Problem 

While simulating a grid connected PV system using co-simulation among PSIM and SIMULINK i was getting error. The error stated that

Algebraic state in algebraic loop containing 'SCMPPT_sensorless_v4_buckboost_ok/Product3' computed at time 0.0005 is Inf or NaN. There may be a singularity in the solution. If the model is correct, try reducing the step size (either by reducing the fixed step size or by tightening the error tolerances).

I tried the suggested methods as shown in figure above. Neither the step size nor the error tolerance worked. The solution was however, simple, and is given below.

Solution:

Connect a very small capacitor (0.05 micro farad in my case) in parallel with the PV module.