Motor current control method and system of electric automobile

Abstract

The invention provides a motor current control method and system of an electric vehicle, and relates to the technical field of motor control. The motor current control method comprises the following steps: acquiring required torque data and motor rotating speed data; demand current information is generated based on the demand torque data; determining torque fluctuation amplitude information according to the required current information and the motor rotating speed data; obtaining a fluctuation torque instruction according to the torque fluctuation amplitude information; generating a motor current instruction according to the required torque data, the required current information and the fluctuation torque instruction; and controlling the motor current of the electric vehicle according to the motor current instruction. According to the motor current control method, the technical effects that the three-phase current can be balanced under the locked-rotor working condition, the global highest temperature rise is reduced, and the current output capacity of the electric vehicle under the locked-rotor condition is improved are achieved.

Description

Technical Field

[0001] The present application relates to the field of motor control technology, and in particular to a motor current control method and system for an electric vehicle. Background Art

[0002] Electric vehicles generally use permanent magnet synchronous motors as drive motors. A typical electric vehicle drive system is powered by a power battery. The motor controller outputs control to the motor through an inverter circuit, thereby controlling the motor current. The motor is connected to the wheels through a reduction mechanism, axles, etc., and the wheels can be braked and locked through calipers. However, when an electric vehicle starts on a slope, the motor needs to output a large torque to the wheels when the wheels are locked, and then release the wheels to allow the vehicle to move forward. Otherwise, the vehicle may not have enough torque after the wheels are released and may roll down the slope. Therefore, when the vehicle starts on a slope, the motor needs to maintain a large torque output for a long time (for example, 3 seconds) in a stalled state.

[0003] Generally, when the permanent magnet synchronous motor is in a stalled condition, the motor's rotation angle does not move, and the current of each phase of the motor is a constant DC current, which will cause serious imbalance in the current of each phase of the motor. The average current of the phase with larger current can reach about 1.5 times that of the non-stalled condition, causing the motor winding and inverter circuit of this phase to heat up seriously. In particular, the semiconductor switch element of the inverter circuit of this phase has a short thermal inertia time, generally only about 1s, causing its hot spot temperature (junction temperature) to rise rapidly during high current stall.

[0004] In addition to the slope starting condition, when the vehicle is parked for charging in winter, the motor controller and the motor need to actively pass current to generate heat. At this time, the motor phase current is also limited due to temperature limitations due to unbalanced three-phase current. Summary of the invention

[0005] The purpose of the present application is to provide a motor current control method, system, electronic device and computer-readable storage medium for an electric vehicle, which can achieve the technical effect of balancing the three-phase current under a stalled rotor condition, reducing the global maximum temperature rise, and thus increasing the current output capacity of the electric vehicle under a stalled rotor condition.

[0006] In a first aspect, the present application provides a motor current control method for an electric vehicle, comprising:

[0007] Obtain required torque data and motor speed data;

[0008] generating demand current information based on the demand torque data;

[0009] Determine torque fluctuation amplitude information according to the demand current information and the motor speed data;

[0010] Obtaining a fluctuation torque command according to the torque fluctuation amplitude information;

[0011] generating a motor current command according to the required torque data, the required current information and the fluctuating torque command;

[0012] The motor current of the electric vehicle is controlled according to the motor current instruction.

[0013] In the above implementation process, the required current information, torque fluctuation amplitude information and fluctuation torque instruction are obtained through data processing of the required torque data and the motor speed data, and then the motor current instruction is generated according to the required torque data, the required current information and the fluctuation torque instruction to control the motor current of the electric vehicle; the motor current control method of the electric vehicle uses the elastic resonance of the electric drive shaft system to achieve the three-phase current balance of the motor when the vehicle is stationary, thereby increasing the motor current, and can achieve the technical effect of balancing the three-phase current under the stall condition, reducing the global maximum temperature rise, thereby increasing the current output capacity of the electric vehicle under the stall condition. Further, the step of generating the required current information based on the required torque data includes:

[0014] Get car status information;

[0015] The demand current information is generated according to the demand torque data and the vehicle state information.

[0016] In the above implementation process, the vehicle status information is the current status information of the electric vehicle, including the slope start condition (slope start state), the vehicle stationary state charging state, etc.; thereby, the corresponding demand current information is obtained according to the demand torque data and the vehicle status information, thereby improving the accuracy of the demand current information.

[0017] Further, the step of generating the required current information according to the required torque data and the vehicle state information comprises:

[0018] If the vehicle state information is a hill-start state, determining a DQ axis current command according to MTPA control and the required torque data;

[0019] If the vehicle state information is a stationary charging state, obtaining motor heating current information, and determining a DQ axis current instruction according to the required torque data and the motor heating current information;

[0020] The demand current information is generated according to the DQ axis current instruction.

[0021] Further, the step of determining the torque fluctuation amplitude information according to the demand current information and the motor speed data includes:

[0022] If the demand current information is less than the preset current threshold or the motor speed data is greater than the preset speed threshold, determining that the torque fluctuation amplitude information is zero;

[0023] If the demand current information is greater than or equal to a preset current threshold and the motor speed data is less than or equal to a preset speed threshold, the torque fluctuation amplitude information is determined according to a preset processing method, the demand current information and the motor speed data, wherein the preset processing method includes one or more of a calibration method, a simulation method, a theoretical model method, and a closed-loop control method.

[0024] Further, the step of generating a motor current command according to the required torque data, the required current information and the fluctuating torque command comprises:

[0025] Obtaining preset instruction generation information according to vehicle status information;

[0026] The required torque data, the required current information and the fluctuation torque instruction are processed according to preset instruction generation information to generate a motor current instruction.

[0027] In the above implementation process, preset instruction generation information is obtained according to the vehicle status information, wherein the preset instruction generation information can adopt a corresponding calculation method according to the different positions of the demand current information, process the demand torque data, demand current information and fluctuating torque instructions and generate a motor current instruction, thereby improving the accuracy of the motor current instruction.

[0028] Furthermore, the step of controlling the motor current of the electric vehicle according to the motor current instruction includes:

[0029] A PWM wave signal is generated according to the motor current instruction, and the motor current of the electric vehicle is controlled by the PWM wave signal.

[0030] In a second aspect, the present application provides a motor current control system for an electric vehicle, comprising:

[0031] An acquisition module is used to acquire required torque data and motor speed data;

[0032] A demand current module, configured to generate demand current information based on the demand torque data;

[0033] A torque fluctuation amplitude module, used to determine torque fluctuation amplitude information according to the demand current information and the motor speed data;

[0034] A fluctuation torque module, used for obtaining a fluctuation torque instruction according to torque fluctuation amplitude information;

[0035] A motor current module, used for generating a motor current instruction according to the required torque data, the required current information and the fluctuating torque instruction;

[0036] The control module is used to control the motor current of the electric vehicle according to the motor current instruction.

[0037] Furthermore, the demand current module is used for:

[0038] Get car status information;

[0039] The demand current information is generated according to the demand torque data and the vehicle state information.

[0040] Furthermore, the demand current module is also used for:

[0041] If the vehicle state information is a hill-start state, determining a DQ axis current command according to MTPA control and the required torque data;

[0042] If the vehicle state information is a stationary charging state, obtaining motor heating current information, and determining a DQ axis current instruction according to the required torque data and the motor heating current information;

[0043] The demand current information is generated according to the DQ axis current instruction.

[0044] Furthermore, the torque fluctuation amplitude module is used to:

[0045] If the demand current information is less than the preset current threshold or the motor speed data is greater than the preset speed threshold, determining that the torque fluctuation amplitude information is zero;

[0046] If the demand current information is greater than or equal to a preset current threshold and the motor speed data is less than or equal to a preset speed threshold, the torque fluctuation amplitude information is determined according to a preset processing method, the demand current information and the motor speed data, wherein the preset processing method includes one or more of a calibration method, a simulation method, a theoretical model method, and a closed-loop control method.

[0047] Furthermore, the motor current module is used for:

[0048] Obtaining preset instruction generation information according to vehicle status information;

[0049] The required torque data, the required current information and the fluctuation torque instruction are processed according to preset instruction generation information to generate a motor current instruction.

[0050] Furthermore, the control module is used for:

[0051] A PWM wave signal is generated according to the motor current instruction, and the motor current of the electric vehicle is controlled by the PWM wave signal.

[0052] In a third aspect, the present application provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method described in any one of the first aspects when executing the computer program.

[0053] In a fourth aspect, the present application provides a computer-readable storage medium, on which instructions are stored. When the instructions are executed on a computer, the computer executes the method as described in any one of the first aspects.

[0054] In a fifth aspect, the present application provides a computer program product, which, when running on a computer, enables the computer to execute the method as described in any one of the first aspects.

[0055] Other features and advantages disclosed in the present application will be described in the following description, or some features and advantages can be inferred or determined without doubt from the description, or can be learned by implementing the above-mentioned technology disclosed in the present application.

[0056] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0058] Figure 1 A schematic diagram of the structure of an electric vehicle drive system provided in an embodiment of the present application;

[0059] Figure 2 A schematic diagram of a permanent magnet synchronous motor under a locked-rotor condition provided in an embodiment of the present application;

[0060] Figure 3 A schematic diagram of a flow chart of a motor current control method for an electric vehicle provided in an embodiment of the present application;

[0061] Figure 4 A schematic flow chart of another motor current control method for an electric vehicle provided in an embodiment of the present application;

[0062] Figure 5 A signal processing diagram of a motor current control method for an electric vehicle provided in an embodiment of the present application;

[0063] Figure 6 A signal processing diagram of the first motor current instruction provided in an embodiment of the present application;

[0064] Figure 7 A schematic diagram of the first type of demand current information provided in an embodiment of the present application;

[0065] Figure 8 A signal processing diagram of a second motor current instruction provided in an embodiment of the present application;

[0066] Fig. 9 A schematic diagram of the second type of demand current information provided in an embodiment of the present application;

[0067] Fig.10 A signal processing diagram of a third motor current instruction provided in an embodiment of the present application;

[0068] Fig.11 A schematic diagram of a third type of demand current information provided in an embodiment of the present application;

[0069] Fig.12 A schematic diagram of a dynamic model of a drive shaft system provided in an embodiment of the present application;

[0070] Fig.13 A schematic diagram of the amplitude-frequency and phase-frequency characteristic curves of the transfer function provided in the embodiment of the present application;

[0071] Fig.14 A schematic diagram of a first simulation result provided in an embodiment of the present application;

[0072] Fig.15 A schematic diagram of the motor current vector swinging back and forth in the stator coordinate system provided in an embodiment of the present application;

[0073] Fig.16 A signal processing diagram of a fourth motor current instruction provided in an embodiment of the present application;

[0074] Fig.17 A schematic diagram of a fourth type of demand current information provided in an embodiment of the present application;

[0075] Fig.18 A schematic diagram of a second simulation result provided in an embodiment of the present application;

[0076] Fig.19 A structural block diagram of a motor current control system for an electric vehicle provided in an embodiment of the present application;

[0077] Fig. 20A structural block diagram of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0078] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0079] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0080] Generally, electric vehicles generally use permanent magnet synchronous motors as drive motors. Figure 1 , Figure 1 A schematic diagram of the structure of an electric vehicle drive system provided in an embodiment of the present application; Figure 1 The figure shows a typical electric vehicle drive system, which is powered by a power battery. The motor controller outputs control to the motor through an inverter circuit, thereby controlling the motor current. The motor is connected to the wheels through a reduction mechanism, a half shaft, etc., and the wheels can be braked and locked by calipers.

[0081] When an electric vehicle starts on a slope, the motor needs to output a large torque to the wheels first when the wheels are locked, and then release the wheels to allow the vehicle to move forward. Otherwise, the vehicle may not have enough torque after the wheels are released and may roll down the slope. Therefore, when the vehicle starts on a slope, the motor needs to maintain a large torque output for a long time (for example, 3 seconds) in a locked state.

[0082] However, see Figure 2 , Figure 2 A schematic diagram of a permanent magnet synchronous motor under a stalled rotor condition provided for an embodiment of the present application; when the permanent magnet synchronous motor is in a stalled rotor condition, since the motor rotation angle does not move, the current of each phase of the motor is embodied as a constant DC, which will cause serious imbalance in the current of each phase of the motor. The phase with a larger current has an average current magnitude of about 1.5 times that of the phase under a non-stalled rotor condition, causing serious heating of the motor winding and inverter circuit of the phase. In particular, the inverter circuit of this phase has a small thermal inertia time of its semiconductor switch element, generally only about 1s, causing its hot spot temperature (junction temperature) to rise rapidly when the current is stalled. Moreover, in addition to the slope start condition, when the vehicle is parked and charged in winter, the motor controller and the motor need to actively pass current to heat, and at this time, the motor phase current is also limited due to temperature restrictions due to the imbalance of the three-phase current.

[0083] Therefore, the industry has the following demand: while keeping the hardware such as semiconductor modules unchanged, through software optimization, the three-phase current can be balanced under stalled conditions, the global maximum temperature rise can be reduced, and thus the current output capacity of electric vehicles under stalled conditions can be increased.

[0084] In view of the technical problems raised above, the embodiments of the present application provide a motor current control method, system, electronic device and computer-readable storage medium for an electric vehicle, which can achieve the technical effect of balancing the three-phase current under a stalled rotor condition, reducing the global maximum temperature rise, and thus increasing the current output capacity of the electric vehicle under a stalled rotor condition; please participate in Figure 3 , Figure 3 A flow chart of a motor current control method for an electric vehicle provided in an embodiment of the present application is provided. The motor current control method is applied to a drive motor of an electric vehicle, and the method comprises the following steps:

[0085] S100: Obtain required torque data and motor speed data;

[0086] S200: generating demand current information based on demand torque data;

[0087] For example, the required torque data can be determined according to specific needs; for example, when the vehicle is in a slope start condition, a large torque needs to be output, and the DQ axis current command of the drive motor is generally determined according to the MTPA (Maximum Torque Per Ampere) principle; when the vehicle is charging in a stationary state, the DQ axis current command is determined according to the output torque demand and the motor heating current; wherein the DQ axis current command can be a rectangular coordinate system representation (I d0 , I q0 ), can also be expressed in polar coordinates: the current vector magnitude I s0 and timing angle (The angle that the vector rotates counterclockwise relative to the positive direction of the D axis);

[0088] Optionally, the motor speed data may be the real-time speed of the drive motor; in the embodiment of the present application, the demand current information may be a DQ axis current instruction.

[0089] S300: Determine torque fluctuation amplitude information according to demand current information and motor speed data;

[0090] In some implementations, when the motor speed data is high enough (e.g., above 100 rpm), or the demand current information is low enough and there is no risk of overheating, no torque fluctuation is performed, and the torque fluctuation amplitude is zero;

[0091] Optionally, in working conditions where torque fluctuation is required, in specific implementations, the relationship between the torque fluctuation amplitude and the required current and motor speed can be obtained through calibration, simulation or theoretical model calculation, or the torque fluctuation amplitude can be adjusted in real time using a closed-loop control method.

[0092] S400: Obtaining a fluctuation torque instruction according to the torque fluctuation amplitude information;

[0093] Exemplarily, according to the given torque fluctuation amplitude information, the electric drive shaft system resonance frequency is used as the fluctuation frequency to calculate and generate a fluctuating torque signal, such as a torque signal that fluctuates according to a sine wave. In a specific implementation, the fluctuating torque signal can also be other forms of fluctuating waveforms, such as a triangular wave or a square wave, which is only used as an example and not as a limitation.

[0094] S500: Generate a motor current command according to the required torque data, the required current information and the fluctuating torque command;

[0095] S600: Control the motor current of the electric vehicle according to the motor current command.

[0096] Exemplarily, the motor current command is calculated based on the demand current information or the demand torque data and the fluctuation torque command. d0 , I q0 ) can be used to obtain the corresponding motor current command according to the different positions of the motor.

[0097] In some embodiments, the motor current control method of the electric vehicle provided in the embodiment of the present application obtains demand current information, torque fluctuation amplitude information and fluctuation torque instructions through data processing of demand torque data and motor speed data, and then generates a motor current instruction according to the demand torque data, demand current information and fluctuation torque instruction to control the motor current of the electric vehicle; the motor current control method of the electric vehicle utilizes the elastic resonance of the electric drive shaft system to achieve three-phase current balance of the motor when the vehicle is stationary, thereby increasing the motor current, and can achieve balanced three-phase current under stalled conditions, reduce the global maximum temperature rise, and thus increase the current output capacity of the electric vehicle under stalled conditions. Technical effect.

[0098] See also Figure 4 , Figure 4 A schematic flow chart of another motor current control method for an electric vehicle provided in an embodiment of the present application.

[0099] Exemplarily, S200: the step of generating required current information based on required torque data includes:

[0100] S210: Obtaining vehicle status information;

[0101] S220: Generate required current information according to the required torque data and the vehicle status information.

[0102] Exemplarily, the vehicle status information is the current status information of the electric vehicle, including hill-start conditions (hill-start state), vehicle stationary state charging state, etc.; thereby, corresponding demand current information is obtained according to the demand torque data and the vehicle status information, thereby improving the accuracy of the demand current information.

[0103] Exemplarily, S220: the step of generating the required current information according to the required torque data and the vehicle state information includes:

[0104] If the vehicle status information is a hill-start state, the DQ axis current command is determined according to the MTPA control and required torque data;

[0105] If the vehicle status information is a stationary charging state, the motor heating current information is obtained, and the DQ axis current command is determined according to the required torque data and the motor heating current information;

[0106] Generates demand current information based on the DQ axis current command.

[0107] Exemplarily, S300: the step of determining torque fluctuation amplitude information according to demand current information and motor speed data includes:

[0108] If the demand current information is less than the current preset threshold or the motor speed data is greater than the speed preset threshold, it is determined that the torque fluctuation amplitude information is zero;

[0109] If the demand current information is greater than or equal to the preset current threshold and the motor speed data is less than or equal to the preset speed threshold, the torque fluctuation amplitude information is determined according to the preset processing method, the demand current information and the motor speed data, wherein the preset processing method includes one or more of a calibration method, a simulation method, a theoretical model method, and a closed-loop control method.

[0110] Exemplarily, S500: the step of generating a motor current command according to the required torque data, the required current information and the fluctuating torque command includes:

[0111] S510: Obtaining preset instruction generation information according to the vehicle status information;

[0112] S520: Processing the required torque data, the required current information and the fluctuation torque instruction according to the preset instruction generation information to generate a motor current instruction.

[0113] Exemplarily, preset instruction generation information is obtained based on vehicle status information, wherein the preset instruction generation information can adopt corresponding calculation methods according to the different locations of demand current information, process demand torque data, demand current information and fluctuating torque instructions and generate motor current instructions, thereby improving the accuracy of the motor current instructions.

[0114] Exemplarily, S600: the step of controlling the motor current of the electric vehicle according to the motor current instruction includes:

[0115] S610: Generate a PWM wave signal according to the motor current command, and control the motor current of the electric vehicle through the PWM wave signal.

[0116] In some embodiments, in combination Figure 3 to Figure 4 As shown, the main process of the motor current control method of the electric vehicle provided by the embodiment of the present application is: calculating the demand current information corresponding to the demand torque based on the demand torque data; determining the torque fluctuation amplitude information according to the demand current information and the motor speed data; calculating the fluctuation torque instruction according to the resonance frequency according to the torque fluctuation amplitude information and the resonance frequency of the drive shaft system of the whole vehicle; calculating the motor current instruction according to the demand torque data or the demand current information and the fluctuation torque instruction; controlling the motor current according to the motor current instruction;

[0117] The specific signal processing of the motor current control method of electric vehicles is as follows Figure 5 As shown, Figure 5 A signal processing diagram of a motor current control method for an electric vehicle provided in an embodiment of the present application, wherein the motor current control method for an electric vehicle comprises the following steps:

[0118] (1) Calculate the required current information based on the required torque data: This step is determined according to specific requirements; for example, when starting on a slope, a larger torque is required, and the DQ axis current command is generally determined according to the MTPA principle. When the vehicle is charging at rest, the DQ axis current command is determined based on the output torque demand and the motor heating current; the DQ axis current command can be expressed in a rectangular coordinate system (I d0 , I q0 ), can also be expressed in polar coordinates: the current vector magnitude I s0 and timing angle (The angle that the vector rotates counterclockwise relative to the positive direction of the D axis);

[0119] (2) Calculation of torque fluctuation amplitude information: When the speed is high enough (for example, above 100 rpm) or the demand current is low enough without the risk of overheating, no torque fluctuation is performed and the torque fluctuation amplitude is zero;

[0120] In the working condition where torque fluctuation is required, in the specific implementation, the relationship between the torque fluctuation amplitude and the required current and the motor speed can be obtained through calibration, simulation or theoretical model calculation, or the torque fluctuation amplitude can be adjusted in real time by adopting a closed-loop control method;

[0121] (3) Calculation of the fluctuating torque command: According to the given torque fluctuation amplitude information, the fluctuating torque command is calculated with the resonant frequency of the electric drive shaft system as the fluctuation frequency, such as the torque command according to the sine wave fluctuation; the calculation formula of the fluctuating torque command is as follows:

[0122]

[0123] Among them, T amp is the torque fluctuation amplitude information, f h is the torque fluctuation frequency, which is equal to the resonant frequency of the electric drive shaft system (actually it can be 50% to 200% of the resonant frequency);

[0124] In a specific implementation, the fluctuating torque command may also be other forms of fluctuating waveforms, such as a triangular wave or a square wave.

[0125] (4) Calculation of motor current command: The motor current command is calculated based on the demand current information or demand torque data and the fluctuation torque. d0 , I q0 ) is located in different places, different calculation methods are used; for example:

[0126] ① Slope start condition:

[0127] The first method to obtain the motor current command: see Figure 6 and Figure 7 , Figure 6 A signal processing diagram of the first motor current instruction provided in an embodiment of the present application, Figure 7 A schematic diagram of the first type of demand current information provided in an embodiment of the present application; the demand torque and the fluctuating torque are added to obtain the final torque command, and then the motor current command (Id, Iq) is calculated according to the MTPA (maximum torque per ampere) principle;

[0128] The second method to obtain the motor current command: see Figure 8 and Fig. 9 , Figure 8 A signal processing diagram of the second motor current instruction provided in an embodiment of the present application, Fig. 9 A schematic diagram of the second type of demand current information provided in an embodiment of the present application; maintaining the demand current timing angle unchanged, and generating a fluctuating torque by adjusting the current vector Is;

[0129] ②Electric drive active heating condition:

[0130] See also Fig.10 and Fig.11 , Fig.10 A signal processing diagram of the third motor current instruction provided in an embodiment of the present application, Fig.11 A schematic diagram of the third type of demand current information provided in the embodiment of the present application; for the electric drive active heating condition, since the demand torque is generally small at this time, the calculated DQ current command is not on the MTPA line, but is relatively close to the D axis, and the torque fluctuation is insensitive to the change of the current amplitude Is. Therefore, the current amplitude Is is kept unchanged, and the fluctuating torque is generated by changing the current vector advance angle;

[0131] (V) Current closed-loop control: This link is used to control the motor current to follow the motor current command, and its output is a PWM wave signal used to control the inverter circuit.

[0132] For example, in order to balance the three-phase current of the motor when the vehicle is stationary, the current vector must be made to swing or rotate in the stator coordinate system. If the current vector rotates in the stator coordinate system at this time, the torque cannot be effectively output. Therefore, we can only try to make the current swing back and forth in the stator coordinate system. Due to the need for torque output, the current in the rotor coordinate system basically does not change, so we can only try to make the rotor coordinate system swing relative to the stator, that is, the rotor itself must swing back and forth relative to the stator, and the swing frequency must be high enough. Due to the elasticity of the vehicle drive shaft system, the motor rotor can swing back and forth relying on the elasticity of the shaft system, and the natural resonant frequency of the shaft system is about 5 to 15 Hz, which is significantly larger than the dynamic bandwidth of the inverter thermal resistance network (about 1 Hz). Therefore, the present application scheme uses the elastic resonance of the electric drive shaft system to achieve the balance of the three-phase current of the motor when the vehicle is stationary, thereby increasing the motor current;

[0133] See also Fig.12 , Fig.12 A schematic diagram of a dynamic model of a drive shaft system provided in an embodiment of the present application; Fig.12 As shown in the figure, when the vehicle wheels are locked, the motor rotor moment of inertia is Jm. The motor rotor and the driving wheel are connected through a reduction mechanism and a half-axle, which can be equivalent to an elastic shaft with a stiffness of K and a viscous resistance coefficient C. The transfer function from the motor torque T to the motor rotor angle θ is:

[0134]

[0135] See also Fig.13 , Fig.13A schematic diagram of the amplitude-frequency and phase-frequency characteristic curves of the transfer function provided in the embodiment of the present application; since the viscous drag coefficient of the shaft system is small, the shaft system is in an underdamped state and there is a resonant frequency, at which a slight torque fluctuation can cause an obvious oscillation of the motor rotor angle;

[0136] Therefore, when the motor is in a stalled state, only a small fluctuation torque needs to be superimposed on the stall torque to cause the motor rotor to fluctuate back and forth within a larger rotation angle range, so that the motor is approximately in a rotating state, thereby making the current of each phase of the motor relatively balanced again, and finally reducing the junction temperature of the semiconductor switch, thereby allowing a larger stall torque output;

[0137] The simulation results are as follows Fig.14 As shown in the figure, on the required torque of 300Nm, a fluctuating torque with an amplitude of 5Nm and a fluctuation frequency of 6.8Hz is superimposed, causing the motor rotor to swing back and forth with a swing amplitude of ±90deg. The heating power of the upper tube of the U phase is no longer maintained at the worst working condition (1021W), but fluctuates at 6.8Hz, and its average value drops to 380W, thereby significantly reducing the temperature rise.

[0138] In addition, in the calculation of torque fluctuation amplitude information, for MOSFET type power modules, the motor current vector can be allowed to swing back and forth by ±90 degrees in the stator coordinate system; for IGBT type power modules with independent anti-parallel diode packaging, it is preferred to allow the motor current vector to swing back and forth by 180 degrees in the stator coordinate system, such as Fig.15 As shown, Fig.15 A schematic diagram of the motor current vector swinging back and forth in the stator coordinate system provided in an embodiment of the present application.

[0139] For example, under the condition that the heating limit is met, the smaller the rotor swing amplitude is, the better, because the larger the rotor swing amplitude is, the greater the vibration and noise of the whole vehicle will be, which will affect the comfort of the whole vehicle;

[0140] In order to ensure balanced heating of the three phases, the motor current vector can be allowed to swing within the range of ±180 degrees, so that the three phase currents are basically balanced and the heating condition is similar to the normal speed condition;

[0141] For MOSFET type devices, regardless of whether the current is positive or negative, almost all the current flows through the MOSFET channel. When the device is locked, the switching frequency is low and the switching loss can be basically ignored. Therefore, the heat generation power roughly conforms to the relationship shown in the following formula, that is, the heat generation power is only related to the normality of the current. The formula example is as follows:

[0142] P loss,U (t)≈R on,MOSFET I u (t) 2 ;

[0143] Where P loss,U (t) is the instantaneous loss of the tube on the U-phase inverter bridge, I u (t) is the instantaneous current of phase U;

[0144] Because I u When (t) is a sinusoidal signal with a period of T, I u (t) 2 The integral within any 0.5T duration is the same, so for MOSFET type devices, the current only needs to swing within the range of ±90 degrees to ensure balanced heating of the three phases;

[0145] For IGBT type devices, when the current is positive, it flows through the active switch, and when the current is negative, it flows through the independent anti-parallel diode. Therefore, the motor current vector needs to swing ±180 degrees in the stator coordinate system to better heat the 6 active switches and 6 anti-parallel diodes in 3 phases.

[0146] In addition, in the calculation of the motor current command, in the case of slope starting conditions that require large torque output, in addition to the ordinary MTPA principle calculation, an innovative method is: d ,I q ) command to meet the torque fluctuation requirements, while letting (I d ,I q ) The timing angle of the vector also swings greatly according to a certain correlation, thereby reducing the swing of the rotor angle, reducing vehicle vibration and improving comfort. Please refer to Fig.16 and Fig.17 , Fig.16 A signal processing diagram of the fourth motor current instruction provided in an embodiment of the present application, Fig.17 A schematic diagram of the fourth type of demand current information provided in the embodiment of the present application; the specific method is as follows:

[0147] S1: Calculate the corresponding DQ current point (I d0 ,I q0 ), the corresponding vector angle is φ0;

[0148] S2: Calculate the timing angle of the swing:

[0149]

[0150] Where: φ amp is the amplitude of the timing swing, which can generally be obtained by actual vehicle calibration. h is the shaft system resonance frequency;

[0151] It should be noted that the waveform of the timing swing should lead the torque fluctuation waveform by 90 degrees, which is a key feature. In the DQ coordinate system, it is (I d ,I q )The current point will move clockwise on the trajectory;

[0152] S3: Calculate the DQ axis current command based on the current vector timing and the final torque command. For a given torque and current vector timing, there is a unique current command, so the specific implementation of the current command calculation link is a trivial mathematical calculation or table lookup process;

[0153] The essence of the above method is that the current vector swings in the DQ coordinate system, and the DQ coordinate system swings relative to the stator due to the fluctuating torque. By controlling the phases of the two swings so that they are in phase, the swing of the current vector in the stator coordinate system can be made larger than the swing of the rotor.

[0154] Specifically, under the above method, because the shaft system is in a resonant state, according to the amplitude-frequency characteristics and phase-frequency characteristics, the amplitude of the motor rotor angle θr is T amp / (2πf h C), the phase lags 90 degrees relative to the torque fluctuation waveform, so its waveform is:

[0155]

[0156] Where θr0 is the average rotation angle, corresponding to the angle that the rotor rotates due to the elasticity of the shaft system under T0 torque drive;

[0157] The vector angle of the current vector in the stator coordinate system is:

[0158]

[0159] It can be seen that the timing angle fluctuation and the rotor fluctuation angle are added in the same phase. amp You can follow φ amp The rotor angle fluctuation decreases with the increase of.

[0160] The simulation results are as follows Fig.18 As shown in the figure, in this simulation example, the torque fluctuation amplitude is reduced from 5Nm to 3.3Nm, and the rotor fluctuation angle is reduced from ±90deg to ±60deg.

[0161] See also Fig.19 , Fig.19 This is a structural block diagram of a motor current control system of an electric vehicle provided in an embodiment of the present application. The motor current control system of the electric vehicle includes:

[0162] An acquisition module 100 is used to acquire required torque data and motor speed data;

[0163] The demand current module 200 is used to generate demand current information based on the demand torque data;

[0164] The torque fluctuation amplitude module 300 is used to determine the torque fluctuation amplitude information according to the required current information and the motor speed data;

[0165] The fluctuation torque module 400 is used to obtain the fluctuation torque instruction according to the torque fluctuation amplitude information;

[0166] The motor current module 500 is used to generate a motor current command according to the required torque data, the required current information and the fluctuating torque command;

[0167] The control module 600 is used to control the motor current of the electric vehicle according to the motor current instruction.

[0168] Exemplarily, the demand current module 200 is used to:

[0169] Get car status information;

[0170] The demand current information is generated according to the demand torque data and the vehicle status information.

[0171] Exemplarily, the demand current module 200 is further configured to:

[0172] If the vehicle status information is a hill-start state, the DQ axis current command is determined according to the MTPA control and required torque data;

[0173] If the vehicle status information is a stationary charging state, the motor heating current information is obtained, and the DQ axis current command is determined according to the required torque data and the motor heating current information;

[0174] Generates demand current information based on the DQ axis current command.

[0175] Exemplarily, the torque fluctuation amplitude module 300 is used to:

[0176] If the demand current information is less than the preset current threshold or the motor speed data is greater than the preset speed threshold, it is determined that the torque fluctuation amplitude information is zero;

[0177] If the demand current information is greater than or equal to the preset current threshold and the motor speed data is less than or equal to the preset speed threshold, the torque fluctuation amplitude information is determined according to the preset processing method, the demand current information and the motor speed data, wherein the preset processing method includes one or more of a calibration method, a simulation method, a theoretical model method, and a closed-loop control method.

[0178] Exemplarily, the motor current module 500 is used to:

[0179] Obtaining preset instruction generation information according to vehicle status information;

[0180] The information generated by the preset command processes the required torque data, the required current information and the fluctuation torque command to generate the motor current command.

[0181] Exemplarily, the control module 600 is used to:

[0182] A PWM wave signal is generated according to the motor current command, and the motor current of the electric vehicle is controlled by the PWM wave signal.

[0183] It should be noted that the motor current control system of the electric vehicle provided in the embodiment of the present application is Figures 3 to 18 The method embodiments shown correspond to each other and will not be described again here to avoid repetition.

[0184] This application also provides an electronic device, see Fig. 20 , Fig. 20 A block diagram of an electronic device provided in an embodiment of the present application. The electronic device may include a processor 510, a communication interface 520, a memory 530, and at least one communication bus 540. The communication bus 540 is used to realize direct connection and communication between these components. The communication interface 520 of the electronic device in the embodiment of the present application is used to communicate signaling or data with other node devices. The processor 510 may be an integrated circuit chip with signal processing capabilities.

[0185] The processor 510 mentioned above can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components. The methods, steps and logic block diagrams disclosed in the embodiments of the present application can be implemented or executed. The general-purpose processor can be a microprocessor or the processor 510 can also be any conventional processor, etc.

[0186] The memory 530 may be, but is not limited to, a random access memory (RAM), a read only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electric erasable programmable read-only memory (EEPROM), etc. The memory 530 stores computer-readable instructions. When the computer-readable instructions are executed by the processor 510, the electronic device can execute the above-mentioned Figures 3 to 18 The method embodiment involves various steps.

[0187] Optionally, the electronic device may further include a storage controller and an input / output unit.

[0188] The memory 530, storage controller, processor 510, peripheral interface, input and output unit components are directly or indirectly electrically connected to each other to achieve data transmission or interaction. For example, these components can be electrically connected to each other via one or more communication buses 540. The processor 510 is used to execute executable modules stored in the memory 530, such as software function modules or computer programs included in the electronic device.

[0189] The input and output unit is used to provide users with the task creation and to create a start optional time period or preset execution time for the task to realize the interaction between the user and the server. The input and output unit can be, but is not limited to, a mouse and a keyboard.

[0190] Understandably, Fig. 20 The structure shown is for illustration only, and the electronic device may also include Fig. 20 More or fewer components as shown, or with Fig. 20 Different configurations are shown. Fig. 20 Each component shown in the figure can be implemented by hardware, software or a combination thereof.

[0191] An embodiment of the present application further provides a storage medium having instructions stored thereon. When the instructions are run on a computer, the computer program is executed by a processor to implement the method described in the method embodiment. To avoid repetition, the method will not be described here.

[0192] The present application also provides a computer program product, which, when executed on a computer, enables the computer to execute the method described in the method embodiment.

[0193] In several embodiments provided in the present application, it should be understood that the disclosed devices and methods can also be implemented in other ways. The device embodiments described above are merely schematic. For example, the flowcharts and block diagrams in the accompanying drawings show the possible architecture, functions and operations of the devices, methods and computer program products according to multiple embodiments of the present application. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, a program segment or a part of a code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart, and the combination of boxes in the block diagram and / or flowchart can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0194] In addition, the functional modules in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0195] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0196] The above description is only an embodiment of the present application and is not intended to limit the scope of protection of the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0197] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

[0198] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

Claims

1. A motor current control method for an electric vehicle, characterized in that: include: Obtain required torque data and motor speed data; generating demand current information based on the demand torque data; Determine torque fluctuation amplitude information according to the demand current information and the motor speed data; Obtaining a fluctuation torque command according to the torque fluctuation amplitude information; generating a motor current command according to the required torque data, the required current information and the fluctuating torque command; The motor current of the electric vehicle is controlled according to the motor current instruction.

2. The motor current control method of an electric vehicle according to claim 1, characterized in that: The step of generating the required current information based on the required torque data comprises: Get car status information; The demand current information is generated according to the demand torque data and the vehicle state information.

3. The motor current control method of an electric vehicle according to claim 2, characterized in that: The step of generating the required current information according to the required torque data and the vehicle state information comprises: If the vehicle state information is a hill-start state, determining a DQ axis current command according to MTPA control and the required torque data; If the vehicle state information is a stationary charging state, obtaining motor heating current information, and determining a DQ axis current instruction according to the required torque data and the motor heating current information; The demand current information is generated according to the DQ axis current instruction.

4. The motor current control method of an electric vehicle according to claim 1, characterized in that: The step of determining the torque fluctuation amplitude information according to the demand current information and the motor speed data comprises: If the demand current information is less than the preset current threshold or the motor speed data is greater than the preset speed threshold, determining that the torque fluctuation amplitude information is zero; If the demand current information is greater than or equal to a preset current threshold and the motor speed data is less than or equal to a preset speed threshold, the torque fluctuation amplitude information is determined according to a preset processing method, the demand current information and the motor speed data, wherein the preset processing method includes one or more of a calibration method, a simulation method, a theoretical model method, and a closed-loop control method.

5. The motor current control method of an electric vehicle according to claim 1, characterized in that: The step of generating a motor current command according to the required torque data, the required current information and the fluctuating torque command comprises: Obtaining preset instruction generation information according to vehicle status information; The required torque data, the required current information and the fluctuation torque instruction are processed according to preset instruction generation information to generate a motor current instruction.

6. The motor current control method of an electric vehicle according to claim 1, characterized in that: The step of controlling the motor current of the electric vehicle according to the motor current instruction comprises: A PWM wave signal is generated according to the motor current instruction, and the motor current of the electric vehicle is controlled by the PWM wave signal.

7. A motor current control system for an electric vehicle, characterized in that: include: An acquisition module is used to acquire required torque data and motor speed data; A demand current module, configured to generate demand current information based on the demand torque data; A torque fluctuation amplitude module, used to determine torque fluctuation amplitude information according to the demand current information and the motor speed data; A fluctuation torque module, used for obtaining a fluctuation torque instruction according to torque fluctuation amplitude information; A motor current module, used for generating a motor current instruction according to the required torque data, the required current information and the fluctuating torque instruction; The control module is used to control the motor current of the electric vehicle according to the motor current instruction.

8. The motor current control system of the electric vehicle according to claim 7, characterized in that: The demand current module is used to: Get car status information; The demand current information is generated according to the demand torque data and the vehicle state information.

9. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the motor current control method for an electric vehicle as described in any one of claims 1 to 6 when executing the computer program.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores instructions, and when the instructions are executed on a computer, the computer executes the motor current control method for an electric vehicle according to any one of claims 1 to 6.

Images