阅读说明：本技术 一种开关磁阻变档电机 (Switched reluctance gear-shifting motor ) 是由 吴建华 陈礼 甘醇 于 2021-09-03 设计创作，主要内容包括：本发明公开了一种开关磁阻变档电机,包括开关磁阻电机的各相定子绕组和SPTD快续流变档电路,所述各相定子绕组均分为若干个分段绕组,SPTD快续流变档电路用于根据开关磁阻电机运行档位的需求,对各相定子绕组中各个分段绕组之间的连接方式进行调整以构成一条或多条支路。其中连接方式的切换采用零区电流变档控制方法。电机低速时,分段绕组采用串联方式,增加各相定子绕组中的串联匝数,电机的峰值转矩增大,此时为低速档；电机高速时,分段绕组采用并联方式,减少各相定子绕组中的串联匝数,电机的峰值功率和转速均增大,此时为高速档；分段绕组的数量大于2时,通过改变分段绕组之间的连接方式,获得所述电机两个档位以上的多个档位的变档运行。(The invention discloses a switched reluctance gear-shifting motor which comprises stator windings of all phases of the switched reluctance motor and an SPTD (fast pulse time division) fast follow current gear-shifting circuit, wherein the stator windings of all phases are uniformly divided into a plurality of segmented windings, and the SPTD fast follow current gear-shifting circuit is used for adjusting the connection mode among the segmented windings in the stator windings of all phases according to the requirement of the operating gear of the switched reluctance motor so as to form one or more branch circuits. The switching of the connection mode adopts a zero zone current gear shifting control method. When the motor is in a low speed, the sectional windings are connected in series, the number of series turns in each phase of stator winding is increased, the peak torque of the motor is increased, and the motor is in a low speed gear at the moment; when the motor is in a high speed, the sectional windings adopt a parallel connection mode, the number of series turns in each phase of stator winding is reduced, the peak power and the rotating speed of the motor are both increased, and the motor is in a high-speed gear at the moment; and when the number of the sectional windings is more than 2, the gear shifting operation of a plurality of gears of the motor above two gears is obtained by changing the connection mode among the sectional windings.)

1. The switched reluctance gear-shifting motor is characterized by comprising stator windings of all phases of the switched reluctance motor and an SPTD (fast pulse time division) fast follow current gear-shifting circuit, wherein the stator windings of all phases are uniformly divided into a plurality of segmented windings, the SPTD fast follow current gear-shifting circuit is used for adjusting the connection mode among the segmented windings in the stator windings of all phases according to the requirement of the switched reluctance motor on the running gear to form one or more branch circuits, and the connection mode comprises a series connection mode, a parallel connection mode and a series-parallel connection mode.

2. The switched reluctance variable speed motor of claim 1 wherein each of the segment windings in each phase stator winding has the same number of turns, resistance and inductance.

3. The switched reluctance shift motor of claim 1 wherein the SPTD fast freewheel shift circuit includes power switching tubes and diodes, diodes are connected in series in the forward direction between the segment windings of each phase of stator windings, and power switching tubes are connected in parallel between the segment windings of each phase of stator windings and the diodes.

4. The switched reluctance geared motor of claim 3, wherein a freewheeling diode is connected in series in the forward direction in each of the parallel branches.

5. A zero zone current shift control method of a switched reluctance shift motor according to any one of claims 1 to 4, comprising: when the motor runs at a low speed, the sectional windings in the stator windings of all phases are connected in series, so that the number of series-connected turns in the stator windings of all phases is increased, the peak torque of the motor is increased, and the gear of the motor is a low-speed gear at the moment; when the motor runs at a high speed, the segmented windings in the stator windings of all phases are connected in parallel, so that the number of turns in series in the stator windings of all phases is reduced, the peak power and the rotating speed of the motor are increased, and the gear of the motor is a high-speed gear; and when the number of the sectional windings in each phase of stator winding is more than 2, the connection mode between the sectional windings in each phase of stator winding is changed, so that the gear shifting operation of a plurality of gears above two gears of the motor is obtained.

6. The zero zone current gear shifting control method according to claim 5, characterized in that when the motor speed is higher than the gear shifting speed and needs gear shifting, detecting whether the current in each phase stator winding is at the zero zone position, if so, increasing the number of branches in each phase stator winding; and when the rotating speed of the motor is lower than the gear shifting rotating speed and the downshift is required, detecting whether the current in each phase of stator winding is at a zero zone position, and if so, reducing the number of branches in each phase of stator winding.

7. The zero zone current shift control method according to claim 6, wherein when the connection modes of the segment windings are switched, the control signal for switching the segment windings is combined with the rotor position of the motor for detecting whether the current in the stator windings of each phase is in the zero zone position and determining whether the rotor position is in a given switching interval.

8. The zone-zero current shift control method as claimed in claim 7, wherein the given switching interval of the rotor position is within the current zero zone.

Technical Field

The invention relates to the technical field of switched reluctance motors, in particular to a switched reluctance gear shifting motor.

Background

With the aggravation of global environmental problems and resource problems, novel full electric vehicles such as electric vehicles, electric ships and electric armored vehicles and ships are rapidly developed. Common motors of all-electric vehicles and ships comprise asynchronous motors, permanent magnet synchronous motors and switched reluctance motors, and the switched reluctance motors become important options of future electric drive systems due to the advantages of simple structure, high reliability, low cost, wide rotating speed range, simplicity in control and the like.

When the full-electric vehicle ship starts or runs at a low speed, a driving system of the full-electric vehicle ship needs to provide a large torque to overcome resistance, so that quick starting or acceleration is realized; when the fully electric vehicle ship normally runs, a driving system of the fully electric vehicle ship needs to provide a wide constant power area range so as to improve the traveling speed. The driving system formed by matching the traditional motor and the reduction gearbox with the fixed reduction ratio is difficult to meet the characteristic requirements of low-speed large torque, high-speed large power, high rotating speed range and high efficiency of the full-electric vehicle and the ship; if the combination of the traditional motor and the gearbox is adopted, the complexity is high, the reliability and the operating efficiency of a driving system are reduced, and the advantage of the speed regulation characteristic of the motor cannot be fully exerted.

The method for realizing the switching of the torque characteristics of the motor by using the series-parallel connection of the motor windings is a common motor speed expanding and starting method, for example, the Y-delta starting of an asynchronous motor is widely applied, however, the hard switching working mode inevitably brings about serious peak voltage due to the fact that the motor is an inductive load, and the hard switching working mode causes the problem of reliability which is difficult to overcome for a full-electric vehicle ship requiring frequent start-stop, acceleration and climbing work.

At present, domestic and foreign researches or patents disclose technical schemes of a plurality of motor winding series-parallel connection modes, but the key problems of peak voltage in the winding switching process are lack of reliable control strategies and control circuits capable of realizing frequent switching.

The specification with publication number CN108173474A discloses a speed-regulating permanent magnet synchronous motor based on changing winding connection mode and a control method thereof, which changes the maximum value of motor phase voltage to increase the speed expansion range and improve the motor efficiency by winding dynamic star-delta transformation during the motor operation, but no specific topological structure is given in the invention.

The specification with publication number CN208209843U discloses a segmented winding motor controller, which uses a diode three-phase rectifier bridge and a thyristor to respectively form high and low speed switching parts, and all or half of the windings are switched in through a control switch S1. However, the utility model does not consider the problem of afterflow of the cut-off winding in the switching process.

The specification with the publication number of CN108649725A discloses a motor winding switching device and a control method, the device comprises a motor stator winding, three phases of the motor stator winding are divided into two sections, one section is a high-speed and low-speed driving winding, the number of turns is W1, and the whole winding is an ABC winding; the other section is a low-speed driving winding, the number of turns is W2, and the whole winding is an abc winding; in the invention, two groups of three-phase uncontrolled rectifier bridges and thyristors are adopted to form a high-speed and low-speed switching circuit, one thyristor is closed and the other thyristor is conducted when the current crosses zero, and the switching between a full winding and a half winding is realized. However, the invention has the disadvantages that the follow current time is too long during switching, the torque of the motor is reduced, obvious rotating speed drop is generated, only half of windings are used after switching, and the utilization rate of the windings is low.

The specification with publication number CN106961195A discloses a series-parallel switching method for windings of a single-phase asynchronous motor, the single-phase asynchronous motor and equipment, wherein the single-phase asynchronous motor comprises: the switching device comprises a main phase winding, an auxiliary phase winding and a switching device, wherein the main phase winding comprises at least two winding coils; and the switching device is used for adjusting the connection mode between at least two winding coils of the main phase winding according to the operation data of the single-phase asynchronous motor. However, the invention is only analyzed in principle and a specific implementation scheme is not given.

Disclosure of Invention

The invention aims to provide a switched reluctance shift motor for realizing electronic shift driving of a full-electric vehicle and a ship, which solves the problem of rapid follow current in the winding switching process of the switched reluctance motor and thoroughly eliminates the impact damage of peak voltage to a power switch tube during winding switching.

A switched reluctance gear-shifting motor comprises stator windings of all phases of the switched reluctance motor and an SPTD (fast pulse time division) fast follow current gear-shifting circuit, wherein the stator windings of all phases are uniformly divided into a plurality of segmented windings, the SPTD fast follow current gear-shifting circuit is used for adjusting the connection mode among the segmented windings in the stator windings of all phases according to the requirement of the switched reluctance motor on running gears so as to form one or more branch circuits, and the connection mode comprises a series connection mode, a parallel connection mode and a series-parallel connection mode.

The switched reluctance gear shifting motor realizes gear shifting operation by utilizing the principle of changing the torque and rotating speed characteristics of the motor by switching the connection mode among the segmented windings of the switched reluctance motor.

The number of turns, the resistance and the inductance of each sectional winding in each phase of stator winding are the same, so that the controllability and no circulating current during the adjustment of the connection mode among the sectional windings are ensured.

The SPTD fast follow current gear shifting circuit comprises a power switch tube and diodes, the diodes are connected in series in the forward direction between the segmented windings in each phase of stator winding, and the power switch tube is connected in parallel between the segmented windings and the diodes in each phase of stator winding.

The parallel branches are connected with a freewheeling diode in series in the forward direction, and the freewheeling diode prevents the winding current from freewheeling through the anti-parallel diode inside the power switch tube.

When the power switch tube is turned off, diodes which are connected in series in the forward direction between the segmented windings are conducted; when the power switch tube is conducted, the diodes connected in series in the forward direction between the segmented windings are turned off due to the fact that the diodes bear reverse direct current bus voltage. When the motor is in a follow current or demagnetization state, the power switch tube bears reverse collector-emitter voltage, so current cannot flow, and the winding current follows current through the diodes connected in series between the segmented windings.

The invention also provides a zero-zone current gear shifting control method based on the switched reluctance gear shifting motor, which ensures the working requirements of frequent start, stop, acceleration and climbing of the full-electric vehicle and the ship and realizes the reliable gear shifting operation of the motor.

When the motor runs at a low speed, the sectional windings in the stator windings of all phases are connected in series, so that the number of series-connected turns in the stator windings of all phases is increased, the peak torque of the motor is increased, and the gear of the motor is a low-speed gear at the moment; when the motor runs at a high speed, the segmented windings in the stator windings of all phases are connected in parallel, so that the number of turns in series in the stator windings of all phases is reduced, the peak power and the rotating speed of the motor are increased, and the gear of the motor is a high-speed gear; when the number of the segmented windings in each phase of stator winding is more than 2, the connection mode among the segmented windings in each phase of stator winding is changed into a series connection mode, a parallel connection mode or a series-parallel connection mode, so that the gear shifting operation of a plurality of gears above two gears of the motor is obtained.

When the rotating speed of the motor is higher than the gear shifting rotating speed and the gear shifting is needed, detecting whether the current in each phase of stator winding of the motor is in a zero zone position, if so, increasing the number of branches in each phase of stator winding to reduce the number of turns of each phase in series, for example, switching the series connection mode into the parallel connection mode among the segmented windings according to the requirement of the operating gear of the motor; when the rotating speed of the motor is lower than the gear shifting rotating speed and downshifting is needed, whether the current in each phase of stator winding of the motor is in a zero zone position or not is detected, if so, the number of branches in each phase of stator winding is reduced to increase the number of turns of each phase in series, for example, the parallel connection mode is switched to the series connection mode among the segmented windings according to the requirement of the operating gear of the motor.

The gear shifting rotating speed is a rotating speed switching point when the motor shifts gears. The gear shifting rotating speed is used for describing a gear shifting principle, the gear shifting rotating speed can not be set to be a fixed rotating speed value, and the gear shifting rotating speed is set to be related to adjustment and calibration of the working mode of the electric vehicle and the ship and habit of a driver.

Preferably, when the connection mode of the segment windings is switched, the control signal for switching the segment windings is combined with the position of the rotor of the motor, and is used for detecting whether the current in each phase of stator winding is in a zero zone position and judging whether the position of the rotor is in a given switching interval. If the position of the rotor is in a given switching interval, switching the connection mode among the sectional windings; and if the rotor position is outside the given switching interval, the connection mode of the segmented windings is not switched. The detection of whether the rotor position is in a given switching interval can ensure the safety of the gear shifting process, avoid the generation of peak voltage, prevent the misjudgment of a current zero region caused by the error of a current detection link,

further preferably, the given switching interval of the rotor position is located within a current zero region.

Compared with the prior art, the invention has the advantages that:

1. the invention realizes the switched reluctance variable-gear motor based on the series-parallel switching of the segmented windings, so that the motor has the variable-gear speed regulation of a plurality of gears, plays the role of adding a multi-gear gearbox to the motor, cancels or reduces the requirement on a mechanical gearbox, effectively expands the speed regulation range of the motor and improves the low-speed peak torque; the electronic gear-shifting driving system meets the performance requirements of the electric vehicle and the ship under different working conditions, and realizes high integration level, high reliability and low weight.

2. The invention adopts the zero zone current gear shifting control method, thoroughly solves the problem of peak voltage caused by current change in the switching process of the sectional winding, ensures the safety of power electronic devices and the insulation safety of the motor winding, and meets the performance requirements of various working conditions such as frequent start-stop, acceleration, climbing and the like of electric vehicles and ships.

3. The invention greatly improves the range of the high-efficiency region of the motor under the global working condition and enhances the endurance mileage of the full-electric vehicle ship.

Drawings

Fig. 1(a) is a schematic diagram of a shift circuit of a two-gear three-phase 6/4-pole switched reluctance shift motor according to an embodiment of the present invention.

Fig. 1(b) is a schematic diagram of a shift circuit of a three-gear three-phase 12/8-pole switched reluctance shift motor according to an embodiment of the present invention.

Fig. 2 is a schematic view of a topology structure of a switched reluctance shift motor according to an embodiment of the present invention.

Fig. 3(a) is a schematic diagram of the low range operating circuit of the three-phase 6/4 pole switched reluctance shift motor shown in fig. 1 (a).

Fig. 3(b) is a schematic diagram of the high-speed operating circuit of the three-phase 6/4-pole switched reluctance shift motor shown in fig. 1 (a).

Fig. 4(a) is a schematic diagram of the low-speed operation circuit of the three-speed three-phase 12/8-pole switched reluctance shift motor shown in fig. 1 (b).

FIG. 4(b) is a schematic diagram of a mid-speed operating circuit for the three-speed, three-phase 12/8 pole switched reluctance shift motor shown in FIG. 1 (b).

FIG. 4(c) is a schematic diagram of the high range operating circuit of the three-speed three-phase 12/8-pole switched reluctance shift motor shown in FIG. 1 (b).

Fig. 5 is a schematic diagram of a phase current waveform and a given switching interval for a switched reluctance geared motor in an embodiment of the present invention.

Fig. 6 is a schematic diagram of a current flow direction when the power switching tubes in two parallel branches are turned off, in which the segment windings are connected in series, in the excitation state of the switched reluctance motor in the embodiment of the present invention.

Fig. 7 is a schematic diagram of a current flow direction when the power switching tubes in two parallel branches are turned off, in which the segment windings are connected in series, in the freewheeling state of the switched reluctance motor in the embodiment of the present invention.

Fig. 8 is a schematic diagram of a current flow direction when the power switching tubes in two parallel branches are turned off, in which the segment windings are connected in series, in the demagnetized state of the switched reluctance motor according to the embodiment of the present invention.

Fig. 9 is a schematic diagram of a current flow direction when the segment windings are in a parallel connection mode and the power switching tubes in two parallel branches are conducted in an excited state of the switched reluctance motor in the embodiment of the present invention.

Fig. 10 is a schematic diagram of a current flow direction when the segment windings are in a parallel connection mode and the power switching tubes in two parallel branches are turned on in the switched reluctance motor according to the embodiment of the present invention.

Fig. 11 is a schematic diagram of a current flow direction when the segmented windings are in a parallel connection mode and the power switching tubes in two parallel branches are turned on in the demagnetized state of the switched reluctance motor according to the embodiment of the present invention.

Fig. 12 is a schematic diagram of the current flow in the two parallel branches during freewheeling when they lack a forward series diode in accordance with an embodiment of the present invention.

Detailed Description

The switched reluctance gear-shifting motor comprises stator windings of all phases of the switched reluctance motor and an SPTD (fast pulse-width modulation) fast follow current gear-shifting circuit, wherein the stator windings of all phases are uniformly divided into a plurality of segmented windings, the SPTD fast follow current gear-shifting circuit is used for adjusting the connection mode among the segmented windings in the stator windings of all phases according to the requirement of the switched reluctance motor on operating gears so as to form one or more branch circuits, and the connection mode comprises a series connection mode, a parallel connection mode and a series-parallel connection mode.

Example 1:

as shown in fig. 1(a), a two-gear three-phase 6/4-pole switched reluctance shift motor is taken as an example.

The switched reluctance motor winding is composed of an A-phase stator winding, a B-phase stator winding and a C-phase stator winding, wherein the A-phase stator winding is divided into two sections of sectional windings: a1 and A2. The B-phase stator winding is divided into two sections of segmented windings as follows: b1 and B2. The C-phase stator winding is divided into two sections of segmented windings: c1, C2.

Wherein, the numbers of turns, the resistances, the inductances and the like of A1 and A2, B1 and B2, and C1 and C2 are all the same.

An asymmetric half-bridge type power conversion circuit is adopted in a three-phase 6/4-pole switched reluctance motor, an A-phase power conversion circuit consists of two power switching tubes of V1 and V2 and two freewheeling diodes of D1 and D2, a B-phase power conversion circuit consists of two power switching tubes of V3 and V4 and two freewheeling diodes of D3 and D4, a C-phase power conversion circuit consists of two power switching tubes of V5 and V6 and two freewheeling diodes of D5 and D6, the power switching tubes bear direct-current bus voltage, and the two power switching tubes can be simultaneously turned off or only one power switching tube can be turned off during chopping; the freewheeling diode is only conducting when the winding freewheels.

The on-off of the power switch tube is related to the position of the rotor of the motor and the control mode, and the motor is conducted in sequence according to the position of each phase of the rotor when in normal operation.

As shown in fig. 2, a diode DA3 is connected in series between the two segment windings a1 and a2 in the forward direction, and power switching tubes VA1 and VA2 are connected in parallel across a1 and DA3 and across a2 and DA3, respectively; in order to ensure fast freewheeling, freewheeling diodes DA1, DA2 are connected in series in the VA1 and VA2 circuits in the forward direction to prevent the winding current from freewheeling through the anti-parallel diodes inside VA1, VA 2.

The series diode DA3 is conducted when the gear is low, the power switch tubes VA1 and VA2 are turned off when the gear is low, the two sections of windings A1 and A2 are connected in series to the power conversion circuit, and the gear-shifting motor runs at the low gear; the power switch tubes VA1 and VA2 are conducted at high-speed gear, at the moment, the connection mode of the windings A1 and A2 is switched from series connection to parallel connection, the gear-shifting motor is switched from low-speed gear to high-speed gear, and the diode DA3 is switched off due to the fact that reverse direct-current bus voltage is borne.

When the motor is operated in a low gear, a1 is connected with a2 in series, B1 is connected with B2 in series, and C1 is connected with C2 in series, so that an operation circuit of the low gear with the number of branches being 1 is formed, as shown in fig. 3 (a). When the motor runs at a high-speed gear, a1 is connected with a2 in parallel, B1 is connected with B2 in parallel, and C1 is connected with C2 in parallel, so that a high-speed gear running circuit with the number of branches being 2 is formed, as shown in fig. 3 (B).

In low-gear operation, the two coils are connected in series through a diode DA3, and then VA1 and VA2 are turned off; when the high-speed gear runs, the two coils are connected in parallel through power switch tubes VA1 and VA2, and then DA3 is turned off due to the fact that the reverse direct current bus voltage is borne.

Example 2:

as shown in fig. 1(b), a three-gear three-phase 12/8-pole switched reluctance shift motor is taken as an example.

The switched reluctance motor winding is composed of an A-phase stator winding, a B-phase stator winding and a C-phase stator winding, wherein the A-phase stator winding is divided into four sections of segmented windings: a1, A2, A3 and A4. The B-phase stator winding is divided into four sections of segmented windings as follows: b1, B2, B3 and B4. The C-phase stator winding is divided into four sections of segmented windings as follows: c1, C2, C3 and C4.

The number of turns, the resistance and the inductance of the sectional windings in the A-phase stator winding, the B-phase stator winding and the C-phase stator winding are the same.

Diodes are connected in series between the segmented windings in the A-phase stator winding, the B-phase stator winding and the C-phase stator winding in the forward direction, and power switch tubes are connected in parallel between the segmented windings and the diodes in the A-phase stator winding, the B-phase stator winding and the C-phase stator winding. In order to realize three connection modes of sectional winding series connection, parallel connection and series-parallel connection, two power switch tubes VA5 and VA6 are added between the A-phase SPTD fast follow current shift circuit and the power conversion circuit, two power switch tubes VB5 and VB6 are added between the B-phase SPTD fast follow current shift circuit and the power conversion circuit, and two power switch tubes VC5 and VC6 are added between the C-phase SPTD fast follow current shift circuit and the power conversion circuit

The parallel branches are all connected with a freewheeling diode in series in the forward direction, so that the winding current is prevented from freewheeling through the anti-parallel diode in the power switch tube.

When the motor is operated in a low gear, a1, a2, A3 and a4 are connected in series, B1, B2, B3 and B4 are connected in series, and C1, C2, C3 and C4 are connected in series, which form a low-gear operation circuit with the number of branches a equal to 1, as shown in fig. 4 (a). When the motor is operated at the middle gear, a1, a2, A3 and a4 are connected in series-parallel, B1, B2, B3 and B4 are connected in series-parallel, and C1, C2, C3 and C4 are connected in series-parallel, which form a middle gear operation circuit with the branch number a equal to 2, as shown in fig. 4 (B). When the motor runs in a high-speed gear, all the components A1, A2, A3 and A4 are connected in parallel, all the components B1, B2, B3 and B4 are connected in parallel, and all the components C1, C2, C3 and C4 are connected in parallel, so that a high-speed gear running circuit with the branch number a equal to 4 is formed, as shown in FIG. 4 (C).

Taking the two-gear three-phase 6/4-pole switched reluctance variable-speed motor in embodiment 1 as an example, a process of switching the on-off state of each device in the circuit and the connection mode between the segment windings in each phase of stator winding in different connection modes is described:

as shown in fig. 5, the zero zone current shift control method based on the switched reluctance shift motor comprises the following steps: after the demagnetization of the motor is finished and before the next period comes, the current is maintained at 0A and is kept unchanged; the switching of the connection mode of the segmented windings is carried out by utilizing the zero-zone current characteristic of the switched reluctance motor, the problem of voltage spike is effectively solved, and the requirements of frequent working conditions such as frequent start-stop, acceleration, climbing and the like of the full-electric vehicle ship are met.

When the rotating speed of the motor is higher than the gear shifting rotating speed and the gear shifting is needed, detecting whether the current in each phase of stator winding of the motor is in a zero zone position, if so, conducting a power switch tube, and switching the series connection mode between the segmented windings into the parallel connection mode; when the rotating speed of the motor is lower than the gear shifting rotating speed and the motor needs to shift down, whether the current in each phase of stator winding of the motor is at a zero zone position or not is detected, if the current is at the zero zone position, the power switch tube is turned off, and the parallel connection mode between the segmented windings is switched into the series connection mode. The above shifting method realizes smooth switching between gears.

The gear shifting rotating speed is a rotating speed switching point when the motor shifts gears. The gear shifting rotating speed is used for describing a gear shifting principle, the gear shifting rotating speed can not be set to be a fixed rotating speed value, and the gear shifting rotating speed is set to be related to the adjustment and calibration of the working mode of the electric vehicle and the ship and the habit of a driver.

In actual operation, in order to prevent misjudgment of a current zero zone caused by current detection link errors, a control signal is combined with the position of a motor rotor, so that whether the current in each phase of stator winding of the motor is in the zero zone position or not is detected, and whether the position of the rotor is in a given switching interval or not is judged.

If the position of the rotor is in a given switching interval, switching the connection mode among the sectional windings; and if the rotor position is outside the given switching interval, the connection mode between the segmented windings is not switched. Whether the position of the rotor is in a given switching interval or not is detected, so that the safety of the gear shifting process can be ensured, and the generation of peak voltage is avoided. The misjudgment of a current zero area caused by current detection link errors is prevented.

The given switching interval of the rotor position selects a middle region within the current zero region, which is preferably the central part of the current zero region and which accounts for 90% of the current zero region, avoiding both edges of the current zero region.

As shown in fig. 6, when the motor is in the low gear operation, the diode DA3 is turned on, and no on signal is applied to VA1 and VA2, and VA1 and VA2 are in the off state.

As shown in fig. 7, when the motor is in low-speed operation, V1 is turned off, V2 is maintained in an on state, winding current flows from a1 through DA3, a2, V2 and D2, and returns to a1, voltage across the segment winding is zero, current is slowly reduced, and the speed of current reduction is determined by the time constant of the current loop.

As shown in fig. 8, when the motor is in low-speed operation, V1 and V2 are both turned off, the winding current flows through DA3, a2, D1, the dc bus power supply and D2, and returns to a1, the segment winding bears the reverse dc bus voltage, the segment winding demagnetizes rapidly, and the current drops to zero rapidly.

As shown in fig. 9, when the motor is in high-speed operation, the current flows through V1 and then is divided into two parts, one part flows through a1, VA1 and DA1, and the other part flows through VA2, DA2 and a 2; after being recombined, the mixed power flows through V2 and returns to the DC bus power supply, and at the moment, the DA3 bears the reverse DC bus voltage and is cut off.

As shown in fig. 10, when the motor is in high-speed operation, V1 is turned off, V2 is turned on, and VA1 and VA2 receive on signals, but the polarities of the induced voltages across windings a1 and a2 are left negative and right positive, which results in that the voltages between the collectors and the emitters of VA1 and VA2 are negative, and current cannot flow through VA1 and VA2, which is shown in fig. 7.

As shown in fig. 11, when V1 and V2 are turned off simultaneously when the motor is in high-speed operation, current cannot flow through VA1 and VA2, and the current flows as shown in fig. 8.

As shown in fig. 12, the branches VA1 and VA2 lack forward series diodes, the current dropping speed when the winding freewheels is determined by the time constant of the current loop, the current dropping is slow, and the phase current is liable to not drop to zero before the next conduction period comes in the demagnetization stage, on one hand, the zero zone current gear shifting control method cannot be used, so that the motor cannot shift gears reliably; on the other hand, the long follow current can cause the motor to generate large negative torque, and the normal operation of the motor is influenced.