Modular dual-stator hybrid excitation switched reluctance motor and control method thereof

Abstract

The application relates to the field of motor equipment, in particular to a modular double-stator hybrid excitation switched reluctance motor and a control method thereof. The motor comprises an outer ring stator and an inner ring stator, and a double salient pole rotor is arranged between the outer ring stator and the inner ring stator. The outer ring stator is of a salient pole structure and comprises an outer ring stator yoke, an outer ring stator excitation pole and an outer ring stator auxiliary pole. An outer excitation winding is arranged around the outer ring stator auxiliary pole. Permanent magnets are arranged between the end portions of the outer ring stator excitation pole and the outer ring stator auxiliary pole. The permanent magnets have first magnetic induction lines. When the outer ring coil is electrified, the outer ring stator has second magnetic induction lines. When the double salient pole rotor cooperates with the outer ring stator to form a magnetic circuit, the magnetic circuit formed between the first magnetic induction lines and the double salient pole rotor and the magnetic circuit formed between the second magnetic induction lines and the double salient pole rotor are in the same direction. Without increasing the volume of the motor, greater torque can be generated, that is, the torque density of the motor is increased.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electric machines, and more particularly, to a modular dual-stator hybrid excitation switched reluctance machine and a control method thereof. BACKGROUND

[0002] The conventional switched reluctance machine is a doubly salient structure machine, which has neither winding coil nor permanent magnet on the rotor. The switched reluctance machine works in continuous switching state, and its operation follows the principle of minimum reluctance. The switched reluctance machine has large starting torque, simple structure, small starting current and wide speed range, and is widely used in the fields of aviation, aerospace, electric vehicles and household appliances.

[0003] However, since the conventional switched reluctance machine has neither permanent magnet on the stator nor on the rotor, if a larger power and torque are needed, the excitation power needs to be increased, which will increase the cost of the motor drive system and reduce the torque density and power density of the motor.

[0004] In order to overcome the shortcomings of the conventional switched reluctance machine, people have proposed to embed permanent magnets in the motor to improve the performance of the switched reluctance machine based on the conventional switched reluctance machine. For example, the structure disclosed in the Chinese patent No. 200810209754.2, Switched Reluctance Machine, can improve the torque density and power density and reduce the torque ripple of the motor by embedding permanent magnets.

[0005] Then, the switched reluctance machine with embedded permanent magnets has different positions of embedded permanent magnets, which need to be determined according to the structure and requirements of the motor. The magnetic field of the motor cannot be generated by the mixed excitation of the excitation winding and the permanent magnet to obtain higher efficiency torque density and larger torque through the installation of permanent magnets. SUMMARY

[0006] The first object of the present application is to provide a switched reluctance machine which can obtain higher efficiency hybrid excitation through the installation of permanent magnets and the setting of dual stators.

[0007] To achieve the aforementioned first objective, the following technical means are employed: a modular dual-stator hybrid excitation switched reluctance motor, comprising an outer stator and an inner stator, with a doubly salient pole rotor disposed between the outer and inner stators. The outer stator has a salient pole structure, including an outer stator yoke, an outer stator excitation pole, and an outer stator auxiliary pole. An external excitation winding is disposed around the outer stator auxiliary pole. A permanent magnet is disposed between the ends of the outer stator excitation pole and the outer stator auxiliary pole. The permanent magnet has a first magnetic field line. When the outer coil is energized, the outer stator has a second magnetic field line. When the doubly salient pole rotor and the outer stator cooperate to form a magnetic circuit, the magnetic circuit formed between the first magnetic field line and the doubly salient pole rotor and the magnetic circuit formed between the second magnetic field line and the doubly salient pole rotor have the same direction.

[0008] The above scheme involves applying high-performance rare-earth permanent magnet materials (i.e., permanent magnets) to a switched reluctance motor, resulting in a magnetic field generated by a combination of excitation windings and permanent magnets. In this invention, the motor's electromagnetic torque originates partly from reluctance torque and partly from the permanent magnet torque of the permanent magnets. This generates greater torque without increasing the motor's size, thus increasing its torque density. It also outputs more power without increasing the motor's size, thus increasing its power density. Since the magnetic circuit formed between the second magnetic field line and the doubly salient pole rotor has the same direction as the magnetic circuit formed between the first magnetic field line and the doubly salient pole rotor, the addition of permanent magnets increases the magnetic circuit density. The motor's electromagnetic torque is composed of reluctance torque and permanent magnet torque, thus increasing the electromagnetic torque, as expressed by the torque pulse expression T. R =ΔT / T avg The permanent magnet does not affect the peak-to-peak value ΔT of the electromagnetic torque, while the average torque T avg The torque pulse T is increased due to the addition of a permanent magnet. R The reduction was achieved after the addition of permanent magnets.

[0009] Further optimization is as follows: the outer ring stator is composed of six outer modular stators, each outer modular stator includes an outer modular stator yoke, and outer modular excitation poles facing the inner ring stator are provided at both ends of the outer modular stator yoke, and outer modular auxiliary poles facing the inner ring stator are provided in the middle of the outer modular stator yoke.

[0010] A further optimization is made by winding a continuous external excitation winding on the external modular auxiliary pole.

[0011] The above solution improves fault tolerance by transforming the outer stator into a modular stator. If the permanent magnet loses its magnetism due to high temperature or violent mechanical impact, the excitation winding in the motor can still generate an excitation magnetic field through electrical excitation. If the excitation winding fails to generate an electrical excitation magnetic field due to excessive instantaneous current or breakdown caused by excessive voltage, the permanent magnet in the motor can still generate a permanent magnetic field to serve as the excitation magnetic field. As long as either the permanent magnet or the excitation winding can provide an excitation magnetic field, the motor can continue to operate. Furthermore, each modular stator has one... The external excitation winding is formed by continuous windings, which means that there is only one set of excitation windings between the two excitation poles of each modular stator. In contrast, ordinary outer ring stators require excitation windings to be wound on each excitation pole, which means that there are two sets of excitation windings between each pair of adjacent excitation poles. Therefore, compared with the outer ring stator in the prior art, the winding cross-sectional area in the external modular stator of this invention is larger. The winding cross-sectional area when winding one excitation winding in the same size slot is twice that when winding two excitation windings. The copper loss generated by the motor winding is small, the motor temperature rise is small, and the efficiency is high.

[0012] Further optimization: The permanent magnets are respectively disposed between the ends of the external modular excitation pole and the external modular auxiliary pole.

[0013] The above solution can prevent the excitation winding from falling out of the external modular stator.

[0014] Further optimization is as follows: The inner ring stator includes an inner modular stator, which includes alternating first inner ring stators and second inner ring stators. Each of the first and second inner ring stators has three units. The first inner ring stator includes a first inner ring stator yoke, with a first inner ring excitation pole facing the outer ring stator at each end of the first inner ring stator yoke, and a first inner ring auxiliary pole facing the outer ring stator at the middle of the first inner ring stator yoke. The second inner ring stator includes a second inner ring stator yoke, with a second inner ring excitation pole facing the outer ring stator at each end of the second inner ring stator yoke.

[0015] Further optimization is as follows: a continuous first internal excitation winding is wound on the first inner ring auxiliary pole, and a second internal excitation winding is wound on the second inner ring excitation pole.

[0016] The above scheme can further improve the fault tolerance rate by dividing the inner stator into a first inner stator and a second inner stator. Due to the use of a double salient pole rotor, the double salient pole rotor can also form an excitation effect with the inner stator. By winding a first inner excitation winding and a second inner excitation winding, the magnetic circuit density and electromagnetic torque of the double salient pole rotor can be further improved.

[0017] Further optimization involves leaving air gaps between the double salient pole rotor and both the outer and inner stators.

[0018] The second objective of this invention is to provide a control method for the modular dual-stator hybrid excitation switched reluctance motor described above.

[0019] To achieve the second objective mentioned above, the following technical means are employed: a control method for a modular dual-stator hybrid excitation switched reluctance motor based on the aforementioned technical solution.

[0020] Step 1: Measure the rotor position and phase current of the motor;

[0021] Step 2: From the given reference rotational speed ω ref The difference between the measured actual motor speed ω and the actual speed ω is calculated and input into the PI control module for proportional-integral control, and the required duty cycle D is calculated.

[0022] Step 3: Input the duty cycle D calculated by the PI control module into the PWM module, and control it according to the given control frequency f. con Generate the corresponding PWM waveform;

[0023] Step 4: Based on the rotor position θ measured in Step 1 and the given opening angle θ on and the shut-off angle θ off The control signal g is calculated.

[0024] Step 5: Based on the control signal g calculated in Step 5 and the given maximum current I... max Based on the motor current i measured in step one, determine whether current chopping is required and obtain the control signal g'.

[0025] Step 6: Convert the control signal g' obtained in Step 5 into phase voltage signals through the drive device and apply them to the switched reluctance motor to make the switched reluctance motor run.

[0026] Further optimization: The formula for calculating the duty cycle D in step two is:

[0027] D=K p e+K i ∫e·dt

[0028] Among them, K p K is the proportionality coefficient. i Here, is the integral coefficient, and 'e' is the speed error. The calculation method is as follows:

[0029] e = ω ref -ω;

[0030] In step three, the duty cycle D and the control frequency f conThe relationship is:

[0031] D = T up / T con

[0032] Among them, T up The high-level duration is T, and the control period is T. con Control period T con The calculation formula is as follows:

[0033] T con =1 / f con .

[0034] Further optimization is as follows: In step four, the rotor position θ is compared with the given opening angle θ. on and the shut-off angle θ off Comparison: If the rotor position is greater than the opening angle θ on And less than the shut-off angle θ off If the current is greater than the maximum current, output 1; otherwise, output 0. In step five, compare the current of each phase with the maximum current. If the current of a motor phase is greater than the maximum current, output 0. If the current of a motor phase is less than the maximum current, keep the output in step four.

[0035] The above scheme involves current limiting protection to prevent the switching transistor or other components from burning out due to excessive current. It requires comparing the phase current with the maximum current limit. If the phase current is greater than the maximum current limit, the corresponding switching transistor is turned off, and the corresponding control signal is 0. Conversely, if the phase current is less than the maximum current limit, it means that current limiting protection is not required, and control is performed according to the control signal in the previous step. The output here refers to the control signal g.

[0036] Further optimization is as follows: The driving device in step six is ​​an asymmetric half-bridge power converter. The asymmetric half-bridge power converter is a new type of converter that uses complementary control technology. It has the advantages of high efficiency and simple structure.

[0037] Further optimization is as follows: The measurement tool in step one is an encoder. The rotor position is detected by an encoder or other sensors that can monitor rotor position information. The current of each phase is measured by a Hall current sensor, an electromagnetic current transformer, or other sensors that can monitor the motor current value.

[0038] The advantages of this invention compared to the prior art are:

[0039] (1) The outer stator excitation winding and permanent magnet of the motor of the present invention are located on the outside of the motor and are close to the outer casing, which facilitates the heat dissipation of the motor;

[0040] (2) The outer modular stator and the first inner ring stator of the motor of the present invention are wound with only one excitation winding. The cross-sectional area of ​​the winding is large, the copper loss generated by the motor winding is small, the motor temperature rise is small, and the efficiency is high.

[0041] (3) The motor of the present invention adopts a modular stator, and the excitation windings on each independent stator block can be wound separately, which facilitates the realization of automated winding operation.

[0042] (4) The outer surface of the rotor of the present invention is cylindrical, resulting in low wind wear loss;

[0043] (5) The phase-to-phase magnetic circuit and electrical circuit of the motor of the present invention are independent, with strong isolation capability and strong fault tolerance performance;

[0044] (6) The permanent magnet of the motor of the present invention is installed between the external modular excitation pole and the external modular auxiliary pole. By means of the permanent magnet magnetic field generated by the permanent magnet, the saturation degree of the excitation magnetic field generated by the excitation winding is reduced, the equivalent air gap length of the motor of the present invention is reduced, the excitation current of the winding is reduced, and the power density and torque density of the motor are improved.

[0045] (7) The motor of the present invention adopts a double stator structure and a double salient pole structure, which allows the motor torque to be generated by the outer stator, the inner stator and the permanent magnet, thereby reducing the torque pulsation of the generated torque. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the switched reluctance motor in this embodiment;

[0047] Figure 2 This is a schematic diagram of the external modular stator structure in this embodiment;

[0048] Figure 3 This is a schematic diagram of the first inner ring stator structure in this embodiment;

[0049] Figure 4 This is a schematic diagram of the second inner ring stator structure in this embodiment;

[0050] Figure 5 This is a schematic diagram of the double salient pole rotor structure in this embodiment;

[0051] Figure 6 This is a schematic diagram of the magnetic field lines distribution generated by the permanent magnet and the excitation coil when the doubly salient pole rotor and the outer stator are aligned in the switched reluctance motor of this embodiment.

[0052] Figure 7 This is a schematic diagram of the magnetic field lines generated by the permanent magnet and the excitation coil when the doubly salient pole rotor and the inner ring stator are aligned in the switched reluctance motor of this embodiment.

[0053] Figure 8This is a schematic diagram of the magnetic field distribution when the outer stator and the doubly salient pole rotor are aligned when the single-phase winding of the outer stator is energized in this embodiment.

[0054] Figure 9 This is a finite element simulation result of the magnetic field line distribution when the outer stator and the doubly salient pole rotor are aligned when the single-phase winding of the outer stator is energized in this embodiment.

[0055] Figure 10 This is a schematic diagram of the magnetic field distribution when the inner stator and the doubly salient pole rotor are aligned when the single-phase winding of the inner stator is energized in this embodiment.

[0056] Figure 11 This is a finite element simulation result of the magnetic field line distribution when the inner stator and the doubly salient pole rotor are aligned in the inner stator single-phase winding of this embodiment are energized.

[0057] Figure 12 This is a control flowchart of the switched reluctance motor in this embodiment;

[0058] Figure 13 This is the topology diagram of the six-phase asymmetrical half-bridge power converter in this embodiment.

[0059] In the diagram, 1. External modular stator; 11. External modular stator yoke; 12. External modular excitation pole; 13. External modular auxiliary pole; 2. Double salient pole rotor; 21. Rotor yoke; 22. External rotor pole; 23. Internal rotor pole; 31. First inner ring stator; 311. First inner ring stator yoke; 312. First inner ring excitation pole; 313. First inner ring auxiliary pole; 32. Second inner ring stator; 321. Second inner ring stator yoke; 322. Second inner ring excitation pole; 4. Permanent magnet; 5. External excitation winding; 61. First internal excitation winding; 62. Second internal excitation winding; 71. First magnetic field line; 72. Second magnetic field line; 73. Third magnetic field line. Detailed Implementation

[0060] The invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are merely descriptive and are not intended to limit the scope of protection of the present invention.

[0061] Example

[0062] A modular dual-stator hybrid excitation switched reluctance motor, see appendix. Figures 1-11 It includes an outer stator, an inner stator, and a doubly salient pole rotor 2 located between them. The doubly salient pole rotor 2 consists of a rotor yoke 21, an outer rotor pole 22, and an inner rotor pole 23. The outer rotor pole 22 and the inner rotor pole 23 are staggered. See the appendix for details. Figure 5 The structure shown in the image.

[0063] The outer stator comprises six outer modular stator blocks 1 wound around each other. Each outer modular stator block 1 includes an outer modular stator yoke. Excitation poles are located at both ends of the outer modular stator yoke, and an auxiliary pole is located in the middle. A permanent magnet 4 is positioned between the excitation poles and the auxiliary poles. An external excitation winding 5 is wound around the auxiliary pole. Each external excitation winding 5 on the outer modular stator is formed by a single, continuous winding. These six external excitation windings 5 ​​constitute a three-phase winding, with each phase consisting of two external excitation windings 5 ​​connected in series. (Further details are attached.) Figure 8 This is a schematic diagram of the magnetic field distribution when the outer stator and the doubly salient pole rotor 2 are aligned and the single-phase winding of the outer stator are energized. Here, it can be seen that the first magnetic field line 71 formed by the external excitation winding 5 will form a first magnetic circuit after passing through the outer rotor pole 22 of the doubly salient pole rotor 2. The second magnetic field line 72 generated by the permanent magnet 4 will also form a second magnetic circuit after passing through the outer rotor pole 22 of the doubly salient pole rotor 2. Furthermore, the directions of the first and second magnetic circuits are the same, creating a mixed excitation effect on the doubly salient pole rotor 2. Combined with the attached... Figure 6 and attached Figure 9 This allows for a clearer view of the changes in magnetic field lines.

[0064] The inner stator consists of three alternating first inner stator sections 31 and three second inner stator sections 32. Each first inner stator section 31 includes a first inner stator yoke 311, a first inner excitation pole 312, and a first inner auxiliary pole 313. A first inner excitation winding 61 is wound around the first inner auxiliary pole 313. Each second inner stator section 32 includes a second inner stator yoke 321 and a second inner excitation pole 322. A second inner excitation winding 62 is wound around each second inner excitation pole 322. (See attached diagram.) Figure 10 The diagram shows the magnetic field distribution when the inner stator and the doubly salient pole rotor 2 are aligned, with the single-phase winding of the inner stator energized. Here, we can see that the third magnetic field line 73 generated by the first internal excitation winding 61 and the second internal excitation winding 62 will form a third magnetic field loop with the internal rotor pole 23 of the doubly salient pole rotor 2, further providing electromagnetic torque to the doubly salient pole rotor 2. The diagram and finite element simulation results when the inner stator and the doubly salient pole rotor 2 are aligned are as follows: Figure 11 As shown, at this time only one phase is conducting, and the conducting phase has excitation current, while the other five phases have no excitation current; the magnetic field lines of the conducting phase on the inner ring stator side are closed through the second inner ring rotor yoke 21 and the internal rotor pole 23; the non-conducting phase on the inner ring stator side has some leakage magnetic field lines; there is no conducting phase on the outer ring stator side, and the excitation magnetic field lines of the permanent magnet 4 are closed through the outer modular stator 1 yoke, the outer modular excitation pole 12 and the outer modular auxiliary pole 13.

[0065] This embodiment also proposes a control scheme that matches the aforementioned modular dual-stator hybrid excitation switched reluctance motor, as shown in the control flowchart below.Figure 12 As shown, the specific steps are as follows: Step 1: Measure the rotor position and phase current values ​​of the motor; use an encoder to detect the rotor position; use a Hall current sensor and an electromagnetic current transformer to detect the phase current values ​​of the motor.

[0066] Step 2: From the given reference rotational speed ω ref The difference between the measured actual motor speed ω and the actual speed ω is calculated and input into the PI control module for proportional-integral control, thus calculating the required duty cycle D. The formula for calculating the duty cycle D is: D = K p e+K i ∫e·dt

[0067] Among them, K p K is the proportionality coefficient. i Let be the integral coefficient, and e be the rotational speed error. The calculation method for e is as follows:

[0068] e = ω ref -ω.

[0069] Step 3: Input the duty cycle D calculated by the PI control module into the PWM module, and control it according to the given control frequency f. con This generates the corresponding PWM waveform; the duty cycle D and the control frequency f con The relationship is: D = T up / T con

[0070] Among them, T up The high-level duration is T, and the control period is T. con Control period T con The calculation formula is as follows:

[0071] T con =1 / f con .

[0072] Step 4: Based on the rotor position θ measured in Step 1 and the given opening angle θ on and the shut-off angle θ off The control signal g is calculated; the rotor position θ is compared with the given turn-on angle θ. on and the shut-off angle θ off In comparison, if the rotor position is greater than the opening angle θ on And less than the shut-off angle θ off Output 1 if the condition is met, otherwise output 0.

[0073] Step 5: Based on the control signal g calculated in Step 5 and the given maximum current I... maxBased on the motor current i measured in step one, determine whether current chopping is required and obtain the control signal g'; compare the current of each phase with the maximum current. If the motor phase current is greater than the maximum current, output 0; if the motor phase current is less than the maximum current, maintain the output in step four.

[0074] Step Six: The control signal g' obtained in Step Five is converted into phase voltage signals by the drive device and applied to the switched reluctance motor to make the switched reluctance motor run. The drive device is an asymmetrical half-bridge power converter. Its topology is as follows: Figure 13 As shown, the asymmetric half-bridge power converter is a new type of converter that uses complementary control technology. It has the advantages of high efficiency and simple structure.

[0075] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A modular dual-stator hybrid excitation switched reluctance motor, characterized in that, The system includes an outer stator and an inner stator, with a double salient pole rotor (2) positioned between them. The outer stator has a salient pole structure, including an outer stator yoke, an outer stator excitation pole, and an outer stator auxiliary pole. An external excitation winding (5) is arranged around the outer stator auxiliary pole. A permanent magnet (4) is positioned between the ends of the outer stator excitation pole and the outer stator auxiliary pole. The permanent magnet (4) has a first magnetic field line (71). When the outer coil is energized, the outer stator has a second magnetic field line (72). When the double salient pole rotor (2) and the outer stator cooperate to form a magnetic circuit, the magnetic circuit formed between the first magnetic field line (71) and the double salient pole rotor (2) and the magnetic circuit formed between the second magnetic field line (72) and the double salient pole rotor (2) are in the same direction. The inner stator... The stator includes an inner modular stator, which includes alternating first inner ring stator (31) and second inner ring stator (32). There are three of each of the first inner ring stator (31) and the second inner ring stator (32). The first inner ring stator (31) includes a first inner ring stator yoke (311). At the ends of the first inner ring stator yoke (311), there are first inner ring excitation poles (312) facing the outer ring stator. At the middle of the first inner ring stator yoke (311), there are first inner ring auxiliary poles (313) facing the outer ring stator. The second inner ring stator (32) includes a second inner ring stator yoke (321). At both ends of the second inner ring stator yoke (321), there are second inner ring excitation poles (322) facing the outer ring stator.

2. The modular dual-stator hybrid excitation switched reluctance motor according to claim 1, characterized in that, The outer ring stator is composed of six outer modular stators (1). Each outer modular stator (1) includes an outer modular stator (1) yoke. Both ends of the outer modular stator (1) yoke are provided with outer modular excitation poles (12) facing the inner ring stator. The middle part of the outer modular stator (1) yoke is provided with an outer modular auxiliary pole (13) facing the inner ring stator.

3. A modular dual-stator hybrid excitation switched reluctance motor according to claim 2, characterized in that, A continuous external excitation winding (5) is wound on the external modular auxiliary pole (13).

4. A modular dual-stator hybrid excitation switched reluctance motor according to claim 2, characterized in that, The permanent magnet (4) is respectively disposed between the ends of the external modular excitation pole (12) and the external modular auxiliary pole (13).

5. A modular dual-stator hybrid excitation switched reluctance motor according to claim 1, characterized in that, A continuous first internal excitation winding (61) is wound on the first inner ring auxiliary pole (313), and a second internal excitation winding (62) is wound on the second inner ring excitation pole (322).

6. A modular dual-stator hybrid excitation switched reluctance motor according to claim 1, characterized in that, An air gap is left between the double salient pole rotor and both the outer and inner stators.

7. A control method for a modular dual-stator hybrid excitation switched reluctance motor as described in any one of claims 1-6, characterized in that, Step 1: Measure the rotor position and phase current of the motor; Step 2: From the given reference rotational speed ω ref The difference between the measured actual motor speed ω and the actual speed ω is calculated and input into the PI control module for proportional-integral control, and the required duty cycle D is calculated. Step 3: Input the duty cycle D calculated by the PI control module into the PWM module, and control it according to the given control frequency f. con Generate the corresponding PWM waveform; Step 4: Based on the rotor position θ measured in Step 1 and the given opening angle θ on and the shut-off angle θ off The control signal g is calculated. Step 5: Based on the control signal g calculated in Step 5 and the given maximum current I... max Based on the motor current i measured in step one, determine whether current chopping is required and obtain the control signal g'. Step 6: Convert the control signal g' obtained in Step 5 into phase voltage signals through the drive device and apply them to the switched reluctance motor to make the switched reluctance motor run.

8. The control method according to claim 7, characterized in that, The formula for calculating the duty cycle D in step two is: D=K p ·e+K i ∫e·dt Among them, K p K is the proportionality coefficient. i Here, e is the integral coefficient, and e is the rotational speed error. The calculation method is as follows: e = ω ref -ω; In step three, the duty cycle D and the control frequency f con The relationship is: D=T up / T con Among them, T up The high-level duration is T, and the control period is T. con Control period T con The calculation formula is as follows: T con =1 / f con .

9. The control method according to claim 7, characterized in that, In step four, the rotor position θ is compared with the given opening angle θ. on and the shut-off angle θ off In comparison, if the rotor position is greater than the opening angle θ on And less than the shut-off angle θ off If the current is greater than the maximum current, output 1; otherwise, output 0. In step five, compare the current of each phase with the maximum current. If the current of a motor phase is greater than the maximum current, output 0. If the current of a motor phase is less than the maximum current, keep the output in step four.

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