DC Microgrid Voltage Stability Through Inertia Enhancement Using a Bidirectional DC-DC Converter

Today, the presence of energy storage systems along with the alternative nature of renewable energy sources has become undeniable and one of these types of systems is battery energy storage systems. The most important factor in studying the stability of DC microgrids (DCMGs) is the stabilization of the DC bus voltage when an error occurs on its reference value. Therefore, batteries along with power electronic converters play an important role in maintaining DCMG stability. In this paper, the use of Cascaded Buck-Boost Converter (CBBC) can be considered as a suitable alternative to bidirectional buck-boost converter due to such advantages as high power density, ۹۸ % efficiency, and higher operating temperature in battery. The control strategy is applied in the microgrid implemented in the converter system set with storage, and Virtual DC Machine (VDCM) is based on charging and discharging battery through CBBC. In the studied control method, the theoretical properties of the DC machine, which is responsible for amplifying the virtual inertia in the system, are directed to the CBBC for correct switching. VDCM can be changed from motoring to generating mode or vice versa, regardless of mechanical machinery. Therefore, the proposed control system is simulated in an islanded DCMG in Matlab/Simulink and the stability of the studied system is analyzed according to the small-signal model of the proposed control and converter units. According to the simulation results and small-signal model analysis, the stability of the proposed idea under different scenarios is confirmed.

Keywords:

Renewable energy source (RES) , DC microgrid (DCMG) , cascaded buck-boost converter (CBBC) , virtual inertia , virtual DC machine (VDCM) , DC bus