I have installed matlab 2013a in my computer. Everything works fine. But when I typed in powerlib in prompt it says cannot find library. Can anyone say how to install this library manually?
Here is the answer given by @Jonas on SO. As @Edric mentioned, (1) There is no installation of SimPowerSystems in your copy of Matlab. Type (2) Your installation of SimPowerSystems is somehow corrupt. This has never happened to me in Matlab so far, but with modern technology, anything is possible. A fresh install should solve this. 

