There are three components to vCenter Converter - The Server, Agent and the Worker

In order to enable verbose logging on each of the components, backup and edit the below files at:
%programdata%\VMware\VMware vCenter Converter Standalone\
converter-agent.xml
converter-server.xml
converter-worker.xml

In each file change the log level from “info” to “verbose” under the following element

<log>  
    ...  
    <level>info</level>  
</log>

Restart the converter services to apply the above changes.