Comparative Analysis of PLL Structures in Electric Power System with Load Variations

This paper presents a comparative study between algorithms for phase-angle and frequency detection, also known as Phase-Locked Loop (PLL), which be based on the theory of instantaneous active power (pPLL) and on the theory of synchronous reference frame system (dqPLL). To extract the components of a positive frequency chain, the Dual Second Order Generalized Integrator (DSOGI) structure was used. One of the main advantages of DSOGI is to be highly resistant to network disturbances, such as a frequency oscillation observed across the load variations that occur constantly in Electric Power Systems (EPS). Therefore, considering an EPS model, it is observed that the implemented control generates a frequency deviation due to the type of frequency regulator used. This characteristic is attractive to validate and verify the efficiency of the designed algorithms, in order to demonstrate the theoretical development and performance of the algorithms used to reject the network frequency deviations. Simulation results show the performance of the DSOGI-pPLL and DSOGI-dqPLL algorithms in the face of frequency changes caused by the load variation in EPS.