Mitigation of power oscillations for energy harvesting capability improvement of grid-connected renewable energy systems

Abstract

The increasing penetration of renewable energy sources in the power system raises several challenges from the power quality and output power fluctuations point of view. However, the output power oscillations and power quality problems caused by the low order harmonic oscillations at the second-order frequency of the utility grid on the dc-link capacitor are emerging as major issues for the efficient operation of power converters. In this manner, a novel method based on modification in the control algorithm to alleviate the output power oscillation and reduce the output current total harmonic distortion is proposed. The proposed control approach seems as a promising solution for the satisfactory grid operation of renewable energy sources regarding not requiring any additional circuit and increment in the capacity of the dc-link capacitor. Moreover, mitigation of oscillations enhances the active power reference tracking capability of the controller that enables the overall efficiency improvement of the system. The performed case studies reveal that the overall efficiency rate of the system is increased by 1.3%. On the other hand, the output current harmonic distortion is decreased below 3% even under low power operating conditions. Also, the complexity level of the control algorithm is quite low for real-time implementation.