WO2020083985A1

WO2020083985A1 - Method and device for load-free determining of load-dependent positioning parameters of a synchronous machine without a position sensor

Info

Publication number: WO2020083985A1
Application number: PCT/EP2019/078879
Authority: WO
Inventors: Peter Landsmann; Dirk Paulus; Sascha Kühl
Original assignee: Kostal Drives Technology Gmbh
Priority date: 2018-10-24
Filing date: 2019-10-23
Publication date: 2020-04-30

Abstract

The invention relates to a method or a device for load-free determining of load-dependent positioning parameters of a synchronous machine without a position sensor, which is controlled via pulsed terminal voltages from which, and in combination with the measured current response, the inductance or admittance is calculated or wherein from the load-free lowest and the load-free highest differential inductance are known, wherein based on the load-free lowest and the load-free highest differential inductance and the short-circuit current, the magnetic saturation behaviour under the load of the absolute inductance and/or the magnetic anisotropy of the synchronous machine is predicted and used in the position-sensor-free control operation for positioning.

Description

Method and device for load-free determination of load-dependent position assignment

Parameters of a synchronous machine without position encoder

1 State of the art

Processes that enable efficient control of a synchronous machine without position encoder (often referred to as "encoderless" or "sensorless" control) are divided into two classes:

1. Basic wave method [1] [2] [3] evaluate the voltage induced under motion, deliver very good signal properties at medium and high speeds, but fail in the lower speed range, especially when stationary. For operation under load (saturation), fundamental wave methods require a current-dependent parameterization of the inductance [4] [5]

2. Anisotropy-based methods [6] [7] [8] evaluate the positional dependency of the inductance of the machine, which does not require a speed, but have several problems and hurdles that explain why many applications still have one today Position encoder (with its disadvantages) need. For operation under load (saturation), anisotropy-based methods require a current-dependent parameterization of the anisotropy shift [9] [10] [11] [12].

Encoderless control of synchronous machines in the entire speed range is implemented by a combination of methods from both classes [8] [13].

Magnetic simulation data can be used to determine the current-dependent course of inductance and anisotropy shift [14] [15], which deviate from reality and require access to the machine design. Or these curves can be measured on a test bench with a load machine and position encoder [16] [17], which in practice can be too time-consuming or impossible if an unknown synchronous machine is to be connected in the field.

For the connection of an unknown synchronous machine there are approaches for initial parameter identification with neglect of the current dependency [18] [19], which become imprecise / unstable when operating under increased load. Other approaches also use short-term macroscopic excitation [20] [21] [22] to identify the load dependency, which inevitably goes hand in hand with torque peaks that are not acceptable in every application and also the results of the unblocked rotor

Falsify identification.

The change in inductance (in the event of a change in current) can alternatively be tracked using online identification methods [23] [24] [25] [26], which, however, are delayed in principle (factor 10-1000 slower than the actual change) ) and are therefore accurate / stable only when stationary.

Approaches to identification also exist for the anisotropy shift [27]

[28] in operation, which, however, is a correctly (non-linear) parameterized fundamental wave model! require and only deliver good results if operating points in a certain speed range with as different torque values as possible have been run through over a sufficient period of time, which cannot be assumed in all applications.

2 basics

The following is a general explanation, also regarding optional embodiments of the invention. Show:

Fig. 1 rotor cross-sections with surface-mounted (left) and with buried

(right) permanent magnets, soft magnetic material hatched, permanent flux cut indicated by triangle

Fig. 2 Qualitative representation of the current-flow relationship in the d direction with differential inductors

Fig. 3 Qualitative representation of the current-flow relationship in the q direction with differential and absolute inductors

Fig. 4 current vector summation in rotor coordinates and anisotropy shift in geometrically isotropic machines Fig. 5 Qualitative course of the anisotropy amount over the amount of the saturation current

Fig. 6 Stro m vekto rs u m m ation in stator coordinates and resulting dependency of the amount and the angle of the saturation current on the rotor position

7a-f curves of 3 geometrically isotropic (SPM) and 3 geometrically anisotropic (IPM) PM synchronous machines calculated from measured data, each plotted against the normalized load

in each case above: the course of the absolute inductance L

Measured (continuous) and according to the saturation assumption (dashed), each vertically centered: the course of the resulting fundamental wave angle error without (dotted) and

with (dashed) saturation assumption, and below: the course of the anisotropy-based estimation error in electrical degrees without (ge

scores) and with (dashed) saturation assumption. The vertical dotted line marks the nominal current according to the nameplate.

8a-c Experimental results of the closed sensorless control loop with SPM3 in each case plotted over time in seconds; the estimated rotor position in [rad] at the top, the q-current in vertical

estimated rotor coordinates and each below the anisotropy base

Estimated error Fig. 8a shows the operation without saturation

supply assumption, Fig. 8b with assumption for the anisotropy shift and Fig. 8c with assumption for the unique rotor position assignment (RPA).

It is pointed out that the figures only show exemplary arrangements of machines or courses of physical quantities, and that the method described here and its embodiments are not limited to the representations in the figures.

The term “machine” is used here in the sense of an “electrical machine”, ie an electric motor or an electrical generator.

Fundamental wave methods use the general voltage equation of the machine

Knowing the parameters of resistance R _s and absolute q inductance L _q, the rotor position 9 _r can be calculated from the time profiles of current and voltage at medium and high speeds, for example using the following calculation rule

The so-called absolute inductances L _d and L _{q are defined} as the quotient of flux linkage (flow for short) and current and are characterized in that they have only one axis reference (eg q) in the subscript

Anisotropy-based methods use the high-frequency relationship

which results, for example, according to [29], [30] or [31] without knowledge of the parameters of the anisotropy angle

can be calculated. Knowing the iast-dependent anisotropy shift, the measured ansitropy angle can be used during operation

Assign rotor position estimate to § _r

The so-called differential inductances and as a derivative of the

River defined by the current and bear two axis references in the subscript

Usually the flow across the stream is non-linear, which is why the values

and are current dependent. The special value of a current-dependent quantity at zero current {so-called Value in the de-energized state) is characterized by the additional variable index 0 - in the case of differential inductances, for example and

However, anisotropy methods often work with voltage injection and evaluate that

Current response, which is why the inverse differential inductance is relevant, which is often simply referred to as admittance Y.

Here the so-called anisotropy amount Y _& is half the difference between the directionally largest and smallest admittance

and indicates how strong the directional dependence of the RF current response is. Direction dependency (Greek anisotropy) always means: Dependence on the direction of the current-voltage relationship (not the rotor position) over which various differential inductance values are effective (acting in the d-direction

_or, in q-direction and

In the de-energized state, the coupling component is approximately zero, which means that

simplified (18)

The anisotropy angle () _u is the direction of the smallest differential inductance and consequently the largest admittance. The direction of the largest differential inductance and consequently the smallest admittance is offset by ± 90 ° (electrical). The anisotropy angle can therefore be calculated from both variables, for example as follows

Furthermore, two classes are distinguished within the scope of the embodiments described here with regard to the rotor topology of synchronous machines:

1.

Synchronous machines have a rotor cross-section in which the amount and shape of the soft magnetic material do not differ between the different magnetic paths of the phase windings, so that their magnetic anisotropy is based solely on the fact that the exciting element (e.g. permanent magnet or excitation winding) localizes the soft magnetic material ( depending on the direction). The magnetic anisotropy of these machines in the de-energized state is usually smaller, namely

2nd

Synchronous machines show a rotor cross-section in which the amount and / or shape of the soft magnetic material between distinguishes the different magnetic paths of the phase windings, which creates an additional anisotropic component. As a result, the magnetic anisotropy of these machines in the de-energized state is usually greater, namely

1 shows a typical example of a geometrically isotropic machine on the left and a typical example of a geometrically anisotropic machine on the right. Only the hatched areas have a high magnetic conductivity and, due to the geometry of the right cross section, lead to a significantly increased inductance in the q direction.

Regardless of the actual geometry, most machines can be assigned to their corresponding class on the basis of the clamping behavior if the initially found anisotropy is compared against the threshold value 20%.

3 saturation assumptions

A method for the load-free determination of load-dependent position assignment parameters of a synchronous machine without a position encoder is presented below. The synchronous machine is controlled via clocked clamping voltages, from which the inductance or admittance is calculated in connection with the measured current response. As an alternative to this calculation, the smallest load-free and the largest load-free differential inductance can also be known. From the smallest and the most

the largest load-free differential inductor and and the short-circuit

current the magnetic saturation behavior under load of the absolute inductance

and the magnetic anisotropy of the synchronous machine are predicted and compensated for in position-less control mode and / or used for position assignment.

In some embodiments, a load-free differential inductance corresponds to the derivative of the flux linkage after the current (cf. (10) - (12>) at the operating point with zero current. In some embodiments, the smallest and the largest differential inductance are the direction-dependent smallest and largest differential inductance values of an operating point, the directional dependency corresponding to the magnetic anisotropy.

If the smallest load-free and the largest load-free differential inductance L _dd0 and L _{qq0 are} not known, these values can be calculated from the current-voltage relationship by electrical excitation of the machines. The excitation can be, for example, test pulses, sinusoidal voltage profiles or a discrete-time voltage injection pattern. There are easily different approaches to the calculation, which usually relate the voltage excitation and the current response (eg current amplitude or current difference per time interval) in relation. For anisotropy methods with a time-discrete injection pattern [31] [32], for example, the anisotropy amount U _D and the isotropic component U _{S can be} internal calculation variables, from their values and the isotropic component at zero current and the inductances, for example

can be calculated as follows

But any other rules for calculating a differential inductance can also be used to measure the values

and

to provide as a basis for the method described in this document and / or for the described embodiments.

Even if differential inductances are only directly effective for anisotropy methods, in some embodiments they are also used to parameterize fundamental wave methods.

The short circuit current is generally one for excitation by the permanent magnet

(PM) (or through the excitation winding) equivalent amount of current, for example ^{■ Embossed} in negative d direction to extinguish the river chain

leads, or

^■ occurs when the shaft drives quickly (eg nominal speed) in the event of a short circuit in the terminals, or

^{Is determined} according to a principle that is physically equivalent to the aforementioned methods, or

^« Which is determined using one of the following calculation rules as part of the saturation assumption presented.

However, any other rules for calculating an amount of current equivalent to the excitation by the PM (or the field winding) can be used to determine the value of the short-circuit current for that described in this document

To provide methods and / or for the described embodiments.

The basic idea of the saturation assumption and all of its embodiments is that in the de-energized state the machine is saturated to a certain degree in the d-direction by the PM and unsaturated in the q-direction and that the same degree of saturation will be present in the q-direction, if the short-circuit current i _{pm is} impressed in the q direction. Specifically, some designs are subject to the assumption that the q-axis (direction perpendicular to the PM) assumes the same magnetic behavior as the d -axis (direction of the PM) in the de-energized state when in q direction the short-circuit current is impressed.

2 shows qualitatively an exemplary current-flow relationship in the d direction, which has a curved shape due to the saturation of the soft magnetic material. Without d-current i _d = 0, the flow is the same as the PM flow _h and the

The rise (indicated by the dashed tangent with the rise triangle) is equal to the differential d inductance in the de-energized state

Flow extinguished i}> _{d ~} 0, the iron consequently unsaturated and, according to the saturation assumption, the rise in the flow curve equals the differential q inductance in the de-energized state

When connecting an unknown synchronous machine, the PM flow ip _{pm can} usually be calculated from the nameplate data (e.g. 0.471 times the nominal torque divided by the nominal current and number of pole pairs) or alternatively determined by rotating the shaft (e.g. from the ratio of induced voltage to speed).

Based on this data

can now within the scope of the saturation assumption the short-circuit current

_m can be calculated as follows. In Fig. 2 it can be seen that for d-currents between

all increase values between

o lie, the exact transition depending on the machine

gig can vary.

In some embodiments, the short circuit current is now

_p as the quotient from the excitation or PM flow chaining divided by a combination of the load-free

smallest and the load-free largest differential inductance

and

calculated. This calculation can be carried out as follows, for example

whereby the influence of the respective inductance can be weighted by means of and.

In some embodiments, the combination corresponds to averaging, for example with the coefficients.

that the mean increase equals the mean of the edge increases

so that can be calculated as follows

Alternatively, the short-circuit current can, for example, by a short-circuit ver

to be determined. Regardless of its determination, the short-circuit current i _{pm is} a key parameter for the following calculations of parameters for fundamental wave methods in section 3.1 and for anisotropy methods in sections 3.2 and 3.3. The presented calculation approaches for the parameters for anisotropy methods are preferably applicable to geometrically isotropic machine types. Therefore, in some embodiments, compensation and / or use for the location assignment of the anisotropy saturation calculations only takes place if the difference between the no-load largest and the no-load differential inductance is less than 20% of their sum.

3.1 fundamental wave inductance

One parameter of fundamental wave methods that is stored depending on the current to take account of saturation is, for example, the absolute inductance in the q direction

V In some embodiments, the absolute inductance Lq is calculated as a parameter for evaluating the induced voltage in such a way that, based on its value valid at zero current, it also has the largest differential-free inductance without load

increasing current so that when the short-circuit current is reached ()

is equal to the mean value of the smallest and largest differential inductance (L i t0 and Iw o).

3 shows an exemplary current-flow relationship in the q direction, which for a geometrically isotropic machine is the same as that in the d direction - with the difference that the curves are shifted horizontally relative to one another in such a way that the q curve symmetrically through the origin and the d-curve runs through -tprn.

According to the above saturation assumption, the following exemplary embodiments are subject to when reached where the rise is also.

However, the absolute inductance Lq has a value different from Lqq, as the dotted lines illustrate.

In order to conclude from the (possibly injection-based measured) differential inductances and on the course of the absolute inductance),

For example, it is initially assumed that the course of the differential inductivity L _q qii _q ) is linear and symmetrical L.

According to (11), this results, for example, by integration

and according to (6) the course, for example, by division

where mL was expressed using (25). results

uncj is therefore consistent with the calculation of the short-circuit current (25).

0 results in (29) and thus corresponds to the fact that the differenti for zero current

elle and the absolute inductance are the same.

For example, with this linear law (29) or (30) - (31) based on the initially measurable and / or calculable parameters and the saturation of the

central fundamental wave parameter L _{q can be} approximated. This approximation applies well to geometrically isotropic machines. In the case of geometrically anisotropic machines, this approximation is subject to errors in the conservative range - that is, the Saturation is compensated too weakly because the actuation behavior of the soft magnetic material in the q direction cannot be derived from the d direction, but can still be used.

Compensation according to this approximation is better than no compensation. Therefore, the law for the current dependence of the fundamental inductance (29) or (30) ~ (31) can be applied to all PM machines - for geometrically isotropic as well as for geometrically anisotropic.

3.2 Anisotropy shift

The anisotropy of geometrically isotropic machines is caused by local ones

Saturation of the soft magnetic material, which is maximum in the non-energized state in the PM direction. Then the anisotropy is aligned with the rotor and rotates approximately with it when rotating. When a torque-generating current is impressed, a relative shift between the rotor and anisotropy is shown, because the current oriented transversely to the PM influences the saturation state.

In some embodiments, a saturation current vector is calculated by vectorially adding the phase current vector and the short-circuit current vector, the short-circuit current vector having the magnitude of the short-circuit current and oriented in the direction of the PM.

In the following exemplary description of the embodiment, the saturation current vector by ft, the phase current vector by ft and the short-circuit current vector

gate represented by - each expressed in stator coordinates (superscript s). The same vectors are represented in rotor coordinates, ft and ft

The short-circuit current and the current in the stator development

overlap now

for example linear and the sum gives the saturation current

whose direction specifies the saturation maximum and thus aligns the anisotropy.

This results in the so-called anisotropy shift 0 _lir, ie the shift in the anisotropy _angle relative to the rotor (or the anisotropy angle in rotor coordinates) after the saturation current has been aligned in rotor coordinates

Thus, in some embodiments, the anisotropy shift is used as a parameter

for evaluating the magnetic anisotropy, it is calculated so that it increases with increasing phase current in such a way that the assumed orientation of the anisotropy corresponds to the direction of the saturation current vector

4 shows an example of how the short-circuit current and the stator current in the rotor

coordinates are added vectorially, resulting in the saturation current

_ί results in the alignment in rotor coordinates of geometrically isotropic machines being the same as the anisotropy shift.

This shift angle

is, for example, in operation under load from the measured anisotropy angle

(Result of the anisotropy identification, eg one of the methods [6] [7] [8] [31]) subtracted in order to obtain the estimated rotor position

Because in geometrically isotropic machines the so-called maximum torque-per-ampere (MTPA) solistream trajectory is almost on the q-axis, these machines are usually operated in the lower speed range without a d-nominal current component. This can be simplified (35)

The latter linear approximation (38) behaves for example in the area

tends to be conservative (no overcompensation) with approximation errors up to less than 3.7 °, whereby it is more computationally economical than (37), especially because of the factor

is constant in operation.

3.3 Parameters for clear anisotropy-rotor position assignment

In addition, the anisotropy amount depends on the saturation current

_{Including t} , a rule for unambiguous rotor position _assignment can also be derived from the values known at the beginning /, _{d f0} , i _qqQ and i _pm .

In some embodiments, the anisotropy amount K _D is calculated as a parameter for a clear anisotropy rotor position assignment in such a way that it increases progressively from its value effective at zero current above the saturation current amount

which is shown qualitatively in FIG. 5

According to (40), the effective at zero current becomes effective in some embodiments

Value of the anisotropy amount from the load-free differential inductors

and determined.

In concrete terms, a progressive course means that the increase in f _A (x) for positive arguments x is always positive and increases with increasing arguments

In some embodiments, the progressive increase in the anisotropy amount corresponds to an increase proportional to the third power of the saturation current amount. This is represented, for example, by the following formula:

An anisotropy vector can be constructed from the anisotropy amount and anisotropy orientation

in which all variables U _D and 0 _! from the saturation current vector

_f depend. In contrast to (37), it cannot be assumed for the derivation of the unique rotor position assignment that the d-current component is zero

and it does not, for example, the anisotropy shift relative to the rotor

but the anisotropy angle in stator coordinates

used, which can be described as follows depending on the saturation current in stator coordinates

6 shows an example of how the short-circuit current i in (47)

and add the stator current vectorially in stator coordinates and give the saturation current in stator coordinates. Varying the rotor angle 0 _r with a constant stator current

(SFC condition) the short-circuit current moves on a concentric

Circular path (dotted line) and the saturation current consequently on a circular path shifted by tf (dashed line). On this shifted circular path, both its amount and its angle change over the rotor rotation,

which justifies (43) and (47).

With (

the anisotropy vector y _{A can} now be expressed, for example, as a function of the current in stator coordinates tf and the rotor position Q _r

which, according to [33], is the basis for calculating a clear rotor position assignment rule.

So in some embodiments, a model anisotropy vector

constructed which has the length of the Anisotropiebetrags {Y _A) and is aligned in two-fold anisotropy angle (2q _a), wherein the anisotropy angle corresponds to (q _a) the sum of rotor position (0 _r) and Anisotropieverschiebung (q _ίIT) so that the model Anisotropy vector as a function of phase current _vector (i *) and rotor position (0 _r ) is described. This model anisotropy vector is then represented by, for example.

Two exemplary embodiments are described below, which convert (49) into a unique position assignment rule ().

3.3.1 Linear position assignment

In some embodiments, the positional dependence of the model anisotropy vector is linearized for various stator-fixed current values in the target current working point uses a linear position assignment rule, which is a projection of the measured anisotropy vector

corresponds to the linearization applicable to the measured current.

For this purpose, the dependency of the function (49) on the rotor position () _r under the boundary condition of an unchanged current in stator coordinates if = const. (the so-called SFC trajectory) linearized in the target current operating point.

As previously mentioned, in geometrically isotropic machines, the target current operating point lies on the q axis

Around this working point (50) can be linearized using the virtual shift h (small value, e.g. 1 °)

where m _A ^{s is} the rise and yf _{0 is} the offset of the straight line that describes (49) in and near the working point

An exemplary linear one can now be made from these linearized parameters ml and yj ₀

Location assignment rule can be derived

that of a projection of the measured anisotropy vector onto the Ge

rade with transfer of the associated angle value.

Because there is no information about anisotropy harmonics within the scope of this exemplary saturation assumption, and yj ₀ already contain all available information for a current amount | if |. For this purpose, evaluation in double current coordinates according to [33] can be carried out

This can be calculated in a simplified manner, for example within the framework of this saturation assumption, by using (49) for the current angle and

is evaluated

An exemplary linear position assignment rule can now be derived from (51) and (52) or (58) and (59)

where (60) - (62) can be calculated in advance and it suffices to just (63) in

To process operation. The coefficients k _x , k _y and fc _{0 are} stored model parameters and and the current result of the current measurement and anisotropy

Pie identification in operation. In some embodiments, the location assignment coefficients k _x , k _y and k _{0 are determined} only once after the initial determination of the inductances L _dd0 , L _qqü and the PM-

Flow value i (> _pm (or the short-circuit current i _pm ) for several q-current values is calculated using (58H62), (48) and (25) and stored as a table above the current. Then it is sufficient to operate the current current Current value matching coefficients)

select / interpolate and assign the rotor position using (63).

3.3.2 Search approach

In some embodiments, the anisotropy model (e.g.

respectively

the measured current and a variable rotor position estimate (

This estimate is varied in such a way that the model best matches the current anisotropy measurement (e.g.

or> _D ) matches.

For this purpose, the point of the SFC model trajectory y £ (i _{| S} ), which is close to the measured value und and the associated one, can be searched for, for example, for the location assignment in operation

Position value can be used as an estimate. For example, based on (58), the model based on (48) is now considered with a variable rotor position value $ _r

where q ₍ and i \ _} are measured values during operation and e _r is varied so that the model matches the current measured value y as closely as possible.

Shaping corresponds to varying to best match a minimization of the distance between the model value and the measured value

The extreme point found can then be adopted as an estimated value § _r . For example, a gradient descent method can be used to minimize it

where the prefactor fe · depends on the position dependency

Bandwidth of the tracking of § _r can scale.

4 Experimental results

7a-f verify the saturation assumptions for the fundamental wave inductance and the anisotropy shift using three geometrically isotropic (SPM) and three geometrically anisotropic (1PM) synchronous machines from 6 different manufacturers with different values for nominal power and anisotropy ratio (SR). The vertical dotted lines, which mark the nominal load, relate the overload range shown and the point with short-circuit current (< _q / i _pm = 1).

The estimation errors caused by the fundamental wave inductance are significantly reduced in all machines using the saturation assumption compared to the operation with neglect of saturation, ie with constant parameter L _q . For all SPMs, that estimation error does not exceed an error threshold of 5 ° electrically in a practical four-fold overload, while errors of up to 20 ° occur with constant L _q . With IPMs, those estimation errors are larger (<10 ° electrical in the load range shown) than with SPMs, but nevertheless significantly less than when operating with constant L _q. Therefore, using the saturation assumption of the fundamental wave inductance can also make sense for geometrically anisotropic machines.

The estimation errors caused by the anisotropy shift are significantly reduced in geometrically isotropic machines using the saturation assumption compared to operation without taking saturation into account, ie with direct use of the anisotropy angle as the rotor position value. In SPMs, that estimation error with saturation assumption usually remains less than 7 ° electrical, while with q _ίh . = 0 up to 60 ° errors occur. However, SPM1 also represents a more difficult case where the estimation error also increases up to 15 ° with saturation assumption. In contrast, with IPMs those anisotropy estimation errors are not only significantly larger than with SPMs, but also also often larger in amount than when using the anisotropy angle as the rotor position value. It is therefore not sensible to use the saturation assumption for the anisotropy shift in geometrically anisotropic machines.

8a-c compares the experimental results from the encoderless operation with the geometrically isotropic machine SPM3 under parameterization without assumption of saturation, with anisotropy displacement assumption and with assumption for the unique rotor position assignment according to the embodiment in section 3.3.1. In all cases, the SPM3 was driven slowly by a load machine and its rotor position was estimated exclusively based on anisotropy and used to transform the field-oriented current control. The q nominal current was slowly increased from t = 0, so that it is reached at approx.0.6s nominal current and at approx. 3s short-circuit current i _pm . Without assumption of saturation (Fig. 8a), the middle (flarmonic masked) estimate increases quickly, exceeds 10 ° at nominal current and the control circuit becomes unstable before the short-circuit current is reached. With the assumption about the anisotropy shift presented (FIG. 8b), the average estimation error only exceeds the 10 ° threshold at approximately three times the nominal current and can therefore still be used for efficient current control even at higher torques. In this case, too, the control circuit becomes unstable before the short-circuit current is reached, because the relationship between the anisotropy angle and the rotor position becomes ambiguous [34]. With the assumption presented for a clear rotor position assignment (FIG. 8c), the mean estimation error remains less than 10 ° in the entire load range and can therefore be used for an efficient current control without torque limitation. In addition, the control loop does not become unstable even at high loads because the causes described in [34] do not apply to this type of assignment. In all cases are in the estimated rotoriage and especially in

However, there are two and six periodic harmonics, which are caused by a stator-fixed and a negative fourth anisotropy harmonic [32], which are not considered in the presented method. However, additional consideration of this or further harmonics is also not ruled out in any of the previous embodiments.

Other aspects concern:

(i) A device for controlling and regulating a induction machine, comprising a stator and a rotor, with one having a device for detecting a Number of phase currents and with a controller for controlling the PWM converter, which is set up and designed to carry out the method as described above; and one

(ii) Synchronous machine comprising a stator and a rotor with or without permanent magnets, with a device for control and / or regulation as described in point (i).

5 Summary

Today's established, highly efficient control of electrical machines requires that the rotor angle is known at all times, i.e. is usually measured. Without this knowledge, only significantly inefficient control methods can be used. The measurement is carried out during operation by means of a sensor attached to the rotor shaft - the so-called rotor position encoder or encoder for short.

Donors have a number of disadvantages, such as Increased system costs, reduced robustness, increased probability of failure and larger space requirements, which are the reason for the great industrial interest in obtaining the angle signal without using an encoder and using it for efficient control.

Methods that make this possible are called "sensorless" or sensorless "control and are divided into two classes:

1. Basic wave methods evaluate the voltage induced under motion, deliver very good signal properties at medium and high speeds, but fail in the lower speed range, especially when stationary.

2. Anisotropy-based methods evaluate the position dependency of the inductance of the machine, which does not require a speed, but have several problems and hurdles that explain why many applications still require a position encoder (with its disadvantages).

Both process classes require certain magnetic parameters of the machine in order to be able to calculate the rotor position from voltage and current. By magnetic However, these parameters depend on the current status. The quality and stability of the position estimate at high loads thus depends on the accuracy of the knowledge of the saturation behavior of the parameters.

The saturation behavior for a machine type can either be derived with average accuracy from the data of the computer-aided machine design, or can be determined experimentally with high accuracy on a test bench with position encoder and load machine. Often, however, both options are not available, e.g. if an unknown synchronous machine is connected to a converter and should achieve the best possible control results based on short initialization tests. Because these tests should also often be torque-free, a direct measurement of the actuation behavior is not always possible.

The embodiments described here relate certain physical properties of a synchronous machine to one another in such a way that rules can be derived in order to draw conclusions from the measurement values obtained in the torque-free state of the saturation behavior under load up to multiple overloads. This now enables even synchronous machines to be controlled stably and efficiently without a position encoder after a short, torque-free initiation measurement without a test bench (usual condition in the field) in the entire speed and load range up to multiple overloads.

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Claims

1 . Method for the load-free determination of load-dependent position assignment parameters of a synchronous machine without a position encoder, which is via clocked

Clamp voltages are controlled, from which the inductance or admittance is calculated in connection with the measured current response, or the smallest load-free and the largest load-free differential inductance are known.

whereby from the load-free smallest and the load-free largest differential inductance and the short-circuit current, the magnetic saturation behavior under load of the absolute inductance and / or the magnetic anisotropy of the

Synchronous machine is predicted and is used for position assignment in position-less control mode.

2. The method according to claim 1,

the magnetic saturation behavior is predicted under load of the absolute inductance and / or the magnetic anisotropy of the synchronous machine and is compensated for in control mode without position encoder.

3. The method according to any one of the preceding claims,

where a load-free differential inductance corresponds to the derivation of the flux linkage after the current at the operating point with zero current.

4. The method according to any one of the preceding claims,

the smallest and the largest differential inductance being the directionally smallest and largest differential inductance value of an operating point, the directional dependence corresponding to the magnetic anisotropy.

5. The method according to any one of the preceding claims,

the value of the short-circuit current corresponds to the amount of the stator current which is set at zero voltage at the rated speed.

6. The method according to any one of the preceding claims,

where the short-circuit current as a quotient from the excitation or Permanent magnet flux linkage divided by a combination of the smallest and the largest inductance.

7. Procedure according to claim 6,

where the combination corresponds to averaging.

8. The method according to any one of the preceding claims,

the method being based on the assumption that the q-axis, i.e. Direction across the permanent magnet, assumes the same magnetic behavior as the d-axis, i.e. Direction of the permanent magnet, in the de-energized state, if the short-circuit current is impressed in the q direction.

9. The method according to any one of the preceding claims,

where the absolute inductance L _q as a parameter for evaluating the induced

Voltage is calculated in such a way that, based on its value at zero current, the iastfree largest differential inductance, it decreases with increasing current so that when the short-circuit current is reached it equals the mean value of the no-load smallest and the no-load largest differential inductance.

10. The method according to any one of claims 1 to 8,

where a saturation current vector by vectorial addition of a

Phase current vector and a short-circuit current vector is calculated, the short-circuit current vector having the magnitude of the short-circuit current and being oriented in the direction of the permanent magnet.

1 1. The method according to claim 10,

the anisotropy shift β _ar being calculated as a parameter for evaluating the magnetic anisotropy so that it increases with increasing

Phase current increases so that the assumed alignment of the anisotropy corresponds to the direction of the saturation current vector.

12. The method according to any one of claims 10 or 1 1,

wherein the anisotropy amount Y _D is calculated as a parameter for the unique anisotropy rotor position assignment in such a way that it starts from Effective zero current value Y _D0 increases progressively above the saturation current amount.

13. The method according to claim 12,

where the value of the anisotropy amount effective at zero current

from the load-free smallest and the load-free largest differential inductance.

14. The method according to claim 12 or 13,

the progressive increase corresponding to an increase proportional to the third power of the saturation current.

15. The method according to any one of claims 1 1 to 14,

a model anisotropy vector is constructed that measures the length of the

Has anisotropy amount and is aligned in two anisotropy angles, the anisotropy angle being the sum of the rotor position and

Antsotropy shift corresponds, so that the model anisotropy vector is described as a function of phase current vector and rotor position.

16. The method according to claim 15,

the positional dependence of the model anisotropy vector for various stator-fixed current values in the setpoint current operating point is linearized and a linear position assignment rule is used which corresponds to a projection of the measured anisotropy vector onto the linearization applicable to the measured current.

17. The method according to claim 15,

the measured current and a variable rotor position estimated value are fed to the anisotropy model, this estimated value being varied such that the model best matches a current anisotropy measured value.

18. The method according to claim 1 7,

where the variation corresponds to a minimization of the distance between the model value and the measured value to best match.

19. The method according to any one of claims 10 to 18,

where compensation and / or use to assign the position of the anisotropy saturation calculations only takes place if the difference between the load-free largest and the iast-free smallest differential inductance is less than 20% of their sum.

20. Device for controlling and regulating a induction machine, comprising a stator and a rotor, with a controllable PWM converter for outputting clocked clamping voltages, with a device for detecting a number of phase currents and with a controller for controlling the PWM converter, the is set up and designed to carry out the method according to one of the preceding claims.

21st Synchronous machine comprising a stator and a rotor with or without

Permanent magnets, with a device for control and / or regulation according to claim 20.