Hi

I am trying to interface a DC/DC converter that has a Constant Current Output with an inverter that has an MPPT regulated input .

To do this I need a DC/DC converter with the following features - Input : Constant Voltage regulated input and Output : simulated PV solar regulated output . I would be interested to know how this could be implemented and if there is an implementation of this type of converter already available that I could use . Here are some draft specifications for the DC/DC converter : Input Voltage : 125V DC approx ( CV regulated) , Output Voltage 60-100V approx (simulated PV solar regulated)

Open to suggestions and ideas .

 

A solar panel has a constant current output below the MPPT point and a constant voltage output above.
A DC/DC converter with a constant current output must also have a maximum output voltage, so at some point it must transition from CC to CV.
What happens when you join the two together? It seems to me that they are similar enough to make it worth trying.

 

Why do you need to simulate a solar panel? A power supply/converter with decent power limiting fold-back protection (not hiccup mode) works.
https://forum.allaboutcircuits.com/...c-controlled-battery-array.32879/post-1482098

 

Hi

I am trying to interface a DC/DC converter that has a Constant Current Output with an inverter that has an MPPT regulated input .

To do this I need a DC/DC converter with the following features - Input : Constant Voltage regulated input and Output : simulated PV solar regulated output . I would be interested to know how this could be implemented and if there is an implementation of this type of converter already available that I could use . Here are some draft specifications for the DC/DC converter : Input Voltage : 125V DC approx ( CV regulated) , Output Voltage 60-100V approx (simulated PV solar regulated)

Open to suggestions and ideas .

Hi BJE - I realise this is an old question, but I have an almost identical problem and wonder if you were able to find a suitable solution. My specific issue is that I built a push-pull dc to dc inverter (48v to 325v) which works fine at full output (3A), however when the load (a GT inverter) changes and demands more current, the current limit circuitry reduces the duty cycle as expected and limits the o/p current , but causes massive overheating of the fets - any ideas would be welcome.

 

I am asking just exactly what is the targeted goal of the exercise. That matters

 

I am asking just exactly what is the targeted goal of the exercise. That matters

Hi, sure, the goal is to simulate a solar array into a Grid Tie inverter, so as to enable use of battery energy overnight - so, the scheme is 48v battery >>> DC-DC converter with constant current o/p at around 350v open circuit >>> solar input of Grid Tie inverter.
The issue is that occasionally the GT inverter demands a higher current, which in turn is limited by the DC-DC converter controller by reducing the duty cycle - this in turn is creating an over heating issue with the FET's in the DC-DC converter (push-pull) when very low duty cycle is demanded.

I know the obvious first thought is to use bigger FET's, but it's not practical with my build. I also know I can now bye Hybrid inverters to replace the existing GT's, but I am treating this project as a learning trip and I hate being beaten !!

Hope that helps..

PS: I have 4 separate DC-DC converters feeding the 4 input strings of a single GT inverter - It works fine with only a couple of strings powered up (A1 & A2), but occasionally blows FET's on the other channels (B1 & B2) randomly, through over heating when, I suspect, the pulse width is too low in current limit mode.

 

INTERESTING! So it seems that an alternate scheme to feed the battery power directly into the "single Grid-Tie Inverter, and currently it is implemented by a battery powered simulation of the solar cell feed into the G-T inverter.
Evidently that G-T inverter is not able to operate from the battery supply directly.
One possible option that could be more efficient would be a switching scheme to put sections of the 48 volt battery pack in series, to provide the higher voltage simulating the PV array. Certainly that would require some serious switching, but if it was done with mechanically held automated switches it could be almost lossless. Certaily it would avoid using an inverter system.