System and method for admittance model identification for inverter-based resources
A system and method for obtaining frequency-domain admittance/impedance using a few sets of time-series data. Utilizing an Eigensystem Realization Algorithm (ERA) or a dynamic mode decomposition (DMD), the input/output frequency-domain model reflecting voltage/current relationship is identified, and admittance/impedance identification is demonstrated for a grid-connected inverter-based resource (IBR) system. The proposed approach provides a powerful tool to replace the state-of-the-art harmonic injection methodology.
1. A method for admittance identification of a grid-connected inverter-based resource (IBR), the method comprising:
capturing transient data in response to at least two independent time-domain events on a bus between a grid-connected IBR and a power grid;
sampling the captured transient data to generate sampled transient data;
generating an s-domain expression of the transient data from the sampled transient data; and
identifying a dq-frame admittance model of the IBR from the s-domain expression of the transient data.
2. The method of claim 1 , wherein the at least two independent time-domain events comprises a first time-domain event and a second time-domain event and wherein the method further comprises:
capturing a first set of transient data in response to the first time-domain event; and
capturing a second set of transient data in response to the second time-domain event.
3. The method of claim 1 , wherein the at least two independent time-domain events are step change events.
4. The method of claim 1 , wherein the at least two independent time-domain events are voltage perturbations on the bus and wherein capturing the transient data in response to the at least two independent time-domain events on the bus comprises measuring a transient current flowing to the IBR.
5. The method of claim 1 , wherein the at least two independent time-domain events are voltage perturbations on the bus and wherein capturing the transient data in response to the at least two independent time-domain events on the bus comprises measuring a transient voltage time-series data at a terminal voltage of the IBR.
6. The method of claim 1 , wherein sampling the captured transient data to generate the sampled transient data comprises sampling the captured transient data at equal intervals and wherein generating the s-domain expression of the transient data further comprises
applying an Eigensystem Realization Algorithm (ERA) to the sampled transient data to generate the s-domain expression of the transient data.
7. The method of claim 1 , wherein sampling the captured transient data to generate the sampled transient data comprises sampling the captured transient data at equal intervals and wherein generating the s-domain expression of the transient data further comprises
applying dynamic mode decomposition (DMD) to the sampled transient data to generate the s-domain expression of the transient data.
8. The method of claim 7 , further comprising denoising the s-domain expression of the transient data.
9. The method of claim 1 , wherein the transient data is captured during real-time operation of the IBR.
10. The method of claim 1 , wherein the at least two independent time-domain events are the result of external perturbations outside of the IBR device.
11. The method of claim 1 , wherein the IBR is a wind resource or a photovoltaic solar resource.
12. A method for admittance identification of a grid-connected voltage source converter inverter-based resource (IBR), the method comprising:
capturing a first set of transient data in response to a first time-domain event on a bus between a grid-connected inverter-based resource (IBR) and) a power grid, wherein the first set of transient data comprises transient data for a first current flowing to the IBR in response to the first time-domain event on the bus and a first transient data for a bus voltage;
capturing a second set of transient data in response to a second time-domain event on the bus between the IBR and the power grid, wherein the second time-domain event is independent of the first time-domain event and wherein the second set of transient data comprises transient data for a second current flowing to the IBR in response to the second time-domain event on the bus and a second transient data for the bus voltage; and
identifying a dq-frame admittance model of the grid-connected IBR from the first set of transient data and the second set of transient data.
13. The method of claim 12 , further comprising:
sampling the captured transient data at equal intervals to generate sampled transient data; and
applying an Eigensystem Realization Algorithm (ERA) to the sampled transient data to generate an s-domain expression of the transient data.
14. The method of claim 12 , further comprising:
sampling the captured transient data at equal intervals to generate sampled transient data; and
applying dynamic mode decomposition (DMD) to the sampled transient data to generate an s-domain expression of the transient data.
15. The method of claim 13 , further comprising denoising the s-domain expression of the transient data.
16. The method of claim 14 , further comprising denoising the s-domain expression of the transient data.
17. A system for measuring an admittance of a grid-connected inverter-based resource (IBR), the system comprising:
a measurement unit coupled to a point of interconnection (POI) between a power grid and an inverter-based resource (IBR);
the measurement unit for:
capturing transient data in response to at least two independent time-domain events on a bus between the IBR and the power grid;
sampling the captured transient data to generate sampled transient data;
generating an s-domain expression of the transient data from the sampled transient data; and
identifying a dq-frame admittance model of the IBR from the s-domain expression of the transient data.
18. The system of claim 17 , wherein the at least two independent time-domain events are voltage perturbations on the bus and wherein capturing the transient data in response to the at least two independent time-domain events on the bus comprises measuring a transient current flowing to the IBR.
19. The system of claim 17 , wherein the at least two independent time-domain events are voltage perturbations on the bus and wherein capturing the transient data in response to the at least two independent time-domain events on the bus comprises measuring a transient voltage time-series data at the POI.
20. The system of claim 17 , wherein the IBR is a wind resource or a photovoltaic solar resource.