For my research work I need to have a tool for simulation on Distributed Generation. I have inquired Homer too and it is suitable also but cost matters.
Have you checked the simulation packages available in R to see if any are useful to you. All of R is free for download. I have attached a basic level R book.
AnyLogic PLE is the only free simulation software that combines discrete event, system dynamics, and agent-based simulation methods so you can model any real-world system or process.
I developed a model in matlab and I also used HOMER for modeling distributed electricity generation units. You might find these reports and articles helpful for your study:
Thesis Assessment of Renewable Energy Based Micro-Grids for Small Communities