Solar energy conversion and utilization system

摘要

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.

主权项

1. DC to AC conversion apparatus for converting power from a DC source to produce an 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, wherein the second repetition frequency is a multiple equal to the same said number N of said first repetition frequency.