System and method for maximizing power output of photovoltaic strings
First Claim
1. A photovoltaic (PV) system comprising:
- a plurality of PV strings configured to generate a string output power responsive to received solar irradiation, each of the plurality of PV strings having an optimal string voltage at which a string output power is maximized;
a DC link connected to the plurality of PV strings, wherein the plurality of PV strings are connected to the DC link in a parallel arrangement such that each of the plurality of PV strings operates at a variable DC link voltage;
a PV inverter electrically connected to the DC link to receive a DC output therefrom, the PV inverter configured to control the DC link voltage; and
a plurality of delta DC/DC converters electrically connected to the plurality of PV strings such that each of the plurality of delta DC/DC converter is connected to at least one PV string, wherein each DC/DC converter receives the DC link voltage from the DC link and is configured to provide a tuning voltage to the DC link voltage at which its respective PV string operates in order to bring the string voltage for that PV string to its optimal string voltage, the tuning voltage of each delta DC/DC converter being a difference between the DC link voltage and a respective optimal string voltage.
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Accused Products
Abstract
A PV system includes a plurality of PV strings each having an optimal string voltage at which a string output power is maximized. The PV strings are connected to a DC link in a parallel arrangement such that each PV strings operates at a variable DC link voltage. A PV inverter is connected to the DC link to receive a DC output, with the PV inverter controlling the DC link voltage. Delta DC/DC converters are connected to the PV strings, with each DC/DC converter receiving the DC link voltage from the DC link and providing a tuning voltage to the DC link voltage at which its respective PV string operates in order to bring the string voltage for that PV string to its optimal string voltage. The tuning voltage of each delta DC/DC converter is the difference between the DC link voltage and a respective optimal string voltage.
11 Citations
23 Claims
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1. A photovoltaic (PV) system comprising:
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a plurality of PV strings configured to generate a string output power responsive to received solar irradiation, each of the plurality of PV strings having an optimal string voltage at which a string output power is maximized; a DC link connected to the plurality of PV strings, wherein the plurality of PV strings are connected to the DC link in a parallel arrangement such that each of the plurality of PV strings operates at a variable DC link voltage; a PV inverter electrically connected to the DC link to receive a DC output therefrom, the PV inverter configured to control the DC link voltage; and a plurality of delta DC/DC converters electrically connected to the plurality of PV strings such that each of the plurality of delta DC/DC converter is connected to at least one PV string, wherein each DC/DC converter receives the DC link voltage from the DC link and is configured to provide a tuning voltage to the DC link voltage at which its respective PV string operates in order to bring the string voltage for that PV string to its optimal string voltage, the tuning voltage of each delta DC/DC converter being a difference between the DC link voltage and a respective optimal string voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for maximizing power output of a photovoltaic (PV) system including a plurality of PV strings in a parallel arrangement, the method comprising:
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operating each of the plurality of PV strings at a DC bus voltage, with the DC bus voltage being determined by a PV inverter that is coupled to the plurality of PV strings by way of a DC bus; providing the DC bus voltage to a delta DC/DC converter electrically connected to each PV string; determining an optimal string voltage for each PV string at which a string output power is maximized, the optimal string voltage for each PV string being determined from a respective string current and string voltage; comparing, for each PV string, the DC bus voltage to the optimal string voltage of each respective PV string; selectively controlling each delta DC/DC converter based on the comparison of the DC bus voltage and the optimal string voltage of its respective PV string; and operating each PV string at its respective optimal string voltage based on the selective controlling of each DC/DC converter. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A photovoltaic (PV) system comprising:
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a PV inverter; a DC link electrically coupled to the PV inverter and operating at a DC link voltage, wherein the DC link voltage is a variable voltage that is determined by the PV inverter according to a global maximum power point tracking (MPPT) algorithm; a plurality of PV strings connected to the DC link in a parallel arrangement and being configured to generate a string output power responsive to received solar irradiation, wherein each of the plurality of PV strings has an optimal string voltage at which the string output power is maximized; and a plurality of delta DC/DC converters connected to the plurality of PV strings, with each delta DC/DC converter being connected to at least one PV string and to the DC link to receive the DC link voltage therefrom; wherein each delta DC/DC converter comprises a controller programmed to; determine the optimal string voltage for its respective PV string at which the string output power is maximized based on a string current and string voltage of its respective PV string; compare the DC link voltage to the optimal string voltage of its respective PV string; determine an output voltage needed to bring the string voltage for its respective PV string to its optimal string voltage, with the output voltage being a difference between the DC link voltage and the respective optimal string voltage; and cause the delta DC/DC converter to generate the output voltage, the output voltage being applied to the respective PV string to generate a string voltage equal to the optimal string voltage. - View Dependent Claims (20, 21, 22, 23)
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Specification