SOLAR ENERGY CONVERSION AND UTILIZATION SYSTEM
First Claim
1. DC to AC conversion apparatus for converting power from a DC source to produce an AC power output waveform at a first repetition frequency, comprisinga set of at least one live AC output terminals,at least one output terminal designated as a ground, neutral or reference potential terminal;
- a floating DC power source having a positive and a negative terminal connected respectively to the positive and negative DC input terminals of a DC to AC converter, wherein the DC to AC converter causes;
(1) an AC output waveform at said first repetition frequency and having a voltage relative to one of said at least one ground, neutral or reference potential terminals to appear with a unique phase at each of a number N at least equal to one of said set of live AC output terminals, and(2) a common-mode voltage waveform at a second repetition frequency to appear relative to one of said at least one ground, neutral or reference potential terminals and in the same phase on both of said positive and negative terminals of said DC power source.
1 Assignment
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Accused Products
Abstract
A 1, 2 or 3-phase DC to AC converter system for reducing the cost of solar energy installations achieves cost reduction by eliminating low-frequency power transformers. One DC input polarity is selectively switched to an output terminal when the instantaneous AC output from a second output terminal is desired to be of the opposite polarity, while the other DC input polarity is used to form an approximation to a segment of a sine wave of the desired polarity at the second output terminal. A common-mode AC signal is thereby created on the balanced DC input lines at a frequency which is a multiple of 1, 2 or 3 times the AC output frequency and which is useful for detecting ground faults in the DC circuit.
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Citations
20 Claims
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1. DC to AC conversion apparatus for converting power from a DC source to produce an AC power output waveform at a first repetition frequency, comprising
a set of at least one live AC output terminals, at least one output terminal designated as a ground, neutral or reference potential terminal; -
a floating DC power source having a positive and a negative terminal connected respectively to the positive and negative DC input terminals of a DC to AC converter, wherein the DC to AC converter causes; (1) an AC output waveform at said first repetition frequency and having a voltage relative to one of said at least one ground, neutral or reference potential terminals to appear with a unique phase at each of a number N at least equal to one of said set of live AC output terminals, and (2) a common-mode voltage waveform at a second repetition frequency to appear relative to one of said at least one ground, neutral or reference potential terminals and in the same phase on both of said positive and negative terminals of said DC power source. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of converting power from a direct current source with improved efficiency to provide AC output power at a standard voltage and frequency and to a number of output terminals corresponding to the number of phases required, comprising:
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Configuring said direct current source to be floating; connecting the negative line from said direct current source to a first output terminal required to be instantaneously negative relative to all other output terminals while deriving from the direct current source positive voltage line the instantaneous voltages required to be output from the other output terminals relative to said first terminal, in a rotating sequence with connecting the positive line from said direct current source to a next-in-sequence output terminal required to be instantaneously positive relative to all other output terminals while deriving from the negative line of the direct current source the instantaneous voltages relative to said next-in-sequence terminal required to be output from the other terminals; selecting the timing of said rotating sequence such that a common mode waveform with a characteristic repetition frequency appears in phase on both the direct current source positive and negative lines. - View Dependent Claims (9, 10, 11, 12, 13, 20)
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14. In a solar energy installation comprising a photovoltaic solar array and a DC to AC converter having a DC input with positive and negative conductors routed in parallel with an array grounding conductor and an AC output having an output waveform with an output repetition frequency, a method of detecting a ground leak in the DC wiring to the solar array, comprising:
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creating a common-mode AC probe signal waveform from said DC to AC converter at a characteristic repetition frequency that is in phase on both said DC positive and negative input conductors; passing said positive and negative conductors from the array through a detector adapted to detect an unusual current with said common mode waveform at said characteristic repetition frequency and upon detection of said unusual current providing an indication of the presence of an unwanted ground leak. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification