Comparative Evaluation of Different Grounding Methods on the DC Side During Steady-State Operation of Low-Voltage DC Distribution Network

This research presents a comparative analysis of the effects of various grounding methods at the DC side of the Low-Voltage DC (LV-DC) distribution network, employing a single two-level voltage source converter (VSC). The study investigates how different DC-side grounding configurations influence the steady-state operation of the distribution system. An assessment framework is established using three critical steady-state performance indicators: common-mode voltage, zero-sequence current to ground, and leakage current. The analysis begins with the derivation of the common-mode voltage expression based on the VSC structure. Subsequently, employing bilateral Fourier decomposition of the AC voltage at the VSC valve side, the zero-sequence equivalent circuit for the three-phase VSC is deduced, along with the calculation expression for zero-sequence current to ground. The research further delves into the generation of leakage current and its influencing factors, following established definitions. Lastly, by comprehensively analyzing the influencing factors of the three steady-state indicators and contrasting the effects of different DC-side grounding methods on system stability, the study concludes that a non-grounded DC side exhibits superior steady-state operational characteristics, a conclusion substantiated through simulation verification.