Evaluation of two positive sequence filters for an interface between electromagnetic transient and phasor solutions

For the transient simulation of large power systems, it is sometimes necessary to represent a part of the network using electromagnetic transient models and the rest of the system using RMS fundamental frequency phasor models. The interface between the two parts of the network involves converting instantaneous three phase quantities into phasor quantities. One possible option for this conversion is to use a Phase Locked Loop with a positive sequence filter. This paper compares the performance of two types of positive sequence filters that can be used with Synchronous Reference Frame Phase Locked Loop (SRF PLL) to extract the angle information of a three phase unbalanced power system. This study focuses on two methods: (i) Sinusoidal Signal Integrator Phase Locked Loop (SSI-PLL); and (ii) the Extended Phase Locked Loop (Extended PLL). It is shown that the Extended PLL has better performance in speed and has zero steady state error compared to the SSI-PLL.