A Novel Strategy Based on Linear Active Disturbance Rejection Control for Harmonic Detection and Compensation in Low Voltage AC Microgrid

In an AC microgrid, harmonic distortion is mainly caused by power electronic equipment and nonlinear loads. In this paper, linear active disturbance rejection control (LADRC) is used to control the fundamental current at the point of common coupling (PCC). Meanwhile, an active power filter (APF) is added to eliminate the harmonic current generated by the nonlinear loads. The tracking differentiator (TD) in active disturbance rejection control (ADRC) serves as a low-pass filter (LPF) in the harmonic detection algorithm of APF. Compared to traditional harmonic detection algorithms, the improved strategy solves the contradiction between rapidity, accuracy, and overshoot of filtering. LADRC has good performance of disturbance rejection, internal decoupling, and accessible parameters tuning. It can observe the internal uncertainty and external disturbance of the system as the total disturbance through the extended state observer (ESO), and compensate it in time through state feedback to make the system achieve the desired performance. The abilities of resonance suppression for LCL-type filter and internal decoupling of LADRC demonstrates its advantages through frequency domain analysis and simulation. The proposed strategy was simulated in MATLAB/SIMULINK and realized in the experimental hardware platform, and the effectiveness of the proposed strategy is approved.