A couple of points why smart inverters are needed to facilitate integration of renewables:
http://www.electroiq.com/articles/pvw/print/volume-20100/issue-6/features/sma...

• differentiate between a true unintentional island case and a case where grid support from the PV plant is required.
• make solar power more dispatchable by treating all inverters as a sort of "virtual power plant."
• The efficiency of the solar power plant as a whole depends not only on electrical conversion efficiency, but also on efficacy of the maximum power point tracking algorithm in the inverter. The maximum power point tracking (MPPT) algorithm adjusts PV system voltage
  continually as environmental conditions change to extract maximum energy from the solar array.
• solar inverters, which typically represent some 6%-8% of the system cost, have caused about 80% of system downtime. 

A new technology lets each solar panel be its own AC source. More efficient (it is claimed), but also potentially interesting for algorithmic optimisation of the operation of a large array of panels, I think.
http://en.wikipedia.org/wiki/Solar_micro-inverter