Motor control method and air conditioner

Abstract

The invention discloses a motor control method and an air conditioner, and relates to the field of motor control, the motor control method is applied to a motor control device, and the motor control device comprises a vector control module, a phase extraction module and a beat frequency suppression module. Inputting the direct current bus voltage to a phase extraction module to obtain a target power grid angle when the frequency of the ripple in the direct current bus voltage has a preset multiple relation with the power grid frequency and the frequency of the ripple and the electric frequency of a motor generate a beat frequency phenomenon; inputting the target power grid angle and the current sampling value under the rotating coordinate system into a beat frequency suppression module to obtain a harmonic compensation amount corresponding to the current sampling value; and injecting the harmonic compensation quantity into a current control loop in the vector control module to obtain a target modulation signal for controlling the motor. By means of phase locking and harmonic injection, the beat frequency component in the operation process of the motor is reduced, then the beat frequency of the electric frequency and the ripple frequency of the motor is restrained, and the rotating speed control stability of the motor is improved.

Description

Technical Field

[0001] The present application relates to the field of motor control, and in particular to a motor control method and an air conditioner. Background Art

[0002] In the field of variable frequency air conditioning control, motors are used to drive components such as compressors, indoor and outdoor fans, and control the speed of compressors and indoor and outdoor fans, so that the air conditioner can flexibly adjust the cooling or heating power according to the indoor temperature, achieving efficient energy saving and temperature control.

[0003] In vector control scenarios where a motor drives a compressor, it's necessary to monitor the DC bus voltage. The DC bus voltage of a single-phase input power supply exhibits ripple at twice the grid frequency, while the DC bus voltage of a three-phase input power supply exhibits ripple at six times the grid frequency. However, when the motor's electrical frequency and the DC bus voltage ripple frequency are close, the interaction between the two produces a beat frequency phenomenon, leading to unstable motor control of the compressor's speed, accompanied by problems such as compressor current distortion and increased motor vibration and noise. Therefore, a method to effectively suppress this beat frequency phenomenon is urgently needed. Summary of the Invention

[0004] The present application provides a motor control method and an air conditioner, which can reduce the component corresponding to the beat frequency during the motor control operation process.

[0005] In a first aspect, a motor control method is provided, which is applied to a motor control device. The motor control device includes a vector control module, a phase extraction module, and a beat frequency suppression module.

[0006] The motor control method includes: when the frequency of the ripple in the DC bus voltage is in a preset multiple relationship with the grid frequency, and the frequency of the ripple produces a beat frequency phenomenon with the electrical frequency of the motor, the DC bus voltage is input into a phase extraction module, the ripple is extracted based on the frequency of the ripple, and a target grid angle is obtained, and the frequency of the ripple is in a preset multiple relationship with the grid frequency; the target grid angle and the current sampling value in the rotating coordinate system are input into a beat frequency suppression module to obtain a harmonic compensation amount corresponding to the current sampling value; the harmonic compensation amount is injected into the current control loop in the vector control module to obtain a target modulation signal, and the target modulation signal is used to control the motor.

[0007] It should be noted that the grid angle (such as the target grid angle) is related to the grid phase, and the grid phase is achieved by detecting and tracking the grid angle.

[0008] This motor control method uses a voltage input phase extraction module to extract the ripple frequency when the DC bus voltage is a preset multiple of the grid frequency and beats the motor's electrical frequency. This ripple is then applied to the voltage input phase extraction module to obtain the target grid angle. This ripple is then combined with the current sampling value in the rotating coordinate system and applied to the beat frequency suppression module to obtain the harmonic compensation. This is then injected into the vector control current loop to generate the target modulation signal. This scheme locks the grid phase. Once the grid phase is locked, the grid voltage's angular position at a specific moment is determined, serving as a reference for phase synchronization between the inverter circuit output and the grid. This effectively suppresses the interference of beat frequency harmonics on the current, improving the stability and phase synchronization of the motor under vector control.

[0009] In addition, this solution constructs a closed-loop control in which phase locking and harmonic compensation are injected into the vector control module. Since the closed-loop control is more stable, the stability of the motor speed control is improved. By suppressing the beat frequency component, the speed fluctuation caused by torque pulsation is effectively reduced, thereby improving the speed control accuracy. At the same time, the harmonic distortion rate of load current such as compressors is reduced, and the electromagnetic force fluctuation caused by current distortion is reduced, thereby eliminating the source of motor vibration and noise, and providing a smoother and more efficient operating environment for the corresponding motor drive system.

[0010] In one possible implementation, the beat frequency suppression module includes a first conversion unit, a harmonic processing unit, and a second conversion unit. The target grid angle and the current sampling value in the rotating coordinate system are input into the beat frequency suppression module to obtain the harmonic compensation amount corresponding to the current sampling value, including: inputting the target grid angle and the current sampling value in the rotating coordinate system into the first conversion unit to obtain a frequency domain signal corresponding to the current sampling value; inputting the frequency domain signal into the harmonic processing unit for filtering processing, proportional integral processing, and limiting processing to obtain a target signal corresponding to the frequency domain signal after adjustment; inputting the target signal and the target grid angle into the second conversion unit to obtain the harmonic compensation amount corresponding to the target signal, where the harmonic compensation amount is the signal after the target signal is converted from the frequency domain to the time domain.

[0011] In one possible implementation, the harmonic processing unit includes a low-pass filter, a first proportional-integral controller, and a first limiter. The frequency domain signal is input into the harmonic processing unit for filtering, proportional-integral, and limiting processing to obtain a target signal corresponding to the frequency domain signal adjustment, including: inputting the frequency domain signal into the low-pass filter for preset low-pass filtering to obtain a filtered harmonic characteristic signal; based on the first proportional-integral controller, calculating the difference between the harmonic characteristic signal and the first reference value to generate a first adjustment amount; inputting the first adjustment amount into the first limiter for limiting adjustment to obtain the target signal.

[0012] In the closed-loop control of harmonic injection in the embodiment of the present application, the beat frequency suppression module performs frequency domain conversion, harmonic processing and time domain compensation on the current sampling values ​​in the rotating coordinate system based on the target grid angle, and then determines the harmonic compensation amount corresponding to the harmonics in the current sampling value, and injects the harmonic compensation amount into the current control loop in the vector control module. This harmonic injection method realizes closed-loop control, reduces the beat frequency component during the operation of the motor, and improves the overall robustness.

[0013] In one possible implementation, the target grid angle and the current sampling value in the rotating coordinate system are input into the beat frequency suppression module to obtain the harmonic compensation amount corresponding to the current sampling value, including: inputting the target grid angle and the q-axis current sampling value into the beat frequency suppression module to obtain the q-axis compensation amount, the current sampling value includes the q-axis current sampling value, and the harmonic compensation amount includes the q-axis compensation amount.

[0014] In addition, the harmonic compensation amount is injected into the current control loop in the vector control module to obtain a target modulation signal, including: superimposing the q-axis compensation amount on the q-axis current command value to obtain a corrected q-axis current value; injecting the q-axis current value into the current control loop to obtain a first modulation signal, and the target modulation signal includes the first modulation signal.

[0015] In the closed-loop control system of harmonic injection, the current sampling value i fb Including q-axis current sampling value i qfb and d-axis current sampling value i dfb , harmonic compensation amount i cmp Including q-axis compensation i qcmp and d-axis compensation i dcmp Taking permanent magnet synchronous motor control as an example, since the q-axis current determines the electromagnetic torque output, its beat frequency energy is significantly higher than that of the d-axis. Therefore, in certain application scenarios, selectively suppressing the beat frequency of only the q-axis current can optimize system performance.

[0016] In one possible implementation, the target grid angle and the current sampling value in the rotating coordinate system are input into the beat frequency suppression module to obtain the harmonic compensation amount corresponding to the current sampling value, including: inputting the target grid angle, the d-axis current sampling value, and the q-axis current sampling value into the beat frequency suppression module to obtain the d-axis compensation amount and the q-axis compensation amount; the current sampling value includes the d-axis current sampling value and the q-axis current sampling value, and the harmonic compensation amount includes the d-axis compensation amount and the q-axis compensation amount.

[0017] In addition, the harmonic compensation amount is injected into the current control loop in the vector control module to obtain a target modulation signal, including: superimposing the q-axis compensation amount on the q-axis current command value to obtain a corrected q-axis current value; superimposing the d-axis compensation amount on the d-axis current command value to obtain a corrected d-axis current value; injecting the q-axis current value and the d-axis current value into the current control loop to obtain a second modulation signal, and the target modulation signal includes the second modulation signal.

[0018] In scenarios such as hardware platforms with sufficient computing power, the q-axis current sampling value i can be simultaneously qfb and d-axis current sampling value i dfb Implementing a beat frequency suppression strategy, processing the current sampling values ​​of the two axes separately through two independent beat frequency suppression loops, can further improve the beat frequency suppression effect compared with only suppressing the current of the q-axis.

[0019] In one possible implementation, the phase extraction module includes a signal conversion unit, a harmonic extraction unit, and a phase determination unit. The DC bus voltage is input into the phase extraction module to obtain a target grid angle, including: inputting the DC bus voltage into the signal conversion unit to obtain a discrete-time signal corresponding to the DC bus voltage; inputting the discrete-time signal into the harmonic extraction unit for band-pass filtering to obtain a sinusoidal signal of the DC bus voltage; and inputting the sinusoidal signal into the phase determination unit for phase locking to obtain the target grid angle.

[0020] In addition, the phase determination unit includes a second-order generalized integrator, a second proportional-integral controller and a second limiter. The sinusoidal signal is input into the phase determination unit for phase locking to obtain a target grid angle, including: inputting the sinusoidal signal into the second-order generalized integrator to obtain an orthogonal signal corresponding to the sinusoidal signal; performing Park transformation on the sinusoidal signal and the orthogonal signal to obtain the q-axis voltage of the ripple; calculating the difference between the q-axis voltage and the second reference value based on the second proportional-integral controller to generate a second adjustment amount; inputting the second adjustment amount into the second limiter for limited adjustment to obtain the target grid angle, and the target grid angle is used to indicate the Park transformation.

[0021] The frequency coupling relationship between the ripple in the DC bus voltage and the grid fundamental is used to identify the instantaneous phase of the component with the same frequency as the grid fundamental from the ripple signal through filtering and conditioning steps such as a second-order generalized integrator. This phase of the component is then connected to a phase-locked loop (PLL) and tracked through closed-loop steps such as phase detection, loop filtering, and voltage-controlled oscillation. Because the frequency of the component is strictly consistent with the grid fundamental, and the phase difference can be dynamically calibrated to a minimum steady-state value through the PLL, it is equivalent to the phase of the grid fundamental, i.e., the target grid angle.

[0022] In a second aspect, a motor control device is provided, comprising a memory and a processor, wherein the processor is configured to execute any one of the motor control methods in the first aspect. The device may be a terminal device or a chip within the terminal device.

[0023] In a third aspect, an air conditioner is provided, comprising a motor control device, the motor control device being configured to execute any one of the motor control methods in the first aspect.

[0024] It can be understood that the beneficial effects of the second to third aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic structural diagram of a frequency converter is shown;

[0026] Figure 2 The figure shows the time domain waveform of the current generated by the beat frequency phenomenon in the motor control of the compressor;

[0027] Figure 3 A schematic diagram showing spectrum analysis of the q-axis current in compressor control is shown;

[0028] Figure 4 A schematic diagram of a motor control device provided by some embodiments of the present application is shown;

[0029] Figure 5 A schematic diagram showing a beat frequency suppression module in a motor control device provided in some embodiments of the present application is shown;

[0030] Figure 6 A schematic diagram illustrating another beat frequency suppression module in a motor control device provided in some embodiments of the present application is shown;

[0031] Figure 7 A schematic diagram showing each transformation unit in a beat frequency suppression module provided in some embodiments of the present application is shown;

[0032] Figure 8 A schematic diagram illustrating another beat frequency suppression module in a motor control device provided in some embodiments of the present application is shown;

[0033] Figure 9 A schematic diagram illustrating another beat frequency suppression module in a motor control device provided in some embodiments of the present application is shown;

[0034] Figure 10 A schematic diagram illustrating another beat frequency suppression module in a motor control device provided in some embodiments of the present application is shown;

[0035] Figure 11A schematic diagram of another motor control device provided by some embodiments of the present application is shown;

[0036] Figure 12 A schematic diagram showing magnetic pole position and axis error is shown;

[0037] Figure 13 A schematic diagram showing a phase extraction module in a motor control device provided in some embodiments of the present application is shown;

[0038] Figure 14 A schematic diagram of another motor control device provided by some embodiments of the present application is shown;

[0039] Figure 15 A schematic diagram illustrating another phase extraction module in a motor control device provided in some embodiments of the present application is shown;

[0040] Figure 16 A flow chart of a motor control method provided by some embodiments of the present application is shown;

[0041] Figure 17 A schematic diagram of the current time domain waveform of the compressor controlled by the motor control method according to an embodiment of the present application after injecting harmonics is shown;

[0042] Figure 18 A schematic diagram showing spectrum analysis of the q-axis current in compressor control according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0044] It should be understood that the “multiple” mentioned in this application refers to two or more. In the description of this application, unless otherwise specified, “ / ” means or, for example, A / B can mean A or B; “and / or” in this article is merely a description of the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in order to facilitate the clear description of the technical solution of this application, words such as “first” and “second” are used to distinguish between identical or similar items with basically the same functions and effects. Those skilled in the art can understand that words such as “first” and “second” do not limit the quantity and execution order, and words such as “first” and “second” do not necessarily limit them to be different.

[0045] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in other embodiments" appearing in different places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. Furthermore, the terms "including," "comprising," "having," and their variations all mean "including but not limited to," unless otherwise specifically emphasized.

[0046] Before explaining in detail the motor control method and the air conditioner provided in some embodiments of the present application, the application scenarios and related technologies of the motor control method and the air conditioner are first explained.

[0047] An inverter air conditioner controls the compressor speed by adjusting the power supply frequency through a frequency converter. The inverter first rectifies the fixed grid frequency (e.g., 50Hz, 60Hz) into direct current, which is then inverted into frequency-adjustable alternating current (e.g., 10Hz to 120Hz). This drives the compressor motor to achieve stepless speed change. When there is a high demand for cooling or heating, the inverter outputs a high-frequency current to make the compressor run at high speed, achieving rapid cooling or heating. When the temperature approaches the set point, it switches to a low-frequency current to maintain low-speed operation, reducing energy consumption fluctuations.

[0048] In the field of variable-frequency air conditioning control, permanent magnet synchronous motors (PMSMs) are widely used in rail transit, CNC systems, port equipment, and electrical appliances due to their advantages such as high efficiency and energy saving, excellent speed regulation, high reliability, and environmental friendliness. For example, in air conditioners, core components such as the compressor and indoor and outdoor fans can all be controlled by PMSMs. In other words, the compressor motor can be a PMSM.

[0049] It should be noted that electrical frequency refers to the number of times that alternating current completes periodic changes per unit time. In variable-frequency air conditioners, the electrical frequency of the permanent magnet synchronous motor can be dynamically adjusted within a certain range (such as 10Hz to 120Hz), thereby achieving dynamic changes in motor speed and compressor speed.

[0050] The compressor is powered by a permanent magnet synchronous motor. The inverter in a variable frequency air conditioner adjusts the speed of the permanent magnet synchronous motor by varying the power supply frequency and voltage. The permanent magnet synchronous motor drives the compressor's rotor and other components, precisely controlling the compressor's operating frequency and refrigerant circulation. This allows the air conditioner to flexibly adjust cooling or heating capacity based on changes in indoor and outdoor temperatures and the set temperature, achieving both energy savings and temperature control.

[0051] Figure 1 A schematic diagram of the structure of a frequency converter is shown in FIG. Figure 1 As shown, the frequency converter 100 includes a rectifier circuit 110 , a filter circuit 120 and an inverter circuit 130 .

[0052] The rectifier circuit 110 converts AC power into smoother DC power, including single-phase and three-phase rectification. The rectifier circuit 110 is typically composed of multiple diodes, thyristors, and other components, and can be designed into various structures according to different needs, such as half-wave rectifier circuits, full-wave rectifier circuits, and bridge rectifier circuits. The rectifier circuit 110 can be controllable or uncontrollable. A controlled rectifier circuit controls the output DC voltage by controlling the conduction angle of controllable components such as thyristors; an uncontrolled rectifier circuit cannot control the output voltage; the output DC voltage depends on the input AC voltage and the structure of the rectifier circuit.

[0053] The filter circuit 120 is used to filter out ripple and high-frequency noise in the rectified DC power, making the DC voltage more stable. The filter circuit 120 usually uses a large-capacity electrolytic capacitor or an LC filter network to filter out the ripple of the rectified voltage and provide a stable DC bus voltage.

[0054] It should be noted that the DC waveform output from a single-phase input power supply after single-phase rectification (such as bridge rectification) is a full-wave rectified waveform with a frequency twice that of the input single-phase AC power frequency (e.g., when the input grid frequency is 50Hz, the ripple frequency is 100Hz). Although the filter circuit can smooth the ripple, it cannot completely eliminate periodic fluctuations, so the DC bus voltage exhibits ripple at twice the frequency. Furthermore, the voltage output from a three-phase input power supply after three-phase rectification (such as three-phase bridge rectification) is the line voltage envelope of the three-phase voltage, with six voltage peaks occurring within each cycle, at a frequency six times that of the input three-phase AC power frequency (e.g., when the input grid frequency is 50Hz, the ripple frequency is 300Hz). Although the filter circuit can attenuate the ripple amplitude, it cannot change its frequency characteristics, so the DC bus voltage exhibits ripple at sextuple the frequency. In other words, the DC bus voltage is composed of a DC component and a superimposed ripple (AC component).

[0055] The inverter circuit 130 is mainly composed of power devices such as insulated gate bipolar transistors (IGBTs). By controlling the on- and off-sequence and time of the IGBTs, it can output AC voltages of different frequencies and amplitudes, which are used to convert DC power into AC power with adjustable frequency and voltage to power the permanent magnet synchronous motor.

[0056] Taking the operation of a motor-driven compressor as an example, in its vector control, the DC bus voltage is collected, and the α-axis voltage and β-axis voltage in the αβ coordinate system are converted into space vectors based on space vector pulse width modulation (SVPWM). The action time of each basic vector is calculated based on the DC bus voltage, and a PWM signal is generated to drive the inverter circuit. The stator voltage vector required by the motor is synthesized to achieve magnetic field control.

[0057] For single-phase power input, after rectification, the DC bus voltage will produce ripple at twice the grid frequency, e.g., 100 Hz for a 50 Hz grid frequency. For three-phase power input, after rectification, the DC bus voltage will exhibit ripple at six times the grid frequency, e.g., 300 Hz for a 50 Hz grid frequency. However, when the motor's electrical frequency approaches the DC bus voltage ripple frequency, the interaction between the motor's electrical frequency and the two produces a beat frequency phenomenon, resulting in unstable motor control of the compressor's speed, accompanied by problems such as compressor current distortion and increased motor vibration and noise.

[0058] In view of this, an embodiment of the present application provides a motor control method and an air conditioner. The motor control method is applied to a motor control device, and the motor control device includes a vector control module, a phase extraction module, and a beat frequency suppression module. When the frequency of the ripple in the DC bus voltage has a preset multiple relationship with the grid frequency, and the frequency of the ripple produces a beat frequency phenomenon with the electrical frequency of the motor, the DC bus voltage is input into the phase extraction module to obtain the target grid angle; the target grid angle and the current sampling value in the rotating coordinate system are input into the beat frequency suppression module to obtain the harmonic compensation amount corresponding to the current sampling value; the harmonic compensation amount is injected into the current control loop in the vector control module to obtain a target modulation signal for controlling the motor. This solution reduces the beat frequency component during the operation of the motor by phase locking and harmonic injection, thereby suppressing the beat frequency between the electrical frequency of the motor and the ripple frequency, and improving the stability of the motor speed control.

[0059] For example, in a single-phase power input scenario, a 50Hz AC power grid will generate a 100Hz ripple in the DC bus voltage after passing through a single-phase bridge rectifier. Due to the mechanical characteristics of the compressor, its current spectrum contains high-energy electrical frequency components. When the motor's electrical frequency approaches the DC bus voltage ripple frequency, the two energies interact and beat with each other.

[0060] Figure 2 The figure shows the current time domain waveform diagram caused by the beat frequency phenomenon in the motor control of the compressor. When the 50Hz AC is rectified by a single-phase bridge, a 100Hz ripple component is introduced into the DC bus. When the motor's electrical frequency is 130Hz and close to the 100Hz ripple, the beat frequency phenomenon occurs due to the proximity of the two frequencies (100Hz and 130Hz). Figure 2 As shown, the high-frequency component in the current time domain waveform 210 corresponds to the electrical frequency of the motor (130Hz), and the low-frequency undulating envelope is generated by the beat frequency. The envelope frequency is approximately the difference between the two frequencies (130Hz-100Hz=30Hz). The waveform shows the characteristics of high-frequency carrier and low-frequency envelope; due to the strong energy of the 100Hz ripple, the waveform peak is amplified after the beat frequency, reflecting that the system has the risk of speed fluctuation and current distortion.

[0061] Figure 3 FIG. 4 shows a schematic diagram of a spectrum analysis of the q-axis current in the compressor control, wherein the spectrum analysis refers to a Fast Fourier Transform (FFT) spectrum analysis. Figure 3 As shown, from the FFT spectrum, the amplitude proportion of the 130Hz fundamental component shows a small characteristic, while the effective value of the spectrum amplitude of the 100H frequency band reaches 220, which is significantly higher than the energy proportion of the fundamental component. In view of this, it is necessary to adopt the beat frequency suppression corresponding to the motor control method proposed in some embodiments of the present application to reduce the spectrum amplitude of the 100Hz frequency band.

[0062] The motor control method proposed in this application will be described below with reference to the accompanying drawings through the following exemplary embodiments. The motor control methods in the following embodiments can all be implemented in the above-mentioned motor control device. Figure 4 A schematic diagram of a motor control device provided by some embodiments of the present application is shown, and a description is given by taking the motor control device driving a permanent magnet synchronous motor as an example. Figure 4 As shown, the motor control device includes a vector control module 410 , a phase extraction module 420 and a beat frequency suppression module 430 .

[0063] The vector control module 410 is a field oriented control (FOC) module for the permanent magnet synchronous motor. Specifically, the vector control module 410 converts the stator current i of the permanent magnet synchronous motor in the three-phase coordinate system intoa 、i b 、i c , transformed into the current in the two-phase stationary coordinate system (also known as the αβ coordinate system), including the α-axis current i α and β-axis current i β , and then transformed into the current in the rotating coordinate system (i.e. the current sampling value i fb ), including direct-axis current and quadrature-axis current. The direct-axis current corresponds to the excitation component (controls the magnetic field), and the quadrature-axis current corresponds to the torque component (controls the output torque), realizing decoupling control of the stator magnetic field and the rotor magnetic field, making the control of the AC motor equivalent to the independent control of the excitation component and the torque component of the DC motor; closed-loop control of the motor current is achieved through the current control loop (hereinafter referred to as the current loop).

[0064] At the same time, a pulse width modulation unit (such as space vector pulse width modulation, etc.) is provided in the vector control module 410. The pulse width modulation unit generates a target modulation signal based on the relevant voltage signal obtained after decoupling control. This target modulation signal is used to drive the inverter circuit in the inverter to reasonably adjust the on and off of the power switching devices in the inverter circuit, thereby controlling the operating state of the motor.

[0065] In motor control, when the motor's electrical frequency and the frequency of the ripple in the DC bus voltage generate a beat frequency phenomenon due to frequency coupling, the DC bus voltage is processed by the phase extraction module 420 to extract the ripple based on the frequency of the ripple and determine the target grid angle (i.e., θ g ).

[0066] It's important to note that the grid angle (e.g., target grid angle) is related to the grid phase, which is achieved by detecting and tracking the grid angle. When locking the grid phase, the grid voltage's angular position at a specific moment is obtained, used as a reference to synchronize the inverter circuit output with the grid phase, ensuring the stability of the phase relationship during the power conversion process.

[0067] The phase extraction module 420 uses signal processing technology to identify the component (i.e., ripple) that has a preset multiple relationship with the grid fundamental wave from the DC bus voltage and tracks its phase in real time. Since the voltage component corresponding to the ripple maintains frequency synchronization with the grid voltage and the phase is calibrated, after closed-loop adjustment by the phase-locked loop, its phase can be equivalent to the grid fundamental wave phase, thereby achieving precise locking of the grid phase. In addition, since the current phase is consistent with the grid phase, the current can be further synchronized and controlled by the target grid angle. In other words, by using the locked grid phase as a reference, the current phase synchronization, amplitude adjustment or vector control can be achieved to ensure power matching and stable operation between the system and the grid.

[0068] The component of the DC bus voltage ripple that has the same frequency as the grid fundamental wave is generated by grid voltage rectification. Its frequency is synchronized with the grid voltage, and their phases have a fixed mapping relationship (for example, in a single-phase rectification scenario, when the ripple frequency is twice the fundamental wave, its phase is mathematically related to the fundamental wave phase). This feature enables the phase-locked loop to quickly lock onto the grid phase directly through the ripple component, eliminating the need for additional grid voltage sampling, reducing signal transmission and sampling delays, and improving real-time performance.

[0069] The grid angle is used to describe the mathematical phase position of the periodic changes in the grid voltage or current. The grid angle refers to the phase of the grid fundamental voltage (such as a 50 Hz sine wave) that changes over time.

[0070] When the motor's electrical frequency beats the DC bus voltage ripple frequency, the ripple frequency and the grid frequency have a preset multiple relationship, which is determined by the rectifier circuit in the inverter and the number of grid phases:

[0071] In single-phase rectification scenarios (such as single-phase bridge rectification), the DC side voltage is a full-wave rectified waveform, and the ripple frequency is twice the grid fundamental frequency (for example, when the grid frequency is 50 Hz, the ripple frequency is 100 Hz). If there are multiple rectification or filtering links, higher-order frequency ripples such as 4x and 6x may also be derived.

[0072] In a three-phase rectification scenario (such as a three-phase bridge rectifier), the DC side voltage is the envelope of the three-phase line voltage. Six voltage peaks occur in each grid cycle, and the ripple frequency is six times the grid fundamental frequency (for example, when the grid frequency is 50 Hz, the ripple frequency is 300 Hz). Similarly, higher-order frequency multiplication ripples such as 12 times and 18 times can be derived.

[0073] Therefore, the multiple relationship between the ripple frequency and the grid frequency can be summarized as 2k times (k is a positive integer determined by the rectification topology and filtering characteristics). In typical scenarios, it is 2 times, 4 times (single-phase) or 6 times, 12 times (three-phase), etc.

[0074] Taking a single-phase rectification scenario as an example, when the DC bus voltage ripple frequency is twice or four times the grid fundamental frequency, phase extraction module 420 processes the ripple to obtain the target grid angle. If the DC bus voltage ripple contains components at both twice and four times the grid fundamental frequency, phase extraction module 420 uses multi-band filtering to prioritize extracting characteristic components in the ripple with the same frequency as the grid fundamental. These components are then processed to generate the target grid angle. Alternatively, the target grid angle can be determined by combining processing results from multiple frequency bands.

[0075] When the motor's electrical frequency and the ripple frequency produce a beat frequency phenomenon, the phase extraction module 420 identifies the component in the ripple that has the same frequency as the grid fundamental wave, tracks its phase through a phase-locked loop, and equivalently obtains the target grid angle, providing a phase reference for the beat frequency suppression function.

[0076] The beat frequency suppression module 430 is used to perform frequency domain conversion, harmonic processing and time domain compensation on the current sampling value in the rotating coordinate system according to the target grid angle, and then determine the harmonic compensation amount corresponding to the current sampling value (i.e., i cmp ).

[0077] Both frequency domain conversion and time domain compensation perform coordinate transformations based on the target grid angle. Frequency domain conversion maps the time domain current signal to a frequency domain signal in a rotating coordinate system, while time domain compensation reconstructs the current signal after frequency domain processing into a time domain compensation signal.

[0078] In some embodiments, the frequency domain conversion maps the time domain current signal to a frequency domain signal in a rotating coordinate system through Fourier transform, and the time domain compensation reconstructs the current signal after frequency domain processing into a time domain compensation signal through inverse Fourier transform.

[0079] Beat frequency suppression module 430 is also used to inject harmonic compensation into the current control loop of vector control module 410, achieving beat frequency suppression and compensation for the current in the rotating coordinate system. This allows vector control module 410 to obtain a target modulation signal for driving an inverter circuit (such as an inverter) to control the motor. This injection of harmonic compensation into the current control loop of vector control module 410 is a closed-loop control method that improves the robustness of motor control.

[0080] It should be understood that the motor control device may refer to a motor drive system, which includes a frequency converter, a vector control module 410, a phase extraction module 420 and a beat frequency suppression module 430; please refer to the above description and will not be repeated here.

[0081] It should be noted that Figure 4 The connection relationship between the modules shown is only a schematic illustration and does not constitute a limitation on the connection relationship between the modules in the motor control device. In other embodiments of the present application, the motor control device may include Figure 4 More or fewer components than those shown, or the motor control device may include Figure 4 Combinations of some of the components shown, or the motor control device may include Figure 4 Subcomponents of some of the components shown. Also, each component can be implemented by hardware, software, or a combination of software and hardware. It should be understood that if each component is implemented by software, no additional hardware is required, and the implementation is simpler.

[0082] An embodiment of the present application provides a motor control device, which includes a vector control module, a phase extraction module, and a beat frequency suppression module. When the frequency of the ripple in the DC bus voltage has a preset multiple relationship with the grid frequency, and the frequency of the ripple produces a beat frequency phenomenon with the electrical frequency of the motor, the phase extraction module processes the DC bus voltage to obtain a target grid angle; the beat frequency suppression module performs frequency domain conversion, harmonic processing, and time domain compensation on the current sampling value in the rotating coordinate system based on the target grid angle, and then determines the harmonic compensation amount corresponding to the harmonic in the current sampling value, injects the harmonic compensation amount into the current control loop in the vector control module, and obtains a target modulation signal for driving the inverter circuit to control the motor. This solution realizes closed-loop control through phase locking and harmonic injection, reduces the beat frequency component during the operation of the motor, and suppresses the beat frequency between the electrical frequency and the ripple frequency of the motor.

[0083] This solution captures the beat frequency component between the motor's electrical frequency and ripple frequency by constructing a closed-loop control system combining phase locking and harmonic injection. The phase-locked loop (PLL) tracks the grid phase in real time, ensuring synchronization of the control signal with the motor's fundamental frequency. Simultaneously, frequency-domain analysis of the current signal locates the beat frequency harmonic components and converts them into easily manageable DC or low-frequency AC components. After processing, this generates a reverse harmonic compensation that is injected into the current loop, dynamically offsetting the original beat frequency interference.

[0084] The above closed-loop mechanism improves the stability of motor speed control. By suppressing the beat frequency component, it effectively reduces the speed fluctuation caused by torque pulsation, thereby improving the speed control accuracy. At the same time, it reduces the harmonic distortion rate (Total Harmonic Distortion, THD) of the compressor current and the electromagnetic force fluctuation caused by current distortion, thereby eliminating the root causes of motor vibration and noise, thereby providing a smoother and more efficient operating environment for the corresponding motor drive system.

[0085] Figure 5 FIG. 1 shows a schematic diagram of a beat frequency suppression module in a motor control device provided in some embodiments of the present application, such as Figure 5 As shown, the beat frequency suppression module includes a first conversion unit 431 , a harmonic processing unit 432 and a second conversion unit 433 .

[0086] The first transformation unit 431 is used to perform frequency domain conversion on the current sampling value in the rotating coordinate system according to the target grid angle to obtain a frequency domain signal corresponding to the current sampling value, wherein the frequency domain conversion maps the time domain current signal to the frequency domain signal in the rotating coordinate system.

[0087] The harmonic processing unit 432 is used to perform filtering, proportional integration and limiting processing on the frequency domain signal to obtain a target signal corresponding to the frequency domain signal after adjustment. Figure 6FIG. 1 shows a schematic diagram of another beat frequency suppression module in a motor control device provided in some embodiments of the present application, such as Figure 6 As shown, the harmonic processing unit 432 in the beat frequency suppression module includes a low-pass filter 432A, a first proportional-integral controller 432B and a first limiter 432C.

[0088] The low-pass filter 432A is used to perform a preset low-pass filter on the frequency domain signal input to obtain a filtered harmonic characteristic signal; the first proportional integral controller 432B is used to calculate the difference between the harmonic characteristic signal and the first reference value to generate a first adjustment amount; the first limiter 432C is used to limit and adjust the first adjustment amount input to obtain a target signal.

[0089] Among them, the frequency domain signal is first processed by a low-pass filter 432A (LPF) to extract the DC component in the frequency domain signal, and then the DC component is used as a control variable and subtracted from the set first reference value. The difference is input into the first proportional-integral controller 432B. After adjustment by the first proportional-integral controller 432B, the output range is limited by the first limiter 432C to obtain the target signal.

[0090] like Figure 5 、 Figure 6 As shown, the second conversion unit 433 is used to perform time domain compensation on the target signal after harmonic processing according to the target grid angle to obtain the harmonic compensation amount corresponding to the target signal, wherein the time domain compensation reconstructs the current signal after frequency domain processing into a time domain compensation signal.

[0091] Among them, the first transformation unit 431 can be based on the fast Fourier transform (Fast Fourier Transform, FFT), discrete Fourier transform (Discrete Fourier Transform, DFT), etc. in Fourier transform; the second transformation unit 433 can be based on the inverse fast Fourier transform (Inverse Fast Fourier Transform, IFFT), inverse discrete Fourier transform (Inverse Fast Fourier Transform, IDFT), etc. in Fourier transform.

[0092] Figure 7 Schematic diagram showing each transformation unit in the beat frequency suppression module provided in some embodiments of the present application, such as Figure 7 As shown in (1), the first transformation unit 431 is FFT, based on ωt=θ g The coordinate mapping relationship is obtained by Fourier series expansion, which converts the time domain input signal (i.e. the current sampling value i fb) is converted into frequency domain signals Yd and Yq in the rotating coordinate system, which is equivalent to converting the current sampling value i fb Projecting to the rotating coordinate system, the decoupling of the DC component and the harmonic component is achieved, where Yd and Yq correspond to the amplitude and phase information of the DC component respectively. Through frequency domain decomposition, specific frequency harmonics can be suppressed by low-pass filters to achieve the current sampling value i fb Filtering and reconstruction.

[0093] Taking the single-phase power input scenario as an example, when there is 100Hz harmonic, according to the target grid angle θ g Perform Fourier series expansion to ensure accurate 100Hz phase information and align the phase when injecting harmonic compensation, where the grid angular frequency ω g .

[0094] Among them, the d-axis current i d and q-axis current i q The Fourier expansion of is:

[0095]

[0096] Where, I d,0 , I q,0 Refers to the constant DC component in the current signal in the dq coordinate system, I dn , I qn is the nth harmonic torque amplitude, ω is the mechanical angular frequency of the fundamental wave, is the phase of the nth harmonic.

[0097] The angular frequency corresponding to 100Hz is 2ω g For example, the d-axis current i d and q-axis current i q The Fourier expansion of the double frequency of the power grid frequency is:

[0098]

[0099] Where, I d,0 , I q,0 Refers to the constant DC component in the current signal in the dq coordinate system, I d2 , I q2 is the second harmonic torque amplitude, 2ω g is the angular frequency corresponding to the doubled frequency, is the phase of the 2nd harmonic.

[0100] like Figure 7 As shown in (2), the second transform unit 433 is IFFT, based on ωt=θ g The coordinate mapping relationship is used to perform inverse Fourier transform on the target signals Xd and Xq after frequency domain processing in the rotating coordinate system and reconstruct them into time domain signals (i.e., harmonic compensation amount icmp ), this process is equivalent to restoring the DC component after frequency domain processing to the DC component with θ g The frequency-to-time domain mapping achieved through inverse Fourier transform ensures that the harmonically processed signal remains strictly synchronized with the grid phase in the time domain, providing time-domain instructions for current loop compensation.

[0101] When the first transform unit 431 is FFT and the second transform unit 433 is IFFT, Figure 8 FIG. 1 shows a schematic diagram of another beat frequency suppression module in a motor control device provided in some embodiments of the present application, such as Figure 8 As shown, FFT is based on the target grid angle θ g The corresponding coordinate mapping relationship is expanded by Fourier series to convert the current sampling value i fb Convert it into frequency domain signals Yd and Yq in the rotating coordinate system, filter Yd and Yq through LPF respectively, extract the DC component in Yd or Yq, then use the DC component as the control variable, make a difference with the set reference value 0, input the difference into the PI controller, after adjustment by the PI controller, and then limit the output signal range through the limiting process to obtain the target signals Xd and Xq, perform inverse Fourier transform on Xd and Xq, and reconstruct them into the harmonic compensation amount i cmp .

[0102] It should be noted that the current sampling value i fb Including q-axis current sampling value i qfb and d-axis current sampling value i dfb , harmonic compensation amount i cmp Including q-axis compensation i qcmp and d-axis compensation i dcmp Taking permanent magnet synchronous motor control as an example, since the q-axis current determines the electromagnetic torque output, its beat frequency energy is significantly higher than that of the d-axis (e.g., the q-axis can be 5-10 times that of the d-axis). Therefore, in certain application scenarios, selectively suppressing the beat frequency of only the q-axis current can optimize system performance.

[0103] Figure 9 FIG. 1 shows a schematic diagram of another beat frequency suppression module in a motor control device provided in some embodiments of the present application, such as Figure 9 As shown, FFT is based on the target grid angle θ g The corresponding coordinate mapping relationship is expanded by Fourier series to convert the q-axis current sampling value i qfbThe frequency domain signal is converted into a frequency domain signal in the rotating coordinate system, and the frequency domain signal is filtered by LPF to extract the DC component in the frequency domain signal. Then, the DC component is used as the control variable and the difference is made with the set reference value 0. The difference is input into the PI controller. After adjustment by the PI controller, the output control amount is ensured to be within the safe range through the limit processing to obtain the target signal. The target signal is subjected to inverse Fourier transform and reconstructed into the q-axis compensation amount i qcmp The above-mentioned beat frequency suppression is performed only on the q-axis current, which can reduce the amount of calculation by about half while maintaining a high beat frequency suppression effect.

[0104] In some embodiments, the beat frequency suppression can be performed on both the q-axis and d-axis currents to improve the beat frequency suppression effect. Figure 10 FIG. 1 shows a schematic diagram of another beat frequency suppression module in a motor control device provided in some embodiments of the present application, such as Figure 10 As shown, FFT is based on the target grid angle θ g The corresponding coordinate mapping relationship is expanded by Fourier series to convert the q-axis current sampling value i qfb The frequency domain signal is converted into a frequency domain signal in the rotating coordinate system, and the frequency domain signal is filtered by LPF to extract the DC component in the frequency domain signal. Then, the DC component is used as the control variable and the difference is made with the set reference value 0. The difference is input into the PI controller. After adjustment by the PI controller, the output control amount is ensured to be within the safe range through the limit processing to obtain the target signal. The target signal is subjected to inverse Fourier transform and reconstructed into the q-axis compensation amount i qcmp And, FFT is based on the target grid angle θ g The corresponding coordinate mapping relationship is expanded by Fourier series to convert the d-axis current sampling value i dfb The frequency domain signal is converted into a frequency domain signal in the rotating coordinate system, and the frequency domain signal is filtered by LPF to extract the DC component in the frequency domain signal. Then, the DC component is used as the control variable and the difference is made with the set reference value 0. The difference is input into the PI controller. After adjustment by the PI controller, the output control amount is ensured to be within the safe range through the limit processing to obtain the target signal. The target signal is subjected to inverse Fourier transform and reconstructed into the d-axis compensation amount i dcmp .

[0105] In scenarios where the computing power is sufficient on a hardware platform (such as a dual-core DSP or FPGA), the q-axis current sampling value i qfb and d-axis current sampling value i dfb Implementing a beat frequency suppression strategy, processing the current sampling values ​​of the two axes separately through two independent beat frequency suppression loops, can further improve the beat frequency suppression effect compared with only suppressing the current of the q-axis.

[0106] It should be noted that the above Figures 5 to 10In the beat frequency suppression module shown, each component can be implemented by hardware, software, or a combination of software and hardware.

[0107] Figure 11 A schematic diagram of another motor control device provided in some embodiments of the present application is shown, taking driving a permanent magnet synchronous motor as an example. Figure 11 As shown, the vector control module 410 includes Clark transformation, Park transformation, speed loop, current loop, inverse Park transformation and SVPWM.

[0108] The three-phase AC power output by the permanent magnet synchronous motor a 、i b 、i c , which is converted into the α-axis current i in the αβ coordinate system through Clark transformation α and β-axis current i β , and transmits it to the Park transform, which converts the received α-axis current i α , β-axis current i β and rotor electrical angle θ e , the α-axis current i α and β-axis current i β Converted to the q-axis current sampling value i in the rotating coordinate system qfb and d-axis current sampling value i dfb .

[0109] The working process of the speed loop is: the angular frequency command value ω * The difference between the angular frequency ω is input to the proportional-integral (PI) controller for speed regulation, which outputs the q-axis current command value. Realize closed-loop control of motor speed.

[0110] It should be understood that in the embodiment of the present application, the harmonic compensation amount output by the beat frequency suppression module 430 is injected into the current loop in the vector control module 410. In some embodiments, the harmonic compensation amount can be injected into the current command value; in other embodiments, the harmonic compensation amount can be injected into the current sampling value.

[0111] It should also be understood that the harmonic compensation amount includes the d-axis compensation amount and the q-axis compensation amount. The beat frequency suppression of the q-axis current can be performed only by the q-axis compensation amount, or the beat frequency suppression of the q-axis current can be performed by the q-axis compensation amount and the beat frequency suppression of the d-axis current can be performed by the d-axis compensation amount.

[0112] Therefore, the above-mentioned positions for injecting harmonic compensation and the specific compensation amounts of harmonic compensation can be combined to obtain a variety of examples: injecting current sampling values ​​with harmonic compensation to suppress the beat frequency of the q-axis current; injecting current sampling values ​​with harmonic compensation to suppress the beat frequency of both the q-axis current and the d-axis current; injecting current command values ​​with harmonic compensation to suppress the beat frequency of the q-axis current; injecting current command values ​​with harmonic compensation to suppress the beat frequency of both the q-axis current and the d-axis current.

[0113] Taking the harmonic compensation amount injection current sampling value and the beat frequency suppression of the q-axis current and the d-axis current as an example, a detailed description is given, as follows: Figure 11 As shown, the working process of the corresponding current loop is: the q-axis current command value With the q-axis current (i.e. the q-axis current sampling value i qfb and q-axis compensation i qcmp The difference between the sum of the values ​​of the q-axis current Δi q ), d-axis current command value With the d-axis current (ie, the d-axis current sampling value i dfb and d-axis compensation i dcmp The difference between the sum of the values ​​of the d-axis current Δi d ) is input to the PI controller for current regulation and outputs the d-axis voltage command value and q-axis voltage command value Realize closed-loop control of motor current.

[0114] In other embodiments, taking the injection of harmonic compensation into the current command value to perform beat frequency suppression on the q-axis current as an example, the harmonic compensation is injected into the current control loop in the vector control module to obtain a target modulation signal, specifically including: superimposing the q-axis compensation onto the q-axis current command value to obtain a corrected q-axis current value; and injecting the q-axis current value into the current control loop to obtain a target modulation signal (i.e., a first modulation signal).

[0115] Because the q-axis current determines the electromagnetic torque output, its beat frequency energy is significantly higher than that of the d-axis. Therefore, in certain application scenarios, only the q-axis current can be subjected to beat frequency suppression, reducing computational and control complexity. By adding q-axis harmonic compensation to the current command value and processing the corrected current value through the current control loop, the q-axis current beat frequency is effectively suppressed. The generated first modulation signal precisely controls the q-axis current waveform, improving system operational stability.

[0116] In other embodiments, taking the example of injecting harmonic compensation into the current command value and performing beat frequency suppression on both the q-axis current and the d-axis current, the harmonic compensation is injected into the current control loop in the vector control module to obtain a target modulation signal, specifically including: superimposing the q-axis compensation onto the q-axis current command value to obtain a corrected q-axis current value; superimposing the d-axis compensation onto the d-axis current command value to obtain a corrected d-axis current value; and injecting the q-axis current value and the d-axis current value into the current loop to obtain a target modulation signal (i.e., a second modulation signal).

[0117] At the same time, harmonic compensation is superimposed on the q-axis and d-axis current command values. The corrected dual-axis current values ​​act synergistically on the current loop. The obtained second modulation signal can comprehensively suppress the dual-axis current beat frequency and enhance the dynamic performance and anti-interference ability of the system under complex working conditions.

[0118] In other embodiments, taking the injection of harmonic compensation into the current sampling value to perform beat frequency suppression on the q-axis current as an example, the harmonic compensation is injected into the current control loop in the vector control module to obtain a target modulation signal, specifically including: superimposing the q-axis compensation onto the q-axis current sampling value to obtain a corrected q-axis current value; injecting the q-axis current value into the current control loop to obtain a target modulation signal (i.e., a third modulation signal).

[0119] Because the q-axis current determines the electromagnetic torque output, its beat frequency energy is significantly higher than that of the d-axis. Therefore, in certain application scenarios, only the q-axis current can be subjected to beat frequency suppression, reducing computational and control complexity. By superimposing the q-axis harmonic compensation on the current sampling value and passing it through the current control loop to generate a third modulation signal, this method tracks and suppresses the q-axis current beat frequency in real time, enabling rapid response to current changes and optimizing the system's transient control performance.

[0120] Figure 12 The schematic diagram of the magnetic pole position and axis error is shown in FIG. The position observer is used to estimate the motor rotor position. The actual rotor position axes are the d-axis and the q-axis, as shown in FIG. Figure 12 As shown, at startup, the virtual axis (i.e., dc axis) leads the actual d axis angle Δθ (i.e., axis error), as shown in Figure 12 The phase-locked loop (PLL) sends the axis error Δθ output by the position observer to the PLL to obtain the rotor electrical angle θ e and real-time speed ω e The motor speed is then closed-loop controlled via the speed loop. During closed-loop operation, Δθ is controlled to zero, aligning the virtual and actual axes and achieving sensorless position control of the permanent magnet synchronous motor rotor.

[0121] Inverse Park transform receives the d-axis voltage command value q-axis voltage command value and rotor electrical angle θe Then, the d-axis voltage command value in the rotating coordinate system is and q-axis voltage command value Converted to the α-axis voltage u in the αβ coordinate system α and β-axis voltage u β , the α-axis voltage u α , β-axis voltage u β The α-axis voltage and β-axis voltage in the αβ coordinate system are converted into space vectors by inputting into SVPWM. The action time of each basic vector is calculated based on the DC bus voltage to obtain the target modulation signal. The target modulation signal acts on the inverter to control the permanent magnet synchronous motor.

[0122] It should be noted that motor startup involves three phases: positioning, synchronous acceleration, and closed-loop switching. The synchronous acceleration phase leverages the motor's power angle and torque self-balancing principle to gradually reduce shaft error. When the speed reaches a set constant value and the shaft error is sufficiently minimized, open-loop control switches to closed-loop speed control.

[0123] The motor control method corresponding to the motor control device provided in some embodiments of the present application is as follows: when the frequency of the ripple in the DC bus voltage is in a preset multiple relationship with the grid frequency, and the frequency of the ripple produces a beat frequency phenomenon with the electrical frequency of the motor, the DC bus voltage is input into the phase extraction module to obtain the target grid angle; the target grid angle and the current sampling value in the rotating coordinate system are input into the beat frequency suppression module to obtain the harmonic compensation amount corresponding to the current sampling value; the harmonic compensation amount is injected into the current control loop in the vector control module to achieve closed-loop control of the motor current, improve the robustness of the control, and use the obtained target modulation signal for motor control. The embodiments of the present application reduce the beat frequency component during the operation of the motor by phase locking and harmonic injection, thereby suppressing the beat frequency between the electrical frequency of the motor and the ripple frequency, and improving the stability of the motor speed control.

[0124] In order to obtain the phase of the power grid, phase extraction is required. Figure 13 A schematic diagram of a phase extraction module in a motor control device provided in some embodiments of the present application is shown. Figure 13 As shown, the phase extraction module 420 includes a signal conversion unit 421, a harmonic extraction unit 422 and a phase determination unit 423. The signal conversion unit 421 is used to convert the DC bus voltage u dc Converted into the corresponding discrete-time signal u dc_s ; Harmonic extraction unit 422 is used to discrete time signal u dc_s Perform bandpass filtering to obtain the sinusoidal signal u of the DC bus voltage dc_α , wherein the harmonic extraction unit 422 can be a bandpass filter or a high-pass filter. The phase determination unit 423 is used to determine the phase of the sinusoidal signal u dc_αPerform phase locking to obtain the target grid angle θ g .

[0125] It should be understood that the phase extraction module relies on the above-mentioned signal processing method to identify the real-time phase of the component with the same frequency as the grid fundamental wave from the DC bus voltage; for example, in a single-phase rectification scenario, it identifies the angle of the grid's second frequency, or in a three-phase rectification scenario, it identifies the angle of the grid's sixth frequency.

[0126] Figure 14 A schematic diagram of another motor control device provided in some embodiments of the present application is shown, taking driving a permanent magnet synchronous motor as an example. Figure 14 As shown, the phase extraction module 420 includes a zero-order hold (ZOH), a band pass filter (BPF), and a second-order generalized integrator phase-locked loop (SOGI-PLL).

[0127] That is, the signal conversion unit 421 may be ZOH, which converts the continuous signal into a discrete signal, that is, converts the DC bus voltage (continuous signal) into the corresponding discrete time signal u dc_s (discrete signal).

[0128] When the harmonic extraction unit 422 may be a BPF, its transfer function B1(s) is expressed as:

[0129]

[0130] Where ξ1 is the damping ratio, which determines the bandwidth of the BPF, s is the complex frequency variable, and ω g is the angular frequency.

[0131] In the single-phase rectification scenario, BPF allows the discrete time signal u of 90Hz-110Hz dc_s By, then from the discrete time signal u dc_s Extract harmonics around 100Hz from the three-phase rectifier. In the three-phase rectifier scenario, BPF allows discrete time signals u of 290Hz-310Hz. dc_s By, then from the discrete time signal u dc_s Extract the harmonics around 300Hz.

[0132] After passing through the BPF, the sinusoidal signal u of the DC bus voltage is obtained dc_α , the sinusoidal signal u dc_α Input to SOGI-PLL for phase locking to obtain the target grid angle. For example, if the discrete time signal u dc_sAfter extracting the harmonics of about 100Hz, that is, the sinusoidal signal, it can be phase-locked through SOGI-PLL to obtain the double frequency angle of the power grid; if the discrete time signal u dc_s After extracting the 300Hz harmonics, or sinusoidal signals, from the CMOS, SOGI-PLL is used to phase-lock the signal and obtain the grid's sixth-order frequency angle. This determines the target grid angle, facilitating subsequent Fourier expansion based on the target grid angle.

[0133] Figure 15 A schematic diagram of another phase extraction module in a motor control device provided in some embodiments of the present application is shown. Figure 15 As shown, when the phase determination unit is a SOGI-PLL, the SOGI-PLL includes a second-order generalized integrator (SOGI), a second proportional integral controller (PI) and a second limiter.

[0134] The sinusoidal signal u dc_α Input to the second-order generalized integrator to obtain the orthogonal signal u corresponding to the sinusoidal signal dc_β ; Transform the sinusoidal signal u dc_α , orthogonal signal u dc_β Perform Park transformation to obtain the ripple q-axis voltage u dc_q Based on the second proportional integral controller, the q-axis voltage u dc_q The difference between the second reference value and the second reference value is calculated to generate a second adjustment amount; the second adjustment amount is input to the second limiter for limiting adjustment to obtain the target grid angle θ g , the target grid angle is also used to indicate Park transformation.

[0135] The second-order generalized integrator can be processed as follows:

[0136]

[0137] Where H d (s) is the d-axis transfer function, H q (s) is the q-axis transfer function, ω is the angular frequency, for example, in a single-phase rectification scenario, ω = 2Pi × 50 rad / s; k is the damping coefficient, which can be 1.414; v′ and qv′ are the output sinusoidal and quadrature signals, and v(s) is the Laplace transform of the input signal.

[0138] In SOGI-PLL, the sinusoidal signal u is obtained by SOGI and the output of the bandpass filter dc_α , and the corresponding orthogonal signal u dc_β ; After Park transformation, the q-axis voltage u is obtained dc_q ,u dc_q =cosθg ×u dc_β -sinθ g ×u dc_α According to the vector principle of the power supply, when the q-axis voltage is controlled to 0 (the second reference value), the phase can be locked to obtain the target grid angle θ g ; That is, through PI control u dc_q Approaching 0 to achieve phase locking.

[0139] The frequency coupling between the DC bus voltage ripple and the grid fundamental is determined by filtering and conditioning steps such as a second-order generalized integrator (SOGI). This phase component, coupled with the grid fundamental's frequency, is then identified from the ripple signal. This phase component is then fed into a phase-locked loop (PLL) and tracked through closed-loop processes such as phase detection, loop filtering, and voltage-controlled oscillation. Because the frequency of this component is strictly consistent with the grid fundamental's frequency, and the phase difference can be dynamically calibrated to a minimum steady-state value through the PLL, it is then equivalent to the phase of the grid fundamental (i.e., the target grid angle).

[0140] To facilitate a further understanding of the technical solutions in some embodiments of the present application, the following describes in detail the technical solutions of the motor control method and how the technical solutions solve the above-mentioned technical problems in conjunction with some specific embodiments and drawings. The various embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. Obviously, the described embodiments are part of the embodiments of the present application, not all of them.

[0141] Some embodiments of the present application provide a motor control method, which is applied to a motor drive system and compensates for current harmonics in vector control, including the following steps (1) to (3):

[0142] (1) When the frequency of the ripple in the DC bus voltage has a preset multiple relationship with the grid frequency and the ripple frequency produces a beat frequency phenomenon with the electrical frequency of the motor, the ripple is extracted from the DC bus voltage based on the ripple frequency and the target grid angle corresponding to the ripple is determined.

[0143] Among them, the discrete-time signal corresponding to the DC bus voltage is first determined; the discrete-time signal is then band-pass filtered (allowing the component corresponding to the ripple frequency to pass) to obtain the sinusoidal signal of the DC bus voltage (i.e., extracting the ripple); the sinusoidal signal is phase-locked to obtain the target grid angle.

[0144] (2) Based on the target grid angle and the current sampling value in the rotating coordinate system, the harmonic compensation amount corresponding to the current sampling value is obtained. The harmonic compensation amount is used to eliminate the beat frequency component in the current sampling value, which is generated by the ripple.

[0145] Among them, the target grid angle and the current sampling value in the rotating coordinate system are converted into the frequency domain to obtain the frequency domain signal corresponding to the current sampling value; the frequency domain signal is then subjected to low-pass filtering, proportional integral processing and limiting processing to obtain the target signal corresponding to the frequency domain signal adjustment; and the target signal and the target grid angle input are then compensated in the time domain to obtain the harmonic compensation amount corresponding to the target signal.

[0146] It should be noted that the current sampling values ​​in the rotating coordinate system may include only the q-axis current sampling values, or may include both the d-axis current sampling values ​​and the q-axis current sampling values.

[0147] (3) Based on the harmonic compensation amount, current control and current-voltage conversion are performed to obtain the target modulation signal to control the motor.

[0148] The current control is performed based on the harmonic compensation amount, which may be performed by adding the harmonic compensation amount to the current command value or by adding the harmonic compensation amount to the current sampling value.

[0149] For the current sampling value in the rotating coordinate system based on the target grid angle in step (2), determining the harmonic compensation amount corresponding to the current sampling value includes frequency domain conversion, filtering processing and time domain compensation, including the following steps:

[0150] First, the current sampling value in the rotating coordinate system is converted into the frequency domain based on the target grid angle to obtain the frequency domain signal corresponding to the current sampling value;

[0151] Secondly, the frequency domain signal is filtered, proportionally integrated, and limited to obtain a target signal corresponding to the frequency domain signal adjustment; specifically, the frequency domain signal is preset filtered to obtain a filtered harmonic characteristic signal; the difference between the harmonic characteristic signal and the first reference value is calculated to generate a first adjustment amount; and the first adjustment amount is limited and adjusted to obtain a target signal.

[0152] Finally, the target signal is compensated in the time domain based on the target grid angle to obtain the harmonic compensation amount corresponding to the target signal.

[0153] In some embodiments, if only the q-axis current sampling value in the current sampling value is compensated, the corresponding process of the above step (2) is: the q-axis current sampling value is converted into the frequency domain based on the target grid angle to obtain the q-axis compensation amount, and the harmonic compensation amount includes the q-axis compensation amount.

[0154] Furthermore, the above-mentioned step (3) performs current control and current-voltage conversion based on the harmonic compensation amount to obtain a target modulation signal, including superimposing the q-axis compensation amount to the q-axis current command value to obtain a corrected q-axis current value; and then performs current control and current-voltage conversion on the q-axis current value to obtain a first modulation signal, and the target modulation signal includes the first modulation signal.

[0155] In other embodiments, if both the q-axis current sampling value and the d-axis current sampling value in the current sampling value are compensated, the process corresponding to the above step (2) is: based on the target grid angle, the d-axis current sampling value and the q-axis current sampling value are converted into the frequency domain to obtain the d-axis compensation amount and the q-axis compensation amount; the current sampling value includes the d-axis current sampling value and the q-axis current sampling value, and the harmonic compensation amount includes the d-axis compensation amount and the q-axis compensation amount.

[0156] Furthermore, the above-mentioned step (3) performs current control and current-voltage conversion based on the harmonic compensation amount to obtain a target modulation signal, including: superimposing the q-axis compensation amount on the q-axis current command value to obtain a corrected q-axis current value; superimposing the d-axis compensation amount on the d-axis current command value to obtain a corrected d-axis current value; performing current control and current-voltage conversion on the q-axis current value and the d-axis current value to obtain a second modulation signal, and the target modulation signal includes the second modulation signal.

[0157] In the above step (1), the ripple is extracted from the DC bus voltage based on the frequency of the ripple, and the target grid angle corresponding to the ripple is determined, including the following steps: first, the DC bus voltage is converted into a discrete time signal corresponding to the DC bus voltage; second, the discrete time signal is band-pass filtered based on the frequency of the ripple to obtain a sinusoidal signal of the DC bus voltage; then, the sinusoidal signal is phase-locked to determine the target grid angle corresponding to the ripple; the process of determining the target grid angle is as follows: determining the orthogonal signal corresponding to the sinusoidal signal; performing Park transformation on the sinusoidal signal and the orthogonal signal to obtain the q-axis voltage of the ripple; calculating the difference between the q-axis voltage and the second reference value to generate a second adjustment amount; performing limit adjustment on the second adjustment amount to obtain the target grid angle, and the target grid angle is used to indicate the Park transformation.

[0158] It should be understood that the implementation process of the above steps can be referred to the above Figures 4 to 15 The detailed description of the motor control device will not be repeated here.

[0159] Figure 16 A flow chart of a motor control method provided by some embodiments of the present application is shown, which is applied to the above Figures 4 to 15 Motor control device, it should be noted that Figures 4 to 15 The motor control device can be implemented in hardware, software, or a combination of software and hardware, such as Figure 16 As shown, the motor control method includes the following steps:

[0160] S510: When the frequency of the ripple in the DC bus voltage is a preset multiple of the grid frequency and the ripple frequency beats the electrical frequency of the motor, the DC bus voltage is input into a phase extraction module to obtain a target grid angle.

[0161] Among them, the phase extraction module is used to extract voltage based on the frequency of the ripple, that is, to separate the ripple and determine the target grid angle corresponding to the ripple.

[0162] S520: Input the target grid angle and the current sampling value in the rotating coordinate system into the beat frequency suppression module to obtain the harmonic compensation amount corresponding to the current sampling value.

[0163] Harmonic compensation is used to eliminate the beat frequency component in the current sampling value, which is generated by the ripple. The beat frequency suppression module is used to perform frequency domain conversion, harmonic processing, and time domain compensation on the current sampling value to determine the corresponding harmonic compensation amount in the current sampling value.

[0164] S530 : Injecting the harmonic compensation amount into the current control loop in the vector control module to obtain a target modulation signal, which is used to control the motor.

[0165] It should be understood that the implementation process of steps 510 to 530 can be referred to the above Figures 4 to 15 The detailed description of the motor control device will not be repeated here.

[0166] In some embodiments of the present application, a motor control method is provided, which is applied to Figure 14 The motor drive system shown includes the following steps (1) to (7):

[0167] (1) When the frequency of the ripple in the DC bus voltage is a preset multiple of the grid frequency and the motor's electrical frequency and the frequency of the ripple in the DC bus voltage produce a beat frequency phenomenon, the DC bus voltage is input to ZOH to obtain the discrete time signal u corresponding to the DC bus voltage. dc_s ;

[0168] (2) The discrete time signal u dc_s Input to BPF for bandpass filtering to obtain the sinusoidal signal u of DC bus voltage dc_α ;

[0169] (3) The sinusoidal signal u dc_α Input to SOGI-PLL for phase locking to obtain the target grid angle θ g ;

[0170] by Figure 10 Taking the beat frequency suppression module shown in the figure as an example, it also includes:

[0171] (4) Set the target grid angle θ g , q-axis current sampling value i in the rotating coordinate system qfbInput to FFT to obtain the frequency domain signal corresponding to the current sampling value; filter the frequency domain signal through LPF to extract the DC component in the frequency domain signal; use the DC component as the control variable, make a difference with the set reference value 0, and input the difference into the PI controller. After adjustment by the PI controller, the output control amount is ensured to be within the safe range through limiting processing to obtain the target signal; input the target signal into IFFT for inverse Fourier transform and reconstruct it into the q-axis compensation amount i qcmp ;

[0172] (5) Set the target grid angle θ g , d-axis current sampling value i in the rotating coordinate system dfb Input to FFT to obtain the frequency domain signal corresponding to the current sampling value; filter the frequency domain signal through LPF to extract the DC component in the frequency domain signal; use the DC component as the control variable, make a difference with the set reference value 0, and input the difference into the PI controller. After adjustment by the PI controller, the output control amount is ensured to be within the safe range through limiting processing to obtain the target signal; input the target signal into IFFT for inverse Fourier transform and reconstruct it into the d-axis compensation amount i dcmp ;

[0173] (6) Add the q-axis compensation amount to i qcmp To q-axis current sampling value i qfb , get the corrected q-axis current value; set the d-axis compensation value i dcmp Superimposed on the d-axis current sampling value i dfb , get the corrected d-axis current value;

[0174] (7) The q-axis current value and the d-axis current value are injected into the current loop to obtain the target modulation signal P. The target modulation signal acts on the inverter to control the permanent magnet synchronous motor.

[0175] After the above motor control method, Figure 17 FIG. 1 shows a schematic diagram of the current time domain waveform of the compressor controlled by the motor control method according to an embodiment of the present application after injecting harmonics. Figure 17 As shown, the waveform of the time domain waveform 220 of the current is more regular and the fluctuation is more stable. The harmonic injection effect presents a more regular periodic change, which alleviates the beat frequency phenomenon and has a significant suppressing effect on the beat frequency phenomenon.

[0176] Figure 18 FIG. 1 shows a schematic diagram of a spectrum analysis of the q-axis current in the compressor control according to an embodiment of the present application. The spectrum analysis refers to a fast Fourier transform spectrum analysis, such as Figure 18 As shown in the FFT spectrum, the effective value of the spectrum amplitude in the 100Hz frequency band changes from Figure 3The 220 in the figure is reduced to 60. Therefore, the beat frequency suppression corresponding to the motor control method proposed in some embodiments of the present application reduces the spectrum amplitude of the 100Hz frequency band, effectively reducing the 100Hz spectrum component in the motor current, thereby reducing motor noise and vibration and improving motor stability.

[0177] The present application also provides an air conditioner including a motor control device configured to execute the aforementioned motor control methods. The motor control device includes a vector control module, a phase extraction module, and a beat frequency suppression module. In an air conditioner, the motor control device controls the motor, which in turn drives air conditioner components such as a compressor and indoor and outdoor fans.

[0178] It should be understood that the air conditioner also includes a refrigeration system, a controller, etc. The refrigeration system includes a compressor, a condenser, an evaporator, a throttling device, etc. The controller is used to control the temperature, wind speed, mode, etc.

[0179] It should be understood that the air conditioners provided in some embodiments of the present application are variable-frequency air conditioners, which can have various implementation forms, such as central air conditioning and multi-split air conditioners. Central air conditioning is a system that uses one or more outdoor units to deliver cooling or heating to multiple indoor areas through a system such as air ducts or hot and cold water pipes, thereby achieving centralized air conditioning for an entire building or larger space. Multi-split air conditioners are a special form of central air conditioning.

[0180] An embodiment of the present application also provides an air conditioning system, comprising one or more air conditioners, each of which includes a motor control device, the motor control device comprising a vector control module, a phase extraction module, and a beat frequency suppression module. While the air conditioner is operating via a transformer-connected power source, the motor control device in the air conditioner is configured to execute the aforementioned motor control methods.

[0181] Specific details such as specific system structures and technologies are provided for the purpose of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details.

[0182] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative; for example, the division of modules is merely a logical functional division, and actual implementation may employ other division methods; for example, multiple units or components may be combined or integrated into another module, or some features may be omitted.

[0183] The above are only specific embodiments of the present application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A motor control method, characterized in that: Applied to a motor control device, the motor control device includes a vector control module, a phase extraction module and a beat frequency suppression module; the motor control method includes: When the frequency of the ripple in the DC bus voltage is a preset multiple of the grid frequency and the frequency of the ripple beats the electrical frequency of the motor, the DC bus voltage is input into the phase extraction module to obtain a target grid angle. The phase extraction module is configured to extract the ripple based on the frequency of the ripple and determine a target grid angle corresponding to the ripple. Inputting the target grid angle and the current sampling value in the rotating coordinate system into the beat frequency suppression module to obtain a harmonic compensation amount corresponding to the current sampling value, wherein the harmonic compensation amount is used to eliminate the beat frequency component in the current sampling value, wherein the beat frequency component is generated by the ripple; The harmonic compensation amount is injected into the current control loop in the vector control module to obtain a target modulation signal, and the target modulation signal is used to control the motor.

2. The motor control method according to claim 1, wherein: The beat frequency suppression module includes a first conversion unit, a harmonic processing unit, and a second conversion unit. The target grid angle and the current sampling value in the rotating coordinate system are input into the beat frequency suppression module to obtain the harmonic compensation amount corresponding to the current sampling value, including: Inputting the target grid angle and the current sampling value in the rotating coordinate system into the first transformation unit to obtain a frequency domain signal corresponding to the current sampling value; Inputting the frequency domain signal into the harmonic processing unit for filtering, proportional integral processing and limiting processing to obtain a target signal corresponding to the frequency domain signal after adjustment; The target signal and the target grid angle are input into the second conversion unit to obtain the harmonic compensation amount corresponding to the target signal, where the harmonic compensation amount is a signal obtained by converting the target signal from the frequency domain to the time domain.

3. The motor control method according to claim 2, wherein: The harmonic processing unit includes a low-pass filter, a first proportional-integral controller, and a first limiter. The frequency domain signal is input into the harmonic processing unit for filtering, proportional-integral, and limiting processing to obtain a target signal corresponding to the frequency domain signal after adjustment, including: Inputting the frequency domain signal into a low-pass filter for preset low-pass filtering to obtain a filtered harmonic characteristic signal; Calculating a difference between the harmonic characteristic signal and a first reference value based on the first proportional-integral controller to generate a first adjustment value; The first adjustment amount is input into the first limiter for limit adjustment to obtain the target signal.

4. The motor control method according to any one of claims 1 to 3, characterized in that: The step of inputting the target grid angle and the current sampling value in the rotating coordinate system into the beat frequency suppression module to obtain the harmonic compensation amount corresponding to the current sampling value includes: The target grid angle and the q-axis current sampling value are input into the beat frequency suppression module to obtain the q-axis compensation amount, the current sampling value includes the q-axis current sampling value, and the harmonic compensation amount includes the q-axis compensation amount.

5. The motor control method according to claim 4, wherein: The step of injecting the harmonic compensation amount into the current control loop in the vector control module to obtain a target modulation signal includes: Adding the q-axis compensation value to the q-axis current command value to obtain a corrected q-axis current value; The q-axis current value is injected into the current control loop to obtain a first modulation signal, and the target modulation signal includes the first modulation signal.

6. The motor control method according to any one of claims 1 to 3, characterized in that: The step of inputting the target grid angle and the current sampling value in the rotating coordinate system into the beat frequency suppression module to obtain the harmonic compensation amount corresponding to the current sampling value includes: The target grid angle, d-axis current sampling value, and q-axis current sampling value are input into the beat frequency suppression module to obtain the d-axis compensation amount and the q-axis compensation amount; the current sampling value includes the d-axis current sampling value and the q-axis current sampling value, and the harmonic compensation amount includes the d-axis compensation amount and the q-axis compensation amount.

7. The motor control method according to claim 6, wherein: The step of injecting the harmonic compensation amount into the current control loop in the vector control module to obtain a target modulation signal includes: Adding the q-axis compensation value to the q-axis current command value to obtain a corrected q-axis current value; Adding the d-axis compensation value to the d-axis current command value to obtain a corrected d-axis current value; The q-axis current value and the d-axis current value are injected into the current control loop to obtain a second modulation signal, and the target modulation signal includes the second modulation signal.

8. The motor control method according to any one of claims 1 to 3, characterized in that: The phase extraction module includes a signal conversion unit, a harmonic extraction unit, and a phase determination unit. Inputting the DC bus voltage into the phase extraction module to obtain a target grid angle includes: Inputting the DC bus voltage into the signal conversion unit to obtain a discrete-time signal corresponding to the DC bus voltage; Inputting the discrete-time signal into the harmonic extraction unit for bandpass filtering to obtain a sinusoidal signal of the DC bus voltage; The sinusoidal signal is input into the phase determination unit for phase locking to obtain the target grid angle.

9. The motor control method according to claim 8, characterized in that: The phase determination unit includes a second-order generalized integrator, a second proportional integral controller, and a second limiter. Inputting the sinusoidal signal into the phase determination unit for phase locking to obtain the target grid angle includes: Inputting the sinusoidal signal into a second-order generalized integrator to obtain an orthogonal signal corresponding to the sinusoidal signal; Performing Park transformation on the sinusoidal signal and the quadrature signal to obtain the q-axis voltage of the ripple; performing a calculation on a difference between the q-axis voltage and a second reference value based on the second proportional-integral controller to generate a second adjustment value; The second adjustment amount is input into the second limiter for limiting adjustment to obtain the target grid angle, and the target grid angle is used to indicate the Park transformation.

10. An air conditioner, characterized in that: The motor control device comprises a motor control device, wherein the motor control device is configured to execute the motor control method according to any one of claims 1 to 9.

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