DE102024111179B4 - Position detection device for an electric machine - Google Patents

Abstract

The present disclosure relates to a position detection device (1) for an electrical machine (2), comprising a current measuring device (3) for measuring a short-circuit current of the electrical machine (2), and a phase control system (4) which has an input parameter related to the short-circuit current and an output parameter related to a position of the electrical machine, wherein in the phase control system (4) all phase quantities of the short-circuit current are each processed individually by a phase control loop (7, 8, 9).

Description

The invention relates to a position detection device for an electric machine, comprising a current measuring device for measuring a short-circuit current of the electric machine, and a phase control system that has an input parameter related to the short-circuit current and an output parameter related to a position of the electric machine.

In particular, for precise control or regulation of an electrical machine, it is necessary to know the position of the electrical machine, i.e., in particular, the position of a rotor of the electrical machine relative to the position of a stator of the electrical machine.

• US 2010 / 0 259 207 A1 offenbart eine Steuereinheit für einen Wechselstrommotor.
• DE 10 2017 222 841 A1 offenbart ein Verfahren zur Bestimmung einer Drehwinkelposition einer Kurbelwelle einer Brennkraftmaschine.
• DE 11 2018 007 480 T5 offenbart eine Drehwinkelkorrektur-Berechnungseinheit, die einen Korrekturbetrag eines Drehwinkels einer Synchronmaschine berechnet.
• EP 3 736 969 B1 offenbart ein Verfahren zur Bestimmung der Position eines frei drehbaren Rotors in einem Permanentmagnetmotor.

Typically, the rotor position of an electric machine is detected using a rotor position sensor. Due to unavoidable manufacturing tolerances, the position detected/measured by the rotor position sensor does not correspond exactly to the actual position of the rotor, but rather exhibits a certain offset, commonly referred to as the offset angle. Therefore, it is necessary, particularly once or before commissioning the electric machine, to compare the actual position of the rotor with the position detected/measured by the rotor position sensor and to determine the offset angle in order to be able to mathematically correct the position detected/measured by the rotor position sensor during operation.

• US 2010 / 0 259 207 A1 reveals a control unit for an AC motor.
• DE 10 2017 222 841 A1 discloses a method for determining the angular position of a crankshaft of an internal combustion engine.
• DE 11 2018 007 480 T5 discloses a rotation angle correction calculation unit that calculates a correction amount for a rotation angle of a synchronous machine.
• EP 3 736 969 B1 discloses a method for determining the position of a freely rotatable rotor in a permanent magnet motor.

From the state of the art, for example the DE 10 2022 117 835 A1 , it is already known to detect the actual position (of the rotor) of the electric machine with a current measuring device for measuring a short-circuit current of the electric machine and a phase control system that has an input parameter related to the short-circuit current and an output parameter related to a position of the electric machine.

In particular, the DE 10 2022 117 835 A1 A rotor position detection system for the rotor position of an electric motor comprising at least one stator and at least one rotor rotatable relative to the stator with changes in rotor position, and at least two motor phases, wherein the rotor position is detected as a function of a rotor position reference value calculated from electrical operating parameters of the at least two motor phases, wherein the electrical operating parameters for calculating the rotor position reference value are referenced to a stator-fixed reference system.

However, a disadvantage of this is that existing asymmetries in the electrical machine or, if applicable, in the power electronics can affect the accuracy of the results, especially with regard to measurement technology.

The task, therefore, is to avoid or at least reduce the disadvantages. In particular, a position detection device should be provided that enables particularly simple and accurate detection of the electric machine's position.

The problem is solved by a position detection device with the features of claim 1. Advantageous further developments are the subject of the dependent claims.

The invention relates to a position detection device for an electric machine, comprising a current measuring device for measuring a short-circuit current of the electric machine, and a phase control system that has an input parameter related to the short-circuit current and an output parameter related to the position of the electric machine. In the phase control system, all phase variables/phase variables of the short-circuit current are each processed individually by a (separate, independent) phase control loop. In particular, the position of the electric machine is determined without using a position measured by a rotor position sensor. This has the advantage that the position determination can be particularly accurate and, in particular, independent of any manufacturing-related offset between the electric machine and the rotor position sensor.

According to a preferred embodiment, the position detection device can include a rotor position sensor for measuring a rotation angle of the electric machine, wherein an offset angle between the position of the electric machine and a rotation angle measured by the rotor position sensor is determined. Knowing the offset angle allows for adjustments to the rotation angle during operation. The measured rotation angle position can be used.

According to the invention, the phase control system can have three phase control loops, each with a bandpass-filtered phase signal as its output. This improves the computation.

According to the preferred embodiment, the three phase-locked loops can (additionally) each have an output signal that leads the bandpass-filtered phase by 90°. This means that two sinusoidal signals, offset by 90°, with the same frequency and amplitude are generated.

According to the preferred embodiment, each of the three phase-locked loops can have a phase parameter of the short-circuit current as its input signal. The short-circuit current constitutes a suitable input parameter. Alternatively, and with adaptation of the phase-locked system, an open-circuit voltage could also be used.

According to the invention, the phase control system can have a computation block downstream of the three phase-locked loops. This means that the computation block receives as its input a signal related to the output parameters of the three phase-locked loops. In particular, the output parameters of the three phase-locked loops can be fed directly to the computation block.

According to the preferred embodiment, the calculation block can have one or more symmetrical phase variables as an output signal.

According to the preferred embodiment, the computation block can take the (three) bandpass-filtered phase quantities as an input signal. That is, the computation block generates a signal from the bandpass-filtered phase quantities.

According to the preferred embodiment, the computation block can take as its input the (three) signals that lead the bandpass-filtered phase quantities by 90°. This means that the computation block also uses the signals offset by 90° to generate a signal.

According to the preferred embodiment, the phase control system can have a further phase control loop downstream of the computation block. This means that the further phase control loop has as its input a signal related to the output parameter(s) of the computation block. In particular, the output parameter of the computation block can be fed directly to the further phase control loop.

According to the preferred embodiment, the further phase-locked loop can have a phase angle of the short-circuit current as an output parameter. Furthermore, the further phase-locked loop can have an amplitude of the short-circuit current as an output parameter.

According to a preferred embodiment, an offset between the measured rotor angle and the phase angle of the short-circuit current can be averaged over several values. This allows periodic and/or stochastic effects to be suppressed.

According to a preferred embodiment, the phase angle of the short-circuit current and/or an offset between the measured rotor angle and the phase angle of the short-circuit current can be determined under different system conditions. This allows systematic deviations to be taken into account.

According to a preferred embodiment, the phase angle of the short-circuit current and/or an offset between the measured rotor angle and the phase angle of the short-circuit current can be changed by a correction value. Preferably, the correction value can be determined application- and/or condition-specifically.

In other words, the present disclosure relates to offset angle determination by a phase-locked loop with stator-fixed short-circuit phase variables. The background to this is that, in an electric drive, manufacturing tolerances necessitate adjustment between the rotor position sensor/rotor position encoder and the electric machine/electric motor after assembly. Specifically, the disclosure relates to a system comprising an electric machine with at least one phase, at least one rotor, and at least one stator; power electronics that control the phases of the electric machine and can establish a short circuit and/or freewheeling of the phases; a measuring device for the current of the phases of the electric machine and the power electronics; and an angle encoder system that can measure an angle between the rotor and stator of the electric machine. The procedure is as follows: When the rotor speed of the electric machine is not zero, the machine is short-circuited by the power electronics. The phase variables/phase variables are considered in a two-phase or multi-phase stator-fixed coordinate system. Therefore, it does not need to be transformed into the rotor-fixed dq coordinate system. The angle of the electric machine is determined based on the phase dimensions in the stator-fixed coordinate system. Comparing this angle with the rotor position sensor angle yields the offset angle. This offers the following advantages: Regarding ASIL (Automotive Safety Integrity Level) integrity, no RPS angle (rotor position sensor angle) is required to determine the electric machine angle. Furthermore, the use of a so-called αβ-PLL (phase-locked loop), which operates in the stator-fixed coordinate system, results in low frequency and phase overshoot due to errors in the input signal. Accurate results can also be achieved even with existing asymmetries in the electric machine and power electronics, particularly in the measurement technology. The design of the electric machine angle determination based on the phase parameters in the stator-fixed coordinate system is possible in the following three variants: In an αβ-PLL, the measured phase parameters of the electric machine are transformed into the stator-fixed αβ-coordinate system, and the phase angle is determined by a phase-locked loop using the addition theorem. In an αβ-Sin-Cos-PLL, unlike in the αβ-PLL, if a rotor position sensor with a sine-cosine output is used, these signals can be used instead of those determined from the estimated angle. In a 3-phase enhanced PLL (3EPLL), unlike in the αβ-PLL and the αβ-Sin-Cos-PLL, the phase parameters can be fed directly to a three-phase PLL.

• 1 zeigt eine schematische Darstellung einer Positionserfassungsvorrichtung,
• 2 zeigt einen Aufbau des Phasenregelsystems,
• 3 zeigt einen Aufbau einer elektrischen Maschine,
• 4 zeigt einen Zusammenhang zwischen einem statorfesten und einem rotorfesten Bezugsystem,
• 5 zeigt einen beispielhaften Aufbau einer Phasenregelschleife, und
• 6 bis 8 zeigen alternative Möglichkeiten zur Rotorwinkelbestimmung.

The revelation is explained below with the help of drawings:

• 1 shows a schematic representation of a position detection device,
• 2 shows a structure of the phase control system,
• 3 shows the structure of an electric machine,
• 4 shows a relationship between a stator-fixed and a rotor-fixed reference frame,
• 5 shows an exemplary setup of a phase-controlled loop, and
• 6 to 8 show alternative methods for determining rotor angle.

The figures are purely schematic and serve solely to aid in understanding the present revelation. Identical elements are marked with the same reference symbols.

1 Figure 1 shows a schematic representation of a position detection device 1 according to the present disclosure. The position detection device 1 serves to detect an (actual) position γ _EM of an electric machine 2 (see also Figure 1). 3 The position detection device 1 has a current measuring device 3 for measuring a short-circuit current I _ASC of the electrical machine 2.

Furthermore, the position detection device 1 has a phase control system 4. The phase control system 4 has an input parameter related to the short-circuit current I _ASC and an output parameter related to a position of the electric machine 2.

In particular, the position detection device 1 can include power electronics 5. The power electronics 5 serve to put the (rotating) electric machine 2 (AC side) into a short circuit.

Furthermore, the position detection device 1 can include a rotor position sensor 6 for measuring a rotation angle γ _EM of the electric machine 2. The rotor position sensor 6 detects the measured rotation angle γ _RPS , which has an offset θ _Offs to the (actual) position (see also 4 ).

2 Figure 4 shows the structure of phase control system 4. In phase control system 4, the short-circuit current I_{_ASC} serves as the input parameter. The short-circuit current I_{_ASC} has three phase parameters: I _{_U}, I_{_V}, and I_{_W} . A U-phase I_{_U} of the short-circuit current I_{_ASC} serves as the input parameter for a first phase control loop 7. A V-phase I_v of the short-circuit current I_{_ASC} serves as the input parameter for a second phase control loop 8. A W-phase I_w of the short-circuit current I_{_ASC} serves as the input parameter for a third phase control loop 9. The first phase control loop 7, the second phase control loop 8, and the third phase control loop 9 are independent of each other. This means that each phase parameter I_{_U}, I_{_V}, and I_{_W} of the short-circuit current I_{_ASC} is processed individually by its own phase control loop 7, 8, and 9, respectively.

The first phase-locked loop 7 (in particular an enhanced phase-locked loop, EPLL) has an output parameter _I'U relative to the phase U _I. The output parameter _I'U can, in particular, be a bandpass-filtered parameter of the phase U _I. Furthermore, the first phase-locked loop 7 can have an output parameter jI'U relative to the phase U _I , which is offset by 90° from the output parameter _I'U . This means that in the first phase-locked loop 7, two sinusoidal signals are generated that have the same amplitude and the same frequency, but are shifted by 90° relative to each other, with the output parameter _jI'U leading by 90°.

The second phase-locked loop 8 (in particular an enhanced phase-locked loop, EPLL) has an output parameter _I'V relative to the V-phase Iv. The output parameter _I'V can, in particular, be a bandpass-filtered parameter of the V-phase _Iv. Furthermore, the second phase-locked loop 8 can have an output parameter _jI'V relative to the V-phase _Iv , which is offset by 90° from the output parameter _I'V . This means that two sinusoidal signals are generated in the second phase-locked loop 8, which have the same amplitude and the same frequency, but are shifted by 90° relative to each other, with the output parameter _jI'V leading by 90°.

The third phase-locked loop 9 (in particular an enhanced phase-locked loop, EPLL) has an output parameter _I'W relative to the W-phase I_{_W}. The output parameter _I'W can, in particular, be a bandpass-filtered parameter of the W-phase I_{_W.} Furthermore, the third phase-locked loop 9 can have an output parameter _jI'W relative to the W-phase I_{_W} , which is offset by 90° from the output parameter _I'W . This means that in the third phase-locked loop 9, two sinusoidal signals are generated that have the same amplitude and the same frequency, but are shifted by 90° relative to each other, with the output parameter _jI'W leading by 90°.

The output parameters _I'U , jI'U, _I'V , _jI'V , _I'W , _jI'W of the three phase-locked loops 7, 8, ₉ form an input signal for a computation block 10 (in particular, a so-called ISC computation block, Instantaneous Symmetrical Components computation block). The computation block can, in particular, have one or more symmetrical current sequence(s) as output parameters I ⁺ _U , I ⁺ _V, or I ⁺ _W , where I ⁺ _U , I ⁺ _V , and I ⁺ _W are symmetrical components.

The output parameter I ⁺ _U , I ⁺ _V , or I ⁺ _W of calculation block 10 forms an input parameter for a fourth phase-locked loop 11 (in particular, an enhanced phase-locked loop, or EPLL). The fourth phase-locked loop 11 can, in particular, have a phase angle of the short-circuit current I _ASC as an output parameter θ _IASC . Furthermore, the fourth phase-locked loop 11 can have an amplitude of the short-circuit current I _ASC as an output parameter I ⁺ _mag .

A difference between a measured rotor angle _γRPS and the phase angle _γIASC of the short-circuit current _IASC results in an offset _θASC,RPS . From the offset _θASC,RPS and the phase angle _θIASC of the short-circuit current _IASC, an offset _θOffs can be determined, which is a shift between the measured rotor angle _γRPS and the actual rotor angle _γEM .

The difference can be averaged over several values. Furthermore, the phase angle _θIASC or the offset _θASC,RPS can be determined for different system states. Additionally, the phase angle _θIASC or the offset _θASC,RPS can be modified by a correction value. This correction value can be determined application- and/or state-specifically, particularly taking into account rotational speed, temperature, machine parameters, and/or the amplitude of the short-circuit current.

3 Figure 1 shows the basic structure of the electric machine 2. The electric machine 2 has a stator 12 and a rotor 13 that can rotate about an axis of rotation relative to the stator 12, as well as three motor phases, each of which is supplied with a phase voltage for the operation of the electric machine 2. When the rotor 13 rotates relative to the stator 12, the rotor position changes, which is the rotational position of the rotor 13 relative to the stator 12.

4 This figure shows a relationship between a stator-fixed αβ reference frame and a rotor-fixed dq reference frame, in which the electrical operating quantities present during the operation of the electric machine 2 can be described. In the stator-fixed αβ reference frame, the α-axis is aligned with the direction of a coil of the electric machine 2. In the rotor-fixed dq reference frame, the d-axis is aligned with the magnetic flux density. The angles denoted by γ refer to the stator-fixed αβ reference frame. The rotation angle relationships denoted by θ refer to the rotor-fixed dq reference frame.

The d-axis, or a vector representing the rotor position, forms a field angle γ _EM . A vector representing the short-circuit current I _ASC forms a field angle γ _IASC . A vector representing the rotor position sensor, or a measured rotor position RPS, forms a field angle γ _RPS . The offset θ _Offs exists between the rotor position vector and the rotor position sensor vector. The offset θ _ASC,RPS exists between the short-circuit current vector I _ASC and the rotor position sensor vector. The rotation angle relationship θ _IASC exists between the d-axis and the short-circuit current vector I _ASC .

5 shows an exemplary setup of a phase-controlled loop, such as the first phase-controlled loop 7, the second phase-controlled loop 8, the third phase-controlled loop 9 and/or the fourth phase-controlled loop 11.

6 to 8 show alternative ways to determine the actual rotor angle γ _EM .

List of reference symbols

1

Position detection device

2

electric machine

3

Current measuring device

4

Phase control system

5

Power electronics

6

Rotor position sensor

7

first phase-locked loop

8

second phase-locked loop

9

third phase-locked loop

10

Calculation block

11

fourth phase-locked loop

12

stator

13

rotor

Claims (8)

Position detection device (1) for an electric machine (2), comprising a current measuring device (3) for measuring a short-circuit current of the electric machine (2), and a phase control system (4) which has an input parameter related to the short-circuit current and an output parameter related to a position of the electric machine (2), wherein in the phase control system (4) all phase quantities of the short-circuit current are each processed individually by a phase control loop (7, 8, 9), wherein the phase control system (4) has three phase control loops (7, 8, 9), each of which has a bandpass-filtered phase quantity as an output signal, characterized in that the phase control system (4) has a calculation block (10) downstream of the three phase control loops (7, 8, 9), which has a symmetrical phase quantity as an output signal. Position detection device (1) according Claim 1 , characterized in that the position detection device (1) has a rotor position sensor (6) for measuring a rotation angle of the electric machine (2), wherein an offset angle between the position of the electric machine (2) and a rotation angle measured by the rotor position sensor (6) is determined. Position detection device (1) according Claim 1 or 2 , characterized in that the three phase-controlled loops (7, 8, 9) each have a phase parameter of the short-circuit current as an input signal. Position detection device (1) according to one of the Claims 1 until 3 , characterized in that the calculation block (10) has the bandpass filtered phase quantities as an input signal. Position detection device (1) according to one of the Claim 1 until 4 , characterized in that the phase control system (4) has a further phase control loop (11) downstream of the calculation block (10), which has a phase angle of the short-circuit current as an output parameter. Position detection device (1) according to one of the Claims 2 until 5 , characterized in that an offset between the measured rotor angle and a phase angle of the short-circuit current is averaged over several values. Position detection device (1) according to one of the Claims 2 until 6 , characterized in that a phase angle of the short-circuit current and/or an offset between the measured rotor angle and the phase angle of the short-circuit current is determined for different system states. Position detection device (1) according to one of the Claims 2 until 7 , characterized in that a phase angle of the short-circuit current and/or an offset between the measured rotor angle and the phase angle of the short-circuit current is changed by a correction value.