Fan motor current and torque collaborative optimization control method

Abstract

The application provides a fan motor current and torque collaborative optimization control method, comprising the following steps: identifying a torque compression inflection point appearing after a direct-axis current deepening according to an internal resistance sharp rise characteristic, determining a re-distribution direction of the direct-axis and quadrature-axis currents in a weak magnetic speed expansion area in combination with a motor speed; deepening the direct-axis current according to the re-distribution direction, monitoring a terminal voltage drop degree caused by an increase in copper loss, and obtaining a maximum available torque drop degree under the weak magnetic current distribution; analyzing whether the maximum available torque drop degree exceeds a torque permission range, if yes, dynamically adjusting the direct-axis and quadrature-axis current distribution according to the terminal voltage drop degree, and obtaining an optimized weak magnetic current distribution direction; and combining the motor speed and the optimized weak magnetic current distribution direction, identifying a current and torque collaborative working point required for high-grade wind speed output by using a support vector machine algorithm, and obtaining a current distribution scheme for stable output of the high-grade wind speed.

Description

Technical Field

[0001] This invention relates to the field of information technology, and in particular to a method for coordinated optimization control of fan motor current and torque. Background Technology

[0002] In the field of modern fan motor control, researching how to optimize the coordinated control of current and torque is crucial, as it directly affects the operating efficiency and lifespan of the equipment. This is especially true in portable or battery-powered scenarios, where efficient control methods can significantly improve user experience and extend battery life. Research in this area not only reflects technological progress but is also key to meeting energy conservation and environmental protection needs. However, some existing control methods often struggle to account for the combined effects of multiple dynamic factors when facing complex operating conditions. Particularly in battery-powered environments, relying solely on traditional control strategies makes it difficult to adapt to drastic fluctuations in power supply status, causing the system to fail to maintain expected performance output at certain critical moments. This limitation makes the equipment prone to performance instability in actual use. For example, a sharp increase in battery internal resistance directly leads to a rapid drop in terminal voltage, which in turn forces the motor control system to adjust its current distribution strategy, thus affecting torque output capability. This causal chain means that when the system attempts to expand its speed range, the voltage drop may instead limit torque output, ultimately resulting in an ineffective widening or even reduction of the speed range. Specifically, when a fan operates at high speeds, a sharp increase in internal resistance causes a rapid drop in terminal voltage as the battery charge approaches its critical point. To maintain the fan speed, the system must increase a specific current component, which in turn exacerbates the voltage drop, creating a vicious cycle. For example, in a portable fan usage scenario, a user wants to continuously enjoy strong airflow in hot weather, but due to insufficient battery power, the fan speed gradually decreases, even failing to maintain high-speed output, significantly diminishing the user experience. Therefore, how to balance the contradiction between current distribution and torque output under conditions of low battery power and unstable terminal voltage, ensuring stable fan operation at high speeds, is a key problem that this research urgently needs to solve. Summary of the Invention

[0003] This invention provides a method for coordinated optimization control of fan motor current and torque, the method comprising: The battery terminal voltage is collected in real time by the bus voltage acquisition unit, and the direct-axis current, quadrature-axis current and motor speed are obtained by the phase current detection unit. The characteristics of the sharp rise in internal resistance of the battery at the end of the charge are evaluated based on the changes in battery terminal voltage and quadrature and direct-axis currents. Based on the steep increase in internal resistance, the torque compression inflection point that appears after the direct-axis current deepens is identified, and the redistribution direction of the direct-axis quadrature-axis current in the field weakening expansion region is determined in combination with the motor speed. The direct-axis current is further processed according to the redistribution direction, and the degree of voltage drop caused by the increase in copper loss is monitored to obtain the maximum available torque reduction under the weak magnetic current distribution. Analyze whether the maximum available torque drop exceeds the torque permissible range. If it does, dynamically adjust the direct-axis and quadrature-axis current distribution according to the degree of terminal voltage drop to obtain the optimized field weakening current distribution direction. Combining the motor speed with the optimized field weakening current distribution direction, the support vector machine algorithm is used to identify the current-torque coordinated operating point required for high-speed wind output, and a current distribution scheme for stable high-speed wind output is obtained. By updating the current distribution of the fan motor through a current distribution scheme that ensures stable output at high fan speeds, adjusting the control signal of the fan drive unit, and determining the speed maintenance range under field weakening control, stable output at high fan speeds can be achieved.

[0004] Preferably, the step of acquiring the battery terminal voltage in real time through the bus voltage acquisition unit, obtaining the direct-axis current, quadrature-axis current, and motor speed through the phase current detection unit, and evaluating the steep increase characteristic of the internal resistance of the charged battery based on the changes in battery terminal voltage and quadrature-axis and direct-axis currents includes: The terminal voltage between the positive and negative terminals of the battery is continuously measured according to a preset sampling period to obtain the terminal voltage time sequence. The phase current in the three-phase stationary coordinate system is decomposed into the direct-axis current and the quadrature-axis current in the rotating coordinate system by Park transformation. The terminal voltage time series, the direct-axis current, the quadrature-axis current, and the motor speed are aligned with a unified timestamp to construct a multi-channel synchronous sampling dataset, which is then converted into a recursive estimation sequence of the battery's equivalent internal resistance using a sliding window. By comparing the slope of the recursive estimation sequence with the slope baseline of the battery during the stable discharge phase at full charge, the inflection point and the magnitude of the increase in the equivalent internal resistance trajectory are calibrated to obtain the characteristic curve of the steep increase in battery internal resistance at the end of the charge phase.

[0005] Preferably, the step of identifying the torque compression inflection point that appears after the direct-axis current deepens based on the steep increase in internal resistance, and determining the redistribution direction of the direct-axis quadrature-axis current in the field weakening and speed-enhancing region in combination with the motor speed, includes: By obtaining the characteristic curve of the steep increase in internal resistance of the battery at the end of the charge, the direct-axis current is gradually increased in depth along the direction of weak magnetic field at a preset step size. Based on the product of the increase in direct-axis current and the equivalent internal resistance value given by the characteristic curve of the steep increase in internal resistance, the second drop of the voltage at the lower end of each direct-axis current value is determined. For each direct-axis current and its corresponding quadrature-axis current, a family of torque curves with direct-axis current as the horizontal axis and electromagnetic torque as the vertical axis is constructed based on the mathematical model of permanent magnet synchronous motor. The first derivative of electromagnetic torque along the direction of increasing direct-axis current is used to obtain a derivative sequence. The direct-axis current value corresponding to the zero-crossing position in the derivative sequence that changes from positive to negative is marked as the torque compression inflection point. The motor speed is divided into several speed ranges in the field weakening and speed expansion zone. The maximum demagnetization depth of the corresponding range is obtained by working backward from the secondary drop and the inverter bus voltage utilization rate. A subset of inflection points that do not exceed the maximum demagnetization depth is selected from the torque compression inflection points. The direction in which the direct-axis current moves toward the inflection point value in the subset of inflection points and the quadrature-axis current moves toward the remaining margin under the same current amplitude constraint is marked as the redistribution direction of the direct-axis and quadrature-axis currents in the field weakening and speed expansion zone.

[0006] Preferably, the step of deepening the direct-axis current processing according to the redistribution direction, monitoring the degree of voltage drop caused by increased copper losses, and obtaining the maximum usable torque reduction under the weak magnetic current distribution includes: The current value of the direct-axis current is gradually increased according to the polarity indicated by the direct-axis current component in the redistribution direction by a preset step size, and the quadrature-axis current is simultaneously supplemented according to the amplitude indicated by the quadrature-axis current component in the redistribution direction to obtain a gradually changing weak magnetic current distribution sequence. Based on the mathematical model of the permanent magnet synchronous motor, the copper loss increment in each step of the field weakening current distribution sequence compared to the previous step is calculated. The terminal voltage drop monitoring value is synchronously collected by the bus voltage acquisition unit, and the copper loss increment is correlated with the terminal voltage drop monitoring value according to the step. Based on the terminal voltage drop monitoring value, the upper limit of the available quadrature shaft current for each gear is deduced, and then substituted into the mathematical model of the permanent magnet synchronous motor to obtain the recalculated available torque value for that gear. The maximum value of the torque drop for each gear is taken as the maximum available torque drop.

[0007] Preferably, the step of analyzing whether the maximum available torque drop exceeds the permissible torque range, and if so, dynamically adjusting the direct-axis and quadrature-axis current distribution based on the voltage drop at the terminals to obtain an optimized field-weakening current distribution direction, includes: The maximum available torque reduction is compared with the upper limit of torque reduction in the preset torque allowable range, which is pre-established based on the difference between the rated torque corresponding to the high fan speed setting and the minimum torque required for startup. If the torque reduction exceeds the upper limit, the current direction of the field weakening current distribution is marked as out of bounds. Obtain the terminal voltage drop monitoring value corresponding to the over-limit current distribution direction, divide the terminal voltage drop monitoring value into several drop intervals according to the preset tolerance level, and extract the direct axis current back-off step size and quadrature axis current compensation step size corresponding to the drop interval from the tolerance level adjustment rule. The direct-axis and quadrature-axis current values ​​are backed up and compensated according to the back-up step size and compensation step size, and iteratively evaluated until the torque reduction value after backing up falls within the torque permissible range. The corresponding direction vector is then calibrated as the optimized magnetic weakening current distribution direction.

[0008] Preferably, the step of combining the motor speed and the optimized field-weakening current distribution direction, and using a support vector machine algorithm to identify the current-torque coordinated operating point required for high-speed wind speed output, to obtain a current distribution scheme for stable high-speed wind speed output, includes: The motor speed, the direct-axis current component and quadrature-axis current component in the optimized field weakening current distribution direction, and the electromagnetic torque value and copper loss increment value obtained from the historical operation record are combined into a multi-dimensional feature vector. For the operating condition segment that operates continuously and stably at a high wind speed and whose measured speed remains within the nominal speed error band of the gear, a positive sample label is applied to the corresponding multidimensional feature vector. For the operating condition segment where the measured speed drops out of the error band or the torque drops beyond the torque permissible range, a negative sample label is applied to obtain the operating condition sample training set. The radial basis function is used to map the multidimensional feature vectors to a high-dimensional space on the training set of the working condition samples, and the classification hyperplane equation that maximizes the margin between positive and negative samples is solved. Extract the motor speed, direct-axis current, and quadrature-axis current values ​​corresponding to the support vectors whose absolute values ​​of the Lagrange multipliers are greater than a preset threshold, and use them as a candidate set of current-torque coordinated operating points. The high-speed wind speed range from the starting speed to the rated maximum speed is divided into several speed nodes. For each speed node, the neighborhood support vector is selected from the candidate set. The first and second current values ​​corresponding to the geometric distance to the classification hyperplane equation are sorted and concatenated to obtain the current distribution scheme for the stable output of the high-speed wind speed.

[0009] Preferably, the method of updating the fan motor current distribution through a high-speed stable output current distribution scheme, adjusting the control signal of the fan drive unit, determining the speed maintenance range under field weakening control, and achieving stable output of high-speed fan includes: Write the target value of the direct-axis and quadrature-axis current indexed by the motor speed in the current distribution scheme of the high-speed stable output into the current loop setpoint register, and update the current direct-axis current setpoint and quadrature-axis current setpoint. The pulse width modulation signal of the fan drive unit is generated by the current loop according to the updated value, and the adjusted drive control signal is obtained. The fan motor is driven by the adjusted drive control signal. The measured motor speed is collected and compared with the speed nodes in the current distribution scheme one by one. The range of nodes whose measured speed continuously falls within the nominal speed error band of the preset gear is calibrated as the speed maintenance range under the field weakening control. Within the speed maintenance range, the current loop setpoint is updated according to the current distribution scheme.

[0010] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects: This invention discloses a method for coordinated optimization control of current and torque in a fan motor, addressing the problem of voltage drop and torque compression during field weakening control caused by a sharp increase in internal resistance at the battery charging end, making it difficult to maintain stable high-speed output. This invention acquires real-time data on battery terminal voltage, AC and DC axis currents, and motor speed to assess the characteristics of the sharp increase in internal resistance and identify the torque compression inflection point. Based on this, it monitors the voltage drop and the decrease in maximum usable torque caused by increased copper losses. When the torque drop exceeds the permissible range, the AC and DC axis current distribution is dynamically adjusted, and a support vector machine algorithm is used to identify the current-torque coordinated operating point required for high-speed output. Finally, by updating the current distribution scheme and adjusting the control signal, the speed maintenance range under field weakening control is determined, effectively overcoming the torque limitation caused by the voltage drop and achieving stable high-speed output. Attached Figure Description

[0011] Figure 1 This is a flowchart of the fan motor current and torque coordinated optimization control method of the present invention.

[0012] Figure 2 This is a schematic diagram of the fan motor current and torque coordinated optimization control method of the present invention.

[0013] Figure 3 This is another schematic diagram of the fan motor current and torque coordinated optimization control method of the present invention. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0015] like Figures 1-3 The fan motor current and torque co-optimization control method in this embodiment may specifically include: Step S101: The battery terminal voltage is collected in real time by the bus voltage acquisition unit, and the direct-axis current, quadrature-axis current and motor speed are obtained by the phase current detection unit. The characteristics of the sharp rise in internal resistance of the charged battery are evaluated based on the changes in battery terminal voltage and quadrature and direct-axis currents.

[0016] The terminal voltage between the positive and negative terminals of the battery is continuously measured by the bus voltage acquisition unit at a preset sampling period to obtain the terminal voltage time sequence. Simultaneously, the phase current in the three-phase stator windings of the motor is detected by the phase current detection unit. The current in the three-phase stationary coordinate system is decomposed into direct-axis current and quadrature-axis current in the rotating coordinate system using Park transform. The motor speed is obtained by measuring the speed of the motor shaft end encoder. The terminal voltage time sequence, the direct-axis current, the quadrature-axis current, and the motor speed are aligned with a unified timestamp to construct a multi-channel synchronous sampling dataset. A sliding window is used to extract the terminal voltage and direct-axis / quadrature-axis current subsequences within adjacent time periods from the multi-channel synchronous sampling dataset. For each window, the ratio of the terminal voltage drop relative to the direct-axis current increment and the ratio relative to the quadrature-axis current increment are calculated to obtain the instantaneous response curve of the terminal voltage as a function of current. The instantaneous response curve is converted into the battery's equivalent internal resistance value according to the Ohm relationship, and the conversion result is segmented and classified according to the motor speed to obtain a recursive estimate sequence of the equivalent internal resistance under the sliding window in different speed ranges. The slope of the equivalent internal resistance change is extracted in the time dimension of the recursive estimation sequence. The slope is compared with the slope baseline obtained from the stable discharge stage of the battery at full charge. If the slope is continuously higher than the slope baseline and exceeds a set threshold, the battery is determined to have entered the end-of-charge interval. In the end-of-charge interval, the inflection point and the rise amplitude of the equivalent internal resistance increase trajectory are calibrated by combining the synchronicity of the terminal voltage drop and the fluctuations of the direct-axis current and the quadrature-axis current, so as to obtain the characteristic curve of the steep rise of the battery internal resistance at the end of the charge.

[0017] This implementation method is applied to the field weakening control scenario of portable or battery-powered fan motors. In response to the phenomenon of sharp increase in internal resistance exhibited by lithium-ion battery packs at the end of the charging stage, the coupling relationship between terminal voltage and direct-axis quadrature-axis current is identified online, thereby providing a data basis for subsequent adjustment of current distribution direction.

[0018] In one embodiment, the bus voltage acquisition unit uses a differential voltage sampling circuit connected to the positive and negative terminals of the battery pack. The terminal voltage is continuously measured via an isolated operational amplifier and an analog-to-digital converter, with a sampling period of 100 microseconds to 1 millisecond to obtain the terminal voltage timing sequence. The phase current detection unit consists of Hall current sensors and precision sampling resistors arranged on the U-phase and V-phase windings of the motor. It detects the phase current of two phases in real time, and the third phase current is obtained by inverting the sum of the first two phase currents according to Kirchhoff's current law.

[0019] Specifically, the Parker transformation is a standard coordinate transformation method used in motor control to convert physical quantities in a three-phase stationary coordinate system into physical quantities in a rotating coordinate system. The Parker transformation consists of two stages: the first stage is the Clarke transformation, which converts the three-phase currents (U-phase, V-phase, W-phase) into the α-axis current iα and β-axis current iβ in a stationary two-phase coordinate system; the second stage is a rotational transformation with the rotor magnetic pole position angle θ as the rotational reference, converting iα and iβ into the direct-axis current id and quadrature-axis current iq in the rotating coordinate system, where θ is obtained from the position signal synchronously output by the motor shaft-end encoder during speed measurement. The direct-axis current id is used to characterize the current component along the rotor magnetic pole direction and plays a role in field weakening and demagnetizing; the quadrature-axis current iq is used to characterize the current component along the direction perpendicular to the magnetic pole and plays a role in generating electromagnetic torque.

[0020] It should be noted that the terminal voltage time sequence, the direct-axis current, the quadrature-axis current, and the motor speed come from different acquisition channels, resulting in sampling phase differences. Therefore, when aligning with a unified timestamp, a linear interpolation method is used to map the voltage sampling points to the current sampling times, constructing a multi-channel synchronous sampling dataset with complete values ​​from all four channels at each time point. Based on this multi-channel synchronous sampling dataset, an adjustable-length sliding window is used to truncate the terminal voltage subsequence and the direct-axis and quadrature-axis current subsequence within adjacent time periods.

[0021] In one possible implementation, the sliding window length is between 5 and 20 milliseconds, the window step size is half the window length, and adjacent windows overlap to smooth the estimation results.

[0022] Specifically, for each window, the difference between the maximum and minimum terminal voltage values ​​within that window is first taken as the terminal voltage drop ΔU, the difference between the first and last values ​​of the direct-axis current is taken as the direct-axis current increment Δid, and the difference between the first and last values ​​of the quadrature-axis current is taken as the quadrature-axis current increment Δiq. Then, the ratios ΔU / Δid and ΔU / Δiq are calculated respectively. These two ratios, arranged over time, form the instantaneous response curve of the terminal voltage versus current change. Then, based on the Ohmic relation U=IR, the instantaneous response curve is converted, and ΔU / Δid and ΔU / Δiq are weighted and combined to obtain the equivalent internal resistance R of the battery within that window. The weighting is allocated according to the absolute value ratio of the direct-axis current increment and the quadrature-axis current increment, with the sum of the weights set to 1 to avoid drastic fluctuations in the conversion result when the current increment of a certain axis approaches 0. Furthermore, the aforementioned conversion results are segmented and categorized according to the motor speed. For example, the speed is divided into several intervals, with 500 RPM as one level. The equivalent internal resistance value R of each window is assigned to its corresponding speed interval, and then arranged in chronological order within the interval to obtain a recursive estimate sequence of the equivalent internal resistance under the sliding window for different speed intervals. This approach is used because the distribution of copper and iron losses in the fan motor differs between low and high speeds; segmentation avoids estimation errors caused by sudden changes in speed. Based on the recursive estimate sequence, the equivalent internal resistance values ​​of adjacent windows are compared using a difference quotient calculation to obtain the slope k of the equivalent internal resistance change. The slope baseline is obtained by statistically averaging the slopes of the equivalent internal resistance change during the battery's discharge phase from full charge to 70% of rated capacity, and then adding three times the standard deviation, reflecting the upper limit of slope fluctuation under normal discharge conditions.

[0023] Understandably, if the slope of change is consistently higher than the slope baseline and exceeds a set threshold (e.g., the threshold is 1.5 times the slope baseline) and lasts for more than 5 consecutive windows, the battery is determined to have entered the end-of-charge range. Within this end-of-charge range, the synchronicity between the terminal voltage drop and the stator current amplitude fluctuation is calculated. The stator current amplitude Is is synthesized from the direct-axis current Id and the quadrature-axis current Iq, meaning Is equal to the square root of the sum of the squares of Id and Iq. Continuous sampling values ​​of Is constitute the stator current amplitude fluctuation curve. The synchronicity is determined by the Pearson correlation coefficient between the terminal voltage drop curve and the stator current amplitude fluctuation curve. When the correlation coefficient is higher than 0.85, the inflection point of the corresponding equivalent internal resistance recursive estimation sequence is marked as the starting point of the steep increase in internal resistance, and the difference between the peak value of the equivalent internal resistance after the starting point and the value at the starting point is marked as the increase amplitude. The starting point of the steep increase in internal resistance and the increase amplitude together constitute the end-of-charge battery internal resistance steep increase characteristic curve. This characteristic curve was subsequently used as the input basis for adjusting the direction of the weak magnetic current distribution, providing a quantitative reference for the stable high-speed output of the fan motor at the critical point of battery charge.

[0024] Step S102: Identify the torque compression inflection point that appears after the direct-axis current deepens based on the steep increase in internal resistance, and determine the redistribution direction of the direct-axis and quadrature-axis currents in the field weakening and speed expansion region by combining the motor speed.

[0025] By acquiring the characteristic curve of the steep increase in internal resistance of the charged battery, the direct-axis current is gradually increased in depth along the direction of magnetic weakening at preset steps. Based on the product of the increase in direct-axis current and the equivalent internal resistance value given by the steep increase in internal resistance curve, the second drop in voltage at the lower end of each direct-axis current value relative to the original drop is determined. For each direct-axis current and the corresponding quadrature-axis current, the stator copper loss increment and electromagnetic torque value are calculated according to the mathematical model of permanent magnet synchronous motor, and a family of torque curves is constructed with direct-axis current as the horizontal axis, electromagnetic torque as the vertical axis, and quadrature-axis current as the parameter. For each curve in the family of torque curves, the first derivative of the electromagnetic torque is calculated along the direction of increasing direct-axis current to obtain a derivative sequence of the electromagnetic torque as a function of the direct-axis current. The zero-crossing position where the derivative value changes from positive to negative is retrieved from the derivative sequence, and the corresponding direct-axis current value is designated as the torque compression inflection point. The direct-axis current value corresponding to the torque compression inflection point is associated with and archived with the second-order voltage drop value to obtain a torque compression inflection point dataset. The motor speed is obtained and divided into several speed ranges in the field weakening expansion zone. For each speed range, the maximum demagnetization depth is calculated by working backwards from the second drop in terminal voltage and the inverter bus voltage utilization rate. Then, a subset of inflection points whose direct-axis current values ​​do not exceed the maximum demagnetization depth is selected from the torque compression inflection point dataset. The current phasors formed by the direct-axis current and quadrature-axis current corresponding to each inflection point in the subset are sorted. The direction in which the direct-axis current moves from its current value toward the inflection point value in the subset, and the direction in which the quadrature-axis current moves toward the remaining margin under the same current amplitude constraint, is marked as the redistribution direction of the direct-axis and quadrature-axis currents in the field weakening expansion zone.

[0026] This implementation method connects with the previously obtained characteristic curve of the steep increase in internal resistance of the charged battery at the end of the charge. In response to the torque attenuation problem caused by the drop in terminal voltage in the weak magnetic expansion region of the fan motor, the redistribution direction of the direct axis and quadrature axis current is determined, thereby providing a directional basis for the current-torque coordination at subsequent high fan speed settings.

[0027] Specifically, the direct-axis current is incremented stepwise along the magnetic weakening direction with a preset step size. One implementation of the preset step size is 5% of the rated phase current amplitude, meaning that each increment of the direct-axis current value increases by 5% of the rated phase current amplitude compared to the previous increment, representing a demagnetizing component. The increment of the direct-axis current for each increment is then multiplied by the equivalent internal resistance value given by the steep increase curve of the internal resistance to obtain the second voltage drop at that increment. This second voltage drop is then superimposed on the original voltage drop at the battery under this charged state to obtain the total voltage drop. Finally, the current open-circuit voltage of the battery is subtracted from the total voltage drop to calculate the actual usable voltage at the inverter's DC bus for that increment of the direct-axis current value.

[0028] It should be noted that the mathematical model of the permanent magnet synchronous motor is a standard model used in the field of field weakening control to describe the mapping relationship between stator voltage, current, and electromagnetic torque, and includes two parts: the stator voltage equation and the electromagnetic torque equation. Under the stator voltage equation, the direct-axis voltage ud equals the product of the stator resistance Rs and the direct-axis current id minus the product of the quadrature-axis inductance Lq, the quadrature-axis current iq, and the rotor electric angular velocity ω; the quadrature-axis voltage uq equals the product of Rs and iq plus the product of the direct-axis inductance Ld, id, and ω, plus the product of the rotor permanent magnet flux linkage ψf and ω. Under the electromagnetic torque equation, the electromagnetic torque Te equals 1.5 × pn × (ψf × iq + (Ld - Lq) × id × iq). The stator copper loss increment P is then taken as 1.5 times the product of the squares of Rs, id, and iq, i.e., P = 1.5Rs(id 2 +iq 2 ), where P is the stator copper loss increment, Rs is the stator resistance, id is the direct-axis current, and iq is the quadrature-axis current. Based on the electromagnetic torque equation, for each direct-axis current value, the corresponding electromagnetic torque value and stator copper loss increment value are recorded one by one within the feasible region where the quadrature-axis current value is constrained by both the current amplitude and the actual usable voltage.

[0029] In one embodiment, the direct-axis current value is used as the horizontal axis, the electromagnetic torque value as the vertical axis, and the quadrature-axis current value as a family parameter. The aforementioned recorded data are connected to construct a family of torque curves. Each curve in the family of torque curves corresponds to a quadrature-axis current level. Further, a first-order difference operation is performed on the electromagnetic torque value on each curve in the family of torque curves along the direction of increasing direct-axis current to obtain a derivative sequence of the electromagnetic torque as a function of the direct-axis current.

[0030] Understandably, in the initial stage of the increasing direct-axis current, the weakening effect of field weakening and demagnetizing reduces the air gap flux linkage, allowing the quadrature-axis current to increase, resulting in an upward trend in the electromagnetic torque and a positive derivative sequence. When the direct-axis current increases to a certain level, the quadrature-axis current compression caused by the second-order drop in terminal voltage begins to dominate, the electromagnetic torque decreases, and the derivative sequence changes from positive to negative. The zero-crossing points where the derivative values ​​change from positive to negative are retrieved from the derivative sequence. The direct-axis current values ​​corresponding to these zero-crossing points are marked as torque compression inflection points. The direct-axis current values ​​corresponding to these inflection points are then linked with the second-order drop in terminal voltage values ​​and archived to obtain a torque compression inflection point dataset. The motor speed is obtained and evenly divided into several speed ranges from the initial speed of the field weakening speed-enhancing zone to the rated maximum speed.

[0031] Preferably, the speed settings are in 500 RPM intervals.

[0032] Specifically, for each speed setting, the maximum demagnetization depth is calculated in reverse as follows: First, the upper limit of the output phase voltage amplitude for that speed setting is obtained by multiplying the DC bus voltage and the inverter modulation coefficient. Then, the second voltage drop at the terminals is subtracted to obtain the actual usable phase voltage amplitude U for that speed setting. Under the constraint that the quadrature-axis current iq is 0, the direct-axis current id is obtained by inverse solving the stator voltage equation U=ω(Ld×id+ψf), where ω is the angular velocity, Ld is the direct-axis inductance, and ψf is the permanent magnet flux linkage. The absolute value of id is the maximum demagnetization depth for that speed setting. Then, inflection points whose absolute values ​​of the direct-axis current do not exceed the maximum demagnetization depth are selected from the torque compression inflection point dataset to form a subset of inflection points for that speed setting. For each inflection point in the subset of inflection points, the direct-axis current and quadrature-axis current constitute current phasors. The current phasors are sorted from largest to smallest according to the electromagnetic torque value, and the first current phasor in the sorted set is taken as the target phasor. In one implementation, the direction in which the direct-axis current moves towards the direct-axis current value in the target phasor, and the direction in which the quadrature-axis current compensates for the remaining margin under the same current amplitude constraint circle with unchanged current vector magnitude, is defined as the redistribution direction of the direct-axis and quadrature-axis currents in the field weakening propagation region. This redistribution direction is output as a two-dimensional direction vector, where the horizontal and vertical components of the direction vector represent the positive and negative values ​​and magnitudes of the adjustment of the direct-axis and quadrature-axis currents, respectively, serving as the directional basis for subsequent field weakening current allocation processing.

[0033] Step S103: The direct-axis current is deepened according to the redistribution direction, and the degree of voltage drop caused by the increase in copper loss is monitored to obtain the maximum available torque reduction under the weak magnetic current distribution.

[0034] The direction of the direct-axis and quadrature-axis current redistribution in the field weakening and speed-enhancing region output from the previous stage is obtained. The current value of the direct-axis current is progressively increased step-by-step along the polarity indicated by the direct-axis current component in the redistribution direction, using a preset step size. For each increased direct-axis current value, the quadrature-axis current is simultaneously supplemented according to the amplitude indicated by the quadrature-axis current component in the redistribution direction. The increased direct-axis current value and the corresponding quadrature-axis current value are paired and stored to obtain a progressively changing field weakening current distribution sequence. For each increased direct-axis current value and the corresponding quadrature-axis current value in the field weakening current distribution sequence, the copper loss increment at that level compared to before the increase is calculated based on the permanent magnet synchronous motor mathematical model. The measured battery terminal voltage at that level is simultaneously acquired through the bus voltage acquisition unit. The difference between the terminal voltage value and the voltage value at the beginning of the increase is taken as the terminal voltage drop monitoring value. The copper loss increment and the terminal voltage drop monitoring value are correlated by level to obtain the copper loss-terminal voltage drop monitoring sequence. For each level of the copper loss-terminal voltage drop monitoring sequence, the available upper limit of the quadrature axis current under that level is calculated based on the mathematical model of the permanent magnet synchronous motor. The original quadrature axis current value is replaced by the available upper limit and then substituted back into the mathematical model of the permanent magnet synchronous motor to obtain the recalculated available torque value under that level. The absolute value of the difference between the available torque value and the maximum torque value before deepening is taken as the torque reduction value. The maximum value is taken from the torque reduction values ​​of each level to obtain the maximum available torque reduction under the field weakening current distribution.

[0035] This embodiment builds upon the previously obtained redistribution direction of the direct-axis and quadrature-axis currents in the field-weakening acceleration region. It quantifies and evaluates the deepening behavior of the field-weakening current in the fan motor at the end of its charging phase and its impact on available torque, thus providing a basis for determining the degree of reduction in current distribution optimization. In one embodiment, the redistribution direction is given in the form of a two-dimensional direction vector, containing two elements: the polarity of the direct-axis component and the magnitude of the quadrature-axis component. The polarity of the direct-axis component indicates that the direct-axis current should deepen along the field-weakening demagnetizing direction, and the magnitude of the quadrature-axis component indicates the magnitude of the quadrature-axis current that should be compensated under the same current magnitude constraint circle.

[0036] Specifically, the current value of the direct-axis current is progressively increased according to a preset step size.

[0037] Preferably, the preset step size is between 3% and 8% of the rated phase current amplitude, for example, 5%. For each increment, the quadrature-axis current is synchronously supplemented according to the amplitude of the quadrature-axis component in the redistribution direction, ensuring that the square root of the sum of the square of the increased direct-axis current value and the square of the quadrature-axis current value remains within the rated phase current amplitude of the motor. The increased direct-axis current value and the corresponding quadrature-axis current value for each increment are paired and stored to form the field-weakening current distribution sequence.

[0038] It should be noted that the calculation of the copper loss increment is based on the stator winding copper loss expression in the mathematical model of the permanent magnet synchronous motor. The stator winding copper loss expression is Pcu equal to the sum of 1.5 multiplied by Rs multiplied by the square of id and the square of iq, where Pcu is the stator winding copper loss, Rs is the stator resistance, id is the direct-axis current, and iq is the quadrature-axis current. The stator resistance Rs is calculated in real-time by the motor controller based on a pre-calibrated reference resistance value at 20 degrees Celsius and the motor stator temperature collected in real-time by a temperature sensor, combined with the temperature coefficient of the copper conductor. For example, if the reference resistance is 0.05 ohms and the temperature coefficient is 0.00393, when the real-time temperature is 80 degrees Celsius, Rs is calculated to be 0.06179 ohms. For each level in the weak magnetic current distribution sequence, first, the id and iq values ​​for that level are substituted into the expression to obtain the stator copper loss value for that level. Then, the initial values ​​of id and iq before the current level is increased are substituted into the expression to obtain the initial stator copper loss value before the current level is increased. The difference between the current level and the initial stator copper loss value is taken as the copper loss increment for that level. The copper loss increment reflects the additional heat generation cost incurred to achieve the current distribution for that level. Furthermore, the battery terminal voltage is synchronously acquired by the bus voltage acquisition unit when the current level increases.

[0039] Specifically, the average of the terminal voltages at several sampling points that have stabilized after the enhancement process is taken as the measured terminal voltage value for that range. The difference between the measured terminal voltage value and the initial terminal voltage value obtained in the same way before the enhancement process is taken as the terminal voltage drop monitoring value. The copper loss increment and the terminal voltage drop monitoring value for each range are associated and archived according to the range number to form the copper loss-terminal voltage drop monitoring sequence. The monitoring sequence is arranged in binary form for each range, reflecting the synchronous correspondence between the increase in copper loss and the drop in terminal voltage.

[0040] Understandably, the existence of the terminal voltage drop monitoring value reduces the actual phase voltage amplitude that the inverter can apply to the motor.

[0041] In one embodiment, for each level in the copper loss and terminal voltage drop monitoring sequence, the terminal voltage drop monitoring value for that level is first subtracted from the available phase voltage amplitude before the increase, to obtain the actual available phase voltage amplitude U for that level. The specific formula is as follows: , Where U represents the actual usable phase voltage amplitude under this range, U base This indicates the phase voltage amplitude that can be used before deepening. This indicates the voltage drop monitoring value for this range.

[0042] Based on the stator voltage equation in the mathematical model of the permanent magnet synchronous motor, the actual usable phase voltage amplitude U is used as the upper limit constraint of the combined amplitude of the direct-axis voltage and the quadrature-axis voltage. According to the stator voltage equation: , Where R is the stator resistance, i d For direct-axis current, i q Let L be the quadrature-axis current, ω be the electric angular velocity, and L be the cross-axis current. d For a direct-axis inductor, L q Let f be the quadrature-axis inductance, f be the permanent magnet flux linkage, and U be the actual usable phase voltage amplitude. This equation is used to solve for the upper limit of the quadrature-axis current under voltage constraints.

[0043] Then, replace the original quadrature-axis current value with the available upper limit and input it into the electromagnetic torque expression in the mathematical model of the permanent magnet synchronous motor to obtain the recalculated available torque value for this gear. Take the absolute value of the difference between the available torque value and the maximum torque value obtained under the maximum torque condition before deepening, and use it as the torque reduction value for this gear.

[0044] In one embodiment, the torque drop values ​​for each level are scanned, and the maximum value is taken as the maximum available torque drop under the field weakening current allocation. The maximum available torque drop reflects the most unfavorable torque loss allowed by advancing in the redistribution direction, serving as a quantitative input for whether subsequent current allocation needs to be rolled back or replanned.

[0045] Step S104: Analyze whether the maximum available torque drop exceeds the torque allowable range. If it does, dynamically adjust the direct-axis quadrature-axis current distribution according to the voltage drop at the terminals to obtain the optimized magnetic weakening current distribution direction.

[0046] The maximum available torque reduction under the field weakening current distribution is obtained, and the maximum available torque reduction is compared with the upper limit of torque reduction given in the preset torque allowable range. The torque allowable range is pre-established based on the difference between the rated torque corresponding to the high-speed fan and the minimum torque required for startup. If the maximum available torque reduction is higher than the upper limit of torque reduction, the current field weakening current distribution direction is marked as out of bounds, and the current distribution result with out-of-bounds marking is obtained. For the out-of-bounds current allocation direction in the current allocation result with out-of-bounds marker, obtain the terminal voltage drop monitoring value under the corresponding range of the out-of-bounds current allocation direction, and divide the terminal voltage drop monitoring value into several drop ranges according to the preset tolerance range; extract the direct-axis current backoff step size and quadrature-axis current compensation step size corresponding to the drop range from the preset tolerance range adjustment rules, and store the tolerance range adjustment rules in a table in advance with the drop range as the key and the backoff step size and compensation step size as the value; backoff and compensate the current direct-axis current and quadrature-axis current values ​​according to the backoff step size and compensation step size to obtain the backoffed direct-axis and quadrature-axis current values. Substitute the reverted direct-axis quadrature-axis current value into the aforementioned permanent magnet synchronous motor mathematical model, and re-evaluate the available torque under the reverted direct-axis quadrature-axis current value. The difference between the reverted available torque and the maximum torque before deepening is taken as the reverted torque reduction value. If the reverted torque reduction value still exceeds the upper limit of the torque reduction, iterative reversion is performed according to the tolerance level adjustment rule until the reverted torque reduction value falls within the torque permissible range. The direction vector corresponding to the direct-axis quadrature-axis current value that finally satisfies the torque permissible range is calibrated as the optimized field weakening current distribution direction.

[0047] This embodiment builds upon the previously obtained data on the maximum usable torque reduction under the weak magnetic current distribution. In response to the possibility that this reduction might exceed the range that the fan can withstand at its high speed setting due to a drop in terminal voltage, the direct-axis and quadrature-axis current distribution directions are dynamically reversed and compensated. This provides a directional correction basis for maintaining the high speed of the fan motor at the end of the charging phase.

[0048] Specifically, the torque permissible range is pre-established based on the difference between the rated torque value corresponding to the high-speed fan setting and the minimum torque value required for fan startup.

[0049] Preferably, the minimum electromagnetic torque required to maintain stable impeller rotation at the fan's high speed setting is denoted as T0, and the rated torque on the motor nameplate is denoted as Tn. The upper limit of torque reduction is then taken as the difference between Tn and T0. A larger upper limit indicates a greater allowable torque loss; conversely, a smaller upper limit requires more stringent correction for out-of-bounds situations. The maximum usable torque reduction is compared with the upper limit. If the maximum usable torque reduction is higher than the upper limit, the direction of the weak magnetic current distribution is tagged with an out-of-bounds label and added to the out-of-bounds current distribution result set for subsequent rollback processing.

[0050] It should be noted that the voltage drop monitoring value is derived from the ratio of the difference between the battery terminal voltage before and after the previous stage to the battery's fully charged terminal voltage.

[0051] In one embodiment, the terminal voltage drop monitoring value is divided into 3 to 5 drop ranges according to a preset tolerance level. For example, the terminal voltage drop monitoring value in the range of 0% to 3% is classified as a slight drop range, the terminal voltage drop monitoring value in the range of 3% to 6% is classified as a moderate drop range, and the terminal voltage drop monitoring value in the range of more than 6% is classified as a severe drop range. The granularity of the drop range division is matched according to the rated bus voltage level of the fan motor and the state of charge curve of the battery. The tolerance level adjustment rule is pre-stored in the non-volatile storage area of ​​the motor controller in the form of a lookup table. The lookup table uses the drop range as the index key and the direct axis current backoff step size Δid and the quadrature axis current compensation step size Δiq as the corresponding value fields.

[0052] In one embodiment, for a slight voltage drop range, Δid is taken as 2% of the rated phase current amplitude and Δiq is taken as 1% of the rated phase current amplitude; for a moderate voltage drop range, Δid is taken as 5% of the rated phase current amplitude and Δiq is taken as 3% of the rated phase current amplitude; for a severe voltage drop range, Δid is taken as 8% of the rated phase current amplitude and Δiq is taken as 5% of the rated phase current amplitude. The direction of Δid is opposite to the original direction of the direct-axis current increase, that is, it moderately withdraws the increased demagnetizing component; the direction of Δiq is along the direction of increasing electromagnetic torque.

[0053] Specifically, the current direct-axis current value is reduced and backed down according to Δid given in the lookup table, and the current quadrature-axis current value is compensated for according to Δiq given in the lookup table. The direct-axis current value after backing down and compensation is denoted as id′, and the quadrature-axis current value is denoted as iq′, constituting the backed-down direct-axis and quadrature-axis current values. Substituting id′ and iq′ into the electromagnetic torque expression in the aforementioned permanent magnet synchronous motor mathematical model, the usable torque value Te′ after backing down is obtained. The torque value recorded by the system when it is in the maximum torque condition before the field weakening is deepened is extracted, and this value is defined as the maximum torque value Tm. The absolute value of the difference between Te′ and Tm is taken as the torque reduction value ΔT′ after backing down.

[0054] Understandably, if ΔT′ still exceeds the upper limit of torque reduction, then id′ and iq′ are used as the new current values ​​for the direct-axis quadrature-axis current, and the tolerance gear adjustment rule is queried again to continue the rollback and compensation until ΔT′ falls within the torque permissible range. In one embodiment, the upper limit of the number of iterations is 5. If convergence is not achieved after exceeding the upper limit, the system rolls back to the weak magnetic current distribution direction of the previous stable gear. The stable gear is defined as the tolerance gear that most recently met the torque permissible range and had a torque fluctuation rate of less than 0.02 before the current iteration. The system stores the corresponding gear state in a cache each time it successfully converges. When the iteration fails to converge, the system directly calls the weak magnetic current distribution direction corresponding to the most recently recorded stable gear in the cache. The two-dimensional direction vector corresponding to id′ and iq′ that finally meet the torque permissible range is calibrated as the optimized weak magnetic current distribution direction and used as the direction input for subsequent high-speed wind current torque co-operating point search.

[0055] Step S105: Combining the motor speed and the optimized field weakening current distribution direction, the support vector machine algorithm is used to identify the current-torque coordinated operating point required for high-speed wind speed output, and a current distribution scheme for stable high-speed wind speed output is obtained.

[0056] By acquiring the motor speed and the optimized field weakening current distribution direction, the motor speed, the direct-axis current component and quadrature-axis current component in the optimized field weakening current distribution direction, and the electromagnetic torque value and copper loss increment value obtained synchronously from historical operation records are combined into a multi-dimensional feature vector. For the operating condition segments in the historical operation records where the fan motor runs continuously and stably at a high wind speed and the measured speed remains within the preset error band of the nominal speed of the gear, the multi-dimensional feature vector corresponding to the operating condition segment is labeled with a positive sample. For the operating condition segments where the measured speed drops out of the error band or the torque drops beyond the torque permissible range, a negative sample label is applied to obtain the operating condition sample training set. The support vector machine (SVM) algorithm is used for classification training on the training set of the operating condition samples. The SVM algorithm uses a radial basis function (RBF) kernel to map the multidimensional feature vectors to a high-dimensional space and solves the classification hyperplane equation that maximizes the margin between positive and negative samples. The classification hyperplane equation describes the boundary between stable and unstable output operating conditions. For the classification hyperplane equation, support vectors and their corresponding Lagrange multipliers are extracted. The motor speed, direct-axis current, and quadrature-axis current values ​​corresponding to the support vectors whose absolute values ​​of the Lagrange multipliers are greater than a preset threshold are combined and labeled as a candidate set of current-torque coordinated operating points. For the candidate set of current-torque coordinated operating points, the area from the starting speed of the high-speed setting to the rated maximum speed is divided into several speed nodes by sampling at equal intervals. For each speed node, support vectors are selected from the candidate set whose absolute value of the difference between the motor speed value and the speed node is less than a preset neighborhood width. The selected support vectors are sorted in descending order of their geometric distance to the classification hyperplane equation. The direct-axis current value and quadrature-axis current value corresponding to the first support vector in the sorting are taken as the operating point current value under that speed node. The operating point current values ​​of all speed nodes are concatenated according to the speed node number to obtain the current distribution scheme for stable output at high-speed settings.

[0057] This embodiment builds upon the optimized field weakening current distribution direction obtained previously. To address the need for the fan motor to maintain coordinated current and torque output at a high fan speed during the final stage of charging, it identifies the stable operating point between the motor speed and the field weakening current distribution direction, thereby obtaining a current distribution scheme that can directly drive the inverter.

[0058] Specifically, the multidimensional feature vector consists of five components: motor speed component, direct-axis current component, quadrature-axis current component, electromagnetic torque component, and copper loss increment component. The motor speed component is derived from the actual measurement by the motor shaft encoder; the direct-axis and quadrature-axis current components are derived from the two-dimensional direction vector values ​​in the optimized field-weakening current distribution direction; the electromagnetic torque component is derived from the measured torque value synchronously provided by the torque sensor or flux linkage estimator during high-speed operation; and the copper loss increment component is the difference between the measured copper loss obtained by inversely calculating the product of stator winding temperature rise and stator resistance, and the reference copper loss value under the initial field-weakening state. The reference copper loss value is calculated by multiplying the sum of the squares of the direct-axis current and quadrature-axis current under the initial field-weakening state by the stator resistance. For example, when the stator resistance is 0.5 ohms and the initial total effective current is 10 amperes, the reference copper loss is 50 watts.

[0059] It should be noted that the determination of positive and negative sample labels for the operating condition segments is based on two rules. In one embodiment, rule one is: if the measured motor speed consistently falls within the preset gear nominal speed error band throughout the duration of the operating condition segment, and this error band is formed by a fluctuation range of 5% to 10% above and below the gear nominal speed (for example, a fluctuation range of 5% above and below), then the multidimensional feature vector corresponding to the operating condition segment is labeled with a positive sample label. Rule two is: if the measured motor speed falls outside the preset gear nominal speed error band, or if the drop in measured torque relative to rated torque exceeds the allowable torque range, then a negative sample label is assigned. The operating condition sample training set is stored by pairing the multidimensional feature vector with its corresponding sample label.

[0060] Preferably, the ratio of positive samples to negative samples in the training set of the working condition samples is controlled between 1:1 and 1:2 to avoid class imbalance during the classification training stage. The support vector machine algorithm is a classic supervised classification learning method, and its core idea is to solve for a classification hyperface that can separate positive samples and negative samples with the maximum margin.

[0061] In one possible implementation, the training process of the support vector machine algorithm includes four steps: First, the input multidimensional feature vector is standardized and then input into the radial basis kernel function for nonlinear transformation. Next, the transformed features are substituted into the dual programming problem and optimized using the sequence minimum optimization algorithm to obtain the Lagrange multipliers corresponding to each sample. Then, samples with the absolute value of the Lagrange multipliers greater than 0.000001 are identified as support vectors. Finally, the support vectors and their corresponding Lagrange multipliers are weighted and synthesized to form the classification hyperplane equation as the model output.

[0062] Specifically, the radial basis function (RBF) represents the similarity between any two multidimensional feature vectors x and y as an exponential function with base e and exponent 2 (negative x minus y) squared L2 divided by twice the kernel width σ squared, where the kernel width σ is between 0.5 and 1 times the mean feature distance in the work condition sample training set. The mean feature distance is calculated by summing the Euclidean distance between any two sample feature vectors in the work condition sample training set and dividing by the total number of sample pairs. The RBF projects the linearly inseparable positive and negative samples in the five-dimensional feature space to a higher-dimensional implicit space, allowing the two classes of samples to be separated by a hyperface in this space. The set of Lagrange multipliers obtained by solving the dual programming problem corresponds to one sample in the work condition sample training set for each multiplier.

[0063] In one embodiment, samples with an absolute value of the Lagrange multiplier greater than 10 to the power of -6 are identified as support vectors, while the remaining samples are identified as non-support vectors. The support vectors represent key samples near the classification hypersurface equation, and also represent the critical current-torque combination between stable and unstable output conditions.

[0064] Understandably, the motor speed, direct-axis current, and quadrature-axis current values ​​in each support vector are extracted and combined into a triplet. All triplets corresponding to the support vectors converge to form the candidate set of the current-torque coordinated operating point. Each triplet in this candidate set is located near a critical surface on the stable output condition side, possessing stable reachability. Furthermore, the speed range from the starting speed of the high-speed fan to the rated maximum speed is divided into several speed nodes by sampling at equal intervals.

[0065] For example, the speed range of 1800 rpm to 3000 rpm is divided into 13 speed nodes at 100 rpm intervals. The preset neighborhood width is preferably 50 rpm, meaning that support vectors in the candidate set whose speed values ​​fall within 50 rpm above or below the speed node are selected for inclusion in the corresponding node. For each speed node, the subset of support vectors selected is sorted in descending order of their geometric distance to the classification hyperplane equation. Let the geometric distance be D. Where F is the weighted decision value of the kernel function. a i Let y be the Lagrange multiplier of the i-th support vector. i Let K be the class label of the i-th support vector, K be the radial basis function value of the i-th support vector and the current calculated vector, and b be the bias term.

[0066] W is the L2 norm of the normal vector in the classification hypersurface equation, which addresses the problem of the implicit existence of normal vectors under high-dimensional mappings. , Where n represents the total number of samples, a i and a j Let y represent the coefficient parameters of the i-th and j-th samples. i and y j K represents the label values ​​of the i-th and j-th samples. ij The kernel function value or similarity metric between the i-th and j-th samples is represented by the summation symbol, which indicates the summation of all combinations of i and j. The square root of the summation result is then taken to obtain W. A larger geometric distance indicates that the support vector penetrates deeper into the positive sample region, and the corresponding current-torque combination has a higher stability margin under terminal voltage fluctuations. The direct-axis current value and quadrature-axis current value corresponding to the first-ranked support vector are used as the operating point current value at that speed node. Finally, the operating point current values ​​of all speed nodes are concatenated according to the speed node number to form a current allocation lookup table indexed by motor speed and containing the target values ​​of the direct-axis current and quadrature-axis current. This current allocation lookup table represents the current allocation scheme for stable high-speed fan output. It can be retrieved in real-time during fan controller operation and used as the set value directly output to the inverter current loop, thereby supporting continuous high-speed fan motor output at the end of the charging phase.

[0067] Step S106: Update the fan motor current distribution through the current distribution scheme for stable high-speed output, adjust the control signal of the fan drive unit, determine the speed maintenance range under weak field control, and achieve stable high-speed output.

[0068] The current distribution scheme for stable high-speed output is obtained. The target values ​​of the direct-axis and quadrature-axis currents indexed by the motor speed in the current distribution scheme are written into the current loop setpoint register, and the current direct-axis current setpoint and quadrature-axis current setpoint are updated. The pulse width modulation signal of the fan drive unit is generated by the current loop according to the updated value to obtain the adjusted drive control signal. The fan motor is driven by the adjusted drive control signal, and the measured motor speed is collected and compared with the speed nodes in the current distribution scheme one by one. The node range in which the measured speed continuously falls within the nominal speed error band of the preset gear is calibrated as the speed maintenance range under weak field control. Within the speed maintenance range, the current loop setpoint is updated according to the current distribution scheme to achieve stable high-speed output.

[0069] This embodiment builds upon the previously obtained current distribution scheme for stable high-speed output, and elaborates on the implementation process of the current distribution scheme on the fan motor controller side, thereby achieving continuous and stable high-speed output of the fan motor at the end of the charging phase.

[0070] Specifically, the current distribution scheme is stored in the motor controller's operating memory area in the form of a lookup table. In one embodiment, the controller reads the lookup table at a preset refresh cycle between 10 milliseconds and 50 milliseconds, indexes the lookup table according to the current measured motor speed, obtains the direct-axis current target value and the quadrature-axis current target value at the corresponding speed node, and writes the direct-axis current target value and the quadrature-axis current target value into the current loop setpoint register to update the current direct-axis current setpoint and quadrature-axis current setpoint. The current loop tracks the setpoint value in the setpoint register using a proportional-integral adjustment method, outputs the corresponding direct-axis voltage command and quadrature-axis voltage command, and then generates pulse width modulation signals for driving the six switching transistors of the inverter through space vector modulation, forming the adjusted drive control signal.

[0071] It should be noted that the preset gear nominal speed error range is formed by taking the nominal speed value of the fan at the high speed setting and making a fluctuation range of 5% to 10% above and below it.

[0072] For example, for a high-speed fan setting with a nominal speed of 2400 rpm, the error band is the speed range between 2160 rpm and 2640 rpm.

[0073] In one embodiment, the controller continuously records the measured motor speed values ​​according to the preset refresh cycle. For each speed node in the current distribution scheme, the controller retains the speed nodes where the measured motor speed falls within the error band for more than 20 consecutive refresh cycles. The speed band covered by the consecutive speed nodes is the speed maintenance range under the field weakening control. Further, the controller acquires the motor bus voltage in real time through a voltage sampling circuit and calculates the terminal voltage drop monitoring value by dividing the difference between the rated bus voltage and the real-time bus voltage by the rated bus voltage. Within the speed maintenance range, the controller continuously updates the current loop setpoint according to the direct-axis quadrature-axis current target value under the corresponding speed node in the current distribution scheme, ensuring that the output electromagnetic torque of the fan motor remains within the permissible torque range despite fluctuations in the terminal voltage drop monitoring value. Once the speed maintenance range under the field weakening control is determined, the fan drive unit operates in a closed loop within this range according to the scheme, thereby achieving stable high-speed output.

[0074] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A fan motor current and torque co-optimization control method, characterized in that, The method includes: The battery terminal voltage is collected in real time by the bus voltage acquisition unit, and the direct-axis current, quadrature-axis current and motor speed are obtained by the phase current detection unit. The characteristics of the sharp rise in internal resistance of the battery at the end of the charge are evaluated based on the changes in battery terminal voltage and quadrature and direct-axis currents. Based on the steep increase in internal resistance, the torque compression inflection point that appears after the direct-axis current deepens is identified, and the redistribution direction of the direct-axis quadrature-axis current in the field weakening expansion region is determined in combination with the motor speed. The direct-axis current is further processed according to the redistribution direction, and the degree of voltage drop caused by the increase in copper loss is monitored to obtain the maximum available torque reduction under the weak magnetic current distribution. Analyze whether the maximum available torque drop exceeds the torque permissible range. If it does, dynamically adjust the direct-axis and quadrature-axis current distribution according to the degree of terminal voltage drop to obtain the optimized field weakening current distribution direction. Combining the motor speed with the optimized field weakening current distribution direction, the support vector machine algorithm is used to identify the current-torque coordinated operating point required for high-speed wind output, and a current distribution scheme for stable high-speed wind output is obtained. By updating the current distribution of the fan motor through a current distribution scheme that ensures stable output at high fan speeds, adjusting the control signal of the fan drive unit, and determining the speed maintenance range under field weakening control, stable output at high fan speeds can be achieved.

2. The method of claim 1, wherein, The method involves real-time acquisition of battery terminal voltage via a bus voltage acquisition unit, combined with the acquisition of direct-axis current, quadrature-axis current, and motor speed via a phase current detection unit. The method then evaluates the steep increase in internal resistance at the charged end of the battery based on changes in battery terminal voltage and quadrature-axis and direct-axis currents, including: The terminal voltage between the positive and negative terminals of the battery is continuously measured according to a preset sampling period to obtain the terminal voltage time sequence. The phase current in the three-phase stationary coordinate system is decomposed into the direct-axis current and the quadrature-axis current in the rotating coordinate system by Park transformation. The terminal voltage time series, the direct-axis current, the quadrature-axis current, and the motor speed are aligned with a unified timestamp to construct a multi-channel synchronous sampling dataset, which is then converted into a recursive estimation sequence of the battery's equivalent internal resistance using a sliding window. By comparing the slope of the recursive estimation sequence with the slope baseline of the battery during the stable discharge phase at full charge, the inflection point and the magnitude of the increase in the equivalent internal resistance trajectory are calibrated to obtain the characteristic curve of the steep increase in battery internal resistance at the end of the charge phase.

3. The method of claim 1, wherein, The step of identifying the torque compression inflection point after the direct-axis current deepens based on the steep increase in internal resistance, and determining the redistribution direction of the direct-axis quadrature-axis current in the field weakening and speed-enhancing region in conjunction with the motor speed, includes: By obtaining the characteristic curve of the steep increase in internal resistance of the battery at the end of the charge, the direct-axis current is gradually increased in depth along the direction of weak magnetic field at a preset step size. Based on the product of the increase in direct-axis current and the equivalent internal resistance value given by the characteristic curve of the steep increase in internal resistance, the second drop of the voltage at the lower end of each direct-axis current value is determined. For each direct-axis current and its corresponding quadrature-axis current, a family of torque curves with direct-axis current as the horizontal axis and electromagnetic torque as the vertical axis is constructed based on the mathematical model of permanent magnet synchronous motor. The first derivative of electromagnetic torque along the direction of increasing direct-axis current is used to obtain a derivative sequence. The direct-axis current value corresponding to the zero-crossing position in the derivative sequence that changes from positive to negative is marked as the torque compression inflection point. The motor speed is divided into several speed ranges in the field weakening and speed expansion zone. The maximum demagnetization depth of the corresponding range is obtained by working backward from the secondary drop and the inverter bus voltage utilization rate. A subset of inflection points that do not exceed the maximum demagnetization depth is selected from the torque compression inflection points. The direction in which the direct-axis current moves toward the inflection point value in the subset of inflection points and the quadrature-axis current moves toward the remaining margin under the same current amplitude constraint is marked as the redistribution direction of the direct-axis and quadrature-axis currents in the field weakening and speed expansion zone.

4. The method of claim 1, wherein, The process of deepening the direct-axis current according to the redistribution direction, monitoring the degree of voltage drop caused by increased copper losses, and obtaining the maximum usable torque reduction under weak magnetic current distribution includes: The current value of the direct-axis current is gradually increased according to the polarity indicated by the direct-axis current component in the redistribution direction by a preset step size, and the quadrature-axis current is simultaneously supplemented according to the amplitude indicated by the quadrature-axis current component in the redistribution direction to obtain a gradually changing weak magnetic current distribution sequence. Based on the mathematical model of the permanent magnet synchronous motor, the copper loss increment in each step of the field weakening current distribution sequence compared to the previous step is calculated. The terminal voltage drop monitoring value is synchronously collected by the bus voltage acquisition unit, and the copper loss increment is correlated with the terminal voltage drop monitoring value according to the step. Based on the terminal voltage drop monitoring value, the upper limit of the available quadrature shaft current for each gear is deduced, and then substituted into the mathematical model of the permanent magnet synchronous motor to obtain the recalculated available torque value for that gear. The maximum value of the torque drop for each gear is taken as the maximum available torque drop.

5. The method of claim 1, wherein, The analysis determines whether the maximum usable torque drop exceeds the permissible torque range. If it does, the direct-axis and quadrature-axis current distribution is dynamically adjusted based on the voltage drop at the terminals to obtain an optimized field-weakening current distribution direction, including: The maximum available torque reduction is compared with the upper limit of torque reduction in the preset torque allowable range, which is pre-established based on the difference between the rated torque corresponding to the high fan speed setting and the minimum torque required for startup. If the torque reduction exceeds the upper limit, the current direction of the field weakening current distribution is marked as out of bounds. Obtain the terminal voltage drop monitoring value corresponding to the over-limit current distribution direction, divide the terminal voltage drop monitoring value into several drop intervals according to the preset tolerance level, and extract the direct axis current back-off step size and quadrature axis current compensation step size corresponding to the drop interval from the tolerance level adjustment rule. The direct-axis and quadrature-axis current values ​​are backed up and compensated according to the back-up step size and compensation step size, and iteratively evaluated until the torque reduction value after backing up falls within the torque permissible range. The corresponding direction vector is then calibrated as the optimized magnetic weakening current distribution direction.

6. The method of claim 1, wherein, The method combines the motor speed with the optimized field-weakening current distribution direction, and uses a support vector machine algorithm to identify the current-torque coordinated operating point required for high-speed wind output, thereby obtaining a current distribution scheme for stable high-speed wind output, including: The motor speed, the direct-axis current component and quadrature-axis current component in the optimized field weakening current distribution direction, and the electromagnetic torque value and copper loss increment value obtained from the historical operation record are combined into a multi-dimensional feature vector. For the operating condition segment that operates continuously and stably at a high wind speed and whose measured speed remains within the nominal speed error band of the gear, a positive sample label is applied to the corresponding multidimensional feature vector. For the operating condition segment where the measured speed drops out of the error band or the torque drops beyond the torque permissible range, a negative sample label is applied to obtain the operating condition sample training set. The radial basis function is used to map the multidimensional feature vectors to a high-dimensional space on the training set of the working condition samples, and the classification hyperplane equation that maximizes the margin between positive and negative samples is solved. Extract the motor speed, direct-axis current, and quadrature-axis current values ​​corresponding to the support vectors whose absolute values ​​of the Lagrange multipliers are greater than a preset threshold, and use them as a candidate set of current-torque coordinated operating points. The high-speed wind speed range from the starting speed to the rated maximum speed is divided into several speed nodes. For each speed node, the neighborhood support vector is selected from the candidate set. The first and second current values ​​corresponding to the geometric distance to the classification hyperplane equation are sorted and concatenated to obtain the current distribution scheme for the stable output of the high-speed wind speed.

7. The fan motor current and torque coordinated optimization control method according to claim 1, characterized in that, The method of updating the fan motor current distribution through a high-speed stable output current distribution scheme, adjusting the control signal of the fan drive unit, and determining the speed maintenance range under field weakening control to achieve stable output of high-speed fan includes: Write the target value of the direct-axis and quadrature-axis current indexed by the motor speed in the current distribution scheme of the high-speed stable output into the current loop setpoint register, and update the current direct-axis current setpoint and quadrature-axis current setpoint. The pulse width modulation signal of the fan drive unit is generated by the current loop according to the updated value, and the adjusted drive control signal is obtained. The fan motor is driven by the adjusted drive control signal. The measured motor speed is collected and compared with the speed nodes in the current distribution scheme one by one. The range of nodes whose measured speed continuously falls within the nominal speed error band of the preset gear is calibrated as the speed maintenance range under the field weakening control. Within the speed maintenance range, the current loop setpoint is updated according to the current distribution scheme.

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