Control of DFIG-SPV-BES Microgrid With CBF Prefiltered SOGI-FLL Based Synchronization

This paper demonstrates an integration of wind-solar fed microgrid enabled with improved power quality (PQ) performance and seamless operational mode transition capability. Wind turbine is a variable speed type realized by a doubly fed induction generator (DFIG). Solar photovoltaic (SPV) array is integrated to DC-link of DFIG's back-to-back converters via a maximum power extraction DC/DC converter. DC-link is also supported by battery-energy-storage to maintain voltage level and continuity of power during low generation and grid outage. An adaptive variable step size gradient descent total least squares (VSS-GDTLS) based power injection control is implemented for grid-side-converter during grid-tied operation to improve PQ performance. VSS is sum of square of active unit-template and instantaneous fundamental weight. This approach improves convergence compared to conventional fixed step approach. Seamless transition is achieved by using a pre-filter enabled frequency and phase angle estimation tool. A complex band-pass filter (CBF) enabled second-order generalized-integrator type frequency locked loop (SOGI-FLL) technique is used for frequency and phase angle estimations. Microgrid laced with control techniques is tested on a laboratory setup and various dynamic conditions are emulated to validate satisfactory performance of microgrid.