Power battery heating method for asynchronous motor of electric vehicle

Abstract

A method for heating a power battery of an asynchronous motor of an electric vehicle comprises the following steps: 1) setting a first speed threshold and a second speed threshold of a drive motor; 2) obtaining the current real-time speed of the drive motor and outputting an excitation current command and a torque current command in the following manner to control the waste heat output power of the drive motor: 2-1) if the real-time speed is less than the first speed threshold, setting the excitation current command output value of the drive motor to a first excitation current component vector, and the torque current command output value to a first torque current component vector; 2-2) if the second speed threshold is greater than or equal to the real-time speed or greater than the first speed threshold, setting the excitation current command output value of the drive motor to a second excitation current component vector, and the torque current command output value to a second torque current component vector; 2-3) if the real-time speed is greater than or equal to the second speed threshold, setting the excitation current command output value of the drive motor to a third excitation current component vector, and the torque current command output value to a third torque current component vector.

Description

Technical Field

[0001] The present invention relates to the field of electric vehicles, and in particular to a method for heating a power battery of an asynchronous motor of an electric vehicle. Background Art

[0002] As we all know, electric vehicles are powered by electricity, with power batteries driving the vehicle's electric motor, thereby propelling the vehicle. The primary function of a power battery is to provide continuous power to the vehicle and support cyclical charging. However, current mainstream power batteries are unable to maintain their own temperature within the normal operating range when operating in low-temperature environments. This drop in temperature slows the battery's internal reactions, resulting in a decrease in its charge and discharge performance, and in severe cases, even affecting its lifespan and safety. Therefore, when using power batteries to drive vehicles in low-temperature environments, heating technology is required to maintain the battery's operating temperature within the normal range to ensure proper battery performance.

[0003] At present, the mainstream power battery heating technologies are divided into the following two categories:

[0004] ① Direct heating: For example, external equipment such as heaters are placed on the surface of the power battery to heat the battery to increase the operating temperature of the battery.

[0005] Although the "direct heating" method can make the power battery simple and direct and can quickly increase the operating temperature of the battery, it requires additional equipment and energy, and has certain requirements for the uniformity of battery heating. Not only is the cost high, but it also requires a large amount of electricity to provide heat, which leads to a reduction in the vehicle's endurance and a serious waste of the limited and precious electricity resources of electric vehicles.

[0006] ② Indirect heating: For example, the waste heat generated by the drive motor during operation is transferred to the power battery for heating using a medium in a heat transfer unit. The medium used can be a recyclable gas or liquid.

[0007] As we all know, the output voltage of the drive motor controller has an upper limit. For example, in a certain model of electric vehicle, when the speed of the drive motor increases to 9000 rpm, the output voltage of the drive motor controller will reach the upper limit, and the speed of the drive motor can no longer be increased by increasing the output voltage. Since the output voltage of the drive motor controller is the product of the excitation current and the speed of the drive motor, that is, when the output voltage of the drive motor controller cannot be increased any further (i.e., it remains fixed), if you want to increase the speed of the drive motor again, you can only reduce the excitation current to achieve the goal. However, once the excitation current is reduced, the waste heat output power of the drive motor will not be able to meet the heating requirements of the power battery in a low-temperature environment.

[0008] Publication No. CN113794416A, "Motor Control Method, Device, Power System, Vehicle, and Storage Medium," uses an asynchronous motor as the vehicle's drive motor. By increasing the excitation current, the motor's waste heat output is increased. Active power losses in the motor windings and core are transferred as waste heat to the power battery. This waste heat is generated solely through a strong excitation method that enhances air gap magnetic field saturation (i.e., only increasing the excitation current is used to increase the motor's waste heat output) to meet the power battery's heating needs in low-temperature environments. Based on the above analysis, this method is clearly only suitable for heating the power battery at low vehicle speeds. Once the vehicle reaches high speeds, not only will the increased excitation current be unable to meet the power battery's heating needs, but it will also result in a significant waste of electrical energy, significantly reducing the electric vehicle's range. Summary of the Invention

[0009] The purpose of the present invention is to address the corresponding deficiencies in the existing technology and provide a power battery heating method for an asynchronous motor of an electric vehicle. By reasonably controlling the excitation current and torque current distribution corresponding to the working current of the drive motor, the heating requirements of the power battery in a low-temperature environment can be fully met regardless of whether the vehicle is driving at low speed or high speed, thereby saving the vehicle's electrical energy resources and greatly improving the endurance of the electric vehicle.

[0010] The purpose of the present invention is to adopt the following scheme to achieve:

[0011] A method for heating a power battery of an asynchronous motor of an electric vehicle comprises the following steps:

[0012] 1) Setting a first speed threshold and a second speed threshold of the drive motor;

[0013] 2) Obtaining the current real-time speed of the drive motor, comparing the real-time speed with the first speed threshold and the second speed threshold, and outputting an excitation current command and a torque current command in the following manner to control the waste heat output power of the drive motor:

[0014] 2-1) If the real-time speed is less than the first speed threshold, the excitation current command output value of the drive motor is set to the first excitation current component vector, and the torque current command output value is set to the first torque current component vector;

[0015] 2-2) If the second speed threshold ≥ the real-time speed ≥ the first speed threshold, the excitation current command output value of the drive motor is set to the second excitation current component vector, and the torque current command output value is set to the second torque current component vector;

[0016] 2-3) If the real-time speed is greater than the second speed threshold, the excitation current command output value of the drive motor is set to the third excitation current component vector, and the torque current command output value is set to the third torque current component vector.

[0017] Preferably, the first speed threshold is obtained by:

[0018] ① Set the DC voltage utilization threshold range of the drive motor controller;

[0019] ② Increase the speed of the drive motor according to the preset step size;

[0020] ③ When the DC voltage utilization rate of the drive motor controller reaches the DC voltage utilization rate threshold range, the real-time speed of the drive motor at this time is taken as the first speed threshold.

[0021] Preferably, the DC voltage utilization rate of the drive motor controller is calculated according to the following formula:

[0022]

[0023] Where m is the DC voltage utilization rate of the drive motor controller, U s is the peak value of the sine wave of the three-phase AC phase voltage at the output end of the drive motor controller, u dc is the DC voltage at the input of the motor controller.

[0024] Preferably, the second speed threshold is obtained by:

[0025] ① Increase the speed of the drive motor according to the preset step size;

[0026] ② When the energy loss power of the drive motor and the motor controller is greater than the waste heat output power of the drive motor, the real-time speed of the drive motor at this time is taken as the second speed threshold.

[0027] Preferably, the first excitation current component vector and the first torque current component vector are determined by querying a first current distribution reference table according to the current target torque and real-time speed of the driving motor;

[0028] The second excitation current component vector and the second torque current component vector are determined by querying a second current distribution reference table according to the current target torque and real-time speed of the driving motor;

[0029] The third excitation current component vector and the third torque current component vector are determined by querying a third current distribution reference table according to the current target torque and real-time speed of the driving motor.

[0030] Preferably, the data in the first current distribution reference table are determined in a bench test in the following manner:

[0031] ① Set the initial value of the driving motor's operating current and the current single change;

[0032] ② After the real-time speed of the drive motor reaches the preset drive motor speed using the dynamometer, adjust the operating current of the drive motor according to the single current change until the real-time output torque of the drive motor is equal to the preset drive motor target torque, and record the drive motor operating current value at this time;

[0033] ③ Change the preset target torque of the drive motor and repeat steps ① to ③ until all the drive motor operating current values ​​corresponding to the preset target torque of the drive motor at the drive motor speed are recorded;

[0034] ④ Change the preset drive motor speed and repeat steps ① to ④ until all preset drive motor speeds and drive motor target torques corresponding to the drive motor operating current values ​​are recorded and stored in the first current distribution reference table;

[0035] ⑤ After setting the waste heat demand power according to the factory parameters of the power battery, the excitation current component vector and the torque current component vector corresponding to the operating current value of each drive motor in the first current distribution reference table are determined in the following manner and stored in the first current distribution reference table:

[0036] (1) Select any driving motor operating current value whose excitation current component and torque current component are not determined in the first current distribution reference table as the current driving motor operating current, so that the current driving motor output torque and real-time speed both reach the torque value and speed value corresponding to the driving motor operating current value in the first current distribution reference table;

[0037] ⑵In Adjust the angle between the excitation current component vector corresponding to the operating current value of the drive motor and the M-axis in the MT coordinate system within the range until the waste heat output power of the drive motor is greater than the waste heat power required by the power battery. Record the value of the angle at this time, and calculate the excitation current component vector and torque current component vector corresponding to the operating current value of the drive motor according to the following first current distribution formula:

[0038] i M-1 =i1×cos(θ1)

[0039] i T-1 =i1×sin(θ1)

[0040] Where i1 is the working current value of the driving motor in the first current distribution reference table, i M-1 The excitation current component corresponding to the working current value of the driving motor in the first current distribution reference table, i T-1 is the torque current component vector corresponding to the working current value of the driving motor in the first current distribution reference table, θ1 is the angle between the excitation current component vector corresponding to the working current value of the driving motor in the first current distribution reference table and the M axis in the MT coordinate system;

[0041] ⑶ Repeat steps ⑴ to ⑵ until the excitation current component vectors and torque current component vectors corresponding to the working current values ​​of all driving motors in the first current distribution reference table are determined.

[0042] Preferably, the data in the second current distribution reference table are determined in a bench test in the following manner:

[0043] ① Set the initial value of the driving motor's operating current and the current single change;

[0044] ② After the real-time speed of the drive motor reaches the preset drive motor speed using the dynamometer, adjust the operating current of the drive motor according to the single current change until the real-time output torque of the drive motor is equal to the preset drive motor target torque, and record the drive motor operating current value at this time;

[0045] ③ Change the preset target torque of the drive motor and repeat steps ① to ③ until all the drive motor operating current values ​​corresponding to the preset target torque of the drive motor at the drive motor speed are recorded;

[0046] ④ Change the preset drive motor speed and repeat steps ① to ④ until all the preset drive motor speeds and drive motor target torques corresponding to the drive motor operating current values ​​are recorded and stored in the second current distribution reference table;

[0047] ⑤ After setting the waste heat demand power according to the factory parameters of the power battery, determine the excitation current component vector and torque current component vector corresponding to the operating current value of each drive motor in the second current distribution reference table in the following manner and store them in the second current distribution reference table:

[0048] (1) Select any driving motor operating current value whose excitation current component and torque current component are not determined in the second current distribution reference table as the current driving motor operating current, so that the current driving motor output torque and real-time speed both reach the torque value and speed value corresponding to the driving motor operating current value in the second current distribution reference table;

[0049] ⑵In Adjust the angle between the excitation current component vector corresponding to the operating current value of the drive motor and the M-axis in the MT coordinate system within the specified range until the waste heat output power of the drive motor is greater than the waste heat power required by the power battery. Record the value of the angle at this time and calculate the excitation current component vector and torque current component vector corresponding to the operating current value of the drive motor according to the following second current distribution formula:

[0050] i M-2 =i2×cos(θ2)

[0051] i T-2 =i²×sin(θ²)

[0052] Where i2 is the working current value of the driving motor in the second current distribution reference table, i M-2 The excitation current component corresponding to the working current value of the driving motor in the second current distribution reference table, i T-2 is the torque current component vector corresponding to the working current value of the driving motor in the second current distribution reference table, θ2 is the angle between the excitation current component vector corresponding to the working current value of the driving motor in the second current distribution reference table and the M axis in the MT coordinate system;

[0053] ⑶ Repeat steps ⑴ to ⑵ until the excitation current component vectors and torque current component vectors corresponding to the working current values ​​of all driving motors in the second current distribution reference table are determined.

[0054] Preferably, the data in the third current distribution reference table are determined in a bench test in the following manner:

[0055] ① Set the initial value of the driving motor's operating current and the current single change;

[0056] ② After the real-time speed of the drive motor reaches the preset drive motor speed using the dynamometer, adjust the operating current of the drive motor according to the single current change until the real-time output torque of the drive motor is equal to the preset drive motor target torque, and record the drive motor operating current value at this time;

[0057] ③ Change the preset target torque of the drive motor and repeat steps ① to ③ until all the drive motor operating current values ​​corresponding to the preset target torque of the drive motor at the drive motor speed are recorded;

[0058] ④ Change the preset drive motor speed and repeat steps ① to ④ until all the preset drive motor speeds and drive motor target torques corresponding to the drive motor operating current values ​​are recorded and stored in the third current distribution reference table;

[0059] ⑤ Calculate the excitation current component vector and torque current component vector corresponding to the working current value of each drive motor in the third current distribution reference table according to the following third current distribution formula, and store them in the third current distribution reference table:

[0060]

[0061]

[0062] Where i3 is the working current value of the driving motor in the third current distribution reference table, i M-3 is the excitation current component corresponding to the working current value of the driving motor in the third current distribution reference table, i T-3is the torque current component vector corresponding to the working current value of the driving motor in the third current distribution reference table, and π is the radian corresponding to the flat angle.

[0063] The advantage of the present invention is that, by reasonably controlling the excitation current and torque current distribution corresponding to the working current of the drive motor, the heating requirements of the power battery in a low-temperature environment can be fully met regardless of whether the car is driving at low speed or high speed, thereby saving the car's electrical energy resources and greatly improving the endurance of the electric vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 This is a schematic diagram of the connection between the drive motor, drive motor controller, heat transfer unit and power battery of the present invention;

[0065] Figure 2 is a flow chart of the present invention;

[0066] Figure 3 A schematic diagram of the angle between the excitation current component vector corresponding to the working current value of the driving motor in the first current distribution reference table and the M axis in the MT coordinate system;

[0067] Figure 4 This is a schematic diagram of the angle between the excitation current component vector corresponding to the working current value of the driving motor in the second current distribution reference table and the M axis in the MT coordinate system. DETAILED DESCRIPTION

[0068] like Figures 1 to 4 As shown, a method for heating a power battery of an asynchronous motor of an electric vehicle comprises the following steps:

[0069] 1) Setting the first speed threshold and the second speed threshold of the drive motor respectively;

[0070] 2) Obtaining the current real-time speed of the drive motor, comparing the real-time speed with the first speed threshold and the second speed threshold, and outputting an excitation current command and a torque current command in the following manner to control the waste heat output power of the drive motor:

[0071] 2-1) If the real-time speed is less than the first speed threshold, the excitation current command output value of the drive motor is set to the first excitation current component, and the torque current command output value is set to the first torque current component. The heating mode at this time is the first heating mode;

[0072] The first excitation current component vector and the first torque current component vector are determined by querying a first current distribution reference table according to the current target torque and real-time speed of the driving motor;

[0073] In this embodiment, the data in the first current distribution reference table are determined in a bench test in the following manner:

[0074] ① Set the initial value of the driving motor's operating current and the current single change;

[0075] ② After the real-time speed of the drive motor reaches the preset drive motor speed using the dynamometer, adjust the operating current of the drive motor according to the single current change until the real-time output torque of the drive motor is equal to the preset drive motor target torque, and record the drive motor operating current value at this time;

[0076] At this time, the current output torque and speed of the drive motor correspond to the operating current value of the drive motor;

[0077] ③ Maintaining the preset drive motor speed unchanged, changing the preset drive motor target torque, and repeating steps ① to ③ until all drive motor operating current values ​​corresponding to the preset drive motor target torques at the drive motor speed are recorded;

[0078] ④ Change the preset drive motor speed and repeat steps ① to ④ until all preset drive motor speeds and drive motor target torques corresponding to the drive motor operating current values ​​are recorded and stored in the first current distribution reference table;

[0079] ⑤ After setting the waste heat demand power according to the factory parameters of the power battery, the excitation current component vector and the torque current component vector corresponding to the operating current value of each drive motor in the first current distribution reference table are determined in the following manner and stored in the first current distribution reference table:

[0080] (1) Select any driving motor operating current value whose excitation current component and torque current component are not determined in the first current distribution reference table as the current driving motor operating current, so that the current driving motor output torque and real-time speed both reach the torque value and speed value corresponding to the driving motor operating current value in the first current distribution reference table;

[0081] ⑵In Adjust the angle between the excitation current component vector corresponding to the operating current value of the drive motor and the M-axis in the MT coordinate system within the specified range until the waste heat output power of the drive motor is greater than the waste heat power demand of the power battery. Record the value of the angle at this time and substitute it into the following formula to calculate the excitation current component vector and torque current component vector corresponding to the operating current value of the drive motor:

[0082] i M-1 =i1×cos(θ1)

[0083] i T-1 =i1×sin(θ1)

[0084] Where i1 is the working current value of the driving motor in the first current distribution reference table, i M-1The excitation current component corresponding to the working current value of the driving motor in the first current distribution reference table, i T-1 is the torque current component corresponding to the working current value of the driving motor in the first current distribution reference table, θ1 is the angle between the excitation current component corresponding to the working current value of the driving motor in the first current distribution reference table and the M axis in the MT coordinate system, that is, θ1 is the inverse tangent function The function value of ;

[0085] ⑶ Repeat steps ⑴ to ⑵ until the excitation current component vectors and torque current component vectors corresponding to all the driving motor working current values ​​in the first current distribution reference table are determined.

[0086] According to the above method, the first current distribution reference table finally obtained is shown in Table 1:

[0087] Table 1 First current distribution reference table

[0088]

[0089] In Table 1, n1, n2, n3, ..., n m are all the speed values ​​of the driving motor, τ1, τ2, τ3, ..., τ m are the target torque values ​​of the driving motor, i 1-m-k It means that in the first heating mode, the target torque of the driving motor is τ k , speed is n m The working current value of the drive motor is i M-1-m-k It means that in the first heating mode, the target torque of the driving motor is τ k , speed is n m The excitation current component corresponding to the working current value of the drive motor is i T-1-m-k It means that in the first heating mode, the target torque of the driving motor is τ k , speed is n m The torque current component vector corresponding to the working current value of the drive motor when .

[0090] 2-2) If the second speed threshold ≥ the real-time speed ≥ the first speed threshold, the excitation current command output value of the drive motor is set to the second excitation current component, and the torque current command output value is set to the second torque current component. The heating mode at this time is the second heating mode;

[0091] The second excitation current component vector and the second torque current component vector are determined by querying a second current distribution reference table according to the current target torque and real-time speed of the driving motor;

[0092] In this embodiment, the data in the second current distribution reference table are determined in a bench test in the following manner:

[0093] ① Set the initial value of the driving motor's operating current and the current single change;

[0094] ② After the real-time speed of the drive motor reaches the preset drive motor speed using the dynamometer, adjust the operating current of the drive motor according to the single current change until the real-time output torque of the drive motor is equal to the preset drive motor target torque, and record the drive motor operating current value at this time;

[0095] At this time, the current output torque and speed of the drive motor correspond to the operating current value of the drive motor;

[0096] ③ Maintaining the preset drive motor speed unchanged, changing the preset drive motor target torque, and repeating steps ① to ③ until all drive motor operating current values ​​corresponding to the preset drive motor target torques at the drive motor speed are recorded;

[0097] ④ Change the preset drive motor speed and repeat steps ① to ④ until all the preset drive motor speeds and drive motor target torques corresponding to the drive motor operating current values ​​are recorded and stored in the second current distribution reference table;

[0098] ⑤ After setting the waste heat demand power according to the factory parameters of the power battery, determine the excitation current component vector and torque current component vector corresponding to the operating current value of each drive motor in the second current distribution reference table in the following manner and store them in the second current distribution reference table:

[0099] (1) Select any driving motor operating current value whose excitation current component and torque current component are not determined in the second current distribution reference table as the current driving motor operating current, so that the current driving motor output torque and real-time speed both reach the torque value and speed value corresponding to the driving motor operating current value in the second current distribution reference table;

[0100] ⑵In Adjust the angle between the excitation current component vector corresponding to the operating current value of the drive motor and the M-axis in the MT coordinate system within the specified range until the waste heat output power of the drive motor is greater than the waste heat power demand of the power battery. Record the value of the angle at this time and substitute it into the following formula to calculate the excitation current component vector and torque current component vector corresponding to the operating current value of the drive motor:

[0101] i M-2 =i2×cos(θ2)

[0102] i T-2 =i2×sin(θ2)

[0103] Where i2 is the working current value of the driving motor in the second current distribution reference table, i M-2The excitation current component corresponding to the working current value of the driving motor in the second current distribution reference table, i T-2 is the torque current component corresponding to the working current value of the driving motor in the second current distribution reference table, θ2 is the angle between the excitation current component corresponding to the working current value of the driving motor in the second current distribution reference table and the M axis in the MT coordinate system, that is, θ2 is the inverse tangent function The function value of ;

[0104] ⑶ Repeat steps ⑴ to ⑵ until the excitation current component vectors and torque current component vectors corresponding to all the driving motor working current values ​​in the second current distribution reference table are determined.

[0105] According to the above method, the second current distribution reference table finally obtained is shown in Table 2:

[0106] Table 2 Second current distribution reference table

[0107]

[0108] In Table 2, n1, n2, n3, ..., n m are all the speed values ​​of the driving motor, τ1, τ2, τ3, ..., τ m are the target torque values ​​of the driving motor, i 2-m-k It means that in the second heating mode, the target torque of the driving motor is τ k , speed is n m The working current value of the drive motor is i M-2-m-k It means that in the second heating mode, the target torque of the driving motor is τ k , speed is n m The excitation current component corresponding to the working current value of the drive motor is i T-2-m-k It means that in the second heating mode, the target torque of the driving motor is τ k , speed is n m The torque current component vector corresponding to the working current value of the drive motor when .

[0109] 2-3) If the real-time speed is greater than the second speed threshold, the excitation current command output value of the drive motor is set to the third excitation current component, and the torque current command output value is set to the third torque current component. The heating mode at this time is the third heating mode.

[0110] The third excitation current component vector and the third torque current component vector are determined by querying a third current distribution reference table according to the current target torque and real-time speed of the driving motor.

[0111] In this embodiment, the data in the third current distribution reference table are determined in bench tests in the following manner:

[0112] ① Set the initial value of the driving motor's operating current and the current single change;

[0113] ② After the real-time speed of the drive motor reaches the preset drive motor speed using the dynamometer, adjust the operating current of the drive motor according to the single current change until the real-time output torque of the drive motor is equal to the preset drive motor target torque, and record the drive motor operating current value at this time;

[0114] At this time, the current output torque of the drive motor and the speed of the drive motor correspond to the operating current value of the drive motor.

[0115] ③ Maintaining the preset drive motor speed unchanged, changing the preset drive motor target torque, and repeating steps ① to ③ until all drive motor operating current values ​​corresponding to the preset drive motor target torques at the drive motor speed are recorded;

[0116] ④ Change the preset drive motor speed and repeat steps ① to ④ until all the preset drive motor speeds and drive motor target torques corresponding to the drive motor operating current values ​​are recorded and stored in the third current distribution reference table;

[0117] ⑤ Calculate the excitation current component and torque current component corresponding to the operating current value of each drive motor in the third current distribution reference table according to the following third current distribution formula, and record them in the third current distribution reference table:

[0118]

[0119]

[0120] Where i3 is the working current value of the driving motor in the third current distribution reference table, i M-3 is the excitation current component corresponding to the working current value of the driving motor in the third current distribution reference table, i T-3 is the torque current component vector corresponding to the working current value of the driving motor in the third current distribution reference table, and π is the radian corresponding to the flat angle.

[0121] According to the above method, the third current distribution reference table finally obtained is shown in Table 3:

[0122] Table 3 Third current distribution reference table

[0123]

[0124] In Table 3, n1, n2, n3, ..., n m are all the speed values ​​of the driving motor, τ1, τ2, τ3, ..., τ m are the target torque values ​​of the driving motor, i 3-m-kIt means that in the third heating mode, the target torque of the driving motor is τ k , speed is n m The working current value of the drive motor is i M-3-m-k It means that in the third heating mode, the target torque of the driving motor is τ k , speed is n m The excitation current component corresponding to the working current value of the drive motor is i T-3-m-k It means that in the third heating mode, the target torque of the driving motor is τ k , speed is n m The torque current component vector corresponding to the working current value of the drive motor when .

[0125] The first speed threshold and the second speed threshold are both calibrated values, obtained through bench testing.

[0126] In this embodiment, the first speed threshold is obtained in a bench test in the following manner:

[0127] ① Set the DC voltage utilization threshold range of the drive motor controller;

[0128] ② Use the dynamometer to drive the motor shaft of the drive motor to rotate, and increase the speed of the drive motor according to the preset step size;

[0129] ③ When the DC voltage utilization rate of the drive motor controller reaches the DC voltage utilization rate threshold range, the real-time speed of the drive motor at this time is taken as the first speed threshold.

[0130] In the bench test, the DC voltage utilization rate of the drive motor controller can be calculated according to the following formula:

[0131]

[0132] Where m is the DC voltage utilization rate of the drive motor controller, U s is the peak value of the sine wave of the three-phase AC phase voltage at the output end of the drive motor controller, u dc is the DC voltage at the input of the motor controller.

[0133] Since the DC voltage utilization ratio m of the drive motor controller generally ranges from 0 to 1.1, when the DC voltage utilization ratio is greater than 1, harmonics are introduced into the drive motor current, causing torque fluctuations and increasing motor noise. Since a higher DC voltage utilization ratio increases the harmonics and noise generated, to maximize the use of input electrical energy while minimizing noise generated during motor operation, in this embodiment, the DC voltage utilization ratio threshold of the drive motor controller is set to a range of 1 to 1.05.

[0134] The second speed threshold is obtained in a bench test by the following method:

[0135] ① Use the dynamometer to drive the motor shaft of the drive motor to rotate, and increase the speed of the drive motor according to the preset step size;

[0136] ② When the energy loss power of the drive motor and the motor controller is greater than the waste heat output power of the drive motor, the real-time speed of the drive motor at this time is taken as the second speed threshold.

[0137] In this embodiment, the energy loss power of the drive motor and the motor controller, and the waste heat output power of the drive motor can be obtained by a power analyzer installed on the test bench.

[0138] After setting the first speed threshold and the second speed threshold, the vehicle selects the heating mode of the power battery according to the real-time speed of the drive motor while driving. In the corresponding heating mode, the excitation current component vector and the torque current component vector are obtained by looking up the table according to the current target torque of the drive motor and the real-time speed, and the output of the driving motor working current is adjusted.

[0139] It is particularly important to note that if the current drive motor target torque or real-time speed does not have corresponding data in the current distribution reference table, it is necessary to first use the interpolation method to determine the current drive motor target torque and the drive motor operating current corresponding to the real-time speed, and then calculate the corresponding excitation current component vector and torque current component vector according to each current distribution formula.

[0140] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made to the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for heating a power battery of an asynchronous motor of an electric vehicle, characterized in that: The following steps are involved: 1) Set the first speed threshold and second speed threshold of the drive motor: 1-1) The first speed threshold is obtained by: ① Set the DC voltage utilization threshold range of the drive motor controller; ② Increase the speed of the drive motor according to the preset step size; ③ When the DC voltage utilization rate of the drive motor controller reaches the DC voltage utilization rate threshold range, the real-time speed of the drive motor at this time is taken as the first speed threshold; 1-2) The second speed threshold is obtained by: ① Increase the speed of the drive motor according to the preset step size; ② When the energy loss power of the drive motor and the motor controller is greater than the waste heat output power of the drive motor, the real-time speed of the drive motor at this time is taken as the second speed threshold; 2) Obtaining the current real-time speed of the drive motor, comparing the real-time speed with the first speed threshold and the second speed threshold, and outputting an excitation current command and a torque current command in the following manner to control the waste heat output power of the drive motor: 2-1) If the real-time speed is less than the first speed threshold, the excitation current command output value of the drive motor is the first excitation current component vector, and the torque current command output value is the first torque current component vector; 2-2) If the second speed threshold ≥ the real-time speed ≥ the first speed threshold, the excitation current command output value of the drive motor is the second excitation current component vector, and the torque current command output value is the second torque current component vector; 2-3) If the real-time speed is greater than the second speed threshold, the excitation current command output value of the drive motor is the third excitation current component vector, and the torque current command output value is the third torque current component vector.

2. The method for heating a power battery of an asynchronous motor of an electric vehicle according to claim 1, characterized in that: The DC voltage utilization rate of the drive motor controller is calculated according to the following formula: Where m is the DC voltage utilization rate of the drive motor controller, U s is the peak value of the sine wave of the three-phase AC phase voltage at the output end of the drive motor controller, u dc is the DC voltage at the input of the motor controller.

3. The method for heating a power battery of an asynchronous motor of an electric vehicle according to claim 1, characterized in that: The first excitation current component vector and the first torque current component vector are determined by querying a first current distribution reference table according to the current target torque and real-time speed of the driving motor; The second excitation current component vector and the second torque current component vector are determined by querying a second current distribution reference table according to the current target torque and real-time speed of the driving motor; The third excitation current component vector and the third torque current component vector are determined by querying a third current distribution reference table according to the current target torque and real-time speed of the driving motor.

4. The method for heating a power battery of an asynchronous motor of an electric vehicle according to claim 3, characterized in that: The data in the first current distribution reference table are determined in the bench test in the following manner: ① Set the initial value of the driving motor's operating current and the current single change; ② After the real-time speed of the drive motor reaches the preset drive motor speed using the dynamometer, adjust the operating current of the drive motor according to the single current change until the real-time output torque of the drive motor is equal to the preset drive motor target torque, and record the drive motor operating current value at this time; ③ Change the preset target torque of the drive motor and repeat steps ① to ③ until all the drive motor operating current values ​​corresponding to the preset target torque of the drive motor at the drive motor speed are recorded; ④ Change the preset drive motor speed and repeat steps ① to ④ until all preset drive motor speeds and drive motor target torques corresponding to the drive motor operating current values ​​are recorded and stored in the first current distribution reference table; ⑤ After setting the waste heat demand power according to the factory parameters of the power battery, the excitation current component vector and the torque current component vector corresponding to the operating current value of each drive motor in the first current distribution reference table are determined in the following manner and stored in the first current distribution reference table: (1) Select any driving motor operating current value whose excitation current component vector and torque current component vector are not determined in the first current distribution reference table as the current driving motor operating current; ⑵In Adjust the angle between the excitation current component vector corresponding to the operating current value of the drive motor and the M-axis in the MT coordinate system within the range until the waste heat output power of the drive motor is greater than the waste heat power required by the power battery. Record the value of the angle at this time, and calculate the excitation current component vector and torque current component vector corresponding to the operating current value of the drive motor according to the following first current distribution formula: i M-1 =i1×cos(θ1) i T-1 =i1×sin(θ1) Where i1 is the working current value of the driving motor in the first current distribution reference table, i M-1 The excitation current component corresponding to the working current value of the driving motor in the first current distribution reference table, i T-1 is the torque current component vector corresponding to the working current value of the driving motor in the first current distribution reference table, θ1 is the angle between the excitation current component vector corresponding to the working current value of the driving motor in the first current distribution reference table and the M axis in the MT coordinate system; ⑶ Repeat steps ⑴ to ⑵ until the excitation current component vectors and torque current component vectors corresponding to all the driving motor working current values ​​in the first current distribution reference table are determined.

5. The method for heating a power battery of an asynchronous motor of an electric vehicle according to claim 3, characterized in that: The data in the second current distribution reference table are determined in bench tests in the following manner: ① Set the initial value of the driving motor's operating current and the current single change; ② After the real-time speed of the drive motor reaches the preset drive motor speed using the dynamometer, adjust the operating current of the drive motor according to the single current change until the real-time output torque of the drive motor is equal to the preset drive motor target torque, and record the drive motor operating current value at this time; ③ Change the preset target torque of the drive motor and repeat steps ① to ③ until all the drive motor operating current values ​​corresponding to the preset target torque of the drive motor at the drive motor speed are recorded; ④ Change the preset drive motor speed and repeat steps ① to ④ until all the preset drive motor speeds and drive motor target torques corresponding to the drive motor operating current values ​​are recorded and stored in the second current distribution reference table; ⑤ After setting the waste heat demand power according to the factory parameters of the power battery, determine the excitation current component vector and torque current component vector corresponding to the operating current value of each drive motor in the second current distribution reference table in the following manner and store them in the second current distribution reference table: (1) Select any driving motor operating current value of an undetermined excitation current component vector and torque current component vector in the second current distribution reference table as the current driving motor operating current; ⑵In Adjust the angle between the excitation current component vector corresponding to the operating current value of the drive motor and the M-axis in the MT coordinate system within the specified range until the waste heat output power of the drive motor is greater than the waste heat power required by the power battery. Record the value of the angle at this time and calculate the excitation current component vector and torque current component vector corresponding to the operating current value of the drive motor according to the following second current distribution formula: i M-2 =i2×cos(θ2) i T-2 =i2×sin(θ2) Where i2 is the working current value of the driving motor in the second current distribution reference table, i M-2 The excitation current component corresponding to the working current value of the driving motor in the second current distribution reference table, i T-2 is the torque current component vector corresponding to the working current value of the driving motor in the second current distribution reference table, θ2 is the angle between the excitation current component vector corresponding to the working current value of the driving motor in the second current distribution reference table and the M axis in the MT coordinate system; ⑶ Repeat steps ⑴ to ⑵ until the excitation current component vectors and torque current component vectors corresponding to all the driving motor working current values ​​in the second current distribution reference table are determined.

6. The method for heating a power battery of an asynchronous motor of an electric vehicle according to claim 3, characterized in that: The data in the third current distribution reference table are determined in bench tests in the following manner: ① Set the initial value of the driving motor's operating current and the current single change; ② After the real-time speed of the drive motor reaches the preset drive motor speed using the dynamometer, adjust the operating current of the drive motor according to the single current change until the real-time output torque of the drive motor is equal to the preset drive motor target torque, and record the drive motor operating current value at this time; ③ Change the preset target torque of the drive motor and repeat steps ① to ③ until all the drive motor operating current values ​​corresponding to the preset target torque of the drive motor at the drive motor speed are recorded; ④ Change the preset drive motor speed and repeat steps ① to ④ until all the preset drive motor speeds and drive motor target torques corresponding to the drive motor operating current values ​​are recorded and stored in the third current distribution reference table; ⑤ Calculate the excitation current component and torque current component corresponding to the operating current value of each drive motor in the third current distribution reference table according to the following third current distribution formula, and record them in the third current distribution reference table: Where i3 is the working current value of the driving motor in the third current distribution reference table, i M-3 is the excitation current component corresponding to the working current value of the driving motor in the third current distribution reference table, i T-3 is the torque current component vector corresponding to the working current value of the driving motor in the third current distribution reference table, and π is the radian corresponding to the flat angle.

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