Recent content by fourtytwo

Abstraction is ok if you don't need exact timing and total control of the hardware! When you have self-destructing hardware with high energies around it's a bit better to have cast iron control of what's going on or BANG :unsure: usually expensive!! Ohh I wouldn't countenance anything...

Yup just like here in Lincolnshire, I wanted to absorb those peaks without chopping them off by interfering with MPPT straight away and in many cases the average is nowhere near any sensible limit hence the thermal limiting by averaging over a long period as what I am really trying to do is...

It's my own design and it is rather customized in that it is directly connected to a water tank heater that always gets priority any surplus being sent to the grid with export strictly controlled (as I don't get paid for it). The software is entirely assembly language for speed running on a...

So to summarize your commercial inverter doesn't really have the facilities needed to control multiple parallel strings, I am not surprised as the available controls seem very limited. In your specific case the new string would be connected by a cable having a loop resistance of an Ohm, quite...

Yup you got it exactly! There are some plots on another thread of mine illustrating this here

See post #7!

Well by the sounds of it you really are going to rely on that fuse for fire protection so I hope you take into account the mounting and cooling of that cable in calculating it's hoped for ampacity!

Ahh very interesting, do you know what Voc is for your array (measure with breaker open) then set the target voltage maybe 20V below Voc and make sure it sticks there as it's only operating point. I think your comments with a commercial product and similar parallel strings very relevant to this...

IMOP that's quite likely a dangerous assumption, after all, it want's 5500W+losses from the input and it will use whatever combination of volts and amps it fancies to obtain it!

I think this is confusing MPPT & "target voltages" maybe ? Surely this "target voltage" is constant voltage and is a mode that avoids the use of any MPPT algorithm at all.

I found the manual so impenetrable I could not find any reference to those settings however fixing the array voltage is not going to limit the available current! Are you saying you would use a wire and hence a fuse below Isc for those panels ?

Longevity of the inverter and panels! Ohmic losses (heat) increase at the square of current so if the opportunity arises to run at 10A vs 15A I will take it. Peak to average ratio is also important in the PWM as it affects transformer and inductor dissipation and so running at different PV...

It all depends on weather your array suffers shading (as mine do) and large variations in temperature (most do), both cause vmpp to shift around in voltage at times quite dramatically, I can for example be running on only one of four panels(others being shaded) so vmpp is only one quarter of...

Well there are actually two loops, an inner PID loop that controls voltage, that is it continuously adjusts the PWM to maintain a set PV voltage and then there is the outer MPPT loop that runs much slower and determines the setpoint voltage for the PIV loop. In the case of the periodic scan MPPT...

Hello I have a ~1Kw inverter with two ~1Kw PV strings in parallel pointing in slightly different directions. As expected MPPT handled the combination with no problem even though there was a voltage difference. However what I was not expecting is that when up against the inverter power limit in...