Method for controlling an inverter of a vehicle

Abstract

To provide a control method of a vehicle inverter.SOLUTION: A vehicle 10 includes an inverter 14, an electric motor 20, a control unit 12, and a detection element 18. The control unit 12 includes a pulse width generator 15 for generating pulses. At least one vehicle parameter is detected by the corresponding detection element 18 at predetermined time intervals. A plurality of pulse width signals is generated by the pulse generator 15 on the basis of the detected at least one vehicle parameter. Depending on the generated pulse width signal for the detected at least one vehicle parameter, at least one switching strategy of the inverter 14 is controlled by the control unit 12 in order to achieve maximum rotational flux and maximum efficiency of the vehicle 10.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for controlling and calibrating a vehicle inverter. [Background technology]

[0002] Background technology Electric motors used in hybrid / electric vehicles have various efficiency curves, and much of the efficiency is controlled by the inverter for different torque, speed, and high-voltage battery characteristics. The current state-of-the-art technology uses theoretical formulas to fix the efficiency of the inverter, the electric motor, and switching strategies for the inverter at different torque / speed characteristics. This method is neither very accurate nor efficient. Various parameters of the inverter used to control electric motors, such as permanent magnet synchronous motors used in hybrid electric vehicles, need to be calibrated for multiple current and voltage vector values ​​to provide accurate torque values. One such parameter is the inductance value of the electric motor's stator coil. Manually calibrating the electric motor's inductance parameters on a test bench for different ranges of shaft current is time-consuming, error-prone, and inaccurate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 6,046,554 Summary of the Invention [Problem to be solved by the invention]

[0004] Prior art document U.S. Pat. No. 6,046,554 (US6046554) discloses a motor operable with a supply current, having a first motor winding that provides a motor back-EMF during motor operation. The first motor generates a predetermined nominal torque at a predetermined nominal rotational speed, corresponding to a predetermined operating current and a predetermined nominal back-EMF. The above parameters are calibrated by supplying a supply current to the motor. The motor is operated at a known rotational speed, and an EMF indication of the motor back-EMF is obtained by decelerating the motor from the known rotational speed by disconnecting the supply current from the motor. [Means for solving the problem]

[0005] The different modes of the invention are disclosed in detail in the specification and are further illustrated in the accompanying drawings. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a diagram illustrating a control unit of a vehicle according to an embodiment of the present invention. [Figure 2] 1 illustrates a flowchart of a method for calibrating an inverter of a hybrid vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0007] Detailed Description of the Embodiments FIG. 1 illustrates a control unit 12 for a vehicle 10 according to one embodiment of the vehicle. The control unit 12 detects at least one vehicle parameter at predetermined time intervals and generates a pulse-width signal based on the detected at least one vehicle parameter. The control unit 12 controls at least one switching strategy of an inverter 14 of the vehicle 10 depending on the generated pulse-width signal for the detected at least one vehicle parameter to achieve maximum rotational flux of the hybrid vehicle 10. The vehicle 10 is selected from a group of vehicles including hybrid vehicles, electric vehicles, etc. The control unit 12 controls the switching strategy of the inverter 14 of the vehicle 10 to achieve maximum efficiency during maximum rotational flux generation. The control and calibration functions for the inverter 14 are implemented in a vehicle or electric motor test bench.

[0008] Further, the configuration and components of the inverter 14 in the hybrid vehicle 10 are described below. The inverter 14 supplies power from the battery 22 to the electric motor 20. The inverter 14 includes at least six switches 16 connected as shown in FIG. 1. According to one embodiment of the present invention, the switches 16 are insulated gate bipolar transistors. The electric motor 20 according to one embodiment of the present invention is a permanent magnet synchronous motor. However, it is not limited to the one disclosed above and can be any electric motor 20 used in various applications. At least one sensing element 18 configured to sense at least one vehicle parameter is connected to and located near the electric motor 20, or is incorporated into the electric motor 20 as needed. The at least one sensing element 18 is selected from a group of sensing elements including a torque sensor, a speed sensor, a shaft vibration sensor, etc.

[0009] The control unit 12 is selected from a group of control units including a microcontroller, a microprocessor, an ASCII chip, an IC chip, etc. The at least one vehicle parameter is selected from a group of parameters including a motor speed, a generated torque, an input voltage, a vibration of the motor shaft, harmonics generated in the stator current lines, an audible frequency range relative to the switching frequency, and a generated heat amount. The control unit 12 includes a pulse width generator 15 for generating a series of pulses to be supplied to the switches 16 of the inverter 14. The control unit 12 provides a plurality of switching strategies to the switches of the inverter 14 based on the detected at least one vehicle parameter. The control unit 12 controls the at least one switching strategy to be provided to the inverter 14, the at least one switching strategy including providing a plurality of pulse width signals having different duty cycles to the inverter based on the detected at least one vehicle parameter. The control unit 12 is configured to provide the pulse width signals to at least three switches 16 of the inverter 14 in the at least one switching strategy.

[0010] 2 shows a flowchart of a method for calibrating an inverter of a hybrid vehicle 10. In step S1, at least one vehicle parameter is detected by a corresponding detection element 18 at each predetermined time interval. In step S2, a pulse width signal is generated by a pulse generator 15 based on the detected at least one vehicle parameter. In step S3, at least one switching strategy of the inverter 14 is controlled by the control unit 12 depending on the pulse width signal generated for the detected at least one vehicle parameter to achieve maximum rotational flux with the highest efficiency in the hybrid vehicle / electric motor test bench 10.

[0011] The control unit 12 receives the current torque, speed, and high-voltage line values ​​at which the hybrid vehicle 10 is operating. The control unit 12 varies the required speed, torque, and input high voltage supplied to the inverter and test bench system based on predetermined motor torque vs. speed vs. high-voltage characteristics stored in the control unit 12. Based on the received speed and torque values, the control unit 12 determines the pulse width signal to be supplied to the switches 16 of the inverter 14 to achieve maximum rotational flux. The control unit 12 supplies a series of pulse width signals including different duty cycle, pulse width, and frequency values. The control unit 12 varies the switching strategies by varying the above-mentioned parameters of the pulse width signals. The control unit 12 varies the pulse width signal parameters, such as duty cycle, pulse width, and frequency values, and different combinations of the above-mentioned parameters are applied to the switches 16 of the inverter 14 so that rotational flux can be achieved for all switching strategies.

[0012] For each switching strategy, the control unit 12 compares the torque generated in the vehicle 10 with the desired torque. For example, if the torque generated is equal to the desired torque value (stored in the control unit 12), the generated mechanical power is calculated using the torque and speed values. The inverter efficiency is calculated based on the input power supplied to the inverter 14 from the battery 22 using the inverter voltage and current values ​​obtained from the voltage and current sensor 18 and the calculated mechanical power. In addition to the inverter efficiency, vehicle parameters such as those described above (motor shaft vibration, harmonics generated in the stator lines, audible frequency range relative to the switching frequency, heat generation, etc.) are calculated. Upon detecting the completion of the combination of switching strategies provided to the inverter 14 (giving a complete rotational magnetic flux), the control unit 12 determines one switching strategy in which the above vehicle parameters do not deviate significantly from their predetermined values. The determined switching strategy is stored in the control unit 12 for further use.

[0013] For example, the control unit 12 provides a pulse-width signal at a frequency of 6 KHz, with a duty cycle initialized to 50%. Because the inverter 14 includes six switches, the pulse-width signal is provided to three switches 16 with different waveform configurations, such as T1=0 ms, T2=4 ms, and T3=8 ms for the first switch. Once the above switching strategy is provided to the inverter 14, the control unit 12 determines at least one vehicle parameter and a variation of the vehicle parameter with a predetermined value. For example, the control unit 12 determines the rotational flux generated for the provided switching strategy, and based on the amount of rotational flux generated, the control unit 12 stores the switching strategy.

[0014] If the generated rotational flux is not at its maximum value or does not equal the predetermined value, the control unit 12 changes the parameters of the pulse width signal to frequency (6 kHz), duty cycle (60%), and waveform configuration to T1=3 ms, T2=5 ms, and T3=7 ms, and the process disclosed above continues. The control unit 12 changes one or more parameters of the pulse width to supply to the switches of the inverter 14 to achieve the maximum rotational flux. Upon detecting completion of all combinations of the pulse width signal parameters, the control unit 12 determines and stores in the control unit 12 the switching strategy that provided the maximum rotational flux for the corresponding torque, speed, and high voltage values ​​of the vehicle / test bench 10. The control unit 12 continues this process for multiple torque, speed, and high voltage values ​​of the vehicle 10, and multiple switching strategies are stored in the control unit 12 based on the variation of at least one vehicle parameter of the vehicle 10 from the predetermined value.

[0015] By using the methods disclosed above, the efficiency of the electric motor 20 is improved through the use of automatic calibration and learning switching strategy techniques. The power usage used by the electric motor 20 of the hybrid vehicle 10 is minimized. With the same power input provided to the electric motor 20, efficiency is improved and more driving range is achieved. By making the calibration process more accurate, manual intervention is reduced. Harmonics, vibrations, and audio frequencies for different speeds, torques, and high voltage ranges are automatically optimized.

[0016] It should be understood that the embodiments described above are merely exemplary and are not intended to limit the scope of the invention. Many such embodiments and other modifications and variations of the embodiments described herein are contemplated. The scope of the invention is limited only by the claims.

Claims

1. A method for controlling an inverter (14) for supplying power from a battery (22) to an electric motor (20) of a hybrid vehicle (10), comprising: detecting at least one vehicle parameter by a corresponding sensing element (18) for each predetermined time interval; generating a pulse width signal by a pulse generator (15) based on the detected at least one vehicle parameter; controlling, by a control unit (12), switching of the inverter (14) in dependence on the generated pulse width signal for the detected at least one vehicle parameter; Including, a duty cycle value, a pulse pattern, and a supply frequency of at least one of the pulse width signals that achieves the highest efficiency in a test bench of the electric motor (20) of the hybrid vehicle (10) are stored in the control unit (12) when the duty cycle value, the pulse pattern, and the supply frequency of the pulse width signal are supplied to the inverter (14); The method of claim 1, wherein the pulse width signal supplied to the inverter is determined based on the duty cycle value stored in the control unit, the pulse pattern, and the supply frequency of the pulse width signal.

2. 2. The method of claim 1, wherein the at least one vehicle parameter is selected from a group of parameters including a motor speed of the electric motor, a torque generated by the electric motor, an input voltage of the inverter, vibrations of a motor shaft of the electric motor, harmonics generated in a stator line of the electric motor, and a heat quantity generated by the electric motor.

3. 2. The method of claim 1, wherein controlling the switching of the inverter (14) comprises providing a plurality of pulse width signals to the inverter (14) having different duty cycles and pulse patterns based on the detected at least one vehicle parameter.

4. A control unit (12) for a hybrid vehicle (10), comprising: The control unit (12) Detecting at least one vehicle parameter at each predetermined time interval; generating a pulse width signal based on the detected at least one vehicle parameter; controlling switching of an inverter (14) for supplying power from a battery (22) of the hybrid vehicle (10) to an electric motor (20) in dependence on the generated pulse width signal for the detected at least one vehicle parameter; It is structured as follows: The control unit (12) storing a duty cycle value, a pulse pattern, and a supply frequency of at least one of the pulse width signals that achieves the highest efficiency on a test bench of the electric motor (20) of the hybrid vehicle (10) when the duty cycle value, the pulse pattern, and the supply frequency of the pulse width signal are supplied to the inverter (14); determining the pulse width signal to be supplied to the inverter (14) based on the duty cycle value stored in the control unit (12), the pulse pattern, and the supply frequency of the pulse width signal; The control unit (12) is configured to:

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