Maximum power point tracking for a power generator
A maximum power point tracking method and system for use with a power generator comprises sampling instantaneous output voltage and current of the power generator at a first instant in time and at a second instant in time to obtain first and second power samples, generating a reference voltage or current signal from a difference of the first and second power samples; comparing the reference voltage or current to the instantaneous power generator voltage or current and generating at least one gating signal; and repeating so as to minimize the difference of the first and second power samples; wherein the gating signal affects magnitude of the output voltage and current of the power generator; wherein the maximum power point is tracked when the difference signal is minimized. The power generator may be at least one photovoltaic cell, wind turbine, or fuel cell.
1. A method of tracking a maximum power point of a power generator, comprising:
(i) obtaining first and second power samples from a product of instantaneous output voltage and current of the power generator at a first instant in time and at a second instant in time, respectively,
wherein the instantaneous voltage or current at a first instant in time is always greater than the instantaneous voltage or current at a second instant in time, or
wherein the instantaneous voltage or current at a first instant in time is always less than the instantaneous voltage or current at a second instant in time;
(ii) using a first controller to generate a reference voltage signal or a reference current signal from a difference of the first and second power samples;
(iii) using a second controller to generate at least one gating signal for a power converter from a difference of the reference voltage signal or reference current signal and an instantaneous power generator voltage or current, the at least one gating signal being generated at a next instant in time; and
(iv) repeating (i) to (iii) so as to minimize the difference of the first and second power samples;
wherein the power converter affects magnitude of the output voltage and current of the power generator; and
wherein the maximum power point is tracked when the difference of the first and second power samples is minimized.
2. The method of claim 1 , wherein generating a reference voltage or current signal from a difference of the first and second power samples includes using a proportional-integral (PI) controller.
3. The method of claim 1 , comprising sweeping the output voltage of the power generator for a range of maximum power points, determining a global maximum power point, and setting a starting point for maximum power point tracking as close as possible to the global maximum power point.
4. The method of claim 1 , wherein the power generator is a photovoltaic cell, a wind turbine, or a fuel cell.
5. The method of claim 1 , wherein the power generator comprises at least one photovoltaic cell.
6. A maximum power point tracker for a power generator, comprising:
(i) a sampling circuit that provides first and second power samples from a product of instantaneous output voltage and current of the power generator at a first instant in time and at a second instant in time, respectively,
wherein the instantaneous voltage or current at a first instant in time is always greater than the instantaneous voltage or current at a second instant in time, or
wherein the instantaneous voltage or current at a first instant in time is always less than the instantaneous voltage or current at a second instant in time;
(ii) a first controller that generates a reference voltage signal or a reference current signal from a difference of the first and second power sample; and
(iii) a second controller that generates at least one gating signal for a power converter from a difference of the reference voltage signal or reference current signal and an instantaneous power generator voltage or current, the at least one gating signal being generated at a next instant in time;
wherein the power converter affects magnitude of the output voltage and current of the power generator; and
wherein the maximum power point is tracked when the difference of the first and second power samples is minimized.
7. The maximum power point tracker of claim 6 , wherein the first controller that generates the reference voltage or current signal comprises a proportional-integral (PI) controller.
8. The maximum power point tracker of claim 6 , comprising a circuit that sweeps the output voltage of the power generator for a range of maximum power points, determines a global maximum power point, and sets a starting point for maximum power point tracking as close as possible to the global maximum power point.
9. The maximum power point tracker of claim 6 , wherein the power generator is a photovoltaic cell, a wind turbine, or a fuel cell.
10. The maximum power point tracker of claim 6 , wherein the power generator comprises at least one photovoltaic cell.
11. A micro-inverter for a power generator, comprising:
the maximum power point tracker of claim 6 ; and
a power converter.
12. The micro-inverter of claim 11 , wherein the power converter comprises a DC-DC converter and a DC-AC inverter.
13. The micro-inverter of claim 11 , wherein the power converter generates a sinusoidal output current from the power generator output.
14. The micro-inverter of claim 11 , wherein the power generator is a photovoltaic cell, a wind turbine, or a fuel cell.
15. The micro-inverter of claim 11 , wherein the power generator comprises at least one photovoltaic cell.
16. A power generation system, comprising:
the micro-inverter of claim 11 ; and
at least one power generator.
17. The system of claim 16 , wherein the power generator is a photovoltaic cell, a wind turbine, or a fuel cell.
18. The system of claim 16 , wherein the power generator comprises at least one photovoltaic cell.