Parallel connected inverters
A distributed power system wherein a plurality of power converters are connected in parallel and share the power conversion load according to a prescribed function, but each power converter autonomously determines its share of power conversion. Each power converter operates according to its own power conversion formula/function, such that overall the parallel-connected converters share the power conversion load in a predetermined manner.
1. A distributed power system comprising:
a direct current (DC) power source;
a plurality of inverters with respective inverter inputs adapted for connection in parallel to said DC power source and with respective inverter outputs adapted for connection in parallel; and
a plurality of control modules coupled respectively to said inverter inputs and outputs, wherein for each inverter said respective control module includes:
(i) a voltage loop block configured to sense a voltage at the input and to compare the voltage at the input to at least one previously specified reference voltage and to output a current reference signal based on the comparison; and
(ii) a current loop block configured to sense an input current to the inverter and to compare said current reference signal with a current signal proportional to the input current of the inverter to adjust the input current until an input power equilibrates.
2. The distributed power system according to claim 1 , further comprising:
a power module having an input coupled to said DC power source and an output coupled to said inverter inputs.
3. The distributed power system according to claim 2 , wherein said power module is configured to maintain maximum peak power at said input of said power module coupled to said DC power source.
4. The distributed power system according to claim 2 , wherein said power module is configured to control at maximum peak power at said output of said power module to said inverter inputs.
5. The distributed power system according to claim 1 , further comprising:
a single maximum peak power tracking module connecting said DC power source to said control modules.
6. In a distributed power system including:
a direct current (DC) power source;
a plurality of inverters with respective inverter inputs adapted for connection in parallel to the DC power source and with respective inverter outputs adapted for connection in parallel; a method comprising the steps of:
the inverters inverting power from the DC power source to an output power; and
for each inverter, sensing a current and a voltage at the input of the inverter,
comparing the voltage at the input of the inverter to at least one previously specified reference voltage to produce a voltage comparison,
outputting a current reference signal based on the voltage comparison,
comparing the current reference signal with a current signal proportional to the input current of the inverter, and
adjusting the input current until an input power equilibrates.
7. The method according to claim 6 , further comprising the step of:
maintaining maximum peak power at said inverter inputs coupled to said DC power source.
8. The method of claim 6 , further comprising the steps of:
autonomously controlling current drawn by each of said inverters from a DC input, wherein said controlling current is responsive to said DC input; to thereby reach an equilibrium in said DC input, whereby each inverter autonomously draws a portion of a load of inverting power from said DC input to output power to distribute the load.
9. A distributed power system comprising:
a direct current (DC) power source;
a plurality of power converters with respective power converter inputs adapted for connection in parallel to said DC power source and with respective power converter outputs adapted for connection in parallel; and
a plurality of control modules connected respectively to said power converter inputs and outputs,
wherein for each converter said respective control module includes:
(i) a voltage loop block configured to sense a voltage at the input and to compare the voltage at the input to at least one previously specified reference voltage and to output a current reference signal based on the comparison; and
(ii) a current loop block configured to sense an input current to the converter and to compare said current reference signal with a current signal proportional to the input current of the converter to adjust the input current until an input power equilibrates.
10. The distributed power system of claim 9 , wherein the plurality of power converters comprise a plurality of inverters.
11. The distributed power system of claim 9 , wherein each of the plurality of control modules vary the current draw of the respective converter according to one of DC power or DC voltage provided by the DC power source.
12. The distributed power system of claim 9 , wherein each of the plurality of control modules vary the current draw of the respective converter so as to maintain a functional relationship between said input current and said input voltage of said respective converter.
13. The distributed power system of claim 12 , wherein the functional relationship is the same for all of the control modules.
14. The distributed power system of claim 9 , wherein the DC power source comprises a plurality of power generating elements coupled to provide a single DC power output.
15. A system for controlling load balancing of a plurality of inverters with respective DC inputs adapted for connection in parallel to a DC power source, the system comprising:
for each of the inverters, a control module operatively attached to the inverters, wherein the control module is configured for individually controlling current drawn by each one of said inverters from the respective DC input, wherein said controlling current is responsive to said respective DC input;
whereby the inverter is configured to autonomously draw a portion of a load of inverting power from said respective DC input and convert said portion to output power, while avoiding master/slave control between the control modules; and
wherein for each inverter said control module includes:
(i) a voltage loop block configured to sense the voltage at the input and to compare the voltage at the input to at least one previously specified reference voltage and to output a current reference signal based on the comparison; and
(ii) a current loop block configured to sense the input current to the inverter and to compare said current reference signal with a current signal proportional to the input current of the inverter to adjust the input current until the input power equilibrates.