For stability studies, it is not essential to model GPU. In this case, the modelling of the controller shown in Fig.3.11 can be simplified greatly by also assuming that SVC does not generate harmonics. The block diagram of the controller in this case is shown in Fig.3.13. Here the voltage regulator is typically a PI controller as shown in Fig.3.14. The proportional gain (KP) may be set zero unless a faster response is required. The transfer function Hm(s) represents a low pass filter as given below: