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.

中文翻译：

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多源直流配电系统中的多重谐振和稳定性增强研究


本文解决了多源直流配电系统（DPS）中的谐振问题。与单源直流DPS中谐振频率几乎由单个压控变换器的LC滤波器固定不同，多源变换器和直流母线之间的线路阻抗会在较宽的频率范围内引起复杂的母线电压振荡，因此可能会导致系统不稳定。本文系统地研究了线路阻抗对多源直流DPS的多次谐振和稳定性问题的影响。从理论上推导了多个谐振频率和幅度峰值，然后给出了负载变换器截止频率的设计边界，以提高系统稳定性。针对基于阻抗的稳定性准则不可避免的交叉点，本文还提出了通过在负载转换器中插入串联虚拟阻抗（SVI）或并联虚拟阻抗（PVI）来增强稳定性的方法，其中建议采用双环控制方案来减小幅度倾斜并避免在高频范围内相交。最后搭建了双源直流DPS并验证了上述分析。