A method for selectively protecting a drive motor of a vehicle from stalling current

Abstract

The application discloses a kind of vehicle-mounted drive motor selective stall current protection method, comprising the following steps S1, detecting motor rotor position;S2, detecting single-phase current sum;S3, adjusting stall current;Same torque demand, in a 360 ° electrical angle period, the numerical value of different angle three-phase current is different.Size is measured by rotor position angle detection circuit, motor rotor position, the minimum value corresponding to the electrical angle is selected in 3 single-phase maximum current value to stall, motor and controller stall loss minimum, thermal management is safer;Without additional detection configuration, parameter measurement, heat loss calculation, utilize original detection condition, by control algorithm, the most reasonable stall current is used, reduce single-phase maximum heat generation, reduce motor and controller thermal damage risk;In determining given torque loss, only determine rotor position this variable, the variable acquisition speed is fast, more timely control, and small amount of calculation.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a selective stall current protection method for a vehicle-mounted drive motor. Background Art

[0002] To ensure safe driving and a comfortable driving experience, vehicles must have an anti-slope function. This prevents the vehicle from moving in the opposite direction when a directional travel command is issued, requiring the motor to be locked. Conventional strategies immediately lock the motor upon receiving a lock command, resulting in a random rotor position and a potential lock current of 1.

[0003] This stall condition is extremely harsh on the motor and controller. During normal operation, the motor's three-phase current alternates between 0 and 1, generating uniform heat across all three phases. However, a stall condition occurs at a fixed angle, with fixed currents in at least one phase, where the current is between 0.866 and 1, causing extreme heat generation. This causes the motor and controller to heat up significantly, with a short ramp-up time and a long thermal response time for the temperature sensor. This means that even though the heating component has heated up, the temperature measured by the temperature sensor has not yet reached the actual component's temperature, or the thermal protection threshold. This prevents the controller from implementing thermal protection measures in a timely manner, potentially causing thermal damage to the motor and controller.

[0004] For example, a method for thermal balancing inverter power modules under stalled-rotor conditions, published in Chinese patent literature and with publication number CN 111711409 A, discloses the stall angle and temperature rise, the inverter's power module type, current, bus voltage, on / off resistance, inverter modulation mode, and stall position as inputs, and outputs the IGBT / Diode power. However, due to the excessive number of acquisition elements and slow variable acquisition speed, this method cannot achieve timely and effective control and requires a large amount of calculation. Summary of the Invention

[0005] In order to solve the problem in the prior art that motor stall thermal protection cannot be performed in real time through temperature measuring elements, the present invention provides a selective stall current protection method for a vehicle-mounted drive motor, which performs preventive control by controlling stall parameters and adopts a safe stall current without increasing costs, thereby reducing the risk of thermal damage to the motor and controller.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A selective locked-rotor current protection method for a vehicle-mounted drive motor comprises the following steps:

[0008] S1, detect the motor rotor position;

[0009] S2, detect the sum of single-phase current;

[0010] S3. Adjust the stall current. Within a 360-degree electrical angle range, the three-phase current values ​​vary with the electrical angle. Selecting the appropriate electrical angle position for stalling minimizes the motor and controller current values, and the sum of the three-phase current values, thereby minimizing single-phase heating power. By dividing the electrical angle, the position with the lowest three-phase current can be selected.

[0011] Preferably, S1 includes detecting the motor rotor position by a rotor position angle detection circuit, where the motor rotor position is an integer multiple of the electrical angle. The electrical angle is divided into integer multiples of 30° and divided into 12 positions within the 360° electrical angle range to facilitate control.

[0012] Preferably, S1 further includes dividing the motor rotor position into odd-numbered electrical angle positions and even-numbered electrical angle positions. The integer multiples of 30° are further divided into odd-numbered and integer multiples of 30°. The even-numbered positions of 30° include 0°, 60°, 120°, 180°, 240°, and 300° electrical angle positions, and the odd-numbered positions of 30° include 30°, 90°, 150°, 210°, 270°, and 330° electrical angle positions. This facilitates control.

[0013] Preferably, S2 includes calculating the sum of the three single-phase current values ​​at odd multiples of the electrical angle position and the sum of the three single-phase current values ​​at even multiples of the electrical angle position. The sum of the three single-phase current values ​​at even multiples of the electrical angle position is 1.732, and the sum of the three single-phase current values ​​at odd multiples of the electrical angle position is 2.

[0014] Preferably, S3 includes determining the motor heating power, which includes the single-phase maximum heating power and the sum of the three-phase heating power at different motor rotor positions. The motor heating power is mainly copper loss, which is proportional to the square of the current and the DC resistance of the winding. The single-phase maximum heating power and the sum of the three-phase heating power at odd and even electrical angle positions are compared, and the position with the minimum value is selected for stalling. This minimizes the motor stall loss.

[0015] Preferably, S3 includes determining the heating power of the controller, which includes the sum of the single-phase maximum heating power and the three-phase heating power at different motor rotor positions. The heating device of the controller is mainly a power module. The heating power is proportional to the duty cycle, the collector saturation voltage drop of the power module, the current, the switching frequency, the switching loss, the DC voltage, and the forward voltage drop of the diode. The single-phase maximum heating power and the sum of the three-phase heating power at the odd and even multiple electrical angle positions are compared, and the position with the minimum value is selected for stalling. This achieves the minimum stall loss of the controller.

[0016] Preferably, S3 includes adjusting the stall current by controlling stall parameters, which include the stalled motor position and the minimum and maximum single-phase currents. The temperature sensor has a response time of seconds, and the temperature rises rapidly during stall. The temperature sensor cannot promptly reflect the winding and power module temperatures, and the controller cannot provide timely thermal protection. Controlling the stall parameters and stall time to reduce the risk of thermal damage to the power module is the safest approach.

[0017] As a preferred method, the stall parameter is controlled for preventive control and thermal protection is provided by a temperature measuring element. When the stall parameter is adjusted, a pre-collection signal is simultaneously sent to the temperature measuring element. This enables pre-control and simultaneous activation of temperature control, greatly improving the response rate of the temperature measuring element.

[0018] The present invention has the following advantages:

[0019] (1) For the same torque requirement, within a 360° electrical angle cycle, the three-phase current values ​​at different angles are different. The rotor position of the motor is measured through the rotor position angle detection circuit, and the electrical angle corresponding to the minimum value among the three single-phase maximum current values ​​is selected for stalling. The stalling loss of the motor and controller is minimized, and thermal management is safer. (2) No additional detection configuration, parameter measurement, or heat loss calculation is added. The original detection conditions are utilized, and the most reasonable stalling current is adopted through the control algorithm to reduce the maximum heat generation of the single phase and reduce the risk of thermal damage to the motor and controller. (3) When determining the loss under a given torque, only the rotor position variable is judged. This variable has a fast acquisition speed, can be controlled more timely, and has a small amount of calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] To more clearly illustrate the technical solutions of the present invention or the prior art, the following briefly introduces the drawings required for the embodiments or the prior art descriptions. Obviously, the drawings described below are merely illustrative, and those skilled in the art can derive other implementation drawings based on the provided drawings without inventive effort.

[0021] Figure 1 It is a diagram of the steps of the method of the present invention.

[0022] Figure 2 It is a waveform diagram of the three-phase current in one electrical angle cycle in the present invention.

[0023] In the picture:

[0024] 1-U phase current; 2-W phase current; 3-V phase current; 4-maximum single-phase current; 5-square of maximum single-phase current; 6-sum of current values. DETAILED DESCRIPTION

[0025] The following specific embodiments illustrate the implementation of the present invention. Obviously, the embodiments described are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0026] like Figure 1 As shown, in a preferred embodiment, the present invention discloses a vehicle-mounted drive motor selective stall current protection method, comprising the following steps:

[0027] S1. Detect the motor rotor position. The rotor position is detected by the rotor position angle detection circuit. The motor rotor position is an integer multiple of the electrical angle. The electrical angle is divided into integer multiples of 30° and 12 positions within the 360° electrical angle range. The motor rotor position is divided into odd and even electrical angle positions. The integer multiples of 30° are further divided into odd and integer multiples of 30°. The even multiples of 30° include 0°, 60°, 120°, 180°, 240°, and 300° electrical angle positions, while the odd multiples of 30° include 30°, 90°, 150°, 210°, 270°, and 330° electrical angle positions.

[0028] S2. Detect the sum of the single-phase currents; calculate the sum of the three single-phase current values ​​at odd multiples of the electrical angle position and the sum of the three single-phase current values ​​at even multiples of the electrical angle position. When the three single-phase currents are even multiples, they are 0.866, 0, and 0.866, the maximum single-phase current is 0.866, and the sum of the three single-phase current values ​​is 1.732; when the three single-phase currents are odd multiples, they are 1, 0.5, and 0.5, the maximum single-phase current is 1, and the sum of the three single-phase current values ​​is 2.

[0029] S3. Adjust the stall current. Determine the motor heating power. The motor heating power includes the sum of the single-phase maximum heating power and the three-phase heating power at different motor rotor positions. The motor heating power is mainly copper loss, which is proportional to the square of the current and proportional to the DC resistance of the winding. Compare the single-phase maximum heating power and the sum of the three-phase heating power at odd and even electrical angle positions, and select the position with the minimum value for stalling. The sum of the single-phase maximum heating power and the three-phase heating power at the even position is 0.75 and 0.75 times the sum of the single-phase maximum heating power and the three-phase heating power at the odd position. This minimizes the motor stall loss. Determine the controller heating power. The controller heating power includes the sum of the single-phase maximum heating power and the three-phase heating power at different motor rotor positions. The controller's heating components are primarily power modules. Heat generation is proportional to the duty cycle, collector saturation voltage drop, current, switching frequency, switching losses, DC voltage, and diode forward voltage drop. The controller compares the maximum single-phase power and the sum of the three-phase power at odd and even electrical angle positions, respectively. The position with the minimum value is then selected for stalling. The sum of the maximum single-phase power and the three-phase power at even angle positions is 0.866 and 0.866 times the sum of the maximum single-phase power and the three-phase power at odd angle positions, respectively. This minimizes stall losses in the controller. Stall parameters are controlled for preventive control and thermal protection is provided by a temperature sensor. When adjusting the stall parameters, a pre-acquisition signal is simultaneously sent to the temperature sensor. This enables simultaneous pre-control and temperature control, significantly improving the temperature sensor's response speed. Upon receiving the pre-acquisition signal, the temperature sensor adjusts the cooling controller based on the rate of temperature change, significantly improving response speed.

[0030] When in use, within the 360° electrical angle range, the three-phase current values ​​change with the electrical angle. Selecting the appropriate electrical angle position for stalling can minimize the motor and controller current values, and the sum of the three-phase current values ​​is also minimized, that is, the single-phase heating power is minimized. By dividing the electrical angle, the position with the minimum three-phase current can be selected. Figure 2 As shown, it includes U-phase current 1, W-phase current 2, V-phase current 3, single-phase current maximum value 4, square of single-phase current maximum value 5 and sum of current values ​​6.

[0031] Control the stall parameters to adjust the stall current. Stall parameters include the stalled motor position and the maximum and minimum single-phase currents. The temperature sensor's response time is in seconds. During a stall, the temperature rises rapidly, and the temperature sensor cannot promptly reflect the winding and power module temperatures. Consequently, the controller cannot initiate thermal protection measures in a timely manner. Controlling the stall parameters and stall time is the safest approach to reduce the risk of thermal damage to the power module.

[0032] When the motor is stalled, the heating power P of the motor winding is D =I 2*R, I is the motor winding current, and R is the motor winding DC resistance. After the motor is designed, the winding resistance value is fixed. To reduce the heat power, the only way is to reduce the stall current. The controller module heat loss is divided into IGBT switching loss P T-SW 、IGBT conduction loss P T-CON , diode switching loss P D-SW , diode conduction loss P D-CON .

[0033] P T-SW ∝f(f sw ,E SW ,I C , V DC ), f sw Fixed value, E SW is the switching loss of the module, an inherent characteristic that cannot be changed, I C is the collector current of the IGBT, which is equal to the amplitude of the motor current and is controllable. The control purpose of this patent is to DC It is a DC voltage and cannot be changed.

[0034] P T-CON =V CE *I C *d,V CE is the saturation voltage drop of the module IGBT, which is an inherent characteristic of the component and cannot be changed. C It is the collector current of the IGBT, which is equal to the amplitude of the motor current and is controllable. The control purpose of this patent is that d is the module opening duty cycle during stall. Once the motor is designed and the stall torque target value is given, it is an inherent characteristic and cannot be changed.

[0035] P D-SW ∝f(f sw ,E ERC ,I F , V DC ), f sw Fixed value, E ERC is the switching loss of the module, an inherent characteristic that cannot be changed, I F is the diode freewheeling current, which can be considered equal to I C , V DC It is a DC voltage and cannot be changed.

[0036] P D-SW =V F *I F *(1-d), V F is the forward voltage drop of the module diode, which is an inherent characteristic of the component and cannot be changed. F is the diode freewheeling current, which can be considered equal to Ic, and d is the duty cycle, which cannot be changed.

[0037] When in use, the three-phase currents of the motor are: I U =Isinωt,I V =Isin(ωt-120°), I W =Isin(ωt+120°). See the table below for special angles. Per-unit value = actual current value / current reference value. The current reference value can be the maximum current.

[0038] Table 1. Three-phase current meter in electrical angle

[0039]

[0040] At electrical angles of 0°, 60°, 120°, 180°, 240°, and 300°, the three single-phase current values ​​(absolute values) are 0.866, 0, and 0.866, respectively. The maximum single-phase current is 0.866, and the sum of the three single-phase current values ​​is 1.732. At these angles, the stall current is most reasonable. The maximum single-phase heat generation power of the motor is P0 = (0.866 * I). 2 *R=0.75*I 2* R, the sum of the three-phase heating power of the motor is (0.866*I) 2 *R+0+(0.866*I) 2 *R=1.5*I 2* R. Controller's single-phase maximum heating power P K =(P T-SW +P T-CON +P D-SW +P D-CON )∝f(I), at this time the controller is single-phase maximum heating power = 0.866P K The sum of the three-phase heating power of the controller is 0.866P K +0+0.866P K =1.732P K .

[0041] At electrical angles of 30°, 90°, 150°, 210°, 270°, and 330°, the three single-phase current values ​​(absolute values) are 1, 0.5, and 0.5, respectively. The maximum single-phase current is 1, and the sum of the three single-phase current values ​​is 2. The stall current is the worst at these angles. The maximum single-phase heating power of the motor is P 30 =I 2* R, the sum of the three-phase heating power of the motor is I 2* R+(0.5*I) 2 *R+(0.5*I) 2 *R=1.5*I 2* R. The maximum single-phase heating power of the controller is P K , the sum of the three-phase heating power of the controller is PK +0.5P K +0.5P K =2P K The risk of stalling is greatest at these locations.

[0042] By performing stall at different electrical angles, there are obvious differences in heat loss, which are summarized as follows:

[0043] Table 2. Heat loss in electrical angle

[0044]

[0045] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made thereto. Therefore, such modifications and improvements, without departing from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A method for selective stall current protection of a vehicle-mounted drive motor, characterized in that: The steps include: S1. Detect the motor rotor position, divide the electrical angle into integer multiples of 30°, divide the electrical angle into 12 positions within the 360° electrical angle range, divide the motor rotor position into odd-number electrical angle positions and even-number electrical angle positions, and further divide the integer multiple positions of 30° into odd-number and integer multiples of 30°; S2, detect the sum of single-phase current; S3. Adjust the locked-rotor current, compare the single-phase maximum heating power and the sum of the three-phase heating power at odd-number multiple electrical angle positions and even-number multiple electrical angle positions, and select the position with the minimum value to lock the rotor.

2. The method for selective stall current protection of a vehicle-mounted drive motor according to claim 1, characterized in that: S1 includes detecting the motor rotor position through a rotor position angle detection circuit, where the motor rotor position is an integer multiple of the electrical angle.

3. A selective locked-rotor current protection method for a vehicle-mounted drive motor according to claim 1 or 2, characterized in that: S1 also includes dividing the motor rotor position into odd multiples of electrical angle positions and even multiples of electrical angle positions; the even multiples of 30° include 0°, 60°, 120°, 180°, 240°, and 300° electrical angle positions, and the odd multiples of 30° include 30°, 90°, 150°, 210°, 270°, and 330° electrical angle positions.

4. The method for selective stall current protection of a vehicle-mounted drive motor according to claim 3, characterized in that: S2 includes calculating the sum of the three single-phase current values ​​at odd multiples of the electrical angle position and the sum of the three single-phase current values ​​at even multiples of the electrical angle position; when the three single-phase currents are even multiples, they are 0.866, 0, and 0.866, the maximum single-phase current is 0.866, and the sum of the three single-phase current values ​​is 1.732; when the three single-phase currents are odd multiples, they are 1, 0.5, and 0.5, the maximum single-phase current is 1, and the sum of the three single-phase current values ​​is 2.

5. A vehicle-mounted drive motor selective locked-rotor current protection method according to claim 1 or 4, characterized in that: S3 includes determining the motor heating power, where the motor heating power includes the sum of the single-phase maximum heating power and the three-phase heating power at different motor rotor positions.

6. The method for selective locked-rotor current protection of a vehicle-mounted drive motor according to claim 5, characterized in that: S3 includes determining the heating power of the controller, where the heating power of the controller includes the sum of the single-phase maximum heating power and the three-phase heating power at different motor rotor positions.

7. The method for selective stall current protection of a vehicle-mounted drive motor according to claim 1, characterized in that: S3 includes adjusting the stall current by controlling the stall parameters, the stall parameters including the stall motor position and the minimum value of the single-phase maximum current; the sum of the single-phase maximum heating power and the three-phase heating power at the even multiple position is 0.866 times the sum of the single-phase maximum heating power and the three-phase heating power at the odd multiple position.

Images