Dynamic Power Sharing Assisted Hybrid Controller for PV Fed Isolated dc Microgrid

Abstract

This article presents a hybrid control strategy to improve the control and power sharing of a hybrid energy storage system (HESS) used in an isolated dc microgrid. While the photovoltaic panel is the primary energy source, the battery and supercapacitor work together to meet the additional power requirements. A modification to the traditional filter method for dividing the average and transient HESS current components is done by replacing the low pass filter (LPF) with a rate limiter to ensure proper power splitting and smoother battery discharge. The rate limiter integrates power balance into the system and allows for the integration of battery discharge rates, eliminating the problems caused by the unintentional selection of the cut-off frequency. In addition, the HESS current outputs are no longer affected by low order LPF phase delay. A simple prediction based current control is proposed for HESS current regulation to precisely track the rate-limited current references and avoid common windup concerns associated with proportional integral (PI) controllers arising from system nonlinearities and uncertainties. The proposed control approach can reduce the peak overshoot below 2% and settling time during disturbances less than 15%. Simulation and experimental investigations are carried out to validate the effectiveness of the proposed method.