An Adaptive Frequency PLL Approach for Grid Connected Multifunctional Inverter for Residential Applications

This paper presents an adaptive frequency Phase locked loop (PLL) based approach for grid connected multifunctional inverter is presented for residential applications. The proposed control structure deals with non-linear loads and also non ideal grid voltages like magnitude variation, frequency variation, unbalance harmonics, etc. and can effectively address the DC offset in a voltage signal which in turn improves the power quality. A third order generalized integrator based PLL with adaptive frequency and DC offset elimination blocks will effectively deal with the power grid voltage fluctuations, frequency variations and eliminate the phase difference between PLL output. This approach is implemented as control algorithm for single-stage single-phase grid connected multifunctional inverter topology for PV applications which feeds energy to the grid. The Maximum Power Point Tracking is obtained by Perturb & Observe method for extracting maximum power from a Photovoltaic system. A detailed analysis with the proposed control technique is presented in this paper. Experimental tests are conducted at various operating conditions to describe and verify the performance of the proposed control using MATLAB / Simulink.