Air conditioner and its fan control method

Abstract

This application discloses an air conditioner and its fan control method. The method determines the fundamental harmonic current command based on the quadrature-axis current command value and the harmonic characteristics of the back electromotive force (EMF). It eliminates the need for complex algorithms such as torque observers, repetitive control, or iterative learning control, generating the reference value for harmonic injection through simple calculations. Based on this, the method extracts the amplitude of the sixth harmonic torque fluctuation based on the electrical angular velocity, and uses a preset command value as the target value and the amplitude of the sixth harmonic torque fluctuation as the feedback value for closed-loop feedback control to obtain the current correction harmonic command value. This achieves online monitoring and dynamic compensation of the actual operating state of the fan motor. This closed-loop feedback control uses speed fluctuations as the direct feedback quantity, without relying on precise identification of fan motor parameters. It effectively eliminates residual torque pulsation caused by individual differences in the back EMF harmonics of the fan motor, temperature drift, and flux attenuation, significantly improving the robustness and consistency of torque pulsation suppression.

Description

Technical Field

[0001] This application relates to the field of air conditioning technology, and in particular to an air conditioner and its fan control method. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) are widely used in household appliances such as indoor and outdoor fans of air conditioners due to their advantages of high efficiency, high power density, and wide speed range. Among them, surface-mounted PMSMs (SPMSMs) have become the preferred solution for air conditioning fan systems due to their simple structure, low cost, and convenient control.

[0003] Ideally, the back electromotive force (EMF) of a surface-mounted permanent magnet synchronous motor is sinusoidal, and a constant electromagnetic torque can be generated when a sinusoidal current is applied. However, in actual motors, factors such as magnetic circuit saturation, uneven distribution of permanent magnets, winding space compression, and manufacturing process deviations inevitably result in harmonic components in the back EMF waveform, especially the 5th and 7th harmonics. These harmonic components interact with the fundamental current, generating 6th and 12th electromagnetic torque pulsations through cross-coupling effects. These torque pulsations are transmitted to the fan blades via a mechanical transmission chain, inducing broadband aerodynamic noise within the narrow volute space, thus compromising the equipment's quiet operation requirements. Simultaneously, they exacerbate the stress load on rotating components such as bearings, reducing the long-term operational stability of the equipment.

[0004] In related technologies, torque ripple suppression schemes for permanent magnet synchronous motors generally rely on torque observers, repetitive control, iterative learning control (ILC), or complex mathematical operations. The algorithms are highly complex and require high-performance digital signal processors (DSPs) or ARM core chips. It is difficult to achieve real-time control on low-cost, low-computing-power microcontrollers (MCUs) widely used in home appliances such as air conditioners.

[0005] Therefore, it is necessary to optimize the torque pulsation suppression scheme of the air conditioner fan motor. Summary of the Invention

[0006] To address the aforementioned problems, this application provides a fan control method for an air conditioner. The method includes: when torque pulsation occurs in the fan, determining a fundamental harmonic current command based on the fan's quadrature-axis current command value and back electromotive force harmonic characteristics; acquiring the fan's electrical angular velocity, extracting the amplitude of the sixth harmonic torque fluctuation based on the electrical angular velocity, and performing closed-loop feedback control with a preset command value as the target value and the sixth harmonic torque fluctuation amplitude as the feedback value to obtain a current-corrected harmonic command value; superimposing the current-corrected harmonic command value and the fundamental harmonic current command to obtain a target current harmonic command; inputting the target current harmonic command into the fan's current loop for control to obtain a harmonic injection voltage; and controlling the fan's operation based on the harmonic injection voltage and the fundamental voltage command.

[0007] Thus, in the above technical solution, the fundamental harmonic current command is determined based on the quadrature-axis current command value and the back EMF harmonic characteristics. Complex algorithms such as torque observers, repetitive control, or iterative learning control are unnecessary; the baseline value for harmonic injection can be generated through simple calculations. Based on this, the amplitude of the sixth harmonic torque fluctuation is extracted based on the electrical angular velocity. Using a preset command value as the target value and the amplitude of this sixth harmonic torque fluctuation as the feedback value, closed-loop feedback control is performed to obtain the current correction harmonic command value, achieving online monitoring and dynamic compensation of the actual operating state of the wind turbine motor. This closed-loop feedback control uses speed fluctuations as the direct feedback quantity, without relying on the precise identification of wind turbine motor parameters. It can effectively eliminate residual torque pulsation caused by individual differences in the back EMF harmonics of the wind turbine motor, temperature drift, and flux attenuation, significantly improving the robustness and consistency of torque pulsation suppression.

[0008] In some embodiments of this application, when the fan has torque pulsation, before determining the basic harmonic current command based on the cross-axis current command value and back electromotive force harmonic characteristics of the fan, the method further includes: sampling the mechanical speed of the fan at a first preset period and obtaining the speed fluctuation value for a first preset duration; using a second preset duration as a statistical window, when the number of times the speed fluctuation value reaches or exceeds a preset threshold exceeds a preset number, determining that the fan has torque pulsation.

[0009] In the above technical solution, the mechanical speed of the fan is sampled at a first preset cycle for a first preset duration to obtain the speed fluctuation value. Then, frequency statistics are performed using a second preset duration as a statistical window, thus achieving reliable determination of torque pulsation. This determination mechanism, through multi-cycle statistics and threshold filtering, effectively eliminates misjudgments caused by instantaneous interference and occasional fluctuations, ensuring that the subsequent harmonic injection function is only activated when there is a genuine continuous torque pulsation. This avoids unnecessary control switching and harmonic current injection, reduces system losses and ineffective controller calculations, and improves the stability and economy of air conditioner fan operation.

[0010] In some embodiments of this application, the back EMF harmonic characteristics include the proportion of the 5th harmonic sinusoidal amplitude and the proportion of the 7th harmonic sinusoidal amplitude of the back EMF; based on the cross-axis current command value of the wind turbine and the back EMF harmonic characteristics, determining the fundamental harmonic current command includes: determining the proportion of the 5th harmonic direct-axis current and the proportion of the 5th harmonic cross-axis current based on the proportion of the 5th harmonic sinusoidal amplitude and the proportion of the 7th harmonic sinusoidal amplitude of the back EMF; multiplying the cross-axis current command value of the wind turbine by the proportion of the 5th harmonic cross-axis current to obtain the cross-axis fundamental harmonic command value; multiplying the cross-axis current command value of the wind turbine by the proportion of the 5th harmonic direct-axis current to obtain the direct-axis fundamental harmonic command value; the cross-axis fundamental harmonic command value and the direct-axis fundamental harmonic command value constitute the fundamental harmonic current command.

[0011] In the above technical solution, the fundamental harmonic current command is obtained by multiplying the quadrature-axis current command value by the proportions of the 5th harmonic direct-axis current and the 5th harmonic quadrature-axis current, respectively. This achieves adaptive matching between the harmonic injection amount and the real-time load conditions. Furthermore, only two multiplication operations are required to generate the fundamental harmonic command, eliminating the need for complex real-time harmonic calculations. This significantly reduces the online computational burden, allowing low-cost microcontrollers to meet real-time control requirements. It is particularly suitable for low-cost chip platforms in home appliances such as air conditioners.

[0012] In some embodiments of this application, determining the proportion of the 5th harmonic direct-axis current and the proportion of the 5th harmonic quadrature-axis current based on the proportion of the 5th harmonic sinusoidal amplitude of the back EMF and the proportion of the 7th harmonic sinusoidal amplitude of the back EMF includes: calculating the proportion of the sinusoidal amplitude of the compensation current and the proportion of the cosine amplitude of the compensation current required to suppress the 6th torque pulsation based on the proportion of the 5th harmonic sinusoidal amplitude of the back EMF and the proportion of the 7th harmonic sinusoidal amplitude of the back EMF; and converting the proportion of the sinusoidal amplitude of the compensation current and the proportion of the cosine amplitude of the compensation current into the proportion of the 5th harmonic direct-axis current and the proportion of the 5th harmonic quadrature-axis current through coordinate transformation.

[0013] In the above technical solution, the sinusoidal and cosine amplitude proportions of the compensation current are calculated based on the proportions of the 5th and 7th harmonic sinusoidal amplitudes of the back EMF. Then, through coordinate transformation, the proportions of the 5th harmonic direct-axis current and quadrature-axis current are obtained, thus completely constructing a conversion link from the inherent harmonic characteristics of the wind turbine motor to executable control parameters. This offline preprocessing method moves the complex harmonic analysis and coordinate transformation calculations to the development stage, avoiding complex calculations during online operation. Furthermore, by extracting the actual back EMF waveform of the wind turbine motor rather than relying on theoretical models, the accuracy and specificity of the harmonic characteristics are ensured, providing a reliable benchmark for subsequent online dynamic correction.

[0014] In some embodiments of this application, extracting the amplitude of the 6th harmonic torque fluctuation based on the electrical angular velocity includes: multiplying the electrical angular velocity by the pole-log correlation coefficient to obtain a first calculation result; multiplying the first calculation result by the sine and cosine values ​​of 6 times the electrical angle, respectively, and obtaining the sine and cosine component amplitudes of the 6th harmonic torque fluctuation after low-pass filtering; and synthesizing the amplitude of the 6th harmonic torque fluctuation based on the sine and cosine component amplitudes.

[0015] In the above technical solution, the sixth harmonic component is extracted by multiplying the electrical angular velocity by the pole-log correlation coefficient, and then multiplying it by the sine and cosine values ​​of six times the electrical angle, respectively, followed by low-pass filtering. This achieves accurate extraction of the sixth harmonic amplitude. This method utilizes the orthogonality of trigonometric functions and the frequency selectivity of the low-pass filter to decouple the sixth harmonic component from the complex speed signal. It eliminates the need for full-spectrum FFT analysis by a high-performance processor, requiring only simple multiplication and filtering operations. While ensuring extraction accuracy, it significantly reduces the requirements for chip computing power and sampling frequency, making it suitable for real-time signal processing in low-cost controllers.

[0016] In some embodiments of this application, closed-loop feedback control is performed with a preset command value as the target value and the amplitude of the 6th harmonic torque fluctuation as the feedback value to obtain the current correction harmonic command value. This includes: using zero as the target value and the amplitude of the 6th harmonic torque fluctuation as the feedback value to input to a proportional-integral (PI) controller; outputting a quadrature-axis current dynamic correction harmonic command value through the PPI controller, and calculating a direct-axis current dynamic correction harmonic command value based on the proportional relationship between the direct-axis component and the quadrature-axis component in the basic harmonic current command; the quadrature-axis current dynamic correction harmonic command value and the direct-axis current dynamic correction harmonic command value constitute the current correction harmonic command value.

[0017] In the above technical solution, a closed-loop feedback control is constructed to eliminate the sixth harmonic torque fluctuation by using zero as the target value and the amplitude of the sixth harmonic torque fluctuation as the feedback value input to the proportional-integral controller and outputting a dynamic harmonic correction command value for the quadrature-axis current. The dynamic harmonic correction command value for the direct-axis current is then calculated according to the proportional relationship between the direct-axis and quadrature-axis components in the basic harmonic current command. This closed-loop control targets zero; as long as the amplitude of the sixth harmonic torque fluctuation is detected to be non-zero, the proportional-integral controller continuously outputs the correction current until the fluctuation amplitude converges to zero, achieving zero steady-state error suppression of torque pulsation. Simultaneously, the calculation of the dynamic harmonic correction command value for the direct-axis current through proportional allocation ensures the correct direction of the correction current in the fifth harmonic dq-axis coordinate system, avoiding compensation failure or the increase of secondary harmonics due to axial component mismatch.

[0018] In some embodiments of this application, the target current harmonic command is input into the current loop of the wind turbine for control to obtain the harmonic injection voltage. This includes: performing proportional-integral adjustment on the target current harmonic command and the 5th harmonic component extracted from the actual current of the wind turbine to obtain the 5th harmonic quadrature-axis command voltage and the 5th harmonic direct-axis command voltage; and converting the 5th harmonic quadrature-axis command voltage and the 5th harmonic direct-axis command voltage into three-phase harmonic voltage command values ​​through coordinate transformation, which are used as the harmonic injection voltage.

[0019] In the above technical solution, the fifth harmonic direct-axis command voltage and quadrature-axis command voltage are obtained by proportional-integral adjustment of the target current harmonic command and the fifth harmonic component extracted from the actual current. These are then converted into three-phase harmonic voltage command values ​​through coordinate transformation, achieving closed-loop tracking control of the harmonic current. This current loop control ensures that the injected harmonic current accurately tracks the command value, suppresses the deviation between the actual current and the command value, and improves the accuracy and stability of harmonic injection. Simultaneously, the coordinate transformation converts the dq-axis control quantity into a three-phase voltage command, connecting it to the existing fundamental voltage control architecture without requiring hardware modifications. Furthermore, the injected harmonic voltage reflects the harmonic voltage component applied to the motor windings for accurate tracking of the harmonic current command. Its amplitude and phase are dynamically determined by the closed-loop adjustment of the current loop, ensuring that the actual harmonic current injected into the motor remains consistent with the target command, thereby achieving precise compensation for torque ripple.

[0020] In some embodiments of this application, controlling the operation of the wind turbine based on the harmonic injection voltage and the fundamental voltage command includes: superimposing the harmonic injection voltage and the fundamental voltage command to obtain a total three-phase voltage command signal; and outputting the total three-phase voltage command signal to the wind turbine through a PWM generation stage.

[0021] In the above technical solution, the total three-phase voltage command signal is obtained by superimposing the harmonic injection voltage and the fundamental voltage command, and then the drive signal is output through the PWM generation stage. This eliminates the need for a separate harmonic voltage output channel, reuses existing fundamental voltage control paths and PWM modulation resources, simplifies the hardware structure, and reduces system costs.

[0022] In some embodiments of this application, the fan is the indoor fan or outdoor fan of the air conditioner, and the motor of the fan is a surface-mounted permanent magnet synchronous motor.

[0023] In the above technical solution, the fan motor adopts a surface-mounted permanent magnet synchronous motor, which has the characteristic that the quadrature axis inductance and the direct axis inductance are approximately equal. It is suitable for adopting a simplified control strategy with zero direct axis current, and the electromagnetic torque is controlled by adjusting the quadrature axis current, which makes the calculation and injection of harmonic current simpler.

[0024] This application also provides an air conditioner, which includes an air conditioner body, a fan, and a controller, wherein the fan is disposed in the air conditioner body; the controller is electrically connected to the fan and is configured to execute the aforementioned control method.

[0025] In the above technical solution, the air conditioner controller determines the basic harmonic current command based on the quadrature-axis current command value and the harmonic characteristics of the back electromotive force. This eliminates the need for complex algorithms such as torque observers, repetitive control, or iterative learning control; the reference value for harmonic injection can be generated through simple calculations. Based on this, the amplitude of the sixth harmonic torque fluctuation is extracted based on the electrical angular velocity. A closed-loop feedback control is then performed, using a preset command value as the target value and the amplitude of this sixth harmonic torque fluctuation as the feedback value, to obtain the current correction harmonic command value. This achieves online monitoring and dynamic compensation of the actual operating state of the fan motor. This closed-loop feedback control uses speed fluctuations as the direct feedback quantity, without relying on the precise identification of fan motor parameters. It effectively eliminates residual torque pulsation caused by individual differences in the fan motor's back electromotive force harmonics, temperature drift, and flux attenuation, significantly improving the robustness and consistency of torque pulsation suppression.

[0026] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0027] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the specification, serve to explain the principles of this application.

[0028] Figure 1 A partial structural block diagram of an air conditioner according to one embodiment of this application is shown.

[0029] Figure 2 A flowchart of an air conditioner fan control method according to an embodiment of this application is shown.

[0030] Figure 3 It shows Figure 2 The detailed flowchart of step S210 is shown.

[0031] Figure 4 It shows Figure 2 The detailed flowchart of step S220 is shown.

[0032] Figure 5 It shows Figure 4 The detailed flowchart of step S410 is shown.

[0033] Figure 6 It shows Figure 2 The detailed flowchart of step S230 is shown.

[0034] Figure 7It shows Figure 2 The detailed flowchart of step S240 is shown.

[0035] Figure 8 It shows Figure 2 The detailed flowchart of step S250 is shown.

[0036] Figure 9 It shows Figure 2 The detailed flowchart of step S260 is shown.

[0037] Figure 10 A flowchart of another embodiment of the air conditioner fan control method of this application is shown.

[0038] Figure 11 A control block diagram of an air conditioner fan according to an embodiment of this application is shown.

[0039] Figure 12 The simulation results of phase current, torque, and speed at 800 rpm are shown in the figure.

[0040] Figure 13 The diagram shows a comparison of phase current harmonic analysis at 800 rpm according to this application.

[0041] Figure 14 The diagram shows a comparison of harmonic analysis of the electromagnetic torque at 800 rpm according to this application.

[0042] Figure 15 The diagram shows a comparison of harmonic analysis at 800 rpm according to this application.

[0043] The annotations in the attached figures are explained as follows: 10. Fan; 20. Controller. Detailed Implementation

[0044] To make the objectives, implementation methods and advantages of this application clearer, the exemplary implementation methods of this application will be clearly and completely described below with reference to the accompanying drawings of the exemplary embodiments of this application. Obviously, the described exemplary embodiments are only some embodiments of this application, and not all embodiments.

[0045] It should be noted that the brief descriptions of terms in this application are only for the convenience of understanding the embodiments described below, and are not intended to limit the embodiments of this application. Unless otherwise stated, these terms should be understood in their ordinary and common meaning.

[0046] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0047] In the description of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0048] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0049] Explanation of technical terms: Surface-mounted permanent magnet synchronous motor: The magnets are surface-mounted on the rotor surface of the motor, and the quadrature axis inductance is approximately equal to the direct axis inductance.

[0050] The 5th and 7th harmonics of back electromotive force refer to the periodic fluctuation components of back electromotive force with frequencies of 5 times and 7 times the fundamental frequency of the motor, respectively.

[0051] 6th and 12th order torque components: These refer to torque pulsations with frequencies 6 to 12 times the fundamental frequency of the motor.

[0052] The 6th harmonic refers to a periodic oscillation component with a frequency six times that of the fundamental frequency of the motor, generated by the cross-coupling of the 5th and 7th harmonics of the back electromotive force.

[0053] The 12th harmonic refers to a periodic oscillation component with a frequency 12 times that of the fundamental frequency of the motor, which is generated by the second cross-coupling of the 5th and 7th harmonics of the back electromotive force.

[0054] Fast Fourier Transform (FFT): An algorithm that efficiently converts discrete time-domain signals into frequency-domain components and accurately quantifies the amplitude and phase of each harmonic.

[0055] In related technologies, the following main solutions are used to suppress torque ripple in permanent magnet synchronous motors: Harmonic current calculation schemes based on complex algorithms. These schemes suppress torque ripple by calculating the amplitude and phase of the required injected harmonic current in real time. However, calculating the required harmonic current for suppressing torque ripple involves complex inverse trigonometric function operations, resulting in high computational complexity and poor real-time performance. Furthermore, they place high demands on the computing power of the control chip, making real-time control difficult to implement on low-cost, low-computing-power chips.

[0056] Closed-loop suppression schemes based on torque observers. These schemes estimate electromagnetic torque in real time by constructing a torque observer, and then extract harmonic components for compensation. However, torque observers have complex structures and involve multiplication operations between 8×8 and 8×1 matrices, which not only consumes a lot of computational resources, but also significantly affects the observation accuracy due to changes in motor parameters, resulting in insufficient robustness.

[0057] Offline solutions based on search or iterative optimization. These solutions find the optimal harmonic injection parameters through offline simulation or experimentation. Using a search method, the amplitude and phase of the harmonics are continuously increased or decreased to find the amplitude and phase with the lowest simulation noise, which is time-consuming; moreover, the noise is obtained through simulation, which cannot adapt to parameter drift and individual differences in actual motor operation, making it difficult to guarantee the suppression effect.

[0058] High-performance solutions based on spectrum analysis. These solutions extract harmonic information by performing spectrum analysis on the load signal. This requires performing Fourier spectrum analysis on the load signal, necessitating the use of high-performance chips to ensure a high sampling frequency. The computational load of signal processing is large, significantly increasing hardware costs, making them unsuitable for low-cost home appliances.

[0059] Low-speed response schemes for mechanical speed pulsation. These schemes mainly suppress speed fluctuations in mechanical systems, but have limited control bandwidth and are difficult to respond to torque pulsations caused by high-frequency electrical harmonics. Furthermore, the inertial filtering effect of mechanical components reduces the high-frequency suppression effect.

[0060] In view of this, this application designs a novel air conditioner fan control method. It determines the fundamental harmonic current command based on the quadrature-axis current command value and the harmonic characteristics of the back EMF, eliminating the need for complex algorithms such as torque observers, repetitive control, or iterative learning control. The baseline value for harmonic injection can be generated through simple calculations. Based on this, the amplitude of the sixth harmonic torque fluctuation is extracted based on the electrical angular velocity. Using a preset command value as the target value and the amplitude of this sixth harmonic torque fluctuation as the feedback value, closed-loop feedback control is performed to obtain the current correction harmonic command value, achieving online monitoring and dynamic compensation of the actual operating state of the fan motor. This closed-loop feedback control uses speed fluctuations as the direct feedback quantity, without relying on the precise identification of fan motor parameters. It can effectively eliminate residual torque pulsation caused by individual differences in the back EMF harmonics of the fan motor, temperature drift, and flux attenuation, significantly improving the robustness and consistency of torque pulsation suppression.

[0061] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0062] Figure 1 A partial structural block diagram of an air conditioner according to one embodiment of this application is shown.

[0063] The air conditioner in this embodiment includes an air conditioning unit (not shown in the figure), a fan 10, and a controller 20.

[0064] The air conditioner unit may include a casing structure and components such as a compressor, condenser, throttling device, and evaporator housed within the casing structure. The air conditioner executes a cooling / heating cycle through the compressor, condenser, throttling device, and evaporator. This cycle includes a series of processes: compression, condensation, expansion, and evaporation. The compressor compresses refrigerant gas at high temperature and pressure and discharges the compressed refrigerant gas. The discharged refrigerant gas flows into the condenser, where it condenses the compressed refrigerant into a liquid phase, releasing heat to the surrounding environment. The throttling device expands the high-temperature, high-pressure liquid refrigerant condensed in the condenser into a low-pressure liquid refrigerant phase. The evaporator evaporates the refrigerant expanded in the throttling device and returns the low-temperature, low-pressure refrigerant gas to the compressor. The evaporator achieves the cooling effect by utilizing the latent heat of refrigerant evaporation to exchange heat with the material being cooled. Throughout the cooling / heating cycle, the air conditioner regulates the temperature of the indoor space.

[0065] An air duct is formed inside the shell structure to guide airflow circulation. A fan 10 is mounted on the shell structure, specifically within the air duct, and may include an indoor fan and / or an outdoor fan to drive airflow for heat exchange. The indoor fan is located in the air duct corresponding to the evaporator, causing indoor air to flow over the evaporator surface, exchange heat with the low-temperature refrigerant, and then be blown into the indoor space. The outdoor fan is located in the air duct corresponding to the condenser, causing outdoor air to flow over the condenser surface, carrying away the heat released by refrigerant condensation.

[0066] In some embodiments, the motors of the indoor and / or outdoor fans are surface-mounted permanent magnet synchronous motors. Surface-mounted permanent magnet synchronous motors have the characteristic that the quadrature-axis inductance is approximately equal to the direct-axis inductance, making them suitable for a simplified control strategy with zero direct-axis (d-axis) current. Electromagnetic torque is controlled only by adjusting the quadrature-axis (q-axis) current, simplifying the calculation and injection of harmonic currents. Alternatively, the motors of the indoor and / or outdoor fans can be interior permanent magnet synchronous motors (Interior IPMSMs).

[0067] The controller 20 is electrically connected to the fan 10 and is typically housed within an electrical control box within a housing structure. The controller 20 sends control signals to the fan 10 to control its operation. The controller 20 includes a processor and a memory. The memory can pre-store the back electromotive force (EMF) harmonic characteristic parameters of the fan motor. These parameters may include the percentage of the 5th harmonic amplitude and the percentage of the 7th harmonic amplitude of the back EMF.

[0068] The processor of controller 20 is configured to execute a fan control method. When torque pulsation is detected in the fan, the fundamental harmonic current command is determined based on the cross-axis current command value and back electromotive force harmonic characteristics of the fan. At the same time, the amplitude of the sixth harmonic torque fluctuation is extracted based on the electrical angular velocity of the fan. A current correction harmonic command value is generated through closed-loop feedback control. The target current harmonic command is obtained by superimposing the current correction harmonic command value and the fundamental harmonic current command. The harmonic injection voltage is obtained through current loop control. After being superimposed on the fundamental voltage command, a drive signal is generated through pulse width modulation to control the operation of the fan motor, thereby suppressing torque pulsation, reducing vibration and noise caused by torque pulsation, and ensuring the quietness and stability of the air conditioner during the cooling / heating cycle.

[0069] Figure 2 A flowchart of an air conditioner fan control method according to an embodiment of this application is shown, as follows: Figure 2 As shown, the control method includes at least steps S210 to S260, which are described in detail below.

[0070] In step S210, it is determined whether there is torque pulsation in the fan. If so, step S220 is executed.

[0071] In some embodiments, the presence of torque pulsation in the fan is determined by detecting fluctuations in the fan's mechanical speed. For example... Figure 3 As shown, the steps for determining whether the fan has torque pulsation include steps S310 to S330, which are described in detail below.

[0072] In step S310, the mechanical speed of the fan is sampled at a first preset period and the speed fluctuation value is obtained after a first preset duration.

[0073] The first preset period and the first preset duration can be preset duration values.

[0074] The speed fluctuation value refers to the difference between the maximum and minimum values ​​of the fan's mechanical speed within a preset detection period, i.e., the first preset period. It is used to quantitatively characterize the degree of fluctuation of the fan speed within the detection cycle.

[0075] In step S320, using the second preset duration as the statistical window, when the number of times the speed fluctuation value reaches or exceeds the preset threshold exceeds the preset number, step S330 is executed.

[0076] The second preset duration can be a pre-set duration value. The preset threshold can be a pre-set rotational speed fluctuation value. The preset number of times can be a pre-set number of times.

[0077] That is, using the second preset duration as a statistical window, the number of detection cycles within this window in which the speed fluctuation value reaches the preset threshold is counted; if the number of detection cycles in which the speed fluctuation value reaches the preset threshold is large enough, it indicates that the speed fluctuation of the fan is not an accidental instantaneous disturbance, but a continuous regular pulsation, thus determining that the fan has torque pulsation that needs to be suppressed.

[0078] In step S330, it is determined that there is torque pulsation in the fan.

[0079] By sampling the mechanical speed of the fan at a first preset cycle for a first preset duration to obtain the speed fluctuation value, and then performing frequency statistics using a second preset duration as the statistical window, reliable determination of torque pulsation is achieved. This determination mechanism, through multi-cycle statistics and threshold filtering, effectively eliminates misjudgments caused by instantaneous interference and occasional fluctuations, ensuring that the subsequent harmonic injection function is only activated when there is a genuine continuous torque pulsation. This avoids unnecessary control switching and harmonic current injection, reduces system losses and ineffective controller calculations, and improves the stability and economy of air conditioner fan operation.

[0080] In some embodiments, the first preset period is 100ms, the first preset duration is 10s, the second preset duration is 2min, the preset threshold is 10rpm, and the preset number of times is 10. That is, with a sampling period of 100ms, continuous detection is performed for 10s, and the difference between the maximum and minimum speed values ​​within this period is recorded as the speed fluctuation value; then, the next 10s detection is performed to obtain the speed fluctuation value for the next period, and so on. With a statistical window of 2min, if the number of times the speed fluctuation value is greater than 10rpm exceeds 10 times within this window, it is determined that the fan has torque pulsation, and subsequent steps are performed to inject 5th current harmonics into the phase current of the fan motor to suppress speed fluctuation; otherwise, harmonic injection is not required, and the fan operates according to the fundamental frequency control.

[0081] In step S220, the fundamental harmonic current command is determined based on the cross-axis current command value and the harmonic characteristics of the back electromotive force of the wind turbine.

[0082] In some embodiments, the harmonic characteristics of the back electromotive force include the proportion of the 5th harmonic sinusoidal amplitude and the proportion of the 7th harmonic sinusoidal amplitude. For example... Figure 4 As shown, the steps for determining the foundation harmonic current command based on the cross-axis current command value and back electromotive force harmonic characteristics of the wind turbine include steps S410 to S430, which are described in detail below.

[0083] In step S410, based on the proportion of the 5th harmonic sinusoidal amplitude of the back electromotive force and the proportion of the 7th harmonic sinusoidal amplitude of the back electromotive force, the proportion of the 5th harmonic direct-axis current and the proportion of the 5th harmonic quadrature-axis current are determined.

[0084] In step S420, the cross-axis current command value of the wind turbine is multiplied by the proportion of the 5th harmonic cross-axis current to obtain the cross-axis foundation harmonic command value.

[0085] In step S430, the cross-axis current command value of the wind turbine is multiplied by the proportion of the 5th harmonic direct-axis current to obtain the direct-axis foundation harmonic command value.

[0086] The quadrature-axis foundation harmonic command value and the direct-axis foundation harmonic command value constitute the foundation harmonic current command.

[0087] The fundamental harmonic current command is obtained by multiplying the quadrature-axis current command value by the proportions of the 5th harmonic direct-axis current and the 5th harmonic quadrature-axis current, respectively. This achieves adaptive matching between the harmonic injection amount and the real-time load conditions. Furthermore, the fundamental harmonic command can be generated with only two multiplication operations, eliminating the need for complex real-time harmonic calculations. This significantly reduces the online computational burden, allowing low-cost microcontrollers to meet real-time control requirements. It is particularly suitable for low-cost chip platforms in home appliances such as air conditioners.

[0088] The back EMF harmonic characteristics are obtained during the controller development phase through offline testing or motor model simulation and are pre-stored in the controller memory. The process of obtaining the back EMF harmonic characteristics may include: acquiring the back EMF waveform of the wind turbine, and extracting the proportion of the 5th harmonic sine amplitude and the 7th harmonic sine amplitude from the back EMF waveform.

[0089] The back electromotive force (EMF) waveform of the wind turbine can be obtained through offline testing or finite element simulation. The wind turbine motor is three-phase symmetrical, and its back EMF waveform is symmetrical about the origin, constituting an odd function. Therefore, the 5th and 7th harmonics of the back EMF contain only sinusoidal components, with zero cosine components. The simplified time-domain expression for the 5th and 7th harmonics of the wind turbine motor is as follows: (1) in, e a_5th+7th , e b_5th+7th , e c_5th+7th These are the 5th and 7th total back electromotive force harmonics of the three phases a, b, and c, respectively. h 5th , h 7th These represent the percentages of the 5th harmonic sinusoidal amplitude and the 7th harmonic sinusoidal amplitude in the back EMF waveform, respectively. ω is the electric angular velocity, and ψf is the amplitude of the permanent magnet flux linkage.

[0090] Extracting the proportion of the fifth harmonic sine amplitude of the back electromotive force waveform h 5th The proportion of the 7th harmonic sinusoidal amplitude of the back electromotive force h 7th The proportion of the fifth harmonic sinusoidal amplitude of the back electromotive force h 5th The ratio of the sinusoidal amplitude of the 5th harmonic component to the fundamental amplitude in the back electromotive force waveform is given by the value of the 7th harmonic sinusoidal amplitude. h 7th It is the ratio of the sinusoidal amplitude of the 7th harmonic component to the amplitude of the fundamental wave in the back electromotive force waveform. h 5th , h 7th It is used to quantitatively describe the degree to which the back electromotive force waveform deviates from an ideal sine wave.

[0091] like Figure 5 As shown, the steps for determining the proportion of the 5th harmonic direct-axis current and the 5th harmonic quadrature-axis current based on the proportion of the 5th harmonic sinusoidal amplitude of the back electromotive force and the proportion of the 7th harmonic sinusoidal amplitude of the back electromotive force include steps S510 to S520, which are described in detail below.

[0092] In step S510, based on the proportion of the 5th harmonic sinusoidal amplitude of the back EMF and the proportion of the 7th harmonic sinusoidal amplitude of the back EMF, the proportion of the sinusoidal amplitude of the compensation current and the proportion of the cosine amplitude of the compensation current required to suppress the 6th torque pulsation are calculated.

[0093] The following explains how to obtain the sine amplitude ratio and cosine amplitude ratio of the compensation current required to suppress 6th-order torque ripples: By superimposing the fundamental back electromotive force (EMF) with the harmonics in the time-domain expression (1) above, we can obtain the overall expression for the three back EMFs: (2) in, e a , e b , e c The total back electromotive force of the three phases a, b, and c are respectively. h 5th , h 7th These represent the percentages of the 5th harmonic sinusoidal amplitude and the 7th harmonic sinusoidal amplitude in the back EMF waveform, respectively. ω is the electric angular velocity, and ψf is the amplitude of the permanent magnet flux linkage.

[0094] With the direct-axis current set to zero, the fundamental current of each phase of the fan motor is in phase with the fundamental back electromotive force. The fundamental expression for the three-phase current is as follows: (3) in, i a_1th , i b_1th , i c_1th Let A, B, and C be the three-phase fundamental currents, respectively, and ω be the electric angular velocity. I m This represents the amplitude of the phase current.

[0095] Because the three-phase back electromotive force contains harmonics, torque pulsation is generated during operation, which in turn causes harmonics in the three-phase current. The actual three-phase current also needs to have harmonics superimposed on the fundamental frequency. By writing the current expression in the form of Fourier fundamental and harmonic superposition, we can obtain: (4) in, i a , i b , i c These are the total currents of the three phases a, b, and c, respectively. d 5th , d 7th The percentage of the sinusoidal amplitude of the 5th / 7th order compensation current. q 5th , q 7th The percentage of the 5th / 7th order compensation current cosine amplitude, where ω is the electric angular velocity. I m This represents the amplitude of the phase current.

[0096] Substituting equations (2) and (4) into the torque formula and simplifying it, we can obtain the expression for the electromagnetic torque with harmonics: (5) in, T For electromagnetic torque, h 5th , h 7th These represent the proportions of the 5th harmonic sine wave amplitude and the 7th harmonic sine wave amplitude in the back electromotive force waveform, respectively. d 5th , d 7th The percentage of the sinusoidal amplitude of the 5th / 7th order compensation current. q 5th , q 7th The percentage of the 5th / 7th order compensation current cosine amplitude, where ω is the electric angular velocity. Ω Where ψ is the mechanical angular velocity, and ψf is the flux linkage amplitude of the permanent magnet. I mThis represents the amplitude of the phase current.

[0097] As shown in equation (5), the torque contains 6th and 12th harmonic components. To eliminate the 6th and 12th torque pulsations, the sine and cosine amplitudes of the 6th and 12th torque harmonics in equation (5) are set to zero. This yields the amplitude of the three-phase 5 / 7 harmonic current to be injected. See the following equation: (6) h 5th , h 7th These represent the proportions of the 5th harmonic sinusoidal amplitude and the 7th harmonic sinusoidal amplitude in the back EMF waveform, respectively, which have been obtained through prior testing or simulation. Solving equation (6) yields the proportion of the compensation current amplitude to be injected: (7) in, h 5th , h 7th These represent the proportions of the 5th harmonic sine wave amplitude and the 7th harmonic sine wave amplitude in the back electromotive force waveform, respectively. d 5th , d 7th To compensate for the proportion of the sinusoidal current amplitude, q 5th , q 7th To compensate for the proportion of the current cosine amplitude.

[0098] As shown in equation (7) above, injecting only the sinusoidal component of the 5th harmonic is sufficient to eliminate both the 6th and 12th harmonic torque ripples, eliminating the need for injecting the 7th harmonic current. The sinusoidal component of the 5th harmonic to be injected is: (8) Equation (8) can be transformed into: (9) in, i a5th_ref , i b5th_ref , i c5th_ref These are the command values ​​for the 5th harmonic currents of the three phases a, b, and c, respectively. h 5th , h 7th These represent the percentage of the 5th harmonic sinusoidal amplitude and the 7th harmonic sinusoidal amplitude in the back EMF waveform, respectively, while iq_ref is the quadrature shaft current command value output by the speed loop.

[0099] In step S520, the proportion of the sine amplitude of the compensation current and the proportion of the cosine amplitude of the compensation current are converted into the proportion of the 5th harmonic direct-axis current and the proportion of the 5th harmonic quadrature-axis current through coordinate transformation.

[0100] That is, through coordinate transformation, the proportion of sinusoidal and cosine amplitudes of the compensation current are converted into the proportion of direct-axis current and quadrature-axis current under the 5th harmonic dq axis. Figure 5 In the illustrated embodiment, the sinusoidal and cosine amplitude proportions of the compensation current are calculated based on the proportions of the 5th and 7th harmonic sinusoidal amplitudes of the back EMF. Then, through coordinate transformation, the proportions of the 5th harmonic direct-axis current and quadrature-axis current are obtained, thus fully constructing the conversion link from the inherent harmonic characteristics of the wind turbine motor to executable control parameters. This offline preprocessing method moves the complex harmonic analysis and coordinate transformation calculations to the development stage, avoiding complex calculations during online operation. Furthermore, by extracting the actual back EMF waveform of the wind turbine motor rather than relying on theoretical models, the accuracy and specificity of the harmonic characteristics are ensured, providing a reliable benchmark for subsequent online dynamic correction.

[0101] Since the rotation direction of the 5th harmonic dq-axis coordinate system is opposite to that of the fundamental dq-axis coordinate system, and the rotation speed is 5 times that of the fundamental wave, the transformation matrix from the abc three-phase coordinate system to the 5th harmonic dq-axis coordinate system is: (10) i d5e_ref , i q5e_ref These represent the direct-axis and quadrature-axis fundamental harmonic command values ​​in the 5th harmonic dq-axis coordinate system, respectively. i a5th_ref , i b5th_ref , i c5th_ref These are the command values ​​for the 5th harmonic currents of the three phases abc, respectively, and θ is the electrical angle.

[0102] Due to individual variations in the mass production of wind turbine motors, there is a deviation between the actual back electromotive force harmonics and the offline test values. Even after injecting only the basic harmonic current command, the 6th / 12th harmonic may still remain in the electromagnetic torque. This residual torque pulsation will cause a 6th-order periodic fluctuation in the mechanical angular velocity. Therefore, further dynamic correction is required, namely the following steps S230-S250.

[0103] In step S230, the electrical angular velocity of the wind turbine is obtained, and the amplitude of the sixth harmonic torque fluctuation is extracted based on the electrical angular velocity.

[0104] The electrical angular velocity of the wind turbine can be obtained from a position sensor. If no position sensor is installed, an estimation algorithm can be used to obtain the electrical angular velocity.

[0105] In some embodiments, such as Figure 6 As shown, the steps for extracting the amplitude of the 6th harmonic torque fluctuation based on electrical angular velocity include the following steps S610-S630, which are described in detail below.

[0106] In step S610, the electrical angular velocity is multiplied by the pole pair correlation coefficient to obtain the first calculation result.

[0107] The pole pair correlation coefficient is determined by the number of motor pole pairs p. n The decision is made so that subsequent multiplication with sin(6θ) and cos(6θ) followed by low-pass filtering directly yields the DC component proportional to the amplitude of the 6th harmonic torque fluctuation. The first calculation result converts the angular velocity information in the mechanical domain into an equivalent physical quantity related to the electromagnetic torque pulsation. By introducing a pole-log coefficient, a correct proportional relationship between the electrical angular velocity and the mechanical angular velocity is established, providing a standardized input signal for the subsequent extraction of the 6th harmonic quadrature component.

[0108] In step S620, the first calculation result is multiplied by the sine and cosine values ​​of 6 times the electrical angle, respectively. After low-pass filtering, the amplitude of the sine component and the amplitude of the cosine component of the 6th harmonic torque fluctuation are obtained.

[0109] That is, the first calculation result is compared with the sine value of 6 times the electrical angle. Multiply the results and then pass them through a low-pass filter (LPF) to obtain the sinusoidal component amplitude of the 6th harmonic torque ripple. Then, multiply the first result by the cosine of six times the electrical angle. Multiply the values ​​and then pass them through a low-pass filter (LPF) to obtain the cosine component amplitude of the 6th harmonic torque ripple.

[0110] In step S630, the amplitude of the sixth harmonic torque fluctuation is synthesized based on the amplitude of the sine component and the amplitude of the cosine component.

[0111] The amplitude of the sixth harmonic torque fluctuation is synthesized based on the amplitudes of the sine and cosine components, which is essentially a vector operation that combines two orthogonal components into a total amplitude. Specifically, the sixth harmonic torque fluctuation can be decomposed into two orthogonal components in the sine and cosine directions in a rotating coordinate system. The square root of the sum of the squares of the sine and cosine component amplitudes is the scalar representation of the sixth harmonic torque fluctuation amplitude, used to quantify the actual intensity of the current torque pulsation.

[0112] By multiplying the electrical angular velocity by the pole-log correlation coefficient, and then multiplying it by the sine and cosine values ​​of six times the electrical angle respectively, followed by low-pass filtering to extract the sixth harmonic component, the amplitude of the sixth torque ripple is accurately extracted. This method utilizes the orthogonality of trigonometric functions and the frequency selectivity of the low-pass filter to decouple the sixth harmonic component from the complex speed signal. It eliminates the need for full-spectrum FFT analysis by a high-performance processor, requiring only simple multiplication and filtering operations. This significantly reduces the requirements for chip computing power and sampling frequency while ensuring extraction accuracy, making it suitable for real-time signal processing in low-cost controllers.

[0113] In step S240, closed-loop feedback control is performed with a preset command value as the target value and the 6th harmonic torque fluctuation amplitude as the feedback value to obtain the current correction harmonic command value.

[0114] In some embodiments, such as Figure 7 As shown, the steps for obtaining the current correction harmonic command value by performing closed-loop feedback control with a preset command value as the target value and the 6th harmonic torque fluctuation amplitude value as the feedback value include the following steps S710-S730, which are described in detail below.

[0115] In step S710, zero is used as the target value, and the amplitude of the sixth harmonic torque fluctuation is used as the feedback value to input the proportional-integral controller.

[0116] In step S720, the proportional-integral regulator outputs a dynamic harmonic correction command value for the quadrature-axis current.

[0117] In step S730, the direct-axis current dynamic correction harmonic command value is calculated based on the ratio of the direct-axis component to the quadrature-axis component in the fundamental harmonic current command.

[0118] Among them, the dynamic harmonic correction command value of quadrature-axis current and the dynamic harmonic correction command value of direct-axis current constitute the current correction harmonic command value.

[0119] By using zero as the target value and the amplitude of the 6th harmonic torque fluctuation as the feedback value input to the proportional-integral (PI) controller, and outputting a dynamic harmonic correction command value for the quadrature-axis current, and then calculating the dynamic harmonic correction command value for the direct-axis current according to the proportional relationship between the direct-axis and quadrature-axis components in the basic harmonic current command, a closed-loop feedback control aimed at eliminating the 6th harmonic speed fluctuation is constructed. This closed-loop control targets zero; as long as the amplitude of the 6th harmonic torque fluctuation is detected to be non-zero, the PPI controller continuously outputs the correction current until the fluctuation amplitude converges to zero, achieving zero steady-state error suppression of torque pulsation. Simultaneously, by calculating the dynamic harmonic correction command value for the direct-axis current through proportional allocation, the correct direction of the correction current in the 5th harmonic dq-axis coordinate system is ensured, avoiding compensation failure or the increase of secondary harmonics due to axial component mismatch.

[0120] In step S250, the target current harmonic command is obtained by superimposing the current correction harmonic command value and the basic harmonic current command. The target current harmonic command is then input into the current loop of the fan for control, thereby obtaining the harmonic injection voltage.

[0121] The process of superimposing the current correction harmonic command value with the fundamental harmonic current command to obtain the target current harmonic command is a vector synthesis process. Specifically, the fundamental harmonic current command includes direct-axis fundamental harmonic command values ​​and quadrature-axis fundamental harmonic command values, which represent the ideal compensation amount calculated based on the wind turbine motor theoretical model. The current correction harmonic command value includes direct-axis dynamic current correction harmonic command values ​​and quadrature-axis dynamic current correction harmonic command values, which represent the real-time compensation amount for individual differences and actual operating deviations of the wind turbine motor. During the superposition process, the dynamic correction command in the direct-axis direction is added to the direct-axis fundamental harmonic command, and the dynamic correction command in the quadrature-axis direction is added to the quadrature-axis fundamental harmonic command, resulting in a total of 5th harmonic direct-axis current command and a total of 5th harmonic quadrature-axis current command, which together constitute the target current harmonic command. The target current harmonic command incorporates both pre-calculated reference harmonic information and real-time feedback dynamic correction information, achieving an organic fusion of pre-programming and adaptive behavior. This ensures that the harmonic injection amount can accurately match the harmonic characteristics of the actual wind turbine motor, thereby achieving the optimal torque ripple suppression effect.

[0122] Inputting the target current harmonic command into the wind turbine's current loop for control, resulting in the harmonic injection voltage, is the process of converting the harmonic current command into an executable voltage control signal. In some embodiments, such as... Figure 8 As shown, the steps to input the target current harmonic command into the current loop of the wind turbine for control and obtain the harmonic injection voltage include the following steps S810-S820, which are described in detail below.

[0123] In step S810, the target current harmonic command and the 5th harmonic component extracted from the actual current of the wind turbine are proportionally and integrally adjusted to obtain the 5th harmonic quadrature axis command voltage and the 5th harmonic direct axis command voltage.

[0124] In step S820, the 5th harmonic quadrature axis command voltage and the 5th harmonic direct axis command voltage are converted into three-phase harmonic voltage command values ​​through coordinate transformation, which are used as harmonic injection voltages.

[0125] The target current harmonic command includes a total 5th harmonic direct-axis current command and a total 5th harmonic quadrature-axis current command. First, the target current harmonic command is compared with the 5th harmonic component extracted from the actual current of the wind turbine to obtain the current deviation. This current deviation is input to the proportional-integral (PI) regulator of the 5th harmonic dq-axis current loop. The PI regulator performs calculations based on the magnitude and accumulation of the deviation, and outputs the 5th harmonic direct-axis command voltage and the 5th harmonic quadrature-axis command voltage. Subsequently, the 5th harmonic dq-axis command voltage is transformed to the abc three-phase coordinate system through coordinate transformation to obtain the three-phase harmonic voltage command value, i.e., the harmonic injection voltage.

[0126] By proportional-integral adjustment of the target current harmonic command and the fifth harmonic component extracted from the actual current to obtain the fifth harmonic direct-axis command voltage and quadrature-axis command voltage, and then converting them into three-phase harmonic voltage command values ​​through coordinate transformation, closed-loop tracking control of the harmonic current is achieved. This current loop control ensures that the injected harmonic current can accurately track the command value, suppresses the deviation between the actual current and the command value, and improves the accuracy and stability of harmonic injection. At the same time, the dq-axis control quantity is converted into a three-phase voltage command through coordinate transformation, which can be connected to the existing fundamental voltage control architecture without hardware modification. Moreover, the harmonic injection voltage reflects the harmonic voltage component applied to the motor windings for accurate tracking of the harmonic current command. Its amplitude and phase are dynamically determined by the closed-loop adjustment of the current loop, ensuring that the actual harmonic current injected into the motor is consistent with the target command, thereby achieving precise compensation for torque ripple.

[0127] In step S260, the operation of the fan is controlled based on the harmonic injection voltage and the fundamental voltage command.

[0128] In some embodiments, such as Figure 9 As shown, the steps for controlling the operation of the fan based on the harmonic injection voltage and the fundamental voltage command include the following steps S910-S920, which are described in detail below.

[0129] In step S910, the harmonic injection voltage is superimposed with the fundamental voltage command to obtain the total three-phase voltage command signal.

[0130] In step S920, the total three-phase voltage command signal is generated by the PWM generation stage and output as a drive signal to the fan.

[0131] The total three-phase voltage command signal is obtained by superimposing the harmonic injection voltage and the fundamental voltage command, and then output as a drive signal through the PWM generation stage. This eliminates the need for a separate harmonic voltage output channel, reuses existing fundamental voltage control paths and PWM modulation resources, simplifies the hardware structure, and reduces system costs.

[0132] Figure 10A flowchart of another embodiment of an air conditioner fan control method according to this application is shown. Figure 10 As shown, in one embodiment, the air conditioner fan control method includes the following steps: Step 1: Torque Ripple Detection and Triggering The controller monitors the mechanical speed of the fan in real time after the fan motor starts. It samples the speed in a 100ms first preset period for a first preset duration of 10s, obtaining the difference between the maximum and minimum speed values ​​within one period as the speed fluctuation value. Then, it enters the next 10s detection period to obtain the speed fluctuation value for the next period, and this process is repeated cyclically. A second preset duration of 2 minutes is used as a statistical window. If the number of times the speed fluctuation value exceeds a preset threshold of 10 rpm within this statistical window exceeds a preset number of 10, it is determined that the fan has continuous torque pulsation, and five current harmonics are injected into the motor phase current to suppress the speed fluctuation. Otherwise, the fan is considered to be running smoothly, and harmonic injection control is not required; that is, Steps 2 to 7 are not required.

[0133] Step 2: Obtaining Back EMF Harmonic Characteristics and Calculating Compensation Current The back EMF waveform of the wind turbine is obtained through offline testing or motor model simulation, and the proportion of the fifth harmonic sine amplitude of the back EMF is extracted. h 5th The proportion of the 7th harmonic sinusoidal amplitude of the back electromotive force h 7th As a pre-stored back electromotive force harmonic characteristic; based on the proportion of the sinusoidal amplitude of this 5th harmonic. h 5th The proportion of the 7th harmonic sinusoidal amplitude of the back electromotive force h 7th Calculate the proportion of the sinusoidal amplitude of the compensation current required to suppress the sixth torque ripple. d 5th and the proportion of cosine amplitude of compensation current q 5th .

[0134] Step 3: Generate Basic Harmonic Current Command During online operation, the proportion of the sinusoidal amplitude of the compensation current is determined by a coordinate transformation from the abc coordinate axis to the 5th harmonic dq coordinate axis. d 5th and the proportion of cosine amplitude of compensation current q 5th Conversion to 5th harmonic direct-axis current ratio i d5per and the proportion of the 5th harmonic quadrature axis current i q5per The quadrature-axis current command value output by the speed loop. i q_refMultiply by the proportion of the direct-axis current of the 5th harmonic respectively i d5per and the proportion of the 5th harmonic quadrature axis current i q5per Obtain the direct-axis foundation harmonic command value. i d5e_ref and cross-axis basic harmonic command value i q5e_ref The two together constitute the basic harmonic current command.

[0135] Step 4: Extraction and Dynamic Correction of 6th Harmonic Torque Fluctuation Amplitude The electrical angular velocity ω is multiplied by the pole pair correlation coefficient. The result is then multiplied by the sine and cosine values ​​of six times the electrical angle, respectively. After low-pass filtering, the amplitudes of the sine and cosine components of the sixth harmonic torque fluctuation are obtained, and these are synthesized to obtain the amplitude of the sixth harmonic torque fluctuation. A closed-loop feedback control is implemented using zero as the preset command value as the target value and the amplitude of this sixth harmonic torque fluctuation as the feedback value. The proportional-integral regulator outputs a quadrature-axis current to dynamically correct the harmonic command value. i q5Ad_ref And according to the direct-axis component in the fundamental harmonic current command i d5e_ref With cross axis components i q5e_ref The proportional relationship is used to calculate the direct-axis current dynamic correction harmonic command value. i d5Ad_ref .

[0136] Step 5: Target Current Harmonic Command Generation Dynamically correct harmonic command value for quadrature axis current i q5Ad_ref and direct-axis current dynamic correction harmonic command value i d5Ad_ref Respectively related to the cross-axis foundation harmonic command values i q5e_ref Harmonic command values ​​of the direct axis i d5e_ref Superimposed, the total 5th harmonic quadrature-axis current command value is obtained. i q5th_ref The total 5th harmonic direct-axis current command value i d5th_ref This refers to the target current harmonic command.

[0137] Step 6: Harmonic Current Loop Control and Voltage Transformation Target current harmonic command i q5th_ref , i d5th_ref The 5th harmonic component extracted from the actual current of the wind turbine i q5th ,i d5th Proportional-integral control is performed to obtain the 5th harmonic direct-axis command voltage and the 5th harmonic quadrature-axis command voltage. , The 5th harmonic direct-axis command voltage and quadrature-axis command voltage are transformed using coordinate transformation. , Transform to the abc three-phase coordinate system to obtain the three-phase harmonic voltage command values. , , That is, harmonic injection voltage.

[0138] Step 7: Voltage superposition and motor drive Harmonic injection voltage , , With fundamental voltage command , , The total three-phase voltage command signal is obtained by superimposing the signals. , , The total voltage command signal , , The PWM generation stage outputs six PWM drive signals to drive the fan motor, achieving specified harmonic injection and suppressing torque pulsation.

[0139] Figure 11 A control block diagram of an air conditioner fan according to an embodiment of this application is shown.

[0140] like Figure 11 As shown, after the wind turbine motor starts, the controller first obtains the electrical angular velocity ω and electrical angle θ through a position estimation module that suppresses the 6th harmonic of the angle. This module estimates the rotor position and speed from the three-phase current and three-phase voltage information based on a sensorless FOC algorithm, while filtering to eliminate angle estimation jitter caused by harmonics. The electrical angular velocity ω is sent to the speed regulator PIs, along with the speed command value ω. After comparison, the quadrature-axis current command value is output through proportional-integral calculation. i q_ref This command value serves as the control quantity for the speed loop, determining the magnitude of the wind turbine motor's output torque. On the other hand, the electrical angular velocity ω is sent to the dynamic harmonic correction control module to extract the amplitude of the 6th harmonic torque fluctuation online.

[0141] In the dynamic harmonic correction control module, the electrical angular velocity ω is multiplied by the reciprocal of the pole pair number 1 / pn and a coefficient of 2 to obtain the first calculation result. This result is divided into two parallel branches: the upper branch multiplies by sin(6θ) and then filters out the AC component using a low-pass filter (LPF) to obtain the sinusoidal component amplitude A_6th of the 6th harmonic torque fluctuation; the lower branch multiplies by cos(6θ) and then filters out the AC component using another low-pass filter (LPF) to obtain the cosine component amplitude B_6th of the 6th harmonic torque fluctuation. The sinusoidal and cosine component amplitudes are then combined to obtain the 6th harmonic torque fluctuation amplitude. This amplitude is used as a feedback value and fed into the proportional-integral (PI) controller, where it is compared with the target value of zero. The PI controller outputs a quadrature-axis current dynamic harmonic correction command value based on the deviation. i q5Ad_ref Meanwhile, according to the ratio of the direct-axis component to the quadrature-axis component in the fundamental harmonic current command... i d5e_ref / i q5e_ref Calculate the direct-axis current dynamic correction harmonic command value i d5Ad_ref The dynamic harmonic correction command value of the quadrature-axis current and the dynamic harmonic correction command value of the direct-axis current together constitute the current correction harmonic command value.

[0142] The basic harmonic current command is generated using an offline pre-programming method. During the controller development phase, the back EMF waveform of the motor is obtained through offline testing or motor model simulation, and the proportion of the fifth harmonic sinusoidal amplitude of the back EMF is extracted. h 5th The proportion of the 7th harmonic sinusoidal amplitude of the back electromotive force h 7th These two amplitude ratios are pre-stored in the controller memory as back EMF harmonic characteristics. During online operation, based on these two amplitude ratios, the required compensation current sinusoidal amplitude ratio for suppressing the 6th torque ripple is calculated. d 5th = h 7th - h 5th and the proportion of cosine amplitude of compensation current q 5th =0. The ratio of the compensation current amplitude to the quadrature-axis current command value. i q_ref Multiplying these yields the 5th harmonic current command in the abc three-phase coordinate system. Then, through a coordinate transformation from the abc coordinate axis to the 5th harmonic dq coordinate axis, it is converted into the 5th harmonic direct-axis current ratio. i d5per and the proportion of the 5th harmonic quadrature axis current i q5per The quadrature axis current command value i q_refMultiply by the pre-stored direct-axis current ratio and quadrature-axis current ratio respectively to obtain the direct-axis fundamental harmonic command value. i d5e_ref and cross-axis basic harmonic command value i q5e_ref The two together constitute the basic harmonic current command.

[0143] The current correction harmonic command value is added to the corresponding component of the fundamental harmonic current command at the superposition point to obtain the total 5th harmonic quadrature-axis current command value. i q5th_ref The total 5th harmonic direct-axis current command value i d5th_ref This refers to the target current harmonic command. The target current harmonic command undergoes rate limiting by a harmonic command smoothing control module to avoid current surges and torque jumps caused by sudden harmonic current changes, thus enhancing the stability of the transition state. The smoothed target current harmonic command is then fed into the 5th dq-axis current loop, where it is proportionally and integrally adjusted with the 5th harmonic component extracted from the actual current to output the 5th harmonic direct-axis command voltage and the 5th harmonic quadrature-axis command voltage. , The command voltage undergoes five coordinate transformations from the dq axis to the abc axis to convert it into a three-phase harmonic voltage command value. , , That is, harmonic injection voltage.

[0144] In the fundamental control path, the quadrature-axis current command value output by the speed loop i q_ref With direct-axis current command value i d_ref The current (=0) is fed into the current regulator PIC, compared with the actual fundamental dq-axis current feedback, and then, through proportional-integral (PI) calculation, outputs the fundamental direct-axis voltage command and the fundamental quadrature-axis voltage command. The fundamental dq-axis voltage command undergoes a coordinate transformation from dq to αβ axis, and then a coordinate transformation from αβ to abc axis, to convert it into a three-phase fundamental voltage command. , , The harmonic injection voltage is superimposed with the fundamental voltage command to obtain the total three-phase voltage command signal. This total voltage command signal is then subjected to space vector pulse width modulation (SPWM) through a PWM generation stage, outputting six PWM drive signals to drive the surface-mount permanent magnet synchronous motor. The three-phase current output by the motor is sampled; a portion is used for coordinate transformation and feedback of the fundamental control, while the other portion is used to extract the 5th harmonic component as feedback for the harmonic current loop, forming a complete closed-loop control.

[0145] Through the synergistic effect of the above two-level architecture, the pre-programmed basic harmonic instructions eliminate the theoretical 6th and 12th torque pulsations, while the dynamic correction harmonic instructions compensate for the residual pulsations caused by individual differences in the motor in real time through closed-loop feedback, so that the amplitude of the 6th harmonic torque fluctuation converges to zero. Ultimately, high-precision torque pulsation suppression with low computing power requirements is achieved, ensuring the quietness and stability of the air conditioner fan operation.

[0146] Figure 12 It can be seen that, compared with the traditional programming current method, the electromagnetic torque pulsation and mechanical speed pulsation of the fan motor are significantly improved after adopting the air conditioner fan control method of this application.

[0147] Figures 13 to 15 Further harmonic analysis was performed on the simulation results using Fast Fourier Transform (FFT). Figure 13 As can be seen, compared with the traditional programming current method, the proportion of the fifth current harmonic amplitude in this application is adjusted from 10.3% to 11%. The additional 0.7% harmonic current is generated by the current correction harmonic command value. This incremental part is used to eliminate the residual torque pulsation phenomenon caused by individual differences in motor back EMF harmonics.

[0148] Depend on Figure 14 It can be seen that the proportion of the 6th harmonic torque pulsation decreased from 3.19% to 2.0%, and the fluctuation amplitude decreased by 37.3%. This is because the closed-loop feedback control can generate current correction harmonic command values ​​in real time according to the amplitude of the 6th harmonic torque fluctuation. Even if the fan motor has back EMF harmonic deviation, it can still achieve accurate torque pulsation suppression.

[0149] Depend on Figure 15 It can be seen that the 6th harmonic speed pulsation was reduced from 0.01% (corresponding to 0.08 rpm) to 0.004% (corresponding to 0.032 rpm), and the fluctuation amplitude was reduced by 60%, proving that the suppression effect of this application on the 6th harmonic torque pulsation is better than that of the traditional programming current method.

[0150] In summary, the air conditioner fan control method provided in this application adopts a two-stage architecture of pre-programmed basic harmonic current commands and online dynamic correction, combining the technical advantages of low computational power requirements and high suppression accuracy. In the basic harmonic current command generation stage, the 5th and 7th harmonic sinusoidal amplitude proportions of the motor back EMF are obtained through offline testing or motor model simulation. Based on the motor torque expressions of the 5th and 7th back EMF harmonics, the sinusoidal and cosine amplitude proportions of the compensation current required to suppress 6th torque ripple are calculated. The pre-stored 5th harmonic direct-axis current proportion and 5th harmonic quadrature-axis current proportion are obtained through coordinate transformation. During online operation, the basic harmonic current command is obtained by multiplying the pre-stored proportions by the quadrature-axis current command value output by the speed loop. This eliminates the need for complex algorithms such as torque observers, repetitive control, or iterative learning control, resulting in minimal computational load, fast response speed, and suitability for low-cost, low-computing-power chip platforms.

[0151] During the dynamic correction phase, the amplitude of the sixth harmonic torque fluctuation is extracted based on the electrical angular velocity. Using zero as the target value and this sixth harmonic torque fluctuation amplitude as the feedback value, closed-loop feedback control is performed to obtain the current correction harmonic command value. This value is then superimposed on the basic harmonic current command to obtain the target current harmonic command. This closed-loop feedback control generates a dynamic current harmonic command based on the real-time fluctuation of the sixth harmonic velocity, and corrects the basic harmonic command in real time, causing the amplitude of the sixth harmonic torque fluctuation to converge to zero. This effectively eliminates residual torque ripple caused by individual differences in motor back EMF harmonics, temperature drift, and flux attenuation, significantly improving the robustness and consistency of torque ripple suppression.

[0152] In addition, during the generation of basic harmonic commands, the proportion of compensation current amplitude is calculated by setting the sine and cosine amplitudes of the 6th and 12th torque harmonics to zero. This ensures that the 6th torque pulsation is suppressed without increasing the 12th torque pulsation, thus avoiding the introduction of noise in other frequency bands and ensuring the quietness and stability of the air conditioner fan operation.

[0153] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of this application is limited only by the appended claims.

Claims

1. A method for controlling an air conditioner fan, characterized in that, The control method includes: When the fan has torque pulsation, the basic harmonic current command is determined based on the cross-axis current command value and back electromotive force harmonic characteristics of the fan. The electrical angular velocity of the fan is obtained, the amplitude of the sixth harmonic torque fluctuation is extracted based on the electrical angular velocity, and closed-loop feedback control is performed with a preset command value as the target value and the amplitude of the sixth harmonic torque fluctuation as the feedback value to obtain the current correction harmonic command value. The target current harmonic command is obtained by superimposing the current correction harmonic command value and the fundamental harmonic current command. The target current harmonic command is input into the current loop of the wind turbine for control to obtain the harmonic injection voltage. Based on the harmonic injection voltage and the fundamental voltage command, the operation of the wind turbine is controlled.

2. The control method according to claim 1, characterized in that, When the wind turbine experiences torque pulsation, before determining the fundamental harmonic current command based on the wind turbine's quadrature-axis current command value and back electromotive force harmonic characteristics, the following steps are also included: The mechanical speed of the fan is sampled at a first preset period and the speed fluctuation value is obtained after a first preset duration. Using the second preset duration as a statistical window, when the number of times the speed fluctuation value reaches or exceeds the preset threshold exceeds the preset number, it is determined that the fan has torque pulsation.

3. The control method according to claim 1, characterized in that, The back EMF harmonic characteristics include the proportion of the 5th harmonic sinusoidal amplitude and the proportion of the 7th harmonic sinusoidal amplitude of the back EMF. Based on the cross-axis current command value and back electromotive force harmonic characteristics of the wind turbine, the fundamental harmonic current command is determined, including: Based on the proportion of the 5th harmonic sinusoidal amplitude of the back electromotive force and the proportion of the 7th harmonic sinusoidal amplitude of the back electromotive force, the proportion of the 5th harmonic direct-axis current and the proportion of the 5th harmonic quadrature-axis current are determined. Multiply the cross-axis current command value of the wind turbine by the proportion of the 5th harmonic cross-axis current to obtain the cross-axis basic harmonic command value; Multiply the quadrature axis current command value of the wind turbine by the proportion of the 5th harmonic direct axis current to obtain the direct axis foundation harmonic command value; The quadrature-axis foundation harmonic command value and the direct-axis foundation harmonic command value constitute the foundation harmonic current command.

4. The control method according to claim 3, characterized in that, Based on the proportions of the 5th harmonic sinusoidal amplitude and the 7th harmonic sinusoidal amplitude of the back electromotive force, the proportions of the 5th harmonic direct-axis current and the 5th harmonic quadrature-axis current are determined, including: Based on the proportion of the 5th harmonic sinusoidal amplitude of the back EMF and the proportion of the 7th harmonic sinusoidal amplitude of the back EMF, calculate the proportion of the sinusoidal amplitude of the compensation current and the proportion of the cosine amplitude of the compensation current required to suppress the 6th torque pulsation. The proportions of the sine amplitude and the cosine amplitude of the compensation current are converted into the proportions of the 5th harmonic direct-axis current and the 5th harmonic quadrature-axis current through coordinate transformation.

5. The control method according to any one of claims 1 to 4, characterized in that, The amplitude of the 6th harmonic torque fluctuation is extracted based on the electrical angular velocity, including: Multiply the electrical angular velocity by the pole pair correlation coefficient to obtain the first calculation result; The first calculation result is multiplied by the sine and cosine values ​​of 6 times the electrical angle, respectively. After low-pass filtering, the amplitude of the sine component and the amplitude of the cosine component of the 6th harmonic torque fluctuation are obtained. The amplitude of the 6th harmonic torque fluctuation is synthesized based on the amplitude of the sine component and the amplitude of the cosine component.

6. The control method according to any one of claims 1 to 4, characterized in that, Using a preset command value as the target value and the amplitude of the sixth harmonic torque fluctuation as the feedback value, closed-loop feedback control is performed to obtain the current correction harmonic command value, including: With zero as the target value, the amplitude of the sixth harmonic torque fluctuation is used as the feedback value input to the proportional-integral controller. The proportional-integral regulator outputs a dynamic harmonic correction command value for the quadrature-axis current, and calculates the dynamic harmonic correction command value for the direct-axis current based on the proportional relationship between the direct-axis component and the quadrature-axis component in the basic harmonic current command. The quadrature-axis current dynamic correction harmonic command value and the direct-axis current dynamic correction harmonic command value constitute the current correction harmonic command value.

7. The control method according to any one of claims 1 to 4, characterized in that, The target current harmonic command is input into the current loop of the wind turbine for control, resulting in the harmonic injection voltage, including: The target current harmonic command and the fifth harmonic component extracted from the actual current of the wind turbine are proportionally and integrally adjusted to obtain the fifth harmonic quadrature axis command voltage and the fifth harmonic direct axis command voltage. Through coordinate transformation, the 5th harmonic quadrature-axis command voltage and the 5th harmonic direct-axis command voltage are converted into three-phase harmonic voltage command values, which are used as the harmonic injection voltage.

8. The control method according to any one of claims 1 to 4, characterized in that, Based on the harmonic injection voltage and fundamental voltage commands, the operation of the wind turbine is controlled, including: The harmonic injection voltage is superimposed with the fundamental voltage command to obtain the total three-phase voltage command signal; The total three-phase voltage command signal is generated by a PWM generation circuit and output as a drive signal to the fan.

9. The control method according to claim 1, characterized in that, The fan is either the indoor fan or the outdoor fan of the air conditioner, and the motor of the fan is a surface-mounted permanent magnet synchronous motor.

10. An air conditioner, characterized in that, include: Air conditioner body; The fan is installed in the main body of the air conditioner; A controller electrically connected to the wind turbine, configured to perform the control method as described in any one of claims 1 to 9.

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