Method and apparatus for controlling a turbogenerator system

1. An apparatus for controlling a turbogenerator in a turbogenerator system when a power electronics circuit of the turbogenerator system is unable to provide a sufficient load on the turbogenerator to prevent the turbogenerator from accelerating uncontrollably, the apparatus comprising:

a monitor comprising:

a first sensing device configured to detect a condition of the turbogenerator and output a turbogenerator detection signal, wherein the turbogenerator is configured to recover waste energy from an engine; and

a second sensing device configured to detect a condition of a grid and output a grid detection signal;

a brake controller configured to:

responsive to the turbogenerator detection signal, issue a first brake control signal for operating a brake to prevent the turbogenerator from accelerating uncontrollably; and

issue a second brake control signal for operating the brake to permit resumption of normal operation of the turbogenerator, and wherein the power electronics circuit is deactivated during a grid disturbance; and

a trigger circuit configured to, in response to the grid detection signal from the second sensing device indicating a cessation of the grid disturbance, reactivate the power electronics unit and begin exporting power to the grid.

2. The apparatus of claim 1 , wherein the brake is a physical brake responsive to the first and second brake control signals to apply and remove, respectively, a braking force to control the speed of the turbogenerator.

3. The apparatus of claim 1 , wherein the brake is a brake circuit responsive to the first and second brake control signals to apply and remove, respectively, a braking force to control the speed of the turbogenerator.

4. The apparatus of claim 1 , wherein the trigger circuit is configured to, in response to the grid detection signal indicating a grid disturbance, de-activate the power electronics unit.

5. The apparatus of claim 1 , wherein the brake controller comprises:

a rectifier circuit arranged to rectify an AC output from the turbogenerator and to supply the rectified output to the brake circuit; and

a switching device configured to issue the first and second brake control signals for controlling the supply of the rectified output to a brake circuit.

6. The apparatus of claim 1 , wherein the power electronics unit comprises:

a convertor circuit configured to generate an AC output; and

a contactor circuit configured to supply a power output in synchronization with the grid, wherein the trigger circuit is configured to, in response to the grid detection signal from the second sensing device indicating a cessation of the grid disturbance, activate the convertor circuit and the contactor circuit and initiate a re-synchronization with the grid.

7. The apparatus of claim 1 , wherein the second sensing device is configured to monitor at least one of grid frequency, grid voltage, and grid current with respect to predetermined upper and lower thresholds for generating the grid detection signal.

8. A method for controlling a turbogenerator in a turbogenerator system when a power electronics circuit of the turbogenerator system is unable to provide a sufficient load on the turbogenerator to prevent the turbogenerator from accelerating uncontrollably, the method comprising:

detecting, by a first sensing device, a condition of the turbogenerator,

outputting, by the first sensing device, a turbogenerator detection signal;

issuing, by a brake controller and in response to the turbogenerator detection signal, a first brake control signal for switching on a brake to prevent the turbogenerator from accelerating uncontrollably, wherein the power electronics circuit is deactivated during a grid disturbance;

issuing, by the brake controller, a second brake control signal for switching off the brake to permit resumption of normal operation of the turbogenerator;

detecting, by a second sensing device, a condition of a grid;

outputting, by the second sensing device, a grid detection signal;

reactivating, by a trigger circuit and in response to the grid detection signal from the second sensing device indicating a cessation of the grid disturbance, the power electronics unit and beginning exporting power to the grid.

9. The method of claim 8 , wherein the brake is a physical brake responsive to the first and second brake control signals to apply and remove, respectively, a braking force to control the speed of the turbogenerator.

10. The method of claim 8 , wherein the brake is a brake circuit responsive to the first and second brake control signals to apply and remove, respectively, a braking force to control the speed of the turbogenerator.

11. The method of claim 8 , further comprising de-activating, by the trigger circuit, the power electronics unit in response to a further grid detection signal from the second sensing device indicating a grid disturbance.

12. The method of claim 8 , wherein the brake controller comprises a rectifier circuit and a switching device, the method further comprising:

operating the brake by means of an output from the rectifier circuit, wherein the rectifier circuit is configured to rectify an AC output from the turbogenerator; and

wherein the switching device is configured to issue the first and second brake control signals and control the supply of the rectified output to a brake circuit.

13. The method according to claim 8 , wherein the power electronics unit comprises a convertor circuit configured to generate an AC output and a contactor circuit configured to supply a power output in synchronization with the grid, the method further comprising:

responding to the grid detection output from the second sensing device indicating a cessation of the grid disturbance by activating the convertor circuit and the contactor circuit and by initiating a re-synchronization with the grid.

14. The method according to claim 8 , further comprising monitoring, by the second sensing device, at least one of grid frequency, grid voltage and grid current with respect to predetermined upper and lower thresholds for generating the grid detection output.