I doubt this is of any use now, but if someone see's this post in the future who has the same questions. I might be able to help.
The one thing that ever 'bugged' our plants, was when we had inverters without filters, and also DOL motors with their enormous startup currents.
I start my project for my HNC next year, and mine will be based on Inverter technologies and how to reduce harmonics etc.
Use experience from problems you've had in the past and then use the project to figure it out, and hopefully, get a solution.
Linked In - http://www.linkedin.com/in/chrissj91