I think that any of us had meet the situation when we needed to create an Excel output from internal table in background. There is a really nice project called ABAP2XLSX which gives you to possibility ...
You may saw before the article Create XLSX/MHTML file from internal table in background and you may have use it without any issues before, but it seems that in newer releases of SAP (definitelly >= 7.50) ...
... XLSX/MHTML file from internal table in background and probably also somewhere in the net. To make it easier here are ready methods to create LVC and SLIS field catalogs from internal table using CL_SALV_CONTROLLER_METADATA ...