阅读说明：本技术 无轴承开关磁阻电机的全周期悬浮及转矩补偿控制方法 (Full-period suspension and torque compensation control method of bearingless switched reluctance motor ) 是由 刘泽远 陈梅 梁智 蒋伟 王振 于 2021-04-12 设计创作，主要内容包括：本发明公开了电机领域的一种无轴承开关磁阻电机的全周期悬浮及转矩补偿控制方法,旨在解决现有的悬浮力控制机理制约,需要对每个绕组的电流独立控制,导致功率变换器数量需求大,控制成本高,电流斩波控制使得功率开关管的开关次数频繁、开关损耗高,增加了控制成本的技术问题。所述无轴承开关磁阻电机包括定子和转子；所述定子为带有多个定子齿的凸极结构,且每个定子齿上均设有一套绕组；所述转子由用于产生悬浮力的圆柱转子和用于产生转矩和悬浮力的凸极转子构成；所述绕组包括A、B、C三相绕组,所述A相绕组由空间上相差90～°且独立控制的四个绕组构成。本发明不仅减少功率开关管使用个数,降低控制成本；而且控制简单,实施便利。(The invention discloses a full-period suspension and torque compensation control method of a bearingless switched reluctance motor in the field of motors, and aims to solve the technical problems that the existing suspension force control mechanism is restricted, the current of each winding needs to be independently controlled, so that the quantity requirement of a power converter is large, the control cost is high, the current chopping control causes frequent switching times and high switching loss of a power switching tube, and the control cost is increased. The bearingless switched reluctance motor comprises a stator and a rotor; the stator is of a salient pole structure with a plurality of stator teeth, and each stator tooth is provided with a set of winding; the rotor is composed of a cylindrical rotor for generating a levitation force and a salient pole rotor for generating a torque and a levitation force; the windings comprise A, B, C three-phase windings, and the A-phase windings are spatially separated by 90 DEG ° And four windings controlled independently. The invention not only reduces the number of power switch tubes used, but also reduces the control cost; and the control is simple and the implementation is convenient.)

1. A full-period suspension and torque compensation control method of a bearingless switched reluctance motor is characterized by comprising the following steps: the bearingless switched reluctance motor comprises a stator and a rotor;

the stator is of a salient pole structure with a plurality of stator teeth, and each stator tooth is provided with a set of winding;

the rotor is composed of a cylindrical rotor for generating a levitation force and a salient pole rotor for generating a torque and a levitation force;

the windings comprise A, B, C three-phase windings, and the A-phase winding is composed of four windings which have 90-degree phase difference in space and are independently controlled; B. the phase C winding is formed by connecting four windings with a phase difference of 90 degrees in space in series, the A, B, C three-phase windings respectively have a phase difference of 30 degrees in space, the phase A winding is conducted in a full period, the phase A winding is asymmetrically excited and generates torque and suspension force, and the phase B, C winding is respectively conducted and only generates torque;

the full-period suspension and torque compensation control method of the bearingless switched reluctance motor comprises the following specific steps:

step A, according to the position angle theta of the rotor, obtaining A, B, C respective excitation intervals of the three-phase winding;

b, calculating a real-time displacement signal difference of the rotor, and enabling the signal difference to pass through a proportional-integral-derivative controller to obtain a given value of the suspension force required by the A-phase winding;

step C, calculating the rotation speed difference of the rotor, and obtaining the current chopping limit i through a proportional integral derivative controller_p ^*；

Step D, calculating and obtaining the given torque exciting current i of the A-phase winding according to the exciting interval of the A-phase winding_ma ^*；

Step E, setting a torque exciting current i according to the A-phase winding_ma ^*Obtaining the given torque exciting current i of the B-phase winding_mb ^*；

Step F, obtaining the given torque exciting current i of the C-phase winding_mc ^*；

Step G, collecting A, B, C actual torque current i of each phase in real time by using a current chopping control method_ma、i_mb、i_mcAnd make it track the given torque exciting current i of each phase respectively_ma ^*、i_mb ^*、i_mc ^*Further realizing torque adjustment;

step H, collecting the actual current i of each winding of the phase A in real time by using a current chopping control method_a1～i_a4And makes it track a given current i_a1 ^*～i_a4 ^*And further realize the suspension force adjustment.

2. The full-period levitation and torque compensation control method of a bearingless switched reluctance motor as claimed in claim 1, wherein the number of stator teeth of the stator is 12 and the number of teeth of the salient pole rotor is 8.

3. The full-period levitation and torque compensation control method of the bearingless switched reluctance motor as claimed in claim 2, wherein the step a comprises:

step A-1, teeth of stator and rotor of the A-phase winding are formedThe axis coincidence position is defined as a zero degree position; the periodic angle of the rotor isFour windings of the A-phase winding are conducted in a full period, and the conduction interval isWhen in useWhen the phase A winding is in a zero state, the four windings of the phase A winding start to be excited and conducted;

step A-2, when theta is equal to theta_onbWhen the power switch tube of the B-phase winding power circuit is switched on, the B-phase winding starts to carry out torque excitation, and when theta is equal to theta_offbWhen the excitation is finished, the power switch tube of the phase B winding power circuit is turned off, and the phase B winding finishes the excitation; wherein, theta_onb、θ_offbRespectively an on angle and an off angle, theta, of the B-phase winding power circuit_onbHas a value range ofθ_offbHas a value range ofThe conduction angle of the B-phase winding is (theta)_offb-θ_onb) The value range is

Step A-3, when theta is equal to theta_oncWhen the power switch tube of the C-phase winding power circuit is switched on, the C-phase winding starts to be excited by torque, and when theta is equal to theta_offcWhen the excitation is finished, the power switch tube of the C-phase winding power circuit is turned off, and the C-phase winding finishes the excitation; wherein, theta_onc、θ_offcRespectively the on angle and the off angle of the C-phase winding power circuit,

4. the full-period levitation and torque compensation control method of the bearingless switched reluctance motor as claimed in claim 2, wherein the step B comprises:

b-1, acquiring actual values alpha and beta of the eccentric displacement of the rotor in the X-axis direction and the Y-axis direction, wherein the X-axis is positioned in the horizontal direction, the Y-axis is positioned in the vertical direction, and the difference between the X-axis and the Y-axis is 90 degrees;

step B-2, the actual values alpha and beta of the eccentric displacement are respectively compared with the given reference value alpha of the eccentric displacement^*And beta^*Subtracting to obtain real-time displacement signal differences delta alpha and delta beta in the X-axis direction and the Y-axis direction respectively, and respectively passing the real-time displacement signal differences delta alpha and delta beta through respective proportional-integral-derivative controllers to obtain a given value F of the suspension force of the phase A winding in the X-axis direction_x ^*And given value F of suspension force in Y-axis direction_y ^*。

5. The full-period levitation and torque compensation control method of the bearingless switched reluctance motor as claimed in claim 2, wherein the step C comprises:

step C-1, the angular speed omega of the actual rotor is compared with the set reference angular speed omega^*Subtracting to obtain a rotation speed difference delta omega;

c-2, obtaining a current chopping limit value i by the rotation speed difference delta omega through a proportional integral derivative controller_p ^*。

6. The method as claimed in claim 2, wherein the step D comprises:

d-1, judging an excitation interval where the A-phase winding is located according to the position angle theta of the rotor detected in real time;

step D-2 whenNamely, when the A-phase winding is in an inductance rising region, the A-phase winding generates positive torque; calculating formula according to suspension force of composite rotor single-winding bearingless switched reluctance motor And torque calculation formulaIs solved to obtain

Order toIs obtained whenI.e. a given torque current when the a-phase winding is in the rise region of the inductance

Wherein N is the number of turns of the coil, K_f1(theta) is the suspension coefficient of the salient pole rotor,K_f2is the coefficient of the suspension force of the cylindrical rotor,J_t(θ) is the torque coefficient, expressed in the inductance rise region as:in the inductance dip region asIn the formula of₀For vacuum permeability, r is the salient rotor radius, l₀Is the average length of the air gap, h is the axial length of the salient pole rotor, h_MIs the axial length of the cylindrical rotor, c is a constant of 1.49; i.e. i_sa1For levitation current of A-phase winding in X-axis direction, i_sa2The suspension current of the A-phase winding in the Y-axis direction is obtained; k_fIs the total suspension coefficient of the motor and has an expression of K_f＝4N²(K_f1(θ)+K_f2)；

Step D-3, whenNamely, when the A-phase winding is in an inductance reduction zone, the A-phase winding generates negative torque; in the inductance descending area of the phase A winding, according to a torque calculation formula of the composite rotor single-winding bearingless switched reluctance motor, the given torque current of the phase A winding generating the minimum negative torque in the inductance descending area is calculated through the deviation calculation and the solution; the torque expression:and (3) calculating a partial derivative:obtaining the given torque current of the A-phase winding generating the minimum negative torque in the inductance reduction region

Step D-4, whenAndthat is, the torque current of the A-phase winding in the inductance plateau region is based on the average torque formulaResolving to obtain; the A phase winding is in the conduction intervalHas an average torque ofObtained by resolvingWhen the temperature of the water is higher than the set temperature,the A phase winding is in the conduction intervalHas an average torque ofObtained by resolvingWhen the temperature of the water is higher than the set temperature,

7. the full-period levitation and torque compensation control method of the bearingless switched reluctance motor as claimed in claim 2, wherein the step E comprises:

step E-1, calculating a given resultant torque T^*(ii) a Torque compensation is carried out on negative torque generated by the phase-A winding in an inductance reduction area by the phase-B winding; thus whenI.e. a given resultant torque of the machine when the a-phase winding is in the inductance dip region

Step E-2, the obtained given torque current of the A-phase winding in the inductance reduction areaSubstituting into the formula for calculating torqueTo obtainThus synthesizing the torque T^*Is expressed asOrder toObtaining a given torque exciting current of the B-phase winding as

8. The full-period levitation and torque compensation control method of the bearingless switched reluctance motor as claimed in claim 2, wherein the step H comprises:

step H-1, according to the given suspension force F of the A-phase winding in the X-axis direction_x ^*Given suspension force F in the Y-axis direction_y ^*Torque winding current i_ma ^*And current calculation formulaCalculating to obtain the given suspension current of the A-phase winding in the X-axis directioni_sa1 ^*Given levitation current i in the Y-axis direction_sa2 ^*；

Step H-2, according to the given suspension current i of the A-phase winding in the X-axis direction_sa1 ^*Given levitation current i in the Y-axis direction_sa2 ^*And a current calculation formula Calculating to obtain given values i of the suspension currents of four windings of the A-phase winding_a1 ^*、i_a2 ^*、i_a3 ^*、i_a4 ^*；

Step H-3, collecting the actual current i of each winding of the phase A in real time by using a current chopping control method_a1～i_a4And makes it track a given current i_a1 ^*～i_a4 ^*And further realize the suspension force adjustment.

Technical Field

The invention relates to a full-period suspension and torque compensation control method of a bearingless switched reluctance motor, and belongs to the technical field of motors.

Background

A bearingless switched reluctance motor is a novel magnetic suspension motor developed in the 90 s of the 20 th century. The bearingless switched reluctance motor integrates two functions of rotation and suspension, so that the problems of loss, heating and the like caused by bearingless friction during high-speed operation can be effectively solved, and the high-speed adaptability of the switched reluctance motor can be further exerted, thereby strengthening the application basis of the switched reluctance motor in the high-speed fields of aerospace, flywheel energy storage, ships and warships and the like.

With the continuous and deep research, people gradually realize whether the restriction between effective output areas between torque and suspension force can be solved, whether the suspension and rotation functions can be subjected to decoupling control or not, and whether the suspension control precision is high or not at high speed can be realized, and the method plays a crucial role in fully playing the high-speed performance of the bearingless switched reluctance motor or not.

The asymmetric suspension excitation in the inductance flat top area and the torque excitation in the inductance ascending area effectively break through the restriction of the effective output interval of the torque and the suspension force of the traditional bearingless switched reluctance motor, thereby being beneficial to realizing the decoupling control of the torque and the suspension force of the bearingless switched reluctance motor.

However, due to the restriction of the suspension force control mechanism, the current of each winding needs to be independently controlled, so that the requirement on the number of power converters is high, the control cost is high, the switching times of the power switching tube are frequent due to the current chopping control, the switching loss is high, and the control cost is further increased. Therefore, a full-period suspension and torque compensation control method of the bearingless switched reluctance motor is provided to solve the problems.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, provides a full-period suspension and torque compensation control method for a bearingless switched reluctance motor, and solves the technical problems that the conventional suspension force control mechanism is restricted, the current of each winding needs to be independently controlled, the quantity requirement of power converters is high, the control cost is high, the current chopping control causes frequent switching times and high switching loss of a power switching tube, and the control cost is increased.

In order to achieve the purpose, the invention is realized by adopting the following technical scheme:

the invention provides a full-period suspension and torque compensation control method of a bearingless switched reluctance motor, wherein the bearingless switched reluctance motor comprises a stator and a rotor;

the stator is of a salient pole structure with a plurality of stator teeth, and each stator tooth is provided with a set of winding;

the rotor is composed of a cylindrical rotor for generating a levitation force and a salient pole rotor for generating a torque and a levitation force;

the windings comprise A, B, C three-phase windings, and the A-phase winding is composed of four windings which are separated by 90 degrees in space and are controlled independently; the B, C phase winding is formed by connecting four windings with a 90-degree difference in space in series, the A, B, C three-phase windings respectively have a 30-degree difference in space, the A phase winding is conducted in a full period, the A phase winding is asymmetrically excited and generates torque and suspension force, and the B, C phase winding is respectively conducted and only generates torque;

the full-period suspension and torque compensation control method of the bearingless switched reluctance motor comprises the following specific steps:

step A, according to the position angle theta of the rotor, obtaining A, B, C respective excitation intervals of the three-phase winding;

b, calculating a real-time displacement signal difference of the rotor, and enabling the signal difference to pass through a proportional-integral-derivative controller to obtain a given value of the suspension force required by the A-phase winding;

step C, calculating the rotation speed difference of the rotor, and obtaining the current chopping limit i through a proportional integral derivative controller_p ^*；

Step D, calculating and obtaining the given torque exciting current i of the A-phase winding according to the exciting interval of the A-phase winding_ma ^*；

Step E, setting a torque exciting current i according to the A-phase winding_ma ^*Obtaining the given torque exciting current i of the B-phase winding_mb ^*；

Step F, obtaining the given torque exciting current i of the C-phase winding_mc ^*；

Step G, collecting A, B, C actual torque current i of each phase in real time by using a current chopping control method_ma、i_mb、i_mcAnd make it track the given torque exciting current i of each phase respectively_ma ^*、i_mb ^*、i_mc ^*Further realizing torque adjustment;

step H, collecting the actual current i of each winding of the phase A in real time by using a current chopping control method_a1～i_a4And makes it track a given current i_a1 ^*～i_a4 ^*And further realize the suspension force adjustment.

As a further technical scheme of the invention, the number of teeth of the stator is 12, and the number of teeth of the salient pole rotor is 8.

As a further technical solution of the present invention, the step a includes:

step A-1, defining the coincidence position of the tooth axes of the stator and the rotor of the phase A winding as a zero-degree position; the periodic angle of the rotor isFour windings of the A-phase winding are conducted in a full period, and the conduction interval isWhen in useWhen the phase A winding is in a zero state, the four windings of the phase A winding start to be excited and conducted;

step A-2, when theta is equal to theta_onbWhen the power switch tube of the B-phase winding power circuit is switched on, the B-phase winding starts to carry out torque excitation, and when theta is equal to theta_offbWhen the excitation is finished, the power switch tube of the phase B winding power circuit is turned off, and the phase B winding finishes the excitation; wherein, theta_onb、θ_offbRespectively an on angle and an off angle, theta, of the B-phase winding power circuit_onbHas a value range ofθ_offbHas a value range ofThe conduction angle of the B-phase winding is (theta)_offb-θ_onb) The value range is

Step A-3, when theta is equal to theta_oncWhen the power switch tube of the C-phase winding power circuit is switched on, the C-phase winding starts to be excited by torque, and when theta is equal to theta_offcWhen the excitation is finished, the power switch tube of the C-phase winding power circuit is turned off, and the C-phase winding finishes the excitation; wherein, theta_onc、θ_offcRespectively the on angle and the off angle of the C-phase winding power circuit,

as a further technical solution of the present invention, the step B includes:

b-1, acquiring actual values alpha and beta of the eccentric displacement of the rotor in the X-axis direction and the Y-axis direction, wherein the X-axis is positioned in the horizontal direction, the Y-axis is positioned in the vertical direction, and the difference between the X-axis and the Y-axis is 90 degrees;

step B-2, the actual values alpha and beta of the eccentric displacement are respectively compared with the given reference value alpha of the eccentric displacement^*And beta^*Subtracting to obtain real-time displacement signal differences delta alpha and delta beta in the X-axis direction and the Y-axis direction respectively, and respectively passing the real-time displacement signal differences delta alpha and delta beta through respective proportional-integral-derivative controllers to obtain a given value F of the suspension force of the phase A winding in the X-axis direction_x ^*And given value F of suspension force in Y-axis direction_y ^*。

As a further technical solution of the present invention, the step C includes:

step C-1, the angular speed omega of the actual rotor is compared with the set reference angular speed omega^*Subtracting to obtain a rotation speed difference delta omega;

step C-2, the rotation speed difference delta omega is subjected to proportional integral microA sub-controller for obtaining a current chopping limit value i_p ^*。

As a further technical solution of the present invention, the step D includes:

d-1, judging an excitation interval where the A-phase winding is located according to the position angle theta detected in real time;

step D-2, whenNamely, when the A-phase winding is in an inductance rising region, the A-phase winding generates positive torque; calculating formula according to suspension force of composite rotor single-winding bearingless switched reluctance motor And torque calculation formulaIs solved to obtain

Order toCan be obtained whenI.e. a given torque current when the a-phase winding is in the rise region of the inductance

Wherein N is the number of turns of the coil, K_f1(theta) is the suspension coefficient of the salient pole rotor,K_f2is the coefficient of the suspension force of the cylindrical rotor,J_t(θ) is the torque coefficient, which can be expressed in the inductance rise region as:in the inductance dip region can be expressed asIn the formula of₀For vacuum permeability, r is the salient rotor radius, θ is the position angle, l₀Is the average length of the air gap, h is the axial length of the salient pole rotor, h_MIs the axial length of the cylindrical rotor, c is a constant of 1.49; i.e. i_sa1For levitation current of A-phase winding in X-axis direction, i_sa2The suspension current of the A-phase winding in the Y-axis direction is obtained; k_fTotal coefficient of suspension of the motor, and K_f＝4N²(K_f1(θ)+K_f2)；

Step D-3, whenNamely, when the A-phase winding is in an inductance reduction zone, the A-phase winding generates negative torque; in the inductance descending area of the phase A winding, according to a torque calculation formula of the composite rotor single-winding bearingless switched reluctance motor, the given torque current of the phase A winding generating the minimum negative torque in the inductance descending area is calculated through the deviation calculation and the solution; the torque expression:and (3) calculating a partial derivative:obtaining the given torque current of the A-phase winding generating the minimum negative torque in the inductance reduction region

Step D-4, whenAndthat is, the torque current when the A-phase winding is in the inductance plateau region can be calculated according to the average torque formulaResolving to obtain; the A phase winding is in the conduction intervalHas an average torque ofObtained by resolvingWhen the temperature of the water is higher than the set temperature,the A phase winding is in the conduction intervalHas an average torque ofObtained by resolvingWhen the temperature of the water is higher than the set temperature,

as a further technical solution of the present invention, the step E includes:

step E-1, calculating a given resultant torque T^*(ii) a Torque compensation is carried out on negative torque generated by the phase-A winding in an inductance reduction area by the phase-B winding; thus whenI.e. the A-phase winding is in the inductance dip region, the motor is givenResultant torque

Step E-2, the obtained given torque current of the A-phase winding in the inductance reduction areaSubstituting into the formula for calculating torqueCan obtain the productThus synthesizing the torque T^*Can be expressed asOrder toGiven torque exciting current of B-phase winding is obtained

As a further technical solution of the present invention, the step H includes:

step H-1, according to the given suspension force F of the A-phase winding in the X-axis direction_x ^*Given suspension force F in the Y-axis direction_y ^*Torque winding current i_ma ^*And current calculation formulaCalculating to obtain a given suspension current i of the A-phase winding in the X-axis direction_sa1 ^*Given levitation current i in the Y-axis direction_sa2 ^*；

Step H-2, according to the given suspension current i of the A-phase winding in the X-axis direction_sa1 ^*Given levitation current i in the Y-axis direction_sa2 ^*And a current calculation formula Calculating to obtain given values i of the suspension currents of four windings of the A-phase winding_a1 ^*、i_a2 ^*、i_a3 ^*、i_a4 ^*；

Step H-3, collecting the actual current i of each winding of the phase A in real time by using a current chopping control method_a1～i_a4And makes it track a given current i_a1 ^*～i_a4 ^*And further realize the suspension force adjustment.

Compared with the prior art, the invention has the following beneficial effects:

the invention discloses a minimum torque compensation control method of a composite rotor single-winding bearingless switched reluctance motor, wherein a stator of the motor is of a salient pole structure, the number of teeth of the stator is 12, only one set of winding is arranged on each stator tooth, a rotor is composed of a salient pole rotor and a cylindrical rotor, the cylindrical rotor is used for generating suspension force, and the number of teeth of the salient pole rotor is 8 and is used for generating torque and suspension force. The phase A winding is composed of 4 windings with 90-degree spatial difference, and the 4 windings are independently controlled; B. the C-phase winding is formed by connecting 4 windings with a 90-degree spatial difference in series, and A, B, C three-phase windings have a 30-degree spatial difference respectively; in the control method, the torque is provided by A, B, C three phases in turn, and the suspension force is provided by the A-phase winding independently; the phase A winding is conducted in a full period and is excited asymmetrically to generate torque and suspension force; B. the C-phase windings are respectively conducted, and the conduction angles of the C-phase windings are all in the rangeAnd the phase difference is 15 degrees, and the B, C phase winding only generates torque; in the control method, on the premise of maintaining normal suspension of the motor, the negative torque generated by the A-phase winding in an inductance descending area is minimized, and the negative torque is compensated by the B-phase winding to reach a normal level; the suspension force and the torque are only changed along with the current of the suspension winding and the rotor position angleThe direction of the current of the suspension winding and the direction of the current of the torque winding are not changed when the power converter is controlled, so that the power converter only needs to adopt a power converter with a single current direction, the number of power switching tubes can be obviously reduced, and the cost of the power converter is further reduced; by using the technical scheme of the invention, the using number of the power switching tubes is reduced, and the control cost is reduced; and the control is simple and the implementation is convenient.

Drawings

Fig. 1 is a schematic structural diagram of an 12/8-pole composite rotor single-winding bearingless switched reluctance motor to which the control method provided by the embodiment of the invention is applied;

fig. 2 is a schematic diagram of inductance and current waveforms of each phase winding in the control method provided by the embodiment of the invention;

FIG. 3 is a system block diagram of a control method provided by an embodiment of the invention;

fig. 4 is a block diagram of a method for calculating a current of a phase winding floating winding in a control method provided by an embodiment of the present invention;

in the figure: 1. a stator; 2. a salient pole rotor; 3. a cylindrical rotor; 4. an air gap.

Detailed Description

The control method provided by the embodiment of the invention is suitable for a bearingless switched reluctance motor, and is a structural schematic diagram of a three-phase 12/8-pole composite rotor single-winding bearingless switched reluctance motor as shown in fig. 1. Where 1 is the stator, 2 is the salient pole rotor, 3 is the cylindrical rotor, and 4 is the air gap. The stator 1 is in a salient pole structure, the number of stator teeth is 12, and each stator tooth is provided with only one set of winding; the phase A winding consists of 4 coils which are separated by 90 degrees, and each winding is independently controlled; the phase B winding is formed by connecting 4 coils which are separated by 90 degrees in series; the rest 4X coils are connected in series to form a C-phase winding; A. b, C the three-phase windings are respectively separated by 30 degrees in space; the rotor comprises cylindrical rotor 3 and salient pole rotor 2, and cylindrical rotor 3 is cylindrical structure, and salient pole rotor 2 is salient pole structure, and the rotor tooth number is 8.

Fig. 2 is a schematic diagram illustrating inductance and current waveforms of each phase winding in the control method according to the embodiment of the present invention; the phase A winding is conducted in the whole period and excited asymmetrically,providing torque and levitation force; in an inductance rising area, the A-phase winding provides positive torque and suspension force; in an inductance descending area, the phase A winding provides minimum negative torque on the premise of ensuring the normal suspension of the motor; in the inductance flat top area, the A-phase winding only provides a suspension force; because the A-phase winding adopts a constant conduction control mode, the suspension current is a continuous and periodically-changed curve, and the period angle isAt the aligned position (position angle θ is 0), the levitation current is minimized, and at the misaligned position (position angle)Or angle of position) The levitation current is maximum. Due to the proximity of the misalignment positionAnd12/8 the reluctance of the compound rotor bearingless switch reluctance motor is basically constant, the suspension force in the interval is also basically constant, and is not related to the rotor position angle theta, so the suspension current is also basically constant. B. The current of the C two-phase winding is controlled to be in a square wave form, the periodic change rule is adopted, and the period angle is also adoptedB. The C-phase windings are respectively conducted, and the conduction angle rangesAnd switched on with a 15 deg. difference.

In the intervalTorque is provided by the C-phase winding, calculated from the average torqueAnd the C-phase winding is in the intervalTorque exciting current i_mc＝i_pIs solved to obtain the intervalAverage torque of

In the intervalThe torque is provided by the A-phase winding and is calculated by the average torque calculation formulaAnd the A-phase winding is in the intervalTorque exciting currentSolved to obtain in the intervalAverage torque of

In the intervalThe torque is provided by A, B two phases, wherein the A phase winding produces negative torque and the B phase winding produces positive torque, resulting in torqueIn the interval by A phase windingAverage torque ofAnd the A-phase winding is in the intervalTorque exciting currentThe B phase winding is in the intervalAverage torque ofAnd the B-phase winding is in the intervalTorque exciting currentSolved to obtain in the intervalAverage torque of

In the intervalTorque is provided by the C-phase winding, calculated from the average torqueAnd the C-phase winding is in the intervalTorque exciting current i_mc＝i_pIs solved to obtain the intervalAverage torque of

From the above, the average torque is equal in one rotor period angle, and the magnitude thereof is

Fig. 3 is a system block diagram of a minimum torque compensation control method of a three-phase 12/8-pole composite rotor single-winding bearingless switched reluctance motor. In the control method, the suspension force of the motor is provided by the A-phase winding independently, and in an inductance ascending region and an inductance descending region of the A-phase winding, the suspension force is generated by the cylindrical rotor 3 and the salient pole rotor 2; in the inductance plateau region, the salient pole rotor 2 and the stator 1 are in a completely misaligned position, and therefore the generated levitation force is small, which is provided by the cylindrical rotor 3.

The specific control process is as follows: the difference between the actual displacement and the given displacement in the X-axis and Y-axis directions obtained by displacement detection is subjected to a Proportional Integral Derivative (PID) procedure to obtain the given suspension force F of the A-phase winding in the X-axis and Y-axis directions respectively_x ^*、F_y ^*(ii) a The difference value between the actual angular velocity and the given angular velocity obtained by the rotation speed obtained by position detection through rotation speed calculation is subjected to a proportional integral derivative link to obtain a current chopping limit i_p ^*(ii) a Given suspension force F of A-phase winding in X-axis and Y-axis directions_x ^*、F_y ^*And current chopping limit i_p ^*Obtaining the given torque current i of the A-phase winding through current calculation_ma ^*Given torque current i of the B-phase winding_mb ^*Giving torque current i to the C-phase winding_mc ^*(ii) a Given torque current i of A-phase winding_ma ^*Then the given suspension current i of 4 windings of the A-phase winding is obtained through current distribution calculation_a1 ^*～i_a4 ^*(ii) a The detected actual current i of 4 windings of the A-phase winding is controlled by current chopping_a1～i_a4TrackingGiven current i_a1 ^*～i_a4 ^*B-phase winding actual torque current i_mbTracking a given torque current i_mb ^*Actual torque current i of phase C winding_mcTracking a given torque current i_mc ^*Thereby realizing the real-time adjustment of the torque and the suspension force.

Fig. 4 is a block diagram of a calculation method of a given levitation current of each winding of the a-phase in the control method. Given suspension force F of X axis and Y axis of A-phase winding obtained through proportional integral derivative element_x ^*、F_y ^*Calculating the formula according to the suspension force:

and the constraint equation:

the given suspension current of each winding of the A phase is obtained as follows:

the invention discloses a minimum torque compensation control method for a composite rotor single-winding bearingless switched reluctance motor, and belongs to the field of control of bearingless switched reluctance motors. The stator 1 of the motor is in a salient pole structure, the number of teeth of the stator 1 is 12, only one set of winding is arranged on each stator 1, the rotor is composed of a salient pole rotor 2 and a cylindrical rotor 3, the cylindrical rotor 3 is used for generating suspension force, and the number of teeth of the salient pole rotor 2 is 8 and is used for generating torque and suspension force. The phase A winding is composed of 4 windings with 90-degree spatial difference, and the 4 windings are independently controlled; B. the C-phase winding is formed by connecting 4 windings with a 90-degree spatial difference in series, and A, B, C three-phase windings have a 30-degree spatial difference respectively; in the control method, the torque is provided by A, B, C three phases in turn, and the suspension force is provided by the A-phase winding independently; a phase windingPeriodically conducting and asymmetrically exciting to generate torque and suspension force; B. the C-phase windings are respectively conducted, and the conduction angles of the C-phase windings are all in the rangeAnd the phase difference is 15 degrees, and the B, C phase winding only generates torque; in the control method, on the premise of maintaining normal suspension of the motor, the negative torque generated by the A-phase winding in an inductance reduction area is minimized, and the negative torque is compensated by the B-phase winding to reach a normal level, and the control method specifically comprises the following steps:

step A, collecting a rotor position angle theta, and judging the excitation state of each phase;

step A-1, defining the superposition position of the winding stator and rotor tooth axes of phase A as a zero-degree position; one rotor period angle ofThe A-phase winding is conducted in 4 windings in a full period with the conduction interval beingWhen in useAt this time, the a-phase winding 4 windings start to be excited and conducted.

Step A-2, when theta is equal to theta_onbWhen the power switch tube of the B-phase winding power circuit is switched on, the B-phase winding starts to carry out torque excitation, and when theta is equal to theta_offbWhen the excitation is finished, the power switch tube of the phase B winding power circuit is turned off, and the phase B winding finishes the excitation; wherein, theta_onb、θ_offbRespectively the on angle and the off angle, theta, of the B-phase winding power circuit_onbHas a value range ofθ_offbHas a value range ofThe conduction angle of the B-phase winding is (theta)_offb-θ_onb) The value range is

Step A-3, when theta is equal to theta_oncWhen the power switch tube of the C-phase winding power circuit is switched on, the C-phase winding starts to carry out torque excitation, and when theta is equal to theta_offcWhen the excitation is finished, the power switch tube of the C-phase winding power circuit is turned off, and the C-phase winding finishes the excitation; wherein, theta_onc、θ_offcRespectively the on angle and the off angle of the C-phase winding power circuit,

b, acquiring a given value of the suspension force required by the phase A winding;

b-1, acquiring radial displacement alpha and radial displacement beta in the X-axis direction and the Y-axis direction, wherein the X-axis is positioned in the horizontal direction, the Y-axis is positioned in the vertical direction, and the X-axis and the Y-axis are different by 90 degrees;

step B-2, respectively connecting the real-time displacement signals alpha and beta with a given reference displacement signal alpha^*And beta^*Subtracting to obtain real-time displacement signal differences delta alpha and delta beta in the X-axis direction and the Y-axis direction respectively, and respectively passing the real-time displacement signal differences delta alpha and delta beta through respective proportional-integral-derivative controllers to obtain a given value F of the suspension force of the phase A winding in the X-axis direction_x ^*And given levitation force F in the Y-axis direction_y ^*；

Step C, obtaining current chopping limit i_p ^*The method comprises the following specific steps:

step C-1, the actual rotor angular speed omega is compared with the set reference angular speed omega^*Subtracting to obtain a rotation speed difference delta omega;

step C-2, obtaining a current chopping limit value i through a proportional integral derivative controller according to the rotation speed difference delta omega_p ^*；

Step D: obtaining a given torque exciting current i of the A-phase winding_ma ^*；

D-1, judging an excitation interval where the A-phase winding is located according to the position angle theta of the rotor detected in real time;

step D-2, whenNamely, when the A-phase winding is in an inductance rising region, the A-phase winding generates positive torque; calculating formula according to suspension force of composite rotor single-winding bearingless switched reluctance motor And torque calculation formulaIs solved to obtain

Order toCan be obtained whenI.e. a given torque current when the a-phase winding is in the rise region of the inductance

Wherein N is the number of turns of the coil, K_f1(theta) is a coefficient of suspension force of the salient pole rotor 2, which is related to the position angle,K_f2the suspension coefficient of the cylindrical rotor 3 is not changed along with the change of the position angle,J_t(θ) is the torque coefficient, which is a function of the dimensional parameters of the motor itself and the rotor position angle, and can be expressed as:in the inductance dip region can be expressed asIn the formula of₀For vacuum permeability, r is the radius of salient-pole rotor 2, θ is the position angle, l₀Is the average length of the air gap 4, h is the axial length of the salient pole rotor 2, h_MIs the axial length of the cylindrical rotor 3, c is a constant of 1.49; i.e. i_sa1For levitation current of A-phase winding in X-axis direction, i_sa2The suspension current of the A-phase winding in the Y-axis direction is obtained; k_fIs the total suspension coefficient of the motor, and K_f＝4N²(K_f1(θ)+K_f2)；

Step D-3, whenNamely, when the A-phase winding is in an inductance reduction zone, the A-phase winding generates negative torque; in the control method, in an inductance descending area of the A-phase winding, the minimum negative torque is required to be generated on the premise of ensuring the normal suspension of the motor; the method can calculate the given torque current of the minimum negative torque generated by the A-phase winding in an inductance reduction area according to a torque calculation formula of the composite rotor single-winding bearingless switched reluctance motor and the deviation calculation of the torque calculation formula; the torque expression:and (3) calculating a partial derivative:obtaining the given torque current of the A-phase winding generating the minimum negative torque in the inductance reduction region

Step D-4, whenAndthat is, the torque current when the A-phase winding is in the inductance plateau region can be calculated according to the average torque formulaResolving to obtain; the A phase winding is in the conduction intervalHas an average torque ofObtained by resolvingWhen the temperature of the water is higher than the set temperature,the A phase winding is in the conduction intervalHas an average torque ofObtained by resolvingWhen the temperature of the water is higher than the set temperature,

step E, obtaining the torque excitation given current of the B-phase winding

Step E-1, calculating a given resultant torque T^*(ii) a In the control method, the B-phase winding is used for carrying out torque compensation on the negative torque generated by the A-phase winding in an inductance reduction area; thus whenI.e. the A-phase winding is in the inductive dipGiven resultant torque of the electric machine at zone time

Step E-2, the obtained given torque current of the A-phase winding in the inductance reduction areaSubstituting into the formula for calculating torqueCan obtain the productThus synthesizing the torque T^*Can be expressed asOrder toGiven torque current of the B-phase winding is obtained

Step F, obtaining the given torque exciting current of the C-phase windingIn the control method, the C-phase winding is normally conducted, and the given torque current is equal to the current chopping limit value

Step G, adjusting torque; the actual torque current i of each phase is collected A, B, C in real time by using a current chopping control method_ma、i_mb、i_mcAnd make it track the given torque exciting current i of each phase respectively_ma ^*、i_mb ^*、i_mc ^*Further realizing torque adjustment;

step H, adjusting the suspension force, and specifically comprising the following steps;

h-1, independently providing all the suspension force by the A-phase winding in the control; according to the given suspension force F of the A-phase winding in the X-axis direction_x ^*Given suspension force F in the Y-axis direction_y ^*Torque winding current i_ma ^*And current calculation formulaCalculating to obtain a given suspension current i of the A-phase winding in the X-axis direction_sa1 ^*Given levitation current i in the Y-axis direction_sa2 ^*；

Step H-2, according to the given suspension current i of the A-phase winding in the X-axis direction_sa1 ^*Given levitation current i in the Y-axis direction_sa2 ^*And a current calculation formula Calculating to obtain given values i of the suspension currents of four windings of the A-phase winding_a1 ^*、i_a2 ^*、i_a3 ^*、i_a4 ^*；

Step H-3, collecting the actual current i of each winding of the phase A in real time by using a current chopping control method_a1～i_a4And makes it track a given current i_a1 ^*～i_a4 ^*And further realize the suspension force adjustment.

In conclusion, the phase A winding is conducted in the full period to generate torque and levitation force; B. the C-phase winding is conducted for 15 degrees respectively, and only torque is generated; because the phase A winding is conducted in a full period, positive torque and suspension force are generated in an inductance rising area; only generating a suspension force in an inductance flat top area, wherein the torque is provided by a C-phase winding; generating negative torque in an inductance reduction area, and performing torque compensation on the negative torque; in the control method, on the basis of maintaining normal suspension force, the negative torque generated by the A-phase winding in an inductance reduction area is minimized, and the B-phase winding is used for compensating the negative torque to reach a normal level; because the suspension force and the torque are changed only along with the change of the current of the suspension winding and the position angle of the rotor, the directions of the current of the suspension winding and the current of the torque winding are not changed during control, so that only a power changer with a single current direction is adopted, the number of power switch tubes can be obviously reduced, and the cost of the power changer is further reduced.

Other advantages and modifications will readily occur to those skilled in the art, based upon the foregoing description. Therefore, the present invention is not limited to the above specific examples, and one embodiment of the present invention will be described in detail and exemplarily by way of example only. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiments as a basis for designing or modifying other structures for carrying out the same purposes of the present invention without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.