Distributed power generation interface

1. A controller for a power circuit that interfaces distributed power generation with a power distribution grid, comprising:

a first circuit that receives signals corresponding to the distributed power generation voltage and current, and outputs to the power circuit a signal for controlling the voltage or current of the distributed power generation;

a dc voltage or dc current controller that receives a dc voltage or dc current of the power circuit and generates a power signal;

a current reference generator that receives the power signal from the dc voltage or dc current controller and receives signals corresponding to the power distribution grid voltage and current, and outputs a current reference signal;

an output current controller that minimizes a difference between the output grid current and the current reference signal from the current reference generator and outputs a first control signal;

a harmonic rejection and/or dc rejection circuit that receives a signal corresponding to the power distribution grid voltage or current and outputs a second control signal; and

a second circuit that receives the first and second control signals and outputs at least one gating signal that controls the power circuit;

such that substantially harmonic-free and/or dc-free power is delivered to the power distribution grid.

2. The controller of claim 1 , wherein the power circuit includes a current source inverter.

3. The controller of claim 1 , wherein the power circuit includes a voltage source inverter.

4. The controller of claim 1 , wherein the distributed power generation includes at least one photovoltaic (PV) module.

5. The controller of claim 1 , wherein the current reference generator:

(i) includes nonlinear elements;

(ii) includes an instantaneous power calculator that generates an instantaneous power reference signal; and

(iii) generates the current reference signal from the instantaneous power reference signal and the grid voltage and current.

6. The controller of claim 5 , including an enhanced phase locked loop (EPLL).

7. The controller of claim 6 , wherein the EPLL provides a phase angle of the grid voltage which is used to generate the instantaneous power reference signal.

8. The controller of claim 1 , wherein the controller accepts real and reactive power commands to control real and reactive power delivered to the power distribution grid.

9. The controller of claim 8 , wherein the real and reactive power commands are set externally.

10. The controller of claim 8 , wherein the real power command is generated by a proportional integral (PI) controller operating on a dc-link voltage error, on a dc link current error, or on a dc-link energy error.

11. The controller of claim 1 , wherein the current reference generator comprises an energy calculator, a notch filter, and at least one PI controller.

12. The controller of claim 11 , including an EPLL.

13. The controller of claim 12 , wherein the EPLL generates parallel and orthogonal signals corresponding to the grid voltage.

14. The controller of claim 13 , wherein a first PI controller operates on an error between (i) a reference energy signal and (ii) an actual energy signal corresponding to the dc voltage of the power circuit, and multiplies a PI output with the parallel signal from the EPLL to generate a real current component of the current reference signal.

15. The controller of claim 13 , wherein a second PI controller operates on an error between (i) a reference reactive power signal and (ii) an actual reactive power signal corresponding to the output power of the power circuit, and multiplies a PI output with the orthogonal signal from the EPLL to generate a reactive component of the current reference signal.

16. The controller of claim 1 , wherein the current controller includes a semi-state feedback control structure combined with a resonant-type output feedback portion.

17. The controller of claim 1 , wherein the current controller includes a semi-state feedback control structure combined with a resonant-type output feedback portion and a soft-start feed forward controller.

18. The controller of claim 17 , wherein the current controller includes one or more resonant-type output feedback portions.

19. The controller of claim 18 , wherein each resonant-type output feedback portion corresponds to a harmonic of the grid voltage.

20. The controller of claim 17 , wherein the current controller includes:

(i) one or more resonant-type harmonic controllers acting on grid current;

(ii) an integrating controller acting on grid current;

(iii) a wide band hail ionic controller in parallel with the resonant-type controller;

(iv) a wide band harmonic controller in series with the resonant-type controller; or

(v) a wide band feed forward harmonic compensator acting on the grid voltage signal; or

(vi) at least a portion of one or more of (i) to (v).

21. The controller of claim 20 , wherein the wide band harmonic controller has a proportional, proportional-derivative, lead, or lead-lag configuration.

22. The controller of claim 20 , wherein the wide band feed forward harmonic compensator has a proportional, proportional-derivative, lead, or lead-lag configuration.

23. The controller of claim 1 , including a maximum power point tracker.