CN108923698B - Motor control method for predicting voltage vector sequence - Google Patents

Motor control method for predicting voltage vector sequence Download PDF

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CN108923698B
CN108923698B CN201810726241.2A CN201810726241A CN108923698B CN 108923698 B CN108923698 B CN 108923698B CN 201810726241 A CN201810726241 A CN 201810726241A CN 108923698 B CN108923698 B CN 108923698B
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vector
voltage vector
voltage
flux linkage
stator flux
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CN108923698A (en
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夏长亮
李晨
周湛清
阎彦
史婷娜
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Tianjin University
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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
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/10—Arrangements for controlling torque ripple, e.g. providing reduced torque ripple
    • 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
    • H02P27/12—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 pulsing by guiding the flux vector, current vector or voltage vector on a circle or a closed curve, e.g. for direct torque control
    • 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
    • H02P2207/00—Indexing scheme relating to controlling arrangements characterised by the type of motor
    • H02P2207/05—Synchronous machines, e.g. with permanent magnets or DC excitation

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Abstract

The invention discloses a motor control method for predicting a voltage vector sequence, which comprises the following steps: through the influence of the sequencing of all voltage vectors in the two-level voltage source inverter on the fluctuation of the stator flux linkage vector, 12 voltage vector sequences beneficial to optimizing the control performance of the stator flux linkage vector are screened out; sequencing 12 voltage vectors and bringing the voltage vectors into a predictive control set to establish a novel voltage vector sequence control set; taking the effective value of the fluctuation amount of the stator flux linkage vector in one control period as an evaluation index; evaluating stator flux linkage vector errors at each voltage vector switching moment in each control period, and constructing an evaluation function; the action time of each basic voltage vector is obtained by a two-step method of confirming the phase angle and then confirming the amplitude. The invention reduces the torque fluctuation and flux linkage fluctuation of the permanent magnet synchronous motor, thereby enabling the motor to run more stably.

Description

Motor control method for predicting voltage vector sequence
Technical Field
The invention relates to the field of control of permanent magnet synchronous motors, in particular to a permanent magnet synchronous motor system suitable for feeding in a two-level voltage source inverter, and particularly relates to the field of motor control considering the running performance of a motor under the condition of torque prediction control. The invention can be applied to the fields of motor speed regulation, power electronic control and the like.
Background
The permanent magnet synchronous motor has the advantages of simple structure, high power density, wide speed regulation range and the like, and is widely applied to the fields of elevator dragging, numerical control machines, railway traction systems and the like. The limited control set prediction torque control has the advantages of flexible implementation method, easy implementation in a multivariable system, high dynamic response speed and the like. With the continuous development of microprocessor technology, the limited control set predictive torque control has gained more and more attention and has been widely researched in permanent magnet synchronous motor systems.
In a permanent magnet synchronous motor system fed by a two-level voltage source inverter, only 8 basic voltage vectors with fixed amplitudes and phase angles are arranged in a control set of a limited control set prediction torque control strategy, and an optimal basic voltage vector is selected to act in each control period. Therefore, the limited control set predicts a low degree of freedom in controlling the torque control, and the torque, the flux linkage, and the like cannot be accurately controlled. In order to improve the control performance of the limited control set predicted torque control, the related scholars improve the control freedom and accuracy of the limited control set predicted torque control, namely the multi-vector predicted torque control, by applying a plurality of basic voltage vectors in one control cycle.
However, when the voltage vectors are applied in different sequences, the state quantities of the stator flux linkage vector, the electromagnetic torque, etc. of the motor may travel in different tracks, i.e., different flux linkage and torque fluctuations may occur. The multi-vector prediction torque control currently applied to a permanent magnet synchronous motor system aims at optimizing the control performance of a motor at the end of each control period, namely, the running tracks of state quantities such as stator flux linkage vectors, electromagnetic torque and the like are guaranteed to meet the control requirements at the end of each control period, and the influence on electromagnetic torque and stator flux linkage fluctuation when applied voltage vectors are arranged in different sequences is not considered. Therefore, the steady-state control performance of the multi-vector predicted torque control can be further improved by selecting the optimal voltage vector arrangement order.
Disclosure of Invention
The invention provides a motor control method for predicting a voltage vector sequence, which is used for reducing the torque fluctuation and flux linkage fluctuation of a permanent magnet synchronous motor so as to enable the motor to run more stably, and is described in detail as follows:
a method of motor control that predicts a sequence of voltage vectors, the method comprising the steps of:
through the influence of the sequencing of all voltage vectors in the two-level voltage source inverter on the fluctuation of the stator flux linkage vector, 12 voltage vector sequences beneficial to optimizing the control performance of the stator flux linkage vector are screened out;
sequencing 12 voltage vectors and bringing the voltage vectors into a predictive control set to establish a novel voltage vector sequence control set;
taking the effective value of the fluctuation amount of the stator flux linkage vector in one control period as an evaluation index;
evaluating stator flux linkage vector errors at each voltage vector switching moment in each control period, and constructing an evaluation function;
the action time of each basic voltage vector is obtained by a two-step method of confirming the phase angle and then confirming the amplitude.
Wherein, the sequencing of 12 voltage vectors is brought into a control set of predictive control, and the establishment of a novel voltage vector sequence control set specifically comprises:
Figure BDA0001719800010000021
further, the specific example of using the effective value of the fluctuation amount of the stator flux linkage vector in one control period as an evaluation index is as follows:
the effective value expression of the stator flux linkage vector fluctuation corresponding to different voltage vector orderings is as follows:
Figure BDA0001719800010000022
wherein VS ═ a, B, C, D; psis mA predicted value representing the switching time of each voltage vector in each control period of the stator flux linkage vector;
Figure BDA0001719800010000023
in the formula, #s0Representing the initial value of the stator flux linkage vector in each control period; sl＝Vs,l-Rsis(k) In which V iss,lRepresenting the vector of the applied base voltage at the ith of each control cycle; t islthRepresents Vs,lThe action time of (1).
In a specific implementation, the evaluation function is specifically:
Figure BDA0001719800010000024
Figure BDA0001719800010000025
wherein λ isNA weight factor representing a stator flux linkage vector error term at the end of each control period; psis mA predicted value representing the switching time of each voltage vector in each control period of the stator flux linkage vector; psis0Representing the initial value of the stator flux linkage vector in each control period; slRepresenting the stator flux linkage vector rate of change; t islthRepresents Vs,lThe action time of (c); vs,lRepresenting the vector of the applied base voltage at the ith of each control cycle.
Further, the two-step method of determining the phase angle and then determining the amplitude value is specifically to calculate the action time of each basic voltage vector as follows:
Figure BDA0001719800010000031
Figure BDA0001719800010000032
in the formula,. DELTA.psis＝ψs *-ψs(k)；S1And S2Stator flux linkage vector rate of change Sl。
The technical scheme provided by the invention has the beneficial effects that:
1. the method screens out all voltage vector sequences which are beneficial to optimizing stator flux linkage vector control performance in the two-level voltage source inverter, brings the screened voltage vector sequences into a control set, designs a voltage vector sequence control set, and establishes an evaluation system to select the optimal voltage vector sequence;
2. the method can be applied to the fields of motor speed regulation, power electronic control and the like, and has the advantages that the steady state fluctuation quantity of the electromagnetic torque and the stator flux linkage is effectively reduced by reasonably selecting the action sequence of the voltage vector, so that the motor can run more stably; meanwhile, the current distortion rate of the motor stator can be reduced, and the motor loss caused by current harmonics in the motor running process is reduced;
3. the method reduces the overall calculation complexity of the algorithm by reducing the voltage vector sequencing number to be evaluated in advance. The calculation efficiency is improved.
Drawings
FIG. 1 is a flow diagram of a predictive sequence control strategy implementation;
FIG. 2 is a topology diagram of a two-level voltage source inverter fed PMSM system;
FIG. 3 is a two-level voltage source inverter voltage vector diagram;
FIG. 4 is a block diagram of a predictive sequence control strategy architecture;
FIG. 5 is a sequence diagram of six voltage vectors in the voltage vector combination I ordered and corresponding to the switches;
wherein, (a) is a switching sequence diagram when the voltage vectors in the voltage vector combination I are applied according to the vector sequence VS ═ A; (b) the switching sequence diagram is applied when the voltage vectors in the voltage vector combination I are applied according to the vector sequence VS ═ B; (c) the switching sequence diagram is applied when the voltage vectors in the voltage vector combination I are applied according to the vector sequence VS-C; (d) the switching sequence diagram is used when the voltage vectors in the voltage vector combination I are applied according to the vector sequence VS-D; (e) the switching sequence diagram is applied when the voltage vectors in the voltage vector combination I are applied according to the vector sequence VS ═ E; (f) and the switching sequence diagram is applied when the voltage vectors in the voltage vector combination I are applied according to the vector sequence VS-F.
FIG. 6 is a trace of a stator flux linkage vector during a control cycle;
FIG. 7 is a diagram showing the difference between the effective values of the stator flux linkage vector fluctuation corresponding to any two kinds of voltage vector sequences in the voltage vector combination I;
wherein (a) is eA-eB(ii) a (b) Is eA-eC(ii) a (c) Is eA-eD(ii) a (d) Is eB-eC(ii) a (e) Is eB-eD(ii) a (f) Is eC-eD。
FIG. 8 is a graph of a transient experimental waveform of the predicted voltage vector sequence algorithm of the present invention;
FIG. 9 is a comparison of steady state performance of the predicted voltage vector sequence algorithm of the present invention versus conventional multi-vector predicted torque control;
wherein, (a) is a traditional two-vector prediction torque control steady-state oscillogram; (b) a steady state waveform diagram for three vector predicted torque control based on a discrete space vector modulation strategy; (c) is a steady state waveform diagram of the algorithm proposed by the present invention.
Fig. 10 compares the steady state performance with the optimal voltage vector ordering versus only a single kind of voltage vector ordering.
Wherein, (a) is a steady state experimental waveform chart when only 6 voltage vectors corresponding to VS ═ C in the table I are adopted for sorting; (b) the waveform diagram is a steady-state experimental waveform diagram when only 6 voltage vectors corresponding to VS-A in the table I are adopted for sorting; (c) the steady state experimental waveform diagram for selecting the optimal voltage vector ordering by using the method is provided.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention are described in further detail below.
Example 1
A method of motor control for predicting a sequence of voltage vectors, see fig. 1, the method comprising the steps of:
101: the influence of all voltage vector sequences in the two-level voltage source inverter on the fluctuation of the stator flux linkage vector is analyzed through quantization, and all voltage vector sequences which are beneficial to optimizing the control performance of the stator flux linkage vector are screened out;
102: all voltage vector sequences are brought into a predictive control set, and a novel voltage vector sequence control set is established; taking the effective value of the fluctuation amount of the stator flux linkage vector in one control period as an evaluation index;
103: evaluating stator flux linkage vector errors at each voltage vector switching moment in each control period, and constructing an evaluation function;
104: the action time of each basic voltage vector is obtained by a two-step method of confirming the phase angle and then confirming the amplitude.
In summary, in the embodiment of the present invention, the voltage vector sorting is brought into the control set through the steps 101 to 104, a novel voltage vector sorting control set is designed, and the stator flux linkage vector error value at each voltage vector switching time in each control period is evaluated through the constructed evaluation function, so as to select the optimal voltage vector sorting that minimizes the evaluation function. The method reduces the torque fluctuation and the stator flux linkage fluctuation on the basis of ensuring the good dynamic performance of the permanent magnet synchronous motor system through the steps, and meets various requirements in practical application.
Example 2
The scheme of example 1 is further described below with reference to fig. 2-7, and specific calculation formulas, which are described in detail below:
firstly, establishing a mathematical model of a permanent magnet synchronous motor:
in fig. 2, the switching states of the upper and lower bridge arms IGBT of the two-level voltage source inverter are complementary, so S can be usedA、 SBAnd SCThe switching states of an upper bridge arm IGBT and a lower bridge arm IGBT of three phases (A, B and C) of the level voltage source inverter are respectively shown, a 1 represents that the upper bridge arm IGBT is in an on state and the lower bridge arm IGBT is in an off state, and a 0 represents that the upper bridge arm IGBT is in the off state and the lower bridge arm IGBT is in the on state.
The level voltage source inverter has 8 switch combinations in total, output phase voltages corresponding to the 8 switch combinations are converted into a space vector form, and effective voltage space vectors with 6 amplitude values and fixed space phase angles can be obtained: v1(100)、 V2(110)、V3(010)、V4(011)、V5(001)、V6(101) (ii) a And 2 zero vectors: v0(000)、V7(111) As shown in fig. 3.
By a voltage vector V1For example, 100 indicates that the upper arm of the phase a is on, the lower arm is off, the upper arms of the phase B and the phase C are off, the lower arm is on, and the meanings of the other 5 effective voltage space vectors are analogized, which is not described in detail in the embodiments of the present invention. Wherein the effective voltage vector V1～V6The subscripts of (a) are the voltage vector hexagons in figure 3 numbered in the counterclockwise direction.
The voltage space vector can be expressed as follows:
Figure BDA0001719800010000051
in formula (1), VxRepresents the basic voltage vector, x is 0,1, …, 7; vdcRepresents a dc-side bus voltage; a ═ ej2 π/3。
Under a two-phase static coordinate system, an equation of a voltage vector and a stator flux linkage vector of the permanent magnet synchronous motor can be expressed as follows:
Figure BDA0001719800010000052
in the formula (2), Vs、isAnd psisRespectively representing a stator voltage vector, a stator current vector and a stator flux linkage vector; rsRepresenting the stator resistance; l issRepresenting the stator inductance; psifA rotor flux linkage vector.
Considering that the control period is short enough, the formula (2) can be discretized by Euler first-order forward difference method, and the stator flux linkage vector is at (k +1) TsThe predicted value of the time can be obtained by the following formula:
ψs(k+1)＝ψs(k)+VsTs-Rsis(k)Ts (3)
in formula (3), TsRepresents a control period; i.e. is(k) For the stator current vector measured at the k-th instant, phis(k) The stator flux linkage vector is observed by a flux linkage observer at the kth moment.
The euler first-order forward difference method is well known to those skilled in the art, and is not described in detail in the embodiments of the present invention.
Since the mechanical time constant of the permanent magnet synchronous motor is much larger than the electrical time constant, it can be assumed that the rotation angular velocity of the rotor flux linkage vector is constant within one control period, and thus the rotor flux linkage vector is at (k +1) TsThe phase angle at time is:
∠ψf(k+1)＝∠ψf(k)+ωrTs (4)
in formula (4), ωrThe rotating electrical angular velocity, angle psi, representing the rotor flux linkage vectorf(k) For rotor flux linkage vector at kTsThe phase angle of the time of day. Rotor flux linkage vector is in (k +1) TsThe predicted value at that time is:
Figure BDA0001719800010000061
in the formula (5), | ψfAnd | represents the amplitude of the rotor flux linkage vector and is a constant.
Permanent magnet synchronous motor at (k +1) TsThe electromagnetic torque at a time can be expressed as follows:
Figure BDA0001719800010000062
in formula (6), npRepresenting the number of pole pairs of the motor (a term of art).
Secondly, establishing a prediction sequence control set:
the two-level voltage source inverter has 6 effective basic voltage vectors and 2 zero vectors: v0(000)、V1(100)、 V2(110)、V3(010)、V4(011)、V5(001)、V6(101)、V7(111)。
The multi-vector predicted torque control applies a plurality of voltage vectors in one control cycle, and when 2 effective basic voltage vectors and 1 zero vector are applied in one control cycleTwo adjacent effective basic voltage vectors can be arbitrarily selected from the 6 effective basic voltage vectors and combined with the zero vector, so that 6 Vector Combinations (VC) are provided in total: and VC is I: v1,V2, V0/V7、VC＝II：V2,V3,V0/V7、VC＝III：V3,V4,V0/V7、VC＝IV：V4,V5,V0/V7、VC＝V：V5,V6, V0/V7And VC ═ VI: v6,V1,V0/V7。
In the embodiment of the invention, the voltage vectors in each voltage vector combination are applied according to a 5-segment symmetric manner. Taking the voltage vector combination VC ═ I as an example, when 2 effective voltage vectors V in the voltage vector combination are applied in one control period1, V2And zero vector V0Or V7In this case, the voltage vectors are arranged in the following 6 orders in one control cycle: v1-V2-V7-V2-V1、V2-V1-V0-V1-V2、V0-V1-V2-V1-V0、V7-V2-V1-V2-V7、V1-V7-V2-V7-V1、 V2-V0-V1-V0-V2。
Similarly, analyzing the arrangement sequence of the voltage vectors in the other 5 voltage vector combinations in each control period, it can be summarized that the 6 voltage vector orderings (VS ═ a, B, …, F) of the voltage vectors in the 6 voltage vector combinations in each control period can be collectively expressed as follows:
VS＝A：Vi-Vj-V7-Vj-Vi、VS＝B：Vj-Vi-V0-Vi-Vj、VS＝C：V0-Vi-Vj-Vi-V0、VS＝D：V7-Vj-Vi-Vj-V7、 VS＝E：Vi-V7-Vj-V7-Viand VS ═ F: vj-V0-Vi-V0-VjWhere (i, j) ═ 1,2), (3,2), (3,4), (5,4), (5,6), (1,6), where VS denotes the number of voltage vector ranks, and the 6 voltage vector ranks are respectively numbered a to B. In the above 6 voltage vector sorting, zero vector V0Or V7The selection of (c) is based on the lowest switching frequency.
Taking the voltage vector combination I as an example, the switching sequence corresponding to the 6 vector orderings is shown in fig. 5. As can be seen from comparing fig. 5(a) - (F), the voltage vector orderings a-D only have one-phase switching state change during each vector switching process, while the voltage vector orderings E and F have two-phase switching states simultaneously changed during the vector switching process. Therefore, in order to reduce the switching frequency and the switching times of the switching states, the voltage vector sorting E and F are eliminated. Similarly, 2 voltage vector orderings can be eliminated by analyzing the voltage vector orderings corresponding to other 5 voltage vector combinations II-VI. Therefore, the voltage vector ordering to be analyzed is shown in table 1.
TABLE 1
Figure BDA0001719800010000071
In order to quantitatively analyze the influence of different voltage vector sequences in the table 1 on the control performance of the stator flux linkage vector, the method
In the present embodiment, the effective value of the fluctuation amount of the stator flux linkage vector in one control cycle is used as the evaluation index. Different voltages
The effective value expression of the stator flux linkage vector fluctuation corresponding to the vector sorting is as follows:
Figure BDA0001719800010000081
wherein VS ═ a, B, C, D; psis m(m-1, 2, …,5) represents the voltage of the stator flux linkage vector in each control cycleThe predicted value at the time of vector switching. According to formula (3) there are:
Figure BDA0001719800010000082
in the formula, #s0Representing the initial value of the stator flux linkage vector in each control period; sl＝Vs,l-Rsis(k) In which V iss,lRepresenting the vector of the applied base voltage at the ith of each control cycle; t islthRepresents Vs,lThe action time of (1).
Optionally one of the voltage vector combinations listed above, the basic voltage vector V in the combinationi、Vj、V0/V7Corresponding 4 voltage vector sequences are substituted in formula (8) in consideration of Vs,l＝Vs,5，Vs,2＝Vs,4，T1th＝T5th，T2th＝T4th，ψs mThe trace of the amplitude of (c) in one control cycle is shown in fig. 6.
The formula (8) is substituted into the formula (7), the stator resistance term is ignored, and the effective value expression of the stator flux linkage error under the 4 voltage vector sequences corresponding to any one voltage vector combination is as follows:
Figure BDA0001719800010000083
Figure BDA0001719800010000084
Figure BDA0001719800010000085
Figure BDA0001719800010000086
in the formula, e0＝ψs *-ψs0；Ti、TjAnd T0Respectively representing effective voltage vectors Vi、VjTime of action with zero vector. As can be seen from equations (9) to (12), the effective value of flux linkage vector fluctuation corresponding to the four voltage vector orderings is related to the selection of the basic voltage vector and the respective action time thereof. The magnitude relation between the flux linkage vector fluctuation effective values corresponding to the voltage vector sequencing is compared by performing difference on pairwise equations (9) to (12), and the following expression can be obtained through arrangement:
Figure BDA0001719800010000091
Figure BDA0001719800010000092
Figure BDA0001719800010000093
Figure BDA0001719800010000094
Figure BDA0001719800010000095
Figure BDA0001719800010000096
in order to compare the magnitude relation between the effective values of the stator flux linkage errors under different switching sequences more intuitively, three-dimensional graphs are respectively drawn according to the expressions (13) to (18), as shown in fig. 7. In FIG. 7, the x-axis is the voltage vector ViTime of action TiThe y-axis being the voltage vector VjTime of action TjZ-axis is the flux linkage between different voltage vector orderingsThe difference between the effective values of the vector fluctuation. In FIG. 7, the control period and the magnitude of the voltage vector are normalized, i.e., the control period TsAnd magnitude of vector of basic voltage | Vi|、|VjAll are 1.
As can be seen from FIGS. 7(b) and 7(e), eAIs constantly equal to or less than eC，eBIs constantly equal to or less than eDThe results show that the voltage vector ordering C and D is not always optimal. Therefore, the vector sequences C and D can be eliminated, and in the actual implementation process of the control algorithm, only the influence of the vector sequences A and B on flux linkage vector fluctuation needs to be evaluated, namely the voltage vector sequence in a red dotted frame in the table I. In both types of voltage vector ordering, the zero vector is distributed in the middle of the effective voltage vector.
By analyzing the influence of different voltage vector orderings on the stator flux linkage vector fluctuation of the motor, the voltage vector ordering beneficial to reducing the stator flux linkage vector fluctuation amount is screened out, and meanwhile, in order to reduce the switching state switching times and reduce the switching frequency, the embodiment of the invention only needs to evaluate 12 types of A and B voltage vector orderings. Therefore, all voltage vectors that need to be analyzed by the embodiment of the present invention are sorted as shown in table 2.
TABLE 2
Figure BDA0001719800010000097
Figure BDA0001719800010000101
And (4) sequencing 12 voltage vectors and incorporating the voltage vectors into a predictive control set to establish a novel voltage vector sequence control set. The control set may be represented by:
Figure BDA0001719800010000102
thirdly, constructing an evaluation function:
in order to evaluate the influence of the voltage vector sequencing in the control set on the stator flux vector fluctuation amount, the embodiment of the invention evaluates the stator flux vector errors at each voltage vector switching time in each control period. Therefore, the embodiment of the present invention constructs the evaluation function as follows:
Figure BDA0001719800010000103
in formula (20), λNRepresenting the weight factor of the stator flux linkage vector error term at the end time of each control period, and determining the importance degree of the stator flux linkage vector error term at the end time of the control period; psis m(m-1, 2, …,5) represents the predicted value of the stator flux linkage vector at each voltage vector switching time in each control cycle; psis0Representing the initial value of the stator flux linkage vector in each control period; sl＝Vs,l-Rsis(k) Represents the rate of change of the stator flux linkage vector, where Vs,l(1,2, …, m) represents the l-th applied base voltage vector in each control period; t islthRepresents Vs,lThe action time of (1). Since the voltage vector is applied in a five-segment symmetric manner, Vs,1＝Vs,5，Vs,2＝Vs,4，S1＝S5，S2＝S4。
The angle calculation formula of the reference stator flux linkage vector is as follows:
Figure BDA0001719800010000104
in formula (21), Te *And | ψs *And | respectively represents the reference electromagnetic torque and the reference stator flux linkage vector magnitude.
The reference stator flux linkage vector expression formula is as follows:
ψs *＝|ψs *|∠ψs * (22)
fourthly, calculating the action time of the basic voltage vectors in different voltage vector sequences:
evaluating the evaluation function J under the sequence of each voltage vector1Minimum action time T of each basic voltage vectorlthThe problem with (1,2, …,5) is a convex optimization problem with constraints. Because the solving process is complex and online calculation cannot be realized, the embodiment of the invention adopts a step-by-step solving method to obtain the action time of the voltage vector. Formula (20)
The action time of each voltage vector can be respectively expressed as T1th＝T5th＝0.5μθμnTs，T2th＝T4th＝0.5(1-μθ)μnTs，
T3th＝(1-μn)TsWherein 0 is not more than mun≤1，0≤μθLess than or equal to 1. Coefficient munDetermine VsAnd when μnWhen 1 hour VsAlways falls on the boundary of the voltage vector hexagon; coefficient muθDetermines the equivalent composite vector VsThe angle of (c).
By first determining VsIs re-determined by phase angle ofsThe step of amplitude values finds the action time of each elementary voltage vector. Firstly, set VsIs the maximum value, coefficient munFormula (20) is substituted by 1, and evaluation function J is evaluated1Finding the unknown quantity muθTo find the derivative of order dJ1/dμθMu 0θ. To muθThe solution of (2) is a typical quadratic optimization problem, and after neglecting the influence of the resistance term, the solution is shown as follows:
Figure BDA0001719800010000111
in the formula,. DELTA.psis＝ψs *-ψs(k)；S1And S2Is the stator flux linkage vector change rate S in the formula (20)lSince the voltage vector is applied in a five-segment symmetric manner, S can be used1Substituted for S5，S2By replacing S4And is neglected inAfter influence of stator resistance term S3＝0。
Then set munFor unknown quantities, the calculated μθIn formula (20), evaluation function J is evaluated1Finding the unknown quantity munTo find the derivative of order dJ1/dμnMu 0θ. To munThe solution of (a) is also a quadratic optimization problem, ignoring the stator resistance term for simplifying the calculation formula, the display solution is as follows:
Figure BDA0001719800010000112
wherein, in order to reduce the expression complexity of the formula (24), mu is usedmRepresents 1-. mu.θ。
Is solved to obtain muθAnd munThen, the action time T of each voltage vector in the voltage vector sequencing can be obtained1th～T5th。
Sorting the basic voltage vector V in each alternative voltage vector in the control set CSs,lAnd each basic voltage vector Vs,lTime of action T1th～T5thSubstituting into the evaluation function J1In the method, the error of stator flux linkage vector when applying different voltage vector sequences is evaluated, so as to select an evaluation function J1The smallest voltage vector is ranked as the optimal ranking. Finally, the switching signal S of the three-phase bridge arm corresponding to the optimal voltage vector sequence is obtainedA、SB、SCAnd outputs it to the inverter.
And fifthly, realizing a permanent magnet synchronous motor prediction sequence control strategy:
evaluating all voltage vector orderings by an exhaustive method results in a large amount of computation. Thus, embodiments of the present invention utilize the optimization problem of classical finite control set predictive torque control to reduce the number of alternative voltage vector orderings in advance.
The optimization problem can be expressed as follows:
Figure BDA0001719800010000121
phi in equation (3)s(k +1) is replaced by psis *Then equation (25) can be rewritten as:
ψs *＝ψs(k)+Vs *Ts-Rsis(k)Ts(26)
in the formula, Vs *Representing a reference voltage vector that meets the requirements for stator flux linkage vector dead-beat control.
By substituting formula (25) with formula (3) and formula (26), formula (25) can be rewritten as:
Figure BDA0001719800010000122
according to formula (27), J3The magnitude of the value is related to the distance between the basic voltage vector and the reference voltage vector. Thus, the distance V, which is the 2 effective fundamental voltage vectors that minimize the value of equation (27)s *The last 3 voltage vectors are 2 effective basic voltage vectors (denoted as V respectively)x optAnd Vx sub) And zero vector V0,7. Due to the distance Vs *The last 2 valid basic voltage vectors are necessarily adjacent, therefore, the embodiment of the present invention reduces the voltage vector ordering to be evaluated from 12 to the voltage vector combination (V)x opt、Vx sub、V0\V7) Corresponding 2 voltage vector orderings.
Therefore, by solving the optimization problem in equation (25), J is selected among the 6 effective fundamental voltage vectors2Minimum and next-to-minimum Vx optAnd Vx sub. Combining voltage vectors (V)x opt、Vx sub、V0\V7) Corresponding 2 kinds of voltage vector sequencing are substituted into an evaluation function J in an equation (20)1The optimal voltage vector ordering can be selected by performing the evaluation. Whereby the number of voltage vector orderings to be evaluated is reducedThe number of the plants is 2.
In conclusion, the motor can run more stably through the steps; meanwhile, the current distortion rate of the motor stator can be reduced, the motor loss caused by current harmonics in the motor operation process is reduced, and various requirements in practical application are met.
Example 3
The feasibility verification of the schemes of examples 1 and 2 is performed below in conjunction with specific experimental data, fig. 8-10, and simulation waveforms, as described in detail below:
the embodiment of the invention is tested and verified in a 6.0kW permanent magnet synchronous motor system. The motor parameters are shown in table 3. In the experimental test platform, a Digital Signal Processor (DSP) TMS320F28335 performed the implementation of the algorithm and the load was provided by an 11.2kW induction motor, which was controlled by S120 manufactured by siemens.
TABLE 3
Figure BDA0001719800010000131
First, transient performance verification
Fig. 8 shows the transient performance experimental waveform of the algorithm proposed in the example of the present invention. In the experimental process, the rotating speed of the motor is 100r/min, the load is 50Nm, then the given rotating speed of the motor is suddenly changed to 200r/min, and finally the load of the motor is suddenly changed to 100 Nm. It can be seen from fig. 8 that the torque and the stator flux linkage of the motor can accurately track the given value thereof, and the tracking performance is good.
Second, comparison with Steady State Performance of conventional Multi-vector predicted Torque control
The experiment compares the steady state performance of the algorithm provided by the embodiment of the invention with a two-vector predicted torque control algorithm and a three-vector predicted torque control algorithm based on a discrete space vector modulation strategy, wherein the control period of the two-vector predicted torque control algorithm is 100 mu s, and the control period of the three-vector predicted torque control algorithm and the provided algorithm is 200 mu s. Of the three algorithms, the switching frequency fswAll are around 3.4kHz, and are chargedThe operation conditions of the machine are as follows: rotation speed 200r/min, load torque 100 Nm.
Fig. 9 shows steady state experimental waveforms of a two-vector predicted torque control algorithm, a three-vector predicted torque control algorithm based on a discrete space vector modulation strategy, and the proposed algorithm. As can be seen by comparing fig. 9(a) - (c), the torque and flux linkage fluctuations are the largest in fig. 9(a), and the stator current THD is also the largest, and the torque and flux linkage fluctuations are smaller in fig. 9(b) compared to fig. 9(a), and the current THD is further reduced, indicating that the steady-state performance of the three-vector predicted torque control is better than that of the two-vector predicted torque control. However, compared with fig. 9(a) and 9(b), the torque, flux linkage fluctuation and current THD of fig. 9(c) are all minimal, and the comparison result shows that the torque, stator flux linkage fluctuation and current THD of the proposed algorithm are all significantly reduced compared with the conventional multi-vector predicted torque control. Therefore, steady-state experimental results show that the algorithm provided by the embodiment of the invention further improves the steady-state performance compared with the traditional multi-vector prediction torque control algorithm.
Three, steady state performance verification
Fig. 10 shows steady state waveform diagrams of electromagnetic torque, stator flux linkage, stator current, and voltage vector selection when different types of voltage vector ordering are selected. Fig. 10(a) shows the steady state experimental waveforms when only the 6 voltage vectors corresponding to VS ═ C in table I are used for sorting; fig. 10(b) shows the steady state experimental waveforms when only the 6 voltage vectors corresponding to VS ═ a in table I are used for sorting; fig. 10(c) shows the steady state experimental waveform of the proposed algorithm of the present example. In the figure, VS 1,2 and 3 correspond to VS a, B and C, respectively. In the experiment, the motor speed is 200r/min and the load torque is 100 Nm. Comparing the experimental waveforms of the torque and the stator flux linkage in fig. 10, it can be seen that the torque and the stator flux linkage fluctuation of the algorithm provided in the example of the present invention are both smaller than the voltage vector sorting corresponding to only VS ═ a or VS ═ C, and the electromagnetic torque and the stator flux linkage fluctuation are the largest when the voltage vector sorting is performed only in 6 kinds corresponding to VS ═ C, which is consistent with the theoretical analysis result in the example two.
In the embodiment of the present invention, except for the specific description of the model of each device, the model of other devices is not limited, as long as the device can perform the above functions.
Those skilled in the art will appreciate that the drawings are only schematic illustrations of preferred embodiments, and the above-described embodiments of the present invention are merely provided for description and do not represent the merits of the embodiments.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (4)

1. A method of motor control that predicts a sequence of voltage vectors, the method comprising the steps of:
through the influence of the sequencing of all voltage vectors in the two-level voltage source inverter on the fluctuation of the stator flux linkage vector, 12 voltage vector sequences beneficial to optimizing the control performance of the stator flux linkage vector are screened out;
sequencing 12 voltage vectors and bringing the voltage vectors into a predictive control set to establish a novel voltage vector sequence control set;
taking the effective value of the fluctuation amount of the stator flux linkage vector in one control period as an evaluation index;
evaluating stator flux linkage vector errors at each voltage vector switching moment in each control period, and constructing an evaluation function;
the action time of each basic voltage vector is solved by a two-step method of confirming the phase angle and then confirming the amplitude;
wherein all voltage vectors in the two-level voltage source inverter are ordered as:
when VC ═ I: voltage vector ordering VS ═ a of V1-V2-V7-V2-V1The voltage vector order VS is V2-V1-V0-V1-V2The voltage vector order VS is C is V0-V1-V2-V1-V0The voltage vector order VS is D is V7-V2-V1-V2-V7；
When VC ═ II:voltage vector ordering VS ═ a of V3-V2-V7-V2-V3The voltage vector order VS is V2-V3-V0-V3-V2The voltage vector order VS is C is V0-V3-V2-V3-V0The voltage vector order VS is D is V7-V2-V3-V2-V7；
When VC ═ III: voltage vector ordering VS ═ a of V3-V4-V7-V4-V3The voltage vector order VS is V4-V3-V0-V3-V4The voltage vector order VS is C is V0-V3-V4-V3-V0The voltage vector order VS is D is V7-V4-V3-V4-V7；
When VC is equal to IV: voltage vector ordering VS ═ a of V5-V4-V7-V4-V5The voltage vector order VS is V4-V5-V0-V5-V4The voltage vector order VS is C is V0-V5-V4-V5-V0The voltage vector order VS is D is V7-V4-V5-V4-V7；
When VC ═ V: voltage vector ordering VS ═ a of V5-V6-V7-V6-V5The voltage vector order VS is V6-V5-V0-V5-V6The voltage vector order VS is C is V0-V5-V6-V5-V0The voltage vector order VS is D is V7-V6-V5-V6-V7；
When VC ═ VI: voltage vector ordering VS ═ a of V1-V6-V7-V6-V1The voltage vector order VS is V6-V1-V0-V1-V6The voltage vector order VS is C is V0-V1-V6-V1-V0The voltage vector order VS is D is V7-V6-V1-V6-V7；
Wherein, V0、V1、V2、V3、V4、V5、V6And V7The voltage source inverter is used for representing 8 basic voltage vectors output by a two-level voltage source inverter, wherein subscripts 0-7 represent the reference numbers of the basic voltage vectors respectively, and V1、V2、V3、V4、V5And V6Representing the effective fundamental voltage vector, V0And V7Is a zero vector; VC denotes a voltage vector combination consisting of any two adjacent effective basic voltage vectors and a zero vector, and VC ═ I corresponds to the vector combination: v1,V2,V0Or V7VC ═ II corresponds to the vector combination: v2,V3,V0Or V7VC ═ III corresponds to vector combinations: v3,V4,V0Or V7VC ═ IV corresponds to vector combinations: v4,V5,V0Or V7VC corresponds to a vector combination: v5,V6,V0Or V7VC ═ VI corresponds to vector combinations: v6,V1,V0Or V7(ii) a I. II, III, IV, V and VI denote the reference numbers of the vector combinations; VS represents a voltage vector sequence formed by arranging a plurality of basic voltage vectors in different voltage vector combinations in different orders in one control period, and VS is equal to a, B, C and D; A. b, C and D denote the labels for voltage vector ordering;
the 12 voltage vectors which are beneficial to optimizing the stator flux linkage vector control performance are ordered as follows:
when VC ═ I: voltage vector ordering VS ═ a of V1-V2-V7-V2-V1The voltage vector order VS is V2-V1-V0-V1-V2；
When VC ═ II: voltage vector ordering VS ═ a of V3-V2-V7-V2-V3The voltage vector order VS is V2-V3-V0-V3-V2；
When VC ═ III: voltage vector ordering VS ═ a of V3-V4-V7-V4-V3The voltage vector order VS is V4-V3-V0-V3-V4；
When VC is equal to IV: voltage vector ordering VS ═ a of V5-V4-V7-V4-V5The voltage vector order VS is V4-V5-V0-V5-V4；
When VC ═ V: voltage vector ordering VS ═ a of V5-V6-V7-V6-V5The voltage vector order VS is V6-V5-V0-V5-V6；
When VC ═ VI: voltage vector ordering VS ═ a of V1-V6-V7-V6-V1The voltage vector order VS is V6-V1-V0-V1-V6；
The method comprises the steps of bringing 12 voltage vector sequences into a predictive control set, and specifically establishing a novel voltage vector sequence control set as follows:
Figure FDA0003429193420000021
2. the motor control method for predicting a voltage vector sequence according to claim 1, wherein the evaluation index using an effective value of a fluctuation amount of the stator flux linkage vector in one control cycle is specifically:
the effective value expression of the stator flux linkage vector fluctuation corresponding to different voltage vector orderings is as follows:
Figure FDA0003429193420000022
in the formula, a subscript VS represents a reference number of voltage vector sorting, and VS ═ a, B, C, D; t issRepresents a control period; psis *Is a reference stator flux linkage vector; psis mA predicted value representing the switching time of each voltage vector in each control period of the stator flux linkage vector;
Figure FDA0003429193420000031
in the formula, #s0Representing the initial value of the stator flux linkage vector in each control period; slRepresents Vs,lRate of change of stator flux linkage vector under influence, and Sl＝Vs,l-Rsis(k) In which V iss,lRepresents the ith applied basic voltage vector in the sequence of different voltage vectors in a control period, wherein l is 1,2,3,4, 5; rsRepresenting the stator resistance; i.e. is(k) The measured stator current vector at the kth moment; t islthRepresenting the l applied basic voltage vector Vs,lThe action time of (1).
3. The method according to claim 1, wherein the evaluation function is specifically:
Figure FDA0003429193420000032
Figure FDA0003429193420000033
in the formula, λNA weight factor representing a stator flux linkage vector error term at the end of each control period; psis *Is a reference stator flux linkage vector; psis mA predicted value representing the switching time of each voltage vector in each control period of the stator flux linkage vector; psis 5A predicted value representing the action ending time of the 5 th applied basic voltage vector of the stator flux linkage vector in one control period; psis0Representing the initial value of the stator flux linkage vector in each control period; slRepresents Vs,lRate of change of stator flux linkage vector under influence, and Sl＝Vs,l-Rsis(k) In which V iss,lRepresenting the ith applied basic voltage vector in different voltage vector sequences in a control period; rsRepresenting the stator resistance; i.e. is(k) The measured stator current vector at the kth moment; t islthRepresenting the l applied basic voltage vector Vs,lThe action time of (1).
4. The method as claimed in claim 1, wherein the step of determining the action time of each basic voltage vector by determining the phase angle and then determining the amplitude comprises:
the action time of each basic voltage vector is respectively represented as T1th、T2th、T3th、T4thAnd T5thAnd, T1th＝T5th＝0.5μθμnTs，T2th＝T4th＝0.5(1-μθ)μnTs，T3th＝(1-μn)TsWherein 0 is not more than muθ≤1，0≤μn≤1；
Wherein, muθAnd munThe calculation steps are as follows:
Figure FDA0003429193420000034
Figure FDA0003429193420000035
in the formula, λNWeights representing stator flux linkage vector error terms at the end of each control periodA factor; delta psis＝ψs *-ψs(k) Wherein ψs *For reference stator flux linkage vector, #s(k) A stator flux linkage vector is obtained by observing at the kth moment by using a flux linkage observer; s1＝Vs,1-Rsis(k)，S2＝Vs,2-Rsis(k) Wherein R issRepresenting the stator resistance, i, of a permanent-magnet synchronous machines(k) Representing the stator current vector measured at the kth time; vs,1Representing the applied basic voltage vector of the No. 1 in different voltage vector sequences in a control period; vs,2Representing the 2 nd applied basic voltage vector in different voltage vector sequences in one control period; t issRepresents a control period; mu.smRepresents 1-. mu.θ。
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