System and method of decoupling drivetrain related power oscillations of an inverter-based resource from active power injected into the electrical grid
A method for decoupling a mechanical drivetrain resonance mode of an inverter-based resource from the external electrical system includes receiving one or more voltage feedback signals at a node between the inverter-based resource and the external electrical system. The method also includes filtering the one or more voltage feedback signals to extract changes in a voltage at a frequency associated with the drivetrain resonance mode. Further, the method includes determining at least one current command or power command based on the filtered one or more voltage feedback signals. Moreover, the method includes controlling the power converter according to the at least one current command and controlling the energy buffer according to the power command so as to reduce or eliminate the changes in the voltage at the frequency associated with the drivetrain resonance mode.
1. A method for decoupling a mechanical drivetrain resonance mode of an inverter-based resource from an external electrical system, the inverter-based resource having a power converter, a generator, and an energy buffer, the method comprising:
receiving, via a controller, one or more voltage feedback signals at a node between the inverter-based resource and the external electrical system;
filtering, via the controller, the one or more voltage feedback signals to extract changes in a voltage at a frequency associated with the drivetrain resonance mode;
determining, via the controller, at least one current command or power command based on the filtered one or more voltage feedback signals; and
controlling the power converter according to the at least one current command and controlling the energy buffer according to the power command so as to reduce or eliminate the changes in the voltage at the frequency associated with the drivetrain resonance mode.
2. The method of claim 1 , wherein the one or more voltage feedback signals comprise x and y voltage feedback signals.
3. The method of claim 1 , further comprising calculating, via the controller, an angle rotating at a desired predetermined frequency associated with the inverter-based resource.
4. The method of claim 3 , wherein filtering the one or more voltage feedback signals to extract the changes in the voltage at the frequency associated with the drivetrain resonance mode further comprises:
filtering, via a first filter, the one or more voltage feedback signals to remove one or more direct current (DC) components associated with a fundamental frequency; and
subsequently filtering, via a second filter, the one or more voltage feedback signals to remove high frequency components not associated with the desired predetermined frequency.
5. The method of claim 4 , wherein the first filter is a high-pass filter and the second filter is a low-pass filter.
6. The method of claim 4 , further comprising:
rotating, via the controller, the one or more voltage feedback signals from a synchronous reference frame to a reference frame rotating at the desired predetermined frequency after filtering via the first filter and before filtering via the second filter,
wherein in the reference frame, components of a terminal voltage of the inverter-based resource oscillating at the desired predetermined frequency appear as direct current (DC) components.
7. The method of claim 6 , wherein determining the at least one current command or the power command based on the filtered one or more voltage feedback signals further comprises:
generating, via an integral controller of the controller, an output using the rotated one or more voltage feedback signals,
wherein an intended reference voltage at the desired predetermined frequency of the integral controller is set to zero (0) and the output of the integral controller is a shunt current injection needed to drive the changes in the voltage at the predetermined frequency to zero.
8. The method of claim 7 , wherein determining the at least one current command or the power command based on the filtered one or more voltage feedback signals further comprises:
rotating the output associated with the desired predetermined frequency back to the synchronous reference frame to generate a desired current; and
determining the at least one current command or the power command based on the desired current.
9. The method of claim 8 , wherein rotating the output associated with the desired predetermined frequency back to the synchronous reference frame further comprises applying a predetermined phase shift setting.
10. The method of claim 1 , wherein the energy buffer comprises one of a dynamic brake, a capacitor, or a battery.
11. The method of claim 1 , wherein the inverter-based resource comprises one of a wind turbine power system, a solar power system, a hydro-generator, or combinations thereof.
12. An inverter-based resource connected to an external electrical system, the inverter-based resource comprising:
a generator;
an energy buffer;
a power converter coupled to the generator; and
a controller comprising at least one processor configured to perform a plurality of operations, the plurality of operations comprising:
receiving one or more voltage feedback signals at a node between the inverter-based resource and the external electrical system;
filtering the one or more voltage feedback signals to extract changes in voltage at a frequency associated with a drivetrain resonance mode;
determining at least one current command or power command based on the filtered one or more voltage feedback signals; and
controlling the power converter according to the at least one current command and controlling the energy buffer according to the power command so as to reduce or eliminate the changes in the voltage at the frequency associated with the drivetrain resonance mode.
13. The inverter-based resource of claim 12 , wherein the one or more voltage feedback signals comprise x and y voltage feedback signals.
14. The inverter-based resource of claim 12 , wherein the plurality of operations further comprises:
calculating an angle rotating at a desired predetermined frequency associated with the inverter-based resource.
15. The inverter-based resource of claim 14 , wherein filtering the one or more voltage feedback signals to extract the changes in the voltage at the frequency associated with the drivetrain resonance mode further comprises:
filtering, via a first filter, the one or more voltage feedback signals to remove one or more direct current (DC) components associated with a fundamental frequency; and
subsequently filtering, via a second filter, the one or more voltage feedback signals to remove high frequency components not associated with the desired predetermined frequency.
16. The inverter-based resource of claim 15 , wherein the plurality of operations further comprises:
rotating the one or more voltage feedback signals from a synchronous reference frame to a reference frame rotating at the desired predetermined frequency after filtering via the first filter and before filtering via the second filter,
wherein in the reference frame, components of a terminal voltage of the inverter-based resource oscillating at the desired predetermined frequency appear as direct current (DC) components.
17. The inverter-based resource of claim 16 , wherein determining the at least one current command or the power command based on the filtered one or more voltage feedback signals further comprises:
generating, via an integral controller of the controller, an output using the rotated one or more voltage feedback signals,
wherein an intended reference voltage at the desired predetermined frequency of the integral controller is set to zero (0) and the output of the integral controller is a shunt current injection needed to drive the changes in the voltage at the predetermined frequency to zero.
18. The inverter-based resource of claim 17 , wherein determining the at least one current command or the power command based on the filtered one or more voltage feedback signals further comprises:
rotating the output associated with the desired predetermined frequency back to the synchronous reference frame to generate a desired current; and
determining the at least one current command or the power command based on the desired current.
19. The inverter-based resource of claim 18 , wherein rotating the output associated with the desired predetermined frequency back to the synchronous reference frame further comprises applying a predetermined phase shift setting.
20. The inverter-based resource of claim 12 , wherein the energy buffer comprises one of a dynamic brake, a capacitor, or a battery, and wherein the inverter-based resource comprises one of a wind turbine power system, a solar power system, a hydro-generator, or combinations thereof.