A method and system for discharging residual electricity of a direct current bus of a permanent magnet motor

Abstract

The application discloses a kind of permanent magnet motor DC bus residual power bleeder method and system, active discharge instruction activates, motor controller periodically given Q-axis discharge current, D-axis discharge current, the Q-axis discharge current is 0, the D-axis discharge current starts from 0 and sequentially reduces to target value in linear trend, control motor works, discharge is carried out through the winding of motor, until the discharge end condition is satisfied and exit discharge process.This application adopts the method of current control, motor controller gives Q-axis discharge current 0, and gives a larger D-axis discharge current, motor control mode is space vector pulse width modulation, residual energy is consumed on motor winding by controllable current, ensure that motor does not produce torque in the process of discharging, all energy is converted into heat and consumed in motor, so as to reduce bus voltage to within safe range as soon as possible, with the advantages of simple method, easy to realize, strong practicability, high reliability.

Description

Technical Field

[0001] This invention belongs to the field of automotive technology, specifically relating to a method and system for discharging residual current from the DC bus of a permanent magnet motor. Background Technology

[0002] When the vehicle's main power supply is cut off, residual energy (voltage) will remain on the DC bus capacitor of the motor. Current methods for discharging residual current on the DC bus typically employ methods such as discharge resistors, switching losses, and redundant discharge from auxiliary drive components. These methods suffer from drawbacks such as slow discharge speed, increased costs due to the need for additional circuitry, or the requirement for the motor to rotate to a designated position before discharge. These approaches are not suitable for the motor system's emergency stop discharge requirements in accident situations. Furthermore, these methods also suffer from low discharge reliability. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide a simple and highly safe method and system for discharging residual current from the DC bus of a permanent magnet motor.

[0004] The technical solution adopted in this invention is: a method for residual current discharge of DC bus of permanent magnet motor. When the active discharge command is activated, the motor controller periodically gives the Q-axis discharge current and the D-axis discharge current. The Q-axis discharge current is 0, and the D-axis discharge current decreases linearly from 0 to the target value. The motor controller controls the motor to work and discharges through the motor windings until the discharge end condition is met and the discharge process is exited.

[0005] Furthermore, the process for determining the D-axis discharge current is as follows:

[0006] Set the rated discharge current and discharge regulation coefficient, and determine the discharge cutoff current value based on the rated discharge current and discharge regulation coefficient;

[0007] Set a given period for the decrease in slope and current, and determine the ramp value based on the decrease in slope and the given period;

[0008] The output value is the sum of the ramp value and the D-axis discharge current given in the previous cycle.

[0009] The output value is compared with the discharge cutoff current value. If the output value is less than the discharge cutoff current value, the D-axis discharge current of the current cycle is the output value; if the output value is greater than or equal to the discharge current value, the D-axis discharge current of the current cycle is the discharge cutoff current value.

[0010] Furthermore, the discharge cutoff current value is the product of the rated discharge current and the discharge regulation coefficient.

[0011] Furthermore, the slope value is the product of the decreasing slope and the given period.

[0012] Furthermore, the discharge termination condition is determined to be met when any of the following conditions are satisfied:

[0013] A. Within a set time period, the bus voltage value decreases to less than or equal to the set voltage and remains so for a certain period of time;

[0014] B. The active discharge command flag is 0.

[0015] A residual current discharge system for a permanent magnet motor DC bus, comprising:

[0016] The vehicle controller is used to issue active discharge activation commands or active discharge stop commands.

[0017] The motor controller is used to periodically provide the Q-axis discharge current and D-axis discharge current when it receives an active discharge activation command. The Q-axis discharge current is 0, and the D-axis discharge current decreases linearly from 0 to the target value, thereby controlling the motor to operate and discharge through the motor windings. When it receives an active discharge stop command, it provides the D-axis command current and Q-axis command current to control the motor to operate and output torque normally.

[0018] Furthermore, the motor controller includes

[0019] The discharge current module is used to output the rated discharge current to the ramp module and the Q-axis discharge current to the switching module.

[0020] The instruction module is used to output the D-axis instruction current and Q-axis instruction current to the switching module;

[0021] The ramp module is used to determine the D-axis discharge current based on the rated discharge current and output it to the selector module;

[0022] The selector module is used to output the Q-axis discharge current and D-axis discharge current to the motor controller when an active discharge activation command is received; and to output the D-axis command current and Q-axis command current to the motor controller when an active discharge stop command is received.

[0023] Furthermore, the process for determining the D-axis discharge current is as follows:

[0024] Set the discharge regulation coefficient, and determine the discharge cutoff current value based on the rated discharge current and the discharge regulation coefficient;

[0025] Set a given period for the decrease in slope and current, and determine the ramp value based on the decrease in slope and the given period;

[0026] The output value is the sum of the ramp value and the D-axis discharge current given in the previous cycle.

[0027] The output value is compared with the discharge cutoff current value. If the output value is less than the discharge cutoff current value, the D-axis discharge current of the current cycle is the output value; if the output value is greater than or equal to the discharge current value, the D-axis discharge current of the current cycle is the discharge cutoff current value.

[0028] Furthermore, the discharge cutoff current value is the product of the rated discharge current and the discharge adjustment coefficient; the slope value is the product of the reduction slope and the given period.

[0029] Furthermore, the active discharge stop command is determined when any of the following conditions are met:

[0030] A. Within a set time period, the bus voltage value decreases to less than or equal to the set voltage and remains so for a certain period of time;

[0031] B. A signal with the active discharge command flag bit set to 0 was received.

[0032] The beneficial effects of this invention are as follows:

[0033] This invention employs a current control method and adds a selection module. When the motor controller receives an active discharge activation command, the motor controller sets the Q-axis discharge current to 0 and provides a larger D-axis discharge current. The motor control mode is space vector pulse width modulation, and the subsequent process is the same as vector control: inputting IPARK changes, inputting SVPWM module, and outputting PWM waveform. The entire process discharges through the motor windings, that is, the residual energy is consumed in the motor windings through a controllable current, and it is ensured that the motor does not generate torque during the discharge process. In other words, all the energy is converted into heat and consumed inside the motor, thereby quickly reducing the bus voltage to within a safe range. It has the advantages of being simple, easy to implement, highly practical, and highly reliable.

[0034] This invention provides a current ramp module that, when given a weak magnetic current, can transition the D-axis discharge current to the target value at a certain slope, preventing torque pulsation during the discharge process from affecting safety or the overall vehicle driving experience. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the SVPWM principle during discharge in this invention.

[0036] Figure 2 This is a schematic diagram illustrating the principle of the vehicle controller outputting the D-axis current of the present invention.

[0037] Figure 3 This is a schematic diagram illustrating the principle of the vehicle controller outputting the Q-axis current of the present invention.

[0038] Figure 4 This is a flowchart of the D-axis discharge current output by the ramp module of the present invention.

[0039] Figure 5 This is a simulation diagram of the D-axis discharge current given in this invention.

[0040] Figure 6 This is a model diagram of the discharge process exiting the present invention. Detailed Implementation

[0041] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0042] like Figure 1 As shown, this invention provides a method for residual current discharge from the DC bus of a permanent magnet motor. When the active discharge command is activated, the motor controller periodically provides the Q-axis discharge current (IQ) and the D-axis discharge current (ID). The motor control method is space vector pulse width modulation (SPWM), and the subsequent process is the same as vector control: IPARK changes, then enters the SVPWM module, and outputs a PWM waveform. The Q-axis discharge current is 0, and the D-axis discharge current decreases linearly from 0 to a target value. The motor controller controls the motor to operate, discharging through the motor windings until the discharge termination condition is met, at which point the discharge process ends. This invention dissipates residual energy in the motor windings through controllable current and ensures that the motor does not generate torque during the discharge process; that is, all energy is converted into heat and consumed internally by the motor, thereby quickly reducing the bus voltage to a safe range. This method has the advantages of being simple, easy to implement, highly practical, and highly reliable.

[0043] Figure 1 The vector control process is as follows: The rotor position angle θ of the motor is acquired and sent to the PARK coordinate transformation unit; the three-phase currents Ib and Ic of the motor are acquired and sent to the CLARK coordinate transformation unit. Then, based on the position angle, the three-phase currents are transformed to obtain the feedback currents Id and Iq in the rotating coordinate system. Next, based on the given currents Id and IQ, the given voltages Ud and Uq are determined via the current regulator PI and sent to the IPARK unit. The given voltages are then transformed to obtain the stationary voltages in the two-phase stationary coordinate system and sent to the SVPWM unit. The SVPWM unit calculates the three-phase square wave duty cycle based on the voltages Ua and Uβ and sends it to the inverter. The inverter outputs the three-phase voltages based on the three-phase square wave duty cycle.

[0044] In the above scheme, to prevent torque pulsation during the discharge process from affecting safety or the overall vehicle driving experience, the current ID is given according to a certain slope. For example... Figure 4 As shown, the process for determining the D-axis discharge current is as follows:

[0045] Set the rated discharge current and discharge regulation coefficient. The rated discharge current is a negative value. Determine the discharge cut-off current value (i.e., the target value mentioned above) based on the rated discharge current and discharge regulation coefficient. The discharge cut-off current value is generally greater than the rated discharge current. Therefore, when the discharge regulation coefficient is greater than 1, the discharge cut-off current value is the rated discharge current divided by the discharge regulation coefficient. When the discharge regulation coefficient is less than 1, the discharge cut-off current value is the product of the rated discharge current and the discharge regulation coefficient.

[0046] A given period is set for the reduction slope and current, and a ramp value is determined based on the reduction slope and the given period; the ramp value is the product of the reduction slope and the given period.

[0047] The output value is the sum of the ramp value and the D-axis discharge current given in the previous cycle.

[0048] The output value is compared with the discharge cutoff current value. If the output value is less than the discharge cutoff current value, the D-axis discharge current of the current cycle is the output value; if the output value is greater than or equal to the discharge current value, the D-axis discharge current of the current cycle is the discharge cutoff current value.

[0049] In the above scheme, the vehicle controller determines that the discharge termination condition is met when any of the following conditions are satisfied:

[0050] A. Within a set time period, the bus voltage value decreases to less than or equal to the set voltage and remains so for a certain period of time;

[0051] B. The active discharge command flag is 0.

[0052] To achieve the above-mentioned method for residual current discharge from the DC bus of a permanent magnet motor, the present invention also provides a residual current discharge system for the DC bus of a permanent magnet motor, including...

[0053] The vehicle controller is used to output active discharge activation commands or active discharge stop commands;

[0054] The motor controller is used to periodically provide the Q-axis discharge current and D-axis discharge current when it receives an active discharge activation command. The Q-axis discharge current is 0, and the D-axis discharge current decreases linearly from 0 to the target value, thereby controlling the motor to operate and discharge through the motor windings. When it receives an active discharge stop command, it provides the D-axis command current and Q-axis command current to control the motor to operate and output torque normally.

[0055] In the above scheme, the motor controller includes

[0056] The discharge current module is used to output the rated discharge current to the ramp module and the Q-axis discharge current to the switching module.

[0057] The instruction module is used to output the D-axis instruction current and Q-axis instruction current to the switching module;

[0058] The ramp module is used to determine the D-axis discharge current based on the rated discharge current and output it to the selector module;

[0059] The selector module is used to output the Q-axis discharge current and D-axis discharge current to the motor controller when an active discharge activation command is received; and to output the D-axis command current and Q-axis command current to the motor controller when an active discharge stop command is received.

[0060] The given current includes the Q-axis discharge current and the D-axis discharge current. The vehicle controller has two discharge judgment items: the ID active discharge judgment item and the IQ active discharge judgment item, such as... Figure 2 , Figure 3 As shown, the input signals for the ID active discharge judgment item are active discharge command, D-axis command current, and D-axis active discharge current; the input signals for the IQ active discharge judgment item are active discharge command, Q-axis command current, and Q-axis active discharge current.

[0061] When an active discharge activation command is received, the active discharge command can be set to 1. The selection module determines that the input value is greater than 0, and selection modules 1 and 2 are connected to the D-axis discharge current value and the Q-axis discharge current value, where the Q-axis discharge current value is 0.

[0062] When an active discharge stop command is received (i.e., active discharge command = 0), the switching module determines whether to connect the D-axis command current and the Q-axis command current. Then, SVPWM is connected to the motor vector control model to perform normal motor speed / torque control.

[0063] After the active discharge command is activated, the ID value is taken as the D-axis discharge current, and the IQ value is taken as the Q-axis discharge current. Here, IQ is taken as 0.

[0064] Upon receiving the active discharge command, the controller enters active discharge mode. At this time, the Q-axis current setpoint is set to 0, and the D-axis current setpoint slopes down from 0 to a target value.

[0065] The input signals for the ramp module are the program running cycle and the rated discharge current. It is used to reduce the D-axis current setpoint from 0 to half of the rated discharge current within 10ms, and output the D-axis discharge current value.

[0066] During testing, the motor enable status in the CAN communication module was set to 0, and the motor active discharge command in the message was set to 1. A rated discharge current of -100A was used for testing. It can be seen that the output ID value slopes down from 0, dropping to half the rated discharge current (-50A) within 500ms. The test results meet the requirements. Figure 5 As shown.

[0067] like Figure 6 As shown, when active discharge exits, the bus voltage value is determined. Simultaneously, the active discharge command (if the command is 1, an active discharge activation command is output; otherwise, it is 0, an active discharge stop command is output) and the real-time bus voltage value are extracted from the CAN bus communication message. The bus voltage value is then checked to see if it is less than the voltage limit. For ease of explanation, the voltage limit is set to 60V, but it can also be set to 36V or other human safety voltages. To ensure that the acquired bus voltage value is ≤60V for safety, a certain time period is used to judge the acquired voltage value. If the acquired bus voltage value is ≤60V within a specified time period (e.g., 20ms), and is ≤60V for 10 consecutive time periods, the true value is output to the AND function, where it is ANDed with the active discharge command. An active discharge stop command is then issued, and the active discharge completion flag is set to 1, at which point the tube is sealed and the machine is stopped.

[0068] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0069] To make the description of this disclosure more detailed and complete, illustrative descriptions of the embodiments and specific examples of the present invention have been provided above; however, this is not the only form of implementing or utilizing the specific examples of the present invention. The embodiments cover the features of multiple specific examples and the method steps and their order for constructing and operating these specific examples. However, other specific examples may also be used to achieve the same or equivalent functions and order of steps.

[0070] In the above detailed description, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features of the single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, wherein each claim stands alone as a preferred embodiment of the invention.

[0071] The disclosed embodiments have been described above to enable any person skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit and scope of this disclosure. Therefore, this disclosure is not limited to the embodiments given herein, but is consistent with the broadest scope of the principles and novel features disclosed in this application.

[0072] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Contents not described in detail in this specification belong to prior art known to those skilled in the art.

Claims

1. A method for residual energy bleed-off of a direct current bus of a permanent magnet electric machine, characterized in that: When the active discharge instruction is activated, the motor controller periodically gives a Q-axis discharge current and a D-axis discharge current, the Q-axis discharge current is 0, and the D-axis discharge current decreases from 0 to a target value in a linear trend, the motor controller controls the motor to work and discharge through the winding of the motor until the discharge end condition is met and the discharge process is exited; The determination process of the D-axis discharge current is: The rated discharge current and the discharge adjustment coefficient are set, the rated discharge current is a negative value, the discharge cutoff current value is determined according to the rated discharge current and the discharge adjustment coefficient, and the discharge cutoff current value is taken as the target value; When the discharge adjustment coefficient is greater than 1, the discharge cutoff current value is the rated discharge current divided by the discharge adjustment coefficient; when the discharge adjustment coefficient is less than 1, the discharge cutoff current value is the product of the rated discharge current and the discharge adjustment coefficient; The decreasing slope and the current given period are set, and the slope value is determined according to the decreasing slope and the given period; The sum of the slope value and the D-axis discharge current given in the last period is taken as the output value; The output value is compared with the discharge cutoff current value, if the output value is less than the discharge cutoff current value, the D-axis discharge current of the current period is the output value; If the output value is greater than or equal to the discharge current value, the D-axis discharge current of the current period is the discharge cutoff current value.

2. The permanent magnet machine DC bus residual energy bleed-off method of claim 1, wherein: The slope value is the product of the decreasing slope and the given period.

3. The permanent magnet machine DC bus residual energy bleed-off method of claim 1, wherein: When any of the following conditions is met, it is determined that the discharge end condition is met: A. Within a set time, the bus voltage value decreases to less than or equal to a set voltage and lasts for a certain time; B. The active discharge instruction flag is 0.

4. A permanent magnet machine DC bus residual energy bleed-off system characterized by: It comprises The whole vehicle controller is used to send an active discharge activation instruction or an active discharge stop instruction; The motor controller is used to periodically give a Q-axis discharge current and a D-axis discharge current when receiving the active discharge activation instruction, the Q-axis discharge current is 0, the D-axis discharge current decreases from 0 to a target value in a linear trend, controls the motor to work and discharge through the winding of the motor; for receiving the active discharge stop instruction, the D-axis instruction current and the Q-axis instruction current are given, the motor is controlled to work and normally output torque; The determination process of the D-axis discharge current is: The discharge adjustment coefficient is set, the discharge cutoff current value is determined according to the rated discharge current and the discharge adjustment coefficient, and the discharge cutoff current value is taken as the target value; when the discharge adjustment coefficient is greater than 1, the discharge cutoff current value is the rated discharge current divided by the discharge adjustment coefficient; when the discharge adjustment coefficient is less than 1, the discharge cutoff current value is the product of the rated discharge current and the discharge adjustment coefficient; The decreasing slope and the current given period are set, and the slope value is determined according to the decreasing slope and the given period; The sum of the slope value and the D-axis discharge current given in the last period is taken as the output value; The output value is compared with the discharge cutoff current value, if the output value is less than the discharge cutoff current value, the D-axis discharge current of the current period is the output value; If the output value is greater than or equal to the discharge current value, the D-axis discharge current of the current period is the discharge cutoff current value.

5. The permanent magnet machine DC bus residual energy bleed-off system of claim 4, wherein: The motor controller comprises The discharge current module is used to output the rated discharge current to the slope module and output the Q-axis discharge current to the selection module. The instruction module is configured to output the D-axis instruction current and the Q-axis instruction current to the selection and switching module. The slope module is configured to determine the D-axis discharge current according to the rated discharge current and output the D-axis discharge current to the selection and switching module. The selection and switching module is configured to output the Q-axis discharge current and the D-axis discharge current to the motor controller when receiving the active discharge activation instruction, and output the D-axis instruction current and the Q-axis instruction current to the motor controller when receiving the active discharge stop instruction.

6. The permanent magnet machine DC bus residual energy bleed off system of claim 4, wherein: The slope value is the product of the decreasing slope and the given period.

7. The permanent magnet machine DC bus residual energy bleed off system of claim 4, wherein: When any of the following conditions is met, it is determined that the active discharge stop instruction is output: A. Within a set time, the bus voltage value is reduced to less than or equal to the set voltage and lasts for a certain time; B. Receiving a signal of the active discharge instruction flag bit being 0.

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