Single Phase Solar Inverter creating voltage fluctuation

[fllniks]

Hello,

I have recently installed a small solar system for a home and facing some problem. I am unable to understand the issue and hoping that experts at this forum can help me. Below I am writing all the details of the installation

Installation for home
Installed 1.5kW (6 x 250W) panels with a 2.4kW Single Phase Hybrid Solar Inverter (By hybrid, I mean that it works with grid, solar & batteries with solar being given priority to charge the batteries as well as power the load. If not enough solar power is available then grid power is used to charge the batteries).
Do note that there is no feed-in system; all the energy from solar is either used in the home or stored in the batteries.

In-built solar controller: 50Amps
System Voltage: 24V
Batteries: 2 x 12V 200Ah
Connection: The customer's has a three phase connection. Solar inverter is connected on the one of the phases on which the load that needs to be powered by solar/batteries is connected.

Load: Primarily lights & fans with a small refrigerator (total load is about 1kW)
Problem: Sometimes suddenly lights will go dim or become too bright. Similarly fan speeds will change. Clearly this is because of voltage fluctuation.
There is no fluctuation on other phases and grid voltage is stable.

Any suggestions on how to solve the issue or at least any guesses why voltage fluctuation is happening suddenly?

[Sunking]

Well for one if you are trying to deliver 1000 watt load at 24 volts requires a minimum 350 AH battery to prevent excessive voltage sag at high power levels. Secondly the other two phases would have to be electrically isolated from the solar.

[inetdog]

The most common reason for lights dimming (or getting brighter) with a change in load is excessive resistance in the wiring connecting you to the grid. That included POCO wires and transformers even though you have no direct control over them.
With grid tied solar in the picture you have to deal with changes in generated power as well as changes in loads.

If you have excessive voltage drop in your wiring, then putting a large GTI on the same system/circuit/phase/branch/feeder will cause a voltage RISE equal to the voltage drop which would have been caused by a load of the same total power. That is the way a GTI has to work and there is no way around that. If you get used to the higher light output (and reduced life) caused by the higher voltage when the GTI is producing, then a temporary loss of that GTI power will be seen as the lights dimming.
A GTI may dip its output in response to a passing cloud or may turn itself off completely for a few minutes (five for UL listed products) in response to an apparent anomaly in the grid power voltage or frequency.