Adaptive Control Strategy for Grid-Connected Inverters under Variable Renewable Conditions

Abstract

This is worsened by facilities that have led to the growing infiltration of renewable energy sources, which is fostering challenge in the operations of grid-connected inverter systems because of the speedy variability of power, irradiance variability, and dynamic grid impedance provisions. Traditional fixed-parameter PI/PR current controllers that are popular to use however, have reduced performance when the load grid is weak or faces voltage perturbation, and that rapidly changing renewable signals can cause high harmonic distortion and reduced transient response. The paper presents a real-time gain adjustment based on online estimation of the system parameters as an adaptive current control system strategy to improve on robustness and tracking accuracy. The new controller is proposed to be dynamic in compensation of the change in the grid impedance and intermittent supply of renewable power as well as in controlling dq-axis current without affecting the current regulation on the dq-axis. The system is checked by rigorous MATLAB/Simulink simulations, hardware-in-the-loop (HIL) testing under a wide variety of operating sessions, such as irradiance step loads and voltage sags, low short-circuit ratio (SCR) when testing. Comparison of the results reveals that the gross harmonic distortion (THD) is greatly reduced, settling time is greatly improved, disturbance rejection capability is also greatly enhanced, and current tracking accuracy is also greatly improved over conventional controllers. An adaptive strategy can sustain harmonic values within the IEEE 519 limit and meet the IEC power quality standard and is the correct choice whenever the aim is to ensure consistent grid integration of renewable energy systems using variable operating conditions.