A low vibration and noise SVPWM overmodulation method

Abstract

The invention discloses a low vibration and noise SVPWM overmodulation method, which is based on a modulation system consisting of a given modulation ratio calculation link, a switching angle calculation link, a switching modulation ratio calculation link, an output modulation ratio selection link and a conventional SVPWM calculation link. The given modulation ratio calculation link calculates a given modulation ratio under a current bus voltage according to a given AC and DC axis voltage, the switching angle calculation link calculates a switching angle of the modulation ratio according to a given modulation ratio, the switching modulation ratio calculation link calculates actual modulation ratios in different areas according to the modulation ratio switching angle, the output modulation ratio selection link selects an actual modulation ratio given according to a current magnetic field angle, and the conventional SVPWM calculation link calculates a switch tube drive signal according to the given modulation ratio using the law of conservation of impulse.

Description

Technical Field

[0001] The present invention belongs to the field of power electronics and electric transmission, and specifically relates to a low vibration and noise SVPWM overmodulation method, which is suitable for SVPWM overmodulation sites with strict requirements on vibration and noise, and is particularly suitable for the field of integrated power systems of ships driven by permanent magnet synchronous motors. Background Art

[0002] With the continuous improvement of the performance of materials such as permanent magnets and alloys and the development of advanced control theory, high-efficiency motors such as permanent magnet synchronous motors are widely used in electric vehicles, wind power generation, ships and other power conversion fields due to their advantages in power factor and efficiency. As competition becomes increasingly fierce, operating efficiency, vibration and noise have become important factors in determining the success of equipment.

[0003] SVPWM overmodulation control can increase the fundamental voltage output by the power conversion module, providing a higher degree of freedom for the operation control of equipment such as permanent magnet synchronous motors, and has received extensive attention and research from scholars at home and abroad. The current main research direction is to improve and optimize the minimum phase error, amplitude error and component error under overmodulation control, as well as overmodulation research under non-typical topologies such as multi-level and multi-phase output. However, the existing SVPWM overmodulation control has the following disadvantages:

[0004] 1) The low-frequency band is rich in harmonic content. The fundamental frequency characteristic frequency components can be suppressed by harmonic control strategies such as resonance, but there are currently no effective suppression measures for other low-frequency harmonic components.

[0005] 2) The setting and feedback of the output voltage fundamental amplitude (modulation ratio) are nonlinear, and the consistency of the control system performance in the linear modulation area and the overmodulation area cannot be guaranteed. Summary of the invention

[0006] The purpose of the invention is to address the above problems and propose a simple, reliable and low-vibration and noise SVPWM overmodulation method suitable for engineering applications.

[0007] The technical solution adopted by the present invention to solve the technical problem is: a low vibration and noise SVPWM overmodulation method, used for power conversion modules such as rectifiers or inverters, based on a modulation system consisting of a given modulation ratio calculation link, a switching angle calculation link, a switching modulation ratio calculation link, an output modulation ratio selection link and a conventional SVPWM calculation link connected in sequence, the steps are as follows:

[0008] Step 1: According to the given AC and DC axis voltage, the given modulation ratio m under the current bus voltage is calculated through the given modulation ratio calculation link. r :

[0009] Step 1.1, through the current, flux linkage and other control algorithms, obtain the given direct axis voltage component ud and the quadrature axis voltage component u q ;

[0010] Step 1.2, calculate the given voltage amplitude

[0011] Step 1.3, according to the current bus voltage u dc Calculate the given modulation ratio

[0012] Step 2: Based on the given modulation ratio m r , the switching angles θ1 and θ2 of the modulation ratio are calculated through the switching angle calculation link;

[0013] Step 3: According to the modulation ratio switching angle, the actual modulation ratio m in different areas is calculated by switching the modulation ratio calculation link. r1 and m r2 ;

[0014] Step 4: Magnetic field angle θ according to current requirements e , select the actual modulation ratio given by the output modulation ratio selection link m f ;

[0015] Step 5: Given m according to the actual modulation ratio f , using the law of conservation of impulse, the switch tube drive signal is calculated through the conventional SVPWM calculation link.

[0016] Further, the step 2 specifically includes:

[0017] Step 2.1, determine the given modulation ratio m r The switching voltage modulation ratio m is set to swtich The size of m r >m swtich , then execute step 2.2, otherwise execute step 2.3;

[0018] Step 2.2, set area I and area II to be based on the given modulation ratio m r Re-divided sectors, set the I zone switching angle θ1 = θ switch , where θ switch is the preset area switching angle, and then calculate the switching angle θ2 of zone II according to the following formula, and then go to step 3:

[0019]

[0020] Step 2.3, set the switching angle θ2 of zone II = 0, and then calculate the switching angle θ1 of zone I according to the following formula:

[0021]

[0022] Furthermore, in step 3, the given modulation ratio m of zone I is calculated according to the switching angle θ1 of zone I and the switching angle θ2 of zone II. r1 =1 / cosθ1 and the modulation ratio m is given in zone II r2 =1 / cos(θ1+θ2).

[0023] Furthermore, in step 4, the magnetic field angle θ is e Select the actual modulation ratio currently required given m f :When θ e ≤θ1m f =1; when θ1<θ e ≤θ1+θ2 f =m r1 ; When θ e >θ1+θ2 f =m r2 .

[0024] The beneficial effect of the present invention is that by switching the voltage modulation ratio in different regions, SVPWM overmodulation is achieved on the basis of increasing only a specific electrical frequency harmonic component and maintaining a linear relationship between a given output voltage fundamental amplitude and feedback.

[0025] The modulation method of the present invention can reduce the vibration noise under SVPWM overmodulation, and is suitable for the rail transportation and marine propulsion fields that have overmodulation control of permanent magnet synchronous motors and strict requirements on low-frequency vibration noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of the modulation system of the present invention;

[0027] Figure 2 is the SVPWM vector diagram corresponding to Embodiment 2 of the present invention;

[0028] Figure 3 is θ in Example 2 of the present invention switch =0.2838, the mapping diagram of the modulation ratio and the switching angle θ1 / θ2.

[0029] The figures are marked as follows: 1—given modulation ratio calculation link, 2—switching angle calculation link, 3—switching modulation ratio calculation link, 4—output modulation ratio selection link, 5—conventional SVPWM calculation link. DETAILED DESCRIPTION

[0030] The specific implementation of the present invention is described below in conjunction with the accompanying drawings and examples so that those skilled in the art can better understand the present invention.

[0031] Example 1

[0032] Reference Figure 1 As shown, as a first embodiment, the present invention discloses a low vibration and noise SVPWM overmodulation method, which is used for an electric energy conversion module such as a rectifier or an inverter, based on a control system consisting of a given modulation ratio calculation link 1, a switching angle calculation link 2, a switching modulation ratio calculation link 3, an output modulation ratio selection link 4 and a conventional SVPWM calculation link 5 connected in sequence, wherein the modulation method includes the following steps:

[0033] Step 1: Calculate the given modulation ratio m under the current bus voltage according to the given AC and DC axis voltages r .

[0034] Specifically include:

[0035] Step 1.1, through the current, flux linkage and other control algorithms, obtain the given direct axis voltage component u d and the quadrature axis voltage component u q .

[0036] Step 1.2, calculate the given voltage amplitude

[0037] Step 1.3, according to the current bus voltage u dc Calculate the given modulation ratio

[0038] Step 2: Based on the given modulation ratio m r , the switching angles θ1 and θ2 of the modulation ratio are calculated through the switching angle calculation link 2.

[0039] Specifically include:

[0040] Step 2.1, determine the given modulation ratio m r The switching voltage modulation ratio m swtich The size of m swtich is the preset switching voltage modulation ratio, if m r >m swtich , then go to step 2.2, otherwise go to step 2.3.

[0041] Step 2.2, such as Figure 2 As shown, area I and area II are based on a given modulation ratio m r Re-divided sectors, set the switching angle θ1 = θ switch , where θ switch Switch the angle for the preset area, calculate θ2 according to the following formula, and then go to step 3.

[0042]

[0043] Step 2.3, set the switching angle θ2 of zone II = 0, and then calculate the switching angle θ1 of zone I according to the following formula:

[0044]

[0045] In order to avoid complex calculations within the digital control and reduce the calculation time, in steps 2.2 and 2.3, a table lookup method can be used to store the modulation ratio m in the chip in advance. r Mapping table with angles θ1 and θ2.

[0046] Step 3: Calculate the modulation ratio m of zone I according to the switching angles θ1 and θ2. r1 =1 / cosθ1 and II zone modulation ratio m r2 =1 / cos(θ1+θ2).

[0047] Step 4: According to the required magnetic field angle θ e , select and judge the current required voltage modulation ratio m f ,like Figure 2 As shown in red. e When ≤θ1, m f =1; when θ1<θ e ≤θ1+θ2, m f =m r1 ; When θ e >θ1+θ2, m f =m r2 .

[0048] It should be noted that, due to the use of projection mapping, only the overmodulation situation in zone I needs to be judged.

[0049] Step 5: Calculate the switch tube drive signal based on the given modulation ratio and the law of conservation of impulse.

[0050] Example 2

[0051] like Figure 3 As shown, a three-phase permanent magnet synchronous motor vector control system is used as an example to specifically illustrate the implementation method of the control method. The motor has a rated power of 87kW, a rated phase voltage effective value of 268V, and a rated speed of 810r / min.

[0052] Step 1: Calculate the given modulation ratio m under the current bus voltage according to the given AC and DC axis voltages r , specifically including:

[0053] Step 1.1, through the current, flux linkage and other control algorithms, obtain the given direct axis voltage component u d =-14V and quadrature axis voltage component u q =269.5V;

[0054] Step 1.2, calculate the given voltage amplitude u s=269.86V;

[0055] Step 1.3, calculate the given voltage modulation ratio m r =1.025, where u dc =456V.

[0056] Step 2: Based on the given modulation ratio m r , calculate the switching angles θ1 and θ2 of the modulation ratio, specifically including:

[0057] Step 2.1, determine the given voltage modulation ratio m r The switching voltage modulation ratio m swtich The size of m swtich =1.0193, m r >m swtich , then execute step 2.2;

[0058] Step 2.2, set the switching angle θ1 = θ switch , where θ switch =0.2838, then calculate θ2=0.045, and then go to step 3.

[0059] The modulation ratio m is stored in advance in the chip r The mapping table with angles θ1 and θ2 is as follows Figure 3 shown.

[0060] Step 3: Calculate the modulation ratio m of zone I according to the switching angles θ1 and θ2. r1 =1.0417 and II zone modulation ratio m r2 =1.0566.

[0061] Step 4: According to the required magnetic field angle θ e =0.315, select the voltage modulation ratio m required for the current f At this time, when θ1<θ e ≤θ1+θ2, m f =m r1 .

[0062] Step 5, it is necessary to calculate the switch tube drive signal based on the given modulation ratio and apply the law of conservation of impulse.

[0063] The above embodiments are only illustrative of the principles and effects of the present invention, as well as some embodiments of its application. For those skilled in the art, several modifications and improvements may be made without departing from the creative concept of the present invention, and all of these belong to the protection scope of the present invention.

Claims

1. A low vibration noise SVPWM overmodulation method, characterized in that: A modulation system consisting of a given modulation ratio calculation link (1), a switching angle calculation link (2), a switching modulation ratio calculation link (3), an output modulation ratio selection link (4) and a conventional SVPWM calculation link (5) is provided. The steps are as follows: Step 1: Calculate the given modulation ratio m under the current bus voltage through the given modulation ratio calculation link (1). r : Step 1.1, obtain the given direct-axis voltage component u through the current and flux control algorithm d and the quadrature axis voltage component u q ; Step 1.2, calculate the given voltage amplitude Step 1.3, according to the current bus voltage u dc Calculate the given modulation ratio Step 2: Based on the given modulation ratio m r , the switching angles θ1 and θ2 of the modulation ratio are calculated through the switching angle calculation link (2): Step 2.1, determine the given modulation ratio m r The switching voltage modulation ratio m is set to swtich The size of m r >m swtich , then execute step 2.2, otherwise execute step 2.3; Step 2.2, set area I and area II to be based on the given modulation ratio m r Re-divided sectors, I zone switching angle θ1 = θ switch , where θ switch is the preset area switching angle, and then the switching angle θ2 of zone II is calculated according to the following formula: Step 2.3, set the switching angle θ2 of zone II = 0, and then calculate the switching angle θ1 of zone I according to the following formula: Step 3, by switching the modulation ratio calculation link (3), calculate the actual modulation ratio m in different areas r1 and m r2 ; Step 4: Magnetic field angle θ according to current requirements e , select the actual modulation ratio given by the output modulation ratio selection link (4) f ; Step 5: Given m according to the actual modulation ratio f , using the law of conservation of impulse, the switch tube drive signal is calculated through the conventional SVPWM calculation link (5).

2. A low vibration noise SVPWM overmodulation method according to claim 1, characterized in that: In step 3, the given modulation ratio m of zone I is calculated according to the switching angle θ1 of zone I and the switching angle θ2 of zone II. r1 =1 / cosθ1 and the modulation ratio m is given in zone II r2 =1 / cos(θ1+θ2).

3. A low vibration noise SVPWM overmodulation method according to claim 2, characterized in that: In step 4, the magnetic field angle θ is as required. e Select the actual modulation ratio currently required given m f :When θ e ≤θ1m f =1; when θ1<θ e ≤θ1+θ2 f =m r1 ; When θ e >θ1+θ2 f =m r2 .

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