Homebrew Inverter

This page will show the design and construction of my inverter. I finished the global design already! Also check out the basics of an inverter design.

Global Design

picture not available

The picture shows my work sofar..... More details to come!

Global design schematic

Short description of above global design for the inverter:

• Input switches open when input voltage bbecomes higher than converter can handle. (should only occur when no power can be delivered to the grid)
• R is a 100A resistor for current sensing.
• C is a 100,000 uF capacitor 40V that buffers for the current during the AC phase top.
• Power meter is an independent device, registering KWh and instantaneous power.
• DC sense is input voltage + current (or open solar-voltage), for MPP adjustment.
• The inverter is driven by a microprocesssor, generating the switching signals and sensing the current through the switches. Multiple switch-bridges (modular) may be used to increase total power. Example: 3x800Watt output.
• Trafo accepts the 17 volt sine wave and transforms it into 230 volt for the grid. Multiple transformers may be used in parallel. Ri of one trafo at 17v: < 0,1 ohms.
• Line filter is a common mode choke + cappacitors.
• Output switch is a relais, isolating thee inverter when no power is generated.
• Standby supply delivers a constant voltaage to power meter and microprocessor.
• AC sense comes from the Standby transforrmer, its purpose is a monitoring of the Over-voltage, Under-voltage and Phase/Frequency limits of the grid.

I am also waiting for input from a friend about his opinion on my global design. if you have a clear view, please mail to cwater@proxim.com!

In the mean time, I'll start designing the connection box ("Cables of all Modules, unite!"). I try to keep the system flexible by wiring each individual module to the connection box. This way I can decide on the system voltage later! The result is shown below.

[Cable spaghetti.] - picture unavailable

Schematic panel connection.

The schematics show the way the panels are connected to achieve the input voltage for a commercial inverter that I use at this moment. The large panels are 24 Volt models, the 50 Watt panels are 12 Volt. The MPP voltage of the large panels is around 33V, so the inverter usually get a little under 100V, depending on temperature and sunshine and the max current is 27 Amp.

The future has arrived, in the picture above: I have installed the extra string of panels at June 15, 1999, so the power has risen to a peak of 2900 Watt.

Every panel is wired to the connection box inside, there the panels are switched in series or parallel. So I can easily change my system's voltage when required. (and I got the cable for free, otherwise I might have decided differently)