A current ripple optimization DPWM modulation method for driving a six-phase permanent magnet synchronous motor

Abstract

The application discloses a current ripple optimization DPWM modulation method for driving a six-phase permanent magnet synchronous motor, and specifically comprises the following steps: S1, obtaining six-phase reference voltages and performing normalization; S2, taking stator three-phase windings with a mutual difference of 120 DEG as a group, taking stator three-phase windings with a spatial difference of 30 DEG electric angle from the previous group as a group, and respectively obtaining the maximum value, the minimum value and the intermediate value in the normalized reference voltage instantaneous value of each group; S3, according to the result of S2, a common mode component is calculated; S4, the common mode component of S3 is superimposed on the corresponding reference voltage modulation wave respectively, and a DPWM modulation wave capable of optimizing the output current ripple is obtained, and the six-phase switching tube is driven to work. The application determines the optimal clamping position area of the current ripple by comparing the reference voltage components in real time, reduces the switching loss of the system, improves the output current waveform quality, adopts the common mode component injection method, avoids the complex vector calculation process, and has good application value.

Description

Technical Field

[0001] This invention relates to the field of motor drive control technology, and in particular to a current ripple optimized DPWM modulation method for driving a six-phase permanent magnet synchronous motor. Background Technology

[0002] Compared to three-phase motors, multiphase motors offer higher redundancy and greater fault tolerance, effectively improving the safety and reliability of drive systems. Multiphase motor drive systems have broad application prospects in applications requiring high reliability and high power output, such as electric ship propulsion, electric vehicles, and aerospace.

[0003] The main losses in multiphase motor drive systems come from the switching losses of the converter transistors. Under the Discontinuous Pulse Width Modulation (DPWM) strategy, the transistors are clamped and do not operate for 1 / 3 of the fundamental frequency period, resulting in only 2 / 3 of the switching frequency compared to the traditional Space Vector Pulse Width Modulation (SVPWM) strategy, significantly reducing switching losses. Therefore, the DPWM modulation strategy is widely used in multiphase motor drive systems.

[0004] Output current harmonics are an important performance indicator of multiphase motor systems. However, traditional DPWM modulation strategies suffer from poor AC output current quality and large total harmonic distortion (THD) because the switching transistor does not operate within 1 / 3 of the voltage fundamental cycle. Summary of the Invention

[0005] To address this issue, this invention provides a current ripple-optimized DPWM modulation method for driving a six-phase permanent magnet synchronous motor, solving the problem of large output current ripple under traditional DPWM modulation strategies. By reducing system switching losses, it decreases output current harmonics and improves the quality of the output current waveform.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a current ripple optimization DPWM modulation method for driving a six-phase permanent magnet synchronous motor, the method comprising the following steps:

[0008] S1: Obtain the six-phase sinusoidal reference voltage and normalize it (based on the DC bus voltage Vdc);

[0009] S2: Take a set of stator three-phase windings that are 120° out of phase as one group (abc three-phase as one group), and another set of stator three-phase windings that are 30° out of phase with the previous group as one group (uvw three-phase as one group), and obtain the maximum, minimum and intermediate values ​​of the reference voltage instantaneous values ​​after standardization in each group.

[0010] S3: If, in this group, the median value of the instantaneous values ​​of the per-unit three-phase reference voltages is greater than 0, and the difference between the maximum and minimum values ​​is greater than 1 / 2, then the injected common-mode component must cause the minimum phase of the three-phase reference voltages to be clamped to the negative bus. In this case, the minimum phase modulation wave is always less than the carrier wave, and the bridge arm output clamp is clamped to the negative bus. If, in this case, the median value of the instantaneous values ​​of the per-unit three-phase reference voltages is greater than 0, and the difference between the maximum and minimum values ​​is not greater than 1 / 2, then the injected common-mode component must cause the maximum phase of the three-phase reference voltages to be clamped to the positive bus. In this case, the maximum phase modulation wave is always greater than the carrier wave, and the bridge arm output clamp is clamped to the positive bus. If, in this group, the median value of the instantaneous values ​​of the per-unit three-phase reference voltage is not greater than 0, and the difference between the maximum and minimum values ​​is not greater than 1 / 2, then the injected common-mode component must cause the minimum phase of the three-phase reference voltage to be positioned at the negative bus. At this time, the minimum phase modulation wave is always less than the carrier wave, and the bridge arm output is positioned at the negative bus. If, in this group, the median value of the instantaneous values ​​of the per-unit three-phase reference voltage is not greater than 0, and the difference between the maximum and minimum values ​​is greater than 1 / 2, then the injected common-mode component must cause the maximum phase of the three-phase reference voltage to be positioned at the positive bus. At this time, the maximum phase modulation wave is always greater than the carrier wave, and the bridge arm output is positioned at the positive bus.

[0011] S4: The obtained common-mode components are superimposed on the corresponding sinusoidal reference voltage modulation waves to obtain DPWM modulation waves that can optimize the output current ripple, and drive the switching transistors of the six-phase permanent magnet synchronous motor to work.

[0012] Compared with existing technologies, this invention discloses a current ripple optimized DPWM modulation method for driving a six-phase permanent magnet synchronous motor. By comparing the magnitude of the reference voltage components in real time, different common-mode components are injected, thereby reducing output current harmonics while lowering system switching losses. Furthermore, this method is simple to implement and has high application value. Attached Figure Description

[0013] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1This is a flowchart of the current ripple optimization DPWM modulation method for driving a six-phase permanent magnet synchronous motor according to the present invention.

[0015] Figure 2 This is a topology diagram of the drive circuit for a six-phase permanent magnet synchronous motor.

[0016] Figure 3 The simulated waveforms of the six-phase initial sinusoidal voltage modulation wave after standardization, the injected common-mode component, the voltage modulation wave after injecting the common-mode component, and the six-phase output current are shown in this invention.

[0017] Figure 4 The simulated waveforms of the modulated voltage wave of phase a, the output current of phase a, and the pulse of the upper transistor of phase a after standardization in this invention are shown.

[0018] Figure 5 This is a simulation waveform of the electromagnetic torque and mechanical angular velocity output by the six-phase permanent magnet synchronous motor when the load torque suddenly changes from 0 to 50 N·m at 0.2s in this invention.

[0019] Figure 6 The results show the comparison of the THD of the output currents of phase A and phase U under DPWM0, DPWM1, DPWM2, DPWM3, DPWMmax, DPWMmin and the method proposed in this invention. Detailed Implementation

[0020] The present invention will be further described and illustrated below with reference to specific embodiments. The embodiments described are merely examples of the content of this disclosure and do not limit the scope of the invention. The technical features of each embodiment in the present invention can be combined accordingly, provided that there is no mutual conflict.

[0021] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or modules, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, modules, and / or groups thereof.

[0022] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0023] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. These embodiments do not constitute a limitation on the embodiments of the present invention.

[0024] It should be understood by those skilled in the art that the accompanying drawings are merely schematic diagrams of one embodiment, and the components or devices shown in the drawings are not necessarily essential for implementing the present invention.

[0025] This invention provides a current ripple optimization DPWM modulation method for driving a six-phase permanent magnet synchronous motor. The method involves superimposing a sinusoidal voltage modulation wave with a common-mode component to form a 60° clamping DPWM modulation wave. Compared to traditional DPWM methods, this method can simultaneously optimize current ripple and reduce switching losses. The method includes the following steps:

[0026] S1: Obtain the six-phase sinusoidal reference voltage and standardize it;

[0027] S2: Take a set of stator three-phase windings that are 120° out of phase as one group (abc three-phase as one group), and another set of stator three-phase windings that are 30° out of phase with the previous group as one group (uvw three-phase as one group), and obtain the maximum, minimum and intermediate values ​​of the reference voltage instantaneous values ​​after standardization in each group.

[0028] S3: If, in this group, the median value of the instantaneous values ​​of the per-unit three-phase reference voltages is greater than 0, and the difference between the maximum and minimum values ​​is greater than 1 / 2, then the injected common-mode component must cause the minimum phase of the three-phase reference voltages to be clamped to the negative bus. In this case, the minimum phase modulation wave is always less than the carrier wave, and the bridge arm output clamp is clamped to the negative bus. If, in this case, the median value of the instantaneous values ​​of the per-unit three-phase reference voltages is greater than 0, and the difference between the maximum and minimum values ​​is not greater than 1 / 2, then the injected common-mode component must cause the maximum phase of the three-phase reference voltages to be clamped to the positive bus. In this case, the maximum phase modulation wave is always greater than the carrier wave, and the bridge arm output clamp is clamped to the positive bus. If, in this group, the median value of the instantaneous values ​​of the per-unit three-phase reference voltage is not greater than 0, and the difference between the maximum and minimum values ​​is not greater than 1 / 2, then the injected common-mode component must cause the minimum phase of the three-phase reference voltage to be positioned at the negative bus. At this time, the minimum phase modulation wave is always less than the carrier wave, and the bridge arm output is positioned at the negative bus. If, in this group, the median value of the instantaneous values ​​of the per-unit three-phase reference voltage is not greater than 0, and the difference between the maximum and minimum values ​​is greater than 1 / 2, then the injected common-mode component must cause the maximum phase of the three-phase reference voltage to be positioned at the positive bus. At this time, the maximum phase modulation wave is always greater than the carrier wave, and the bridge arm output is positioned at the positive bus.

[0029] S4: The obtained common-mode components are superimposed on the corresponding sinusoidal reference voltage modulation waves to obtain DPWM modulation waves that can optimize the output current ripple, and drive the switching transistors of the six-phase permanent magnet synchronous motor to work.

[0030] The controlled object in this embodiment is a permanent magnet synchronous motor with a dual 3-phase Y-connected winding structure, such as... Figure 2 Based on the 6-phase structure of the motor, the frequency converter is designed with a dual 3-phase half-bridge topology to match it. Each inverter half-bridge adopts a two-level structure, and each phase contains two complementary power switching transistors.

[0031] To further implement the above technical solutions, such as Figure 1 The specific content of step S2 is as follows:

[0032] A set of three-phase stator windings with a phase difference of 120° is used as one group (the three phases abc are used as one group), and another set of three-phase stator windings with a phase difference of 30° electrical angle from the previous group is used as one group (the three phases uvw are used as one group).

[0033] u 1min =min(u a ,u b ,u c )

[0034] u 1max =max(u a ,u b ,u c )

[0035] u 1mid =u a +u b +u c -(u 1min +u 1max )

[0036] u 2min =min(u u ,u v ,u w )

[0037] u 2max =max(u u ,u v ,u w )

[0038] u 2mid =u u +u v +u w -(u 2min +u 2max )

[0039] Among them, u a u b u c u u u v u wThe per-unit instantaneous value of the six-phase reference voltage (based on the DC bus voltage Vdc), u 1min u 1max u 1mid These are the per-unit instantaneous values ​​of the three-phase reference voltage, u. a u b u c The minimum, maximum, and median values ​​in u 2min u 2max u 2mid These are the instantaneous values ​​of the other three phase reference voltages after per-unit scaling, u. u u v u w The minimum, maximum, and median values ​​in the range.

[0040] To further implement the above technical solution, the specific content of step S3 is as follows: Compare the three phases as a group. For the three phases abc, if the per-unit instantaneous value of the three-phase reference voltage u... a u b u c The intermediate value u in 1mid Greater than 0, and the maximum value u 1max With minimum value u 1min When the difference is greater than 1 / 2, the injected common-mode component is:

[0041] u 1cm =-u 1min

[0042] At this time, the minimum phase modulation wave is always less than the carrier wave, and the output of the minimum phase bridge arm in the abc three-phase reference voltage is clamped to the negative bus.

[0043] If the normalized instantaneous value of the three-phase reference voltage u a u b u c The intermediate value u in 1mid Greater than 0, and the maximum value u 1max With minimum value u 1min If the difference is no greater than 1 / 2, then the injected common-mode component is:

[0044] u 1cm =1-u 1max

[0045] At this time, the maximum phase modulation wave is always greater than the carrier wave, and the output of the maximum phase bridge arm in the three-phase reference voltage of abc is clamped to the positive bus.

[0046] If the normalized instantaneous value of the three-phase reference voltage u a u b u c The intermediate value u in 1midNot greater than 0, and the maximum value u 1max With minimum value u 1min If the difference is no greater than 1 / 2, then the injected common-mode component is:

[0047] u 1cm =-u 1min

[0048] At this time, the minimum phase modulation wave is always less than the carrier wave, and the output of the minimum phase bridge arm in the abc three-phase reference voltage is clamped to the negative bus.

[0049] If the normalized instantaneous value of the three-phase reference voltage u a u b u c The intermediate value u in 1mid Not greater than 0, and the maximum value u 1max With minimum value u 1min When the difference is greater than 1 / 2, the injected common-mode component is:

[0050] u 1cm =1-u 1max

[0051] At this time, the maximum phase modulation wave is always greater than the carrier wave, and the output of the maximum phase bridge arm in the three-phase reference voltage of abc is clamped to the positive bus.

[0052] For the three-phase uvw, if the per-unit instantaneous value of the three-phase reference voltage u u u v u w The intermediate value u in 2mid Greater than 0, and the maximum value u 2max With minimum value u 2min When the difference is greater than 1 / 2, the injected common-mode component is:

[0053] u 2cm =-u 2min

[0054] At this time, the minimum phase modulation wave is always less than the carrier wave, and the minimum phase bridge arm output of the three-phase reference voltage is connected to the negative bus.

[0055] If the normalized instantaneous value of the three-phase reference voltage u u u v u w The intermediate value u in 2mid Greater than 0, and the maximum value u 2max With minimum value u 2min If the difference is no greater than 1 / 2, then the injected common-mode component is:

[0056] u 2cm =1-u 2max

[0057] At this time, the maximum phase modulation wave is always greater than the carrier wave, and the output of the maximum phase bridge arm in the three-phase reference voltage is connected to the positive bus.

[0058] If the normalized instantaneous value of the three-phase reference voltage u u u v u w The intermediate value u in 2mid Not greater than 0, and the maximum value u 2max With minimum value u 2min If the difference is no greater than 1 / 2, then the injected common-mode component is:

[0059] u 2cm =-u 2min

[0060] At this time, the minimum phase modulation wave is always less than the carrier wave, and the minimum phase bridge arm output of the three-phase reference voltage is connected to the negative bus.

[0061] If the normalized instantaneous value of the three-phase reference voltage u u u v u w The intermediate value u in 2mid Not greater than 0, and the maximum value u 2max With minimum value u 2min When the difference is greater than 1 / 2, the injected common-mode component is:

[0062] u 2cm =1-u 2max

[0063] At this time, the maximum phase modulation wave is always greater than the carrier wave, and the output of the maximum phase bridge arm in the three-phase reference voltage is connected to the positive bus.

[0064] To further implement the above technical solution, the specific content of step S4 is as follows:

[0065] u a * =u a +u 1cm

[0066] u b * =u b +u 1cm

[0067] u c * =u c +u 1cm

[0068] u u * =u u +u2cm

[0069] u v * =u v +u 2cm

[0070] u w * =u w +u 2cm

[0071] Among them, u a *,u b *,u c *,u u *,u v *,u w * represents the six-phase voltage modulation wave after common-mode component injection.

[0072] Figure 3 The simulated waveforms are: the initial sinusoidal voltage modulation wave of the six phases after standardization in this invention, the injected common-mode component calculated by the method of this invention, the voltage modulation wave after injecting the common-mode component, and the simulated waveforms of the six-phase output current.

[0073] Figure 4 These are the simulated waveforms of the modulated voltage wave of phase a, the output current of phase a, and the pulse of the upper tube of phase a after standardization in this invention.

[0074] Figure 5 This is a simulation waveform of the electromagnetic torque and mechanical angular velocity output by the six-phase permanent magnet synchronous motor when the load torque suddenly changes from 0 to 50 N·m at 0.2 s. It can be seen that during the sudden load application, the motor torque pulsation is small, and the actual speed can promptly track the given speed.

[0075] Figure 6 The table compares the THD of the output current in phase A and phase U under DPWM0, DPWM1, DPWM2, DPWM3, DPWMmax, DPWMmin, and the method proposed in this invention. It can be seen that the THD of the output current under the method proposed in this invention is lower than that of the traditional DPWM modulation strategy, indicating that this method further optimizes the output current waveform quality and reduces output current ripple while reducing switching losses.

[0076] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A current ripple optimized DPWM modulation method for driving a six-phase permanent magnet synchronous motor, characterized in that, The process includes the following steps: S1: Obtain the six-phase sinusoidal reference voltage and standardize it; S2: Take a set of stator three-phase windings that are 120° out of phase as one group, and another set of stator three-phase windings that are 30° out of phase with the previous group as another group. Obtain the maximum, minimum and intermediate values ​​of the instantaneous reference voltage after standardization in each group. S3: If, in this group, the median value of the instantaneous values ​​of the per-unit three-phase reference voltages is greater than 0, and the difference between the maximum and minimum values ​​is greater than 1 / 2, then the injected common-mode component must cause the minimum phase of the three-phase reference voltages to be clamped to the negative bus. In this case, the minimum phase modulation wave is always less than the carrier wave, and the bridge arm output clamp is clamped to the negative bus. If, in this case, the median value of the instantaneous values ​​of the per-unit three-phase reference voltages is greater than 0, and the difference between the maximum and minimum values ​​is not greater than 1 / 2, then the injected common-mode component must cause the maximum phase of the three-phase reference voltages to be clamped to the positive bus. In this case, the maximum phase modulation wave is always greater than the carrier wave, and the bridge arm output clamp is clamped to the positive bus. If, in this group, the median value of the instantaneous values ​​of the per-unit three-phase reference voltage is not greater than 0, and the difference between the maximum and minimum values ​​is not greater than 1 / 2, then the injected common-mode component must cause the minimum phase of the three-phase reference voltage to be positioned at the negative bus. At this time, the minimum phase modulation wave is always less than the carrier wave, and the bridge arm output is positioned at the negative bus. If, in this group, the median value of the instantaneous values ​​of the per-unit three-phase reference voltage is not greater than 0, and the difference between the maximum and minimum values ​​is greater than 1 / 2, then the injected common-mode component must cause the maximum phase of the three-phase reference voltage to be positioned at the positive bus. At this time, the maximum phase modulation wave is always greater than the carrier wave, and the bridge arm output is positioned at the positive bus. S4: The obtained common-mode components are superimposed on the corresponding sinusoidal reference voltage modulation waves to obtain DPWM modulation waves that can optimize the output current ripple, and drive the switching transistors of the six-phase permanent magnet synchronous motor to work.

2. The current ripple optimization DPWM modulation method for driving a six-phase permanent magnet synchronous motor according to claim 1, characterized in that, Step S2 specifically involves: A set of stator three-phase windings abc, which are 120° out of phase, is considered as one group; and another set of stator three-phase windings uvw, which are 30° out of phase with the previous group, is considered as another group. u 1min = min(u a ,u b ,u c ) u 1max = max(u a ,u b ,u c ) in 1mid =in a +in b +in c -(in 1min +in 1max ) u 2min = min(u u ,u v ,u w ) u 2max = max(u u ,u v ,u w ) in 2mid =in u +in v +in w -(in 2min +in 2max ) Among them, u a u b u c u u u v u w This represents the per-unit value of the instantaneous six-phase reference voltage, with the per-unit reference value being the DC bus voltage Vdc. 1min u 1max u 1mid These are the per-unit instantaneous values ​​of the three-phase reference voltage, u. a u b u c The minimum, maximum, and median values ​​in u 2min u 2max u 2mid These are the instantaneous values ​​of the other three phase reference voltages after per-unit scaling, u. u u v u w The minimum, maximum, and median values ​​in the range.

3. The current ripple optimization DPWM modulation method for driving a six-phase permanent magnet synchronous motor according to claim 2, characterized in that, Step S3 specifically involves: comparing the three phases as a group; for the three phases abc, if the per-unit instantaneous value of the three-phase reference voltage u... a u b u c The intermediate value u in 1mid Greater than 0, and the maximum value u 1max With minimum value u 1min When the difference is greater than 1 / 2, the injected common-mode component is: in 1cm =-in 1min At this time, the minimum phase modulation wave is always less than the carrier wave, and the output of the minimum phase bridge arm in the abc three-phase reference voltage is clamped to the negative bus. If the normalized instantaneous value of the three-phase reference voltage u a u b u c The intermediate value u in 1mid Greater than 0, and the maximum value u 1max With minimum value u 1min If the difference is no greater than 1 / 2, then the injected common-mode component is: in 1cm =1-in 1max At this time, the maximum phase modulation wave is always greater than the carrier wave, and the output of the maximum phase bridge arm in the three-phase reference voltage of abc is clamped to the positive bus. If the normalized instantaneous value of the three-phase reference voltage u a u b u c The intermediate value u in 1mid Not greater than 0, and the maximum value u 1max With minimum value u 1min If the difference is no greater than 1 / 2, then the injected common-mode component is: in 1cm =-in 1min At this time, the minimum phase modulation wave is always less than the carrier wave, and the output of the minimum phase bridge arm in the abc three-phase reference voltage is clamped to the negative bus. If the normalized instantaneous value of the three-phase reference voltage u a u b u c The intermediate value u in 1mid Not greater than 0, and the maximum value u 1max With minimum value u 1min When the difference is greater than 1 / 2, the injected common-mode component is: in 1cm =1-in 1max At this time, the maximum phase modulation wave is always greater than the carrier wave, and the output of the maximum phase bridge arm in the three-phase reference voltage of abc is clamped to the positive bus. For the three-phase uvw, if the per-unit instantaneous value of the three-phase reference voltage u u u v u w The intermediate value u in 2mid Greater than 0, and the maximum value u 2max With minimum value u 2min When the difference is greater than 1 / 2, the injected common-mode component is: in 2cm =-in 2min At this time, the minimum phase modulation wave is always less than the carrier wave, and the output of the minimum phase bridge arm in the three-phase reference voltage is clamped to the negative bus. If the normalized instantaneous value of the three-phase reference voltage u u u v u w The intermediate value u in 2mid Greater than 0, and the maximum value u 2max With minimum value u 2min If the difference is no greater than 1 / 2, then the injected common-mode component is: in 2cm =1-in 2max At this time, the maximum phase modulation wave is always greater than the carrier wave, and the output of the maximum phase bridge arm in the three-phase reference voltage is clamped to the positive bus. If the normalized instantaneous value of the three-phase reference voltage u u u v u w The intermediate value u in 2mid Not greater than 0, and the maximum value u 2max With minimum value u 2min If the difference is no greater than 1 / 2, then the injected common-mode component is: in 2cm =-in 2min At this time, the minimum phase modulation wave is always less than the carrier wave, and the output of the minimum phase bridge arm in the three-phase reference voltage is clamped to the negative bus. If the normalized instantaneous value of the three-phase reference voltage u u u v u w The intermediate value u in 2mid Not greater than 0, and the maximum value u 2max With minimum value u 2min When the difference is greater than 1 / 2, the injected common-mode component is: in 2cm =1-in 2max At this time, the maximum phase modulation wave is always greater than the carrier wave, and the output of the maximum phase bridge arm in the three-phase reference voltage is connected to the positive bus.

4. The current ripple optimized DPWM modulation method for driving a six-phase permanent magnet synchronous motor according to claim 3, characterized in that, Step S4 specifically involves: in a * =in a +in 1cm in b * =in b +in 1cm in c * =in c +in 1cm in u * =in u +in 2cm in v * =in v +in 2cm in w * =in w +in 2cm Among them, u a *,u b *,u c *,u u *,u v *,u w * represents the six-phase voltage modulation wave after common-mode component injection.

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