Distributed power harvesting systems using DC power sources
A photovoltaic panel with multiple photovoltaic sub-strings including serially-connected photovoltaic cells and having direct current (DC) outputs adapted for interconnection in parallel into a parallel-connected DC power source. A direct current (DC) power converter including input terminals and output terminals is adapted for coupling to the parallel-connected DC power source and for converting an input power received at the input terminals to an output power at the output terminals. The direct current (DC) power converter optionally has a control loop configured to set the input power received at the input terminals according to a previously determined criterion. The control loop may be adapted to receive a feedback signal from the input terminals for maximizing the input power. A bypass diode is typically connected in shunt across the input terminals of the converter. The bypass diode functions by passing current during a failure of any of the sub-strings and/or a partial shading of the sub-strings. The bypass diode may be a single bypass diode connected across the parallel-connected DC power source. The DC power converter may convert the input power at high current to the output power at a lower current. The output terminals may be connectible with wire cables to a load, and the DC power converter is configured to reduce energy loss through the wire cables to the load.
1. A photovoltaic panel comprising:
a plurality of photovoltaic sub-strings each including serially-connected photovoltaic cells, wherein the plurality of photovoltaic sub-strings are connected in parallel across power source terminals;
a direct current power converter including input terminals connected to said power source terminals, wherein the direct current power converter is configured to convert input power received at said input terminals to an output power at output terminals; and
a bypass diode connected in shunt across said input terminals of said converter.
2. The photovoltaic panel of claim 1 , wherein said direct current power converter has a control loop configured to set the input power received at said input terminals according to a previously determined criterion.
3. The photovoltaic panel of claim 1 , wherein said direct current power converter has a control loop adapted to maximize the input power by setting a voltage at the input terminals.
4. The photovoltaic panel of claim 1 , wherein said bypass diode passes current in response to a failure of any of said plurality of photovoltaic sub-strings or a partial shading of said plurality of photovoltaic sub-strings.
5. The photovoltaic panel of claim 1 , wherein said bypass diode is a single bypass diode connected across the power source terminals.
6. The photovoltaic panel of claim 1 , wherein said direct current power converter converts said input power at a first current to said output power at a second current lower than the first current.
7. A distributed power harvesting system comprising:
a photovoltaic panel having a plurality of photovoltaic sub-strings each including serially-connected photovoltaic cells, wherein said plurality of photovoltaic sub-strings are connected in parallel to parallel-connected DC power source terminals;
a power converter with input terminals connected to said parallel-connected DC power source terminals; and
a bypass diode connected across said parallel-connected DC power source terminals.
8. The distributed power harvesting system according to claim 7 , further comprising:
a load connected to output terminals of the power converter.
9. The distributed power harvesting system according to claim 7 , wherein said power converter includes a control loop configured to set input power received at said input terminals according to a previously determined criterion.
10. The distributed power harvesting system according to claim 9 wherein said previously determined criterion comprises a maximum power point algorithm.
11. A method comprising:
connecting a plurality of photovoltaic sub-strings in parallel to parallel-connected DC power source terminals, wherein each of the plurality of photovoltaic sub-strings comprises serially-connected photovoltaic cells;
attaching input terminals of a power converter to the parallel-connected DC power source terminals; and
attaching a single bypass diode across said parallel-connected DC power source terminals.
12. The method according to claim 11 , further comprising:
converting power by the power converter from the input terminals to output terminals of the power converter; and
during said converting, maximizing the power received at the input terminals according to a maximum power point tracking control loop.
13. The method according to claim 11 , further comprising:
connecting output terminals of the power converter to a load;
converting power by the power converter from the input terminals to the output terminals; and
while said converting power, reducing current output from the output terminals, thereby reducing energy losses.