Common-mode voltage suppression method for dual three-phase motor driven by five-leg inverter

Abstract

The application discloses a common-mode voltage suppression method of a double three-phase motor driven by a five-bridge inverter, and belongs to the technical field of power generation, power transformation or power distribution. The method obtains an intersection diagram of five-phase inverter output voltage and a carrier ratio straight line under different carrier signals, selects carrier signals according to the principle of reducing the amplitude common-mode voltage area and lowering the common-mode voltage change frequency, carries out PWM comparison between five-phase bridge arm modulation signals and the selected carrier signals, and obtains five-phase PWM signals. The control method of the application can realize common-mode voltage suppression of the double three-phase motor driven by the five-bridge inverter without adding hardware, only by improving the controller algorithm, has the characteristics of strong portability, reduces the system common-mode electromagnetic interference, can effectively protect the motor bearing from electric corrosion, and improves the reliability of the motor system.

Description

TECHNICAL FIELD

[0001] The application relates to the fields of new energy, aerospace, ship propulsion, and the like, and discloses a common-mode voltage suppression method for a dual three-phase permanent magnet synchronous motor (DTP-PMSM) driven by a five-bridge-arm inverter, so as to adapt to the feature that the motor control degree of freedom is reduced under the common-bridge-arm working condition, solve the problem that the common-mode voltage amplitude is increased, and belong to the technical field of power generation, power transformation or power distribution. BACKGROUND

[0002] Compared with a traditional three-phase permanent magnet synchronous motor, the DTP-PMSM has the advantages of phase redundancy, low torque ripple and low phase current rating in a low-voltage high-power occasion, and is widely applied to fields such as locomotive traction, aerospace and ship propulsion. According to the phase shift angle of the two sets of windings, the dual three-phase permanent magnet synchronous motor can be divided into a symmetric dual three-phase permanent magnet synchronous motor and an asymmetric dual three-phase permanent magnet synchronous motor, wherein the phase shift angle between the two sets of windings of the asymmetric dual three-phase permanent magnet synchronous motor is 30°, and the structure naturally eliminates 12k+6 (k=0, 1…) torque ripples, so that the asymmetric dual three-phase permanent magnet synchronous motor is more widely applied. The traditional dual three-phase permanent magnet synchronous motor drive needs six inverter bridge arms, while the five-bridge-arm inverter drive dual three-phase permanent magnet synchronous motor can save the use of two power devices, reduce the system cost, and when a single-phase bridge arm fails, switching to five-bridge-arm drive can run at a reduced speed and load, so the five-bridge-arm inverter drive can be used as a fault-tolerant control method.

[0003] Pulse width modulation (PWM) is one of the most commonly used control techniques in power electronic converters, which can convert analog signal instructions into digital signal form output. The generated PWM pulse signal drives the semiconductor switching device to switch at high frequency and high speed, and outputs a series of high-frequency voltage pulses with equal amplitude and varying width to equivalent reference voltage. The application of PWM technology plays an important role in improving system output voltage, current waveform, reducing harmonic distortion, improving voltage utilization rate and conversion efficiency, etc. However, it also brings some problems, especially the generation of common-mode voltage, which can damage the motor insulation, introduce common-mode current, cause the motor bearing to fail due to current erosion, and further cause problems such as increased motor vibration and motor rotor ring rupture, greatly shortening the service life of the motor.

[0004] A common-mode voltage general elimination technique of dual three-phase motor selects a specific space vector to form a zero common-mode voltage virtual vector, synthesizes a corresponding zero common-mode voltage reference voltage vector for different sectors, and adjusts the duty cycle of the zero vector, but this method needs enough zero common-mode vectors for synthesizing virtual vectors, and when a five-bridge arm inverter is driven, the motor control freedom degree is reduced, the number of voltage vectors is reduced from 64 to 32, which greatly affects the implementation effect of the technology, therefore, the technology cannot meet the common-mode voltage suppression requirements of dual three-phase motor under different control freedom degrees. A common-mode voltage general suppression technique of odd-phase alternating current motor, the PWM signal is phase-shifted, and the amplitude and frequency of the common-mode voltage are reduced by pulse phase-shifted cancellation, but this method is only suitable for odd-phase alternating current motor, and cannot solve the common-mode voltage problem of five-bridge arm inverter driven dual three-phase motor.

[0005] In summary, the prior art has not solved the technical problem of common-mode voltage suppression of five-bridge arm inverter driven dual three-phase motor, and the present application aims to propose a common-mode voltage suppression algorithm based on carrier-based PWM (CBPWM) to overcome the defects that the existing common-mode voltage suppression technology cannot be applied to five-bridge arm inverter driven dual three-phase motor. SUMMARY

[0006] The present application aims to overcome the deficiencies of the above background art, and proposes a common-mode voltage suppression method for dual three-phase permanent magnet synchronous motor driven by five-bridge arm inverter, which obtains output voltage waveforms of different carriers by using intersection plotting method, and reduces high amplitude common-mode voltage and common-mode voltage variation frequency as the principle, selects appropriate carrier waveform and phase shift angle according to the intersection diagram analysis result, avoids the disadvantage of traditional synthesis virtual vector method that needs to synthesize voltage vectors, simplifies the algorithm complexity of suppressing common-mode voltage, and realizes the purpose of suppressing common-mode voltage of five-bridge arm inverter driven dual three-phase motor.

[0007] The present application adopts the following technical solutions to achieve the above invention purposes:

[0008] A control method for suppressing common-mode voltage of five-bridge arm driven dual three-phase motor, comprising the following steps:

[0009] Step one: collect six-phase current, DC bus voltage and rotor position angle information of dual three-phase permanent magnet synchronous motor in stationary coordinate system;

[0010] Step two: perform Clarke transformation and Park transformation on the six-phase current of dual three-phase permanent magnet synchronous motor in stationary coordinate system, obtain d-axis component and q-axis component of dq subspace current, x-axis component and y-axis component of harmonic subspace current, and because the motor neutral point is isolated, the zero sequence subspace current is zero, the Clarke transformation and Park transformation equations are as follows:

[0011]

[0012] Step three: closed loop control is performed on the d-axis component and the q-axis component of the dq subspace current, the x-axis component and the y-axis component of the harmonic subspace current, the d-axis voltage given value and the q-axis voltage given value of the dq subspace are obtained, the x-axis voltage given value and the y-axis voltage given value of the harmonic subspace are obtained, open loop control is performed on the o1-axis component and the o2-axis component of the zero sequence subspace current, and the o1-axis voltage given value and the o2-axis voltage given value of the zero sequence subspace are initialized as 0;

[0013] Step four: Clarke inverse transformation and Park inverse transformation are performed on the d-axis voltage given value and the q-axis voltage given value of the dq subspace current and the x-axis voltage given value and the y-axis voltage given value of the harmonic subspace current, to obtain the six-phase winding reference voltage u A * B * C * X * Y * Z *

[0014] Step five: in order to realize five-bridge-arm driving of a double three-phase motor, two-phase windings of the motor need to share one bridge arm, the motor C-phase winding and the X-phase winding share the inverter bridge arm No. 3 in the application. The given voltage of the X-phase winding is superimposed on u A * B * C * , to form the given voltage u1 * , u2 * , u3 * of the No. 1, No. 2 and No. 3 bridge arms, the given voltage of the C-phase winding is superimposed on u Y * Z * , to form the given voltage u4 * , u5 * of the No. 4 and No. 5 bridge arms, the given voltage is applied to the Y-phase and the Z-phase of the second set of windings of the motor through chopper control, so that five-bridge-arm modulation signals are obtained,

[0015]

[0016] ​​​​​​​​​Step six: the five-phase modulation signals of the bridge arms 1, 2, 3, 4 and 5 are subjected to PWM modulation of different carriers to obtain the intersection diagram of the five-phase inverter output voltage and the carrier ratio straight line under different carrier signals, the common-mode voltage amplitude corresponding to the carrier phase shift under the selected different carrier waveforms is obtained according to the overlapping area of the positive and negative areas of each output phase voltage of the inverter after superposition, the carrier signal is selected according to the principle of reducing the high-amplitude common-mode voltage and reducing the common-mode voltage change frequency, the five-phase bridge arm modulation signals are compared with the selected carrier signals to obtain the corresponding five-phase PWM signals, and finally the common-mode voltage suppression of the five-bridge-arm-driven double three-phase motor is realized.

[0017] Further, the different carrier signals in step six include but are not limited to triangular carrier and sawtooth carrier, when the carrier signal is a triangular wave, the carrier ratio is limited to when the carrier signal is a sawtooth wave, the carrier ratio is limited to

[0018] Further, the conversion rate of the five-phase bridge arm modulation signal is less than the conversion rate of the carrier signal selected in step six, wherein k o is the conversion rate of the five-phase bridge arm modulation signal, and M is the modulation degree.

[0019] The technical scheme adopted by the present application has the following beneficial effects:

[0020] (1) Based on the carrier PWM modulation principle and the intersection plotting method, the present application selects different carriers to analyze the single-phase bridge arm output voltage, plots the five-phase bridge arm inverter output voltage in the same plane, analyzes the motor common-mode voltage amplitude and change frequency according to the intersection of the inverter output voltage and the carrier ratio, and then realizes the carrier-based PWM modulation. Compared with the traditional SVPWM algorithm, the carrier PWM modulation is more intuitive and effective, easy to analyze and simple in algorithm.

[0021] (2) The algorithm complexity of the present application is low, the intersection plotting method can theoretically obtain the system common-mode voltage value in advance, without the need for synthesizing voltage vectors, only the improvement of the controller algorithm software part is needed in the actual electric control system, without the need for adding hardware, easy to realize verification, and with the characteristics of strong portability.

[0022] (3) The present application considers the particularity of the five-bridge-arm-driven double three-phase motor control, optimizes the carrier waveform according to the amplitude and change frequency of the common-mode voltage under different carriers, and compared with the traditional triangular carrier, the optimized carrier can effectively reduce the common-mode voltage amplitude and change frequency, which is conducive to suppressing the interference of the common-mode voltage on the system, effectively protecting the motor bearing from current erosion, and improving the reliability of the motor system. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1The circuit topology diagram of the five-bridge-arm inverter driving a double three-phase motor control system.

[0024] Figure 2 The CBPWM control block diagram of the five-bridge-arm inverter driving a double three-phase motor.

[0025] Figure 3(a) is a cross plot of the output voltage of a phase bridge arm and the carrier ratio straight line under the action of a sine modulation wave and a triangular carrier according to the present application.

[0026] Figure 3(b) is a cross plot of the output voltage of a phase bridge arm and the carrier ratio straight line under the action of a sine modulation wave and a left oblique sawtooth carrier according to the present application.

[0027] Figure 3(c) is a cross plot of the output voltage of a phase bridge arm and the carrier ratio straight line under the action of a sine modulation wave and a right oblique sawtooth carrier according to the present application.

[0028] Figure 4 The cross plot of the output voltage of the inverter and the carrier ratio straight line when the triangular carrier is selected according to the present application.

[0029] Figure 5 The cross plot of the output voltage of the inverter and the carrier ratio straight line when the double sawtooth carrier is selected according to the present application.

[0030] Figure 6 The common-mode voltage simulation diagram when the triangular carrier is selected according to the present application.

[0031] Figure 7 The common-mode voltage simulation diagram when the double sawtooth carrier is selected according to the present application. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below in combination with the drawings and implementation examples. It should be understood that the specific implementation examples described herein are only used to explain the present application. In addition, the technical features involved in each implementation method of the present application described below can be combined with each other as long as they do not conflict with each other.

[0033] The 30° phase shift angle double three-phase motor used in this embodiment is shown in Figure 1 The two sets of windings of the double three-phase motor are winding 1 and winding 2, the phase shift angle between the two sets of windings is 30°, and both sets of windings adopt Y-type connection mode and have two independent neutral points.

[0034] In this embodiment, i A , i B , i C , i X , i Y , i Z represents the actual value of the phase current, i d represents the d-axis current, i qrepresents q-axis current, i α ,represents α-β subspace current, i β ,represents harmonic subspace current, i x ,represents zero sequence subspace current; u y o1 o2 A * B * C * X * Y * Z * represents phase voltage given value, u1 * , u2 * , u3 * , u4 * , u5 * is five-phase inverter corresponding given voltage after zero sequence voltage injection. VSD transformation below represents Clarke and Park transformation matrix of double three-phase PMSM when operating in normal mode.

[0035] A common-mode voltage suppression method of a double three-phase motor driven by a five-bridge-arm inverter provided by the present application is realized based on a VSD decoupling control strategy, and a system block diagram of the control strategy is shown as Figure 2 The system mainly includes a speed outer ring, a current inner ring, coordinate transformation, and a modulation signal generation, etc.

[0036] The motor given reference speed n * is taken as the input of the speed outer ring, and the speed n of the encoder output is taken as the feedback actual speed, and the difference between the two is obtained through the speed outer ring PI controller to obtain i q * , in the given reference current in the d-q coordinate system in the current inner ring. d = 0 control, so i d * is set to 0.

[0037] The actual current in the current inner ring is obtained by the following operation: the six-phase current i A , i B , i C , i X , i Y , i Z measured in the stationary coordinate system is subjected to VSD transformation, that is, Clarke transformation is first performed to double three-phase current i A , i B , i C , i​​​​​X 、i Y 、i Z Converted into six current components i in the α-β-xy-o1-o2 coordinate system α 、i β 、i x 、i y 、i o1 、i o2 , but for the dual three-phase motor with neutral point isolation, the zero-sequence subspace current i o1 with i o2 It is always equal to zero, so the subsequent control only needs to consider four current components. Then perform Park transformation on the α-β subspace variables to convert the current i α 、i β Converted to dq subspace current i d 、i q , obtain the four current components i in the dqxy coordinate system d 、i q 、i x 、i y The Clarke transformation and Park transformation equations are as follows:

[0038]

[0039] In formula (2), I4 is the fourth-order unit matrix. The current components obtained during the VSD conversion process include the current components in the dq space (or α-β space) that are strongly related to the electromagnetic torque and the current components in the harmonic subspace xy space.

[0040] will i d 、i q 、i x 、i y The four-phase current is used as feedback, and the difference between it and the reference current is sent to the current PI controller to obtain the output voltage given by u d * 、u q * 、u x * 、u y * When the five-leg inverter is driven, zero-sequence voltage injection is required. d * 、u q * 、u x * 、u y * Perform inverse Clarke and inverse Park transformations to obtain the six-phase winding reference voltage u in the stationary coordinate system. A * 、uB * 、u C * 、u X * 、u Y * 、u Z * 。

[0041] To realize five-bridge-arm driving dual three-phase motor, two-phase windings of the motor need to share a bridge arm, the present application selects C-phase winding and X-phase winding of the motor to share inverter No.3 bridge arm, as shown in the figure. Figure 1 The given voltage u X * of the X-phase winding is superimposed to u A * , u B * , u C * , to form the given voltage u1 * , u2 * , u3 * of No.1, 2, 3 bridge arms, u1 * , u2 * , u3 * are applied to A, B, C three phases of the first set of windings of the motor through chopper control, simultaneously, u3 * is applied to X phase of the second set of windings of the motor through chopper control, the given voltage u C * of the C-phase winding is superimposed to u Y * , u Z * , to form the given voltage u4 * , u5 * of No.4, 5 bridge arms, u4 * , u5 * are applied to Y, Z two phases of the second set of windings of the motor through chopper control, so as to obtain five-bridge-arm modulation signals. Zero sequence voltage injection is shown in the following formula:

[0042]

[0043] In formula (3), u1 * , u2 * , u3 * , u4 * , u5 * are voltage reference values of five-phase inverter bridge arms respectively.

[0044] The modulation signals of the first, second, third, fourth and fifth bridge arms are subjected to carrier CBPWM modulation. Different carrier waveforms, common-mode voltage amplitudes and frequencies corresponding to carrier phase shifts are selected according to the intersection plotting method. Appropriate carriers are selected according to the intersection plotting analysis results. Five-phase PWM signals S1, S2, S3, S4 and S5 are obtained according to the PWM comparison results of the five-phase bridge arm modulation signals and the finally selected carrier signals, and the common-mode voltage suppression of the five-bridge-arm-driven dual three-phase motor is finally realized.

[0045] The intersection plotting method is used to explain how the PWM pulse signals for controlling the inverter output voltage are generated in the CBPWM strategy. Taking a sine PWM based on a triangular carrier with a modulation index M = 0.8 as an example, the principle of the inverter output phase voltage is shown in Fig. 3(a), where ω c , ω o are the angular frequencies of the triangular carrier and the sine modulation wave, in the xy plane, the x-axis represents the phase information varying with the triangular carrier angular frequency ω c , x = ω c t, the y-axis represents the phase information varying with the sine modulation wave angular frequency ω o , y = ω o t, the blue area represents that the output voltage of a phase bridge arm is V dc / 2 when the inverter is driven by the sine PWM based on the triangular carrier, the red curve represents the contour curve of the inverter output phase voltage when the inverter is driven by the sine PWM based on the triangular carrier, and the area in the xy plane defined by the contour curve of the inverter output phase voltage represents that the output voltage of a phase bridge arm is -V dc / 2. Figs. 3(b) and 3(c) respectively show the intersection plots of the SPWM method based on the left and right inclined sawtooth carriers; for a digital control system based on the STM32 series, the left and right inclined sawtooth carriers can be realized in the configuration timer counting mode. Over time, the points on the xy plane will reflect a carrier ratio straight line with a slope of ω o / ω c , and the switching output voltage waveform changes at each intersection point of the contour curve of the inverter output phase voltage and the carrier ratio straight line. By comparing the contour curve of the inverter output phase voltage with the carrier ratio straight line in each switching period, the intersection plot of the inverter output phase voltage and the carrier ratio in the corresponding switching period can be obtained.

[0046] For the CBPWM modulation method, there is a slew rate limit for the modulation signal. To avoid multiple switching transitions within one carrier period, the slew rate k o of the final modulation signal should be less than the slew rate k c of the carrier. For a sine modulation signal, the slew rate expression is:

[0047]

[0048] It can be seen that when the modulation degree M = 1, k o The maximum value can be reached. For the triangular carrier and the sawtooth carrier, the absolute switching rate is ω c / π and ω c / 2π, respectively. Therefore, based on the switching rate limit, the carrier ratio limit of the triangular carrier and the sawtooth carrier is:

[0049]

[0050] The common-mode voltage of the neutral-point isolated dual three-phase motor is defined as:

[0051] V cm =(V cm1 +V cm2 ) / 2=(V A +V B +V C +V X +V Y +V Z ) / 6 (7)

[0052] In the above formula, V i (i = A, B, C, X, Y, Z) is the output voltage of each phase bridge arm, corresponding to V dc / 2 or -V dc / 2, where V dc denotes the DC bus voltage, V cm1 and V cm2 are the common-mode voltages corresponding to winding 1 and winding 2, respectively.

[0053] In the present application, the C-X common bridge arm mode is selected for the motor, and when calculating the common-mode voltage, the output voltage value of the X bridge arm is always consistent with the output voltage of the C bridge arm, so the X bridge arm can be ignored, and the output voltage of the C bridge arm is calculated as twice, that is, the output voltage of the C bridge arm corresponds to V dc and -V dc , as follows:

[0054] V cm =(V cm1 +V cm2 ) / 2=(V A +V B +2V C +V Y +V Z ) / 6 (8)

[0055] When the profile curves of the output voltages of the five-phase bridge arms in the five-bridge-arm inverter are plotted on the same xy plane, the intersection diagram of the entire five-phase inverter output voltage and the carrier ratio is obtained, so the common-mode voltage amplitude and the variation frequency can be directly obtained from the sum of the switching states of all bridge arms.

[0056] Figure 4 The intersection graph of the inverter output voltage and the carrier ratio is selected when the triangular wave is selected as the carrier in the CBPWM strategy of the five-bridge-arm driving dual three-phase motor. The phase of the five-phase bridge arm output voltage profile curve on the x-axis is the same because the five-phase bridge arms share one triangular carrier. However, because the phases of the modulation signals of the bridge arms are different, the phases of the bridge arm output voltage profile curves on the y-axis are different, and correspond to 0°, 120°, 240°, 150°, and 270° phase shift angles, respectively. The areas divided by the contour lines of the intersection graph are mutually overlapped. The overlapping area I represents that the common-mode voltage amplitude of the superposition of the positive and negative areas of the five bridge arm output voltages is -V dc / 2, the overlapping area II represents that the common-mode voltage amplitude of the superposition of the positive and negative areas of the five bridge arm output voltages is -V dc / 3, the overlapping area III represents that the common-mode voltage amplitude of the superposition of the positive and negative areas of the five bridge arm output voltages is -V dc / 6, the overlapping area IV represents that the common-mode voltage amplitude of the superposition of the positive and negative areas of the five bridge arm output voltages is 0, and the overlapping area V represents that the common-mode voltage amplitude of the superposition of the positive and negative areas of the five bridge arm output voltages is V dc / 6, the overlapping area VI represents that the common-mode voltage amplitude of the superposition of the positive and negative areas of the five bridge arm output voltages is V dc / 3, and the overlapping area VII represents that the common-mode voltage amplitude of the superposition of the positive and negative areas of the five bridge arm output voltages is V dc / 2. The relationship between the different types of overlapping areas and the corresponding common-mode voltage values is shown in Table 1.

[0057] Table 1 Relationship between area number and common-mode voltage amplitude

[0058] Region number I II III IV V VI VII V cm ]]> - V dc / 2]] - V dc / 3]] - V dc / 6]] 0 V dc / 6]] V dc / 3]]> V dc / 2]]>

[0059] In the present application, the carrier angular frequency ω c = 2π×10krad / s, the modulation signal angular frequency ω o = 2π×50rad / s, and the slope of the carrier ratio straight line is 0.005. With the passage of time t, the carrier ratio straight line passes through different overlapping areas, and the system outputs different common-mode voltage values. It is easy to know that the maximum amplitude of the common-mode voltage is V dc / 2, and the average changes 10 times per switching period. Figure 6 The simulation result of the common-mode voltage of the dual three-phase motor when the triangular wave is selected as the carrier in the CBPWM strategy of the five-bridge-arm driving dual three-phase motor.

[0060] The analysis principle of the cross-point plot method is known, and different kinds of overlapping regions result in different common-mode voltage levels. Therefore, when the regions with high common-mode voltage amplitude, such as I, VII, are reduced, the common-mode voltage amplitude is reduced accordingly. In order to reduce the common-mode voltage amplitude and frequency, the present application adopts double sawtooth carrier, that is, two sets of windings are respectively selected to use left and right oblique sawtooth waves as carriers. FIG. 3(b) and FIG. 3(c) respectively show the intersection diagrams of the winding 1 and winding 2 bridge arm output voltage with the carrier ratio straight line in a switching cycle. It can be seen that the high common-mode voltage overlapping regions of the winding 1 and winding 2 are opposite in a switching cycle, and without considering the carrier phase shift, the y-axis phase shift angle between the five-bridge-arm modulation signals naturally leads to the reduction of the type of overlapping regions and the absence of high common-mode voltage regions. From the above, it can be seen that the common-mode voltage amplitude of the double three-phase motor is reduced by 33.3% compared with the traditional five-bridge-arm modulation method, and the common-mode voltage changes 5 times per switching cycle, and the frequency is reduced by 50%. Figure 5 It can be seen that the maximum amplitude of the common-mode voltage of the system is V dc / 3, the common-mode voltage amplitude is reduced by 33.3%, and the common-mode voltage changes 5 times per switching cycle, and the frequency is reduced by 50%. Figure 7 The simulation results of the common-mode voltage of the double three-phase motor when the double sawtooth waves are selected as the carrier in the CBPWM strategy of the five-bridge-arm driving double three-phase motor.

[0061] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above specific embodiments, and the above specific embodiments and the description in the specification are only for further illustration of the principles and preparation effects of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the present application. The scope of the present application is defined by the claims and their equivalents.

Claims

1. A method for common-mode voltage suppression of dual three-phase machines driven by a five-leg inverter, characterized in that, The method comprises the following steps: Step one, collecting six-phase currents in the static coordinate system of the dual three-phase motor, DC bus voltage and rotor position angle; Step two, performing Clarke transformation and Park transformation on the six-phase currents in the static coordinate system of the dual three-phase motor to obtain dq subspace currents and harmonic subspace currents; Step three, performing closed-loop control on the dq subspace currents and harmonic subspace currents respectively, performing open-loop control on the zero-sequence subspace current, obtaining dq subspace d-axis voltage given value and q-axis voltage given value, harmonic subspace x-axis voltage given value and y-axis voltage given value, and initializing zero-sequence subspace o1 and o2-axis voltage given values to 0; Step four, performing Clarke inverse transformation and Park inverse transformation on the dq subspace d-axis voltage given value and q-axis voltage given value, and the harmonic subspace x-axis voltage given value and y-axis voltage given value to obtain six-phase winding reference voltages in the static coordinate system; Step five, obtaining five-phase bridge arm modulation signals according to the sharing condition of the five-phase inverter bridge arm and the six-phase winding reference voltages in the static coordinate system; Step six, obtaining the intersection graph of the five-phase inverter output voltage and the carrier ratio straight line under different carrier signals, selecting carrier signals according to the principle of reducing high-amplitude common-mode voltage and reducing common-mode voltage change frequency, performing PWM comparison on the five-phase bridge arm modulation signals and the selected carrier signals to obtain five-phase PWM signals.

2. The common-mode voltage suppression method for dual three-phase motor driven by five-leg inverter according to claim 1, characterized in that, The specific method for obtaining the intersection of the five-phase inverter output voltage and the carrier ratio straight line under different carrier signals in step six is: taking the carrier angle frequency ω c The phase information of the change is the x-axis, and the carrier angle frequency ω o The phase information of the change is the y-axis, and the profile curve of the inverter output phase voltage in each switching axis under different carrier signals is obtained in the xy plane.

3. The common-mode voltage suppression method for dual three-phase motor driven by five-leg inverter according to claim 2, characterized in that, In step six, the carrier signals are selected according to the principle of reducing high-amplitude common-mode voltage and reducing common-mode voltage change frequency, specifically: for the intersection graph of the profile curve of each switching axis inverter output phase voltage and the carrier ratio straight line under different carrier signals obtained in the xy plane, the amplitude and switching frequency of the common-mode voltage under each carrier are obtained according to the overlapping region after the positive and negative regions of each output phase voltage of the inverter under different carrier signals are superimposed, and the carrier signal with the least high-amplitude common-mode voltage and the minimum common-mode voltage change frequency is selected.

4. The common-mode voltage suppression method for dual three-phase motor driven by five-leg inverter according to claim 3, characterized in that, In step six, the different carrier signals include but are not limited to triangular carrier and sawtooth carrier.

5. The common-mode voltage suppression method for dual three-phase motor driven by five-leg inverter according to claim 4, characterized in that, In step six, when the carrier signal is a triangular wave, the carrier ratio limit is 6. The common-mode voltage suppression method for dual three-phase motor driven by five-leg inverter according to claim 4, characterized in that, In step six, when the carrier signal is a sawtooth wave, the carrier ratio limit is 7. The common-mode voltage suppression method for dual three-phase motor driven by five-leg inverter according to any one of claims 2 to 6, characterized in that, a slew rate of the five-phase bridge leg modulation signal is less than a slew rate of the step six selected carrier signal, where k o is a slew rate of the five-phase bridge leg modulation signal, and M is a modulation index.

8. The common-mode voltage suppression method for dual three-phase motor driven by five-leg inverter according to claim 7, characterized in that, The equation of the step two for Clarke transformation and Park transformation of six-phase current under static coordinate system of double three-phase motor is: θ is rotor position angle, and I4 is four-order unit matrix.

9. The common-mode voltage suppression method for dual three-phase motor driven by five-leg inverter according to claim 8, characterized in that, In step five, the five-phase bridge arm modulation signals are obtained by injecting zero-sequence voltage according to the sharing condition of the five-phase inverter bridge arm and the six-phase winding reference voltages in the static coordinate system, and when the C-phase winding and the X-phase winding share one bridge arm, the zero-sequence voltage injection equation is specifically wherein, u A * (t), u B * (t), u C * (t), u X * (t), u Y * (t), u Z * (t) respectively represent the given values of A, B, C, X, Y, Z phase voltages at time t, u1 * (t), u2 * (t), u3 * (t), u4 * (t), u5 * (t) is the given voltage of the five-phase bridge arm at time t after the injection of the zero sequence voltage.

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