Fuzzy logic-based technique for enhancement of kalman filter based PLL

Abstract

In grid connected applications power electronic converters need to be synchronized correctly with the power system. Quick and precise positive/negative sequence extraction of the grid voltage is the major challenge in synchronization. Phase-locked loop (PLL) is well known method for phase angle and frequency detection. Up to now numerous PLL based techniques are proposed to perform this task. This paper deals with the proposing a modified Kalman-filter based PLL (KF-PLL). The performance of this PLL depends on how to properly tune the frequency identifier system. Therefore to enhance the performance of this PLL a fuzzy based technique is proposed which effectively makes the Kalman-based PLL better. The designed fuzzy system adjusts k_u parameter which is responsible for speed of the convergence of real time frequency identifier block of the KF-PLL system. The proposed detection system is simple, and precisely finds the fundamental component of grid voltage within one cycle, that is fast enough for almost all synchronization application. Meanwhile, the method guaranties the zero steady state error in complicated harmonic scenarios, including all typical single phase and three phase harmonics. The simulation results depict the influence of fuzzy logic technique on KF-PLL improvement.