AES-FLL control of RES powered microgrid for power quality improvement with synchronization control

In this paper, AES-FLL (Advanced Extremum-Seeking Frequency Locked Loop) control with DC-offset-rejection capability for power quality improvement is proposed. The attributes of the AES-FLL are a precise estimation of fundamental load current with low steady-state oscillations, fast dynamic response, DC-offset rejection capability and low THD. Further, the AES-FLL is capable of extracting the fundamental component of grid voltages and generates harmonic free reference grid current under weak grid conditions. Moreover, reactive power compensation, harmonics mitigation, unity power factor and coordinated power flow operation are accomplished using the AES-FLL control approach. A seamless transition is achieved from the grid-connected operating mode to the standalone operating mode during the grid outage to ensure power continuity. The grid synchronization is achieved through the LPN-PLL (Low-Pass Notch Filter Phase Locked Loop) control approach. Comparative analysis of the VSC (Voltage Source Converter) control approach AES-FLL and grid synchronization approach LPN-PLL with the conventional methods is presented. The performance of the microgrid is demonstrated by simulation and then presented a prototype experimental validation under nonlinear loads.