A single-phase permanent magnet synchronous motor driving system spurious frequency suppression method

Abstract

This invention discloses a beat frequency suppression method for a single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system based on shaft current harmonic injection, belonging to the field of motor drive control technology. The method includes: acquiring the grid voltage phase angle and calculating the beat frequency reference angle; extracting low-frequency beat frequency components from the three-phase stator current and obtaining the shaft beat frequency current component through coordinate transformation; identifying the amplitude and phase of the shaft beat frequency compensation current through a dual-channel PI closed loop based on orthogonal demodulation; and superimposing the beat frequency compensation current onto the shaft current command. This method extracts the low-frequency beat frequency components from the three-phase stator current, calculates the amplitude and phase of the shaft beat frequency compensation current, and injects the obtained compensation amount into the shaft current command. The PI closed loop enables online dynamic optimization of the compensation parameters, automatically compensating for phase deviations caused by changes in system parameters, and effectively suppressing motor current beat frequency envelope oscillations.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet synchronous motor drive control technology, and in particular to a beat frequency suppression method for a single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system. Background Technology

[0002] In recent years, with the increasing performance requirements of the market for motor drive systems, interior permanent magnet synchronous motor (IPMSM) drive systems are developing towards integration and refinement. Traditional systems use large-capacity electrolytic capacitors at the bus terminal to stabilize the bus voltage. The electrolyte in these capacitors is prone to evaporation, affecting the system's reliability and high-temperature resistance. Furthermore, the large size of these capacitors increases the system's physical dimensions and manufacturing costs. In addition, drive systems typically require power factor correction circuits to reduce grid pollution and improve the power factor; however, these circuits generate additional power losses, further increasing size and cost.

[0003] To overcome the aforementioned drawbacks, electrolytic capacitor-free drive systems, which use small-capacity film capacitors instead of electrolytic capacitors, have gradually gained attention. This structure can significantly improve system reliability and power density, while reducing system size and cost. However, for single-phase electrolytic capacitor-free permanent magnet synchronous motor drive systems, the DC bus voltage exhibits significant fluctuations at twice the grid frequency due to the drastically reduced bus capacitor value. When the inverter output voltage frequency is close to the bus voltage fluctuation frequency, the bus voltage fluctuation component couples with the inverter output voltage, causing low-frequency beat frequency phenomena in the motor phase current. This phenomenon manifests as periodic oscillations in the phase current envelope, which leads to additional energy losses and system noise, and degrades motor operating performance.

[0004] Traditional techniques for beat frequency suppression mainly fall into the following three categories.

[0005] The first type of scheme is based on feedforward compensation. Feedforward compensation is characterized by its simple algorithm and good performance. Its basic principle can be summarized as using the reciprocal of the instantaneous bus voltage value to compensate the modulation ratio or pulse width in real time, ensuring that the inverter can modulate the target voltage required by the motor even under fluctuating bus voltage, eliminating harmonic components caused by bus voltage fluctuations, and suppressing beat frequency phenomena. The paper "Modelling and control of three-phase grid-connected power supply with small DC-link capacitor for electrolysers" proposes a linear observer for predicting bus voltage, which can eliminate bus voltage fluctuations and thus suppress beat frequency. However, this method has low algorithm accuracy when bus voltage fluctuations are severe.

[0006] The second type of scheme is based on frequency compensation. It suppresses beat current caused by fluctuation components by compensating for the inverter's operating frequency, thus eliminating the beat frequency phenomenon. The literature "A Beat-Free Current Control Method for DC Bus Voltage Fluctuations in Traction Converters" starts with the change in bus voltage amplitude and the initial phase angle. It calculates the frequency of inverter output voltage compensation using the bus voltage fluctuation components and the motor angular velocity to suppress beat frequency. This method can suppress low-order beat frequency components to a certain extent, but it also introduces higher-order harmonics. When the motor speed is high, the higher-order harmonics in the motor stator current cannot be ignored.

[0007] The third type of scheme is based on feedback compensation. Feedback compensation is highly dependent on the closed-loop bandwidth. This method adjusts the actual feedback value by subtracting the reference value and using PI control, ultimately making the target value follow the reference value, thus bringing the system to a stable state. The literature "Beat-less control of electrolytic capacitor-less airconditioning motor drive system" proposes a beat frequency suppression method based on current tracking. By moving the modulating wave in SVPWM modulation up and down by the current tracker, a compensation voltage is generated in the inverter output voltage. The harmonics of the compensation voltage cancel out the harmonics caused by bus voltage fluctuations, thereby suppressing the beat frequency component in the phase current.

[0008] Existing solutions mostly focus on three-phase systems, where the bus voltage fluctuates according to a sixth harmonic, or are limited to the periodic fluctuating load conditions of single-phase systems. There is insufficient research on the beat frequency phenomenon under constant load conditions in single-phase drive systems. Therefore, how to effectively suppress the phase current beat frequency oscillation in single-phase capacitorless permanent magnet synchronous motor drive systems through algorithms has become an urgent technical problem to be solved. Summary of the Invention

[0009] The purpose of this invention is to address the limitations of existing technologies by providing a method based on... A method for suppressing the beat frequency of a single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system with shaft current harmonic injection can suppress the motor current beat frequency phenomenon at a specific speed and frequency, reduce the motor current beat frequency amplitude, and the compensation parameters can be adaptively adjusted, making it applicable to various load conditions.

[0010] To achieve the above objectives, the present invention provides a method for suppressing beat frequency in a capacitor-free permanent magnet synchronous motor drive system, comprising the following steps: The phase angle of the grid voltage is obtained and summed with the feedforward correction angle to obtain the beat frequency reference angle that is in phase with the beat frequency fluctuation of the motor current. The feedforward correction angle is the phase difference angle between the beat frequency component of the motor current and the grid voltage, and its value is determined by the inherent phase shift parameter of the system. The three-phase stator current of the motor is acquired in real time, and the beat frequency harmonic component is extracted through a low-pass filter. The component in the rotating coordinate system is then extracted through coordinate transformation. Shaft beat frequency current; The The beat frequency current is projected onto the orthogonal axis of the beat frequency reference angle to extract the DC error signal, construct a closed loop of the DC error signal, and use 0 as the given value of the closed loop DC error signal. The PI controller is used for control to obtain the orthogonal control parameters of the beat frequency compensation current command. Synthesized based on the orthogonal control parameters and the beat frequency reference angle Shaft beat frequency compensation current command, and superimposed it on the original The shaft current command generates the final [current]. Shaft current command, while maintaining The beat frequency compensation component is always zero, for the final The shaft current command is subjected to voltage limit constraint and amplitude limiting processing and applied to the SVPWM control loop to achieve beat frequency suppression of the system.

[0011] First, for a single-phase permanent magnet synchronous motor drive system without electrolytic capacitors, a low-frequency beat frequency envelope analysis model of the stator phase current is established.

[0012] S11: The single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system uses small-capacity film capacitors instead of traditional large-capacity electrolytic capacitors at the DC bus, resulting in a decrease in the system's DC bus voltage. It is difficult to maintain a constant frequency, exhibiting significant fluctuations at twice the grid-side power frequency, as shown in the following mathematical expression.

[0013] (1) in, This represents the average value of the bus voltage. This represents the amplitude of the bus voltage fluctuation. , The angular frequency of the power grid. The frequency of bus voltage fluctuation. For time, This represents the phase of the bus voltage fluctuation.

[0014] S12: Inverter output phase voltage The expression: (2) in, This represents the harmonic order of the inverter's output voltage. Stator current rotation angular frequency Let be the system modulation ratio of the inverter. Considering only the fundamental component with the greatest influence, by combining equations (1) and (2), we obtain... Expression expansion: (3) The second and third items are the motor voltage fluctuation components caused by the bus voltage fluctuation component. , When the voltages are close, the motor voltage will contain a low-frequency component with a non-negligible amplitude. This allows us to determine the beat frequency. : (4) (5) in It is the stator current rotation frequency. It is the frequency of bus voltage fluctuation. This refers to the motor speed. This represents the number of pole pairs of the motor.

[0015] S13: Regarding the motor phase current The amplitude of the beat frequency component is derived, and the motor phase current is... It can be represented as: (6) In the formula, These are the current amplitudes of each frequency component. It is the phase angle of each frequency component. It is the angular frequency of the back electromotive force. Since the frequency of the back electromotive force is equal to the rotational frequency of the stator current, therefore... .

[0016] S14: For angular frequency of Low-frequency AC signals, complex impedance of the stator phase circuit of a permanent magnet synchronous motor for: (7) in, The resistance of the stator winding, This is the equivalent inductance of the stator winding.

[0017] Based on equations (6) and (7), the magnitude of the beat frequency current amplitude component can be derived: (8) In one embodiment: S21: Extract the grid voltage phase angle from the grid voltage using a SOGI (second-order generalized integrator) phase-locked loop. .

[0018] S22: Obtain the beat frequency reference angle using formula (9) .in It is the phase difference angle between the beat frequency component of the motor current and the grid voltage, and its value is fixed relative to the phase of the grid voltage.

[0019] (9) S31: Extract beat frequency harmonic components from three-phase current using a low-pass filter.

[0020] S32: via Axis coordinate transformation Beat frequency component of shaft current.

[0021] S41: Constructing a frame rate reference angle An orthogonal beat frequency reference coordinate system is used as the baseline, where The axis is a cosine axis. The axis is the sine wave. Extract the following: Shaft beat frequency current In the orthogonal beat frequency coordinate system , Components on the axis: (10) (11) Passing these two components through a low-pass filter yields a clean DC error signal. Using 0 as a reference command, the difference between each of the two clean DC error signals is calculated, resulting in two difference signals. These difference signals are then controlled by a PI controller to provide real-time feedback. , The value of .

[0022] S51: Adjust the cosine axis compensation parameters and sine axis compensation parameters Synthesize according to the following formula Shaft beat frequency compensation current command : (12) S52: Dual-channel PI controller can achieve dynamic optimization. , In steady state, an equivalent phase shift is generated to compensate for the residual phase deviation, thereby improving the parameter robustness of the strategy.

[0023] The present invention also provides an electronic device, comprising: a computer-readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is used to read executable instructions stored in the computer-readable storage medium and execute the above-described method.

[0024] The present invention also provides a computer-readable storage medium storing computer instructions for causing a processor to perform the above-described method.

[0025] The present invention also provides a computer program product, including a computer program or instructions that, when executed by a processor, implement the above-described method.

[0026] Overall, compared with the prior art, the present invention has the following beneficial effects: 1. Effective suppression of beat frequency components at specific rotational speeds and frequencies. This invention extracts the phase angle of the grid voltage and calculates the beat frequency reference angle by combining it with the system impedance hysteresis angle, thus constructing a beat frequency reference coordinate system. The d-axis beat frequency current is projected onto the orthogonal axis of this coordinate system and injected in reverse, achieving effective suppression of beat frequency components.

[0027] 2. It exhibits good parameter adaptability and robustness. This invention employs a dual-channel PI control loop to perform closed-loop adjustment on the DC error signal after quadrature demodulation, which can adaptively compensate for phase deviations and improve the robustness of the strategy to fluctuations in operating conditions.

[0028] 3. This ensures system stability and maintains a high power factor on the grid side. This invention only considers... The q-axis beat frequency compensation current command discards the injection of the q-axis, and retains sufficient voltage margin by sacrificing part of the beat frequency suppression effect to avoid system runaway; at the same time, combined with the feedforward power compensation module, the present invention maintains a high grid-side power factor while suppressing beat frequency oscillation, so that the grid-side current harmonics meet the grid connection requirements. Attached Figure Description

[0029] Figure 1 This is a topology diagram of a single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system provided in one embodiment of the present invention.

[0030] Figure 2This is an overall control block diagram of a single-phase electrolytic capacitor-free drive system using the solution of the present invention, provided in one embodiment of the present invention.

[0031] Figure 3 Provided in one embodiment of the present invention Block diagram of the axis command injection beat frequency suppression strategy.

[0032] Figure 4 In one embodiment of the present invention, the electrolytic capacitor-free permanent magnet synchronous motor is operating under the following conditions: Dynamic trajectory and voltage constraints within the axial plane.

[0033] Figure 5 This is a block diagram of a feedforward compensation strategy provided in one embodiment of the present invention.

[0034] Figure 6 This is a vector diagram of feedforward compensation voltage under different superposition methods provided in one embodiment of the present invention.

[0035] Figure 7 The following are examples of motor current beat frequency envelope (a) and harmonic analysis (b) under a load torque of 1440 rpm and 3.5 Nm provided in one embodiment of the present invention; and motor current beat frequency envelope (c) and harmonic analysis (d) under a beat frequency suppression scheme at a load torque of 1440 rpm and 3.5 Nm.

[0036] Figure 8 The following is a simulation waveform diagram provided in one embodiment of the present invention at 1440 rpm and 10% rated load (0.375 Nm). Among them, (e) and (f) are the motor phase current waveforms before and after adopting the present invention, respectively.

[0037] Figure 9 The following is a simulation waveform diagram provided in one embodiment of the present invention at 1440 rpm and 50% rated load (1.875 Nm). Among them, (e) and (f) are the motor phase current waveforms before and after using the present invention, respectively.

[0038] Figure 10 This is a simulation waveform diagram provided in one embodiment of the present invention at 1440 rpm and rated load (3.75 Nm). (e) and (f) show the motor phase current waveforms before and after applying the present invention, respectively.

[0039] Figure 11 The above is a waveform diagram of a system using a comparative scheme under a load of 1440 rpm and 3.75 Nm, provided in one embodiment of the present invention. (e) and (f) show the grid-side current waveform and motor phase current waveform, respectively, using the comparative scheme.

[0040] Figure 12This paper presents a frequency domain analysis of the grid-side current and a comparison of the power factor before and after suppression under 1440 rpm and 93.3% rated load (3.5 Nm) on a simulation platform provided in one embodiment of the present invention.

[0041] Figure 13 This is a diagram showing the relationship between the grid-side power factor and load of different schemes at a speed of 1440 rpm under the simulation platform provided in one embodiment of the present invention.

[0042] Figure 14 This is a schematic diagram of an experimental platform provided in one embodiment of the present invention.

[0043] Figure 15 The image shows the actual waveforms of the motor at 1440 rpm and 93.3% of the rated load (3.5 Nm) on a physical platform provided in one embodiment of the present invention. (e) and (f) show the motor phase current waveforms before and after using the present invention, respectively.

[0044] Figure 16 This is a comparison of the grid-side current waveforms before and after suppression by the embodiment of the present invention at 1440 rpm and 93.3% of the rated load (3.5 Nm) on a physical platform provided in one embodiment of the present invention.

[0045] Figure 17 This paper presents a frequency domain analysis of the grid-side current and a comparison of the power factor before and after suppression under 1440 rpm and 93.3% rated load (3.5 Nm) on a physical platform provided in one embodiment of the present invention.

[0046] Figure 18 This is a diagram showing the relationship between the grid-side power factor and load of different schemes at a speed of 1440 rpm on a physical platform provided in one embodiment of the present invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0048] This invention provides a method for suppressing beat frequency in a capacitor-free permanent magnet synchronous motor drive system, comprising the following steps: The phase angle of the grid voltage is obtained and summed with the feedforward correction angle to obtain the beat frequency reference angle that is in phase with the beat frequency fluctuation of the motor current. The feedforward correction angle is the phase difference angle between the beat frequency component of the motor current and the grid voltage, and its value is determined by the inherent phase shift parameter of the system. The three-phase stator current of the motor is acquired in real time, and the beat frequency harmonic component is extracted through a low-pass filter. The component in the rotating coordinate system is then extracted through coordinate transformation. Shaft beat frequency current; The The beat frequency current is projected onto the orthogonal axis of the beat frequency reference angle to extract the DC error signal, construct a closed loop of the DC error signal, and use 0 as the given value of the closed loop DC error signal. The PI controller is used for control to obtain the orthogonal control parameters of the beat frequency compensation current command. Synthesized based on the orthogonal control parameters and the beat frequency reference angle Shaft beat frequency compensation current command, and superimposed it on the original The shaft current command generates the final [current]. Shaft current command, while maintaining The beat frequency compensation component is always zero, for the final The shaft current command is subjected to voltage limit constraint and amplitude limiting processing and applied to the SVPWM control loop to achieve beat frequency suppression of the system.

[0049] like Figure 1 As shown, this embodiment of the invention provides a topology for a single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system. Based on this topology, the overall control of the single-phase electrolytic capacitor-free drive system of this embodiment is as follows: Figure 2 As shown. This system collects motor speed data via sensors. ,Location and three-phase current 、 The three-phase current can be obtained by Clark transformation and Park transformation. Shaft feedback current. The grid-side phase angle obtained through a PI regulator and a phase-locked loop (PLL). Together A shaft current setting strategy is used to generate a base current command. Based on this, combined with the aforementioned... Axis command injection beat frequency suppression strategy generates beat frequency compensation current command ,right The shaft command current is superimposed and corrected, and the voltage reference value is obtained through a dual closed-loop current PI regulator. After passing through the feedforward power compensation module, IPark converter, IClark converter and SVPWM module, the system can effectively suppress the motor phase current beat frequency phenomenon while ensuring stable system operation.

[0050] Regarding the beat frequency suppression method for a single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system, the specific implementation steps given in this embodiment are as follows: S1: Ignoring higher harmonics in the motor current and considering only the fundamental frequency and the main disturbance frequency, an intuitive simplified analysis model of the beat frequency envelope is established for a single-phase permanent magnet synchronous motor drive system without electrolytic capacitors.

[0051] S2: Obtain the grid voltage phase angle and calculate the beat frequency reference angle based on the grid voltage phase angle and the system's inherent phase shift parameters. Extract the grid voltage phase angle from the grid voltage using a SOGI (second-order generalized integrator) phase-locked loop. Calculate the phase difference angle between the beat frequency component and the grid voltage based on the inherent phase shift of the rectifier fluctuation, the stator impedance hysteresis angle, and the inherent delay of the digital system. Superimpose the grid voltage phase angle and the phase difference angle to obtain the beat frequency reference angle.

[0052] S3: Extract the low-frequency beat frequency component from the three-phase stator current and obtain it through coordinate transformation. Beat frequency current component. Real-time three-phase stator current of a permanent magnet synchronous motor is acquired, and low-frequency beat frequency harmonic components are extracted through low-pass filtering. The filtered three-phase current is then transformed to a two-phase rotating coordinate system using Clark and Park transforms. The beat frequency component is separated from the shaft current and used as... Shaft beat frequency current component.

[0053] S4: Based on orthogonal demodulation, adaptive closed-loop adjustment is used to control the signal from the... Identifying from the beat frequency current component The amplitude and phase parameters of the beat frequency compensation current. The aforementioned... The beat frequency current component is projected onto the cosine and sine axes of the beat frequency reference angle, respectively, to obtain the first error component. Second error component The first and second error components are low-pass filtered, with zero as the reference value, and then closed-loop control is performed through the first and second PI controllers, respectively. The output of the first PI controller is used as the cosine axis compensation parameter X, and the output of the second PI controller is used as the sine axis compensation parameter Y.

[0054] S5: Generate based on the identified compensation parameters and beat frequency reference angle Shaft beat frequency compensation current command, superimposed on Shaft current command. It is synthesized using the cosine axis compensation parameter X and the sine axis compensation parameter Y according to the following formula. Shaft beat frequency compensation current command. The aforementioned Axis beat frequency compensation current command superimposed on the original Shaft current command To obtain the final Axis current command. Implements beat frequency suppression for the system at a specific frequency.

[0055] Furthermore, the calculation process of the beat frequency analysis model in step S1 is as follows: S11: The single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system uses a small-capacity film capacitor instead of the traditional large-capacity electrolytic capacitor at the DC bus terminal, reducing the DC bus voltage. It cannot remain constant, but instead exhibits significant fluctuations at twice the grid-side power grid frequency, as shown in the following mathematical expression.

[0056] (13) in, This represents the average value of the bus voltage. This represents the amplitude of the bus voltage fluctuation. The angular frequency of the power grid. For time, This represents the phase of the bus voltage fluctuation.

[0057] set up , The angular frequency of the bus voltage fluctuation. Given the angular frequency of the stator current rotation, the expression for the motor phase voltage output by the inverter is as follows: (14) in, This represents the harmonic order of the inverter's output voltage. Let be the modulation ratio. Considering only the first-order component, substituting equation (13) into equation (14) yields: (15) S12: Simplify and expand equation (15) using the product-to-sum formula of trigonometric functions: (16) The second and third terms are the motor voltage fluctuation components caused by the bus voltage fluctuation component, when the stator current rotational angular frequency... Angular frequency of bus voltage fluctuation When they are close (i.e.) The stator voltage of a motor contains low-frequency components with non-negligible amplitude, which in turn generates significant low-frequency envelope oscillations in the stator phase current, known as beat frequency. The corresponding physical beat frequency is... for: (17) (18) in It is the stator current rotation frequency. It is the frequency of bus voltage fluctuation. This refers to the motor speed. This represents the number of pole pairs of the motor.

[0058] S13: Regarding the motor phase current Based on the amplitude of the beat frequency component, the three-phase time-domain voltage equation of the permanent magnet synchronous motor is derived as follows: (19) in, It is the resistance of the winding. It is the self-inductance of the winding. It is the mutual inductance between the windings. It's the back electromotive force. Assuming the motor is three-phase symmetrical, the self-inductance and mutual inductance can be combined into an equivalent inductance, and the motor windings are linear. Then, according to the superposition principle, the motor phase current... It can also be decomposed into corresponding components of these frequencies. Motor phase current. It can be represented as: (20) in, These are the current amplitudes of each frequency component. It is the phase angle of each frequency component. It is the angular frequency corresponding to the back electromotive force frequency. Since the back electromotive force frequency is equal to the stator current rotation frequency, therefore... In equation (20), the first term fundamental current and the fourth term back electromotive force induced current, which have the same frequency, can be superimposed with the same frequency and phase to form a single stator fundamental current term. ,in This represents the new initial phase of the stator fundamental current term after merging. Equation (20) can be rewritten as the following three terms: (twenty one) in For the fundamental current term, , For beat frequency, This is a high-frequency harmonic term. When... 、 When they are close, it can be considered that This refers to the amplitude of the beat frequency current component. Assuming the inductance and resistance of the motor are constant, the relationship between voltage and current can be mapped one-to-one for each frequency component.

[0059] S14: For angular frequency of Low-frequency AC signals, complex impedance of the stator phase circuit of a permanent magnet synchronous motor for: (twenty two) in, The resistance of the stator winding, This is the equivalent inductance of the stator winding.

[0060] Based on equations (20), (21), and (22), the magnitude of the beat frequency current amplitude component can be derived: (twenty three) From the above derivation, the beat frequency and the corresponding beat current amplitude for electrolytic capacitor-free beat frequency phenomena can be obtained. The smaller the value, the larger the amplitude of the current beat frequency component. Typically, for this type of beat frequency, feedforward compensation by changing the modulation ratio can compensate for the bus voltage fluctuation component, thereby eliminating the beat frequency. However, in single-phase bus drive systems without electrolytic capacitors, this characteristic of second harmonic bus voltage fluctuation is usually used to improve grid-side current and increase the system's grid-side power factor. In this case, the second harmonic bus voltage is no longer considered a disturbance error, but rather serves as the fundamental frequency of the bus voltage to maintain system drive and current waveform correction. This second harmonic fluctuation should not be eliminated as a disturbance.

[0061] Furthermore, the calculation process for the beat frequency reference angle in step S2 is as follows: S21: By Figure 3 It can be seen that the phase angle of the grid voltage can be extracted from the grid voltage using a SOGI (second-order generalized integrator) phase-locked loop. .

[0062] S22: Obtain the beat frequency reference angle using formula (24) .in It is the phase difference angle between the motor current beat frequency component and the grid voltage. Its value is fixed relative to the grid voltage phase and is caused by the inherent phase shift of the rectified fluctuation. Stator high-frequency impedance hysteresis angle and the inherent latency of digital systems The calculation formulas are shown in equations (25), (26), and (27), respectively.

[0063] (twenty four) (25) (26) (27) Furthermore, in step S3 The process for extracting the beat frequency current component is as follows: S31: Constructing the concept of beat frequency current The beat frequency harmonic components in the three-phase current are extracted by a second-order low-pass filter, and then... Axis coordinate transformation .

[0064] The transfer function of the second-order low-pass filter is as follows: (28) In the formula, is the continuous-domain transfer function of a second-order low-pass filter; s is the Laplace transform operator; This is the inherent angular frequency of the filter, used to determine the filter's bandwidth; The damping ratio of the filter determines the shape of the frequency response near the cutoff frequency and the overshoot of the time-domain step response. The three-phase beat current is extracted from the three-phase current using a second-order low-pass filter. .

[0065] S32: Three-phase stationary coordinate system ( ) to a two-phase rotating coordinate system ( The transformation formula for ) is: (29) Thus obtain Shaft beat frequency current .

[0066] S33: To synchronize the beat frequency injection angle with the grid voltage angle, The axis command injection formula is designed as follows: (30) In the formula , The amplitude and phase of the injected waveform are determined, and their values ​​can be obtained through an adaptive closed loop based on quadrature demodulation. Figure 4 This indicates that only to The reason for the injection of harmonics in axis commands is that, in a capacitor-free drive system, the voltage limit ellipse of the system periodically contracts due to the periodic decrease in bus voltage. If simultaneously... Harmonic injection into the shaft can easily exceed the voltage limit at the bus voltage trough, leading to controller malfunction. Therefore, this is addressed by discarding [the harmful components]. When the shaft injection strategy is used, the dynamic trajectory of the current is contracted, thereby ensuring the stability of the control system.

[0067] Furthermore, the calculation process for the perpendicular axis error signal value in step S4 is as follows: S41: Constructing a frame rate reference angle An orthogonal beat frequency reference coordinate system is used as the baseline, where The axis is a cosine axis. The axis is sinusoidal. The beat frequency current is extracted separately. Components on the X and Y axes: (31) (32) By filtering out high-frequency components from these two error components using a low-pass filter, a pure DC error signal can be obtained. Using 0 as the reference command and the two pure quadrature and direct-axis error signals as feedback, the output is controlled by a PI controller to obtain the real-time feedback X and Y values.

[0068] Furthermore, in step S5 The calculation process for shaft current command compensation is as follows: S51: The cosine axis compensation parameter X and the sine axis compensation parameter Y are synthesized according to the following formula. Shaft beat frequency compensation current command: (33) S52: As Figure 3 As shown A block diagram of the axis command injection beat frequency suppression strategy. The dual-channel PI controller dynamically optimizes X and Y, automatically generating an equivalent phase shift in steady state to compensate for residual phase deviation, thus improving the parameter robustness of the strategy.

[0069] Among them, the The shaft beat frequency compensation current command is only superimposed to Shaft current command, not to The shaft current command is injected into any beat frequency compensation component, in the example, the original The shaft current command is given using an indirect power control strategy. In a system without electrolytic capacitors, the periodic decrease in bus voltage causes the voltage limit ellipse to periodically contract, such as... Figure 4 As shown, only to Shaft-injected compensation current can make the current vector in Adjusting the axial direction allows for a greater safety margin within the voltage limit ellipse, effectively preventing breaches of voltage limit constraints.

[0070] S53: For the superimposed... The axis current command applies a limiting process based on voltage limit elliptic constraints: (34) in , They are respectively shaft and Shaft inductor, This is the DC bus voltage. The rotor's electrical angular frequency, The angular frequency of the power grid. for Upper limit of shaft current, It is a permanent magnet flux linkage.

[0071] Figure 2In the overall control block diagram of the single-phase electrolytic capacitor-free drive system, the specific details of the feedforward power compensation module are as follows: Figure 5 , Figure 6 As shown.

[0072] Analysis of Implementation Results: Based on the implementation of this invention... Based on the axial harmonic injection beat frequency strategy, superimposing a feedforward power compensation module on the system can maintain a high grid-side power factor while suppressing the system beat frequency. Figure 7 , Figure 8 , Figure 9 , Figure 10 The effects of the embodiments of the present invention on suppressing beat frequency phenomenon under different working conditions are demonstrated respectively. Figure 11 This is an experimental result of a beat frequency suppression scheme based on a beat frequency coordinate system. Figure 12 , Figure 13 The figures reflect the harmonic content of the grid-side current and the grid-side power factor under different operating conditions in the embodiments of the present invention. As can be seen from the figures above, the embodiments of the present invention can significantly reduce the fluctuation of the motor current beat frequency envelope under various operating conditions. Under the operating conditions of 1440 rpm speed and 3.5 Nm load torque, the embodiments of the present invention can reduce the 4 Hz harmonic component in the motor current from 2.5 A to 1.7 A, and the fluctuation amplitude of the motor current envelope from 6.36 A to 2.8 A, while the grid-side power factor remains stable at 96.59%.

[0073] Figure 14 This refers to the physical motor platform used in the testing of embodiments of the present invention. For example... Figure 15 , Figure 16 , Figure 17 , Figure 18 As shown, the solution mentioned in this invention, when combined with a feedforward power compensation module, can effectively reduce the beat frequency oscillation of the system motor current while maintaining a sufficiently high grid-side power factor, and the grid-side current meets the IEC 61000-3-2 standard.

[0074] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for suppressing beat frequency in a single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system, characterized in that, Includes the following steps: The phase angle of the grid voltage is obtained and summed with the feedforward correction angle to obtain the beat frequency reference angle that is in phase with the beat frequency fluctuation of the motor current. The feedforward correction angle is the phase difference angle between the beat frequency component of the motor current and the grid voltage, and its value is determined by the inherent phase shift parameter of the system. The three-phase stator current of the motor is acquired in real time, and the beat frequency harmonic component is extracted through a low-pass filter. The component in the rotating coordinate system is then extracted through coordinate transformation. Shaft beat frequency current; The The beat frequency current is projected onto the orthogonal axis of the beat frequency reference angle to extract the DC error signal, construct a closed loop of the DC error signal, and use 0 as the given value of the closed loop DC error signal. The PI controller is used for control to obtain the orthogonal control parameters of the beat frequency compensation current command. Synthesized based on the orthogonal control parameters and the beat frequency reference angle Shaft beat frequency compensation current command, and superimposed it on the original The shaft current command generates the final [current]. Shaft current command, while maintaining The beat frequency compensation component is always zero, for the final The shaft current command is subjected to voltage limit constraint and amplitude limiting processing and applied to the SVPWM control loop to achieve beat frequency suppression of the system.

2. The beat frequency suppression method for a single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system according to claim 1, characterized in that, The beat frequency reference angle is expressed as follows: in, The phase angle of the grid voltage. For feedforward correction angle, The inherent phase shift of the rectified ripple, The stator high-frequency impedance hysteresis angle. This is due to the inherent latency of digital systems.

3. The beat frequency suppression method for a single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system according to claim 1, characterized in that, The transfer function of the low-pass filter is: Where s is the Laplace transform operator; This is the inherent angular frequency of the low-pass filter, used to determine the filter's bandwidth; is the damping ratio of the filter.

4. The beat frequency suppression method for a single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system according to claim 2, characterized in that, The quadrature control parameters for the beat frequency compensation current command are obtained specifically by: Will Shaft beat frequency current Projected onto the orthogonal axis of the beat frequency reference angle to extract the DC error signal: DC error signal and A pure DC error signal is obtained by filtering out high-frequency components through a low-pass filter. Taking 0 as the reference command, the difference between the signal and the two pure DC error signals is calculated. The two difference signals are then controlled by a PI controller to output the values ​​of the quadrature control parameters X and Y of the beat frequency compensation current command.

5. The beat frequency suppression method for a single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system according to claim 4, characterized in that, Synthetic Shaft beat frequency compensation current command is .

6. The beat frequency suppression method for a single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system according to claim 1, characterized in that, For the final The shaft current command undergoes voltage limit constraint and amplitude limiting processing, specifically as follows: in , They are respectively shaft and Shaft inductor, This is the DC bus voltage. The rotor's electrical angular frequency, The angular frequency of the power grid. for Upper limit of shaft current, It is a permanent magnet flux linkage.

7. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the beat frequency suppression method for a single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system as described in any one of claims 1 to 6.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the beat frequency suppression method for a single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system as described in any one of claims 1 to 6.

9. A computer program product, comprising a computer program or instructions, characterized in that, When the computer program or instructions are executed by the processor, they implement the steps of the beat frequency suppression method for a single-phase electrolytic capacitor-free permanent magnet synchronous motor drive system as described in any one of claims 1 to 6.

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