Estimation of rotor operating parameters

Abstract

A method for estimating rotor operating parameters of an electric motor is described, wherein the electric motor includes a plurality of winding sets, the plurality of winding sets being wound to have a phase shift between the winding sets, the rotor operating parameters including rotor position and / or rotor speed, the method comprising: for each winding set, deriving initial rotor operating parameters based on current and voltage of the corresponding winding set; for at least two winding sets and for at least one predetermined harmonic, calculating rotor operating parameter harmonic correction terms based on the initial rotor operating parameters of the at least two winding sets; for at least one winding set, calculating corrected rotor operating parameters based on the initial operating parameters of the winding set and the 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.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for estimating rotor operating parameters of an electric machine, the electric machine comprising a plurality of winding sets wound with phase shifts between the winding sets, and a controller for controlling a generator comprising the apparatus. Background Art

[0002] The synchronous motor comprises a stator and a rotor capable of rotating relative to the stator. The stator may comprise one or more multi-phase winding sets, and the rotor may comprise permanent magnets. The motor may be an externally excited motor.

[0003] Controlling a permanent magnet synchronous motor requires knowledge of the rotor speed and position. Estimation methods are often used to avoid additional sensors and reduce the hardware requirements implemented in the converter control system. Speed / position estimators using EMF-based observers are a conventional choice, which utilizes measured currents and reference voltages that are readily available in the control system.

[0004] Morimoto, "Sensorless control strategy for salient-pole PMSMbased on extended EMF in rotating reference frame" (IEEE Transactions on Industry Applications, Vol. 38, No. 4, July / August 2002), discloses a control strategy for a salient-pole permanent magnet synchronous motor (PMSM). Thus, a model of a salient-pole PMSM using extended electromotive force (EMF) in a rotating reference frame is used to estimate both the position and speed of the rotor.

[0005] 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 improper behavior of the observer and consequent estimation errors. The error in the estimated position is critical to the overall control performance and may lead to control instability, and attempts to attenuate the harmonics with the aid of digital filters will introduce additional errors in speed and position due to phase delays.

[0006] The presence of harmonics in the feedback signals (current and voltage) used by the back-EMF based speed observer may lead to inaccurate speed estimation and / or position estimation of the rotor. Therefore, in order to improve the performance of the speed observation method, it is desirable to attenuate such harmonic content.

[0007] It has been observed that conventional methods do not provide sufficiently accurate estimates of the position and / or speed of the rotor in all cases and in all configurations of the generator. Therefore, there may be a need for a method and apparatus for estimating rotor operating parameters of an electrical 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, wherein the accuracy of the estimated rotor position and / or rotor speed is improved compared to conventional methods. Summary of the invention

[0008] This need can be met by the subject matter according to the independent claim. Advantageous embodiments of the invention are described by the dependent claims.

[0009] According to an embodiment of the present invention, a method for estimating rotor operating parameters of an electric motor is provided, wherein the electric motor comprises a plurality of winding sets, the plurality of winding sets being wound to have 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 a (e.g., measured) current and a (e.g., reference) voltage of the corresponding winding set; for at least two winding sets and for at least one predetermined harmonic, 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 one winding set, calculating corrected rotor operating parameters based on the initial operating parameters of the winding set and the 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.

[0010] Thus, embodiments of the present invention provide a simple solution for removing dominant harmonics in estimated position and speed in a phase-shifted multi-winding motor, i.e. a fractional slot concentrated winding (FSCW) motor. Embodiments of the present invention thereby make it possible to avoid implementing additional filters (to attenuate undesirable harmonics).

[0011] The method may be implemented partly in hardware and / or software, for example as a module or unit in a controller of a generator, in particular a wind turbine controller.

[0012] The electric machine may comprise a rotor on which permanent magnets are mounted. The electric 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 more phases. The electric 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 when 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 a first winding set and a second winding set.

[0013] The initial rotor operating parameters may be derived, for example, as described in the above-mentioned publication "Sensorless control strategy for salient-pole PMSM based on 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, for example two, three, four or even more predetermined harmonics. The predetermined harmonics may depend on the configuration of the motor, in particular on the number of winding sets and / or the phase shifts between the winding sets. The motor may include 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.

[0014] Calculating the rotor operating parameter harmonic correction term for a specific winding set requires receiving the initial rotor operating parameters of at least one other winding set. The rotor operating parameter harmonic correction term can correct (one or more) undesirable harmonic components included in the initial rotor operating parameters. Thus, calculating the rotor operating parameter harmonic correction term can also depend on the phase shift between the winding sets. The corresponding rotor operating parameter harmonic correction term can, for example, involve subtracting the initial rotor operating parameters of the considered winding set from the initial rotor operating parameters from another winding set, and can additionally, for example, subtract the phase shift between the winding sets from it. Therefore, calculating the rotor operating parameter harmonic correction term can be obtained by subtracting and / or summing the initial rotor operating parameters of at least two winding sets (including the considered winding set and at least one other winding set), and involves the phase shift between the winding sets. Therefore, the arithmetic unit can be applied to calculate the rotor operating parameter harmonic correction term. In particular, the harmonic correction term can be based on the initial rotor operating parameters of at least two or three or all winding sets included in the motor.

[0015] The corrected rotor operating parameters may be corrected for the undesirable harmonic component(s), and may also be obtained by performing simple arithmetic, for example involving subtracting the corrective term from the initial rotor operating parameters.

[0016] The rotor operating parameter may, for example, include one or more components, such as rotor position and / or rotor speed. When the corrected rotor operating parameter is substantially free of one or more predetermined harmonic components, the corrected rotor operating parameter 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 parameter may thereby be improved.

[0017] The method can 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 can be applied to any number of phases, such as two phases, three phases, four phases, five phases or even more phases. Furthermore, the method can be adapted to attenuate or substantially remove more than one predetermined harmonic, such as two, three, four, five or even more predetermined harmonics. This may depend on the configuration of the electric machine, in particular on the number of winding sets and / or the phase shift between the winding sets.

[0018] The electric machine may include a stator having a set of windings wound or arranged in a plurality of different winding topologies, including, for example, a concentrated winding topology and a distributed winding topology. Thus, the method is applicable to electric machines of many conventional configurations.

[0019] According to an embodiment of the present invention, calculating the rotor operating parameter harmonic correction term includes: calculating the rotor position harmonic correction term based on the initial rotor position of at least two winding sets; and / or calculating the rotor speed harmonic correction term based on the initial rotor speed of the at least two winding sets.

[0020] Thus, conventionally required rotor operating parameters, namely rotor position and rotor speed, can be supported by the method for estimation. The rotor position can be given, for example, as the angular position of the rotor relative to a reference position in a circumferential direction. The rotor speed can be given, for example, in rpm. The rotor position and rotor speed may be required in any transformation module, for example, a controller.

[0021] According to an embodiment of the present invention, calculating the corrected rotor operating parameters includes: calculating the corrected rotor position based on the initial rotor position of the winding set and the rotor position harmonic correction term of the winding set; and / or calculating the corrected rotor speed based on the initial rotor speed of the winding set and the rotor speed harmonic correction term of the winding set.

[0022] The corrected rotor position and / or rotor speed can be directly input to a control module or control element requiring the rotor position and / or rotor speed without the need to additionally apply a filter element. The corresponding corrected rotor operating parameters can also be derived by applying simple arithmetic, such as subtracting the corresponding rotor operating parameter harmonic correction term from the initial rotor operating parameters (i.e., initial rotor position / rotor speed). Thereby, the calculation can be performed in a simple manner.

[0023] According to an embodiment of the present invention, the at least two winding sets include a winding set for which the corresponding correction term is calculated and at least one other winding set. The other winding set may be phase-shifted by the phase shift between the winding sets relative to the winding set for which the corresponding correction term is calculated. In the calculation of the predetermined harmonic, it may be assumed that the corresponding positions of the rotor relative to the different winding sets are also phase-shifted by the product of the harmonic and the phase shift between the winding sets. Therefore, 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, in particular the fundamental electrical frequency).

[0024] According to an embodiment of the present invention, the calculation of the rotor position harmonic correction term is also based on the winding set phase shift. The rotor position harmonic correction term can, for example, depend on the difference between the initial rotor position of the considered winding set and the initial rotor position of another (e.g., immediately adjacent) winding set, which is further subtracted from the phase shift between the winding sets, where the result can be divided by 2. Thus, the correction term can be easily calculated.

[0025] According to an embodiment of the invention, at least one predetermined harmonic to be attenuated in the harmonic correction rotor operating parameters comprises a harmonic h_0 = 2π / (nγ), wherein n is the number of winding sets and γ is the phase shift between the winding sets, wherein the number of phases of each winding set is in particular three. Given the configuration of the generator or motor, i.e. given the number of winding sets and the phase shift between the winding sets, the harmonic h_0 may be considered the most dominant harmonic. It may be highly desirable to attenuate errors in this dominant harmonic h_0, as may be achieved by this embodiment.

[0026] According to an embodiment of the present invention, at least one predetermined harmonic to be attenuated in the harmonic correction rotor operating parameters comprises a harmonic h_k = 2π / (nγ)(1 + 2k / (n-1)), wherein 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 harmonics so as to also attenuate higher harmonics of the dominant harmonics. Thus, the accuracy of the estimation of the rotor position and / or rotor speed may be further improved.

[0027] According to an embodiment of the present invention, at least one predetermined harmonic includes a first predetermined harmonic and at least one second predetermined harmonic, wherein the first predetermined harmonic h_1 to be attenuated in the harmonic correction rotor operating parameters is h_1 = 2π / (nγ)(1 +2k_1 / (n-1)), wherein the second predetermined harmonic h_2 to be attenuated in the harmonic correction rotor operating parameters is h_2 = 2π / (nγ)(1 + 2k_2 / (n-1)), wherein n is the number of winding sets, γ is the winding set phase shift between the winding sets, k_1, k_2 are integers equal to or greater than 0, wherein k_1 is not equal to k_2, wherein the number of phases is in particular three, wherein, in particular: the motor 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 6th harmonic and the second harmonic is the 12th harmonic.

[0028] Thus, embodiments of the present invention allow at least two predetermined harmonics or even more predetermined harmonics to be attenuated in the initial rotor operating parameters (including harmonic errors). It may only be possible to simultaneously attenuate or remove certain combinations of different harmonics (e.g., multiples of at least one predetermined harmonic), which may depend on the configuration and construction of the motor.

[0029] According to an embodiment of the invention, the motor has two, in particular three-phase, winding sets, wherein the winding set phase shift is 30° and the predetermined harmonic is the 6th harmonic (for example and may also include the 18th harmonic) and / or wherein the winding set phase shift is 90° and the predetermined harmonic is the 2nd harmonic. Thereby, motors of typical configurations are supported. In particular, it is possible to simultaneously eliminate 2f and 6f harmonics in the corrected rotor operating parameters.

[0030] According to an embodiment of the invention, the electric machine has three winding sets, in particular three-phase, wherein the winding set phase shift is 20° (or 40°) and the predetermined harmonics are the 6th and 12th harmonics.

[0031] According to an embodiment of the invention, the motor has four, in particular three-phase, winding sets, wherein the phase shift between the winding sets is, for example, equally limited to 15°, and the first predetermined harmonic is the 6th harmonic and / or (wherein the winding set phase shift is, for example, 15°) and the second predetermined harmonic is the 12th harmonic.

[0032] According to an embodiment of the present invention, the motor is configured as a fractional slot type with a multi-winding stator, in particular with a concentrated winding topology or a distributed winding topology, wherein the motor in particular comprises a rotor with permanent magnets. Thus, conventionally available motors can be supported.

[0033] The stator of the motor may be, for example, a segmented stator. A concentrated winding topology may be characterized in that the coils belonging to one phase may be wound or arranged around one tooth. A distributed winding topology may be characterized in that the coils of one phase may be wound around more than one tooth, such as two, three, four, six or even more teeth. A fractional slot multi-winding stator may be characterized by a fractional number of slots per pole per phase, i.e. the number of slots divided by the number of poles and divided by the number of phases. Unlike an integer concentrated winding motor, which may be only a fractional slot motor, a distributed winding motor may be either an integer or a fractional slot motor.

[0034] According to an embodiment of the present invention, a method for controlling a motor is provided, the motor comprising a plurality of winding sets wound to have a phase shift between the winding sets, the method comprising: executing a method according to one of the aforementioned embodiments; and controlling the motor based on a corrected rotor operating parameter of at least one winding set.

[0035] The method may be performed or implemented, for example, by a controller of an electrical machine, in particular a generator controller, or may be performed, in particular, by a wind turbine controller.The improved estimation of rotor operating parameters may be used, for example, in the following control elements: frame transformation; adaptive filter; and decoupling terms in a fundamental current controller.

[0036] It should be understood that the features of the method for estimating rotor operating parameters of an electric motor disclosed, described, applied or provided, alone or in any combination, may also be applied, alone or in any combination, to an apparatus for estimating rotor operating parameters of an electric motor comprising multiple winding sets according to an embodiment of the present invention, and vice versa.

[0037] According to an embodiment of the present invention, there is provided a device for estimating rotor operating parameters of a motor comprising a plurality of winding sets, wherein the plurality of winding sets are wound to have a phase shift between the winding sets, the rotor operating parameters comprising rotor position and / or rotor speed, the device comprising a processor adapted to: for each winding set, derive initial rotor operating parameters based on current and voltage of the corresponding winding set; for at least two winding sets and for at least one predetermined harmonic, calculate rotor operating parameter harmonic correction terms based on the initial rotor operating parameters of the at least two winding sets; for at least one winding set, calculate corrected rotor operating parameters based on the initial operating parameters of the winding set and the rotor operating parameter harmonic correction terms of the winding set.

[0038] The apparatus may be implemented, for example, by a general-purpose processor which may execute a computer program comprising instructions for performing the method steps.

[0039] 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: an apparatus according to the preceding embodiments; and at least one control element receiving a corrected rotor operating parameter as input.

[0040] Furthermore, a wind turbine is provided, comprising the controller and also comprising the electrical machine, in particular a generator.

[0041] The aspects defined above and further aspects of the invention are apparent from the examples of embodiment described hereinafter and are explained with reference to the examples of embodiment.The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A generator system according to an embodiment of the present invention is schematically shown, comprising a controller for controlling the generator;

[0043] Figure 2 Schematically shows Figure 1 The controller shown in , which includes a device for estimating rotor operating parameters according to an embodiment of the present invention;

[0044] Figure 3 , Figure 4 and Figure 5 A graph showing rotor operating parameters estimated by an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0045] Embodiments of the 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.

[0046] Figure 1 The generator system 1 schematically shown in the figure comprises an electric machine 3 and a controller 5 for controlling the generator 3 according to an embodiment of the present invention. The controller 5 comprises a device 7 for estimating rotor operating parameters of the electric machine, the electric machine comprising a plurality of winding sets, the plurality of winding sets being wound with phase shifts 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. Typically, the corrected rotor operating parameters may include a corrected rotor position θ1^(11) of a first winding set and a corrected rotor position θ2^(12) of a second winding set and corresponding rotor speeds ω1^, ω2^(13, 14).

[0047] Figure 1The motor 3 shown in FIG. 1 is a motor including two winding sets, i.e., a first winding set 15 including wires wound into coils 15a, 15b, 15c and a second winding set 17 formed by wires and coils 17a, 17b, 17c. In particular, the two winding sets are three-phase winding sets, each of which provides phase A, phase B and phase C. As shown in FIG. Figure 1 As can be understood in the figure, the two winding sets 15, 17 are phase-shifted by an electrical angle of 30° relative to each other. The motor 3 further comprises permanent magnets 19 mounted at a rotor 21 (eg, an outer rotor).

[0048] The device 7 comprises a processor, not explicitly shown, adapted to receive (measured) currents 23 and 25 from the first and second winding sets 15a, 15b, 15c, 17a, 17b, 17c, respectively, and also reference voltages 27 and 29 of the first and second winding sets 15, 17, respectively.

[0049] Based on the currents 23, 25 and the voltages 27, 29, the device 7 derives initial rotor operating parameters (i.e. initial rotor positions and initial rotor speeds) for each corresponding winding set based on the currents 23, 25 and the voltages 27, 29. 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 6th harmonic). Furthermore, the arrangement 7 is suitable for calculating corrected rotor operating parameters, i.e. corrected rotor positions θ1^, θ2^ for the two winding sets 15, 17, and corrected rotor speeds ω1^, ω2^ for the two winding sets, as also marked with reference numerals 11, 12, 13, 14.

[0050] The controller 5 outputs control signals 32, 34. Thus, the control signal 32 can be supplied to the corresponding first converter 35 connected to the first winding set 15a, 15b, 15c, for example. The control signal 34 can be supplied to the second converter 37 connected to the second winding set 17a, 17b, 17c, for example. Figure 1 as shown in .

[0051] Figure 2 The controller 5 is shown in more detail, in particular in an embodiment of two separate but interacting controller parts 31, 33. However, the controller 5 may also be embodied as a single controller. Figure 2 The controller 5 shown in FIG. 5 comprises a first controller part 31 controlling the first winding set 15 a , 15 b , 15 c and comprises a second controller part 33 controlling the second winding set 17 a , 17 b , 17 c by generating and supplying respective control signals 32 and 34 .

[0052] The controller 5 comprises a device 7 configured with a first device part 7a and a second device part 7b. 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, 17c. From the respective current and voltage of each winding set, the respective device parts 7a, 7b calculate initial rotor operating parameters, which are denoted below as θ1, ω1 (39) for the first winding set and θ2, ω2 (41) for the second winding set. These initial rotor operating parameters (39, 41) are erroneous because they contain higher harmonic content.

[0053] In order to correct the harmonic error, the device parts 7a, 7b calculate the following equation: 1,6 ^、θ 2,6 ^ represents the corresponding rotor operating parameter harmonic correction term, wherein the second index indicates the harmonic to be attenuated. Based on the initial rotor operating parameters and the corresponding harmonic correction term, the device parts 7a, 7b calculate the corresponding corrected rotor operating parameters, namely the corrected rotor position 11 of the first winding set (also represented as θ1^) and the corrected rotor speed 13 of the first winding set (also represented as ω1^). The device part 7b thus calculates the corrected rotor position 12 of the second winding set and the corrected rotor speed 14 of the second winding set. Thereby, the device parts 7a, 7b are communicatively connected so as to allow the exchange of the initial rotor operating parameters 39 of the first winding set (especially including the initial rotor position and the initial rotor speed) and the exchange of the initial rotor operating parameters 41 of the second winding set (preferably also including the initial rotor position and the initial rotor speed).

[0054] The corrected rotor position and rotor speed 11, 13 of the first winding set are input to several control elements, such as a modulation control element 43, which calculates a current reference Id1_ref based on the voltage 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. Moreover, element 45 may receive the corrected rotor parameters 11, 13 of the first winding set. A DC link controller 47 calculates a reference Iq1_ref of the q component of the current, which together with the measured q component Iq1 of the current is supplied to a current controller 48 of the q component. The current controllers 45, 48 output respective components Vd1, Vq1 of the voltage, which are supplied to a voltage collector 49. The voltage collector may receive further input 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 which ultimately derives therefrom a converter control signal 32, e.g. comprising a pulse width modulated signal supplied to the gate of a controllable switch within the first converter 35 (see Figure 1 ).

[0055] The second controller part 33 is arranged similarly to the first controller 31 and also uses the corrected rotor operating parameters 12, 14 of the second winding sets 17a, 17b, 17c, respectively, in several control elements.

[0056] It should be understood that Figure 1 The illustrated embodiment merely exemplarily describes an estimation method for attenuating the 6th harmonic in position and speed using a dual-winding FSCW motor 3 with a 30° phase shift.

[0057] like Figure 2 As shown, the controller is implemented as two different controller parts 31, 33, which have the ability to communicate with each other to exchange initial rotor operating parameters 39, 41. Alternatively, the controller 5 can be implemented as a single controller. Figure 1 In the generator 3 shown, the dominant harmonic will be 6f, so the position estimate from both systems is given by (defining the initial rotor position and initial rotor speed):

[0058]

[0059] where θ0 is a harmonic-free sawtooth signal varying between 0 and 360°. Note that the initial rotor position (e.g., Figure 2 The signals in 39 and 41) contain 6th harmonics, which can therefore be described as,

[0060]

[0061]

[0062] From this, the rotor operating parameter harmonic correction term can be calculated as:

[0063]

[0064] Based on this correction term and the initial rotor operating parameters (ie, the initial rotor position), the following corrected rotor position can be calculated as:

[0065]

[0066] Similarly, the 6th harmonic in the speed can be calculated and used for harmonic cancellation:

[0067]

[0068] From this harmonic correction term, the corrected rotor speed can be derived.

[0069] The compensation term (or correction term) derived above is given exemplarily for the elimination of 6f in position and velocity. In this example, 6f is a predetermined harmonic.

[0070] Figure 3 , Figure 4 and Figure 5 The simulation results verifying the estimation method are shown. Figure 3 , Figure 4 , Figure 5 The horizontal axis 55 in FIG. 5 represents time, while the vertical axes 57, 59, and 61 represent angle, angle error, and speed, respectively. Figure 3 In FIG. 6 , curve 63 represents the initial rotor position of the first winding set, curve 65 represents the initial rotor position of the second winding set, and curve 67 represents the corrected rotor position of the first winding set.

[0071] exist Figure 4 In FIG. 6 , curve 64 represents the error in the rotor position of 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. Thus, effective cancellation of the dominant 6th harmonic is achieved.

[0072] exist Figure 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 the rotor speed 73 does include only the 6th harmonic which is very much damped, and is different from the initial rotor speeds 69, 71 which are conventionally estimated as the rotor speed.

[0073] The method can be generalized for any phase shift and any number of windings. Thus, the method can be used for any combination of phase shift (γ) and number of windings (n) with the first dominant harmonic (h_0) to be eliminated given by: h_0 = 2π / (nγ), where n is equal to or greater than 2.

[0074] The equation also considering the higher harmonics to be eliminated becomes more complicated, which is derived as an example of a multiple three-phase machine as: h_k = 2π / (nγ)(1 + 2k / (n-1)), k is equal to or greater than 0. Therefore, in a dual FSCW design with a 30° phase shift, in addition to the 6f ripple, other harmonics such as 18f and 30f can also be removed from the estimated position and velocity.

[0075] In cases where it is desirable to remove 2f ripple from position and velocity, a dual three-phase machine can be designed with a 90 degree phase shift. Other ripples such as 6f and 10f can also be removed. This approach can also be easily extended to any number of windings, as long as a given phase shift (γ) between the winding sets is considered.

[0076] Some examples are:

[0077] 1) For a triple three-phase machine where there is a 20 degree (or 40 degree) electrical phase shift between the systems, the 6f and 12f ripples in the estimated speed and position can be removed by using three initial estimated angles and some manipulation,

[0078]

[0079] in

[0080]

[0081] It should be noted that the initial angle in the harmonic angle is assumed to be zero, but can be any value without affecting the final result.

[0082] The ripple-free angles for 6f and 12f can be derived as follows,

[0083]

[0084] and the ripple in angle can be derived as,

[0085]

[0086] The generator speed and its content of 6f and 12f ripple can be derived in a similar manner.

[0087] A quadruple three-phase machine can be designed so that the 6f and 12f harmonics can be eliminated using two phase shifts. The estimation of the ripple in speed and position can be done by dividing the system into two pairs.

[0088] General formulas for deriving corresponding corrected rotor operating parameters can be derived for a range of harmonics to be attenuated, and the harmonics can then be eliminated for a given motor design.

[0089] Embodiments of the invention may enable an estimation of the rotor position and rotor speed with higher accuracy, wherein, in particular, harmonics are attenuated. Thereby, an improvement in the overall control performance may be achieved. Furthermore, additional filters may be avoided, which may simplify the design and may also increase robustness. The method may be applied or adapted to estimate the rotor position / speed in other multiple three-phase motors or motors with a number of phases other than three.

[0090] It should be noted that the term "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Moreover, elements described in association with different embodiments may be combined. It should also be noted that the reference numerals in the claims should not be interpreted as limiting the scope of the claims.

Claims

1. A method for estimating rotor operating parameters (θ, ω) of an electric machine (3), characterized in that: The motor (3) comprises a plurality of winding sets (15a, 15b, 15c, 17a, 17b, 17c), the plurality of winding sets (15a, 15b, 15c, 17a, 17b, 17c) being wound with phase shifts between the winding sets, the rotor operating parameters comprising a rotor position (θ) and / or a rotor speed (ω), the method comprising: For each winding set (15, 17), deriving initial rotor operating parameters (39) based on the current (23) and voltage (27) of the corresponding winding set (15); For at least two winding sets (15, 17) and for at least one predetermined harmonic (h), calculating rotor operating parameter harmonic correction terms based on initial rotor operating parameters (39, θ1, ω1; 41, θ2, ω2) of the at least two winding sets (15, 17); For at least one winding set (15, 17), based on initial rotor operating parameters (39, 41) of the winding set and rotor operating parameter harmonic correction terms of the winding set, corrected rotor operating parameters (11, 13, 12, 14) are calculated, wherein the corrected rotor operating parameters cause at least one predetermined harmonic to be removed or at least attenuated, and The predetermined harmonic depends on the number of winding sets and / or the phase shift between winding sets.

2. The method according to claim 1, wherein: Calculating the rotor operating parameter harmonic correction term includes: Calculating rotor position harmonic correction terms based on initial rotor positions (θ1, θ2) of at least two winding sets (15, 17); and / or Based on the initial rotor speeds (ω1, ω2) of the at least two winding sets (15, 17), a rotor speed harmonic correction term is calculated.

3. The method according to claim 2, 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 (θ1, θ2) of the winding set and the rotor position harmonic correction term of the winding set; and / or Based on the initial rotor speed (ω1, ω2) of the winding set and the rotor speed harmonic correction term of the winding set, a corrected rotor speed (13, 14) is calculated.

4. The method according to any one of claims 1 to 3, wherein: The at least two winding sets (15, 17) include a winding set (15) for which a corresponding correction term is calculated and include at least one other winding set (17).

5. The method according to claim 2 or 3, wherein: The calculation of the rotor position harmonic correction term is also based on the winding set phase shift (γ).

6. The method according to any one of claims 1 to 3, wherein: The at least one predetermined harmonic to be attenuated in the corrected rotor operating parameter comprises harmonic h_0=2π / (nγ), wherein n is the number of winding sets and γ is the winding set phase shift between the winding sets.

7. The method according to claim 6, wherein: The number of phases is three.

8. The method according to any one of claims 1 to 3, wherein: The at least one predetermined harmonic to be attenuated in the corrected rotor operating parameters includes the harmonic h_k=2π / (nγ)(1+2k / (n-1)), where n is the number of winding sets, γ is the winding set phase shift between the winding sets, and k is an integer equal to or greater than 0.

9. The method according to claim 8, wherein: The number of phases is three.

10. The method according to any one of claims 1 to 3, wherein: The at least one predetermined harmonic includes a first predetermined harmonic and at least one second predetermined harmonic, wherein the first predetermined harmonic h_1 to be attenuated in the corrected rotor operating parameters is h_1=2π / (nγ)(1+2k_1 / (n-1)), wherein the second predetermined harmonic h_2 to be attenuated in the corrected rotor operating parameters is h_2=2π / (nγ)(1+2k_2 / (n-1)), Wherein, 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 greater than 0, wherein k_1 is not equal to k_2.

11. The method according to claim 10, in, The number of phases is three, And wherein the motor has three winding sets, wherein the winding set phase shift is 20°, wherein k_1=0 and k_2=1, wherein the first predetermined harmonic is the 6th harmonic and the second predetermined harmonic is the 12th harmonic.

12. The method according to any one of claims 1 to 3, wherein: The motor (3) has two three-phase winding sets. wherein the winding set phase shift is 30° and the predetermined harmonic is the 6th harmonic; and / or Wherein, the winding set phase shift is 90° and the predetermined harmonic is the 2nd harmonic.

13. The method according to claim 10, wherein: The motor has three three-phase winding sets, wherein the winding set phase shift is 20°, and the first predetermined harmonic and the second predetermined harmonic are the 6th and 12th harmonics; and / or Wherein, the winding set phase shift is 40°, and the first predetermined harmonic and the second predetermined harmonic are the 6th and 12th harmonics.

14. The method according to claim 10, wherein: The motor has four three-phase winding sets, wherein the winding set phase shift is 15°, and the first predetermined harmonic is the 6th harmonic; and / or Wherein, the winding set phase shift is 15°, and the second predetermined harmonic is the 12th harmonic.

15. The method according to any one of claims 1 to 3, wherein: The stator of the motor (3) is configured as a fractional-slot multi-winding set stator.

16. The method according to claim 15, wherein: The fractional-slot multi-winding set stator has a concentrated winding topology structure or a distributed winding topology structure.

17. The method according to claim 15, wherein: The electric machine comprises a rotor (21) having permanent magnets (19).

18. A method for controlling a motor (3), characterized in that: The electric machine (3) comprises a plurality of winding sets (15, 17) which are wound with a phase shift between the winding sets, and the method comprises: Performing the method according to any one of claims 1 to 17; and The electric machine (3) is controlled (32, 34) based on a corrected rotor operating parameter (11, 13, 12, 14) of at least one winding set.

19. A device (7; 7a, 7b) for estimating rotor operating parameters (θ, ω) of an electric machine (3), characterized in that The motor (3) comprises 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: For each winding set, deriving initial rotor operating parameters (39, 41) based on the current (23, 25) and voltage (27, 29) of the corresponding winding set (15, 17); calculating rotor operating parameter harmonic correction terms for at least two winding sets and for at least one predetermined harmonic based on initial rotor operating parameters (39, 41) of the at least two winding sets; For at least one winding set, based on the initial rotor operating parameters (39, 41) of the winding set and the rotor operating parameter harmonic correction term of the winding set, a corrected rotor operating parameter (11, 13, 12, 14) is calculated, The predetermined harmonic depends on the number of winding sets and / or the phase shift between winding sets.

20. A controller (4) for controlling a generator, characterized in that The controller comprises: The device (7; 7a, 7b) according to claim 19; and At least one control element (9) receives as input corrected rotor operating parameters (11, 12, 13, 14).

21. The controller (4) according to claim 20, wherein: The generator is a generator of a wind turbine.

Images