Pulse width modulation method, pulse width modulation device and control system of permanent magnet synchronous motor

Abstract

The present invention discloses a pulse width modulation method, a pulse width modulation device and a control system for a permanent magnet synchronous motor. The pulse width modulation method includes: obtaining a first voltage value and a second voltage value in a two-phase stationary coordinate system, and calculating a three-phase original modulation wave; calculating a zero-sequence component according to the maximum value and the minimum value in the three-phase original modulation wave; calculating a three-phase original duty cycle according to the three-phase original modulation wave and the zero-sequence component, and performing coordinate transformation on the three-phase original duty cycle to obtain a space vector in the two-phase stationary coordinate system; when the space vector exceeds the area of ​​a regular hexagon of a unit length centered at the origin in the two-phase stationary coordinate system, overmodulating the three-phase original duty cycle to obtain a three-phase PWM duty cycle. The method can reduce the calculation complexity, reduce the PWM duty cycle update delay, and take into account overmodulation, thereby improving the torque control smoothness.

Description

Technical Field

[0001] The present invention relates to the technical field of space vector pulse width modulation, and in particular to a pulse width modulation method, a pulse width modulation device and a control system of a permanent magnet synchronous motor. Background Art

[0002] At present, the SVPWM (Space Vector Pulse Width Modulation) scheme adopted in the prior art needs to determine the sector where the voltage vector is located, and adopts different calculation methods according to different sectors to calculate the duty cycle. Since there are six sectors in total, six formulas are required for calculation, resulting in complicated calculation steps. The prior art also adopts an SPWM scheme based on zero-sequence component injection to reduce the calculation complexity, but it cannot take into account the overmodulation algorithm. Summary of the invention

[0003] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art, and to provide a pulse width modulation method, a pulse width modulation device and a control system for a permanent magnet synchronous motor, which can reduce the calculation complexity, reduce the PWM duty cycle update delay, take into account overmodulation, and improve the torque control smoothness.

[0004] In a first aspect, an embodiment of the present invention provides a pulse width modulation method of a permanent magnet synchronous motor, comprising:

[0005] Obtaining a first voltage value and a second voltage value in a two-phase stationary coordinate system, and calculating and obtaining a three-phase original modulation wave;

[0006] The zero-sequence component is calculated according to the maximum value and the minimum value in the three-phase original modulation wave;

[0007] Calculating the three-phase original duty cycle according to the three-phase original modulation wave and the zero-sequence component, and performing coordinate transformation on the three-phase original duty cycle to obtain the space vector in the two-phase stationary coordinate system;

[0008] When the space vector exceeds the area of ​​a regular hexagon of unit length centered at the origin in the two-phase stationary coordinate system, the three-phase original duty cycle is overmodulated to obtain a three-phase PWM duty cycle.

[0009] The pulse width modulation method provided by the embodiment of the present invention has at least the following beneficial effects: the zero-sequence component to be injected is calculated by adopting the maximum value and the minimum value of the three-phase original modulation wave, and the three-phase original modulation wave is combined with the injected zero-sequence component to calculate the three-phase original duty cycle. There is no need to adopt different calculation formulas to calculate the duty cycle according to different partitions, which can reduce the calculation complexity, effectively reduce the calculation delay, and thus reduce the PWM duty cycle update delay; in addition, the space vector in the two-phase stationary coordinate system is calculated according to the three-phase original duty. When it is judged according to the space vector that the output voltage corresponding to the three-phase original duty cycle is greater than the maximum allowable value of the system, the three-phase original duty cycle is overmodulated to obtain the final three-phase PWM duty cycle, which can take into account overmodulation and improve the smoothness of torque control.

[0010] In the pulse width modulation method provided in one embodiment, the step of calculating the zero-sequence component according to the maximum value and the minimum value in the three-phase original modulation wave includes:

[0011] The maximum value and the minimum value in the three-phase original modulation wave are added and then multiplied by a first constant to obtain a zero-sequence component.

[0012] In the pulse width modulation method provided in one embodiment, the step of calculating the three-phase original duty cycle according to the three-phase original modulation wave and the zero-sequence component includes:

[0013] The ratio of the three-phase original modulation wave to the bus voltage is subtracted from the second constant, and then the ratio of the zero-sequence component to the bus voltage is subtracted to obtain the three-phase original duty cycle.

[0014] In a pulse width modulation method provided in an embodiment, when the space vector does not exceed the area of ​​a regular hexagon of unit length centered at the origin in the two-phase stationary coordinate system, the three-phase original duty cycle is used as the three-phase PWM duty cycle.

[0015] In the pulse width modulation method provided in one embodiment, the three-phase original modulation wave is calculated by the following formula:

[0016] U A =U α

[0017]

[0018]

[0019] Among them: U A , U B , U C are the A-phase original modulation wave, the B-phase original modulation wave, and the C-phase original modulation wave of the three-phase original modulation wave; U α is the first voltage value, U βis the second voltage value.

[0020] In the pulse width modulation method provided in one embodiment, the zero-sequence component is calculated by the following formula:

[0021]

[0022] Among them, U0 is the zero-sequence component.

[0023] In the pulse width modulation method provided in one embodiment, the three-phase original duty cycle is calculated by the following formula:

[0024]

[0025]

[0026]

[0027] Among them, t A ,t B ,t C are the original duty cycle of phase A, the original duty cycle of phase B, and the original duty cycle of phase C of the three-phase original duty cycle; U dc is the bus voltage.

[0028] In a pulse width modulation method provided in an embodiment, the coordinate transformation includes:

[0029]

[0030]

[0031] Among them, t α ,t β is the coordinate value of the space vector of the three-phase original duty cycle in the two-phase stationary coordinate system.

[0032] In a pulse width modulation method provided in an embodiment, when Then the space vector exceeds the area of ​​a regular hexagon of unit length centered at the origin in the two-phase stationary coordinate system, where:

[0033]

[0034]

[0035]

[0036]

[0037] t out is the modulus of the space vector; θ is the angle value of the space vector in the two-phase stationary coordinate system; It means that θ is Take the remainder; is the distance from the origin of the two-phase stationary coordinate system to the edge of the regular hexagon at the same angle as the space vector.

[0038] In a pulse width modulation method provided in an embodiment, the overmodulation includes:

[0039] When t X ≤0, T X =0

[0040] When 0<t X <1, T X =(t X -t min ) / (t max -t min )

[0041] When t X ≥1, T X =1

[0042] Where X = A, B, C; t max =max(t A , t B , t C );t min =min(t A , t B , t C );T A 、T B 、T C is the three-phase PWM duty cycle.

[0043] In a pulse width modulation method provided in an embodiment, when T X =t X .

[0044] In a second aspect, an embodiment of the present invention provides a pulse width modulation device for a permanent magnet synchronous motor, comprising a memory, a control processor, and a computer program stored in the memory and executable on the control processor, wherein the control processor executes the program to implement the pulse width modulation method as described in the embodiment of the first aspect above.

[0045] In a third aspect, an embodiment of the present invention provides a control system, comprising the pulse width modulation device described in the embodiment of the second aspect.

[0046] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are used to enable a computer to execute the pulse width modulation method described in the embodiment of the first aspect above.

[0047] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the technical solution of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0049] The present invention is further described below in conjunction with the accompanying drawings and embodiments;

[0050] Figure 1 is a flow chart of a pulse width modulation method of a permanent magnet synchronous motor provided by an embodiment of the present invention;

[0051] Figure 2 is a flow chart of calculating the original three-phase duty cycle provided by an embodiment of the present invention;

[0052] Figure 3 is a flow chart of calculating the final three-phase PWM duty cycle based on the three-phase original duty cycle provided by an embodiment of the present invention;

[0053] Figure 4 It is a waveform diagram of the U-phase fundamental wave and the injected zero-sequence component provided by an embodiment of the present invention;

[0054] Figure 5 It is a schematic diagram of a space vector synthesized by three-phase original duty cycles and a regular hexagon of unit length centered at the origin in a two-phase stationary coordinate system provided by an embodiment of the present invention;

[0055] Figure 6 is the distance from the origin to the edge of a regular hexagon of unit length centered at the origin in the αβ coordinate system provided in the embodiment of the present invention Graph of

[0056] Figure 7 It is a waveform diagram of the duty cycle of a three-phase PWM output after the synthetic voltage vector provided by an embodiment of the present invention is between the inscribed circle and the circumscribed circle of a regular hexagon and is overmodulated;

[0057] Figure 8 is a waveform diagram of a three-phase PWM duty cycle in which a synthetic voltage vector provided by an embodiment of the present invention is within an inscribed circle of a regular hexagon;

[0058] Fig. 9 is a waveform diagram of a three-phase PWM duty cycle in which a synthetic voltage vector provided by an embodiment of the present invention is outside the circumscribed circle of a regular hexagon;

[0059] Fig.10 It is a schematic diagram of the FFT analysis result of overmodulating the original duty cycle of the three phases in a limiting manner;

[0060] Fig.11 is a schematic diagram of FFT analysis results of overmodulating the original duty cycle of the three phases provided by an embodiment of the present invention;

[0061] Fig.12 It is a schematic diagram of the structure of a pulse width modulation device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0062] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0063] It should be understood that in the description of the embodiments of the present invention, if there is a description of "first", "second", etc., it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features. "At least one" means one or more, "more than" means more than two, greater than, less than, exceeding, etc. are understood to not include the number itself, above, below, within, etc. are understood to include the number itself, and "several" means one or more, unless otherwise clearly and specifically limited. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. It can be understood that A and / or B can represent the situation where A exists alone, A and B exist at the same time, or B exists alone. Among them, A and B can be singular or plural.

[0064] In addition, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense, for example, it can be a fixed connection or a movable connection, a detachable connection or a non-detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be directly connected or indirectly connected through an intermediate medium. It should be noted that although the logical order is shown in the flowchart, in some cases, the steps shown or described can be performed in a different order from that in the flowchart.

[0065] It should be noted that 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.

[0066] At present, the SVPWM (Space Vector Pulse Width Modulation) scheme adopted in the prior art needs to determine the sector where the voltage vector is located, and adopts different calculation methods according to different sectors to calculate the duty cycle. Since there are six sectors in total, six formulas are required for calculation, resulting in complicated calculation steps. The prior art also adopts an SPWM scheme based on zero-sequence component injection to reduce the calculation complexity, but it cannot take into account the overmodulation algorithm.

[0067] The embodiment of the present invention provides a pulse width modulation method, a pulse width modulation device and a control system for a permanent magnet synchronous motor, by using the maximum value max(U A , U B , U C ) and the minimum value min(U A , U B , U C ) to calculate the zero-sequence component U0 that needs to be injected, the three-phase original modulation wave U A , U B , U C Combined with the injected zero sequence component U0, the original three-phase duty cycle t is calculated A ,t B ,t C There is no need to use different calculation formulas to calculate the duty cycle according to different partitions, which can reduce the calculation complexity, effectively reduce the calculation delay, and thus reduce the PWM duty cycle update delay; in addition, according to the three-phase original duty cycle t A ,t B ,t C Calculate the space vector in the two-phase stationary coordinate system, and determine the original duty cycle t of the three phases according to the space vector A ,t B ,t C When the corresponding output voltage is greater than the maximum allowable value of the system, the original duty cycle t A ,t B ,t C Overmodulation is performed to obtain the final three-phase PWM duty cycle T A 、T B 、T C , which can take into account overmodulation and improve the smoothness of torque control.

[0068] The embodiments of the present invention are further described below in conjunction with the accompanying drawings.

[0069] Figure 1 1 is a flow chart of a pulse width modulation method for a permanent magnet synchronous motor provided by an embodiment of the present invention. Figure 1The first aspect of the present invention provides a pulse width modulation method for a permanent magnet synchronous motor, which is generally used for controlling a permanent magnet synchronous motor. The pulse width modulation method includes but is not limited to steps S110 to S140, wherein:

[0070] Step S110: obtaining a first voltage value and a second voltage value in a two-phase stationary coordinate system, and calculating and obtaining a three-phase original modulation wave.

[0071] It should be noted that the three-phase original modulation wave includes U A , U B , U C , the definitions of the three are as follows:

[0072] U A =U m sinωt

[0073]

[0074]

[0075] In the above formula, U A Represents the original modulation wave of phase A, U B Represents the original modulation wave of phase B, U C represents the original modulation wave of phase C, ω represents the rotation angular velocity of the synthesized voltage vector, t represents time, and U m Indicates the amplitude of the three-phase original modulation wave. In FOC (Field Oriented Control), the three-phase original modulation wave is calculated by the following formula:

[0076] U A =U α

[0077]

[0078]

[0079] In the above formula, U α , U β is the voltage value in the two-phase stationary coordinate system, that is, U α is the first voltage value, U β is the second voltage value. In this embodiment, the first voltage value U α and the second voltage value U β As a known variable, it can be directly obtained from the front-end controller. For example, the PI controller of the current loop outputs the voltage U in the dq coordinate system. d and voltage U q , after coordinate transformation, the first voltage value U is obtained α and the second voltage value U β, the current loop finally outputs the first voltage value U α and the second voltage value U β .

[0080] Step S120: Calculate the zero-sequence component according to the maximum value and the minimum value in the three-phase original modulation wave.

[0081] Exemplarily, in the pulse width modulation method provided in one embodiment, the zero-sequence component is calculated by the following formula:

[0082]

[0083] Among them, U0 is the zero sequence component, max(U A , U B , U C ) represents the original modulation wave U of phase A A 、B phase original modulation wave U B 、C phase original modulation wave U C The maximum value, min(U A , U B , U C ) represents the original modulation wave U of phase A A 、B phase original modulation wave U B 、C phase original modulation wave U C The minimum value in .

[0084] Step S130: Calculate the three-phase original duty cycle according to the three-phase original modulation wave and the zero-sequence component, and perform coordinate transformation on the three-phase original duty cycle to obtain a space vector in the two-phase stationary coordinate system.

[0085] For example, in the pulse width modulation method provided in one embodiment, the three-phase original duty cycle is calculated by the following formula:

[0086]

[0087]

[0088]

[0089] Among them, t A ,t B ,t C are the original duty cycle of phase A, the original duty cycle of phase B, and the original duty cycle of phase C of the three-phase original duty cycle; U dc is the bus voltage.

[0090] It can be understood that the calculated three-phase original duty cycle synthetic space vector should fall within the area of ​​a regular hexagon of unit length centered at the origin in the two-phase stationary coordinate system. In the pulse width modulation method provided in one embodiment, the coordinate transformation of the three-phase original duty cycle synthetic space vector is performed using the following formula:

[0091]

[0092]

[0093] Among them, t α ,t β is the coordinate value of the space vector of the three-phase original duty cycle in the two-phase stationary coordinate system.

[0094] It can be understood that the coordinate value t of the space vector in the two-phase stationary coordinate system is calculated α and t β Then, it can be determined based on the coordinates whether the space vector exceeds the area of ​​the regular hexagon of unit length centered at the origin in the two-phase stationary coordinate system.

[0095] Step S140: when the space vector exceeds the area of ​​a regular hexagon of unit length centered at the origin in the two-phase stationary coordinate system, the three-phase original duty cycle is overmodulated to obtain a three-phase PWM duty cycle.

[0096] Exemplarily, in a pulse width modulation method provided in an embodiment, the overmodulation includes:

[0097] When t X ≤0, T X =0

[0098] When 0<t X <1, T X =(t X -t min ) / (t max -t min )

[0099] When t X ≥1, T X =1

[0100] Where X = A, B, C; t max =max(t A , t B , t C );t min =min(t A , t B , t C );T A 、T B 、TC is the three-phase PWM duty cycle.

[0101] It can be seen that when overmodulation is performed, when the value of the three-phase original duty cycle is less than or equal to 0, the three-phase PWM duty cycle is 0; when the value of the three-phase original duty cycle is greater than or equal to 1, the three-phase PWM duty cycle is 1; when the value of the three-phase original duty cycle is greater than 0 and less than 1, the three-phase PWM duty cycle is calculated according to the formula T X =(t X -t min ) / (t max -t min ) is obtained by performing equivalent scaling.

[0102] According to the pulse width modulation method provided by the embodiment of the present invention, by using the maximum value max(U A , U B , U C ) and the minimum value min(U A , U B , U C ) to calculate the zero-sequence component U0 that needs to be injected, the three-phase original modulation wave U A , U B , U C Combined with the injected zero sequence component U0, the original three-phase duty cycle t is calculated A ,t B ,t C There is no need to use different calculation formulas to calculate the duty cycle according to different partitions, which can reduce the calculation complexity, effectively reduce the calculation delay, and thus reduce the PWM duty cycle update delay; in addition, according to the three-phase original duty cycle t A ,t B ,t C Calculate the space vector in the two-phase stationary coordinate system, and determine the original duty cycle t of the three phases according to the space vector A ,t B ,t C When the corresponding output voltage is greater than the maximum allowable value of the system, the original duty cycle t A ,t B ,t C Overmodulation is performed to obtain the final three-phase PWM duty cycle T A 、T B 、T C , which can take into account overmodulation and improve the smoothness of torque control.

[0103] In a pulse width modulation method provided in another embodiment, the step S120 of calculating the zero-sequence component according to the maximum value and the minimum value in the three-phase original modulation wave includes:

[0104] The maximum value and the minimum value in the three-phase original modulation wave are added and then multiplied by a first constant to obtain a zero-sequence component.

[0105] It is understandable that when the first constant is selected as -1 / 2, it is the calculation method of the zero-sequence component introduced in the example given in the above embodiment. The first constant can also be selected as other values ​​according to actual conditions.

[0106] In a pulse width modulation method provided in another embodiment, the step S130 of calculating the three-phase original duty cycle according to the three-phase original modulation wave and the zero-sequence component includes:

[0107] The ratio of the three-phase original modulation wave to the bus voltage is subtracted from the second constant, and then the ratio of the zero-sequence component to the bus voltage is subtracted to obtain the three-phase original duty cycle.

[0108] It is understandable that when the second constant is selected as 1 / 2, it is the calculation method of the three-phase original duty cycle introduced in the example given in the above embodiment. The second constant can also be selected as other values ​​according to actual conditions.

[0109] In addition, in a pulse width modulation method provided in an embodiment, when the space vector does not exceed the area of ​​a regular hexagon of unit length centered at the origin in the two-phase stationary coordinate system, the three-phase original duty cycle is used as the three-phase PWM duty cycle.

[0110] It can be understood that when the space vector does not exceed the area of ​​the regular hexagon of unit length centered at the origin in the two-phase stationary coordinate system, it means that there is no need to overmodulate the three-phase original duty cycle, so the three-phase original duty cycle can be directly used as the three-phase PWM duty cycle.

[0111] In a pulse width modulation method provided in an embodiment, when Then the space vector exceeds the area of ​​a regular hexagon of unit length centered at the origin in the two-phase stationary coordinate system, where:

[0112]

[0113]

[0114]

[0115]

[0116] t out is the modulus of the space vector; θ is the angle value of the space vector in the two-phase stationary coordinate system; It means that θ is Take the remainder; is the distance from the origin of the two-phase stationary coordinate system to the edge of the regular hexagon at the same angle as the space vector.

[0117] It should be noted that, in this embodiment, it is necessary to first calculate the coordinate value t of the space vector in the two-phase stationary coordinate system. α and t β Calculate the angle value θ of the space vector in the two-phase stationary coordinate system; then use the angle value θ to Take the remainder to get the angle value θ * ; Then calculate the distance from the origin to the regular hexagon of unit length centered at the origin when the angle value is θ in the two-phase stationary coordinate system And calculate the modulus t of the space vector in the two-phase stationary coordinate system out ; Finally, t out and For comparison, This means that the space vector exceeds the area of ​​the regular hexagon of unit length centered at the origin in the two-phase stationary coordinate system, and it is necessary to overmodulate the three-phase original duty cycle to obtain the three-phase PWM duty cycle; when Indicates that the space vector does not exceed the area of ​​a regular hexagon of unit length centered at the origin in the two-phase stationary coordinate system. At this time, T X =t X , where X = A, B, C, that is, the original duty cycle of the three phases t A ,t B ,t C As the three-phase PWM duty cycle T A 、T B 、T C , there is no need to overmodulate the original three-phase duty cycle.

[0118] In addition, in the pulse width modulation method provided in an embodiment, the overmodulating the three-phase original duty cycle to obtain the three-phase PWM duty cycle includes:

[0119] When a phase among the three-phase original duty cycles is less than or equal to 0, the PWM duty cycle of the phase is 0;

[0120] When the PWM duty cycle of a phase among the three-phase original duty cycles is greater than or equal to 1, the PWM duty cycle of the phase is 1;

[0121] When the duty cycle of one phase of the three-phase original duty cycle is greater than 0 and less than 1, the first difference is divided by the second difference to obtain the PWM duty cycle of the phase, wherein: the first difference is the difference between the original duty cycle of the phase and the minimum value of the original duty cycle of the three phases, that is, (t X -t min ), where: X = A, B, C, t min =min(tA , t B , t C ), the second difference is the difference between the maximum and minimum values ​​of the three-phase original duty cycle, that is, (t max -t min ), where: t max =max(t A , t B , t C ), t min =min(t A , t B , t C ).

[0122] Next, combine Figure 2 and Figure 3 , a pulse width modulation method of a permanent magnet synchronous motor provided by an embodiment of the present invention is described in detail, wherein Figure 2 A flow chart for calculating the original three-phase duty cycle provided by an embodiment of the present invention; Figure 3 A flow chart of calculating the final three-phase PWM duty cycle based on the three-phase original duty cycle provided in an embodiment of the present invention.

[0123] The pulse width modulation method of the permanent magnet synchronous motor provided in this embodiment includes two parts. The first part is the calculation of the original duty cycle of the three phases. The calculation process is referred to Figure 2 As shown; the second part is to calculate the final three-phase PWM duty cycle based on the three-phase original duty cycle. The calculation process refers to Figure 3 shown.

[0124] 1. Calculation of three-phase original duty cycle:

[0125] First, obtain the first voltage value U α and the second voltage value U β , the first voltage value U α and the second voltage value U β is the voltage value in the two-phase stationary coordinate system (αβ coordinate system);

[0126] According to the Clarke inverse transform, the three-phase original modulation wave including U A , U B , U C , the calculation process is carried out using the following formula: U A =U α , The U in the above formula A Represents the original modulation wave of phase A, U B Represents the original modulation wave of phase B, U C Represents the original modulation wave of phase C;

[0127] Calculate the original modulation wave U of phase A respectivelyA With bus voltage U dc The ratio of the original modulation wave U of phase B B With bus voltage U dc The ratio of the original modulation wave U of phase C C With bus voltage U dc The ratio of A , the second ratio u B and the third ratio u C , that is: Then according to the first ratio u A , the second ratio u B and the third ratio u C The fourth ratio u0 is calculated by the maximum and minimum values ​​of

[0128] Finally, according to the first ratio u A , the second ratio u B , the third ratio u C And the fourth ratio u0 calculates the three-phase original duty cycle t A ,t B ,t C , the calculation formula is: Where: t A is the original duty cycle of phase A, t B is the original duty cycle of phase B, t C is the original duty cycle of phase C.

[0129] In addition, in addition to calculating the first ratio u A , the second ratio u B , the third ratio u C and the fourth ratio u0, and then according to the first ratio u A , the second ratio u B , the third ratio u C The original duty cycle of the three-phase is calculated by the fourth ratio u0. The following calculation process can also be used for calculation: A , U B , U C Calculate the zero sequence component U0 using the following calculation formula: Then according to the three-phase original modulation wave U A , U B , U C And zero sequence component U0 to calculate the three-phase original duty cycle t A ,t B ,t C , the calculation formula is:

[0130] It can be understood that the original three-phase duty cycle t obtained by the two calculation methods is A ,t B ,t C The results are the same, but the calculation process is slightly different. Among them, the fourth ratio u0 is the ratio of the zero sequence component U0 to the bus voltage U dc Ratio of. Figure 4 , Figure 4 It is a waveform diagram of the U-phase fundamental wave and the injected zero-sequence component provided by an embodiment of the present invention. The sinusoidal waveform curve in the figure represents the U-phase fundamental wave, and the broken line waveform represents the injected zero-sequence component.

[0131] 2. Calculate the final three-phase PWM duty cycle based on the three-phase original duty cycle:

[0132] First, obtain the original three-phase duty cycle t A ,t B ,t C ;

[0133] The coordinate transformation is performed to obtain the space vector in the two-phase stationary coordinate system. The specific calculation formula is: where t α ,t β is the coordinate value of the space vector in the two-phase stationary coordinate system;

[0134] Then, the angle value θ of the space vector in the two-phase stationary coordinate system is calculated using the following formula: Where -π≤θ≤π; then θ is Take the remainder to get θ * ; Then calculate the distance from the origin to the regular hexagon of unit length centered at the origin when the angle value is θ in the two-phase stationary coordinate system The calculation formula is: And calculate the modulus of the space vector Reference Figure 5 , Figure 5 It is a schematic diagram of a space vector synthesized by three-phase original duty cycles and a regular hexagon of unit length centered at the origin in a two-phase stationary coordinate system provided by an embodiment of the present invention; Figure 6 is the distance from the origin to the edge of a regular hexagon of unit length centered at the origin in the αβ coordinate system provided in the embodiment of the present invention Graph of

[0135] If the distance Greater than The space vector does not exceed the area of ​​the regular hexagon of unit length centered at the origin in the two-phase stationary coordinate system, and there is no need to overmodulate the original duty cycle of the three-phase. X =t X, where X = A, B, C, that is, the original duty cycle of the three phases t A ,t B ,t C As the three-phase PWM duty cycle T A 、T B 、T C If the distance Less than or equal to This means that the space vector exceeds the area of ​​a regular hexagon of unit length centered at the origin in the two-phase stationary coordinate system, and it is necessary to overmodulate the three-phase original duty cycle to obtain the three-phase PWM duty cycle;

[0136] The original duty cycle of the three phases t X The method of overmodulation is as follows (X=A, B, C):

[0137] When the three-phase original duty cycle t X Less than or equal to 0, three-phase PWM duty cycle T X The value is 0;

[0138] When the three-phase original duty cycle t X Greater than or equal to 1, three-phase PWM duty cycle T X The value is 1;

[0139] When the three-phase original duty cycle t X Greater than 0 and less than 1, the first difference is divided by the second difference to obtain the three-phase PWM duty cycle T X , where: the first difference is the original duty cycle of the three phases t X The minimum value t of the three-phase original duty cycle min The second difference is the maximum value t of the three-phase original duty cycle max With the minimum value t min The difference, that is, T X =(t X -t min ) / (t max -t min ), where t max =max(t A , t B , t C ), t min =min(t A , t B , t C ).

[0140] Get the final three-phase PWM duty cycle T A 、T B 、T C .

[0141] The results of the above overmodulation method refer to Figures 7 to 11 As shown, Figure 7 It is a waveform diagram of the duty cycle of a three-phase PWM output after the synthetic voltage vector provided by an embodiment of the present invention is between the inscribed circle and the circumscribed circle of a regular hexagon and is overmodulated;

[0142] Figure 8 is a waveform diagram of a three-phase PWM duty cycle in which a synthetic voltage vector provided by an embodiment of the present invention is within an inscribed circle of a regular hexagon; Fig. 9 : is a waveform diagram of the three-phase PWM duty ratio when the synthesized voltage vector is outside the circumscribed circle of the regular hexagon provided by the embodiment of the present invention; it can be seen that when the synthesized voltage vector is between the inscribed circle and the circumscribed circle of the regular hexagon, the part of the three-phase PWM duty ratio exceeding 1 will be adjusted to 1, the part less than 0 will be adjusted to 0, and the rest will be adjusted according to the formula T X =(t X -t min ) / (t max -t min ) is equivalently scaled; when the synthesized voltage vector is within the inscribed circle of the regular hexagon, all three-phase PWM duty ratios are calculated according to the formula T X =(t X -t min ) / (t max -t min ) for equivalent scaling; when the synthesized voltage vector is outside the circumscribed circle of the regular hexagon, the portion of the three-phase PWM duty cycle that exceeds 1 will be adjusted to 1, the portion that is less than 0 will be adjusted to 0, and the rest will be adjusted according to the formula T X =(t X -t min ) / (t max -t min ) for equivalent scaling.

[0143] Fig.10 It is a schematic diagram of the FFT analysis result of overmodulating the original duty cycle of the three phases in a limiting manner; Fig.11 : is a schematic diagram of the FFT analysis result of overmodulating the original duty cycle of the three phases provided by the embodiment of the present invention. Fig.10 and Fig.11 The horizontal axis represents the harmonic order of the modulation result, and the vertical axis represents the percentage relative to the fundamental amplitude. By comparing the FFT analysis results, it can be concluded that the 5th harmonic amplitude obtained by the method of this embodiment is 2.95833% of the fundamental amplitude, while the 5th harmonic amplitude in the comparison scheme is 5.595.6%. Since the 5th harmonic generates torque fluctuations, the lower the 5th harmonic component, the smoother the torque control will be. It can be seen that this embodiment can improve the smoothness of torque control.

[0144] In addition, refer to Fig.12 The second aspect of the present invention provides a pulse width modulation device 1200 for a permanent magnet synchronous motor, comprising a memory 1220, a control processor 1210, and a computer program stored in the memory 1220 and executable on the control processor 1210, wherein the control processor 1210 executes the program to implement the pulse width modulation method described in the first aspect of the present invention, for example, Figure 1 Steps S110 to S140 of the method, or executing Figure 2 and Figure 3 The calculation process in .

[0145] The pulse width modulation device 1200 of the permanent magnet synchronous motor provided by the embodiment of the present invention adopts the maximum value max(U A , U B , U C ) and the minimum value min(U A , U B , U C ) to calculate the zero-sequence component U0 that needs to be injected, the three-phase original modulation wave U A , U B , U C Combined with the injected zero sequence component U0, the original three-phase duty cycle t is calculated. A ,t B ,t C There is no need to use different calculation formulas to calculate the duty cycle according to different partitions, which can reduce the calculation complexity, effectively reduce the calculation delay, and thus reduce the PWM duty cycle update delay; in addition, according to the three-phase original duty cycle t A ,t B ,t C Calculate the space vector in the two-phase stationary coordinate system, and determine the original duty cycle t of the three phases according to the space vector A ,t B ,t C When the corresponding output voltage is greater than the maximum allowable value of the system, the original duty cycle t A ,t B ,t C Overmodulation is performed to obtain the final three-phase PWM duty cycle T A 、T B 、T C , which can take into account overmodulation and improve the smoothness of torque control.

[0146] In addition, the third aspect of the present invention provides a control system, including the pulse width modulation device 1200 described in the second aspect of the present invention.

[0147] According to the control system provided by the embodiment of the present invention, by using the maximum value max(U A , U B , U C ) and the minimum value min(U A , U B , U C ) to calculate the zero-sequence component U0 that needs to be injected, the three-phase original modulation wave U A , U B , U C Combined with the injected zero sequence component U0, the original three-phase duty cycle t is calculated. A ,t B ,t C There is no need to use different calculation formulas to calculate the duty cycle according to different partitions, which can reduce the calculation complexity, effectively reduce the calculation delay, and thus reduce the PWM duty cycle update delay; in addition, according to the three-phase original duty cycle t A ,t B ,t C Calculate the space vector in the two-phase stationary coordinate system, and determine the original duty cycle t of the three phases according to the space vector A ,t B ,t C When the corresponding output voltage is greater than the maximum allowable value of the system, the original duty cycle t A ,t B ,t C Overmodulation is performed to obtain the final three-phase PWM duty cycle T A 、T B 、T C , which can take into account overmodulation and improve the smoothness of torque control.

[0148] In addition, a fourth aspect of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, wherein the computer-executable instructions are used to enable a computer to execute the pulse width modulation method described in the first aspect of the present invention, for example, to execute Figure 1 Steps S110 to S140 of the method, or executing Figure 2 and Figure 3 The calculation process in .

[0149] According to the computer-readable storage medium provided by the embodiment of the present invention, by using the maximum value max(U A , U B , U C ) and the minimum value min(U A , U B , U C) to calculate the zero-sequence component U0 that needs to be injected, the three-phase original modulation wave U A , U B , U C Combined with the injected zero sequence component U0, the original three-phase duty cycle t is calculated. A ,t B ,t C There is no need to use different calculation formulas to calculate the duty cycle according to different partitions, which can reduce the calculation complexity, effectively reduce the calculation delay, and thus reduce the PWM duty cycle update delay; in addition, according to the three-phase original duty cycle t A ,t B ,t C Calculate the space vector in the two-phase stationary coordinate system, and determine the original duty cycle t of the three phases according to the space vector A ,t B ,t C When the corresponding output voltage is greater than the maximum allowable value of the system, the original duty cycle t A ,t B ,t C Overmodulation is performed to obtain the final three-phase PWM duty cycle T A 、T B 、T C , which can take into account overmodulation and improve the smoothness of torque control.

[0150] It will be appreciated by those skilled in the art that all or some of the steps and systems in the disclosed method above may be implemented as software, firmware, hardware and appropriate combinations thereof. Some physical components or all physical components may be implemented as software executed by a control processor, such as a central control processor, a digital signal control processor or a microcontroller, or may be implemented as hardware, or may be implemented as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium or a non-transitory medium and a communication medium or a temporary medium. As known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information such as computer-readable instructions, data structures, program modules or other data. Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disk DVD or other optical disk storage, magnetic cassettes, magnetic tapes, disk storage or other magnetic storage devices, or any other medium that may be used to store desired information and may be accessed by a computer. Furthermore, it is well known to those skilled in the art that communication media typically embodies computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

[0151] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present invention.

Claims

1. A pulse width modulation method for a permanent magnet synchronous motor, characterized in that: include: Obtaining a first voltage value and a second voltage value in a two-phase stationary coordinate system, and calculating and obtaining a three-phase original modulation wave; The zero-sequence component is calculated according to the maximum value and the minimum value in the three-phase original modulation wave; Calculating the three-phase original duty cycle according to the three-phase original modulation wave and the zero-sequence component, and performing coordinate transformation on the three-phase original duty cycle to obtain the space vector in the two-phase stationary coordinate system; When the space vector exceeds the area of ​​a regular hexagon of unit length centered at the origin in the two-phase stationary coordinate system, the three-phase original duty cycle is overmodulated to obtain a three-phase PWM duty cycle; in: when Then the space vector exceeds the area of ​​a regular hexagon of unit length centered at the origin in the two-phase stationary coordinate system, t α ,t β is the coordinate value of the space vector of the three-phase original duty cycle in the two-phase stationary coordinate system; t out is the modulus of the space vector; θ is the angle value of the space vector in the two-phase stationary coordinate system; Indicates that θ is Take the remainder; is the distance from the origin of the two-phase stationary coordinate system to the edge of the regular hexagon at the same angle as the space vector.

2. The pulse width modulation method according to claim 1, characterized in that: The step of calculating the zero-sequence component according to the maximum value and the minimum value in the three-phase original modulation wave comprises: The maximum value and the minimum value in the three-phase original modulation wave are added and then multiplied by a first constant to obtain a zero-sequence component.

3. The pulse width modulation method according to claim 2, characterized in that: The calculating the three-phase original duty cycle according to the three-phase original modulation wave and the zero-sequence component includes: The ratio of the three-phase original modulation wave to the bus voltage is subtracted from the second constant, and then the ratio of the zero-sequence component to the bus voltage is subtracted to obtain the three-phase original duty cycle.

4. The pulse width modulation method according to claim 1, characterized in that: When the space vector does not exceed the area of ​​a regular hexagon of unit length centered at the origin in the two-phase stationary coordinate system, the three-phase original duty cycle is used as the three-phase PWM duty cycle.

5. The pulse width modulation method according to claim 1, characterized in that: The three-phase original modulation wave is calculated by the following formula: IN A =U α Among them: U A , U B , U C are the A-phase original modulation wave, the B-phase original modulation wave, and the C-phase original modulation wave of the three-phase original modulation wave; U α is the first voltage value, U β is the second voltage value.

6. The pulse width modulation method according to claim 5, characterized in that: The zero sequence component is calculated by the following formula: Among them, U0 is the zero-sequence component.

7. The pulse width modulation method according to claim 6, characterized in that: The three-phase original duty cycle is calculated by the following formula: Among them, t A ,t B ,t C are the original duty cycle of phase A, the original duty cycle of phase B, and the original duty cycle of phase C of the three-phase original duty cycle; U dc is the bus voltage.

8. The pulse width modulation method according to claim 7, characterized in that: The coordinate transformation includes: Among them, t α ,t β is the coordinate value of the space vector of the three-phase original duty cycle in the two-phase stationary coordinate system.

9. The pulse width modulation method according to claim 8, characterized in that: The overmodulation includes: When t X ≤0, T X =0 When 0 < t X < 1, T X = (t X - t min ) / (t max - t min ) When t X ≥1, T X =1 Where X = A, B, C; tmax = max(t A , t B , t C ); tmin=min(t A , t B , t C );T A , T B , T C is the three-phase PWM duty cycle.

10. The pulse width modulation method according to claim 9, characterized in that: when T X =t X .

11. A pulse width modulation device for a permanent magnet synchronous motor, characterized in that: The invention comprises a memory, a control processor and a computer program stored in the memory and executable on the control processor, wherein the control processor executes the program to implement the pulse width modulation method according to any one of claims 1 to 10.

12. A control system, characterized in that: Includes the pulse width modulation device as claimed in claim 11.

13. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are used to enable a computer to execute the pulse width modulation method according to any one of claims 1 to 10.

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