A lightweight, highly efficient, and energy-dense hybrid power system for reliable electric flight.

Abstract

Number of phases N phase A lightweight, energy dense, and highly efficient hybrid power system (200) for an electric aircraft (99) includes a prime mover internal combustion engine or gas turbine (300) coupled to a self-cooled, multi-phase, axial-flux, dual Halbach array motor / alternator (306) having a N pha The motor / alternator and regenerative power conversion drive have a neutral connection.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority to U.S. Provisional Patent Application No. 63124236, filed December 11, 2020, entitled "LIGHTWEIGHT, HIGH-EFFICIENCY, ENERGY-DENSE HYBRID POWER SYSTEM FOR RELIABLE ELECTRIC FLIGHT," and U.S. Patent Application No. 17209900, filed March 23, 2021, entitled "LIGHTWEIGHT, HIGH-EFFICIENCY, ENERGY-DENSE HYBRID POWER SYSTEM FOR RELIABLE ELECTRIC FLIGHT," both of which have a common assignee with this application, and their disclosures are incorporated herein by reference.

[0002] background field The implementation disclosed herein relates to a power source for electric propulsion urban air mobility (UAM) vehicles and unmanned aerial vehicles (UAVs) that is energy-density, power-density, efficient, reliable, and supplies power to electric motors driving rotors and propellers, thereby generating lift and / or thrust by a bus voltage less responsive to bus current, with the bus having low voltage and current ripple. More specifically, an engine or other prime mover is configured to power a motor / alternator, and a regenerative power conversion drive unit ("Regenerative Drive Unit") is coupled to the motor / alternator to convert mechanical power into electrical power in the vehicle's power bus. The Regenerative Drive Unit also operates in reverse to power the motor / alternator to start the engine. [Background technology]

[0003] Related technologies Electric propulsion is exciting for aircraft because electric motors can have far higher power / kg than piston or turbine engines, and these electric motors scale up and down more easily than such heat engines. This means that electric propulsion units can be placed in aerodynamically advantageous locations on multirotor aircraft, such as at the wingtips or the ends of the "arms" (often referred to in the industry as "distributed electric propulsion"). However, compared to conventional liquid fuels, electric energy storage batteries are heavy and bulky. This means that the electric propulsion concept is unsuitable for any long-duration flight (which requires a lot of energy) due to the weight and bulk of the batteries.

[0004] Because conventional hybrid electric propulsion has been used to convert very high-energy-density liquid fuels into electrical energy, “distributed electric propulsion” can be combined with high-energy-density liquid fuel energy storage batteries. In such a system, a turbine or piston internal combustion engine ("ICE") converts the liquid fuel into mechanical energy, which is then converted into electrical energy by a motor / alternator and power electronics. However, the mass and not-so-important efficiency of the engine, generator and electronics in the energy conversion chain can make the system very heavy, and the vehicle does not have the capacity to carry enough fuel for very long flights.

[0005] Furthermore, as those skilled in the art will recognize, motors / alternators and power electronics are manufactured to be smaller and lighter, resulting in smaller thermal mass and surface area, making the removal of waste heat from them a limited challenge. These components handle a great deal of power, and even small, high-power motors / alternators can quickly overheat with a further 5% or 2% loss. Typical prior art solutions for cooling involve bolting large heat sinks and cooling fins and placing the system in a high-speed airflow to remove waste heat. In some prior art systems, the thermal management of motors and power electronics can account for roughly 50% of the mass of these systems. Adding heat sink fins to a motor and then placing the motor (or generator) in a high-speed airflow adds "cooling drag" to an aircraft, which also increases the aircraft's power and energy demands, and the weight of the fuel further reduces energy density, lift, and range. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Therefore, it is desirable to overcome these limitations in the field of technology. [Means for solving the problem]

[0007] Summary of the Invention The implementation of this specification involves a DC power bus with N phase With the phases connected, the multiphase regenerative drive unit N phase This provides a lightweight, energy-density, and highly efficient hybrid power system for electric aircraft, featuring a prime mover coupled to a self-cooled, multiphase axial-flux dual Halbach array motor / alternator with connected phases. The battery is connected to a DC power bus. A battery management system is operably connected to the battery. A system control unit is operably connected to the prime mover, battery management system, and multiphase regenerative drive unit.

[0008] In the example implementation, the prime mover is either an internal combustion engine or a gas turbine.

[0009] In further exemplary implementations, N phase It is 3 or greater.

[0010] In an alternative exemplary implementation, N phase It is 6 or greater.

[0011] Further understanding of the implementation of this disclosure is provided by the following detailed description, along with the relevant drawings. [Brief explanation of the drawing]

[0012] Brief explanation of the drawing [Figure 1A] This figure shows an aircraft using an implementation of the present disclosure, configured for takeoff and hovering. [Figure 1B] This figure shows an aircraft using an implementation of the present disclosure, configured for cruising flight. [Figure 2A] This is a diagram showing a cut-out aircraft to disclose an exemplary hybrid power system. [Figure 2B] This is a detailed description of an exemplary hybrid power system within the aircraft. [Figure 3A] This is an example of an implementation configuration with a piston engine as an internal combustion engine (ICE), and an exploded view of its components. [Figure 3B] This graph displays an exemplary performance curve for a four-stroke embodiment of an ICE (Integrated Core Emissions) engine. [Figure 4A] This is a front view of a multiphase dual Halbach array axial gap motor / alternator. [Figure 4B] This is a side view of a multiphase dual Halbach array axial gap motor / alternator. [Figure 5] This is a side view of an exploded motor alternator. [Figure 6A] This is a schematic axial cross-sectional view of half of the motor / alternator shaft, along the axis of symmetry at its center (radial dimensions are compressed to show the extent of all components). [Figure 6B] This is a segment of the circumferential cross-section taken along AA in Figure 6A, clearly indicated in the axial and tangential (tan) directions. [Figure 7A] This is a detailed diagram of wound phase conductors for a three-phase motor / alternator, showing only the arc segments of the windings. [Figure 7B] This shows wound phase conductors for a six-phase motor / alternator, with only the arc segments of the windings shown. [Figure 8] This is a cross-sectional view of the crankshaft of a piston engine, including a motor / alternator and an ICE (Internal Combustion Engine). [Figure 9] This is a functional block diagram of an exemplary implementation, illustrating important connections and interactions. [Figure 10] This is a schematic diagram of the regenerative drive unit for a three-phase motor / alternator. [Figure 11] This is a schematic diagram of an additional half-bridge connected via a conductor to the neutral point of a wired three-phase motor / alternator. [Figure 12] This block diagram shows the control of a MOSFET power bridge for a three-phase regenerative drive unit. [Figure 13] Figure 12 is a detailed diagram of a schematic current control device. [Figure 14] This diagram shows the SVPWM timing block. [Figure 15A] This graph displays the current waveforms related to phase U of the motor / alternator in motor mode and alternator mode / SVPWM sub-mode. [Figure 15B] This graph displays the current waveforms of each phase in alternator mode / synchronous rectifier submode. [Figure 16A] This diagram shows an exemplary six-phase motor / alternator consisting of two three-phase wire connections connected to a regenerative drive unit. [Figure 16B]As shown in Figure 11, this figure illustrates an alternative embodiment comprising two separate regenerative drive units, where additional redundancy is achieved by connecting the neutral point to an additional half-bridge within the regenerative drive unit. [Figure 17] This diagram shows another redundant system where five phases are driven independently. [Figure 18] This is a schematic diagram of the details of the second regenerative drive unit, which is combined with the circuit in Figure 10. [Figure 19] When two power bridges are connected at terminals P+ and P-, the currents Icap in Figure 10 and Figure 18 are...

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[0013] Detailed description of the invention The implementation disclosed herein provides a reliable, lightweight, compact, high-energy-density, and highly efficient hybrid power system for electric aircraft, which in broad terms comprises a self-cooled multiphase axial-flux dual Halbach array electric motor / alternator (where the number of phases is N). phase This includes a "prime mover" (internal combustion engine or gas turbine) coupled to (3 or more) a motor / alternator. phase It is connected to a regenerative drive unit having phases, which is then connected to a DC power bus, battery, battery management system, and system control unit.

[0014] More specifically, in an exemplary implementation, a dual Halbach array motor / alternator mounted on the prime mover is drawn into the rotor-stator gap and cooled by air supplied through the motor / alternator and across the windings using centrifugal force. Therefore, the prime mover can be mounted inside the vehicle, and the motor / alternator cools itself with the drawn-in air. Only a low-drag "NACA" inlet needs to be located on the exterior of the aircraft to ensure air exchange with the internal volume for heat dissipation. Because the motor / alternator, as part of its operation, provides the high-speed airflow necessary for good convection and cooling, additional heat sinks or cooling fins or water-cooled jackets and heat exchangers are not required.

[0015] The implementation of this disclosure is well-suited as an ICE implementation for integration with piston engines. Piston engines generate large torque pulses during the power stroke, and often a large (heavy) flywheel is added to the engine to smooth out the output torque. In aircraft, heavy flywheels are not an option, so whatever is attached to the engine output must be able to withstand the torque fluctuations of the power stroke. The peak torque from a piston engine can be 15 times the engine's average torque output. This means that the torsional strength of the motor / alternator structure must be designed to be 15 times greater than the required nominal average power output torque. The axial flux machine disclosed herein includes a substantially flat disk that is extremely torsion-resistant, so there is virtually no weight penalty to have sufficient strength to handle the pulses of the engine's power stroke.

[0016] Aircraft also have far higher reliability requirements than automobiles. If a car engine fails, the driver can simply pull over to the side of the road. Aircraft do not have this option and are forced to land in a field. And if an electric VTOL aircraft hovering is powered and fails while in "powered-lift" flight mode, it will instantly fall straight to the ground, and most of these aircraft cannot "rotate" as helicopters can (and since helicopters require forward speed to rotate, any true vertical flight path is extremely vulnerable to the dangers of power failure). The preferred dual three-phase (i.e., six-phase) configuration used in exemplary axial flux motors / alternators provides some redundancy. If one winding fails, the other winding still supplies power, although at a lower rating than the entire six-phase motor / alternator. If one of the three-phase windings fails, the aircraft may still have enough power available to land safely, although the available surplus power will decrease and the flight envelope will be reduced.

[0017] Applying the same redundancy to power electronics can present reliability challenges due to the large number of components and complexity. For example, N phaseIf the value is equal to 6, then six-phase electronics are constructed as two independent three-phase systems. Therefore, a failure in one of the three-phase systems does not prevent the other system from continuing to function and supplying partial power to the aircraft.

[0018] Six-phase (12 pulses after rectification) means that the inherent ripple current that occurs during the conversion between the AC alternator and the DC bus is further reduced than in the case of conventional three-phase (6-pulse) power conversion. The reduction in ripple current allows for the use of smaller (and importantly, lighter) bus capacitors (which can account for 25% of the weight of the power conversion electronics), and also significantly reduces the power filtering section for the DC bus, which is another considerable source of mass in the power conversion system.

[0019] 12-pulse conversion, known in the aerospace industry, is generally achieved by using a three-phase alternator (typically a magnetic winding machine rather than a permanent magnet machine as used in exemplary implementations) connected to a heavy "transformer rectifier unit" ("TRU"), which features a phase transformer (heavy electrical steel and copper) with wye and delta windings in the transformer, thereby creating a second set of three phases that are phase-shifted from the original three phases—creating a "six-phase" output which is then rectified. This conversion in the aerospace industry is also only unidirectional in the power generation direction, and not bidirectional as in exemplary implementations where the motor / alternator is also used as a motor for starting. The axial flux winding design allows all six phases to be produced directly from the motor / alternator without any electromagnetic design penalties. Other more common motor / alternators suffer significant penalties in the selection of pole / tooth / slot combinations to produce six phases directly from the motor / alternator.

[0020] As a result, exemplary implementations significantly increase the aircraft's range and capacity while also enhancing reliability and improving safety.

[0021] Complex system designs, such as hybrid power plants for electric aircraft, address a range of system requirements, and the disclosed implementations meet the needs of the system requirements through novel arrangements of component features and the novelty of the components themselves. Various combinations of component features and combinations are optimal depending on the vehicle's mission. Hovering-only aircraft require a relatively consistent average power level throughout all flight phases, while transitional vehicles that switch from hovering to fixed-wing flight may have constant power requirements that vary over a range of four or more. Hovering aircraft have only a small battery pack for "electric fuel backup" to safely land in case of engine failure, and the pack is kept nearly fully charged during flight. Transitional aircraft may have a larger pack used to support high constant power during the takeoff and hovering phases of flight, and the pack may be deeply discharged during the full-length hovering flight phase.

[0022] Hovering vehicles likely operate their prime movers at constant near-peak power and maximum rotational speed to achieve the best power density, while transitional vehicles likely operate their prime movers at less power and lower rotational speed to achieve the best fuel efficiency from the prime mover during times such as cruising. Key system requirements that repeatedly appear in hybrid powerplant designs are the demands for energy density, power density, efficiency, reliability, and power quality (constant bus voltage and low current and voltage ripple). Energy density is a critical feature for long-range missions, as energy needs to be supplied over relatively long periods while vehicle weight is minimized. Hybrid powerplants provide energy density by using liquid fuel as the primary energy source. Power density is a critical feature required for takeoff and emergency maneuvers, where peak power needs to be supplied while weight is minimized. Hybrid powerplants provide power density by including batteries that can store electrical energy and supply it for short periods during takeoff.

[0023] Efficiency is important because it contributes to energy density and power density. Efficiency is also important to minimize thermal stress on components, as inefficiency in components generates heat, which needs to be transferred from the vehicle, which has a cooling system contributing to mass. Reliability is an essential characteristic because loss of power can lead to loss of life, cargo, and the vehicle, which is unacceptable. Power quality contributes to reliable control of the vehicle propulsion system following thrust commands. Furthermore, noise and disturbances in the power bus can cause failures in sensitive components.

[0024] Figure 1A shows an exemplary conventional aircraft such as the NASA GL-10 electric vertical takeoff and landing (eVTOL) aircraft.99 The GL-10 is a transitional eVTOL having a takeoff and hovering configuration100 and a cruising configuration150 shown in Figure 1B.Figure 1A shows a nacelle130 containing lift rotors / propellers such as 120 and electric motors that drive the rotors / propellers.The GL-10 has a total of 10 rotors / propellers.The fuselage110 is connected to the wings112, horizontal stabilizers114 and vertical stabilizers116.The wings, horizontal stabilizers and vertical stabilizers are designed primarily for use in the cruising configuration150.In cruising, six of the 10 rotors / propellers are in a retracted configuration such as 122.Fixed-wing operation efficiently generates lift, thus requiring fewer rotors / propellers, and drag is reduced by retracting the unnecessary rotors / propellers. The fuselage 110 includes a hybrid power plant and one or more crew and passengers, baggage, cargo and navigation equipment, as well as other objects and equipment. The implementations disclosed herein can be applied to such electric aircraft and other vehicles, supplying them with electrical power. There are various forms of electric aircraft, such as fixed-wing electric aircraft, transitional electric aircraft, electric helicopters, quadrotors and multirotors. The implementations of this disclosure are applicable to all types of electric aircraft.

[0025] Figures 2A and 2b show two exemplary hybrid power systems 200 positioned on the fuselage of an electric aircraft 99 in cruising configuration 150. A transversely oriented hybrid power system 200 is shown as an example, while a longitudinal orientation may be applied in alternative configurations. While two hybrid power plants within a single aircraft provide additional redundancy and improve safety, it should be emphasized that a single hybrid power system is sufficient for these purposes.

[0026] Figure 3A shows an exemplary configuration and an exploded view of its components. The relative positions of the components are shown spread out for illustrative purposes, as the components are more densely packed in the aircraft. An exemplary component is the prime mover, in the exemplary configuration, a liquid-cooled internal combustion engine (ICE) 300, which draws fuel from a fuel tank 302 via a fuel path 304. The illustrated embodiment is a two-cylinder, two-stroke piston engine with a separate oil supply unit 305. A four-stroke engine or gas turbine is an alternative prime mover for the ICE. A motor / alternator 306 is mounted on the crankshaft of the ICE 300. (As used herein, the term motor / alternator is defined as a single electromechanical unit capable of operating as a motor in motor mode or as an alternator in alternator mode). Engine exhaust flows through an exhaust manifold 307 to a muffler 308, and then to the engine exhaust section, which is not shown in the diagram in Figure 3A. An intake filter 312 and a pair of electronically controlled carburetors 310 are also shown. Engine coolant flows through pipe 314 and through radiator 316, and the radiator transfers waste heat to the ambient air flowing through it due to the movement of the vehicle or due to fan 323. Coolant bottle 315 stores the coolant, and the coolant may overflow due to thermal expansion of the coolant in the system.

[0027] The engine control system for the hybrid powertrain can be enhanced by various types of sensors, as known in the art of engine control, including sensors for mass flow, cylinder head temperature, intake air temperature, coolant temperature, exhaust gas temperature, and combustion chamber pressure or combustion chamber temperature. The carburetor can be replaced with a fuel oil injection system in the ICE.

[0028] Electrical power to and from the motor / alternator 306 is transferred to the electronics unit 318 through terminal connection 317. Additional signal cables (not shown) may include signal cables for the axial angle or electrical angle of the motor / alternator 306. The electronics unit 318 includes regenerative drive electronics and manages the power flow to and from the motor / alternator and system control unit. The electronics unit 318 is connected to a DC bus 319, which in turn connects to the battery 320 and the propulsion motor contained in the nacelle 130 shown in Figure 1A. A battery management system (BMS) 322 is connected to the battery 320.

[0029] Figure 3B shows an exemplary performance curve for a four-stroke piston embodiment of the ICE 300. Similar performance curves exist for two-stroke and gas turbine engines. The peak fuel efficiency curve 350 defines the optimal operating torque at each engine speed. The peak fuel efficiency point 360 is optimal across all engine speeds and gives the minimum net fuel consumption rate (BSFC), which is frequently measured in units of lb / hp-hr or gm / kW-hr. Figure 3B also shows torque-velocity curves for various throttle angles, including the wide-open throttle (WOT) curve 365. The peak power point 370 occurs on the WOT curve. Constant power curves, such as the 100 hp curve 375 and the 0.493 lb / hp-hr (300 gm / kW-hr) curve 380, are also shown. These curves are important for determining optimal prime mover control for both efficiency and power output.

[0030] Figures 4A and 4B show an exemplary motor / alternator 306 of the implementation of the present disclosure, which is a multiphase dual Halbach array axial gap motor / alternator. This motor / alternator is iron-free and eliminates the hysteresis and eddy current losses that occur in iron-core motor / alternators, making it suitable for high-speed, high-power-density applications. The structure of such motor / alternators and their components is described in U.S. Patents 10,574,110 and 10,141,822, which are incorporated herein by reference to their entirety. The stator ring 404 is mounted on the stator winding 500 (shown in Figure 5). The front motor rotor 406 is made of titanium or other non-magnetic structural material and supports the front rotor magnets 407A that form a Halbach array. In the illustrated embodiment, there are six magnets per magnetic cycle, which is equivalent to six magnets per pole pair, i.e., three magnets per pole. Each magnetic pole is supported by three magnets within pockets of the illustrated titanium rotor. The number of magnets per cycle can be any integer greater than or equal to four, and preferably an even integer. Continuous rotational magnetization direction is also possible, as described in J Mallinson, “One-sided fluxes—a magnetic curiosity?”; IEEE Transactions on Magnetics, 9(4):678-682, 1973. An improved magnetization method is required to achieve continuous rotational magnetization direction. Power connector 402, stator support 408, and motor / alternator mounting 410 are also shown.

[0031] Figure 5 shows additional details of the motor / alternator 306, specifically the rear rotor 502 and the self-supporting stator winding 500 attached to the stator ring 404. The front and rear rotors 406 and 502 are fastened together with bolts 504.

[0032] Figures 6A and 6B show further details of the Halbach arrays 407A and 407B of the motor / alternator and the winding configuration for an exemplary three-phase motor / alternator 306. This is for illustrative purposes only, and the claims herein define a three-phase motor / alternator with a number of phases equal to 3. phase This is not limited to multiphase machines. Figure 6A shows a half of the axial cross-section symmetrical around axis 600 at the center of the engine shaft 601. The motor / alternator 306 is self-cooled as air is naturally drawn in through the cooling port 610, creating a flow 612 in the axial gap of the motor. Such a cooling system is lightweight and reliable and contributes to the overall system performance in these respects. Figure 6B is a segment of the peripheral cross-section taken along AA in Figure 6A, showing the axial and tangential (tan) directions. The position of the motor rotor in Figure 6B is such that the axial magnetic field is highest at the phase winding U incorporating the conductor segments 602, 603 and 604. Phases V and W are indicated by letters, where V' and W' indicate that the positive current flow is in the direction away from the plane of the paper, and V and W without prime symbols indicate that the positive current flow is in the direction towards the plane of the paper. The Halbach array focuses the magnetic field in the gap between the Halbach arrays (the front rotor magnet 407A and rear rotor magnet 407B are supported within the front motor rotor 406 and rear motor rotor 502, respectively) in a near-optimal manner, contributing to the power density of the motor / alternator and the entire hybrid power system. The circle surrounding the "X" in 602 indicates that the positive current flow in phase U is directed toward the plane of the paper and toward the engine shaft 601. The circle surrounding the "·" in 603 indicates that the positive current flow in phase U is directed toward the plane of the paper and toward the engine shaft 601. In this embodiment, the Halbach array, front rotor magnet 407A, and rear rotor magnet 407B have six magnets per cycle 606.

[0033] Figure 7A shows further details of the wound phase conductors. Only the arc segments of the winding around the winding center 704 are shown, and the snake-like winding pattern continues along the circle having arc segments 706 and 708 to form the entire annular ring with the phase terminals. The winding center 704 and conductor segment 602 are shown in axial view, rather than radial view in Figure 6A. For phase winding U, the outer end turns 700U and 701U are shown, and the inner end turn 702U is shown. The outer end turns 700B and 701B of phase V are shown, the outer end turns 700W and 701W of phase W are shown, and the inner end turns of phases V and W are shown without reference numerals. The phase conductors are preferably Litz wires to minimize eddy current losses in the windings.

[0034] Figure 7B shows wound phase conductors for a six-phase motor / alternator. Only the arc segments of the windings are shown, and the snake-like winding pattern follows along a circle having arc segments 750 and 760 and a center 770. The segments of the six phases U, V, W, X, Y, and Z are shown, with the larger segment of phase U shown in part by a dashed curve 752. Each phase has terminals for connection to the regenerative drive unit. There are a wide range of winding patterns different from those in Figures 7A and 7B, which may be designed by those skilled in the art of motor design. An important feature required for high reliability is that each point on the phase winding is not close to any other point on the same phase winding, as achieved in the snake-like pattern.

[0035] The snake-like winding pattern ensures that there is no overlap of the phase windings themselves, and thus there is no risk of phase self-short circuits, also known as inter-turning section short circuits. Such short circuits can occur in other prior art winding designs and can be catastrophic in aircraft. In snake-like windings, inter-phase short circuits can occur, but they can be protected in a y-connection with fuses in each phase. Snake-like windings are a significant advantage of the present invention in terms of safety and reliability. Snake-like windings with virtually any number of phases can be constructed and used in this type of motor within the teaching of the implementation embodiments of this disclosure.

[0036] Similarly, in alternative embodiments where high winding reliability is not required, for example, multiple layers of windings 7A may be stacked on top of each other. Multiple layers of windings 7B may also be stacked on top of each other. Various winding geometric shapes can be used, as is known in the art of motor design.

[0037] Figure 8 is a cross-sectional view of a motor / alternator 306 equipped with a piston engine as ICE 300 and a crankshaft 800 terminating on an engine shaft 601 engaged with the motor / alternator. A main bearing 802 and a crankpin 804 engaged with the crankshaft 800 are shown on the crankshaft 800. The axial-gap multiphase motor / alternator 306 provides mechanical robustness, simplicity, and weight reduction when minimizing the cantilever distance 808 from ICE 300. The front motor rotor 406 and rear motor rotor 502 are rotatably supported by the bearing 802 of ICE 300. Therefore, no additional bearings are required within the motor / alternator 306, and the system is more robust against vibration and therefore does not require additional mass, making it more reliable. The hybrid power system of the implementation form of this disclosure is also more compact, and the support structure is lighter. Furthermore, because the Halbach array allows the magnetic field to protrude across relatively large gaps, the motor / alternator gap can be designed to be more robust against mechanical movements 806 that increase due to bearing wear and the accumulation of tolerances, further enhancing safety and reliability. In aircraft, since heavy flywheels are not an option, everything attached to the engine output must be able to withstand the torque fluctuations of the power stroke. The peak torque from a piston engine ICE can be 15 times the engine's average torque output. This means that the torsional strength of the motor / alternator structure must be overdesigned by 15 times the required nominal average power output torque. As shown in Figure 8, the axial flux machine used as the motor / alternator 306 disclosed herein includes motor rotors 406, 502 extending radially from the axis 600 of the engine shaft 601 in a substantially flat disk, which is extremely strong torsion, so there is virtually no weight penalty to have sufficient strength to cope with the pulses of the engine's power stroke. Furthermore, the disc-like configuration of the motor rotors 406 and 502 provides relatively large rotational inertia, which functions as a flywheel tightly coupled to the ICE's crankshaft 800.In other words, the motor / alternator 306 plays a role in reducing rotational vibrations, similar to how the flywheel in a conventional piston engine performs this function.

[0038] Figure 9 shows a functional block diagram of the system and its important connections and interactions. Most of the same components are shown in mechanical form in Figure 3. However, note that the system control unit 318A and the regenerative drive unit 318B are shown separately in this drawing, and both are included in the electronics unit 318 shown in Figure 3. Regarding redundancy, note that the hybrid power system may be configured to have multiple battery packs and multiple "power generation set units" consisting of a BMS system or ICE, a system control unit and a regenerative drive unit, as well as auxiliary equipment. The system control unit may be programmed to communicate and cooperate to meet the system power requirements. All redundant units are connected in parallel on the DC bus.

[0039] In FIG. 9, the fuel tank 302 supplies fuel to the ICE 300 via the fuel path 304. The ICE can be a two-stroke, four-stroke or any type of piston engine, can have any number of cylinders or can be a gas turbine. Mechanical energy is transmitted to the motor / alternator 306 via the engine shaft 601 during operation of the ICE, and the alternator continues to supply power. Mechanical energy is transmitted from the motor / alternator 306 when the ICE 300 is started. The dual Halbach array motor / alternator 306 can have three, five, six or any number of phases in a wye, delta or other interconnected configuration. The motor / alternator power terminals are connected via the terminal connection 317 to the regenerative drive section 318B within the electronics unit 318. Further, the motor / alternator 306 transmits the motor / alternator electrical angle 904 measured by a Hall effect sensor or shaft angle sensor to the regenerative drive section 318B for purposes including commutation by the commutator and calculation of the engine RPM. The regenerative drive section 318B functions as a synchronous rectifier or pulse width modulation (PWM) rectifier during power generation or as a motor drive section during startup of the ICE. In the implementations disclosed herein, space vector pulse width modulation is used. However, in alternative implementations, other PWM methods according to either analog or digital control implementations can be used. The regenerative drive section 318B outputs a positive DC current I alt during power generation, and I alt is negative during startup of the ICE. I alt is summed with the battery current I bat at node 906 to result in the bus current I<​​​​​​​

[0040] BMS 322 calculates SOC, I bat Measurement values ​​and V bus The measured values ​​are transmitted via connection path 916 to the system control unit 318A in the electronics unit 318. The regenerative drive unit 318B also measures the bus voltage for internal use. The BMS 322 incorporates a cell voltage sensing circuit, a battery pack current sensor, and a microprocessor that executes algorithms to estimate the charge state from the cell and pack measurements. The BMS 322 may also include a cell temperature sensor and a pack disconnection relay / switch that can be controlled to disconnect the current path connection from the battery pack output to the DC bus. The system control unit 318A receives the motor / alternator angular velocity in revolutions per minute (RPM) from the regenerative drive unit via connection path 914. alt The system control unit 318A also receives the value of and the desired battery charge state (SOC*). The system control unit 318A then receives the throttle command and the regenerative drive unit current command via the connection path 918.

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[0041] In fault-tolerant embodiments of the hybrid power system implementations of this disclosure, the battery pack and / or regenerative drive unit may have disconnection switches, circuit breakers, or disconnection relays controlled by the system control unit. These disconnection switches may be used to isolate faulty electronics or a defective battery pack that could short-circuit the DC bus. If the battery pack is disconnected from the DC bus due to a fault, the control algorithms of the combined engine, motor / alternator, and regenerative drive unit change from the aforementioned power and current control schemes, based on the same overall control scheme using feedforward maps and feedback loops for prime mover speed and DC bus voltage, to an algorithm that adjusts the bus voltage to a constant command value.

[0042] Figure 10 is a schematic diagram of the regenerative drive unit 318B for a three-phase motor / alternator. The regenerative drive unit 318B is connected to the DC bus 319 at terminals + and -, and when the alternator is generating power, it generates current I alt It supplies power to the DC bus. When starting the ICE 300 (also known as "motor mode") alt <0. The current sensor 1001 sends I to the system control device 318A. alt The capacitor 1003, having a value of C, is the main bus capacitor, which maintains the bus voltage of the semiconductor switch power bridge, implemented as a MOSFET power bridge 1007 in this example, during pulse width modulation (PWM), and attenuates the current ripple transmitted to the DC bus 319. Other semiconductor switches, as known in the art, can be used in alternative implementations. i Capacitor 1004 and value L i The inductor 1005, equipped with capacitor C, further attenuates the current and voltage ripple transmitted to the DC bus. i and inductor L i This combination is referred to herein as an electromagnetic interference (EMI) filter. Due to the filtering effect of the main bus capacitor and the EMI filter, alt The current ripple is I cap It is much smaller than that. cap The positive direction of the current is selected to match the current flow during motor mode and is directed into the MOSFET power bridge 1007.

[0043] In motor mode, the peak inter-phase motor / alternator voltage is below the bus voltage, and the regenerative drive unit "shakes" the voltage down to the required phase voltage, drawing power from the bus. In alternator mode and SVPWM submode, the regenerative drive unit pushes the phase voltage up to the bus voltage and outputs power. When the peak inter-phase voltage reaches or slightly exceeds the bus voltage, the push provided by SVPWM is not necessary, and the drive unit operates in synchronous rectifier submode. In synchronous rectifier submode, the MOSFET power bridge 1007 is controlled to mimic a passive diode bridge rectifier—the MOSFETs are switched on as if they were diodes. As a result, the MOSFETs are switched at a much slower speed compared to SVPWM, reducing switching losses and increasing efficiency. A key feature of this implementation is that the generator constants (also known as back EMF constants) of the motor / alternator are selected such that the rotational speed of the engine shaft 601 of the ICE 300, where the peak phase voltage is equal to the bus voltage, is 100% to 115% of the rotational speed at peak engine output 370 (approximately 5600 RPM in the case of the engine curve in Figure 3B). In this way, the peak output point of the ICE is the peak efficiency point of the rectification process. The switching of the MOSFETs in the synchronous rectifier submode is achieved using the electrical angle 904, as it corresponds to the electrical angle when the phase voltage exceeds the bus voltage.

[0044] Figure 10 shows that the MOSFET power bridge 1007 is connected to a bus in a complementary pair, and the binary gate voltage signal b U 1010, b V 1012 and b WIt is also shown that it incorporates six MOSFETs 1007a-1007f, controlled by their respective logic components 1020, 1022, and 1024, indicated by 1014 and the overline. The actual voltage levels corresponding to "on" and "off" depend on the selected MOSFET. In any half-bridge (two transistors (a pair of complementary transistors) connected to the common phase terminals of the motor / alternator 306), either the primary or complementary transistor (e.g., 1007a or 1007d) is turned on at one time. During switching, there is an exception in that one transistor is turned off before the other is turned on for about 1 nanosecond, a few nanoseconds, or tens of nanoseconds to prevent a short circuit in the half-bridge. The regenerative drive unit incorporates a processor 1000 in the form of a microcontroller, digital signal processor, field-programmable gate array (FPGA), microprocessor, or other arithmetic element with associated memory to control current input commands

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[0045] Figure 10 also shows the connection of the regenerative drive unit to an exemplary three-phase motor / alternator 306 at phase terminals U, V, and W. Positive phase current I U , I V and I WThe arrows indicate that the current is alternating current in both alternator mode and motor mode. Phase-to-neutral back EMF voltage source modules 1030, 1032, and 1034 are in phase with the phase current in motor mode and phase-shifted in alternator mode. The equation performed by the phase-to-neutral back EMF voltage modules is shown in the drawing, with the back EMF constant K e Engine shaft angular velocity ω, engine shaft angle θ, and motor pole number N p This corresponds to the following. The neutral point N of the wire connection is shown. The resistance and inductance between phases, or terminals, are R, respectively. φφ and L φφ Therefore, the neutral resistance 1040 and inductance 1042 from the phase are half of these values, and thus R φφ / 2 and L φφ It is equal to / 2. The number of phases is shown to be 3 for illustrative purposes, and additional half-bridges may be added for additional phases at terminals P+ and P-, as described below. Furthermore, half-bridge connections to one or more neutral points in one or more wire connections are possible.

[0046] Compared to the circuit in Figure 10, Figure 11 shows the addition of an additional half-bridge 1100, connected at terminals P+ and P-, in parallel with the MOSFET power bridge 1007, and also connected via conductor 1102 to the neutral point N of a y-connected three-phase motor / alternator. Figure 11 shows a four-legged y-connection enabling a fault-tolerant scheme as described in F. Richardeau, J. Mavier, H. Piquet and G. Gateau, “Fault-Tolerant inverter for on-board aircraft EHA,” 2007 European Conference on Power Electronics and Applications, Aalborg, 2007, pp. 1-9, doi: 10.1109 / EPE.2007.4417537 (referred to by reference in its entirety). In the event of one or more faulty half-bridges or windings, one or more corresponding legs may be disconnected from one of the corresponding solid circuit breakers or relays 1106. Therefore, the neutral path N, which includes the current sensor 1104, provides a current return path. It is understood that the neutral path is not a constant voltage at all, and the name is used for historical reasons. Figure 11 also shows a fuse 1108 that protects against interphase short circuits in the preferred snake-like windings in the multiphase dual Halbach array axial gap motor / alternator 306. It is understood that some embodiments may have a circuit breaker 1106 or a fuse 1108 or both.

[0047] Figure 12 shows a control device 1204 (which may be included in processor 1000) for the MOSFET power bridge 1007 of Figure 10 for the three-phase regenerative drive unit. The illustrated feedback loop is a setpoint in the well-known dq coordinate system.

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[0048] Referring again to Figure 12, the power bridge 1007 controls the phase voltage for the motor / alternator 306, and thus the phase current I measured by the current sensor 1202. U , I V and I W It controls the motor / alternator shaft angle, so the electrical angle is

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[0049] The SVPWM timing module 1230 uses a row vector (b) of the binary switch state. U b V b W ) gives rise to 1010, 1012, and 1014, which define the three half-bridge states of power bridge 1007. The SVPWM switching frequency is generally in the range of 20kHz to 100kHz, and high-performance SiC and GaN MOSFETs enable higher switching frequencies. Electrical frequency ω of motor / alternator 306 e The frequency is generally a maximum of several kHz, and the SVPWM frequency to electrical frequency ratio is generally 10 to 20 or more. These values ​​and ratios are intended for illustrative purposes only, not limitations.

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[0050] The synchronous rectification submode is a submode of another power generation mode and alternator mode. This is achieved by switching switch 1200 to send the output of the synchronous rectification timing block 1231 to the power bridge 1007, which then responds as a bridge rectifier. For illustrative purposes, assume that all MOSFETs in the power bridge 1007 are in the off state. The body diodes of the MOSFETs (e.g., body diode 1008a of MOSFET 1007a) then collectively form a bridge rectifier, supplying power to the bus when the peak phase voltage exceeds the bus voltage by more than the voltage drop across the diodes. During operation in the synchronous rectification submode, at these points in time when the MOSFET body diodes are conducting, the synchronous rectification timing block 1231 turns on its MOSFETs so that the voltage drop is reduced compared to the voltage drop across the body diodes, and the phase current flows only through the reverse on-resistance of the MOSFETs. The synchronous rectification timing block 1231 is configured to turn on each individual MOSFET slightly after the body diodes conduct, thus avoiding forward conduction of the MOSFETs. This mode is used to supply peak power to the bus and reduces switching losses compared to the SVPWM submode of the alternator mode. This operating mode contributes to the overall efficiency of the system. In some embodiments for pure hovering vehicles operating continuously at maximum power, it is cost- and weight-efficient to use only a passive diode bridge rectifier or a synchronous rectifier that always operates in synchronous rectifier submode without PWM capability. In this case, the prime mover is augmented by a separate electric, hand-pull, or externally added starter motor, as the power electronics lack the ability to control the motor / alternator as a motor.

[0051] Transitional eVTOLs require high power during takeoff and hovering, while high efficiency is desirable for long-duration cruising. These requirements are well met by the hybrid power system of the implementation of this disclosure. Note that in Figure 3B, peak power 370 occurs near the maximum engine RPM, but the best fuel consumption point 360 is approximately 50% of peak power and 50% of the speed at peak power. This is typical of piston engine performance, especially four-stroke engines, and matches well with the performance of the two-mode rectifier system used in transitional eVTOLs. During short vertical takeoff and hovering, the ICE 300 operates in peak power and synchronous rectifier submode, and during cruising, the ICE operates in or is switched off in SVPWM submode for peak efficiency and battery charging.

[0052] Figure 13 provides details of the current control device 1224 of Figure 12. The inputs at connectors 1220 and 1208 and the output at connector 1222 in Figure 13 are observed to be compatible with those of the current control device in Figure 12, as expected. Input I q This is the command input in the adder junction 1304.

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[0053] The cross - term blocks 1300 and 1301 can be understood in terms of the electrodynamics of the motor / alternator in dq coordinates. [Number] where s is the Laplace or differential operator, ω is the shaft angular velocity of the motor / alternator, and K e is the back - EMF constant. Note the off - diagonal terms of the above matrix. Exact motor / alternator dq decoupling cancels these off - diagonal terms, diagonalizes the matrix, and decouples the system into two single - input single - output systems that are time - invariant rather than time - varying at a non - constant electrical frequency ω e

[0054] FIG. 14 provides details of the SVPWM timing block of FIG. 12. The SVPWM timing block of FIG. 12, in FIG. 14, has as inputs the vector V αβ =(V α ,V β )T Accept 1401 and output the rapid time-varying switch state (b U ,b V ,b W ) to the power bridge 1007. Labels of various switch states are attached to the vertices of the hexagon in FIG. 14, and it should be noted that the hexagon represents a part of the possible values of V αβ . Since there is no voltage difference between both terminals of the motor / alternator when all half-bridges are high or all are low, the origin 1400 in FIG. 14 is also labeled with both switch states (0,0,0) and (1,1,1). These are both called the "zero state". In the (1,0,0) switch state of 1402, the voltage of the motor / alternator terminals in the αβ coordinates is as shown [Number] , and the voltages of other vertices can be inferred from geometry. For example, the voltage in the (1,1,0) switch state at 1404 is [Number] . The vertices and the origin of the hexagon are only the possible output voltages that can be applied to the motor / alternator. However, by rapidly switching between the vertices and the origin, any voltage within the hexagon can be averaged and applied. For example, for the vector V αβ (1401) shown, it should be considered that the vertices at locations 1400, 1402, and 1404 are labeled with (0,0,0), (1,0,0), (1,1,0), and (1,1,1). By rapidly switching between the states of the vertices of the triangle and using the integration effect of the motor / alternator phase inductance, the desired V αβ can be averaged. In standard SVPWM, for the vector V αβ with respect to the period T SThe sequence that follows within is (0,0,0)→(1,0,0)→(1,1,0)→(1,1,1)→(1,1,0)→(1,0,0)→(0,0,0). The vertices of the triangle are traversed counterclockwise, then clockwise in the reverse direction. The dwell time at each vertex is V αβ This is a matter of degree and is known in the technical field of SVPWM design. The dwell time is given, for example, in Narayanan, G., et al. “Space vector based hybrid PWM techniques for reduced current ripple.” IEEE Transactions on Industrial Electronics 55.4 (2008): 1614-1627, which also describes variations of standard SVPWM that reduce output current ripple—such alternative SVPWM schemes and other PWM schemes may be used in alternative implementations of the present invention. The sequence that brings values ​​to other regions of the hexagon is vector V αβ This corresponds to the vertices of the triangle that contain the value.

[0055] Figure 15A shows exemplary current waveforms of the motor / alternator phase U in motor mode and alternator mode / SVPWM submode. The waveforms have different symbols corresponding to different directions of power flow. SVPWM period T S This is shown in 1501. The waveform is nearly sinusoidal, and period T corresponds to the electrical period of the motor / alternator. Figure 15B shows the current waveforms in the individual phases in alternator mode / synchronous rectifier submode. As expected, the waveform is not sinusoidal due to the current pulses that occur when the interphase voltage exceeds the bus voltage. The pulses are curvilinear due to the non-zero battery impedance and other impedances that affect the phase currents in the real system. Note that there are two peaks in the positive current phase U, which correspond to the negative peaks of phase V in 1502 and phase W in 1500. When these currents are rectified, the resulting bus current has six pulses, as the rising pulses align with the falling pulses.

[0056] Figure 16A shows an exemplary six-phase motor / alternator 306' having two three-phase Y-connections connected to a regenerative drive unit 1600. The regenerative drive unit 1600 consists of two three-phase regenerative drive units sharing a common bus capacitor (circuits in Figures 10 and 18 connected at P+ and P-), referred to herein as a 2×3 redundant system. Connection paths for phases U, V and W are shown, while connection paths for phases X, Y and Z are shown interrupted to avoid disrupting the drawing. Point X on the motor / alternator and regenerative drive unit is connected, as are Y and Z. The regenerative drive unit is connected to a power bus 319. Note that the electrical angle 1606 between phases U and X is 30 degrees. A 60-degree phase angle is undesirable because it would place phases U and Z 180 degrees apart, thus making the torque generating capabilities of these two phases identical. Smoother performance is achievable in both motor and alternator modes under the illustrated relationship, and the bus capacitor current ripple at the motor / alternator rectification frequency is also reduced.

[0057] Figure 16B shows an additional alternative embodiment comprising two separate regenerative drive units 1602, 1604, where additional redundancy is achieved by connecting the neutral point to an additional half-bridge within the regenerative drive unit, as shown in Figure 11. The regenerative drive units are connected to a bus 319 and can be synchronized via a connecting path 1608. This embodiment is defined herein as a 2 × (3 + N) system.

[0058] Figure 17 shows yet another redundant system for the motor / alternator 306”, where five phases are driven independently. Five regenerative drive units 1702, 1704, 1706, 1708 and 1710 are connected to a power bus 319 and can be synchronized via four connection paths 1700. This configuration is referred to herein as the 5I system.

[0059] An additional feature of the implementation of this disclosure is the control of the current of a motor / alternator having one or more faulty phases that are disconnected from the regenerative drive unit. This feature is referred to herein as optimal fault-on-operation rectification (OFOC). The goal is to supply constant power to an available back EMF voltage source, so the motor / alternator supplies a constant torque, which may be positive or negative. V(t) represents the column vector of back EMF voltages of the functioning windings. For example, suppose phase W is faulty and disconnected in Figure 11. Then V(t) = (V U (tPAV) V (t)) T Therefore, the least squares mean square (rms) current vectors of these two phases that supply constant power to the two remaining back electromotive force voltages are: I(t)=(V(t) T V(t)) -1 V(t)P Equation 1 (In the formula, P is the desired power level supplied to the engine shaft by electromagnetic torque.) It can be calculated using the well-known Moore-Penrose inverse matrix (where P is the sum of the desired output power and mechanical losses due to friction, windage, eddy current drag, etc.). It is understood that the benefit of this OFOC can be largely achieved when the current is not exactly as given by Equation 1. When SVPWM is used, there is current ripple and OFOC is approximated, but good performance is still achieved. A sinusoidal back electromotive force is also assumed, but if there is any error in this assumption, the approximation in Equation 1 still yields very good performance. Thus, the definition of OFOC is that of any current waveform

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[0060] Figure 18 shows details of a second regenerative drive unit, combined with the circuit of Figure 10 and incorporated into the regenerative drive unit 1600 of Figure 16A. The circuit of Figure 18 exists independently as the regenerative drive unit 1602 of Figure 16B. The second power bridge 1807 of six additional MOSFETs in Figure 18 is connected to the power bridge 1007 of Figure 10 at terminals P+ and P- in both drawings. The electromotive force voltage 1800 of phase X is shown and is shifted by π / 6 radians (30 degrees) relative to phase U. Similarly, phases Y and Z are shifted by π / 6 radians (30 degrees) relative to phases V and W. The phase conductors U, V, W, X, Y, and Z are combined into a single winding as shown in Figure 7B. In low-power operation, the MOSFETs associated with phases X, Y, and Z are turned off, which may affect the operation of three of the six. In other words, by using only one of the two three-phase motors / alternators, switching losses, which can constitute a large portion of regenerative drive losses at low power, are reduced.

[0061] Figure 19 shows the current I in Figure 10 when two power bridges are connected at terminals P+ and P-. cap and Figure 18

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[0062] Figure 20 shows the sum of the two waveforms in Figure 19, representing the current ripple experienced by the bus capacitor. The RMS ripple can be about half the ripple of an asynchronous system under some operating conditions. This is beneficial because the current ripple rating of a bus capacitor is often one of the limiting design factors that determine the size of the capacitor. Reducing the current ripple of a capacitor increases reliability and reduces weight by reducing the stress on the capacitor and extending its lifespan, or by allowing the use of smaller and lighter capacitors.

[0063] Figure 21A shows the bus voltage ripple of an exemplary three-phase system in a synchronous rectifier submode with the peak bus voltage normalized to 1. There are six pulses 2100 per electrical period T, and the inter-peak voltage ripple 2102 is the peak bus voltage.

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[0064] Figure 21B shows an exemplary six-phase system in a synchronous rectifier submode with the peak bus voltage normalized to 1. There are 12 pulses 2104 per electrical period T, and the inter-peak voltage ripple 2106 is the peak voltage.

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[0065] Figure 22A shows the bus power calculation module used in the system control unit 318A for throttle control and battery charge control. The input to the bus power calculation is V bus , I bat and I alt These measurements include SVPWM switching noise, processor clock noise, ignition noise, rectification-induced current and voltage ripple from the commutator on the bus, and noise at levels depending on the extent to which other noise sources are present. This noise is filtered by noise filter 1 2202, noise filter 2 2204, and noise filter 3 2206, respectively. These filters may be first-order low-pass filters and may include notch filters tuned to specific frequency components in the noise. Tracking notch filters synchronized with the noise source may also be included, as the reference timing of such filters is available within the system. Filtered I bat Signal and I alt The signals are added at the summing node 2200, and the bus current I bus An estimated value is generated, and then multiplied by the bus voltage V at node 2208. bus Multiply by this to get the bus power signal P bus This will result in...

[0066] Figure 22B is located inside the system control unit 318A, and input P busThe system also shows a prime mover throttle control system configured to provide throttle commands depending on the engine RPM. The engine RPM is filtered by a noise filter 4 2210 which may have any or all of the features of noise filters 1, 2, and 3. The throttle control system module 2207 is configured to provide feedforward signals and includes a power-to-throttle feedforward subsystem 2212 which includes at least one of a power-to-rpm map and a power-to-throttle map. These maps are based on engine dynamometer data that informs the control algorithm. The throttle and RPM operating points for maximum fuel economy for each power level are calculated offline and stored in the system control unit 318A for use in the throttle control loop. (Note that in Figure 3B, the maximum fuel efficiency curve 350 coincides with the WOT curve which is above 5100 RPM and at the peak power point 370). This power feedforward minimizes fuel consumption, results in responsive power production, increases available power, and extends range. Furthermore, this approach to feedforward compensates for bus voltage fluctuations. The power-versus-rpm map generates a commanded engine speed RPM*, which differs from the actual RPM at the adder junction 2214. This difference, also called the error signal, is sent to the proportional-integral-derivative (PID) control unit 2218. The output of the PID control unit is added to the power-versus-throttle feedforward signal at the adder 2216, generating a throttle command to the engine at the connection path 918.

[0067] Figure 23 shows the charge control system located within the system control unit 318A. The input to the current feedback to the current subsystem 2306 is the filtered battery current I bat (This is then filtered by the same noise filter 2004 shown in Figure 22A) and the state of charge (SOC) transmitted from the BMS 322 over the connection path 916. The system control unit 318A responds to the SOC signal and the SOC setpoint by sending a regenerative drive unit current command

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[0068] In an alternative embodiment, the difference between SOC and SOC*, as well as the charging algorithm, may be incorporated within the BMS 322, which then signals to the system control unit 318A. The algorithm functions in the same manner as described above, except that certain parts of its function may be moved to different subsystems for convenience. In this case, since different battery packs are swapped inside and outside the vehicle, the charging algorithm may differ due to battery aging or different battery characteristics of different packs. Therefore, having the charging algorithm in the BMS mounted on the battery pack ensures that the system charges each different pack that may be swapped to be appropriate for its particular battery pack.

[0069] The system control unit 318A can be replaced with a mission control unit 318A' as shown in Figure 24. The mission control unit provides output signals 912 and 918 provided by the system control unit. Furthermore, the mission control unit 318A' provides control surface commands 2404 (e.g., for ailerons, rudders, elevators and flaps) and propulsion commands 2406 (e.g., for propellers and lift rotors). The mission control unit not only uses inputs 914 and 916 like the system control unit, but also accepts flight path 2400 and navigation data 2402 as inputs. The flight path may be longitude, latitude and altitude depending on time or control signals from the pilot. The navigation data may be longitude, latitude, heading and altitude from, for example, a GPS system or inertial navigation device. The mission control unit optimizes its control output to maximize mission performance. Performance is a combination of fuel efficiency, engine wear, noise levels and other measures determined by the specific mission. For example, when operating at maximum fuel efficiency, the engine would be controlled to operate near the peak fuel efficiency point 360. During takeoff for a vertical takeoff and landing (VTOL) aircraft, the mission control system may operate the ICE at the peak power point 370 and switch the alternator submode to the synchronous rectifier submode. More generally, the mission can be optimized by switching between ICE off, ICE operation at the peak fuel efficiency point 360, ICE operation along the peak fuel efficiency curve 350, and operation at a wide-open throttle near the peak power point 370. When the required power falls below the power at the peak fuel efficiency point, the ICE alternates between off and the peak fuel efficiency point, and the battery provides a mechanism to average out the output power to the required level, for example, the time spent at maximum fuel efficiency.

[0070] It should also be noted that the mission control unit 318A' or the system control unit 318A may instruct the system to operate in an electric-only mode when certain mission constraints exist. In this mode, the prime mover engine 300 may be completely shut down to reduce noise or thermal signature, and the vehicle may operate as a purely electric vehicle using only battery power. In this mode, all engine control and regenerative control algorithms are deactivated. When the mission control unit / system control unit command returns to hybrid electric-powered flight, a command from the system control unit 318A initiates the start-up sequence. In the start-up sequence, the system control unit uses power from the battery 320 via the regenerative drive unit to provide motor-operating torque to the motor / alternator, as well as enable the operation of the prime mover 300's ignition and refueling systems. Once the system control unit detects that the prime mover is running, providing torque, and accelerating rotational speed, it removes the motor-alternator torque, initializes and starts the current and speed control loops, and then enters the aforementioned SVPWM or synchronous rectification control mode.

[0071] In short, the implementations of the disclosed invention described demonstrate how various combinations of elements, including a dual Halbach array axial-gap iron-free motor / alternator, can provide a lightweight, highly efficient, and energy-density hybrid power system for reliable electric flight. The iron-free motor / alternator offers lower inductance and improved efficiency compared to iron-core motors. When operating as an alternator, this means the output voltage is less sensitive to current, resulting in improved power quality. When operating as a motor, the low inductance means that higher torque can be achieved at lower bus voltages. The advantages of low inductance are also quantified as a power factor close to 1, which has the aforementioned advantages as well as other advantages known in the art.

[0072] This axial gap motor / alternator configuration provides a compact mechanical form when combined with a prime mover—an internal combustion engine or gas turbine as taught in the implementations of the present disclosure. This compact configuration reduces weight and improves vibration performance due to the shorter shaft length of the motor / alternator. The shorter shaft is made more rigid, thereby avoiding rotational mechanical problems associated with structural resonance of the flexible shaft and rotor.

[0073] The rotor's almost planar structure makes it highly robust against torsional impulse loads from the piston engine's power stroke without adding significant structural mass to the rotor. This type of motor / alternator also pumps cooling air naturally throughout its windings, eliminating the need for an additional cooling system—thus reducing weight and increasing reliability. The large diameter, short machine has greater inertia compared to more common machines of the same power and torque rating, and this high inertia is advantageous because internal combustion engines require a certain amount of inertia to overcome the compression stroke, and the use of an axial gap machine acts as a flywheel in the engine, saving additional system mass.

[0074] A dual Halbach array provides a high magnetic field to the motor / alternator, increasing efficiency and power density. The system can be designed with many small magnetic poles, thereby reducing the mass of the motor / alternator due to the thin magnet cross-section achievable with many small magnetic poles. The system then operates at high electrical frequencies, which are inefficient in conventional motor / alternators due to iron losses and reactive voltages. Iron-free motors / alternators do not have the iron loss penalty at high electrical frequencies because they do not contain iron.

[0075] Additional safety and reliability are provided by preferred snake-like windings within axial-gap multiphase motors / alternators. This winding configuration does not overlap itself and is virtually impossible to cause self-short circuits (also known as short circuits between turning points) in single phases. These windings may preferably be made from Litz wire, which reduces undesirable eddy currents in the windings.

[0076] Because snake-like windings can experience phase-to-phase short circuits, the implementation of this disclosure enhances safety by including a fuse in the y-connection so that the short-circuited phase is prevented from functioning. Furthermore, a four-legged y-connection may be used, where a three-phase electrical system has three phase terminal legs and an additional fourth neutral terminal leg, where the three phase windings come together to form a y-connection. Current does not need to flow through the neutral unless there is a fault in the winding or drive with respect to one of the phases. In case of a fault, the neutral connection provides a current return path and continues to operate.

[0077] Optimal fault-to-operate rectification (OFOC) is provided for motors with sinusoidal back EMF waveforms, where the maximum efficiency rectified current for multiple phases is a sinusoidal current in phase with the back EMF voltage. In alternators, the current is completely out of phase. If one or more windings are lost, the rectified current that provides a constant commanded torque at maximum efficiency will inevitably change. OFOC provides maximum efficiency phase currents specific to sinusoidal and non-sinusoidal back EMF waveforms.

[0078] Furthermore, the exemplary six-phase configuration provides redundancy, reliability, and reduced bus voltage and bus current ripple when bridge or synchronous rectifiers are used. The six-phase motor / alternator drive unit can be configured as a single power conversion unit or as two three-phase regenerative power conversion drive units supplying power to a six-phase motor / alternator composed of two three-phase wie windings. In addition to improved performance, this embodiment utilizes more standard and lower-cost three-phase regenerative drive units. The two three-phase systems can be configured as a four-legged wie system.

[0079] In a six-phase motor / alternator composed of two integrated three-phase motors / alternators, it may be desirable to turn off one of the motors / alternators by switching off all the MOSFETs associated with that motor / alternator in order to achieve three of the six phases of operation. When turning a MOSFET on or off, there is a power requirement for charging and discharging the MOSFET gate capacitance, as well as other "fixed overhead" power requirements that are independent of the amount of current switched by the MOSFET. Therefore, at low currents, the fixed overhead can be a relatively large portion of the regenerative drive losses, and the overall efficiency can be increased by using only three of the six available phases. An extension of this idea can be applied to any multiphase motor, where a reduced number of phases may be driven.

[0080] Furthermore, in a six-phase motor / alternator, two three-phase motor / alternator sections are driven by two space vector pulse-width modulation (SVPWM) drive units whose phases are synchronized to reduce current stress on the bus capacitor, required bus capacitance, and regenerative drive bus voltage and current ripple.

[0081] When a motor / alternator is used in alternator mode, there are two sub-modes: a. A submode in which the regenerative drive unit pushes the phase voltage up to the bus voltage. This is defined herein as a PWM submode (or an SVPWM submode by a specific spatial vector PWM implementation). It is understood that various PWM schemes may be used. In this mode, the prime mover speed may be adjusted to a speed that produces the DC bus power required at the best fuel consumption rate. This mode is generally used in partial power operation mode because piston engines generally achieve best fuel consumption at about 50% of peak power and 50% of peak power speed. In this mode, the thermal loss of the regenerative drive unit is divided almost equally between conduction losses and PWM switching losses, so the thermal management system mass is driven by the combined two loss mechanisms. b. A submode in which the regenerative drive unit acts as a synchronous rectifier. In faster prime movers, the peak interphase alternator voltage reaches or slightly exceeds the DC bus voltage, and PWM boost is not required. Switching to synchronous rectification reduces switching losses and increases the efficiency of power conversion electronics. Furthermore, the thermal management requirements and weighting of power electronics are reduced relative to the maximum power handled. However, since the prime mover speed must be strictly tuned to a fixed speed related to the DC bus voltage and DC bus power, there is no flexibility to change the prime mover speed to optimize the prime mover's fuel consumption. This mode is generally used for full-power operation so that the prime mover generally achieves maximum power near its maximum rotational speed. This is called the synchronous rectifier submode.

[0082] In the well-known dq coordinate system used in motor / alternator control, the d current affects the q voltage, and vice versa. These effects increase with speed and can lead to instability and failure in motor / alternator current control. In the implementation of this disclosure, this cross-coupling effect is canceled out in the current control loop, resulting in better system reliability.

[0083] The response time of the internal combustion engine to the electrical demands of the power bus is improved by the novel control scheme of the implementation of the present disclosure. The near-instantaneous response to the bus power is influenced by the RPM setpoint and throttle setpoint. This control technique uses dynamometer data to intelligently calculate the RPM and throttle commands. In some embodiments of the present invention, it is understood that either or both of the RPM setpoint and throttle setpoint information may be used.

[0084] Finally, the use of mission control systems provides a systematic method for refining and resolving the optimal ICE speed and power time profile during a mission. To meet mission requirements, range is optimized, noise is minimized for a given period, or peak power may be delivered during takeoff or other periods.

[0085] Having described in detail various implementation forms required by patent law, those skilled in the art will recognize modifications and substitutions to specific implementation forms disclosed herein. Such modifications fall within the following claims and intent. Within this specification and claims, the terms “include,” “incorporate,” “incorporates,” or “contains,” “include,” “includes,” or “contains,” “has,” “have,” or “contains,” and “contains,” or “contains,” are intended to be an unlimiting enumeration, and additional or equivalent elements may exist. The term “substantially,” as used within this specification and claims, means that the enumerated characteristics, parameters, or values ​​do not need to be strictly achieved, and deviations or variations, including, for example, tolerances, measurement errors, measurement accuracy limits, and other factors known to those skilled in the art, may occur in an amount that does not exclude the effect intended to be provided by the characteristic.

Claims

1. A hybrid power system (200) for an electric aircraft (99), Prime mover (300), A self-cooled multiphase axial flux dual Halbach array motor / alternator (306) having an N-phase is connected to the prime mover. The motor / alternator and the DC power bus (319) are connected to the N ｐｈａｓｅ A multiphase regenerative drive unit (318B) having phases, A battery (320) connected to the DC power bus, A battery management system (322) operably connected to the aforementioned battery, and A system control device (318A) operably connected to the prime mover, the regenerative drive unit, and the battery management system. A hybrid powertrain (200) including a hybrid power system.

2. The hybrid power system according to claim 1, wherein the prime mover is an internal combustion engine (ICE) or gas turbine connected to the motor / alternator by an engine shaft (601), and the system control device is connected to the prime mover to provide at least throttle commands (918).

3. N ｐｈａｓｅ The hybrid power system according to claim 1, wherein the number is 3 or more.

4. N ｐｈａｓｅ The hybrid power system according to claim 1, wherein is 6.

5. The aforementioned system control device controls the regenerative drive unit current command [Math 1] The motor / alternator is configured to emit N ｐｈａｓｅ It has terminals and a neutral point (N), and the regenerative drive unit is A processor (1000) configured to receive the regenerative drive unit current command and in response to issue commands for a plurality of binary gate voltage signals (1010, 1012, 1014, 1020, 1022, 1024), and A semiconductor switch power bridge (1007) having a plurality of semiconductor switches (1007a to 1007f) that respond to the plurality of binary gate voltage signals connected in the complementary pairs, with each complementary pair connected to the common phase terminals (U, V, W) of the motor / alternator. A hybrid power system according to claim 2, including the above.

6. The hybrid power system according to claim 5, further comprising a control device (1204) configured to provide the plurality of binary gate voltage signals in one of a selected pulse-width modulation (PWM) submode, a synchronous rectification submode, or a motor mode.

7. The control device is The motor / alternator receives a phase current, and the phase current (I α I β ) Ｔ Clarke Transmitter Module (1210) configured to provide an output, The foregoing (I α I β ) Ｔ receives the output and is configured to provide the output of the motor / alternator current (I ｄ I ｑ ) Ｔ a park conversion module (1212). The motor / alternator current (I ｄ I ｑ ) Ｔ A current control device (1224) that receives an output and a regenerative drive unit current command, and which responds to the regenerative drive unit current command by voltage (V ｄ V ｑ ) Ｔ A current control device (1224) configured to provide an output, The aforementioned voltage (V ｄ V ｑ ) Ｔ Receive the output and correct the voltage output vector (V α V β ) Ｔ A reverse park conversion module (1226) configured to provide, and The modified voltage output vector (V α V β ) Ｔ A PWM timing module (1230) configured to receive and provide the plurality of binary gate voltage signals to the semiconductor switch power bridge capable of operating in the PWM submode. The hybrid power system according to claim 6, including the following:

8. The hybrid power system according to claim 6, further comprising a control device selectively connectable to the semiconductor switch power bridge, the synchronous rectification timing module (1231) configured to provide the plurality of binary gate voltage signals to the semiconductor switch power bridge, thereby causing the semiconductor switch power bridge to respond as a bridge rectifier capable of operating in the synchronous rectification submode.

9. The hybrid power system according to claim 2, wherein the motor / alternator has a generator constant, and thereby the rotational speed of the engine shaft at which the peak interphase voltage is equal to the bus voltage corresponds to 100% to 115% of the peak rotational speed of the engine shaft at the peak engine output point.

10. The hybrid power system according to claim 9, wherein the motor / alternator output voltage changes by less than +15% from the bus voltage when the peak rotational speed of the engine shaft is the peak engine output point.

11. N ｐｈａｓｅ The hybrid power system according to claim 5, wherein the motor / alternator is equal to 3, and further comprises a half-bridge (1100) connected in parallel with the semiconductor switch power bridge to the common phase terminals (U, V, W) and to the neutral point, which is y-connected to the neutral point (N).

12. N ｐｈａｓｅ The hybrid power system according to claim 1, wherein is equal to 6, and the multiphase regenerative drive unit includes a first three-phase regenerative drive unit (1602) connected to the DC power bus and a second three-phase regenerative drive unit (1604) connected to the DC power bus.

13. The hybrid power system according to claim 1, wherein Nphase is equal to 5, and the multiphase regenerative drive unit includes five singlephase regenerative drive units (1702, 1704, 1706, 1708, 1710) connected to the DC power bus.

14. The prime mover is a piston engine ICE having a crankshaft (800) axially connected to the engine shaft (601), and the motor / alternator is Front motor rotor (406) supporting front rotor magnets (407A) forming a Halbach array, and Rear motor rotor (502) supporting the rear motor magnet (407B) that forms a second Halbach array. Includes, The hybrid power system according to claim 2, wherein the front motor rotor and the rear motor rotor extend radially from the engine shaft and function as a flywheel.

15. The hybrid power system according to claim 14, wherein the front motor rotor and the rear motor rotor are rotatably supported by bearings engaged with the crankshaft.

16. The battery management system is configured to provide a state of charge (SOC) signal to the system control unit, and the system control unit responds to the SOC signal and the SOC setpoint by providing the regenerative drive unit current command [Math 2] The hybrid power system according to claim 5, configured to adjust the following:

17. The aforementioned system control device is Battery current (I ｂａｔ ), current feedback to a current subsystem (2306) that receives the SOC signal and the SOC setpoint, the current feedback configured to provide a PID output, RPM signal and bus power P ｂｕｓ A power-to-current feedforward subsystem (2314) configured to receive signals and provide current commands, and The PID output and the current command are received, and the regenerative drive unit current command is received. [Math 3] Adder (2304) configured to provide The hybrid power system according to claim 16, further comprising:

18. The aforementioned system control device has a bus power P ｂｕｓ The hybrid power system according to claim 5, configured to issue the throttle command in response to a signal and an RPM signal.

19. The aforementioned system control device is P ｂｕｓ The hybrid powertrain according to claim 18, further comprising a throttle control system module (2207) configured to receive signals and the RPM signal and to provide the throttle command.

20. The hybrid power system according to claim 2, wherein the system control device includes a mission control device (318A'), the mission control device receiving a flight path input and a navigation data input, and issuing the throttle command in response to the flight path input.

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