Parameter identification for an induction motor

Abstract

The present invention relates to a method for determining parameters for adjusting an electric drive (1), wherein the electric drive (1) has at least one motor (2). To improve the starting of the electric drive, a current indication is applied as a signal at the three-phase winding terminals (U, V, W) of the motor (2), wherein the d-component and q-component of the stator voltage and stator current are measured at the winding terminals (U, V, W), wherein in a first measurement step (11), a rotating current indication is applied to the three-phase winding terminals (U, V, W) and the motor (2) is oriented such that the excitation current on the q-axis is minimized, wherein in a second measurement step, the excitation winding (7) of the motor (2) is short-circuited while the rotor of the motor (2) is stationary and a current indication is applied to the winding terminals (U, V, W) in the form of a binary noise signal, wherein the stator impedance (Zd) is determined as a first adjustment parameter from the measured values. The invention also relates to an adjustment device (4) for the electric drive (1), wherein the adjustment device (4) is configured to perform this method.

Description

Technical Field

[0001] This invention relates to a method for determining adjustment parameters for adjusting an electric drive using vector control, wherein the electric drive has at least one motor. Furthermore, this invention relates to an adjustment device for an electric drive using vector control, and an electric drive having such an adjustment device, a frequency converter, and a motor. Background Technology

[0002] Electric drives typically consist of at least one frequency converter and a motor. The frequency converter controls or regulates the motor. Different mathematical schemes exist for regulation. One scheme is vector regulation. Here, to parameterize the vector regulation of the frequency converter, motor parameters are needed, which are often derived from the physical description, simulation, or modeling of the motor. However, the required data, presented as equivalent circuit diagram data, often does not exist at all, is incomplete, or contains errors. The parameters required for regulation are also referred to as regulation parameters.

[0003] Currently, the parameters of an electric motor, also known as motor parameters, are determined very time-consumingly during startup through various processes and experiments. Summary of the Invention

[0004] The purpose of this invention is to improve the startup of an electric drive.

[0005] This objective is achieved through a method for determining adjustment parameters for adjusting an electric drive using vector control. The electric drive has at least one motor. A current indication is applied as a signal to the three-phase winding terminals of the motor. The d-components and q-components of the stator voltage and stator current are measured at the winding terminals. In a first measurement step, a rotating current indication is applied to the three-phase winding terminals, and the motor is oriented such that the excitation current on the q-axis is minimized. In a second measurement step, with the motor rotor stationary, the excitation winding of the motor is short-circuited, and a current indication is applied to the three-phase winding terminals as a binary noise signal. The stator impedance, as a first adjustment parameter, is determined by the measured d-components and q-components of the stator voltage and stator current. Furthermore, this objective is achieved through an adjustment device for performing vector control on an electric drive. The adjustment device is configured to perform this method. During the startup phase, at least one adjustment parameter for vector control can be determined and stored using the adjustment device. After the startup phase ends, at least one stored adjustment parameter can be used for vector control. Furthermore, this objective is achieved by an electric drive having a frequency converter and at least one motor, wherein the frequency converter has such a regulating device, wherein voltage measuring devices and current measuring devices are disposed in the electrical connection between the frequency converter and the motor.

[0006] Further advantageous designs of the invention are given in the embodiments.

[0007] Furthermore, this invention is based on the understanding that startup can be improved by determining the impedances on the d-axis and q-axis of the motor in a static measurement, for example, using an adjustment device. Hereinafter, the motor is also referred to as a motor. For this purpose, the motor rotor is first aligned and then fixed. By applying a binary noise signal to the motor terminals, the stator current and stator voltage at the motor's terminals are measured. Then, the required equivalent circuit diagram data is obtained, for example, using numerical methods based on Gauss or Newton. Because these corresponding values ​​are needed as parameters for adjustment, especially for vector adjustment, these values ​​are also called adjustment parameters. These values ​​can be provided independently of the adjustment frequency or can be determined based on the frequency as a so-called frequency response. By using the frequency response as the adjustment parameter, the behavior of the adjustment at various operating points can be optimized. The adjustment can be stabilized precisely at the resonant position, and the reaction force on the load or energy supply network can be reduced.

[0008] Here, the measurement can be performed by a measuring device, also referred to as a measuring box. This measuring box can operate at a relatively low operating voltage, such as 24V or 48V. The measuring box transmits the derived, calculated, and / or determined data to the vector control. Here, the measuring device can be part of the control device or can be located outside the control device. In any case, this relates to a measuring device for an electric actuator for determining the control parameters of the vector control, wherein the measuring device is configured to perform the method according to the invention.

[0009] Here, the motor is measured on the d-axis and q-axis. For this purpose, the d-components and / or q-components of the stator current and / or stator voltage are measured. A current indicator in the form of a binary noise signal is used for excitation measurement. The positioning of the current indicator is achieved by setting the commutation angle accordingly. The d-components and / or q-components of the stator current and / or stator voltage are measured separately. To obtain additional adjustment parameters, the current in the short-circuited excitation winding can also be measured. After processing, for example, through a Fast Fourier Transform (FFT) of the data, the frequency response of the stator impedance or individual adjustment parameters can be calculated as adjustment parameters. Furthermore, when measuring on the d-axis, the frequency response of the ratio of excitation current to stator current can be calculated as another adjustment parameter.

[0010] These frequency responses can then be derived based on known equivalent circuit diagrams on the d-axis and q-axis, and are thus transformed into resistances, inductances, and turns ratios between the excitation and stator windings by skillful selection of equivalent circuit elements, enabling the establishment of the best possible consistency. For this purpose, known interpolation methods can be used.

[0011] Therefore, measurements are taken at a defined location. In the first measurement step, the q-axis is detected by measuring the minimum value of the excitation current. The current indicator rotates at a very low frequency within the machine. Simultaneously, the excitation winding is short-circuited using a separate current measuring device, thereby also allowing the measurement of the excitation current. The induced signal on the excitation winding reaches its minimum value on the q-axis. The corresponding transition angle corresponds to the q-axis. Here, the excitation current can be determined either from the excitation current or from the stator current.

[0012] In an advantageous embodiment of the invention, a binary noise signal is generated using a feedback shift register with a pseudo-random number sequence. The shift register has a shift clock, which generates a preset spectrum. By generating the noise signal using the feedback shift register, it is possible to easily configure it with the spectrum. This current indication can be easily generated, for example, in a converter feeding a motor, and the measurement signal can also be easily configured to the corresponding frequency in frequency response evaluation. Here, the shift clock used to move bits through the register can be advantageously set. Different shift clocks can generate corresponding spectra. Furthermore, for each shift clock, the number of cycles is limited to determine the measurement accuracy and duration. Using a noise signal based on a pseudo-random number sequence, both measurement and evaluation can be performed easily in the regulation or control unit of a converter feeding a motor. This also allows for automatic implementation of these parameter identifications.

[0013] In another advantageous embodiment of the invention, the stator impedance is determined based on the frequency using a Fast Fourier Transform (FFT). The FFT is a simple numerical evaluation of the measurement data and allows for the generation of not only a single frequency-independent parameter but also the frequency response as a control parameter. Therefore, the operating point and behavior of the motor can be described significantly more accurately. Consequently, the motor can be controlled significantly more simply and precisely. Furthermore, critical operating points, such as those caused by resonance, can be described more accurately. Thus, stable control behavior can be achieved at these operating points.

[0014] In another advantageous embodiment of the invention, the frequency response of the stator impedance is calculated for the real and imaginary parts of the stator impedance. It has proven advantageous to describe the complex values ​​of the impedance as real and imaginary parts. This generates a logical relationship with the parameters of the equivalent circuit diagram. Because this equivalent circuit diagram typically forms the basis and physical relationship with respect to the adjustment parameters, adjustment can be established particularly easily. Errors in parameter identification can also be identified in a simple manner based on reliability checks. Therefore, particularly robust and error-resistant adjustment is obtained through this division.

[0015] In another advantageous embodiment of the invention, the excitation current is measured by short-circuiting the excitation winding, wherein the ratio of the excitation current to the stator current is determined from the excitation current and d-component of the stator current as a second adjustment parameter. In this way, additional adjustment parameters can be determined, allowing for further improvements in the adjustment behavior.

[0016] In another advantageous embodiment of the invention, the calculated and / or determined adjustment parameters are stored for use in vector control. Storage also allows the parameters to be calculated externally to the control device. However, even when these parameters are calculated within the control device, the calculation can be performed using its own software program. After the calculation is complete, the data is stored and used for driver adjustment, particularly for vector control. Different software programs, such as those for calculating adjustment parameters and performing adjustment via vector control, can then be executed independently of each other. This optimizes the structure of the control device. Attached Figure Description

[0017] The invention will now be described and explained in more detail with the aid of embodiments shown in the accompanying drawings. The drawings show:

[0018] Figure 1 Showing the electric drive,

[0019] Figure 2 The flowchart is shown, and

[0020] Figure 3 The frequency response of the stator impedance is shown. Detailed Implementation

[0021] Figure 1 An electric drive 1 with a motor 2 is shown, which is powered by a frequency converter 5. The frequency converter 5 has a regulating device 4. This regulating device 4 has a measuring device 3 for performing the proposed method. Here, the measuring device 3 does not necessarily have to be part of the frequency converter 5 or the regulating device 4. However, it is suitable to use the frequency converter 5 as the voltage source for the electric drive 1, the voltage of which is preset by the measuring device 3. The winding terminals U, V, and W are the terminals of the motor 2. These winding terminals are connected to the stator windings of the motor 2. The stator current is measured at the winding terminals U, V, and W using a current measuring device 6, and the voltage between the winding terminals is measured using a voltage measuring device 8. It is sufficient to determine only two of the three voltages or currents, as the third voltage or current can be mathematically determined from the other two.

[0022] In order to determine the adjustment parameters, the signals from the current measuring device 6 and the voltage measuring device 8 are transmitted to the measuring device 3.

[0023] Furthermore, the motor 2 also has an excitation winding 7 in its rotor, which is also referred to as the rotor winding. The excitation winding 7 is short-circuited by means of an additional current measuring device 9. The current measured here can also be transmitted to the measuring device 3. The excitation current can be obtained from the signal of the additional current measuring device 9, and the orientation of the d-axis and q-axis can be performed using this excitation current.

[0024] Figure 2 The flowchart for parameter determination is shown. In the first measurement step 11, the motor is oriented. This means determining the positions of the d-axis and the q-axis, which is offset from it by 90°. For this purpose, a rotational current indicator is fed into motor 2, wherein the q-axis is detected at the minimum value of the excitation current.

[0025] After successfully completing the probe, the method transitions to the second measurement step 12. In this step, the stator current and stator voltage are measured, and the stator impedance Zd is determined as the first adjustment parameter. The measurement can be performed over a frequency range, meaning that the stator impedance is obtained as the frequency response based on different values ​​at different frequencies.

[0026] If the second measurement step is also completed, the regulating device can use these data to perform vector regulation and precisely control and stably regulate motor 2.

[0027] Figure 3 The diagram shows typical measurements of stator impedance, divided into real and imaginary parts. The left ordinate represents the real part, and the right ordinate represents the imaginary part. The frequency response of the stator impedance can be determined from these measurements using well-known interpolation methods.

[0028] In general, the present invention relates to a method for determining parameters for adjusting an electric drive, wherein the electric drive has at least one motor. To improve the starting of the electric drive, a current indication is applied as a signal to the three-phase winding terminals of the motor, wherein the d-component and q-component of the stator voltage and stator current are measured at the winding terminals, respectively. In a first measurement step, a rotating current indication is applied to the three-phase winding terminals and the motor is oriented such that the excitation current on the q-axis is minimized. In a second measurement step, with the motor rotor stationary, the excitation winding of the motor is short-circuited and the current indication is applied to the winding terminals in the form of a binary noise signal. The stator impedance is determined as a first adjustment parameter from the measured values. The invention also relates to an adjustment device for an electric drive, wherein the adjustment device is configured to perform this method.

Claims

1. A method for determining an adjustment parameter for adjusting an electric drive (1) via vector adjustment, wherein The electric drive (1) has at least one electric machine (2), wherein a current indication is applied as a signal to three-phase winding terminals (U, V, W) of the electric machine (2), wherein d and q components of stator voltage and stator current are measured at the winding terminals (U, V, W), respectively, wherein in a first measurement step (11) a rotating current indication is applied to the three-phase winding terminals (U, V, W) and the electric machine (2) is oriented such that the excitation current on the q axis assumes a minimum value, wherein in a second measurement step, with the rotor of the electric machine (2) at rest, the field winding (7) of the electric machine (2) is short-circuited and a current indication is applied to the three-phase winding terminals (U, V, W) in the form of a binary noise signal, wherein from the measured d and q components of the stator voltage and the stator current a stator impedance (Zd) is determined as a first regulation parameter, wherein the binary noise signal is generated from a pseudo-random number sequence with a feedback shift register, wherein the shift register has a shift clock, wherein with the shift clock a predefinable frequency spectrum is generated, wherein with different shift clocks different frequency spectra are generated, and when measured on the d axis the frequency response of the ratio of the field current to the stator current can be calculated as a further regulation parameter.

2. The method of claim 1, wherein, The stator impedance (Zd) is determined from the frequency by means of a fast Fourier transform.

3. The method of claim 1 or 2, wherein, The frequency response of the stator impedance (Zd) is calculated for the real and imaginary parts of the stator impedance (Zd).

4. The method of claim 1 or 2, wherein, measuring the field current (i F ) from the short-circuited field winding (7), wherein the ratio of the field current (i F ) and the d-component is determined as a second regulation parameter from the stator current of the field current (i F ).

5. The method of claim 1 or 2, wherein, The determined, calculated and / or determined regulation parameters are stored for use in the vector regulation.

6. A regulating device (4) for an electric drive (1), the regulating device being designed to perform a vector regulation, wherein The regulation device (4) is designed to carry out the method according to any one of claims 1 to 5, wherein at least one regulation parameter for the vector regulation can be determined and stored by means of the regulation device (4) in a start-up phase, wherein at least one stored regulation parameter can be used for the vector regulation after the end of the start-up phase.

7. An electric drive (1) having: - a frequency converter (5), and - at least one electric machine (2), wherein the frequency converter (5) having a regulation device (4) according to claim 6, wherein voltage measuring devices (8) and current measuring devices (6) are arranged in the electrical connection between the frequency converter (5) and the electric machine (2).

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