Optimal current distribution method for variable-pole multi-phase motor during pole-phase switching

Abstract

The invention relates to the technical field of motor control, discloses an optimal current distribution method of a variable-pole multi-phase motor during pole-phase switching, and can realize online smooth pole-phase switching of the variable-pole multi-phase motor and reduce stator copper loss. Based on the harmonic plane decomposition theory, the invention provides a strategy for maintaining the torque and optimizing the current distribution in the pole-phase switching process of the pole-variable multi-phase motor. The strategy has the main advantages that stable current conversion of the variable-pole multi-phase motor can be promoted, so that torque drop is reduced, and stator copper loss in the switching process is minimized.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor control, and in particular relates to an optimal current distribution method for a variable-pole multi-phase motor when the pole phase is switched. Background Art

[0002] Induction motors still maintain a considerable market share in the drive motors of electric vehicles due to their high reliability, fault tolerance and independence from rare earths. When considering the entire operating cycle of an electric vehicle, the motor is usually required to provide high torque at low speed to achieve vehicle acceleration, while only low torque is required to maintain vehicle speed during high-speed cruising. The executable operating range of a single motor cannot meet the requirements of large-load electric vehicles. Therefore, a mechanical gearbox is usually added between the motor and the wheel as a transmission mechanism to convert the required mechanical operating point into an executable operating point for the motor. However, the use of a mechanical gearbox increases the weight of the vehicle and mechanical wear, and increases maintenance costs.

[0003] As the price of power switching semiconductor devices decreases, multi-phase motors based on induction motors are becoming a viable option for various motor drive systems. Multi-phase motors based on induction motors can dynamically change the pole phase configuration of the motor during operation only through software control, and can combine the torque-speed executable operating points of the same induction motor under different pole phase configurations, thereby expanding the total operating area under the same voltage and current limits.

[0004] However, the current online pole phase switching technology of variable pole multiphase motors still has disadvantages such as a significant drop in torque during the switching process and uneven switching. This is because the current online pole phase switching technology uses different vector space models under different pole phase configurations, which causes switching discontinuity in the model. At present, whether the problem of torque retention during online pole phase switching of variable pole multiphase motors can be solved is one of the key points to accelerate the commercial application of variable pole multiphase motors. Summary of the invention

[0005] In view of the above shortcomings, the object of the present invention is to provide an optimal current distribution method during pole phase switching that can realize online smooth pole phase switching of the pole phase configuration of a variable pole multiphase motor and reduce stator copper loss.

[0006] The optimal current distribution method for a variable-pole multiphase motor during pole phase switching of the present invention comprises the following steps:

[0007] Step 1: Use the harmonic plane method to mathematically model the variable-pole multiphase motor;

[0008] Step 2, determining a d-axis current distribution method of the variable-pole multiphase motor in different harmonic planes when the pole phase is switched;

[0009] Step 3: Determine the q-axis current distribution method of the variable-pole multiphase motor in different harmonic planes when the pole phase is switched.

[0010] Furthermore, the step 1 specifically includes the following steps:

[0011] Step 11, converting the current model of each slot of the variable-pole multiphase motor from the 123-coordinate system to the αβ-coordinate system, and then to the dq-coordinate system;

[0012] Step 1 and 2, give the system state expression of torque under dq-axis.

[0013] Furthermore, the current model of the variable-pole multiphase motor in step 1 is converted from the 123-coordinate system to the αβ-coordinate system by using the following equations (1) to (5), and the current model of the variable-pole multiphase motor in step 1 is converted from the αβ-coordinate system to the dq-coordinate system by using the following equations (6) to (8):

[0014]

[0015] ξ=n mw -mod(n mw ,2) (5);

[0016]

[0017] in, is the state vector of the variable-pole multiphase motor in the 123-coordinate system, is the state vector of the variable-pole multiphase motor in the αβ-coordinate system, n mw is the minimum number of windings, C s is the coordinate system transformation incidence matrix, C s The transposed matrix, T 123→αβ0 is the transformation matrix of the variable-pole multiphase motor from the 123-coordinate system to the αβ-coordinate system, T αβ0→123 is the transformation matrix of the variable-pole multiphase motor from the αβ-coordinate system to the 123-coordinate system, δ is the spatial phase shift angle between the magnetic axes, π is the circumference, ξ is the harmonic spatial correlation parameter in the coordinate system conversion correlation matrix, mod(*) is the remainder function, is the state vector of the variable-pole multiphase motor in the dq-coordinate system, T αβ0→dq0 is the transformation matrix of the variable-pole multiphase motor from the αβ-coordinate system to the dq-coordinate system, h is the harmonic plane, and f s is the stator angular frequency, ν h is the angular frequency multiple corresponding to the hth harmonic plane, is the angular offset corresponding to the hth harmonic plane.

[0018] Furthermore, the torque in steps 1 and 2 is expressed by the system state under the dq-axis as:

[0019]

[0020] Among them, τ e is the motor output torque, p nw is the minimum number of winding pole pairs, ψ R,h is the rotor flux in the hth harmonic plane, i q,h is the q-axis current in the hth harmonic plane.

[0021] Furthermore, in the step 2, the d-axis current distribution method of the variable-pole multiphase motor at different harmonic planes when the pole phase is switched is determined to be a sequential d-axis current distribution method or a cross d-axis current distribution method;

[0022] The sequential d-axis current distribution method is as follows: starting from the start time T of the pole phase switching start To the middle time T mid , the d-axis current i in the new polar configuration plane d,h＝[new] It increases linearly from 0 to the reference value of the d-axis current of the new polar configuration at this t∈[T start ,T mid ] period, the d-axis current i in the old pole phase configuration plane d,h＝[old] Remain unchanged; the intermediate moment T mid After that, the d-axis current i in the new polar configuration plane d,h＝[new] Remains unchanged, the d-axis current i in the old pole phase configuration plane d,h＝[old] It starts to decrease linearly and at the end time T end The d-axis current i in the old pole phase configuration plane d,h＝[old] is reduced to 0; among them,

[0023]

[0024] The cross-type d-axis current distribution method is: from the starting time T of the pole phase switching start Until the end time T end , the d-axis current i in the new polar configuration plane d,h＝[new] It increases linearly from 0 to the reference value of the d-axis current of the new pole-phase configuration. The d-axis current i in the old pole-phase configuration plane d,h＝[old] Decreases linearly until the termination time T end Reduced to 0.

[0025] Furthermore, the specific steps of determining the q-axis current distribution method of the variable-pole multiphase motor in different harmonic planes when the pole phase is switched in step 3 are:

[0026] Step 31: Based on the expression of the system state of the torque under the dq-axis in Steps 1 and 2, taking the switching of two harmonic planes as an example, establish an expression for the torque that the motor can provide;

[0027] Step 32, providing a selection range of q-axis current distribution that satisfies the constant torque;

[0028] Step 33, determining the optimization goal of minimizing stator copper loss during the switching process;

[0029] Step 3 and 4, provide a q-axis current distribution method for a variable-pole multiphase motor in different harmonic planes when the pole phase is switched.

[0030] Furthermore, the expression of the torque that the motor can provide in step 31 is:

[0031]

[0032] Among them, i q,h＝[old] The q-axis current in the old phase configuration plane h = [old], i q,h＝[new] The q-axis current in the new polar configuration plane h = [new], ψ R,h＝[old] is the rotor flux in the old pole phase configuration plane h = [old], ψ R,h＝[new] The rotor flux in the new pole phase configuration plane h = [new].

[0033] Furthermore, the q-axis current distribution selection range in step 32 satisfies the following conditions:

[0034] The current i in the harmonic plane of the new pole-phase configuration q,h＝[old] and the current i in the harmonic plane of the old pole-phase configuration q,h＝[old] The moment falls on the straight line of the two clusters of rotation changes determined by the d-axis current distribution method described in step 2, so as to satisfy the output τ of equation (10) e =τ e,ref unchanged, where τ e,ref is the reference value of output torque.

[0035] Furthermore, the optimization objective expression for minimizing stator copper loss in step 33 is:

[0036]

[0037] Where P is the copper loss expression to be optimized, R s,h＝[old] The stator resistance in the old pole-phase configuration plane h = [old], R s,h＝[new] Configure the stator resistance in the plane h=[new] for the new pole phase.

[0038] Furthermore, the final form of the q-axis current distribution method of the variable-pole multiphase motor in steps three and four at different harmonic planes when the pole phase is switched is calculated according to formula (11'):

[0039]

[0040] in, is the vector form of the q-axis current reference value of different harmonic planes, The q-axis current reference value in the old phase configuration plane h = [old], The q-axis current reference value in the plane h=[new] is configured for the new pole phase.

[0041] The embodiments of the present application have at least the following beneficial effects:

[0042] The present invention aims at the pole phase switching control of the variable pole multiphase motor and uses the harmonic plane method to mathematically model the variable pole multiphase motor. The model ensures the continuity of the model when designing the pole phase configuration switching algorithm of the variable pole multiphase motor.

[0043] The present invention proposes a real-time current distribution method for different harmonic planes of a variable-pole multiphase motor when switching the pole phase configuration. The method not only ensures the continuity of the current in different harmonic planes when switching the pole phase configuration, but also ensures the consistency of the motor output torque when switching the pole phase configuration. In addition, the current distribution method proposed by the present invention can also minimize the stator copper loss of the variable-pole multiphase motor and improve the motor efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A d-axis current distribution method for different harmonic planes of a variable-pole multiphase motor when the pole phase is switched in a specific implementation mode 1;

[0045] Figure 2 A q-axis current distribution method for different harmonic planes of a variable-pole multiphase motor when the pole phase is switched in a specific implementation mode 1 (under the perspective of torque maintenance);

[0046] Figure 3 A q-axis current distribution method for different harmonic planes of a variable-pole multiphase motor when the pole phase is switched in a specific implementation mode 1 (from a time-following perspective);

[0047] Figure 4 It is a diagram of an experimental platform of a variable-pole multiphase motor in a specific implementation mode 1;

[0048] Figure 5 It is a current experimental waveform diagram of the polar phase switching process from harmonic plane 1 to harmonic plane 3 under the sequential d-axis current distribution method proposed in the present invention in the specific implementation mode 1;

[0049] Figure 6 It is a current experimental waveform diagram of the polar phase switching process from harmonic plane 1 to harmonic plane 3 under the cross-type d-axis current distribution method proposed in the present invention in the specific implementation mode 1;

[0050] Figure 7 It is a waveform diagram of the motor output torque experiment in the pole phase switching process from harmonic plane 1 to harmonic plane 3 under the sequential d-axis current distribution method proposed in the present invention in the specific implementation mode 1;

[0051] Figure 8 It is a waveform diagram of the motor output torque experiment in the pole phase switching process from harmonic plane 1 to harmonic plane 3 under the cross d-axis current distribution method proposed in the present invention in the specific implementation mode 1;

[0052] Fig. 9 It is a waveform diagram of the motor stator copper loss power in the pole phase switching process from harmonic plane 1 to harmonic plane 3 under the current distribution method proposed in the present invention in the specific implementation mode 1; DETAILED DESCRIPTION

[0053] Specific implementation method 1: Combination Figures 1 to 9 The present embodiment is described. The optimal current distribution method of a variable-pole multiphase motor during pole phase switching described in the present embodiment comprises the following steps:

[0054] Step 1: Use the harmonic plane method to mathematically model the variable-pole multiphase motor;

[0055] Step 2, determining a d-axis current distribution method of the variable-pole multiphase motor in different harmonic planes when the pole phase is switched;

[0056] Step 3, determining a q-axis current distribution method of the variable-pole multiphase motor in different harmonic planes when the pole phase is switched;

[0057] The specific steps of the harmonic plane method used in step 1 to mathematically model the variable-pole multiphase motor are as follows:

[0058] Step 11, converting the current model of the variable-pole multiphase motor from the 123-coordinate system to the αβ-coordinate system, and then converting the current model of the variable-pole multiphase motor from the αβ-coordinate system to the dq-coordinate system;

[0059] Among them, the coordinate system conversion method used to convert the 123-coordinate system to the αβ-coordinate system is:

[0060]

[0061] ξ=n mw -mod(n mw ,2) (5);

[0062] in, is the state vector of the variable-pole multiphase motor in the 123-coordinate system, is the state vector of the variable-pole multiphase motor in the αβ-coordinate system, n mw is the minimum number of windings, C s is the coordinate system transformation incidence matrix, C s The transposed matrix, T 123→αβ0 is the transformation matrix of the variable-pole multiphase motor from the 123-coordinate system to the αβ-coordinate system, T αβ0→123 is the transformation matrix of the variable-pole multiphase motor from the αβ-coordinate system to the 123-coordinate system, δ is the spatial phase shift angle between the magnetic axes, π is the circumference of the circle, ξ is the harmonic spatial correlation parameter in the coordinate system conversion correlation matrix, and mod(*) is the remainder function.

[0063] On the basis of the above, the coordinate system conversion method used to convert the αβ-coordinate system to the dq-coordinate system is:

[0064]

[0065]

[0066] in, is the state vector of the variable-pole multiphase motor in the dq-coordinate system, T αβ0→dq0 is the transformation matrix of the variable-pole multiphase motor from the αβ-coordinate system to the dq-coordinate system, h is the harmonic plane, and f s is the stator angular frequency, ν h is the angular frequency multiple corresponding to the hth harmonic plane, is the angular offset corresponding to the hth harmonic plane.

[0067] Step 1 and 2: After coordinate transformation in step 1, the torque is expressed by the system state under the dq-axis as:

[0068]

[0069] Among them, τ e is the motor output torque, p nw is the minimum number of winding pole pairs, ψ R,h is the rotor flux in the hth harmonic plane, i q,h is the q-axis current in the hth harmonic plane.

[0070] In step 2, the method for determining the d-axis current distribution of the variable-pole multiphase motor in different harmonic planes when the pole phase is switched is as follows:

[0071] Figure 1Two different d-axis current distribution methods are given;

[0072] Figure 1 (a) is the sequential d-axis current distribution method. In the figure, i d,h＝[old] The d-axis current in the old phase configuration plane h = [old], i d,h＝[old] The d-axis current in the old phase configuration plane h = [new], T start is the starting time of the pole phase switching, T end is the termination time of the pole phase switching, It is the middle moment of the pole phase switching.

[0073] Figure 1 (b) is the cross-type d-axis current distribution method, which is the same as the sequential d-axis current distribution method. In the figure, i d,h＝[old] The d-axis current in the old phase configuration plane h = [old], i d,h＝[new] The d-axis current in the old phase configuration plane h = [new], T start is the starting time of the pole phase switching, T end It is the termination time of the pole phase switching.

[0074] The detailed implementation process of the sequential d-axis current distribution method is:

[0075] At the start time of the pole phase switching t = T start , the d-axis current i in the new polar configuration plane d,h＝[new] The slope should be selected so that the d-axis current in the new pole phase configuration plane can be at the middle moment of pole phase switching t = T mid The reference value of the d-axis current of the new pole phase configuration is reached at this t∈[T start ,T mid ] period, the d-axis current i in the old pole phase configuration plane d,h＝[old] Remain unchanged; at the middle moment of pole phase switching t = T mid , the d-axis current i in the old pole phase configuration plane d,h＝[old] The slope should be selected so that the d-axis current in the old pole-phase configuration plane can be reduced at the termination time t = T end Reach 0.

[0076] The detailed implementation process of the cross-type d-axis current distribution method is:

[0077] At the start time of the pole phase switching t = T start , the d-axis current i in the new polar configuration plane d,h＝[new] The slope should be selected so that the d-axis current in the new pole-phase configuration plane can be stopped at the end time of the pole-phase switching t = T endThe reference value of the d-axis current of the new pole phase configuration is reached. At the same time, at this t∈[T start ,T end ] period, the d-axis current i in the old pole phase configuration plane d,h＝[old] The slope should be selected so that the d-axis current in the old pole-phase configuration plane can be reduced at the termination time t = T end Reach 0.

[0078] The specific implementation of the q-axis current distribution method of the variable-pole multiphase motor in different harmonic planes when the pole phase is switched is as follows:

[0079] Step 31: Based on the expression of the torque system state under the dq-axis provided in step 13, taking the switching of two harmonic planes as an example, at this time, except for the torque provided by the two harmonic planes before and after the pole phase configuration switching during the switching process is 0, at this time, the expression of the torque that the motor can provide is:

[0080]

[0081] Among them, i q,h＝[old] The q-axis current in the old phase configuration plane h = [old], i q,h＝[new] The q-axis current in the new polar configuration plane h = [new], ψ R,h＝[old] is the rotor flux in the old pole phase configuration plane h = [old], ψ R,h＝[new] The rotor flux in the new pole phase configuration plane h = [new].

[0082] Step 32: In order to maintain the invariance of torque during the phase switching process, the output τ of formula (10) must be satisfied e =τ e,ref unchanged, where τ e,ref is the reference value of the output torque. Since the d-axis current in the harmonic plane of the new / old pole phase configuration is changed, this leads to the rotor flux ψ in the harmonic plane of the new / old pole phase configuration R,h＝[old] and ψ R,h＝[new] is variable, according to the two different d-axis current distribution method implementations provided in step 2, two clusters of rotationally variable straight lines can be determined, such as Figure 2 As shown. As long as the selection of q-axis current satisfies its new / old pole phase configuration, the current i in the harmonic plane q,h＝[old] and i q,h＝[new] As long as the rotation angle falls on the changing straight line at all times, the motor output torque can be kept constant.

[0083] Step 3: There are countless q-axis current distribution methods that can be obtained from step 2. In order to reduce the actual difficulty, the specific q-axis current distribution method is determined with the optimization goal of reducing the stator copper loss during the pole phase switching process. The expression of the stator copper loss during the pole phase switching process is:

[0084]

[0085] Among them, P cu,s is the stator copper loss during the pole-phase switching process, R s,h＝[old] The stator resistance in the old pole-phase configuration plane h = [old], R s,h＝[new] Configure the stator resistance in the plane h=[new] for the new pole phase.

[0086] Since the d-axis current distribution has been determined by step 2, the optimization objective expression is simplified to:

[0087]

[0088] Wherein, P is the copper loss expression to be optimized.

[0089] Step 34: Based on the optimization goal of reducing the stator copper loss during the pole phase switching process given in step 33, that is, formula (11'), the final form of the q-axis current distribution method of the variable pole multiphase motor in different harmonic planes during the pole phase switching is calculated as follows:

[0090]

[0091] in, is the vector form of the q-axis current reference value of different harmonic planes, The q-axis current reference value in the old phase configuration plane h = [old], The q-axis current reference value in the plane h=[new] is configured for the new pole phase.

[0092] The variation process of the q-axis current reference value under the sequential d-axis current distribution method obtained by formula (12) is: Figure 2 The curve in (a) is determined by the line connecting points A→B→C→D→E→F→G. The change process of the q-axis current reference value under the cross d-axis current distribution method obtained by formula (12) is: Figure 2 The curve in (b) is determined by the line connecting points A→B→C→D→E→F→G.

[0093] Figure 3 The variation process of the q-axis current reference value obtained by formula (12) with time as the horizontal axis is given, where Figure 3 (a) is the variation process of the q-axis current reference value under the sequential d-axis current distribution method obtained by formula (12), Figure 3 (b) is the variation process of the q-axis current reference value under the cross d-axis current distribution method obtained by formula (12).

[0094] The effectiveness of the present invention is illustrated by experimental results. The experimental platform of the present invention is as follows: Figure 4 shown.

[0095] Figure 5 is a current waveform diagram of the phase switching process from harmonic plane 1 to harmonic plane 3 under the sequential d-axis current distribution method proposed in the present invention, Figure 6 The figure is a current waveform diagram of the pole phase switching process from harmonic plane 1 to harmonic plane 3 under the cross-type d-axis current distribution method proposed in the present invention. The reference current of harmonic plane 1 is 1.5A, and the reference current of harmonic plane 3 is 3.9A. It can be seen from the figure that the proposed method can complete multiple pole phase switching tasks of variable pole motors according to theoretical derivation.

[0096] Figure 7 The output torque waveform of the motor under the sequential d-axis current distribution method proposed in the present invention is: Figure 8 The output torque waveform of the motor under the cross-type d-axis current distribution method proposed in the present invention, where τ shaft is the torque signal measured by the torque sensor. The output torque reference of the motor is 5N·m. It can be seen from the figure that both methods can keep the motor torque output at about 3N·m during the pole phase switching process. The lost torque is caused by motor friction. Comparing the two methods, the motor output torque maintenance under the sequential d-axis current distribution method proposed by the present invention is better than the motor output torque under the cross d-axis current distribution method proposed by the present invention.

[0097] Figure 8 This is a waveform diagram of the stator copper loss power of the motor under the current distribution method proposed in the present invention. It can be seen from the figure that, compared with the two methods, the stator copper loss of the motor under the sequential d-axis current distribution method proposed in the present invention is higher than the stator copper loss of the motor under the cross d-axis current distribution method proposed in the present invention.

[0098] Therefore, if the two current distribution methods proposed in the present invention are selected, it is necessary to comprehensively consider the torque maintenance requirements and loss requirements of the working conditions.

[0099] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims

1. An optimal current distribution method for a variable-pole multiphase motor during pole phase switching, characterized in that: The allocation method includes the following steps: Step 1: Use the harmonic plane method to mathematically model the variable-pole multiphase motor; Step 2, determining a d-axis current distribution method of the variable-pole multiphase motor in different harmonic planes when the pole phase is switched; Step 3: Determine the q-axis current distribution method of the variable-pole multiphase motor in different harmonic planes when the pole phase is switched.

2. The optimal current distribution method of a variable pole multiphase motor during pole phase switching according to claim 1, characterized in that: The step 1 specifically includes the following steps: Step 11, converting the current model of each slot of the variable-pole multiphase motor from the 123-coordinate system to the αβ-coordinate system, and then to the dq-coordinate system; Step 1 and 2, give the system state expression of torque under dq-axis.

3. The optimal current distribution method for a variable pole multiphase motor during pole phase switching according to claim 2, characterized in that: The current model of the variable-pole multiphase motor in step 1 is converted from the 123-coordinate system to the αβ-coordinate system by using equations (1) to (5), and the current model of the variable-pole multiphase motor in step 1 is converted from the αβ-coordinate system to the dq-coordinate system by using equations (6) to (8): ξ=n mw -mod(n mw ,2) (5); in, is the state vector of the variable-pole multiphase motor in the 123-coordinate system, is the state vector of the variable-pole multiphase motor in the αβ-coordinate system, n mw is the minimum number of windings, C s is the coordinate system transformation incidence matrix, C s The transposed matrix, T 123→αβ0 is the transformation matrix of the variable-pole multiphase motor from the 123-coordinate system to the αβ-coordinate system, T αβ0→123 is the transformation matrix of the variable-pole multiphase motor from the αβ-coordinate system to the 123-coordinate system, δ is the spatial phase shift angle between the magnetic axes, π is the circumference, ξ is the harmonic spatial correlation parameter in the coordinate system conversion correlation matrix, mod(*) is the remainder function, is the state vector of the variable-pole multiphase motor in the dq-coordinate system, T αβ0→dq0 is the transformation matrix of the variable-pole multiphase motor from the αβ-coordinate system to the dq-coordinate system, h is the harmonic plane, and f s is the stator angular frequency, ν h is the angular frequency multiple corresponding to the hth harmonic plane, is the angular offset corresponding to the hth harmonic plane.

4. The optimal current distribution method for a variable-pole multiphase motor during pole phase switching according to claim 2, characterized in that: The torque system state under the dq-axis in steps 1 and 2 is expressed as: Among them, τ e is the motor output torque, p nw is the minimum number of winding pole pairs, ψ R,h is the rotor flux in the hth harmonic plane, i q,h is the q-axis current in the hth harmonic plane.

5. The optimal current distribution method for a variable-pole multiphase motor during pole phase switching according to claim 1, characterized in that: In the step 2, determining that the d-axis current distribution method of the variable-pole multiphase motor at different harmonic planes when the pole phase is switched is a sequential d-axis current distribution method or a cross d-axis current distribution method; The sequential d-axis current distribution method is as follows: starting from the start time T of the pole phase switching start To the middle time T mid , the d-axis current i in the new polar configuration plane d,h＝[new] It increases linearly from 0 to the reference value of the d-axis current of the new polar configuration at this t∈[T start ,T mid ] period, the d-axis current i in the old pole phase configuration plane d,h＝[old] Remain unchanged; the intermediate moment T mid After that, the d-axis current i in the new polar configuration plane d,h＝[new] Remains unchanged, the d-axis current i in the old pole phase configuration plane d,h＝[old] It starts to decrease linearly and at the end time T end The d-axis current i in the old pole phase configuration plane d,h＝[old] is reduced to 0; among them, The cross-type d-axis current distribution method is: from the starting time T of the pole phase switching start Until the end time T end , the d-axis current i in the new polar configuration plane d,h＝[new] It increases linearly from 0 to the reference value of the d-axis current of the new pole-phase configuration. The d-axis current i in the old pole-phase configuration plane d,h＝[old] Decreases linearly until the termination time T end Reduced to 0.

6. The optimal current distribution method for a variable-pole multiphase motor during pole phase switching according to claim 1, characterized in that: The specific steps of determining the q-axis current distribution method of the variable-pole multiphase motor in different harmonic planes when the pole phase is switched in step 3 are: Step 31: Based on the expression of the system state of the torque under the dq-axis, taking the switching of two harmonic planes as an example, establish an expression for the torque that the motor can provide; Step 32, providing a selection range of q-axis current distribution that satisfies the constant torque; Step 33, determining the optimization goal of minimizing stator copper loss during the switching process; Step 3 and 4, provide a q-axis current distribution method for a variable-pole multiphase motor in different harmonic planes when the pole phase is switched.

7. The optimal current distribution method for a variable-pole multiphase motor during pole phase switching according to claim 6, characterized in that: The expression for the torque that the motor can provide in step 31 is: Among them, n mw is the minimum number of windings, p nw is the minimum number of winding pole pairs, i q,h＝[old] The q-axis current in the old phase configuration plane h = [old], i q,h＝[new] The q-axis current in the new polar configuration plane h = [new], ψ R,h＝[old] is the rotor flux in the old pole phase configuration plane h = [old], ψ R,h＝[new] The rotor flux in the new pole phase configuration plane h = [new].

8. The optimal current distribution method for a variable-pole multiphase motor during pole phase switching according to claim 7, characterized in that: The q-axis current distribution selection range in step 32 satisfies the following conditions: The current i in the harmonic plane of the new pole-phase configuration q,h＝[old] and the current i in the harmonic plane of the old pole-phase configuration q,h＝[old] The moment falls on the straight line of the two clusters of rotation changes determined by the d-axis current distribution method described in step 2, so as to satisfy the output τ of equation (10) e =τ e,ref unchanged, where τ e,ref is the reference value of output torque.

9. The optimal current distribution method for a variable-pole multiphase motor during pole phase switching according to claim 6, characterized in that: The optimization objective expression for minimizing stator copper loss in step 33 is: Where P is the copper loss expression to be optimized, R s,h＝[old] The stator resistance in the old pole-phase configuration plane h = [old], R s,h＝[new] The stator resistance in the new pole phase configuration plane h = [new], i q,h＝[old] The q-axis current in the old phase configuration plane h = [old], i q,h＝[new] The q-axis current in the new polar configuration plane h = [new], ψ R,h＝[old] is the rotor flux in the old pole phase configuration plane h = [old], ψ R,h＝[new] is the rotor flux in the new pole phase configuration plane h = [new], τ e The motor can provide torque, τ e,ref is the reference value of output torque.

10. The optimal current distribution method of a variable pole multiphase motor during pole phase switching according to claim 9, characterized in that: The final form of the q-axis current distribution method of the variable-pole multiphase motor in steps three and four at different harmonic planes when the pole phase is switched is calculated according to formula (11'): in, is the vector form of the q-axis current reference value of different harmonic planes, The q-axis current reference value in the old phase configuration plane h = [old], The q-axis current reference value in the plane h=[new] is configured for the new pole phase.

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