any one knows how can i control the voltage ? when to use the voltage in the battery and when it runs out when to use the grid ? do i need a software for it ? if so which one ? thanks allot.

Most of the larger battery based grid tied inverters will do this. That is use up batteries and at a point you set voltage wise and/or time wise to switch over to the grid. It is a seamless transition going back to grid with between 1 and 10 millisecond blip when disconnecting from the grid. The inverters also let you stay connected to the grid and just dump access power in to loads. For example our Xantrex XW6048 will first use excess power to power downstream loads and if that doesn't use up the available power the inverter can be set to sell back to the grid.