CN110266238B - Finite state set model prediction PMSM direct torque control simplification method - Google Patents

Finite state set model prediction PMSM direct torque control simplification method Download PDF

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CN110266238B
CN110266238B CN201910610311.2A CN201910610311A CN110266238B CN 110266238 B CN110266238 B CN 110266238B CN 201910610311 A CN201910610311 A CN 201910610311A CN 110266238 B CN110266238 B CN 110266238B
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torque
voltage vector
flux linkage
control
stator flux
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CN110266238A (en
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李耀华
杨启东
任佳越
师浩浩
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Changan 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
    • 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
    • H02P21/28—Stator flux based control
    • H02P21/30—Direct torque control [DTC] or field acceleration method [FAM]
    • 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

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Abstract

The invention discloses a method for simplifying direct torque control of a finite state set model prediction PMSM (permanent magnet synchronous motor), which comprises the steps of calculating a cost function g value, substituting seven basic voltage vector sets, adding a hysteresis control signal, adding a sector position signal and a torque angle signal for judgment, and obtaining a voltage vector with the minimum cost function; adding a current torque angle signal, and simplifying an alternative voltage vector set by taking different hysteresis control signals, sector position signals and ranges of different torque angles as limiting conditions; and according to the torque ripple root-mean-square error, the flux linkage ripple root-mean-square error, the evaluation function average value and the average switching frequency, taking 30 and 45 degrees as dividing boundaries, and reducing the calculation load of model prediction control by adopting a simplified alternative voltage vector set control strategy to realize PMSM direct torque simplified control. The invention reduces the calculation burden and further reduces the times of switching the meter while maintaining good control performance.

Description

Finite state set model prediction PMSM direct torque control simplification method
Technical Field
The invention belongs to the technical field of motor control, and particularly relates to a finite state set model prediction PMSM direct torque control simplification method.
Background
The direct torque control technology is based on a stator flux linkage coordinate system and directly takes the torque as a control object, so that a large amount of calculation and dependency on motor parameters during rotation coordinate transformation are avoided, the dynamic performance is good, and the torque response time is short.
In the direct torque prediction control system of the surface permanent magnet synchronous motor, six basic voltage vectors and two zero voltage vectors are introduced, an evaluation function is introduced, and the voltage vector with the minimum evaluation function is directly output according to the angular position of a stator flux linkage at a static coordinate in the aspect of comprehensive consideration of a torque error and a stator flux linkage error.
However, along with variables and operation functions, the time and complexity of prediction calculation operation are increased, so that a simplified method for predicting PMSM direct torque control based on a finite state set model of a voltage vector utilization rate rule is provided, and the performance of a control system is optimized.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a simplified method for predicting PMSM direct torque control by using a finite state set model, which can reduce the number of prediction operations while keeping the control performance equivalent, and effectively improve the real-time performance of the system.
The invention adopts the following technical scheme:
a finite state set model prediction PMSM direct torque control simplification method comprises the following steps:
s1, calculating a cost function g value through the current torque, the stator flux linkage, the reference torque, the reference flux linkage, the angular position of the stator flux linkage, the stator flux linkage amplitude value at the next moment and the torque value, and bringing seven basic voltage vector sets into the cost function, wherein the model prediction control principle is to select a voltage vector which enables the cost function to be minimum;
s2, adding a hysteresis control signal, adding a sector position signal and a torque angle signal for judgment, and calculating a cost function g value according to the stator flux amplitude and the torque value at the next moment to obtain a voltage vector with the minimum cost function;
s3, adding a current torque angle signal, taking different hysteresis control signals, sector position signals and different torque angle ranges as limiting conditions, abandoning voltage vectors with low utilization rate, switching different alternative voltage alternative sets, and simplifying alternative voltage vector sets;
and S4, according to the torque ripple root mean square error, the flux linkage ripple root mean square error, the evaluation function average value and the average switching frequency, taking 30 and 45 degrees as dividing boundaries, and reducing the calculation load of model prediction control by adopting a simplified alternative voltage vector set control strategy to realize PMSM direct torque simplified control.
Specifically, the simplified alternative voltage vector set control strategy is as follows:
stator flux linkage sector theta1When flux linkage is added and torque is added, the torque angle is less than 45 degrees, and the candidate voltage vector set is { V0，V1，V2，V3Torque angle greater than 45 °, set of candidate voltage vectors as { V }0，V2，V3，V6}；
When the flux linkage is increased and the torque is reduced, the torque angle is less than 30 degrees, and the candidate voltage vector set is { V0，V1，V4，V5，V6Torque angle greater than 30 deg., and set of candidate voltage vectors as { V }0，V5，V6}；
When the flux linkage is reduced and the torque is increased, the torque angle is less than 30 degrees, and the candidate voltage vector set is { V0，V1，V4，V2，V3Torque angle greater than 30 deg., and set of candidate voltage vectors as { V }0，V2，V3}；
When the flux linkage is reduced and the torque is reduced, the torque angle is less than 45 degrees, and the candidate voltage vector set is { V0，V4，V5，V6Torque angle greater than 45 °, set of candidate voltage vectors as { V }0，V3，V5，V6}。
Specifically, in step S1, six basic voltage vectors V from the origin to six vertices of a hexagon are determined from the pm synchronous motor voltage vector diagram1～V6And 1 zero voltage vector, determining the voltage vector with the minimum cost function value according to the torque and the stator flux linkage, and outputting the switching state of the voltage vector, wherein the voltage vector candidate set comprises the following components:
Figure BDA0002122144940000031
the amplitude of 6 non-zero voltage vectors is 2Udc/3，UdcThe zero voltage vector magnitude is zero for the dc bus voltage.
Further, six basic voltage vectors V1～V6Angle of (2)Degree set alpha1-6The calculation is as follows:
α1-6∈{-θs(k),60°-θs(k),120°-θs(k),180°-θs(k),240°-θs(k),300°-θs(k)}
wherein, thetas(k) The stator flux angular position under the static coordinate system.
Specifically, in step S1, the cost function value g and the cost function average value gaveThe calculation is as follows:
Figure BDA0002122144940000032
Figure BDA0002122144940000033
wherein, Te *For reference torque, Te(k +1) is the torque at the next time,
Figure BDA0002122144940000034
for reference to the stator flux linkage,
Figure BDA0002122144940000035
is the stator flux linkage at the next moment.
Further, the flux linkage and torque changes are as follows:
Figure BDA0002122144940000036
Figure BDA0002122144940000037
Figure BDA0002122144940000038
where Δ t is a voltage vectorThe time of action of (a) is,
Figure BDA0002122144940000039
as a vector of voltage, #fIs the rotor flux, delta is the torque angle, and alpha is the angle between the voltage vector and the stator flux.
Specifically, in step S4, the torque ripple root mean square error Trip_RMSEThe calculation is as follows:
Figure BDA0002122144940000041
wherein, TeIs the torque at the present moment in time,
Figure BDA0002122144940000042
for reference torque, n is the number of samples.
Specifically, in step S4, the stator flux linkage ripple root mean square error ψrip_RMSEThe calculation is as follows:
Figure BDA0002122144940000043
wherein psisIs the stator flux linkage at the current moment,
Figure BDA0002122144940000044
for reference stator flux linkage, n is the number of samples.
Specifically, in step S4, the average value m of the evaluation function isaveThe calculation is as follows:
Figure BDA0002122144940000045
wherein n is the number of samples,
Figure BDA0002122144940000046
for reference stator flux linkage, Te *For reference torque, TeFor the rotation of the current timeMoment.
Specifically, in step S4, the average switching frequency faveThe calculation is as follows:
Figure BDA0002122144940000047
where N is the number of samples, NswitchingThe total number of times of switching the inverter, and t is the simulation duration.
Compared with the prior art, the invention has at least the following beneficial effects:
the invention discloses a simplified method for predicting PMSM direct torque control by a finite state set model, which determines a basic voltage vector at the next moment through the angular position of a stator flux linkage, the torque ripple and the stator flux linkage ripple, analyzes from seven basic voltage vectors, calculates a cost function g value through the current torque, the stator flux linkage, a reference torque, the flux linkage and the angular position of the stator flux linkage, and the stator flux linkage amplitude and the torque value at the next moment, and obtains a voltage vector with the minimum cost function.
Furthermore, under the constraint of increasing flux sector, flux and torque hysteresis control and torque angle signal judgment, the cost function g value can be calculated again according to the stator flux amplitude and the torque value at the next moment, and the voltage vector with the minimum cost function can be obtained.
Furthermore, under the additional conditions of adding flux sector, flux and torque hysteresis control and torque angle range, different torque angle intervals are divided according to the trend of the voltage vector utilization rate, different voltage vector alternative sets are switched, and the requirement of simplifying the sets and keeping the good control performance of the system is met.
Furthermore, a series of evaluation indexes are provided for the model prediction system, the provided simplified voltage vector alternative set is compared with seven basic voltage vector sets on the aspect of control performance, and the control system based on the simplified voltage vector alternative set is verified to sacrifice a small amount of control performance so as to reduce the calculation burden of model prediction control.
In conclusion, the invention reduces the calculation burden and further reduces the times of switching the meter while maintaining good control performance.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a diagram of a PMSM model predictive control system using 7 sets of fundamental voltage vectors;
FIG. 2 is a flow chart of a PMSM model predictive control using 7 sets of fundamental voltage vectors;
FIG. 3 is a diagram of a PMSM model predictive control system using a reduced set of fundamental voltage vectors;
FIG. 4 is a flow chart of a PMSM model predictive control using a reduced set of basis voltage vectors;
FIG. 5 is a voltage vector diagram of a permanent magnet synchronous motor;
FIG. 6 is a diagram of a PMSM model predictive control speed waveform using 7 sets of fundamental voltage vectors;
FIG. 7 is a graph of a PMSM model predicted control torque waveform using 7 sets of basis voltage vectors;
FIG. 8 is a graph of a PMSM model predictive control stator flux linkage amplitude waveform using 7 sets of fundamental voltage vectors;
FIG. 9 is a stator flux linkage trajectory diagram under a permanent magnet synchronous motor model predictive control static coordinate system using 7 basic voltage vector sets;
fig. 10 is a graph of a model predictive control a-phase stator current for a permanent magnet synchronous machine using 7 sets of fundamental voltage vectors;
FIG. 11 is a graph of a PMSM model predicted control torque angle waveform using 7 sets of basis voltage vectors;
FIG. 12 is a schematic diagram of a PMSM model predictive control stator flux linkage sector and voltage vectors using 7 sets of fundamental voltage vectors;
FIG. 13 is a graph of a PMSM model predictive control speed waveform using a reduced set of fundamental voltage vectors;
FIG. 14 is a graph of a PMSM model predicted control torque waveform using a reduced set of basis voltage vectors;
FIG. 15 is a graph of a PMSM model predictive control stator flux linkage amplitude waveform using a reduced set of basis voltage vectors;
FIG. 16 is a stator flux linkage trajectory diagram under a PMSM model predictive control stationary coordinate system using a simplified set of fundamental voltage vectors;
fig. 17 is a graph of a permanent magnet synchronous machine model predictive control of a-phase stator current using a reduced set of basis voltage vectors.
Detailed Description
Referring to fig. 1 and 2, the present invention provides a simplified method for predicting PMSM direct torque control based on a finite state set model of voltage vector utilization rule, which first calculates a cost function g value according to a current torque and stator flux linkage, a reference torque and reference flux linkage, and an angular position of the stator flux linkage, and a stator flux linkage amplitude value and a torque value at the next moment, and selects a basic voltage vector with the minimum g value.
Referring to fig. 3 and 4, a hysteresis signal, a sector position signal, and a torque angle are added to simplify a candidate voltage set, and a cost function g value is calculated according to a stator flux amplitude and a torque value at the next time, so as to select a basic voltage vector with the minimum g value.
The invention discloses a finite state set model prediction PMSM direct torque control simplification method, which comprises the following steps:
s1, calculating a cost function g value through the current torque and stator flux linkage, the reference torque and flux linkage and the angular position of the stator flux linkage, and the stator flux linkage amplitude and torque value at the next moment, and bringing seven basic voltage vector sets into the cost function, wherein the model prediction control principle is to select a voltage vector which enables the cost function to be minimum;
referring to fig. 5, six basic voltage vectors V from the origin to six vertices of a hexagon are determined according to the voltage vector diagram of the pm synchronous motor1～V6And 1 zero potentialAnd the voltage vector is used for determining the voltage vector with the minimum cost function value according to the torque and the stator flux linkage, and outputting the switching state of the voltage vector. Wherein the amplitude of 6 non-zero voltage vectors is 2Udc/3，UdcThe zero voltage vector magnitude is zero for the dc bus voltage. The alternative set of voltage vectors is as follows:
Figure BDA0002122144940000071
six basic voltage vectors V1～V6Angle set alpha of1-6The calculation is as follows in equation (2):
α1-6∈{-θs(k),60°-θs(k),120°-θs(k),180°-θs(k),240°-θs(k),300°-θs(k)} (2)
wherein, thetas(k) The stator flux angular position under the static coordinate system.
And according to the torque and the stator flux linkage, determining a voltage vector with the minimum cost function value, and outputting the switching state of the voltage vector.
After the voltage vector is applied, the flux linkage and the torque change as shown in formulas (3) and (4).
Figure BDA0002122144940000081
Figure BDA0002122144940000082
The model prediction cost function is shown in equation (5):
Figure BDA0002122144940000083
the mean value of the model prediction cost function is shown in formula (6):
Figure BDA0002122144940000084
the torque ripple root mean square error is shown in equation (7):
Figure BDA0002122144940000085
the stator flux linkage pulsation root mean square error is shown as formula (8):
Figure BDA0002122144940000086
the average evaluation function is shown in formula (9):
Figure BDA0002122144940000087
the average switching frequency is shown in equation (10):
Figure BDA0002122144940000088
and S2, judging by adding a hysteresis control signal and a sector position signal and a torque angle signal, and calculating the cost function g value again by the stator flux amplitude and the torque value at the next moment to obtain the voltage vector with the minimum cost function.
And S3, adding a current torque angle signal, analyzing that the voltage vector is selected unevenly under different hysteresis control signals and sector position signals, presenting a certain height rule trend along with the voltage utilization rate of the torque angle signal, simplifying an alternative voltage vector set under different torque angle ranges, abandoning part of voltage vectors with lower selection rates, dividing different torque angle intervals, switching different voltage vector sets, and sacrificing a small amount of control performance to reduce the calculation burden of model prediction control.
And S4, comparing the proposed simplified voltage vector alternative set with seven basic voltage vector sets on the aspect of control performance, wherein the proposed simplified voltage vector alternative set comprises a cost function mean value, a torque root mean square error and a stator flux linkage root mean square error, and evaluating the function mean value and the average switching frequency. The verification can achieve the purpose of reducing the operation burden while maintaining good performance.
The simplified alternative voltage vector set control strategy is as follows:
stator flux linkage sector theta1When flux linkage is added and torque is added, the torque angle is less than 45 degrees, and the candidate voltage vector set is { V0，V1，V2，V3Torque angle greater than 45 °, set of candidate voltage vectors as { V }0，V2，V3，V6}；
When the flux linkage is increased and the torque is reduced, the torque angle is less than 30 degrees, and the candidate voltage vector set is { V0，V1，V4，V5，V6Torque angle greater than 30 deg., and set of candidate voltage vectors as { V }0，V5，V6}；
When the flux linkage is reduced and the torque is increased, the torque angle is less than 30 degrees, and the candidate voltage vector set is { V0，V1，V4，V2，V3Torque angle greater than 30 deg., and set of candidate voltage vectors as { V }0，V2，V3}；
When the flux linkage is reduced and the torque is reduced, the torque angle is less than 45 degrees, and the candidate voltage vector set is { V0，V4，V5，V6Torque angle greater than 45 °, set of candidate voltage vectors as { V }0，V3，V5，V6}。
From this alternative voltage vector sets for other stator flux linkage sectors can be derived recursively.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The simulation parameters of the surface permanent magnet synchronous motor system are as follows:
a surface permanent magnet synchronous motor model prediction torque control simulation model is established based on MATLAB/Simulink.
The simulation model is a discrete model, and the sampling period is 5 multiplied by 10 < -5 > s.
The dc bus voltage is 312V.
The parameters of the rotating speed PI regulator are as follows: KP is 5, KI is 10, and the PI regulator output upper and lower limits are [ -35, 35 ].
The reference speed was 60rpm, the load torque was 18n.m, and the corresponding torque angle was 29 °.
The reference stator flux linkage amplitude is 0.3 Wb.
The simulation total duration is 2 s.
The parameters of the surface permanent magnet synchronous motor for simulation are shown in table 1.1.
TABLE 1.1 simulation surface-mounted PMSM parameters
Figure BDA0002122144940000101
Figure BDA0002122144940000111
The simulation results are shown in fig. 6 to 11, and the simulation results indicate that the model predicted torque control performance is good. The steady state torque angles averaged about 29 degrees and varied over a range of about (25 °, 33 °). The model prediction torque control based on the candidate voltage vector set expressed by the formula (1) requires 7 prediction calculations each time, and the calculation amount is large.
Meanwhile, simulation results show that the use of the 7 voltage vectors by the model predictive torque control is not balanced. Defining the voltage vector utilization rate as shown in formula (11), wherein N is the total number of times of voltage vectors applied by model predicted torque control in a certain time period, and Ni is the voltage vector V0～V6Total number of applications.
Figure BDA0002122144940000112
7 voltage vectors V0～V6The utilization over the simulation time 2s is shown in table 1.2.
TABLE 1.2 Voltage vector utilization
Figure BDA0002122144940000113
The stator flux linkage position has some effect on the flux linkage and torque effects of the applied voltage vector. Under the judgment of the stator flux linkage sectors, 7 voltage vectors V under different stator flux linkage sectors0～V6The utilization within the simulation time 2s is shown in table 1.3.
TABLE 1.3 Voltage vector utilization
Figure BDA0002122144940000114
Figure BDA0002122144940000121
The flux and torque increase and decrease control signals output by the flux and torque hysteresis comparators also have certain influence on the voltage utilization rate. Under the judgment of increase and decrease control signals of flux linkage and torque, 7 voltage vectors V under different stator flux linkage sectors0～V6The utilization within the simulation time 2s is shown in tables 1.4 to 1.7, in which the torque hysteresis width is 0.02n.m and the flux linkage hysteresis width is 0.002 Wb.
TABLE 1.4 Voltage vector utilization (increase flux linkage, increase torque)
Figure BDA0002122144940000122
Figure BDA0002122144940000131
TABLE 1.5 Voltage vector utilization (increase flux linkage, decrease torque)
Figure BDA0002122144940000132
TABLE 1.6 Voltage vector utilization (decreasing flux linkage, increasing torque)
Figure BDA0002122144940000133
Figure BDA0002122144940000141
TABLE 1.7 Voltage vector utilization (reduced flux, reduced torque)
θ1 θ2 θ3 θ4 θ5 θ6
V0 39.10％ 44.76％ 41.41％ 47.04％ 43.18％ 41.66％
V1 0.00％ 16.36％ 31.96％ 8.18％ 0.82％ 0.00％
V2 0.00％ 0.00％ 17.05％ 27.44％ 7.83％ 1.54％
V3 0.60％ 0.00％ 0.00％ 16.71％ 32.01％ 8.52％
V4 8.01％ 0.57％ 0.00％ 0.00％ 16.16％ 31.30％
V5 34.83％ 8.57％ 0.71％ 0.00％ 0.00％ 16.97％
V6 17.45％ 29.75％ 8.88％ 0.62％ 0.00％ 0.00％
Studies have shown that changes in torque angle also affect voltage vector utilization. There are 10 different load torques set for different torque angles as shown in table 1.8.
TABLE 1.8 load Torque and Torque Angle
Figure BDA0002122144940000142
Figure BDA0002122144940000151
Fig. 12 shows inverter voltage vectors V0 to V6 and stator flux sectors θ 1 to θ 6. As can be seen from fig. 12, inverter voltage vectors V0-V6 and stator flux linkage sector θ1～θ6In a periodic relationship. Tables 1.4 to 1.7 show that the voltage vector utilization varies substantially periodically in different sectors. Therefore, voltage vectors V0-V6 are used hereinafter in stator flux sector θ1The voltage utilization in the case is an example for detailed analysis. Under different torque angles, voltage vectors V0-V6 are in stator flux sector theta1The voltage vector utilization within is shown in tables 1.9-1.13, respectively.
TABLE 1.9 Voltage vector utilization (increase flux linkage, increase torque)
Figure BDA0002122144940000152
Figure BDA0002122144940000161
TABLE 1.10 Voltage vector utilization (increase flux linkage, decrease torque)
Figure BDA0002122144940000162
Figure BDA0002122144940000171
TABLE 1.11 Voltage vector utilization (decreasing flux linkage, increasing torque)
Figure BDA0002122144940000172
TABLE 1.12 Voltage vector utilization (reduced flux, reduced torque)
Figure BDA0002122144940000173
Figure BDA0002122144940000181
From table 1.9 to table 1.12, it can be seen that: stator flux linkage sector theta1When a flux linkage is added and torque is increased, a torque angle is smaller than 45 degrees, voltage vectors with higher voltage vector utilization rate are { V0, V1, V2 and V3}, a torque angle is larger than 45 degrees, and voltage vectors with higher voltage vector utilization rate are { V0, V2, V3 and V6 };
when the flux linkage is increased and the torque is reduced, the torque angle is smaller than 30 degrees, the voltage vector with higher voltage vector utilization rate is { V0, V1, V4, V5 and V6}, the torque angle is larger than 30 degrees, and the voltage vector with higher voltage vector utilization rate is { V0, V5 and V6 };
when the flux linkage is reduced and the torque is increased, the torque angle is smaller than 30 degrees, the voltage vector with higher voltage vector utilization rate is { V0, V1, V4, V2 and V3}, the torque angle is larger than 30 degrees, and the voltage vector with higher voltage vector utilization rate is { V0, V2 and V3 };
when the flux linkage is reduced and the torque is reduced, the torque angle is smaller than 45 degrees, the voltage vectors with higher voltage vector utilization rate are { V0, V4, V5 and V6}, the torque angle is larger than 45 degrees, and the voltage vectors with higher voltage vector utilization rate are { V0, V3, V5 and V6 }.
From this alternative voltage vector sets for other stator flux linkage sectors can be derived recursively. The simplified alternative voltage set is also formed by taking the voltage vector set with higher voltage utilization rate as the simplified set.
And (3) comparing a series of performance indexes of the simplified alternative voltage set, the 7 basic voltage vector set model predictive control system and the traditional switch table control.
A surface permanent magnet synchronous motor model prediction torque control simulation model is established based on MATLAB/Simulink.
The simulation model is a discrete model, and the sampling period is 5 multiplied by 10 < -5 > s.
The dc bus voltage is 312V.
The parameters of the rotating speed PI regulator are as follows: KP is 5, KI is 10, and the PI regulator output upper and lower limits are [ -35, 35 ].
The reference speed was 60rpm, the load torque was initially 5n.m, stepped to 10n.m at 2s, 15n.m at 4s, 20n.m at 6s, 25n.m at 8s, and 30n.m at 10 s.
The reference stator flux linkage amplitude is 0.3 Wb.
The simulation total duration is 12 s.
The motor parameters of the surface permanent magnet synchronous motor for simulation are the same as those shown in the table 1.1 above, and are not described again here. The simulation waveforms under the three strategies are stable, the control effect is stable and good, and because the waveform diagrams are basically similar, the rotating speed, the torque, the stator flux linkage amplitude, the stator flux linkage track under the static coordinate system and the a-phase stator current under the prediction control of the simplified basic voltage vector set model are only shown as the graphs in fig. 12 to 16.
The performance indexes include: torque ripple root mean square error, flux linkage ripple root mean square error, cost function average, evaluation function average. The simulation evaluation results are shown in Table 1.13
TABLE 1.13 results of simulation evaluation
Figure BDA0002122144940000201
Table 1.13 simulation evaluation results show that a series of evaluation indexes are compared. The control performance of the simplified basic voltage vector set control strategy is extremely close to and slightly inferior to that of the traditional switch table control strategy, and all items are superior to the traditional switch table control strategy, so that the simplified voltage vector set meets the requirement of sacrificing the control performance a little, and the operation burden of reducing the calculation cost function in each period is met.
In summary, the following conclusions are drawn:
the prediction strategy control performance is optimal based on seven basic voltage vector set models, the simplified basic voltage vector set model prediction strategy control is slightly inferior, and the traditional switch table (DTC) is the worst.
The basic voltage vector set model prediction strategy is simplified, the alternative voltage set is reduced, and although the hysteresis signal and the torque angle signal are added, the alternative voltage set is relatively easy to obtain, so that the system basically keeps the original control performance, and the calculation burden is reduced.
The simplified alternative voltage vector set control strategy is as follows:
stator flux linkage sector theta1When flux linkage is added and torque is added, a torque angle is smaller than 45 degrees, a set of candidate voltage vectors is { V0, V1, V2 and V3}, a torque angle is larger than 45 degrees, and a set of candidate voltage vectors is { V0, V2, V3 and V6 };
when flux linkage is increased and torque is reduced, the torque angle is smaller than 30 degrees, the set of candidate voltage vectors is { V0, V1, V4, V5 and V6}, the torque angle is larger than 30 degrees, and the set of candidate voltage vectors is { V0, V5 and V6 };
when the flux linkage is reduced and the torque is increased, the torque angle is smaller than 30 degrees, the set of candidate voltage vectors is { V0, V1, V4, V2 and V3}, the torque angle is larger than 30 degrees, and the set of candidate voltage vectors is { V0, V2 and V3 };
when the flux linkage is reduced and the torque is reduced, the torque angle is smaller than 45 degrees, the set of candidate voltage vectors is { V0, V4, V5 and V6}, the torque angle is larger than 45 degrees, and the set of candidate voltage vectors is { V0, V3, V5 and V6 }. From this alternative voltage vector sets for other stator flux linkage sectors can be derived recursively.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims (9)

1. A method for simplifying direct torque control of a finite state set model prediction PMSM is characterized by comprising the following steps:
s1, calculating a cost function g value through the current torque and the stator flux linkage, the reference torque, the reference stator flux linkage, the angular position of the stator flux linkage, the stator flux linkage amplitude and the torque value at the next moment, and collecting seven basic voltage vectors { V } V0,V1,V2,V3,V4,V5,V6Substituting the cost function with the model predictive control principle, namely selecting the voltage vector which enables the cost function to be minimum;
s2, adding a hysteresis control signal, adding a sector position signal and a torque angle signal for judgment, and calculating a cost function g value according to the stator flux amplitude and the torque value at the next moment to obtain a voltage vector with the minimum cost function;
s3, adding a current torque angle signal, taking different hysteresis control signals, sector position signals and different torque angle ranges as limiting conditions, abandoning voltage vectors with low utilization rate, switching different alternative voltage alternative sets, and simplifying alternative voltage vector sets;
s4, according to the torque ripple root mean square error, the stator flux ripple root mean square error, the evaluation function average value and the average switching frequency, taking the torque angle of 30 degrees and 45 degrees as dividing boundaries, reducing the calculation burden of model prediction control by adopting a simplified alternative voltage vector set control strategy, and realizing direct torque simplified control of the PMSM, wherein the simplified alternative voltage vector set control strategy is as follows:
stator flux linkage sector theta1When flux linkage is added and torque is added, the torque angle is less than 45 degrees, and the candidate voltage vector set is { V0，V1，V2，V3Torque angle greater than 45 °, set of candidate voltage vectors as { V }0，V2，V3，V6}；
When the flux linkage is increased,when reducing torque, the torque angle is less than 30 degrees, and the candidate voltage vector set is { V0，V1，V4，V5，V6Torque angle greater than 30 deg., and set of candidate voltage vectors as { V }0，V5，V6}；
When the flux linkage is reduced and the torque is increased, the torque angle is less than 30 degrees, and the candidate voltage vector set is { V0，V1，V4，V2，V3Torque angle greater than 30 deg., and set of candidate voltage vectors as { V }0，V2，V3}；
When the flux linkage is reduced and the torque is reduced, the torque angle is less than 45 degrees, and the candidate voltage vector set is { V0，V4，V5，V6Torque angle greater than 45 °, set of candidate voltage vectors as { V }0，V3，V5，V6}。
2. The finite state set model predictive PMSM direct torque control simplification method of claim 1, characterized in that in step S1, six basic voltage vectors V from the origin to six vertices of a hexagon are determined from a permanent magnet synchronous motor voltage vector diagram1～V6And 1 zero voltage vector V0And determining a voltage vector with the minimum cost function value according to the torque and the stator flux linkage, and outputting the switching state of the voltage vector, wherein the voltage vector candidate set comprises the following components:
Figure FDA0002922169680000021
the amplitude of 6 non-zero voltage vectors is 2Udc/3，UdcThe zero voltage vector magnitude is zero for the dc bus voltage.
3. The finite state set model predictive PMSM direct torque control reduction method of claim 2, wherein six base voltage vectors V1～V6Angle set alpha of1-6The calculation is as follows:
α1-6∈{-θs(k),60°-θs(k),120°-θs(k),180°-θs(k),240°-θs(k),300°-θs(k)}
wherein, thetas(k) The stator flux angular position under the static coordinate system.
4. The finite state set model predictive PMSM direct torque control simplification method in accordance with claim 1, characterized in that in step S1, the cost function value g and the cost function mean value gaveThe calculation is as follows:
Figure FDA0002922169680000022
Figure FDA0002922169680000023
wherein the content of the first and second substances,
Figure FDA0002922169680000024
for reference torque, Te(k +1) is the torque at the next time,
Figure FDA0002922169680000025
for reference to the stator flux linkage,
Figure FDA0002922169680000026
n is the number of samples for the stator flux linkage at the next time instant.
5. The finite state set model predictive PMSM direct torque control reduction method of claim 4, wherein stator flux linkage and torque variation are as follows:
Figure FDA0002922169680000027
Figure FDA0002922169680000028
Figure FDA0002922169680000029
wherein, Delta t is the action time of the voltage vector,
Figure FDA00029221696800000210
is the stator flux linkage at the current moment,
Figure FDA00029221696800000211
is at presentkThe voltage vector to be applied at a moment, #fIs the rotor flux, delta is the torque angle, alpha is the angle between the voltage vector and the stator flux, LdThe direct-axis synchronous inductance of the motor is represented by p, which is the number of pole pairs of the motor.
6. The finite state set model predictive PMSM direct torque control simplification method of claim 1, characterized in that in step S4, the torque ripple root mean square error Trip_RMSEThe calculation is as follows:
Figure FDA0002922169680000031
wherein, TeIs the torque at the present moment in time,
Figure FDA0002922169680000032
for reference torque, n is the number of samples.
7. The finite state set model predictive PMSM direct torque control simplification method of claim 1, characterized in that in step S4, a decision is madeSub flux linkage ripple root mean square error psirip_RMSEThe calculation is as follows:
Figure FDA0002922169680000033
wherein psisIs the stator flux linkage at the current moment,
Figure FDA0002922169680000034
for reference stator flux linkage, n is the number of samples.
8. The finite state set model predictive PMSM direct torque control simplification method of claim 1, characterized in that in step S4, the function mean m is evaluatedaveThe calculation is as follows:
Figure FDA0002922169680000035
wherein n is the number of samples,
Figure FDA0002922169680000036
for the stator flux linkage at the present moment,
Figure FDA0002922169680000037
for reference stator flux linkage, Te *For reference torque, TeThe torque at the present moment.
9. The finite state set model predictive PMSM direct torque control simplification method of claim 1, characterized in that in step S4, the average switching frequency f isaveThe calculation is as follows:
Figure FDA0002922169680000038
wherein N isswitchingThe total number of times of switching the inverter, and t is the simulation duration.
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