Method, system and storage medium for eliminating common-mode voltage of asymmetric six-phase ac motor

Abstract

The application discloses a kind of non-symmetrical six-phase alternating-current motor common-mode voltage elimination method, system and storage medium, belong to motor control field, method includes: S1, the six-phase current of non-symmetrical six-phase alternating-current motor and rotor position angle are collected;S2, the six-phase current is decomposed to three mutually orthogonal subplanes, and the current under electromechanical energy conversion plane is obtained;S3, the current is converted by rotating coordinate transformation, the converted current is compared with reference current to obtain reference voltage amplitude;S4, according to the reference voltage amplitude and rotor position angle, determine the sector where reference voltage is located, using zero common-mode voltage vector, through space vector modulation synthesis reference voltage;S5, the reference voltage is used to drive two sets of three-phase inverters, so that the common-mode voltage amplitude of output is same, opposite direction.The application can suppress z1-z2 subspace voltage component, eliminate the common-mode voltage of system, relative to SPWM modulation, maximum modulation ratio is greater than 1, can improve the voltage utilization rate of system.

Description

Technical Field

[0001] This invention belongs to the field of motor control, and more specifically, relates to a method, system and storage medium for eliminating common-mode voltage of an asymmetrical six-phase AC motor. Background Technology

[0002] Compared to traditional three-phase AC motors, asymmetrical six-phase AC motors offer advantages such as low voltage, high power output, and higher fault tolerance. Furthermore, the two sets of three-phase stator windings in an asymmetrical six-phase motor employ a 30° phase shift, eliminating the 6n±1 (n=1,3,5,…) harmonics in the rotating magnetic field, resulting in lower space harmonic content and lower torque ripple. Therefore, the application of asymmetrical six-phase AC motors meets the high power and high performance requirements of applications such as electric ship propulsion, electric motor automobiles, and aircraft.

[0003] In motor drive systems, frequency converters use high-frequency pulse sequences to achieve an equivalent reference voltage. While these high-frequency pulses reduce harmonic currents, they inevitably introduce common-mode voltage. Common-mode voltage not only causes more electromagnetic interference but also generates common-mode current that flows through the motor's insulation and bearings, affecting the reliability of the motor system. Common-mode voltage suppression methods can be divided into hardware suppression and software suppression. Hardware suppression methods suppress the propagation path by adding external passive or active filters, while software suppression suppresses the common-mode voltage source by changing the modulation strategy or topology. Software suppression is widely used due to its lower cost and higher power density.

[0004] Currently, software-based common-mode voltage suppression mainly focuses on dual three-phase motors (0° angular offset between the two windings) and symmetrical six-phase motors (60° angular offset between the two windings). However, there is relatively little research on common-mode voltage elimination methods for asymmetrical six-phase motors. One pulse phase-shifting method can achieve common-mode voltage cancellation for asymmetrical six-phase motors, but this method is essentially still SPWM modulation, with a maximum modulation ratio of only 1, resulting in low voltage utilization and complex phase-shifting operation. Summary of the Invention

[0005] To address the shortcomings and improvement needs of existing technologies, this invention provides a method, system, and storage medium for eliminating common-mode voltage in an asymmetrical six-phase AC motor. The purpose is to eliminate the common-mode voltage in an asymmetrical six-phase AC motor while improving the maximum modulation ratio.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for eliminating common-mode voltage in an asymmetrical six-phase AC motor is provided, comprising:

[0007] S1. Collect the six-phase current and rotor position angle θ of the asymmetrical six-phase AC motor;

[0008] S2. The six-phase current is decomposed into three mutually orthogonal sub-planes through space vector decomposition: α-β sub-plane, z1-z2 sub-plane and zero-sequence sub-plane, to obtain the current under the α-β sub-plane; wherein, the α-β sub-plane is the electromechanical energy conversion plane, and the z1-z2 sub-plane is the non-energy conversion plane;

[0009] S3. Transform the current in the α-β subplane using a coordinate rotation method to obtain the current i in the dq plane. d i q , to the current i d i q The reference voltage amplitude is obtained by comparing it with the dq-axis reference current;

[0010] S4. Select six zero common-mode voltage large vectors and two zero common-mode voltage zero vectors within the α-β subplane. The six zero common-mode voltage large vectors divide the α-β subplane into six sectors. Determine the sector where the reference voltage is located based on the reference voltage amplitude and the rotor position angle θ. Using a space vector modulation method, select the two zero common-mode voltage large vectors corresponding to the sector where the reference voltage is located, and synthesize the reference voltage with the two zero common-mode voltage zero vectors. Among them, the zero common-mode voltage large vector is the vector with the longest vector length that satisfies the zero common-mode voltage condition.

[0011] S5. Use the reference voltage to drive two sets of three-phase inverters of the asymmetrical six-phase AC motor so that the output common-mode voltage has the same amplitude but opposite direction.

[0012] Furthermore, in S4, six zero common-mode voltage vectors are selected in the α-β subplane, and the six zero common-mode voltage large vectors are combined with the six zero common-mode voltage medium vectors to form six zero common-mode virtual vectors;

[0013] When using the space vector modulation method, two zero common-mode virtual vectors corresponding to the sector where the reference voltage is located are selected, and the reference voltage is synthesized with the two zero common-mode voltage zero vectors.

[0014] Furthermore, the duty cycle ratio of each of the zero common-mode voltage large vectors to each of the zero common-mode voltage medium vectors is greater than or equal to...

[0015] Furthermore, when using the space vector modulation method, the modulation duration of the two zero common-mode virtual vectors corresponding to the sector where the reference voltage is located, and the two zero common-mode voltage zero vectors, is as follows:

[0016]

[0017] Where t0 represents the modulation time of the two zero common-mode voltage zero vectors, t1 and t2 are the modulation times of the two zero common-mode virtual vectors corresponding to the sector where the reference voltage is located; VV1 and VV2 represent the two zero common-mode virtual vectors, and VVs represents the length of the two zero common-mode virtual vectors; V ref Indicates the magnitude of the reference voltage; This indicates the position angle θ of the rotor relative to the starting point of the sector containing the reference voltage; T S The function indicates the switching period; floor() represents the floor operator.

[0018] Furthermore, the modulation times of each of the zero common-mode voltage large vectors and each of the zero common-mode voltage medium vectors within the sector where the reference voltage is located are as follows:

[0019]

[0020]

[0021] Among them, t i1 t i2 These represent the modulation duration of each of the zero common-mode voltage large vectors and each of the zero common-mode voltage medium vectors within the sector where the reference voltage is located, respectively, and τ is the duty cycle ratio of each of the zero common-mode voltage large vectors and each of the zero common-mode voltage medium vectors.

[0022] Furthermore, during each sector modulation process, the order in which the two large zero common-mode voltage vectors, the two medium zero common-mode voltage vectors, and the two zero common-mode voltage vectors synthesize a reference voltage is as follows:

[0023] Within each switching cycle, the two large vectors of the zero common-mode voltages or the two medium vectors of the zero common-mode voltages are placed consecutively;

[0024] Within each switching cycle, one of the zero common-mode voltage zero vectors is symmetrically located on both sides of the switching cycle, and the other zero common-mode voltage zero vector is located in the middle of the switching cycle;

[0025] The relative order of synthesis of the zero common-mode voltage large vector and the zero common-mode voltage medium vector corresponding to the zero common-mode virtual vector participating in the next sector modulation remains unchanged.

[0026] Furthermore, during each sector modulation process, the voltage vector synthesis order is reversed between two adjacent switching cycles.

[0027] Furthermore, in S3, the current i d i q The reference voltage amplitude obtained after comparison with the dq-axis reference current includes:

[0028] The rotor angular velocity ω is obtained by differentiating the rotor position angle θ. r ;

[0029] The rotor angular velocity ω r With the set reference speed The compared error signal is then used by PI control to obtain the reference currents for the d-axis and q-axis.

[0030] The reference currents of the d-axis and q-axis With respect to the corresponding current i in the dq plane d i q The compared error signal is then used by PI control to obtain the corresponding d-axis and q-axis reference voltages u. d u q This allows us to obtain the reference voltage amplitude along the dq axis.

[0031] According to another aspect of the present invention, an asymmetric six-phase AC motor common-mode voltage elimination system is provided, comprising:

[0032] The acquisition module is used to acquire the six-phase current and rotor position angle θ of an asymmetrical six-phase AC motor.

[0033] The current calculation module is used to decompose the six-phase current into three mutually orthogonal sub-planes through space vector decomposition: α-β sub-plane, z1-z2 sub-plane and zero-sequence sub-plane, to obtain the current under the α-β sub-plane, where the α-β sub-plane is the electromechanical energy conversion plane and the z1-z2 sub-plane is the non-energy conversion plane;

[0034] The reference voltage amplitude calculation module is used to transform the current in the α-β subplane into the current i in the dq plane through a coordinate rotation transformation. d i q , to the current i d i q The reference voltage amplitude is obtained by comparing it with the dq-axis reference current;

[0035] The reference voltage synthesis module is used to select six zero common-mode voltage large vectors and two zero common-mode voltage zero vectors in the α-β subplane. The six zero common-mode voltage large vectors divide the α-β subplane into six sectors. The sector where the reference voltage is located is determined according to the reference voltage amplitude and the rotor position angle θ. Using a space vector modulation method, two zero common-mode voltage large vectors corresponding to the sector where the reference voltage is located are selected, and the reference voltage is synthesized with the two zero common-mode voltage zero vectors. The zero common-mode voltage large vector is the vector with the longest vector length that satisfies the zero common-mode voltage condition.

[0036] The control module is used to drive two sets of three-phase inverters of the asymmetrical six-phase AC motor with the reference voltage, so that the output common-mode voltage has the same amplitude but opposite direction.

[0037] According to another aspect of the invention, a computer-readable storage medium is provided, including a stored computer program; when the computer program is executed by a processor, it controls the device in which the computer-readable storage medium is located to perform the method described in any of the first aspects.

[0038] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0039] (1) The method of the present invention decomposes the six-phase current into spatial vectors and uses spatial vector modulation method. It uses only six zero common-mode voltage large vectors and two zero common-mode voltage zero vectors to synthesize the reference voltage, so that the instantaneous sum of the common-mode voltages output by the two sets of three-phase inverters is zero, thereby eliminating the total common-mode voltage input from the inverter to the asymmetrical six-phase AC motor, thereby eliminating the common-mode noise generated by the asymmetrical six-phase motor. The maximum modulation ratio can reach 1.115, which improves the maximum modulation ratio while eliminating the common-mode voltage of the asymmetrical six-phase AC motor.

[0040] (2) Further, six zero common-mode voltage large vectors and six zero common-mode voltage medium vectors are used to synthesize six zero common-mode virtual vectors. The six zero common-mode virtual vectors are used to realize the vector synthesis of the motor reference voltage. The virtual vectors cancel the distribution relationship of the voltage of the z1-z2 subplane, suppress the voltage of the z1-z2 subplane, and thus reduce the additional losses caused by the non-energy z1-z2 subplane.

[0041] (3) When the duty cycle ratio of each of the zero common-mode voltage large vectors to each of the zero common-mode voltage medium vectors is greater than or equal to At this time, the achievable modulation ratio is between 1.035 and 1.115; when the duty cycle ratio is... The virtual vector completely cancels out the voltage distribution relationship of the z1-z2 subplane, making the average voltage of the z1-z2 subplane in one cycle equivalent to zero, and completely suppressing the additional losses caused by the non-energy z1-z2 subplane.

[0042] (4) The present invention also provides the vector modulation time and the corresponding synthesis sequence of the synthesized reference voltage when using the space vector modulation method. Under the designed vector synthesis sequence, the switch can be operated only once in one switching cycle. When the sector is switched, there is no current jump. This achieves the elimination of common mode voltage at a higher modulation ratio while reducing harmonic current.

[0043] (5) Preferably, when the voltage vector synthesis order in two adjacent switching cycles is opposite, it can ensure that the phase voltage is symmetrical in two consecutive cycles, thus solving the problem that due to the asymmetry of the six-phase PWM, there will be a cumulative offset effect in the entire fundamental cycle, resulting in an imbalance of the fundamental current of the two sets of three-phase windings.

[0044] (6) The method of the present invention also provides a corresponding method for calculating the reference voltage amplitude. Based on the reference voltage amplitude and the rotor position angle θ, the sector in which the reference voltage is located during space vector modulation can be determined.

[0045] In summary, the method of this invention eliminates the common-mode voltage of the system, reduces the common-mode current and common-mode electromagnetic interference of the motor, and compared with SPWM modulation, the maximum modulation ratio of the method of this invention is between 1.035 and 1.115, with a maximum of 1.115, which improves the voltage utilization of the system. At the same time, this invention does not require additional hardware and can be implemented only by improving the software algorithm. It has strong versatility, can protect the motor bearings, and improve the reliability of the system. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the common-mode voltage suppression method of the present invention.

[0047] Figure 2 This is a topology diagram of the asymmetric six-phase AC motor of the present invention.

[0048] Figure 3 The common-mode voltage suppression method of the present invention relates to a signal flow diagram.

[0049] Figures 4(a) and 4(b) are schematic diagrams of the spatial positions of the zero common-mode voltage vector selected in this invention in the α-β subplane and the z1-z2 subplane, respectively.

[0050] Figure 5(a) is a sector division diagram obtained according to the common-mode voltage elimination method of the present invention.

[0051] Figure 5(b) is a schematic diagram of space vector modulation performed according to the common-mode voltage elimination method of the present invention.

[0052] Figures 6(a) and 6(b) are vector allocation diagrams for the first PWM cycle and symmetrical vector allocation diagrams for the second PWM cycle obtained according to the common-mode voltage elimination method of the present invention. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0054] like Figure 1 , Figure 2 As shown, the asymmetric six-phase AC motor common-mode voltage elimination method of the present invention includes six-phase windings A, U, B, V, C, and W. The phase difference between the two sets of three-phase windings is 30°. In this embodiment of the invention, both sets of three-phase windings adopt a Y-type connection. In other embodiments, a delta connection or other connection methods can be used. Figure 1 In the middle, V dc Indicates DC bus voltage; v a v b v c v u v v v w These represent the six-phase voltages of an asymmetrical six-phase AC motor, i a i b i c i u i v i w N1 and N2 represent the six-phase currents of the asymmetrical six-phase AC motor, respectively; N1 and N2 represent the center points of the two sets of three-phase motors, respectively.

[0055] The method includes the following steps:

[0056] S1. Collect the six-phase current i of the asymmetrical six-phase AC motor. x (x = a, b, c, u, v, w), DC bus voltage V dc and rotor position angle θ;

[0057] S2. Decompose the six-phase current into three mutually orthogonal subplanes using space vector decomposition: the α-β subplane, the z1-z2 subplane, and the o1-o2 zero-sequence subplane, to obtain the current corresponding to the α-β subplane; where the α-β subplane is the electromechanical energy conversion plane, and the z1-z2 and o1-o2 zero-sequence subplanes are non-energy planes; the current in the α-β subplane is i α i β .

[0058] S3, based on the current i under the α-β subplane α i β Given the rotor position angle θ, the current i in the rotating coordinate system dq plane is obtained through a coordinate transformation.d i q The amplitude of the dq-axis reference voltage is obtained by comparing it with the dq-axis reference current.

[0059] S4. Select six zero common-mode voltage large vectors and two zero common-mode voltage zero vectors in the α-β subplane. These six zero common-mode voltage large vectors divide the α-β subplane into six sectors. Determine the sector where the reference voltage is located based on the reference voltage amplitude and the rotor position angle θ. Using the space vector modulation method, select the two zero common-mode voltage large vectors corresponding to the sector where the reference voltage is located, and synthesize the reference voltage with the two zero common-mode voltage zero vectors. Among them, the zero common-mode voltage large vector is the longest vector among the vectors that satisfy the zero common-mode voltage condition; the zero common-mode voltage zero vector is the vector with a length of 0 among the vectors that satisfy the zero common-mode voltage condition.

[0060] S5. Use the reference voltage to drive two sets of three-phase inverters for the asymmetrical six-phase AC motor, so that the output common-mode voltage has the same amplitude but opposite direction, thereby eliminating the common-mode voltage generated by the asymmetrical six-phase AC motor.

[0061] As a further preferred design of the present invention, S4 also includes:

[0062] By selecting six zero common-mode voltage vectors and combining the six zero common-mode voltage large vectors and the six zero common-mode voltage medium vectors into six zero common-mode virtual vectors, the average voltage of the z1-z2 subplane can be made equivalent to zero, thus suppressing the additional losses caused by the non-energy z1-z2 subplane.

[0063] When synthesizing the reference voltage, two zero common-mode virtual vectors corresponding to the sector where the reference voltage is located are selected, and the reference voltage is synthesized with the two zero common-mode voltage zero vectors.

[0064] Specifically, in S2, the six-phase current i x (x=a,b,c,u,v,w) are transformed into three corresponding orthogonal subspaces according to formula (1):

[0065]

[0066] Among them, i z1 i z2 Let i be the currents of the six-phase currents decomposed into the z1-z2 subplane via space vector decomposition. o1 i o2 These are the currents of the six-phase currents decomposed into the zero-sequence subplane of o1-o2 through space vector decomposition.

[0067] In S3, the formula for coordinate transformation by rotation is:

[0068]

[0069] Where θ is the rotor position angle, i α i β Let i be the current under the α-β subplane. d i q The current obtained in the rotating coordinate system dq plane.

[0070] like Figure 3 As shown, the current i in the dq plane d i q The amplitude of the dq-axis reference voltage, obtained by comparing it with the dq-axis reference current, includes:

[0071] The rotor angular velocity ω is obtained by differentiating the sampled rotor position angle θ. r ;

[0072] Rotor angular velocity ω r With the set reference speed The compared error signal is used to obtain the q-axis reference current through PI controller 1.

[0073] Reference current Compared with the actual sampled q-axis current i q The compared error signal is used to obtain the q-axis reference voltage u through PI controller 2. q Similarly, the reference voltage u along the d-axis can be obtained. d This allows us to obtain the reference voltage amplitude along the dq axis.

[0074] Specifically, in S4, according to the common-mode voltage generation principle of the asymmetrical six-phase AC motor, achieving zero common-mode voltage requires the sum of the output voltages of the six-phase bridge arms to be zero, as shown in equation (3) below. Figures 4(a) and 4(b) show 60 effective voltage vectors (i.e., voltage vectors with non-zero vector length) and four zero voltage vectors (i.e., voltage vectors with zero vector length) in the α-β subplane and z1-z2 subplane, respectively. The 60 effective voltage vectors are divided into large vectors V according to their vector length. L , medium vector V M Basic vector V B and small vector V S The length of each voltage vector satisfies formula (4), where each voltage vector is obtained by combining the binary number [S]. a S b S c ] and [S u S v S w The two corresponding octal numbers are used for identification. According to the principle of three "1" and three "0" states, the effective voltage vectors with dark arrows in Figures 4(a) and 4(b) satisfy the zero common-mode voltage condition of formula (3).

[0075] Among them, the large vector V at the same position in the α-β subplane L and the mid-vector V M The small vector V corresponding to the z1-z2 subplane S and the mid-vector V M And in opposite directions. For example, the large vector V in the α-β subplane. 64 and the mid-vector V 46 Having the same direction, the corresponding small vector V in the z1-z2 subplane 64 and the mid-vector V 46 And in the opposite direction.

[0076]

[0077]

[0078] To improve the modulation ratio and eliminate the common-mode voltage generated by the asymmetrical six-phase AC motor, six large zero-common-mode voltage vectors (large vectors among the effective voltage vectors that satisfy the zero-common-mode voltage condition) and two zero-common-mode voltage vectors (zero-voltage vectors that satisfy the zero-common-mode voltage condition) are selected in the α-β subplane, achieving a maximum modulation ratio of 1.115. In this embodiment, the two zero-common-mode voltage vectors are V0 and V1. 07 With V 70 .

[0079] Preferably, in order to improve the modulation ratio and eliminate the common-mode voltage generated by the asymmetrical six-phase AC motor, while also suppressing the additional losses caused by the non-energy z1-z2 subplane, six zero common-mode voltage large vectors, six zero common-mode voltage medium vectors, and two zero common-mode voltage zero vectors are selected to synthesize the reference voltage. Wherein, the duty cycle ratio of the selected zero common-mode voltage large vectors to the zero common-mode voltage medium vectors is greater than or equal to...

[0080] When the duty cycle of the large vector of zero common-mode voltage and the medium vector of zero common-mode voltage is equal to When, as shown in formula (5), the virtual vector can completely cancel the distribution relationship of the voltage in the z1-z2 subplane, making its equivalent voltage in the z1-z2 subplane zero, and the maximum modulation ratio that can be achieved is 1.035.

[0081] The six large zero common-mode voltage vectors and the six medium zero common-mode voltage vectors are synthesized into six zero common-mode virtual vectors VVs. The lengths of the synthesized six zero common-mode virtual vectors VVs are shown in formula (6):

[0082]

[0083]

[0084] As shown in Figure 5(a), the six zero common-mode voltage vectors divide the α-β subplane into six sectors, which are as follows:

[0085]

[0086] As shown in Figure 5(b), using the space vector modulation method, during the synthesis of the reference voltage, the modulation times of the two zero common-mode virtual vectors and the two zero common-mode voltage zero vectors corresponding to the sector where the reference voltage is located are as follows:

[0087]

[0088] Where t0 represents the modulation time of the two zero common-mode voltage zero vectors, and t1 and t2 are the modulation times of the two zero common-mode virtual vectors corresponding to the sector where the reference voltage is located, respectively. Based on the duty cycle ratio of the large zero common-mode voltage vector and the medium zero common-mode voltage vector of each synthesized zero common-mode virtual vector, the modulation times of the large zero common-mode voltage vector and the medium zero common-mode voltage vector corresponding to the sector where the reference voltage is located are obtained; that is, the modulation times of each large zero common-mode voltage vector and each medium zero common-mode voltage vector corresponding to the sector where the reference voltage is located are as follows:

[0089]

[0090] Among them, t i1 t i2 τ represents the modulation time of each zero common-mode voltage large vector and each zero common-mode voltage medium vector within the sector where the reference voltage is located, respectively, and τ is the duty cycle ratio of each zero common-mode voltage large vector to each zero common-mode voltage medium vector.

[0091] In this embodiment of the invention, the duty cycle of each zero common-mode voltage large vector and each zero common-mode voltage medium vector is allocated according to formula (5).

[0092] VV1 and VV2 represent two zero common-mode virtual vectors (including length and direction) within the sector containing the reference voltage; V ref Indicates the magnitude of the reference voltage; This indicates the position angle θ of the rotor relative to the starting point of the sector containing the reference voltage; T S The function indicates the switching period; floor() represents the floor operator.

[0093] After obtaining the modulation times of the four effective zero common-mode voltage vectors (two large zero common-mode voltage vectors and two medium zero common-mode voltage vectors) and the two zero zero common-mode voltage vectors within the sector containing the reference voltage, the reference voltage is synthesized according to the following voltage vector synthesis order during the modulation process of each sector to obtain the pulse modulation signal of the motor corresponding to the current sector:

[0094] Within each switching cycle, either the two zero common-mode voltage large vectors are placed consecutively, or the two zero common-mode voltage medium vectors are placed consecutively.

[0095] Within each switching cycle, one zero common-mode voltage zero vector is symmetrically located on both sides of the switching cycle, and another zero common-mode voltage zero vector is located in the middle of the switching cycle;

[0096] The relative order of synthesis of the zero common-mode voltage large vector and the zero common-mode voltage medium vector corresponding to the zero common-mode virtual vector participating in the next sector modulation remains unchanged.

[0097] As shown in formula (9), and referring to Figures 6(a) and 6(b), this is one modulation arrangement sequence in an embodiment of the present invention. Taking the first sector as an example, the voltage vector synthesis sequence for one switching cycle is obtained through the above modulation arrangement sequence as follows: V 07 V 46 V 54 V 70 V 64 V 45 V 07 Zero common-mode voltage zero vector V 07 Symmetrically located on both sides of the switching cycle, with zero common-mode voltage and zero vector V 70 Located in the middle of the switching cycle; vector V in the two zero common-mode voltages 46 V 54 Continuous placement, two zero common-mode voltage large vectors V 64 V 45 Continuous placement; the zero common-mode voltage large vector V in the zero common-mode virtual vector participating in the modulation of the next sector 64 Vector V in zero common-mode voltage 46 The relative order remains unchanged; that is, in the first sector, it is according to V. 46 V 64 In the second sector, the order is still according to V. 46 V 64 The order.

[0098] With the modulation arrangement sequence described above, the switch can operate only once within a switching cycle. There is no current jump during sector switching, which achieves common-mode voltage elimination at a higher modulation ratio while reducing harmonic current.

[0099]

[0100] By employing space vector modulation, and designing the modulation duration and sequence of the four effective zero common-mode voltage vectors and two zero common-mode voltage zero vectors within the sector containing the reference voltage, the corresponding reference voltage for each sector is obtained. This leads to the pulse modulation signals PWM1-PWM6 for each phase arm. PWM1-PWM6 control the two inverters, ensuring that the common-mode voltage outputs from the two inverters have the same amplitude but opposite directions, thus eliminating the common-mode voltage. In Figures 6(a) and 6(b), V... cm1 V cm2 These are the common-mode voltage amplitudes output from the two inverters, respectively. It can be seen that V... cm1 V cm2 Same size, opposite direction.

[0101] Preferably, the voltage vector synthesis order is reversed in two adjacent switching cycles. For example, the voltage vector synthesis order in the first switching cycle is: V 07 V 46 V 54 V 70 V 64 V 45 V 07 The second switching cycle repeats the switching sequence of the first switching cycle in reverse order: V 07 V 45 V 64 V 70 V 54 V 46 V 07 This ensures that the phase voltage is symmetrical in two consecutive cycles, which can solve the problem that the fundamental current of the two sets of three-phase windings is unbalanced due to the cumulative offset effect in the entire fundamental cycle caused by the asymmetry of the six-phase PWM.

[0102] That is, the modulation range of the zero common-mode modulation method in this invention is the inscribed circle of a hexagon composed of six virtual vectors, as shown in Figure 5(b), and the maximum modulation ratio is:

[0103]

[0104] At this maximum modulation ratio, while eliminating the common-mode voltage, it is also able to suppress the additional losses caused by the non-energy z1-z2 subplane.

[0105] When only six zero common-mode voltage large vectors and two zero common-mode voltage zero vectors are selected for reference voltage synthesis in the α-β subplane, the maximum modulation ratio can reach:

[0106]

[0107] Among them, V ref_maxThis indicates the maximum reference voltage.

[0108] According to another aspect of the present invention, an asymmetric six-phase AC motor common-mode voltage elimination system is provided, comprising:

[0109] The acquisition module is used to acquire the six-phase current and rotor position angle θ of an asymmetrical six-phase AC motor.

[0110] The current calculation module is used to decompose the six-phase current into three mutually orthogonal sub-planes through space vector decomposition: α-β sub-plane, z1-z2 sub-plane and o1-o2 zero-sequence sub-plane, to obtain the current under the α-β sub-plane, where the α-β sub-plane is the electromechanical energy conversion plane and the z1-z2 sub-plane is the non-energy conversion plane;

[0111] The reference voltage amplitude calculation module is used to transform the current in the α-β subplane into the current i in the dq plane through a coordinate rotation transformation. d i q , will current i d i q The reference voltage amplitude is obtained by comparing it with the dq-axis reference current;

[0112] The reference voltage synthesis module is used to select six zero common-mode voltage large vectors and two zero common-mode voltage zero vectors within the α-β subplane. The six zero common-mode voltage large vectors divide the α-β subplane into six sectors. The sector where the reference voltage is located is determined based on the reference voltage amplitude and the rotor position angle θ. Using a space vector modulation method, the two zero common-mode voltage large vectors corresponding to the sector where the reference voltage is located are selected and synthesized with the two zero common-mode voltage zero vectors to form the reference voltage. Among them, the zero common-mode voltage large vector is the vector with the longest vector length that satisfies the zero common-mode voltage condition, and the zero common-mode voltage zero vector is the vector with a vector length of 0 that satisfies the zero common-mode voltage condition.

[0113] The control module is used to drive two sets of three-phase inverters of an asymmetrical six-phase AC motor with a reference voltage, so that the output common-mode voltage has the same amplitude but opposite direction.

[0114] Each of the above modules is used to perform the corresponding steps in the above-described method for eliminating common-mode voltage in asymmetrical six-phase AC motors.

[0115] According to another aspect of the present invention, a computer-readable storage medium is provided, including a stored computer program; when the computer program is executed by a processor, it controls the device where the computer-readable storage medium is located to perform each step of the above-described method for eliminating common-mode voltage of an asymmetrical six-phase AC motor.

[0116] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for eliminating common-mode voltage in an asymmetrical six-phase AC motor, characterized in that, include: S1. Collect the six-phase current and rotor position angle of the asymmetrical six-phase AC motor. ; S2. The six-phase current is decomposed into three mutually orthogonal sub-planes through space vector decomposition: α-β sub-plane, z1-z2 sub-plane and zero-sequence sub-plane, to obtain the current under the α-β sub-plane; wherein, the α-β sub-plane is the electromechanical energy conversion plane, and the z1-z2 sub-plane is the non-energy conversion plane; S3. Obtain the current in the dq plane by rotating the coordinates of the current in the α-β subplane. , , to the current , The reference voltage amplitude is obtained by comparing it with the dq-axis reference current; S4. Select six large zero-common-mode voltage vectors and two zero-common-mode voltage vectors within the α-β subplane. The six large zero-common-mode voltage vectors divide the α-β subplane into six sectors. Select six medium zero-common-mode voltage vectors within the α-β subplane. Combine the six large zero-common-mode voltage vectors with the six medium zero-common-mode voltage vectors to form six zero-common-mode virtual vectors. Based on the reference voltage amplitude and the rotor position angle... The sector containing the reference voltage is determined. Using the space vector modulation method, two zero common-mode virtual vectors corresponding to the sector containing the reference voltage are selected and synthesized with the two zero common-mode voltage zero vectors to form the reference voltage. Among them, the large zero common-mode voltage vector is the vector with the longest vector length that satisfies the zero common-mode voltage condition. S5. Use the reference voltage to drive two sets of three-phase inverters of the asymmetrical six-phase AC motor so that the output common-mode voltage has the same amplitude but opposite direction. The duty cycle ratio of each of the zero common-mode voltage large vectors to each of the zero common-mode voltage medium vectors is greater than or equal to ; When using the space vector modulation method, the modulation duration of the two zero common-mode virtual vectors corresponding to the sector where the reference voltage is located, and the two zero common-mode voltage zero vectors, is as follows: in, This represents the modulation duration of the two zero common-mode voltage zero vectors. , These are the modulation times of the two zero common-mode virtual vectors corresponding to the sector where the reference voltage is located; , Let VVs represent two zero common-mode virtual vectors, and VVs represent the lengths of the two zero common-mode virtual vectors. Indicates the magnitude of the reference voltage; Indicates the rotor position angle The position relative to the starting point of the sector where the reference voltage is located; Indicates the switching cycle; This represents the floor operator.

2. The method according to claim 1, characterized in that, The modulation times of the large vector and the medium vector of the zero common-mode voltage corresponding to each sector containing the reference voltage are as follows: in, , These represent the modulation duration of each of the large vectors and medium vectors of the zero common-mode voltages within the sector containing the reference voltage, respectively. The duty cycle ratio of each of the zero common-mode voltage large vectors to each of the zero common-mode voltage medium vectors.

3. The method according to claim 2, characterized in that, During each sector modulation process, the order in which the two large zero common-mode voltage vectors, the two medium zero common-mode voltage vectors, and the two zero common-mode voltage vectors synthesize a reference voltage is as follows: Within each switching cycle, the two large vectors of the zero common-mode voltages or the two medium vectors of the zero common-mode voltages are placed consecutively; Within each switching cycle, one of the zero common-mode voltage zero vectors is symmetrically located on both sides of the switching cycle, and the other zero common-mode voltage zero vector is located in the middle of the switching cycle; The relative order of synthesis of the zero common-mode voltage large vector and the zero common-mode voltage medium vector corresponding to the zero common-mode virtual vector participating in the next sector modulation remains unchanged.

4. The method according to claim 3, characterized in that, During each sector modulation process, the voltage vector synthesis order is reversed between two adjacent switching cycles.

5. The method according to claim 1, characterized in that, In S3, the current , The reference voltage amplitude obtained after comparison with the dq-axis reference current includes: The rotor position angle Differentiate to obtain the rotor angular velocity ; The rotor angular velocity With the set reference speed The compared error signal is then used by PI control to obtain the reference currents for the d-axis and q-axis. , ; The reference currents of the d-axis and q-axis , With the corresponding current in the dq plane respectively , The compared error signal is then used by PI control to obtain the corresponding d-axis and q-axis reference voltages. , This allows us to obtain the reference voltage amplitude along the dq axis.

6. A common-mode voltage elimination system for an asymmetrical six-phase AC motor, characterized in that, include: The data acquisition module is used to acquire the six-phase current and rotor position angle of an asymmetrical six-phase AC motor. ; The current calculation module is used to decompose the six-phase current into three mutually orthogonal sub-planes through space vector decomposition: α-β sub-plane, z1-z2 sub-plane and zero-sequence sub-plane, to obtain the current under the α-β sub-plane, where the α-β sub-plane is the electromechanical energy conversion plane and the z1-z2 sub-plane is the non-energy conversion plane; The reference voltage amplitude calculation module is used to obtain the current in the dq plane by rotating the coordinates of the current in the α-β subplane. , , to the current , The reference voltage amplitude is obtained by comparing it with the dq-axis reference current; The reference voltage synthesis module is used to select six large zero-common-mode voltage vectors and two zero-common-mode voltage vectors within the α-β subplane, wherein the six large zero-common-mode voltage vectors divide the α-β subplane into six sectors; select six medium zero-common-mode voltage vectors within the α-β subplane, and combine the six large zero-common-mode voltage vectors with the six medium zero-common-mode voltage vectors to form six zero-common-mode virtual vectors; and, based on the reference voltage amplitude and the rotor position angle... The sector containing the reference voltage is determined. Using space vector modulation, two zero-common-mode virtual vectors corresponding to the sector containing the reference voltage are selected and synthesized with these two zero-common-mode voltage vectors to form the reference voltage. The larger zero-common-mode voltage vector is the vector with the longest length that satisfies the zero-common-mode voltage condition. The duty cycle ratio of each larger zero-common-mode voltage vector to each of the zero-common-mode voltage vectors is greater than or equal to... ; The control module is used to drive two sets of three-phase inverters of the asymmetrical six-phase AC motor with the reference voltage, so that the output common-mode voltage has the same amplitude but opposite direction; When using the space vector modulation method, the modulation duration of the two zero common-mode virtual vectors corresponding to the sector where the reference voltage is located, and the two zero common-mode voltage zero vectors, is as follows: in, This represents the modulation duration of the two zero common-mode voltage zero vectors. , These are the modulation times of the two zero common-mode virtual vectors corresponding to the sector where the reference voltage is located; , Let VVs represent two zero common-mode virtual vectors, and VVs represent the lengths of the two zero common-mode virtual vectors. Indicates the magnitude of the reference voltage; Indicates the rotor position angle The position relative to the starting point of the sector where the reference voltage is located; Indicates the switching cycle; This represents the floor operator.

7. A computer-readable storage medium, characterized in that, The device includes a stored computer program; when executed by a processor, the computer program controls the device containing the computer-readable storage medium to perform the method described in any one of claims 1-5.

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