Influence of the PLL phase-angle quality on the static and dynamic performance of grid-connected systems

This paper presents some effects that contribute to performance degradation of grid-connected systems, when they are subjected to operate under distorted reference phase-angle signals. In many power electronics applications, grid-tied systems are developed on the synchronous reference frame (SRF) and make use of the synchronous unit vector coordinates to compute their control references. Usually, the unit vector coordinates are generated from the estimation of the utility phase-angle, which is obtained by means of phase-locked loop (PLL) schemes. Thus, static and dynamic disturbances present in the utility voltage can generate distorted phase-angle signals, and, hence, can affect the quality of the synchronous unit vector coordinates. In this paper, two single-phase SRF-based PLL schemes, which operate under distorted utility voltage conditions, as well as distinct bandwidth PI controllers, are used to generate the current control references of a single-phase shunt active power filter (S-APF). Experimental results based on digital signal controller are used to evaluate the problems that can interfere on the S-APF performance.