Downhole power generation system

1. An apparatus for generating electrical power downhole comprising:

a housing located in a drillstring;

a primary flow channel through the housing;

at least two secondary flow channels in the housing, the at least two secondary flow channels laterally displaced from the primary flow channel;

a first fluid driven electrical generator positioned within the primary flow channel;

at least one second fluid driven electrical generator positioned in each of the at least two secondary flow channels; and

at least one controllable flow diverter associated with each of the secondary flow channels, the at least one controllable flow diverter being operable to controllably apportion a fluid flow to the primary flow channel and to at least one of the at least two secondary flow channels to drive the generator therein.

2. The apparatus of claim 1 further comprising a controller operably coupled to each of the fluid driven generators and to each controllable flow diverter wherein the controller acts according to programmed instructions to detect at least one parameter of interest of each of the generators and to actuate each of the flow diverters based on the at least one parameter of interest.

3. The apparatus of claim 2 wherein the at least one parameter of interest is chosen from the group consisting of: generator output voltage and generator rotational speed.

4. The apparatus of claim 1 wherein the at least two secondary flow channels are positioned axially spaced apart along the housing.

5. The apparatus of claim 1 wherein the at least two secondary flow channels are spaced apart circumferentially around the primary flow channel.

6. The apparatus of claim 1 wherein the drillstring comprises wired drill pipe.

7. A method of generating electrical energy downhole comprising;

positioning a housing located in a drillstring;

forming a primary flow channel through the housing;

forming at least two secondary flow channels in the housing, the at least two secondary flow channels laterally displaced from the primary flow channel;

positioning a first fluid driven electrical generator positioned within the primary flow channel;

positioning at least one second fluid driven electrical generator in each of the at least two secondary flow channels; and

using at least one controllable flow diverter to controllably apportion fluid flow to the primary flow channel and to at least one of the at least two secondary flow channels to drive the second fluid driven electrical generator therein.

8. The method of claim 7 further comprising operably coupling a controller to each of the fluid driven generators and to each controllable flow diverter; detecting at least one parameter of interest of each of the generators; and controllably actuating each of the flow diverters based on the least one parameter of interest.

9. The method of claim 8 wherein the at least one parameter of interest is chosen from the group consisting of: generator output voltage and generator rotational speed.

10. The method of claim 7 further comprising positioning the at least two secondary flow channels axially spaced apart along the housing.

11. The method of claim 7 further comprising positioning the at least two secondary flow channels spaced apart circumferentially around the primary flow channel.

12. The method of claim 7 wherein the drillstring comprises wired drill pipe.

13. An apparatus for generating electrical power downhole comprising:

a housing located in a drillstring;

a primary flow channel through the housing;

at least one secondary flow channels in the housing, the at least one secondary flow channel laterally displaced from the primary flow channel;

a first fluid driven electrical generator positioned in the primary flow channel;

at least one second fluid driven electrical generator positioned in the at least one secondary flow channel; and

a controllable flow diverter to controllably apportion the fluid flow to the primary flow channel and the at least one secondary flow channel to drive the generators therein.

14. The apparatus of claim 13 further comprising a controller operably coupled to each of the fluid driven generators and to the controllable flow diverter wherein the controller acts according to programmed instructions to detect at least one parameter of interest of each of the generators and to actuate the flow diverter based on the at least one parameter of interest.

15. The apparatus of claim 14 wherein the at least one parameter of interest is chosen from the group consisting of: generator output voltage and generator rotational speed.