Power Quality and Stability Improvement of Hybrid Energy System Under Weak Grid Environment

Abstract

This paper proposes the control scheme using super-capacitor (SC) in hybrid energy system (HES) under the weak grid condition. Photovoltaic-based HES connected to weak grid is considered as the system under study. The control scheme is designed for power quality improvement, reduction of ripple content in DC link voltage and to improve the stability margin of HES by utilizing SC. The proposed control scheme is very effective in reducing the ripples in the current, improving the dynamic response and damping out the oscillations under transient conditions. Unlike with conventional control, the stability of the DC link voltage controller under the proposed control scheme is independent of weak grid conditions. Drawbacks of the conventional control schemes, due to the coupling terms and variable grid impedance in weak grid condition, are analyzed and illustrated mathematically. Design and stability analysis of the proposed control scheme is described and compared with the conventional control scheme. HES is modeled and simulated in MATLAB Simulink to verify the enhanced performance of the proposed control scheme over conventional control scheme in terms of improvement in DC link voltage profile, reduction in ripple content in power and better dynamic response of HES connected to weak grid.