Maximum power point tracking controllers and associated systems and methods
A maximum power point tracking controller includes an input port for electrically coupling to an electric power source, an output port for electrically coupling to a load, a control switching device, and a control subsystem. The control switching device is adapted to repeatedly switch between its conductive and non-conductive states to transfer power from the input port to the output port. The control subsystem is adapted to control switching of the control switching device to regulate a voltage across the input port, based at least in part on a signal representing current flowing out of the output port, to maximize a signal representing power out of the output port.
1. A method for transferring electric power between an electric power source and a load using a maximum power point tracking controller, comprising:
controlling switching of a control switching device of the maximum power point tracking controller, based at least in part on a signal representing current flowing through energy storage inductance of the maximum power point tracking controller and a reference signal, to regulate a voltage across the electric power source, such that the voltage across the electric power source is greater than or equal to a voltage across the load;
multiplying a signal representing voltage across an output port of the maximum power point tracking controller by a signal representing current flowing through the output port of the maximum power point tracking controller, to generate a signal representing power transferred to the load; and
varying the reference signal so that the signal representing power transferred to the load is maximized.
2. The method of claim 1 , further comprising controlling switching of the control switching device based at least in part on the signal representing current flowing through the energy storage inductance of the maximum power point tracking controller and a difference between magnitude of the voltage across the electric power source and the reference signal.
3. The method of claim 1 , the signal representing current flowing through the output port of the maximum power point tracking controller being a signal representing average current flowing through the energy storage inductance of the maximum power point tracking controller, and the signal representing voltage across the output port of the maximum power point tracking controller being a signal representing average voltage across the output port of the maximum power point tracking controller.
4. The method of claim 3 , further comprising, before the step of multiplying:
scaling the signal representing average current flowing through the energy storage inductance of the maximum power point tracking controller to be within a first range of values; and
scaling the signal representing average voltage across the output port of the maximum power point tracking controller to be within a second range of values.
5. The method of claim 4 , the first range of values being the same as the second range of values.
6. The method of 4 , further comprising fixing a value of the signal representing average current flowing through the energy storage inductance of the maximum power point tracking controller in response to magnitude of current flowing through the energy storage inductance falling below a threshold value.
7. The method of claim 4 , further comprising adding a positive offset to a value of the signal representing average current flowing through the energy storage inductance of the maximum power point tracking controller in response to magnitude of current flowing through the energy storage inductance falling below a threshold value.
8. The method of claim 1 , further comprising decreasing magnitude of the reference signal in response to magnitude of the signal representing current flowing through the energy storage inductance of the maximum power point tracking controller falling below a threshold value.
9. The method of claim 1 , further comprising:
changing magnitude of the reference signal by a first step size when a command to control a duty cycle of the control switching device is below a first threshold value; and
changing magnitude of the reference signal by a second step size, different from the first step size, when the command to control the duty cycle of the control switching device is above a second threshold value.
10. The method of claim 9 , wherein:
the second step size is smaller than the first step size; and
the first threshold value is less than or equal to the second threshold value.
11. The method of claim 1 , further comprising:
changing magnitude of the reference signal at a first rate when a command to control a duty cycle of the control switching device is within a first range of values; and
changing magnitude of the reference signal at a second rate, different from the first rate, when the command to control the duty cycle of the control switching device is within a second rage of values.
12. The method of claim 11 , wherein the second rate is greater than the first rate.
13. The method of claim 12 , wherein:
the first range of values represents a command that the duty cycle of the control switching device be between zero and one hundred percent; and
the second range of values represents a command that the duty cycle of the control switching device be less than zero or greater than one hundred percent.