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 a current limiting diode comprising a gate, a source, and a drain electrically connected to the source by an n-channel or p-channel; wherein the source and the gate are electrically connected by a fill structure comprising a phase-change fill material, and wherein the phase-change fill material is configured to absorb heat from the n-channel or p-channel by changing phase.

Abstract: An aircraft power and propulsion system includes a gas turbine engine having first and second spools, the first spool being a starting spool; first and second DC electrical networks having first and second operating voltages; a first electrical machine joined with the first spool, the first electrical machine having first and a second winding sets; a second electrical machine joined with the second spool; a first, second and third AC:DC converter; and a controllable switching arrangement configured so that a connection to an AC-side of the third AC:DC converter is switchable between a winding of the second electrical machine or the second DC electrical network via an inductor.

Abstract: A power conversion circuitry configured to transition between modes of operation during an electrical fault, including: switching circuitry configured to control currents flowing along a plurality of current paths between respective pairs of nodes, wherein the paths include first and second transistor-diode pairs; and control circuitry connected to the switching circuitry configured to: configure the switching circuitry to transition, when an electrical fault is detected, to a first mode of operation by configuring the transistors to switch to a non-conducting state so currents flow through the diodes, determine when current begins to flow through a diode, and configure the switching circuitry to transition from the first mode to a fault mode of operation by configuring the transistors to sequentially switch to a conducting state so currents flow through the configured transistors. Also, a method of controlling power conversion circuitry to transition between modes of operation during an electrical fault.

Abstract: A power conversion circuitry configured to detect an electrical fault, and methods of detecting an electrical fault in power conversion circuitry, the power conversion circuitry including: switching circuitry configured to control a current flowing along a current path between first and second nodes of the power conversion circuitry; a current sensor connected to the current path, the current sensor configured to measure a rate of change of the current flowing along the current path; and control circuitry connected to the current sensor and the switching circuitry, the control circuitry configured to: detect an electrical fault if a rate of change of the current measured by the current sensor exceeds a fault threshold, and configure the switching circuitry to adjust current flow in the power conversion circuitry when an electrical fault is detected.

Abstract: A power electronics converter including: an input terminal; first and second DC output terminals; a branch having first and second semiconductor switches connected in series between the first and second DC output terminals, the 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; a differential current sensor arranged to measure a differential current signal through the first or second DC terminals; and a controller configured to provide switching signals to each of the first and second switches of the power electronics converter, wherein the controller is further configured to detect a fault in a DC network connected between the first and second DC output terminals upon detection of a peak in an output from the differential current sensor.

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 power electronics converter including: an input terminal; first and second DC output terminals; a branch including first and second semiconductor switches connected in series between the first and second DC output terminals, the 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 resistive damping element connected in series with the DC link capacitor, wherein a damping factor of a circuit including the DC link capacitor, the resistive damping element and an inductance of the circuit with a short between the output terminals is at least 1.

Abstract: A electrical power system comprises: an electrical machine operable to output AC; a DC electrical network; a power electronics converter connected between the AC output of the electrical machine and the DC electrical network and including a plurality of transistors and associated diodes connected in parallel with the transistors; and a controller configured to control switching of the transistors of the converter so that, during normal operation of the electrical power system, the converter rectifies the AC output of the electrical machine to supply the DC electrical network with DC electrical power. The controller is further configured, responsive to a determination to the effect there is a fault in the DC electrical network, to control a voltage source, to inject a voltage to bias the diodes of the converter, and to control the switching of the transistors to control a level of current supplied to the faulted DC electrical network.

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: 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: 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: A DC:DC power converter 10, an electrical power system 100 comprising a DC:DC power converter 10, and a method 500 of operating an electrical power system 100 are described. The DC:DC power converter 10 comprises: a DC:AC converter circuit 11; an AC:DC converter circuit 12; an AC link 13 that connects an AC side of the DC:AC converter circuit 11 to an AC side of the AC:DC converter circuit 12 and has an impedance synthesizer 14 connected therein, the impedance synthesizer 14 comprising an active bridge circuit 140; and a switching controller 15 configured to control a switching operation of a plurality of power semiconductor switches 141L,H, 142L,H of the active bridge circuit 140 and thereby control an output voltage of the impedance synthesizer 14 and an impedance of the AC link 13.

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 aircraft power and propulsion system includes a gas turbine engine having first and second spools, the first spool being a starting spool; first and second DC electrical networks having first and second operating voltages; a first electrical machine joined with the first spool, the first electrical machine having first and a second winding sets; a second electrical machine joined with the second spool; a first, second and third AC:DC converter; and a controllable switching arrangement configured so that a connection to an AC-side of the third AC:DC converter is switchable between a winding of the second electrical machine or the second DC electrical network via an inductor.

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: 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.