Vehicle motor control method, device and electric vehicle

Abstract

The application relates to a vehicle motor control method and device and an electric vehicle. The motor speed and torque are acquired, and the target switching frequency is determined according to the motor speed and torque analysis. The current switching frequency of the modulation signal is acquired. When the working condition changes across the region according to the current switching frequency and the working switching frequency region where the target switching frequency is located, the modulation signal is smoothly transitioned from the current switching frequency to the target switching frequency by using a ramp function, frequency instantaneous jump is avoided, the switching frequency optimization based on the working condition is realized, efficiency loss is reduced, and the motor control reliability is improved.

Description

Technical Field

[0001] This application relates to the field of electric drive technology, and in particular to a vehicle motor control method, device, and electric vehicle. Background Technology

[0002] Currently, most electric two-wheelers use a fixed switching frequency for power supply control via hub motors. While this strategy ensures good current waveform and torque performance under high-speed, heavy-load conditions, it results in significant efficiency losses during actual driving. Reducing these efficiency losses and improving motor control reliability is a pressing issue that needs to be addressed. Summary of the Invention

[0003] Therefore, it is necessary to provide a vehicle motor control method, device, and electric vehicle that reduces efficiency loss and improves motor control reliability in order to address the above problems.

[0004] The first aspect of this application provides a vehicle motor control method, including: Obtain the motor's speed and torque; The target switching frequency is determined based on the analysis of the motor's speed and torque; Obtain the current switching frequency of the modulation signal; the modulation signal is used to control the switching on and off of the switch in the drive module to supply power to the motor; When a cross-regional change in operating conditions is determined based on the operating frequency range where the current switching frequency and the target switching frequency are located, a ramp function is used to smoothly transition the modulation signal from the current switching frequency to the target switching frequency.

[0005] In one embodiment, obtaining the motor's speed and torque includes: acquiring the motor's speed via a Hall sensor; acquiring the motor's current data via a current sampling circuit; performing Clark and Park transformations on the current data; and calculating the motor's torque based on the transformed current.

[0006] In one embodiment, determining the target switching frequency based on the motor's speed and torque analysis includes: determining the required operating switching frequency range based on the motor's speed, and determining the target switching frequency within the operating switching frequency range based on the motor's torque; wherein the motor's speed and the operating switching frequency range have a predetermined correspondence, and the motor's torque within the operating switching frequency range and the target switching frequency have a predetermined correspondence.

[0007] In one embodiment, the ramp function is an S-shaped ramp function, and the calculation formula is as follows: f cur(t) =f old +(f target -f old )×k×(1-cos(π·t / T)); Among them, f cur(t) f is the switching frequency at time t. old f is the switching frequency of the previous control cycle. target denoted as the target switching frequency, k as the gain coefficient, and T as the total transition time.

[0008] In one embodiment, the operating switching frequency region includes a low-frequency region, a mid-frequency region, and a high-frequency region, wherein the lower limit of the mid-frequency region is greater than or equal to the upper limit of the low-frequency region, and the lower limit of the high-frequency region is greater than or equal to the upper limit of the mid-frequency region; the method further includes: injecting odd harmonic current for harmonic compensation when the switching frequency of the modulation signal is in the low-frequency region.

[0009] In one embodiment, harmonic compensation is performed by injecting odd-order harmonic currents, which includes injecting Nth and N+2th harmonic currents in opposite phase in the αβ stationary coordinate system, where N is an odd number.

[0010] In one embodiment, injecting antiphase Nth and N+2 harmonic currents in the αβ stationary coordinate system includes: obtaining the amplitude and phase of the Nth and N+2 harmonic currents based on the three-phase current analysis of the motor; synthesizing antiphase harmonics in the αβ stationary coordinate system based on the amplitude and phase of the Nth and N+2 harmonic currents; superimposing the antiphase harmonics in the αβ stationary coordinate system with the original current reference value; and outputting a modulation signal based on the superimposed current reference value.

[0011] In one embodiment, the method further includes: determining torque ripple based on two consecutively detected torques, and increasing the switching frequency of the modulation signal when the torque ripple exceeds a preset threshold.

[0012] In one embodiment, the operating switching frequency range is divided according to a percentage of the motor's rated speed.

[0013] A second aspect of this application provides a vehicle motor control device, comprising: The data acquisition module is used to acquire the motor's speed and torque, as well as the current switching frequency of the modulation signal; the modulation signal is used to control the switching on and off of the switch in the drive module to supply power to the motor. A frequency analysis module is used to determine the target switching frequency based on the motor's speed and torque analysis. The frequency adjustment module is used to smoothly transition the modulation signal from the current switching frequency to the target switching frequency when the operating conditions change across the working switching frequency range based on the current switching frequency and the target switching frequency.

[0014] A third aspect of this application provides an electric vehicle, including a controller and a motor, wherein the controller is connected to the motor and controls the motor according to the method described above.

[0015] The aforementioned vehicle motor control method, device, and electric vehicle acquire the motor's speed and torque, and determine the target switching frequency based on the analysis of the motor's speed and torque. It acquires the current switching frequency of the modulation signal, and when the operating conditions change across different operating frequency zones based on the current and target switching frequencies, it uses a ramp function to smoothly transition the modulation signal from the current switching frequency to the target switching frequency, avoiding instantaneous frequency jumps. This achieves condition-based adaptive switching frequency optimization, reduces efficiency losses, and improves the reliability of motor control. Attached Figure Description

[0016] Figure 1 This is a flowchart of a vehicle motor control method in one embodiment; Figure 2 This is a schematic diagram of switching frequency partitioning in one embodiment; Figure 3 This is a schematic diagram of the vehicle motor control process in one embodiment; Figure 4 This is a schematic diagram of a smooth switching frequency curve in one embodiment; Figure 5(a) shows the low-frequency waveform in one embodiment without compensation; Figure 5(b) is a waveform diagram of the low-frequency region with compensation in one embodiment; Figure 5(c) is a comparison of the uncompensated and compensated current THD in the low-frequency and high-frequency regions in one embodiment; Figure 6 This is a structural block diagram of a vehicle motor control device in one embodiment. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0019] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0020] Current hub motor drive systems for electric two-wheelers employ Space Vector Pulse Width Modulation (SVPWM) technology. SVPWM control typically uses a fixed switching frequency (usually 12-20kHz). While this strategy ensures good current waveform and torque performance under high-speed, heavy-load conditions, it suffers from significant efficiency losses in actual driving conditions: at low speeds and light loads, switching losses account for 30%-50%, with the fixed frequency leading to redundant switching action; at medium speeds and medium loads, switching losses account for 15%-25%, indicating that frequency and efficiency are not optimally matched; and at high speeds and heavy loads, switching losses account for 10%-15%, with insufficient frequency causing harmonic degradation.

[0021] Based on this, this application provides a vehicle motor control method applicable to hub motor control in two-wheeled electric vehicles. The method acquires the motor's speed and torque, and determines the target switching frequency based on the analysis of these parameters. It acquires the current switching frequency of the modulation signal, and when a cross-regional change in operating conditions occurs, a ramp function is used to smoothly transition the modulation signal from the current switching frequency to the target switching frequency, avoiding instantaneous frequency jumps. This achieves adaptive switching frequency optimization based on operating conditions, reducing efficiency losses and improving motor control reliability.

[0022] In one embodiment, a vehicle motor control method is provided. The vehicle can be a two-wheeled electric vehicle or other electric vehicle, and the motor can be a hub motor. Figure 1 As shown, the method includes: Step S110: Obtain the motor speed and torque.

[0023] The motor's rotational speed ω can be acquired using a Hall sensor, and its current data can be acquired using a current sampling circuit. A controller connects the Hall sensor and the current sampling circuit to receive the motor's rotational speed ω and current data, performs Clark and Park transformations on the current data, and calculates the motor's torque T based on the transformed current. The motor can be a permanent magnet synchronous motor (PMSM) or other types of motor, and the controller can be a control chip such as an MCU or FPGA. In other embodiments, the current sampling circuit can be integrated into the controller.

[0024] Specifically, the current data may include the motor's three-phase currents ia, ib, and ic, as well as the input DC current ibus, to monitor the power supply status in real time. The controller performs Clark transformation on the three-phase currents ia, ib, and ic to generate the current i. α i β The controller then combines the current i α i β The Park transformation is performed on the electrical angle θ of the motor to obtain the currents id and iq in the rotating coordinate system. Finally, the controller calculates the motor torque based on the currents id and iq in the rotating coordinate system. Taking a permanent magnet synchronous motor (PMSM) as an example, the motor torque can be calculated using the torque calculation formula T = 3 / 2p·iq[id(Ld-Lq)+c], where p is the number of pole pairs of the motor, Ld and Lq are the inductances of the motor, and c is the flux linkage of the motor. The motor torque T can then be calculated in real time. In this embodiment, the three-phase currents of the motor undergo an αβ transformation, and the Clarke transformation is used to convert the three-phase system into a two-phase system. Then, the Park transformation is used to convert this two-phase system into a synchronous rotating coordinate system. Finally, combined with the torque calculation formula, the motor torque T can be calculated accurately in real time.

[0025] Step S120: Determine the target switching frequency based on the analysis of the motor's speed and torque.

[0026] This system can pre-establish and save the correspondence between motor speed, torque, and switching frequency. After determining the current motor speed and torque, the desired target switching frequency can be directly obtained by combining the saved correspondence. For example, one can first determine a preliminary working switching frequency range based on the motor speed, and then determine the specific target switching frequency within that range based on the motor torque; or one can first determine a preliminary working switching frequency range based on the motor torque, and then determine the specific target switching frequency within that range based on the motor speed.

[0027] In one embodiment, step S120 includes: determining the required operating switching frequency range based on the motor's rotational speed, and determining the target switching frequency within the operating switching frequency range based on the motor's torque. The motor's rotational speed and the operating switching frequency range have a predetermined correspondence, as do the motor's torque within the operating switching frequency range and the target switching frequency. The switching frequency can be divided into zones before motor control, establishing a correspondence between the motor's rotational speed, torque, and switching frequency. The switching frequency refers to the frequency used to control the switching on and off of the switches in the drive module. The switches in the drive module can be MOSFETs or other types of switching transistors, and the modulation signal can specifically be a PWM signal. The controller uses Space Vector Pulse Width Modulation (SVPWM) to control the output of the PWM signal to the drive module, controlling the on / off switching of the switches within the drive module. After obtaining the motor's rotational speed and torque, the controller first determines the required operating switching frequency range based on the motor's rotational speed, and then determines the specific target switching frequency within the operating switching frequency range based on the motor's torque.

[0028] It is understood that in other embodiments, a correspondence can be established between the motor torque and the operating switching frequency range, as well as a correspondence between the motor speed and the target switching frequency within the operating switching frequency range. The controller first determines the required operating switching frequency range based on the motor torque, and then determines the specific target switching frequency within the operating switching frequency range by combining the motor speed.

[0029] The number of operating switching frequency zones is not unique; for example, the operating switching frequency zones can be divided into low-frequency, mid-frequency, and high-frequency zones. Understandably, the specific number of operating switching frequency zones can be adjusted according to actual needs.

[0030] In one embodiment, the operating switching frequency zone is divided as a percentage of the motor's rated speed. Specifically, different types of motors have different parameters, including rated power, rated speed, and number of pole pairs. Simulations can be performed on different types of motors to determine the relationship between speed, torque, and switching frequency under different motor parameters. The operating switching frequency zone is divided by analyzing the relationship between motor iron losses and switching frequency, or by setting a percentage of the motor's rated speed according to the optimal operating frequency band of the switch in the drive module. For example, based on multiple set percentages of the motor's rated speed, the switching frequency can be divided into three operating switching frequency zones: low-frequency, medium-frequency, and high-frequency. The set percentages used to divide the operating switching frequency zones may be the same or different for different types of motors. In actual motor control, the operating switching frequency zone can be divided according to the current motor parameters, selecting a suitable relationship between the motor's speed, torque, and switching frequency, and adjusting the switching frequency of the modulation signal.

[0031] Specifically, the motor operating conditions are divided into low-frequency, medium-frequency, and high-frequency zones based on the rotational speed ω and torque T, and a corresponding switching frequency range is set for each zone. First, a one-dimensional segmentation is performed using rotational speed ω as the sole partitioning variable, dividing the operating conditions into low-frequency, medium-frequency, and high-frequency zones. Then, a two-dimensional division is performed within the defined intervals, and the upper and lower endpoints of the switching frequency within each interval are determined based on the torque T. For example, if the controller collects data within the rotational speed range s1 to s2, the switching frequency range of the modulated signal is f1 to f2, and the motor torque range is t1 to t2, then a linear mapping can be performed. The torque range t1 to t2 is mapped to the switching frequency range f1 to f2, and the switching frequency range f1 to f2 is mapped to the rotational speed range s1 to s2. This establishes a correspondence between rotational speed, switching frequency, and torque.

[0032] In this embodiment, a surface-mounted hub motor with a rated power of 400W is used as an example. The number of pole pairs is 30, and the rated speed w is 450rpm. The set ratios include 30%, 70%, and 100%. The switching frequency is divided into low-frequency, medium-frequency, and high-frequency zones according to 30%, 70%, and 100% of the rated speed w. Figure 2 and Figure 3 As shown, Figure 2 The horizontal axis represents speed (in rpm) / torque (in N·m), where w is the rated speed of the motor, and T is the torque. max The vertical axis represents the maximum output torque of the motor, with the switching frequency (in kHz) on the horizontal axis. The speed range of 0-0.3 W is considered the low-frequency region, corresponding to a switching frequency range of fl (e.g., 12kHz to 14kHz); the speed range of 0.3 W-0.7 W is considered the mid-frequency region, corresponding to a switching frequency range of fm (e.g., 14kHz to 16kHz); and the speed range of 0.7 W-1.0 W is considered the high-frequency region, corresponding to a switching frequency range of fh (e.g., 16kHz to 20kHz). Then, the corresponding torque ranges are mapped to the low-frequency, mid-frequency, and high-frequency regions, with the low-frequency region corresponding to a torque range of 0-0.3 T. max The torque range corresponding to the mid-frequency region is 0.3T. max -0.7T max The torque range corresponding to the high-frequency region is 0.7T. max -1.0T max It is understandable that the number of operating frequency zones, as well as the numerical range of speed, frequency, and torque within each operating frequency zone, can be adjusted according to the actual situation.

[0033] In actual motor control, the controller collects the motor speed ω and torque T in real time. Based on the motor speed ω, it determines the required operating switching frequency range (e.g., low frequency or high frequency range). Then, combined with the motor torque T, it determines the target switching frequency in the operating switching frequency range. The larger the torque T, the higher the target switching frequency in the corresponding operating switching frequency range.

[0034] Step S130: Obtain the current switching frequency of the modulation signal.

[0035] The modulation signal, specifically a PWM signal, is used to control the switching of switches in the drive module to supply power to the motor. The drive module can be a three-phase inverter. Based on a current reference value, the controller sends a PWM signal to the three-phase inverter using Space Vector Pulse Width Modulation (SVPWM). The three-phase inverter controls the switching of its internal switches according to the received PWM signal, converting the input current and outputting three-phase current to power the motor. While acquiring the current motor speed ω and torque T, the controller can also simultaneously detect the current switching frequency of the modulation signal to analyze whether there have been cross-regional changes in operating conditions.

[0036] Step S140: When the operating condition changes across zones based on the current switching frequency and the target switching frequency, a ramp function is used to smoothly transition the modulation signal from the current switching frequency to the target switching frequency.

[0037] Specifically, after determining the target switching frequency and the current switching frequency of the modulated signal, the controller compares the current switching frequency with the target switching frequency. If they match (either they are identical or the difference is within the allowable range), no frequency adjustment is needed. If they do not match, the controller compares the operating frequency range of the current switching frequency with that of the target switching frequency to analyze whether there is a cross-range change in the operating conditions. If there is no cross-range change (e.g., both the current and target switching frequencies are in the low-frequency or high-frequency range), the modulated signal can be directly adjusted to the target switching frequency. If there is a cross-range change (e.g., the current switching frequency is in the low-frequency / high-frequency range, and the target switching frequency is in the high-frequency / low-frequency range), a ramp function is used to smoothly transition the modulated signal from the current switching frequency to the target switching frequency, avoiding instantaneous frequency jumps.

[0038] There are various ways to smoothly transition the switching frequency of a modulated signal using a ramp function. For example, it can be done by gradually transitioning the modulated signal from the current switching frequency to the target switching frequency according to a set control period (usually on the order of microseconds). In one embodiment, the ramp function is an S-shaped ramp function (Sigmoid function), calculated as follows: f cur(t) =f old +(ftarget -f old )×k×(1-cos(π·t / T)); Among them, f cur(t) f is the switching frequency at time t. old f is the switching frequency of the previous control cycle. target Here, k is the target switching frequency, k is the gain coefficient with a value ranging from 0.5 to 3.0, and in this embodiment, k is set to 0.5. T is the total transition time. By adjusting the value of k, the actual total transition time T can be reduced, thereby achieving the goal of rapidly approaching the target switching frequency.

[0039] like Figure 4 As shown, the horizontal axis represents time (in milliseconds), and the vertical axis represents the switching frequency (in kHz). The solid line represents the smooth switching transition curve when the gain coefficient k = 0.5 (the smoothest), the long dashed line represents the smooth switching transition curve when the gain coefficient k = 1.5, and the dotted dashed line represents the smooth switching transition curve when the gain coefficient k = 3.0 (the steepest). The larger the gain coefficient k, the faster the transition but the closer it is to a step; the smaller the gain coefficient k, the smoother and gentler the transition. The value of the gain coefficient k can be selected according to actual needs. By controlling the switching frequency, the switching transition can be smoothed, avoiding torque shocks caused by instantaneous jumps during the switching process. For example, assuming the current switching frequency is 12kHz and the target switching frequency is 20kHz, the total transition time T is set to 60ms, and the gain coefficient k is set to 0.5. Starting from 12kHz, the switching frequency is gradually transitioned according to the control cycle. Thus, the switching frequency can be controlled to reach 20kHz after several control cycles.

[0040] The above-mentioned vehicle motor control method, when determining the operating condition changes across the operating frequency range based on the current switching frequency and the target switching frequency, uses a ramp function to smoothly transition the modulation signal from the current switching frequency to the target switching frequency, avoiding instantaneous frequency jumps, realizing condition-based adaptive switching frequency optimization, reducing efficiency loss, and improving motor control reliability.

[0041] In one embodiment, the method further includes injecting odd harmonic current for harmonic compensation when the switching frequency of the modulation signal is in the low-frequency region.

[0042] After adjusting the switching frequency, if the switching frequency of the modulation signal is in the low-frequency range (e.g., after frequency reduction processing, transitioning from the high-frequency range to the low-frequency range), the controller injects odd-order harmonic currents for harmonic compensation. During harmonic compensation, Nth and N+2th harmonic currents in opposite phase can be injected in the αβ stationary coordinate system, where N is an odd number. First, the amplitude and phase of the Nth and N+2th harmonic currents are obtained based on the three-phase current analysis of the motor. Based on the amplitude and phase of the Nth and N+2th harmonic currents, an opposite-phase harmonic in the αβ stationary coordinate system is synthesized. Then, the opposite-phase harmonic in the αβ stationary coordinate system is superimposed on the original current reference value, and the modulation signal is output based on the superimposed current reference value.

[0043] Specifically, in the low-frequency region, low-order harmonics caused by dead zones and switching nonlinearities can affect motor performance. Among the odd harmonics, the 3rd harmonic is zero-sequence and does not appear in a three-phase symmetrical system, requiring no compensation; the 5th and 7th harmonics are the most prominent, closest to the fundamental frequency, resulting in the lowest motor inductive reactance and the highest current; the 9th, 11th, and 13th harmonics are naturally attenuated, making compensation cost-effective. Therefore, in this embodiment, the harmonic compensation method involves injecting anti-phase 5th and 7th harmonic currents in the αβ stationary coordinate system, including: obtaining the amplitude and phase of the 5th and 7th harmonic currents based on the three-phase current analysis of the motor; synthesizing anti-phase harmonics in the αβ stationary coordinate system based on the amplitude and phase of the 5th and 7th harmonic currents; superimposing the anti-phase harmonics in the αβ stationary coordinate system with the original current reference value, and outputting a modulation signal based on the superimposed current reference value. The specific process of harmonic compensation is as follows: The sampled three-phase currents ia, ib, and ic are subjected to Clark transformation to obtain the current i. α i β Then, for the current i α i β Perform Park transform to obtain the currents id and iq in the rotating coordinate system. Then, use FFT (Fast Fourier Transform) on the currents id and iq to extract the currents I5 and I7 of the 5th and 7th harmonics and the phases φ5 and φ7.

[0044] The amplitudes of the 5th and 7th harmonics are calculated as follows: I5(f) = I5 max ×(f min / f sw ), I7(f)=I7 max ×(f min / f sw ).

[0045] Wherein, I5(f) and I7(f) are the amplitudes of the 5th and 7th harmonics, respectively. max I7 max It is a constant, f minIt is the minimum switching frequency of the modulated signal, f. sw This represents the current switching frequency of the modulation signal.

[0046] Phase alignment of the 5th and 7th harmonics: θ5=5·θe-φ5, θ7=7·θe-φ7.

[0047] Where θ5 and θ7 are the 5th and 7th harmonic phases after phase alignment, respectively, and θe is the current electrical angle.

[0048] Synthesis of anti-phase harmonic currents: i αc =-I5(f)·cos(θ5)-I7(f)·cos(θ7),i βc =-I5(f)·sin(θ5)-I7(f)·sin(θ7).

[0049] Among them, i αc i βc Let αβ be the antiphase harmonic current in the αβ stationary coordinate system.

[0050] The synthesized anti-phase harmonic current is superimposed on the original current reference value: i α_ref_total =i α_ref +i αc i β_ref_total =i β_ref +i βc .

[0051] Among them, i α_ref and i β_ref This is the original current reference value.

[0052] Finally, based on the superimposed current reference value i α_ref_total i β_ref_total Space vector pulse width modulation (SVPWM) is performed to output a PWM signal to the driver module.

[0053] Combining the above formulas, harmonic compensation, by injecting anti-phase 5th and 7th harmonic currents in the three-phase αβ stationary coordinate system, cancels the current distortion caused by the reduction of the switching frequency. Figures 5(a) to 5(c) are schematic diagrams of harmonic compensation in the low-frequency region, comparing the current waveforms under the two conditions of no compensation and with harmonic compensation, showing that 5th and 7th harmonic compensation significantly improve the current waveform.

[0054] In addition, in one embodiment, the method further includes: determining torque ripple based on two consecutively detected torques, and increasing the switching frequency of the modulation signal when the torque ripple exceeds a preset threshold.

[0055] Specifically, torque pulsation refers to the change in torque detected on both sides consecutively. For example... Figure 3 As shown, a sliding mode observer can be used to continuously detect the motor torque T according to a set torque detection interval (e.g., 1ms). The specific detection method of torque T is described in step S110 and will not be repeated here. The controller continuously acquires the torque detected by the sliding mode observer, calculates the absolute value |T1-T2| of the currently detected torque T1 and the previously detected torque T2, and uses |T1-T2| / T2 as the torque ripple ΔT. If the torque ripple ΔT > a preset threshold (e.g., 3%), it is determined that the torque fluctuation is too large, and the switching frequency of the modulation signal needs to be dynamically adjusted. In this case, the switching frequency of the modulation signal can also be smoothly adjusted using a ramp function. It can be understood that if the torque ripple ΔT ≤ the preset threshold, there is no need to dynamically adjust the switching frequency of the modulation signal. The process can return to the step of determining the torque ripple based on two consecutive torque detections, and the sliding mode observer can continue to detect the torque. The torque ripple is analyzed based on the detected torque to determine whether it exceeds the preset threshold.

[0056] Taking a switching frequency in the range of 14kHz-16kHz as an example, the torque T2 detected by the sliding mode observer in the previous test was 20 N·m, and the switching frequency was 13kHz. The torque T1 currently detected is 25 N·m. Therefore, the torque ripple is (25-20) / 20 = 25% > 3%. Since the torque ripple exceeds the preset threshold, the corresponding switching frequency is adjusted to 15kHz to increase the local switching frequency and reduce torque fluctuations. By automatically adjusting the frequency when the torque fluctuation is too large, a closed-loop protection mechanism of "frequency reduction → monitoring → compensation / adjustment" is formed. It can be understood that when the torque ripple exceeds the preset threshold, the adjustment range of the switching frequency can be set according to the actual situation. For example, it can be set to a fixed value, or the larger the difference between the torque ripple and the preset threshold, the larger the adjustment range.

[0057] Continue to refer to Figure 3 The vehicle motor control method provided in this application, when determining that the operating condition has changed across zones, uses a ramp function to smoothly transition the modulation signal from the current switching frequency to the target switching frequency. After downsampling to the low-frequency region, harmonic compensation is performed by injecting inverse Nth and N+2th harmonic currents, and the local switching frequency is automatically increased when the torque ripple exceeds a preset threshold. Through a progressive process of operating condition perception → frequency partitioning → smooth switching → harmonic compensation → torque closed loop, ultimately reaching the complete control flow of SVPWM modulation and three-phase inverter driving PMSM, the optimal balance between switching losses and torque performance is achieved. This method has the following advantages: 1. Under the premise of ensuring the steady-state torque performance under all operating conditions (torque ripple <3%, current THD meets national standards), the switching loss of PMSM drive is reduced by 25%-40% and the overall vehicle low-speed driving efficiency is improved by 2%-5% through operating condition adaptive switching frequency optimization and harmonic collaborative compensation.

[0058] 2. By dynamically adjusting the PWM switching frequency, the losses of the switching transistors in the drive module are reduced, and the lifespan of the controller is extended.

[0059] 3. Adaptive switching frequency adjustment can reduce the heat generation of components, greatly reduce the risk of controller over-temperature protection, and increase the controller's load-bearing time.

[0060] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0061] Based on the same inventive concept, this application also provides a vehicle motor control device for implementing the vehicle motor control method described above. The solution provided by this device is similar to the solution described in the above method; therefore, the specific limitations in one or more vehicle motor control device embodiments provided below can be found in the limitations of the vehicle motor control method described above, and will not be repeated here.

[0062] In one embodiment, such as Figure 6 As shown, a vehicle motor control device is provided, including: a data acquisition module 110, a frequency analysis module 120, and a frequency adjustment module 130, wherein: The data acquisition module 110 is used to acquire the motor speed and torque, as well as the current switching frequency of the modulation signal; the modulation signal is used to control the switching on and off of the switch in the drive module to supply power to the motor.

[0063] The frequency analysis module 120 is used to determine the target switching frequency based on the analysis of the motor's speed and torque.

[0064] The frequency adjustment module 130 is used to smoothly transition the modulation signal from the current switching frequency to the target switching frequency when the operating conditions change across zones, based on the operating switching frequency zones where the current switching frequency and the target switching frequency are located.

[0065] In one embodiment, the data acquisition module 110 is used to acquire the motor speed through a Hall sensor; acquire the motor current data through a current sampling circuit; perform Clark and Park transformations on the current data; and calculate the motor torque based on the transformed current.

[0066] In one embodiment, the frequency analysis module 120 is further configured to determine the required operating switching frequency range based on the rotational speed, and to determine the target switching frequency in the operating switching frequency range based on the torque; wherein the rotational speed of the motor and the operating switching frequency range have a predetermined correspondence, and the torque of the motor in the operating switching frequency range and the target switching frequency have a predetermined correspondence.

[0067] In one embodiment, the frequency adjustment module 130 is further configured to inject odd harmonic current for harmonic compensation when the switching frequency of the modulation signal is in the low-frequency region.

[0068] In one embodiment, the frequency adjustment module 130 is further configured to determine torque ripple based on the torque detected in two consecutive tests, and increase the switching frequency of the modulation signal when the torque ripple exceeds a preset threshold.

[0069] In one embodiment, an electric vehicle is also provided, including a controller and a motor. The controller is connected to the motor and controls the motor according to the method described above. The controller can be a control chip such as an MCU or FPGA, and the motor can be a permanent magnet synchronous motor.

[0070] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0071] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A vehicle motor control method, characterized in that, include: Obtain the motor's speed and torque; The target switching frequency is determined based on the analysis of the motor's speed and torque; Obtain the current switching frequency of the modulation signal; The modulation signal is used to control the switching on and off of the switch in the drive module to supply power to the motor; When a cross-regional change in operating conditions is determined based on the current switching frequency and the target switching frequency, a ramp function is used to smoothly transition the modulation signal from the current switching frequency to the target switching frequency. The operating switching frequency region includes a low-frequency region, a mid-frequency region, and a high-frequency region. The lower limit of the mid-frequency region is greater than or equal to the upper limit of the low-frequency region, and the lower limit of the high-frequency region is greater than or equal to the upper limit of the mid-frequency region.

2. The method according to claim 1, characterized in that, To obtain the motor's speed and torque, including: The motor speed is collected using a Hall sensor; The motor's current data is collected through a current sampling circuit; The current data is subjected to Clark and Park transformations, and the motor torque is calculated based on the transformed current.

3. The method according to claim 1, characterized in that, The target switching frequency is determined based on the analysis of the motor's speed and torque, including: determining the required operating switching frequency range based on the motor's speed, and determining the target switching frequency within the operating switching frequency range based on the motor's torque; wherein the motor's speed and the operating switching frequency range have a predetermined correspondence, and the motor's torque within the operating switching frequency range and the target switching frequency have a predetermined correspondence.

4. The method according to claim 1, characterized in that, The slope function is an S-shaped slope function, and the calculation formula is: f cur(t) =f old +(f target -f old )×k×(1-cos(π·t / T)); Among them, f cur(t) f is the switching frequency at time t. old f is the switching frequency of the previous control cycle. target denoted as the target switching frequency, k as the gain coefficient, and T as the total transition time.

5. The method according to claim 1, characterized in that, The method also includes: When the switching frequency of the modulation signal is in the low-frequency region, odd harmonic current is injected for harmonic compensation.

6. The method according to claim 5, characterized in that, Harmonic compensation is achieved by injecting odd-order harmonic currents, including injecting Nth and N+2th harmonic currents in opposite phase in the αβ stationary coordinate system, where N is an odd number.

7. The method according to claim 6, characterized in that, Injecting Nth and N+2 harmonic currents in opposite phase in the αβ stationary coordinate system includes: The amplitude and phase of the Nth and N+2th harmonic currents are obtained from the three-phase current analysis of the motor. Based on the amplitude and phase of the Nth and N+2th harmonic currents, antiphase harmonics in the αβ stationary coordinate system are synthesized. The anti-phase harmonic in the αβ stationary coordinate system is superimposed with the original current reference value, and the modulation signal is output based on the superimposed current reference value.

8. The method according to any one of claims 1 to 7, characterized in that, Also includes: The torque ripple is determined based on the torque detected in two consecutive tests, and the switching frequency of the modulation signal is increased when the torque ripple exceeds a preset threshold.

9. The method according to any one of claims 1 to 7, characterized in that, The operating frequency range is determined by dividing the motor into percentages based on its rated speed.

10. A vehicle motor control device, characterized in that, include: The data acquisition module is used to acquire the motor's speed and torque, as well as the current switching frequency of the modulation signal; The modulation signal is used to control the on / off state of the switch in the drive module to supply power to the motor; A frequency analysis module is used to determine the target switching frequency based on the motor's speed and torque analysis. The frequency adjustment module is used to smoothly transition the modulation signal from the current switching frequency to the target switching frequency when the operating condition changes across zones, based on the current switching frequency and the target switching frequency. The operating switching frequency zone includes a low-frequency zone, a mid-frequency zone, and a high-frequency zone. The lower limit of the mid-frequency zone is greater than or equal to the upper limit of the low-frequency zone, and the lower limit of the high-frequency zone is greater than or equal to the upper limit of the mid-frequency zone.

11. An electric vehicle, characterized in that, The device includes a controller and a motor, the controller being connected to the motor, and the motor is controlled according to any one of claims 1 to 9.

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