Method and apparatus for connecting a photovoltaic system to a power grid
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Accused Products
Abstract
An apparatus and a method for preparing connection of a photovoltaic system (Q1) as a first energy source to a power grid (13) by way of a motor generator set (5, 6, 7) is presented. The DC motor (5) is coupled to a three-phase generator (7) by way of a shaft (6), wherein the three-phase generator (7) can be connected to the power grid (13). It has been observed that connecting this type of apparatus to the small or varying power output of the photovoltaic system (Q1) can be difficult and time-consuming. To enable a clean and quick connection, the DC motor (5) is powered with electric DC current from a second DC current source (Q2), wherein the operation of the three-phase generator (7) is matched to the conditions in the power grid (13) with the help of the second DC current source (Q2), and wherein the photovoltaic system (Q1) is connected to the DC motor (5) and the second DC current source (Q2) is disconnected from the DC motor (5) only after a complete match has been attained. This enables a quick and precise connection of the photovoltaic system (Q1) to the power grid (13) with defined parameters using the three-phase generator (7).
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Citations
24 Claims
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1-14. -14. (canceled)
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15. A method for synchronizing an output from a motor-generator set with a power grid, the motor-generator set comprising a DC motor connected via a shaft with a three-phase generator and having a photovoltaic system as a primary energy source and a second DC energy source, said method comprising the steps of:
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connecting the second DC energy source with the DC motor to supply electric energy; matching a rotation speed and phase angle of the three-phase generator to conditions of the power grid with the supplied energy; and after matching is completed, disconnecting the second DC energy source from the DC motor and connecting the photovoltaic system with the DC motor as the primary energy source. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
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24. Apparatus for synchronizing an output from a motor-generator set with a power grid, comprising:
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a photovoltaic system having a plurality of photovoltaic modules and representing a primary DC energy source; a second DC energy source; a three-phase generator having an output switchably electrically connected to a power grid having for supplying a generated AC voltage; a DC motor coupled to the three-phase generator by a shaft and switchably electrically connected to one of the photovoltaic system and the second DC energy source; and a control unit, which controllably drives the DC motor from the second DC energy source, until a line frequency and phase angle of the power grid matches a line frequency and phase angle at the output of the three-phase generator, whereafter the control unit disconnects the second DC energy source from the DC motor and connects the photovoltaic system to the DC motor as primary DC energy source.
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Specification