METHODS FOR MINIMIZING DOUBLE-FREQUENCY RIPPLE POWER IN SINGLE-PHASE POWER CONDITIONERS

• US 20110305050A1
• Filed: 08/23/2011
• Published: 12/15/2011
• Est. Priority Date: 10/11/2007
• Status: Active Grant

• Current Assignee: Enphase Energy Incorporated
• Original Assignee: Solarbridge Technologies Incorporated (Totalenergies Se)
• Inventors: Krein, Philip T., Balog, Robert S. Jr.
• Granted Patent: US 8,325,499 B2
• Time in Patent Office: Days
• US Class Current: 363/39
• CPC Class Codes: H02J 1/02 Arrangements for reducing harmonics or ripples
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 2300/30 The power source being a fuel cell
• CPC Class Codes: H02J 3/1835 with stepless control
• CPC Class Codes: H02J 3/1842 wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters
• CPC Class Codes: H02M 1/143 using compensating arrangements for reducing noise from the supply in transmission systems H04B15/005
• CPC Class Codes: H02M 1/15 using active elements
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y02E 40/20 Active power filtering [APF]
• CPC Class Codes: Y02E 40/30 Reactive power compensation

Abstract

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 includes determining a phase shift of an AC output signal of the power condition and an average AC output power of the power conditioner. The average AC output power may be a predetermined value or a calculated value based on sensed or measured signals. The method further includes generating an AC signal at an energy storage device. The generated AC signal has an amplitude that is a function of the average AC output power and a phase shift substantially equal to 45 degrees minus an amount that is dependent on the determined phase shift. In some embodiments, the phase shift may be determined to be of a non-zero value.

Claims

1. A method for reducing a double-frequency ripple power exchanged between a load and an energy source, the energy source being configured to deliver electrical output power to the load through a single-phase power conditioner, the method comprising:

determining a first phase shift of an alternating current (AC) output signal of the power conditioner;

determining an average AC output power of the power conditioner; and

generating an AC signal at an energy storage device, the AC signal having (i) an amplitude that is a function of the average AC output power and (ii) a phase shift substantially equal to 45 degrees minus an amount that is dependent on the determined first phase shift.

2. The method of claim 1, wherein determining the first phase shift of the AC output signal comprises determining a first phase shift of an AC output current signal of the power conditioner.

3. The method of claim 1, wherein determining the first phase shift comprises:

sensing an AC output voltage signal of the power conditioner;

sensing an AC output current signal of the power conditioner; and

determining a first phase shift based on the AC output voltage signal and the AC output current signal.

4. The method of claim 3, wherein determining the first phase shift based on the AC output voltage signal and the AC output current signal comprises determining the first phase shift of the AC output current signal relative to the AC output voltage signal.

5. The method of claim 1, wherein the first phase shift is non-zero.

6. The method of claim 1, wherein determining the average AC output power comprises setting an average AC output power value equal to a predetermined value and wherein generating the AC signal comprises generating an AC signal having an amplitude that is a function of the average AC output power value.

7. The method of claim 1, wherein determining the average AC output power comprises:

sensing an AC output voltage signal of the power conditioner;

sensing an AC output current signal of the power conditioner; and

calculating the average AC output power as a function of the AC output voltage signal and the AC output current signal.

8. The method of claim 1, wherein generating the AC signal comprises generating an AC signal having a phase shift substantially equal to 45 degrees minus half of the determined first phase shift.

9. The method of claim 1, further comprising:

calculating a phase shift adjustment by dividing the phase shift by two,

wherein generating the AC signal comprises generating an AC signal having a phase shift substantially equal to 45 degrees minus the first phase shift adjustment.

10. The method of claim 1, wherein generating the AC signal at the energy storage device comprises generating the AC signal at one of a capacitor and an inductor.

11. The method of claim 1, wherein generating the AC signal at the energy storage device comprises generating the AC signal at an energy storage device included in the single-phase power conditioner.

12. The method of claim 1, wherein generating the AC signal comprises generating an AC signal having an amplitude dependent on the average AC output power and a capacitance of the energy storage device.

13. The method of claim 12, wherein generating the AC signal comprises generating an AC voltage signal at a capacitive energy storage device, the AC voltage signal having an amplitude substantially equal to:

14. The method of claim 13, wherein generating the AC signal comprises generating an AC signal having a phase shift substantially equal to 45 degrees minus half of the determined first phase shift.

15. The method of claim 13, further comprising:

calculating a phase shift adjustment by dividing the first phase shift by two,

wherein generating the AC signal comprises generating an AC signal having a phase shift substantially equal to 45 degrees minus the phase shift adjustment.

16. The method of claim 13, wherein the first phase shift is non-zero.

17. The method of claim 13, wherein generating the AC signal at the energy storage device comprises generating the AC signal at one of a capacitor and an inductor.

18. The method of claim 17, wherein generating the AC signal at the energy storage device comprises generating the AC signal at an energy storage device included in the single-phase power conditioner.

19. The method of claim 13, wherein generating the AC signal comprises generating an AC signal having a frequency that is double the frequency of the average AC output power.

13-1. A method for reducing a double-frequency ripple power exchanged between a load and an energy source, the energy source being configured to deliver electrical output power to the load through a single-phase power conditioner, the method comprising:

sensing an AC output voltage signal of the power conditioner;

sensing an AC output current signal of the power conditioner;

determining a first phase shift of the AC output current relative to the AC output voltage signal;

determining an average AC output power of the power conditioner as a function of the AC output voltage and the AC output current; and

generating an AC signal at an energy storage device, the AC signal having (i) an amplitude that is a function of the average AC output power, (ii) a frequency dependent upon a frequency of the average AC output power, and (iii) a phase shift substantially equal to 45 degrees minus an amount that is dependent on the determined first phase shift.

20. A method for reducing a double-frequency ripple power exchanged between a load and an energy source, the energy source being configured to deliver electrical output power to the load through a single-phase power conditioner, the method comprising:

determining a first phase shift of an AC output signal of the power conditioner;

determining an average AC output power of the power conditioner;

determining a first AC waveform having (i) an amplitude that is a function of the average AC output and (ii) a phase shift substantially equal to 45 degrees minus an amount that is dependent on the determined first phase shift; and

generating a second AC signal at an energy storage device, the AC second signal having a form that is a piecewise combination of the first AC waveform and an inverse of the first AC waveform.

21. The method of claim 20, wherein determining the first AC waveform comprises determining a first AC waveform having a phase shift substantially equal to 45 degrees minus half of the determined first phase shift.

22. The method of claim 20, generating the second AC signal comprises generating a second AC signal at a capacitive energy storage device, the second AC signal having a voltage determined according to the following equation:

V_C(t)=ABS[V_C*cos(ω

t+θ

)]

wherein V_C is the voltage of the second AC signal, ABS is an absolute value function, ω

is the frequency of the AC output signal, and θ

is the phase shift.

23. The method of claim 20, generating the second AC signal comprises generating a second AC signal at an inductive energy storage device, the second AC signal having a current determined according to the following equation:

I_L(t)=ABS[I_L*cos(ω

t+θ

)]

wherein I_L is the current of the second AC signal, ABS is an absolute value function, ω

is the frequency of the AC output signal, and θ

is the phase shift.