阅读说明：本技术 用于控制超导电机的相移的系统 (System for controlling phase shift of superconducting electrical machine ) 是由 N·B·哈维斯 Y·徐 N·塔帕迪亚 D·A·托里 武安波 于 2020-09-29 设计创作，主要内容包括：本公开内容涉及用于控制超导电机的相移的系统。具体地,一种风力涡轮包括具有电枢和超导场绕组组的超导发电机。电枢包括具有多个电枢绕组的至少一个多相电枢绕组组。超导场绕组组与电枢分隔一间隙。超导场绕组组包括多个场绕组,其中,电枢绕组组和超导场绕组组中的一者是可连接的以随同风力涡轮的旋转构件旋转,以及电枢和超导场绕组组中的另一者是不旋转的。风力涡轮还包括耦合到至少一个多相电枢绕组组的可控功率变换器,以及构造成用以控制可控功率变换器的切换操作以实现多个电枢绕组之间的相移的控制器。(The present disclosure relates to a system for controlling phase shift of a superconducting electrical machine. A wind turbine includes a superconducting generator having an armature and a set of superconducting field windings. The armature includes at least one multi-phase armature winding set having a plurality of armature windings. The superconducting field winding set is separated from the armature by a gap. The superconducting field winding set includes a plurality of field windings, wherein one of the armature winding set and the superconducting field winding set is connectable to rotate with a rotating component of the wind turbine and the other of the armature and the superconducting field winding set is non-rotating. The wind turbine also includes a controllable power converter coupled to the at least one multi-phase armature winding set, and a controller configured to control switching operations of the controllable power converter to achieve a phase shift between the plurality of armature windings.)

1. A wind turbine, comprising:

a superconducting generator comprising an armature and a superconducting field winding set, the armature comprising at least one multiphase armature winding set comprising a plurality of armature windings, the superconducting field winding set separated from the armature by a gap, the superconducting field winding set comprising a plurality of field windings, wherein one of the armature winding set and the superconducting field winding set is connectable for rotation with a rotating component of the wind turbine and the other of the armature and the superconducting field winding set is non-rotating;

a controllable power converter coupled to the at least one multi-phase armature winding set; and

a controller configured to control switching operations of the controllable power converter to achieve a phase shift between the plurality of armature windings.

2. The wind turbine of claim 1, wherein the armature comprises a plurality of multi-phase armature winding sets.

3. The wind turbine of claim 1, further comprising controlling a phase shift between the plurality of armature windings as a function of time.

4. A wind turbine according to claim 1, wherein the controller is configured to control the switching operation of the controllable power converter to achieve the phase shift at a fundamental frequency and/or a switching frequency of the controllable power converter.

5. The wind turbine of claim 4, wherein the controller is configured to phase shift a fundamental frequency of each of the plurality of armature windings relative to another of the plurality of armature windings.

6. The wind turbine of claim 4, wherein the controller is configured to phase shift a carrier signal between each armature winding of the plurality of armature windings relative to another armature winding via a phase shift angle.

7. The wind turbine of claim 1, wherein the controller is configured to control the switching operation of the controllable power converter to achieve the phase shift between the plurality of armature windings by modifying one or more phase shift angles thereof as a function of one or more inputs including at least one of generator commanded power, actual power, current, temperature of the cryogenic region, power supplied to a cryocooler, current supplied to the cryocooler, a measure of heat being dissipated by the cryocooler, and/or combinations thereof.

8. The wind turbine of claim 1, wherein the superconducting field winding set is located in a cryogenic region of the superconducting generator during operation of the wind turbine.

9. The wind turbine of claim 8, wherein the at least one multi-phase armature winding set is located outside of a cryogenic region of the superconducting electrical generator.

10. The wind turbine of claim 8, further comprising a cryocooler for transporting heat from the cryogenic region to the environment via a thermodynamic cycle, the controller being configured to minimize the heat that the cryocooler must dissipate to achieve the phase shift between the plurality of armature windings by controlling the switching operation of the controllable power converter.

Technical Field

The present disclosure relates generally to superconducting electrical machines, such as superconducting wind turbine generators, and more particularly to superconducting electrical machines having controllable phase shift capabilities.

Background

Generally, a superconducting generator includes at least one superconducting coil that generates a static or rotating magnetic field and at least one armature coil that also generates a static or rotating magnetic field (which interacts with the magnetic field from the superconducting coil). In addition, superconducting generators are made by constructing generator field coils (which typically carry substantially direct current) from superconducting materials ("superconductors") instead of conventional copper materials. Superconductors are typically lighter in weight and smaller in size (relative to current carrying capacity) and also more efficient at conducting current (especially at lower frequencies) than conventional conductors such as copper. Thus, the use of superconductors in electrical applications, such as wind turbine generators, provides benefits such as more efficient performance, lower generator weight, non-gearbox direct drive operation, and lower manufacturing and installation costs. Such benefits are particularly useful for offshore wind turbine applications.

The magnetic field generated by the armature coil extends into a zone (zone) maintained at a low temperature within the generator. Due to the relative velocity difference between the armature coil and the magnetic field, the basic armature magnetic field occurs at 0Hz in the low temperature region. However, the spatial and temporal harmonics (harmonic) from the armature magnetic field occur at frequencies greater than 0 Hz. These spatial and temporal harmonics can induce eddy currents within the superconducting coils and surrounding hardware. These eddy currents generate heat that must be dissipated to ambient air through various cryocoolers that maintain the low temperature zone.

Due to the low temperature of the cold reservoir, the carnot's theorem requires that the coefficient of performance (COP), i.e., the inverse of the amount of work that must be supplied to move 1W of heat from the cold reservoir to the environment, be small. This means that even a small loss in the low temperature region may require a large amount of work to dissipate this heat to the environment. It is therefore of critical importance to minimize the generation of eddy currents in cold regions of the generator.

Accordingly, there is a need in the industry for an improved superconducting electrical machine that minimizes losses in low temperature regions.

Disclosure of Invention

Aspects and advantages of the invention will be set forth in part in the description which follows, or may be obvious from the description, or may be learned by practice of the invention.

In one aspect, the present disclosure is directed to a wind turbine. A wind turbine includes a superconducting generator having an armature and a set of superconducting field windings. The armature includes at least one multi-phase armature winding set having a plurality of armature windings. The superconducting field winding set is separated from the armature by a gap. The superconducting field winding set includes a plurality of field windings, wherein one of the armature winding set and the superconducting field winding set is connectable to rotate with a rotating component of the wind turbine and the other of the armature and the superconducting field winding set is non-rotating. The wind turbine also includes a controllable power converter coupled to the at least one multi-phase armature winding set, and a controller configured to control switching operations of the controllable power converter to achieve a phase shift between the plurality of armature windings.

In one embodiment, the armature includes a plurality of multi-phase armature winding sets. Additionally, in one embodiment, the wind turbine includes controlling a phase shift between the plurality of armature windings as a function of time.

In another embodiment, the controller is configured to control the switching operation of the controllable power converter to achieve a phase shift at the fundamental frequency and/or the switching frequency of the controllable power converter.

In further embodiments, the controller is configured to phase shift a fundamental frequency of each of the plurality of armature windings relative to another of the plurality of armature windings. In yet another embodiment, the controller is configured to phase shift the carrier signal between each of the plurality of armature windings relative to another armature winding via a phase shift angle.

In additional embodiments, the controller is configured to control the switching operation of the controllable power converter to achieve a phase shift between the plurality of armature windings by modifying one or more phase shift angles thereof as a function of one or more inputs. In such embodiments, the input(s) may include generator commanded power, actual power, current, temperature of the cryogenic region, power supplied to the cryocooler, a measure of the amount of heat being dissipated by the cryocooler (measurement), and/or combinations thereof.

In several embodiments, the superconducting field winding sets may be located in a cryogenic region of the superconducting generator during operation of the wind turbine. In such embodiments, the polyphase armature winding group(s) may be located outside of the cryogenic region of the superconducting electrical generator.

In yet another embodiment, the wind turbine may include a cryogenic cooler for transporting heat from the low temperature region to the environment via a thermodynamic cycle. In such embodiments, the controller is configured to minimize the amount of heat that the cryocooler must dissipate by controlling the switching operation of the controllable power converter to achieve a phase shift between the plurality of armature windings.

In particular embodiments, the superconducting field winding sets may also be surrounded by heat shields (or heat shields) that are maintained at a predetermined temperature range during operation of the wind turbine. For example, in such embodiments, the predetermined temperature range may be in a range from about 25 kelvin to about 50 kelvin.

In another aspect, the present disclosure is directed to a superconducting electrical machine system. The electric machine system includes a superconducting electric machine having an armature and a superconducting field winding set. The armature includes at least one multi-phase armature winding set having a plurality of armature windings. The superconducting field winding set is separated from the armature by a gap. The superconducting field winding set includes a plurality of field windings, wherein one of the armature winding set and the superconducting field winding set is connectable to rotate with a rotating component of the wind turbine and the other of the armature and the superconducting field winding set is non-rotating. The wind turbine also includes a controllable power converter coupled to the at least one multi-phase armature winding set, and a controller configured to control switching operations of the controllable power converter to achieve a phase shift between the plurality of armature windings. It should also be understood that the superconducting electrical machine system may also include any of the additional features described herein.

In another aspect, the present disclosure is directed to a method of operating an electric machine system. A superconducting electrical machine system has a superconducting electrical machine having an armature and a superconducting field winding set. The armature has at least one multi-phase armature winding set having a plurality of armature windings. The superconducting field winding set is separated from the armature by a gap. The superconducting field winding set has a plurality of field windings, wherein one of the armature winding set and the superconducting field winding set is connectable to rotate with a rotating component of the wind turbine and the other of the armature and the superconducting field winding set is non-rotating. The method includes providing a superconducting field winding set in a cryogenic region of the electric machine during operation of the electric machine system. In addition, the method includes controlling switching operations of the controllable power converter to achieve a phase shift between the plurality of armature windings to minimize losses in the low temperature region. It should also be understood that the method may further comprise any of the additional features and/or steps described herein.

Specifically, the present disclosure also discloses the following technical solutions.

Technical solution 1. a wind turbine comprising:

a superconducting generator comprising an armature and a superconducting field winding set, the armature comprising at least one multiphase armature winding set comprising a plurality of armature windings, the superconducting field winding set separated from the armature by a gap, the superconducting field winding set comprising a plurality of field windings, wherein one of the armature winding set and the superconducting field winding set is connectable for rotation with a rotating component of the wind turbine and the other of the armature and the superconducting field winding set is non-rotating;

a controllable power converter coupled to the at least one multi-phase armature winding set; and

a controller configured to control switching operations of the controllable power converter to achieve a phase shift between the plurality of armature windings.

The wind turbine of claim 1, wherein the armature comprises a plurality of multi-phase armature winding sets.

Claim 3. the wind turbine according to claim 1, further comprising controlling the phase shift between the plurality of armature windings as a function of time.

Solution 4. the wind turbine according to solution 1, characterized in that the controller is configured to control the switching operation of the controllable power converter to achieve the phase shift at the fundamental frequency and/or the switching frequency of the controllable power converter.

The wind turbine of claim 5, wherein the controller is configured to phase shift a fundamental frequency of each of the plurality of armature windings relative to another of the plurality of armature windings.

The wind turbine of claim 6, wherein the controller is configured to phase shift the carrier signal between each of the plurality of armature windings relative to another armature winding via a phase shift angle.

Solution 7. the wind turbine of solution 1, wherein the controller is configured to control the switching operation of the controllable power converter to achieve the phase shift between the plurality of armature windings by modifying one or more phase shift angles thereof as a function of one or more inputs including at least one of generator commanded power, actual power, current, temperature of the low temperature region, power supplied to a cryocooler, current supplied to the cryocooler, a measure of heat being dissipated by the cryocooler, and/or combinations thereof.

Claim 8 the wind turbine of claim 1, wherein the superconducting field winding set is located in a cryogenic region of the superconducting electrical generator during operation of the wind turbine.

Claim 9 the wind turbine of claim 8, wherein the at least one polyphase armature winding set is located outside of a cryogenic region of the superconducting electrical machine.

The wind turbine of claim 8, further comprising a cryocooler for transporting heat from the cryogenic region to the environment via a thermodynamic cycle, wherein the controller is configured to minimize the heat that the cryocooler must dissipate to achieve the phase shift between the plurality of armature windings by controlling the switching operation of the controllable power converter.

Solution 11. the wind turbine of solution 1 wherein the superconducting field winding sets are surrounded by a heat shield that is maintained at a predetermined temperature range during operation of the wind turbine, the predetermined temperature range being in a range from about 25 kelvin to about 50 kelvin.

Technical solution 12 a superconducting motor system, comprising:

a superconducting electrical machine comprising an armature and superconducting field winding sets, the armature comprising at least one multiphase armature winding set comprising a plurality of armature windings, the superconducting field winding set separated from the armature by a gap, the superconducting field winding set comprising a plurality of field windings, wherein one of the armature winding set and the superconducting field winding set is connectable for rotation with a rotating component of the electrical machine and the other of the armature and the superconducting field winding set is non-rotating;

a controllable power converter coupled to the at least one multi-phase armature winding set; and

a controller configured to control switching operations of the controllable power converter to achieve a phase shift between the plurality of armature windings.

Technical means 13. the superconducting motor system according to claim 12, characterized in that the superconducting motor system further comprises: controlling a phase shift between the plurality of armature windings as a function of time.

Claim 14 the superconducting electrical machine system according to claim 12 wherein the controller is configured to control the switching operation of the controllable power converter to effect the phase shift at a fundamental frequency and/or a switching frequency of the controllable power converter.

The superconducting electrical machine system of claim 14 wherein the controller is configured to phase shift a fundamental frequency of each of the plurality of armature windings relative to another of the plurality of armature windings and phase shift a carrier signal between each of the plurality of armature windings relative to another armature winding via a phase shift angle.

Claim 16 the superconducting electrical machine system of claim 14 wherein the superconducting field winding sets are located in a cryogenic region of the superconducting electrical generator during operation of the wind turbine.

The superconducting electrical machine system of claim 12 wherein the controller is configured to control the switching operation of the controllable power converter to achieve the phase shift between the plurality of armature windings by modifying one or more phase shift angles thereof as a function of one or more inputs including at least one of generator commanded power, actual power, current, temperature of the low temperature region, power supplied to a cryocooler, current supplied to the cryocooler, a measure of heat being dissipated by the cryocooler, and/or combinations thereof.

A method of operating a motor system having a superconducting motor with an armature having at least one multi-phase armature winding set having a plurality of armature windings and a superconducting field winding set separated from the armature by a gap, the superconducting field winding set having a plurality of field windings, wherein one of the armature winding set and the superconducting field winding set is connectable to rotate with a rotating component of the wind turbine and the other of the armature and the superconducting field winding set is non-rotating, the method comprising;

providing the superconducting field winding set in a cryogenic region of the electric machine during operation of the electric machine system; and

controlling switching operation of the controllable power converter to achieve a phase shift between the plurality of armature windings so as to minimize losses in the low temperature region.

The method of claim 18, wherein the armature comprises a plurality of multi-phase armature winding sets.

The method of claim 18, wherein the method further comprises controlling the phase shift between the plurality of armature windings as a function of time.

The method of claim 18, wherein controlling the switching operation of the controllable power converter to achieve the phase shift between the plurality of armature windings further comprises: controlling switching operation of the controllable power converter to achieve a phase shift between the plurality of armature windings at a fundamental frequency and/or a switching frequency of the controllable power converter.

The method according to claim 21, characterized in that the method further comprises: phase shifting a fundamental frequency of each of the plurality of armature windings relative to another of the plurality of armature windings.

The method of claim 21, further comprising: phase shifting a carrier signal between each of the plurality of armature windings relative to another armature winding via a phase shift angle.

The method of claim 18, wherein controlling the switching operation of the controllable power converter to achieve the phase shift between the plurality of armature windings further comprises:

modifying one or more phase shift angles thereof as a function of one or more inputs including at least one of generator commanded power, actual power, current, temperature of the cryogenic region, power supplied to a cryocooler, current supplied to the cryocooler, a measure of heat being dissipated by the cryocooler, and/or combinations thereof.

These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention.

Drawings

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

FIG. 1 illustrates a perspective view of an embodiment of a wind turbine having a superconducting generator according to the present disclosure;

FIG. 2 illustrates a cross-sectional view of one embodiment of a superconducting electrical generator according to the present disclosure;

FIG. 3 illustrates a partial cross-sectional view of another embodiment of a superconducting electrical generator according to the present disclosure;

FIG. 4 illustrates a schematic view of one embodiment of a superconducting electrical generator having two three-phase winding sets excited by an electrical power converter in accordance with the present disclosure;

FIG. 5 illustrates a schematic view of another embodiment of a superconducting electrical generator having a single three-phase winding set excited by an electrical power converter in accordance with the present disclosure;

FIG. 6 illustrates a schematic view of one embodiment of a control system for a superconducting electrical generator according to the present disclosure;

FIG. 7 illustrates a phase A current waveform and a phase U current waveform and at φ in accordance with the disclosure₁A graphical Fast Fourier Transform (FFT) of the average of phase a and phase U in the case of = 0;

FIG. 8 illustrates a phase A current waveform and a phase U current waveform and at φ in accordance with the disclosure₁A graphical Fast Fourier Transform (FFT) of the average of phase a and phase U in the case of = pi/6; and

fig. 9 illustrates a flow diagram of one embodiment of a method for operating a superconducting electrical generator according to the present disclosure.

Detailed Description

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment, can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention encompass such modifications and variations as fall within the scope of the appended claims and their equivalents.

The present disclosure encompasses any manner of superconducting electrical machine and is not limited to superconducting generators. For purposes of explanation, the present system is described herein with reference to superconducting generators in general, and wind turbine superconducting generators in particular.

Referring now to the drawings, FIG. 1 illustrates a perspective view of an embodiment of a wind turbine power generation system 10. As shown, the wind turbine 10 generally includes a tower 12 extending from a support surface 14, a nacelle 16 mounted on the tower 12, and a rotor 18 coupled to the nacelle 16. Rotor 18 includes a rotatable hub 20, and at least one rotor blade 22 (three shown) coupled to and extending outwardly from hub 20. Each rotor blade 22 may be spaced about hub 20 to facilitate rotating rotor 18 to enable kinetic energy to be converted from wind power to usable mechanical energy, and subsequently, electrical energy. To this end, rotor 18 is coupled to a generator 24 via a shaft 26. For purposes of this disclosure, generator 24 is a direct drive superconducting generator.

The present invention encompasses a wind turbine power generation system 10 as described above, wherein the generator 24 is configured as a three-phase superconducting generator as set forth below. The present invention also encompasses various methods of operating superconducting electrical generators, particularly wind turbine superconducting electrical generators according to the method aspects set forth below.

Referring now to FIG. 2, illustrated is a cross-sectional view of one embodiment of a superconducting electrical generator 24 according to FIG. 1. While a superconducting generator 24 is illustrated and described herein, it will be understood that the features described herein may be applied to any superconducting electrical machine and are not limited to wind turbine power systems.

As depicted, the generator 24 includes: an outer concentric member 104, which may be a stator; and an inner concentric member 106, which may be a rotor (e.g., in an inner rotor configuration). However, in other embodiments, the outer member 104 may be a rotor of the generator 24 and the inner member 106 may be a stator of the generator 24 (e.g., in an outer rotor configuration). Additionally, as shown, a gap (or "air gap") 105 may be defined between the outer and inner members 104, 106 to allow movement (e.g., rotation) therebetween. The field winding set(s) are attached to, for example, the inner member 106, and the armature is attached to, for example, the outer member 104. The field winding group(s) may be disposed within the armature or external to the armature. For purposes of illustration and not limitation, the field winding set(s) are attached to the inner member 106 and are stationary while the armature is attached to the outer member 104. Also for purposes of illustration and not limitation, the field winding group(s) are stationary while the armature rotates.

Further, as shown, the armature includes at least one multi-phase armature winding set having a plurality of armature windings 108 attached to the outer member 104 or the inner member. The field winding set(s) includes a plurality of field windings 110 attached to the other of the outer or inner members 104, 106. In addition, the superconducting field winding set is separated from the armature by a gap.

The field winding has superconducting properties at sufficiently low temperatures, magnetic fields and current densities. Thus, the field winding operates within one or more low temperature zones. During operation of the generator 24, these windings 108, 110 are in electromagnetic communication.

The field winding carries excitation, wherein a magnetic field is generated by the field winding through which current flows, and the armature winding is connectable to a controllable power converter coupled to the multi-phase armature winding set. Although several windings 108, 110 are depicted, in various embodiments, there may be more or fewer windings 108, 110 and/or windings thereof surrounding the outer member 106 and the inner member 108, for example, to configure the number of poles of the generator 24 and thereby configure (or configure) the frequency of power generation and/or other operating characteristics of the generator 24.

The magnetic field generated by the armature winding 108 is due to a magnetomotive force (MMF) established by the current flowing through the armature winding 108. Due to the discretization of the windings, magnetic saturation within the steel structure, and the pulse width modulation scheme employed by the switching electrical power converter to drive the current waveform to the desired shape, MMF has spatial and temporal harmonics associated with it. While the fundamental MMF component appears at 0Hz for components located in the low temperature zone, MMF harmonics appear at frequencies greater than 0 Hz. These harmonics generate eddy currents in components in the low temperature region and will therefore generate heat which must be dissipated by the cryocooler.

The field winding 110 may be constructed of a superconducting material, such as niobium titanium (NbTi), niobium tin (Nb 3 Sn), or magnesium diboride (MgB 2). Typically, the armature winding 108 is composed of copper and is generally conductive. However, in certain embodiments, the armature windings 108 may also be constructed of superconducting materials such as NbTi, Nb3Sn, or MgB 2. In certain embodiments, the superconducting material may also be a high temperature superconductor, such as YBCO or ReBCO.

Thus, in principle, there are two unique frequency groups of interest in superconducting electrical machines: (1) low frequency harmonics at the 5x, 7x, 11x … fundamental frequency, and (2) high frequency harmonics centered around the 1x, 2x, 3x, … switching frequency. The low frequency harmonics are controlled by the space harmonics of the armature winding 108, while the high frequency harmonics are controlled by the switching functions employed by the electrical power converter that regulates the armature current.

Thus, in one embodiment, the present disclosure relates to reducing low frequency harmonics by utilizing a generator with a phase sequence greater than three. For example, in one embodiment, the present disclosure is directed to a generator having a plurality of three-phase winding sets within an armature. The fundamental currents in these separate three-phase groups can be phase shifted relative to each other to reduce the spatial harmonics of the MMF of the armature within the machine.

More specifically, as shown in fig. 3 and 4, illustrated are various views of one embodiment of a superconducting electrical generator 24 having multiple three-phase winding sets according to the present disclosure. Fig. 3 illustrates a partial cross-sectional view of one embodiment of a superconducting electrical generator 24 having two three-phase winding sets with two notches per pole per phase, with the ABCUVW coil side labeled, according to the present disclosure. Three-phase winding set 102 consists of A, B and the C coil side, while three-phase winding set 103 consists of U, V and the W coil side. Fig. 4 illustrates a schematic view of the embodiment of fig. 3 including two three-phase winding sets 102, 103 of a superconducting electrical generator 24 interfaced to electrical power converters 107, 109 according to the present disclosure. In such embodiments, where the generator 24 includes two three-phase winding sets 102, 103, the neutral point may be buried.

More specifically, fig. 3 illustrates one embodiment of a winding pattern for a generator 24 having two three-phase winding sets 102, 103, wherein the first winding set 102 includes three single-phase armature windings 108 (e.g., A, B and C) and the second winding set 103 includes a different three single-phase armature windings 108 (e.g., U, V and W). In addition, as shown in fig. 3, each of the single-phase armature windings 108 is spatially displaced such that there is a phase (phase) difference (e.g., 120 ° of electricity) between the voltages induced in each of the armature windings 108. Further, each of the three single-phase armature windings 108 is excited at a fundamental frequency. Except for the time phase shift variable phi₁、φ₂And phi₃Except that the basic current in phase UVW is the same as the current in phase ABC.

The reduction of high frequency harmonics is accomplished by modifying the time phase shift between the PWM carriers between the different phase groups. See in particular FIG. 4, #₄Representing the phase shift between the carrier waveforms for the two three-phase winding sets. FIGS. 7 and 8 provide for phase A, phase U, and for φ₄Fast Fourier Transform (FFT) of the current in the average of phase a and phase U. In FIG. 7, φ₁And in fig. 8, =0₁=π/6。

As shown in particular in fig. 7, the basic phase shift between phase a and phase U is zero, but the carrier frequency (or carrier frequency) between the two phases is shifted by 180 degrees (pi radians). The ordinate is the magnitude of the current harmonic in dB with respect to the rated generator current, while the abscissa represents the frequency of the harmonic in Hz. The base current magnitude at 3Hz is equal to 0 dB. The low order harmonics at 15Hz, 21Hz, 33Hz, etc. are not suppressed by averaging (or averaging). Odd switching harmonics (centered around 600Hz, 1800Hz, 3000Hz, etc.) are well suppressed by this method, but even switching harmonics (centered around 1200Hz, 2400Hz, 3600Hz, etc.) are not.

As shown in particular in fig. 8, the fundamental phase shift between phase a and phase U is 30 degrees, and the phase shift between carrier frequencies is 180 degrees (pi radians). The ordinate is the magnitude of the current harmonic in dB with respect to the rated generator current, while the abscissa represents the frequency of the harmonic in Hz. The base current magnitude at 3Hz is equal to 0 dB. The low order harmonics at 15Hz, 21Hz, 33Hz, etc. are suppressed by averaging (or averaging). All switching harmonics are slightly reduced in magnitude, but they are not eliminated to nearly the same extent as they are in fig. 7.

As shown in fig. 7, the low frequency time harmonics are not affected by the phase shift, but the switching harmonics around 600Hz are perfectly cancelled. In contrast, as shown in fig. 8, the low frequency time harmonics are reduced by phase shifting; however, the switching harmonics are only slightly reduced. This means that the mitigation of high frequency temporal harmonics is impaired by the mitigation of spatial harmonic content via the fundamental phase shift.

In the case of low base current load, the losses incident on the low temperature region 112 (fig. 6) will be dominated by the high frequency switching content. In these cases, it may be advantageous to set the phase shift φ₁=φ₂=φ₃=0 while maintaining the carrier phase shift phi₄And (n) = pi. When the fundamental current load is high, the loss from the space harmonics may be of about the same magnitude as the loss of the high frequency time harmonics. Therefore, an optimal phase shift parameter φ must be found₁、φ₂、φ₃、φ₄。

Referring now to FIG. 6, illustrated is an exemplary embodiment of a control system 150 for performing loss minimization according to the present disclosure. As shown, the magnetic field generated by the armature winding 108 extends into a region of the generator 24 that is maintained at a low temperature (referred to as a low temperature region 112). More specifically, as shown, the armature winding 108 may be magnetically coupled to a component located within the low temperature region 112, such as a field winding 110, a coil former, a vacuum vessel, or the like.

For example, in one embodiment, the low temperature region 112 of the superconducting generator 24 may range from about 0 Kelvin (K) to about 5K, such as about 4K, although it should be understood that the region 112 may also include temperatures greater than 5K. More specifically, as shown, the field winding 110 may be coupled to the armature winding 108 outside of the low temperature region 112 of the generator 24. Further, as shown, field winding 110 may be surrounded by heat shield 114 that is maintained at a predetermined temperature range. For example, in one embodiment, the predetermined temperature range may be in a range from about 25K to about 50K. In further embodiments, the region outside of the magnetic field cryostat may be maintained at an operating temperature above ambient temperature, for example about 325K.

Due to the relative velocity difference between the armature and the magnetic field, the basic armature magnetic field occurs at 0Hz in the low temperature region 112. However, spatial and temporal harmonics from the armature magnetic field occur at frequencies greater than 0 Hz. These spatial and temporal harmonics can then induce eddy currents in the superconducting coils and surrounding hardware. These eddy currents generate heat that must be dissipated to the environment via one or more cryocoolers 116 that maintain low temperature zone 112. More specifically, cryocooler(s) 116 are configured to transport heat from cryogenic region 112 to the environment via a thermodynamic cycle (Gifford-McMahon), Stirling (Stirling), magnetocaloric, etc.).

Due to the low temperature of the cold reservoir, the carnot's theorem requires that the coefficient of performance (COP), i.e., the inverse of the amount of work that must be supplied to move 1W of heat from the cold reservoir to the environment, must be small. This means that even a small loss in the low temperature region 112 may require a large amount of work to dissipate the heat to the environment. Therefore, in practical generator designs, it is important to minimize the generation of eddy currents in the low temperature region 112 of the generator 24.

Thus, still referring to fig. 6, the control system 150 may further include a controller 118 communicatively coupled to the controllable power converter(s) 107, 109 to control the switching operation of the controllable power converter(s) 107, 109 to achieve a phase shift between the plurality of armature windings 108. For example, in one embodiment, the controller 118 may be configured to control the phase shift between the plurality of armature windings 108 as a function of time. Further, in one embodiment, the controller 118 may be configured to modify one or more phase shift angles of the fundamental frequency of the single phase armature windings 108 and/or the switching frequency of the generator 24. More specifically, in certain embodiments, the controller 118 described herein may select φ₁=φ₂=φ₃= pi/6, thereby causing the motor to collapse into a six-phase motor, which minimizes space-induced losses.

In such embodiments, the controller 118 may be configured to phase shift the fundamental frequency of each of the plurality of armature windings 108 relative to another of the plurality of armature windings 108. Further, in one embodiment, the controller 118 may be configured to phase shift the carrier signal between each of the plurality of armature windings 108 relative to another armature winding via a phase shift angle.

Thus, as shown, the controller 118 may be configured to optionally receive a first set of inputs 120 representing generator commanded or actual power and/or current. The controller 118 may also be configured to optionally receive a second set of inputs 122 that represent the temperature of the low temperature region 112, the power supplied to the cryocooler 116, the current supplied to the cryocooler 116, and/or a direct measurement of the heat being dissipated. Thus, the controller 118 may employ some combination of the first input 120 and the second input 122 for the purpose of modifying the phase shift angle φ shown in FIG. 4₁-φ₄So that cryocooler 116 must be fed from the field windingThe heat output is minimized.

The controller 118 may be configured to continuously vary the phase shift angle. Some examples of methods that may be employed by the controller 118 are: classical feedback control structures (lag-lead, PID, etc.), feedforward calculations, disturbance and observation nonlinear optimizers, nonlinear adaptive regulators, genetic algorithms, artificial intelligence, etc.

Thus, the superconducting generator 24 of the present disclosure and the method of operating the same minimize losses within the cryogenic region 112. By phase shifting the fundamental and switching harmonics of the generator 24, losses within the low temperature region 112 of the superconducting generator 24 may be reduced by eliminating the non-synchronous field component. This provides a reduction in the number of cryocoolers required to support the superconducting state of the field winding. The reduction in the number of cryocoolers can improve system efficiency, reliability, and reduce cost.

In an alternative embodiment, as shown in fig. 5, generator 24 (not shown) may include a single three-phase armature winding set 102, e.g., with an unburied neutral point. Each armature winding 102 is energized by an electrical power converter 107, 109, 111. In such embodiments, the controller 118 may be configured to independently energize each of the single phase armature windings 102 (e.g., A, B and C) of the single three-phase winding set 102. Further, in one embodiment, the controller 118 may be configured to phase shift the carrier signal between each of the single-phase armature windings 102 relative to another single-phase armature winding via a phase shift angle. As a result, the carrier between the three phases can be passed through the phase shift variable φ₁And phi₂Phase shifting is direct.

Referring now to fig. 9, illustrated is a flow diagram of one embodiment of a method 200 of operating a superconducting electrical machine according to the present disclosure. Generally, the method 200 described herein is primarily applicable to operating the wind turbine 10 described above. However, it should be appreciated that the disclosed method 200 may be performed using any other suitable wind turbine and/or superconducting electrical machine. Additionally, for purposes of illustration and discussion, FIG. 9 depicts steps performed in a particular order. One of ordinary skill in the art, using the disclosure provided herein, will appreciate that the various steps of any of the methods disclosed herein may be adapted, omitted, rearranged or expanded in various ways without departing from the scope of the present disclosure.

As shown at (202), method 200 includes providing a superconducting field winding set in a cryogenic region of an electric machine during operation of the electric machine system. As shown at (204), method 200 includes controlling switching operations of the controllable power converter to achieve a phase shift between the plurality of armature windings to minimize losses in the low temperature region.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. If such other example includes structural elements that do not differ from the literal language of the claims, or if such other example includes equivalent structural elements with insubstantial differences from the literal language of the claims.