Small signal stability analysis of a hybrid AC/DC microgrid with static and dynamic loads

Abstract

Majority of the stability studies conducted on AC and DC microgrids have investigated stability with only static loads in the microgrid. Dynamic loads significantly influence the stability of mirogrids due to their voltage and frequency dependent nature. Therefore, small variation in voltage and frequency can make significant impact on the stability of the microgrid with the presence of dynamic loads. Thus, it is imperative to consider the dynamic loads in the microgrid for stability studies. Moreover, stability issues become more severe if the microgrid is operated in the standalone mode. This paper characterises the small-signal stability of a hybrid AC/DC microgrid with static and dynamic loads using state-space and dynamic simulation models developed in MATLAB/Simulink. This study investigates the critical parameters of the dynamic load which significantly affect the stability of the microgrid. Subsequently, eigenvalue analysis and time-domain simulations have been carried out to investigate the small-signal stability of the hybrid AC/DC microgrid. Eigen-sensitivity analysis has revealed that induction machine rotor resistance has the highest participation on the critical modes of the hybrid AC/DC microgrid. Additionally, the controller gains of the voltage source converters may require re-tuning due to the presence of dynamic loads.