Beat suppression device, motor, air conditioner

Abstract

The application provides a beat frequency suppression device, a motor and an air conditioner. The beat frequency suppression device comprises a detector configured to acquire a direct-current bus ripple frequency of a motor and a mechanical pulsation frequency of a compressor driven by the motor; and a current processor configured to generate a compensation signal according to a current of the motor and the direct-current bus ripple frequency if the direct-current bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor satisfy a current beat frequency condition. The application can generate the compensation signal based on the frequency-fixed direct-current bus ripple frequency and the current of the motor when the direct-current bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor satisfy the current beat frequency condition, can be used to reduce the influence of the direct-current bus ripple frequency in the current on a beat frequency band of the current of the motor, and can suppress the current beat frequency and reduce the vibration and noise of the compressor during low-frequency operation.

Description

Technical Field

[0001] This application relates to the field of variable frequency air conditioning control. More specifically, it relates to a beat frequency suppression device, a motor, and an air conditioner. Background Technology

[0002] In variable frequency air conditioning systems, especially rotary compressors driven by permanent magnet synchronous motors (PMSM), the interaction between the mechanical characteristic pulsations during low-frequency operation and the power supply frequency can easily lead to frequency beats. This phenomenon not only causes current pulsations but also leads to stress problems in the air conditioning piping, increases system vibration and noise, and ultimately reduces user comfort.

[0003] In existing technologies, air conditioning compressors are mostly rotary compressors, especially the twin-rotor compressors commonly used in multi-split systems. Due to the mechanical characteristics of twin-rotor compressors, their speed has a second harmonic component. When using vector control (FOC) technology, SVPWM conversion requires the acquisition of the DC bus voltage, and the AC ripple of the DC bus voltage contains a power supply frequency component. This results in a power supply frequency spectrum in the motor control. When the amplitude of the second harmonic component of the compressor's mechanical speed is high, it will interact with the DC bus voltage ripple, causing beat frequency phenomena, affecting the stability and noise level of the motor. Summary of the Invention

[0004] In view of the problems pointed out in the background art, the embodiments of this application provide a beat frequency suppression device, a motor, and an air conditioner to suppress the current beat frequency of the motor.

[0005] In a first aspect, embodiments of this application provide a beat frequency suppression device, comprising: a detector for acquiring the DC bus ripple frequency of a motor and the mechanical pulsation frequency of a compressor driven by the motor; and a current processor for generating a compensation signal based on the motor current and the DC bus ripple frequency if the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor satisfy a current beat frequency condition; the compensation signal is used to compensate for the DC bus ripple frequency in the current to suppress current beat frequency.

[0006] The technical solutions described above have the following advantages or beneficial effects: When the compressor operates at low frequency, it exhibits mechanical pulsation, resulting in a current component in the motor driving the compressor having a frequency equal to the mechanical pulsation frequency of the compressor and a current component having a frequency equal to the DC bus ripple frequency, causing a beat frequency phenomenon that affects motor operation. The solution of this application, when the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor meet the current beat frequency condition, generates a compensation signal based on the fixed frequency of the DC bus ripple frequency and the motor current. This signal can be used to compensate for the DC bus ripple frequency in the current, thereby suppressing current beat frequency and reducing vibration and noise of the compressor during low-frequency operation.

[0007] In some embodiments of this application, the detector includes a frequency detection unit for calculating the mechanical pulsation frequency based on the operating frequency of the compressor.

[0008] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: The solution of this application can avoid the deployment of additional sensors, reduce hardware costs and simplify the detection process by calculating the mechanical pulsation frequency based on the operating frequency of the compressor through the frequency detection unit.

[0009] In some embodiments of this application, the frequency detection unit is further configured to: determine the frequency amplification factor according to the compressor type; specifically, the frequency detection unit is configured to: calculate the product of the frequency amplification factor and the operating frequency of the compressor, and use the product as the mechanical pulsation frequency of the compressor.

[0010] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: The solution of this application achieves precise matching of mechanical characteristics and beat frequency conditions of different compressors by adaptively adjusting the frequency amplification coefficient according to the compressor type, thereby improving system compatibility.

[0011] In some embodiments of this application, the compressor is a rotary compressor; the frequency detection unit is specifically used to: determine the frequency amplification factor based on the number of rotors of the compressor; wherein the frequency amplification factor is positively correlated with the number of rotors.

[0012] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: The solution of this application, based on the characteristics of rotary compressors, dynamically sets the frequency amplification coefficient in combination with the number of rotors, enhances the accuracy of mechanical pulsation frequency calculation, and avoids overcompensation or undercompensation.

[0013] In some embodiments of this application, the current processor includes: a frequency domain transformation unit for performing frequency domain transformation on the current to obtain a harmonic signal; wherein the frequency of the harmonic signal is n times the DC bus ripple frequency, and n is a positive integer; a DC-DC conversion unit for converting the harmonic signal into a DC signal; a current control unit for controlling the DC signal to zero and outputting a corresponding DC compensation signal; and a time domain transformation unit for performing time domain transformation on the DC compensation signal to obtain a compensation signal.

[0014] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: The solution in this example converts the current from a time-domain signal to a frequency-domain signal and determines a harmonic signal with a frequency that is n times the DC bus ripple frequency, thereby realizing harmonic extraction at a specific frequency; by converting the harmonic signal into a DC signal, it can be used to output a DC compensation signal, and by further performing time-domain conversion on the DC compensation signal, a compensation signal in the form of a time-domain signal can be output.

[0015] In some embodiments of this application, the frequency domain transformation unit is specifically used to: perform Fourier transform based on the angular frequency of the current and the DC bus ripple frequency to obtain the harmonic signal.

[0016] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: The solution in this example avoids full-frequency Fourier transform by performing Fourier transform on the angular frequency of the current at the DC bus ripple frequency, thereby reducing computational resources and improving the extraction efficiency of harmonic signals.

[0017] In some embodiments of this application, the time-domain transformation unit is specifically used to: perform an inverse Fourier transform based on the angular frequency of the DC bus ripple frequency of the DC compensation signal to obtain the compensation signal.

[0018] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: The solution in this example performs inverse Fourier transform based on the angular frequency of the DC compensation signal DC bus ripple frequency, and reconstructs the compensation signal through inverse Fourier transform, ensuring that the compensation signal is strictly synchronized with the original ripple frequency, thereby improving the harmonic cancellation efficiency.

[0019] In some embodiments of this application, the frequency domain transformation unit is further configured to: filter the harmonic signal to remove harmonic signals other than the DC bus ripple frequency.

[0020] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: The solution in this example eliminates non-target harmonic interference by filtering, focuses the DC bus ripple frequency component, reduces noise pollution in the compensation signal, and improves the suppression accuracy.

[0021] In some embodiments of this application, the current control unit is specifically used to: introduce a reference value of zero, control the DC signal to the reference value through an integral controller, and use the control signal output by the integral controller as a DC compensation signal.

[0022] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: The solution in this example uses an integral controller to achieve zero steady-state error tracking of the DC component, avoids residual deviation of proportional control, and improves the accuracy of harmonic component elimination.

[0023] In some embodiments of this application, the DC conversion unit is specifically used to: project the harmonic signal in the dq rotating coordinate system to obtain the d-axis DC component signal and the q-axis DC component signal.

[0024] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: The solution in this example decomposes the harmonic signal in the dq rotating coordinate system, separates the d-axis DC component and the q-axis DC component, which facilitates independent control of the two-axis harmonics and optimizes the compensation effect.

[0025] In some embodiments of this application, the current control unit is specifically used to: control the d-axis DC component signal to zero and output the corresponding DC compensation signal; control the q-axis DC component signal to zero and output the corresponding DC compensation signal.

[0026] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: closed-loop control is performed on the d-axis DC component and the q-axis DC component respectively to achieve synchronous suppression of the current ripple of the two axes, avoid cross interference, and improve the accuracy of beat frequency suppression.

[0027] In some embodiments of this application, the beat frequency suppression device further includes: a current compensation unit, used to superimpose a compensation signal onto the current to compensate for the DC bus ripple frequency in the current, so as to suppress the current beat frequency.

[0028] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: by directly superimposing the compensation signal through the current compensation unit, there is no need to modify the original current loop control architecture, thus reducing the complexity of system transformation.

[0029] In some embodiments of this application, the current includes d-axis current and q-axis current; the current processor is specifically used to: generate a d-axis compensation signal based on the d-axis current of the motor and the DC bus ripple frequency; and generate a q-axis compensation signal based on the q-axis current of the motor and the DC bus ripple frequency.

[0030] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: compensation signals are generated independently for d-axis current and q-axis current, solving the harmonic residue problem caused by two-axis coupling in vector control and improving the suppression capability under all operating conditions.

[0031] In some embodiments of this application, the current compensation unit is specifically used to: superimpose the d-axis compensation signal onto the d-axis current; and superimpose the q-axis compensation signal onto the q-axis current.

[0032] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: the d-axis current and q-axis current are compensated separately, avoiding the introduction of new imbalances by a single compensation signal, ensuring the symmetry of the current waveform, and reducing electromagnetic noise.

[0033] In some embodiments of this application, the current processor further includes: a beat frequency determination unit, which determines that the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor meet the current beat frequency condition if the difference between them is different and within a preset frequency range.

[0034] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: by determining the beat frequency conditions through a preset frequency range, invalid compensation in non-sensitive frequency bands is avoided, and the computational load of the controller is reduced.

[0035] In some embodiments of this application, a motor drive device is also disclosed, comprising: an inverter, a feedback module, and the beat frequency suppression device as described above; the inverter is used to output abc three-phase current to the feedback module; the feedback module is used to convert the abc three-phase current into motor current, and output a feedback signal to the inverter according to the motor current and the corresponding rated current; the feedback module is also used to output the motor current to the beat frequency suppression device; the beat frequency suppression device is used to generate a compensation signal according to the motor current and return a compensation signal to the feedback module.

[0036] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: by integrating the beat frequency suppression device into the motor drive system, closed-loop control of current ripple detection and compensation is realized, the quality of inverter output current is improved, the periodic disturbance of motor torque caused by beat frequency is reduced, and the dynamic response capability of the drive system is enhanced.

[0037] In some embodiments of this application, an electric motor is also involved, which includes the motor drive device described above.

[0038] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: the motor has a built-in integrated beat frequency suppression drive device, which can eliminate the electromagnetic excitation force caused by current harmonics, making the motor run more smoothly and extending the bearing life.

[0039] In some embodiments of this application, an air conditioner is also disclosed, which includes a compressor and the motor described above.

[0040] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: the air conditioner uses an anti-beating frequency motor to drive the compressor, which avoids the speed fluctuations caused by beat frequency from being transmitted to the refrigerant circulation system, thereby improving the energy efficiency ratio and reducing abnormal vibration noise of the compressor, thus improving the user experience. Attached Figure Description

[0041] To more clearly illustrate the implementation methods in the embodiments of this application or related technologies, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0042] Figure 1 The q-axis current beat frequency spectrum provided in the embodiments of this application;

[0043] Figure 2 This is a schematic diagram of the control loop of the motor provided in an embodiment of this application;

[0044] Figure 3 This is a schematic diagram of the beat frequency suppression device provided in the embodiments of this application;

[0045] Figure 4 This is a schematic diagram of q-axis current spectrum analysis provided in an embodiment of this application;

[0046] Figure 5 This is a schematic diagram of the beat frequency suppression device provided in the embodiments of this application;

[0047] Figure 6 This is a schematic diagram of the beat frequency suppression device provided in the embodiments of this application;

[0048] Figure 7 This is a schematic diagram of the beat frequency suppression device provided in the embodiments of this application;

[0049] Figure 8 This is a schematic diagram of the signal processing of the beat frequency suppression device provided in the embodiments of this application;

[0050] Figure 9 This is a schematic diagram of the signal processing of the beat frequency suppression device provided in the embodiments of this application;

[0051] Figure 10 This is a schematic diagram of the signal processing of the beat frequency suppression device provided in the embodiments of this application;

[0052] Figure 11 This is a schematic diagram of the structure of the motor drive device provided in the embodiments of this application.

[0053] Reference numerals: beat frequency suppression device 100, detector 110, current processor 120, frequency detection unit 111, frequency domain conversion unit 121, DC-DC conversion unit 122, current control unit 123, time domain conversion unit 124, current compensation unit 130, motor drive device 900, inverter 300, feedback module 200. Detailed Implementation

[0054] 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.

[0055] 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.

[0056] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover but not exclusively include, for example, a product or device that includes a series of components is not necessarily limited to those that are explicitly listed, but may include other components that are not explicitly listed or that are inherent to such product or device.

[0057] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" 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 between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0058] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0059] Current air conditioner compressors are typically driven by electric motors (such as permanent magnet synchronous motors, PMSMs). For widely used rotary compressors (such as twin-rotor compressors), the periodic meshing characteristics of the rotors generate a second-harmonic mechanical pulsation component during operation. This pulsation couples into the motor current, forming harmonics of the same frequency. Simultaneously, when the motor drive uses FOC control, SVPWM modulation requires sampling the DC bus voltage, which is significantly affected by the power supply frequency: the ripple frequency is 100Hz for single-phase systems (corresponding to a 50Hz power supply), and reaches 300Hz for three-phase systems. When the compressor's mechanical pulsation second-harmonic frequency (e.g., 2 × mechanical speed in a twin-rotor unit) approaches the DC bus ripple frequency (e.g., 100Hz / 300Hz), their interaction produces a beat frequency phenomenon, leading to motor speed fluctuations and a surge in electromagnetic noise, severely reducing air conditioner energy efficiency and user experience. Figure 1 The q-axis current beat frequency spectrum provided in this application embodiment is shown in the figure. The current spectrum contains a periodic beat frequency envelope.

[0060] Figure 2This is a schematic diagram of the control loop of the motor provided in an embodiment of this application. Figure 2 As shown, on the one hand, the field weakening control generates the d-axis current increment Δi d After adjustment by the PI controller, it is related to the given d-axis current reference value i. d * Superimposed, and based on d-axis feedback current i d Generate d-axis voltage command u d *. q-axis current reference value i q * The speed loop ω is given by a PI controller, and further fed back by the PI controller based on the q-axis feedback current i. q Generate q-axis voltage command u q *. u d * and u q * Converted to α / β axis voltage u in stationary coordinates via inverse Park transformation (based on rotor position angle θ) α * and u β * Then, a three-phase PWM wave is generated through SVPWM modulation to drive the inverter, and the output current drives the PMSM motor. On the other hand, the motor's three-phase current (i a i b i c Converted to α / β axis current i via Clark transformation α and i β Then, the d / q axis feedback current i is obtained through Park transformation (based on θ). d and i q Closed-loop correction voltage command. The position observer estimates the motor rotor position based on the d / q axis feedback current i. d and i q and d / q axis feedback voltage u d and u q Determine Δθ (shaft error). The phase-locked loop (PLL) obtains the rotor position θ and angular frequency ω based on the shaft error Δθ output by the position observer, and then performs closed-loop control of the motor speed through the outer speed loop.

[0061] The beat frequency suppression device provided in this application receives the d / q axis feedback current i d and i q Feedback from d-axis current i d The beat frequency-related harmonics are separated from the signal, and the output compensation signal is used as i. dcmp and i d Superposition, i from q-axis current feedback q The beat frequency-related harmonics are separated from the signal, and the output compensation signal is used as i. qcmp with i dSuperposition is used to achieve beat frequency suppression. Other beneficial effects of this example scheme include the fact that the compensation signal is injected through the feedforward channel to avoid interfering with the integration process of the main PI controller, and that the beat frequency suppression device is independent of the main control loop, eliminating the need to refactor the original FOC architecture and facilitating engineering implementation.

[0062] Figure 3 This is a schematic diagram of the beat frequency suppression device provided in the embodiments of this application, as shown below. Figure 3 As shown, the beat frequency suppression device 100 includes: a detector 110 for acquiring the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor driven by the motor; and a current processor 120 for generating a compensation signal based on the motor current and the DC bus ripple frequency if the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor meet the current beat frequency condition; the compensation signal is used to compensate for the DC bus ripple frequency in the current to suppress the current beat frequency.

[0063] For example, when implementing detector 110, a current sensor can be installed on the DC bus side of the motor driver to detect the DC bus ripple frequency, such as by acquiring the current signal in real time at a fixed sampling rate. Optionally, the current spectrum can be analyzed by Fast Fourier Transform (FFT) to identify the high-frequency component with the largest amplitude as the DC bus ripple frequency. Optionally, the DC bus ripple frequency can also be determined according to a preset configuration, such as a ripple frequency of 100Hz for a single-phase power system (corresponding to a 50Hz power supply) and 300Hz for a three-phase power system. The detection method for mechanical pulsation frequency can be, on the one hand, through theoretical calculation. For example, for reciprocating compressors, the mechanical pulsation frequency can be calculated by obtaining parameters related to the piston motion frequency; optionally, for rotary compressors (such as screw compressors and centrifugal compressors), the mechanical pulsation frequency can be calculated by obtaining parameters related to the number of rotor blades and rotational speed. On the other hand, the main pulsation frequency of the compressor can be obtained by installing an acceleration sensor (such as a vibration sensor) and a data acquisition instrument or spectrum analyzer.

[0064] For example, when the current processor 120 detects that the difference between the DC ripple frequency of the bus and the mechanical pulsation frequency is less than 5Hz, it determines that there is a beat frequency risk. Figure 4The diagram illustrates the q-axis current spectrum analysis provided in this embodiment. As shown, when the rotor speed of the dual-rotor motor is 47 rpm, a current component with an amplitude of 500 rms and a frequency of 94 Hz appears in the q-axis current. Simultaneously, the q-axis current also contains a current component from single-phase AC with an amplitude of 260 rms and a frequency of 100 Hz. At this point, the two current components have similar frequencies and relatively large energy (amplitude), causing them to beat each other, resulting in poor motor control stability. It should be noted that the bus DC ripple frequency causing the beat frequency phenomenon is usually fixed, while the mechanical pulsation frequency caused by the low-frequency operation of the compressor typically fluctuates around the bus DC ripple frequency. The solution in this example improves the efficiency of beat frequency suppression by eliminating the fixed bus DC ripple frequency.

[0065] For example, the current processor 120 can separate the d-axis and q-axis current components by performing coordinate transformation (Clarke / Park transformation) on the three-phase current of the motor; it can use an adaptive notch filter to generate reverse harmonic signals for the ripple frequency and achieve accurate cancellation by dynamically adjusting the filter parameters; and it can inject the compensation signal into the current reference value of the motor control loop to correct the inverter output in real time.

[0066] The frequency suppression device of this application includes: a detector for acquiring the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor driven by the motor; and a current processor for generating a compensation signal based on the motor current and the DC bus ripple frequency if the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor meet the current beat frequency condition. The solution of this application, when the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor meet the current beat frequency condition, generates a compensation signal based on the fixed frequency of the DC bus ripple frequency and the motor current. This can be used to reduce the influence of the DC bus ripple frequency in the current on the beat frequency band of the motor current, thereby suppressing current beat frequency and reducing vibration and noise of the compressor during low-frequency operation.

[0067] Figure 5 This is a schematic diagram of the beat frequency suppression device provided in the embodiments of this application, as shown below. Figure 5 As shown, the detector 110 includes a frequency detection unit 111, which is used to calculate the mechanical pulsation frequency based on the operating frequency of the compressor.

[0068] In practical applications, a pre-set compressor type database (such as rotary, scroll, and centrifugal) can be established, with each type associated with a preset mechanical frequency multiplication rule. For example: Twin-rotor compressor: Mechanical pulsation frequency = operating frequency × 4 (2 mechanical impacts per revolution × phase difference between the two rotors). Scroll compressor: Mechanical pulsation frequency = operating frequency × 2 (1 impact per revolution of the single scroll plate). The solution in this application, by calculating the mechanical pulsation frequency based on the compressor's operating frequency through the frequency detection unit 111, avoids the need for additional sensor deployment, reduces hardware costs, and simplifies the detection process.

[0069] In one example, the frequency detection unit 111 is also used to: determine the frequency amplification factor according to the compressor type; specifically, the frequency detection unit 111 is used to: calculate the product of the frequency amplification factor and the operating frequency of the compressor, and use the product as the mechanical pulsation frequency of the compressor.

[0070] In practical applications, for rotary compressors, the frequency amplification factor is dynamically calibrated based on rotor position sensor data during the startup phase. If a rotor phase difference deviates from the theoretical value, the frequency amplification factor is automatically adjusted to ensure frequency calculation accuracy. For example, for centrifugal compressors, the frequency amplification factor k can be set according to the number of impeller blades (e.g., 12 blades) as k = number of blades × 1 (i.e., k = 12), and the mechanical pulsation frequency is calculated as compressor operating frequency × k. The solution in this application adaptively adjusts the frequency amplification factor based on the compressor type, achieving precise matching between the mechanical characteristics and beat frequency conditions of different compressors, thus improving system compatibility.

[0071] In one example, the compressor is a rotary compressor; the frequency detection unit 111 is specifically used to: determine the frequency amplification factor based on the number of rotors of the compressor; wherein the frequency amplification factor is positively correlated with the number of rotors.

[0072] For example, the amplification factor of a dual-rotor compressor is 2, and the mechanical pulsation frequency is calculated as the operating frequency × 2; the amplification factor of a three-rotor compressor is 3, which achieves strict synchronization with the rotor mechanical cycle and precise matching of rotor mechanical characteristics, avoiding frequency misjudgment.

[0073] Figure 6 This is a schematic diagram of the beat frequency suppression device provided in the embodiments of this application, as shown below. Figure 6 As shown, the current processor 120 includes: a frequency domain transformation unit 121, used to perform frequency domain transformation on the current to obtain a harmonic signal; wherein the frequency of the harmonic signal is n times the DC bus ripple frequency, and n is a positive integer; a DC-DC conversion unit 122, used to convert the harmonic signal into a DC signal; a current control unit 123, used to control the DC signal to zero and output a corresponding DC compensation signal; and a time domain transformation unit 124, used to perform time domain transformation on the DC compensation signal to obtain a compensation signal.

[0074] For example, the motor current can be obtained through high-speed sampling; wherein the sampling frequency must satisfy Shannon's theorem, i.e., it must be at least twice the highest harmonic frequency of interest. Optionally, an anti-aliasing filter is also used to filter out high-frequency noise and retain the effective harmonic frequency band. For example, the frequency domain transformation unit 121 can convert the current signal into a frequency domain spectrum through frequency domain analysis methods, such as using Fast Fourier Transform (FFT) or Sliding Window Discrete Fourier Transform (DFT). For example, during the motor startup phase, the DC bus ripple frequency can be identified by spectrum scanning and the value of n can be dynamically set; during the motor operation phase, the fundamental frequency of the bus ripple can be tracked in real time through a phase-locked loop (PLL) according to the ripple frequency drift, and the frequency can be updated by multiples of n.

[0075] For example, the DC-DC conversion unit 122 uses a synchronous demodulator based on a reference frequency (n times the DC bus ripple frequency) to multiply the extracted nth harmonic signal with a reference signal of the same frequency, and then passes the result through a low-pass filter to obtain the DC component. The reference signal is generated by a phase-locked loop to ensure strict synchronization with the bus ripple frequency.

[0076] For example, the current control unit 123 can be a proportional-integral (PI) controller, with the DC component error (target value of zero) as input and the amplitude and phase of the compensation command as output. In practical applications, the control parameters (proportional control parameters and integral control parameters) of the PI controller can be set according to the system response speed and stability requirements. Optionally, an anti-saturation algorithm can also be introduced into the PI controller to prevent the integrator from overflowing during startup or sudden operating conditions.

[0077] After receiving the compensation command (amplitude and phase), the time-domain transformation unit 124 can multiply the compensation command with the reference frequency signal to generate a time-domain compensated waveform. In one example, the time-domain transformation unit 124 can also directly synthesize a sinusoidal signal of the target frequency using an inverse Fourier transform or a digital oscillator. Optionally, a delay compensation algorithm can be used to ensure that the synthesized signal is out of phase with the original ripple current, achieving maximum cancellation effect.

[0078] As an optional step in this example, the compensation signal can also be amplified to the required level by a Class D amplifier or inverter and injected into the current loop control circuit after passing through an isolation transformer.

[0079] The scheme in this example converts the current from a time-domain signal to a frequency-domain signal and determines the harmonic signal with a frequency that is n times the DC bus ripple frequency, thus realizing harmonic extraction at a specific frequency. By converting the harmonic signal into a DC signal, it can be used to output a DC compensation signal. Further time-domain conversion of the DC compensation signal can output a compensation signal in the form of a time-domain signal.

[0080] As another example, the frequency domain transformation unit 121 is specifically used to perform Fourier transform based on the angular frequency of the current and the DC bus ripple frequency to obtain the harmonic signal.

[0081] As another example corresponding to this example, the time-domain transformation unit 124 is specifically used to: perform an inverse Fourier transform based on the angular frequency of the DC bus ripple frequency of the DC compensation signal to obtain the compensation signal.

[0082] It should be noted that in practical applications, these two examples can be implemented in one embodiment to reduce computational load using synchronous demodulation technology, or they can be implemented in different embodiments to improve the flexibility of signal conversion. Specifically, the frequency domain conversion unit, based on the angular frequency of the DC bus ripple frequency, i.e., ω = 2π*f, where f is the bus ripple frequency, generates orthogonal reference signals sin(ωt) and cos(ωt). After multiplying these signals by the motor current signal and integrating, the fundamental component is directly extracted. In this example, by performing a Fourier transform on the angular frequency of the current at the DC bus ripple frequency, a full-frequency Fourier transform is avoided, reducing computational resources and improving the efficiency of harmonic signal extraction.

[0083] Correspondingly, during the inverse Fourier transform, the time-domain transformation unit 124 can reconstruct the time-domain waveform of the compensation signal using the same ω. In this example, the scheme performs an inverse Fourier transform based on the angular frequency of the DC compensation signal's DC bus ripple frequency. By reconstructing the compensation signal through the inverse Fourier transform, it ensures that the compensation signal is strictly synchronized with the original ripple frequency, thereby improving harmonic cancellation efficiency.

[0084] In one example, the frequency domain transformation unit 121 is also used to filter the harmonic signal to remove harmonic signals other than the DC bus ripple frequency.

[0085] After frequency domain transformation, digital filters (such as notch filters or low-pass filters) are used to filter out frequency components other than the DC bus ripple frequency, retaining only the target harmonics. The solution in this example eliminates non-target harmonic interference through filtering, focuses on the DC bus ripple frequency components, reduces noise contamination in the compensation signal, and improves suppression accuracy.

[0086] In one example, the current control unit 123 is specifically used to: introduce a reference value of zero, control the DC signal to the reference value through an integral controller, and use the control signal output by the integral controller as a DC compensation signal.

[0087] For example, the integral controller can be an anti-saturation integral controller. Optionally, the reference value can be gained or lost based on zero. For example, the time constant in the integral controller can be T = 1 / (2πf), where f is the DC bus ripple frequency. The scheme in this example uses an integral controller to achieve zero steady-state error tracking of the DC component, avoiding residual deviation of proportional control and improving the accuracy of harmonic component elimination.

[0088] In one example, the DC conversion unit 122 is specifically used to project the harmonic signal in the dq rotating coordinate system to obtain the d-axis DC component signal and the q-axis DC component signal.

[0089] For example, the DC-DC conversion unit 122 projects the harmonic signal in the dq coordinate system, decomposing it into a d-axis DC component signal and a q-axis DC component signal, where the former corresponds to the ripple amplitude and the latter is used for phase calibration. This example scheme decouples the harmonic signal in the dq rotating coordinate system, separating the d-axis DC component and the q-axis DC component, facilitating independent control of the two-axis harmonics and optimizing the compensation effect.

[0090] In one example, the current control unit 123 is specifically used to: control the d-axis DC component signal to zero and output the corresponding DC compensation signal; control the q-axis DC component signal to zero and output the corresponding DC compensation signal.

[0091] The scheme in this example performs closed-loop control on the d-axis DC component and the q-axis DC component respectively, so as to achieve synchronous suppression of current ripple on both axes, avoid cross interference, and improve the accuracy of beat frequency suppression.

[0092] Figure 7 This is a schematic diagram of the beat frequency suppression device provided in the embodiments of this application, as shown below. Figure 7 As shown, the beat frequency suppression device further includes a current compensation unit 130, which is used to superimpose a compensation signal onto the current to compensate for the DC bus ripple frequency in the current and suppress the current beat frequency.

[0093] In this example, the overcurrent compensation unit 130 directly superimposes the compensation signal, without modifying the original current loop control architecture, thus reducing the complexity of system modification.

[0094] In one example, the current includes d-axis current and q-axis current; the current processor 120 is specifically used to: generate a d-axis compensation signal based on the motor's d-axis current and the DC bus ripple frequency; and generate a q-axis compensation signal based on the motor's q-axis current and the DC bus ripple frequency.

[0095] In practical applications, the three-phase current (i) of the motor is... a i b i cConverted to α / β axis current i via Clark transformation α and i β Then, the d-axis current (i) is obtained through Park transformation. d ) and q-axis current (i q It should be noted that the d-axis current and q-axis current can be used for current signal processing in any of the above embodiments to obtain d-axis compensation signals and q-axis compensation signals. For example, the d-axis current and q-axis current can be subjected to the following Fourier transform at the angular frequency (2π*f) corresponding to the DC bus ripple frequency (f):

[0096]

[0097] Among them, I d,0 and I q,0 For the DC bias of the d-axis current and q-axis current, I dn and I qn Let ω be the amplitude of the nth harmonic of the d-axis current and the q-axis current, and let ω be the angular frequency of the DC bus ripple frequency (f). and The phase of the nth harmonic of the d-axis current and the q-axis current.

[0098] Figure 8 This is a schematic diagram of the signal processing of the beat frequency suppression device provided in an embodiment of this application. Figure 8 As shown, the d-axis current and the motor rotor position (θ = ωt) are input, and a Fourier transform is performed at an angular frequency ω = 2π*f to obtain the nth harmonic signal. Then, the signal is projected into the dq rotating coordinate system to obtain the d-axis DC component signal (Y) of the d-axis current. d ) and q-axis DC component signal (Y q ).

[0099] Figure 9 This is a schematic diagram of the signal processing of the beat frequency suppression device provided in an embodiment of this application. Figure 9 As shown, the d-axis DC component signal (Y) of the d-axis current is... d ) and q-axis DC component signal (Y q Low-pass filtering is performed separately to remove harmonic signals other than the DC bus ripple frequency, and a zero reference value is introduced. Y is then calculated by the Pi controller. d and Y q The corresponding control quantity at the reference value, based on this control quantity, affects Y. d and Y q Amplification is performed to obtain the d-axis DC compensation signal (X) of the d-axis current. d ) and q-axis DC compensation signal (X q Furthermore, Figure 10This is a schematic diagram of the signal processing of the beat frequency suppression device provided in an embodiment of this application. After processing as follows... Figure 10 The signal processing shown will X d and X q The input includes the motor rotor position (θ = ωt), and an inverse Fourier transform is performed based on the angular frequency ω = 2π*f to obtain the d-axis compensation signal (Y). o That is Figure 9 i in qcmp The signal processing flow for the q-axis current is similar to that for the d-axis current, and will not be elaborated further here.

[0100] The solution in this example generates compensation signals independently for the d-axis current and q-axis current, which solves the harmonic residue problem caused by the two-axis coupling in vector control and improves the suppression capability under all operating conditions.

[0101] In one example, the current compensation unit 130 is specifically used to: superimpose the d-axis compensation signal onto the d-axis current; and superimpose the q-axis compensation signal onto the q-axis current.

[0102] The solution in this example compensates for the d-axis current and q-axis current separately, avoiding the introduction of new imbalances by a single compensation signal, ensuring the symmetry of the current waveform, and reducing electromagnetic noise.

[0103] In one example, the current processor 120 further includes a beat frequency determination unit, which determines that the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor meet the current beat frequency condition if the difference between the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor is different and the difference is within a preset frequency range.

[0104] For example, the preset frequency range can be set to be adjustable from 1 to 10 Hz. In practical applications, a beat frequency determination unit can be set up to activate compensation when the difference between the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor is within the preset frequency range; otherwise, it enters sleep mode to reduce power consumption. The solution in this example determines the beat frequency condition through the preset frequency range, avoiding invalid compensation in non-sensitive frequency bands and reducing the computational load on the controller.

[0105] Figure 11 This is a schematic diagram of the structure of the motor drive device provided in an embodiment of this application. Figure 11As shown, the motor drive device 900 includes: an inverter 300, a feedback module 200, and a beat frequency suppression device 100 as described in any of the above embodiments. The inverter 300 outputs three-phase currents (a, b, and c) to the feedback module 200 and the motor. The feedback module 200 converts the three-phase currents (a, b, and c) into motor current and outputs a feedback signal to the inverter 300 based on the motor current and the corresponding rated current. The feedback module 200 also outputs the motor current to the beat frequency suppression device 100. The beat frequency suppression device 100 generates a compensation signal based on the motor current and returns a compensation signal to the feedback module 200.

[0106] The motor drive device 900 in this example can implement the technical solution of the beat frequency suppression device 100 in any of the above embodiments and obtain the corresponding technical effects. Furthermore, by integrating the beat frequency suppression device into the motor drive system, the motor drive device 900 in this example achieves closed-loop control of current ripple detection and compensation, improves the output current quality of the inverter 300, reduces the periodic disturbance of motor torque caused by beat frequency, and enhances the dynamic response capability of the drive system.

[0107] This application also provides a motor, which includes the motor drive device 900 as described in any of the above embodiments.

[0108] The proposed solution incorporates an integrated beat frequency suppression drive device in the motor, which can eliminate electromagnetic excitation caused by current harmonics, making the motor run more smoothly and extending bearing life.

[0109] This application also provides an air conditioner, which includes a compressor and a motor as described in any of the above embodiments.

[0110] The proposed solution uses an anti-beating frequency motor to drive the compressor in the air conditioner, which avoids the speed fluctuations caused by beat frequency from being transmitted to the refrigerant circulation system. This can improve the energy efficiency ratio, reduce abnormal vibration noise of the compressor, and enhance the user experience.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0112] For ease of explanation, the above description has been provided in conjunction with specific embodiments. However, the above exemplary discussion is not intended to be exhaustive or to limit the embodiments to the specific forms disclosed above. Various modifications and variations can be obtained based on the above teachings. The selection and description of the above embodiments are for the purpose of better explaining the principles and practical applications, thereby enabling those skilled in the art to better utilize the above embodiments and various different variations of embodiments suitable for specific application considerations.

Claims

1. A beat frequency suppression device, characterized in that, include: A detector is used to acquire the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor driven by the motor. A current processor is configured to generate a compensation signal based on the current of the motor and the DC bus ripple frequency if the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor meet the current beat frequency condition; the compensation signal is used to compensate for the DC bus ripple frequency in the current to suppress the current beat frequency.

2. The beat frequency suppression device according to claim 1, characterized in that, The detector includes: A frequency detection unit is used to calculate the mechanical pulsation frequency based on the operating frequency of the compressor; Preferably, the frequency detection unit is further configured to: determine the frequency amplification factor according to the compressor type; specifically, the frequency detection unit is configured to: calculate the product of the frequency amplification factor and the operating frequency of the compressor, and use the product as the mechanical pulsation frequency of the compressor; Preferably, the compressor is a rotary compressor; the frequency detection unit is specifically used to: determine the frequency amplification factor based on the number of rotors of the compressor; wherein the frequency amplification factor is positively correlated with the number of rotors.

3. The beat frequency suppression device according to claim 1, characterized in that, The current processor includes: A frequency domain transformation unit is used to perform frequency domain transformation on the current to obtain a harmonic signal; wherein the frequency of the harmonic signal is n times the DC bus ripple frequency, and n is a positive integer; A DC-DC converter unit is used to convert the harmonic signal into a DC signal; A current control unit is used to control the DC signal to zero and output a corresponding DC compensation signal; The time-domain transformation unit is used to perform time-domain transformation on the DC compensation signal to obtain the compensation signal.

4. The beat frequency suppression device according to claim 3, characterized in that, The frequency domain transformation unit is specifically used to: perform Fourier transform based on the current and the angular frequency under the DC bus ripple frequency to obtain the harmonic signal; And / or, the time-domain transformation unit is specifically used to: perform an inverse Fourier transform based on the angular frequency of the DC bus ripple frequency of the DC compensation signal to obtain the compensation signal.

5. The beat frequency suppression device according to claim 3, characterized in that, The frequency domain transformation unit is also used for: The harmonic signal is filtered to remove harmonic signals other than the DC bus ripple frequency. Preferably, the current control unit is specifically used to: introduce a reference value of zero, control the DC signal to the reference value through an integral controller, and use the control signal output by the integral controller as the DC compensation signal.

6. The beat frequency suppression device according to claim 3, characterized in that, The DC-DC conversion unit is specifically used to: project the harmonic signal in the dq rotating coordinate system to obtain the d-axis DC component signal and the q-axis DC component signal; Preferably, the current control unit is specifically used to: control the d-axis DC component signal to zero and output the corresponding DC compensation signal; control the q-axis DC component signal to zero and output the corresponding DC compensation signal.

7. The beat frequency suppression device according to claim 1, characterized in that, The beat frequency suppression device further includes: A current compensation unit is used to superimpose the compensation signal onto the current to compensate for the DC bus ripple frequency in the current and suppress the current beat frequency. Preferably, the current includes d-axis current and q-axis current; the current processor is specifically used to: generate a d-axis compensation signal based on the d-axis current of the motor and the DC bus ripple frequency; and generate a q-axis compensation signal based on the q-axis current of the motor and the DC bus ripple frequency. The current compensation unit is specifically used to: superimpose the d-axis compensation signal onto the d-axis current; and superimpose the q-axis compensation signal onto the q-axis current.

8. The beat frequency suppression device according to any one of claims 1-7, characterized in that, The current processor also includes: The beat frequency determination unit determines that if the DC bus ripple frequency of the motor is different from the mechanical pulsation frequency of the compressor, and the difference is within a preset frequency range, then the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor satisfy the current beat frequency condition.

9. An electric motor, characterized in that, The motor includes a motor drive device; the motor drive device includes: an inverter, a feedback module, and a beat frequency suppression device as described in any one of claims 1-8; The inverter is used to output three-phase current (abc) to the motor and the feedback module; The feedback module is used to convert the three-phase currents abc into the current of the motor, and output a feedback signal to the inverter according to the current of the motor and the corresponding rated current; the feedback module is also used to output the current of the motor to the beat frequency suppression device. The beat frequency suppression device is used to generate a compensation signal based on the current of the motor and return the compensation signal to the feedback module.

10. An air conditioner, characterized in that, The air conditioner includes: a compressor and a motor as described in claim 9.

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