LAUSR

This paper addresses the resonance problem in a multi-source DC distribution power system (DPS). Unlike in a single-source DC DPS where the resonance frequency is almost fixed by the LC filter of the single voltage-controlled converter, line impedances between multiple source converters and DC bus will incur complex bus voltage oscillations at a wide frequency range, and thus may lead to an unstable system. This paper systemically investigates the impact of line impedance on multiple resonances and stability issues of multi-source DC DPSs. Multiple resonance frequencies and magnitude peaks are derived theoretically and then the design boundary of cut-off frequencies of load converters is also given to improve the system stability. With the unavoidable intersection by impedance-based stability criterion, this paper also proposes stability enhancement methods by inserting series virtual impedance (SVI) or parallel virtual impedance (PVI) in load converter, where a double-loop control scheme is suggested to diminish the magnitude dip and avoid the intersection at high frequency range. Finally, a two-source DC DPS is built and verifies the above analysis.