This prject started with the idea to build a cheap inverter for our new house.
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the basic requirments
are:
1) Must be very very reliable, as it will run the whole house 24 hours a day.
2) Must be able to run a variety of loads... ranging from small motors up
to 15HP wood working tools.
Preliminary Specs:
0) 15kw output power,
may only be 8kw per 120v inverter, 16kw at 240v, not sure yet .
1) 48v battery bank
2) 120v RMS AC ouput -- two inverters can be connected in anti phase for 240v.
3) 48v from batteries will be converted to 170v DC at 50khz with ferrite transformers.
4) 170v will then be converted into 120v AC with H bridge
5) carrier frequency will be 19khz
6) the carrier duty cycle will be modulated (PWM) to create a sine wave on
the output
The inverter also has to be very efficient, so as not to waste the 2kw (hydro) input to the battery bank. A PIC microcontroller (PIC16F628) will be used to create the pwm signal with its built in pwm module, which will be modulated with values from a sine table. External gates will be used to send the pwm signal to opposite sides of the H bridge to generate a complete sine wave.
Pin 9 of the PIC is the
PWM output pin.
Pin 6 determines which half bridge the PWM signal goes to.
The two ground points in the schematic are isolated from eachother... the
170v dc supply will be floating.
The idea is that when one side of the H bridge is being sent the pwm signa, the other half will be tied to ground. This method of modulation should;) result in the below waveform.
Numbers above the pulses
are duty cycle.
A high pulse means the lop left and bottom right side of the H bridge are
ON.
The middle line means both the bottom mosfets are ON, shorting the ouputs
to ground.
A Low pulse means the bottom left and top right mosfets are ON.
All of my ideas/theories are open to question... this is by no means a finished project, im sure many faults will be discovered along the road.
hilo90mhz@hotmail.com -- all questions, comments, ideas, criticisms welcome