A motor protection method based on device temperature reference correction

Abstract

The application relates to the technical field of motor protection, and discloses a motor protection method based on device temperature reference correction. The motor current multiple is obtained, the corresponding thermal time constant is obtained according to the current multiple, and the thermal accumulation is calculated. Then, the thermal accumulation is converted into model estimated temperature, and the model estimated temperature is compared with the MOS tube temperature, the PCB temperature, the power board temperature or the radiator temperature actually collected by the controller or the temperature sensor temperature close to the power board, and the greater value is taken as the final estimated protection temperature. When the final estimated protection temperature reaches the preset protection threshold, the controller performs protection actions such as current limiting, power reduction, PWM closing or fault locking. The method not only embodies the current multiple inverse time limit characteristic, but also combines the actual device temperature of the controller to correct the protection temperature, significantly reduces the real thermal risk of the motor controller, enhances the protection effect, and is superior to the prior art.

Description

Technical Field

[0001] This application relates to the field of motor protection technology, specifically a motor protection method based on device temperature reference correction. Background Technology

[0002] In motor drive systems such as permanent magnet synchronous motors and brushless DC motors, the FOC vector control method is widely used. FOC control obtains the d-axis current and q-axis current by acquiring the motor phase current, rotor position or estimating the angle, and then performing Clarke or Park transformation to obtain the d-axis current and q-axis current, thereby achieving decoupled control of the motor flux linkage and torque.

[0003] In actual operation, the motor may experience a continuous high current state due to reasons such as mechanical jamming, sudden load increase, output shaft stall, transmission mechanism jamming, or low-speed high-load operation. At this time, the motor windings, controller MOSFETs, power modules, current sampling resistors, PCB copper foil, and heat sinks will all experience temperature rise. If the protection system reacts too slowly, it may damage the motor or controller; if the protection system reacts too quickly, it may falsely activate during starting shocks, short-term overloads, or transient load changes.

[0004] In existing technologies, common protection methods include fixed current threshold protection, fixed time delay protection, over-temperature protection, and simple inverse-time overcurrent protection. Fixed threshold protection cannot reflect the relationship between current magnitude and heating rate; fixed time delay protection cannot adapt to thermal risks under different current multiples; simple over-temperature protection has temperature sampling lag; and although simple inverse-time current protection considers the current multiple, it usually does not take into account the current actual temperature state of the controller.

[0005] Especially when the motor controller is already under high ambient temperature, high residual temperature of the MOSFET, poor heat dissipation, or after continuous operation, thermal accumulation calculations based solely on the current multiplier model may underestimate the actual thermal risk to the controller. Therefore, a protection method is needed that can reflect the inverse-time characteristic of the current multiplier while also being corrected for the actual device temperature of the controller. Summary of the Invention

[0006] The purpose of this application is to provide a motor protection method based on device temperature reference correction to solve the problems in the prior art.

[0007] To achieve the above objectives, this application provides the following technical solution: a motor protection method based on device temperature reference correction, comprising the following steps: Step A: Obtain the current parameters during motor operation, including: current motor current I, motor rated current or controller rated output current I. rated ; Step B: Calculate the current multiple K based on the current parameters: ; Step C: Obtain the corresponding thermal time constant T based on the current multiple K; Step D: Calculate the current cycle heat accumulation Q based on the current multiple K and the thermal time constant T: Where: Q is the heat accumulation in the current cycle, Q(n-1) is the heat accumulation in the previous cycle, T is the thermal time constant, and K is the current multiple; Step E: Limit the accumulated heat: In the formula: Q max Q represents the maximum cumulative heat output. min This represents the minimum amount of accumulated heat. Step F: Convert the accumulated heat into a model-estimated temperature. In the formula: T model To estimate the temperature for the model, Q is the cumulative heat, and T is the temperature. limit This is the preset temperature calibration value; Step G: Obtain the device temperature T of the motor controller. device ; Step H: Estimate the temperature T using the model. model With respect to the device temperature T device The two values ​​are compared, and the larger value is taken as the final estimated protection temperature T after correction based on the device temperature reference. est : ; Step I: When the final estimated protection temperature T est When the preset protection threshold is reached, the motor protection action is executed.

[0008] Furthermore, the current motor current I can be the q-axis current I. q .

[0009] Furthermore, the current motor current I can be: In the formula: I is the motor current, I d I is the d-axis current. q This is the q-axis current.

[0010] Furthermore, the motor protection actions include at least the following: limiting the q-axis current setpoint, limiting the maximum output current of the motor, reducing the PWM duty cycle, turning off the PWM output, entering a fault lockout state, outputting an overload, stall, overheat, or inverse time protection fault code, or automatically resuming operation after a delay.

[0011] Furthermore, in step C, the thermal time constant T is obtained by looking up the current multiple K in a calibration table.

[0012] Furthermore, the calibration table can be a segmented table, an interpolation table, or a two-dimensional calibration table.

[0013] Furthermore, the device temperature T device It can be at least one of the following: MOSFET temperature, power device temperature, PCB temperature, power board temperature, heat sink temperature, and temperature sensor temperature near the power device.

[0014] Furthermore, the motor protection method based on device temperature reference correction also includes a stall judgment step J. When the motor speed is lower than a preset speed threshold and the current multiple K is higher than a preset current multiple threshold, the motor is determined to be in a stalled or near-stalled state, and the motor protection action is executed.

[0015] The beneficial technical effects of this application are as follows: The motor protection method based on device temperature reference correction provided in this application obtains the motor current multiple, calculates the corresponding thermal time constant based on the current multiple, and then calculates the heat accumulation. Subsequently, the heat accumulation is converted into a model-estimated temperature, which is compared with the actual MOSFET temperature, PCB temperature, power board temperature, heat sink temperature, or temperature sensor temperature near the power board collected by the controller. The larger value is taken as the final estimated protection temperature. When the final estimated protection temperature reaches a preset protection threshold, the controller performs protection actions such as current limiting, derating, PWM shutdown, or fault locking. This method not only reflects the inverse time characteristic of the current multiple but also incorporates the actual device temperature of the controller to correct the protection temperature, significantly reducing the actual thermal risk of the motor controller and enhancing the protection effect, which is superior to existing technologies. Attached Figure Description

[0016] Figure 1 This is a flowchart of the motor protection method based on device temperature reference correction according to this application. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] Please see Figure 1 A motor protection method based on device temperature reference correction includes the following steps: Step A: Obtain the current parameters during motor operation, including: current motor current I, motor rated current or controller rated output current I. rated ; Step B: Calculate the current multiple K based on the current parameters: ; Step C: Obtain the corresponding thermal time constant T based on the current multiple K; Step D: Calculate the cumulative heat Q for the current cycle based on the current multiple K and the thermal time constant T. In the formula: Q is the heat accumulation in the current cycle, Q(n-1) is the heat accumulation in the previous cycle, T is the thermal time constant, and K is the current multiple. Thus, when K>1, the heat accumulation increases; when K=1, the heat accumulation remains unchanged; and when K<1, the heat accumulation decreases. This results in the inverse-time protection characteristic that the larger the current, the shorter the operating time. Step E: Limit the accumulated heat: In the formula: Q max Q represents the maximum cumulative heat output. min The minimum heat accumulation is preferably 0; Step F: Convert the accumulated heat into the model-estimated temperature. In the formula: T model To estimate the temperature for the model, Q is the cumulative heat, and T is the temperature. limit T is the preset temperature calibration value. limt It can be 105℃, or it can be a value determined based on the test results. In this way, the heat accumulation is converted into the model estimated temperature, and the protection variable is converted from the dimensionless heat accumulation to the temperature. Step G: Obtain the device temperature T of the motor controller. device In this embodiment, the device temperature T device Acquired by temperature sampling circuit; Step H: Estimate the temperature T using the model. model With device temperature T device The two values ​​are compared, and the larger value is taken as the final estimated protection temperature T after correction based on the device temperature reference. est : ; Step I: When the final estimated protection temperature T est When the preset protection threshold is reached, the motor protection action is executed. Thus, even if the actual temperature of the motor controller is already high, the model-estimated temperature T calculated by the current thermal accumulation model will still apply. model The temperature is relatively low, and the final estimated protection temperature will not be lower than the actual acquired device temperature T.device This prevents the controller from continuing to allow a large current output under the residual high temperature state, effectively protecting the motor and motor controller.

[0019] More preferably, the current motor current I can be the q-axis current I. q In this way, the value can be obtained directly from the sampling circuit, which simplifies the calculation.

[0020] More preferably, the current motor current I can be: In the formula: I is the motor current, I d I is the d-axis current. q This is the q-axis current.

[0021] In a further preferred embodiment, the motor protection actions include at least one of the following: limiting the q-axis current setpoint, limiting the maximum output current of the motor, reducing the PWM duty cycle, turning off the PWM output, entering a fault lockout state, outputting an overload, stall, overheat, or inverse time protection fault code, or automatically resuming operation after a delay.

[0022] In a further preferred embodiment, in step C, the thermal time constant T is obtained by looking up the current multiple K in a calibration table. In this way, the thermal time constant can be obtained based on the precise correspondence between the current multiple K and the thermal time constant T, making the control more accurate and the protection effect better; at the same time, it improves the calibrability of the protection curve.

[0023] More preferably, the calibration table can be a segmented table, an interpolation table, or a two-dimensional calibration table. For example, in this embodiment, the data in the calibration table is as follows: when K is 0.00000, the corresponding time constant T is 80; when K is 0.50000, the corresponding time constant T is 80; when K is 1.00000, the corresponding time constant T is 80; that is, when K is in the range of 0.00000 to 1.00000, the corresponding time constant T is 80; when K is 1.04993, the corresponding time constant T is 100; when K is 1.39990, the corresponding time constant T is 100; when K is 2.00000, the corresponding time constant T is 100; when K is 3.00000, the corresponding time constant T is 50; when K is 4.00000, the corresponding time constant T is 30; when K is 6.00000, the corresponding time constant T is 30.

[0024] Further preferred, device temperature T device It can be at least one of the following: MOSFET temperature, power device temperature, PCB temperature, power board temperature, heat sink temperature, and temperature sensor temperature near the power device.

[0025] Furthermore, the motor protection method based on device temperature reference correction also includes a stall judgment step J. When the motor speed is lower than a preset speed threshold and the current multiple K is higher than a preset current multiple threshold, the motor is determined to be in a stalled or near-stalled state, and motor protection actions are executed.

[0026] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A motor protection method based on device temperature reference correction, characterized in that, Includes the following steps: Step A: Obtain the current parameters during motor operation, including: current motor current I, motor rated current or controller rated output current I. rated ; Step B: Calculate the current multiple K based on the current parameters: ； Step C: Obtain the corresponding thermal time constant T based on the current multiple K; Step D: Calculate the current cycle heat accumulation Q based on the current multiple K and the thermal time constant T: Where: Q is the heat accumulation in the current cycle, Q(n-1) is the heat accumulation in the previous cycle, T is the thermal time constant, and K is the current multiple; Step E: Limit the accumulated heat Q: In the formula: Q max Q represents the maximum cumulative heat output. min This represents the minimum amount of accumulated heat. Step F: Convert the accumulated heat into a model-estimated temperature. In the formula: T model To estimate the temperature for the model, Q is the cumulative heat, and T is the temperature. limit This is the preset temperature calibration value; Step G: Obtain the device temperature T of the motor controller. device ; Step H: Estimate the temperature T using the model. model With respect to the device temperature T device The two values ​​are compared, and the larger value is taken as the final estimated protection temperature T after correction based on the device temperature reference. est : ； Step I: When the final estimated protection temperature T est When the preset protection threshold is reached, the motor protection action is executed.

2. The motor protection method based on device temperature reference correction according to claim 1, characterized in that: The current motor current I can be the q-axis current I. q .

3. The motor protection method based on device temperature reference correction according to claim 1, characterized in that: The current motor current I can be: In the formula: I is the motor current, I d I is the d-axis current. q This is the q-axis current.

4. The motor protection method based on device temperature reference correction according to claim 1, characterized in that: The motor protection actions include at least the following: limiting the q-axis current setpoint, limiting the maximum output current of the motor, reducing the PWM duty cycle, turning off the PWM output, entering a fault lockout state, outputting an overload, stall, overheat, or inverse time protection fault code, or automatically resuming operation after a delay.

5. The motor protection method based on device temperature reference correction according to claim 1, characterized in that: In step C, the thermal time constant T is obtained by looking up the current multiple K in a calibration table.

6. The motor protection method based on device temperature reference correction according to claim 5, characterized in that: The calibration table can be a segmented table, an interpolation table, or a two-dimensional calibration table.

7. The motor protection method based on device temperature reference correction according to claim 1, characterized in that: The device temperature T device It can be at least one of the following: MOSFET temperature, power device temperature, PCB temperature, power board temperature, heat sink temperature, and temperature sensor temperature near the power device.

8. The motor protection method based on device temperature reference correction according to claim 4, characterized in that: It also includes a stall detection step J, which determines that the motor is in a stalled or near-stalled state when the motor speed is lower than a preset speed threshold and the current multiple K is higher than a preset current multiple threshold, and executes the motor protection action.

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