Method and apparatus for impedance matching in virtual impedance droop controlled power conditioning units
A method and apparatus for setting an impedance of a power conditioning unit (PCU). In one embodiment, the method comprises applying a disturbance to a virtual AC voltage produced by a power conditioning unit (PCU) that is coupled to a power grid, where the disturbance has a first phase; measuring a second phase of the applied disturbance on the power grid; comparing the second phase of the applied disturbance to the first phase of the disturbance; and adjusting, when the second phase differs from the first phase by more than a threshold amount, an impedance of the PCU.
1. A method for setting an impedance of a power conditioning unit (PCU), comprising:
applying a disturbance to a virtual AC voltage produced by a power conditioning unit (PCU) that is coupled to a power grid, where the disturbance has a first phase;
measuring a second phase of the applied disturbance on the power grid;
comparing the second phase of the applied disturbance to the first phase of the disturbance; and
adjusting, when the second phase differs from the first phase by more than a threshold amount, an impedance of the PCU.
2. The method of claim 1 , wherein the disturbance is a tone voltage.
3. The method of claim 2 , wherein the frequency of the tone voltage is within the range of 200 Hz-1 kHz.
4. The method of claim 1 , wherein adjusting the impedance comprises decreasing an impedance ratio when the second phase lags the first phase.
5. The method of claim 1 , wherein adjusting the impedance comprises increasing an impedance ratio when the second phase leads the first phase.
6. The method of claim 1 , wherein the PCU is a DC-AC inverter.
7. The method of claim 5 , wherein the DC-AC inverter is coupled to a photovoltaic (PV) module for receiving a DC input.
8. An apparatus for setting an impedance of a power conditioning unit (PCU), comprising:
a controller, comprising at least one central processing unit, for (i) applying a disturbance to a virtual AC voltage produced by a power conditioning unit (PCU) that is coupled to a power grid, where the disturbance has a first phase; (ii) measuring a second phase of the applied disturbance on the power grid; (iii) comparing the second phase of the applied disturbance to the first phase of the disturbance; and (iv) adjusting, when the second phase differs from the first phase by more than a threshold amount, an impedance of the PCU.
9. The apparatus of claim 8 , wherein the disturbance is a tone voltage.
10. The apparatus of claim 9 , wherein the frequency of the tone voltage is within the range of 200 Hz-1 kHz.
11. The apparatus of claim 8 , wherein adjusting the impedance comprises decreasing an impedance ratio when the second phase lags the first phase.
12. The apparatus of claim 8 , wherein adjusting the impedance comprises increasing an impedance ratio when the second phase leads the first phase.
13. The apparatus of claim 8 , wherein the PCU is a DC-AC inverter.
14. The apparatus of claim 12 , wherein the DC-AC inverter is coupled to a photovoltaic (PV) module for receiving a DC input.
15. A system for setting an impedance of a power conditioning unit (PCU), comprising:
a plurality of DC power sources; and
a plurality of PCUs coupled to the plurality of DC power sources in a one-to-one correspondence, wherein each PCU of the plurality of PCUs comprises a controller, the controller comprising at least one central processing unit, for (i) applying a disturbance to a virtual AC voltage produced by a power conditioning unit (PCU) that is coupled to a power grid, where the disturbance has a first phase; (ii) measuring a second phase of the applied disturbance on the power grid; (iii) comparing the second phase of the applied disturbance to the first phase of the disturbance; and (iv) adjusting, when the second phase differs from the first phase by more than a threshold amount, an impedance of the PCU.
16. The system of claim 15 , wherein adjusting the impedance comprises decreasing an impedance ratio when the second phase lags the first phase.
17. The system of claim 15 , wherein adjusting the impedance comprises increasing an impedance ratio when the second phase leads the first phase.
18. The system of claim 15 , wherein each PCU of the plurality of PCUs is a DC-AC inverter.
19. The system of claim 15 , wherein each DC power source of the plurality of DC power sources is a photovoltaic (PV) module.
20. The system of claim 15 , wherein the disturbance is a tone voltage having a frequency within the range of 200 Hz-1 kHz.