This test case consists in an Infinite Bus with variating voltage and frequency connected to an Alpha Beta load with frequency dependence through a RL line.
For the model, alpha=1.5 and beta=2 while sensitivity to frequency is defined as Kpf=2.0 and Kqd=-2.0.
Between t=2.0s and t=4.0s, the nominal voltage of the infinte bus decreases from 1.0 p..u. to 0.8 p.u.. Between t=6.0s and t=8.0s, the nominal frequency of the infinite bus increases from 1.0 p.u. to 1.05 p.u.
