of the external coil.

[0090] Furthermore, the gradient attenuation adjustment of the compressor frequency based on the difference between the ambient temperature and the second reference temperature satisfies the relationship:

[0091]

[0092] Among them, f new represents the compressor frequency after gradient attenuation adjustment, f current Indicates the current compressor frequency, T env -T base2 represents the difference between the ambient temperature and the second reference temperature, μ represents the attenuation coefficient for controlling the temperature difference on the frequency adjustment, n represents the influence of the difference between the ambient temperature and the second reference temperature on the frequency adjustment, τ represents the attenuation coefficient for adjusting the influence of the difference between the ambient temperature and the second reference temperature on the frequency, Indicates the rate of change of ambient temperature.

[0093] Specifically, μ(T env -T base2 ) n This term makes the effect of temperature difference on frequency adjustment nonlinear. If the temperature difference is small, the frequency change is small; if the temperature difference is large, the frequency change will be more significant. By adjusting n, the sensitivity of temperature difference to frequency adjustment can be controlled. This term is used to simulate the "saturation" effect of the temperature difference after a certain value, that is, when the temperature difference reaches a certain level, the influence of the temperature difference on the frequency will gradually weaken, and the attenuation rate is controlled by the parameter τ; Taking the rate of change of temperature into consideration, if the ambient temperature changes rapidly (for example, the ambient temperature suddenly rises), the frequency adjustment needs to be additionally accelerated or slowed down to adapt to the change of temperature fluctuation.

[0094] In general, by constructing a mathematical model that integrates the nonlinear attenuation of temperature difference, exponential attenuation and the influence of temperature change rate, the reduction amplitude of compressor frequency can be accurately controlled. This model can dynamically adjust the compressor frequency according to the difference between the ambient temperature and the second reference temperature and the change trend to balance the system heat dissipation demand and load capacity. When the ambient temperature is significantly higher than the second reference temperature, the nonlinear attenuation term and exponential attenuation term in the model will amplify the influence of temperature difference on frequency regulation, causing the compressor frequency to drop significantly, thereby reducing system heat generation and relieving the heat dissipation pressure of the external coil; at the same time, the temperature change rate term takes into account the dynamic changes of ambient temperature. When the ambient temperature rises rapidly, the frequency attenuation amplitude will be further increased to quickly adapt to environmental changes and avoid system overheating. The purpose of this adjustment is to actively reduce the compressor frequency in a high temperature environment, prevent the system from overloading or frequently triggering protection shutdown due to poor heat dissipation, and ensure the stable operation of the air-conditioning system. Its function is to dynamically optimize the operating frequency of the compressor under different ambient temperature conditions, especially under high temperature conditions, so that the system can ensure the cooling effect while avoiding heat dissipation problems caused by excessive compressor frequency.

[0095] Preferably, the step of increasing the compressor frequency according to the external coil temperature change rate, the current compressor frequency and the preset operating frequency comprises:

[0096] Obtain the current compressor frequency, and calculate the frequency ratio between the current compressor frequency and the preset operating frequency;

[0097] If the product of the absolute value of the temperature change rate of the outer coil and the frequency ratio exceeds a preset dynamic response threshold, a frequency increase operation is performed;

[0098] The frequency increase operation includes:

[0099] The compressor frequency is gradually increased according to the graded proportional relationship between the absolute value of the rate of change of the temperature of the outer coil and the frequency ratio;

[0100] When executing the frequency increase operation, continuously monitor the absolute value of the temperature change rate of the external coil, and if the absolute value is lower than a preset negative maintenance threshold, terminate the frequency increase operation until the absolute value recovers to be above the negative maintenance threshold, and then re-execute the frequency increase operation until the compressor frequency reaches the preset operating frequency;

[0101] If the rate of change of the temperature of the outer coil turns to a positive value during the frequency increase operation, the operation is immediately terminated and the compressor frequency is adjusted by gradient attenuation based on the difference between the ambient temperature and the second reference temperature.

[0102] The frequency ratio is the ratio of the current compressor frequency to the preset operating frequency, which is used to measure the ratio of the current compressor operating frequency to the maximum allowable frequency; the dynamic response threshold is a pre-set threshold used to determine whether it is necessary to start the frequency increase operation; the graded proportional relationship refers to the pre-set multiple frequency increase amplitude levels according to different combinations of the absolute value of the external coil temperature change rate and the frequency ratio, which are used to control the speed and amplitude of the frequency increase; the negative maintenance threshold is the minimum value that the absolute value of the external coil temperature change rate must maintain during the frequency increase process. If it is lower than this value, the frequency increase is suspended to ensure that the system operates within an appropriate temperature change range; the preset operating frequency is the maximum operating frequency allowed by the compressor, which is used to limit the maximum operating speed of the compressor and can be determined by the air conditioning parameters selected by the user (such as air conditioning temperature, etc.); the difference between the ambient temperature and the second reference temperature can reflect the degree of deviation of the current ambient temperature from the air conditioning design reference temperature; the gradient attenuation adjustment is a method of gradually reducing the compressor frequency according to the difference between the ambient temperature and the reference temperature, which is used to adjust the compressor frequency to adapt to ambient temperature changes.

[0103] Specifically, when the compressor frequency is increased, when the product of the absolute value of the temperature change rate of the external coil and the frequency ratio exceeds the dynamic response threshold, the frequency increase operation is performed to gradually increase the compressor frequency until the preset working frequency is reached. This process ensures that the increase in the compressor frequency is controllable by gradually increasing the compressor frequency according to the graded proportional relationship between the absolute value of the temperature change rate of the external coil and the frequency ratio, and avoids excessive system load or other instability caused by a sudden and substantial increase in frequency. At the same time, the absolute value of the temperature change rate of the external coil is continuously monitored during the frequency increase process. If it is lower than the negative maintenance threshold, the frequency increase is terminated until it recovers to above the threshold and the frequency increase operation is performed again to ensure that the system operates within an appropriate temperature change range. If the temperature change rate of the external coil turns to a positive value, it means that the heat dissipation pressure of the system is reduced. At this time, the frequency increase operation is terminated immediately, and the compressor frequency is adjusted to a more appropriate level according to the difference between the ambient temperature and the second reference temperature. To prevent over-refrigeration or unstable system operation. In general, the purpose of the entire step is to dynamically adjust the compressor frequency according to the real-time external coil temperature changes and the current operating status of the system, so that it can avoid overload or unnecessary energy consumption while meeting the cooling needs, enhance the stability and reliability of the system, reduce the number of unnecessary shutdowns caused by improper frequency adjustment, and improve the user experience.

[0104] For example, parameters such as dynamic response threshold, negative maintenance threshold, graded proportional relationship and preset working frequency are pre-set in the air conditioning control system. The frequency ratio is calculated by real-time monitoring of the temperature change rate of the external coil and the current compressor frequency. When the product of the two exceeds the dynamic response threshold, the absolute value of the temperature change rate is divided into three levels of low, medium and high according to the graded proportional relationship, corresponding to 10%, 20% and 30% of the frequency increase amplitude respectively, and the corresponding amplitude is gradually increased each time the frequency is increased until the preset working frequency is reached. During the frequency increase process, the absolute value of the temperature change rate of the external coil is continuously monitored. If it is lower than the negative maintenance threshold, for example, set to 0.2℃ / min, the frequency increase is suspended until it recovers to above this value and continues to increase. If the temperature change rate turns to a positive value during the increase process, the increase is terminated immediately, and the gradient attenuation adjustment is performed according to the difference between the ambient temperature and the second reference temperature, for example, 10% attenuation when the difference is 5℃, and 20% attenuation when the difference is 10℃.

[0105] Furthermore, the compressor frequency is gradually increased according to the graded proportional relationship between the absolute value of the external coil temperature change rate and the frequency ratio, satisfying the relationship:

[0106]

[0107] Among them, f new Indicates the compressor frequency after the increase, f current Indicates the current compressor frequency. Δf is used to control the amplitude of the compressor frequency change. ratio Indicates the frequency ratio between the current compressor frequency and the preset operating frequency. represents the attenuation coefficient that controls the rate of gradual increase, and t represents the time variable.

[0108] Among them, f new It is the new compressor frequency obtained after calculation, which is used to guide the next operating frequency of the compressor; f current is the actual operating frequency of the compressor, which provides the initial value for frequency adjustment; Δf is an adjustment parameter used to control the amplitude of each frequency adjustment to ensure that the frequency change is within a reasonable range; f ratio It is the ratio of the current frequency to the preset operating frequency, reflecting the ratio of the current frequency to the maximum allowable frequency, and is used to determine the urgency and magnitude of frequency adjustment; It is the attenuation coefficient that controls the frequency increase rate and determines the speed of the frequency adjustment process. The value will make the frequency approach the target value faster; t is the time variable, which is used to track the duration of the frequency adjustment process and ensure that the frequency adjustment is carried out according to the set time characteristics. These parameters work together to ensure that the adjustment of the compressor frequency not only meets the cooling needs of the system, but also ensures the stability of the system and the safety of the equipment. In general, the formula is based on the ratio of the external coil temperature change rate and the current frequency. The exponential function controls the speed of frequency increase so that the frequency gradually approaches the target value.

[0109] Preferably, performing a second adjustment on the duty cycle of the external fan drive motor according to the ambient temperature and the current duty cycle of the external fan drive motor includes:

[0110] If the current ambient temperature is not higher than the external coil temperature, the current duty cycle of the external fan drive motor is set to the lowest value;

[0111] If the current ambient temperature is higher than the external coil temperature, the degree of increase in the external coil temperature caused by the current ambient temperature is calculated based on the difference between the current ambient temperature and the external coil temperature, and the degree of decrease in the external coil temperature caused by the current duty cycle of the external fan drive motor is calculated based on the current duty cycle of the external fan drive motor and the ambient temperature;

[0112] Based on the difference between the degree of temperature drop and the degree of temperature rise, the duty cycle of the external fan drive motor is reduced until the degree of temperature drop and the degree of temperature rise are balanced.

[0113] During the operation of the variable frequency air conditioner, the duty cycle of the external fan drive motor needs to be adjusted according to the relative relationship between the ambient temperature and the external coil temperature. When the ambient temperature is not higher than the external coil temperature, it means that the current external coil has a good heat dissipation effect and is sufficient to cope with the system load. At this time, the external fan duty cycle is set to the minimum value to reduce unnecessary energy consumption and maintain stable operation of the system. When the ambient temperature is higher than the external coil temperature, the high ambient temperature will have an additional heating effect on the external coil. At this time, it is necessary to comprehensively consider the difference between the ambient temperature and the external coil temperature (the degree of heating) and the contribution of the current external fan duty cycle to heat dissipation (the degree of cooling). By comparing the degree of heating and the degree of cooling, the external fan duty cycle is adjusted accordingly until the two reach a balance. The principle of this step is based on the basic principles of thermodynamics and the heat dissipation requirements of the air conditioning system. By dynamically adjusting the external fan duty cycle to balance the heat dissipation and heating factors of the external coil, the system is ensured to operate efficiently and stably under different ambient temperature conditions, reduce the increase in energy consumption and system instability caused by insufficient or excessive heat dissipation, and thus improve the operating efficiency, comfort and reliability of the air conditioner.

[0114] When it is monitored that the current ambient temperature is not higher than the temperature of the external coil, for example, the ambient temperature is 30°C and the temperature of the external coil is 32°C, the air-conditioning control system will directly set the duty cycle of the external fan drive motor to a preset minimum value, assuming it is 40%. The reason for this is that the current ambient temperature is relatively low, and the temperature of the external coil itself can ensure a good heat dissipation effect. The external fan does not need to run at a higher duty cycle. Reducing the duty cycle can reduce energy consumption while maintaining stable operation of the system.

[0115] When the ambient temperature is higher than the temperature of the external coil, for example, the ambient temperature is 35°C and the external coil temperature is 30°C, the air conditioning control system will first evaluate the degree of temperature rise of the external coil temperature caused by the current ambient temperature. Here, the ambient temperature is 5°C higher than the external coil temperature. This 5°C temperature difference means that the high ambient temperature will cause the external coil temperature to rise to a certain extent, which is the degree of temperature rise. At the same time, the control system will also combine the current duty cycle of the external fan drive motor (assuming it is 60%) and the ambient temperature to evaluate the cooling degree of the current external fan. When the duty cycle is 60%, the external fan runs at this ratio, and its heat dissipation effect on the external coil is certain at the current ambient temperature. For example, it can be understood that when the external fan runs at a duty cycle of 60%, it can produce a cooling effect on the external coil related to the current ambient temperature. Assume that the cooling degree at this time is 6°C (this is only a simplified understanding, it will be more complicated in practice, so a specific temperature is used as an example).

[0116] The air conditioning control system compares the degree of temperature rise (5℃) and the degree of temperature drop (6℃), and finds that the degree of temperature drop is greater than the degree of temperature rise, indicating that the current duty cycle of the external fan is too large, and the heat dissipation capacity exceeds the temperature rise caused by the high ambient temperature. Therefore, the control system will reduce the duty cycle of the external fan drive motor, assuming that it is reduced by 5% each time, that is, from 60% to 55%. At this time, the degree of temperature drop is evaluated again. Assuming that the duty cycle is 55%, the degree of temperature drop is 5.5℃, which is still greater than the degree of temperature rise of 5℃. The duty cycle is further reduced to 50%. At this time, the degree of temperature drop may be 5℃, which is balanced with the degree of temperature rise of 5℃. Therefore, the control system keeps the duty cycle of the external fan drive motor running at 50%; through this adjustment, the second adjustment of the duty cycle of the external fan drive motor based on the ambient temperature and the duty cycle of the external fan is realized, so that the temperature of the external coil can be stabilized within a suitable range, ensuring the efficient operation of the air conditioning system, and avoiding problems such as increased energy consumption or insufficient heat dissipation caused by unreasonable duty cycle.

[0117] A control system for undervoltage of an outdoor AC motor of a variable frequency air conditioner, the control system is applied to the control method as described above, and the control system comprises:

[0118] The detection module is used to obtain the power supply voltage of the air conditioner. When the power supply voltage is lower than a preset value, the temperature of the external coil is continuously monitored and the rate of change of the temperature of the internal and external coils in the first time period is recorded;

[0119] The adjustment module is used to perform a first adjustment on the duty cycle of the external fan drive motor according to the external coil temperature change rate, and perform a first operation or a second operation according to the change direction of the external coil temperature change rate within a second time period equal to the first time period, wherein:

[0120] The first operation submodule is used to adjust the compressor frequency according to the ambient temperature and the temperature rise rate of the external coil when the temperature change rate of the external coil is positive;

[0121] The second operating submodule is used to increase the compressor frequency according to the external coil temperature change rate, the current compressor frequency and the preset operating frequency when the external coil temperature change rate is negative, if the compressor frequency is lower than the preset operating frequency; if the compressor frequency is equal to the operating frequency, the duty cycle of the external fan drive motor is adjusted for the second time according to the ambient temperature and the current duty cycle of the external fan drive motor.

[0122] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0123] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for controlling undervoltage of an outdoor AC motor of a variable frequency air conditioner, characterized in that: The control method comprises: Obtain the power supply voltage of the air conditioner. When the power supply voltage is lower than the preset value, continuously monitor the temperature of the external coil and record the temperature change rate of the internal and external coils in the first time period. A first adjustment is performed on the duty cycle of the external fan drive motor according to the external coil temperature change rate, and a first operation or a second operation is performed according to the change direction of the external coil temperature change rate within a second time period equal to the first time period, wherein: The first operation includes adjusting the compressor frequency according to the ambient temperature and the external coil temperature rise rate when the external coil temperature change rate is positive; The second operation includes, when the rate of change of the external coil temperature is negative, if the compressor frequency is lower than the preset operating frequency, increasing the compressor frequency according to the rate of change of the external coil temperature, the current compressor frequency and the preset operating frequency; if the compressor frequency is equal to the operating frequency, performing a second adjustment on the duty cycle of the external fan drive motor according to the ambient temperature and the current duty cycle of the external fan drive motor.

2. The control method according to claim 1, characterized in that: The first adjustment of the duty cycle of the external fan drive motor according to the external coil temperature change rate includes: Get the current supply voltage; Determine the maximum operating duty cycle of the external fan at the current voltage based on the current power supply voltage; When the temperature change rate of the external coil exceeds the first temperature rise rate threshold, the adjustment level is divided based on the temperature change rate of the external coil, and the duty cycle of the external fan drive motor is increased based on the adjustment level until it is equal to the maximum working duty cycle; When the external coil temperature change rate does not exceed the second temperature rise rate threshold, the current duty cycle of the external fan drive motor is maintained when the current external coil temperature value is less than the air conditioner shutdown temperature.

3. The control method according to claim 2, characterized in that: The regulation level is divided based on the temperature change rate of the external coil, and the duty cycle of the external fan drive motor is increased based on the regulation level until it is equal to the maximum working duty cycle, satisfying the relationship: D t+1 =min(D max ,D t +α·ΔD·(V t -V th )·c); Among them, D t+1 represents the target duty cycle of the fan drive motor in the next time period, D t Indicates the current duty cycle of the external fan drive motor, D max Indicates the maximum duty cycle of the external fan drive motor under the current voltage, V t Indicates the current external coil temperature change rate, V th represents the first temperature rise rate threshold, α represents the adjustment coefficient, where α=k·(V nominal -V actual ), k is used to adjust the impact of voltage drop on duty cycle, V nominal Indicates the rated working voltage of the air conditioner, V actual represents the current supply voltage, ΔD represents the fixed increment selected according to the adjustment level, γ represents the ambient temperature compensation factor, γ=1+β(T env -T base1 ), T env Indicates the current ambient temperature, T base1 represents the first reference temperature, and β represents the temperature influence coefficient.

4. The control method according to claim 1, characterized in that: Adjusting the compressor frequency according to the ambient temperature and the external coil temperature rise rate includes: A second reference temperature for adjusting the frequency of the compressor is set based on the ambient temperature, wherein the second reference temperature is used to distinguish between strong and weak working conditions of the heat dissipation efficiency of the external coil; When the ambient temperature is higher than the second reference temperature, a frequency correction factor is generated which is positively correlated with the difference between the ambient temperature and the second reference temperature, and the frequency correction factor is used to quantify the inhibitory effect of the high temperature environment on the heat dissipation capacity of the external coil; If the ambient temperature is higher than the second reference temperature and the current compressor frequency exceeds a preset proportional range of the rated frequency, the compressor frequency is adjusted by gradient attenuation based on the difference between the ambient temperature and the second reference temperature, and the amplitude of the gradient attenuation increases as the difference between the ambient temperature and the second reference temperature increases; If the ambient temperature is lower than or equal to the reference temperature threshold, the current compressor frequency is maintained and the monitoring sensitivity of the external coil temperature rise rate is dynamically adjusted according to the frequency correction factor. When the growth acceleration of the external coil temperature rise rate is monitored to exceed the growth threshold associated with the frequency correction factor, the compressor frequency adjustment is re-triggered.

5. The control method according to claim 4, characterized in that: The gradient attenuation adjustment of the compressor frequency based on the difference between the ambient temperature and the second reference temperature satisfies the relationship: Among them, f new represents the compressor frequency after gradient attenuation adjustment, f current Indicates the current compressor frequency, T env -T base2 represents the difference between the ambient temperature and the second reference temperature, μ represents the attenuation coefficient for controlling the temperature difference on the frequency adjustment, n represents the influence of the difference between the ambient temperature and the second reference temperature on the frequency adjustment, τ represents the attenuation coefficient for adjusting the influence of the difference between the ambient temperature and the second reference temperature on the frequency, Indicates the rate of change of ambient temperature.

6. The control method according to claim 1, characterized in that: The step of increasing the compressor frequency according to the external coil temperature change rate, the current compressor frequency and the preset operating frequency includes: Obtain the current compressor frequency, and calculate the frequency ratio between the current compressor frequency and the preset operating frequency; If the product of the absolute value of the temperature change rate of the outer coil and the frequency ratio exceeds a preset dynamic response threshold, a frequency increase operation is performed; The frequency increase operation includes: The compressor frequency is gradually increased according to the graded proportional relationship between the absolute value of the rate of change of the temperature of the outer coil and the frequency ratio; When executing the frequency increase operation, continuously monitor the absolute value of the temperature change rate of the external coil, and if the absolute value is lower than a preset negative maintenance threshold, terminate the frequency increase operation until the absolute value recovers to be above the negative maintenance threshold, and then re-execute the frequency increase operation until the compressor frequency reaches the preset operating frequency; If the rate of change of the temperature of the outer coil turns to a positive value during the frequency increase operation, the operation is immediately terminated and the compressor frequency is adjusted by gradient attenuation based on the difference between the ambient temperature and the second reference temperature.

7. The control method according to claim 6, characterized in that: The compressor frequency is gradually increased according to the graded proportional relationship between the absolute value of the external coil temperature change rate and the frequency ratio, satisfying the relationship: Among them, f new Indicates the compressor frequency after the increase, f current Indicates the current compressor frequency. Δf is used to control the amplitude of the compressor frequency change. ratio Indicates the frequency ratio between the current compressor frequency and the preset operating frequency. represents the attenuation coefficient that controls the rate of gradual increase, and t represents the time variable.

8. The control method according to claim 1, characterized in that: The second adjustment of the duty cycle of the external fan drive motor according to the ambient temperature and the current duty cycle of the external fan drive motor includes: If the current ambient temperature is not higher than the external coil temperature, the current duty cycle of the external fan drive motor is set to the lowest value; If the current ambient temperature is higher than the external coil temperature, the degree of increase in the external coil temperature caused by the current ambient temperature is calculated based on the difference between the current ambient temperature and the external coil temperature, and the degree of decrease in the external coil temperature caused by the current duty cycle of the external fan drive motor is calculated based on the current duty cycle of the external fan drive motor and the ambient temperature; Based on the difference between the degree of temperature drop and the degree of temperature rise, the duty cycle of the external fan drive motor is reduced until the degree of temperature drop and the degree of temperature rise are balanced.

9. A control system for undervoltage of outdoor AC motor of variable frequency air conditioner, characterized in that: The control system is applied to the control method according to any one of claims 1 to 8, and the control system comprises: The detection module is used to obtain the power supply voltage of the air conditioner. When the power supply voltage is lower than a preset value, the temperature of the external coil is continuously monitored and the rate of change of the temperature of the internal and external coils in the first time period is recorded; The adjustment module is used to perform a first adjustment on the duty cycle of the external fan drive motor according to the external coil temperature change rate, and perform a first operation or a second operation according to the change direction of the external coil temperature change rate within a second time period equal to the first time period, wherein: The first operation submodule is used to adjust the compressor frequency according to the ambient temperature and the temperature rise rate of the external coil when the temperature change rate of the external coil is positive; The second operating submodule is used to increase the compressor frequency according to the external coil temperature change rate, the current compressor frequency and the preset operating frequency when the external coil temperature change rate is negative, if the compressor frequency is lower than the preset operating frequency; if the compressor frequency is equal to the operating frequency, the duty cycle of the external fan drive motor is adjusted for the second time according to the ambient temperature and the current duty cycle of the external fan drive motor.

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