A Novel Fourth-Order Generalized Integrator Based Control Scheme for Multifunctional SECS in the Distribution System

This paper presents a novel fourth-order generalized integrator using a frequency locked loop (FOGI-FLL) based control algorithm for a single-stage three-phase grid-interfaced solar energy conversion system (SECS) with the distribution static compensation (DSTATCOM) capabilities. The proposed FOGI-FLL control algorithm suffices multifarious power quality objectives in the distribution network such as harmonics mitigation, reactive power compensation, load balancing, etc. The FOGI-FLL has good frequency tracking performance along with high dc offset rejection and high-order harmonic filtering capabilities. Simulated results demonstrate the satisfactory response of the system under load unbalancing, variable insolation, and system frequency variation. The effectiveness and advantages of the proposed algorithm are shown by comparing it with conventional algorithms. To validate the control algorithm, an experimental prototype is developed and test results depict the performance and behavior of the system under various conditions such as load unbalancing, variable insolation, photovoltaic (PV) to DSTATCOM mode, DSTATCOM to PV mode, and voltage sag and swell. The total harmonics distortions in grid currents and grid voltages are found well within limits according to IEEE-519 and −929 standards.