Method for detecting dq-axis saturation inductance of synchronous reluctance motor

Abstract

The invention discloses a dq-axis saturation inductance detection method for a synchronous reluctance motor. The method comprises the following steps of: firstly, pre-positioning a magnetic pole position of a rotor; injecting a direct-current voltage in the d-axis direction, and detecting d-axis inductance values under different d-axis currents according to a d-axis current response curve; dC voltage in the q-axis direction is injected, and q-axis inductance values under different q-axis currents are detected according to the q-axis current response curve. According to the invention, the current change rates of a current rising stage under given voltage and a current falling stage under zero voltage are respectively detected, and the dq-axis inductance value of the current rising stage and the dq-axis inductance value of the current falling stage are calculated according to the current change; and the dq inductance value under the current is obtained by averaging the inductance value at the rising stage and the dq inductance value at the falling stage under the same current. The method does not depend on a motor characteristic parameter table provided by a motor manufacturer, improves the versatility of the frequency converter, and enables the frequency converter to drive the synchronous reluctance motor to achieve the optimal performance.

Description

Technical Field

[0001] The invention belongs to the technical field of motor measurement, and in particular relates to a method for detecting dq-axis saturation inductance of a synchronous reluctance motor. Background Art

[0002] Synchronous reluctance motors are widely used in various drive systems due to their low material cost, no magnetic steel, no squirrel cage, and high reliability. The dq axis inductance is one of the key factors for the output reluctance torque accuracy and speed stability of the high-performance vector control of the synchronous reluctance motor. However, the synchronous reluctance motor is affected by the magnetic circuit saturation, and the dq inductance will change with the change of current.

[0003] Therefore, a method for detecting the saturation inductance of the dq axes of a synchronous reluctance motor needs to be proposed urgently. Summary of the invention

[0004] In order to solve the defects in the prior art, the present invention provides a method for detecting the saturation inductance of the dq axes of a synchronous reluctance motor.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] The present invention provides a method for detecting saturation inductance of a dq axis of a synchronous reluctance motor, comprising the following steps:

[0007] S1. First, perform rotor pole position pre-positioning;

[0008] S2. inject a DC voltage in the d-axis direction, and detect the d-axis inductance value under different d-axis currents according to the d-axis current response curve;

[0009] S3. Inject a DC voltage in the q-axis direction, and detect the q-axis inductance value under different q-axis currents according to the q-axis current response curve.

[0010] Preferably, a frequency converter is provided in step S1, the frequency converter is connected to the synchronous reluctance motor, and the frequency converter is provided with a software control unit.

[0011] Preferably, the software control unit gives a d-axis DC voltage instruction with an electrical angle of 0. After the DC voltage instruction is processed by the software control unit, the required DC voltage is injected into the synchronous reluctance motor. The synchronous reluctance motor follows the principle that the magnetic flux is always closed along the path with the smallest magnetic resistance. The rotor pole is pulled into the U phase to perform rotor pole pre-positioning.

[0012] Preferably, the d-axis inductance values ​​under different d-axis currents are detected in step S2, and the steps include: injecting a d-axis DC voltage command and detecting a d-axis rising current response; when the d-axis current exceeds a set maximum current, injecting a zero voltage command and detecting a d-axis falling current response; when the d-axis current is lower than a set minimum current, cutting off the inverter output, calculating the d-axis inductance values ​​under the rising current and falling current according to the rising current response and the falling current response by the following formula, and taking the average of the two inductance values ​​under the same rising current and falling current as the d-axis inductance value under the current;

[0013]

[0014] Among them, L dn+ is the d-axis inductance value at the nth step of d-axis current rise, u d is the d-axis voltage command, R s is the stator resistance, i dn+ is the d-axis current value of the nth step of current rise, i dn-1+ is the d-axis current value at the n-1th step of current rise, t n+ is the moment when the current rises to the nth step, t n-1+ is the moment when the current rises to the n-1th step, L dn- is the d-axis inductance value at the nth step of current drop, i dn-1- is the d-axis current at the n-1th step of current drop, i dn- is the d-axis current at the nth step of current drop, t n- is the moment when the current drops to the nth step, t n-1- is the moment when the current drops by the n-1th step.

[0015] Preferably, the q-axis inductance values ​​under different q-axis currents are detected in step S3, and the steps include: injecting a DC voltage command in the q-axis direction, detecting the q-axis rising current response, injecting a zero voltage command when the q-axis current exceeds the set maximum current, detecting the q-axis falling current response, and cutting off the inverter output when the q-axis current is lower than the set minimum current, calculating the q-axis inductance values ​​under the rising current and falling current according to the rising current response and the falling current response according to the following formula, and taking the average of the two inductance values ​​under the same rising current and falling current as the q-axis inductance value under the current;

[0016]

[0017] Among them, L qn+ is the q-axis inductance value at the nth step of q-axis current rise, u q is the q-axis voltage command, R s is the stator resistance, i qn+ is the q-axis current at the nth step of current rise, i qn-1+is the q-axis current at the n-1th step of current rise, t n+ is the moment when the current rises in the nth step, t n-1+ is the moment when the current rises at the n-1th step; L qn- is the q-axis inductance value at the nth step of current drop, i qn-1- is the q-axis current at the n-1th step of current drop, i qn- is the q-axis current at the nth step of current drop, t n- is the moment when the current drops by the nth step, t n-1- It is the moment when the q-axis current drops by the n-1th step.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention detects the dq-axis inductance value of the synchronous reluctance motor under different currents. In the d-axis and q-axis directions, only one voltage pulse needs to be injected respectively, and the current change rate in the current rising stage at a given voltage and the current falling stage at zero voltage is detected respectively. The dq-axis inductance value in the current rising stage and the dq-axis inductance value in the current falling stage are calculated according to the current change. The rising stage inductance value and the falling stage dq inductance value under the same current are averaged to obtain the dq inductance value under the current. Based on the rated current of the motor, the dq-axis inductance value under different currents is obtained, thereby providing accurate dq-axis inductance parameters for the synchronous reluctance motor vector control to ensure the control performance under different load currents. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the circuit diagram of the d-axis inductance detection of the synchronous reluctance motor;

[0021] Figure 2 It is the circuit diagram of the q-axis inductance detection of the synchronous reluctance motor;

[0022] Figure 3 This is the workflow diagram for dq axis inductance detection;

[0023] Figure 4 Schematic diagram of a method for extracting dq-axis inductance detection data based on current response under dq-axis step voltage;

[0024] Figure 5 The test results of the inverter using the method of the present invention on the dq axis saturation inductance curve of a 1.5Kw synchronous reluctance motor are as follows: Figure 5 a is the UVW three-phase current diagram used for detection, Figure 5 b is the dq axis current response curve, Figure 5 c is the dq axis inductance curve detection result. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0026] like Figures 1 to 5 As shown, this embodiment provides a method for detecting saturation inductance of a synchronous reluctance motor dq axis, comprising the following steps:

[0027] S1. Provide a frequency converter, wherein the frequency converter is connected to a synchronous reluctance motor, and the frequency converter is provided with a software control unit, and the software control unit is based on a dq axis coordinate system.

[0028] S2. With the electrical angle of 0, inject d-axis DC voltage to perform rotor pole pre-positioning;

[0029] S3. After the synchronous reluctance motor rotor magnetic pole pre-positioning is completed, the d-axis inductance detection is started, the d-axis DC voltage is injected, and the d-axis current is detected in real time, and the steps include:

[0030] like Figure 1 As shown, the injected voltage command: Detect the d-axis current.

[0031] like Figure 3 As shown, when the current reaches 0.1 times the rated current of the motor, the current time t is recorded. 1+ , calculate the d-axis inductance at 0.1 times the rated current when the current rises:

[0032] When the current reaches 0.2 times the rated current of the motor, record the current time t 2+ , calculate the d-axis inductance at 0.2 times the rated current when the current rises:

[0033] Among them, L d1+ is the d-axis inductance value of the first step of the d-axis current rise, L d2+ is the d-axis inductance value of the d-axis current rise step 2, u is the d-axis voltage command, R s is the stator resistance, i d2+ is the d-axis current value of the second step of current rise, i d1+ is the d-axis current value of the first step of current rise, t 2+ is the moment of the second step of current rise, t 1+ This is the moment when the current rises to the first step.

[0034] Similarly, when the current reaches 2.0 times the rated current of the motor, record the current time t 20+ , calculate the d-axis inductance at 2 times the rated current when the current rises:

[0035] Among them, Ld20+ is the d-axis inductance value of the 20th step of d-axis current rise, u is the d-axis voltage command, R s is the stator resistance, i d20+ is the d-axis current value at the 20th step of current rise, i d19+ is the d-axis current value at the 19th step of current rise, t 20+ is the moment when the current rises to the 20th step, t 19+ It is the moment when the current rises in the 19th step.

[0036] Modify the voltage command: Continue to detect the d-axis current. When it reaches twice the rated current of the motor, record the current time t 20- , when it reaches 1.9 times the rated current of the motor, record the current time t 19- , calculate the d-axis inductance at 2 times the rated current when the current drops: At this point, the d-axis inductance at 2 times the rated current can be obtained:

[0037] When the current reaches 1.8 times the rated current of the motor, record the current time t 18- , calculate the d-axis inductance at 1.9 times the rated current when the current is decreasing: At this point, the d-axis inductance at 1.9 times the rated current can be obtained:

[0038] Among them, R s is the stator resistance, L d20- is the d-axis inductance value at the 20th step of current drop, L d19- is the d-axis inductance value of the 19th step of current drop, i d18- is the d-axis current at the 18th step of current drop, i d19- is the d-axis current at the 19th step of current drop, i d18- is the d-axis current at the 18th step of current drop, t 20- is the moment when the current drops to the 20th step, t 19- is the moment when the current drops to step 19; t 18- It is the moment of the 18th step of the current decrease. In order to keep the subscripts consistent with the current increase stage, the subscripts of the variables in the current decrease stage in the present invention are numbered in reverse order, and the number of steps of decrease is also described in reverse order, in chronological order, first decrease the nth step, and then decrease the n-1th step.

[0039] Similarly, when the motor current reaches 0.01 times of the rated current, record the current time t 0- Calculate the d-axis inductance at 0.1 times the rated current when the current is decreasing, Now we can get the d-axis inductance at 0.1 times the rated current:

[0040] Among them, R s is the stator resistance, L d1- is the d-axis inductance value of the first step of current drop, i d1- is the d-axis current of the first step of current drop, t 1- is the moment of the first step of current decline; i d0- is the d-axis current at the 0th step of current drop, t 0- is the moment when the current drops to step 0.

[0041] S4. Detecting the q-axis inductance, the steps include:

[0042] like Figure 2 As shown, the injected voltage command: Detect the q-axis current.

[0043] like Figure 3 As shown, when the current reaches 0.1 times the rated current of the motor, the current time t is recorded. 1+ , calculate the q-axis inductance at 0.1 times the rated current when the current rises:

[0044] When the current reaches 0.2 times the rated current of the motor, record the current time t 2+ , calculate the q-axis inductance at 0.2 times the rated current when the current rises:

[0045] Among them, L q1+ is the q-axis inductance value of the first step of q-axis current rise, L q2+ is the q-axis inductance value of the q-axis current rise step 2, u is the q-axis voltage command, R s is the stator resistance, i q2+ is the q-axis current in the second step of current rise, i q1+ is the q-axis current of the first step of current rise, t 2+ is the moment of the second step of current rise, t 1+ It is the moment of the first step of current rise.

[0046] Similarly, when the current reaches 2.0 times the rated current of the motor, record the current time t 20+ , calculate the q-axis inductance at 2 times the rated current when the current rises:

[0047] Among them, L q20+ is the q-axis inductance value of the 20th step of q-axis current rise, u is the q-axis voltage command, R s is the stator resistance, i q20+ is the q-axis current at the 20th step of current rise, i q19+ is the q-axis current at the 19th step of current rise, t 20+ is the moment when the current rises at the 20th step, t19+ It is the moment of the 19th step when the current rises.

[0048] Modify the voltage command: Continue to detect the q-axis current. When it reaches twice the rated current of the motor, record the current time t 20- , when it reaches 1.9 times the rated current of the motor, record the current time t 19- , calculate the q-axis inductance at 2 times the rated current when the current drops: At this point, the q-axis inductance at twice the rated current can be obtained as:

[0049] When the current reaches 1.8 times the rated current of the motor, record the current time t 18- , calculate the q-axis inductance at 1.9 times the rated current when the current is decreasing: At this point, the q-axis inductance at 1.9 times the rated current can be obtained:

[0050] Among them, R s is the stator resistance, L q20- is the q-axis inductance value at the 20th step of current drop, L q19- is the q-axis inductance value of the 19th step of current drop, i q20- is the q-axis current at the 20th step of current drop, i q19- is the q-axis current at the 19th step of current drop, i q18- is the q-axis current at the 18th step of current drop, t 20- is the moment when the current drops to the 20th step, t 19- is the 19th step of the q-axis current drop, t 18- It is the moment when the q-axis current drops to the 18th step.

[0051] Similarly, when the motor current reaches 0.01 times of the rated current, record the current time t 0- Calculate the q-axis inductance at 0.1 times the rated current when the current is decreasing: At this point, the q-axis inductance at 0.1 times the rated current can be obtained:

[0052] Among them, R s is the stator resistance, L q1- is the q-axis inductance value of the first step of current drop, i q1- is the q-axis current of the first step of current drop, i q0- is the q-axis current at the 0th step of current drop, t 1- is the moment of the first step of current drop, t 0- It is the moment when the q-axis current drops to the 0th step.

[0053] S5. The L detected above d1 ,Ld2 ,...,L d20 , L q1 ,L q2 ,...,L q20 Built into the inverter software, when executing synchronous reluctance motor vector control, the corresponding dq axis inductance value is selected according to different id and iq values ​​to obtain the best control performance.

[0054] The frequency converter of the method of the present invention is used to detect the saturation inductance curve of the dq axis of the 1.5Kw synchronous reluctance motor. The results are as follows: Figure 5 shown.

[0055] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for detecting saturation inductance of dq axes of a synchronous reluctance motor, characterized in that: The following steps are involved: S1. First, perform rotor pole position pre-positioning; S2. inject a DC voltage in the d-axis direction, and detect the d-axis inductance value under different d-axis currents according to the d-axis current response curve; S3. Inject a DC voltage in the q-axis direction, and detect the q-axis inductance value under different q-axis currents according to the q-axis current response curve.

2. The method for detecting dq-axis saturation inductance of a synchronous reluctance motor according to claim 1, characterized in that: In the step S1, a frequency converter is provided, the frequency converter is connected to the synchronous reluctance motor, and the frequency converter is provided with a software control unit.

3. The method for detecting dq-axis saturation inductance of a synchronous reluctance motor according to claim 2, characterized in that: The software control unit gives a d-axis DC voltage instruction with an electrical angle of 0. After the DC voltage instruction is processed by the software control unit, the required DC voltage is injected into the synchronous reluctance motor. The synchronous reluctance motor follows the principle that the magnetic flux is always closed along the path with the smallest magnetic resistance. The rotor pole is pulled into the U phase to perform rotor pole pre-positioning.

4. The method for detecting dq-axis saturation inductance of a synchronous reluctance motor according to claim 3, characterized in that: In step S2, the d-axis inductance values ​​under different d-axis currents are detected, and the steps include: injecting a d-axis DC voltage command to detect the d-axis rising current response; when the d-axis current exceeds the set maximum current, injecting a zero voltage command to detect the d-axis falling current response; when the d-axis current is lower than the set minimum current, cutting off the inverter output, calculating the d-axis inductance values ​​under the rising current and falling current according to the rising current response and the falling current response by the following formula, and taking the average of the two inductance values ​​under the same rising current and falling current as the d-axis inductance value under the current; Among them, L dn+ is the d-axis inductance value at the nth step of current rise, u d is the d-axis voltage command, R s is the stator resistance, i dn+ is the d-axis current value of the nth step of current rise, i dn-1+ is the d-axis current value at the n-1th step of current rise, t n+ is the moment when the current rises to the nth step, t n-1+ is the moment when the current rises to the n-1th step, L dn- is the d-axis inductance value at the nth step of current drop, i dn-1- is the d-axis current at the n-1th step of current drop, i dn- is the d-axis current at the nth step of current drop, t n- is the moment when the current drops to the nth step, t n-1- is the moment when the current drops by the n-1th step.

5. The method for detecting dq-axis saturation inductance of a synchronous reluctance motor according to claim 3, characterized in that: In the step S3, the q-axis inductance values ​​under different q-axis currents are detected, and the steps include: injecting a DC voltage command in the q-axis direction, detecting the q-axis rising current response, injecting a zero voltage command when the q-axis current exceeds the set maximum current, detecting the q-axis falling current response, and cutting off the inverter output when the q-axis current is lower than the set minimum current, calculating the q-axis inductance values ​​under the rising current and falling current according to the rising current response and the falling current response according to the following formula, and taking the average of the two inductance values ​​under the same rising current and falling current as the q-axis inductance value under the current; Among them, L qn+ is the q-axis inductance value at the nth step of q-axis current rise, u q is the q-axis voltage command, R s is the stator resistance, i qn+ is the q-axis current at the nth step of current rise, i qn-1+ is the q-axis current at the n-1th step of current rise, t n+ is the moment when the current rises in the nth step, t n-1+ is the moment when the current rises at the n-1th step; L qn- is the q-axis inductance value at the nth step of current drop, i qn-1- is the q-axis current at the n-1th step of current drop, i qn- is the q-axis current at the nth step of current drop, t n- is the moment when the current drops by the nth step, t n-1- is the moment when the current drops by the n-1th step.

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