Distributed substring architecture for maximum power point tracking of energy sources
First Claim
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1. A photovoltaic array system comprising:
- a first string of series-coupled photovoltaic modules, said first string being coupled to a first DC-to-DC converter, wherein the first DC-to-DC converter converts a DC output of the first string for output to a DC bus having DC rails;
a second string of series-coupled photovoltaic modules, said second string being coupled to a second DC-to-DC converter, wherein the second DC-to-DC converter converts a DC output of the second string for output to the DC bus in parallel to the output of the first converter; and
an inverter coupled to the DC bus, said inverter converting the DC outputs of the first and second DC-to-DC converters to an AC output, wherein the DC-to-DC converters are adapted to maintain bus stability by a concerted autonomous current response of the DC-to-DC converters and inverter by controlling a duty cycle of a pulse width modulated signal to a DC-to-DC converter switch responsive to sensed voltage of the DC rails, wherein the voltage of the DC rails is sensed by the DC-to-DC converter, and each DC-to-DC converter autonomously derates its output linearly once the sensed voltage passes a pre-determined threshold, with the aggregate effect of controlling the DC bus voltage in cooperation with other units coupled to the DC rails.
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Abstract
A photovoltaic array system includes multiple strings of series coupled photovoltaic modules to provide current at a voltage dependent on the number of modules in each string and their operating efficiency. Each string is coupled to a DC-to-DC converter to convert the current from each string for output to a DC bus. An inverter is coupled to DC bus to convert the current from the strings of series coupled photovoltaic modules to AC current at a grid-compatible voltage.
8 Citations
20 Claims
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1. A photovoltaic array system comprising:
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a first string of series-coupled photovoltaic modules, said first string being coupled to a first DC-to-DC converter, wherein the first DC-to-DC converter converts a DC output of the first string for output to a DC bus having DC rails; a second string of series-coupled photovoltaic modules, said second string being coupled to a second DC-to-DC converter, wherein the second DC-to-DC converter converts a DC output of the second string for output to the DC bus in parallel to the output of the first converter; and an inverter coupled to the DC bus, said inverter converting the DC outputs of the first and second DC-to-DC converters to an AC output, wherein the DC-to-DC converters are adapted to maintain bus stability by a concerted autonomous current response of the DC-to-DC converters and inverter by controlling a duty cycle of a pulse width modulated signal to a DC-to-DC converter switch responsive to sensed voltage of the DC rails, wherein the voltage of the DC rails is sensed by the DC-to-DC converter, and each DC-to-DC converter autonomously derates its output linearly once the sensed voltage passes a pre-determined threshold, with the aggregate effect of controlling the DC bus voltage in cooperation with other units coupled to the DC rails. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method comprising:
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receiving DC current on DC rails from multiple sets of series coupled photovoltaic modules, the current being at a voltage dependent on the number of modules in each set; independently converting the current from each set to a selected DC set collection voltage; providing the current from each set at the set collection voltage to a set collection line; and providing the currents from each set via the set collection line to an inverter to convert the currents to an AC current, wherein the current from each set at the set collection voltage is autonomously modified by each set and the AC current from the inverter is autonomously modified to maintain bus stability, with the aggregate effect of controlling the DC bus voltage by controlling a duty cycle of a pulse width modulated signal to a DC-to-DC converter switch responsive to DC-to-DC converter sensed voltage of the DC rails, wherein each DC-to-DC converter autonomously derates its output linearly once the sensed voltage passes a pre-determined threshold in cooperation with other units coupled to the DC rails. - View Dependent Claims (18, 19)
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20. A photovoltaic array system comprising:
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a first string of series-coupled photovoltaic modules, said first string being coupled to a first DC-to-DC converter, wherein the first DC-to-DC converter converts a DC output of the first string for output to a DC bus having DC rails; a second string of series-coupled photovoltaic modules, said second string being coupled to a second DC-to-DC converter, wherein the second DC-to-DC converter converts a DC output of the second string for output to the DC bus in parallel to the output of the first converter; and an inverter coupled to the DC bus, said inverter converting the DC outputs of the first and second DC-to-DC converters to an AC output, wherein the DC-to-DC converters are adapted to maintain bus stability by a concerted autonomous current response of the DC-to-DC converters and inverter, with the aggregate effect of controlling the DC bus voltage by controlling a duty cycle of a pulse width modulated signal to a DC-to-DC converter switch responsive to sensed voltage of the DC rails, wherein the voltage of the DC rails is sensed by the DC-to-DC converter, and each DC-to-DC converter autonomously Berates its output linearly once the sensed voltage passes a pre-determined threshold, in cooperation with other units coupled to the DC rails wherein each DC-to-DC converter observe the DC bus voltage and limits its output power to maintain selected limits on the DC bus voltage.
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Specification