MTFOCF Based Control for Grid Connected PV System and Seamless Grid Synchronization

This paper deals with the dynamic and robust control strategy of SPV (Solar Photovoltaic) based nonconventional energy system (NCES) with seamless transition capabilities from an islanded (IL) mode to the grid-connected (GC) mode. It precisely transfers the power to the loads when NCES changes its mode of operation i.e. from IL to GC and vice-versa. In this work, a mixed third and fourth order complex filter (MTFOCF) based control algorithm is presented to control the NCES in GC mode. This control provides DC offset rejection along with harmonics elimination capability. This control performs well at scenario like DC offset, voltage unbalance, swell/sag and regulates power regardless of the load. This algorithm takes care of the problem of poor power quality at the grid and is used for the extraction of sinusoidal fundamental component (SFC) with reduced burden and with an ability of noise rejection unlike the conventional methods. It reduces computation time. Thus, it improves overall system capability of power flow. In IL mode, the proportional resonant (P+R) with SRF based control algorithm is presented to control NCES. For fast and smooth grid synchronization or resynchronization MTFOCF is enforced to phase locked loop (PLL) and established MTFOCF-PLL. MTFOCF-PLL precisely tracks the voltages of the grid even under large frequency variations and it is adaptable to various grid conditions. The system performance of different modes of operation of NCES and effectiveness of control algorithms are simulated at various conditions. The total harmonics distortions (THDs) of the grid and load parameters, are found within the IEEE-519 standard