Generator control arrangement

Abstract

Electrical power generation through a number of generators has efficiency benefits particularly with regard to aerospace applications. However, should parallel operation of these generators be interrupted through malfunction of one of the generators or otherwise, care must be taken in order to maintain the rate of electrical voltage for system demands. Previously it has been known to control parallel operating electrical power generators respectively through voltage control and electrical current control regimes so at least some of the generators must be able to operate under both regimes. This necessitated separate control loops which at least is inconvenient. By providing a common voltage comparator which receives a reference electrical current Vtgt from a transfer comparator 23 it is possible to achieve voltage as well as electrical current control. The transfer comparator is associated with a source of a reference voltage value Vcmd and an electrical current control branch where a reference electrical current value Icmd is compared with a measured electrical current Imea such that an error is passed to a gain device 26. The gain device 26 may be set such that the gain is zero or a value greater than zero. When the gain is zero then the transfer comparator 23 will provide the reference voltage value Vcmd to the voltage comparator 22 whilst if the gain is greater than zero in any situation other than zero error in comparison of Icmd and Imea it will be understood that the transfer comparator 23 will provide a reference value to the voltage comparator 22 which deviates from the necessary desired voltage. In such circumstances, a regulator 20 can adjust the generator to achieve the desired output voltage Vout.

Description

An embodiment in accordance with aspects of the present invention will now be described by way of example only with reference to the accompanying drawings in which:

FIG. 2 is a schematic depiction of a generator control arrangement in accordance with aspects of the present invention;

FIG. 3 is a graphic representation of voltage against electrical current for a generator control arrangement in accordance with aspects of the present invention; and

FIG. 4 is a schematic illustration of a gas turbine engine incorporating a control arrangement in accordance with aspects of the present invention.

Claims

1. A generator control arrangement for an electrical power generator, the arrangement comprising a controller arranged to regulate output voltage from a generator to a target value, the controller including a voltage comparator for comparing a presented voltage with a desired output voltage, the presented voltage derived in a transfer comparator by combination of a reference voltage value and an error value between a reference electrical current value and a measured electrical current value subject to a processor gain whereby the processor gain can be specifically set at one of zero, to enable control by voltage, or greater than zero to enable control by electrical current.

2. An arrangement as claimed in claim 1 wherein the value of the processor gain provides a slope characteristic between a target voltage and measured electrical current whose inclination is dependent upon the specific value of the processor gain toward the target value.

3. An arrangement as claimed in claim 1 wherein the specific value of the processor gain is set to provide an appropriate level of sensitivity in terms of the error value for efficient operation of the generator control arrangement.

4. An electrical power generator incorporating a generator control arrangement as claimed in claim 1.

5. An electrical power arrangement for electrical power generation, the arrangement comprising at least two electrical generators and at least one of the electrical generators having a generator control arrangement as claimed in claim 1.

6. An arrangement as claimed in claim 5 wherein all the electrical generators in the electrical generator arrangement have a generator control arrangement for an electrical power generator, the arrangement comprising a controller arranged to regulate output voltage from a generator to a target value, the controller including a voltage comparator for comparing a presented voltage with a desired output voltage, the presented voltage derived in a transfer comparator by combination of a reference voltage value and an error value between a reference electrical current value and a measured electrical current value subject to a processor gain whereby the processor gain can be specifically set at one of zero, to enable control by voltage, or greater than zero to enable control by electrical current.

7. A gas turbine engine incorporating an electrical generator as claimed in claim 4.

8. A gas turbine engine incorporating a generator arrangement as claimed in claim 5.

9. A method of control of an electrical power generator, the method comprising: (a) determining an electrical current error by comparison of a measured electrical current and a reference electrical current value;(b) providing a reference voltage value;(c) applying a specific processor gain to the electrical current error value and comparing the product of applying the specific processor gain to the electrical current error value with the reference voltage value to provide a target voltage value;(d) comparing the target voltage value with an output voltage value;(e) setting the specific processor gain to zero to provide control by reference to the voltage reference value or setting the specific processor gain to greater than zero to provide control by reference to the reference electrical current value.

10. A method as claimed in claim 9 wherein a switch is provided to alternate between the specific processor gain value at zero and a specific processor gain value greater than zero.

11. A method as claimed in claim 9 wherein the switch allows variation in the specific processor gain value greater than zero.