Changeover Failures

Hi Everyone,

What are the possible causes of changeover failures that you know of?, I have a system that is made up of solar plus a battery storage system as the master, then their is the utility power and the generator as the last option, all controlled from a PLC controller. The changeover seems to sometimes fails to pick up the right source when one goes off, say when the utility power goes off and the generator picks, then it does change to generator. 

  • Do any of the sources ever run in parallel? It's common enough for battery systems to be grid-connected for instance and if that was the case then a grid failure might pull down the voltage detection on both the grid and inverter lines.

    Or it could be dodgy software of course.

    I'm guessing in the wind of course - a lot more detail would be needed for a sensible analysis...

            - Andy.

  • Hi Andy,

    Thanks for your reply, Below is part of the documentations

    First priority is to the solar power followed by grid in daytime and battery in evening time. - Battery capacity is broken into two parts - Normal (say 50%) and Reserve. The Normal battery is emptied ahead of the Grid in the evening, whereas the Reserve battery is retained as a back-up and used towards the end (early morning before new solar day starts).

    - DG is usually not used but will come on once the battery is near its end. As a DG operates best on good loads - more complex algorithms are possible, where if there is a high load and no grid, DG can be run rather than draining the battery.

    At night, during a grid outage, if the load has not reached 25% of the generator load, the BESS will charge from the generator to maintain the minimum generator loading but only up to 40% SOC of the BESS, after that the BESS will switch off the generator and will discharge by powering the load until 12% SOC;

    I am inclined to believe that the problem maybe more towards the controls in the PLC as there is a lot of ifs based on the state of charge (SoC)