Series and shunt DC electric springs

Electric springs (ES) have been proposed as distributed devices for stabilizing the voltage and frequency of AC power systems. Similarly, its DC counterparts in the form of DC electric springs (DC-ES), which are connected in series with non-critical loads to form a smart load, can be applied for the voltage stabilization of DC grids. In this paper, configuration of series and shunt DC-ES and their respective operating modes are discussed. Comparisons are made for both types of ES on their functionalities of DC bus voltage regulation, load harmonics compensation, and fault-ride-through application. Their respective limitations in dealing with different voltage issues have been addressed. Experimental works of DC-ES applied to a 48 V DC micro-grid is conducted for verification. The results show a good agreement with the theoretical analysis, illustrating that the DC-ES can be an effective solution to provide simultaneous functions including DC micro-grid bus voltage regulation, harmonic compensation, and fault-ride-through.