I would like to know if there is any internal structure differance between the excel created with Microsoft Office Interop Excel(Interop) and Microsoft OpenXMLSDK (openxmlsdk)?
I am currently working with an third party application which rejects the excels created with OpenXMLSDK and accepts only excels created with Interop.
To do the compare you can download the Open XML SDK Productivity tool and use the compare feature. This will allow you to take two excel files and compare their internal XML to see if there are any differences.
Another option if you can't get the tool installed is to rename the file in question to a .zip file and then examine the contents that way. There will be a good amount of files in the zip, but you should be able to compare the files using any compare tool on the web like windiff.