Control of DFIG-SPV-BES Microgrid with CBF Prefiltred SOGI-FLL Based Synchronization

This paper demonstrates the integration of windsolar fed microgrid enabled with improved power quality (PQ) performance and seamless operational mode transition capability. The wind turbine is of variable speed type realized by doubly-fed induction generator (DFIG). Solar photovoltaic (SPV) array is integrated to the DC-link of DFIG's back-to-back converters via a maximum power extraction DC/DC converter. The DC-link is also supported by battery-energy-storage to maintain the voltage level and continuity of the power supply during low generation and grid outage. To improve the PQ performance, 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. The VSS is the sum of square of active unit-template and instantaneous fundamental weight. This approach improves the 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. The microgrid laced with the control techniques are simulated in MATLAB environment and various dynamic conditions are emulated to validate the satisfactory performance of the microgrid.