Electrical power systems
Electrical power systems for distributing electrical power in aircraft are described. One such electrical power system comprises: an electrical power source configured to output a number R≥2 of dc power channels, each dc power channel having a respective index r=(1, . . . , R); and a group of N dc load channels connected to the R dc power channels by a switching arrangement, wherein N>R and each dc load channel has a respective index n=(1, . . . , N). The system further comprises, for each respective one of a plurality of the N load channels, a current limiting device (CLD) operable to limit an amount of current flowing from the power channels to a load connectable to the electrical power system via the respective load channel. The electrical power source may comprise one or more batteries.
1. An electrical power system for distributing electrical power in an aircraft, the electrical power system comprising:
an electrical power source configured to output a number R≥2 of dc power channels, each dc power channel having a respective index r=(1, . . . , R);
a group of N dc load channels connected to the R dc power channels by a switching arrangement, wherein N>R and each dc load channel has a respective index n=(1, . . . , N); and
for each respective one of a plurality of the N load channels, a current limiting device (CLD) operable to limit an amount of current flowing from the power channels to a load connectable to the electrical power system via the respective load channel, each respective CLD being bidirectional such that it is further operable to limit an amount of current flowing to the power channels from the load.
2. The electrical power system of claim 1 , in which the electrical power source comprises one or more batteries.
3. The electrical power system of claim 1 , in which each bidirectional CLD includes a pair of unidirectional CLDs connected in anti-parallel.
4. The electrical power system of claim 1 , in which each CLD comprises one or more of:
a passive CLD component;
an active CLD component; and
a superconducting fault current limiter.
5. The electrical power system of claim 1 , in which the CLDs are:
located on a side of the switching arrangement opposite to the power channels; or
located between the power channels and the switching arrangement.
6. The electrical power system of claim 1 , in which the N load channels are connected to one or more loads including at least one propulsive load.
7. The electrical power system of claim 6 , in which the propulsive load comprises an electrical machine comprising at least two submachines.
8. The electrical power system of claim 1 , comprising a set of converter circuits for conversion between direct current flowing in the dc load channels and alternating current for powering one or more ac loads connectable to the electrical power system via the N load channels.
9. The electrical power system of claim 1 , in which the N dc load channels are connected to and power a poly-phase electrical load, and in which the electrical power system comprises a controller configured to control the switching arrangement so that, in a no fault condition, pairs of phases of the poly-phase electrical load are powered by the same power channels so as to cancel harmonics in current supplied by the power channels.
10. The electrical power system of claim 9 , in which the two phases of each pair of phases are electrically separated by 360/P degrees, P being a total number of phases of the poly-phase electrical load.
11. The electrical power system of claim 1 , in which, for each respective one of a number Q≥1 of the N load channels, the switching arrangement is operable to connect the respective load channel to at least two different power channels of the R power channels.
12. The electrical power system of claim 11 , in a no fault condition, each one of the Q load channels is connected to and receives power from both of the two different power channels to which it is connected by the switching arrangement.
13. The electrical system of claim 11 , comprising a controller configured to control operation of the switching arrangement so that, at all times, each one of the Q load channels receives power from only one of the at least two power channels to which it can be connected by the switching arrangement.
14. The electrical power system of claim 11 , comprising a controller configured to control operation of the switching arrangement so that, at all times, each one of the R power channels delivers power to a number of load channels not exceeding ┌N/R┐+1.
15. The electrical power system of claim 1 , in which N≥4.
16. An aircraft propulsion system comprising the electrical power system of claim 1 .
17. The aircraft propulsion system of claim 16 , comprising one or more propulsors, wherein the R power channels of the electrical power system are arranged to deliver power to the one or more propulsors, and the N load channels are electrically connected to one or more non-propulsive loads.
18. An aircraft comprising the electrical power system of claim 1 .