I am exploring if Arduino has enough computing power for a project. It would need to measure line frequency and control 8 Solid State Relays (SSR) maybe as many as 44 SSRs. Turning the relays off/on would cause frequency to change.
The SSRs would start and stop micro inverters as they snyc up with a central inverter. The goal being to stabilize power produced with the Solar PV panels to a changing household load while minimizing battery charge/discharge cycles.
I've seen several examples of Arduino frequency measurement. The question is: Does it have enough power to measure frequency and control SSRs to safely maintain frequency? If yes, how many SSRs can it control without effecting frequency measurement?
control 8 Solid State Relays (SSR) maybe as many as 44 SSRs.
Most SSR use an internal LED and series resistor in their input circuit, so plan on each SSR driven by an arduino output pin will consume around 20ma. Driving 8 SSR, if all commanded on at the same time, puts you close to the total current output for all pins. Of course driving 44 SSR also would require more output pins via external support chips or possibly a mega1280/2560 board, however total SSR input current requirement would need to be increased via external transistors or driver chips.
KE7GKP:
Yes, Arduino is capable of measuring frequency and phase of the power mains.
Whether Arduino is capapable of controlling the SSRs depends on exactly what you mean by "control". The issue being how much precision do you need and how many SSRs are you wanting to control. Arduino has a limited number of outputs. But they can be multiplied using various schemes, but that affects the precision of the timing, etc.
Currently in gathering information stage to see if the project is viable, so some details are not fixed, like how many SSRs the Arduino will control. The Arduino would not need to measure phase. I'm thinking measuring frequency should be enough, then adding or removing power capacity by controlling the micro inverters via the SSRs.
The SSRs to be controlled would be:
MP380D4; 380 VAC, 4 Amp, DC control, in http://www.opto22.com/documents/0859_Solid_State_Relays_data_sheet.pdf on pg 9 or
380D25; 380 VAC 25 Amp, DC control, http://www.opto22.com/documents/0859_Solid_State_Relays_data_sheet.pdf on pg 4
Both take 3 VDC on and 1 VDC off, driving current I'm not sure yet.
Possibly some combination. Or you may suggest something better.
The timing issue is not tested. It looks like the SSRs turn on/off in 0.017 seconds. The micro may take several minutes to sync up to the central inverter frequency & voltage, the Arduino would not need to act again on the same switch immediately.