阅读说明：本技术 降低svpwm电机共模电压的方法 (Method for reducing common-mode voltage of SVPWM motor ) 是由 张永刚 司文凯 倪振兴 肖健 于 2020-11-16 设计创作，主要内容包括：本发明公开了一种降低SVPWM电机共模电压的方法,S1：从前级控制环节获得静止电压坐标系下的电压；S2：应用步骤S1中静止电压坐标系下的电压,选取作用矢量电压；S3：选取反矢量电压；S4：依据步骤S3中确定的反矢量电压重新计算反矢量电压时间；S5：确定扇区矢量的切换点。本发明采用了与SVPWM中作用矢量相反的电压代替零矢量,用于抑制SVPWM的共模电压过高,SVPWM在驱动电机时过大的共模电压存在击穿绝缘油膜造成轴间短路,以至烧坏电机的隐患,快速的共模电压变化也会产生较强的电磁干扰,影响临近的其它器件的稳定运行,降低共模电压的大小有效的避免了电机在共模电压过高的情况下受到的损害,起到延长电机寿命,提高电机运行效率,降低故障率的作用。(The invention discloses a method for reducing common-mode voltage of an SVPWM motor, which comprises the following steps of S1: obtaining the voltage under a static voltage coordinate system from a preceding stage control link; s2: selecting action vector voltage by applying the voltage under the static voltage coordinate system in the step S1; s3: selecting an inverse vector voltage; s4: recalculating the reverse vector voltage time from the reverse vector voltage determined in step S3; s5: a switching point for the sector vector is determined. The voltage opposite to the action vector in the SVPWM is adopted to replace a zero vector, so that the overhigh common-mode voltage of the SVPWM is restrained, the overhigh common-mode voltage of the SVPWM breaks an insulating oil film to cause an inter-shaft short circuit when the SVPWM drives the motor, so that the hidden danger of burning out the motor is caused, the strong electromagnetic interference can be generated due to the rapid common-mode voltage change, the stable operation of other adjacent devices is influenced, the damage of the motor under the condition of overhigh common-mode voltage is effectively avoided by reducing the magnitude of the common-mode voltage, and the effects of prolonging the service life of the motor, improving the operation efficiency of the motor and reducing the failure rate are achieved.)

1. A method for reducing common-mode voltage of an SVPWM motor is characterized by comprising the following steps:

s1: obtaining the voltage under a static voltage coordinate system from a preceding stage control link;

s2: selecting action vector voltage by applying the voltage under the static voltage coordinate system in the step S1;

s3: selecting an inverse vector voltage;

s4: recalculating the reverse vector voltage time from the reverse vector voltage determined in step S3;

s5: a switching point for the sector vector is determined.

2. The method for reducing the common-mode voltage of the SVPWM motor according to claim 1, wherein the selection method of the inverse vector in the step S3 is:

at zero vector U₀When acting, the voltage law of kirchhoff can be obtained

u_ao＝u_bo＝u_co＝-U_dc/2 (1)

The common mode voltage U can be obtained from the formula (1)_cm0

U_cm0＝-U_dc/2 (2)

In the first sector, with a vector voltage U₆When acting alone, get u_ao＝u_bo＝U_dc/2，u_co＝-U_dc/2. Obtaining a vector voltage U according to equation (1)₆Common mode voltage U when in action_cm6＝U_dc/6, at this time in U₆Under the action of the voltage, the output voltage replaces a zero vector and is at a vector voltage U₆When acting alone, get u_ao＝u_bo＝U_dc/2，u_co＝-U_dc/2. Obtaining a vector voltage U according to equation (1)₆Common mode voltage U when in action_cm6＝U_dc/6, at this time in U₆Output voltage under action

At vector voltage U₁When acting alone, u is obtained_ao＝u_bo＝-U_dc/2，u_co＝U_dc/2. Obtaining a common mode voltage U according to formula (1)_cm1＝-U_dc6, when the first sector outputs voltage

The known formulae (3) and (4) are

From the formula (5), U is selected₆Or U₁When the two non-zero voltage vectors act in place of the zero vector, the sum of the output voltages is zero, and the common mode voltage is U_dc/6。

3. The method for reducing the common-mode voltage of the SVPWM motor according to claim 1, wherein the method for calculating the reverse vector voltage time in step S4 is as follows:

in the formula T₄、T₆、Are respectively a voltage U₄、U₆、U₁Time of action, T_sIs U_outTime of action, from the formula

In the formula u_α、u_βRespectively the alpha-axis and beta-axis voltages after Clark transformation, let V₁＝U₆T₆/T_s,V₂＝U₄T₄/T_s，Substituted into formula (7) to obtain

Wherein | U₁|＝|U₆|＝|U₄|＝2U_dc/3 (9)

By substituting formulae (9) and (10) into formula (8), it is possible to obtain:

in the formula of U_dcAnd obtaining the calculation result of the redistribution of the action time of the synthesized voltage vector of other sectors similarly for the voltage of the direct current bus.

Technical Field

The invention relates to the technical field of SVPWM motors, in particular to a method for reducing common-mode voltage of an SVPWM motor.

Background

Nowadays, motors are frequently contacted instruments in our lives, no matter the motors are used for executing parts needing to move in equipment, no matter the motors are used for executing the parts needing to move in spacecraft or submarine with tens of thousands of meters deep submarine, so the requirements on motor control technology are very important, wherein the three-phase motors have very wide application range in the industrial and military fields, the main method for controlling the three-phase motors is Space Vector Pulse Width Modulation (SVPWM) technology, common-mode voltage exists when the SVPWM drives the motors, so that the aging, the heating and the noise of the motors are aggravated, the overlarge common-mode voltage even breaks through an insulating oil film to cause short circuit between shafts, so that the possibility of burning out the motors is caused, strong electromagnetic interference can be generated by the quick common-mode voltage change to influence the stable operation of other adjacent devices, therefore, under the condition of larger voltage in actual control, we need to adopt some necessary methods to reduce the size of the common-mode voltage, the service life of the motor is prolonged.

In many cases, the approach of reducing the common-mode voltage of the motor is to adopt a method of adding a control device, and although the magnitude of the common-mode voltage can be effectively reduced, the following problems can be caused by adding devices in the operation:

1. the use cost is increased, and the production efficiency is reduced;

2. the failure rate of the device is improved, more failure points can exist due to the increase of the devices, and the transistor is often used in a complex occasion, is easily influenced by the external environment and is easily damaged under the condition of improper operation;

3. the difficulty of troubleshooting is increased, and the problem of the main control device or the problem of the auxiliary device cannot be solved quickly due to more devices.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, an object of the present invention is to provide a method for reducing a common-mode voltage of an SVPWM motor, which can effectively avoid damage to the motor when the common-mode voltage is too high, and achieve the effects of prolonging the service life of the motor, improving the operation efficiency of the motor, and reducing the failure rate.

According to the embodiment of the invention, the method for reducing the common-mode voltage of the SVPWM motor comprises the following steps:

s1: obtaining the voltage under a static voltage coordinate system from a preceding stage control link;

s2: selecting action vector voltage by applying the voltage under the static voltage coordinate system in the step S1;

s3: selecting an inverse vector voltage;

s4: recalculating the reverse vector voltage time from the reverse vector voltage determined in step S3;

s5: a switching point for the sector vector is determined.

Preferably, the method for selecting the inverse vector in step S3 is as follows:

at zero vector U₀When acting, the voltage law of kirchhoff can be obtained

u_ao＝u_bo＝u_co＝-U_dc/2 (1)

The common mode voltage U can be obtained from the formula (1)_cm0

U_cm0＝-U_dc/2 (2)

In the first sector, with a vector voltage U₆When acting alone, get u_ao＝u_bo＝U_dc/2，u_co＝-U_dc/2. Obtaining a vector voltage U according to equation (1)₆Common mode voltage U when in action_cm6＝U_dc/6, at this time in U₆Under the action of the voltage, the output voltage replaces a zero vector and is at a vector voltage U₆When acting alone, get u_ao＝u_bo＝U_dc/2，u_co＝-U_dc/2. Obtaining a vector voltage U according to equation (1)₆Common mode voltage U when in action_cm6＝U_dc/6, at this time in U₆Output voltage under action

At vector voltage U₁When acting alone, u is obtained_ao＝u_bo＝-U_dc/2，u_co＝U_dc/2. Obtaining a common mode voltage U according to formula (1)_cm1＝-U_dc6, when the first sector outputs voltage

The known formulae (3) and (4) are

From the formula (5), U is selected₆Or U₁When the two non-zero voltage vectors act in place of the zero vector, the sum of the output voltages is zero, and the common mode voltage is U_dc/6。

Preferably, the method for calculating the reverse vector voltage time in step S4 includes:

T_sU_out＝T₆U₆+T₄U₄+T₁ ^*U₁ (6)

in the formula T₄、T₆、T₁ ^*Are respectively a voltage U₄、U₆、U₁Time of action, T_sIs U_outTime of action, from the formula

In the formula u_α、u_βRespectively the alpha-axis and beta-axis voltages after Clark transformation, let V₁＝U₆T₆/T_s,V₂＝U₄T₄/T_s，V₃＝V₁T₁ ^*/T_sSubstituted into formula (7) to obtain

Wherein | U₁|＝|U₆|＝|U₄|＝2U_dc/3 (9)

T₁ ^*＝T_s-T₄-T₆ (10)

By substituting formulae (9) and (10) into formula (8), it is possible to obtain:

in the formula of U_dcAnd obtaining the calculation result of the redistribution of the action time of the synthesized voltage vector of other sectors similarly for the voltage of the direct current bus.

In the invention, the problem of overhigh common-mode voltage of the SVPWM is restrained by a reverse vector method, and the problem of larger common-mode voltage brought by the zero vector can be effectively reduced by replacing the zero vector with the voltage opposite to the action vector in the SVPWM; the inverse vector method simultaneously redistributes the action time of each sector vector voltage in the SVPWM theory, avoids the problem of action time caused by the fact that the inverse vector replaces the zero vector, effectively reduces the cost compared with a multi-device method, and avoids the problem that the fault rate is increased and other problems caused by a plurality of devices.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

fig. 1 is a flow chart of a method for reducing a common-mode voltage of an SVPWM motor according to the present invention;

FIG. 2 is a schematic diagram of an SVPWM frequency conversion circuit according to the present invention;

FIG. 3 is a voltage space vector diagram proposed by the present invention;

fig. 4 is a voltage vector synthesis diagram proposed by the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

Examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

Referring to fig. 1, a method for reducing a common mode voltage of an SVPWM motor includes the following steps:

s1: obtaining the voltage under a static voltage coordinate system from a preceding stage control link;

s2: selecting action vector voltage by applying the voltage under the static voltage coordinate system in the step S1;

s3: selecting an inverse vector voltage;

s4: recalculating the reverse vector voltage time from the reverse vector voltage determined in step S3;

s5: a switching point for the sector vector is determined.

Firstly, how to select action vectors:

as shown in fig. 3, the selection is made in accordance with fig. 3.

Secondly, how to select the inverse vector mode:

referring to FIG. 2, at zero vector (here, as vector U)₀For example) from kirchhoff's voltage law

u_ao＝u_bo＝u_co＝-U_dc/2 (1)

U_dcFor the DC bus voltage, the common mode voltage can be obtained from equation (1)

U_cm0＝-U_dc/2 (2)

Taking the first sector as an example, selecting a proper non-zero vector to replace the zero vector action to analyze the change condition of the common mode voltage, wherein selecting U₆Or U₁Instead of the zero vector.

At vector voltage U₆When acting alone, get u_ao＝u_bo＝U_dc/2，u_co＝-U_dc/2. Obtaining a vector voltage U according to equation (1)₆Common mode voltage U when in action_cm6＝U_dc/6, at this time in U₆Output under actionVoltage of

At vector voltage U₁When acting alone, u is obtained_ao＝u_bo＝-U_dc/2，u_co＝U_dc/2. Obtaining a common mode voltage U according to formula (1)_cm1＝-U_dc6, when the first sector outputs voltage

The known formulae (3) and (4) are

From the formula (5), U is selected₆Or U₁When the two non-zero voltage vectors act instead of the zero vector, the sum of the output voltages is zero, and the common mode voltage is only U_dc6, the common mode voltage modulus realizes the slave U_dc/2 drop to U_dcAnd the purpose of/6 is to realize the suppression of the common mode voltage. Similarly, the common-mode voltage of the high-voltage transformer can be obtained under the action of other non-zero vectors_dc/6。

TABLE 1 inverse vector method each sector waveform diagram

Thirdly, how to determine the vector voltage time:

for zero vector free action times, a reallocation is required. In the conventional SVPWM theory, the resultant voltage vector U of each sector_outWhen acting onThree vectors (U) allocated to this sector_outTwo adjacent voltage vectors and a zero vector), and the three vectors are multiplied and added with the corresponding action time to obtain a composite voltage vector. When zero vector is replaced by inverse vector, U_outThe contribution time of (c) is redistributed over the new three vectors. The specific distribution process is shown in fig. 4, and fig. 4 is a voltage vector synthesis diagram. The following still takes the first sector as an example to describe the distribution process of the action time of the composite voltage on three vectors.

T_sU_out＝T₆U₆+T₄U₄+T₁ ^*U₁ (6)

In the formula T₄、T₆、T₁ ^*Are respectively a voltage U₄、U₆、U₁Time of action, T_sIs U_outThe duration of action.

From FIG. 4, it can be seen that

In the formula u_αU beta is alpha-axis and beta-axis voltage after Clark conversion respectively, let V₁＝U₆T₆/T_s,V₂＝U₄T₄/T_s，V₃＝V₁T₁ ^*/T_sSubstituted into formula (7) to obtain

Wherein | U₁|＝|U₆|＝|U₄|＝2U_dc/3 (9)

T₁ ^*＝T_s-T₄-T₆ (10)

By substituting formulae (9) and (10) into formula (8), it is possible to obtain:

in the formula of U_dcIs the voltage of the dc bus.

Similarly, the calculation result of the redistribution of the action time of the composite voltage vector of other sectors can be obtained. The specific action time distribution calculation formula is shown in table 2.

TABLE 2 vector action time for each sector

How to determine the switching point

First, defineThe switching point of the 3-phase voltage switching time is T_cm1、T_cm2 and T_cm3And the relationship of each sector is as listed in tables 2-6.

TABLE 3 time switch point T for each sector_cm1、T_cm2And T_cm3

N

1

2

3

4

5

6

Tcm1

Tb

Ta

Ta

Tc

Tc

Tb

Tcm2

Ta

Tc

Tb

Tb

Ta

Tc

Tcm3

Tc

Tb

Tc

Ta

Tb

Ta

And finally, comparing the triangular carrier signal with a certain frequency with each sector vector switching point to generate a PWM pulse signal obtained by the converter.

In summary, the method for reducing the common-mode voltage of the SVPWM motor uses a reverse vector method to inhibit the problem of overhigh common-mode voltage of the SVPWM motor, adopts the voltage opposite to the action vector in the SVPWM to replace the zero vector, can effectively reduce the problem of larger common-mode voltage brought by the zero vector, and reduces the selection number of the vectors, simplifies the calculation amount and further reduces the switching times of a switching tube compared with an adjacent vector method; the inverse vector method simultaneously redistributes the action time of each sector vector voltage in the SVPWM theory, avoids the problem of action time caused by the fact that the inverse vector replaces the zero vector, effectively reduces the cost compared with a multi-device method, and avoids the problem that the fault rate is increased and other problems caused by a plurality of devices.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.