Coupled excitation motor system based on superposition current mechanism for flywheel energy storage

Abstract

The present invention relates to a coupled excitation motor system based on a superposition current mechanism for flywheel energy storage, and belongs to the technical field of hybrid excitation motor system structure. The motor system comprises a motor body and a power converter topology, wherein the motor body comprises a stator, a rotor, a unipolar double-layer ring-type permanent magnet structure and an integrated composite winding, the stator is wound with the integrated composite winding, and the rotor is provided with a unipolar double-layer ring-type permanent magnet structure; the system is designed from the perspective of the motor body and the power converter topology, and the traditional excitation winding and the armature winding are combined into one, which greatly suppresses the motor torque pulsation, improves the power / torque density, optimizes the magnetic adjustment capability, reduces the amount of permanent magnets, and reduces the risk of irreversible demagnetization of permanent magnets, and can effectively improve the wide speed range operation reliability and stability of the motor system for flywheel energy storage.

Description

Technical Field

[0001] The present invention specifically relates to a coupled excitation motor system based on a superposition current mechanism for flywheel energy storage, and belongs to the technical field of hybrid excitation motor system structure. Background Art

[0002] With the popularization and widespread application of new energy technologies such as flywheel energy storage, as an important part of it, motor system design and optimization have received widespread attention in related fields at home and abroad. For the motor system, its design mainly involves motor structure design, power converter topology design, etc. For motor structure design, it mainly focuses on improving motor power / torque density, efficiency and NVH (Noise, Vibration, Harshness) performance by using rare earth permanent magnets to achieve strong market competitiveness. At this stage, a series of new permanent magnet motor structures have emerged, such as synchronous reluctance permanent magnet motor, flux reversal motor and flux switching motor. It is worth mentioning that in order to further reduce the amount of permanent magnets in the motor and widen the operating speed range, domestic and foreign universities and research institutions tend to combine rotor permanent magnet motors with hybrid excitation motor structures. However, due to the coupling relationship between the electric excitation magnetic circuit and the permanent magnet magnetic circuit, it is difficult for the motor system to avoid brush and slip ring structures. For the power converter topology design, its research hotspots are mainly focused on improving the reliability and fault tolerance of the motor system by reasonably designing the topology structure. At present, the more mature structures include diode midpoint clamp type, flying capacitor type and cascade H-bridge type, and they are gradually applied in the industrial field. However, there is still a lot of research content in the power converter topology at this stage, such as the rational use of zero-axis current and the improvement of motor control flexibility. In addition, in order to achieve synchronous control of multiple windings in the motor structure, the power converter part of the motor system is usually large in size, resulting in a large overall heat generation of the system. The above defects will limit the application of motor systems in areas that have space requirements, such as electric vehicles, flywheel energy storage, robot servo joints, etc.

[0003] Based on the application scenarios of flywheel energy storage systems, it can be seen that hybrid excitation motors currently have the following problems:

[0004] (1) There are contradictions in the stator and rotor structure designs. In order to achieve the hybrid excitation effect, the current mainstream hybrid excitation motor is usually a series magnetic circuit structure. For the stator permanent magnet series magnetic circuit hybrid excitation motor, its excitation winding, armature winding and permanent magnet are all located in the stator, which will lead to an overly complex stator structure, low space utilization and increased heat generation. For the rotor permanent magnet series magnetic circuit hybrid excitation motor, since the permanent magnet is located on the rotor side, the excitation winding must also be set on the rotor side, so brushes and slip rings cannot be avoided. Therefore, the current development direction of the hybrid excitation motor system is to achieve brushless while reasonably allocating permanent magnets and excitation windings.

[0005] (2) There is a contradiction between the amount of permanent magnets used and the power density design. Generally, the power density of a hybrid excitation motor is composed of the motor magnetic load and the electric load. Therefore, in order to ensure high power / high torque density, the amount of permanent magnets used in the motor is relatively large. However, this will lead to an increase in the amount of permanent magnets used in the motor. Furthermore, the larger the amount of permanent magnets used, the greater the magnetic resistance in the magnetic circuit, the more electromagnetic force required for electric excitation, and the higher the copper loss of the motor, which increases the difficulty of heat dissipation in the motor.

[0006] (3) The motor body design and the power converter topology design are less correlated. Generally speaking, the motor power converter topology usually adopts a full-bridge inverter / rectifier structure with the same number of phases as the motor body winding. In addition, in order to reduce the power usage cost, a star connection scheme is adopted at the current output end. However, this will make it impossible to reasonably utilize the high-order harmonic components in the motor current, resulting in increased copper losses in the motor system and increased motor torque pulsation. Therefore, it is necessary to increase the overall utilization capacity of the motor system for harmonic currents through reasonable and coordinated design, so as to improve the overall performance and power density of the motor system.

[0007] (4) Functional limitations of motor windings. For conventional hybrid excitation motor systems, the windings can be mainly divided into two categories: excitation windings and armature windings according to their performance. The two types of windings have independent functions and are usually not interchangeable. Therefore, it is known that hybrid excitation motor systems usually require the addition of multiple sets of different types of motor windings to increase the flexibility of the motor's operation. In other words, it is necessary to increase the number of coil types and turns within the limited stator slot space, but this will increase the difficulty of motor wire embedding and processing costs. Summary of the invention

[0008] In view of the technical problems existing in the prior art, the present invention proposes a coupled excitation motor system based on a superposition current mechanism for flywheel energy storage. The motor system described in the technical solution is of a comprehensive design and has a compact structure. The structural features of the motor system proposed in the present invention are as follows: brushless hybrid excitation, highly integrated and multifunctional integrated composite winding, and a rare earth-free unipolar permanent magnet structure. The advantages of the system are: high reliability and high robustness, high power / torque density, high efficiency, wide speed range adjustment range, low permanent magnet usage, strong fault tolerance, and simple winding structure. Therefore, the system described in the present invention belongs to a hybrid excitation motor system with rich power converter topology functions and high reliability.

[0009] In order to achieve the above-mentioned purpose, the coupled excitation motor system based on superposition current mechanism for flywheel energy storage described in the technical solution of the present invention is characterized in that the motor system includes a motor body and a power converter topology,

[0010] The motor body includes a stator, a rotor, a unipolar double-layer ring-type permanent magnet structure and an integrated composite winding. The stator is wound with an integrated composite winding, and the rotor is provided with a unipolar double-layer ring-type permanent magnet structure.

[0011] Among them, the power converter topology includes two sets of five-phase full-bridge structures, both of which are star-connected, and the two sets of windings are short-circuited. Therefore, from a structural point of view, the power converter structure can be considered to be a ten-phase full-bridge structure with a star connection scheme, and can be divided into ten groups according to the nature of the superimposed current.

[0012] As an improvement of the present invention, the stator includes excitation teeth and armature teeth, and an integrated composite winding is wound on the stator teeth. The armature teeth are longer than the excitation teeth, and there are pole shoes on the armature teeth, but no pole shoes on the excitation teeth. The number of excitation teeth is equal to the number of armature teeth, and then a permanent magnet brushless hybrid excitation effect of the rotor can be achieved through a single set of windings.

[0013] As an improvement of the present invention, the stator is an integrated structure, not segmented in the axial direction, and in order to fix the winding, the stator part is designed with fan-shaped slot wedges, and the slot wedge structure is made of epoxy resin material, which can then optimize the stator structure and achieve effective fixation of the winding when the pole shoe structure design is limited.

[0014] As an improvement of the present invention, a set of integrated composite windings based on the superposition current mechanism is wound in the motor body, and has two excitation modes, namely DC excitation and AC excitation, and a DC bias sub-type structure similar to the integer slot distribution winding structure is adopted based on the chain structure. It is worth emphasizing that in order to suppress the even-order air gap magnetic field harmonic components generated by the unipolar permanent magnet structure in the air gap, the winding adopts a distribution form with symmetrical complementary capabilities, which is characterized by making its winding function odd symmetrical, thereby achieving the purpose of filtering.

[0015] As an improvement of the present invention, the motor body rotor structure of the system adopts a new type of unipolar double-layer ring permanent magnet structure to improve the utilization rate of permanent magnets and space utilization rate. From a topological perspective, the unipolar double-layer ring permanent magnet structure is divided into two layers, the first layer is a V-shaped permanent magnet pole, and the second layer is a U-shaped permanent magnet pole, wherein the V-shaped permanent magnet pole has two rectangular permanent magnets, the U-shaped permanent magnet pole has three rectangular permanent magnets, and all rectangular permanent magnets have the same excitation direction. In the V-shaped permanent magnet pole structure, the two rectangular permanent magnets are of the same size. In the U-shaped permanent magnet pole structure, the size of the middle rectangular permanent magnet is larger than the size of the rectangular permanent magnets on both sides, and the sizes of the rectangular permanent magnets on both sides are the same. In addition, the size of each rectangular permanent magnet in the V-shaped permanent magnet pole structure is smaller than the size of each rectangular permanent magnet in the U-shaped permanent magnet pole structure. In addition, the motor permanent magnet pole adopts a unipolar structure, that is, the polarity of all permanent magnet poles remains the same, which can optimize the amount of permanent magnets and then achieve a brushless hybrid excitation effect.

[0016] As an improvement of the present invention, the magnetomotive force generated by the unipolar double-layer ring permanent magnet structure is coupled with the DC excitation and AC excitation in the integrated composite winding, thereby forming a hybrid excitation effect of multiple excitation sources with a relatively simple structure; there are three types of magnetic circuits in the motor body, the first type is the magnetic circuit generated by the permanent magnet excitation source, the second type is the magnetic circuit generated by the DC current in the integrated composite winding, and the third type is the magnetic circuit generated by the AC current in the integrated composite winding, wherein the first type and the third type of magnetic circuits are rotating magnetic circuits, and the second type of magnetic circuit is a stationary magnetic circuit. The above structure can effectively excavate and construct magnetic circuits and reasonably utilize the stator and rotor space.

[0017] As an improvement of the present invention, in the motor body, the number of permanent magnet poles of the motor The number of motor rotor pole pairs Equal, that is , Number of motor stator slots Need to be or A positive integer multiple of Indicates the number of motor phases and permanent magnet poles Number of motor stator slots The relationship between , Represents a positive integer.

[0018] As an improvement of the present invention, in the motor body, the number of pole pairs of the superimposed current magnetomotive force AC excitation part is Not equal to the number of motor rotor pole pairs , superimposed current magnetomotive force DC excitation part pole pair number is equal to , number of coils per phase Equal to the total number of motor coils of , Indicates the number of sub-type coils in each phase, the number of coils in each phase In addition, according to the properties of the superimposed current, each phase winding must be divided into several sub-type coils, and the number of sub-type coils in each phase is Equal to the number of coils per phase , but the above two types of coils are not coils of the same nature.

[0019] As an improvement of the present invention, in the motor body, the yoke of the rotor is provided with three positioning grooves, and the positioning grooves are in a triangular symmetrical geometric relationship with each other, and three positioning protrusions are provided in the concentric axis. The positioning protrusions and the positioning grooves are engaged with each other through gap assembly, and the two ends of the positioning rod are fixed with two aluminum flanges.

[0020] As an improvement of the present invention, in the power converter topology, its structure adopts a star connection Phase winding, applied to For a 2-phase AC motor. For any phase in the phase, half of the coil is in the current superposition mode of forward DC and AC, and the other half of the coil is in the current superposition mode of reverse DC and AC, where the DC is composed of the DC bias current (zero-axis current DC component) in the zero-axis current in the power converter topology.

[0021] In the system power converter topology, one end of the winding is connected to the DC side of the busbar, and the other end is short-circuited. The short-circuited part allows the zero-axis current to pass through. The zero-axis current here will include two types, the first type is the DC component of the zero-axis current, and the second type is the AC component of the zero-axis current, and the frequency of the AC component must meet the fundamental frequency. times. For the DC part of the zero-axis current, it can be used as the DC excitation in the motor body structure integrated composite winding to adjust the air gap magnetic field. For the AC part of the zero-axis current, it can be used as the motor body structure integrated composite winding to directly generate electromagnetic torque and realize position sensorless control.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The design integrates the characteristics of the motor structure and the power converter topology. Through the linkage design, the AC excitation current and DC armature current in the hybrid excitation motor system are superimposed and combined, so that they coexist in the power converter topology and a single set of motor windings. This will effectively simplify the overall structure of the converter and windings, and improve the overall reliability, stability and robustness of the system.

[0024] (2) The system power converter topology utilization rate is higher. For the system topology, through reasonable topology design, Phase star connection structure, and with The combination of the phase motor body can effectively retain the zero-axis current part of the motor system. Among them, the DC component of the zero-axis current can adjust the air gap magnetic field in the motor body structure, and the AC component of the zero-axis current can improve the overall torque output capacity of the motor (high-order harmonic injection method) and realize position sensorless control, etc.

[0025] (3) The system motor structure is simpler and more compact. The compactness of the motor structure is reflected in two aspects. On the one hand, the motor realizes brushless hybrid excitation based on the rotor permanent magnet structure through the alternating distribution structure of armature teeth and excitation teeth. On the other hand, based on the chain structure, through the reasonable integer slot distribution winding structure design, the excitation winding and the armature winding have the same arrangement in the motor, so that the two sets of windings can be integrated into one set of windings, thereby simplifying the complexity of the motor winding structure.

[0026] (4) Stronger winding filtering capability. In order to effectively filter out the even-order interfering harmonic components in the air gap magnetic field, the motor winding adopts a symmetrical winding function structure. Compared with the schemes such as optimizing the tooth structure, the motor axial structure and the rotor structure, the above-mentioned new winding structure can effectively reduce the difficulty of optimization. Only by changing the wire embedding method, the purpose of optimizing the magnetic flux waveform can be achieved. It is worth emphasizing that the core mechanism of the winding magnetic flux optimization of this scheme is not to directly filter out the harmonic magnetic field in the air gap, but to achieve the effect of high-efficiency filtering by suppressing the coil's induction ability to various harmonic magnetic fields (reducing the harmonic winding coefficient).

[0027] (5) It has more flexible control and fault tolerance. Compared with traditional permanent magnet motors, the new motor has AC excitation source, DC excitation source and permanent magnet excitation source, so it has more excitation forms and can still have a certain torque output capacity when the motor fails, so that the motor has higher fault tolerance. In addition, because the motor has two excitation sources, it can more flexibly control the air gap magnetic field of the motor, thereby widening the operating speed range of the motor and improving the performance of the motor under low-speed high-torque, high-speed weak magnetic and other working conditions, thereby increasing the application capability and performance compatibility of the motor in different occasions.

[0028] (6) The risk of irreversible demagnetization of the motor system is lower. For the motor system, due to the use of a unipolar structure, the permanent magnet excitation source is in a rotating state, while the DC excitation source is in a stationary state. The two magnetic fields form a hybrid excitation effect through a special modulated coupling relationship. The above coupling mechanism will effectively alleviate the irreversible demagnetization phenomenon caused by the reverse direction of the DC excitation source and the permanent magnet excitation source.

[0029] (7) The motor system uses less permanent magnets and has higher power. Since the motor body structure adopts a unipolar permanent magnet structure, the amount of permanent magnets used can be greatly reduced in theory. In addition, since some permanent magnets are removed from the permanent magnet excitation magnetic circuit, the total magnetic resistance will be significantly reduced, which will significantly improve the utilization rate of permanent magnets.

[0030] (8) The motor system has a stronger magnetic field gathering ability. Since the motor body structure adopts a unipolar double-layer ring permanent magnet structure, the inner space of the U-shaped permanent magnet pole is effectively utilized, thereby further enhancing the magnetic field gathering ability of the traditional embedded permanent magnet structure. In a limited space, it can effectively improve the utilization rate of the motor permanent magnet and suppress the magnetic field leakage phenomenon of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the structure of the motor body of the present invention.

[0032] Figure 2 This is a schematic diagram of the topological structure of the power converter of the present invention.

[0033] Figure 3 This is a schematic diagram of an integrated composite winding.

[0034] Figure 4 It is a schematic diagram of the structure of a unipolar double-layer ring permanent magnet.

[0035] Figure 5 This is a schematic diagram of the complementary capability of the integrated composite winding of the motor system of the present invention.

[0036] Figure 6 This is a schematic diagram of the output torque of the motor system in the hybrid excitation working state of the present invention.

[0037] Figure 7 is a schematic diagram of the cogging torque waveform of the motor system of the present invention,

[0038] Figure 8 Schematic diagram of actual injected current,

[0039] Fig. 9 Schematic diagram of the DC part of the actual injected current,

[0040] Fig.10 Schematic diagram of the AC part of the actual injected current.

[0041] In the figure: wherein: 1. stator, 2. armature teeth, 3. excitation teeth, 4. rotor, 5. V-shaped permanent magnet pole, 6. U-shaped permanent magnet pole, 7. unipolar double-layer ring permanent magnet structure, 8. positioning groove, 9. star connection point, 10. integrated composite winding, 11. first DC power supply, 12. second DC power supply, 13. insulated gate bipolar transistor, 14. A-phase type 1 winding, 15. A-phase type 2 winding, 16. B-phase type 1 winding, 17. B-phase type 2 winding, 18. C-phase type 1 winding, 19. C-phase type 2 winding, 20. D-phase type 1 winding, 21. D-phase type 2 winding, 22. E-phase type 1 winding, 23. E-phase type 2 winding, 24. winding function amplitude, 25. DC current + AC current, 26. DC current, 27. AC current. DETAILED DESCRIPTION

[0042] In order to deepen the understanding of the present invention, the present embodiment is described in detail below with reference to the accompanying drawings.

[0043] Example 1: See Figure 1 , Figure 2 , which is a schematic diagram of the motor body structure part and the power converter topology part of a coupled excitation motor system based on the superposition current mechanism proposed by the present invention.

[0044] First, for the motor body structure of the system, the stator 1 is located outside the rotor 4, and the stator teeth inside the stator yoke are divided into two different types, armature teeth 2 and excitation teeth 3. The distribution structure of the armature teeth 2 and the excitation teeth 3 is allocated according to the magnetic circuit path. It is worth emphasizing that the main feature of the above two types of stator teeth is the length of the stator tooth body, and it is not required that the tooth width of the excitation tooth 3 is smaller than the armature tooth 2. An integrated composite winding 10 is wound on the stator tooth structure, and the arrangement of the winding structure is as follows: Figure 3As shown. Taking phase A as an example, according to the difference in the direction of current superposition, it can be divided into two subcategories: A1+→A1- and A2-→A2+ (A-phase type 1 winding 14, A-phase type 2 winding 15). It is not difficult to find that the combination of the DC component current and the AC component current of the above two types of A-phase subcategories is different. The specific difference is reflected in the relationship between the direction of the DC current and the direction of the positive half-cycle of the fundamental component of the AC current. The direction of the DC current component of the A1+→A1- subcategory is the same as the direction described in the positive half-cycle of the fundamental component of the AC current, while the direction of the DC current component of the A2-→A2+ subcategory is opposite to the direction described in the positive half-cycle of the fundamental component of the AC current. It should be emphasized that all the above excitations are generated by the same set of windings, which is different from the way conventional hybrid excitation motors are excited. In addition, in order to eliminate the electromagnetic torque pulsation and cogging torque caused by the even-order harmonic magnetic field in the air gap, the motor body structure adopts a symmetrical winding function (odd function) structure, so each phase winding will be composed of two groups of sub-coils, and the two groups of coils are symmetrical structures. In addition to being able to effectively filter out even-order harmonic magnetic fields, the above-mentioned winding structure can also improve the fault-tolerant operation capability of the motor through two groups of coils. A unipolar double-layer ring-type permanent magnet structure 7 is provided in the rotor 4 of the motor body structure, that is, the polarity of all permanent magnet poles remains consistent. For each permanent magnet pole, the side close to the stator 1 is a V-shaped permanent magnet pole 5 structure, and the side close to the center of the rotor is a U-shaped permanent magnet pole 6 structure. Among them, the size of each permanent magnet in the V-shaped permanent magnet pole 5 structure is smaller than the size of each permanent magnet in the U-shaped permanent magnet pole 6 structure. It is worth emphasizing that since the excitation direction of the unipolar double-layer ring-type permanent magnet structure 7 remains the same, its excitation circuit will use the iron core between two adjacent permanent magnet poles as a channel.

[0045] Secondly, for the power converter topology part of the system, each phase converter is connected to the first DC power supply 11 and the second DC power supply 12 respectively, each phase motor winding subclass is controlled by two insulated gate bipolar transistors 13, and the other end of each winding is short-circuited to form a star connection point 9. The difference between this connection structure and the conventional star connection structure is that it does not short-circuit each phase winding as a whole, but distinguishes each phase winding according to the difference in its subclass properties before short-circuiting, so that the zero axis current can be effectively retained, which provides a prerequisite for combining the excitation winding and the armature winding into one on the motor body side.

[0046] Figure 3 Schematic diagram of an integrated composite winding 10. As can be seen from the figure, the new winding is designed based on integer slot distributed winding. In terms of space, the number of pole pairs of the AC excitation part of the winding is Usually equal to ( is the number of rotor pole pairs, is the number of pole pairs of the DC excitation part of the winding). Each phase winding is divided into two subcategories, namely two sub-windings. The two sub-windings are connected at both ends, and the other two ends are directly connected to the power converter topology port to form a closed loop. It is worth noting that according to the superposition characteristics of the current, all phases have two types of sub-windings. It is the complementary structure between the two types of sub-windings that can construct a DC bias current for excitation of the power machine. In addition, the DC part of the superimposed current can generate a static electric excitation magnetic field, which can be modulated into a rotating excitation magnetic field through the iron core part of the rotor, thereby keeping synchronization with the rotor permanent magnet excitation magnetic field and the armature magnetic field, forming a new coupling mechanism.

[0047] Figure 4 It is a schematic diagram of a unipolar double-layer ring permanent magnet structure 7. Unlike the conventional embedded permanent magnet motor structure, this motor adopts both V-type and U-type permanent magnet structures, which can further improve the utilization rate of the rotor space. For the permanent magnet excitation source, its outer side is a U-type permanent magnet pole 6 structure (close to the center of the rotor), so there is a lot of space inside. The present invention utilizes the internal space of the U-type permanent magnet pole 6 structure and designs a V-type permanent magnet pole 5 structure. In addition, the excitation directions of the two types of permanent magnet structures are consistent. It is worth noting that all permanent magnet poles on the rotor maintain unipolarity, so all magnetic circuits will form a loop through the iron core between two adjacent permanent magnet poles. In addition, compared with the U-type permanent magnet pole 6 structure, the cross-sectional area of ​​the V-type permanent magnet pole 5 structure is smaller, so the rotor needs to be divided into two sections in the axial direction during processing. Accordingly, due to the use of a permanent magnet segmented structure, the axial length of each permanent magnet rectangular permanent magnet is significantly reduced, which will effectively solve the danger of permanent magnets being too long and easy to break and permanent magnet loss.

[0048] Figure 5 A schematic diagram of the complementary capability of the novel motor windings of the present invention. First, the winding function expression diagram can be drawn according to the motor winding structure, that is, Figure 5 As shown. Further analysis of the schematic structure shows that the function is an odd function, symmetrical based on the center point. By Fourier decomposition of the above function, it can be obtained that the function is composed of the superposition of odd-order harmonic component functions, so there is no even-order harmonic function. Since there is no even-order harmonic component in the winding function, the even-order harmonic magnetic field in the air gap will not be induced by the winding. In other words, the above motor winding structure has the ability to filter even-order harmonic magnetic fields.

[0049] Figure 6The hybrid excitation capability of the novel motor system described in the present invention is discussed, and the electromagnetic torque output capability of the motor under different DC bias current conditions is analyzed by finite element calculation method. As can be seen from the figure, the torque of the motor increases when the DC current direction is positive, and decreases when the DC current direction is negative, thereby increasing the torque gain capability of the motor in the low-speed area and the speed expansion capability in the high-speed area. In addition, the torque pulsation under the conditions of magnetization, weak magnetic field and no excitation is 2.2%, 0.9% and 2.6% respectively.

[0050] Figure 7 The schematic diagram of the cogging torque waveform of the motor system of the present invention is shown in the figure. As can be seen from the figure, the cogging torque of the motor system is only 47.6 mNm. In addition, it is worth noting that the above cogging torque cycle will satisfy the following equation:

[0051] (1),

[0052] Among them, LCM means the least common multiple, Indicates the number of permanent magnet poles of the motor, It represents the number of stator teeth, which is the sum of the number of field teeth and the number of armature teeth. As can be seen from the above formula, this formula is different from the traditional cogging torque expression.

[0053] Figure 8 — Fig.10 The figure is a schematic diagram of the superimposed current effect of the power converter topology of the motor system described in the present invention. First, it can be seen from the figure that the superimposed current is composed of a DC current and an AC current, and the above current is generated by the power converter topology. Secondly, the DC current will regulate the air gap magnetic field strength based on the field modulation principle, and the AC current will couple with the excitation magnetic field by generating a rotating armature magnetic field, thereby generating an effective output torque in the air gap. It is worth noting that for the new power converter topology described in the present invention, its characteristic is that it can not only pass DC current, but also pass harmonic currents with frequencies that are positive integer multiples of the number of phases, that is, high-order zero-axis currents (harmonic components). Therefore, through this power converter structure, the zero-axis current can be further effectively utilized to increase the power density and torque output capacity of the motor.

[0054] Finally, the overall design of the new motor system is described:

[0055] First, since the present invention uses an unequal tooth structure (excitation teeth and armature teeth), a new magnetic field coupling mechanism is realized. Therefore, the DC excitation source on the stator side needs to use one excitation tooth and one armature tooth at the same time to construct a complete magnetic circuit. Under the condition of Therefore, the number of pole pairs of the superimposed current magnetomotive force AC excitation part is The number of pole pairs of the DC excitation part of the superimposed current magnetomotive force must be met Number of rotor pole pairs In addition, since it is known that the number of pole pairs of the superimposed current magnetomotive force AC excitation part of the present invention is is equal to 1, so it can be known that the number of rotor pole pairs of the motor of the present invention is Need to be set to , which is equal to 9 or 11.

[0056] Secondly, according to the structural characteristics of the motor system, it can be seen that for the same-phase winding, the above winding can be divided into two subcategories according to its filtering and DC bias current type. However, the subcategories are classified differently. First, in terms of filtering, the winding will be classified based on its characteristics when it is used as an armature winding. Since all slots use a single-layer winding structure, and the current direction of the adjacent slot conductors of the same-phase winding must be consistent, it can be seen that adjacent conductors of the same phase belong to the same subcategory, and non-adjacent conductors belong to different subcategories, such as Figure 3 As shown. It is worth emphasizing that the current direction here refers to the flow direction of the AC current fundamental component during the positive half cycle. In terms of DC bias current, the winding will be classified based on its characteristics when it is used as an excitation winding. equal , will cause the DC current in the adjacent slot conductors to have opposite directions, so it can be seen that the adjacent slot conductors with the same phase are not of the same subtype, such as Figure 3 Therefore, according to the above analysis, it can be seen that the two coils in the same phase have different inflow and outflow directions of the total superimposed current due to the different conductor sub-type properties. Taking phase A as an example, they are A1+→A1- and A2-→A2+ respectively.

[0057] Finally, according to the structural characteristics of the power converter topology, taking the five-phase structure described in the present invention as an example, it can be known that for the motor system, although its armature winding is a five-phase structure, for the power converter topology, due to the different superimposed current flows of different coils in the same-phase winding, its properties will be different, so it can be regarded as a ten-phase full-bridge star connection topology. Based on the characteristics of the star connection topology, a path can be provided for all DC currents, solving the problem that the traditional power converter topology cannot inject zero-axis current. In addition, it is worth emphasizing that since the motor system described in the present invention has a sub-class design in terms of the number of phases, compared with the conventional multi-phase motor system, the five-phase motor system described in the present invention has stronger fault tolerance and fault operation capability, which will greatly improve the stability of the motor under long-term operation.

[0058] Therefore, the motor system described in the present invention has been comprehensively designed from aspects such as the power converter, the motor body and the winding structure, which helps to improve the overall functional utilization capability of the motor system, which will greatly improve the electromagnetic performance and reliability of the motor system in the flywheel energy storage.

[0059] The above description is only the structural principle and corresponding features of the motor system of the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention. It should be noted that the above embodiments are not used to limit the protection scope of the present invention, and the equivalent changes or substitutions made on the basis of the above technical solutions fall within the scope of protection of the claims of the present invention.

Claims

1. A coupled excitation motor system based on superposition current mechanism for flywheel energy storage, characterized in that: The motor system includes a motor body and a power converter topology, The motor body comprises a stator (1), a rotor (4), a unipolar double-layer ring-type permanent magnet structure (7) and an integrated composite winding (10); the stator (1) is wound with the integrated composite winding (10), and the rotor (4) is provided with a unipolar double-layer ring-type permanent magnet structure (7); The power converter topology includes two sets of five-phase full-bridge structures, both of which are star-connected, and the two windings are short-circuited; The stator (1) comprises an excitation tooth (3) and an armature tooth (2); an integrated composite winding (10) is wound on the stator tooth; the armature tooth (2) has a longer tooth body than the excitation tooth (3); the armature tooth (2) has a pole shoe, the excitation tooth (3) has no pole shoe, and the number of teeth of the excitation tooth (3) is equal to the number of teeth of the armature tooth (2); The integrated composite winding (10) has two excitation modes, namely, direct current excitation and alternating current excitation. The unipolar double-layer ring-type permanent magnet structure (7) is divided into two layers, the first layer is a V-shaped permanent magnet pole (5), and the second layer is a U-shaped permanent magnet pole (6), wherein the V-shaped permanent magnet pole (5) has two rectangular permanent magnets, and the U-shaped permanent magnet pole (6) has three rectangular permanent magnets, and the excitation directions of all the rectangular permanent magnets are consistent; In the motor body, the yoke of the rotor (4) is provided with three positioning grooves (8), each positioning groove (8) is in a triangular geometric relationship, and three positioning protrusions are arranged in the concentric shaft, the positioning protrusions and the positioning grooves are engaged with each other through gap assembly, and the two ends of the positioning rod are fixed with two aluminum flanges.

2. The coupled excitation motor system based on superposition current mechanism for flywheel energy storage according to claim 1 is characterized in that: The stator (1) is an integrated structure and is not segmented in the axial direction. The stator part is designed with slot wedges, which are made of epoxy resin material.

3. The coupled excitation motor system based on superposition current mechanism for flywheel energy storage according to claim 2 is characterized in that: The magnetomotive force generated by the unipolar double-layer ring permanent magnet structure (7) is coupled with the DC excitation and AC excitation in the integrated composite winding (10), thereby forming a mixed excitation effect of composite excitation source co-excitation; There are three types of magnetic circuits in the motor body, the first type is the magnetic circuit generated by the permanent magnet excitation source, the second type is the magnetic circuit generated by the direct current in the integrated composite winding (10), and the third type is the magnetic circuit generated by the alternating current in the integrated composite winding (10), wherein the first type of magnetic circuit and the third type of magnetic circuit are rotating magnetic circuits, and the second type of magnetic circuit is a stationary magnetic circuit.

4. The coupled excitation motor system based on superposition current mechanism for flywheel energy storage according to claim 1 is characterized in that: In the motor body, the number of permanent magnet poles of the motor is N pm The number of motor rotor pole pairs p r Equal, that is, N pm =p r , Number of motor stator slots N s It must be 2m or a positive integer multiple of 2m, where m represents the number of motor phases and N represents the number of permanent magnet poles of the motor. pm The number of stator slots N S The relationship between must satisfy 2km=N S =2N pm ±2, k represents a positive integer.

5. The coupled excitation motor system based on superposition current mechanism for flywheel energy storage according to claim 4 is characterized in that: In the motor body, the number of pole pairs of the superimposed current magnetomotive force AC excitation part is p sac Not equal to the number of motor rotor poles p r , the number of pole pairs of the superimposed current magnetomotive force DC excitation part p sdc is equal to |p sac ±p r |, the number of coils per phase N ph Equal to the total number of motor coils N t 2 / mN sub , N sub , represents the number of sub-type coils in each phase, the number of coils in each phase N ph It must be an even number and be equal to the number of sub-type coils N in each phase. sub equal.

6. The coupled excitation motor system based on superposition current mechanism for flywheel energy storage according to claim 5 is characterized in that: In the power converter topology, its structure adopts a star-connected 2m-phase winding, which is applied to an m-phase AC motor. For any phase in the m phases, half of the coils are in a positive DC and AC current superposition mode, and the other half of the coils are in a reverse DC and AC current superposition mode, wherein the DC is generated by the zero-axis current in the power converter topology, and the DC part of the zero-axis current can be used for magnetic field regulation, and the AC part is used to increase torque and realize position sensorless control.

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