阅读说明：本技术 估计转子操作参数 (Estimating rotor operating parameters ) 是由 N·M·A·弗莱雷 吴占元 于 2020-09-29 设计创作，主要内容包括：描述了一种估计电机的转子操作参数的方法,所述电机包括多个绕组集,所述多个绕组集被缠绕成在绕组集之间具有相移,所述转子操作参数包括转子位置和/或转子速度,所述方法包括：针对每个绕组集,基于相应绕组集的电流和电压,导出初始转子操作参数；针对至少两个绕组集和针对至少一个预定谐波,基于至少两个绕组集的初始转子操作参数,计算转子操作参数谐波校正项；针对至少一个绕组集,基于该绕组集的初始操作参数和该绕组集的转子操作参数谐波校正项,计算校正的转子操作参数,其中,特别地,所述校正的转子操作参数使至少一个预定谐波被去除或至少被衰减。(A method of estimating rotor operating parameters of an electric machine is described, the electric machine comprising a plurality of winding sets wound with phase shifts between the winding sets, the rotor operating parameters comprising rotor position and/or rotor speed, the method comprising: for each winding set, deriving initial rotor operating parameters based on the current and voltage of the respective winding set; calculating a rotor operating parameter harmonic correction term based on the initial rotor operating parameters of the at least two winding sets for the at least two winding sets and for the at least one predetermined harmonic; for at least one winding set, a corrected rotor operating parameter is calculated based on the initial operating parameter of the winding set and a rotor operating parameter harmonic correction term for the winding set, wherein in particular the corrected rotor operating parameter causes at least one predetermined harmonic to be removed or at least attenuated.)

1. Method of estimating a rotor operating parameter (θ, ω) of an electrical machine (3), the electrical machine (3) comprising a plurality of winding sets (15 a, 15b, 15c, 17a, 17b, 17 c), the plurality of winding sets (15 a, 15b, 15c, 17a, 17b, 17 c) being wound with a phase shift between the winding sets, the rotor operating parameter comprising a rotor position (θ) and/or a rotor speed (ω), the method comprising:

deriving, for each winding set (15, 17), initial rotor operating parameters (39) based on the current (23) and voltage (27) of the respective winding set (15);

calculating a rotor operating parameter harmonic correction term based on initial rotor operating parameters (39, theta 1, omega 1; 41, theta 2, omega 2) of the at least two winding sets (15, 17) for the at least two winding sets (15, 17) and for the at least one predetermined harmonic (h);

for at least one winding set (15, 17), corrected rotor operating parameters (11, 13, 12, 14) are calculated based on initial operating parameters (39, 41) of the winding set and rotor operating parameter harmonic correction terms of the winding set, wherein in particular the corrected rotor operating parameters cause at least one predetermined harmonic to be removed or at least attenuated.

2. The method of the preceding claim, wherein calculating the rotor operating parameter harmonic correction term comprises:

calculating a rotor position harmonic correction term based on initial rotor positions (θ 1, θ 2) of at least two winding sets (15, 17); and/or

Based on the initial rotor speeds (ω 1, ω 2) of the at least two winding sets (15, 17), a rotor speed harmonic correction term is calculated.

3. The method according to one of the preceding claims, wherein calculating the corrected rotor operating parameters (11, 13, 12, 14) comprises:

calculating a corrected rotor position (11, 12) based on the initial rotor position (θ 1, θ 2) of the winding set and a rotor position harmonic correction term for the winding set; and/or

A corrected rotor speed (13, 14) is calculated based on the initial rotor speed (ω 1, ω 2) of the winding set and a rotor speed harmonic correction term for the winding set.

4. The method according to one of the preceding claims, wherein the at least two winding sets (15, 17) comprise a winding set (15) for which a respective correction term is calculated and comprise at least one other winding set (17).

5. Method according to one of the preceding claims, wherein the calculation of the rotor position harmonic correction term is further based on the winding set phase shift (γ).

6. Method according to one of the preceding claims, wherein the at least one predetermined harmonic to be attenuated in the corrected rotor operating parameters comprises the harmonics h _0 = 2 pi/(n γ), wherein n is the number of winding sets and γ is the winding set phase shift between the winding sets, wherein the number of phases is in particular three.

7. The method according to one of the preceding claims, wherein the at least one predetermined harmonic to be attenuated in the corrected rotor operating parameters comprises the harmonic h _ k = 2 pi/(n γ) (1 + 2k/(n-1)), wherein n is the number of winding sets and γ is the winding set phase shift between the winding sets, k is an integer equal to or greater than 0, wherein the number of phases is in particular three.

8. The method according to one of the preceding claims, wherein the at least one predetermined harmonic comprises a first predetermined harmonic and at least one second predetermined harmonic,

wherein the first predetermined harmonic h _1 to be attenuated in the harmonic corrected rotor operating parameter is h _1 = 2 pi/(n γ) (1 + 2k _1/(n-1)),

wherein the second predetermined harmonic h _2 to be attenuated in the harmonic corrected rotor operating parameter is h _2 = 2 pi/(n γ) (1 + 2k _2/(n-1)),

where n is the number of winding sets and γ is the winding set phase shift between the winding sets, k _1, k _2 are integers equal to or larger than 0, where k _1 is not equal to k _2, where the number of phases is in particular three,

wherein, in particular:

the electrical machine has three winding sets, wherein the winding set phase shift is 20 °, wherein k _1 = 0 and k _2 = 1, wherein the first harmonic is the 6 th harmonic and the second harmonic is the 12 th harmonic.

9. Method according to one of the preceding claims, wherein the electrical machine (3) has two winding sets, in particular three phases,

wherein the winding set phase shift is 30 ° and the predetermined harmonic is a 6 th harmonic; and/or

Wherein the winding set phase shift is 90 ° and the predetermined harmonic is a 2 nd harmonic.

10. Method according to one of the preceding claims 1 to 8, wherein the electrical machine has three winding sets, in particular three phases,

wherein the winding set phase shift is 20 ° and the first and second predetermined harmonics are the 6 th and 12 th harmonics; and/or

Wherein the winding set phase shift is 40 ° and the first and second predetermined harmonics are the 6 th and 12 th harmonics.

11. Method according to one of the preceding claims 1 to 8, wherein the electrical machine has four winding sets, in particular three phases,

wherein the winding set phase shift is 15 ° and the first predetermined harmonic is a 6 th harmonic; and/or

Wherein the winding set phase shift is 15 ° and the second predetermined harmonic is a 12 th harmonic.

12. The method according to one of the preceding claims, wherein the stator of the electrical machine (3) is configured as a fractional-slot multi-winding stator, in particular having a concentrated winding topology or a distributed winding topology,

wherein the electrical machine comprises in particular a rotor (21) with permanent magnets (19).

13. A method of controlling an electric machine (3), the electric machine (3) comprising a plurality of winding sets (15, 17), the plurality of winding sets (15, 17) being wound with a phase shift between the winding sets, the method comprising:

performing the method according to one of the preceding claims; and

controlling (32, 34) the electric machine (3) based on the corrected rotor operating parameters (11, 13, 12, 14) of at least one winding set.

14. Device (7; 7a, 7 b) for estimating rotor operating parameters (θ, ω) of an electric machine (3), the electric machine (3) comprising a plurality of winding sets (15, 17), the plurality of winding sets (15, 17) being wound with a phase shift between the winding sets, the rotor operating parameters comprising a rotor position (θ) and/or a rotor speed (ω), the device comprising:

a processor adapted to:

deriving, for each winding set, initial rotor operating parameters (39, 41) based on the current (23, 25) and voltage (27, 29) of the respective winding set (15, 17);

calculating a rotor operating parameter harmonic correction term based on initial rotor operating parameters (39, 41) of the at least two winding sets for the at least two winding sets and for the at least one predetermined harmonic;

for at least one winding set, corrected rotor operating parameters (11, 13, 12, 14) are calculated based on initial operating parameters (39, 41) of the winding set and rotor operating parameter harmonic correction terms for the winding set.

15. Controller (4) for controlling a generator, in particular a generator of a wind turbine, the controller comprising:

the device (7; 7a, 7 b) according to the preceding claim; and

at least one control element (9) receiving as input the harmonic corrected rotor operating parameters (11, 12, 13, 14).

Technical Field

The present invention relates to a method and apparatus for estimating an operating parameter of a rotor of an electric machine comprising a plurality of winding sets wound with a phase shift between the winding sets. The invention also relates to a controller for controlling a generator comprising the device.

Background

The synchronous motor includes a stator and a rotor rotatable relative to the stator. The stator may include one or more polyphase winding sets and the rotor may include permanent magnets. The motor may be an externally energized motor.

Controlling a permanent magnet synchronous motor requires knowledge of the rotor speed and position. Estimation methods are often employed to avoid additional sensors and reduce hardware requirements implemented in the converter control system. A speed/position estimator employing an EMF-based observer is a conventional choice, utilizing measured currents and reference voltages that are readily available in the control system.

"Sensorless control strategy for saturated-polar PMSM based extended EMF in rotating reference frame", published by Morimoto (IEEE Transactions on Industrial Applications, Vol. 38, No. 4, 2002, 7/8) discloses a control strategy for permanent magnet salient pole synchronous motors (PMSM). Thus, a model of salient pole PMSM using an extended electromotive force (EMF) in a rotating reference frame is used to estimate both the position and the speed of the rotor.

For high power permanent magnet generators, non-negligible harmonics are present in the aforementioned current and voltage signals, which are not considered in the observer model, and therefore need to be attenuated in some way to avoid observer misbehaviour and consequent estimation errors. Errors in estimating position are critical to overall control performance and can lead to control instability, and attempts to attenuate harmonics with digital filters will introduce additional errors in velocity and position due to phase delays.

The presence of harmonics in the feedback signals (current and voltage) used by a back-emf-based speed observer can lead to inaccurate speed and/or position estimates for the rotor. Therefore, in order to improve the performance of the speed observation method, it is desirable to attenuate such harmonic content.

It has been observed that conventional methods do not provide a sufficiently accurate estimate of the position and/or speed of the rotor in all situations and in all configurations of the generator. Accordingly, there may be a need for a method and apparatus for estimating rotor operating parameters of an electric machine, the electric machine including a plurality of winding sets wound with phase shifts between the winding sets, the rotor operating parameters including rotor position and/or rotor speed, wherein the accuracy of the estimated rotor position and/or rotor speed is improved compared to conventional methods.

Disclosure of Invention

This need may be met by the subject matter according to the independent claims. Advantageous embodiments of the invention are described by the dependent claims.

According to an embodiment of the invention, there is provided a method of estimating rotor operating parameters of an electric machine, the electric machine comprising a plurality of winding sets wound with a phase shift between the winding sets, the rotor operating parameters comprising a rotor position and/or a rotor speed, the method comprising: for each winding set, deriving initial rotor operating parameters based on (e.g., measured) currents and (e.g., reference) voltages of the respective winding set; calculating rotor operating parameter harmonic correction terms based on the initial rotor operating parameters of at least two (or three or all) winding sets for at least two winding sets and for at least one predetermined harmonic; for at least one winding set, a corrected rotor operating parameter is calculated based on the initial operating parameter of the winding set and a rotor operating parameter harmonic correction term for the winding set, wherein in particular the corrected rotor operating parameter causes at least one predetermined harmonic to be removed or at least attenuated.

Thus, embodiments of the present invention provide a simple solution for removing dominant harmonics in estimated position and speed in phase-shifted multi-winding machines, i.e. Fractional Slot Concentrated Winding (FSCW) machines. Embodiments of the present invention thus enable the implementation of additional filters (to attenuate undesired harmonics) to be avoided.

The method may be partly implemented in hardware and/or software, e.g. as a module or unit in a controller of a generator, in particular a wind turbine controller.

The electric machine may comprise a rotor mounted with permanent magnets. The electrical machine may be a generator, in particular a generator of a wind turbine. Each winding set may provide a plurality of electrical phases, for example two, three, four, five, six or a greater number of phases. The electrical machine may comprise a plurality of winding sets and the phase shift between the winding sets may be related to the electrical phase shift, i.e. the phase difference between the fundamental voltage measured at two different winding sets as the rotor rotates. The phase shift may also involve a structural/physical displacement of the corresponding wires of the two winding sets as an angular offset in the circumferential direction, wherein the corresponding winding sets are arranged at the stator. The winding set phase shift may be, for example, a phase shift between the first winding set and the second winding set.

The initial rotor operating parameters may be derived, for example, as described in the above-mentioned publication "sensory control strategy for present-pole PMSM based extended EMF in rotating reference frame". The initial rotor operating parameters may erroneously include one or more error components that oscillate with at least one predetermined harmonic. The method is capable of correcting the initial rotor operating parameters for more than one predetermined harmonic (e.g., two, three, four, or even more predetermined harmonics). The predetermined harmonic may depend on the configuration of the electrical machine, in particular on the number of winding sets and/or the phase shift between the winding sets. The electrical machine may comprise at least two winding sets or even three winding sets, four winding sets, five winding sets or even more winding sets. One or more currents of a winding set may be measured, one or more voltages of the winding set may be measured, or may be a reference voltage.

Calculating the rotor operating parameter harmonic correction term for a particular winding set requires receiving initial rotor operating parameters for at least one other winding set. The rotor operating parameter harmonic correction term may correct for undesired harmonic component(s) included in the initial rotor operating parameters. Thus, calculating the rotor operating parameter harmonic correction term may also depend on the phase shift between the winding sets. The respective rotor operating parameter harmonic correction term may, for example, involve subtracting the initial rotor operating parameter of the winding set under consideration from the initial rotor operating parameter from another winding set, from which a phase shift between the winding sets may additionally, for example, be subtracted. Thus, calculating the rotor operating parameter harmonic correction term may be obtained by a subtraction and/or summation operation of the initial rotor operating parameters of at least two winding sets (including the winding set under consideration and at least one other winding set) and involving a phase shift between the winding sets. Thus, an arithmetic unit may be applied to calculate the rotor operating parameter harmonic correction terms. In particular, the harmonic correction term may be based on initial rotor operating parameters of at least two or three or all winding sets included in the electric machine.

The corrected rotor operating parameters may be corrected for the undesired harmonic component(s) and may also be obtained by performing simple arithmetic, e.g., involving subtracting correction terms from the initial rotor operating parameters.

The rotor operating parameters may include, for example, one or more components such as rotor position and/or rotor speed. When the corrected rotor operating parameters are substantially free of one or more predetermined harmonic components, the corrected rotor operating parameters may advantageously be used in one or more control modules of the generator controller without any additional filtering. Furthermore, the accuracy of the estimation of the rotor operating parameters may thereby be improved.

The method may be applied to any number of winding sets, such as two winding sets, three winding sets, four winding sets, five winding sets, six winding sets, or even more winding sets. The method may be applied to any number of phases, such as two, three, four, five or even more phases. Furthermore, the method may be adapted to attenuate or substantially remove more than one predetermined harmonic, e.g. two, three, four, five or even more predetermined harmonics. This may depend on the configuration of the electrical machine, in particular on the number of winding sets and/or the phase shift between the winding sets.

The electric machine may include a stator having winding sets wound or arranged in a plurality of different winding topologies, including, for example, concentrated winding topologies and distributed winding topologies. Thus, the method is applicable to many conventionally configured motors.

According to an embodiment of the invention, calculating the rotor operating parameter harmonic correction term comprises: calculating a rotor position harmonic correction term based on the initial rotor positions of the at least two winding sets; and/or calculating a rotor speed harmonic correction term based on the initial rotor speeds of the at least two winding sets.

Thus, conventionally required rotor operating parameters (i.e., rotor position and rotor speed) may be supported by the method for estimation. The rotor position can be given, for example, as the angular position of the rotor in the circumferential direction relative to a reference position. The rotor speed may be given, for example, in rpm. The rotor position and rotor speed may be required in any transformation module, such as a controller.

According to an embodiment of the invention, calculating the corrected rotor operating parameter comprises: calculating a corrected rotor position based on the initial rotor position of the winding set and a rotor position harmonic correction term for the winding set; and/or calculating a corrected rotor speed based on the initial rotor speed for the winding set and a rotor speed harmonic correction term for the winding set.

The corrected rotor position and/or rotor speed may be directly input to a control module or control element requiring rotor position and/or rotor speed without the need for additional application of filter elements. The corresponding corrected rotor operating parameter may also be derived by applying simple arithmetic, such as subtracting the corresponding rotor operating parameter harmonic correction term from the initial rotor operating parameter (i.e., initial rotor position/rotor speed). Thereby, the calculation can be performed in a simple manner.

According to an embodiment of the invention, the at least two winding sets comprise the winding set for which the respective correction term is calculated and comprise at least one other winding set. The other winding set may be phase shifted by a phase shift between the winding sets relative to the winding set for which the respective correction term is calculated. In the calculation with respect to the predetermined harmonic, it can be assumed that the respective position of the rotor with respect to the different winding sets is also in particular phase shifted by the product of the harmonic and the phase shift between the winding sets. Thus, the rotor position harmonic correction term may depend on the phase shift between the winding sets and the predetermined harmonic (expressed as an integer of the fundamental frequency, particularly the fundamental electrical frequency).

According to an embodiment of the invention, the calculation of the rotor position harmonic correction term is also based on winding set phase shifts. The rotor position harmonic correction term may, for example, depend on the difference between the initial rotor position of the winding set under consideration and the initial rotor position of another (e.g., immediately adjacent) winding set, which further subtracts the phase shift between the winding sets, where the result may be divided by 2. Thus, the correction term can be easily calculated.

According to an embodiment of the invention, the at least one predetermined harmonic to be attenuated in the harmonic corrected rotor operating parameters comprises the harmonic h _0 = 2 pi/(n γ), where n is the number of winding sets and γ is the phase shift between the winding sets, where the number of phases of each winding set is in particular three. The harmonic h _0 may be considered to be the most dominant harmonic given the configuration of the generator or machine, i.e. given the number of winding sets and the phase shift between the winding sets. It may be highly desirable to attenuate the error in the dominant harmonic h _0, as this embodiment may achieve.

According to an embodiment of the invention, the at least one predetermined harmonic to be attenuated in the harmonic corrected rotor operating parameter comprises the harmonic h _ k = 2 pi/(n γ) (1 + 2k/(n-1)), where n is the number of winding sets and γ is the phase shift between the winding sets, k is an integer equal to or greater than 0, wherein the number of phases per winding set is in particular three. Thus, embodiments of the present invention may also target multiples of the dominant harmonic to also attenuate higher harmonics of the dominant harmonic. Thereby, the accuracy of the estimation of the rotor position and/or the rotor speed may be further improved.

According to an embodiment of the invention, the at least one predetermined harmonic comprises a first predetermined harmonic and at least one second predetermined harmonic, wherein the first predetermined harmonic h _1 to be attenuated in the harmonic corrected rotor operating parameter is h _1 = 2 pi/(n γ) (1 + 2k _1/(n-1)), wherein the second predetermined harmonic h _2 to be attenuated in the harmonic corrected rotor operating parameter is h _2 = 2 pi/(n γ) (1 + 2k _2/(n-1)), wherein n is the number of winding sets, γ is the winding set phase shift between winding sets, k _1, k _2 are integers equal to or larger than 0, wherein k _1 is not equal to k _2, wherein the number of phases is particularly three, wherein in particular: the electrical machine has three winding sets, wherein the winding set phase shift is 20 °, wherein k _1 = 0 and k _2 = 1, wherein the first harmonic is the 6 th harmonic and the second harmonic is the 12 th harmonic.

Thus, embodiments of the present invention allow for attenuation of at least two predetermined harmonics or even more predetermined harmonics in the initial rotor operating parameters (including harmonic errors). It may only be possible to attenuate or remove a particular combination of different harmonics (e.g., a multiple of at least one predetermined harmonic) at the same time, which may depend on the configuration and construction of the electric machine.

According to an embodiment of the invention, the electrical machine has two, in particular three-phase, winding sets, wherein the winding set phase shift is 30 ° and the predetermined harmonic is a 6 th harmonic (e.g. and may also include an 18 th harmonic) and/or wherein the winding set phase shift is 90 ° and the predetermined harmonic is a 2 nd harmonic. Thus, a typically configured motor is supported. In particular, it is possible to cancel both the 2f and 6f harmonics in the corrected rotor operating parameters.

According to an embodiment of the invention, the electrical machine has three winding sets, in particular three phases, wherein the winding sets phase shift is 20 ° (or 40 °) and the predetermined harmonics are the 6 th and 12 th harmonics.

According to an embodiment of the invention, the electrical machine has four, in particular three-phase, winding sets, wherein the phase shift between the winding sets is defined, for example, equally at 15 °, and the first predetermined harmonic is the 6 th harmonic and/or (wherein the winding set phase shift is, for example, 15 °) and the second predetermined harmonic is the 12 th harmonic.

According to an embodiment of the invention, the electrical machine is configured as a fractional slot type with a multi-winding concentrated stator, in particular with a concentrated winding topology or a distributed winding topology, wherein the electrical machine in particular comprises a rotor with permanent magnets. Thereby, a conventionally available motor can be supported.

The stator of the electrical machine may be a segmented stator, for example. The concentrated winding topology may be characterized in that coils belonging to one phase may be wound or arranged around one tooth. The distributed winding topology may be characterized in that the coils of one phase may surround more than one tooth, such as two, three, four, six, or even more teeth. A fractional-slot multi-winding-set stator may be characterized by a number of fractional slots per phase per pole, i.e. the number of slots divided by the number of poles and divided by the number of phases, different from an integer-concentrated-winding motor, may be only a fractional-slot motor, but a distributed-winding motor may be an integer or fractional-slot motor.

According to an embodiment of the present invention, there is provided a method of controlling an electric machine including a plurality of winding sets wound with a phase shift between the winding sets, the method including: performing a method according to one of the preceding embodiments; and controlling the electric machine based on the corrected rotor operating parameters of the at least one winding set.

The method may be performed or carried out, for example, by a controller of the electrical machine, in particular a generator controller, or may be performed, in particular, by a wind turbine controller. The improved estimation of the rotor operating parameters may for example be used in the following control elements: frame transformation; an adaptive filter; and a decoupling term in the fundamental current controller.

It should be understood that the features of the method for estimating rotor operating parameters of an electrical machine disclosed, described, applied or provided separately or in any combination may also be applied separately or in any combination to an apparatus for estimating rotor operating parameters of an electrical machine comprising a plurality of winding sets according to embodiments of the present invention, and vice versa.

According to an embodiment of the invention, there is provided an apparatus for estimating a rotor operating parameter of an electric machine comprising a plurality of winding sets wound with a phase shift between the winding sets, the rotor operating parameter comprising a rotor position and/or a rotor speed, the apparatus comprising a processor adapted to: for each winding set, deriving initial rotor operating parameters based on the current and voltage of the respective winding set; calculating a rotor operating parameter harmonic correction term based on the initial rotor operating parameters of the at least two winding sets for the at least two winding sets and for the at least one predetermined harmonic; for at least one winding set, a corrected rotor operating parameter is calculated based on the initial operating parameter of the winding set and a rotor operating parameter harmonic correction term for the winding set.

The apparatus may be implemented, for example, by a general-purpose processor which may execute a computer program comprising instructions for performing the steps of the method.

According to an embodiment of the invention, a controller for controlling a generator, in particular a generator of a wind turbine, is provided, the controller comprising: the apparatus according to the preceding embodiment; and at least one control element receiving as input the corrected rotor operating parameter.

Furthermore, a wind turbine is provided, comprising the controller and further comprising the electric machine, in particular a generator.

The above-described and other aspects of the present invention are apparent from and will be elucidated with reference to the embodiments described hereinafter. The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited.

Drawings

FIG. 1 schematically illustrates a generator system including a controller for controlling a generator, according to an embodiment of the invention;

FIG. 2 schematically illustrates the controller shown in FIG. 1 including an apparatus for estimating rotor operating parameters according to an embodiment of the invention;

fig. 3, 4 and 5 show graphs showing rotor operating parameters estimated by an embodiment of the present invention.

Detailed Description

Embodiments of the present invention will now be described with reference to the accompanying drawings. The invention is not limited to the embodiments shown or described. The illustrations in the drawings are in schematic form.

The generator system 1 schematically shown in fig. 1 comprises an electric machine 3 and a controller 5 for controlling the generator 3 according to an embodiment of the invention. The controller 5 comprises means 7 for estimating rotor operating parameters of an electric machine comprising a plurality of winding sets wound with a phase shift between the winding sets, and at least one control element 9 receiving as input corrected rotor operating parameters 11, 13 for at least one winding set. In general, the corrected rotor operating parameters may include a corrected rotor position θ 1^ (11) for the first winding set and a corrected rotor position θ 2^ (12) for the second winding set and corresponding rotor speeds ω 1^, ω 2^ (13, 14).

The electric machine 3 shown in fig. 1 is an electric machine comprising two winding sets, i.e. having a first winding set 15 comprising wire wound into coils 15a, 15b, 15c and comprising a second winding set 17, the second winding set 17 being formed by the wire and the coils 17a, 17b, 17 c. In particular, the two winding sets are three-phase winding sets, each providing phase a, phase B and phase C. As can be understood from fig. 1, the two winding sets 15, 17 are phase-shifted by an electrical angle of 30 ° with respect to each other. The electric machine 3 further comprises permanent magnets 19 mounted at a rotor 21, e.g. an outer rotor.

The device 7 comprises a processor, not explicitly shown, which is adapted to receive the (measured) currents 23 and 25 from the first and second winding sets 15a, 15b, 15c and 17a, 17b, 17c, respectively, and also to receive the reference voltages 27 and 29 of the first and second winding sets 15 and 17, respectively.

Based on currents 23, 25 and voltages 27, 29, device 7 derives initial rotor operating parameters (i.e., initial rotor position and initial rotor speed) based on currents 23, 25 and voltages 27, 29 for each corresponding winding set. Furthermore, the device 7 is arranged to calculate rotor operating parameter harmonic correction terms (as will be described in detail below) based on the initial rotor operating parameters of the two winding sets for the two winding sets 15a, 15b, 15c and 17a, 17b, 17c and for at least one predetermined harmonic (e.g. the 6 th harmonic). Furthermore, the arrangement 7 is adapted to calculate corrected rotor operating parameters, i.e. corrected rotor positions θ 1^, θ 2^ for the two winding sets 15, 17 and corrected rotor speeds ω 1^, ω 2^ for the two winding sets, as also marked with reference numerals 11, 12, 13, 14.

The controller 5 outputs control signals 32, 34. Thereby, the control signal 32 may for example be supplied to a respective first converter 35 connected to the first set of windings 15a, 15b, 15 c. The control signal 34 may for example be supplied to a second converter 37 connected to the second set of windings 17a, 17b, 17c, as shown in fig. 1.

Fig. 2 shows the controller 5 in more detail, in particular in an embodiment with two separate but interacting controller parts 31, 33. However, the controller 5 may also be implemented as a single controller. The controller 5 shown in fig. 2 comprises a first controller portion 31 controlling the first set of windings 15a, 15b, 15c and comprises a second controller portion 33 controlling the second set of windings 17a, 17b, 17c, by generating and supplying respective control signals 32 and 34.

The controller 5 comprises a device 7 configured with a first device part 7a and a second device part 7 b. The device part 7a receives the current 23 and the voltage 27 of the first winding set 15a, 15b, 15c and the device part 7b receives the current 25 and the voltage 29 of the second winding set 17a, 17b, 17 c. From the respective currents and voltages of each winding set, the respective device part 7a, 7b calculates initial rotor operating parameters, which are denoted below as θ 1, ω 1 (39) for the first winding set and θ 2, ω 2 (41) for the second winding set. These initial rotor operating parameters (39, 41) are erroneous because they contain higher order harmonic content.

To correct for this harmonic error, the device parts 7a, 7b calculate the following by θ_1,6^、θ_2,6And a corresponding rotor operating parameter harmonic correction term, wherein the second index (index) indicates the harmonic to be attenuated. Based on the initial rotor operating parameters and the corresponding harmonic correction terms, the device parts 7a, 7b calculate corresponding corrected rotor operating parameters, i.e. the first windingThe corrected rotor position 11 of the set (also denoted as θ 1 ^) and the corrected rotor speed 13 of the first winding set (also denoted as ω 1 ^). The device part 7b thus calculates a corrected rotor position 12 and a corrected rotor speed 14 for the second winding set. Thereby, the device parts 7a, 7b are communicatively coupled so as to allow exchanging initial rotor operating parameters 39 (including in particular the initial rotor position and the initial rotor speed) of the first set of windings and exchanging initial rotor operating parameters 41 (including preferably also the initial rotor position and the initial rotor speed) of the second set of windings.

The corrected rotor position and rotor speed 11, 13 of the first winding set is input to a number of control elements, for example a modulation control element 43, which calculates a current reference Id1_ ref based on the voltages Vd1, Vq1 of the first winding set, which is supplied to a current controller for the d-component of the current, i.e. element 45. Furthermore, the element 45 may receive the corrected rotor parameters 11, 13 of the first winding set. The DC-link controller 47 calculates a reference Iq1_ ref for the q-component of the current, which is supplied to the current controller 48 for the q-component together with the measured q-component Iq1 of the current. The current controllers 45, 48 output respective components of voltage Vd1, Vq1, which are supplied to the voltage collector 49. The voltage collector may receive further inputs of voltages from other functional blocks 51. The voltage collector 49 may also receive the corrected rotor parameters 11, 13 and derive therefrom a voltage reference, which is supplied to a pulse width modulation module 53, from which the pulse width modulation module 53 ultimately derives the converter control signal 32, for example comprising a pulse width modulated signal supplied to the gates of controllable switches within the first converter 35 (see fig. 1).

The second controller portion 33 is arranged similarly to the first controller 31 and also uses the corrected rotor operating parameters 12, 14 of the second winding set 17a, 17b, 17c correspondingly in several control elements.

It should be understood that the embodiment shown in fig. 1 only exemplarily describes an estimation method using a two-winding FSCW motor 3 with a 30 ° phase shift to attenuate the 6 th harmonic in position and speed.

As shown in fig. 2, the controller is implemented as two distinct controller portions 31, 33 having the capability to communicate with each other to exchange initial rotor operating parameters 39, 41. Alternatively, the controller 5 may be implemented as a single controller. In the generator 3 shown in fig. 1, the dominant harmonic will be 6f, so the position estimates from both systems are given by (defining the initial rotor position and initial rotor speed):

wherein, theta₀Is a saw tooth signal without harmonics varying between 0 and 360 deg.. Note that the initial rotor position (e.g., included in signals 39 and 41 in fig. 2) contains the 6 th harmonic, which can therefore be described as,

thus, the rotor operating parameter harmonic correction term can be calculated as:

based on the correction term and the initial rotor operating parameter (i.e., initial rotor position), the following corrected rotor position may be calculated as:

similarly, the 6 th harmonic in speed can be calculated and used for harmonic cancellation:

from the harmonic correction term, a corrected rotor speed can be derived.

The compensation term (or correction term) derived above is given exemplarily for the 6f cancellation in position and velocity. In this example, 6f is a predetermined harmonic.

Fig. 3, 4 and 5 show simulation results of verifying the estimation method. Thus, the abscissa 55 in fig. 3, 4, 5 represents time, while the ordinates 57, 59, 61 represent angle, angle error and velocity, respectively. In fig. 3, curve 63 represents the initial rotor position for the first winding set, curve 65 represents the initial rotor position for the second winding set, and curve 67 represents the corrected rotor position for the first winding set.

In fig. 4, curve 64 represents the error in rotor position for the initial rotor position of the first winding set, curve 66 represents the error in the initial rotor position of the second winding set, and curve 68 represents the error in the corrected rotor position of the first winding set. It can be seen that the angular error of the estimate 68 of the rotor position of the first winding set is very small. Thereby, an effective cancellation of the dominant 6 th harmonic is achieved.

In fig. 5, curve 69 represents the initial rotor speed derived using the first winding set, curve 71 represents the initial rotor speed derived using the second winding set, and curve 73 represents the corrected rotor speed of the rotor. It can be seen that rotor speed 73 does include only the 6 th harmonic which is very attenuated, and differs from the initial rotor speeds 69, 71 which are conventionally estimated as rotor speeds.

The method can be generalized for any phase shift and any number of windings. Thus, the method can be used with any combination of phase shift (γ) and number of windings (n), with the first dominant harmonic (h _ 0) to be cancelled given by: h _0 = 2 pi/(n γ), where n is equal to or greater than 2.

The equation also considering the higher harmonics being cancelled becomes more complex, which is derived as an example of a multiple three-phase motor (multiple three-phase motor) as: h _ k = 2 pi/(n γ) (1 + 2k/(n-1)), k is equal to or greater than 0. Thus, in a dual FSCW design with a 30 ° phase shift, other harmonics, such as 18f and 30f, may be removed from the estimated position and velocity in addition to the 6f ripple (ripple).

In the case where it is desired to remove the 2f ripple from position and speed, a dual three-phase motor (dual three-phase motor) may be designed to have a 90 degree phase shift. Other ripples such as 6f and 10f may also be eliminated. The method can also be easily extended to any number of windings as long as a given phase shift (γ) between the winding sets is taken into account.

Some examples are:

1) for a triple three-phase motor (triple three-phase motor) where there is a 20 degree (or 40 degree) electrical phase shift between the systems, the 6f and 12f ripple in the estimated speed and position can be eliminated by using three initial estimated angles and some operations,

wherein

It should be noted that the initial one of the harmonic angles is assumed to be zero, but can be any value without affecting the final result.

The ripple free angles of 6f and 12f can be derived as follows,

and the ripple in the angle can be derived as,

the generator speed and its 6f and 12f ripple content can be derived in a similar way.

A quadruple three-phase motor (quadrature three-phase motor) can be designed so that the 6f and 12f harmonics can be cancelled using two phase shifts. Estimation of ripple in speed and position can be done by dividing the system into two pairs.

A general formula for deriving the respective corrected rotor operating parameters may be derived for a series of harmonics to be attenuated, and the harmonics may then be cancelled for a given motor design.

Embodiments of the invention may enable estimation of rotor position and rotor speed with higher accuracy, wherein, in particular, harmonics are attenuated. Thereby, an improvement in the overall control performance can be achieved. Furthermore, additional filters may be avoided, which may simplify the design and may also increase robustness. The method is applicable or suitable for estimating rotor position/speed in other multiple three-phase machines or machines having a number different from three phases.

It should be noted that the term "comprising" does not exclude other elements or steps and the "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.