Abstract: An electrical power system 100 is described. The electrical power system 100 comprises: a first electrical sub-system 101, 102, 103, 105 having a first voltage; a second electrical sub-system having a second voltage; a power converter 104, 106 connected between the first electrical sub-system and the second electrical sub-system and configured to convert between the first voltage and the second voltage; an impedance synthesizer 14 connected in an intermediate circuit that connects the power converter to the first electrical sub-system, the impedance synthesizer 14 comprising an active bridge circuit 140. The electrical power system further comprises a control system 150 configured to control a switching operation of a plurality of power semiconductor switches 141L-H, 142L-H of the active bridge circuit 140 to control an output voltage Vout of the impedance synthesizer 14, whereby the impedance synthesizer 14 emulates a Differential-Mode filter or a Common-Mode filter.

Abstract: Aircraft power and propulsion systems and methods thereof; an aircraft power and propulsion system includes: a gas turbine engine having first and second spools; one or more electrical networks; a first electrical machine joined with the first spool; a second electrical machine joined with the second spool; a first power converter having first and second sides; a second power converter having first and second sides; and a controllable switching arrangement in which a connection to the first side of the second power converter is switchable between: a winding of the second electrical machine, or the winding of the first electrical machine.

Abstract: An electrical power system includes: an electrical machine to output AC; DC electrical network; power electronics converter connected between the AC output of the electrical machine and the DC electrical network and having a phase leg having first and second branches respectively having first and second bi-directional MOSFETs; and controller controlling switching of the first and second bi-directional MOSFETs of each phase leg of the converter so that current is commutated between the phase leg first and second branches rectifying the AC input to DC to supply the DC electrical network with DC electrical power. The controller is responsive to a determination to the effect that there is a fault in the DC electrical network, to control the switching of each phase leg first and second bi-directional MOSFETs to switch the converter into a crow-bar configuration in which electrical machine current does not flow to the DC network.

Abstract: An electrical power system 10 and a method 300 of controlling an electrical power system 10 are provided. The electrical power system 10 comprises a DC:DC power converter 100 connected between a DC power source 11 and a DC electrical network 12. The DC electrical network 12 comprises at least a first zone Z1 for powering a first group of one or more electrical loads 12La-b, a second zone Z2 for powering a second group of one or more electrical loads 12Lc-d, a first controllable circuit breaker X1, and a second controllable circuit breaker X2.

Abstract: A power electronics converter comprising: first and second input terminals; first and second DC output terminals; a branch comprising first and second semiconductor switches connected in series between the first and second DC output terminals, the first input terminal connected to a node between the first and second semiconductor switches; a DC link capacitor connected between the first and second DC output terminals; and a reverse biased DC link diode connected across the DC link capacitor.

Abstract: An electrical power system includes: an H-bridge DC:DC power converter including first and second half-bridge circuits having low-side transistors and a high-side transistors, and an inductor connected between AC sides of the first and second half-bridge circuits; a DC power source connected to a first half-bridge circuit DC side; a DC electrical network connected to a second half-bridge circuit DC side; and a control system. The control system: controls the low-side and high-side transistors' switching state of the first and second half-bridge circuits; monitors one or more electrical power system operating parameters and determines whether there is a fault in the DC electrical network; and in response, modifies a switching operation of the low-side and high-side transistors of the first and second half-bridge circuits to supply a controlled amount of current from the DC power source to the DC electrical network.

Abstract: A DC:DC power electronics converter in an electrical power system includes: DC:AC and AC:DC converters; and an AC link connecting AC sides of the converters, the AC link including a transformer having first and second windings connected respectively to AC sides of the converters; a DC power source connected to the DC side of the DC:AC converter; a DC electrical network connected to the DC side of the AC:DC converter; and a control system to: control a switching operation of respective first and second pluralities of transistors of the converters, monitor one or more operating parameters of the electrical power system and determine whether there is a fault in the electrical network, and if so, modify a switching operation of the first and/or second plurality of transistors to supply a controlled amount of fault current from the DC power source to the electrical network via the DC:DC power electronics converter.

Abstract: A DC:DC converter includes: a DC:AC converter circuit having DC and AC sides; an AC:DC converter circuit having DC and sides; an AC link connecting the AC side of the DC:AC circuit and the AC side of the AC:DC converter circuit, the AC link including a transformer having a first winding connected to the AC side of the DC:AC converter circuit and a second winding connected to the AC side of the AC:DC converter; a capacitor; and a switch arrangement having a first state and a second state, wherein: in the first state, the capacitor is connected in series between the AC side of the DC:AC converter circuit and the first winding of the transformer; and in the second state, there is a current path between the AC side of the DC:AC converter circuit and the first winding of the transformer that does not include the capacitor.

Abstract: There is provided an electrical power system comprising: a DC voltage source, a DC electrical network, a DC to AC to DC converter having a primary side connected to the DC voltage source and a secondary side connected to the DC electrical network, and a controller configured to control the DC to AC to DC converter, wherein the controller is configured to: monitor an electrical current or voltage between the DC voltage source and the DC electrical network; determine, based on the monitored electrical current or voltage, whether the DC electrical network is in a fault condition; and increase a switching frequency of the primary side of the DC to AC to DC converter in response to a positive determination that the DC electrical network is in a fault condition.

Abstract: The disclosure relates to an electrical power system for connecting an electrical machine to first and second DC networks operating at different voltages. In an embodiment, an electrical power system comprises: an electrical machine having first, second, third and fourth windings; first, second, third and fourth AC:DC power electronics converters each connected to receive an input AC supply from the respective first, second, third and fourth windings, each AC:DC power electronics converter having first and second DC output terminals connecting the AC:DC power electronics converters to first, second and third DC supply output terminals, wherein the first and second windings are arranged to provide an AC supply to the respective first and second AC:DC power electronics converters in quadrature to each other and the third and fourth windings are arranged to provide an AC supply to the respective third and fourth AC:DC power electronics converters in quadrature to each other.

Abstract: The disclosure relates to power electronics converters having circuit breaker protection for use in case of faults. Example embodiments include a power electronics converter for converting an input AC supply having a plurality of phases to an output DC supply, the converter comprising: a plurality of AC input terminals connectable to the plurality of phases of the AC supply; first and second DC output terminals; a capacitor connected between the first and second DC output terminals; a first MOSFET connected between each of the plurality of AC input terminals and the first DC output terminal; a second MOSFET connected between each of the plurality of AC input terminals and the second DC output terminal; and a third MOSFET reverse connected in series with the first MOSFET between the first DC output terminal and each of the plurality of AC input terminals.

Abstract: An estimation of junction temperatures of transistors in power electronics converter.

Abstract: The disclosure relates to estimation of junction temperatures of transistors in a power electronics converter. Example embodiments include a method of estimating a junction temperature of a transistor in a power electronics converter configured to convert between first and second supply voltages, the method comprising: providing a gate switching signal to the transistor; measuring a rate of change of current through the converter during a switching period of the transistor; and outputting an estimated junction temperature of the transistor based on the measured rate of change of current, wherein the rate of change of current is measured while a gate voltage of the transistor is above a gate threshold voltage and a drain-source voltage across the transistor is above a predetermined fraction of the first or second supply voltage whereby the rate of change of current is measured in a linear region.

Abstract: There is provided a current limiting diode 200 comprising a gate 206, a source 202, a drain 204 electrically connected to the source by an n-channel or p-channel 220 and a thermoelectric generator 208; wherein the source and the gate are electrically connected by a fill structure 210, and wherein the thermoelectric generator is configured to: generate a thermoelectric voltage by absorbing heat from the n-channel or p-channel and rejecting heat to a heat sink in a current limiting condition; and apply the thermoelectric voltage between the gate and the source.

Abstract: An AC to DC conversion device has first and second AC input terminals arranged to be coupled respectively to first and second terminals of a phase of an AC current generator, an H-bridge rectification device comprising two pairs of diodes, each pair being coupled to a respective one of the AC terminals to produce a DC output comprising a rectified back EMF waveform, and a waveform generator. The waveform generator comprises an output coupled to the DC output of the H-bridge rectification device, and is configured to input a unidirectional waveform to the DC output having the same magnitude and fundamental frequency as the rectified back EMF, phase shifted by a predetermined angle relative to the rectified back EMF waveform.

Abstract: Reconfigurable permanent magnet electrical machines and aircraft power and propulsion systems comprising such electrical machines are described. In one aspect, an aircraft power and propulsion system comprises: a gas turbine engine; a permanent magnet electrical machine comprising a rotor drivingly coupled to a spool of the gas turbine engine, and a stator comprising windings controllably switchable between a star configuration and a delta configuration; a DC electrical network; an AC:DC power electronics converter, an AC side of which is connected to terminals of the stator windings of the electrical machine and a DC side of which is connected to the DC electrical network; and a control system. The control system is configured to monitor at least one operating condition of the power and propulsion system and to control the switching of the stator windings between the star configuration and the delta configuration based on the at least one operating condition.

Abstract: A gas turbine engine for an aircraft comprises, in axial flow sequence, a compressor module, a combustor module, and a turbine module, with a first electric machine being rotationally connected to the turbine module. The first electrical machine is configured to generate a maximum electrical power PEM1 (W), and the gas turbine engine is configured to generate a maximum dry thrust T (N); and a ratio S of: S = ( Maximum ? Electrical ? Power ? Generated = P E ? M ? 1 ) ( Maximum ? Dry ? Thrust = T ) is in a range of between 2.0 and 10.0.

Abstract: The disclosure relates to an electrical power system with current fault protection provided by current limiting diodes. Example embodiments include an electrical power system comprising: an electrical machine; an AC:DC power electronics converter connected to receive an input AC supply from the electrical machine and provide an output DC supply across first and second output terminals; a DC bus connected to first and second output terminals of the AC:DC power electronics converter; a load connected across the DC bus; a first circuit breaker switch and a first current limiting diode connected in series between the AC:DC power electronics converter and the DC bus; and a second circuit breaker switch and a second current limiting diode connected in series between the DC bus and the load, wherein the first current limiting diode is configured to limit current to a higher level than the second current limiting diode.

Abstract: Reconfigurable permanent magnet electrical machines and aircraft power and propulsion systems including the electrical machines. An aircraft power and propulsion system includes: a gas turbine engine; DC electrical network; permanent magnet electrical machine including a rotor drivingly coupled to a spool of the engine, and a stator including windings controllably switchable between a star and a delta configuration; an AC-DC power electronics converter, an AC side is connected to terminals of the stator windings and a DC side is connected to the DC electrical network; an additional electrical power source connected to and controllable to supply electrical power to the DC electrical network; and a control system configured to control the switching of the stator windings between the configurations and to control the additional electrical power source to supply electrical power to the DC electrical network during a time interval when the stator is being switched between the configurations.

Abstract: Multi-engine aircraft power and propulsion systems and methods of restarting an engine of a multi-engine aircraft during fight are provided. One such method comprises: determining a condition to the effect that a flame in the combustion equipment of the second gas turbine engine has been extinguished; responsive to the determination, supplying electrical power from the electrical energy storage system to one or more of the electric machines of the second gas turbine engine and operating said one or more electric machines as motors to limit a reduction in a speed of the one or more spools of the second gas turbine engine following extinguishment of the flame in its combustion equipment; and restarting the second gas turbine engine by relighting the combustion equipment of the second gas turbine engine.