A Decentralized Control for Accurate Power Sharing and Precise Voltage Regulation in Hybrid Single-Phase AC/DC Microgrids

Hybrid single-phase ac/dc microgrids (MGs) consist of a dc MG and a single-phase ac MG, interconnected through an interlinking converter (IC). In this configuration, the dc MG naturally experiences a second harmonic current injection caused by the double-frequency component of the ac side instantaneous power. This paper proposes a new decentralized control method by utilization of the injected harmonic for power sharing. The proposed method enables accurate power sharing among dc sources and precise global power sharing among dc and ac sources without imposing any dc side voltage deviation. In this method, each dc source adjusts its power based on the frequency of the harmonic component. Additionally, the IC ensures that the voltage level of the dc MG remains at the rated value. Capacitive virtual impedances are integrated into the dc sources to facilitate second harmonic current sharing among them and prevent the circulation of harmonic current flow between the dc sources and the IC's dc side capacitor. To fulfill the objectives, each dc source simultaneously regulates the second harmonic voltage of its output filter capacitor and the dc component current of its output filter inductor. The effectiveness of the proposed control strategy is demonstrated through time-domain and frequency-domain simulations.