Power Quality Improvement of 3-phase Microgrid Based TOFE under Weak Grid Condition

Abstract

Power quality improvement has gained much attention now a days due to rapid increase of nonlinear loads. The biggest challenge for power converter is to deliver sinusoidal current waveform even during distorted grid condition. In this study, a third order fundamental extractor (TOFE) based control technique is used for power quality improvement for three-phase grid connected solar PV system under weak grid condition. The proposed TOFE based control algorithm is used to extract fundamental of grid voltage for synchronization to the grid. This analysis uses a two-stage conversion scheme. The first stage is the boost converter, which is used to derive maximal power from the solar PV array by applying the incremental conductance (InC) technique. The second stage consist of VSC which not only feeds into the grid, but also mitigates harmonics, compensates for reactive power and keeps the power factor near to unity. The main purpose of proposed control of VSC is to deliver reliable, secure and safe integration while eliminating several power quality issues like DC current rejection, to reduce the THD in the injected grid current, to make power quality better under abnormal grid condition. The PI controller is used to maintain the DC link voltage as desired according to the requirement of system and feedforward term to improve dynamic response of the system. The system is tested in MATLAB/Simulink platform. It can be demonstrated that the system performs satisfactorily and THD of the grid current is within the limits of the IEEE-519 standard.