Disturbance Rejection through Adaptive Frequency Estimation Observer for Wind-Solar Integrated AC Microgrid

The renewable energy generation is the cornerstone component of the greener and cleaner ac microgrid. The high penetration of wind and solar photovoltaic energy sources in the distribution network causes unbalanced voltages, voltage rise, flicker, and internal and external uncertainties leading to disturbance and unreliable operation of the system. This paper presents the performance enhancement of the wind-solar integrated ac microgrid by implementing the adaptive frequency estimation observer (AFEO) aiming for disturbance rejection. The model uncertainties and unknown disturbances are taken care of by nonlinear active disturbance rejection controller based phase-locked loop in conjunction with the AFEO. No detailed mathematical model is required, instead the controller provides decent anti-interference and effortless parameter tuning. The fluctuations in power, interharmonics, current harmonics, and power quality (PQ) issues produced by wind and solar energy resource permeation into the grid, are addressed and mitigated by successful implementation of the AFEO for switching the grid side voltage source converter. The machine side converter obtains its switching pulses from vector control scheme. The encoderless speed and rotor position estimation of the synchronous generator (SG) driven by wind turbine is carried out by back electromotive force technique. The environmental variation of the wind and solar energy are overcome by utilizing perturb and observe scheme for optimal power extraction. Test results are obtained from the laboratory prototype under steady state and dynamic conditions including environmental changes, i.e., intermittent wind speed, solar insolation, and variable load conditions. PQ issues are addressed, investigated, and mitigated successfully.