An Adaptive Differentiation Frequency Based Advanced Reference Current Generator in Grid-Tied PV Applications

In this article, an advanced reference current generator employing a combination of novel dual multi-layer fifth-order generalized integrator and adaptive differentiation frequency locked loop scheme (DMFOGI-dFLL) is proposed for mitigation of harmonics present in a grid-tied photovoltaic (PV) system. The proposed DMFOGI reference current generator is utilized to separate the fundamental constituents from grid voltage distortions, sag, swell, unbalance, frequency variation, and dc offset conditions. In addition, a dFLL is implemented to estimate the system frequency adaptively at grid transient conditions, which is fed as feedback to the pre-filtering unit. Similarly, a fuzzy tuned proportional integral derivative (FPID) voltage controller is incorporated in the proposed controller to maintain the power balance between dc and ac sides by controlling the dc-link voltage. An incremental conductance (IC) control technique is additionally utilized to generate maximum power from the PV source through a boost converter. The proposed system is simulated on MATLAB/SIMULINK under various transient conditions, such as steady state, voltage sag, swell, distorted, unbalance, dynamic load, and load shedding conditions. Moreover, the overall system is developed on a laboratory prototype experimental setup. The simulation outcomes are validated through an experimental platform under above said conditions in respect of total harmonic distortion (THD) of grid current and voltages. Results of the system are found well and also maintained within the standard limits of IEEE-519.