Dual three-phase motor modulation method based on dynamic zero vector distribution

Abstract

The invention discloses a dual three-phase motor modulation method based on dynamic zero vector distribution, and the method comprises the following steps: S1, building dual three-phase motor field orientation control based on vector space decoupling, and calculating the output original voltage of each axis; s2, calculating a reference voltage vector of the two voltage source inverters in a static coordinate system according to the output voltage of each axis, and calculating the output voltage of each phase in the dual three-phase motor; s3, calculating a zero vector difference value of the two voltage source inverters according to the output voltage of each phase; s4, the effective voltage vector action time of the two voltage source inverters is calculated, and then the total action time of corresponding zero vectors is obtained; s5, dynamically distributing zero vector action moments of the two voltage source inverters according to the zero vector difference value and the zero vector total time of the two voltage source inverters; and the conduction time of each switching tube is calculated in combination with the effective vector action time.

Description

Technical Field

[0001] This invention relates to the field of motor modulation technology, and in particular to a dual three-phase motor modulation method based on dynamic zero vector distribution. Background Technology

[0002] Multiphase motor drives have gained widespread attention and application in recent years due to their unique advantages. Compared with three-phase motors, multiphase motors have several outstanding advantages, including: 1) strong fault tolerance, allowing the system to continue operating under derating even when some phase windings fail; 2) uniform power distribution, as multiphase windings reduce the current stress on single phases; and 3) low torque ripple, with a more uniform harmonic distribution resulting from the increased number of phases, which helps to smooth the output torque. Based on these advantages, multiphase motors show broad application prospects in high-power applications such as ship propulsion, electric vehicle traction drives, and high-power wind turbines.

[0003] Among multiphase motors, the dual three-phase motor, as a typical six-phase motor, consists of two sets of three-phase stator windings, spatially separated by 30° electrical degrees. This structure combines the advantages of relatively simple implementation with superior performance.

[0004] However, existing pulse width modulation (PWM) methods for dual three-phase motors still have the following problems:

[0005] 1) The direct extension of traditional three-phase space vector PWM (SVPWM) has shortcomings. It cannot directly form effective control, and the high content of low-order harmonics will lead to additional losses.

[0006] 2) 12-sector SVPWM requires four effective vector synthesis reference voltages, which can accurately synthesize reference voltage vectors in the αβ and xy planes, but it involves frequent switching, high losses, and complex hardware implementation.

[0007] 3) The 24-sector SVPWM improves waveform quality by using five-vector synthesis on the basis of the 12-sector SVPWM, but the sequence selection is more complex and the real-time calculation is greater.

[0008] Furthermore, while carrier-based PWM (CPWM) methods have low computational complexity, they have limited DC bus utilization and harmonic performance, and typically require the injection of zero-sequence voltage, which further complicates the modulation waveform.

[0009] Therefore, there is an urgent need for a new SVPWM method that can improve harmonic performance, facilitate digital implementation, and adapt to the constraints of different controllers. Summary of the Invention

[0010] To address the problems of high harmonic content, frequent switching leading to additional losses, and excessive computation in existing technologies, this invention proposes a dual three-phase motor modulation method based on dynamic zero vector distribution. This method dynamically adjusts the zero vector distribution of the two voltage source inverters, ensuring that a single switch tube switches only once within a carrier cycle, thereby achieving accurate synthesis of the reference voltage vectors in the αβ and xy planes. It also effectively improves harmonic performance and has good digital implementation characteristics.

[0011] To achieve the above objectives, the present invention provides the following technical solution:

[0012] A modulation method for a dual three-phase motor based on dynamic zero vector distribution specifically includes the following steps:

[0013] S1: Establish a field-oriented control system for a dual three-phase motor based on vector space decoupling, and calculate the original output voltage of each axis;

[0014] S2: Based on the output voltage of each axis, calculate the reference voltage vector of the two voltage source inverters in the stationary coordinate system, and calculate the output voltage of each phase in the dual three-phase motor;

[0015] S3: Calculate the zero vector difference between the two voltage source inverters based on the output voltage of each phase;

[0016] S4: Calculate the effective voltage vector action time of the two voltage source inverters respectively, and then obtain the total action time of the corresponding zero vector;

[0017] S5: Based on the zero vector difference and the total zero vector time of the two voltage source inverters, dynamically allocate the zero vector action time of the two voltage source inverters; and calculate the conduction time of each switch in combination with the effective vector action time.

[0018] Preferably, step S1 includes the following steps:

[0019] S1-1: Collect the six-phase current of the dual three-phase motor, and obtain the α-axis current i in the stationary two-phase coordinate system in the αβ plane through VSD coordinate transformation. α and β-axis current i β And the x-axis current i in the stationary two-phase coordinate system in the xy plane. x and y-axis current i y Then the current i α and current i β d is obtained through the Park1 transformation. q d-axis current i in rotating coordinate system d and q-axis current i q Current i x and current i y d is obtained through the Park2 transformation.z q z d in rotating coordinate system z shaft current and q z shaft current

[0020] S1-2: Based on speed feedback ω est And given velocity ω ref Calculate the d-axis, q-axis, and d z axis and q z The shaft outputs the original voltage.

[0021] Preferably, in S1-1, the VSD coordinate transformation is as follows:

[0022]

[0023] In formula (1), i A i B i C i U i V i W These are the stator currents for phases A, B, C, U, V, and W, respectively; i α i represents the α-axis current in the αβ plane; β i represents the β-axis current in the αβ plane; x Represents the x-axis current in the xy-plane; i y Represents the y-axis current in the xy plane; i o1 Represents the current along the o1 axis in the o1o2 plane; i o2 This represents the current along the o12 axis in the o1o2 plane.

[0024] Preferably, in S1-1, Park1 is transformed as follows:

[0025]

[0026] In formula (2), i d d q d-axis current in a rotating coordinate system; i q d q The q-axis current in the rotating coordinate system; θ represents the electrical angle of the motor rotor; i α i represents the α-axis current in the αβ plane; β Represents the β-axis current in the αβ plane;

[0027] Park2 is transformed into:

[0028]

[0029] In formula (3), dz q z d in rotating coordinate system z shaft current; d z q z q in rotating coordinate system z shaft current; i x Represents the x-axis current in the xy-plane; i y This represents the y-axis current in the xy plane.

[0030] Preferably, in S1-2, the d-axis, q-axis, and d z axis and q z The original output voltage of the shaft is:

[0031]

[0032] In formula (4), U d U q , These are the d-axis voltage, q-axis voltage, and d... z Axis voltage and q z Shaft voltage; U d_pidout U q_pidout , Representing the d-axis, q-axis, and d... z axis and q z Shaft output original voltage; -ω e L q i q Indicates the d-axis feedforward term; Represents the q-axis feedforward term; ω e L q zi qz d z Axis feedforward term; -ω e L dz i dz q z Axis feedforward term.

[0033] Preferably, step S2 includes the following steps:

[0034] S2-1: Based on the output voltage of each axis, calculate the reference voltage vector corresponding to the two voltage source inverters in the rotating coordinate system as follows:

[0035]

[0036] In formula (5), These represent the reference voltage vectors of the first voltage source inverter on the d1 and q1 axes, respectively. These represent the reference voltage vectors of the second voltage source inverter on the d2 and q2 axes, respectively; U d U q, These are the d-axis voltage, q-axis voltage, and d... z Axis voltage and q z Shaft voltage;

[0037] S2-2: Perform inverse Park transformation on the reference voltage vector to obtain the voltage U in the stationary two-phase coordinates. α1 U β1 and U α2 U β2 :

[0038]

[0039] In formula (6), U α1 U β1 U represents the voltages along the α1 and β1 axes of the first voltage source inverter in a stationary two-phase coordinate system, respectively; α2 U β2 These represent the voltages of the second voltage source inverter along the α2 and β2 axes in a stationary two-phase coordinate system, respectively.

[0040] S2-3: Perform an inverse Clark transformation on the voltages in the stationary two-phase coordinate system to calculate the voltages of each phase of the six-phase motor:

[0041]

[0042] In formula (7), U A U B U C These represent the output voltages of phases A, B, and C in the first voltage source inverter, respectively; U U U V U W These represent the output voltages of the U-phase, V-phase, and W-phase in the second voltage source inverter, respectively.

[0043] Preferably, in step S3, the formula for calculating the zero vector difference between the two voltage source inverters is:

[0044]

[0045] In formula (8), t 0_diff U represents the zero vector difference between the first voltage source inverter and the second voltage source inverter; min2 U max2 These represent the minimum and maximum voltage values ​​of the second voltage source inverter, respectively; U min1 U max1 These represent the minimum and maximum voltage values ​​of the first voltage source inverter, respectively.

[0046] Preferably, step S4 includes the following steps:

[0047] S4-1: The first voltage source inverter includes a first effective voltage vector and a second effective voltage vector, and the duration of the first effective voltage vector is T. V1_ABC The duration T of the second effective voltage vector V2_ABC Calculations in different sectors require the use of intermediate variables X, Y, and Z, which are specifically represented as follows:

[0048]

[0049] In formula (9), X, Y, and Z represent intermediate variables; T S Indicates the carrier period; U dc Indicates DC bus voltage; U α1 U β1 These represent the voltages of the first voltage source inverter along the α1 and β1 axes in a stationary two-phase coordinate system, respectively.

[0050] S4-2: Calculate the total duration of the corresponding zero vector based on the duration of the effective voltage vector.

[0051] T Z_ABC =T S -(T V1_ABC +T V2_ABC ),T Z_UVW =T S -(T V1_UVW +T V2_UVW (10)

[0052] In formula (10), T Z_ABC T represents the total duration of the zero vector in the first voltage source inverter; Z_UVW T represents the total duration of the zero vector in the second voltage source inverter; V1_UVW T represents the duration of the third effective voltage vector in the second voltage source inverter; V2_UVW This indicates the duration of the fourth effective voltage vector in the second voltage source inverter.

[0053] Preferably, step S5 includes the following steps:

[0054] S5-1: Construct a zero-vector assignment model and obtain the zero-vector action time:

[0055]

[0056] In formula (11), T 0_ABC T 7_ABC T represents the duration of action of the first zero vector and the second zero vector in the first voltage source inverter, respectively; 0_UVW T 7_UVW T represents the duration of the third and fourth zero vectors in the second voltage source inverter, respectively; Z_ABCT represents the total duration of the zero vector in the first voltage source inverter; Z_UVW t represents the total duration of the zero vector in the second voltage source inverter; 0_diff This represents the zero vector difference between the first voltage source inverter and the second voltage source inverter;

[0057] S5-2: Calculate the time switching point of each switch in the two voltage source inverters within the cycle;

[0058]

[0059] In formula (12), T a T b T c These represent the first variable, the second variable, and the third variable, respectively; T 0_ABC T represents the duration of the first zero vector in the first voltage source inverter; V1_ABC T represents the duration of the first effective voltage vector in the first voltage source inverter; V2_ABC This indicates the duration of the second effective voltage vector in the first voltage source inverter;

[0060] Then, the switching time T of phases A, B, and C in the first voltage source inverter is... cm1_ABC T cm2_ABC T cm3_ABC The relationship with each sector is as follows:

[0061] N6 II VI I IV III V <![CDATA[T cm1_ABC ]]> <![CDATA[T b ]]> <![CDATA[T a ]]> <![CDATA[T a ]]> <![CDATA[T c ]]> <![CDATA[T c ]]> <![CDATA[T b ]]> <![CDATA[T cm2_ABC ]]> <![CDATA[T a ]]> <![CDATA[T c ]]> <![CDATA[T b ]]> <![CDATA[T b ]]> <![CDATA[T a ]]> <![CDATA[T c ]]> <![CDATA[T cm3_ABC ]]> <![CDATA[T c ]]> <![CDATA[T b ]]> <![CDATA[T c ]]> <![CDATA[T a ]]> <![CDATA[T b ]]> <![CDATA[T a ]]>

[0062] Similarly, the switching time T of the U, V, and W phase voltages of the second voltage source inverter can be obtained. cm1_UVM T cm2_UVM T cm3_UVM .

[0063] In summary, by adopting the above technical solution, the present invention has at least the following beneficial effects compared with the prior art:

[0064] 1) It effectively utilizes the traditional three-phase SVPWM algorithm, greatly simplifying the calculation process and facilitating digital implementation.

[0065] 2) A single switch only switches once per carrier cycle, without increasing switching losses.

[0066] 3) Unlike the fixed zero vector distribution of traditional methods, this invention dynamically adjusts the distribution of the zero vector according to the current magnitude, which can effectively improve harmonic performance and reduce additional losses. Attached Figure Description

[0067] Figure 1This is a schematic diagram of a dual three-phase motor modulation method based on dynamic zero vector distribution according to an exemplary embodiment of the present invention.

[0068] Figure 2 This is a schematic diagram illustrating the relationship between the αβ subspace coordinate systems under the VSD transformation of a dual three-phase motor according to an exemplary embodiment of the present invention.

[0069] Figure 3 This is a schematic diagram illustrating the relationship between the stationary coordinate systems of two voltage source inverters according to an exemplary embodiment of the present invention.

[0070] Figure 4 This is a schematic diagram of sector partitioning according to an exemplary embodiment of the present invention.

[0071] Figure 5 This is a schematic diagram of the PWM waveform of sector 1 of a dual three-phase motor according to an exemplary embodiment of the present invention. Detailed Implementation

[0072] The present invention will be further described in detail below with reference to embodiments and specific implementation methods. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0073] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0074] This invention provides a modulation method for a dual three-phase motor based on dynamic zero vector distribution, specifically including the following steps:

[0075] S1: Establish a field-oriented control system for a dual three-phase motor based on vector space decomposition (VSD) and calculate the original output voltage of each axis.

[0076] S1-1: Collect the six-phase currents of the dual three-phase motor. The stator currents of phases A, B, C, U, V, and W are i A i B i C i U i V i W The six-phase currents are transformed using VSD coordinates to obtain the α-axis current i in the stationary two-phase coordinate system in the αβ plane.α and β-axis current i β And the x-axis current i in the stationary two-phase coordinate system in the xy plane. x and y-axis current i y Then the current i α and current i β d is obtained through the Park1 transformation. q d-axis current i in rotating coordinate system d and q-axis current i q Current i x and current i y d is obtained through the Park2 transformation. z q z d in rotating coordinate system z shaft current and q z shaft current

[0077] Among them, such as Figure 2 As shown, the VSD coordinate transformation is as follows:

[0078]

[0079] In formula (1), i A i B i C i U i V i W These are the stator currents for phases A, B, C, U, V, and W, respectively; i α i represents the α-axis current in the αβ plane; β i represents the β-axis current in the αβ plane; x Represents the x-axis current in the xy-plane; i y Represents the y-axis current in the xy plane; i o1 Represents the current along the o1 axis in the o1o2 plane; i o2 This represents the current along the o12 axis in the o1o2 plane.

[0080] The Park1 transformation is as follows:

[0081]

[0082] In formula (2), i d d q d-axis current in a rotating coordinate system; i q d q The q-axis current in the rotating coordinate system; θ represents the electrical angle of the motor rotor; i α i represents the α-axis current in the αβ plane; β This represents the β-axis current in the αβ plane.

[0083] The Park2 transformation is as follows:

[0084]

[0085] In formula (3), d z q z d in rotating coordinate system z shaft current; d z q z q in rotating coordinate system z shaft current; i x Represents the x-axis current in the xy-plane; i y This represents the y-axis current in the xy plane.

[0086] S1-2: Based on speed feedback ω est And given velocity ω ref The q-axis current command i can be obtained through the PID controller. q_ref And d-axis current, d z shaft current, q z The current of the shaft is given by i d_ref , All are zero. Based on the current input and current feedback, the d-axis, q-axis, and df axis can be obtained through the PID controller. z axis and q z The original output voltages of the shafts are U d_pidout U q_pidout , and

[0087] Then, to achieve complete decoupling, the feedforward term needs to be calculated, with the d-axis feedforward term being -ω. e L q i q q-axis feedforward term is d z The axis feedforward term is ω e L qz i qz q z The shaft feedforward term is -ω e L dz i dz L d L q L qz L dz They are the d-axis, q-axis, and q-axis, respectively. z axis, d z Shaft inductor, For permanent magnet flux linkage, ω e Let be the electric angular velocity. Then the d-axis voltage, q-axis voltage, and d...z Axis voltage and q z The shaft voltages are respectively:

[0088]

[0089] In formula (4), U d U d , These are the d-axis voltage, q-axis voltage, and d... z Axis voltage and q z Shaft voltage; U d_pidout U q_pidout , Representing the d-axis, q-axis, and d... z axis and q z Shaft output original voltage; -ω e L q i q Indicates the d-axis feedforward term; Represents the q-axis feedforward term; ω e L qz i qz d z Axis feedforward term; -ω e L qz i dz q z Axis feedforward term.

[0090] S2: Calculate the reference voltage vector U of the two voltage source inverters in the stationary coordinate system based on the output voltage of each axis. α1 U β1 and U α2 U β2 Calculate the output voltage U of each phase (A, B, C, U, V, W) of the six-phase motor. A U B U C U U U V U W .

[0091] In this embodiment, the dual three-phase motor is equipped with two voltage source inverters, including a first voltage source inverter and a second voltage source inverter.

[0092] S2-1: Based on the output voltage of each axis, calculate the voltage of the two voltage source inverters at d. z q z The reference voltage vector corresponding to the rotating coordinate system (including the d1q1 rotating coordinate system and the d2q2 rotating coordinate system) is:

[0093]

[0094] In formula (5), These represent the reference voltage vectors of the first voltage source inverter on the d1 and q1 axes, respectively. These represent the reference voltage vectors of the second voltage source inverter on the d2 and q2 axes, respectively; U d U q , These are the d-axis voltage, q-axis voltage, and d... z Axis voltage and q z Shaft voltage.

[0095] In this embodiment, the d1 axis and q1 axis are a set of orthogonal basis vectors of the synchronous rotating coordinate system of the first voltage source inverter, wherein the d1 axis is aligned with the direction of the rotor permanent magnet flux linkage. Similarly, the d2 axis and q2 axis are a set of orthogonal basis vectors of the synchronous rotating coordinate system of the second voltage source inverter, wherein the d2 axis is aligned with the direction of the rotor permanent magnet flux linkage.

[0096] S2-2: As Figure 3 As shown, the reference voltage vector The voltage U in the stationary two-phase coordinate system is obtained by performing inverse Park transformation. α1 U β1 and U α2 U β2 :

[0097]

[0098] In formula (6), U α1 U β1 U represents the voltages along the α1 and β1 axes of the first voltage source inverter in a stationary two-phase coordinate system, respectively; α2 U β2 These represent the voltages of the second voltage source inverter along the α2 and β2 axes in a stationary two-phase coordinate system, respectively.

[0099] S2-3: Perform an inverse Clark transformation on the voltages in the stationary two-phase coordinate system to calculate the voltages of each phase of the six-phase motor.

[0100] In this embodiment, the first voltage source inverter includes phase A, phase B, and phase C, and the second voltage source inverter includes phase U, phase V, and phase W. Therefore, the voltages of each phase are:

[0101]

[0102] In formula (7), U A U B U C These represent the output voltages of phases A, B, and C in the first voltage source inverter, respectively; U U U V U WThese represent the output voltages of the U-phase, V-phase, and W-phase in the second voltage source inverter, respectively.

[0103] S3: Calculate the zero vector difference between the two voltage source inverters based on the output voltage of each phase of the six-phase motor.

[0104] In this embodiment, the maximum voltage U of the first voltage source inverter max1 =max{U A U B U C} and minimum value U min1 =min{U A U B U C The maximum voltage U of the second voltage source inverter max2 =max{U U U V U W} and minimum value U min2 =min{U U U V U W}, then the zero vector difference between the two voltage source inverters is:

[0105]

[0106] In formula (8), t 0_diff U represents the zero vector difference between the first voltage source inverter and the second voltage source inverter; min2 U max2 These represent the minimum and maximum voltage values ​​of the second voltage source inverter, respectively; U min1 U max1 These represent the minimum and maximum voltage values ​​of the first voltage source inverter, respectively.

[0107] S4: Using the traditional SVPWM method, the effective voltage vector action time of the two voltage source inverters is calculated respectively, and then the total action time of the corresponding zero vector is obtained.

[0108] In this embodiment, the calculation method for the operating time of the two voltage source inverters is the same, so the first voltage source inverter will be used as an example for explanation.

[0109] S4-1: The first voltage source inverter includes a first effective voltage vector and a second effective voltage vector. Then the duration T of the first effective voltage vector is... V1_ABC The duration T of the second effective voltage vector V2_ABC The theoretical basis for this calculation is the principle of average value equivalence, which states that within a switching cycle T... SThe basic voltage vectors are combined to make their average value equal to a given voltage vector. Considering the case of six sectors (including I, II, III, IV, V, and VI), T... V1_ABC and T V2_ABC The calculation requires the use of intermediate variables X, Y, and Z, which are specifically expressed as follows:

[0110]

[0111] In formula (9), X, Y, and Z represent intermediate variables; T S Indicates the carrier period; U dc Indicates DC bus voltage; U α1 U β1 These represent the voltages of the first voltage source inverter along the α1 and β1 axes in a stationary two-phase coordinate system, respectively.

[0112] Then the duration T of the first effective voltage vector in the first voltage source inverter V1_ABC The duration T of the second effective voltage vector V2_ABC The relationship varies depending on the sector, as shown in Table 1.

[0113] Table 1. Duration of Effective Voltage Vector in Different Sectors

[0114] N6 II VI I IV III V <![CDATA[T V1_ABC ]]> Z Y -Z -X X -Y <![CDATA[T V2_ABC ]]> Y -X X Z -Y -Z

[0115] Similarly, the duration T of the third effective voltage vector in the second voltage source inverter can be obtained. V1_UVW The duration T of the fourth effective voltage vector V2_UVW .

[0116] S4-2: In this embodiment, the total duration of the corresponding zero vector is calculated based on the duration of the effective voltage vector.

[0117] T Z_ABC =T S -(T V1_ABC +T V2_ABC ),T Z_UVW =T S -(T V1_UVW +T V2_UVW (10)

[0118] In formula (10), T Z_ABC T represents the total duration of the zero vector in the first voltage source inverter; Z_UVW This represents the total duration of the zero vector in the second voltage source inverter.

[0119] S5: Based on the zero vector difference and the total zero vector time of the two voltage source inverters, dynamically allocate the zero vector action time of the two voltage source inverters; and combine the effective vector action time to calculate the conduction time of each switch or the corresponding PWM comparison value, so as to realize that a single switch only switches once in one carrier cycle.

[0120] S5-1: Construct a zero-vector assignment model and obtain the zero-vector action time.

[0121] In this embodiment, the action times of the first zero vector (000) and the second zero vector (111) in the first voltage source inverter are T, respectively. 0_ABC and T 7_ABC The durations of the third zero vector (000) and the third zero vector (111) in the second voltage source inverter are T, respectively. 0_UVW and T 7_UVW The constructed zero-vector assignment model is as follows:

[0122]

[0123] In formula (11), T 0_ABC T 7_ABC T represents the duration of action of the first zero vector and the second zero vector in the first voltage source inverter, respectively; 0_UVW T 7_UVW T represents the duration of the third and fourth zero vectors in the second voltage source inverter, respectively; Z_ABC T represents the total duration of the zero vector in the first voltage source inverter; Z_UVW t represents the total duration of the zero vector in the second voltage source inverter; 0_diff This represents the zero vector difference between the first voltage source inverter and the second voltage source inverter.

[0124] In this embodiment, considering that the solution to the above model is difficult to obtain directly, a simplification is made based on the situation of the sector where the reference voltage is located. According to the U calculated in S1... d U q , Perform an inverse Park coordinate transformation to calculate the output voltage U in the stationary coordinate system. α U β U x U y It adopts a 24-sector partitioning, utilizing U... α U β Calculate the sector N24 of the αβ plane containing the six-phase reference voltage vector, and divide the sector into 24 sectors as follows: Figure 4 As shown.

[0125] When sector N = 1, 4, 5, 8, 9, 12, 13, 16, 17, 20, 21 and 24:

[0126]

[0127] When sectors N = 2, 3, 6, 7, 10, 11, 14, 15, 18, 19, 22, and 23:

[0128]

[0129] According to formulas (12) and (13), T can be determined. 0_ABC T 7_ABC T 0_UVW T 7_UVW Solve the problem.

[0130] S5-2: Calculate the time switching point of each switch in the two voltage source inverters within the cycle.

[0131] In this embodiment, to facilitate the calculation of the time switching points of each switch within the cycle, the following variables need to be defined:

[0132]

[0133] In formula (14), T a T b T c These represent the first variable, the second variable, and the third variable, respectively; T 0_ABC T represents the duration of the first zero vector in the first voltage source inverter; V1_ABC T represents the duration of the first effective voltage vector in the first voltage source inverter; V2_ABC This indicates the duration of the second effective voltage vector in the first voltage source inverter.

[0134] Then, the switching time T of phases A, B, and C in the first voltage source inverter is... cm1_ABC T cm2_ABC T cm3_ABC The relationship with each sector is shown in Table 2 below.

[0135] Table 2. Switching Time Points of the First Voltage Source Inverter in Each Sector

[0136] N6 II VI I IV III V <![CDATA[T cm1_ABC ]]> <![CDATA[T b ]]> <![CDATA[T a ]]> <![CDATA[T a ]]> <![CDATA[T c ]]> <![CDATA[T c ]]> <![CDATA[T b ]]> <![CDATA[T cm2_ABC ]]> <![CDATA[T a ]]> <![CDATA[T c ]]> <![CDATA[T b ]]> <![CDATA[T b ]]> <![CDATA[T a ]]> <![CDATA[T c ]]> <![CDATA[T cm3_ABC ]]> <![CDATA[T c ]]> <![CDATA[T b ]]> <![CDATA[T c ]]> <![CDATA[T a ]]> <![CDATA[T b ]]> <![CDATA[T a ]]>

[0137] Similarly, the switching time T of the U, V, and W phase voltages of the second voltage source inverter can be obtained. cm1_UVM T cm2_UVM T cm3_UVM As shown in Table 3.

[0138] Table 3. Switching Time Points of the Second Voltage Source Inverter in Each Sector

[0139]

[0140]

[0141] In this embodiment, the PWM waveform of each sector can be obtained based on the conduction time of each switching transistor in the two voltage source inverters, such as... Figure 5 The figure shows the waveforms of phases ABC and UVW in sector 1.

[0142] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of the present invention.

Claims

1. A method of modulation for dual three-phase electric machines based on dynamic zero vector distribution, characterized by, Specifically comprising the following steps: S1: establish a dual three-phase motor field-oriented control based on vector space decoupling, calculate the output original voltage of each axis; S2: according to the output voltage of each axis, calculate the reference voltage vector of two voltage source inverters in the stationary coordinate system, and calculate the output voltage of each phase in the dual three-phase motor; S3: calculate the zero vector difference of two voltage source inverters according to the output voltage of each phase; S4: calculate the effective voltage vector action time of two voltage source inverters respectively, and then obtain the total action time of the corresponding zero vector; S5: according to the zero vector difference and the total time of the zero vector of two voltage source inverters, dynamically allocate the zero vector action time of two voltage source inverters; And combine the effective vector action time to calculate the conduction time of each switch tube.

2. A dual three-phase motor modulation method based on dynamic zero vector distribution as claimed in claim 1, wherein, The S1 includes the following steps: S1-1: Collecting six-phase currents of the dual three-phase motor, and obtaining α-axis current i α and β-axis current i β in a stationary two-phase coordinate axis system in αβ plane through VSD coordinate transformation of the six-phase currents, and obtaining x-axis current i x and y-axis current i y in a stationary two-phase coordinate axis system in xy plane; then obtaining d-axis current i α and q-axis current i β in a d-q rotating coordinate axis system through Park1 transformation of the current i q and the current i d , obtaining d-axis current i q and q-axis current i x in a d-q rotating coordinate axis system through Park2 transformation of the current i y and the current i z , obtaining d-axis current i z and q-axis current i z in a d-q rotating coordinate axis system and q-axis current i z in a d-q rotating coordinate axis system S1-2: According to the speed feedback ω est and the speed given ω ref , the d-axis, q-axis, d z axis and q z axis output original voltages.

3. A dual three-phase motor modulation method based on dynamic zero vector distribution as claimed in claim 2, wherein, In the S1-1, the VSD coordinate transformation is: In formula (1), i A , i B , i C , i U , i V , i W are stator currents of phases A, B, C, U, V, W, respectively; i α represents an α-axis current in an αβ plane; i β represents a β-axis current in the αβ plane; i x represents an x-axis current in an xy plane; i y represents a y-axis current in the xy plane; i o1 represents an o1-axis current in an o1o2 plane; i o2 represents an o12-axis current in the o1o2 plane.

4. A dual three-phase motor modulation method based on dynamic zero vector distribution as claimed in claim 2, wherein, In the S1-1, the Park1 transformation is: In Equation (2), i d represents d q represents d-axis current in a rotating coordinate axis system; i q represents d q represents q-axis current in a rotating coordinate axis system; θ represents an electrical angle of a motor rotor; i α represents α-axis current in an αβ plane; i β represents β-axis current in an αβ plane; Park2 transformation is: In equation (3), represents d z q z d in the rotating coordinate axis system z axis current; represents d z q z q in the rotating coordinate axis system z axis current; i x represents x-axis current in the xy plane; i y represents y-axis current in the xy plane.

5. A dual three-phase motor modulation method based on dynamic zero vector distribution as claimed in claim 2, wherein, In the S1-2, the d-axis, q-axis, d z axis and q z axis output the original voltage as: In Equation (4), U d , q , are d-axis voltage, q-axis voltage, d z -axis voltage, and q z -axis voltage, respectively; U d_pidout , q_pidout , represent d-axis, q-axis, d z -axis, and q z -axis output raw voltage, respectively; -ω e L q i q represents a d-axis feedforward term; represents a q-axis feedforward term; ω e L qz i qz represents a d z -axis feedforward term; -ω e L dz i dz represents a q z -axis feedforward term.

6. A dual three-phase motor modulation method based on dynamic zero vector distribution as claimed in claim 1 wherein, The S2 includes the following steps: S2-1: according to the output voltage of each axis, the corresponding reference voltage vector of two voltage source inverters in the rotating coordinate system is calculated as: In formula (5), respectively represent the reference voltage vector of the first voltage source inverter on the d1 axis, q1 axis; respectively represent the reference voltage vector of the second voltage source inverter on the d2 axis, q2 axis;U d , U q , respectively are the d-axis voltage, q-axis voltage, d z axis voltage and q z axis voltage; S2-2: The reference voltage vectors are respectively inverse Park-converted to obtain voltages U α1 , β1 and U α2 , β2 : In Equation (6), U α1 , U β1 represent the voltages of the first voltage source inverter on the α1-axis and β1-axis in the stationary two-phase coordinate, respectively; U α2 , U β2 represent the voltages of the second voltage source inverter on the α2-axis and β2-axis in the stationary two-phase coordinate, respectively; S2-3: the voltage in the stationary two-phase coordinate is inversely Clark transformed, and the voltage of each phase of the six-phase motor is calculated: In formula (7), U A , U B , U C respectively represent output voltages of phase A, phase B and phase C in the first voltage source inverter; U U , U V , U W respectively represent output voltages of phase U, phase V and phase W in the second voltage source inverter.

7. A dual three-phase motor modulation method based on dynamic zero vector distribution as claimed in claim 1 wherein, In the S3, the calculation formula of the zero vector difference of two voltage source inverters is: In formula (8), t 0_diff represents the zero vector difference value of the first voltage source inverter and the second voltage source inverter; U min2 , U max2 respectively represent the voltage minimum value and the voltage maximum value of the second voltage source inverter; U min1 , U max1 respectively represent the voltage minimum value and the voltage maximum value of the first voltage source inverter.

8. A dual three-phase motor modulation method based on dynamic zero vector distribution as claimed in claim 1, wherein, The S4 includes the following steps: S4-1: the first voltage source inverter includes a first effective voltage vector and a second effective voltage vector, the action time T V1_ABC of the second effective voltage vector V2_ABC The calculation in different sectors needs the help of intermediate variables X, Y and Z, which are specifically represented as: In Equation (9), X, Y, and Z represent intermediate variables; T S represents a carrier period; U dc represents a DC bus voltage; U α1 , U β1 respectively represent voltages of the first voltage source inverter on the α1 axis and the β1 axis in the stationary two-phase coordinates. S4-2: calculate the total action time of the corresponding zero vector according to the effective voltage vector action time: T Z_ABC = T S -(T V1_ABC + T V2_ABC ), T Z_UVW = T S -(T V1_UVW + T V2_UVW ) (10) In Equation (10), T Z_ABC represents the total action time of zero vectors in the first voltage source inverter; T Z_UVW represents the total action time of zero vectors in the second voltage source inverter; T V1_UVW represents the action time of the third active voltage vector in the second voltage source inverter; T V2_UVW represents the action time of the fourth active voltage vector in the second voltage source inverter.

9. A dual three-phase motor modulation method based on dynamic zero vector distribution as claimed in claim 1, wherein, The S5 includes the following steps: S5-1: build a zero vector allocation model to obtain the zero vector action time: In formula (11), T 0_ABC , T 7_ABC respectively represent the action time of the first zero vector and the second zero vector in the first voltage source inverter; T 0_UVW , T 7_UVW respectively represent the action time of the third zero vector and the fourth zero vector in the second voltage source inverter; T Z_ABC represents the total action time of the zero vector in the first voltage source inverter; T Z_UVW represents the total action time of the zero vector in the second voltage source inverter; t 0_diff represents the zero vector difference between the first voltage source inverter and the second voltage source inverter. S5-2: calculate the time switching point of each switch in the cycle; In Equation (12), T a , T b , T c represent the first variable, the second variable, and the third variable, respectively; T 0_ABC represents the action time of the first zero vector in the first voltage source inverter; T V1_ABC represents the action time of the first effective voltage vector in the first voltage source inverter; and T V2_ABC represents the action time of the second effective voltage vector in the first voltage source inverter. The switching time points T of the A, B and C phase voltages in the first voltage source inverter cm1_ABC cm2_ABC cm3_ABC The relationship with each sector is:​​ Similarly, the switching time points T of the second voltage source inverter U, V and W phase voltages are obtained cm1_UVM cm2_UVM cm3_UVM .​​

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