阅读说明：本技术 基于独立速度变频发电机的恒定频率和窄带变频电力系统和方法 (Constant frequency and narrow band variable frequency power system and method based on independent speed variable frequency generator ) 是由 高利军 刘生义 于 2020-08-18 设计创作，主要内容包括：本发明涉及基于独立速度变频发电机的恒定频率和窄带变频电力系统和方法。一种系统可包括独立速度变频(ISVF)发电机,其被配置为将来自轴的转矩转换为AC功率信号。ISVF发电机可具有一个或更多个极对,其等效轴频等于轴频乘以极对数量。当等效轴频小于频率下限时,发电机控制单元可将ISVF发电机的发电机输出频率设定为等于AC母线的频率下限,当等效轴频大于频率上限时,将ISVF发电机的发电机输出频率设定为等于AC母线的频率上限,并且当等效轴频介于频率下限和频率上限之间时,将ISVF发电机的发电机输出频率设定为等于等效轴频。(The invention relates to a constant frequency and narrow band variable frequency power system and method based on an independent speed variable frequency generator. A system may include an independent speed variable frequency (isff) generator configured to convert torque from a shaft to an AC power signal. An isff generator may have one or more pole pairs with an equivalent shaft frequency equal to the shaft frequency multiplied by the number of pole pairs. The generator control unit may set the generator output frequency of the isff generator equal to a lower frequency limit of the AC bus when the equivalent shaft frequency is less than the lower frequency limit, set the generator output frequency of the isff generator equal to an upper frequency limit of the AC bus when the equivalent shaft frequency is greater than the upper frequency limit, and set the generator output frequency of the isff generator equal to the equivalent shaft frequency when the equivalent shaft frequency is between the lower frequency limit and the upper frequency limit.)

1. A system (100), comprising:

a prime mover (102) configured to rotate a shaft (106);

an independent speed variable frequency ISVF generator (108) configured to convert torque (130) from the shaft (106) to an alternating current AC power signal (132), wherein the ISVF generator (108) has one or more pole pairs (109), and wherein an equivalent shaft frequency (210) is equal to a shaft frequency (208) of the shaft (106) multiplied by a number of the pole pairs (109);

an AC bus (112) having a lower frequency limit (222) and an upper frequency limit (224); and

a generator control unit (110) configured to:

setting a generator output frequency (502) of the ISVF generator (108) equal to the lower frequency limit (222) when the equivalent shaft frequency (210) is less than the lower frequency limit (222);

setting the generator output frequency (502) of the ISVF generator (108) equal to the upper frequency limit (224) when the equivalent shaft frequency (210) is greater than the upper frequency limit (224); and

setting the generator output frequency (502) of the ISVF generator (108) equal to the equivalent shaft frequency (210) when the equivalent shaft frequency (210) is greater than or equal to the lower frequency limit (222) and less than or equal to the upper frequency limit (224).

2. The system according to claim 1, wherein the generator control unit (110) is configured to generate an excitation signal (134) to control the ISVF generator (108), wherein an equivalent excitation frequency (308) is equal to an excitation frequency (306) of the excitation signal multiplied by the number of pole pairs (109),

wherein setting the generator output frequency (502) equal to the lower frequency limit (222) comprises setting the equivalent excitation frequency (308) as a difference between the lower frequency limit (222) and the equivalent shaft frequency (210),

wherein setting the generator output frequency (502) equal to the upper frequency limit (224) comprises setting the equivalent excitation frequency (308) of the excitation signal equal to a difference between the upper frequency limit (224) and the equivalent shaft frequency (210), and

wherein setting the generator output frequency (502) equal to the equivalent shaft frequency (210) comprises setting the equivalent excitation frequency (308) of the excitation signal to zero.

3. The system of claim 1, further comprising:

a coupling (104) disposed between the prime mover (102) and the shaft (106) and configured to convert a second torque (129) associated with the prime mover (102) to a torque (130) associated with the shaft (106).

4. The system of claim 3, wherein the coupling (104) comprises a fixed ratio gear coupling, a belt, or a combination thereof.

5. The system of any of claims 1-4, wherein the prime mover (102) is configured to rotate the shaft (106) without any constant speed drive coupled therebetween.

6. The system of any of claims 1 to 5, further comprising:

a set of AC loads (114) electrically connected to the AC bus (112), wherein the lower frequency limit (222) and the upper frequency limit (224) are determined based at least in part on operating requirements of the set of AC loads (114).

7. The system of any of claims 1 to 6, further comprising:

an AC-DC AC/DC converter (116) electrically connected to the AC bus (112); and

a Direct Current (DC) bus (118) electrically connected to the AC/DC converter (116), wherein the AC/DC converter (116) is configured to convert the AC power signal (132) on the AC bus (122) to a DC power signal (136) on the DC bus (118).

8. The system of any one of claims 1 to 7, wherein the prime mover (102) is an aircraft engine.

9. A method, comprising the steps of:

rotating a shaft (106) using a prime mover (102);

converting torque (130) from the shaft (106) into an Alternating Current (AC) power signal (132) using an independent speed variable frequency ISVF generator (108), wherein the ISVF generator (108) has one or more pole pairs (109), and wherein an equivalent shaft frequency (210) is equal to a shaft frequency (208) of the shaft (106) multiplied by a number of the pole pairs (109);

applying the AC power signal (132) to an AC bus (112) having a lower frequency limit (222) and an upper frequency limit (224);

setting a generator output frequency (502) of the ISVF generator (108) equal to the lower frequency limit (222) when the equivalent shaft frequency (210) is less than the lower frequency limit (222);

setting the generator output frequency (502) of the ISVF generator (108) equal to the upper frequency limit (224) when the equivalent shaft frequency (210) is greater than the upper frequency limit (224); and

setting the generator output frequency (502) of the ISVF generator (108) equal to the equivalent shaft frequency (210) when the equivalent shaft frequency (210) is between the lower frequency limit (222) and the upper frequency limit (224).

10. The method of claim 9, further comprising:

generating an excitation signal (134) to control the ISVF generator (108), wherein an equivalent excitation frequency (308) is equal to an excitation frequency (306) of the excitation signal multiplied by the number of pole pairs (109),

wherein the step of setting the generator output frequency (502) equal to the lower frequency limit (222) comprises setting the equivalent excitation frequency (308) as the difference between the lower frequency limit (222) and the equivalent shaft frequency (210),

wherein the step of setting the generator output frequency (502) equal to the upper frequency limit (224) comprises setting the equivalent excitation frequency (308) of the excitation signal equal to the difference between the upper frequency limit (224) and the equivalent shaft frequency (210), and

wherein the step of setting the generator output frequency (502) equal to the equivalent shaft frequency (210) comprises setting the equivalent excitation frequency (308) of the excitation signal to zero.

11. The method of claim 9, further comprising:

converting a second torque (129) associated with the prime mover (102) to a torque (130) associated with the shaft (106) using a coupling (104).

12. The method of claim 11, wherein the coupling (104) comprises a fixed ratio gear coupling, a belt, or a combination thereof.

13. The method according to any one of claims 9-12, wherein the step of rotating the shaft (106) is performed without any constant speed drive coupled between the shaft (106) and the prime mover (102).

14. The method of any of claims 9 to 13, wherein an alternating current-to-direct current (AC/DC) converter (116) is electrically connected to the AC bus (112), and wherein a Direct Current (DC) bus (118) is electrically connected to the AC/DC converter (116), the method further comprising:

converting the AC power signal (132) on the AC bus (112) to a DC power signal (136) on the DC bus (118) at the AC/DC converter (116).

15. The method according to any one of claims 9-14, wherein the prime mover (102) is an aircraft engine.

Technical Field

The present disclosure relates generally to the field of power distribution, and in particular, to constant frequency and narrowband power distribution based on Independent Speed Variable Frequency (ISVF) generators.

Background

Induction generators may be used in electrical distribution systems, such as aircraft and other vehicles, to provide Alternating Current (AC) power signals used by various AC loads. AC loads typically have power frequency requirements that limit the AC power signal to a constant frequency or a narrower frequency band than the typical operating frequency band of the prime mover (e.g., engine).

In a typical electrical distribution system, a constant speed drive (or some other type of variable speed transmission) may be provided between the prime mover and the shaft of the generator in order to achieve a constant generator output frequency. Constant speed drives may be complex, heavy and/or bulky. As a result, they may not be suitable for some applications, particularly for aircraft applications. Other disadvantages may exist.

Disclosure of Invention

Systems and methods are disclosed herein that may overcome one or more disadvantages of typical power distribution systems. In an example, a system includes a prime mover configured to rotate a shaft. The system also includes an isff generator configured to convert torque from the shaft to an AC power signal, wherein the isff generator has one or more pole pairs, and wherein the equivalent shaft frequency is equal to the shaft frequency of the shaft multiplied by the number of pole pairs. The system includes an AC bus having a lower frequency limit and an upper frequency limit. The system further includes a generator control unit configured to set a generator output frequency of the isff generator equal to the lower frequency limit when the equivalent shaft frequency is less than the lower frequency limit, set a generator output frequency of the isff generator equal to the upper frequency limit when the equivalent shaft frequency is greater than the upper frequency limit, and set the generator output frequency of the isff generator equal to the equivalent shaft frequency when the equivalent shaft frequency is greater than or equal to the lower frequency limit and less than or equal to the upper frequency limit.

In some examples, the generator control unit is configured to generate an excitation signal to control the isff generator, wherein the equivalent excitation frequency is equal to the excitation frequency of the excitation signal multiplied by the number of pole pairs. In such an example, setting the generator output frequency equal to the lower frequency limit includes setting the equivalent excitation frequency equal to a difference between the lower frequency limit and the equivalent shaft frequency, setting the generator output frequency equal to the upper frequency limit includes setting the equivalent excitation frequency of the excitation signal equal to a difference between the upper frequency limit and the equivalent shaft frequency, and setting the generator output frequency equal to the equivalent shaft frequency includes setting the equivalent excitation frequency of the excitation signal equal to zero.

In some examples, the system includes a coupling disposed between the prime mover and the shaft and configured to convert a second torque associated with the prime mover to a torque associated with the shaft. In some examples, the coupling includes a fixed ratio gear coupling, a belt, or a combination thereof. In some examples, the prime mover is configured to rotate the shaft without any constant speed drive coupled therebetween. In some examples, the system includes a set of AC loads electrically connected to the AC bus, wherein the lower frequency limit and the upper frequency limit are determined based at least in part on operating requirements of the set of AC loads. In some examples, the system may include an alternating current-to-direct current (AC/DC) converter electrically connected to the AC bus and a Direct Current (DC) bus electrically connected to the AC/DC converter, wherein the AC/DC converter is configured to convert an AC power signal on the AC bus to a DC power signal on the DC bus. In some examples, the prime mover is an aircraft engine.

In an example, a method includes rotating a shaft using a prime mover. The method also includes converting torque from the shaft to an AC power signal using an isff generator, wherein the isff generator has one or more pole pairs, and wherein the equivalent shaft frequency is equal to the shaft frequency of the shaft multiplied by the number of pole pairs. The method also includes applying the AC power signal to an AC bus having a lower frequency limit and an upper frequency limit. The method also includes setting a generator output frequency of the ISVF generator equal to the lower frequency limit when the equivalent shaft frequency is less than the lower frequency limit. The method includes setting a generator output frequency of the ISVF generator equal to the upper frequency limit when the equivalent shaft frequency is greater than the upper frequency limit. The method also includes setting a generator output frequency of the ISVF generator equal to the equivalent shaft frequency when the equivalent shaft frequency is between the lower frequency limit and the upper frequency limit.

In some examples, the method comprises generating an excitation signal to control the ISVF generator, wherein the equivalent excitation frequency is equal to the excitation frequency of the excitation signal multiplied by the number of pole pairs, wherein the step of setting the generator output frequency equal to the lower frequency limit comprises setting the equivalent excitation frequency equal to the difference between the lower frequency limit and the equivalent shaft frequency, wherein the step of setting the generator output frequency equal to the upper frequency limit comprises setting the equivalent excitation frequency of the excitation signal equal to the difference between the upper frequency limit and the equivalent shaft frequency, and wherein the step of setting the generator output frequency equal to the equivalent shaft frequency comprises setting the equivalent excitation frequency of the excitation signal equal to zero.

In some examples, the method includes converting a second torque associated with the prime mover to a torque associated with the shaft using the coupling. In some examples, the coupling includes a fixed ratio gear coupling, a belt, or a combination thereof. In some examples, the step of rotating the shaft is performed without any constant speed drive coupled between the shaft and the prime mover. In some examples, the AC/DC converter is electrically connected to the AC bus, and wherein the DC bus is electrically connected to the AC/DC converter. In these examples, the method may include converting, at an AC/DC converter, an AC power signal on an AC bus to a DC power signal on a DC bus.

In an example, a system includes a prime mover configured to rotate a shaft. The system also includes an isff generator configured to convert torque from the shaft to an AC power signal, wherein the isff generator has one or more pole pairs, and wherein the equivalent shaft frequency is equal to the shaft frequency of the shaft multiplied by the number of pole pairs. The system also includes an AC bus and generator control unit configured to generate an excitation signal to control the ISVF generator, wherein the equivalent excitation frequency is equal to the excitation frequency of the excitation signal multiplied by the number of pole pairs, and wherein the generator control unit maintains the constant generator output frequency by setting the equivalent excitation frequency equal to a difference between the constant generator output frequency and the equivalent shaft frequency.

In some examples, the system includes a coupling disposed between the prime mover and the shaft and configured to convert a second torque associated with the prime mover to a torque associated with the shaft, wherein the coupling includes a fixed ratio gear coupling, a belt, or a combination thereof. In some examples, the prime mover is configured to rotate the shaft without any constant speed drive coupled therebetween. In some examples, the system includes a set of AC loads electrically connected to the AC bus, wherein the constant generator output frequency is determined based at least in part on operating requirements of the set of AC loads. In some examples, the system includes an AC/DC converter electrically connected to the AC bus and a DC bus electrically connected to the AC/DC converter, wherein the AC/DC converter is configured to convert an AC power signal on the AC bus to a DC power signal on the DC bus.

Drawings

Fig. 1 is a block diagram of an example of an independent speed variable frequency (isff) generator based power system.

Fig. 2 is a graph relating an axial frequency band to an equivalent axial frequency band and an AC output signal frequency band.

Fig. 3 is a graph relating excitation frequency bands to equivalent excitation frequency bands.

FIG. 4 is a graph depicting the power capacity requirement of the excitation signal as a function of frequency of the excitation signal.

Fig. 5 is a set of graphs comparing the power requirements associated with a first configuration of an isff generator based power system with a second configuration.

Fig. 6 is a flow chart depicting an example of an isff generator based power distribution method.

While the disclosure is susceptible to various modifications and alternative forms, specific examples are shown in the drawings and will be described herein in detail. It should be understood, however, that the disclosure is not intended to be limited to the particular forms disclosed. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.

Detailed Description

Referring to fig. 1, a power system 100 based on an independent speed variable frequency (isff) generator is depicted. As described herein, the system 100 may be configured to generate and distribute electrical power within a narrower frequency band for a given shaft speed range than would be generated using a typical induction generator, without a constant speed drive or other type of transmission.

The system 100 may include a prime mover 102. For example, the prime mover 102 may be an aircraft engine or another type of vehicle engine. The prime mover 102 may be attached to the coupling 104. The coupling 104 may include a fixed gear ratio coupling, a belt coupling, or a combination thereof, and may be configured to convert torque 129 from the prime mover 102 to torque 130 on the shaft 106. The coupling 104 may differ from a constant speed device in that the torque transfer ratio of the coupling 104 may be fixed, rather than variable. The shaft 106 may be attached to an isff generator 108. By using the isff generator 108 instead of a typical induction generator, the system 100 may omit any constant speed drive between the prime mover 102 and the shaft 106.

The isff generator 108 may be configured to convert torque 130 from the shaft 106 into an AC power signal 132. The isff generator 108 may generate the AC power signal 132 such that the frequency of the AC power signal 132 is independent of the shaft speed of the shaft 106. An example of an isff Generator 108 that may be used with the system 100 is further described in U.S. patent application No.15/819,919, filed on 21.11.2017, published as U.S. patent application publication No.2019/0158002 and entitled "Independent Speed Variable Frequency Alternating Current Generator," the contents of which are incorporated by reference in their entirety.

The isff generator 108 may have one or more pole pairs 109. Fig. 1 depicts the isff generator 108 as having two pole pairs 109 (i.e., four poles). However, more or less than two pole pairs are possible and consistent with the present disclosure. The number of pole pairs 109 may act as a multiplier between the frequency of the shaft 106 and the frequency of the AC power signal 132. Thus, the axis 106 may be associated with an equivalent axis frequency that is equal to the axis frequency of the axis 106 multiplied by the number of pole pairs 109.

The system 100 may include a Generator Control Unit (GCU) 110. The generator control unit 110 may be configured to generate an excitation signal 134 to control the isff generator 108. The isff generator 108 may use the excitation signal 134 to generate a rotating magnetic flux at the rotor of the isff generator 108, resulting in the frequency of the AC power signal 132 being the algebraic sum of the frequency of the shaft 106 and the frequency of the excitation signal 134. The number of pole pairs 109 of the isff generator 108 may also affect the contribution of the excitation signal 134 to the AC power signal 132. Thus, the equivalent excitation frequency of the excitation signal 134 may be equal to the excitation frequency of the excitation signal 134 multiplied by the number of pole pairs 109.

The isff generator 108 may be coupled to the AC bus 112. The set of AC loads 114 may be coupled to the AC bus 112 and configured to receive power from the AC bus 112. The set of AC loads 114 may have operating requirements such that the set of AC loads 114 is adapted to operate within an operating frequency band having a lower frequency limit and an upper frequency limit. The operating band may be narrower than the operating band associated with the prime mover 102.

An AC/DC converter 116 may be coupled to the AC bus 112. The AC/DC converter 116 may be configured to convert the AC power signal 132 to a DC power signal 136 and use the DC power signal 136 to power the DC bus 118. The DC load bank 120 may be coupled to the DC bus 118.

A direct current to alternating current (DC/AC) converter 122 may be coupled to the DC bus 118. DC/AC converter 122 may be configured to convert DC power signal 136 to second AC power signal 134 to power second AC bus 124. The set of AC loads 126 may be coupled to the second AC bus 124. The second set of AC loads 126 may have different operating frequencies and voltage requirements than the set of AC loads 114. In some examples, the second set of AC loads 126 corresponds to motor loads (e.g., for actuating a flight surface, etc.).

During operation, the generator control unit 110 may be configured to control the isff generator 108 to generate an AC power signal 132 that falls within a frequency band having a lower frequency limit and an upper frequency limit, which is narrower for a given shaft speed range than would be generated using a typical induction generator. In a first configuration, to achieve this frequency band, the generator control unit 110 may be configured to set the generator output frequency of the isff generator 108 equal to the lower frequency limit in response to the equivalent shaft frequency (e.g., the shaft frequency multiplied by the number of pole pairs 109) being less than the lower frequency limit. The generator control unit 110 may be configured to set the generator output frequency of the isff generator 108 equal to the upper frequency limit in response to the equivalent shaft frequency being greater than the upper frequency limit. In response to the equivalent shaft frequency being greater than or equal to the lower frequency limit and less than or equal to the upper frequency limit, the generator control unit 110 may be configured to set the generator output frequency of the isff generator 108 equal to the equivalent shaft frequency. In the second configuration, the generator control unit 110 may simply maintain a constant generator output frequency, rather than narrowing the frequency band.

A benefit of the system 100 is that by narrowing the frequency range of the AC power signal relative to the rotational frequency range of the shaft using the isff generator 108, the system 100 may omit complex, heavy, and/or bulky equipment (e.g., constant speed drives) between the shaft and the isff generator 108. Another benefit is that the generator control unit 110 may limit the generator output frequency to a constant generator output frequency corresponding to the operating requirements of the AC load set 114. Another benefit is that by narrowing the generator output frequency 504 (shown in fig. 5) to a range having a lower frequency limit and an upper frequency limit where the AC bus 112 can support a range of frequency bands, the load devices can be lighter and less complex due to the favorable operating conditions of the narrow frequency bands as described herein. Other benefits and advantages may exist.

Fig. 2 and 3 depict the concept of an equivalent shaft frequency 210 and an equivalent excitation frequency 308. These frequencies depend on the number of pole pairs 109 associated with the isff generator 108. In the case where there is only one pole pair, the equivalent shaft frequency 210 and the equivalent excitation frequency 308 are equal to the shaft frequency 208 and the excitation frequency 306, respectively.

Referring to fig. 2, a graph relating an axial frequency band 202 to an equivalent axial frequency band 204 and an AC output signal frequency band 206 is depicted. As shown in fig. 2, the axis frequency 208 may fall within the axis frequency band 202. The shaft frequency 208 may represent the frequency at which a prime mover (e.g., prime mover 102) rotates a shaft (e.g., shaft 106). The shaft frequency band 202 may be limited between a lower shaft frequency limit 214 representing the lowest operating frequency at which the prime mover will rotate the shaft and an upper shaft frequency limit 216 representing the highest operating frequency at which the prime mover will rotate the shaft. For illustrative purposes, FIG. 2 depicts the lower axis frequency limit 214 as 100Hz and the upper axis frequency limit 216 as 300 Hz.

The equivalent shaft band 204 may be equal to the number of pole pairs of an isff generator (e.g., the isff generator 108) multiplied by the shaft band 202. In the example of fig. 2, there may be two pole pairs such that if the axial frequency 208 is about 175Hz, the equivalent axial frequency 210 is about 350 Hz. Likewise, the lower equivalent shaft frequency limit 218 may be about 200Hz and the upper equivalent shaft frequency limit 220 may be about 600 Hz. Although the example of fig. 2 contemplates two pole pairs, any number of pole pairs may be used.

Although a typical induction motor will generally generate an AC power signal having a frequency that falls within the equivalent shaft frequency band 204, an isff generator (e.g., the isff generator 108) may be controlled by an excitation signal (e.g., the excitation signal 134) to generate a narrower AC output signal frequency band 206. For example, the AC output signal band 206 may have a lower frequency limit 222 that is greater than the equivalent lower axis frequency limit 218. Likewise, the AC output signal band 206 may have an upper frequency limit 224 that is less than the upper equivalent axis frequency limit 220. Thus, the AC output signal band 206 may be limited to meet the operating requirements of the AC load.

Referring to fig. 3, a graph relating an excitation frequency band 302 to an equivalent excitation frequency band 304 is depicted. An excitation signal (e.g., excitation signal 134) may be applied to a field winding on the rotor of an isff generator (e.g., isff generator 108) to effectively increase or decrease the frequency of the output power signal. The excitation signal may have an excitation frequency 306 that falls within the excitation frequency band 302. Since the number of pole pairs associated with the isff generator affects the output frequency, the equivalent excitation band 304 may be equal to the excitation band 302 multiplied by the number of pole pairs. Likewise, the equivalent excitation frequency 308 may be equal to the excitation frequency 306 multiplied by the number of pole pairs.

In a single pole pair system, the generator output frequency may be the algebraic sum of the shaft frequency and the excitation frequency:

f_Gen＝f_Shaft+f_Excit

for a system with multiple pole pairs, the shaft frequency and excitation frequency may each be multiplied by the number of Pole Pairs (PP):

f_Gen＝(f_Shaft+f_Excit)·PP

wherein f is_ShaftPP is the equivalent axial frequency, f_ExcitPP is the equivalent excitation frequency.

Referring to FIG. 4, a graph 400 depicts a power capacity requirement S of an excitation signal_ExcitWith frequency f of the excitation signal_Excit402, in the space between the two. Although the description in FIG. 4 is applicable to a monopole pair system, those of ordinary skill in the art, with the benefit of this disclosure, will appreciate that these are not without limitationThe concept can be extended to multiple pole pairs. As shown in graph 400, with frequency f_ExcitMoving away from zero, the excitation signal may require more power S_ExcitIn order to maintain a constant power output of the isff generator. Analysis has shown that this relationship can be roughly represented by a conic section as shown. When excitation frequency f_ExcitAt zero (meaning the shaft speed is equal to the generator output frequency), the excitation signal need only provide sufficient power to compensate for power losses at the rotor windings (e.g., y)₀). When the shaft speed of the generator is lower than the output frequency of the generator, the excitation frequency f_ExcitIs positive. In this case, the excitation source provides apparent power to the stator windings. When the shaft speed of the generator is higher than the output frequency of the generator, the excitation frequency f_ExcitIs negative. In this case, the excitation source draws apparent power from the generator shaft. (excitation frequency f)_ExcitFrom the generator' S nominal output frequency), the power capacity S of the excitation signal_ExcitThe higher may be.

Referring to fig. 5, a first graph 500 depicts power requirements associated with a first configuration of the system 100 and is compared to a second graph 550 depicting power requirements associated with a second configuration of the system 100. The first configuration may correspond to a constant frequency output and the second configuration may correspond to a narrowed frequency band output.

As shown in the first graph 500, a generator control unit (e.g., the generator control unit 110) may maintain a constant generator output frequency 504. This may be performed by setting the equivalent excitation frequency 308 equal to the difference between the constant generator output frequency 504 and the equivalent shaft frequency 210. In other words, the generator output frequency 504 may be equal to the algebraic sum of the shaft frequency 208 and the excitation frequency 306:

F_Gen＝f_Shaft(t)+f_Excit(t)

to maintain a constant generator output frequency 504, the excitation frequency 306 may be set to zero when the frequency 208 is equal to the generator output frequency 504, may be set to a positive value when the frequency 208 is less than the generator output frequency 504, and may be set to a negative value when the frequency 208 is greater than the generator output frequency 504:

if f is_Shaft(t)＝F_GenThen f is_Excit(t)＝0

If f is_Shaft(t)＜F_GenThen f is_Excit(t)＞0

If f is_Shaft(t)＞F_GenThen f is_Excit(t)＜0

When considering the pole pair associated with an isff generator, the generator output frequency 504 may be determined as:

F_Gen＝(f_Shaft(t)+f_Excit(t))·PP

to maintain a constant generator output frequency 504, the equivalent excitation frequency 308 may be set to zero when the equivalent shaft frequency 210 is equal to the generator output frequency 504, may be set to a positive value when the equivalent shaft frequency 210 is less than the generator output frequency 504, and may be set to a negative value when the equivalent shaft frequency 210 is greater than the generator output frequency 504:

if (f)_Shaft(t))·PP＝F_GenThen (f)_Excit(t))·PP＝0

If (f)_Shaft(t))·PP＜F_GenThen (f)_Excit(t))·PP＞0

If (f)_Shaft(t))·PP＞F_GenThen (f)_Excit(t))·PP＜0

As shown in the first graph 500, more power is distributed to the excitation signal as the shaft frequency shifts away from the generator output frequency 504. To provide power for a frequency range between the lower equivalent axis frequency limit 218 and the upper equivalent axis frequency limit 220, a relatively high power 506 may be used. Thus, the constant generator output frequency configuration depicted in the first graph 500 may be appropriate when the shaft frequency range is relatively narrow. The configuration depicted in the second graph 550 may be more appropriate for engines utilizing a wider range of shaft frequencies.

As shown in the second graph 550, the generator control unit (e.g., the generator control unit 110) may maintain the generator output frequency 502. The generator output frequency 502 may remain between the lower frequency limit 222 and the upper frequency limit 224, rather than being constant:

F_min≤F_Gen≤F_max

if the shaft frequency 208 is between the lower frequency limit 222 and the upper frequency limit, the generator output frequency 502 may be set equal to the shaft frequency 208 by setting the excitation frequency 306 of the excitation signal to zero. If the shaft frequency 208 is less than the lower frequency limit 222, the generator output frequency 502 may be set equal to the lower frequency limit 222 by setting the excitation frequency 306 to the difference between the lower frequency limit 222 and the shaft frequency 208. If the shaft frequency 208 is greater than the upper frequency limit 224, the generator output frequency 502 may be set equal to the upper frequency limit 224 by setting the excitation frequency 306 of the excitation signal equal to the difference between the upper frequency limit 224 and the shaft frequency 208:

if F_min≤f_Shaft(t)≤F_maxThen f is_Excit(t)＝0

If f is_Shaft(t)≤F_minThen f is_Excit(t)＝F_min-f_Shaft(t)

If f is_Shaft(t)≥F_maxThen f is_Excit(t)＝F_max-f_Shaft(t)

When considering the pole pair associated with an isff generator, if the equivalent shaft frequency 210 is between the lower frequency limit 222 and the upper frequency limit, the generator output frequency 502 may be set equal to the equivalent shaft frequency 210 by setting the equivalent excitation frequency 308 of the excitation signal to zero. If the equivalent shaft frequency 210 is less than the lower frequency limit 222, the generator output frequency 502 may be set equal to the lower frequency limit 222 by setting the equivalent excitation frequency 308 to the difference between the lower frequency limit 222 and the equivalent shaft frequency 210. If the equivalent shaft frequency 210 is greater than the upper frequency limit 224, the generator output frequency 502 may be set equal to the upper frequency limit 224 by setting the equivalent excitation frequency 308 of the excitation signal equal to the difference between the upper frequency limit 224 and the equivalent shaft frequency 210:

if F_min≤(f_Shaft(t))·PP≤F_maxThen (f)_Excit(t))·PP＝0

If (f)_Shaft(t))·PP≤F_minThen (f)_Excit(t))·PP＝F_min-(f_Shaft(t))·PP

If (f)_Shaft(t))·PP≥F_maxThen (f)_Excit(t))·PP＝F_max-(f_Shaft(t))·PP

As shown in the second graph 550, as the shaft frequency shifts away from the generator output frequency 502, more constant magnitude of power is allocated to the excitation signal while the shaft frequency is between the lower frequency limit 222 and the upper frequency limit 224. Thus, a relatively low power 508 may be used for the same axial frequency range. The narrow band generator output frequency configuration depicted in the second graph 550 may be appropriate when the shaft frequency range is relatively wide and the AC load is capable of operating at a frequency between the lower frequency limit 222 and the upper frequency limit 224.

Referring to fig. 6, an example of an isff generator based power distribution method 600 is depicted. The method 600 may include, at 602, rotating a shaft using a prime mover. For example, the prime mover 102 may be used to rotate the shaft 106.

The method 600 may also include, at 604, converting torque from the shaft to an AC power signal using an isff generator, wherein the isff generator has one or more pole pairs, and wherein the equivalent shaft frequency is equal to the shaft frequency of the shaft multiplied by the number of pole pairs. For example, torque 130 from the shaft 106 may be converted into an AC power signal 132 using the isff generator 108.

The method 600 may also include converting a second torque associated with the prime mover to a torque associated with the shaft using the coupling, at 606. For example, the second torque 129 may be converted to a torque 130 using the coupling 104.

The method 600 may also include, at 608, generating an excitation signal to control the isff generator, wherein the equivalent excitation frequency is equal to the excitation frequency of the excitation signal multiplied by the number of pole pairs. For example, the generator control unit 110 may generate the excitation signal 134.

The method 600 may also include, at 610, applying an AC power signal to an AC bus having a lower frequency limit and an upper frequency limit. For example, the AC power signal 132 may be applied to the AC bus 112.

The method 600 may include, at 612, setting a generator output frequency of the ISVF generator equal to the lower frequency limit when the equivalent shaft frequency is less than the lower frequency limit. Setting the generator output frequency of the isff generator equal to the lower frequency limit may include setting the equivalent excitation frequency to a difference between the lower frequency limit and the equivalent shaft frequency at 614.

The method 600 may also include, at 616, setting the generator output frequency of the isff generator equal to the upper frequency limit when the equivalent shaft frequency is greater than the upper frequency limit. Setting the generator output frequency equal to the upper frequency limit may include setting the equivalent excitation frequency of the excitation signal equal to a difference between the upper frequency limit and the equivalent shaft frequency at 618.

The method 600 may include, at 620, setting a generator output frequency of the isff generator equal to the equivalent shaft frequency when the equivalent shaft frequency is between the lower frequency limit and the upper frequency limit. Setting the generator output frequency equal to the equivalent shaft frequency includes setting the equivalent excitation frequency of the excitation signal to zero at 622.

A benefit of the method 600 is that by narrowing the frequency range of the AC power signal relative to the rotational frequency range of the shaft using the isff generator, complex, heavy and/or bulky equipment (e.g., constant speed drive) between the shaft and the isff generator may be omitted. Other advantages may exist.

Furthermore, the present disclosure includes examples in accordance with the following clauses, whereby it is noted that the scope of protection is provided by the claims.

Clause 1. a system, comprising: a prime mover configured to rotate a shaft; an Independent Speed Variable Frequency (ISVF) generator configured to convert torque from a shaft to an Alternating Current (AC) power signal, wherein the ISVF generator has one or more pole pairs, and wherein an equivalent shaft frequency is equal to a shaft frequency of the shaft multiplied by a number of pole pairs; an AC bus having a lower frequency limit and an upper frequency limit; and a generator control unit configured to: when the equivalent shaft frequency is less than the lower frequency limit, setting the generator output frequency of the ISVF generator to be equal to the lower frequency limit; when the equivalent shaft frequency is larger than the upper frequency limit, setting the generator output frequency of the ISVF generator to be equal to the upper frequency limit; and when the equivalent shaft frequency is greater than or equal to the lower frequency limit and less than or equal to the upper frequency limit, setting the generator output frequency of the ISVF generator to be equal to the equivalent shaft frequency.

Clause 2. the system according to clause 1, wherein the generator control unit is configured to generate the excitation signal to control the isff generator, wherein the equivalent excitation frequency is equal to the excitation frequency of the excitation signal multiplied by the number of pole pairs, wherein setting the generator output frequency equal to the lower frequency limit comprises setting the equivalent excitation frequency equal to the difference between the lower frequency limit and the equivalent shaft frequency, wherein setting the generator output frequency equal to the upper frequency limit comprises setting the equivalent excitation frequency of the excitation signal equal to the difference between the upper frequency limit and the equivalent shaft frequency, and wherein setting the generator output frequency equal to the equivalent shaft frequency comprises setting the equivalent excitation frequency of the excitation signal equal to zero.

Clause 3. the system of clause 1, further comprising: a coupling disposed between the prime mover and the shaft and configured to convert a second torque associated with the prime mover to a torque associated with the shaft.

Clause 4. the system of clause 3, wherein the coupling comprises a fixed ratio gear coupling, a belt, or a combination thereof.

Clause 5. the system of any of clauses 1-4, wherein the prime mover is configured to rotate the shaft without any constant speed drive coupled therebetween.

Clause 6. the system of any of clauses 1-5, further comprising: a set of AC loads electrically connected to the AC bus, wherein the lower frequency limit and the upper frequency limit are determined based at least in part on operating requirements of the set of AC loads.

Clause 7. the system of any of clauses 1-6, further comprising: an alternating current-to-direct current (AC/DC) converter electrically connected to the AC bus; and a Direct Current (DC) bus electrically connected to the AC/DC converter, wherein the AC/DC converter is configured to convert an AC power signal on the AC bus to a DC power signal on the DC bus.

Clause 8. the system of any of clauses 1-7, wherein the prime mover is an aircraft engine.

Clause 9. a method, comprising: rotating a shaft using a prime mover; converting torque from a shaft to an Alternating Current (AC) power signal using an independent speed variable frequency (isff) generator, wherein the isff generator has one or more pole pairs, and wherein an equivalent shaft frequency is equal to a shaft frequency of the shaft multiplied by a number of pole pairs; applying an AC power signal to an AC bus having a lower frequency limit and an upper frequency limit; when the equivalent shaft frequency is less than the lower frequency limit, setting the generator output frequency of the ISVF generator to be equal to the lower frequency limit; when the equivalent shaft frequency is larger than the upper frequency limit, setting the generator output frequency of the ISVF generator to be equal to the upper frequency limit; and when the equivalent shaft frequency is between the lower frequency limit and the upper frequency limit, setting the generator output frequency of the ISVF generator to be equal to the equivalent shaft frequency.

Clause 10. the method of clause 9, further comprising: generating an excitation signal to control the isff generator, wherein the equivalent excitation frequency is equal to the excitation frequency of the excitation signal multiplied by the number of pole pairs, wherein setting the generator output frequency equal to the lower frequency limit comprises setting the equivalent excitation frequency equal to the difference between the lower frequency limit and the equivalent shaft frequency, wherein setting the generator output frequency equal to the upper frequency limit comprises setting the equivalent excitation frequency of the excitation signal equal to the difference between the upper frequency limit and the equivalent shaft frequency, and wherein setting the generator output frequency equal to the equivalent shaft frequency comprises setting the equivalent excitation frequency of the excitation signal equal to zero.

Clause 11. the method of clause 9, further comprising: a second torque associated with the prime mover is converted to a torque associated with the shaft using the coupling.

Clause 12. the method of clause 11, wherein the coupling comprises a fixed ratio gear coupling, a belt, or a combination thereof.

Clause 13. the method of any of clauses 9-12, wherein the step of rotating the shaft is performed without any constant speed drive coupled between the shaft and the prime mover.

Clause 14. the method of any of clauses 9-13, wherein an alternating current-to-direct current (AC/DC) converter is electrically connected to the AC bus, and wherein the Direct Current (DC) bus is electrically connected to the AC/DC converter, the method further comprising: an AC power signal on the AC bus is converted to a DC power signal on the DC bus at an AC/DC converter.

Clause 15. the method of any one of clauses 9 to 14, wherein the prime mover is an aircraft engine.

Clause 16. a system, comprising: a prime mover configured to rotate a shaft; an Independent Speed Variable Frequency (ISVF) generator configured to convert torque from a shaft to an Alternating Current (AC) power signal, wherein the ISVF generator has one or more pole pairs, and wherein an equivalent shaft frequency is equal to a shaft frequency of the shaft multiplied by a number of pole pairs; an AC bus; and a generator control unit configured to generate an excitation signal to control the ISVF generator, wherein the equivalent excitation frequency is equal to the excitation frequency of the excitation signal multiplied by the number of pole pairs, and wherein the generator control unit maintains the constant generator output frequency by setting the equivalent excitation frequency equal to a difference between the constant generator output frequency and the equivalent shaft frequency.

Clause 17. the system of clause 16, further comprising: a coupling disposed between the prime mover and the shaft and configured to convert a second torque associated with the prime mover to a torque associated with the shaft, wherein the coupling comprises a fixed ratio gear coupling, a belt, or a combination thereof.

Clause 18. the system of any of clauses 16-17, wherein the prime mover is configured to rotate the shaft without any constant speed drive coupled therebetween.

Clause 19. the system of any of clauses 16-18, further comprising: a set of AC loads electrically connected to the AC bus, wherein the constant generator output frequency is determined based at least in part on operating requirements of the set of AC loads.

Clause 20. the system of any one of clauses 16 to 19, further comprising: an alternating current-to-direct current (AC/DC) converter electrically connected to the AC bus; and a Direct Current (DC) bus electrically connected to the AC/DC converter, wherein the AC/DC converter is configured to convert an AC power signal on the AC bus to a DC power signal on the DC bus.

While various examples have been shown and described, the present disclosure is not limited thereto, and will be understood to include all such modifications and changes as would be apparent to those skilled in the art.