ELECTRICAL DISTRIBUTION SYSTEM

• US 20130002014A1
• Filed: 06/15/2012
• Published: 01/03/2013
• Est. Priority Date: 06/28/2011
• Status: Active Grant

• Current Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Original Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Inventors: MOORE, Gareth E., HILL, Jason E., GARVEY, Seamus
• Granted Patent: US 9,172,250 B2
• Time in Patent Office: Days
• US Class Current: 307/9.1
• CPC Class Codes: B64D 2221/00 Electric power distribution systems onboard aircraft
• CPC Class Codes: H02J 2300/10 The dispersed energy generation being of fossil origin, e.g. diesel generators
• CPC Class Codes: H02J 2310/44 for aircrafts
• CPC Class Codes: H02J 3/08 Synchronising of networks
• CPC Class Codes: H02J 3/34 Arrangements for transfer of electric power between networks of substantially different frequency
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/40 Synchronising a generator for connection to a network or to another generator

Abstract

An electrical generating system for aircraft with one or more engines includes a plurality of generators associated with the engines so as to produce respective AC outputs. The frequencies of these outputs can differ from each other, as a result of differing engine speeds and/or deliberate design, but they are to be connected to a common bus to avoid redundancy of wiring. One or more converters are present between the generators and the bus for adjusting the output frequency of the generators to provide an AC output voltage at a common bus frequency. The system includes a control system for setting the AC bus frequency in such a way that it can vary with time. The bus frequency may follow the natural frequency of the engine, and only small converters are needed to make the already approximately equal generator frequencies identical, so that they can all feed the common bus.

Claims

1. An electrical distribution system for co-operation with one or more engines, comprising a plurality of generators associated with the engines, driven at mechanical frequencies that can differ from each other, a common bus to which power output of the generators is to be supplied, and one or more converters between each generator and the bus for influencing the frequency of the output of the generators;

in which the system further includes a control system for setting the AC bus frequency in such a way that it can vary with time, the control system acting to control the converters to feed energy into or draw energy from the generators so that all generators supply an output at the bus frequency.

2. An electrical system according to claim 1, in which the control system is adapted to monitor the mechanical frequency of the generators continually and to calculate a suitable bus frequency.

3. An electrical system according to claim 2, in which the control system includes converter controllers associated with the converters and communication lines between these controllers.

4. An electrical system according to claim 1, in which one or more of the generators is a Doubly Fed Induction Generator.

5. An electrical system according to claim 1, in which the converters converters are connected to their respective generators generators via respective power transfer devices.

6. An aircraft including an electrical system according to claim 1 for supplying its electrical power.

7. An aircraft according to claim 6 and having two engines, there being two generators associated with each engine.

8. An aircraft including at least one engine, a plurality of generators associated with the or each engine, driven at mechanical frequencies that can differ from each other, a common bus to which the output power of the generator is to be supplied, and one or more converters between each generators and the bus for influencing the frequency of the output of the generators;

in which the system further includes a control system for setting the AC bus frequency in such a way that it can vary with time.

9. A method of distributing electrical power generated by one or more engines by means of a plurality of generators associated with the or each engine driven at differing mechanical frequencies, a common bus to which the power is to be supplied, and one or more converters between each generators and the bus for influencing the frequency of the output of the generators;

in which the converters are operated in such a way that at an instant the generators all output power at the same frequency, but the mechanical frequency varies with time as the engine speed varies.

10. A method according to claim 9, in which the difference between the mechanical speed of the generators is at most 5%.

11. A method according to claim 9 further comprising the steps of selecting a primary generator from the plurality of generators;

and adjusting the output frequency of the remaining of the plurality of generators to match the primary generator.