Multifunctional Grid Interfaced Solar Based Microgrid with Seamless Mode Transition

This work presents an adaptive control approach of solar Photovoltaic (PV) based nonconventional energy system (NCES) with seamless changeover proficiency from an islanded mode (ILM) to grid-connected mode (GCM). The NCES has a capability to feed the load both in GCM and ILM and it operates smoothly during mode shifting from IL to GC and vice-versa. The unknown disruptions and uncertainties of NCES in GC mode are taken care by proportional plus multilayer modified third order sinusoidal signals integrator (P+M3rdOSSI) with multilayer harmonic decoupling network (MHDN). The concern like power fluctuations, DC offset, unbalance in voltage are successfully taken care by P+M3rdOSSI with MHDN. With the help of this algorithm, the sinusoidal quadrature fundamental component (SQFC) is extracted and reduces computational time. At the point of linkage (POL), the power quality gets improve with this control. It improves overall system performance as it operates adequately in steady state and transient conditions. To control the NCES in an ILM, the proportional plus resonant (P+R) based control algorithm is used. The steady state error gets reduced and system become robust with the help of
$\mathrm{P}+\mathrm{R}$
based controller as compared to conventional PI control method, and hence zero steady-state error is achieve. A dual quadrature second order generalized integrator (DQSOGI) based PLL is used for precise and smooth synchronization and resynchronization of grid. DQSOGI based PLL improves system performance without affecting the stability. During frequency variation, it effectively follows the voltages of the grid and the load and it is adjustable to different conditions of grid. Moreover, total harmonic distortions (THDs) of the load and grid parameters are in the limits of the IEEE-519 standard.