Fig. 3d shows the performance of the system for the change in SPV
insolation level. The system has been working under steady-state
conditions before time t = .3 s. The VSC performs the function of
harmonics mitigation and feeding real power into the grid. At time t
= .3 s, the SPV insolation level is changed from 1000 to 700 W/m2.
The PV power decreases as a result of changes in the SPV insolation
level. The effect can be seen in terms of decrease in VSC current and
the grid current. The load current is the same during this time and the
active power component of VSC current decreases. The harmonics
demanded by the load remain the same, hence that part of VSC
current remains same before and after time t = .3 s.