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

Abstract

The invention discloses a common-mode voltage suppression method for dual three-phase motors driven by a five-bridge-arm inverter, and belongs to the technical field of power generation, power transformation or power distribution. The method comprises the following steps: acquiring a cross plot of output voltage of a five-phase inverter and a carrier ratio straight line under different carrier signals, selecting a carrier signal by taking reduction of an amplitude common-mode voltage region and reduction of a common-mode voltage change frequency as principles, and performing PWM comparison on a five-phase bridge arm modulation signal and the selected carrier signal to obtain a five-phase PWM signal. According to the control method, hardware does not need to be additionally arranged, common-mode voltage suppression of the five-bridge-arm-driven dual three-phase motor can be achieved only by improving a controller algorithm, the method has the advantage of being high in portability, common-mode electromagnetic interference of the system is reduced, electric erosion of a motor bearing can be effectively protected, and the reliability of the motor system is improved.

Description

Technical Field

[0001] The present invention relates to the fields of new energy, aerospace, ship propulsion, etc., and specifically 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 to adapt to the characteristic of reduced motor control freedom under common-bridge-arm working conditions and solve the problem of increased common-mode voltage amplitude variation. The invention belongs to the technical field of power generation, power transformation or power distribution. Background Art

[0002] In low-voltage and high-power applications, compared with traditional three-phase permanent magnet synchronous motors, DTP-PMSM has the advantages of phase redundancy, low torque pulsation, and low phase current rating, and is widely used in locomotive traction, aerospace, and ship propulsion. According to the phase shift angle of the two sets of internal windings, the dual three-phase permanent magnet synchronous motor can be divided into a symmetrical dual three-phase permanent magnet synchronous motor and an asymmetrical dual three-phase permanent magnet synchronous motor. Among them, the phase shift angle between the two sets of windings of the asymmetrical dual three-phase permanent magnet synchronous motor is 30°. This structure naturally eliminates 12k+6 (k=0,1…) times of torque pulsation, so it has been more widely used. The traditional dual three-phase permanent magnet synchronous motor drive requires six inverter bridge arms, while the five-bridge-arm inverter drive of the dual three-phase permanent magnet synchronous motor can save the use of two power devices and reduce system costs. When a single-phase bridge arm fails, switching to the five-bridge-arm drive can reduce 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 technologies in power electronic converters. It can convert analog signal instructions into digital signal 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 be equivalent to the reference voltage. The application of PWM technology plays an important role in improving the system output voltage and current waveform, reducing harmonic distortion, and improving voltage utilization and conversion efficiency. However, it also brings some problems. In particular, the generation of common-mode voltage will damage the motor insulation, introduce common-mode current, and cause the motor bearing to fail due to current erosion, which in turn causes problems such as increased motor vibration and motor rotor ring fracture, greatly shortening the service life of the motor.

[0004] A universal common-mode voltage elimination technology for dual three-phase motors selects specific space vectors to form a zero common-mode voltage virtual vector, synthesizes the corresponding zero common-mode voltage reference voltage vector for different sectors, and adjusts the duty cycle of the zero vector. However, this method requires sufficient zero common-mode vectors for synthesizing virtual vectors. When driven by a five-arm inverter, the motor control freedom decreases, and the number of voltage vectors is reduced from 64 to 32, which greatly affects the implementation effect of the technology. Therefore, this technology cannot meet the common-mode voltage suppression requirements of dual three-phase motors under different control freedoms. A universal common-mode voltage suppression technology for odd-phase AC motors phase-shifts the PWM signal and reduces the amplitude and frequency of the common-mode voltage by pulse phase shift cancellation. However, this method is only applicable to odd-phase AC motors and cannot solve the common-mode voltage problem of dual three-phase motors driven by five-arm inverters.

[0005] In summary, the prior art has not yet solved the technical problem of common-mode voltage suppression of a five-leg inverter driving a dual three-phase motor. The present invention aims to propose a common-mode voltage suppression algorithm based on carrier-based PWM (CBPWM) to overcome the defect that the prior common-mode voltage suppression technology cannot be applied to a five-leg inverter driving a dual three-phase motor. Summary of the invention

[0006] The purpose of the present invention is to address the deficiencies of the above-mentioned background technology and propose a method for suppressing the common-mode voltage of a dual three-phase permanent magnet synchronous motor driven by a five-arm inverter. The output voltage waveforms of different carriers are obtained by using the intersection plotting method. The principles are to reduce the high-amplitude common-mode voltage and reduce the common-mode voltage change frequency. According to the intersection plot analysis results, a suitable carrier waveform and phase shift angle are selected to avoid the disadvantage that the traditional synthetic virtual vector method needs to synthesize the voltage vector, simplify the algorithm complexity of suppressing the common-mode voltage, and achieve the purpose of the invention of suppressing the common-mode voltage of the dual three-phase motor driven by the five-arm inverter.

[0007] The present invention adopts the following technical solutions to achieve the above-mentioned invention object:

[0008] A control method for suppressing common mode voltage of a dual three-phase motor driven by five bridge arms comprises the following steps:

[0009] Step 1: Collect six-phase current, DC bus voltage and rotor position angle information of the dual three-phase permanent magnet synchronous motor in a stationary coordinate system;

[0010] Step 2: Perform Clarke transformation and Park transformation on the six-phase current of the dual three-phase permanent magnet synchronous motor in the stationary coordinate system to obtain the d-axis component and q-axis component of the dq subspace current and the x-axis component and y-axis component of the harmonic subspace current. Since the neutral point of the motor is isolated, the zero-sequence subspace current is zero. The Clarke transformation and Park transformation equations are as follows:

[0011]

[0012] Step 3: Perform closed-loop control on the d-axis component and q-axis component of the dq subspace current, and the x-axis component and y-axis component of the harmonic subspace current, obtain the d-axis voltage given and q-axis voltage given in the dq subspace, and the x-axis voltage given and y-axis voltage given in the harmonic subspace, perform open-loop control on the o1 and o2 axis components of the zero-sequence subspace current, and initialize the zero-sequence subspace o1 and o2 axis voltage given to 0;

[0013] Step 4: Perform Clarke inverse transformation and Park inverse transformation on the dq subspace current d, q-axis voltage given and harmonic subspace current x, y-axis voltage given components to obtain the six-phase winding reference voltage u in the stationary coordinate system. A * 、u B * 、u C * 、u X * 、u Y * 、u Z * ;

[0014] Step 5: To achieve five-bridge-arm driving of dual three-phase motors, the two-phase windings of the motor need to share one bridge arm. The present invention selects the C-phase winding and the X-phase winding of the motor to share the inverter bridge arm 3. The given voltage of the X-phase winding is superimposed on u A * 、u B * 、u C * , forming a given voltage u1 for bridge arms 1, 2, and 3 * 、u2 * 、u3 * , applied to the A, B, and C phases of the first set of motor windings through chopper control, and the given voltage of the C phase winding is superimposed on u Y * 、u Z * , forming a given voltage u4 for bridge arms 4 and 5 * 、u5 * , through chopping control applied to the second set of windings Y and Z of the motor, so as to obtain the five-bridge arm modulation signal,

[0015]

[0016] Step six: Perform PWM modulation with different carriers on the five-phase modulation signals of bridge arms 1, 2, 3, 4, and 5, and obtain the intersection diagram of the output voltage of the five-phase inverter and the carrier ratio straight line under different carrier signals. According to the overlapping area after the superposition of the positive and negative areas of the output phase voltage of the inverter under different carrier signals, obtain the common-mode voltage amplitude and switching frequency corresponding to the wave shift under different carrier waveforms. Select the carrier signal based on the principle of reducing the high-amplitude common-mode voltage and reducing the common-mode voltage change frequency. Perform PWM comparison between the five-phase bridge arm modulation signal and the selected carrier signal to obtain the corresponding five-phase PWM signal, and finally realize the common-mode voltage suppression of the five-bridge arm driving dual three-phase motor.

[0017] Furthermore, in step 6, different carrier signals include but are not limited to: triangular carrier, 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] Furthermore, 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. Among them, k o is the conversion rate of the five-phase bridge arm modulation signal, and M is the modulation index.

[0019] The present invention adopts the above technical solution and has the following beneficial effects:

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

[0021] (2) The algorithm of the present invention has low complexity. The intersection plotting method can theoretically obtain the common-mode voltage value of the system in advance without synthesizing the voltage vector. In the actual electronic control system, only the controller algorithm software part needs to be improved without adding hardware. It is easy to implement verification and has the characteristics of strong portability.

[0022] (3) The present invention takes into account the particularity of the five-bridge-arm driven dual three-phase motor control and optimizes the carrier waveform according to the amplitude and change frequency of the common-mode voltage under different carriers. Compared with the traditional triangular carrier, the optimized carrier can effectively reduce the amplitude and change frequency of the common-mode voltage, which is beneficial to suppress the interference of the common-mode voltage on the system, effectively protect the motor bearings from current erosion, and improve the reliability of the motor system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1This is the circuit topology diagram of the five-leg inverter driving dual three-phase motor control system.

[0024] Figure 2 CBPWM control block diagram of a five-leg inverter driving dual three-phase motors.

[0025] FIG. 3( a ) is an intersection diagram of the output voltage of a phase bridge arm and the carrier ratio straight line under the action of a sinusoidal modulation wave and a triangular carrier according to the present invention.

[0026] FIG3( b ) is an intersection diagram of the output voltage of a phase bridge arm and the carrier ratio straight line under the action of a sinusoidal modulation wave and a left-slanted sawtooth carrier according to the present invention.

[0027] FIG3( c ) is an intersection diagram of the output voltage of a phase bridge arm and the carrier ratio straight line under the action of a sinusoidal modulation wave and a right-sloped sawtooth carrier according to the present invention.

[0028] Figure 4 The intersection diagram of the voltage output by the inverter and the carrier ratio straight line when a triangular carrier is selected for the present invention.

[0029] Figure 5 The intersection diagram of the voltage output by the inverter and the carrier ratio straight line when the double sawtooth carrier is selected for the present invention.

[0030] Figure 6 This is a common mode voltage simulation diagram when a triangular carrier is selected for the present invention.

[0031] Figure 7 The common mode voltage simulation diagram when a double sawtooth carrier is selected for the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and implementation cases. It should be understood that the specific implementation cases described herein are only used to explain the present invention. In addition, the technical features involved in each implementation method of the present invention described below can be combined with each other as long as they do not conflict with each other.

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

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

[0035] The common mode voltage suppression method of a dual three-phase motor driven by a five-leg inverter proposed in the present invention is implemented based on the decoupling control strategy of VSD. The system block diagram of the control strategy is as follows: Figure 2 As shown in the figure, the system mainly includes speed outer loop, current inner loop, coordinate transformation and modulation signal generation.

[0036] The motor is given a reference speed n * As the input of the speed outer loop, the speed n output by the encoder is used as the feedback actual speed. After the difference between the two is made, the speed outer loop PI controller obtains the i in the given reference current in the dq coordinate system in the current inner loop. q * , due to the use of i d =0 control, so here i d * Set to 0.

[0037] The actual current in the current inner loop is obtained as follows: the six-phase current i in the stationary coordinate system is measured A 、i B 、i C 、i X 、i Y 、i Z To perform VSD transformation, first perform Clarke transformation to convert the dual three-phase current i A 、i B 、i C 、iX 、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 is always equal to zero, so the subsequent control only needs to consider four current components. Then, Park transformation is performed 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 a fourth-order unit matrix. The current components obtained during the VSD transformation 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 driven by a five-leg inverter, 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] In order to realize five-bridge-arm driving of dual three-phase motors, the two-phase windings of the motor need to share one bridge arm. The present invention selects the C-phase winding and the X-phase winding of the motor to share the inverter No. 3 bridge arm, such as Figure 1 As shown. Set the given voltage u of the X-phase winding X * Superimpose to u A * 、u B * 、u C * , forming a given voltage u1 for bridge arms 1, 2, and 3 * 、u2 * 、u3 * , u1 * 、u2 * 、u3 * The chopper control is applied to the A, B, and C phases of the first set of motor windings. At the same time, u3 * The given voltage u is applied to the X-phase and C-phase windings of the second set of windings of the motor through chopper control. C * Superposition u Y * 、u Z * , forming a given voltage u4 for bridge arms 4 and 5 * 、u5 * ,u4 * 、u5 * The five-bridge-arm modulation signal is obtained by applying the Y and Z phases of the second winding of the motor through chopping control. The zero-sequence voltage injection is shown as follows:

[0042]

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

[0044] Carrier CBPWM modulation is performed on the modulation signals of bridge arms 1, 2, 3, 4, and 5. The waveforms of different carriers, the common-mode voltage amplitude and frequency corresponding to the carrier shift are selected according to the intersection plotting method, and the appropriate carrier is selected according to the intersection plotting analysis results. Then, the five-phase PWM signals S1, S2, S3, S4, and S5 are obtained based on the PWM comparison results of the five-phase bridge arm modulation signals and the finally selected carrier signal, and finally the common-mode voltage suppression of the five-bridge arm driving dual three-phase motor is realized.

[0045] The intersection plot method is used to explain how the PWM pulse signal that controls the inverter output voltage is generated in the CBPWM strategy. Taking the triangle carrier-based sinusoidal PWM with a modulation index of M = 0.8 as an example, the principle of the inverter output phase voltage is shown in Figure 3(a), where ω c ,ω o is the angular frequency of the triangular carrier and the sinusoidal modulation wave. In the xy plane, the x-axis represents the angular frequency ω of the triangular carrier. c Changing phase information, x = ω c t, the y-axis represents the angular frequency ω of the sinusoidal modulation wave o Changing phase information, y = ω o t, the blue area indicates that the output voltage of one phase bridge arm when the inverter is driven by sinusoidal PWM based on triangular carrier is V dc / 2, the red curve represents the contour curve of the inverter output phase voltage when driven by sinusoidal PWM based on a triangular carrier. The area defined by the contour curve of the inverter output phase voltage in the xy plane represents that the output voltage of one phase bridge arm is -V dc / 2. Figure 3(b) and Figure 3(c) show the cross-plots of the SPWM method based on the left-slanted sawtooth carrier and the right-slanted sawtooth carrier, respectively; for the digital control system based on the STM32 series, the left-slanted sawtooth carrier and the right-slanted sawtooth carrier can be implemented in the configuration timer counting mode. As time goes by, the points on the xy plane will be reflected as a line with a slope of ω o / ω c The carrier ratio straight line is a straight line, and the switching output voltage waveform changes at each intersection 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 cycle, the intersection diagram of the inverter output phase voltage and the carrier ratio in the corresponding switching cycle can be obtained.

[0046] For the CBPWM modulation method, the modulation signal has a conversion rate limit. In order to avoid multiple switching changes within a carrier cycle, the conversion rate k of the final modulation signal is o Should be less than the carrier slew rate k c For a sinusoidal modulated signal, the conversion rate expression is:

[0047]

[0048] It can be seen that when the modulation index M = 1, k o The absolute conversion rates for the triangular carrier and sawtooth carrier are ω c / π and ω c / 2π. Therefore, based on the slew rate limitation, the carrier ratio limits for the triangular carrier and sawtooth carrier are:

[0049]

[0050] The common mode voltage of a dual three-phase motor with neutral point isolation 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 Refers to the DC bus voltage, V cm1 and V cm2 They are the common mode voltages corresponding to winding 1 and winding 2 respectively.

[0053] In the present invention, the motor selects the CX common bridge arm mode. 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. Therefore, 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 contour 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 output voltage of the entire five-phase inverter and the carrier ratio can be obtained. Therefore, the common-mode voltage amplitude and change frequency can be intuitively obtained from the sum of the switching states of all bridge arms.

[0056] Figure 4 This is the intersection diagram of the inverter output voltage and carrier ratio when a triangle wave is selected as the carrier in the CBPWM strategy for driving a dual three-phase motor with five bridge arms. The five-phase bridge arms share a triangular carrier, so the phase of the contour curves of the output voltage of the five-phase bridge arms on the x-axis is the same, but due to the different phases of the modulation signals of each bridge arm, the phases of the output voltage contour curves of each bridge arm on the y-axis are different, corresponding to 0°, 120°, 240°, 150°, and 270° phase shift angles, respectively. The intersection diagram is composed of overlapping areas divided by contour lines. The overlapping area I indicates that the common-mode voltage amplitude after the positive and negative areas of the five bridge arm output voltages are superimposed is -V dc / 2, the overlapping area II indicates that the common mode voltage amplitude after the positive and negative areas of the 5 bridge arm output voltages are superimposed is -V dc / 3, the overlapping area III indicates that the common mode voltage amplitude after the positive and negative areas of the 5 bridge arm output voltages are superimposed is -V dc / 6, the overlapping area IV indicates that the common mode voltage amplitude after the positive and negative regions of the five bridge arm output voltages are superimposed is 0, and the overlapping area V indicates that the common mode voltage amplitude after the positive and negative regions of the five bridge arm output voltages are superimposed is V dc / 6, the overlapping area VI indicates that the common-mode voltage amplitude after the positive and negative regions of the five bridge arm output voltages are superimposed is V dc / 3, the overlapping area Ⅶ indicates that the common-mode voltage amplitude after the positive and negative regions of the five bridge arm output voltages are superimposed is V dc / 2, the relationship between different types of overlapping areas and corresponding common-mode voltage values ​​is shown in Table 1.

[0057] Table 1 Correspondence between region number and common mode voltage amplitude

[0058] Area No. I II III IV V VI VII <![CDATA[V cm ]]> <![CDATA[-V dc / 2]]> <![CDATA[-V dc / 3]]> <![CDATA[-V dc / 6]]> 0 <![CDATA[V dc / 6]]> <![CDATA[V dc / 3]]> <![CDATA[V dc / 2]]>

[0059] In the present invention, the carrier angular frequency ω is selected c =2π×10krad / s, modulation signal angular frequency ω o =2π×50rad / s, the slope of the carrier ratio line is 0.005. As time t passes, the carrier ratio line passes through different overlapping areas, corresponding to different common-mode voltage values ​​output by the system. It is easy to know that the maximum amplitude of the common-mode voltage is V dc / 2, changing 10 times per switching cycle on average. Figure 6 The simulation results of the common-mode voltage of the dual three-phase motor when the triangle wave is selected as the carrier in the CBPWM strategy of the five-bridge-arm driven dual three-phase motor.

[0060] According to the analysis principle of the known intersection plotting method, different types of overlapping areas lead to different common-mode voltage levels. Therefore, when the areas with high common-mode voltage amplitudes such as I and VII decrease, the common-mode voltage amplitude decreases accordingly. In order to reduce the common-mode voltage amplitude and frequency, the present invention adopts a double sawtooth carrier, that is, the two sets of windings use left-slanted sawtooth waves and right-slanted sawtooth waves as carriers, respectively. Figure 3 (b) and Figure 3 (c) respectively show the intersection diagrams of the bridge arm output voltage and carrier ratio straight line of winding 1 and winding 2 in one switching cycle. It can be seen that the high common-mode voltage overlapping areas of winding 1 and winding 2 are opposite in one switching cycle. Without considering the carrier phase shift, the y-axis phase shift angle between the five bridge arm modulation signals will naturally lead to a reduction in the type of overlapping areas and the absence of high common-mode voltage areas. From Figure 5 It can be seen that the maximum amplitude of the system common mode voltage is V dc / 3, a 33.3% reduction, 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 dual three-phase motor when the double sawtooth wave is selected as the carrier in the CBPWM strategy of the five-bridge-arm driven dual three-phase motor.

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

Claims

1. A method for suppressing common-mode voltage of a dual three-phase motor driven by a five-leg inverter, characterized in that: The steps include: Step 1: Collect six-phase current, DC bus voltage and rotor position angle of the dual three-phase motor in a stationary coordinate system; Step 2: Perform Clarke transformation and Park transformation on the six-phase current of the dual three-phase motor in the stationary coordinate system to obtain the dq subspace current and the harmonic subspace current; Step three, respectively perform closed-loop control on the dq subspace current and the harmonic subspace current, perform open-loop control on the zero-sequence subspace current, obtain the dq subspace d-axis voltage setting and q-axis voltage setting, the harmonic subspace x-axis voltage setting and y-axis voltage setting, and initialize the zero-sequence subspace o1 and o2 axis voltage settings to 0; Step 4, performing Clarke inverse transformation and Park inverse transformation on the d-axis voltage given and q-axis voltage given in the dq subspace, and the x-axis voltage given and y-axis voltage given in the harmonic subspace, to obtain the six-phase winding reference voltage in the stationary coordinate system; Step 5, obtaining a five-phase bridge arm modulation signal according to the common situation of the five-phase inverter bridge arm and the six-phase winding reference voltage in the stationary coordinate system; Step six, obtain the intersection diagram of the five-phase inverter output voltage and the carrier ratio straight line under different carrier signals, select the carrier signal based on the principle of reducing high-amplitude common-mode voltage and reducing the common-mode voltage change frequency, perform PWM comparison on the five-phase bridge arm modulation signal and the selected carrier signal, and obtain the five-phase PWM signal.

2. The common mode voltage suppression method of a dual three-phase motor driven by a five-leg inverter according to claim 1, characterized in that: The specific method of obtaining the intersection diagram of the five-phase inverter output voltage and the carrier ratio straight line under different carrier signals in step 6 is: c The phase information of the change is the x-axis, which represents the change of the angular frequency ω of the sinusoidal modulation wave. o The changing phase information is the y-axis, and the intersection diagram of the contour curve of the inverter output phase voltage in each switching axis under different carrier signals and the carrier ratio straight line is obtained in the xy plane.

3. The common mode voltage suppression method of a dual three-phase motor driven by a five-leg inverter according to claim 2, characterized in that: In the step six, the carrier signal is selected based on the principle of reducing high-amplitude common-mode voltage and lowering the common-mode voltage change frequency, specifically: for the intersection diagram of the contour curve of the inverter output phase voltage in each switching axis under different carrier signals obtained in the xy plane and the carrier ratio straight line, the amplitude and switching frequency of the common-mode voltage under each carrier are obtained according to the overlapping area after the positive and negative areas 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 smallest common-mode voltage change frequency is selected.

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

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

8. The common mode voltage suppression method for dual three-phase motors driven by a five-leg inverter according to claim 7, characterized in that: The equations for performing Clarke transformation and Park transformation on the six-phase current of the dual three-phase motor in the stationary coordinate system in step 2 are: θ is the rotor position angle, and I4 is the fourth-order unit matrix.

9. The common mode voltage suppression method of a dual three-phase motor driven by a five-leg inverter according to claim 8, characterized in that: In step 5, according to the shared situation of the five-phase inverter bridge arm and the six-phase winding reference voltage in the stationary coordinate system, the five-phase bridge arm modulation signal is obtained by injecting zero-sequence voltage. When the C-phase winding and the X-phase winding share one bridge arm, the zero-sequence voltage injection equation is specifically as follows: Among them, u A * (t),u B * (t),u C * (t),u X * (t),u Y * (t),u Z * (t) represents the given voltage values ​​of phases A, B, C, X, Y, and Z at time t, respectively, 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 zero-sequence voltage is injected.

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