Electric motor driving apparatus, electric motor and air conditioner

Abstract

Provided in some embodiments of the present application are an electric motor driving apparatus, an electric motor and an air conditioner. The electric motor driving apparatus comprises: an inverter, which is configured to output abc three-phase currents; a feedback module, which is configured to receive the abc three-phase currents, perform coordinate transform on the abc three-phase currents, output a feedback signal to the inverter by means of PI control and on the basis of currents subjected to coordinate transform and corresponding basic currents, and output the currents subjected to coordinate transform; and a beat-frequency suppression apparatus, which is configured to receive the currents subjected to coordinate transform, generate a compensation signal by means of Fourier transform and integral control and on the basis of the currents subjected to coordinate transform, and return the compensation signal to the feedback module.

Description

Motor drive unit, motor, air conditioner

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 2025103617533, filed on March 25, 2025; and to Chinese Patent Application No. 2025103617815, filed on March 25, 2025; the entire contents of all the aforementioned Chinese patent applications are incorporated herein by reference. Technical Field

[0003] Some embodiments of this application relate to the field of variable frequency air conditioning control. More specifically, it relates to a motor drive device, a motor, and an air conditioner. Background Technology

[0004] 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.

[0005] In related 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 phenomenon, affecting the stability and noise level of the motor. Summary of the Invention

[0006] Some embodiments of this application provide a motor drive device, the motor drive device comprising:

[0007] The inverter is configured to output three-phase currents abc.

[0008] The feedback module is configured to receive the three-phase currents abc; perform coordinate transformation on the three-phase currents abc; output a feedback signal to the inverter through PI control based on the coordinate-transformed current and the corresponding calibration current; and output the coordinate-transformed current.

[0009] The beat frequency suppression device is configured to receive the current after coordinate transformation; generate a compensation signal based on the current after coordinate transformation through Fourier transform and integral control, and return the compensation signal to the feedback module.

[0010] In some embodiments of this application, the beat frequency suppression device includes:

[0011] The detector is configured to acquire the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the motor-driven compressor.

[0012] The current processor is configured to generate the compensation signal based on the current after coordinate transformation 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.

[0013] In some embodiments of this application, the detector includes a frequency detection unit configured to calculate the mechanical pulsation frequency based on the operating frequency of the compressor through a product operation.

[0014] In some embodiments of this application, the frequency detection unit is configured as follows:

[0015] Based on the compressor type, the frequency amplification factor is determined using a pre-set compressor type database;

[0016] Calculate the product of the frequency amplification factor and the compressor's operating frequency, and use this product as the compressor's mechanical pulsation frequency.

[0017] In some embodiments of this application, the compressor is a rotary compressor; the frequency detection unit is configured to determine the frequency amplification factor based on the number of rotors of the compressor through a preset coefficient correspondence; wherein the frequency amplification factor is positively correlated with the number of rotors.

[0018] In some embodiments of this application, the current processor includes:

[0019] The frequency domain transformation unit is configured to perform frequency domain transformation on the current to obtain harmonic signals; wherein the frequency of the harmonic signals is n times the DC bus ripple frequency, and n is a positive integer;

[0020] A DC-DC converter unit is configured to convert harmonic signals into DC signals;

[0021] The current control unit is configured to control the DC signal to zero and output a corresponding DC compensation signal;

[0022] The time-domain transformation unit is configured to perform time-domain transformation on the DC compensation signal to obtain the compensation signal.

[0023] In some embodiments of this application, the frequency domain transformation unit is configured to perform Fourier transform based on the angular frequency of the current and the DC bus ripple frequency to obtain harmonic signals; and to filter the harmonic signals to remove harmonic signals other than the DC bus ripple frequency.

[0024] The time-domain transformation unit is configured 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.

[0025] In some embodiments of this application, the current control unit is configured 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.

[0026] In some embodiments of this application, the DC conversion unit is configured 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.

[0027] The current control unit is configured as follows:

[0028] The DC component signal of the d-axis is controlled to zero and the corresponding DC compensation signal is output.

[0029] The q-axis DC component signal is controlled to zero and the corresponding DC compensation signal is output.

[0030] In some embodiments of this application, the beat frequency suppression device further includes:

[0031] The current compensation unit is configured 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.

[0032] In some embodiments of this application, the current includes d-axis current and q-axis current; the current processor is configured as follows:

[0033] Based on the motor's d-axis current and DC bus ripple frequency, a d-axis compensation signal is generated through Fourier transform and integral control.

[0034] Based on the q-axis current of the motor and the DC bus ripple frequency, a q-axis compensation signal is generated through Fourier transform and integral control.

[0035] In some embodiments of this application, the current compensation unit is configured as follows:

[0036] Superimpose the d-axis compensation signal onto the d-axis current;

[0037] The q-axis compensation signal is superimposed on the q-axis current.

[0038] In some embodiments of this application, the current processor further includes:

[0039] The beat frequency determination unit is configured to determine 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 meet the current beat frequency condition.

[0040] In some embodiments of this application, an electric motor is also involved, which includes the motor drive device described above.

[0041] In some embodiments of this application, an air conditioner is also disclosed, which includes the motor described above. Attached Figure Description

[0042] To more clearly illustrate the implementation methods in some embodiments or related technologies of this application, 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.

[0043] Figure 1 shows the q-axis current beat frequency spectrum provided in some embodiments of this application;

[0044] Figure 2 is a schematic diagram of the control loop of a motor provided in some embodiments of this application;

[0045] Figure 3 is a schematic diagram of the beat frequency suppression device provided in some embodiments of this application;

[0046] Figure 4 is a schematic diagram of q-axis current spectrum analysis provided in some embodiments of this application;

[0047] Figure 5 is a schematic diagram of the beat frequency suppression device provided in some embodiments of this application;

[0048] Figure 6 is a schematic diagram of the beat frequency suppression device provided in some embodiments of this application;

[0049] Figure 7 is a schematic diagram of the beat frequency suppression device provided in some embodiments of this application;

[0050] Figure 8 is a schematic diagram of signal processing of a beat frequency suppression device provided in some embodiments of this application;

[0051] Figure 9 is a schematic diagram of signal processing of a beat frequency suppression device provided in some embodiments of this application;

[0052] Figure 10 is a schematic diagram of signal processing of a beat frequency suppression device provided in some embodiments of this application;

[0053] Figure 11 is a schematic diagram of the structure of a motor drive device provided in some embodiments of this application;

[0054] Figure 12 is a schematic diagram of the structure of a current processor provided in some embodiments of this application.

[0055] 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, beat frequency determination unit 125, current compensation unit 130, motor drive device 900, inverter 300, feedback module 200. Detailed Implementation

[0056] To make the 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 some exemplary embodiments of this application. Obviously, the exemplary embodiments described are only some embodiments of this application, and not all embodiments.

[0057] It should be noted that the brief descriptions of terms in some embodiments of this application are only for the convenience of understanding the implementation methods described below, and are not intended to limit the implementation methods of this application. Unless otherwise stated, these terms should be understood in their ordinary and common meaning.

[0058] 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.

[0059] 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 an indirect connection through an intermediate medium, or to the internal communication 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.

[0060] The following disclosure provides many different implementations or examples for different structures to implement some embodiments of this application. To simplify the disclosure of some embodiments of this application, components and arrangements of specific examples are described below. Of course, these are merely examples and are not intended to limit the embodiments of this application. Furthermore, some embodiments of this application may repeat reference numerals and / or reference letters in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed. In addition, some embodiments of this application provide examples of various specific processes and materials, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0061] Air conditioner compressors in related technologies are typically driven by electric motors (such as permanent magnet synchronous motors, PMSM). 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 (Field-Oriented Control) control, SVPWM (Space Vector Pulse Width Modulation) modulation requires sampling the DC bus voltage. This bus voltage is significantly affected by the power supply frequency, exhibiting ripple: 100Hz for single-phase systems (corresponding to a 50Hz power supply), and up to 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 shows the q-axis current beat frequency spectrum provided in some embodiments of this application. As shown in the figure, there is a periodic beat frequency envelope in the current spectrum.

[0062] Figure 2 is a schematic diagram of the control loop of a motor provided in some embodiments of this application. As shown in Figure 2, on one hand, 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 by a 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.

[0063] Some embodiments of this application provide a beat frequency suppression device that receives 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 Superimposed, 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 d Superposition is used to achieve beat frequency suppression. Other beneficial effects of some embodiments of this application include, for example, the compensation signal is injected through a feedforward channel to avoid interfering with the integration process of the main PI controller, and the beat frequency suppression device is independent of the main control loop, which facilitates engineering implementation without the need to reconstruct the original FOC architecture.

[0064] In some embodiments, the beat frequency suppression device can integrate a short-time Fourier transform (STFT), an adaptive filter, or a sliding window Fourier analysis module to extract the beat frequency characteristics in the d-axis and q-axis feedback currents in the frequency domain, and automatically identify the center frequency and envelope frequency of the beat frequency components. It can compare and identify the beat frequency with the bus ripple frequency (e.g., 100Hz / 300Hz) and the compressor's second harmonic mechanical frequency (e.g., 2×N_rpm), thereby extracting the beat frequency excitation frequency more accurately. A bandpass filter is used to extract the beat frequency harmonic components within the target frequency band. The bandwidth and center frequency can be adaptively adjusted to adapt to changes in the beat frequency point under different operating conditions, improving the system's environmental robustness and frequency tracking capability. The beat frequency components output by the beat frequency extraction module, after phase compensation and gain adjustment, are injected into the original feedback currents id and iq as compensation signals (idcmp, iqcmp) for the d-axis and q-axis currents, respectively. This channel is independent of the PI controller's main loop and uses a feedforward structure to effectively avoid introducing integral deviations and prevent interference with the PI control accuracy. It supports parallel compensation of multiple beat frequency points, and is suitable for scenarios with multiple beat frequency excitation sources (such as multiple harmonics of the bus, harmonics of multi-stage compressors, etc.). The compensation module supports a multi-channel structure and can activate different frequency channels as needed to perform frequency separation and compensation superposition.

[0065] Figure 3 is a schematic diagram of the beat frequency suppression device provided in some embodiments of this application. As shown in Figure 3, the beat frequency suppression device 100 includes:

[0066] Detector 110 is configured to acquire the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the motor-driven compressor.

[0067] The current processor 120 is configured to generate a compensation signal based on the current after coordinate transformation 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.

[0068] In some embodiments of this application, 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. In some embodiments of this application, the current spectrum can also be analyzed by Fast Fourier Transform (FFT) to identify the high-frequency component with the largest amplitude as the DC bus ripple frequency. In some embodiments of this application, 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 achieved through theoretical calculation. In some embodiments of this application, for reciprocating compressors, the mechanical pulsation frequency can be calculated by obtaining parameters related to the piston motion frequency; in some embodiments of this application, 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. Alternatively, 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.

[0069] In some embodiments of this application, when the current processor 120 detects that the difference between the bus DC ripple frequency and the mechanical pulsation frequency is less than 5Hz, it determines that there is a frequency beat risk. Figure 4 is a schematic diagram of q-axis current spectrum analysis provided in some embodiments of this application. As shown in Figure 4, when the rotor speed of the dual-rotor electronic motor is 47 rpm, a current component with an amplitude of 500 rms and a frequency of 94Hz appears in the q-axis current of the motor. At the same time, there is also a current component with an amplitude of 260 rms and a frequency of 100Hz from single-phase AC power. At this time, the two current components have similar frequencies and large energy (amplitude), and the two current components beat each other, resulting in poor motor control stability. It should be noted that the bus DC ripple frequency that causes the frequency beat phenomenon is usually fixed, while the mechanical pulsation frequency caused by the low-frequency operation of the compressor usually fluctuates around the bus DC ripple frequency. In some embodiments of this application, by eliminating the fixed bus DC ripple frequency, the efficiency of frequency beat suppression can be improved.

[0070] In some embodiments of this application, 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 relatively 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.

[0071] The frequency suppression device of some embodiments of this application includes:

[0072] The detector is configured to acquire the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the motor-driven compressor.

[0073] A current processor is configured to generate a compensation signal based on the coordinate-transformed current and the DC bus ripple frequency, through Fourier transform and integral control, if the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor satisfy the current beat frequency condition. In some embodiments of this application, when the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor satisfy the current beat frequency condition, the compensation signal generated based on the fixed frequency of the DC bus ripple frequency and the coordinate-transformed current can be used to reduce the influence of the DC bus ripple frequency in the current on certain beat frequency bands of the motor current, thereby suppressing current beat frequency and reducing the vibration and noise of the compressor during low-frequency operation.

[0074] In some embodiments, detector 110 can acquire signals through bus-side current or voltage sensors; extract frequencies using methods such as Fast Fourier Transform (FFT), periodic averaging, and Hilbert transform; or preset frequencies for different power supply systems using empirical data / operating condition mapping methods; in some embodiments, the ripple frequency can also be inferred by analyzing the inverter drive waveform (such as the PWM signal spectrum). Detector 110 can derive the mechanical pulsation frequency based on the motor encoder's speed and combined with compressor structural parameters (such as the number of blades and pistons); it can also introduce three-dimensional acceleration sensors, structural acoustic sensors, etc., for actual measurement; or it can call historical vibration frequency values ​​recorded in the operating database and compare them with the current state for judgment. Detector 110 can integrate an adaptive tracking module: dynamically updating frequency parameters as compressor speed, system voltage, or environmental load changes; and using algorithms such as Kalman filters and adaptive harmonic extractors to track frequency drift, improving detection accuracy and real-time performance. In some embodiments, the current processor 120 can use a frequency-selective bandpass filter to extract the target beat frequency signal and adjust its gain and phase; it can achieve reverse matching (reverse same-frequency synthesis) with the interference signal through Hilbert transform, delay line or phase-locked loop (PLL) module to improve the compensation effect; it can identify and dynamically adjust the center frequency and damping factor of the notch filter in real time; it can adapt to the offset caused by the bus ripple frequency changing with the operating conditions to improve robustness.

[0075] Figure 5 is a schematic diagram of the beat frequency suppression device provided in some embodiments of this application. As shown in Figure 5, the detector 110 includes a frequency detection unit 111, configured to calculate the mechanical pulsation frequency by multiplication operation based on the operating frequency of the compressor.

[0076] 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). In some embodiments of this application, calculating the mechanical pulsation frequency based on the compressor's operating frequency using the frequency detection unit 111 avoids the need for additional sensor deployment, reduces hardware costs, and simplifies the detection process. In some embodiments of this application, the frequency detection unit 111 is configured to: determine the frequency amplification factor based on the compressor type using a pre-set compressor type database; calculate the product of the frequency amplification factor and the compressor's operating frequency, and use this product as the compressor's mechanical pulsation frequency.

[0077] 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. In some embodiments of this application, 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. In some embodiments of this application, the frequency amplification factor is adaptively adjusted by compressor type to achieve a more accurate match between the mechanical characteristics of different compressors and the beat frequency conditions, improving system compatibility.

[0078] In some embodiments of this application, the compressor is a rotary compressor; the frequency detection unit 111 is configured to determine the frequency amplification factor based on the number of rotors of the compressor through a preset coefficient correspondence; wherein the frequency amplification factor is positively correlated with the number of rotors. In some embodiments of this application, the amplification factor corresponding to 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, achieving strict synchronization with the rotor mechanical cycle and precise matching of rotor mechanical characteristics, avoiding frequency misjudgment.

[0079] In some embodiments, the operating frequency can be read from the target frequency (such as the inverter output frequency) set in the motor controller; applicable to variable frequency drive systems, the operating frequency command is obtained through the control register or communication protocol such as MODBUS; the actual operating frequency of the motor can be deduced from the motor encoder, Hall sensor or back EMF signal; applicable to servo compressor systems with closed-loop control; if the controller or sensor is unavailable, the main low-frequency components can be extracted as the operating frequency by performing a Fourier transform on the three-phase current of the motor.

[0080] Figure 6 is a schematic diagram of the beat frequency suppression device provided in some embodiments of this application. As shown in Figure 6, the current processor 120 includes:

[0081] Frequency domain transformation unit 121 is configured 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;

[0082] DC-DC conversion unit 122 is configured to convert harmonic signals into DC signals;

[0083] The current control unit 123 is configured to control the DC signal to zero and output a corresponding DC compensation signal;

[0084] The time-domain transformation unit 124 is configured to perform time-domain transformation on the DC compensation signal to obtain the compensation signal.

[0085] In some embodiments of this application, the motor current can be obtained through high-speed sampling; wherein, the sampling frequency must satisfy Shannon's theorem, that is, it must be at least twice the highest harmonic frequency of interest. In some embodiments of this application, high-frequency noise is also filtered out by an anti-aliasing filter, retaining the effective harmonic frequency band. In some embodiments of this application, 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). In some embodiments of this application, 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 by a phase-locked loop (PLL) according to the ripple frequency drift, and the frequency can be updated by multiples of n.

[0086] In some embodiments of this application, 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.

[0087] In some embodiments of this application, the current control unit 123 may employ a proportional-integral (PI) controller, with the DC component error (target value 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. In some embodiments of this application, an anti-saturation algorithm may also be introduced into the PI controller to prevent the integrator from overflowing during startup or sudden operating conditions.

[0088] After receiving the compensation command (amplitude, 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 some embodiments of this application, 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. In some embodiments of this application, a delay compensation algorithm can also be used to ensure that the synthesized signal is out of phase with the original ripple current, achieving maximum cancellation effect. In some embodiments of this application, the compensation signal can also be amplified to the required level of the system using a Class D amplifier or inverter, and then injected into the current loop control circuit after passing through an isolation transformer.

[0089] In some embodiments of this application, the current is converted from a time-domain signal to a frequency-domain signal, and a harmonic signal with a frequency n times the DC bus ripple frequency is determined, 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.

[0090] In some embodiments of this application, the frequency domain transformation unit 121 is configured to perform a Fourier transform based on the angular frequency of the current and the DC bus ripple frequency to obtain the harmonic signal. In some embodiments of this application, the time domain transformation unit 124 is configured to perform an inverse Fourier transform based on the angular frequency of the DC compensation signal under the DC bus ripple frequency to obtain the compensation signal. It should be noted that in practical applications, the operations of some of the above embodiments can be performed in the same embodiment to reduce the amount of computation by using synchronous demodulation technology, or they can be performed in different embodiments to improve the flexibility of signal conversion. Among them, the frequency domain transformation unit is configured to generate orthogonal reference signals sin(ωt) and cos(ωt) based on the angular frequency of the DC bus ripple frequency, i.e., ω = 2π*f, where f is the bus ripple frequency. After multiplying with the current signal of the motor and integrating, the fundamental component is directly extracted. In some embodiments of this application, by performing a Fourier transform on the angular frequency of the current under the DC bus ripple frequency, the full-frequency Fourier transform is avoided, the computational resources are reduced, and the extraction efficiency of the harmonic signal is improved.

[0091] In some embodiments of this application, during inverse Fourier transform, the time-domain transformation unit 124 can reconstruct the time-domain waveform of the compensation signal using the same ω. In some embodiments of this application, inverse Fourier transform is performed based on the angular frequency at the DC bus ripple frequency of the DC compensation signal. The compensation signal is reconstructed through inverse Fourier transform, ensuring strict synchronization between the compensation signal and the original ripple frequency, thereby improving harmonic cancellation efficiency.

[0092] In some embodiments of this application, the frequency domain transformation unit 121 is configured to filter the harmonic signal to remove harmonic signals other than the DC bus ripple frequency. After frequency domain transformation, frequency components other than the DC bus ripple frequency are filtered out by digital filters (such as notch filters or low-pass filters), retaining only the target harmonics. In some embodiments of this application, filtering eliminates non-target harmonic interference, focuses the DC bus ripple frequency component, reduces noise pollution in the compensation signal, and improves suppression accuracy.

[0093] In some embodiments of this application, the current control unit 123 is configured 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. In some embodiments of this application, the integral controller can be an anti-saturation integral controller. In some embodiments of this application, the reference value can also be gained or lost based on zero. In some embodiments of this application, the time constant in the integral controller can be T = 1 / (2πf), where f is the DC bus ripple frequency. In some embodiments of this application, an integral controller is used 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.

[0094] In some embodiments of this application, the DC-DC conversion unit 122 is configured to project the harmonic signal in a dq rotating coordinate system to obtain a d-axis DC component signal and a q-axis DC component signal. In some embodiments of this application, the DC-DC conversion unit 122 is configured to project 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. In some embodiments of this application, the harmonic signal is decoupled and controlled 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 improving compensation.

[0095] In some embodiments of this application, the current control unit 123 is configured 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. In some embodiments of this application, closed-loop control is performed on the d-axis DC component and the q-axis DC component respectively, achieving synchronous suppression of the current ripple on both axes, avoiding cross-interference, and improving the accuracy of beat frequency suppression.

[0096] In some embodiments of this application, the frequency domain converter 121 includes a high-speed analog-to-digital converter, an anti-aliasing analog filter, and a digital signal processing chip configured to perform a fast Fourier transform (FFT) to obtain spectral information of the current signal; the DC-DC converter 122 includes a synchronous demodulator and a phase-locked loop (PLL), wherein the synchronous demodulator is composed of a hardware multiplier and an integrating filter, capable of demodulating the target harmonic component into a DC value; the current controller 123 includes a digital proportional-integral controller and an anti-saturation protector, outputting the amplitude and phase of a compensation signal corresponding to the target DC value; the time domain converter 124 includes a direct digital frequency synthesizer (DDS) or an inverse Fourier transform, used to generate a time-domain compensation signal, which is then amplified by an inverter driver and injected into the current control loop.

[0097] Figure 7 is a schematic diagram of the beat frequency suppression device provided in some embodiments of this application. As shown in Figure 7, the beat frequency suppression device further includes:

[0098] The current compensation unit 130 is configured to superimpose a compensation signal onto the current to compensate for the DC bus ripple frequency in the current and suppress current beat frequency. In some embodiments of this application, the current compensation unit 130 is configured to directly superimpose the compensation signal, without modifying the original current loop control architecture, thus reducing the complexity of system modification.

[0099] In some embodiments of this application, the current includes d-axis current and q-axis current; the current processor 120 is configured to: generate a d-axis compensation signal based on the motor's d-axis current and the DC bus ripple frequency through Fourier transform and integral control; and generate a q-axis compensation signal based on the motor's q-axis current and the DC bus ripple frequency through Fourier transform and integral control. In practical applications, 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-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. In some embodiments of this application, 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):

[0100] Among them, I d,0 and I q,0 For the DC bias of the d-axis and q-axis currents, 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.

[0101] Figure 8 is a schematic diagram of signal processing for a beat frequency suppression device provided in some embodiments of this application. As shown in Figure 8, 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 ).

[0102] Figure 9 is a schematic diagram of signal processing for a beat frequency suppression device provided in some embodiments of this application. As shown in Figure 9, the d-axis DC component signal (Y) of the d-axis current is processed. 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 Further, Figure 10 is a schematic diagram of signal processing for a beat frequency suppression device provided in some embodiments of this application. After signal processing as shown in Figure 10, 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, i in Figure 9 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.

[0103] In some embodiments of this application, compensation signals are generated independently for the d-axis current and q-axis current to solve the harmonic residue problem caused by two-axis coupling in vector control and improve the suppression capability under all operating conditions. In some embodiments of this application, the current compensation unit 130 is configured to: superimpose the d-axis compensation signal onto the d-axis current; and superimpose the q-axis compensation signal onto the q-axis current. In some embodiments of this application, the d-axis current and q-axis current are compensated separately to avoid introducing new imbalances with a single compensation signal, ensure the symmetry of the current waveform, and reduce electromagnetic noise.

[0104] In some embodiments of this application, the current processor 120 further includes a beat frequency determination unit 125, configured to determine 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. In some embodiments of this application, the preset frequency range can be set to be adjustable from 1 to 10 Hz. In practical applications, the beat frequency determination unit can be set 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 a sleep mode to reduce power consumption. In some embodiments of this application, the beat frequency condition is determined by the preset frequency range to avoid invalid compensation in non-sensitive frequency bands and reduce the computational load on the controller.

[0105] Figure 11 is a schematic diagram of the structure of a motor drive device provided in some embodiments of this application. As shown in Figure 11, 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. In some embodiments, the inverter 300 is configured to output three-phase currents abc to the feedback module 200 and the motor; the feedback module 200 is configured to perform coordinate transformation on the three-phase currents abc, and output a feedback signal to the inverter 300 through PI control based on the coordinate-transformed current and the corresponding calibration current; the feedback module 200 is also configured to output the coordinate-transformed current to the beat frequency suppression device 100; the beat frequency suppression device 100 is configured to generate a compensation signal based on the coordinate-transformed current through Fourier transform and integral control, and return the compensation signal to the feedback module 200.

[0106] The motor drive device 900 of some embodiments of this application 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, the motor drive device 900 of some embodiments of this application integrates the beat frequency suppression device into the motor drive system to achieve closed-loop control of current ripple detection and compensation, improve the output current quality of the inverter 300, reduce the periodic disturbance of the motor torque caused by the beat frequency, and enhance the dynamic response capability of the drive system.

[0107] Some embodiments of this application also provide a motor, including the motor drive device 900 as described in any of the above embodiments. In some embodiments of this application, the motor has a built-in integrated beat frequency suppression drive device, which can eliminate electromagnetic excitation force caused by current harmonics, making the motor run more smoothly and extending bearing life. Some embodiments of this application also provide an air conditioner, which includes the motor as described in any of the above embodiments. In some embodiments of this application, the air conditioner uses an anti-beat frequency motor to drive the compressor, avoiding the transmission of speed fluctuations caused by beat frequency to the refrigerant circulation system, which can improve the energy efficiency ratio and reduce abnormal vibration noise of the compressor, thus improving the user experience.

[0108] 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.

[0109] For ease of explanation, the above description has been provided in conjunction with specific embodiments. However, the discussion in some embodiments of this application 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 use the described embodiments and various different variations of embodiments suitable for specific applications.

Claims

1. A motor drive device, comprising: The inverter is configured to output three-phase currents abc. The feedback module is configured to receive the three-phase currents of phases a, b, and c. The three-phase currents abc are transformed into coordinates; based on the transformed currents and the corresponding calibration currents, a feedback signal is output to the inverter via PI control; and the transformed currents are output. The beat frequency suppression device is configured to receive the current after coordinate transformation; generate a compensation signal based on the current after coordinate transformation through Fourier transform and integral control, and return the compensation signal to the feedback module.

2. The motor drive device according to claim 1, wherein, The beat frequency suppression device includes: The detector is configured to acquire the DC bus ripple frequency of the motor and the mechanical pulsation frequency of the compressor driven by the motor. The current processor is configured to generate the compensation signal based on the coordinate-transformed current and the DC bus ripple frequency, through Fourier transform and integral control, 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.

3. The motor drive device according to claim 2, wherein, The detector includes: The frequency detection unit is configured to calculate the mechanical pulsation frequency based on the operating frequency of the compressor through a product operation.

4. The motor drive device according to claim 3, wherein, The frequency detection unit is configured as follows: Based on the compressor type, the frequency amplification factor is determined using a pre-set compressor type database; Calculate the product of the frequency amplification factor and the operating frequency of the compressor, and use this product as the mechanical pulsation frequency of the compressor.

5. The motor drive device according to claim 3, wherein, The compressor is a rotary compressor; the frequency detection unit is configured to determine the frequency amplification factor based on the number of rotors of the compressor and a preset coefficient correspondence; wherein the frequency amplification factor is positively correlated with the number of rotors.

6. The motor drive device according to claim 2, wherein, The current processor includes: The frequency domain transformation unit is configured 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 configured to convert the harmonic signal into a DC signal; The current control unit is configured to control the DC signal to zero and output a corresponding DC compensation signal; The time-domain transformation unit is configured to perform time-domain transformation on the DC compensation signal to obtain the compensation signal.

7. The motor drive device according to claim 6, wherein, The frequency domain transformation unit is configured to perform Fourier transform based on the current and the angular frequency under the DC bus ripple frequency to obtain the harmonic signal; and to filter the harmonic signal to filter out harmonic signals other than the DC bus ripple frequency. The time-domain transformation unit is configured 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.

8. The motor drive device according to claim 6, wherein, The current control unit is configured 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.

9. The motor drive device according to claim 6, wherein, The DC-DC conversion unit is configured 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. The current control unit is configured as follows: The DC component signal of the d-axis is controlled to zero and the corresponding DC compensation signal is output. The q-axis DC component signal is controlled to zero and the corresponding DC compensation signal is output.

10. The motor drive device according to claim 2, wherein, The beat frequency suppression device further includes: The current compensation unit is configured to superimpose the compensation signal onto the current to compensate for the DC bus ripple frequency in the current, thereby suppressing the current beat frequency.

11. The motor drive device according to claim 10, wherein, The current includes d-axis current and q-axis current; the current processor is configured as follows: Based on the d-axis current of the motor and the DC bus ripple frequency, a d-axis compensation signal is generated through Fourier transform and integral control. Based on the q-axis current of the motor and the DC bus ripple frequency, a q-axis compensation signal is generated through Fourier transform and integral control.

12. The motor drive device according to claim 11, wherein, The current compensation unit is configured as follows: The d-axis compensation signal is superimposed onto the d-axis current; The q-axis compensation signal is superimposed on the q-axis current.

13. The motor drive device according to claim 2, wherein, The current processor also includes: The beat frequency determination unit is configured to determine 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.

14. An electric motor, comprising the motor drive device as described in any one of claims 1-14.

15. An air conditioner, comprising: The motor as described in claim 14.

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