Independent speed variable frequency alternator and method for generating independent speed variable frequency alternating current

Abstract

The present application relates to an independent speed variable frequency alternator device and an independent speed variable frequency alternator device may include a rotor and a stator, the rotor being configured to rotate relative to the stator. The device may also include a magnetic field source, attached to the rotor and configured to generate a first rotating magnetic field when the rotor rotates, wherein the rotational frequency of the first rotating magnetic field depends on the rotational frequency of the rotor. The device may also include a main rotor winding, attached to the rotor and configured to generate a second rotating magnetic field when the rotor rotates, wherein the rotational frequency of the second rotating magnetic field is independent of the rotational frequency of the rotor.

Description

Technical Field

[0001] The present application relates generally to the field of alternators, and more particularly to independent speed variable frequency alternators. Background Art

[0002] Aircraft and other vehicles often include systems that rely on an AC power source. In a conventional aircraft, AC power can be generated by the rotation of a primary prime mover attached to a generator (e.g., a permanent magnet generator). A three-phase power winding can be used within the generator to convert the magnetic field rotating with the prime mover into an AC power signal. Therefore, the frequency, amplitude, and phase of the power initially generated by a single conventional generator can depend on the rotational frequency of the prime mover.

[0003] To generate AC power with independent or variable frequency, a conventional aircraft electric propulsion train may include two stages of power conversion: first, conversion from the generated AC power signal to a direct current (DC) power signal; and second, conversion from the DC power signal to an independent frequency AC power signal, which may be used to drive an electric motor for propulsion or for other AC powered devices within the vehicle. Having two converter stages may reduce the efficiency of AC power generation and may significantly increase the weight of the aircraft system. Additional disadvantages may exist. Summary of the invention

[0004] The present invention discloses systems and methods that can overcome at least one of the above disadvantages.For example, a stand-alone variable speed alternator apparatus can include a rotor and a stator, wherein the rotational frequency of a rotating magnetic field associated with a main winding of the rotor is independent of the rotational frequency of the rotor.

[0005] In one embodiment, an independent speed variable frequency alternator device includes a rotor and a stator, the rotor being configured to rotate relative to the stator. The device also includes a magnetic field source attached to the rotor and configured to generate a first rotating magnetic field when the rotor rotates, wherein the rotational frequency of the first rotating magnetic field depends on the rotational frequency of the rotor. The device also includes a main rotor winding attached to the rotor and configured to generate a second rotating magnetic field when the rotor rotates, wherein the rotational frequency of the second rotating magnetic field is independent of the rotational frequency of the rotor.

[0006] In some embodiments, the magnetic field source comprises a permanent magnet. In some embodiments, the apparatus comprises a pilot winding attached to the stator and configured to convert the first rotating magnetic field into an AC power signal.

[0007] In some embodiments, the device includes a generator control unit configured to modulate the AC power signal to generate a high-frequency AC power signal and transmit it to the rotor, wherein the frequency of the high-frequency AC power signal is greater than the rotation frequency of the rotor. In some embodiments, the device includes a high-frequency transformer configured to transmit the high-frequency AC power signal from the stator to the rotor. In some embodiments, the high-frequency transformer includes a first power transformer winding attached to the stator and a second power transformer winding attached to the rotor, wherein the first power transformer winding is configured to transfer the high-frequency AC power signal to the second power transformer winding. In some embodiments, the high-frequency transformer omits a contact power transmission mechanism between the stator and the rotor.

[0008] In some embodiments, the device includes a rectifier, which is attached to the rotor and configured to convert a high-frequency AC power signal into a DC power signal. In some embodiments, the device includes an inverter, which is attached to the rotor and configured to convert a DC power signal into a main field AC power signal, wherein the main rotor winding is driven by the main field AC power signal. In some embodiments, the device includes a generator control unit, which is coupled to the inverter and configured to control the main field AC power signal, thereby controlling the rotation speed, direction, amplitude or any combination thereof of the second rotating magnetic field relative to the rotor. In some embodiments, the generator control unit includes a control circuit attached to the stator and a control circuit attached to the rotor, wherein the control circuit attached to the rotor includes at least one proportional-integral-differential (PID) controller. In some embodiments, at least one PID controller is coupled to the inverter to control the frequency of the second rotating magnetic field, and the control circuit attached to the rotor includes another PID controller coupled to the inverter to control the amplitude of the second rotating magnetic field. In some embodiments, the control circuit attached to the stator is communicatively coupled to the control circuit attached to the rotor via a control signal coupler, and the control signal coupler includes at least one first communication disk attached to the stator and at least one second communication disk attached to the rotor. In some embodiments, the first communication disk comprises an optical signal source and the second communication disk comprises a phototransistor. In some embodiments, the apparatus comprises a main stator winding configured to convert the second rotating magnetic field into an AC power signal.

[0009] In one embodiment, a method for generating independent speed variable frequency AC includes: generating a first rotating magnetic field at a magnetic field source attached to the rotor when the rotor rotates, wherein the rotation frequency of the first rotating magnetic field depends on the rotation frequency of the rotor. The method also includes: generating a second rotating magnetic field at a main rotor winding attached to the rotor when the rotor rotates, wherein the rotation frequency of the second rotating magnetic field is independent of the rotation frequency of the rotor. The method also includes: converting the second rotating magnetic field into an AC power signal at the main stator winding attached to the stator.

[0010] In some embodiments, the method includes: converting a first rotating magnetic field into an AC power signal; modulating the AC power signal to generate a high-frequency AC power signal; transmitting the high-frequency AC power signal from the stator to the rotor; converting the high-frequency AC power signal into a DC power signal; and converting the DC power signal into a main field AC power signal, wherein the main field AC power signal is used to drive the main rotor winding. In some embodiments, the method includes: receiving a reference frequency signal from a generator control unit; generating a first intermediate frequency signal, which is the difference between the reference frequency signal and a rotor frequency signal associated with the rotation frequency of the rotor; generating a second intermediate frequency signal, which is the difference between the first intermediate frequency signal and the main field frequency signal associated with the rotation frequency of the second rotating magnetic field relative to the rotor; and converting the second intermediate frequency signal into an inverter control signal to direct the inverter to change the main field AC power signal to accelerate or slow down the rotation of the second rotating magnetic field relative to the rotor.

[0011] In some embodiments, the first intermediate frequency signal is transmitted from the stator to the rotor via a control signal coupler, the control signal coupler comprising at least one first communication disk attached to the stator and at least one second communication disk attached to the rotor. In some embodiments, generating the second rotating magnetic field also includes determining the sign of the first intermediate frequency signal, and generating a second inverter control signal to direct the inverter so that the second rotating magnetic field rotates relative to the rotor in a direction corresponding to the sign of the intermediate signal. In some embodiments, the method includes: receiving a reference voltage signal from a generator control unit; generating an intermediate voltage signal, which is the difference between the reference voltage signal and a voltage signal associated with the AC power signal; and converting the intermediate voltage signal into an inverter control signal to direct the inverter to change the main AC power signal to increase or decrease the amplitude of the second rotating magnetic field.

[0012] In one embodiment, an alternator rotor apparatus includes a magnetic field source configured to generate a first rotating magnetic field when the rotor rotates, wherein the rotational frequency of the first rotating magnetic field depends on the rotational frequency of the rotor. The apparatus also includes a main rotor winding configured to generate a second rotating magnetic field when the rotor rotates, wherein the rotational frequency of the second rotating magnetic field is independent of the rotational frequency of the rotor.

[0013] In some embodiments, the device also includes: a power transformer winding configured to receive a high-frequency AC power signal; a rectifier configured to convert the high-frequency AC power signal into a DC power signal; and an inverter configured to convert the DC power signal into a main field AC power signal, wherein the main field AC power signal is used to drive the main rotor winding. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1is a schematic diagram depicting an embodiment of an independent speed variable frequency alternator apparatus,

[0015] Figure 2 is a block diagram depicting an embodiment of a signal control system for an independent speed variable frequency alternator,

[0016] Figure 3 is a diagram depicting an embodiment of a control signal coupler for a stand-alone variable frequency alternator apparatus,

[0017] Figure 4 is a flow chart depicting an embodiment of a method for generating independent speed variable frequency alternating current,

[0018] Figure 5 is a flow chart depicting an embodiment of a method for generating an independent speed variable frequency alternating current controlled rotating magnetic field.

[0019] Although the present application is susceptible to modification into various variations and alternatives, specific embodiments have been shown by way of example in the accompanying drawings and described in detail below. However, it should be understood that this is not intended to limit the present application to the specific form disclosed. On the contrary, it is intended to cover all variations, equivalents and alternatives within the scope of the present application. DETAILED DESCRIPTION

[0020] Reference Figure 1 , which depicts an embodiment of a stand-alone variable speed alternator apparatus 100. The apparatus 100 may include a rotor 102 and a stator 104. Figure 1 Features of the rotor 102 and stator 104 are depicted in various stages of generating AC. For example, components of the rotor 102 and stator 104 may correspond to a pilot permanent magnet generator (PMG) stage 106, a high frequency (HF) transformer stage 108, a field control stage 110, and a host stage 112.

[0021] The rotor 102 can be rotated by a prime mover 118. For example, the prime mover can be a turbine engine or another mechanism for imparting rotation. The rotor 102 can include a magnetic field source 120. In some embodiments, the magnetic field source 120 can be a permanent magnet. The device 100 can also include a pilot winding 122 positioned on the stator 104.

[0022] In the pilot PMG phase 106, the prime mover 118 can cause the rotor 102 to rotate relative to the stator 104. As the rotor 102 rotates, the magnetic field source 120 fixed to the rotor 102 and its associated magnetic field can also rotate. The pilot winding 122 can be configured such that the rotation of the magnetic field source 120 generates a three-phase AC power signal. The three-phase AC power signal can have a frequency corresponding to the rotation frequency of the rotor 102 depending on the rotation frequency of the rotor 102.

[0023] The device 100 may also include a generator control unit 124. The generator control unit 124 may perform a plurality of control functions within the device 100. To perform these functions, the generator control unit 124 may include a power modulator circuit (not shown). The generator control unit 124 may also include a processor (not shown) configured to generate control signals. For example, the generator control unit 124 may include a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), a peripheral interface controller (PIC), another type of microprocessor, and / or a combination thereof. It may be implemented as an integrated circuit, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a combination of logic gate circuits, other types of digital or analog electrical design components, or a combination thereof.

[0024] The device 100 may include a first HF transformer winding 126 positioned on the stator 104 and a second HF transformer winding 128 positioned on the rotor 102. The HF transformer windings 126, 128 may together constitute an HF transformer to transmit power from the stator 104 to the rotor 102. At the HF transformer stage 108, the generator control unit 124 may modulate the three-phase AC power signal received from the pilot winding 122 to generate an HF three-phase AC power signal. High frequency as used herein means that the frequency of the signal is greater than the rotation frequency of the rotor 102. As the frequency of the HF three-phase power signal increases, the effect of the rotation of the rotor 102 becomes less significant. This enables the HF three-phase power signal to be transmitted from the first HF transformer winding 126 to the second HF transformer winding 128 without generating significant interference or power loss due to the rotation of the rotor 102. Power is transmitted through the HF transformer windings 126, 128, so the HF transformer stage 108 can omit the contact power transmission mechanism between the stator 104 and the rotor 102. For example, conventional power transmission mechanisms may include slip rings or similar contact power transmission mechanisms, while the device 100 omits these contact mechanisms. By eliminating contact between the stator 104 and the rotor 102, performance issues such as arcing, wear, and contact resistance may be avoided. This may improve reliability, reduce maintenance costs, reduce downtime, and reduce power losses. Other advantages may exist.

[0025] The device 100 may also include a rectifier 130 and an inverter 132. The generator control unit 124 may communicate with the inverter 132 via a control signal coupler 136. At the magnetic field control stage 110, the HF three-phase power signal may be transmitted from the second HF transformer winding 128 to the rectifier 130. The rectifier 130 may convert the HF three-phase AC power signal into a DC power signal. The DC power signal may then be transmitted to the inverter 132. The inverter 132 may be configured to receive a control signal from the generator control unit 124 via the control signal coupler 136. Based on the switching parameters set by the generator control unit 124 via the control signal, the inverter 132 may convert the DC power signal into a three-phase AC power signal. By controlling the switching within the inverter 132, the generator control unit 124 may control the frequency, phase, amplitude and / or other properties of the three-phase AC power signal.

[0026] The device 100 may include a main rotor winding 134 and a main stator winding 138. In the main stage 112, the three-phase AC power signal from the inverter 132 can drive the main rotor field winding 134 to generate a magnetic field that rotates relative to the rotor 102. By controlling the three-phase AC power signal, the generator control unit 124 can control the direction, rotation frequency, amplitude and / or phase of the magnetic field relative to the rotor 102. A rotating magnetic field can be generated by the additional rotation of the rotor 102, and its rotation frequency is independent of the rotation frequency of the rotor 102. In this way, the frequency of the three-phase AC power signal generated at the main stator winding 138 can also be independent of the rotation frequency of the rotor 102. Although the main rotor field winding 134 is described as a three-phase winding, it will be understood by those of ordinary skill in the art who have the benefit of this application that an alternative winding arrangement including more than three phases can be used to generate a magnetic field that rotates relative to the rotor 102.

[0027] The apparatus 100 may include a power distribution line 140 to provide power to systems and / or devices (not shown). In some embodiments, the power distribution line 140 may provide power to a vehicle, such as, but not limited to, an aircraft or spacecraft, and may be used to drive a propulsion motor.

[0028] A benefit of the apparatus 100 is that by establishing a magnetic field at the main rotor field winding 134 that rotates relative to the rotor 102, a three-phase AC power signal can be generated at the main stator winding 138 having a frequency, phase, and amplitude that is independent of the rotational frequency or phase of the rotor 102 and independent of the strength of the permanent magnets attached to the rotor 102. Other advantages may exist.

[0029] Reference Figure 2, which depicts a control signal system 200 for an independent speed variable frequency alternator. The control signal system 200 is functionally depicted as including summing points 206, 218, 244, absolute value functions 212, 234, and sign function 250. Although each element is described functionally, each element may be implemented using structural components. For example, the first summing point 206 may be implemented as logic hardware (digital logic gates or analog comparator circuits) or software running within the generator control unit 124 (e.g., Figure 1 102). The second summing junction 218 may be implemented using logic hardware and / or a processor attached to the rotor 102. Likewise, the third summing junction 244 may be implemented as logic hardware and / or software running within the generator control unit 124. The absolute value functions 212, 234 and the sign function 250 may also be implemented as logic hardware and / or software running on a processor attached to the rotor 102.

[0030] Although Figure 1 The generator control unit 124 is described as being attached to the stator 104, but various controller components may also be attached to the rotor 102. For example, while the summing junction 218, the absolute value functions 212, 234, and the sign function 250 may be considered part of the generator control unit 124, they may be implemented as circuits attached to the rotor 102.

[0031] The system 200 may receive a reference frequency signal 202. The reference frequency signal 202 may represent the desired frequency of the AC power source. Specifically, the AC power source may be used in aerospace applications and may power a propulsion motor and / or other systems and devices. The reference frequency signal 202 may be a constant input signal that is "hard-wired" into the generator control unit 124, or it may be an adjustable input. For example, the system 200 may be configured to output a variable frequency to meet the needs of a particular load. In the case where a constant frequency is required, it may output a fixed frequency. In other cases, for example, when the load is a motor, the system 200 may output a variable frequency to meet speed variation requirements. The reference frequency signal 202 may be generated by software running at a processor (e.g., a processor of the generator control unit 124) or by other logic and / or hardware. In an illustrative example, the reference frequency signal 202 may be equal to 400 Hz. This frequency is for illustrative purposes only. As described above, the reference frequency signal 202 may be static or dynamic and may be modified based on a particular load.

[0032] The reference frequency signal 202 may be combined with the rotor frequency signal 204 at a first summing junction 206, and a first intermediate signal 208 may be generated that represents the difference between the reference frequency signal 202 and the rotor frequency signal 204. Conceptually, the first intermediate signal 208 may represent a desired change from the measured rotational frequency of the rotor 102 to the rotational frequency of the rotating magnetic field. With respect to the illustrative example above, if the rotor frequency signal 204 is equal to 300 Hz, the first intermediate signal 208 would be equal to 100 Hz, which represents the desired increase in frequency from the rotational frequency of the rotor (i.e., 300 Hz) to equal the reference frequency signal 202 (i.e., 400 Hz). The first intermediate signal 208 may be transmitted from the stator (e.g., the stator 104) to the rotor 102 via the control signal coupler 136.

[0033] At the rotor 102, the first intermediate signal 208 may be input into an absolute value function 212 to generate an amplitude signal 214 of the first intermediate signal 208. At a second summing point 218, the amplitude signal 214 of the first intermediate signal 208 may be combined with an amplitude signal 216 of the main field frequency signal 232 to generate a second intermediate signal 220. The second intermediate signal 220 may represent the difference between the amplitude of the first intermediate signal 208 and the amplitude of the main field frequency signal 232. In other words, the second intermediate signal 220 may represent a desired change in the rotational frequency of the main rotating magnetic field relative to the current rotational frequency of the main rotating magnetic field at the rotor main field winding 134. Continuing with the example above, if the main field frequency signal 232 is equal to 90 Hz, the second intermediate signal 220 will be equal to 10 Hz, which represents a desired increase in the rotating magnetic field relative to the rotational frequency of the rotor 102.

[0034] In other words, in the illustrative example, the main rotating magnetic field can rotate at a frequency of 90 Hz relative to the rotor 102, and the rotor 102 can rotate at a frequency of 300 Hz relative to the stator 104. Therefore, the main rotating magnetic field can rotate at a frequency of 390 Hz relative to the stator 104. In order to generate a power signal with a frequency of 400 Hz, the rotation frequency of the main rotating magnetic field needs to be increased by 10 Hz. Thus, in this example, the second intermediate signal 220 will be equal to 10 Hz.

[0035] The second intermediate signal 220 may be provided to a first proportional-integral-derivative (PID) controller 222. The first PID controller 222 may convert the second intermediate signal 220 into an inverter control signal 224, which directs the inverter 132 to adjust the three-phase current 228 provided to the rotor main field winding 134. A rotating magnetic field may be established when the three-phase current 228 passes through the rotor main field winding 134, wherein the frequency, amplitude, and phase of the rotating magnetic field depend on the frequency, amplitude, and phase of the three-phase current 228. By adjusting the three-phase current 228, the inverter 132 may control the rotation of the rotating magnetic field relative to the rotor 102, thereby distinguishing the rotation frequency of the rotating magnetic field from the rotation frequency of the rotor 102. The first PID controller 222 may be part of the generator control unit 124 and may be coupled to the rotor 102.

[0036] Based on the three-phase current 228, a main field frequency signal 232 can be measured and derived for use as a feedback signal at the second summing junction 218. The main field frequency signal 232 can be passed through an absolute value function 234 to generate an amplitude signal 216 of the main field frequency signal 232 used at the second summing junction 218. Similarly, the rotor speed encoder can measure and derive a rotor frequency signal 204 based on the rotational frequency of the rotor 102. The motor speed encoder can include a first portion 236 attached to the rotor, and a second portion 237 attached to the stator. In some embodiments, the first portion can be a magnetic source or light source, and the second portion 237 can be a detector configured to calculate the rotational frequency of the rotor 102 based on a signal received from the magnetic source or light source. The rotor frequency signal 204 can be provided as a feedback signal used at the first summing junction 206.

[0037] The first intermediate signal 208 may also be passed to a sign function 250. The sign function 250 may convert the first intermediate signal 208 into a direction signal 252. The direction signal 252 may indicate a desired rotational direction of the rotating magnetic field relative to the rotor 102. A negative direction signal may indicate that the desired rotational frequency is less than the rotational frequency of the rotor 102. A positive direction signal may indicate that the desired rotational frequency is greater than the rotational frequency of the rotor 102. The inverter 132 may use the direction signal 252 to control the three-phase current 228 to achieve the desired rotational direction of the rotating magnetic field relative to the rotor 102.

[0038] The system 200 may also receive a reference voltage signal 238. The reference voltage signal 238 may represent a desired voltage of the AC power source. Specifically, the AC power source may be used in aerospace applications and may power a propulsion motor and / or other systems and devices. The reference voltage signal 238 may be a constant input signal that is "hard-wired" into the generator control unit 124, or it may be an adjustable input. The reference voltage signal may be generated by software running on a processor (e.g., a processor of the generator control unit 124) or by other logic and / or hardware. In an illustrative example, the reference voltage signal 238 may be equal to 105V AC or 230V AC.

[0039] The reference voltage signal 238 may be combined with the stator output voltage signal 242 at a third summing junction 244, and a third intermediate signal 240 may be generated that represents the difference between the reference voltage signal 238 and the stator output voltage signal 242. Conceptually, the third intermediate signal 240 may represent a desired change in voltage generated at the primary stator winding 138 by the rotating magnetic field at the rotor main field winding 134. The third intermediate signal 240 may be transmitted from the stator (e.g., the stator 104) to the rotor 102 via the control signal coupler 136.

[0040] The third intermediate signal 240 may be provided to a second PID controller 246. The second PID controller 246 may convert the third intermediate signal 240 into an inverter control signal 248 that instructs the inverter 132 to adjust the three-phase current 228 provided to the rotor main field winding 134. Specifically, the magnitude of the three-phase current 228 may be adjusted to increase or decrease the amplitude of the rotating magnetic field, thereby generating a higher or lower voltage at the main stator winding 138. Like the first PID controller 222, the second PID controller 246 may be part of the generator control unit 124 and may be coupled to the rotor 102.

[0041] A benefit of system 200 is that each of the phase, amplitude, and frequency of the rotating magnetic field may be controlled at rotor main field winding 134 to produce AC power at primary stator winding 138 having a frequency, phase, and voltage that is independent of the frequency of rotor 102. Other advantages may exist.

[0042] Reference Figure 3, which depicts an embodiment of a control signal coupler 136 for a stand-alone variable speed alternator device. The control signal coupler 136 may include a first transceiver 302 and a second transceiver 304. In some embodiments, the control signal coupler 136 may be configured for unidirectional communication. In that case, the first transceiver 302 may actually be a transmitter, and the second transceiver 304 may actually be a receiver, or vice versa.

[0043] The control signal coupler 136 may also include a first communication disk 306 that may be attached to a stator (e.g., stator 104), and one or more second communication disks 308 that may be attached to the rotor 102. In some embodiments, the first communication disk 306 may include a light source (e.g., a transmitter) and the second communication disk 308 may include a light detector (e.g., a phototransistor).

[0044] During operation, a control signal 310 may be sent to the first transceiver 302. As the rotor 102 rotates, the first transceiver 302 may transmit data from the first communication disk 306 to the one or more second communication disks 308. The transmission may be timed so that the transmission occurs when the one or more second communication disks 308 are facing the first communication disk 306. When the one or more second communication disks 308 are facing away from the first communication disk, the transmission is paused. Although Figure 3 Four second communication trays 308 are depicted, but there may be more or less than four. Having more second communication trays 308 may reduce communication interruptions.

[0045] One benefit of the control signal coupler 136 is that it can produce less friction than a contact signal coupler. This can result in less power loss at the device 100. As described herein, by eliminating contact between the stator 104 and the rotor 102, performance issues such as arcing, wear, and contact resistance can be avoided. This can improve reliability, reduce maintenance costs, reduce downtime, and reduce power losses. There can be other advantages.

[0046] Reference Figure 4 , which depicts an embodiment of a method 400 for generating independent speed variable frequency AC. The method 400 may include: at 402, at a magnetic field source attached to a rotor, generating a first rotating magnetic field when the rotor rotates, wherein the rotational frequency of the first rotating magnetic field depends on the rotational frequency of the rotor. For example, when the rotor 102 rotates, the first rotating magnetic field may be generated at the magnetic field source 120.

[0047] The method 400 may further include: converting the first rotating magnetic field into an AC power signal at step 404 . For example, the pilot winding 122 may be configured to convert the first rotating magnetic field into an AC power signal that is transmitted to the generator control unit 124 .

[0048] The method 400 may further include: modulating the AC power signal to generate a high frequency AC power signal at 406 . For example, the generator control unit 124 may modulate the AC power signal to generate a HF three-phase AC power signal, which is transmitted to the first HF transformer winding 126 .

[0049] The method 400 may include, at step 408 , transmitting the high frequency AC power signal from the stator to the rotor. For example, the first HF transformer winding 126 may transmit the HF AC power signal to the second HF transformer winding 128 .

[0050] The method 400 may further include: at step 410 , converting the high frequency AC power signal into a DC power signal. For example, the rectifier 130 may convert the HF AC power signal into a DC power signal that is transmitted to the inverter 132 .

[0051] The method 400 may also include, at step 412, converting the DC power signal into a main AC power signal, wherein the main AC power signal is used to drive a main rotor winding attached to the rotor. For example, the inverter 132 may convert the DC power signal into a main AC power signal to drive the main rotor winding 134.

[0052] The method 400 may include, at step 414, generating a second rotating magnetic field at the main rotor winding when the rotor rotates, wherein the rotation frequency of the second rotating magnetic field is independent of the rotation frequency of the rotor. For example, the main rotor winding 134 may generate a second rotating magnetic field that rotates independently of the rotor 102 based on the main field AC power signal.

[0053] The method 400 may also include converting the second rotating magnetic field into an AC power signal at a main stator winding attached to the stator at step 416. For example, the main stator winding 138 may convert the second rotating magnetic field into an AC power signal for distribution to various AC systems.

[0054] A benefit of method 400 is that by generating a second rotating magnetic field that rotates independently of rotor 102, the frequency, phase, and amplitude of the power signal of the AC system can be independent of the rotational frequency of rotor 102. In addition, fewer power conversion stages may be required compared to conventional constant speed power generation systems that include additional stages for power generation. With fewer stages required, method 400 can be performed with higher efficiency and lower weight requirements. Other advantages may exist.

[0055] Reference Figure 5 , which depicts a method 500 for generating an independent speed variable frequency alternating current controlled rotating magnetic field. The method 500 may be used with Figure 4Method 400 is used in combination with, or as Figure 4 A portion of method 400 is used.

[0056] The method 500 may include receiving a reference frequency signal from a generator control unit at step 502. For example, the reference frequency signal 202 may be received at the generator control unit 124.

[0057] The method 500 may also include generating a first intermediate frequency signal, which is a difference between the reference frequency signal and a rotor frequency signal associated with the rotational frequency of the rotor, at step 504. For example, the first intermediate signal 208 may be generated.

[0058] The method 500 may also include transmitting the first intermediate frequency signal from the stator to the rotor via a control signal coupler including at least one first communication disk attached to the stator and at least one second communication disk attached to the rotor at step 506. For example, the first intermediate signal 208 may be transmitted to the rotor 102 via the control signal coupler 136, which may include the first communication disk 306 and the at least one second communication disk 308.

[0059] The method 500 may further include generating a second intermediate frequency signal, which is a difference between the first intermediate frequency signal and a main field frequency signal associated with the second magnetic field relative to the rotational frequency of the rotor, at step 508. For example, the second intermediate signal 220 may be generated.

[0060] The method 500 may include: at step 510, converting the second intermediate frequency signal into an inverter control signal to direct the inverter to change the main field AC power signal to accelerate or slow down the rotation of the second rotating magnetic field relative to the rotor. For example, the second intermediate signal 220 may be converted into an inverter control signal 224 at the first PID controller 222.

[0061] The method 500 may also include, at step 512, determining the sign of the first intermediate signal and generating a second inverter control signal to direct the inverter to rotate the second rotating magnetic field relative to the rotor in a direction corresponding to the sign of the intermediate signal. For example, the sign of the first intermediate signal 208 may be determined at the sign function 250 and transmitted to the inverter 132.

[0062] The method 500 may further include receiving a reference voltage signal from the generator control unit at step 514 . For example, the reference voltage signal 238 may be received from the generator control unit 124 .

[0063] The method 500 may include generating an intermediate voltage signal that is a difference between the reference voltage signal and a voltage signal associated with the AC power signal at step 516. For example, the intermediate voltage signal 240 may be generated.

[0064] The method 500 may further include: at step 518, converting the intermediate voltage signal into an inverter control signal to direct the inverter to change the main field AC power signal to increase or decrease the amplitude of the second rotating magnetic field. For example, the intermediate voltage signal 240 may be converted into the inverter control signal 248.

[0065] In addition, the present application includes embodiments according to the following items:

[0066] Item 1: An independent speed variable frequency AC (alternating current) generator device, comprising: a rotor and a stator, the rotor being configured to rotate relative to the stator; a magnetic field source attached to the rotor and configured to generate a first rotating magnetic field when the rotor rotates, wherein the rotation frequency of the first rotating magnetic field depends on the rotation frequency of the rotor; a main rotor winding attached to the rotor and configured to generate a second rotating magnetic field when the rotor rotates, wherein the rotation frequency of the second rotating magnetic field is independent of the rotation frequency of the rotor.

[0067] Item 2: The apparatus of Item 1, wherein the magnetic field source comprises a permanent magnet.

[0068] Item 3: The apparatus of Item 1, further comprising: a pilot winding attached to the stator and configured to convert the first rotating magnetic field into an AC power signal.

[0069] Item 4: The device according to item claim 3 further includes: a generator control unit configured to modulate the AC power signal to generate a high-frequency AC power signal for transmission to the rotor, wherein the frequency of the high-frequency AC power signal is greater than the rotation frequency of the rotor.

[0070] Item 5: The apparatus of Item 1, further comprising a high frequency transformer configured to transmit a high frequency AC power signal from the stator to the rotor.

[0071] Item 6: An apparatus according to Item 5, wherein the high-frequency transformer includes a first power transformer winding attached to the stator and a second power transformer winding attached to the rotor, wherein the first power transformer winding is configured to transmit a high-frequency AC power signal to the second power transformer winding.

[0072] Item 7: The apparatus according to Item 5, wherein the high frequency transformer omits a contact power transmission mechanism between the stator and the rotor.

[0073] Item 8: The apparatus of Item 1, further comprising: a rectifier attached to the rotor and configured to convert the high frequency AC power signal into a DC power signal.

[0074] Item 9: The apparatus of Item 1, further comprising: an inverter attached to the rotor and configured to convert the DC power signal into a main AC power signal, wherein the main rotor winding is driven using the main AC power signal.

[0075] Item 10: The apparatus according to Item 9 further comprises: a generator control unit coupled to the inverter and configured to control the main field AC power signal, thereby controlling the rotation speed, direction, amplitude or any combination thereof of the second rotating magnetic field relative to the rotor.

[0076] Item 11: An apparatus according to item 10, wherein the generator control unit includes a control circuit attached to the stator and a control circuit attached to the rotor, wherein the control circuit attached to the rotor includes at least one proportional-integral-derivative (PID) controller.

[0077] Item 12: The apparatus of Item 11, wherein at least one PID controller is coupled to the inverter to control the frequency of the second rotating magnetic field, and the control circuit attached to the rotor includes an additional PID controller coupled to the inverter to control the second rotation amplitude.

[0078] Item 13: An apparatus according to Item 11, wherein the control circuit attached to the stator is communicatively coupled to the control circuit attached to the rotor via a control signal coupler, the control signal coupler comprising at least one first communication disk attached to the stator, and at least one second communication disk attached to the rotor.

[0079] Item 14: The apparatus of Item 13, wherein the first communication disk comprises an optical signal source and the second communication disk comprises a phototransistor.

[0080] Item 15: The apparatus of Item 1, further comprising: a main stator winding configured to convert the second rotating magnetic field into an AC power signal.

[0081] Item 16: A method for generating independent speed variable frequency alternating current, comprising: generating a first rotating magnetic field at a magnetic field source attached to the rotor when the rotor rotates, wherein the rotation frequency of the first rotating magnetic field depends on the rotation frequency of the rotor; generating a second rotating magnetic field at a main rotor winding attached to the rotor when the rotor rotates, wherein the rotation frequency of the second rotating magnetic field is independent of the rotation frequency of the rotor; and converting the second rotating magnetic field into an AC power signal at the main stator winding attached to the stator.

[0082] Item 17: The method according to Item 16 also includes: converting the first rotating magnetic field into an AC power signal; modulating the AC power signal to generate a high-frequency AC power signal; transmitting the high-frequency AC power signal from the stator to the rotor; converting the high-frequency AC power signal into a DC power signal; and converting the DC power signal into a main field AC power signal, wherein the main field AC power signal is used to drive the main rotor winding.

[0083] Item 18: A method according to Item 16, wherein generating a second rotating magnetic field includes: receiving a reference frequency signal from a generator control unit; generating a first intermediate frequency signal, which is the difference between the reference frequency signal and a rotor frequency signal associated with the rotation frequency of the rotor; generating a second intermediate frequency signal, which is the difference between the first intermediate frequency signal and a main field frequency signal associated with the rotation frequency of the second rotating magnetic field relative to the rotor; and converting the second intermediate frequency signal into an inverter control signal to direct the inverter to change the main field AC power signal to accelerate or slow down the rotation of the second rotating magnetic field relative to the magnetic field of the rotor.

[0084] Item 19: The method of Item 18, wherein the first intermediate frequency signal is transmitted from the stator to the rotor via a control signal coupler, the control signal coupler comprising at least one first communication disk attached to the stator and at least one second communication disk attached to the rotor.

[0085] Item 20: A method according to Item 18, wherein generating a second rotating magnetic field also includes determining the sign of the first intermediate frequency signal, and generating a second inverter control signal to guide the inverter so that the second rotating magnetic field rotates relative to the rotor in a direction corresponding to the sign of the intermediate signal.

[0086] Item 21: The method according to Item 18 also includes: receiving a reference voltage signal from a generator control unit; generating an intermediate voltage signal, which is the difference between the reference voltage signal and a voltage signal associated with the AC power signal; and converting the intermediate voltage signal into an inverter control signal to direct the inverter to change the main field AC power signal to increase or decrease the amplitude of the second rotating magnetic field.

[0087] Item 22: An AC generator rotor device, comprising: a magnetic field source, configured to generate a first rotating magnetic field when the rotor rotates, wherein the rotation frequency of the first rotating magnetic field depends on the rotation frequency of the rotor; and a main rotor winding, configured to generate a second rotating magnetic field when the rotor rotates, wherein the rotation frequency of the second rotating magnetic field is independent of the rotation frequency of the rotor.

[0088] Item 23: The device according to Item 22 further includes: a power transformer winding configured to receive a high-frequency AC power signal; a rectifier configured to convert the high-frequency AC power signal into a DC (direct current) power signal; and an inverter configured to convert the DC power signal into a main field AC power signal, wherein the main field AC power signal is used to drive the main rotor winding.

[0089] Although various embodiments have been shown and described herein in detail, the present application is not limited thereto and is to be construed as including all such changes and modifications as are apparent to those skilled in the art.

Claims

1. An independent speed variable frequency alternator device, comprising: a rotor and a stator, the rotor being configured to rotate relative to the stator; a magnetic field source attached to the rotor and configured to generate a first rotating magnetic field when the rotor rotates, wherein a rotational frequency of the first rotating magnetic field depends on a rotational frequency of the rotor; a main rotor winding attached to the rotor and configured to generate a second rotating magnetic field when the rotor rotates, wherein a rotational frequency of the second rotating magnetic field is independent of the rotational frequency of the rotor, wherein the main rotor winding is a three-phase or multi-phase winding; an inverter attached to the rotor and configured to convert a DC power signal into a main field AC power signal, wherein the main field AC power signal is utilized to drive the main rotor winding; a generator control unit coupled to the inverter and configured to control the main field AC power signal to control the rotation speed, direction and amplitude of the second rotating magnetic field relative to the rotor, wherein the generator control unit includes a control circuit attached to the stator and a control circuit attached to the rotor; and The main stator winding is configured to convert the second rotating magnetic field into an AC power signal.

2. The device according to claim 1, wherein: The magnetic field source includes a permanent magnet.

3. The device according to claim 1, further comprising: A pilot winding is attached to the stator and is configured to convert the first rotating magnetic field into an AC power signal.

4. The apparatus according to claim 1, further comprising: A high frequency transformer is configured to transmit a high frequency AC power signal from the stator to the rotor.

5. The apparatus according to claim 1, further comprising: A rectifier is attached to the rotor and configured to convert a high frequency AC power signal into a DC power signal.

6. A method for generating independent speed variable frequency alternating current, comprising: generating a first rotating magnetic field at a magnetic field source attached to the rotor when the rotor rotates, wherein a rotation frequency of the first rotating magnetic field depends on a rotation frequency of the rotor; and generating a second rotating magnetic field at a main rotor winding attached to the rotor when the rotor rotates, wherein the main rotor winding is a three-phase or multi-phase winding, wherein a rotation frequency of the second rotating magnetic field is independent of a rotation frequency of the rotor; converting the second rotating magnetic field into an AC power signal at a main stator winding attached to the stator, Wherein, generating the second rotating magnetic field comprises: receiving a reference frequency signal from a generator control unit; generating a first intermediate frequency signal, the first intermediate frequency signal being a difference between the reference frequency signal and a rotor frequency signal, the rotor frequency signal being related to a rotation frequency of the rotor; generating a second intermediate frequency signal, the second intermediate frequency signal being a difference between the first intermediate frequency signal and a main magnetic field frequency signal, the main magnetic field frequency signal being related to a rotational frequency of a second rotating magnetic field relative to the rotor; and The second intermediate frequency signal is converted into an inverter control signal to direct the inverter to change the main magnetic field AC power signal to accelerate or slow down the rotation of the second rotating magnetic field relative to the magnetic field of the rotor.

7. The method according to claim 6, further comprising: converting the first rotating magnetic field into an AC power signal; Modulating the AC power signal to generate a high-frequency AC power signal; transmitting the high frequency AC power signal from the stator to the rotor; converting the high frequency AC power signal into a DC power signal; and The DC power signal is converted into a main magnetic field AC power signal, wherein the main magnetic field AC power signal is used to drive the main rotor winding.

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