Power converter and system for engine starter generator

Abstract

The invention relates to a power converter and a system for an engine starter generator. A power converter system includes an asynchronous induction generator electrically coupled to an inverter / converter / controller (ICC). The ICC may be coupled to an electrical load. The ICC may include an AC-DC converter and a DC-DC converter. The DC-DC converter is configured to operate at a duty cycle substantially equal to 1 in a first mode of operation. In the event of a short-circuit fault in the electrical load, the DC-DC converter is configured to operate at a duty cycle of less than 1 in the second mode of operation.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 571,746, filed on March 29, 2024, which is incorporated herein in its entirety. Technical Field

[0002] The present disclosure generally relates to power converter systems for electric machines. More specifically, the present disclosure relates to power converters and systems for induction generators, such as induction starter / generators for aircraft engines. Background Art

[0003] Electric machines, such as electric motors or generators, are used for energy conversion. In the aircraft industry, it's common to combine motor and generator modes within the same machine, with the motor used to start the engine and, depending on the mode, also functioning as a generator. Regardless of the mode, the machine typically includes a rotor with rotor windings that are driven to rotate by a rotational source, such as a machine or electric motor. For some aircraft, this source might be a gas turbine engine. Summary of the Invention Technical Solution 1. A power converter electrically connected between an induction generator and an electrical load, the power converter comprising: an inverter / converter / controller (ICC) electrically couplable to the induction generator, the ICC comprising: an AC-DC converter electrically coupled to the induction generator at a first end to receive an AC voltage therefrom and configured to output a first DC voltage at a second end; a DC-DC converter electrically coupled to the second end of the AC-DC converter via a first DC power line and a second DC power line to receive the first DC voltage therefrom, the DC-DC converter being electrically coupled to the electrical load via a first DC output line and a second DC output line to provide a second DC voltage thereto, the DC-DC converter comprising: a semiconductor switching device electrically coupled to the first DC power line; and an inductor electrically coupled in series between the semiconductor switching device and the first DC output line; and a controller module communicatively coupled to the DC-DC converter and configured to control operation of the semiconductor switching device; wherein, in a first operating condition, the semiconductor switching device is configured to operate with a duty cycle substantially equal to 1; and Wherein, under a second operating condition, in response to a short circuit fault in the electrical load, the semiconductor switching device is configured to operate with a duty cycle less than 1. Technical Solution 2. The power converter according to any of the preceding technical solutions further includes a capacitor connecting the first DC output line and the second DC output line, and wherein, during operation under the first operating condition, the inductor and the capacitor define a choke. Technical Solution 3. The power converter according to any of the preceding technical solutions further includes a freewheeling semiconductor device electrically connected between the semiconductor switch device and the second DC output line. Technical Solution 4. A power converter according to any of the preceding technical solutions, wherein the freewheeling semiconductor device is a diode electrically connected to the semiconductor switching device at a cathode terminal and electrically connected to the second DC output line at an anode terminal. Technical Solution 5. The power converter according to any of the preceding technical solutions further includes an auxiliary DC power source selectively electrically coupled to the first DC power line and the second DC power line. Technical Solution 6. A power converter according to any of the preceding technical solutions, wherein, under the first operating condition, the semiconductor switching device is configured to operate in a constant on state. Technical Solution 7. A power converter according to any of the preceding technical solutions, wherein, in the second operating condition, the DC-DC converter is further configured to operate as a DC buck converter. Technical Solution 8. A power converter according to any preceding technical solution, wherein the DC-DC converter is configured to operate under the second operating condition for a predetermined period of time. Technical Solution 9. A power converter according to any of the preceding technical solutions, wherein, under the first operating condition, the first DC voltage is substantially equal to the second DC voltage. Technical Solution 10. A power converter according to any preceding technical solution, wherein, under the second operating condition, the first DC voltage is greater than the second DC voltage. Technical Solution 11. The power converter according to any of the preceding technical solutions, wherein the controller module is also communicatively coupled to the AC-DC converter and configured to control the operation thereof. Technical Solution 12. A power converter according to any of the preceding technical solutions, wherein the ICC is arranged in a bidirectional topology. Technical Solution 13. A power converter system electrically connectable to an electrical load, the system comprising: asynchronous induction generators; an ICC electrically coupled to the asynchronous induction generator, the ICC comprising: an AC-DC converter electrically coupled to the asynchronous induction generator at a first end to receive an AC voltage therefrom and configured to output a first DC voltage at a second end; a DC-DC converter electrically coupled to the second end of the AC-DC converter via a first DC power line and a second DC power line to receive the first DC voltage therefrom, the DC-DC converter being electrically coupled to the electrical load via a first DC output line and a second DC output line to provide a second DC voltage thereto, the DC-DC converter comprising: a semiconductor switching device electrically coupled to the first DC power line; a freewheeling semiconductor device electrically coupled between the semiconductor switching device and the second DC output line; and an inductor electrically coupled to the semiconductor switching device at a first end and electrically coupled to the first DC output line at a second end; a controller module communicatively coupled to the DC-DC converter and configured to control operation of the semiconductor switching device; wherein, in a first operating condition, the semiconductor switching device is configured to operate with a duty cycle substantially equal to 1; and Wherein, under a second operating condition, in response to a short circuit fault in the electrical load, the semiconductor switching device is configured to operate with a duty cycle less than 1. Technical Solution 14. The power converter system according to any of the preceding technical solutions further includes an auxiliary DC power source selectively electrically coupled to the first DC power line and the second DC power line. Technical Solution 15. The power converter system according to any of the preceding technical solutions, wherein the asynchronous induction generator is a squirrel cage induction machine. Technical Solution 16. The power converter system according to any of the preceding technical solutions, wherein the asynchronous induction generator is arranged as a starter / generator having a starter operating mode and a generator operating mode. Technical Solution 17. The power converter system according to any of the preceding technical solutions, wherein the asynchronous induction generator is a wet chamber machine. Technical Solution 18. The power converter system according to any of the preceding technical solutions, wherein the asynchronous induction generator is fluidly coupled to an accessory gearbox (AGB). Technical Solution 19. The power converter system according to any of the preceding technical solutions, wherein the asynchronous induction generator receives oil flow from the AGB. Technical Solution 20. A power converter system according to any of the preceding technical solutions, wherein the asynchronous induction generator comprises a stator and a rotor, and further defines a one-way oil path passing therethrough in fluid communication with the rotor and the stator. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] A complete and sufficient disclosure, including the best mode thereof, to one skilled in the art is set forth in this specification, which refers to the accompanying drawings, in which:

[0005] Figure 1 is an isometric view of a gas turbine engine with a generator according to various aspects described herein.

[0006] Figure 2 According to the various aspects described in this article Figure 1 Isometric view of the exterior of the generator.

[0007] Figure 3 is a schematic diagram of a power converter system according to various aspects described herein.

[0008] Figure 4 is a schematic block diagram of a generator induction machine with a one-way oil circuit according to various aspects described herein. DETAILED DESCRIPTION

[0009] The exemplary drawings are for illustration purposes only, and the dimensions, positions, orders, and relative sizes reflected in the drawings may vary. In addition, the number and placement of the various components depicted in the drawings are also non-limiting examples of aspects related to the present disclosure.

[0010] As used herein, the word "exemplary" means "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, unless expressly stated otherwise, all aspects described herein are to be considered exemplary.

[0011] As used herein, the term "set" or "set" of elements may be any number of elements, including only one.

[0012] As used herein, the terms "first," "second," and "third," etc. are used interchangeably to distinguish one component from another and are not intended to indicate the position or importance of individual components. Unless the context clearly dictates otherwise, the singular forms "a," "an," and "the" include plural references.

[0013] Approximate language may be used herein throughout the specification and claims to modify any quantitative expression that can be allowed to vary without causing a change in the basic function to which it is related. Therefore, a value modified by one or more terms such as "about," "approximately," "substantially," and "substantially" is not limited to the exact value specified. In at least some cases, approximate language may correspond to the precision of an instrument used to measure the value, or the precision of a method or machine used to construct or manufacture a component and / or circuit. In at least some cases, approximate language may correspond to the precision of an instrument used to measure the value, or the precision of a method or machine used to construct or manufacture a component and / or circuit. For example, approximate language may refer to being within 1%, 2%, 4%, 5%, 10%, 15%, or 20% of a single value, a range of values, and / or the endpoints of a range of values. Here and throughout the specification and claims, range limitations are combinable and interchangeable, and unless the context or language indicates otherwise, these ranges are defined and include all subranges contained therein. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints can be independently combined with each other.

[0014] All directional references (e.g., inside, outside, up, down, radial, axial, proximal, distal, up, down, upward, downward, left, right, lateral, front, back, top, bottom, above, below, vertical, horizontal, clockwise, counterclockwise, upstream, downstream, rear, near, etc.) are used only for identification purposes to help the reader understand the present disclosure and are not intended to be limiting, especially with respect to the position, orientation, or use of the present disclosure. It should also be understood that the specific aspects shown in the drawings and described in the following description are merely exemplary aspects of the present disclosure. Therefore, specific dimensions and other physical characteristics related to the aspects disclosed herein should not be considered limiting.

[0015] As used herein, the term "axial" or "axially" refers to a dimension along the longitudinal axis of the generator or along the longitudinal axis of a component disposed within the generator.

[0016] As used herein, the terms "radial" or "radially" refer to a dimension extending between a central longitudinal axis, an outer periphery, or a circular or annular member disposed therebetween.

[0017] Connection references (e.g., attachment, coupling, connection, and linking) should be interpreted broadly, and unless otherwise indicated, connection references may include intermediate components between a set of elements and relative motion between elements. Therefore, a connection reference does not necessarily mean that two elements are directly connected and are in a fixed relationship to each other. In a non-limiting example, a connection or disconnection can be selectively configured to provide, enable, disable, etc., electrical connections between corresponding elements. A non-limiting example power distribution bus connection or disconnection can be enabled or operated by a switch, bus connection logic, or any other connector configured to enable or disable power to the electrical load applied to the bus. In addition, as used herein, "electrically connected" or "electrically coupled" may include wired or wireless connections. The exemplary figures are for illustrative purposes only, and the dimensions, positions, order, and relative sizes reflected in the accompanying drawings may vary.

[0018] Although terms such as "voltage," "current," and "power" may be used herein, those skilled in the art will appreciate that these terms may be used in conjunction with one another when describing various aspects of a circuit or circuit operation. Thus, as used herein, the term "power" may refer to voltage, current, or both voltage and current.

[0019] As used herein, the term "semiconductor device" refers to a semiconductor component, device, wafer, or chip that performs a specific function, such as a power transistor, a power diode, or an analog amplifier, as non-limiting examples. A typical semiconductor device may include input / output (I / O) interconnects for connecting the semiconductor device to an external circuit and electrically coupling to internal components within the semiconductor device. The semiconductor devices described herein may be power semiconductor devices used as electrically controllable switches or converters in power electronic circuits, such as, for example, switch-mode power supplies. Non-limiting examples of semiconductor devices include insulated gate bipolar transistors (IGBTs), metal oxide semiconductor field effect transistors (MOSFETs), bipolar junction transistors (BJTs), integrated gate-commutated thyristors (IGCTs), gate-turn-off (GTO) thyristors, silicon-controlled rectifiers (SCRs), diodes, or other devices or combinations of devices including materials such as silicon (Si), silicon carbide (SiC), gallium nitride (GaN), and gallium arsenide (GaAs). The semiconductor device may also be a digital logic device, such as a microprocessor, a microcontroller, a memory device, a video processor, or an application-specific integrated circuit (ASIC), as non-limiting examples.

[0020] As used herein, a "switching device" or "switch" refers to an electrical device that can be controlled to operate or switch between a first state and a second state, wherein in the first state, the switching device is "closed" to enable current to flow from the switch input to the switch output, and in the second state, the switching device is "open" to prevent current from flowing between the switch input and the switch output. In a non-limiting example, a connection or disconnection (such as a connection enabled or disabled by a controllable switching element) can be selectively configured to provide, enable, disable, etc. an electrical connection between corresponding elements. An exemplary embodiment may include a MOSFET switch that can be controlled by a voltage applied to the switch. Additional switching devices or additional silicon-based power switches may be included. Other non-limiting aspects may include any switching device that can switch between a low resistance state and a high resistance state in response to an electrical signal. For example, the switching devices in various aspects may include, but are not limited to, any type of switching device, including, for example, a transistor, a gate commutated thyristor, a field effect transistor (FET), an IGBT, a MOSFET, a gate turn-off thyristor, an electrostatic induction transistor, an electrostatic induction thyristor, or a combination thereof.

[0021] As used herein, the term "duty cycle" refers to the ratio of the time a switching device in a circuit is conducting or "on" to the switching period of "on" plus "off." A constant on duty cycle is equal to one, and a constant off duty cycle is equal to zero.

[0022] As used herein, a "freewheeling semiconductor device" refers to any semiconductor device electrically coupled in parallel with an inductor in a DC-DC converter, configured to operatively eliminate a sudden voltage spike across the inductor due to a current interruption or a sudden voltage drop. For example, the freewheeling semiconductor device may be a diode, a MOSFET, or the like.

[0023] As used herein, a “module” that includes or incorporates, runs, operates, or otherwise performs or produces a functional operation or operational result may be incorporated into or included in the form of a program code stored in a memory or executed by a controller module or processor.

[0024] As used herein, a "controller" or "module," such as a "controller module" or "gate driver," may include a component configured or adapted to provide instructions, control, operation, or any form of communication to an operable component to affect its operation. Such a controller or module may include any known processor, microcontroller, or logic device, including, but not limited to, a field programmable gate array (FPGA), a complex programmable logic device (CPLD), an application specific integrated circuit (ASIC), a full authority digital engine control (FADEC), a proportional controller (PC), a proportional integral controller (PI), a proportional differential controller (PD), a proportional integral differential controller (PID), a hardware accelerated logic controller (e.g., for encoding, decoding, transcoding, etc.), or a combination thereof. Although described herein as including separate elements, in non-limiting aspects, such controllers and modules may be combined on one or more devices, including a common device, such as a single processor or microcontroller. Non-limiting examples of such controllers or modules may be configured or adapted to run, operate, or otherwise execute program code to achieve operational or functional results, including performing various methods, functions, processing tasks, calculations, comparisons, sensing, or measurement values, etc., to enable or achieve the technical operations or operations described herein. Operation or function result can be based on one or more inputs, stored data values, sensed or measured values, true or false indications, etc. Although "program code" is described, non-limiting examples of operable or executable instruction groups can include routines, programs, objects, components, data structures, algorithms, etc., which have the technical effect of performing specific tasks or realizing specific abstract data types. In another non-limiting example, the controller module or switch module can also include a data storage component accessible by the processor, including memory (whether transient, volatile or non-transient) or non-volatile memory. Other non-limiting examples of memory can include random access memory (RAM), read-only memory (ROM), flash memory or one or more different types of portable electronic memory, such as optical discs, DVDs, CD-ROMs, flash drives, universal serial bus (USB) drives, etc., or any suitable combination of these types of memory. In one example, program code can be stored in a memory in a machine-readable format accessible by a processor. In addition, the memory can store various data, data types, sensed or measured data values, inputs, generated or processed data, etc. that can be accessed by the processor when providing instructions, controls or operations to affect functions or operational results, as described herein.

[0025] For illustrative purposes, exemplary aspects will be described herein in the context of electric machines, such as alternating current (AC) power generation sources and AC to direct current (DC) power converters for aircraft. In non-limiting examples, the electric machine may be in the form of a generator, a motor, a permanent magnet generator (PMG), or a starter / generator (S / G). However, it will be understood that the aspects of the present disclosure described herein are not limited thereto and may have general applicability to other electric machines or systems. It will also be understood that the present disclosure is generally applicable to power conversion systems in non-aircraft applications, including other mobile applications and non-mobile industrial and commercial applications. For example, applicable mobile environments may include aircraft, spacecraft, space launch vehicles, satellites, locomotives, automobiles, and the like. Commercial environments may include manufacturing facilities or power generation and distribution facilities or infrastructure. Furthermore, while aspects of the present disclosure will be described herein with respect to induction machines, for the sake of brevity, other aspects are not so limited. For example, in non-limiting aspects, an induction machine may include a brushless starter / generator without departing from the scope of the present disclosure. It is also contemplated that aspects of the present disclosure may be incorporated into any electric machine.

[0026] As used herein, a "wet" cavity generator includes a cavity that houses a rotor and stator, with the rotor and stator being exposed to a free liquid coolant (e.g., a coolant that moves freely within the cavity). In contrast, a "dry" cavity generator's rotor and stator may be cooled by a coolant contained in confined, fluid-tight channels (e.g., not freely moving around the cavity). Aspects of the present disclosure are applicable to both wet and dry cavity generators.

[0027] Electric machines, such as conventional wound rotor generators, are a source of electrical energy for industrial and commercial applications. They are commonly used to convert the mechanical power output of steam turbines, gas turbines, reciprocating engines, and hydroelectric turbines into electrical power. Typically, these machines include a central rotatable assembly, or "rotor," surrounded by a stationary assembly, or "stator." An air gap separates the rotor and stator. The rotor may include a rotatable element that defines a central axis of rotation and a periphery. The rotor typically includes a rotatable shaft and a rotor core having one or more sets of electrically conductive rotor windings. The rotor windings may be wound around the periphery. The rotor windings are typically wound axially around a set of posts or rotor teeth, defining slots therebetween. The number of rotor winding sets typically defines the number of electrical phases of the machine. A portion of the windings of a conventional rotor (e.g., the end turns) typically extends through the rotor or overhangs the rotor. In some electric machines, the rotor winding end turns are supported and / or covered by a housing, cover, or other structure.

[0028] In operation, the rotor of a conventional electric motor is driven to rotate by a rotation source, such as a machine or an electric motor, which for some aircraft may be a gas turbine engine. The rotor typically rotates at a relatively high rotational speed per minute (rpm) (e.g., 20,000-500,000 rpm). In many cases, the rotor can rotate relative to the stator in response to an electric current. The current passing through the rotor and stator generates heat. For example, heat is generated in the rotor due to the current flowing through the windings and the changing magnetic field present in the rotor, resulting in an increase in the temperature of the rotor. Heat may also be caused by, for example, stator core losses, which are caused by hysteresis or eddy currents generated during operation. It is desirable to cool the rotor and stator to protect the motor from damage and increase the motor power density to allow more power to be obtained from an electric motor with a smaller physical size.

[0029] Furthermore, because there is a relatively linear relationship between motor speed and shaft power, increasing the rated speed of a generator can improve its power density and efficiency. Consequently, there is a growing demand for operating conventional motors at increasingly higher speeds. However, operating conventional motors at higher speeds generates more heat that needs to be reduced or removed.

[0030] In some cases, heat can be removed by passing an air flow across and through the motor. In other cases, oil or other liquid coolant is passed through the electric motor near the stator. The liquid coolant typically flows through channels formed in the motor housing near the stator and also passes through the rotor shaft in both directions in a so-called two-way arrangement. In still other cases, the coolant passes through channels formed in the stator core. In some cases, liquid coolant or oil is sprayed on the end turn portions of the rotor windings and stator windings, which extend through or depend from the rotor or stator, respectively (e.g., at the axial ends of the motor). Typically, heat is removed from the oil by passing the oil through a heat exchanger.

[0031] Aircraft gas turbine engines typically include a fan section followed by a core engine having, in a series flow arrangement, a compressor that compresses the airflow entering the engine, a combustor that burns a mixture of fuel and air, and a high-pressure turbine section followed by a low-pressure turbine section that extracts energy from the airflow exhausted by the core engine to power the fan section that generates thrust.

[0032] Aircraft and aircraft engine accessories are mechanically driven by the engine via a power output shaft connected to the engine's accessory gearbox. Among the accessories mounted to the gearbox are the starter motor for starting the gas turbine engine and the generator for generating electrical power for the aircraft. It is known to provide a single starter / generator to provide both starting and electrical power generation. Both brushed and brushless starter / generators, referred to as brushed and brushless, are used for both power generation and starting in aircraft gas turbine engines. Typically, an air and / or oil cooler is used to cool the starter / generator.

[0033] The power generated by the starter / generator is typically provided to a power converter and then provided to the electrical load. A power converter typically converts an input voltage waveform into a specified output voltage waveform with controllable frequency, phase, amplitude or polarity. A power converter can be used to convert a DC voltage to an AC voltage (DC-AC), or from DC to DC (e.g., DC-DC), or from AC to DC (e.g., AC-DC). Conventional power converters are typically made of one or more conversion stages. The conversion stage can also be arranged as a step-down or "buck" converter (e.g., a DC-DC power converter that reduces the voltage received at its input (supply) to its output (load)). Alternatively, the conversion stage can also be arranged as a "step-up" or boost converter (e.g., a DC-DC power converter that increases the voltage from its input to its output). Other converters can also be arranged to selectively operate in step-down or step-up mode.

[0034] An asynchronous generator, also known as an induction generator or generator induction machine, is an electric machine with a rotor and a stator that converts mechanical energy into alternating current (AC) electricity. An induction generator generates electrical power when its rotor rotates faster than synchronous speed (e.g., the rotational speed of the magnetic field within the generator, typically equal to 120 times the frequency / number of poles). Typically, a turbine or engine is coupled to the induction machine rotor to drive the rotor above synchronous speed. Induction generators are typically more robust, easier to control, and less expensive than other types of generators, such as brushless generators and synchronous generators.

[0035] However, unlike synchronous generators, induction generators are not self-magnetizing. Induction generators utilize a reactive excitation current source to generate magnetizing flux (reactive power) in the stator to induce rotor current. For example, in some cases, once the induction generator begins generating power, reactive excitation current can be supplied to the induction generator from the electrical load. However, if the electrical load loses power or experiences a voltage sag (e.g., during an electrical fault), the induction generator cannot use residual magnetism to restart. Therefore, when operating to provide electrical power to a load, in the event of a fault condition in the load that causes a voltage sag, the induction generator is isolated from the load to avoid loss of reactive excitation.

[0036] Aspects as disclosed herein enable the use of asynchronous induction generators and asynchronous induction starter / generators in aircraft applications. For example, aspects as disclosed herein advantageously provide an induction starter / generator with a power converter (e.g., inverter / converter / controller) that can maintain the excitation voltage of the starter generator in the event of a fault condition in the electrical load. It is also desirable to reduce the amount and complexity of cooling equipment for the starter / generator. Furthermore, by enabling the use of induction starter / generators (e.g., squirrel cage starter / generators) in aircraft applications, aspects as disclosed herein can also enable the use of a single-pass oil flow through the induction starter / generator (which can achieve more efficient cooling than conventional multi-pass oil flow) without a heat exchanger, using shared oil wet cavity cooling of the induction starter / generator.

[0037] Figure 1 A gas turbine engine 10 having an accessory gearbox (AGB) 12 and an electric motor or generator 14 is shown in accordance with one aspect of the present disclosure. The gas turbine engine 10 may be a turbofan engine, such as the General Electric GEnx or CF6 series engines, commonly used in modern commercial and military aviation, or the gas turbine engine 10 may be various other known gas turbine engines, such as a turboprop engine or a turboshaft engine. The AGB 12 may be coupled to a turbine shaft (not shown) of the gas turbine engine 10 via a mechanical power take-off 16. The type and details of the gas turbine engine 10 are not relevant to the present disclosure and will not be further described herein. Although a generator 14, such as an AC induction generator, is shown and described, aspects of the present disclosure may include any electric motor or generator.

[0038] Figure 2 A non-limiting example generator 14 and its housing 18 are shown in accordance with non-limiting aspects of the present disclosure. The generator 14 may include a clamping interface 20 for clamping the generator 14 to an AGB (not shown). A plurality of electrical connections may be provided on the exterior of the generator 14 to provide for the transmission of electrical power to and from the generator 14. For example, the electrical connections may be further connected to a power converter (e.g., such as a Figure 3) and is then connected to an electrical power distribution node (not shown) of an aircraft having a gas turbine engine 10 to provide power to various items on the aircraft, such as energizing an electrical environmental control system, highly transient electrical loads, electrical de-icing loads, lights, and seatback monitors. In one non-limiting example, further components (e.g., converters, etc.) may be integrated with the generator 14 or may be located remotely, remotely from, or separate from the generator 14. The generator 14 may include a liquid coolant system for cooling or dissipating heat generated by components of or near the generator 14, a non-limiting example of which may be the gas turbine engine 10. For example, the generator 14 may include a liquid cooling system that uses oil as a coolant.

[0039] The liquid cooling system may include a cooling fluid inlet port 82 and a cooling fluid outlet port 84 for controlling the supply of coolant to the generator 14. In one non-limiting example, the cooling fluid inlet and outlet ports 82, 84 may be used to cool at least a portion of the rotor or stator of the generator 14. The liquid cooling system may also include a second coolant outlet port 91, which is shown at a rotatable shaft portion of the generator 14. Although not shown, aspects of the present disclosure may also include other liquid cooling system components, such as a liquid coolant reservoir fluidly coupled to the cooling fluid inlet port 82, the rotatable shaft coolant inlet port, the cooling fluid outlet port 84, or the generator coolant outlet port, and a liquid coolant pump for forcing coolant through the ports 82, 84, or the generator 14. While a liquid cooling system for a dry-cavity generator is shown and described for ease of understanding, aspects of the present disclosure are applicable to any wet-cavity or dry-cavity generator. For example, as discussed in more detail herein, aspects may include a wet-cavity generator, such as a shared-oil wet-cavity generator.

[0040] Figure 3 1 is a block diagram of a power converter system 100 that can be coupled to an electrical load 110 according to non-limiting aspects. The power converter system 100 can include an induction generator 102 electrically coupled to a power converter 101. In non-limiting aspects, the induction generator 102 can be an induction starter / generator. For example, in non-limiting aspects, the induction generator 102 can be an asynchronous induction generator, such as a squirrel-cage induction machine. In some non-limiting aspects, the induction generator 102 can be a wet-cavity machine.

[0041] The power converter 101 may include an inverter / converter / controller (ICC) 104. The ICC 104 may include an AC-DC converter 106, a DC-DC converter 120, a DC-DC gate driver 130, and a controller module 112. In non-limiting aspects, the DC-DC converter 120 may include a semiconductor switching device 121, an inductor 125, a filter capacitor 127, and a freewheeling semiconductor device, such as a freewheeling diode 123. The inductor 125 and the filter capacitor 127 may be arranged to collectively define a choke or an inductor-capacitor (LC) filter 126. In non-limiting aspects, the power converter 101 may include an auxiliary DC power source 108 and a switching device 109.

[0042] As will be discussed in greater detail herein, in non-limiting aspects, the ICC 104 can be configured in a bidirectional topology. In such aspects, the direction of electrical power flow between the induction generator 102 and the electrical load 110 can depend on the operating mode of the system 100. In one example, the bidirectional topology can enable the ICC 104 to selectively receive an AC electrical power input from the induction generator 102 and provide a DC electrical power output to the electrical load 110 in a first operating mode (e.g., a generator mode). In another example, the bidirectional topology can enable the ICC 104 to selectively receive a DC electrical power input from the electrical load 110 and provide an AC electrical power output to the induction generator 102 in a second operating mode (e.g., a starter mode). For simplicity of description, unless otherwise noted, elements of the system 100 will be discussed and labeled herein in the context of the first operating mode, wherein the ICC 104 receives AC electrical power as input from the induction generator 102 and wherein the ICC 104 provides a DC electrical power output to the electrical load 110.

[0043] The AC-DC converter 106 includes a first terminal 107a (e.g., an AC input terminal) and a second terminal 107b (e.g., a DC output terminal). The induction generator 102 can be electrically coupled to the first terminal 107a of the AC-DC converter 106 via a set of generator AC power lines 102a, 102b, 102c to provide an AC voltage Vgen (e.g., a three-phase AC voltage) thereto.

[0044] The AC-DC converter 106 can be electrically coupled to the DC-DC converter 120 at the second end 107b via the first DC power line 106a and the second DC power line 106b to provide the first DC voltage Vcon thereto. For example, in non-limiting aspects, the first DC power line 106a can be a positive DC bus and the second DC power line 106b can be a negative DC bus.

[0045] The DC-DC converter 120 includes a first terminal 128 (e.g., a DC input terminal) and a second terminal 129 (e.g., a DC output terminal). The DC-DC converter 120 is coupled to the second terminal 107b of the AC-DC converter 106. For example, the first terminal 128 of the DC-DC converter 120 can be electrically coupled to the first and second DC power lines 106a, 106b (e.g., a positive DC bus and a negative DC bus, respectively).

[0046] The DC-DC converter 120 can be electrically coupled to the electrical load 110 via a first ICC output line 104a and electrically coupled to a second ICC output line 104b at a second terminal 129 of the DC-DC converter 120. The DC-DC converter 120 can be configured to provide an ICC output current Iout at a second DC voltage Vout to the electrical load 110 via the first ICC output line 104a and the second ICC output line 104b. The second DC voltage output Vout can be defined between the first and second ICC output lines 104a, 104b. For example, in non-limiting aspects, the first ICC output line 104a can be a positive DC bus and the second ICC output line 104b can be a negative DC bus. In non-limiting aspects, the second ICC output line 104b can be coupled to an electrical ground.

[0047] As will be discussed in greater detail herein, in a first operating mode of the DC-DC converter, the first DC output voltage Vcon of the AC-DC converter 106 may be equal to the second DC voltage output Vout of the DC-DC converter 120 , and in a second operating mode of the DC-DC converter, the first DC output voltage Vcon may be greater than the second DC output voltage Vout.

[0048] Auxiliary DC power source 108 is configured to provide a third DC voltage Vaux. In non-limiting aspects, auxiliary DC power source 108 can be, for example, a battery, a supercapacitor, or a DC bus. Auxiliary DC power source 108 can be selectively coupled to second terminal 107b of AC-DC converter 106 via switching device 109. For example, in non-limiting aspects, the output of auxiliary DC power source 108 can be electrically coupled to first DC power line 106a via first auxiliary DC output line 108a, and electrically coupled to second DC power line 106b via second auxiliary DC output line 108b to provide the third DC voltage thereto.

[0049] The controller module 112 may be communicatively coupled to the switching device 109 , the AC-DC converter 106 , and the DC-DC gate driver 130 to control their respective operations. In non-limiting aspects, the auxiliary DC power source 108 may be electrically coupled to the controller module 112 to supply power thereto.

[0050] In non-limiting aspects, the semiconductor switching device 121 can be an N-channel MOSFET, as shown. In non-limiting aspects, the inductor 125 can be electrically coupled in series between the semiconductor switching device 121 and the first ICC output line 104a. For example, one end (e.g., the drain terminal) of the semiconductor switching device 121 can be connected to the first DC power line 106a (e.g., the positive DC bus), and the other end (e.g., the source terminal) of the semiconductor switching device 121 can be connected to the first ICC output line 104a (e.g., the positive DC bus) via the inductor 125. In non-limiting aspects, the inductor 125 can be electrically coupled to the source terminal of the semiconductor switching device 121 at a first end and electrically coupled to the first ICC output line 104a or the electrical load 110 at a second end. The freewheeling diode 123 can be electrically coupled in parallel to the LC filter 126 defined by the inductor 125 and the filter capacitor 127. For example, the freewheeling diode 123 may be electrically coupled to the source terminal of the semiconductor switching device 121 at a cathode terminal and electrically coupled to the second ICC output line 104b or ground at an anode terminal.The filter capacitor 127 may be electrically coupled between the first DC power line 106a and the second DC power line 106b.

[0051] In the illustrated aspect, the induction generator 102 can be a starter / generator. In one non-limiting example, the induction generator 102 can be configured as a generator rated for 47,000 rpm, with a generator speed range of approximately 29,140 rpm to 47,000 rpm. For example, in a non-limiting aspect, the induction generator 102 can be a high-speed, squirrel-cage, hairpin-wound stator, three-phase induction machine configured to provide an AC voltage Vgen of approximately 115 VAC for a 120 VDC system output. In other non-limiting exemplary aspects, the induction generator 102 can be configured to provide an AC voltage Vgen of approximately 230 VAC for a + / - 270 VDC system output during operation as a generator. In other aspects, the induction generator 102 can be configured to provide any output phase voltage without departing from the scope of the present disclosure.

[0052] The ICC 104 may include an AC-DC converter 106 configured to convert the AC voltage Vgen of the induction generator 102 into a first DC voltage Vcon. For example, in non-limiting aspects, the ICC 104 may be configured to convert the AC voltage Vgen to 270 VDC for an output voltage Vout of 270 VDC, or to convert the AC voltage Vgen to 540 VDC for an output voltage Vout of + / - 270 VDC.

[0053] In non-limiting aspects, during operation, the ICC 104 can selectively operate in one of a starter mode and a generator mode. For example, during startup or excitation of the induction generator 102, the ICC 104 can operate in the starter mode. During operation in the starter mode, the AC-DC converter 106 can operate as a DC-AC inverter, thereby allowing electrical power to flow from the electrical load 110 to the induction generator 102. In this case, the second terminal 107b of the AC-DC converter 106 can be an input terminal, and the first terminal 107a can be an output terminal.

[0054] Alternatively, after the induction machine is started (e.g., the induction generator 102 rotates faster than its synchronous speed), the ICC 104 can operate in generator mode. During operation in generator mode, the AC-DC converter 106 can operate as an AC-DC converter, allowing electrical power to flow from the induction generator 102 to the electrical load 110. In this case, the first terminal 107a of the AC-DC converter 106 can be an input terminal, and the second terminal 107b can be an output terminal.

[0055] In various non-limiting aspects, the auxiliary DC power source 108 selectively provides electrical power to the AC-DC converter 106 or the DC-DC converter 120 depending on the operating mode of the ICC 104. For example, as shown, the auxiliary DC power source 108 can be selectively coupled to the first DC power line 106a and the second DC power line 106b at the second terminal 107b of the AC-DC converter 106 and the first terminal 128 of the DC-DC converter.

[0056] Thus, when the ICC 104 operates in the starter mode, the auxiliary DC power source 108 may implement an initial excitation current for the induction generator 102 by providing DC electric power to the AC-DC converter 106 (eg, at the second terminal 107 b ).

[0057] Conversely, when the ICC 104 is operating in generator mode, the auxiliary DC power source 108 can provide DC power to the DC-DC converter 120. For example, in non-limiting aspects, the auxiliary DC power source 108 can be electrically coupled to the DC-DC gate driver 130 to selectively provide control power thereto and control its operation. In other non-limiting aspects, the auxiliary DC power source 108 can additionally or alternatively provide DC power to the DC-DC converter 120 to compensate for any power losses in the AC-DC converter 106.

[0058] Regardless of whether the ICC 104 is operating in startup mode or generator mode, the auxiliary DC power source 108 can also provide DC power to the controller module 112 to power its operation. Additionally or alternatively, in certain non-limiting aspects, when the ICC 104 is operating in generator mode, the output of the AC-DC converter 106 can supply power to the control module 112. Thus, in certain non-limiting aspects, the auxiliary DC power source 108 and the AC-DC converter 106 can be a redundant pair.

[0059] When operating in generator mode, DC-DC converter 120 may operate based on operating conditions in electrical load 110. For example, DC-DC converter 120 may operate based on a "normal," no-fault condition (e.g., no electrical fault in electrical load 110) or a first operating condition, or, in the event of an electrical fault (e.g., a short circuit in the electrical load), DC-DC converter 120 may operate based on a fault or a second operating condition.

[0060] In operation, when the ICC 104 operates in generator mode (e.g., with the induction generator 102 running and the AC-DC converter 106 providing a DC voltage Vcon to the DC-DC converter 120) and the electrical load 110 operates in a "normal" or fault-free state (e.g., no short-circuit fault is present in the electrical load 110), the controller module 112 is configured to control the DC-DC converter 120 based on a first operating condition. In the first operating condition, the controller module 112 controls the operation of the DC / DC gate driver 130 to maintain the semiconductor switching device 121 in a conductive state (e.g., a substantially "constantly on" state), while the freewheeling diode 123 is in a non-conductive state and the inductor 125 is fully charged (e.g., substantially acting as a short circuit). In this first operating condition, the DC-DC converter 120 operates substantially as an LC filter (e.g., via the LC filter 126). Under the first operating condition, the first DC output voltage Vcon (e.g., the input voltage to the DC-DC converter 120 via the first and second DC power lines 106a, 106b) can be equal to the second DC output voltage Vout (e.g., the output voltage of the DC-DC converter 120 at the first and second ICC output lines 104a, 104b).

[0061] When the ICC 104 is operating in generator mode and the electrical load 110 is in a fault state (e.g., a short circuit fault event in the electrical load 110), the controller module 112 can control the DC-DC converter 120 under a second operating condition based on the fault in the electrical load 110. In non-limiting aspects, the DC-DC converter 120 can operate under the second operating condition for a predetermined period of time. It will be appreciated that due to the short circuit fault in the electrical load 110, the second DC output voltage Vout will drop significantly (e.g., from 270 volts DC to approximately 2.7 volts DC). When operating under the second operating condition, the DC-DC converter 120 can operate as a step-down DC buck converter and perform closed-loop control based on the first DC output voltage Vcon of the AC-DC converter 106 (e.g., across the first and second DC power lines 106a, 106b). For example, the controller module 112 can be configured to control the DC-DC gate driver 130 to output a drive signal (e.g., a PWM control signal) to the semiconductor switching device 121 to adjust the duty cycle of the semiconductor switching device 121. The duty cycle of the semiconductor switching device 121 may determine the average DC voltage and / or current applied to the electrical load 110 via the first and second ICC output lines 104 a , 104 b .

[0062] It will be appreciated that the semiconductor switch device 121 may have a relatively low resistance when turned on or conducting, and a relatively high resistance when turned off or non-conducting. When conducting, little power is dissipated in the semiconductor switch device 121. When the semiconductor switch device 121 is turned off (e.g., based on a drive signal from the DC-DC gate driver 130), the freewheeling diode 123 operates to provide a path for the induced current (e.g., from the inductor 125) to flow, thereby preventing a voltage spike across the semiconductor switch device 121 during the turn-off period.

[0063] During operation under the second operating condition, the controller module 112 can control the operation of the DC-DC gate driver 130 to set a predetermined, relatively low duty cycle (e.g., less than 1), and thereby limit the output current Iout of the ICC 104 to a predetermined, relatively low value (e.g., 10% of the output current Iout provided during the first condition immediately prior to the fault) until the short-circuit fault condition in the electrical load 110 is cleared. Thus, when operating under the second operating condition, the DC-DC converter 120 maintains the first DC output voltage Vcon at the output of the AC-DC converter 106 while simultaneously reducing or decreasing the second DC output voltage Vout at the output of the ICC 104. By maintaining the first DC output voltage Vcon at the output of the AC-DC converter 106, the excitation voltage of the induction generator 102 can be maintained. In this sense, the DC-DC converter 120 isolates the AC-DC converter 106 and the induction generator 102 from the sudden voltage drop and relatively large fault current that would otherwise occur, typically associated with a short-circuit fault in the electrical load 110.

[0064] It will be appreciated that the actual duration of the second operating mode (e.g., the duration of the output current lout during operation in the second operating condition) may be limited by various factors, such as the size of the inductor 125 and the total impedance of the electrical load 110. Accordingly, the duration of the second operating condition may be predetermined, for example by selecting the size of the inductor 125, or adjusting the duty cycle of the semiconductor switching device 121, or both, depending on the circumstances, to allow a predetermined amount of time (e.g., 3.4-4.7 seconds) to clear the short circuit fault in the electrical load 110.

[0065] It is contemplated that for short circuit faults lasting longer than a predetermined amount of time (e.g., longer than 4.7 seconds), an automatic disconnect switch (not shown), such as a circuit breaker, may be provided in series between the DC-DC converter 120 and the electrical load to enable automatic fault detection and short circuit protection and coordination of the ICC 104 and the induction generator 102.

[0066] It should be noted that Figure 3 The topology of the DC-DC converter 120 is merely exemplary and is not intended to limit the present disclosure. For example, although Figure 3 The semiconductor freewheeling device is shown and described as a freewheeling diode 123, but is not limited thereto. For example, in other non-limiting aspects, Figure 3The freewheeling diode 123 may be replaced by another semiconductor freewheeling device (such as a MOSFET), wherein one end (e.g., the drain terminal) of the MOSFET is electrically coupled to the source terminal of the semiconductor switching device 121, and the other end (e.g., the source terminal) of the MOSFET is electrically coupled to the second ICC output line 104b or ground. The operation of the MOSFET may be controlled by the controller module 112.

[0067] For ease of description and understanding, Figure 3 The semiconductor switching device 121 is depicted in the exemplary non-limiting aspects as comprising a single semiconductor switching device 121. However, aspects having any number of semiconductor switching devices for the semiconductor switching device 121 are also contemplated. Furthermore, the semiconductor switching device 121 is discussed and described herein as comprising a SiC MOSFET. Other aspects are not so limited, and the ICC 104 may include other types of switching devices. Other non-limiting examples of the semiconductor switching device 121 may include a transistor, a gate commutated thyristor, a FET, a MOSFET, an IGBT, a gate turn-off thyristor, an electrostatic induction transistor, an electrostatic induction thyristor, or a combination thereof. Furthermore, the materials used to form the semiconductor switching device 121 may include, but are not limited to, silicon (Si), germanium (Ge), SiC, gallium nitride (GaN), or a combination thereof.

[0068] As disclosed herein, in the event of a short circuit fault on the electrical load 110, various aspects can electrically isolate the induction generator 102 and the AC-DC converter 106 by maintaining the first DC output voltage Vcon while controllingly reducing the second DC output voltage Vout via operation of the DC-DC converter 120. These aspects can overcome some of the aforementioned shortcomings of synchronous generators (e.g., squirrel cage induction motor / generators) and brushed DC generators and enable asynchronous generators to be used in, for example, aviation applications.

[0069] For example, aspects as disclosed herein advantageously provide a power converter (e.g., inverter / converter / controller) that can maintain the excitation voltage to the starter generator during a fault condition in the electrical load. Aspects as disclosed herein can also reduce the number and complexity of cooling devices for the starter / generator. Furthermore, by enabling the use of squirrel-cage starter / generators in aircraft applications, aspects as disclosed herein can also enable shared oil wet cavity cooling of the squirrel-cage starter / generator using a single-pass oil flow through the inductive starter / generator (which can achieve more efficient cooling than traditional multi-pass oil flow) without the need for a heat exchanger.

[0070] Furthermore, using an asynchronous-type squirrel-cage configuration for induction generator 102 can advantageously eliminate the use of a rotating rectifier, as typically used with synchronous generators. Furthermore, the asynchronous generator induction machine can further eliminate or reduce the varnish or other insulating coating typically used on the rotor windings of synchronous generators and brushed DC generators. The coating typically provided on the motor windings of synchronous generators generally prohibits the use of oil to cool the rotor windings, as the varnish typically contaminates the oil as it circulates along the rotor core and rotor windings. Therefore, using an asynchronous-type squirrel-cage configuration for induction generator 102 can also advantageously enable the motor to utilize a shared oil "wet cavity" cooling system, thereby eliminating the use of an oil sump and reducing the size, weight, and cost of the generator. The shared oil system, "wet cavity" configuration, can reduce or eliminate gearbox oil contamination often experienced in "wet cavity / injection oil cooling" systems, such as when the generator insulation and / or varnish materials age.

[0071] Figure 4 FIG2 is a schematic block diagram of an exemplary generator induction machine 202 and engine accessory gearbox (AGB) 200, with some components omitted for clarity. The generator induction machine 202 and the AGB 200 have a shared oil, wet cavity cooling system. In this shared oil, wet cavity cooling system, cooling oil is shared between the generator induction machine 202 and the AGB 200. A one-way oil passage 225 is indicated by a series of solid lines, with arrows indicating the direction of oil flow. An oil injection 266 portion of the one-way oil passage 225 is indicated by dashed lines, with arrows indicating the direction of the oil injection 266. The one-way oil passage 225 is in fluid communication with the AGB 200.

[0072] Generator induction machine 202 can be fluidically coupled to AGB 200. Generator induction machine 202 can be an asynchronous induction machine and includes a rotor 205 (e.g., a high-speed squirrel cage rotor), a stator 204, and a housing 206. Stator 204 and rotor 205 define a gap 212 therebetween. Rotor 205 and stator 204 can be enclosed within housing 206. Housing 206 is mounted externally to AGB 200. Rotor 205 can include a rotatable hollow shaft 208 that defines a portion of a one-way oil passage 225. Hollow shaft 208 is supported by internal bearings 209 of induction generator 102. One-way oil passage 225 is also in fluid communication with rotor 205 and stator 204.

[0073] Shell 206 may be formed from any known material and method, including but not limited to die casting of a high-strength and lightweight metal such as aluminum, stainless steel, iron, or titanium. Shell 206 may be formed to a thickness that provides mechanical rigidity without adding unnecessary weight to the overall assembly and, therefore, the aircraft.

[0074] The rotatable hollow shaft 208 may be constructed from any known materials and methods, including but not limited to extruding or machining high-strength metal alloys, such as alloys containing aluminum, iron, nickel, chromium, titanium, tungsten, vanadium, or molybdenum.

[0075] The stator 204 remains stationary relative to the rotor 205. The stator 204 can be formed from a steel core laminate that supports a copper magnet wire coil, such as a hairpin wire (not shown). In an exemplary aspect, the coil can be configured to define a fixed number of magnetic poles. In a non-limiting aspect, the rotor 205 can include a steel laminate core that defines a set of circumferentially spaced slots and supports a set of aluminum or copper bars (not shown) disposed within the slots. The hollow shaft 208 is rotatably coupled to a rotatable AGB shaft (not shown).

[0076] In non-limiting aspects, the one-way oil passage 225 includes an oil jacket 226 that at least partially surrounds the outer periphery of the stator 204. In some aspects, the oil jacket 226 may be integrally formed with the housing 206. The oil jacket 226 may define cooling channels or passages 304 for the one-way oil to flow through the passage. The passages 304 may extend helically, axially, radially, or any combination thereof. Oil may flow from the passages 304 through the one-way oil passage 225 and into the hollow shaft 208. The rotatable hollow shaft 208 may further define a bore (not shown) extending radially therethrough. Oil may flow from the rotatable hollow shaft 208 through the bores and be ejected radially outward onto the end turns of the rotor 205 and stator 204 (e.g., at the axial ends of the generator inductor 202). The oil may further be ejected outward from the rotatable hollow shaft 208 onto the internal bearing 209. The ejected oil may be collected in the passages 304 and returned to the AGB 200. Oil flow is shared between the AGB 200 and the generator induction machine 202 via oil fittings 308 and 310, which fluidly couple the AGB 200 and the induction generator 102. In this way, heat generated in the generator induction machine 202 is removed by oil (not shown) through convection and conduction to the AGB 200. The shared oil wet cavity cooling system with the one-way oil circuit 225 eliminates the need for large oil sumps or reservoirs, dedicated heat exchangers, or oil pumps typically used in conventional shared oil systems. Furthermore, because the asynchronous squirrel-cage generator induction machine 202 does not have floating rectifiers or varnished rotor windings, as is typical in synchronous generator induction machines, during operation, oil flowing through the one-way oil circuit 225 does not encounter rotating rectifiers or any insulating coatings (e.g., varnish) that could cause oil degradation.

[0077] In addition to the embodiments and configurations shown in the above figures, many other possible embodiments and configurations are contemplated by the present disclosure. Furthermore, the design and placement of various components (such as the starter / generator, power converter, AGB, or components thereof) can be rearranged so that many different inline configurations can be achieved.

[0078] To the extent not already described, the various features and configurations of each aspect may be used in combination with one another. The fact that a feature may not be shown in all aspects does not mean it cannot be shown, but rather serves the purpose of simplicity of description. Thus, various features from different aspects may be mixed and matched to form new aspects, whether or not the new aspects are explicitly described. Any combination or permutation of the features described herein is encompassed by this disclosure.

[0079] This written description uses examples to disclose aspects of the present disclosure, including the best mode, and to enable any person skilled in the art to practice aspects of the present disclosure, including making and using any devices or systems and performing any incorporated methods. The features disclosed in the foregoing description or drawings may be material for implementing the present disclosure in its various forms, either alone or in any combination. The various features, aspects, and advantages of the present disclosure may also be embodied in any arrangement of the aspects of the present disclosure, including but not limited to the following technical solutions as defined in the enumerated aspects:

[0080] A power converter electrically connectable between an induction generator and an electrical load, the power converter comprising: an inverter / converter / controller (ICC) electrically connectable to the induction generator, the ICC comprising: an AC-DC converter electrically connected to the induction generator at a first end to receive an AC voltage therefrom and configured to output a first DC voltage at a second end; a DC-DC converter electrically connected to a second end of the AC-DC converter via a first DC power line and a second DC power line to receive a first DC voltage therefrom, the DC-DC converter electrically connectable to the electrical load via a first DC output line and a second DC output line to provide a second DC voltage thereto, the DC-DC converter comprising: a semiconductor switching device electrically connected to the first DC power line; and an inductor electrically connected in series between the semiconductor switching device and the first DC output line; and A controller module is communicatively coupled to the DC-DC converter and configured to control operation of the semiconductor switching device; wherein, under a first operating condition, the semiconductor switching device is configured to operate with a duty cycle substantially equal to 1; and wherein, under a second operating condition, in response to a short circuit fault in the electrical load, the semiconductor switching device is configured to operate with a duty cycle less than 1.

[0081] A power converter according to any preceding clause, further comprising a capacitor coupling the first DC output line and the second DC output line, and wherein during operation under the first operating condition, the inductor and the capacitor define a choke.

[0082] A power converter according to any preceding clause, further comprising a freewheeling semiconductor device electrically coupled between the semiconductor switching device and the second DC output line.

[0083] A power converter according to any preceding clause, wherein the freewheeling semiconductor device is a diode electrically coupled to the semiconductor switching device at a cathode terminal and to the second DC output line at an anode terminal.

[0084] A power converter according to any preceding clause, further comprising an auxiliary DC power source selectively electrically coupled to the first DC power line and the second DC power line.

[0085] A power converter according to any preceding clause, wherein, in the first operating condition, the semiconductor switching device is configured to operate in a constant on-state.

[0086] A power converter according to any preceding clause, wherein, in the second operating condition, the DC-DC converter is further configured to operate as a DC buck converter.

[0087] A power converter according to any preceding clause, wherein the DC-DC converter is configured to operate in the second operating condition for a predetermined period of time.

[0088] A power converter according to any preceding clause, wherein, in the first operating condition, the first DC voltage is substantially equal to the second DC voltage.

[0089] A power converter according to any preceding clause, wherein, in the second operating condition, the first DC voltage is greater than the second DC voltage.

[0090] A power converter according to any preceding clause, wherein the controller module is further communicatively coupled to the AC-DC converter and configured to control operation thereof.

[0091] A power converter according to any preceding clause, wherein the ICC is arranged in a bidirectional topology.

[0092] A power converter system electrically connectable to an electrical load, the system comprising: an asynchronous induction generator; an ICC electrically connected to the asynchronous induction generator, the ICC comprising: an AC-DC converter electrically connected to the asynchronous induction generator at a first end to receive an AC voltage therefrom and configured to output a first DC voltage at a second end; a DC-DC converter electrically connected to a second end of the AC-DC converter via a first DC power line and a second DC power line to receive a first DC voltage therefrom, the DC-DC converter being electrically connectable to the electrical load via a first DC output line and a second DC output line to provide a second DC voltage thereto, The invention comprises: a semiconductor switching device electrically connected to a first DC power line; a freewheeling semiconductor device electrically connected between the semiconductor switching device and a second DC output line; and an inductor electrically connected to the semiconductor switching device at a first end and electrically connected to the first DC output line at a second end; a controller module communicatively connected to the DC-DC converter and configured to control the operation of the semiconductor switching device; wherein, under a first operating condition, the semiconductor switching device is configured to operate with a duty cycle substantially equal to 1; and wherein, under a second operating condition, in response to a short circuit fault in the electrical load, the semiconductor switching device is configured to operate with a duty cycle less than 1.

[0093] A power converter system according to any preceding clause, further comprising an auxiliary DC power source selectively electrically coupled to the first DC power line and the second DC power line.

[0094] A power converter system according to any preceding clause, wherein the asynchronous induction generator is a squirrel cage induction machine.

[0095] A power converter system according to any preceding clause, wherein the asynchronous induction generator is arranged as a starter / generator having a starter mode of operation and a generator mode of operation.

[0096] A power converter system according to any preceding clause, wherein the asynchronous induction generator is a wet cavity machine.

[0097] A power converter according to any preceding clause, wherein the asynchronous induction generator is fluidly coupled to an accessory gearbox (AGB).

[0098] A power converter system according to any preceding clause, wherein the asynchronous induction generator receives oil flow from the AGB.

[0099] A power converter system according to any preceding clause, wherein the asynchronous induction generator comprises a stator, a rotor, and further defines a one-way oil path therethrough in fluid communication with the rotor and the stator.

Claims

1. A power converter electrically connectable between an induction generator and an electrical load, the power converter comprising: an inverter / converter / controller (ICC) electrically couplable to the induction generator, the ICC comprising: an AC-DC converter electrically coupled to the induction generator at a first end to receive an AC voltage therefrom and configured to output a first DC voltage at a second end; a DC-DC converter electrically coupled to the second end of the AC-DC converter via a first DC power line and a second DC power line to receive the first DC voltage therefrom, the DC-DC converter being electrically coupled to the electrical load via a first DC output line and a second DC output line to provide a second DC voltage thereto, the DC-DC converter comprising: a semiconductor switching device electrically coupled to the first DC power line; and an inductor electrically coupled in series between the semiconductor switching device and the first DC output line; and a controller module communicatively coupled to the DC-DC converter and configured to control operation of the semiconductor switching device; wherein, in a first operating condition, the semiconductor switching device is configured to operate with a duty cycle substantially equal to 1; and Wherein, under a second operating condition, in response to a short circuit fault in the electrical load, the semiconductor switching device is configured to operate with a duty cycle less than 1.

2. The power converter according to claim 1, further comprising a capacitor coupling the first DC output line and the second DC output line, and wherein During operation under the first operating condition, the inductor and capacitor define a choke. 3 . The power converter of claim 1 , further comprising a freewheeling semiconductor device electrically coupled between the semiconductor switching device and the second DC output line. 4 . The power converter of claim 1 , further comprising an auxiliary DC power source selectively electrically coupled to the first DC power line and the second DC power line.

5. The power converter according to claim 1, wherein In the first operating condition, the semiconductor switching device is configured to operate in a constant on-state.

6. The power converter according to claim 1, wherein In the first operating condition, the first DC voltage is substantially equal to the second DC voltage; and wherein in the second operating condition, the first DC voltage is greater than the second DC voltage.

7. A power converter system electrically connectable to an electrical load, the system comprising: asynchronous induction generators; an ICC electrically coupled to the asynchronous induction generator, the ICC comprising: an AC-DC converter electrically coupled to the asynchronous induction generator at a first end to receive an AC voltage therefrom and configured to output a first DC voltage at a second end; a DC-DC converter electrically coupled to the second end of the AC-DC converter via a first DC power line and a second DC power line to receive the first DC voltage therefrom, the DC-DC converter being electrically coupled to the electrical load via a first DC output line and a second DC output line to provide a second DC voltage thereto, the DC-DC converter comprising: a semiconductor switching device electrically coupled to the first DC power line; a freewheeling semiconductor device electrically coupled between the semiconductor switching device and the second DC output line; and an inductor electrically coupled to the semiconductor switching device at a first end, and electrically coupled at a second end to the first DC output line; a controller module communicatively coupled to the DC-DC converter and configured to control operation of the semiconductor switching device; wherein, in a first operating condition, the semiconductor switching device is configured to operate with a duty cycle substantially equal to 1; and Wherein, under a second operating condition, in response to a short circuit fault in the electrical load, the semiconductor switching device is configured to operate with a duty cycle less than 1. 8 . The power converter system of claim 7 , further comprising an auxiliary DC power source selectively electrically coupled to the first DC power line and the second DC power line.

9. The power converter system according to claim 7, wherein: The asynchronous induction generator is fluidly coupled to an accessory gearbox (AGB) to receive an oil flow therefrom.

10. The power converter system according to claim 9, wherein: The asynchronous induction generator includes a stator and a rotor, and further defines a one-way oil path therethrough in fluid communication with the rotor and the stator.

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