CN108599665B - Linear induction motor minimum loss control method and system containing normal force - Google Patents

Linear induction motor minimum loss control method and system containing normal force Download PDF

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CN108599665B
CN108599665B CN201810463451.7A CN201810463451A CN108599665B CN 108599665 B CN108599665 B CN 108599665B CN 201810463451 A CN201810463451 A CN 201810463451A CN 108599665 B CN108599665 B CN 108599665B
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linear induction
induction motor
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axis current
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CN108599665A (en
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徐伟
胡冬
佃仁俊
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Huazhong University of Science and Technology
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
    • H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
    • H02P25/06—Linear motors
    • H02P25/062—Linear motors of the induction type
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/14—Estimation or adaptation of machine parameters, e.g. flux, current or voltage
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/22—Current control, e.g. using a current control loop
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/24—Vector control not involving the use of rotor position or rotor speed sensors
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
    • H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
    • H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
    • H02P27/08—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P2209/00—Indexing scheme relating to controlling arrangements characterised by the waveform of the supplied voltage or current
    • H02P2209/11—Sinusoidal waveform

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  • Power Engineering (AREA)
  • Control Of Ac Motors In General (AREA)
  • Control Of Linear Motors (AREA)

Abstract

The invention discloses a method and a system for controlling the minimum loss of a linear induction motor containing normal force, which comprehensively analyze the copper loss and the iron loss of the linear induction motor and establish a loss model of the linear induction motor; and normal force influence is introduced into the loss model, a new optimization objective function is established, an analytical solution and a numerical solution of the optimal flux linkage are provided, the optimal flux linkage required by the operation of the linear induction motor containing the normal force influence can be rapidly calculated, and the motor loss and the normal force are simultaneously reduced under different working conditions.

Description

Linear induction motor minimum loss control method and system containing normal force
Technical Field
The invention belongs to the field of linear induction motors, and particularly relates to a method and a system for controlling the minimum loss of a linear induction motor with normal force.
Background
The linear induction motor can generate thrust without a transmission mechanism, has the advantages of simple structure, large acceleration and deceleration, small mechanical loss, small maintenance amount and the like, and is widely applied to the industrial fields of rail transit, servo systems, conveyor belts and the like.
However, the linear induction motor is affected by the special structure of the primary magnetic circuit, the primary width and the like, and a longitudinal side end effect and a transverse edge effect (collectively called side end effect) exist during operation, so that the motor parameters change violently, the operation performance is reduced, and the loss is increased. Meanwhile, most linear induction motors, such as urban rail transit, conveyor belts and the like, operate in a light-load state for a long time, and generate huge copper loss under constant excitation, so that the efficiency of the motor is reduced.
Meanwhile, the linear induction motor has a normal force perpendicular to the thrust direction during operation due to interaction between the primary and secondary currents and the primary and secondary magnetic fields. The normal force can reach 5 times of the thrust force, the apparent weight of the linear induction motor is obviously increased, the running resistance of the motor is increased, the loss is increased, and the dynamic performance is reduced. In rail traffic and other situations, the normal force will also cause bending of the guide rail, wheel loss, etc.
Therefore, a proper control mode is needed, the loss of the linear induction motor is reduced, meanwhile, the normal force is optimally controlled, and the influence of the normal force on the operation of the motor is reduced. However, there is no comprehensive and practical control method for reducing the loss of the linear induction motor and optimizing the normal force.
Disclosure of Invention
In view of the above problems, the present invention provides a method and a system for controlling the minimum loss of a linear induction motor with a normal force, which can reduce the loss of the linear induction motor and effectively reduce the normal force.
In order to achieve the above object, the present invention provides a method for controlling minimum loss of a linear induction motor including normal force influence, which comprises:
(1) collecting primary current i of linear induction motorA、iBAnd collecting the velocity v of the linear induction motor2；
(2) From motor speed v2Calculating to obtain the secondary angular frequency omegar(ii) a From motor primary current iA、iBCombining the ABC- αβ coordinate transformation with the secondary angular frequency omega of the motorrCalculating to obtain actual secondary d-axis flux linkage psi of linear induction motordrAngle of secondary flux linkage theta1From the motor primary current iA、iBCombined secondary flux linkage angle theta1Obtaining primary d-axis current i through calculation after ABC-dq coordinate transformationdsWith primary q-axis current iqs；
(3) Based on the obtained primary d-axis current idsWith primary q-axis current iqsCalculating the normal force F of the linear induction motorn；
(4) Establishing an optimized objective function of the linear induction motor containing the influence of the normal force: j ═ Ploss(ψdr)+fnv2|Fn|，Ploss(ψdr) Is a linear induction motor loss, fnIs the normal force weight coefficient;
(5) the secondary d-axis flux linkage obtained when the optimization objective function J of the linear induction motor is minimum is the optimal flux linkage
Figure BDA0001661459750000021
(6) Will the actual secondary d-axis flux linkage psidrWith optimal flux linkage
Figure BDA0001661459750000022
After comparison, the primary d-axis current control quantity is obtained through PI regulation
Figure BDA0001661459750000023
Will the actual secondary angular frequency ωrWith a given value
Figure BDA0001661459750000024
After comparison, obtaining primary q-axis current control quantity through PI regulation
Figure BDA0001661459750000025
(7) Will the actual primary d-axis current idsAnd primary d-axis current control quantity
Figure BDA0001661459750000026
After comparison, obtaining primary d-axis voltage control quantity through PI regulation
Figure BDA0001661459750000027
Will the actual primary q-axis current iqsWith primary q-axis current control
Figure BDA0001661459750000028
After comparison, obtaining primary q-axis voltage control quantity through PI regulation
Figure BDA0001661459750000029
Controlling the primary d-axis voltage
Figure BDA00016614597500000210
Primary q-axis voltage control quantity
Figure BDA00016614597500000211
Space vector pulse width after dq- αβ coordinate transformationModulating and controlling the inverter to drive the linear induction motor to operate.
Preferably, the step (3) is based on the obtained primary d-axis current idsWith primary q-axis current iqsCalculating the normal force F of the linear induction motornThe specific implementation mode is as follows:
(31) based on the obtained primary d-axis current idsWith primary q-axis current iqsCalculating slip angular frequency
Figure BDA0001661459750000031
Combined with secondary angular frequency of the motor
Figure BDA0001661459750000032
Calculating the primary angular frequency omegas＝ωr+ωslAnd slip
Figure BDA0001661459750000033
(32) Calculating the amplitude of the primary traveling wave current layer
Figure BDA0001661459750000034
Wherein L isme、RreRespectively an equivalent excitation inductance and an equivalent secondary resistance which take into account the influence of the side effect,
Figure BDA0001661459750000035
is the secondary flux linkage phasor, msIs the number of primary phases, WsFor the primary phase with a number of turns, k, in serieswsIs the primary winding coefficient, nppIs the actual pole pair number of the linear induction motor, tau is the pole distance, LrIs an equivalent secondary resistance;
(33) according to the primary travelling wave current layer amplitude J1Calculating to obtain normal force of linear induction motor
Figure BDA0001661459750000036
Wherein lsFor length of linear induction motor, lambdasIs the motor width, mu0Is the vacuum permeability, s is the slip, RmIs the magnetic Reynolds number, τ is the polar distance, geTo an equivalent electromagnetic air gap length, J1The amplitude of the primary traveling wave current layer is shown, and pi is the circumferential rate.
Preferably, the linear induction motor loss in the step (4) is
Figure BDA0001661459750000037
Wherein the loss factor a1、a2、a3、a4And a5The expressions of (A) are respectively:
Figure BDA0001661459750000038
Figure BDA0001661459750000039
Figure BDA0001661459750000041
Figure BDA0001661459750000042
Figure BDA0001661459750000043
wherein L isls、LlrPrimary leakage inductance, secondary leakage inductance, Rs、RcRespectively primary resistance, iron loss resistance, omegarTo the secondary angular frequency, LsThe equivalent primary inductance is obtained, and F is the motor thrust.
Preferably, the motor thrust force
Figure BDA0001661459750000044
Wherein ids、iqs、idc、iqcPrimary d-axis current, primary q-axis current, iron loss resistance branch d-axis current, iron loss resistance branch q-axis current, psiqrFor secondary q-axis flux linkage, #drIs the secondary d-axis flux linkage.
Preferably, the equivalent excitation inductance L ismeEquivalent secondary resistance RreComprises the following steps: l isme＝KxCxLm， Rre＝KrCrRrWherein L ismFor exciting inductance, RrIs a secondary resistance, KrCorrection factor for the secondary resistance of the longitudinal side effect, KxCorrection coefficient of excitation inductance for longitudinal side effect, CrCorrection of the secondary resistance for lateral edge effects, CxAnd the correction coefficient is a transverse edge effect excitation inductance correction coefficient.
Preferably, the magnetic flux linkage obtained at the time of J minimum is the optimum magnetic flux linkage
Figure BDA0001661459750000045
The optimal flux linkage analytic solution is as follows:
Figure BDA0001661459750000046
in the formula (I), the compound is shown in the specification,
Figure BDA0001661459750000047
Figure BDA0001661459750000051
the optimal flux linkage numerical solution is iteratively solved by a Newton-Raphson method, and the iteration process is as follows:
Figure BDA0001661459750000052
wherein J 'and J' are respectively the first derivative and the second derivative of J, and the initial value of iteration is as follows: psidr(0)＝a3/a′1。
The present invention also provides a system for controlling a minimum loss of a linear induction motor including a normal force effect, comprising:
a controller for controlling the motor speed v2Calculating to obtain the secondary angular frequency omegar(ii) a From motor primary current iA、iBCombining the ABC- αβ coordinate transformation with the secondary angular frequency omega of the motorrCalculating to obtain actual secondary d-axis flux linkage psi of linear induction motordrAngle of secondary flux linkage theta1From the motor primary current iA、iBCombined secondary flux linkage angle theta1Obtaining primary d-axis current i through calculation after ABC-dq coordinate transformationdsWith primary q-axis current iqs(ii) a Based on the obtained primary d-axis current idsWith primary q-axis current iqsCalculating the normal force F of the linear induction motorn(ii) a Establishing an optimized objective function of the linear induction motor containing the influence of the normal force: j ═ Ploss(ψdr)+fnv2|Fn|，Ploss(ψdr) Is a linear induction motor loss, fnIs the normal force weight coefficient; the secondary d-axis flux linkage obtained when the optimization objective function J of the linear induction motor is minimum is the optimal flux linkage
Figure BDA0001661459750000053
A first comparator for comparing the actual secondary d-axis flux linkage psidrWith optimal flux linkage
Figure BDA0001661459750000054
Comparing;
a first PI regulator for regulating the result compared by the first comparator to obtain a primary d-axis current control quantity
Figure BDA0001661459750000055
A second comparator for comparing the actual motor secondary angular frequency ωrWith a given value
Figure BDA0001661459750000056
Comparing;
a second PI regulator for regulating the result compared by the second comparator to obtain a primary q-axis current control quantity
Figure BDA0001661459750000057
A third comparator for comparing the actual primary d-axis current idsAnd primary d-axis current control quantity
Figure BDA0001661459750000061
Comparing;
a third PI regulator for regulating the result compared by the third comparator to obtain a primary d-axis voltage control quantity
Figure BDA0001661459750000062
A fourth comparator for comparing the actual primary q-axis current iqsWith primary q-axis current control
Figure BDA0001661459750000063
Comparing;
a fourth PI regulator for regulating the result compared by the fourth comparator to obtain the primary q-axis voltage control quantity
Figure BDA0001661459750000064
The controller is also used for controlling the primary d-axis voltage
Figure BDA0001661459750000065
Primary q-axis voltage control quantity
Figure BDA0001661459750000066
And carrying out space vector pulse width modulation after dq- αβ coordinate transformation, and controlling an inverter to drive a linear induction motor to operate.
Generally, compared with the prior art, the above technical solutions conceived by the present invention mainly have the following technical advantages: the optimal flux linkage required by the operation of the linear induction motor containing the influence of the normal force can be quickly calculated, and the motor loss and the normal force can be simultaneously reduced under different working conditions.
Drawings
Fig. 1(a) - (b) are d-q axis equivalent circuits of a linear induction motor in an embodiment of the present invention, where fig. 1(a) is the d axis equivalent circuit and fig. 1(b) is the q axis equivalent circuit.
Fig. 2 is a single-phase equivalent circuit model of the linear induction motor.
Fig. 3 is a schematic diagram of the linear induction motor minimum loss control including normal force effects.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
1. Linear induction motor loss model
Fig. 1(a) - (b) are d-q axis equivalent circuits of a linear induction motor in an embodiment of the present invention, where fig. 1(a) is the d axis equivalent circuit and fig. 1(b) is the q axis equivalent circuit. In FIGS. 1(a) - (b), KrCorrection factor for the secondary resistance of the longitudinal side effect, KxCorrection coefficient of excitation inductance for longitudinal side effect, CrCorrection of the secondary resistance for lateral edge effects, CxCorrection factor, L, for transverse edge effect excitation inductancels、LmAnd LlrPrimary leakage inductance, excitation inductance and secondary leakage inductance, Rs、RcAnd RrRespectively a primary resistance, an iron loss resistance and a secondary resistance. In particular, the equivalent excitation inductance and the equivalent secondary resistance considering the side effect influence are defined as
Figure BDA0001661459750000071
Defining an equivalent primary inductance and an equivalent secondary inductance as
Figure BDA0001661459750000072
Based on FIGS. 1(a) - (b), the equation for the voltage of the linear induction motor can be obtained as
Figure BDA0001661459750000073
In the formula uds、uqsPrimary d-axis voltage, primary q-axis voltage, ids、iqs、idr、iqrPrimary d-axis current, primary q-axis current, secondary d-axis current, secondary q-axis current, psids、ψqs、ψdr、ψqrAre respectively primary d-axis flux linkage, primary q-axis flux linkage, secondary d-axis flux linkage and secondary q-axis flux linkage, omegas、ωslPrimary angular frequency, slip angular frequency, respectively, and p is a differential operator.
The flux linkage equation of the linear induction motor is
Figure BDA0001661459750000081
In the formula idc、iqcD-axis current of the iron loss resistance branch and q-axis current, i of the iron loss resistance branchdm、iqmThe d-axis current and the q-axis current of the excitation branch are respectively.
The voltage and current equations of the iron loss branch are respectively
Figure BDA0001661459750000082
Figure BDA0001661459750000083
Thrust of the linear induction motor is
Figure BDA0001661459750000084
Wherein τ is the polar distance.
The copper and iron losses of the linear induction motor can be expressed as
Figure BDA0001661459750000085
In the secondary magnetic field orientation, based on equations (3) - (7), it can be solved
Figure BDA0001661459750000091
In addition, the method can be used for producing a composite material
ωs＝ωr+ωsl(10)
Wherein, ω isrFor secondary angular frequencies, further
Figure BDA0001661459750000092
Substituting the formulas (9) to (11) into the formula (8) to obtain the loss model of the linear induction motor
Figure BDA0001661459750000093
In the formula, the loss factor a1、a2、a3、a4And a5Is defined as
Figure BDA0001661459750000094
Figure BDA0001661459750000095
Figure BDA0001661459750000096
Figure BDA0001661459750000097
Figure BDA0001661459750000101
2. Normal force of linear induction motor
The normal force of the linear induction motor is calculated by the following formula
Figure BDA0001661459750000102
In the formula IsFor length of linear induction motor, lambdasIs the motor width, mu0Is the vacuum permeability, s is the slip, RmIs the magnetic Reynolds number, geTo an equivalent electromagnetic air gap length, J1Is the amplitude of the primary traveling wave current layer.
Equivalent electromagnetic air gap length geCalculated from the following equation
ge＝kc(gm+d) (19)
Wherein, gmIs the mechanical air gap length, d is the secondary guide plate thickness, kcIs the kat-coefficient.
Magnetic Reynolds number RmIs defined as
Rm＝σtμ0v1(20)
In the formula, v1For synchronous linear velocity of motor, σtIs the equivalent conductivity of the secondary surface, expressed as
σt＝dσ2(21)
Wherein σ2Is the secondary guide plate conductivity.
Slip s is
Figure BDA0001661459750000103
The primary traveling wave current layer amplitude can be expressed as
Figure BDA0001661459750000104
In the formula, msIs the number of primary phases, WsFor the primary phase with a number of turns, k, in serieswsIs the primary winding coefficient, nppIs a linear induction motorThe number of the inter-pole pairs,
Figure BDA0001661459750000105
is the primary current phasor.
FIG. 2 is a single-phase equivalent circuit model of a linear induction motor, as can be seen from FIG. 2
Figure BDA0001661459750000111
Figure BDA0001661459750000112
In the formula (I), the compound is shown in the specification,
Figure BDA0001661459750000113
is the phasor of the secondary current,
Figure BDA0001661459750000114
is the secondary flux linkage phasor. Thus, can obtain
Figure BDA0001661459750000115
By substituting formulae (23) and (26) for formula (18)
Figure BDA0001661459750000116
When the secondary magnetic field is oriented downwards and constant-power coordinate transformation is adopted
Figure BDA0001661459750000117
The resulting normal force as a function of secondary flux linkage is
Figure BDA0001661459750000118
In the formula, kFnIs the normal force coefficient, which is defined as
Figure BDA0001661459750000119
3. Linear induction motor minimum loss control method containing normal force influence
Linear induction motor optimization objective function including normal force influence is
J＝Ploss+fnv2|Fn| (31)
In the formula (f)nIs a normal force weight coefficient, an empirical value; v. of2Is the motor speed.
By substituting formulae (12) and (29) for formula (31)
Figure BDA00016614597500001110
Wherein, coefficient a'1Is composed of
a′1＝a1+fnv2|kFn| (33)
First and second derivatives are taken separately for (32):
Figure BDA0001661459750000121
Figure BDA0001661459750000122
based on the above derivation, it can be demonstrated that: to pair
Figure BDA0001661459750000123
And
Figure BDA0001661459750000124
is invariably provided with
J″＞0 (36)
Let equation (34) equal zero, i.e.
Figure BDA0001661459750000125
Due to the fact that
Figure BDA0001661459750000126
Figure BDA0001661459750000127
Therefore, it can be seen that the unique solution of equation (37), i.e., the unique minimum value of equation (32), exists. Solving equation (37) to obtain the optimal flux linkage analytic solution
Figure BDA0001661459750000128
In the formula
Figure BDA0001661459750000129
Figure BDA00016614597500001210
In order to avoid complex evolution calculation in the solving process, the optimal flux linkage can also be obtained by a numerical method, the invention adopts a Newton-Raphson method to carry out iterative solution, and the iterative principle is
Figure BDA0001661459750000131
Selecting an initial iteration value of
ψdr(0)＝a3/a′1(44)
Due to the uniqueness of the extreme point, the stable value can be quickly converged by 3-4 iterations, so that the required optimal flux linkage can be obtained
Figure BDA0001661459750000132
Fig. 3 is a control schematic diagram of the minimum loss control of the linear induction motor including the influence of the normal force in the embodiment of the present invention, and the specific implementation steps are as follows:
(1) collecting primary current of linear induction motoriA、iBAnd collecting the velocity v of the linear induction motor2；
(2) From motor speed v2Calculating to obtain the secondary angular frequency omegar(ii) a From motor primary current iA、iBCombining the ABC- αβ coordinate transformation with the secondary angular frequency omega of the motorrCalculating to obtain actual secondary d-axis flux linkage psi of linear induction motordrAngle of secondary flux linkage theta1From the motor primary current iA、iBCombined secondary flux linkage angle theta1Obtaining primary d-axis current i through calculation after ABC-dq coordinate transformationdsWith primary q-axis current iqs；
(3) Based on the obtained primary d-axis current idsWith primary q-axis current iqsCalculating the normal force F of the linear induction motorn；
(4) Establishing an optimized objective function of the linear induction motor containing the influence of the normal force: j ═ Ploss(ψdr)+fnv2|Fn|，Ploss(ψdr) Is a linear induction motor loss, fnIs the normal force weight coefficient;
(5) the secondary d-axis flux linkage obtained when the optimization objective function J of the linear induction motor is minimum is the optimal flux linkage
Figure BDA0001661459750000133
(6) Will the actual secondary d-axis flux linkage psidrWith optimal flux linkage
Figure BDA0001661459750000134
After comparison, the primary d-axis current control quantity is obtained through PI regulation
Figure BDA0001661459750000135
Will the actual secondary angular frequency ωrWith a given value
Figure BDA0001661459750000136
After comparison, obtaining primary q-axis current control quantity through PI regulation
Figure BDA0001661459750000137
(7) Will the actual primary d-axis current idsAnd primary d-axis current control quantity
Figure BDA0001661459750000141
After comparison, obtaining primary d-axis voltage control quantity through PI regulation
Figure BDA0001661459750000142
Will the actual primary q-axis current iqsWith primary q-axis current control
Figure BDA0001661459750000143
After comparison, obtaining primary q-axis voltage control quantity through PI regulation
Figure BDA0001661459750000144
Controlling the primary d-axis voltage
Figure BDA0001661459750000145
Primary q-axis voltage control quantity
Figure BDA0001661459750000146
And carrying out Space Vector Pulse Width Modulation (SVPWM) after the dq- αβ coordinate transformation, and controlling the inverter to drive the linear induction motor to operate.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (7)

1. A method for controlling the minimum loss of a linear induction motor containing a normal force is characterized by comprising the following steps:
(1) collecting primary current i of linear induction motorA、iBAnd collecting the velocity v of the linear induction motor2；
(2) From motor speed v2Calculating to obtain the secondary angular frequency omegar(ii) a From motor primary current iA、iBCombining the ABC- αβ coordinate transformation with the secondary angular frequency omega of the motorrCalculating to obtain actual secondary d-axis flux linkage psi of linear induction motordrAngle of secondary flux linkage theta1From the motor primary current iA、iBCombined secondary flux linkage angle theta1Obtaining primary d-axis current i through calculation after ABC-dq coordinate transformationdsWith primary q-axis current iqs；
(3) Based on the obtained primary d-axis current idsWith primary q-axis current iqsCalculating the normal force F of the linear induction motorn(ii) a The method specifically comprises the following steps: based on the obtained primary d-axis current idsWith primary q-axis current iqsCalculating the amplitude J of the primary traveling wave current layer1And according to the amplitude J of the primary traveling wave current layer1Calculating to obtain normal force of linear induction motor
Figure FDA0002486444060000011
Wherein lsFor length of linear induction motor, lambdasIs the motor width, mu0Is the vacuum permeability, s is the slip, RmIs the magnetic Reynolds number, τ is the polar distance, geThe length of an equivalent electromagnetic air gap is shown, and pi is the circumferential rate;
(4) based on a d-q axis equivalent circuit of the linear induction motor, establishing an optimized objective function of the linear induction motor containing normal force influence: j ═ Ploss(ψdr)+fnv2|Fn|，Ploss(ψdr) The loss of the linear induction motor comprises copper loss and iron loss, wherein an iron loss resistor corresponding to the iron loss is connected with an excitation branch in parallel in the equivalent circuit and is arranged before primary leakage inductance; f. ofnIs a normal force weight coefficient, an empirical value; wherein based on the equivalent circuit, the secondary d-axis flux linkage psidrFor the independent variable, P is derivedloss(ψdr)；
(5) The secondary d-axis flux linkage obtained when the optimization objective function J of the linear induction motor is minimum is the optimal flux linkage
Figure FDA0002486444060000021
(6) Will the actual secondary d-axis flux linkage psidrWith optimal flux linkage
Figure FDA0002486444060000022
After comparison, the primary d-axis current control quantity is obtained through PI regulation
Figure FDA0002486444060000023
Will the actual secondary angular frequency ωrWith a given value
Figure FDA0002486444060000024
After comparison, obtaining primary q-axis current control quantity through PI regulation
Figure FDA0002486444060000025
(7) Will the actual primary d-axis current idsAnd primary d-axis current control quantity
Figure FDA0002486444060000026
After comparison, obtaining primary d-axis voltage control quantity through PI regulation
Figure FDA0002486444060000027
Will the actual primary q-axis current iqsWith primary q-axis current control
Figure FDA0002486444060000028
After comparison, obtaining primary q-axis voltage control quantity through PI regulation
Figure FDA0002486444060000029
Controlling the primary d-axis voltage
Figure FDA00024864440600000210
Primary q-axis voltage control quantity
Figure FDA00024864440600000211
And carrying out space vector pulse width modulation after dq- αβ coordinate transformation, and controlling an inverter to drive a linear induction motor to operate.
2. The linear induction motor minimum loss control method of claim 1, wherein the step (3) is based on the obtained primary d-axis current idsWith primary q-axis current iqsCalculating the normal force F of the linear induction motornThe specific implementation mode is as follows:
(31) based on the obtained primary d-axis current idsWith primary q-axis current iqsCalculating slip angular frequency
Figure FDA00024864440600000212
Combined with secondary angular frequency of the motor
Figure FDA00024864440600000213
Calculating the primary angular frequency omegas＝ωr+ωslAnd slip
Figure FDA00024864440600000214
(32) Calculating the amplitude of the primary traveling wave current layer
Figure FDA00024864440600000215
Wherein L isme、RreRespectively an equivalent excitation inductance and an equivalent secondary resistance which take into account the influence of the side effect,
Figure FDA00024864440600000216
is the secondary flux linkage phasor, msIs the number of primary phases, WsFor the primary phase with a number of turns, k, in serieswsIs the primary winding coefficient, nppIs the actual pole pair number of the linear induction motor, tau is the pole distance, LrIs an equivalent secondary resistance;
(33) according to the primary travelling wave current layer amplitude J1Calculating to obtain the normal direction of the linear induction motorForce of
Figure FDA0002486444060000031
Wherein lsFor length of linear induction motor, lambdasIs the motor width, mu0Is the vacuum permeability, s is the slip, RmIs the magnetic Reynolds number, τ is the polar distance, geTo an equivalent electromagnetic air gap length, J1The amplitude of the primary traveling wave current layer is shown, and pi is the circumferential rate.
3. The linear induction motor minimum loss control method according to claim 2, wherein the linear induction motor loss in the step (4) is
Figure FDA0002486444060000032
Wherein the loss factor a1、a2、a3、a4And a5The expressions of (A) are respectively:
Figure FDA0002486444060000033
Figure FDA0002486444060000034
Figure FDA0002486444060000035
Figure FDA0002486444060000036
Figure FDA0002486444060000037
wherein L isls、LlrPrimary leakage inductance, secondary leakage inductance, Rs、RcRespectively primary resistance, iron loss resistance, omegarTo the secondary angular frequency, LsIs equal toThe effective primary inductance, F is the motor thrust.
4. The linear induction motor minimum loss control method of claim 3, wherein the motor thrust force
Figure FDA0002486444060000038
Wherein ids、iqs、idc、iqcPrimary d-axis current, primary q-axis current, iron loss resistance branch d-axis current, iron loss resistance branch q-axis current, psiqrFor secondary q-axis flux linkage, #drIs the secondary d-axis flux linkage.
5. The linear induction motor minimum loss control method according to claim 3, wherein the flux linkage obtained at the time of J minimum is an optimum flux linkage
Figure FDA0002486444060000041
The optimal flux linkage analytic solution is as follows:
Figure FDA0002486444060000042
in the formula
Figure FDA0002486444060000043
Figure FDA0002486444060000044
The optimal flux linkage numerical solution is iteratively solved by a Newton-Raphson method, and the iteration process is as follows:
Figure FDA0002486444060000045
wherein J 'and J' are respectively the first derivative and the second derivative of J, and the initial value of iteration is: psidr(0)＝a3/a′1；a′1＝a1+fnv2|kFn|，kFnIs the normal force coefficient.
6. The linear induction motor minimum loss control method according to claim 2, 3 or 4, characterized in that the equivalent field inductance LmeEquivalent secondary resistance RreComprises the following steps: l isme＝KxCxLm，Rre＝KrCrRrWherein L ismFor exciting inductance, RrIs a secondary resistance, KrCorrection factor for the secondary resistance of the longitudinal side effect, KxCorrection coefficient of excitation inductance for longitudinal side effect, CrCorrection of the secondary resistance for lateral edge effects, CxAnd the correction coefficient is a transverse edge effect excitation inductance correction coefficient.
7. A linear induction motor minimum loss control system incorporating normal force, comprising:
a controller for controlling the motor speed v2Calculating to obtain the secondary angular frequency omegar(ii) a From motor primary current iA、iBCombining the ABC- αβ coordinate transformation with the secondary angular frequency omega of the motorrCalculating to obtain actual secondary d-axis flux linkage psi of linear induction motordrAngle of secondary flux linkage theta1From the motor primary current iA、iBCombined secondary flux linkage angle theta1Obtaining primary d-axis current i through calculation after ABC-dq coordinate transformationdsWith primary q-axis current iqs(ii) a Based on the obtained primary d-axis current idsWith primary q-axis current iqsCalculating the normal force F of the linear induction motorn(ii) a The method specifically comprises the following steps: based on the obtained primary d-axis current idsWith primary q-axis current iqsCalculating the amplitude J of the primary traveling wave current layer1And according to the amplitude J of the primary traveling wave current layer1Calculating to obtain normal force of linear induction motor
Figure FDA0002486444060000051
Wherein lsFor length of linear induction motor, lambdasIs the motor width, mu0Is the vacuum permeability, s is the slip, RmIs the magnetic Reynolds number, τ is the polar distance, geThe length of an equivalent electromagnetic air gap is shown, and pi is the circumferential rate; based on a d-q axis equivalent circuit of the linear induction motor, establishing an optimized objective function of the linear induction motor containing normal force influence: j ═ Ploss(ψdr)+fnv2|Fn|，Ploss(ψdr) The loss including copper loss and iron loss is of a linear induction motor, wherein an iron loss resistor corresponding to the iron loss is connected with an excitation branch in parallel in the equivalent circuit and is arranged before primary leakage inductance, fnIs a normal force weight coefficient, an empirical value; wherein based on the equivalent circuit, the secondary d-axis flux linkage psidrFor the independent variable, P is derivedloss(ψdr) (ii) a The secondary d-axis flux linkage obtained when the optimization objective function J of the linear induction motor is minimum is the optimal flux linkage
Figure FDA0002486444060000052
A first comparator for comparing the actual secondary d-axis flux linkage psidrWith optimal flux linkage
Figure FDA0002486444060000053
Comparing;
a first PI regulator for regulating the result compared by the first comparator to obtain a primary d-axis current control quantity
Figure FDA0002486444060000054
A second comparator for comparing the actual motor secondary angular frequency ωrWith a given value
Figure FDA0002486444060000055
Comparing;
a second PI regulator for regulating the result compared by the second comparator to obtain a primary q-axis current control quantity
Figure FDA0002486444060000056
A third comparator for comparing the actual primary d-axis current idsAnd primary d-axis current control quantity
Figure FDA0002486444060000061
Comparing;
a third PI regulator for regulating the result compared by the third comparator to obtain a primary d-axis voltage control quantity
Figure FDA0002486444060000062
A fourth comparator for comparing the actual primary q-axis current iqsWith primary q-axis current control
Figure FDA0002486444060000063
Comparing;
a fourth PI regulator for regulating the result compared by the fourth comparator to obtain the primary q-axis voltage control quantity
Figure FDA0002486444060000064
The controller is also used for controlling the primary d-axis voltage
Figure FDA0002486444060000065
Primary q-axis voltage control quantity
Figure FDA0002486444060000066
And carrying out space vector pulse width modulation after dq- αβ coordinate transformation, and controlling an inverter to drive a linear induction motor to operate.
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