Decentralized Load Sharing in a Low-Voltage Direct Current Microgrid With an Adaptive Droop Approach Based on a Superimposed Frequency

Conventional droop methods for load sharing control in low-voltage direct current microgrids suffer from poor power sharing and voltage regulation, especially in the case when operating many dc sources with long feeders. Hence, the communication-based approaches are employed to improve the load sharing accuracy and voltage regulation. To avoid using such an infrastructure and the corresponding effects on the reliability and stability, an adaptive droop controller based on a superimposed frequency is proposed in this paper. Load sharing accuracy is improved by adapting the droop gains utilizing an introduced ac power. The secondary controller locally estimates and compensates the voltage drop due to the droop controller. The proposed power sharing approach can properly control the load sharing and voltage regulation without utilizing any extra communication system. The effectiveness of the proposed control system is verified by simulations and experimental tests.