- SimPowerSystems has more simplified (piecewise-linear) component models and is better suited for large system simulations where you can sacrifice some detail for simulation speed.
- SimElectronics has more detailed component models and can incorporate thermal effects. This is better for calculating losses, for example.
- http://www.mathworks.com/videos/modeling-and-simulation-of-pv-solar-power-inverters-81813.html
- http://www.mathworks.com/matlabcentral/fileexchange/34752-grid-connected-pv-array