Electrical power grid for a downhole BHA

1. A string of downhole tools comprising:

an electrical power grid electrically connecting at least a first power generating tool and a second power consuming tool in the string; and

the power generating tool including a power generator, an electric load, and a power management controller, the power management controller configured to automatically selectively electrically connect and disconnect the power generating tool to and from the power grid,

wherein the power management controller is configured to connect a tool bus on the power generating tool to the power grid when a DC voltage level on the tool bus is greater than a predetermined value;

wherein the power management controller comprises an integrated circuit switch configured to close when the DC voltage level on the tool bus is greater than the predetermined value and open when the DC voltage level on the tool bus is less than the predetermined value;

wherein the power management controller comprises an integrated circuit switch configured to repeatedly open and close at a predetermined frequency when the DC voltage level on the tool bus is greater than the predetermined value and open when the DC voltage level on the tool bus is less than the predetermined value, said repeated opening and closing operative to provide AC power to the power grid.

2. The string of tools of claim 1 , wherein the power management controller is configured to connect the power generating tool to the power grid when the power generating tool has surplus electrical power available.

3. The string of tools of claim 1 , wherein the power generating tool and the power consuming tool are connected via a hardwired electrical connection.

4. The string of tools of claim 1 , wherein the power generating tool and the power consuming tool are connected via an inductive coupling.

5. The string of tools of claim 1 , wherein the power generating tool comprises a rotary steerable drilling tool and the power generator comprises a drilling fluid flow-driven turbine.

6. The string of tools of claim 1 , wherein the string comprises a plurality of power generating tools, each of which includes a power generator, an electric load, and a

power management controller configured to selectively electrically connect and disconnect the corresponding power generating tool to and from the power grid.

7. The string of tools of claim 1 , wherein the string comprises a plurality of power consuming tools, each of which includes an electric load and a power management controller configured to selectively electrically connect and disconnect the corresponding power consuming tool to and from the power grid.

8. The string of tools of claim 1 , wherein the power generating tool further comprises a rectifier and an inverter, the rectifier being configured to convert AC power produced by the power generator to DC power on a tool bus, the inverter being configured to convert DC power on the tool bus to AC power for an electric actuator, the power management controller configured to connect the tool bus to the power grid when surplus electrical power is available on the tool bus.

9. A string of downhole tools comprising:

an electrical power grid electrically connecting at least first and second downhole tools in the string, each of which generates an consumes electrical power; and

each of the tools including a power management controller, the power management controller configured to automatically selectively electrically connect and disconnect the corresponding tool to and from the power grid wherein the power management controller is configured to connect a corresponding tool to the power grid (i) when a DC voltage level on a tool bus is greater than a first predetermined value or (ii) when the DC voltage level on the tool bus is less than a second predetermined value;

wherein: the power management controller comprises first and second integrated circuit switches:

the first switch being configured to close when the DC voltage level on the tool bus is greater than the first predetermined value and open when the DC voltage level on the tool bus is less than the first predetermined value; and

the second switch being configured to close when the DC voltage level on the tool bus is less than the second predetermined value and open when the DC voltage level on the tool bus is greater than the second predetermined value

wherein: the power management controller comprises first and second integrated circuit switches;

the first switch configured to repeatedly open and close at a predetermined frequency when the DC voltage level on the tool bus is greater than the predetermined value and open when the DC voltage level on the tool bus is greater than the predetermined value and open when the DC voltage level on the tool bus is less than the predetermined value, and repeated opening and closing operative to provide AC power to the power grid; and the second switch being configured to close when the DC voltage on the tool bus is less than the second predetermined value and open when the DC voltage level on the tool bus is greater than the second predetermined value and

wherein the power management controller further comprises rectifying circuitry configured to rectify AC power on the power grid to DC power on the tool bus when the second switch is closed.

10. The string of tools of claim 9 , wherein the power management controller is configured to connect the corresponding tool to the power grid (i) when surplus electrical power is available in the tool so as to provide electrical power to the power grid or (ii) when insufficient electrical power is available in the tool so as to obtain electrical power from the grid.

11. The string of tools of claim 9 , wherein the first and second downhole tools are connected via a hardwired electrical connection.

12. The string of tools of claim 9 , wherein the first and second downhole tools are connected via an inductive coupling.