Inverter for interfacing advanced energy sources to a utility grid

• US 4,445,049 A
• Filed: 12/28/1981
• Issued: 04/24/1984
• Est. Priority Date: 12/28/1981
• Status: Expired due to Fees

• Current Assignee: General Electric Company, United States Department of Energy (Government of the United States of America)
• Original Assignee: General Electric Company
• Inventors: Steigerwald, Robert L.
• Primary Examiner(s): BEHA JR, WILLIAM
• Application Number:
  US06/334,844
• Time in Patent Office: 848 Days
• Field of Search: 363/41, 363/71, 363/79, 363/96, 363/136, 363/139, 323/906, 323/300, 307/45, 307/46, 320/32, 320/35
• US Class Current: 307/45
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02M 3/3155 with automatic control of the output voltage or current
• CPC Class Codes: H02M 7/5152 with separate extinguishing means
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y10S 323/906 Solar cell systems

Abstract

A transistor is operated in the PWM mode such that a hlaf sine wave of current is delivered first to one-half of a distribution transformer and then the other as determined by steering thyristors operated at the fundamental sinusoidal frequency. Power to the transistor is supplied by a dc source such as a solar array and the power is converted such that a sinusoidal current is injected into a utility at near unity power factor.

Claims

1. A dc-to-ac inverter for injecting a sinusoidal current waveform into an ac utility grid from a dc source comprising:

gate controllable chopping switch means in series with said dc source;

at least two steering switch means for connecting said gate controllable switch means to opposite sides of said load;

means for alternately gating said two steering switch means at the fundamental frequency of the desired sinusoidal waveform to alternately provide current flow in a first direction through said load and a second direction opposite to the first; and

means for pulse width modulating the gate controllable switch means to achieve sinusoidal current delivered to said utility grid at near unity power factor, said pulse width modulating means having means for sensing current supplied to said utility grid, means for generating a sinusoidal current reference waveform, and comparator means having hysteresis for comparing current supplied to said utility grid to said sinusoidal current reference waveform, and supplying switching pulses to said gate controllable switching means to confine the current supplied to the utility grid to a predetermined band about said sinusoidal current reference waveform.

2. The inverter of claim 1 wherein said gate controllable switch means is a transistor.

3. The inverter of claim 1 wherein said steering switch means is a phase controlled thyristor.

4. A dc-to-ac inverter for injecting a sinusoidal current waveform into a center tapped utility grid transformer from a dc source comprising:

gate controllable chopping switch means in series with said dc source;

two steering switch means for connecting said gate controllable switch means to each half of said center tapped transformer;

means for alternately gating said two steering switch means at the fundamental frequency of the desired sinusoidal waveform to alternately provide current flow in a first direction through one half of said center tapped transformer and in a second direction through the other half of said center tapped transformer; and

means for pulse width modulating the gate controllable switching means to achieve sinusoidal current delivered to said utility grid transformer at near unity power factor, said pulse width modulating means having means for sensing current supplied to said transformer, means for generating a sinusoidal current reference waveform, and comparator means having hysteresis for comparing current supplied to said utility transformer to said sinusoidal current reference waveform, and supplying switching pulses to said gate controllable switching means to confine the current supplied to the utility grid transformer to a predetermined band about said sinusoidal current reference waveform.

5. The inverter of claim 4 wherein said gate controllable switch means is a transistor.

6. The inverter of claim 4 wherein said steering switch means is a phase controlled thyristor.

7. A dc-to-ac inverter for providing a sinusoidal waveform to an external center-taped load from a center tapped dc source comprising:

two gate controllable switch means each one in series with one half of said center tapped dc source a first pair of steering switch means for connecting one of said two gate controllable switch means to first one half of said center tapped load and then the other a second pair of steering switch means for connecting the other gate controllable switch means to first one half of said center tapped load and then the other;

first means for alternately gating said first pair of steering switch means at the fundamental frequency of the desired sinusoidal waveform to alternately provide current flow in a first direction in one half of the load and in a second direction opposite to the first in the other half of the load;

second means for alternately gating said second pair of steering switch means at the fundamental frequency of the desired sinusoidal waveform to alternately provide current flow in a first direction which is the same direction as current being provided by said means for gating said first pair but in the other half of said load from current provided by said first means and providing current flow in a second direction in which is the same direction as current being provided by said second means but in the other half of said load from current provided by said second means;

means for pulse width modulating the first gate controllable switching means to achieve sinusoidal current delivered to said load; and

means for pulse width modulating said second gate controllable switching means to achieve sinusoidal current delivered to said load.

8. The inverter of claim 7 wherein said means for pulse width modulating comprises:

means for sensing current supplied to said load;

means for generating a sinusoidal current reference waveform; and

comparator means having hysteresis for comparing current supplied to said load with said sinusoidal current waveform and supplying switching pulses to confine the current supplied to the load to a predetermined band about said sinusoidal current reference waveform.

9. The inverter of claim 7 wherein said gate controllable switch means is a transistor.

10. The inverter of claim 7 wherein said steering switch means is a phase controlled thyristor.