Current bypass for distributed power harvesting systems using DC power sources
A converter circuit providing multiple current bypass routes between the output leads to provide reliability in a series connection of several converters. If the converter malfunctions due to component failure, the current bypass routes provide a path for the current that views the malfunctioning converter as substantially a short. Diodes prevent backflow into the power source connected to the converter. Redundancy is provided in the bypass portions of the converter circuit that provides alternate parallel paths in case a defective component in one of the paths opens the circuit along that path. In one example, the converter is implemented as a buck plus boost converter where either the buck or the boost portion or both are operative responsive to a controller controlling the switches of both portions. Most of the converter circuit may be implemented in an integrated circuit.
1. A distributed power harvesting system comprising:
a plurality of power sources each providing DC power;
a plurality of converters, each converter comprising:
input terminals receiving input voltage from, and coupled to, a respective power source from the plurality of power sources;
output terminals for providing an output voltage;
circuitry operatively connected to said input terminals and output terminals, wherein said circuitry receives and converts the input voltage to the output voltage, the circuitry comprising a buck portion providing a stepped down output voltage, a boost portion connected to the buck portion and adapted to provide a stepped up output voltage, and a controller selectively engaging the buck portion and/or the boost portion;
at least two bypass paths adapted for bypassing at least part of the circuitry; wherein; and
a maximum power point tracking circuits coupled to a respective power source for tracking power input from the respective power source, wherein the controller selectively engages the buck portion or the boost portion or both in response to signal from the maximum power point tracking circuit.
2. The distributed power harvesting system of claim 1 , wherein the at least two bypass paths circumvent the buck portion and the boost portion.
3. The distributed power harvesting system of claim 1 , wherein at least one of the at least two bypass paths passes through the buck portion.
4. The distributed power harvesting system of claim 1 , wherein at least one of the at least two bypass paths passes through the boost portion.
5. The distributed power harvesting system of claim 1 , wherein at least one of the bypass paths comprises:
a first current path circumventing the buck portion and the boost portion;
a second current path passing through the buck portion; and
a third current path passing through the boost portion.
6. The distributed power harvesting system of claim 5 , wherein the buck portion and the boost portion share an inductive coil;
wherein at least one of the first, second and third, current paths passes through the inductive coil; and,
wherein at least one of the first, second and third, current paths circumvents the inductive coil.
7. The distributed power harvesting system of claim 1 ,
wherein the buck portion and boost portion share an inductor; and
wherein the buck portion comprises a buck switching circuitry and a buck switching bypass path; and
wherein the boost portion comprises a boost switching circuitry and a boost switching bypass path.
8. The distributed power harvesting system of claim 7 , wherein:
the buck switching circuitry comprises a plurality of buck switching elements and the buck switching bypass path comprises a plurality of current paths, each bypassing one of the buck switching elements; and
the boost switching circuitry comprises a plurality of boost switching elements and the boost switching bypass path comprises a plurality of current paths, each bypassing one of the boost switching element.
9. The distributed power harvesting system of claim 1 ,
wherein the output terminals are coupled in series to at least one other converter, to thereby generate a series connection of the plurality of converters, the distributed power harvesting system further comprising:
an inverter coupled to the series connection of the plurality of converters and changing a direct current input from the converters to an alternating current output.
10. The distributed power harvesting system of claim 1 , further comprising:
an inverter coupled to each of the plurality of converters and forming an AC module together with the converter,
wherein the AC modules are coupled in parallel to provide a collective current from the distributed power harvesting system, and
wherein each converter comprises at least one current blocking element for preventing a short through the converter in a reverse direction.
11. The distributed power harvesting system of claim 1 , wherein at least a portion each of the converters is implemented in an integrated circuit.
12. The distributed power harvesting system of claim 1 , wherein at least one of the power sources comprises a solar panel.
13. The distributed power harvesting system of claim 1 , wherein at least one of the power sources is a fuel cell.
14. A DC-to-DC power converter for converting an input voltage from a DC power source to an output voltage, the DC-to-DC power converter comprising:
a buck portion providing a stepped down output voltage;
a boost portion connected to the buck circuit and adapted to provide a stepped up output voltage;
an inductor coupled to the buck portion and the boost portion;
a controller engaging the buck portion and the boost portion;
a maximum power point tracking (MPPT) circuit for providing a MPPT input signal, wherein the controller selectively engages the buck portion or the boost portion or both in response to the MPPT input signal; and,
a boost bypass path providing a current path adapted for bypassing the boost portion through the buck portion.
15. The DC-to-DC power converter of claim 14 , further comprising:
a diode coupled in parallel with a first switch of the buck portion,
wherein a current through the diode and a current through a parasitic diode associated with the first switch are parallel.
16. The DC-to-DC power converter of claim 14 , further comprising a buck bypass path providing a current path bypassing the buck portion through the boost portion.
17. The DC-to-DC power converter of claim 16 , further comprising:
a first switch of the boost portion;
a parasitic diode across said first portion;
a diode coupled in parallel with said first switch of the boost portion;
wherein a current through the diode and a current through a parasitic diode are parallel.
18. The DC-to-DC power converter of claim 14 , wherein a portion of the DC-to-DC power converter is implemented in an integrated circuit.
19. A distributed DC photovoltaic power harvesting system comprising:
a plurality of solar panels, each converting solar energy into DC output;
a plurality of converters, each coupled to one of the solar panels, and each providing converted DC output; and
an inverter coupled to a series connection of the converters and changing a DC input from the converters to an AC output;
wherein each of the converters includes:
a negative input lead and a positive input lead
a negative output lead and a positive output lead;
a first diode coupled to the negative output lead;
a second diode coupled to the positive output lead;
a maximum power point tracking circuit for tracking power input from the respective solar panel;
a buck portion for providing a stepped down output voltage;
a boost portion for providing a stepped up output voltage;
an inductor coupled between the first diode and the second diode, the inductor being shared by the buck portion and the boost portion; and
a controller for selectively engaging the buck portion or the boost portion or both responsive to the maximum power point tracking circuit;
wherein a first current bypass route passes from the negative output lead to the first diode, to the inductor, to the second diode and to the positive output lead,
wherein the first diode and the second diode prevent current flow from the positive output lead to the negative output lead.
20. The distributed DC photovoltaic power harvesting system of claim 19 , further comprising a second current bypass route passing from the negative output lead to the second switch, to the inductor and to the positive output lead.
21. The distributed DC photovoltaic power harvesting system of claim 20 , further comprising a third current bypass route passing from the negative output lead to the first diode, to the inductor, to the second diode and to the positive output lead.