A three-phase unbalanced load-based vehicle-mounted permanent magnet motor torque fluctuation reduction method

Abstract

This invention discloses a method for reducing torque fluctuation of an on-board permanent magnet motor based on a three-phase unbalanced load. The method involves sampling the DC bus voltage based on a pre-constructed on-board permanent magnet synchronous generator system and feeding the obtained DC bus voltage back to U. dc The output is sent to the filter module, which then obtains the harmonic frequency of the DC bus voltage fluctuation. Next, the frequency parameters of the notch filter and the peak filter are set, and the DC bus voltage filtering feedback command U is output through the filter module. dcfdb Subsequently, the quadrature-axis voltage command U is output sequentially through the first PI regulator and the second PI regulator. d and direct-axis voltage command U q The control signal of the switching transistor is then obtained through the space voltage vector modulation module SVPWM to drive the three-phase full-bridge rectifier circuit. This invention has the function of reducing the pulsation of motor torque under unbalanced load while ensuring safety, and is suitable for widespread promotion and use.

Description

Technical Field

[0001] This invention relates to the field of power generation control technology, specifically to a method for reducing torque fluctuations in a vehicle-mounted permanent magnet motor based on a three-phase unbalanced load. Background Technology

[0002] Energy is an important material guarantee for social production and national economic development. In order to reduce carbon dioxide emissions, the transportation industry, represented by vehicles, ships and aviation, is undergoing an electrification transformation, such as hybrid and pure electric vehicles, multi-electric ships and all-electric and multi-electric aircraft. These modes of transportation are characterized by high mobility, large power demand and the need for independent power supply systems.

[0003] Currently, in three-phase power supply systems, because the loads connected to each phase cannot be completely balanced, the three-phase voltage and current at the power supply point are prone to imbalance, causing line damage. Moreover, this also has an adverse effect on the motors at the power supply point, jeopardizing their normal operation and causing torque sag. Therefore, it is necessary to design a method to reduce torque fluctuations of vehicle-mounted permanent magnet motors based on three-phase unbalanced loads. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and to better solve the problem of three-phase load imbalance encountered when the generator is connected to an external load. The unbalanced load will lead to increased power loss in the line, affecting the safe operation of electrical equipment, and will also cause the torque of the permanent magnet generator to tilt, resulting in a reduction in bearing life. This invention provides a method for reducing torque fluctuation of vehicle-mounted permanent magnet motors based on three-phase unbalanced loads. It has the function of reducing the pulsation of motor torque under unbalanced loads while ensuring safety.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for reducing torque ripple in an on-board permanent magnet motor based on a three-phase unbalanced load includes the following steps:

[0007] Step (A): Construct the vehicle-mounted permanent magnet synchronous generator system;

[0008] Step (B) involves sampling the DC bus voltage based on the constructed on-board permanent magnet synchronous generator system and feeding the obtained DC bus voltage back to U. dc The output is sent to the filter module, and the harmonic frequency of the DC bus voltage fluctuation is obtained through the filter module.

[0009] Step (C): Set the frequency parameters of the notch filter and the peak filter according to the harmonic frequency of the DC bus voltage fluctuation, and output the DC bus voltage filtering feedback command U through the filter module.dcfdb ;

[0010] Step (D) sends the DC bus voltage command U dcref With DC bus voltage filter feedback command U dcfdb The difference is calculated, and the difference value is obtained. Then, the difference value is passed through the first PI regulator to obtain the quadrature axis current command i. qref ;

[0011] Step (E) utilizes the quadrature axis current command i qref and direct-axis current command i dref Obtain quadrature axis voltage command U d and direct-axis voltage command U q ;

[0012] Step (F) will transfer the quadrature axis voltage command U d and direct-axis voltage command U q The space voltage vector modulation module (SVPWM) obtains the control signal of the switching transistor to drive the three-phase full-bridge rectifier circuit, thereby reducing the torque fluctuation of the vehicle-mounted permanent magnet motor.

[0013] The aforementioned method for reducing torque fluctuation of a vehicle-mounted permanent magnet motor based on a three-phase unbalanced load includes, in step (A), a vehicle-mounted permanent magnet synchronous generator system comprising an engine, a permanent magnet synchronous generator, a three-phase full-bridge rectifier circuit, a three-phase four-wire inverter circuit, an LC filter, a current sensor, a main control board, a filter module, and a generator controller.

[0014] In the aforementioned method for reducing torque fluctuation of a vehicle-mounted permanent magnet motor based on a three-phase unbalanced load, in step (B), the filter module determines the harmonic frequency to be filtered out based on the harmonic frequency of the DC-side voltage pulsation obtained from sampling.

[0015] In the aforementioned method for reducing torque fluctuation of a vehicle-mounted permanent magnet motor based on a three-phase unbalanced load, in step (C), a peak filter is used to suppress the increase of bus voltage fluctuation, and a notch filter is used to dynamically limit torque pulsation. The superposition of the notch filter and the peak filter can serve as the feedback quantity of the voltage loop. The gain K of the peak filter is adjusted according to the effect of the notch filter, and the value of K is between 0 and 1.

[0016] The aforementioned method for reducing torque fluctuation of an on-board permanent magnet motor based on a three-phase unbalanced load, in step (D), the DC bus voltage command U dcref It is a constant value.

[0017] The aforementioned method for reducing torque ripple in an on-board permanent magnet motor based on a three-phase unbalanced load, in step (E), the direct-axis current command i dref The value is 0, while the quadrature axis voltage command U d and direct-axis voltage command U qThe specific steps to obtain it are as follows:

[0018] Step (E1) employs a dual-loop vector control method with an outer voltage loop and an inner current loop on the rectifier side. The electrical angle of the permanent magnet motor is obtained through a decoding circuit, and the three-phase armature current is obtained using a Hall current sensor. Then, coordinate transformation is used to convert the three-phase AC energy into two-phase DC energy, which is used as the feedback value i for the voltage-current dual-loop control. q and i d ;

[0019] Step (E2) involves transferring the quadrature-axis current command i. qref and direct-axis current command i dref Respectively with feedback value i q and i d The difference is calculated and passed through the second PI regulator before being output to the feedforward decoupling module. At the same time, the rotor point angular velocity ω after differentiating the electrical angle of the permanent magnet motor is obtained. e It is also output to the feedforward decoupling module;

[0020] Step (E3) involves obtaining the quadrature-axis voltage command U from the feedforward decoupling module. d and direct-axis voltage command U q .

[0021] The beneficial effects of this invention are as follows: This invention can determine the harmonic frequency to be filtered out based on the harmonic frequency of the DC-side voltage pulsation obtained from the current sampling. The notch filter can input the voltage signal obtained from the bus as feedback to the voltage loop through the filter module, and the voltage after adding the notch filter is corrected by the first PI regulator. Then, a notch filter control method for torque pulsation is adopted, and the center frequency of the notch filter is set according to the harmonic frequency of the voltage pulsation of the unbalanced load system. The problem of increased bus voltage pulsation is suppressed by adding a peak filter. This effectively achieves the function of reducing motor torque pulsation under unbalanced loads while ensuring safety. The notch filter in the filter module is for reducing torque pulsation, while the peak filter is for suppressing the increase in voltage pulsation caused by adding the notch filter. Furthermore, the selection is based on the requirement that the working voltage of the bus capacitor should be less than 80% of its rated voltage and the motor torque fluctuation should be within 5%, ensuring a safe and suitable result. Attached Figure Description

[0022] Figure 1 This is a block diagram of the permanent magnet synchronous generator system of the present invention;

[0023] Figure 2 This is a schematic diagram of the three-phase full-bridge rectifier unit of the present invention;

[0024] Figure 3 This is a schematic diagram of the filter module Bode in an embodiment of the present invention;

[0025] Figure 4 This is a comparison chart of motor torque and bus voltage fluctuations with and without a filter module in an embodiment of the present invention. Detailed Implementation

[0026] The present invention will now be further described with reference to the accompanying drawings.

[0027] like Figure 1 As shown, the present invention provides a method for reducing torque fluctuation of an on-board permanent magnet motor based on a three-phase unbalanced load, comprising the following steps:

[0028] Step (A): Construct the vehicle-mounted permanent magnet synchronous generator system;

[0029] The CRRC-mounted permanent magnet synchronous generator system includes an engine, a permanent magnet synchronous generator, a three-phase full-bridge rectifier circuit, a three-phase four-wire inverter circuit, an LC filter, a current sensor, a main control board, a filter module, and a unit controller.

[0030] Step (B) involves sampling the DC bus voltage based on the constructed on-board permanent magnet synchronous generator system and feeding the obtained DC bus voltage back to U. dc The output is sent to the filter module, and the harmonic frequency of the DC bus voltage fluctuation is obtained through the filter module.

[0031] The filter module determines the harmonic frequency to be filtered out based on the harmonic frequency of the DC-side voltage pulsation obtained from sampling.

[0032] like Figure 2 As shown, in step (C), the frequency parameters of the notch filter and the peak filter are set according to the harmonic frequency of the DC bus voltage fluctuation, and the DC bus voltage filtering feedback command U is output through the filter module. dcfdb ;

[0033] Among them, the peak filter is used to suppress the increase of bus voltage fluctuation, and the notch filter is used to dynamically limit torque pulsation. The superposition of the notch filter and the peak filter can be used as the feedback quantity of the voltage loop. The gain K of the peak filter is adjusted according to the effect of the notch filter, and the value of K is between 0 and 1.

[0034] When K is 0, the torque ripple suppression effect is the best, but the bus voltage fluctuation is the most obvious. As the value of K increases, the suppression effect on torque ripple decreases, and the fluctuation of bus voltage gradually decreases. When K is 1, the filter module has no effect on torque ripple suppression, but the rate of rise of bus voltage is smaller than before correction.

[0035] Step (D) involves combining the DC bus voltage command Udcref with the DC bus voltage filter feedback command U.dcfdb The difference is calculated, and the difference value is obtained. Then, the difference value is passed through the first PI regulator to obtain the quadrature axis current command i. qref ;

[0036] Among them, DC bus voltage command U dcref It is a constant value;

[0037] Step (E) utilizes the quadrature axis current command i qref and direct-axis current command i dref Obtain quadrature axis voltage command U d and direct-axis voltage command U q ;

[0038] Among them, the direct-axis current command i dref The value is 0, while the quadrature axis voltage command U d and direct-axis voltage command U q The specific steps to obtain it are as follows:

[0039] Step (E1) employs a dual-loop vector control method with an outer voltage loop and an inner current loop on the rectifier side. The electrical angle of the permanent magnet motor is obtained through a decoding circuit, and the three-phase armature current is obtained using a Hall current sensor. Then, coordinate transformation is used to convert the three-phase AC energy into two-phase DC energy, which is used as the feedback value i for the voltage-current dual-loop control. q and i d ;

[0040] Step (E2) involves transferring the quadrature-axis current command i. qref and direct-axis current command i dref Respectively with feedback value i q and i d The difference is calculated and passed through the second PI regulator before being output to the feedforward decoupling module. At the same time, the rotor point angular velocity ω after differentiating the electrical angle of the permanent magnet motor is obtained. e It is also output to the feedforward decoupling module;

[0041] Step (E3) involves obtaining the quadrature-axis voltage command U from the feedforward decoupling module. d and direct-axis voltage command U q ;

[0042] Step (F) will transfer the quadrature axis voltage command U d and direct-axis voltage command U q The space voltage vector modulation module (SVPWM) obtains the control signal of the switching transistor to drive the three-phase full-bridge rectifier circuit, thereby reducing the torque fluctuation of the vehicle-mounted permanent magnet motor.

[0043] To better illustrate the effects of the present invention, a specific embodiment of the present invention is described below;

[0044] like Figure 3As shown, the left side is the Bode plot of the notch filter. According to the plot, the center frequency of the notch filter is 200 rad / s, meaning it filters out the 100 Hz AC component of the bus voltage. The right side is the Bode plot of the peak filter, which extracts the 100 Hz harmonics to make them fluctuate at the same frequency as the bus voltage, thereby suppressing the increase in bus voltage fluctuations.

[0045] like Figure 4 The figures show a comparison of motor torque and bus voltage fluctuations with and without a filter. Figure (a) shows the comparison of motor torque fluctuations with and without a filter. As can be seen from the figure, the motor torque fluctuation is significantly reduced with the filter module. Figure (b) shows the comparison of bus voltage fluctuations with and without a filter. As can be seen from the figure, adding a filter module increases the amplitude of the bus voltage fluctuation. At this point, the gain K is zero, and the bus voltage fluctuation is at its maximum. However, this situation is consistent with the maximum operating voltage of the bus capacitor.

[0046] In summary, the present invention provides a method for reducing torque fluctuation of a vehicle-mounted permanent magnet motor based on a three-phase unbalanced load. Firstly, it determines the harmonic frequency to be filtered based on the harmonic frequency of the DC-side voltage pulsation obtained from the current sampling. The notch filter uses the voltage signal obtained from the bus as feedback input to the voltage loop via a filter module, and the voltage after adding the notch filter is corrected by a first PI regulator. Then, a notch filter control method for torque pulsation is employed. The center frequency of the notch filter is set according to the harmonic frequency of the voltage pulsation in the unbalanced load system, and a peak filter is added to suppress the increase in bus voltage pulsation. This method effectively achieves the function of reducing motor torque pulsation under unbalanced loads while ensuring safety.

[0047] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for reducing torque ripple in a vehicle-mounted permanent magnet motor based on a three-phase unbalanced load, characterized in that: Includes the following steps, Step (A): Construct the vehicle-mounted permanent magnet synchronous generator system; Step (B): Based on the constructed vehicle-mounted permanent magnet synchronous generator system, the DC bus voltage is sampled, and the obtained DC bus voltage is fed back to U. dc The output is sent to the filter module, and the harmonic frequency of the DC bus voltage fluctuation is obtained through the filter module. Step (C): Set the frequency parameters of the notch filter and the peak filter according to the harmonic frequency of the DC bus voltage fluctuation, and output the DC bus voltage filtering feedback command U through the filter module. dcfdb The peak filter is used to suppress the increase of bus voltage fluctuation, and the notch filter is used to dynamically limit torque pulsation. The superposition of the notch filter and the peak filter can be used as the feedback quantity of the voltage loop. The gain K of the peak filter is adjusted according to the effect of the notch filter, and the value of K is between 0 and 1. Step (D) transfers the DC bus voltage command U dcref With DC bus voltage filter feedback command U dcfdb The difference is calculated, and the difference value is obtained. Then, the difference value is passed through the first PI regulator to obtain the quadrature axis current command i. qref ; Step (E), using the quadrature axis current command i qref and direct-axis current command i dref Obtain quadrature axis voltage command U d and direct-axis voltage command U q ; Step (F) will transfer the quadrature axis voltage command U d and direct-axis voltage command U q The space voltage vector modulation module (SVPWM) obtains the control signal of the switching transistor to drive the three-phase full-bridge rectifier circuit, thereby reducing the torque fluctuation of the vehicle-mounted permanent magnet motor.

2. The method for reducing torque fluctuation of an on-board permanent magnet motor based on a three-phase unbalanced load according to claim 1, characterized in that: The vehicle-mounted permanent magnet synchronous generator system in step (A) includes an engine, a permanent magnet synchronous generator, a three-phase full-bridge rectifier circuit, a three-phase four-wire inverter circuit, an LC filter, a current sensor, a main control board, a filter module, and a generator controller.

3. The method for reducing torque fluctuation of an on-board permanent magnet motor based on a three-phase unbalanced load according to claim 2, characterized in that: In step (B), the filter module determines the harmonic frequency to be filtered out based on the harmonic frequency of the DC side voltage pulsation obtained from the sampling.

4. The method for reducing torque fluctuation of an on-board permanent magnet motor based on a three-phase unbalanced load according to claim 3, characterized in that: DC bus voltage command U in step (D) dcref It is a constant value.

5. The method for reducing torque fluctuation of an on-board permanent magnet motor based on a three-phase unbalanced load according to claim 4, characterized in that: Direct-axis current command i in step (E) dref The value is 0, while the quadrature axis voltage command U d and direct-axis voltage command U q The specific steps to obtain it are as follows: Step (E1) employs a dual-loop vector control method with an outer voltage loop and an inner current loop on the rectifier side. The electrical angle of the permanent magnet motor is obtained through a decoding circuit, and the three-phase armature current is obtained using a Hall current sensor. Then, coordinate transformation is used to convert the three-phase AC energy into two-phase DC energy, which is used as the feedback value i for the voltage and current dual-loop control. q and i d ; Step (E2), transfer the quadrature axis current command i qref and direct-axis current command i dref Respectively compared with feedback value i q and i d The difference is calculated and passed through the second PI regulator before being output to the feedforward decoupling module. At the same time, the rotor point angular velocity ω after differentiating the electrical angle of the permanent magnet motor is obtained. e It is also output to the feedforward decoupling module; Step (E3) involves obtaining the quadrature-axis voltage command U from the feedforward decoupling module. d and direct-axis voltage command U q .

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