Permanent magnet synchronous motor efficiency improvement method, storage medium and vehicle

Abstract

The application provides a permanent magnet synchronous motor efficiency improving method, a storage medium and a vehicle, and the method comprises the following steps: acquiring vehicle data in real time, wherein the vehicle data comprises a driving mode, a current motor speed, a motor bus voltage and a motor request torque of a vehicle controller; determining whether a preset dynamic current control enabling condition is met according to the vehicle data; when the enabling condition is met, querying a pre-set speed-optimal current table according to the current motor speed to obtain an optimal current vector corresponding to the current motor speed, wherein the optimal current vector enables the motor to operate at a highest efficiency point at the current motor speed; calculating a duty cycle of the optimal current vector in a dynamic current control period; and sending a pulse current instruction to the motor controller according to the duty cycle in the dynamic current control period. The application effectively solves the technical problem that the electric drive system efficiency of an electric vehicle is low under common working conditions, and greatly improves the average operating efficiency of the motor.

Description

Technical Field

[0001] This invention relates to the field of vehicles, and more particularly to a method for improving the efficiency of a permanent magnet synchronous motor, a storage medium, and a vehicle. Background Technology

[0002] Permanent magnet synchronous motors have become a core component of electric vehicle drive systems due to their high power density, high efficiency, and excellent speed regulation performance. Improving the overall efficiency of the electric drive system is of paramount importance for extending the driving range of electric vehicles and reducing energy consumption.

[0003] In actual operation of electric vehicles, especially under simulated urban road cycles (such as CLTC conditions), vehicles frequently accelerate, decelerate, and cruise at low speeds, causing the drive motor to operate in a range of low to medium speeds and low torque requirements. Under such conditions, if a traditional vector control strategy is used, the motor's operating point is often far from its highest efficiency region, resulting in a significant decrease in motor efficiency and an increase in system energy consumption. This is a key technical problem currently restricting the improvement of the urban driving range of electric vehicles.

[0004] Meanwhile, the power loss of the motor controller (inverter), especially the switching losses of the power switching devices, accounts for a considerable proportion of the overall losses in the electric drive system. Under traditional control strategies, even if the motor output torque is very small, the inverter still needs to operate in a high-frequency pulse width modulation mode. The continuous switching action generates considerable switching losses, further reducing system efficiency.

[0005] Furthermore, some existing optimization control strategies designed to improve efficiency under specific operating conditions may alter torque output characteristics, introducing torque fluctuations or current harmonics. This can negatively impact driving smoothness and ride comfort, and even cause perceptible noise, vibration, and acoustic roughness issues, thus impairing the overall NVH performance of the vehicle. Therefore, effectively expanding the high-efficiency operating range of the motor and reducing controller losses while ensuring driving quality and NVH performance has become a pressing technical challenge in this field. Summary of the Invention

[0006] Based on the above problems, this invention proposes a method for improving the efficiency of permanent magnet synchronous motors, a storage medium, and a vehicle. This invention effectively solves the technical problem of low efficiency in the electric drive system of electric vehicles under common operating conditions. The dynamic current control strategy of this invention switches the traditional continuous low-current control mode to a pulse control mode that dynamically switches between high-efficiency point current and zero current. This allows the motor to operate at its highest efficiency region near the current speed while maintaining the same average torque output, thereby significantly improving the average operating efficiency of the motor itself. Simultaneously, during the zero-current phase of the pulse cycle, the power switching transistors of the motor controller are turned off, completely eliminating switching losses during this period and significantly improving inverter efficiency. The simultaneous improvement in motor efficiency and inverter efficiency jointly reduces the total energy consumption of the electric drive system.

[0007] This invention proposes a method for improving the efficiency of a permanent magnet synchronous motor, comprising:

[0008] Real-time acquisition of vehicle data, including driving mode, current motor speed, motor bus voltage, and motor torque requested by the vehicle controller; and determination of whether preset dynamic current control activation conditions are met based on the vehicle data. When the activation conditions are met, the pre-calibrated speed-optimal current table is consulted based on the current motor speed to obtain the optimal current vector corresponding to the current motor speed. The optimal current vector enables the motor to operate at its highest efficiency point at the current motor speed. Calculate the duty cycle of the optimal current vector for one dynamic current control cycle; Within a dynamic current control cycle, a pulse current command is sent to the motor controller according to the duty cycle. The pulse current command includes: outputting the optimal current vector in the first time period, outputting zero current in the second time period, and causing the motor controller to turn off its power switch in the second time period.

[0009] In addition, the step of determining whether the preset dynamic current control activation conditions are met based on the vehicle data includes: a mode determination step and a selection step; The mode determination steps include: if the driving mode is determined to be energy-saving mode, the maximum and minimum motor speeds for enabling dynamic current control are determined based on the motor bus voltage; if the current motor speed is determined to be less than the maximum motor speed but greater than the minimum motor speed, the selection step is then initiated. The selection steps include: querying the pre-calibrated speed-maximum control torque table based on the current motor speed to obtain the maximum torque for dynamic current control; if it is determined that the requested torque of the motor is less than the maximum torque, then entering the dynamic current control motor mode.

[0010] Furthermore, determining the maximum and minimum motor speeds for activating dynamic current control based on the motor bus voltage includes: The maximum motor speed is the maximum speed of the motor when the dynamic current control motor mode is turned on under rated voltage, and at the same time, the back electromotive force does not exceed the motor bus voltage. According to the formula Calculate the minimum motor speed, where The motor frequency at the minimum motor speed. This refers to the motor speed. This represents the number of pole pairs of the motor. The frequency is controlled by dynamic current.

[0011] In addition, the speed-maximum control torque table is a table showing the correspondence between the speed at which dynamic torque control can be activated under rated voltage and the maximum torque.

[0012] In addition, the calculation method for the maximum and minimum motor speeds under non-rated voltage is based on the ratio between voltage and speed.

[0013] Furthermore, the optimal current vector includes the optimal D-axis current. and optimal Q-axis current .

[0014] Furthermore, the duty cycle for calculating the optimal current vector over one dynamic current control cycle includes: Duty_current=Kp +Ki ; in, For torque error, Kp is the proportional coefficient, and Ki is the integral coefficient. This is the integral value of the torque error over one dynamic torque control cycle; = - ; This represents the average torque of the motor's actual torque over one dynamic current control cycle. , T represents the real-time torque of the motor and the dynamic current control cycle.

[0015] In addition, based on the duty cycle (Duty_current), a signal is sent to the motor controller. The motor controller controls the motor operation based on the pulse current command.

[0016] The present invention also proposes a storage medium that stores computer instructions, which, when executed by a computer, are used to perform the method for improving the efficiency of a permanent magnet synchronous motor as described in any of the preceding claims.

[0017] The present invention also proposes a vehicle that employs the method for improving the efficiency of a permanent magnet synchronous motor as described in any of the preceding claims.

[0018] This invention effectively solves the technical problem of low efficiency in electric drive systems of electric vehicles under common operating conditions. The dynamic current control strategy of this invention switches the traditional continuous low-current control mode to a pulse control mode that dynamically switches between high-efficiency current and zero current. This ensures that, while outputting the same average torque, the motor's operating point is constrained to the vicinity of its highest efficiency region at the current speed, thereby significantly improving the average operating efficiency of the motor itself. Simultaneously, during the zero-current phase of the pulse cycle, the power switch of the motor controller is turned off, completely eliminating switching losses during this period and significantly improving inverter efficiency. The simultaneous improvement in motor efficiency and inverter efficiency jointly reduces the total energy consumption of the electric drive system. Attached Figure Description

[0019] Figure 1 A flowchart of a method for improving the efficiency of a permanent magnet synchronous motor according to an embodiment of the present invention; Figure 2 A schematic diagram of a pre-calibrated speed-maximum control torque table provided in one embodiment of the present invention; Figure 3 A schematic diagram of a pre-calibrated speed-optimal ammeter provided in one embodiment of the present invention; Figure 4 A schematic diagram illustrating the transmission of pulse current commands based on an optimal current vector and duty cycle, according to an embodiment of the present invention; Figure 5 A distribution diagram of motor efficiency provided for one embodiment of the present invention; Figure 6 A flowchart of a method for improving the efficiency of a permanent magnet synchronous motor provided in an embodiment of the present invention. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. This description is intended only to illustrate specific embodiments of the invention and does not constitute any limitation on the invention. The scope of protection of the invention is defined by the claims.

[0021] Reference Figure 1 This invention proposes a method for improving the efficiency of a permanent magnet synchronous motor, comprising: Step S001: Real-time acquisition of vehicle data, including driving mode, current motor speed, motor bus voltage and motor requested torque of the vehicle controller; and determination of whether the preset dynamic current control activation conditions are met based on the vehicle data. Step S002: When the activation conditions are met, the pre-calibrated speed-optimal current table is queried according to the current speed of the motor to obtain the optimal current vector corresponding to the current speed of the motor. The optimal current vector enables the motor to run at the highest efficiency point at the current speed of the motor. Step S003: Calculate the duty cycle of the optimal current vector for one dynamic current control cycle; Step S004: Within a dynamic current control cycle, a pulse current command is sent to the motor controller according to the duty cycle; the pulse current command includes: outputting the optimal current vector in the first time period, outputting zero current in the second time period, and causing the motor controller to turn off its power switching transistor in the second time period.

[0022] like Figure 5 As shown, the motor efficiency has a peak point within the speed range of 1000-7000 RPM. The main idea of ​​this invention is to improve both motor and inverter efficiency by decomposing the motor's current request value into pulses of zero current and the operating current at the peak efficiency point. This ensures the motor always operates at its peak efficiency, effectively improving motor efficiency. Simultaneously, during the period when the motor torque is decomposed into zero current, the motor controller is in a closed state. During this period, the power module experiences no switching losses, thus improving the efficiency of the motor controller.

[0023] In step S001, real-time vehicle data is acquired, including: driving mode, current motor speed, motor bus voltage, and motor requested torque from the vehicle controller. Optionally, the "Driving Mode" is used to determine whether the current vehicle driving mode is suitable for entering "Dynamic Current Control." For example, "Dynamic Current Control" can only be entered when the vehicle is in "Energy Saving Mode" or an equivalent mode (such as Economy Mode). This is because the core of Dynamic Current Control is switching between "High-Efficiency Current Pulse" and "Zero Current." Although we ensure smooth macroscopic torque through high-frequency control, from a microscopic and theoretical perspective, it may introduce high-frequency, inaudible electromagnetic noise: the change in switching mode may cause the motor or inverter to emit extremely high-frequency sounds different from continuous PWM. In the zero-current phase, the motor is in a "disconnected" state. Although the time is extremely short, when the driver suddenly requests maximum torque, the system needs to re-establish the magnetic field and current from the "zero current" state. Its theoretical initial response speed may be slightly lower than that of the traditional control mode, which is always in a standby state (although this difference may be in the millisecond range and is difficult to perceive in daily driving). Therefore, whether to enable "Dynamic Current Control" depends on whether the current driver's demand is to maximize driving range and prioritize energy efficiency.

[0024] The emphasis on "bus" in the motor bus voltage data is because dynamic current control requires shutting down the inverter during the "zero current phase." At this time, the motor's back electromotive force (EMF) is proportional to the speed. If the speed is too high, the back EMF may exceed the bus voltage, causing inverter damage. Bus voltage is a necessary parameter for calculating the safe speed window (PulseSpdmax / min). In the activation logic, the speed dynamically changes with the voltage (a higher voltage allows for a higher upper limit on the allowed speed). Without the voltage parameter, safe and adaptive control cannot be achieved, resulting in an incomplete solution.

[0025] Optionally, the current motor speed and the requested motor torque are used in the following process: the determination of whether the preset dynamic current control activation conditions are met based on the vehicle data includes: a mode determination step and a selection step; The mode determination steps include: if the driving mode is determined to be energy-saving mode, the maximum and minimum motor speeds for enabling dynamic current control are determined based on the motor bus voltage; if the current motor speed is determined to be less than the maximum motor speed but greater than the minimum motor speed, the selection step is then initiated. The selection steps include: querying the pre-calibrated speed-maximum control torque table based on the motor's current speed, such as... Figure 2 As shown, the maximum torque of dynamic current control is obtained. If it is determined that the motor's requested torque is less than the maximum torque, the motor enters the dynamic current control mode.

[0026] The first row of the speed-maximum control torque table represents the speed at which dynamic current control can be activated under rated voltage. The second row represents the maximum torque at which dynamic current control can be activated (which can also define the maximum torque for generator operation). The purpose of calibrating this table is to find the highest efficiency torque point corresponding to the motor's current speed, while limiting the effective range of dynamic current control. That is, when the motor's requested torque by the vehicle controller exceeds the maximum torque at the motor's current speed, dynamic current control will not be activated. The table is generated as follows: After the motor's routine calibration, efficiency tests are performed, and the highest efficiency torque point at each motor speed is selected based on the efficiency test results.

[0027] In step S002, when the activation condition is met, the pre-calibrated speed-optimal current table is queried based on the current motor speed, such as... Figure 3 As shown, the optimal current vector corresponding to the current speed of the motor is obtained. The optimal current vector enables the motor to operate at its highest efficiency point at the current speed. The optimal current vector includes the D-axis and Q-axis currents. The D-axis (Direct Axis) is the axis coinciding with the direction of the magnetic field and is primarily used to control the magnitude of the magnetic field. The Q-axis (Quadrature Axis) is the axis perpendicular to the motor's magnetic field and is mainly responsible for controlling the rate of change of the motor's kinetic energy.

[0028] Optionally, the speed-optimal current meter can be obtained through calibration or testing. Calibration involves giving a given motor speed (e.g., 1000 or 2000 RPM) and then adjusting the current command based on the motor system efficiency feedback from the motor test bench to obtain the current command at the optimal efficiency. Testing involves using the speed-maximum torque meter mentioned above to test the D and Q axis currents at the corresponding speed and torque.

[0029] According to Figure 3 The current at the D and Q axis current points with the highest efficiency at the current speed of the motor is obtained by linearly looking up the table in the table.

[0030] In step S003, the duty cycle of the optimal current vector for one dynamic current control cycle is calculated; In real-world scenarios, the requested torque from the motor (e.g., 20 Nm) is typically less than the maximum torque corresponding to the motor's highest efficiency point at its current speed (e.g., 80 Nm). Therefore, duty cycle calculations are needed to convert the high torque into the low torque required by the driver. For example, a duty cycle of 20 / 80 = 0.25 means that within one control cycle, the maximum torque is output for 25% of the time, and zero torque is output for 75% of the time, resulting in an average torque of 20 Nm. By scientifically allocating the ratio of "efficient operating time" to "zero current time," the efficiency of the motor itself is maximized while the inverter switching losses are minimized, thereby achieving a comprehensive improvement in the overall efficiency of the electric drive system.

[0031] In step S004, within one dynamic current control cycle, a pulse current command is sent to the motor controller according to the duty cycle. The pulse current command includes: outputting the optimal current vector in the first time period, outputting zero current in the second time period, and causing the motor controller to turn off its power switch in the second time period. Finally, based on the duty cycle `Duty_current`, a pulse current command is sent to the motor controller. The motor controller controls the motor operation based on the pulse current command. A space current vector is defined at the "optimal efficiency operating point"; Duty_current determines the "application ratio" of this vector over time to achieve precise tracking of the requested torque. For example... Figure 4 As shown, I_best is the optimal current vector. Figure 4 To send pulse current commands based on the optimal current and duty cycle, where I_best calculates the currents on the D and Q axes respectively. .

[0032] This invention employs a dynamic current control strategy, which avoids the motor operating in the low-efficiency range of low speed and low torque, ensuring the motor continuously operates in its most efficient region and improving operating efficiency. Simultaneously, it reduces switching losses in the motor controller, improving inverter efficiency. Furthermore, it ensures smooth actual output torque, preventing drivability and NVH (noise, vibration, and harshness) issues.

[0033] NVH stands for Noise, Vibration, and Harshness.

[0034] Because the entire electric drive system's transmission chain to the wheels (motor rotor, reducer, half-shaft, wheels) has enormous mechanical inertia, the mechanical system simply cannot respond in time to large torque pulsations. Ultimately, the average rotational speed of the motor rotor is determined by the vehicle's driving resistance and the driver's demands, presenting a smooth curve that does not fluctuate with large torque pulsations. The acceleration felt by the driver and passengers is continuous.

[0035] Although the control command is a "pulse," the motor winding is a large inductor, and the current cannot change abruptly. When switching from the "optimal current" command to the "0 current" command, the winding current decays slowly through the inverter's freewheeling diode, forming a falling edge; when switching back from the "0 current" command to the "optimal current" command, the inductor suppresses the rate of current rise, and the current rises exponentially, forming a rising edge. Therefore, the overall current change is smooth.

[0036] "Dynamic current control" is not blindly activated under all operating conditions. For example, when the speed is too low, the mechanical filtering effect deteriorates, and torque pulsation is more easily converted into speed fluctuation. This solution sets a minimum speed threshold and automatically deactivates "dynamic current control" under extremely low-speed conditions such as starting and creeping, avoiding possible jerking.

[0037] When the motor requests high torque (such as during rapid acceleration or hill climbing), the system automatically disengages from "dynamic current control." At this point, the driver requires a quick and powerful response, rather than prioritizing efficiency. This ensures that drivability remains unaffected.

[0038] When power response requirements are not high and minor compromises in energy saving (such as extremely subtle, imperceptible high-frequency vibrations) are permissible, "dynamic current control" is activated. By calculating the duty cycle in real time based on the ratio of requested torque to the high-efficiency torque, and using millisecond-level dynamic current control cycles for high-frequency switching, the average torque output by the motor is strictly matched to the driver's request, ensuring a smooth and continuous transition. The significant mechanical system inertia naturally acts as a low-pass filter for high-frequency torque pulsations, thus guaranteeing a smooth experience of vehicle dynamics from the pedal input, completely eliminating additional noise, vibration, and noise and harshness (NVH) problems introduced by the control strategy.

[0039] This invention effectively solves the technical problem of low efficiency in electric drive systems of electric vehicles under common operating conditions. The dynamic current control strategy of this invention switches the traditional continuous low-current control mode to a pulse control mode that dynamically switches between high-efficiency current and zero current. This ensures that, while outputting the same average torque, the motor's operating point is constrained to the vicinity of its highest efficiency region at the current speed, thereby significantly improving the average operating efficiency of the motor itself. Simultaneously, during the zero-current phase of the pulse cycle, the power switch of the motor controller is turned off, completely eliminating switching losses during this period and significantly improving inverter efficiency. The simultaneous improvement in motor efficiency and inverter efficiency jointly reduces the total energy consumption of the electric drive system.

[0040] In one embodiment, the step of determining whether the preset dynamic current control activation conditions are met based on vehicle data includes: a mode determination step and a selection step; The mode determination steps include: if the driving mode is determined to be energy-saving mode, the maximum and minimum motor speeds for enabling dynamic current control are determined based on the motor bus voltage; if the current motor speed is determined to be less than the maximum motor speed but greater than the minimum motor speed, the selection step is then initiated. The selection steps include: querying the pre-calibrated speed-maximum control torque table based on the current motor speed to obtain the maximum torque for dynamic current control; if it is determined that the requested torque of the motor is less than the maximum torque, then entering the dynamic current control motor mode.

[0041] In the mode determination step, after confirming that it is in energy-saving mode, the range of motor speeds that allow dynamic current control to be enabled is dynamically calculated based on the current real-time collected motor bus voltage (Udc), that is, a safe speed window is determined: minimum motor speed (PulseSpdmin) and maximum motor speed (PulseSpdmax).

[0042] Determining the maximum motor speed (PulseSpdmax): The core safety principle is to ensure that the peak value of the back electromotive force generated by the motor rotation does not exceed the bus voltage during the "zero current" phase of dynamic current control, thus preventing overvoltage breakdown of the inverter power transistors. In a preferred embodiment, the maximum speed reference value that meets this safety condition under the rated bus voltage is first determined through simulation or testing. In actual operation, the real-time PulseSpdmax is obtained by dynamically scaling the current actual bus voltage to the rated voltage in a proportional relationship. That is: PulseSpdmax = PulseSpdmax - Rated Bus Voltage (Udc / Udc_rated).

[0043] Determination of the minimum motor speed (PulseSpdmin): The core control principle is to ensure that the current electrical frequency of the motor is high enough so that the high-frequency pulse modulation of dynamic current control can be effectively executed, avoiding deterioration of the control effect or perceptible torque fluctuations caused by too low frequency. Specifically, the minimum speed needs to satisfy that the corresponding fundamental frequency of the motor is higher than the minimum operating frequency of dynamic current control.

[0044] Speed condition judgment: After calculating PulseSpdmin and PulseSpdmax at the current voltage, it is judged whether the current actual speed (Motorspd) of the motor satisfies PulseSpdmin < Motorspd < PulseSpdmax. If it is satisfied, it indicates that the motor is operating in a speed range that is both safe (back electromotive force controllable) and suitable (electrical frequency sufficient) for dynamic current control.

[0045] The speed - maximum control torque table is as Figure 2 shown. The first row in the speed - maximum control torque table is the speed at which dynamic current control can be started under the rated voltage, and the second row is the maximum torque at which dynamic current control can be started (which can also define the maximum torque for power generation). The purpose of calibrating this table is to find the highest - efficiency torque point corresponding to the current speed of the motor, and at the same time limit the effective range of dynamic current control, that is, when the motor request torque of the vehicle controller is greater than the maximum torque at the current speed of the motor, dynamic current control is not started. The formation process of this table: After the conventional calibration of the motor is completed, an efficiency test is carried out, and the highest - efficiency torque point at each motor speed is selected according to the results of the efficiency test.

[0046] In the selection step, according to the current motor speed (Motorspd), a speed - maximum control torque table pre - calibrated through bench tests is queried. This table establishes the boundary value (PulseTqmax) of the maximum request torque that allows dynamic current control to be enabled at different speeds. The physical meaning of this PulseTqmax is: at this speed, when the request torque is less than this value, the system efficiency gain brought by using dynamic current control (i.e., synthesizing small torques with high - efficiency large - current pulses) is the most significant; when the request torque is greater than this value, it is more appropriate to directly adopt the traditional continuous current control method.

[0047] Obtain the real-time motor torque request value (Tqreq) from the vehicle controller and compare it with the maximum control torque boundary (PulseTqmax) at the current speed obtained by looking up the table. If Tqreq < PulseTqmax, it indicates that the current torque request is in the "small torque" range. In this range, adopting dynamic current control can effectively improve efficiency, so the system officially enters the dynamic current control mode. If Tqreq ≥ PulseTqmax, it means that the current torque demand is large, and the system will exit the dynamic current control and switch back to the original high-performance continuous control mode to ensure sufficient power response.

[0048] The two-stage judgment method of this embodiment fundamentally prevents the risk of overvoltage of the back electromotive force caused by turning off the inverter at high speed through the voltage-adaptive safe speed window, ensures the safety of the power devices, and improves the system reliability. Through torque boundary comparison, the dynamic current control strategy can be accurately activated only under the "small torque" working conditions where the efficiency improvement effect is significant. It avoids the problems of delayed power response or decreased efficiency that may occur when misusing this strategy under large torque requests, and realizes the working condition adaptability and efficiency optimization of the control strategy.

[0049] In one of the embodiments, the determination of the maximum motor speed and the minimum motor speed for starting the dynamic current control according to the motor bus voltage includes: The maximum motor speed is the maximum speed of the motor when starting the dynamic current control mode at the rated voltage, and at the same time, the back electromotive force does not exceed the motor bus voltage; According to the formula Calculate the minimum motor speed, where is the motor frequency at the minimum motor speed, is the motor speed, is the number of pole pairs of the motor, is the dynamic current control frequency.

[0050] is the preset minimum effective frequency of dynamic current control (such as 50Hz). From this, the minimum speed threshold PulseSpdmin is inversely deduced. Similarly, this threshold can also be adjusted proportionally according to the motor bus voltage.

[0051] The primary purpose of setting the maximum motor speed is to prevent high-voltage surges to the inverter during the "zero-current" phase of dynamic current control. When a permanent magnet synchronous motor rotates, its permanent magnets induce a back electromotive force (Back-EMF) in the stator windings. The magnitude of this Back-EMF is proportional to the motor speed. During the "zero-current" phase, all inverter switches are off, and the motor functions like a rotating generator. If the motor speed is too high at this time, the peak Back-EMF may exceed the DC bus voltage (Udc), causing current to flow backward through the inverter's freewheeling diodes into the DC bus, generating huge instantaneous current and voltage spikes that seriously threaten the safety of power devices. Based on this principle, the determination of PulseSpdmax follows the safety criterion that "the peak Back-EMF does not exceed the real-time bus voltage."

[0052] Setting a minimum motor speed is crucial to ensure the effective implementation of the dynamic current control strategy and to avoid undesirable vibration and noise (NVH). Dynamic current control relies on high-frequency switching between "optimal current" and "zero current" states. The effectiveness of this switching process is limited by the dynamic response capability of the motor winding current. If the motor speed is too low, the corresponding electrical frequency is also too low. In this case, the high-frequency current pulse modulation may mismatch with the motor's fundamental electromagnetic cycle, causing the current to fail to build up or decay to the target value within the set short period. This results in low-frequency pulse torque fluctuations being difficult to filter out by mechanical inertia, potentially transforming into perceptible speed fluctuations or vibrations. Furthermore, excessively low modulation frequencies may fall within the range of frequencies sensitive to human hearing, producing a "humming" sound. To ensure control performance and NVH, a minimum electrical frequency needs to be set. (e.g., 100-200Hz) serves as a threshold for effectively and smoothly implementing dynamic current control.

[0053] In one embodiment, the speed-maximum control torque table is a table showing the correspondence between the speed at which dynamic torque control can be activated under rated voltage and the maximum torque.

[0054] like Figure 2 As shown in the table, the first row of the speed-maximum control torque table represents the speed at which dynamic current control can be activated under rated voltage, and the second row represents the maximum torque at which dynamic current control can be activated (which can also define the maximum torque for generator operation). The purpose of calibrating this table is to find the highest efficiency torque point corresponding to the motor's current speed, while limiting the effective range of dynamic current control. That is, when the motor's requested torque by the vehicle controller exceeds the maximum torque at the motor's current speed, dynamic current control will not be activated. The table is generated as follows: After the motor's routine calibration is completed, an efficiency test is performed, and the highest efficiency torque point at each motor speed is selected based on the efficiency test results.

[0055] In one embodiment, the maximum and minimum motor speeds under non-rated voltage conditions are calculated by converting them according to the ratio between voltage and speed.

[0056] In this embodiment, the maximum speed reference value that meets this safety condition under the rated bus voltage is first determined through simulation or testing. In actual operation, the speed is then dynamically scaled proportionally to the ratio of the current actual bus voltage to the rated voltage to obtain the real-time PulseSpdmax. That is: PulseSpdmax = PulseSpdmax - Rated Bus Voltage (Udc / Udc_rated).

[0057] In one embodiment, the optimal current vector includes the optimal D-axis current. and optimal Q-axis current .

[0058] The optimal current vector includes the D-axis and Q-axis currents. The D-axis (Direct Axis) is the axis coinciding with the direction of the magnetic field and is primarily used to control the magnitude of the magnetic field. The Q-axis (Quadrature Axis) is the axis perpendicular to the motor's magnetic field and is mainly responsible for controlling the rate of change of the motor's kinetic energy.

[0059] In one embodiment, the duty cycle of calculating the optimal current vector over one dynamic current control cycle includes: Duty_current=Kp +Ki ; in, For torque error, Kp is the proportional coefficient, and Ki is the integral coefficient. This is the integral value of the torque error over one dynamic torque control cycle; = - ; This represents the average torque of the motor's actual torque over one dynamic current control cycle. , T represents the real-time torque of the motor and the dynamic current control cycle.

[0060] The duty cycle calculation method based on torque error PI closed-loop control introduced in this embodiment brings higher-order control performance and system robustness compared to simple open-loop calculation.

[0061] In one embodiment, a timer is sent to the motor controller based on the duty cycle (Duty_current). The motor controller controls the motor operation based on the pulse current command.

[0062] The duty cycle calculation method based on torque error PI closed-loop control introduced in this embodiment, compared with simple open-loop calculation, brings higher-order control performance and system robustness. like Figure 6 As shown, in one embodiment, the overall process of a method for improving the efficiency of a permanent magnet synchronous motor is given.

[0063] The present invention also proposes a storage medium that stores computer instructions, which, when executed by a computer, are used to perform the method for improving the efficiency of a permanent magnet synchronous motor as described in any of the preceding claims.

[0064] This invention effectively solves the technical problem of low efficiency in electric drive systems of electric vehicles under common operating conditions. The dynamic current control strategy of this invention switches the traditional continuous low-current control mode to a pulse control mode that dynamically switches between high-efficiency current and zero current. This ensures that, while outputting the same average torque, the motor's operating point is constrained to the vicinity of its highest efficiency region at the current speed, thereby significantly improving the average operating efficiency of the motor itself. Simultaneously, during the zero-current phase of the pulse cycle, the power switch of the motor controller is turned off, completely eliminating switching losses during this period and significantly improving inverter efficiency. The simultaneous improvement in motor efficiency and inverter efficiency jointly reduces the total energy consumption of the electric drive system.

[0065] The present invention also proposes a vehicle that employs the method for improving the efficiency of a permanent magnet synchronous motor as described in any of the preceding claims.

[0066] This invention effectively solves the technical problem of low efficiency in electric drive systems of electric vehicles under common operating conditions. The dynamic current control strategy of this invention switches the traditional continuous low-current control mode to a pulse control mode that dynamically switches between high-efficiency current and zero current. This ensures that, while outputting the same average torque, the motor's operating point is constrained to the vicinity of its highest efficiency region at the current speed, thereby significantly improving the average operating efficiency of the motor itself. Simultaneously, during the zero-current phase of the pulse cycle, the power switch of the motor controller is turned off, completely eliminating switching losses during this period and significantly improving inverter efficiency. The simultaneous improvement in motor efficiency and inverter efficiency jointly reduces the total energy consumption of the electric drive system.

[0067] As needed, the above technical solutions can be combined to achieve the best technical effect.

[0068] The above are merely the principles and preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several other modifications can be made based on the principles of the present invention, and these modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for improving the efficiency of a permanent magnet synchronous motor, characterized in that, include: Real-time acquisition of vehicle data, including driving mode, current motor speed, motor bus voltage, and motor torque requested by the vehicle controller; and determination of whether preset dynamic current control activation conditions are met based on the vehicle data. When the activation conditions are met, the pre-calibrated speed-optimal current table is consulted based on the current motor speed to obtain the optimal current vector corresponding to the current motor speed. The optimal current vector enables the motor to operate at its highest efficiency point at the current motor speed. Calculate the duty cycle of the optimal current vector for one dynamic current control cycle; Within a dynamic current control cycle, a pulse current command is sent to the motor controller according to the duty cycle. The pulse current command includes: outputting the optimal current vector in the first time period, outputting zero current in the second time period, and causing the motor controller to turn off its power switch in the second time period.

2. The method for improving the efficiency of a permanent magnet synchronous motor according to claim 1, characterized in that, The step of determining whether the preset dynamic current control activation conditions are met based on vehicle data includes: a mode determination step and a selection step; The mode determination steps include: if the driving mode is determined to be energy-saving mode, the maximum and minimum motor speeds for enabling dynamic current control are determined based on the motor bus voltage; if the current motor speed is determined to be less than the maximum motor speed but greater than the minimum motor speed, the selection step is then initiated. The selection steps include: querying the pre-calibrated speed-maximum control torque table based on the current motor speed to obtain the maximum torque for dynamic current control; if it is determined that the requested torque of the motor is less than the maximum torque, then entering the dynamic current control motor mode.

3. The method for improving the efficiency of a permanent magnet synchronous motor according to claim 2, characterized in that, The determination of the maximum and minimum motor speeds for activating dynamic current control based on the motor bus voltage includes: The maximum motor speed is the maximum speed of the motor when the dynamic current control motor mode is turned on under rated voltage, and at the same time, the back electromotive force does not exceed the motor bus voltage. According to the formula Calculate the minimum motor speed, where The motor frequency at the minimum motor speed. This refers to the motor speed. This represents the number of pole pairs of the motor. The frequency is controlled by dynamic current.

4. The method for improving the efficiency of a permanent magnet synchronous motor according to claim 2, characterized in that, The speed-maximum control torque table is a table showing the correspondence between the speed at which dynamic torque control can be activated under rated voltage and the maximum torque.

5. The method for improving the efficiency of a permanent magnet synchronous motor according to claim 2, characterized in that, The calculation method for the maximum and minimum motor speeds under non-rated voltage is based on the proportional relationship between voltage and speed.

6. The method for improving the efficiency of a permanent magnet synchronous motor according to claim 1, characterized in that, The optimal current vector includes the optimal D-axis current. and optimal Q-axis current .

7. The method for improving the efficiency of a permanent magnet synchronous motor according to claim 6, characterized in that, The duty cycle of the calculated optimal current vector over one dynamic current control cycle includes: Duty_current=Kp +Ki ; in, For torque error, Kp is the proportional coefficient, and Ki is the integral coefficient. This is the integral value of the torque error over one dynamic torque control cycle; = - ; This represents the average torque of the motor's actual torque over one dynamic current control cycle. ， T represents the real-time torque of the motor and the dynamic current control cycle.

8. The method for improving the efficiency of a permanent magnet synchronous motor according to claim 7, characterized in that, Based on the duty cycle (Duty_current), send to the motor controller The motor controller controls the motor operation based on the pulse current command.

9. A storage medium, characterized in that, The storage medium stores computer instructions, which, when executed by the computer, are used to perform the method for improving the efficiency of a permanent magnet synchronous motor as described in any one of claims 1 to 8.

10. A vehicle, characterized in that, The method for improving the efficiency of a permanent magnet synchronous motor as described in any one of claims 1 to 8 is adopted.

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