CN112491316B - Correction method for asynchronous motor stator resistance identification - Google Patents

Abstract

The invention relates to the asynchronous motor parameter technology, in particular to a correction method for identifying stator resistance of an asynchronous motor, which comprises the following steps of firstly, introducing direct current twice, and recording a wave-generating comparison value, a direct current bus voltage value and output current; secondly, recording the delay time of the upper edge and the lower edge of the pulse wave in the two direct current processes; thirdly, reconstructing the output voltage, and calculating the uncorrected stator resistance of the output voltage; and finally, correcting the duty ratio according to the delay time of the upper edge and the lower edge, reconstructing the output voltage and calculating the corrected stator resistance. The method utilizes the delay time of the upper edge and the lower edge of the actually measured pulse to compensate the duty ratio, and improves the accuracy of the system in identifying the stator resistance of the asynchronous motor. Compared with the traditional identification method, the identification precision of the stator resistance is improved.

Description

Correction method for asynchronous motor stator resistance identification

Technical Field

The invention belongs to the technical field of asynchronous motor parameters, and particularly relates to a correction method for asynchronous motor stator resistance identification.

Background

In vector control, one important factor affecting the orientation of the magnetic field is the motor parameters. If some parameters of the motor are inaccurate (identification errors are large or the parameters change in real time), the magnetic field orientation is inaccurate, and the static and dynamic characteristics of the control system are influenced.

When the asynchronous motor adopts direct vector control, the rotor flux linkage amplitude, the phase and the slip frequency need to be identified according to motor parameters; when indirect vector control is adopted, parameters are required to be used for calculating slip frequency. When open-loop vector control is adopted, motor parameters are also needed to identify the rotating speed. The rotor resistance value determines the accuracy of the rotor time constant value, which is the key to the system magnetic field orientation, and the stator resistance identification accuracy is the premise of the rotor resistance identification accuracy.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a correction method for identifying the stator resistance of an asynchronous motor.

In order to solve the technical problems, the invention adopts the following technical scheme: a correction method for asynchronous motor stator resistance identification comprises the following steps:

step 1, introducing direct current twice, and recording a wave-generating comparison value, a direct current bus voltage value and output current;

step 2, recording the delay time of the upper edge and the lower edge of the pulse wave in the two direct current processes;

step 3, reconstructing output voltage and calculating the uncorrected stator resistance of the output voltage;

and 4, correcting the duty ratio according to the upper and lower edge delay time, reconstructing the output voltage, and calculating the corrected stator resistance.

In the above method for correcting stator resistance identification of an asynchronous motor, the step 1 is implemented by:

step 1.1, introducing direct current 50% rated current, recording PWM wave-generating comparison values Cmpr _ 50% _1, Cmpr _ 50% _2 and Cmpr _ 50% _3 of the direct current, and outputting current I₁；

Step 1.2, introducing direct current 100% rated current, recording PWM wave-generating comparison values Cmpr _ 100% _1, Cmpr _ 100% _2 and Cmpr _ 100% _3 of the direct current, and outputting current I₂；

Step 1.3, recording the voltage value U of the direct current bus during the test_dcThe carrier frequency of the wave transmission is f, the period of the wave transmission is T_s。

In the above method for correcting stator resistance identification of an asynchronous motor, the step 2 includes:

step 2.1, when the rated current is 50%, the delay time of the upper edge and the lower edge of the three-phase bridge arm of the inverter bridge A, B, C is t_{50％_A_S},t_{50％_A_X},t_{50％_B_S},t_{50％_B_X},t_{50％_C_S},t_{50％_C_X}；

Step 2.2, when the rated current is 100%, the delay time of the upper edge and the lower edge of the three-phase bridge arm of the inverter bridge A, B, C is t_{100％_A_S},t_{100％_A_X},t_{100％_B_S},t_{100％_B_X},t_{100％_C_S},t_{100％_C_X}。

In the above method for correcting stator resistance identification of an asynchronous motor, the step 3 is implemented by:

step 3.1, calculating duty ratios according to the wave-sending comparison values, wherein the conduction duty ratios of the tubes on the inverter bridge are respectively as follows:

D_{50％_1}＝(T_s-Cmpr_50％_1)/T_s，D_{50％_2}＝(T_s-Cmpr_50％_2)/T_s，D_{50％_3}＝(T_s-Cmpr_50％_3)/T_s，D_{100％_1}＝(T_s-Cmpr_100％_1)/T_s，D_{100％_2}＝(T_s-Cmpr_100％_2)/T_s，D_{100％_3}＝(T_s-Cmpr_100％_3)/T_s

wherein D_{50％_1}，D_{50％_2}，D_{50％_3}Is divided into the conduction duty ratio of the tubes on the inverter bridge when 50 percent of rated current is introduced, D_{100％_1}，D_{100％_2}，D_{100％_3}Respectively representing the conduction duty ratios of the tubes on the inverter bridge when 100% rated current is introduced;

step 3.2, reconstructing phase voltage U of voltage and 50% rated current according to the comparison value₁The phase voltage at 100% rated current is U₂Wherein:

the stator resistance before correction can be obtained

In the above method for correcting stator resistance identification of an asynchronous motor, the step 4 is implemented by:

step 4.1, when the delay time of the upper edge and the lower edge of the output voltage pulse is considered, the duty ratio of the upper edge and the lower edge in the whole pulse period is delayed when the direct current 50 percent of rated current is introduced

The duty ratio of the upper and lower edge delay in the whole pulse period when the DC 100% rated current is introduced is

Step 4.2, corresponding corrected phase voltage U at 50% rated current₃The phase voltage at 100% of the rated current is U₄；

Corrected stator resistance

The invention has the beneficial effects that: the invention utilizes the delay time of the upper edge and the lower edge of the actually measured pulse to compensate the duty ratio, thereby improving the accuracy of the system for identifying the stator resistance of the asynchronous motor. Compared with the traditional identification method, the identification precision of the stator resistance is improved.

Drawings

Fig. 1 is a flowchart of a correction method for identifying stator resistance of an asynchronous motor according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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.

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The present invention is further illustrated by the following examples, which are not to be construed as limiting the invention.

According to the embodiment, the duty ratio in theoretical calculation is compensated according to the delay time of the upper edge and the lower edge of the actually measured voltage pulse at the output end of the frequency converter, and compared with the traditional identification method, the stator resistance identification precision is improved.

As shown in fig. 1, the present embodiment is implemented by the following technical solutions, and a method for correcting identification of stator resistance of an asynchronous motor includes:

and S1, introducing direct current twice, and recording the wave-generating comparison value, the direct current bus voltage value and the output current.

And S2, recording the delay time of the upper edge and the lower edge of the pulse wave in the two direct current processes.

And S3, reconstructing the output voltage and calculating the uncorrected stator resistance.

And S4, correcting the duty ratio according to the upper and lower edge delay time, reconstructing the output voltage and calculating the corrected stator resistance.

And S5, verifying the feasibility of the correction method.

In specific implementation, firstly, a DC 50% rated current is introduced, PWM wave-generating comparison values Cmpr _ 50% _1, Cmpr _ 50% _2 and Cmpr _ 50% _3 are recorded, and an output current I is output₁. The DC 100% rated current is introduced, the PWM wave-generating comparison values Cmpr _ 100% _1, Cmpr _ 100% _2 and Cmpr _ 100% _3 are recorded, and the output current I is output₂. Recording DC bus voltage value U during test_dcThe carrier frequency of the wave is f, and the period of the wave is T_s。

Secondly, due to hardware reasons, the voltage pulse during wave sending is not an ideal step pulse, but has upper and lower edge delays, and the delay time of the upper and lower edges of the three-phase bridge arm of the inverter bridge A, B, C is t when the rated current is 50 percent_{50％_A_S},t_{50％_A_X},t_{50％_B_S},t_{50％_B_X},t_{50％_C_S},t_{50％_C_X}. The delay time of the upper edge and the lower edge of a three-phase bridge arm of the inverter bridge A, B, C at 100 percent rated current is t_{100％_A_S},t_{100％_A_X},t_{100％_B_S},t_{100％_B_X},t_{100％_C_S},t_{100％_C_X}。

Thirdly, calculating the duty ratio according to the wave-sending comparison value, wherein the conduction duty ratio on the inverter bridge is respectively as follows:

D_{50％_1}＝(T_s-Cmpr_50％_1)/T_s，D_{50％_2}＝(T_s-Cmpr_50％_2)/T_s，D_{50％_3}＝(T_s-Cmpr_50％_3)/T_s，D_{100％_1}＝(T_s-Cmpr_100％_1)/T_s，D_{100％_2}＝(T_s-Cmpr_100％_2)/T_s，D_{100％_3}＝(T_s-Cmpr_100％_3)/T_s

wherein D_{50％_1}，D_{50％_2}，D_{50％_3}Is divided into the conduction duty ratio of the tubes on the inverter bridge when 50 percent of rated current is introduced, D_{100％_1}，D_{100％_2}，D_{100％_3}Respectively is the conduction duty ratio of the tubes on the inverter bridge when 100 percent of rated current is introduced.

Reconstructing the phase voltage U at 50% of the rated current from the comparison values₁The phase voltage at 100% rated current is U₂Wherein:

can reach the stator resistance before correction

Then, due toFor hardware reasons, the output voltage pulse cannot be of a step type, and in such a difference calculation method, an error in the duty ratio greatly affects the numerical calculation result. When the delay time of the upper edge and the lower edge of the output voltage pulse is considered, the duty ratio of the upper edge and the lower edge delay in the whole pulse period when the direct current is introduced for 50 percent of rated current is

The duty ratio of the upper edge and the lower edge of the pulse delay in the whole pulse period is equal to

Corresponding corrected 50% rated current phase voltage U₃The phase voltage at 100% rated current is U₄。

Corrected stator resistance

Finally, a 150A frequency converter with 55KW asynchronous motor is used for parameter identification and comparison test, and the resistance value of the stator is 0.11043 omega measured by an electric bridge. The stator resistance was identified to be 0.1444 Ω before the correction and 0.120879 Ω after the correction. Specific data are shown in the following table.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims (1)

1. A correction method for asynchronous motor stator resistance identification is characterized by comprising the following steps:

step 1, introducing direct current twice, and recording a wave-generating comparison value, a direct current bus voltage value and output current;

step 2, recording the delay time of the upper edge and the lower edge of the pulse wave in the two direct current processes;

step 3, reconstructing output voltage and calculating the uncorrected stator resistance of the output voltage;

step 4, correcting the duty ratio according to the upper and lower edge delay time, reconstructing the output voltage, and calculating the corrected stator resistance;

the implementation of step 1 comprises:

step 1.1, introducing direct current 50% rated current, recording PWM wave-generating comparison values Cmpr _ 50% _1, Cmpr _ 50% _2 and Cmpr _ 50% _3 of the direct current, and outputting current I₁；

Step 1.2, introducing direct current 100% rated current, recording PWM wave-generating comparison values Cmpr _ 100% _1, Cmpr _ 100% _2 and Cmpr _ 100% _3 of the direct current, and outputting current I₂；

Step 1.3, recording the voltage value U of the direct current bus during the test_dcThe carrier frequency of the wave is f, and the period of the wave is T_s；

The implementation of the step 2 comprises the following steps:

step 2.1, the delay time of the upper edge and the lower edge of the three-phase bridge arm of the inverter bridge A, B, C at 50 percent of rated current are t respectively_{50％_A_S},t_{50％_A_X},t_{50％_B_S},t_{50％_B_X},t_{50％_C_S},t_{50％_C_X}；

Step 2.2, upper and lower parts of three-phase bridge arm of inverter bridge A, B, C at 100% rated currentThe edge delay times are respectively t_{100％_A_S},t_{100％_A_X},t_{100％_B_S},t_{100％_B_X},t_{100％_C_S},t_{100％_C_X}；

The implementation of the step 3 comprises the following steps:

step 3.1, calculating duty ratios according to the wave-sending comparison values, wherein the conduction duty ratios of the tubes on the inverter bridge are respectively as follows:

D_{50％_1}＝(T_s-Cmpr_50％_1)/T_s，D_{50％_2}＝(T_s-Cmpr_50％_2)/T_s，D_{50％_3}＝(T_s-Cmpr_50％_3)/T_s，D_{100％_1}＝(T_s-Cmpr_100％_1)/T_s，D_{100％_2}＝(T_s-Cmpr_100％_2)/T_s，D_{100％_3}＝(T_s-Cmpr_100％_3)/T_s

wherein D_{50％_1}，D_{50％_2}，D_{50％_3}Dividing the current into a conduction duty ratio D of the tube on the inverter bridge when 50% of rated current is introduced_{100％_1}，D_{100％_2}，D_{100％_3}Respectively representing the conduction duty ratios of the tubes on the inverter bridge when 100% rated current is introduced;

step 3.2, reconstructing phase voltage U of voltage and 50% rated current according to the comparison value₁The phase voltage at 100% rated current is U₂Wherein:

the stator resistance before correction can be obtained

The implementation of the step 4 comprises the following steps:

step 4.1, when the output is consideredWhen the upper and lower edges of the voltage pulse are delayed for a time, the duty ratio of the upper and lower edges of the voltage pulse delayed in the whole pulse period when the direct current is introduced for 50 percent of rated current is

The duty ratio of the upper edge and the lower edge of the pulse delay in the whole pulse period is equal to

Step 4.2, corresponding corrected phase voltage U at 50% rated current₃The phase voltage at 100% rated current is U₄；

Corrected stator resistance

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