Solar Management Question

A little thought experiment suggests that when the grid voltage is high, it doesn't seem to need any more power from the solar panels. So it is better to store the harvested energy and supply it to the grid when the voltage is low. So, rather than keep changing knackered MOSFETs, increase the storage to the economic limit of practicability and stop there.

Someone must have designed the system to work within the available parameters. What about a telephone call to talk it through with that individual?

Thanks PW: The system as you describe works fine with some neighbors.

Their voltage is like 235- 238. It is in this small difference that the problems arise. The inverters need to absorb and ventilate the extra energy when the voltage is too high in the grid. I figured out that an extra fan helps me out but not enough to be on the safe side. The biggest concern now is to keep the battery voltage in acceptable limits. There must be some comparator circuitry to take care of it. It works fine when I am standby and keep the battery between 25 and 27.5 volts. Heavy duty DC relays need also close to .8 amps. At the end causing lots of wasted power. A call to supplier learned me that this is the design voltage.

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Not a timeswitch, then? Why not export at night?

I'm surprised the charging controller doesn't have a dumping load. You should check with the mfg, maybe it is an addable option.

I do not control the solar charging. The panels are connected to the batteries.

I try to keep the charge between the battery limits with switching more inverters on and off, but need a reference like a VU bar meter with 20 A relais.

Thanks also. The only night option is a problem, the batteries can easily get overloaded during the daytime. It can happen in 10 minutes with the sun we have here. It is just a matter of clouds or no clouds. I pick it up later. Have an urgent matter.

That is close to how we coupled generators to power grids when I was a Naval nuclear engineer. The generator to be coupled to the grid would be running at a slightly higher frequency than the grid. There was a meter that showed whether they were in phase or out of phase and by how much. When they were close to in phase, but with the generator being brought on line slightly faster (higher frequency) and slightly leading, the connection was made. It was done manually.

That works fine with a mechanical generator because it will automatically sync itself to the line through inductive slip and loading of the engine but inverters have to sense the line to stay in sync. I'm sure his inverter(s) are designed to do this but if they only go up to 250V (is that RMS?) then the current is going to be limited.

I think an autotransformer should take care of it but OP should consult the mfg. Surely OP is not the first person to have this problem.

I owe you all more info:

Total panels installed: 40 pieces - Max available power: 6.800 Watts.

Battery bank: 24 Volts, 6 groups parallel 1.200Ah.

Inverters: 26 in parallel - 13 over each phase to neutral.

The inverters measure the grid at a frequency of 16.000 Hz (quartz crystal triggered) and immediately send a pulse, higher than the measured value back into the grid.

This allows a cos phi of 0.99 to 1.

This frequency can be measured at the output but completely disintegrates after meeting the first line transformer.

In full sun, currents from the panels can run up to 200 Amps to the batteries. Critical is when the batteries are getting charged, close to Upper limit. The panel curve moves closer to the MPPT ( 17,3 X 2 Volts) and the output increases faster and faster then.