pwm mosfet driver/controller for grid-tie inverter application and optimization

Dear all

i'd like to project and build a controller for optimizing an inverter/solar application to make these things:

    • use a on-grid inverter
    • configure the inverter in grid-tie mode, getting the AC frequence from the grid but limiting or cutting off the current from the solar strings to produce only the required energy
    • connect the a battery pack to one of the DC input of the inverter, for producing the missing energy

How to make that?

    • using a TA i want to monitor the current going/coming to/from the grid and when the current from is decreasing, i want to limit the current using a PWM logic on the DC input
    • using a TA i want to monitor the current going/coming to/from the grid and when the current from is increasing, i want to increase the current going from batteries to inverter (obviously with some additional checks on battery level and current values)

So, basically i want to control 2 inverter DC strings (one real and one simulated with a battery pack) with a voltage of 350/400V and 8/12 A, do you have a suggestion for

  • type of mosfet to use
  • heating dissipation
  • pwm driver to control the mosfet gate
  • type of TA to use (one for AC/220V and one for DC/240V)

Thanks to all in advance for any consideration!

If you have to ask here you are not qualified to handle anything involving a grid-tied inverter.

Buy a certified safe product so you don't electrocute the power company staff.

...R

Thanks Robin2 for your answer i understand.

yust to share my idea....

in my question i've specified that i'll use an on-grid certified inverter, i don't want to touch/change anything related to the inverter, i want to use its capabilities to work in an on-grid enviroment....BUT i'd like to optimize the management of a DC input that is not coming from the solar string but from the battery pack.

Example:

#1
inverter DC input 1 (solar string): 2kW
inverter DC input 2 (battery pack): 0kW
home load: 1kW
Energy balance: 1kW that goes to the grid

#2
inverter DC input 1 (solar string): 2kW
inverter DC input 2 (battery pack): 0kW
home load: 3kW
Energy balance: 1kW that comes from the grid

#3
inverter DC input 1 (solar string): 2kW
inverter DC input 2 (battery pack): 1kW
home load: 3kW
Energy balance: 0

#4
inverter DC input 1 (solar string): 0kW
inverter DC input 2 (battery pack): 0.4kW
home load: 0.5kW
Energy balance: 0.1 kW that comes from the grid

What a want to do, is something that handle the examples #3 and #4, i'm interested to just optimize the usage of the battery pack when my loads are compatible with the battery pack, and when the load is lower i'd like to limit it with a PWM logic.

In this scenario i don't have any risk of electrocute on the company staff, as the inverter is a standard on-grid product and is powered on from the grid.

I'm just using a DC input on the inverter, obviously i need a controller on it to limit the current to avoid any kind of battery damage or component overheating, but is all on the DC side of the system.

What do you think about that?

I think your use of language is causing confusion. In my world "outputs" come from something and "inputs" go into something. You said (for example) "a DC input that is not coming from". I would call that an output or I would say it is "going to"

Anyway, having got that off my chest, I'm still not sure what you want to do.

I guess you want the Arduino to detect the current flowing FROM the solar panels and to know (how?) the amount of current that could be taken FROM the battery so as to use the battery in preference to importing power FROM the grid.

Or maybe, a variation on that, to impose an upper limit (how would it be set?) on the amount of current drawn from the battery and drawing the balance of the domestic load from the grid.

AFAIK it is possible to get sensors that can measure the different currents and make the data available to the Arduino. However I suspect an effective control system would be either very simple (and may not need an Arduino) or extraordinarily complex.

One of the problems is that solar output can vary dramatically in fractions of a second.

Another issue to consider is whether your system might be "fighting" with the logic in the grid-tie ineverter's software.

And it can be very difficult to identify the remaining capacity in a battery system while it is in use.

...R

Hi,
Can you draw a simple block diagram of what you want to do please, just draw and photograph your project.

It sounds like you have an on-grid inverter and solar PV cells and you want to put a battery pack on the PV side and manage how the PV current goes to battery or inverter.

You want to control how much energy goes to the inverter and have the rest go to the batteries until they are fully charged.

Tom...... :slight_smile:

I suspect the only way to do this is to find an inverter that supports this. Inverters manage
MPP tracking and assume they have full control of the attached PV strings in order to be able to do this.

Now many inverter support grid tie and battery backup, example outback, imeon etc. but if you want build, you must know step by step, how it work with minimal part. (MPPT,Inverter On grid)
I have suggestion to this project with simple configuration, use MPPT to charge battery, if battery full, connect mppt to grid tie inverter(system 48Volt), if grid condition off, inverter switch to off grid mode. Basicly it is only one transformer, can use as battery charger(old design inverter-charger), and give additional program to syncronize with grid.

There ant any grid Tie Inverters that I know of that will permit power to be fed into the grid if its coming from a battery.
What make and model of Grid Tie Inverter are you using?
A normal grid Tie Inverter designed for Solar panels wont work with a battery connected to it , as the MPPT tracker will never find a peak power point as batteries dont have one.

what happened to your project ?

LOL. house burned down?