Methods for minimizing double-frequency ripple power in single-phase power conditioners
View Patent ↗A method is provided for minimizing a double-frequency ripple power exchanged between a load and an energy source, the energy source delivering electrical power to the load through a single-phase power conditioner, and the power conditioner being coupled to an energy storage device. The method senses a first AC waveform at the output of the power conditioner, generates a second AC waveform at the energy storage device, the second AC waveform having the same frequency as the first AC waveform, and shifts the second AC waveform by a phase shift equal to π/4 radians relative to a phase of the first AC waveform, thereby minimizing the double-frequency ripple power in the power supplied by the energy source.
1. A method for minimizing a double-frequency ripple power exchanged between a load and an energy source, the energy source delivering electrical power to the load through a single-phase power conditioner, and the power conditioner being coupled to an energy storage device, the method comprising:
sensing a first AC waveform at the output of the power conditioner;
generating a second AC waveform at the energy storage device, the second AC waveform having the same frequency as the first AC waveform; and
shifting the second AC waveform by a phase shift equal to about π/4 radians relative to a phase of the first AC waveform, thereby minimizing the double-frequency ripple power in the power supplied by the energy source.
2. The method of claim 1 , wherein the energy storage device is an ultracapacitor, a capacitor, or an inductor.
3. The method of claim 1 , wherein the energy storage device is coupled to the power conditioner through an interface which controls a flow of electrical power into and out of the energy storage device.
4. The method of claim 3 , wherein the interface is a power converter or a power inverter.
5. The method of claim 1 , wherein the energy source is a photovoltaic array, fuel cell, or any other DC energy source.
6. The method of claim 1 , wherein the second AC waveform is controlled by alternatively conducting and blocking the flow of power from the energy storage device to the power conditioner.
7. The method of claim 6 , wherein the control of the second AC waveform is performed via pulse width modulation (PWM), delta modulation, or hysteretic control.
8. The method of claim 1 , wherein the energy storage device is integral to the power conditioner.
9. The method of claim 1 , wherein the power supplied from the energy source is the sum of power delivered to the output of the power conditioner and the power delivered to the energy storage device.
10. An apparatus for minimizing a double-frequency ripple power exchanged between a load and an energy source, the energy source delivering electrical energy to the load through a single-phase power conditioner, and the power conditioner being coupled to an energy storage device, the apparatus comprising:
a sensing unit for sensing a first AC waveform at the output of the power conditioner; and
a controlling unit for generating a second AC waveform at the output of the energy storage device, the second AC waveform having the same frequency as the first AC waveform, and for shifting the second AC waveform by a phase shift equal to about π/4 radians relative to a phase of the first AC waveform, thereby minimizing the double-frequency ripple power in the power supplied by the energy source.
11. The apparatus of claim 10 , wherein the energy storage device is an ultracapacitor, a capacitor, or an inductor.
12. The apparatus of claim 10 , wherein the energy storage device is coupled to the power conditioner through an interface which controls a flow of electrical energy into and out of the energy storage device.
13. The apparatus of claim 12 , wherein the interface is a power converter or a power inverter.
14. The apparatus of claim 10 , wherein the energy source is a photovoltaic array, fuel cell, or any other dc energy source.
15. The apparatus of claim 10 , wherein the second AC waveform is controlled by alternatively conducting and blocking the flow of power from the energy storage device to the power conditioner.
16. The apparatus of claim 15 , wherein the control of the second AC waveform is performed via pulse width modulation (PWM), delta modulation, or hysteretic control.
17. The apparatus of claim 10 , wherein the energy storage device is integral to the power conditioner.
18. The apparatus of claim 10 , wherein the power supplied from the energy source is the sum of power delivered to the output of the power conditioner and the power from the energy storage device.
19. A tangible computer readable medium comprising instructions which when executed by a computer system causes the computer to implement a method for minimizing a double-frequency ripple power exchanged between a load and an energy source, the energy source delivering electrical power to the load through a single-phase power conditioner, and the power conditioner being coupled to an energy storage device, the method comprising the steps of:
sensing a first AC waveform at the output of the power conditioner;
generating a second AC waveform at the output of the energy storage device, the second AC waveform having the same frequency as the first AC waveform; and
shifting the second AC waveform by a phase shift equal to about π/4 radians relative to a phase of the first AC waveform, thereby minimizing the double-frequency ripple power in the power supplied by the energy source.
20. A system for performing a method for minimizing a double-frequency ripple power exchanged between a load and an energy source, the energy source delivering electrical power to the load through a single-phase power conditioner, and the power conditioner being coupled to an energy storage device, the system comprising:
at least one processor programmed to sense a first AC waveform at the output of the power conditioner;
at least one processor programmed to generate a second AC waveform at the output of the energy device, the second AC waveform having the same frequency as the first AC waveform; and
at least one processor programmed to shift the second AC waveform by a phase shift equal to about π/4 radians relative to a phase of the first AC waveform, thereby minimizing the double-frequency ripple power in the power supplied by the energy source.
21. A method for minimizing a double-frequency ripple power exchanged between a load and an energy source, the energy source delivering electrical power to the load through a single-phase power conditioner, and the power conditioner being coupled to an energy storage device, the method comprising the steps of:
sensing a first AC waveform at the output of the power conditioner;
generating a second AC waveform, the second ac waveform having the same frequency as the first AC waveform;
shifting the second waveform to provide an equivalent phase shift equal to about π/4 radians relative to a phase of the first AC waveform; and
generating a third AC waveform at the energy storage device, the third AC waveform having a form that is a piecewise combination of the second AC waveform and its inverse, thereby minimizing the double-frequency ripple power in the power supplied by the energy source, and maintaining either positive voltage or positive current delivered to the energy storage device at all times.