A Method for Calibrating Harmonic Current Commands of a Permanent Magnet Synchronous Motor in a New Energy Vehicle

Abstract

The present invention discloses a method for calibrating harmonic current commands of a permanent magnet synchronous motor for new energy vehicles. The control target torque starts from the initial torque and sequentially changes according to the first step length until the final calibrated torque; at each target torque, the control speed starts from the initial speed and sequentially changes according to the second step length until the final calibrated speed; according to the recorded data, the optimized speed points corresponding to the order noise spikes at each target torque are obtained; the dynamometer is controlled to output a torque of the target torque and a speed of the optimized speed point corresponding to the target torque; the amplitude and phase of the target current are adjusted to change according to a certain rule, and the order harmonic current control target values at all target torques are obtained, completing the calibration of the harmonic current commands. The calibration method of the present invention is simple and easy to implement, and can effectively achieve the purpose of finding the optimal order noise harmonic current control on the premise of minimizing the impact on the total system efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor control, and particularly relates to a method for calibrating harmonic current commands of a permanent magnet synchronous motor for new energy vehicles. Background Art

[0002] At present, the requirements for vehicle comfort are getting higher and higher, which poses new challenges to the optimization of the vibration and noise of permanent magnet synchronous motors. The harmonic current injection control strategy can effectively reduce the order vibration and reduce the order noise.

[0003] At present, the key points and difficulties of harmonic current injection are the harmonic current control algorithm and the acquisition of the harmonic current target current. The harmonic current control algorithm mainly focuses on the stability and effectiveness of the control algorithm. The current algorithms and analysis methods cannot effectively obtain the optimized harmonic current target value. The existing calibration schemes belong to full current scanning, with a long calibration period and cumbersome work. The purpose of obtaining the harmonic current target value is to analyze the injected specified harmonic current component to achieve the purpose of canceling the order force. This direction has always been a blind spot for harmonic injection noise reduction and suppression. Summary of the Invention

[0004] The purpose of the present invention is to solve the deficiencies existing in the above background art, and provide a method for calibrating harmonic current commands of a permanent magnet synchronous motor for new energy vehicles, which can effectively achieve the purpose of finding the optimal order noise harmonic current control on the premise of minimizing the impact on the overall system efficiency.

[0005] The technical solution adopted by the present invention is: a method for calibrating harmonic current commands of a permanent magnet synchronous motor for new energy vehicles, including the following steps:

[0006] Step 1, control the target torque to change sequentially from the initial torque according to the first step length until the final calibration torque;

[0007] Step 2, at each target torque, control the speed to change sequentially from the initial speed according to the second step length until the final calibration speed;

[0008] Step 3, obtain the optimized speed point corresponding to the order noise peak at each target torque according to the data recorded during the change of torque and speed;

[0009] Step 4, control the dynamometer to output a torque of the target torque and a speed of the optimized speed point corresponding to the target torque;

[0010] Step 5, adjust the amplitude and phase of the target current to change according to a certain rule, and find the amplitude and phase of the target current corresponding to the lowest order noise as the order harmonic current control target value at the target torque;

[0011] Step 6: Control the replacement output torque and speed, and repeat Step 5 until the order harmonic current control target values at all target torques are obtained, completing the calibration of the harmonic current command.

[0012] Further, in the said Step 3, the process of obtaining the optimized speed points corresponding to each target torque at the order noise spikes according to the data recorded during the torque and speed change is as follows:

[0013] At each target torque, record the order noise corresponding to each speed respectively. After the speed change is completed, find one or more order noises from the recorded data in descending order as the order noise spikes at this target torque, and the one or more speeds corresponding to the order noise spikes are the optimized speed points.

[0014] Further, in the said Step 5, the process of adjusting the amplitude and phase of the target current to change according to a certain rule and finding the amplitude and phase of the target current corresponding to the lowest order noise is as follows:

[0015] Control the current amplitude of the target current to change in turn from the initial amplitude according to the third step length until the final calibrated current amplitude;

[0016] At each current amplitude, control the current phase to change in turn within a certain range according to the fourth step length, record the order noise corresponding to each current phase, and take the current phase corresponding to the minimum order noise as the optimal phase at this current amplitude;

[0017] Compare the magnitudes of the minimum order noises at all current amplitudes, and take the current phase and current amplitude corresponding to the lowest order noise as the amplitude and phase of the target current.

[0018] Further, for the initial current amplitude, the change range of the current phase is 0° to 360°.

[0019] Further, for the nth current amplitude, the change range of the current phase is α n-1 - θ° to α n-1 + θ°, where n is a positive integer greater than 1, and α n-1 is the current phase corresponding to the lowest order noise at the (n - 1)th current amplitude, and θ is a calibrated value, generally taking 90°.

[0020] Even further, the calibrated current amplitude is 3% of the fundamental wave current.

[0021] The present invention obtains the amplitude and phase of harmonic current injection under a specified torque through a calibration scheme. During the calibration process, the corresponding order noise optimization speed points are obtained by finding order noise spikes, and then based on this, the current amplitude and phase changes are controlled to obtain the order noise decibel values under different currents. The minimum order noise decibel value is found and used as the control target current for harmonic current injection under this torque. This method can effectively find the control target value of the specified order harmonic current and ensure that it has no adverse impact on the fundamental wave current control. The calibration method of the present invention is simple and easy to implement, and can effectively achieve the purpose of finding the optimal order noise harmonic current control on the premise of minimizing the impact on the overall system efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the calibration flowchart of the present invention.

[0023] Figure 2 It is the flowchart of the target current of the present invention changing according to a certain rule. DETAILED DESCRIPTION OF THE INVENTION

[0024] The following further describes the specific embodiments of the present invention with reference to the accompanying drawings. It should be noted here that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation to the present invention. In addition, 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.

[0025] As Figure 1 , Figure 2 shown, the present invention provides a method for calibrating harmonic current commands of a permanent magnet synchronous motor for a new energy vehicle, including two parts: finding order noise spikes and cyclically optimizing to obtain the current amplitude.

[0026] Finding order noise spikes: Normally, it is necessary to collect the noise of the motor at different torques and speeds. Since harmonic injection mainly targets the injection of harmonic currents of a specified order and improves the noise components of the specified order, it is necessary to analyze the collected order noise. To simulate the actual vehicle conditions, experiments are selected to be carried out according to the percentage of the external characteristic. That is, after arranging the noise collection equipment, the torque command is output according to the percentage of the external characteristic, and the dynamometer speed is controlled to increase at a fixed slope under a positive torque command and decrease at a fixed slope under a negative torque command.

[0027] The collected order noise data is a set of two-dimensional curves with the rotational speed on the abscissa and the noise decibel value on the ordinate. Since the human ear is most sensitive to sudden noises, it is necessary to sort out and analyze the order noise mutations on the curve, or the rotational speed points where the order noise exceeds the target line most severely. The purpose of harmonic injection is to improve the rotational speed points where the order noise mutation exceeds the target line most severely. Considering that there is a maximum rotational speed effective range for harmonic injection, that is, after exceeding this range, the carrier ratio is seriously insufficient, resulting in the inability to close the loop control of the specified harmonic current, or the injected harmonic current is non-sinusoidal with more harmonic content. Therefore, when looking for the optimization target points, it is necessary to find the optimized rotational speed points within the maximum rotational speed effective range. Divide the full torque range section according to the equal ratio relationship to find the order noise optimized rotational speed points. The specific steps are as follows:

[0028] Step 1: Control the target torque to change sequentially from the initial torque according to the first step length until the final calibrated torque. The value of the first step length can be 5 - 80 N, and the calibrated torque is determined according to the maximum control ability of the electric drive assembly. The direction of the target torque change can be increasing or decreasing.

[0029] Step 2: At each target torque, control the rotational speed to change sequentially from the initial rotational speed according to the second step length until the final calibrated rotational speed. The value of the second step length can be 100 - 300 rpm, and the direction of the rotational speed change can be increasing or decreasing.

[0030] Step 3: At each target torque, record the order noise corresponding to each rotational speed respectively. After the rotational speed change is completed, find one or more order noises from the recorded data in descending order as the order noise peaks corresponding to the target torque. Then the one or more rotational speeds corresponding to the order noise peaks are the optimized rotational speed points.

[0031] Taking an electric drive assembly with a power of 160 kW, a peak torque of 320 N, and 4 pole pairs as an example, describe the process of finding the order noise peaks. The order noises to be optimized are the 24th order and the 48th order, that is, the harmonic currents to be injected are -5 and +7 to optimize the 24th order noise of the motor, and -11 and +13th order current harmonics need to be injected to optimize the 48th order noise of the motor. Due to the limitation of the maximum rotational speed effective range, the maximum control range of the harmonic current for suppressing the 24th order noise is 0 - 4000 rpm, and the maximum control range of the harmonic current for suppressing the 48th order noise is 0 - 2500 rpm.

[0032] Divide 320 N evenly into 10 equal parts, with each part being 32 N. That is, the torque step is 32. The rotational speed starts from 0 rpm and increases in steps of 200 rpm per second (electrically) to 4000 rpm, or starts from 4000 rpm and decreases in steps of 200 rpm per second (generating electricity) to 0 rpm. The noise acquisition design collects noise data to obtain the rotational speed points that need to be optimized at this torque. The rotational speed points for 24 - order optimization can be approximately selected at 1600 rpm, and the rotational speed points for 48 - order optimization can be approximately selected at 2000 rpm. Record the rotational speed points that need to be optimized at different torques to prepare for subsequent work.

[0033] Obtain the current amplitude through cyclic optimization: According to the rotational speed points of the order noise that need to be optimized at different torques obtained during the process of finding the order noise peaks, control the dynamometer to output the rotational speed to this optimized rotational speed, control the total assembly torque to the target torque, and the noise analysis equipment analyzes the order noise at this rotational speed and torque online. For 24 - order noise, for a 4 - pole motor, control the 7th - harmonic current to 0 and adjust the target current of the 5th - harmonic. For 48 - order noise, control the 13th - harmonic current to 0 and adjust the target current of the 11th - harmonic. The specific steps are as follows:

[0034] The first step: Control the dynamometer to output the torque as the initial torque and the rotational speed as the optimized rotational speed point corresponding to the initial torque;

[0035] The second step: Set the amplitude of the target current to 0 and record the order noise decibel value;

[0036] The third step: Fix the amplitude of the target current at the minimum step size, and increase the phase of the current from 0 in appropriate steps until 360 degrees. Record the order noise decibel values at different angles and find the angle α1 with the minimum noise;

[0037] The fourth step: Increase the current amplitude step size by an appropriate value once, and offset by a sufficient angle in the positive and negative directions at the angle corresponding to the minimum noise found in the third step, that is, in the range of α1 - 90° to α1 + 90°. Use this as the optimization boundary for the angle at this current. Increase the angle in appropriate steps until the entire angle range is searched, and record the angle α2 with the minimum noise in this range.

[0038] The fifth step: Increase the current amplitude in steps and repeat the process of the fourth step until the maximum value of the current amplitude at this torque is reached (too large harmonic current has an adverse effect on the system efficiency. For balance, generally control the injected harmonic content within 3% of the fundamental current). Record the minimum order noise decibel values for all combinations.

[0039] Step 6: Compare the order noise decibel values under the control of the above five steps at different harmonic current control amplitudes and phases, and find the minimum order noise decibel value as the control target current for harmonic current injection at this torque.

[0040] Step 7: Replace the control torque and the corresponding rotational speed, and repeat the above six steps until the optimal harmonic current injection control target currents at all torques are found.

[0041] According to the above steps, the order harmonic current control target values at different torques can be obtained, generally including the 24th order and the 48th order.

[0042] Taking an electric drive assembly with a power of 160 kW, a peak torque of 320 N, and 4 pole pairs as an example, the minimum step size of the harmonic current amplitude is defined as 1 A, the minimum step size of the angle is defined as 10 degrees, and the positive and negative offset angles are defined as 90 degrees.

[0043] According to the harmonic control current target values at different torques obtained by cyclic optimization, organize these current target values into a two-dimensional table related to torque, distinguish between the electric and generating modes, and find the corresponding harmonic control target current according to the current state and the current target torque to achieve the control of harmonic current, thereby achieving the purpose of reducing order noise and optimizing the driving experience.

[0044] Through the present invention, the purpose of finding the optimal order noise harmonic current control can be effectively achieved on the premise of minimizing the impact on the efficiency of the assembly system.

[0045] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

Claims

1. A method for calibrating the harmonic current command of a permanent magnet synchronous motor in a new energy vehicle, characterized in that, Including the following steps: Step 1, control the target torque to change sequentially from the initial torque according to the first step length until the final calibrated torque; Step 2, at each target torque, control the speed to change sequentially from the initial speed according to the second step length until the final calibrated speed; Step 3, obtain the optimized speed points corresponding to each target torque at the order noise peak according to the data recorded during the change of torque and speed; Step 4, control the dynamometer to output a torque of the target torque and a speed of the optimized speed point corresponding to the target torque; Step 5, adjust the amplitude and phase of the target current to change according to a certain rule, and find the amplitude and phase of the target current corresponding to the lowest order noise as the control target value of the order harmonic current at the target torque; Step 6, control to change the output torque and speed, and repeat Step 5 until the control target values of the order harmonic currents at all target torques are obtained, completing the calibration of the harmonic current command.

2. The method for calibrating the harmonic current command of the permanent magnet synchronous motor of the new energy vehicle according to claim 1, wherein In the said Step 3, the process of obtaining the optimized speed points corresponding to each target torque at the order noise peak according to the data recorded during the change of torque and speed is as follows: At each target torque, record the order noise corresponding to each speed respectively. After the speed change is completed, find one or more order noises from the recorded data in descending order as the order noise peaks at the target torque, and the one or more speeds corresponding to the order noise peaks are the optimized speed points.

3. The method for calibrating the harmonic current command of the permanent magnet synchronous motor of the new energy vehicle according to claim 1, wherein, In the said Step 5, the process of adjusting the amplitude and phase of the target current to change according to a certain rule and finding the amplitude and phase of the target current corresponding to the lowest order noise is as follows: Control the current amplitude of the target current to change sequentially from the initial amplitude according to the third step length until the final calibrated current amplitude; At each current amplitude, control the current phase to change sequentially within a certain range according to the fourth step length, record the order noise corresponding to each current phase, and use the current phase corresponding to the minimum order noise as the optimal phase at the current amplitude; Compare the magnitudes of the minimum order noises at all current amplitudes, and use the current phase and current amplitude corresponding to the lowest order noise as the amplitude and phase of the target current.

4. The harmonic current command calibration method for the permanent magnet synchronous motor of a new energy vehicle according to claim 3, wherein: For the initial current amplitude, the change range of the current phase is 0° to 360°.

5. The method for calibrating the harmonic current command of the permanent magnet synchronous motor of the new energy vehicle according to claim 3, wherein: For the nth current amplitude, the change range of the current phase is α n-1 -θ° to α n-1 +θ°, where n is a positive integer greater than 1, and α n-1 is the current phase corresponding to the lowest order noise at the (n - 1)th current amplitude, and θ is a calibration value.

6. The method for calibrating the harmonic current command of the permanent magnet synchronous motor of the new energy vehicle according to claim 3, wherein: The calibrated current amplitude is 3% of the fundamental wave current.

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