Method for observing magnetic flux linkage of ac motor rotor

Abstract

The application provides a method for observing rotor flux of an alternating current motor, and belongs to the technical field of motor control. The method comprises the following steps: calculating rotor observation flux based on a first voltage-type flux calculation model and stator voltage and stator current in a two-phase static coordinate system; obtaining an amplitude deviation by subtracting the amplitude of the rotor rated flux from the amplitude of the rotor observation flux, and obtaining a deviation compensation quantity by multiplying the amplitude deviation by a proportional integral operation; and compensating and correcting the first voltage-type flux calculation model based on the deviation compensation quantity to obtain a voltage-type flux calculation model with compensation correction, so that the amplitude of the rotor observation flux converges. The application converges the rotor observation flux to the rotor given flux by connecting a correction link based on the traditional voltage-type flux calculation model, and finally realizes accurate flux position observation.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to a method for observing the rotor flux linkage of an AC motor. Background Technology

[0002] With the advancement of technology, industrial applications have placed higher demands on the speed and torque response of motor drive systems. Vector control technology, due to its superior performance, has also received widespread attention in the field of motor control.

[0003] In field-oriented control (FOC) of asynchronous motors, rotor flux orientation is often used to decouple the active and reactive power of the rotor, achieving high-performance control. Rotor flux orientation first requires obtaining the rotor flux of the asynchronous motor. Commonly used asynchronous motor rotor flux observers are of two types: one based on a current model and the other based on a voltage model.

[0004] Traditional sensorless vector control requires the installation of encoders, which increases system cost. Furthermore, encoder reliability is difficult to guarantee under conditions of high vibration, heavy oil contamination, and strong electromagnetic interference. Therefore, research on sensorless vector control has become a current hot topic. The key to achieving sensorless vector control lies in obtaining accurate motor flux linkage position. Currently, most methods utilize inverter output voltage and current combined with a motor model to estimate rotor flux linkage.

[0005] Taking asynchronous motors as an example, traditional voltage-type rotor flux linkage calculation methods include an integral stage. However, due to high-frequency noise or even DC bias in the voltage and current sampling circuits of frequency converter systems, the integral calculation suffers from offset issues and cannot be directly used in engineering applications. To address this, scholars have proposed using a low-pass filter stage to replace the integral stage, or adding a high-pass filter. While these methods can avoid the integral offset problem, they also introduce new issues such as phase offset and phase compensation. Especially for the wide operating frequency range of frequency converters, the selection of the filter cutoff frequency and the determination of the phase compensation amount require more parameters to be involved in the calculation, resulting in the disadvantages of this method in application, such as having many parameters and a large range of parameter variations. Summary of the Invention

[0006] The purpose of this invention is to provide a method for observing the rotor flux linkage of an AC motor, which solves the integration offset problem in the traditional voltage-type flux linkage calculation model.

[0007] To achieve the above objectives, embodiments of the present invention provide a method for observing the rotor flux linkage of an AC motor, the method comprising:

[0008] The rotor flux linkage is calculated based on the first voltage-type flux linkage calculation model and the stator voltage and stator current in the two-phase stationary coordinate system.

[0009] The amplitude deviation is obtained by subtracting the amplitude of the rotor rated flux linkage from the amplitude of the rotor observed flux linkage. The amplitude deviation is then multiplied by the stator current after proportional integration to obtain the deviation compensation amount.

[0010] The first voltage-type flux linkage calculation model is compensated and corrected based on the deviation compensation amount, resulting in a voltage-type flux linkage calculation model with compensation and correction, which makes the amplitude of the rotor observed flux linkage converge.

[0011] The present invention has the following beneficial effects: By adding a correction stage to the traditional voltage-type flux linkage calculation model, the present invention enables the observed flux linkage of the rotor to converge to the given flux linkage of the rotor, and finally achieves accurate flux linkage position observation, effectively avoiding the integral offset problem. Moreover, the implementation process is simple and easy to implement in engineering applications. Attached Figure Description

[0012] Figure 1 A flowchart illustrating the steps of the AC motor rotor flux observation method provided in this embodiment of the invention;

[0013] Figure 2 This is a flowchart illustrating the steps for calculating amplitude deviation provided in an embodiment of the present invention.

[0014] Figure 3 This diagram illustrates the structural framework of the AC motor rotor flux observation system provided in an embodiment of the present invention.

[0015] Figure 4 This is a simulation diagram of the traditional voltage-type flux linkage observation model before convergence, provided in an embodiment of the present invention.

[0016] Figure 5 The simulation diagram shows the convergence of the voltage-type flux linkage observation model with compensation and correction provided in the embodiment of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific implementation methods and the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. Furthermore, in the following description, descriptions of well-known structures and technologies are omitted to avoid obscuring the concepts of the present invention.

[0018] Example 1

[0019] Figure 1 A flowchart illustrating the steps of the AC motor rotor flux observation method provided in this embodiment of the invention is shown below. Figure 1 This invention provides a method for observing the rotor flux linkage of an AC motor, the method comprising:

[0020] Step S110: Calculate the rotor observed flux linkage based on the first voltage-type flux linkage calculation model and the stator voltage and stator current in the two-phase stationary coordinate system.

[0021] Step S120: Subtract the rated flux linkage amplitude of the rotor from the observed flux linkage amplitude of the rotor to obtain the amplitude deviation, and then multiply the amplitude deviation by the stator current to obtain the deviation compensation amount after performing proportional integral calculation.

[0022] Step S130: Based on the deviation compensation amount, the first voltage-type flux linkage calculation model is compensated and corrected to obtain a voltage-type flux linkage calculation model with compensation and correction, so that the amplitude of the rotor observed flux linkage converges.

[0023] In an alternative embodiment, before calculating the rotor observation flux linkage, the method further includes:

[0024] The collected stator current is transformed by coordinate transformation to obtain the stator current along the α and β axes in a two-phase stationary coordinate system. The command voltage output by the frequency converter is also transformed by coordinate transformation to obtain the stator voltage along the α and β axes in a two-phase stationary coordinate system.

[0025] In an optional embodiment, the stator currents along the α and β axes in the two-phase stationary coordinate system are obtained by coordinate transformation using the following equation (1):

[0026]

[0027] in, This represents the U-phase current of the motor. This represents the V-phase current of the motor. Represents the stator current along the α axis. This represents the stator current along the β axis.

[0028] In an optional embodiment, the stator voltages along the α and β axes in the two-phase stationary coordinate system are obtained by coordinate transformation using the following equation (2):

[0029]

[0030] in, Indicates the D-axis command voltage. Indicates the Q-axis command voltage. Represents the stator voltage along the α axis. This represents the stator voltage along the β axis.

[0031] , It can be obtained by sampling the output voltage and transforming it into coordinates. Furthermore, in engineering applications, the command voltage output by the frequency converter can be used instead.

[0032] Figure 2 A flowchart illustrating the steps for calculating amplitude deviation provided in this embodiment of the invention is shown below. Figure 2 This invention provides a method for observing the rotor flux linkage of an AC motor. In one optional embodiment, the calculation of amplitude deviation includes:

[0033] Step S100: Based on the rotor observed flux linkage, calculate the rotor observed flux linkage amplitudes along the α and β axes in the two-phase stationary coordinate system;

[0034] Step S200: Subtract the rotor's rated flux linkage amplitude from the rotor's observed flux linkage amplitude to obtain the amplitude deviation.

[0035] In an optional embodiment, the rotor observed flux linkage amplitude and amplitude deviation are calculated using the following formula (4):

[0036]

[0037] in, Represents the amplitude of the observed flux linkage on the rotor. , The rotor flux linkage is observed in a two-phase stationary coordinate system, where e represents the amplitude deviation. This represents the rated flux linkage amplitude of the rotor.

[0038] In an optional embodiment, the deviation compensation amount is calculated using the following formula (5):

[0039]

[0040] in, This indicates that the amplitude deviation has been calculated using a PI proportional-integral method. Indicates proportional gain. Indicates integral gain. This represents the amount of deviation compensation for the α-axis. This represents the amount of deviation compensation for the β-axis.

[0041] The deviation compensation amount is calculated by performing a PI proportional-integral operation on the observed flux linkage deviation and then... and Multiply to get and Deviation compensation amount.

[0042] In an optional embodiment, the voltage-type flux linkage calculation model with compensation correction is as follows:

[0043]

[0044] in, , For rotor observation flux in a two-phase stationary coordinate system, , The stator voltage is in a two-phase stationary coordinate system. , The stator current is in a two-phase stationary coordinate system. , , , These represent the stator inductance, rotor inductance, mutual inductance, and stator resistance, respectively. This represents the leakage flux coefficient of the motor.

[0045] It is known that the voltage model for calculating rotor flux linkage can be obtained from the stator voltage equation and flux linkage equation of the motor:

[0046]

[0047] In one alternative embodiment, the rated flux linkage amplitude of the rotor is calculated from the inverter motor parameters.

[0048]

[0049] This is the rated voltage of the motor. This is the rated current of the motor. For stator inductance, The rated frequency of the motor. This is the rated flux linkage amplitude of the rotor.

[0050] This invention incorporates a correction step into the traditional voltage-type flux linkage calculation model, causing the observed flux linkage to converge toward a given flux linkage, thereby achieving accurate flux linkage position observation. This effectively avoids the integration offset problem and is simple to implement in engineering applications.

[0051] This invention obtains the observed flux linkage amplitude by calculating the amplitudes of the observed α and β axis flux linkages (Formula 4), and then compares the observed flux linkage amplitude with the given flux linkage amplitude. Subtracting the two values, we obtain the observed flux linkage amplitude deviation e. We then perform a PI proportional-integral operation on this deviation (Formula 5), ​​and multiply the result by the current current value (Formula 6) to obtain the integral compensation value of the αβ axis. Finally, by combining the traditional voltage-type rotor flux linkage calculation method, we can compensate and correct the integral element to obtain (Formula 7), thus forming an integral element with compensation and correction. This effectively avoids the above-mentioned shortcomings of pure integration, thereby achieving accurate observation of the rotor flux linkage.

[0052] Figure 4 This is a simulation diagram showing the traditional voltage-type flux linkage observation model before convergence.

[0053] Figure 5 The simulation diagram shows the convergence of the voltage-type flux linkage observation model with compensation and correction provided in the embodiment of the present invention.

[0054] Figure 4 , Figure 5In the diagram, the X-axis represents time, the Y-axis represents the rotor flux linkage value, ch1 represents the rated flux linkage amplitude of the rotor, ch2 represents the observed flux linkage amplitude of the rotor, ch3 represents the observed flux linkage value along the α-axis, and ch4 represents the observed flux linkage value along the β-axis.

[0055] The following example uses a 7.5KW three-phase asynchronous motor. Figure 4 For observation results using the traditional voltage-type flux linkage observation model, such as Figure 4 This indicates the oscillations of the rotor's rated flux linkage amplitude and the observed flux linkage amplitude, with the observation results shifting over time.

[0056] Figure 5 It represents the rotor's rated flux linkage amplitude and the observed flux linkage amplitude, achieving rapid convergence within 0.1 seconds.

[0057] Example 2

[0058] In an optional embodiment, after calculating the rotor observed flux linkage amplitude, the rotor observed flux linkage amplitude is... Low-pass filtering is performed to obtain ,use Replace the rotor rated flux amplitude This avoids the steady-state deviation between the actual observed rotor flux amplitude and the rated rotor flux amplitude, which would cause the observed rotor flux amplitude to oscillate around the rated rotor flux amplitude, thus further improving the stability of the flux observer. The observed rotor flux amplitude is low-pass filtered using the following formula (9):

[0059]

[0060] Wherein, LPF represents a low-pass filter, and the cutoff frequency is taken as the rated frequency of the motor. 1 / 10 of. Example 3

[0061] Figure 3 This diagram illustrates the structural framework of the AC motor rotor flux observation system provided in this embodiment of the invention, with reference to... Figure 3 This invention provides a system for observing the rotor flux linkage of an AC motor, the system comprising:

[0062] The calculation module is used to calculate the rotor observed flux linkage based on the first voltage-type flux linkage calculation model and the stator voltage and stator current in the two-phase stationary coordinate system.

[0063] The compensation module is used to subtract the amplitude of the rotor's rated flux linkage from the amplitude of the rotor's observed flux linkage to obtain the amplitude deviation, and then multiply the amplitude deviation by the stator current to obtain the deviation compensation amount after performing proportional-integral calculation.

[0064] The convergence module is used to compensate and correct the first voltage-type flux linkage calculation model based on the deviation compensation amount, so as to obtain a voltage-type flux linkage calculation model with compensation and correction, thereby converging the amplitude of the rotor observed flux linkage.

[0065] In an optional embodiment, before calculating the rotor observed flux linkage, the calculation module is also used to perform coordinate transformation on the collected stator current to obtain the stator current on the α and β axes in the two-phase stationary coordinate system, and to perform coordinate transformation on the command voltage output by the frequency converter to obtain the stator voltage on the α and β axes in the two-phase stationary coordinate system.

[0066] In an optional embodiment, the calculation module is used to obtain the stator currents along the α and β axes in a two-phase stationary coordinate system by performing coordinate transformation using the following equation (1):

[0067]

[0068] in, This represents the U-phase current of the motor. This represents the V-phase current of the motor. Represents the stator current along the α axis. This represents the stator current along the β axis.

[0069] , The data is obtained by sampling the UV phase current of the frequency converter and then transforming it into coordinates.

[0070] In an optional embodiment, the calculation module is used to obtain the stator voltages along the α and β axes in a two-phase stationary coordinate system by performing coordinate transformation using the following equation (2):

[0071]

[0072] in, Indicates the D-axis command voltage. Indicates the Q-axis command voltage. Represents the stator voltage along the α axis. This represents the stator voltage along the β axis.

[0073] In an optional embodiment, the compensation module is used to calculate the rotor observed flux linkage amplitudes of the α and β axes in a two-phase stationary coordinate system based on the rotor observed flux linkage; it is also used to subtract the rotor rated flux linkage amplitude from the rotor observed flux linkage amplitude to obtain the amplitude deviation.

[0074] In an optional embodiment, the compensation module is used to calculate the rotor observed flux linkage amplitude and amplitude deviation using the following formula (4):

[0075]

[0076] in, Represents the amplitude of the observed flux linkage on the rotor. , The rotor flux linkage is observed in a two-phase stationary coordinate system, where e represents the amplitude deviation. This represents the rotor's rated flux linkage amplitude. The compensation module compensates for this by... , The amplitude of the observed flux linkage of the rotor is obtained by taking the square root of the sum of squares.

[0077] In an optional embodiment, the compensation module is used to calculate the deviation compensation amount using the following formula (5):

[0078]

[0079] in, This indicates that the amplitude deviation has been calculated using a PI proportional-integral method. Indicates proportional gain. Indicates integral gain. This represents the amount of deviation compensation for the α-axis. This represents the amount of deviation compensation for the β-axis.

[0080] In an optional embodiment, the voltage-type flux linkage calculation model with compensation correction is as follows:

[0081]

[0082] in, , For rotor observation flux in a two-phase stationary coordinate system, , The stator voltage is in a two-phase stationary coordinate system. , The stator current is in a two-phase stationary coordinate system. , , , These represent the stator inductance, rotor inductance, mutual inductance, and stator resistance, respectively. This represents the leakage flux coefficient of the motor.

[0083] It is known that the voltage model for calculating rotor flux linkage can be obtained from the stator voltage equation and flux linkage equation of the motor:

[0084]

[0085] In one alternative embodiment, the rated flux linkage amplitude of the rotor is calculated from the motor parameters.

[0086]

[0087] This is the rated voltage of the motor. This is the rated current of the motor. For stator inductance, The rated frequency of the motor. This is the rated flux linkage amplitude of the rotor.

[0088] This invention incorporates a correction step into the traditional voltage-type flux linkage calculation model, causing the observed flux linkage to converge toward a given flux linkage, thereby achieving accurate flux linkage position observation. This effectively avoids the integration offset problem and is simple to implement in engineering applications.

[0089] Example 4

[0090] In an optional embodiment, after calculating the rotor observed flux linkage amplitude, the rotor observed flux linkage amplitude is... Low-pass filtering is performed to obtain ,use Replace the rotor rated flux amplitude This avoids the steady-state deviation between the actual observed rotor flux amplitude and the rated rotor flux amplitude, which would cause the observed rotor flux amplitude to oscillate around the rated rotor flux amplitude, thus further improving the stability of the flux observer. The observed rotor flux amplitude is low-pass filtered using the following formula (9):

[0091]

[0092] Wherein, LPF represents a low-pass filter, and the cutoff frequency is taken as the rated frequency of the motor. 1 / 10 of.

[0093] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for observing the rotor flux linkage of an AC motor, characterized in that, The method includes: The rotor flux linkage is calculated based on the first voltage-type flux linkage calculation model and the stator voltage and stator current in the two-phase stationary coordinate system. The amplitude deviation e is obtained by subtracting the amplitude of the rotor's rated flux linkage from the amplitude of the observed flux linkage. The amplitude deviation is then multiplied by the stator current after performing a proportional-integral operation to obtain the deviation compensation amount. The deviation compensation amount is calculated using the following formulas (5) and (6): in, This indicates that the amplitude deviation has been calculated using a PI proportional-integral method. Indicates proportional gain. Indicates integral gain. This represents the amount of deviation compensation for the α-axis. This represents the amount of deviation compensation for the β-axis. Represents the stator current along the α axis. This represents the stator current along the β axis, and e represents the amplitude deviation. The first voltage-type flux linkage calculation model is compensated and corrected based on the deviation compensation amount to obtain a voltage-type flux linkage calculation model with compensation and correction, thereby converging the amplitude of the rotor observed flux linkage.

2. The method according to claim 1, characterized in that, The observed flux linkage amplitude and amplitude deviation of the rotor are calculated using the following formula (4): in, Represents the amplitude of the observed flux linkage on the rotor. , The rotor flux linkage is observed in a two-phase stationary coordinate system, where e represents the amplitude deviation. This represents the rated flux linkage amplitude of the rotor.

3. The method according to claim 1, characterized in that, The voltage-type flux linkage calculation model with compensation correction is as follows: in, , For rotor observation flux in a two-phase stationary coordinate system, , The stator voltage is in a two-phase stationary coordinate system. , The stator current is in a two-phase stationary coordinate system. , , , These represent the stator inductance, rotor inductance, mutual inductance, and stator resistance, respectively. This represents the leakage flux coefficient of the motor.

4. The method according to claim 1, characterized in that, Before calculating the amplitude deviation, the method further includes: calculating the rotor rated flux amplitude based on the motor parameters, and calculating the rotor rated flux amplitude using the following formula (8): in, This is the rated flux linkage amplitude of the rotor. This is the rated voltage of the motor. This is the rated current of the motor. For stator inductance, The rated frequency of the motor. Indicates mutual intuition. Indicates rotor inductance, σ represents the stator resistance, and σ is the motor leakage flux coefficient.

5. A system for observing rotor flux linkage of an AC motor, characterized in that, The system includes: The calculation module is used to calculate the rotor observed flux linkage based on the first voltage-type flux linkage calculation model and the stator voltage and stator current in the two-phase stationary coordinate system. The compensation module subtracts the amplitude of the rotor's rated flux linkage from the amplitude of the observed flux linkage to obtain the amplitude deviation, and then performs proportional-integral calculation on the amplitude deviation and multiplies it by the stator current to obtain the deviation compensation amount. The convergence module is used to compensate and correct the first voltage-type flux linkage calculation model based on the deviation compensation amount, so as to obtain a voltage-type flux linkage calculation model with compensation and correction, thereby converging the amplitude of the rotor observed flux linkage.

6. The system according to claim 5, characterized in that, The compensation module is used to calculate the observed flux linkage amplitude and amplitude deviation of the rotor using the following formula (4): in, Represents the amplitude of the observed flux linkage on the rotor. , The rotor flux linkage is observed in a two-phase stationary coordinate system, where e represents the amplitude deviation. This represents the rated flux linkage amplitude of the rotor.

7. The system according to claim 6, characterized in that, The compensation module is also used to calculate the deviation compensation amount by using the following formulas (5) and (6): Equation (5) calculates the value of the rotor flux amplitude deviation after PI operation, and Equation (6) corrects the deviation compensation amount by combining the stator current component. This indicates that the amplitude deviation has been calculated using a PI proportional-integral method. Indicates proportional gain. Indicates integral gain. This represents the amount of deviation compensation for the α-axis. This represents the amount of deviation compensation for the β-axis. Represents the stator current along the α axis. This represents the stator current along the β axis.

8. The system according to claim 6, characterized in that, The voltage-type flux linkage calculation model with compensation and correction is as follows: in, , For rotor observation flux in a two-phase stationary coordinate system, , The stator voltage is in a two-phase stationary coordinate system. , The stator current is in a two-phase stationary coordinate system. , , , These represent the stator inductance, rotor inductance, mutual inductance, and stator resistance, respectively. The leakage flux coefficient of the motor. This represents the amount of deviation compensation for the α-axis. This represents the amount of deviation compensation for the β-axis.

9. The system according to claim 6, characterized in that, The calculation module is also used to calculate the rated flux linkage amplitude of the rotor based on the motor parameters before calculating the amplitude deviation, and to calculate the rated flux linkage amplitude of the rotor by the following formula (8): in, This is the rated flux linkage amplitude of the rotor. This is the rated voltage of the motor. This is the rated current of the motor. For stator inductance, The rated frequency of the motor. Indicates mutual intuition. Indicates rotor inductance, σ represents the stator resistance, and σ is the motor leakage flux coefficient.

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