An integrated rule-based power management and dynamic feed-forward low voltage ride through scheme for a grid-connected hybrid energy system

Abstract

Power generation from a grid-integrated renewable energy generator embedded with backup sources to form a hybrid energy system possesses convincing features of high efficiency and zero emissions. Control for felicitating apt power sharing and for providing ancillary services such as low voltage ride through (LVRT) is necessary for the compliance of grid codes. However, the simultaneous control coordination for meeting these control objectives is challenging due to the dynamic nature of renewable generators and utility grid. Hence, this paper proposes an integrated power management strategy (PMS) and LVRT control scheme for such systems. A wind energy conversion system backed up by a battery energy storage system, proton exchange fuel cell, and electrolyzer is considered in this work. A reduced rule-based power management control scheme is proposed for the considered system where the request made by the grid operator is kept in priority. Further, a dynamic current feed-forward based LVRT control scheme based on negative sequence current minimization is presented for the grid-interfaced inverter. The inverter control is coupled with an inherent mode selection capability between the grid feeding mode and LVRT mode in order to realize the proposed integrated control objectives. The validation of the proposed PMS and LVRT control is justified by detailing relevant mathematical control models and also by realizing practical case scenarios such as variable wind speed, load demand, grid power request, and occurrences of balanced and unbalanced voltage sag. The obtained simulation results show the cordial response of the system with the proposed control strategies.