CN101299553A - A full-cycle power generation operation control method for a bearingless switched reluctance motor - Google Patents

Abstract

The invention relates to a full-cycle power generation operation control method of a bearingless switched reluctance motor, which belongs to the power generation technology of a bearingless switched reluctance motor. In this method, the suspension windings on each stator tooth pole are independently controlled, and the main windings on the stator tooth poles of each phase are connected in series to form a full-cycle power generation winding. By controlling the difference in the currents of the two radially opposite suspension windings, the air gap magnetic field established by the two suspension windings is unbalanced, so as to achieve the purpose of generating an asymmetrical radial magnetic pulling force. The suspension winding current is used as the excitation current for power generation, providing excitation energy to the main winding in the full cycle, and the main winding is used as the power generation winding to output electric energy and provide it to the load after rectification, realizing the full cycle power generation of the bearingless switched reluctance motor, effectively Improving the utilization rate of the levitation winding and increasing the power density of the bearingless switched reluctance generator lay the foundation for the application of the bearingless switched reluctance motor in the field of high-speed power generation with high power density requirements.

Description

A full-cycle power generation operation control method for a bearingless switched reluctance motor

1. Technical field

The invention relates to a method for controlling the power generation operation of a bearingless switched reluctance motor, which belongs to the power generation technology of a bearingless switched reluctance motor.

2. Background technology

Switched reluctance motor (hereinafter referred to as SRM) has the characteristics of simple structure, convenient maintenance, low cost, high temperature resistance, high fault tolerance and inherent high-speed adaptability, and has important applications in aerospace, military, civil and other fields feature. Bearingless switched reluctance motor (hereinafter referred to as BSRM), which integrates the functions of magnetic bearing and motor, realizes the magnetic levitation operation at the same time, because it does not need an independent radial magnetic bearing, the volume and weight are greatly reduced. The power density can be further increased. Figure 1 and Figure 2 are schematic cross-sectional views of 12/8-pole SRM and BSRM when one phase is turned on (the other two-phase windings are not marked). Compared with SRM, BSRM only adds another set of windings (hereinafter referred to as suspension windings) on the basis of the original set of stator windings (hereinafter referred to as main windings) to change the uniformity of the air gap magnetic field. The unbalanced magnetic field on both sides produces asymmetrical radial magnetic pull, so as to achieve the purpose of adjusting the radial position of the rotor. Due to the dual functions of rotation and suspension, the high-speed adaptability of BSRM is further improved, and it has better application advantages in all-electric/multi-electric aircraft, ships, tanks and other fields. Combined with the excellent four-quadrant operation capability of SRM, the application of bearingless technology also provides SRM with great potential in the fields of distributed power generation systems, uninterruptible power supplies (UPS) and flywheel energy storage systems for renewable energy generation, and electric/hybrid vehicles. Applications create the conditions.

The traditional switched reluctance motor adopts a periodic time-sharing power generation mode. Compared with the permanent magnet motor, the power density is its limitation. Many scholars have proposed several methods to improve the performance of the motor, including installing permanent magnets on the stator teeth, embedding permanent magnets in the rotor slots, adding additional windings to assist excitation, and adding additional windings as damping windings. Permanent magnet doubly salient motors and electrically excited doubly salient motors are formed by adding permanent magnets or additional excitation windings to the stator of switched reluctance motors. The ultimate goal of these changes made in the switched reluctance motor is to increase its power density and improve its running performance. However, none of them combined the increase of power density with the high-speed adaptability of switched reluctance motors. The practice of adding permanent magnets even weakened the application advantages of switched reluctance motors in harsh operating environments, thus limiting its application range.

3. Contents of the invention

1. Purpose of the invention

The present invention studies a bearingless switched reluctance motor power generation operation control method that integrates magnetic levitation and power generation functions and has a double-winding structure and full-cycle power generation function, in order to construct a high-performance generator from the perspective of improving power density and high-speed adaptability. Realize its application in high-speed power generation fields such as aerospace, aviation starter power generation systems, integrated power units, flywheel energy storage batteries, and environmental control systems.

2. Technical solution

The full-cycle power generation operation control method of the bearingless switched reluctance motor of the present invention is:

The suspension winding on each stator tooth pole is independently controlled, and the main winding on the stator tooth pole of each phase is connected in series to form a full-cycle power generation winding. The current of the suspension winding is controlled by the power converter, so that the suspension winding controls the suspension of the motor and simultaneously undertakes the excitation. On the one hand, the two radially opposite suspension windings pass currents of different sizes to unbalance the magnetic field on both sides of a pair of poles of the rotor, thereby generating an asymmetrical magnetic pull to achieve the purpose of dynamically adjusting the radial position of the rotor; the other On the one hand, the suspension winding current is used as the excitation current for power generation. During the rotation of the motor, the phase inductance changes and the flux linkage of the main winding turns changes, thereby inducing an induced potential in the main winding. When the main winding forms a loop, there is an induction current is generated. After the suspension winding is excited, when there is a freewheeling circuit, part of the excitation energy in the suspension winding will return to the power supply, and the rest will be transferred to the main winding, so that the main winding still has power output; when there is no freewheeling circuit in the suspension winding, the The excitation energy of the system will all be transferred to the main winding, and the main winding will continue to generate electricity by freewheeling, thus realizing the full-cycle power generation of the entire phase duty cycle.

4. Description of drawings

Figure 1 is a schematic cross-sectional view of an ordinary switched reluctance motor.

Fig. 2 is a schematic cross-sectional view of a bearingless switched reluctance motor.

Fig. 3 is a schematic diagram of a full-cycle power generation structure of a bearingless switched reluctance motor.

Meanings of symbols in the figure: 1-stator, 2-rotor, 3-magnetic force line, 4-common switched reluctance motor winding, 5-main winding of bearingless switched reluctance motor, 6-suspension winding of bearingless switched reluctance motor, 7- Asymmetric half-bridge power converter, 8-rectifier device.

5. Specific implementation

1. Take the 12/8 bearingless switched reluctance generator as an example. As shown in Figure 3, the suspension windings on each stator tooth pole are independently controlled, while the main windings on the four stator tooth poles of each phase are connected in series to form a full-cycle power generation winding. The power converter of the suspension winding adopts an asymmetrical half-bridge power converter structure, and other types of power converters can also be used; the main winding is in a full-cycle power generation state, and the DC load can be powered by simply connecting the winding output terminal to the rectifier .

2. As shown in Figure 3, taking the two suspension windings in the horizontal direction as an example, the suspension winding on the right is fed with a larger current, and the suspension winding on the left is fed with a smaller current, resulting in the magnetic density of the air gap on the right side in the horizontal direction being greater than The magnetic density of the left air gap, so the rotor is moved to the right by the eccentric magnetic pull to the right. When the left suspension winding is supplied with a large current and the left suspension winding is supplied with a small current, the rotor will be forced to the left and move to the left. Similarly, the movement of the rotor in the vertical direction can be controlled, so as to achieve the purpose of dynamically adjusting the radial position of the rotor.

3. The suspension winding is responsible for the excitation while controlling the suspension of the motor. The current of the suspension winding is used as the excitation current for power generation. During the rotation of the motor, the change of the phase inductance causes the flux linkage of the main winding turn chain to change, so that in the main winding An induced potential is induced, and an induced current is generated when the output terminal of the main winding is connected to a rectifier device and a DC load to form a loop. After the suspension winding is excited, when there is a freewheeling circuit, part of the excitation energy in the suspension winding will return to the power supply, and the rest will be transferred to the main winding; when there is no freewheeling circuit in the suspension winding, all the excitation energy in the suspension winding will be transferred to the main winding. winding. As shown in Figure 3, the power converter of the suspension winding adopts an asymmetrical half-bridge structure. After the excitation of the suspension winding is completed, the excitation energy in the suspension winding will return to the power supply through the freewheeling diode part, and the rest will be transferred to the main winding. The main winding has power output during the whole phase working cycle, realizing full-cycle power generation.

4. In order to facilitate the control of the levitation force, the windings of each phase provide the radial force to levitate the rotor in turn. Therefore, in the BSRM with 12/8 structure, the width of the levitation interval of each phase accounts for 1/3 of the period of the phase inductance, that is, 15°( mechanical angle, the same below). If it is greater than 15°, the two-phase excitation regions will overlap. At this time, if the two phases jointly provide the levitation force, it will involve the optimal distribution of the two-phase levitation force, which increases the difficulty of control. For power generation, the excitation width must be as large as possible within a certain range to increase the power generation, but the range of levitation force generated by each phase is still set to [-7.5°, 7.5°]. In order to prevent the current outside the levitation zone from generating radial levitation force, the currents of the levitation windings on the four stator tooth poles outside the zone are equal, so that no asymmetrical magnetic pull force will be generated.

5. The motor structure can adopt 12/8 poles, 8/6 poles, etc.

6. If the rotating shaft is tightly matched with the mechanical bearing, that is, the rotor does not need suspension control, the suspension winding is only used as the excitation winding for the main winding to generate electricity, and the full-cycle power generation operation of the motor can also be realized.

Claims (1)

1. A bearingless switched reluctance motor full-cycle power generation operation control method is characterized in that the suspension windings on each stator tooth pole are all independently controlled, and the main windings on each phase stator tooth pole are connected in series to form a full-cycle power generation winding. The current of the levitation winding is controlled by the power converter, so that the levitation winding bears the excitation function while controlling the levitation of the motor. On the one hand, the two diametrically opposite levitation windings pass currents of different magnitudes so that the magnetic fields on both sides of the rotor pair poles are different. balance, so as to generate asymmetrical magnetic pull, and achieve the purpose of dynamically adjusting the radial position of the rotor; on the other hand, the levitation winding current is used as the excitation current for power generation. During the rotation of the motor, the phase inductance changes, resulting in the magnetic flux of the main winding turn chain. The chain changes, so that the induced potential is induced in the main winding. When the main winding forms a loop, an induced current will be generated. After the suspension winding is excited, when there is a freewheeling circuit, part of the excitation energy in the suspension winding will return to the power supply, and the rest will return to the power supply. Transfer to the main winding; when there is no freewheeling circuit in the suspension winding, all the excitation energy in the suspension winding will be transferred to the main winding, and the main winding will continuously output electric energy, so as to realize the full-cycle power generation of the entire phase duty cycle.

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