CN112564578A - High-efficiency control method for permanent magnet synchronous motor - Google Patents

High-efficiency control method for permanent magnet synchronous motor Download PDF

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CN112564578A
CN112564578A CN202011324905.6A CN202011324905A CN112564578A CN 112564578 A CN112564578 A CN 112564578A CN 202011324905 A CN202011324905 A CN 202011324905A CN 112564578 A CN112564578 A CN 112564578A
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motor
current
axis
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flux linkage
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王家升
魏海峰
张懿
王浩陈
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Jiangsu 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
    • H02P23/00—Arrangements or methods for the control of AC motors characterised by a control method other than vector control
    • H02P23/0077—Characterised by the use of a particular software algorithm
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/34—Testing dynamo-electric machines
    • G01R31/343—Testing dynamo-electric machines in operation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F16/00—Information retrieval; Database structures therefor; File system structures therefor
    • G06F16/90—Details of database functions independent of the retrieved data types
    • G06F16/901—Indexing; Data structures therefor; Storage structures
    • G06F16/9017—Indexing; Data structures therefor; Storage structures using directory or table look-up
    • 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
    • H02P23/00—Arrangements or methods for the control of AC motors characterised by a control method other than vector control
    • H02P23/14—Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, current or voltage

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Abstract

The invention discloses a high-efficiency control method of a permanent magnet synchronous motor, which comprises the following steps: screening a low-speed MTPA (maximum torque to current ratio) working point, namely a first working area working point, through a motor parameter correlation formula; obtaining a group of high-speed weak magnetic voltage limit ellipse working points through a rack test; importing the bench test acquired data into MATLAB, and fitting the rest working points of the second working area by using a data fitting tool box of the MATLAB; merging all the acquired points into a table by taking the stator phase voltage peak value as a boundary; and inquiring a generated table through the given torque and the feedback speed to directly obtain the optimal working current in the current state. By adopting the technical scheme, the table data is less, and the occupied storage space is less; the motor operation area is processed separately, and current compensation is carried out in the weak magnetic voltage limit elliptical area, so that control is more comprehensive and accurate.

Description

High-efficiency control method for permanent magnet synchronous motor
Technical Field
The invention belongs to the technical field of motor drive control. More particularly, the present invention relates to a high efficiency control method for a permanent magnet synchronous motor.
Background
With the continuous development of economy, the number of automobiles is rapidly increased, and in the era of vigorously advocating environmental protection in China, electric automobiles become a necessary development trend. The motor drive control system of the electric automobile is used as a core component of the electric automobile, and is a fundamental guarantee for improving the driving performance, the driving mileage, the reliability and the safety of the electric automobile. A drive system of an electric vehicle requires a torque-rotation speed characteristic with a wide vehicle running speed range and a large load variation.
The traditional Proportional Integral (PI) regulator is easy to generate overshoot and oscillation regulation processes, the dynamic performance is influenced, and the high-performance requirement required by an electric automobile is difficult to meet. The hysteresis control has good rapidity, but has the defects of large ripple, unfixed switching frequency and the like, and is not suitable for high-performance control occasions.
Aiming at the defects of wide adjusting range, low response speed and the like of the traditional current loop, the patent provides an accurate table look-up method, and the method can accurately control the motor in a low-speed MTPA (maximum torque current ratio) working area and a weak magnetic voltage limit ellipse working area by improving the precision of direct-axis current and quadrature-axis current, so that the efficiency and the dynamic response performance of a control system are improved.
Disclosure of Invention
The invention provides a high-efficiency control method for a permanent magnet synchronous motor, which aims to improve the precision of direct-axis current and quadrature-axis current in a full-speed range, realize the precise control of the torque of the permanent magnet synchronous motor and solve the problems of wide regulation range, low response speed and the like of the traditional current loop.
The invention provides a high-efficiency control method of a permanent magnet synchronous motor, which specifically comprises the following steps:
step 1: screening out a low-speed MTPA (maximum torque-current ratio) working point, namely a first working area working point (the first working area is a low-speed MTPA working area, and the second working area is a high-speed weak-magnetic voltage limit ellipse working area) through a motor parameter correlation formula;
step 2: obtaining a group of high-speed weak magnetic voltage limit ellipse working points through a rack test;
and step 3: importing the bench test acquired data into MATLAB, and fitting the rest working points of the second working area by using a data fitting tool box of the MATLAB;
and 4, step 4: merging all the acquired points into a table by taking the stator phase voltage peak value as a boundary;
and 5: and inquiring a generated table through the given torque and the feedback speed to directly obtain the optimal working current in the current state.
Optionally, the motor parameter correlation formula in step 1 is as follows:
stator voltage equation:
Figure BDA0002792374570000021
us 2＝ud 2+uq 2
wherein, R is the very small stator resistance which can be ignored; "u" is a units"is the stator phase voltage; "u" is a unitd"is the d-axis voltage; "u" is a unitq"is the q-axis voltage; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor; ' omegae"is the rotation speed of the motor;
Figure BDA0002792374570000022
is the flux linkage of the motor.
Electromagnetic torque equation:
Figure BDA0002792374570000023
wherein "P" isn"is the pole pair number of the motor; "Te"is the torque of the motor; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure BDA0002792374570000024
is the flux linkage of the motor.
If the maximum stator current I is 500A, we can:
id 2+iq 2≤5002
wherein, "id"is d-axis current; "iq"is the q-axis current.
By combining the two formulas, the electromagnetic torque can be obtained within a range of-349 to 349 N.m, and the electromagnetic torque can be selected within a range of-300 to 300 N.m according to actual conditions.
The electromagnetic torque equation is a necessary condition for the operation of the motor and is limited by other factors, and the specific formula is as follows:
Figure BDA0002792374570000031
wherein "u" iss"is stator phase voltage" Udc"is the bus voltage.
To obtain the maximum torque current ratio, the following equation can be set
id 2+iq 2＝h2
According to the Lagrange multiplier method, the minimum value of h is ensured, and an MTPA equation can be obtained:
Figure BDA0002792374570000032
wherein "h" is the stator current; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure BDA0002792374570000033
is the flux linkage of the motor.
The electromagnetic torque equation is a state equation of the motor operation, and the three equations are constraint equations of the motor operation.
Alternatively, the electromagnetic torque equation in step 1 may calculate corresponding id、iqAnd (4) screening out current values meeting the requirements through three constraint equations, namely the current values are the working points of the MTPA in the first working area.
Optionally, the specific method for obtaining a group of high-speed weak magnetic voltage limit ellipse working points through the bench test in the step 2 is as follows:
two motors are utilized to carry out dragging on the test bench, the upper computer is used for operating and accompanying the tested motor to give the rotating speed, and the upper computer is used for operating the tested motor to give is(ii) a The accompany-testing machine selects a low rotating speed, and 10 rotating speed points are selected between the selected low rotating speed and the peak rotating speed according to the same step length. At each rotating speed point, operating the tested motor by the upper computer to give is，isThe value of which is added from 0 to the stator phase voltage peak usmaxRecord i at this timesA value of (d); at the present isAnd i added to the peak power of the motorsSelecting 10 points among the values to record data, and recording the rotating speed, the torque and the id、iqThe value of (c).
Optionally, in the step 3, the bench test acquired data is imported into MATLAB, and the remaining working points of the second working area are fitted by using a data fitting toolbox of MATLAB, which specifically includes:
importing the weak magnetic voltage limit ellipse working point data into MATLAB, and inputting torque, rotating speed and idAnd iqWriting the correlation expression into a custom function Liner Fitting in an MATLAB Fitting tool box CFTOOL, and Fitting the rest points in the second working area according to the existing data points;
the weak magnetic voltage limit circle torque, the rotating speed idAnd iqThe relationship between the following is specified:
rotational speed id、iqThe relationship between them is:
Figure BDA0002792374570000041
wherein "u" issmax"is the stator phase voltage peak; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure BDA0002792374570000042
is the flux linkage of the motor; .
Torque, id、iqThe relationship between is the electromagnetic torque equation:
Figure BDA0002792374570000043
wherein "T" ise"is the torque of the motor; "Pn"is the pole pair number of the motor; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure BDA0002792374570000044
is the flux linkage of the motor.
Optionally, in step 3, the back electromotive force of the motor is too high and the rotation value is prone to be inaccurate, and the change of the flux linkage is large, which may cause inaccurate flux weakening points and inaccurate current distribution, so that the current distribution at these points needs to be modified. And in the weak magnetic voltage limit ellipse working area, compensating the dq axis current by adopting a voltage feedback control strategy.
The step of compensating the dq-axis current by adopting the voltage feedback control strategy specifically comprises the following steps:
step 31: in order to make the corrected current closer to an accurate solution, the invention estimates the variation of the flux linkage by adopting the voltage difference before and after the flux linkage variation, and estimates the variation of the flux linkage by adopting the voltage difference before and after the flux linkage variation, namely the voltage U before the flux linkage variation1Voltage U after flux linkage change2The difference is controlled by a PI regulator to obtainEstimated flux linkage variation
Figure BDA0002792374570000057
Wherein the voltages before and after the change are calculated as follows:
Figure BDA0002792374570000051
Figure BDA0002792374570000052
wherein, the 'U' is1"is the voltage before flux linkage change; 'U' is provided2"is voltage after flux linkage change; 'U' is providedd"is the d-axis voltage; 'U' is providedq"is the q-axis voltage; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure BDA0002792374570000058
is the flux linkage of the motor; ' omegae"is the rotation speed of the motor.
When the voltage drop is ignored, the d-axis voltage and the q-axis voltage are calculated as follows:
Figure BDA0002792374570000053
Figure BDA0002792374570000054
wherein, the 'U' isd"is the d-axis voltage; 'U' is providedq"is the q-axis voltage; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure BDA0002792374570000055
is the flux linkage of the motor;
Figure BDA0002792374570000056
to estimate flux linkage variation; ' omegae"is the rotation speed of the motor.
Step 32: when the flux weakening voltage limit ellipse is controlled, the stator phase voltage reaches UsmaxCombining torque, rotational speed, idAnd iqWith respect to the current i, is obtaineddAnd iqDerivative of (a):
Figure BDA0002792374570000061
Figure BDA0002792374570000062
wherein, "id' is the derivative of the d-axis current; "iq' is the derivative of the q-axis current; "Te"is the torque of the motor; "Pn"is the pole pair number of the motor; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure BDA0002792374570000063
is the flux linkage of the motor.
Step 33: when the flux linkage changes, the compensated current solving adopts the following formula:
Figure BDA0002792374570000064
Figure BDA0002792374570000065
wherein, "id *"is the compensated d-axis current; "iq *"is the compensated q-axis current; "id' is the derivative of the d-axis current; "iq' is the derivative of the q-axis current; "id"is d-axis current; "iq"is the q-axis current;
Figure BDA0002792374570000066
to estimate the flux linkage variation.
Direct lookup of the table current i from the given torque and the current speed signal of the motordAnd iqWhen considering flux linkage variation, the table current is added with the compensation current to obtain a completely new current value id *And iq *。
Optionally, in step 4, the stator phase voltage peak value u is usedsmaxAs a boundary, the stator phase voltage usLess than the stator phase voltage peak usmaxThe working point of the time is taken as the working point of the first working area; stator phase voltage usEqual to the stator phase voltage peak usmaxThe working point of the time is taken as a working point of a second working area; and sequentially arranging and combining the components into a table according to the sequence.
Optionally, in step 5, when the stator phase voltage u is fed back, the stator phase voltage u is fed backsLess than the stator phase voltage peak usmaxDirectly inquiring a first working area MTPA table through given torque to obtain the optimal working current i in the current stated、iq(ii) a When the stator phase voltage u is fed backsEqual to the stator phase voltage peak usmaxThen, the voltage limit elliptic table of the second working area is directly inquired through the given torque and the feedback rotating speed, and the inquired current is added with the compensation current to obtain the optimal working current i of the current stated、iq。
The invention at least comprises the following beneficial effects:
1. the invention adopts the method of screening data and fitting data of a data fitting tool box of MATLAB by adopting the motor parameter correlation formula, solves the problems of table data redundancy and the like of the traditional table look-up method, and ensures that the table data is less and the occupied storage space is small.
2. The invention adopts a method of separately processing the motor operation area and performing current compensation in the weak magnetic voltage limit elliptical area, solves the problems of wide adjustment range, low response speed and the like of the traditional current loop, improves the current precision, the efficiency and the dynamic response performance of a control system, and leads the control to be more comprehensive and accurate.
Drawings
The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:
fig. 1 is a flowchart of a method for controlling the efficiency of a permanent magnet synchronous motor according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a table look-up method for a motor working area according to the present invention;
fig. 3 is a schematic diagram of real-time changes in feedback torque and phase current according to an embodiment of the present invention.
Detailed Description
The invention is further explained below with reference to the drawings and the embodiments.
The invention relates to a high-efficiency control method for a permanent magnet synchronous motor. The invention aims to solve the problems in the prior art, overcome the defects, improve the precision of given direct axis current and quadrature axis current and realize the precise control of the torque of the permanent magnet synchronous machine.
As shown in fig. 1 to 2, the present invention provides a high efficiency control method for a permanent magnet synchronous motor, which specifically includes the following steps:
step S1: the method comprises the following steps of screening out low-speed MTPA (maximum torque-current ratio) working points, namely first working area working points (a first working area is a low-speed MTPA working area, and a second working area is a high-speed weak-magnetic voltage limit ellipse working area) through a motor parameter correlation formula, and specifically comprises the following steps:
the motor parameter correlation formula is as follows:
stator voltage equation:
Figure BDA0002792374570000081
us 2＝ud 2+uq 2
wherein, R is the very small stator resistance which can be ignored; "u" is a units"is the stator phase voltage; "u" is a unitd"is the d-axis voltage; "u" is a unitq"is the q-axis voltage; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor; ' omegae"is the rotation speed of the motor;
Figure BDA0002792374570000083
is the flux linkage of the motor.
Electromagnetic torque equation:
Figure BDA0002792374570000082
wherein "P" isn"is the pole pair number of the motor; "Te"is the torque of the motor; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure BDA0002792374570000084
is the flux linkage of the motor.
If the maximum stator current I is 500A, we can:
id 2+iq 2≤5002
wherein, "id"is d-axis current; "iq"is the q-axis current.
By combining the two formulas, the electromagnetic torque can be obtained within a range of-349 to 349 N.m, and the electromagnetic torque can be selected within a range of-300 to 300 N.m according to actual conditions.
The electromagnetic torque equation is a necessary condition for the operation of the motor and is limited by other factors, and the specific formula is as follows:
Figure BDA0002792374570000091
wherein "u" iss"is stator phase voltage" Udc"is the bus voltage.
To obtain the maximum torque current ratio, the following equation can be set
id 2+iq 2＝h2
According to the Lagrange multiplier method, the minimum value of h is ensured, and an MTPA equation can be obtained:
Figure BDA0002792374570000092
wherein "h" is the stator current; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure BDA0002792374570000093
is the flux linkage of the motor.
The electromagnetic torque equation is a state equation of the motor operation, and the three equations are constraint equations of the motor operation.
Corresponding i can be calculated according to an electromagnetic torque equationd、iqAnd (4) screening out current values meeting the requirements through three constraint equations, namely the current values are the working points of the MTPA in the first working area.
Step S2: a group of high-speed weak magnetic voltage limit ellipse working points are obtained through bench testing, and the method specifically comprises the following steps:
two motors are utilized to carry out dragging on the test bench, the upper computer is used for operating and accompanying the tested motor to give the rotating speed, and the upper computer is used for operating the tested motor to give is(ii) a The accompany-testing machine selects a low rotating speed, and 10 rotating speed points are selected between the selected low rotating speed and the peak rotating speed according to the same step length. At each rotating speed point, operating the tested motor by the upper computer to give is，isThe value of which is added from 0 to the stator phase voltage peak usmaxRecord i at this timesA value of (d); at the present isAnd i added to the peak power of the motorsSelecting 10 points among the values to record data, and recording the rotating speed, the torque and the id、iqThe value of (c).
Step S3: importing the bench test acquired data into MATLAB, and fitting the rest working points of the second working area by using a data fitting toolbox of the MATLAB, wherein the method comprises the following specific steps:
importing weak magnetic voltage limit ellipse working point data obtained by bench test into MATLAB, and inputting torque, rotating speed and idAnd iqWriting the correlation expression into a custom function Liner Fitting in an MATLAB Fitting tool box CFTOOL, and Fitting the rest points in the second working area according to the existing data points;
the weak magnetic voltage limit circle torque, the rotating speed idAnd iqThe relationship between the following is specified:
rotational speed id、iqThe relationship between them is:
Figure BDA0002792374570000101
wherein "u" issmax"is the stator phase voltage peak; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure BDA0002792374570000102
is the flux linkage of the motor; .
Torque, id、iqThe relationship between is the electromagnetic torque equation:
Figure BDA0002792374570000103
wherein "T" ise"is the torque of the motor; "Pn"is the pole pair number of the motor; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure BDA0002792374570000104
is the flux linkage of the motor.
In practical application, when the motor is at high speed, the back electromotive force of the motor is too high, the rotation value is easy to be inaccurate, the change of the flux linkage is large, weak magnetic points are inaccurate, current distribution is not correct, and therefore the current distribution of the weak magnetic points needs to be corrected. And in the weak magnetic voltage limit ellipse working area, compensating the dq axis current by adopting a voltage feedback control strategy.
The step of compensating the dq-axis current by adopting the voltage feedback control strategy specifically comprises the following steps:
step S31: in order to make the corrected current closer to an accurate solution, the invention estimates the variation of the flux linkage by adopting the voltage difference before and after the flux linkage variation, and estimates the variation of the flux linkage by adopting the voltage difference before and after the flux linkage variation, namely the voltage U before the flux linkage variation1Voltage U after flux linkage change2The difference is controlled by a PI regulator to obtain an estimated flux linkage variation
Figure BDA0002792374570000115
Wherein the voltages before and after the change are calculated as follows:
Figure BDA0002792374570000111
Figure BDA0002792374570000112
wherein, the 'U' is1"is the voltage before flux linkage change; 'U' is provided2"is voltage after flux linkage change; 'U' is providedd"is the d-axis voltage; 'U' is providedq"is the q-axis voltage; "id"is d-axis current; "iq"is the q-axis current; "Ld' as d-axis of motorThe excitation inductance of (2); "Lq"is the excitation inductance of the q axis of the motor;
Figure BDA0002792374570000116
is the flux linkage of the motor; ' omegae"is the rotation speed of the motor.
When the voltage drop is ignored, the d-axis voltage and the q-axis voltage are calculated as follows:
Figure BDA0002792374570000113
Figure BDA0002792374570000114
wherein, the 'U' isd"is the d-axis voltage; 'U' is providedq"is the q-axis voltage; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure BDA0002792374570000117
is the flux linkage of the motor;
Figure BDA0002792374570000118
to estimate flux linkage variation; ' omegae"is the rotation speed of the motor.
Step S32: when the flux weakening voltage limit ellipse is controlled, the stator phase voltage reaches UsmaxCombining torque, rotational speed, idAnd iqWith respect to the current i, is obtaineddAnd iqDerivative of (a):
Figure BDA0002792374570000121
Figure BDA0002792374570000122
wherein, "id' is the derivative of the d-axis current; "iq' is the derivative of the q-axis current; "Te"is the torque of the motor; "Pn"is the pole pair number of the motor; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure BDA0002792374570000123
is the flux linkage of the motor.
Step S33: when the flux linkage changes, the compensated current solving adopts the following formula:
Figure BDA0002792374570000124
Figure BDA0002792374570000125
wherein, "id *"is the compensated d-axis current; "iq *"is the compensated q-axis current; "id' is the derivative of the d-axis current; "iq' is the derivative of the q-axis current; "id"is d-axis current; "iq"is the q-axis current;
Figure BDA0002792374570000126
to estimate the flux linkage variation.
Direct lookup of the table current i from the given torque and the current speed signal of the motordAnd iqWhen considering flux linkage variation, the table current is added with the compensation current to obtain a completely new current value id *And iq *。
Step S4: and combining all the acquired points into a table by taking the stator phase voltage peak value as a boundary, wherein the method specifically comprises the following steps:
by the peak value u of the stator phase voltagesmaxAs a boundary, the stator phase voltage usLess than the stator phase voltage peak usmaxThe working point of the time is taken as the working point of the first working area; stator phase voltage usEqual to the stator phase voltage peak usmaxThe working point of the time is taken as a working point of a second working area; and sequentially arranging and combining the components into a table according to the sequence.
Step S5: the method comprises the following steps of directly obtaining the optimal working current in the current state by inquiring a generated table through given torque and feedback speed, and specifically comprises the following steps:
when the stator phase voltage u is fed backsLess than the stator phase voltage peak usmaxDirectly inquiring a first working area MTPA table through given torque to obtain the optimal working current i in the current stated、iq(ii) a When the stator phase voltage u is fed backsEqual to the stator phase voltage peak usmaxThen, the voltage limit elliptic table of the second working area is directly inquired through the given torque and the feedback rotating speed, and the inquired current is added with the compensation current to obtain the optimal working current i of the current stated、iq。
Specifically, as shown in fig. 3, which is a graph of real-time variation of the feedback torque and the phase current of the motor during the test in the implementation of the present invention, it can be seen from the proportional relationship between the feedback torque and the phase current in the graph that the operation efficiency of the motor is high, which proves the effectiveness and the control accuracy of the method of the present invention.
The invention has been described above with reference to the accompanying drawings, it is obvious that the invention is not limited to the specific implementation in the above-described manner, and it is within the scope of the invention to apply the inventive concept and solution to other applications without substantial modification.

Claims (8)

1. A high-efficiency control method for a permanent magnet synchronous motor is characterized by comprising the following steps: the method comprises the following steps:
step 1: screening out a low-speed MTPA (maximum torque-current ratio) working point, namely a first working area working point (the first working area is a low-speed MTPA working area, and the second working area is a high-speed weak-magnetic voltage limit ellipse working area) through a motor parameter correlation formula;
step 2: obtaining a group of high-speed weak magnetic voltage limit ellipse working points through a rack test;
and step 3: importing the bench test acquired data into MATLAB, and fitting the rest working points of the second working area by using a data fitting tool box of the MATLAB;
and 4, step 4: merging all the acquired points into a table by taking the stator phase voltage peak value as a boundary;
and 5: and inquiring a generated table through the given torque and the feedback speed to directly obtain the optimal working current in the current state.
2. The method for controlling the efficiency of the permanent magnet synchronous motor according to claim 1, wherein the motor parameter correlation formula in the step 1 is as follows:
stator voltage equation:
Figure FDA0002792374560000011
us 2＝ud 2+uq 2
wherein, R is the very small stator resistance which can be ignored; "u" is a units"is the stator phase voltage; "u" is a unitd"is the d-axis voltage; "u" is a unitq"is the q-axis voltage; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor; ' omegae"is the rotation speed of the motor;
Figure FDA0002792374560000013
is the flux linkage of the motor;
electromagnetic torque equation:
Figure FDA0002792374560000012
wherein "P" isn"is the pole pair number of the motor; "Te"is the torque of the motor; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure FDA0002792374560000021
is the flux linkage of the motor;
if the maximum stator current I is 500A, we can:
id 2+iq 2≤5002
wherein, "id"is d-axis current; "iq"is the q-axis current;
combining the two formulas, the range of the electromagnetic torque can be solved to be-349 N.m, and the range of the electromagnetic torque is selected to be-300 N.m according to the actual situation;
the electromagnetic torque equation is a necessary condition for the operation of the motor and is limited by other factors, and the specific formula is as follows:
Figure FDA0002792374560000022
wherein "u" iss"is stator phase voltage" Udc"is the bus voltage.
To obtain the maximum torque current ratio, the following equation can be set
id 2+iq 2＝h2
According to the Lagrange multiplier method, the minimum value of h is ensured, and an MTPA equation can be obtained:
Figure FDA0002792374560000023
wherein "h" is the stator current; "idIs d-axis electricityA stream; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure FDA0002792374560000024
is the flux linkage of the motor;
the electromagnetic torque equation is a state equation of the motor operation, and the three equations are constraint equations of the motor operation.
3. The method as claimed in claim 2, wherein the electromagnetic torque equation in step 1 is used to calculate id、iqAnd (4) screening out current values meeting the requirements through three constraint equations, namely the current values are the working points of the MTPA in the first working area.
4. The method for controlling the efficiency of the permanent magnet synchronous motor according to claim 1, wherein the specific method for obtaining a group of high-speed weak-magnetic voltage limit ellipse working points through the bench test in the step 2 is as follows:
two motors are utilized to carry out dragging on the test bench, the upper computer is used for operating and accompanying the tested motor to give the rotating speed, and the upper computer is used for operating the tested motor to give is(ii) a The accompany-testing machine selects a low rotating speed, and 10 rotating speed points are selected between the selected low rotating speed and the peak rotating speed according to the same step length. At each rotating speed point, operating the tested motor by the upper computer to give is，isThe value of which is added from 0 to the stator phase voltage peak us maxRecord i at this timesA value of (d); at the present isAnd i added to the peak power of the motorsSelecting 10 points among the values to record data, and recording the rotating speed, the torque and the id、iqThe value of (c).
5. The method for controlling the efficiency of the permanent magnet synchronous motor according to claim 4, wherein in the step 3, the bench test acquisition data is imported into MATLAB, and the rest working points in the second working area are fitted by using a data fitting toolbox of the MATLAB, and the specific method is as follows:
importing the weak magnetic voltage limit ellipse working point data into MATLAB, and inputting torque, rotating speed and idAnd iqWriting the correlation expression into a custom function Liner Fitting in an MATLAB Fitting tool box CFTOOL, and Fitting the rest points in the second working area according to the existing data points;
the weak magnetic voltage limit circle torque, the rotating speed idAnd iqThe relationship between the following is specified:
rotational speed id、iqThe relationship between them is:
Figure FDA0002792374560000031
wherein "u" issmax"is the stator phase voltage peak; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure FDA0002792374560000032
is the flux linkage of the motor; .
Torque, id、iqThe relationship between is the electromagnetic torque equation:
Figure FDA0002792374560000033
wherein "T" ise"is the torque of the motor; "Pn"is the pole pair number of the motor; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure FDA0002792374560000041
being flux linkages of electric machines。
6. The method for controlling the efficiency of the permanent magnet synchronous motor according to claim 5, wherein the back electromotive force of the motor is too high and the rotation variation value is prone to be inaccurate at high speed in the step 3, and the variation of the flux linkage is large, which results in inaccurate flux weakening points and inaccurate current distribution, so that the current distribution of the points needs to be modified; in a weak magnetic voltage limit ellipse working area, compensating the dq axis current by adopting a voltage feedback control strategy;
the step of compensating the dq-axis current by adopting the voltage feedback control strategy specifically comprises the following steps:
step 31: in order to make the corrected current closer to an accurate solution, the invention estimates the variation of the flux linkage by adopting the voltage difference before and after the flux linkage variation, and estimates the variation of the flux linkage by adopting the voltage difference before and after the flux linkage variation, namely the voltage U before the flux linkage variation1Voltage U after flux linkage change2The difference is controlled by a PI regulator to obtain an estimated flux linkage variation
Figure FDA0002792374560000047
Wherein the voltages before and after the change are calculated as follows:
Figure FDA0002792374560000042
Figure FDA0002792374560000043
wherein, the 'U' is1"is the voltage before flux linkage change; 'U' is provided2"is voltage after flux linkage change; 'U' is providedd"is the d-axis voltage; 'U' is providedq"is the q-axis voltage; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure FDA0002792374560000048
is the flux linkage of the motor; ' omegae"is the rotation speed of the motor;
when the voltage drop is ignored, the d-axis voltage and the q-axis voltage are calculated as follows:
Figure FDA0002792374560000045
Figure FDA0002792374560000046
wherein, the 'U' isd"is the d-axis voltage; 'U' is providedq"is the q-axis voltage; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure FDA0002792374560000051
is the flux linkage of the motor;
Figure FDA0002792374560000052
to estimate flux linkage variation; ' omegae"is the rotation speed of the motor;
step 32: when the flux weakening voltage limit ellipse is controlled, the stator phase voltage reaches UsmaxCombining torque, rotational speed, idAnd iqWith respect to the current i, is obtaineddAnd iqDerivative of (a):
Figure FDA0002792374560000053
Figure FDA0002792374560000054
wherein "id' is the derivative of the d-axis current; "iq' is the derivative of the q-axis current; "Te"is the torque of the motor; "Pn"is the pole pair number of the motor; "id"is d-axis current; "iq"is the q-axis current; "Ld"is the excitation inductance of the d-axis of the motor; "Lq"is the excitation inductance of the q axis of the motor;
Figure FDA0002792374560000055
is the flux linkage of the motor;
step 33: when the flux linkage changes, the compensated current solving adopts the following formula:
Figure FDA0002792374560000056
Figure FDA0002792374560000057
wherein, "id *"is the compensated d-axis current; "iq *"is the compensated q-axis current; "id' is the derivative of the d-axis current; "iq' is the derivative of the q-axis current; "id"is d-axis current; "iq"is the q-axis current;
Figure FDA0002792374560000061
to estimate flux linkage variation;
direct lookup of the table current i from the given torque and the current speed signal of the motordAnd iqWhen considering flux linkage variation, the table current is added with the compensation current to obtain a completely new current value id *And iq *。
7. The method as claimed in claim 1, wherein the peak value u of the stator phase voltage in step 4 is used as the peak value of the stator phase voltages maxAs a boundary, the stator phase voltage usLess than the stator phase voltage peak us maxThe working point of the time is taken as the working point of the first working area; stator phase voltage usEqual to the stator phase voltage peak us maxThe working point of the time is taken as a working point of a second working area; and sequentially arranging and combining the components into a table according to the sequence.
8. The method as claimed in claim 7, wherein the step 5 is performed when the stator phase voltage u is fed backsLess than the stator phase voltage peak us maxDirectly inquiring a first working area MTPA table through given torque to obtain the optimal working current i in the current stated、iq(ii) a When the stator phase voltage u is fed backsEqual to the stator phase voltage peak us maxThen, the voltage limit elliptic table of the second working area is directly inquired through the given torque and the feedback rotating speed, and the inquired current is added with the compensation current to obtain the optimal working current i of the current stated、iq。
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