Motor drive control method for preventing battery overcurrent of new energy automobile

Abstract

The invention relates to a motor drive control method for preventing battery overcurrent of a new energy automobile, which comprises the following steps of: distinguishing a battery recharging mode and a battery discharging mode according to an automobile state; when the motor is in a battery recharging mode, the maximum allowable kinetic energy feedback torque of the motor is calculated; when the motor is in the battery discharge mode, calculating the maximum allowable discharge driving torque of the motor; carrying out filtering processing on the calculated torque value, and calculating an output torque value; the motor can be effectively controlled only by monitoring the current state of the battery, the overcurrent of the battery can be prevented, and the design cost can be reduced.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle technology, and in particular to a motor drive control method for preventing overcurrent in new energy vehicle batteries. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the safety and reliability of power battery systems, as core energy components, have become a key focus of industry attention. Battery overcurrent refers to the phenomenon where the current exceeds the battery's maximum safety limit during charging and discharging, which may lead to serious consequences such as battery thermal runaway, lifespan degradation, or even fire and explosion. During vehicle operation, the motor drive system, as the main energy-consuming unit, directly affects the fluctuation characteristics of battery current through its control strategy. For example, during rapid acceleration, hill climbing, or sudden load changes, the rapid response of the motor torque may cause the battery to discharge a large current instantaneously, triggering the overcurrent protection of the battery management system (BMS), and even causing the high-voltage relay to melt. Existing protection technologies mainly rely on two types of solutions: one is to detect the battery overcurrent state and limit the power of the drive motor after the battery overcurrent occurs to prevent the risk of overcurrent failure from further expanding; the other is to monitor the current of each electrical appliance to calculate the total auxiliary drive current and further calculate the motor power limit requirements based on the battery capacity. Both of the above solutions can reduce the risk of overcurrent. However, the first solution is a post-overcurrent protection and does not solve the overcurrent problem. For the second solution, changes in electrical appliances will affect the control algorithm itself, and all electrical appliances need to have current sensor modules added, which increases the design cost. Summary of the Invention

[0003] The purpose of this invention is to provide a motor drive control method for preventing overcurrent in the batteries of new energy vehicles, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A method for controlling the motor drive to prevent overcurrent in the battery of a new energy vehicle includes:

[0006] Based on the vehicle's status, distinguish between battery charging mode and battery discharging mode;

[0007] When the motor is in battery recharge mode, the maximum allowable kinetic energy feedback torque of the motor is calculated;

[0008] When the motor is in battery discharge mode, calculate the maximum allowable discharge drive torque of the motor;

[0009] The calculated torque value is filtered to obtain the output torque value.

[0010] As a further explanation of the invention, the power battery voltage is obtained. Maximum permissible recharge pulse current of the power battery Power battery current I, motor speed n, motor real-time torque Calculate the maximum allowable kinetic energy feedback torque of the motor. The calculation formula is:

[0011] .

[0012] As a further explanation of the invention, the power battery voltage is obtained. Maximum permissible discharge pulse current of power battery Power battery current I, motor speed n, motor system efficiency Real-time torque of the motor Calculate the maximum allowable discharge drive torque of the motor. The calculation formula is:

[0013] .

[0014] As a further explanation of the invention, the variation range of the calculated torque value in the current cycle is limited based on the output torque value of the previous cycle.

[0015] As a further explanation of the invention, the difference between the calculated torque value of the current cycle and the output torque value of the previous cycle is calculated.

[0016] Let A be the threshold value for the change in the direction of increase;

[0017] When the difference is positive and greater than A, the output torque value of the current cycle is limited to the output torque value of the previous cycle plus A; otherwise, the calculated torque value of the current cycle is directly output.

[0018] Let B be the threshold for the change in the direction of decrease;

[0019] When the difference is negative and its absolute value is greater than B, the output torque value of the current cycle is restricted to the output torque value of the previous cycle minus B; otherwise, the calculated torque value of the current cycle is directly output.

[0020] As a further explanation of the invention, the threshold B for the amount of change in the decreasing direction is greater than the threshold A for the amount of change in the increasing direction.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention can effectively control the motor simply by monitoring the battery current status, which can prevent battery overcurrent and reduce design costs. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0024] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0025] like Figure 1 As shown: A motor drive control method for preventing overcurrent in new energy vehicle batteries, comprising:

[0026] Based on the vehicle's status, distinguish between battery charging mode and battery discharging mode;

[0027] When the motor is in battery recharge mode, the maximum allowable kinetic energy feedback torque of the motor is calculated;

[0028] When the motor is in battery discharge mode, calculate the maximum allowable discharge drive torque of the motor;

[0029] The calculated torque value is filtered to obtain the output torque value.

[0030] The above describes a process where overcurrent protection is achieved through closed-loop current control of the BMS (Battery Management System), torque smoothing is ensured through filtering, and jitter is eliminated by using different torque limit step sizes. The entire process eliminates the need to independently consider the real-time current consumption of each appliance. Effective motor control can be achieved simply by monitoring the battery current status, preventing battery overcurrent and reducing design costs.

[0031] Obtain the power battery voltage (Unit: V) Maximum permissible recharge pulse current of power battery (Unit: A), Power battery current I (Unit: A), Motor speed n (Unit: r / min), Real-time motor torque (Unit: N·m) Calculate the maximum allowable kinetic energy feedback torque of the motor. (Unit: N·m); The calculation formula is:

[0032] .

[0033] When the motor is in battery recharge mode, the focus is primarily on energy recovery control. This is combined with power... Torque and motor speed Physical relationship: The above calculation formula can be obtained, in which ( The calculation yields the additional torque allowed by the battery's remaining recharge capacity, plus the real-time torque of the motor. The sum of the two is the maximum allowable kinetic energy feedback torque of the motor. The motor's kinetic energy recovery torque does not exceed This algorithm takes into account both the power consumption of the auxiliary drive and its limiting function, thus maximizing energy recovery within a safe and permissible range.

[0034] Obtain the power battery voltage Maximum permissible discharge pulse current of power battery Power battery current I, motor speed n, motor system efficiency (Unit: %), Real-time torque of motor Calculate the maximum allowable discharge drive torque of the motor. The calculation formula is:

[0035] .

[0036] When the motor is in battery discharge mode, this primarily applies to conventional drives. (Power considerations are also taken into account.) Torque and motor speed Based on the physical relationship, the above calculation formula can be obtained, in which the efficiency of the motor system is... The system efficiency is obtained by checking the motor MAP using the motor speed and power; The calculation yields the torque that can be increased beyond the battery's remaining discharge capacity, plus the motor's real-time torque. The sum of the two is the maximum permissible discharge drive torque of the motor. This algorithm takes into account both the power consumption of the auxiliary drive and its limiting function, and can release energy to the maximum extent within the safe and permissible range.

[0037] The two modes mentioned above can calculate the upper limit of torque, but considering that the motor drive response will have a certain delay, when the actual current is at the edge of the battery's maximum current, it is easy to cause oscillation adjustment. Therefore, the following filtering algorithm is introduced.

[0038] The range of change in the calculated torque value for the current cycle is limited based on the output torque value of the previous cycle.

[0039] Furthermore, the difference between the calculated torque value of the current cycle and the output torque value of the previous cycle is calculated;

[0040] Let A be the threshold value for the change in the direction of increase;

[0041] When the difference is positive and greater than A, the output torque value of the current cycle is limited to the output torque value of the previous cycle plus A; otherwise, the calculated torque value of the current cycle is directly output.

[0042] Let B be the threshold for the change in the direction of decrease;

[0043] When the difference is negative and its absolute value is greater than B, the output torque value of the current cycle is restricted to the output torque value of the previous cycle minus B; otherwise, the calculated torque value of the current cycle is directly output.

[0044] The threshold B for the amount of change in the decreasing direction is greater than the threshold A for the amount of change in the increasing direction.

[0045] The above filtering algorithm outputs torque values ​​by increasing or decreasing step size limits. Different step sizes are used to ensure data smoothness and protection requirements. Increasing or decreasing different step size limits by increasing torque can effectively prevent jitter. To further ensure that the system does not overcurrent, the torque reduction step size is usually set to be larger. The A and B values ​​are calibrated according to the actual situation.

[0046] Example 1

[0047] When the vehicle is in kinetic energy recovery mode, the motor is in battery recharging mode and the torque is negative.

[0048] Input power battery voltage 600V, maximum allowable recharge pulse current of the power battery The current is 200A, the power battery current I is 60A, the motor speed is 6000r / min, and the real-time motor torque is... The value is 80 N·m; based on the calculation formula for the maximum allowable kinetic energy feedback torque of the motor, the maximum allowable kinetic energy feedback torque of the motor is output. ;

[0049] +80 = 213.7 N·m;

[0050] Calculated torque value for the current cycle Perform filtering, such as filtering the output torque value from the previous cycle. If the torque value is 200 N·m, then the output torque value of the current cycle is limited to the output torque value of the previous cycle plus A (2 N·m). In this case, the output torque value of the current cycle is limited to 202 N·m. For example, if the output torque value of the previous cycle is 230 N·m, then the output torque value of the current cycle is limited to the output torque value of the previous cycle minus B (10 N·m). In this case, the output torque value of the current cycle is limited to 220 N·m. The calculation for the next cycle is still 213.7 N·m, so the output is 213.7 N·m.

[0051] Example 2

[0052] When the vehicle is in driving mode, the motor is in battery discharge mode and the torque is positive.

[0053] Input power battery voltage 600V, maximum allowable discharge pulse current of the power battery The current is 200A, the power battery current I is 60A, the motor speed is 6000r / min, and the real-time motor torque is... 80 N·m Based on the formula for calculating the maximum permissible discharge drive torque of the motor, the maximum permissible discharge drive torque of the motor is output. ;

[0054] +80 = 200.33;

[0055] Calculated torque value for the current cycle Perform filtering, such as filtering the output torque value from the previous cycle. If the torque value is 190 N·m, then the output torque value of the current cycle is limited to the output torque value of the previous cycle plus A (2 N·m). In this case, the output torque value of the current cycle is limited to 192 N·m. For example, the output torque value of the previous cycle... If the torque value is 215 N·m, then the output torque value of the current cycle is limited to the output torque value of the previous cycle minus B (10 N·m). At this time, the output torque value of the current cycle is limited to 205 N·m. The calculation for the next cycle is still 200.33 N·m, so the output is 200.33 N·m.

[0056] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A motor drive control method for preventing overcurrent in new energy vehicle batteries, characterized in that, include: Based on the vehicle's status, distinguish between battery charging mode and battery discharging mode; When the motor is in battery recharge mode, the maximum allowable kinetic energy feedback torque of the motor is calculated; When the motor is in battery discharge mode, calculate the maximum allowable discharge drive torque of the motor; The calculated torque value is filtered to obtain the output torque value.

2. The motor drive control method for preventing overcurrent in new energy vehicle batteries as described in claim 1, characterized in that, Obtain the power battery voltage Maximum permissible recharge pulse current of the power battery Power battery current I, motor speed n, motor real-time torque Calculate the maximum allowable kinetic energy feedback torque of the motor. The calculation formula is: 。 3. The motor drive control method for preventing overcurrent in new energy vehicle batteries as described in claim 1, characterized in that, Obtain the power battery voltage Maximum permissible discharge pulse current of power battery Power battery current I, motor speed n, motor system efficiency Real-time torque of the motor Calculate the maximum allowable discharge drive torque of the motor. The calculation formula is: 。 4. The motor drive control method for preventing overcurrent in new energy vehicle batteries as described in claim 2 or 3, characterized in that, The range of change in the calculated torque value for the current cycle is limited based on the output torque value of the previous cycle.

5. The motor drive control method for preventing overcurrent in new energy vehicle batteries as described in claim 4, characterized in that, Calculate the difference between the calculated torque value of the current cycle and the output torque value of the previous cycle; Let A be the threshold value for the change in the direction of increase; When the difference is positive and greater than A, the output torque value of the current cycle is limited to the output torque value of the previous cycle plus A. Otherwise, directly output the calculated torque value for the current cycle; Let B be the threshold for the change in the direction of decrease; When the difference is negative and its absolute value is greater than B, the output torque value of the current cycle is restricted to the output torque value of the previous cycle minus B; otherwise, the calculated torque value of the current cycle is directly output.

6. The motor drive control method for preventing overcurrent in new energy vehicle batteries as described in claim 5, characterized in that, The threshold B for the amount of change in the decreasing direction is greater than the threshold A for the amount of change in the increasing direction.

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