Study on System-Level Fault Characteristics of Distributed Generation in Low-Voltage DC Systems

As more and more distributed generations are connected to the grid by converters, the topology and operation mode of the DC system undergo fundamental changes, leading to complex changes in fault characteristics. In this paper, the fault characteristics of distributed generation and its converters are analyzed from the perspective of short-circuit faults. Then simplified circuit models of distributed generation with converters are established to analyze system-level fault characteristics, including photovoltaic with Boost converter and energy storage with bidirectional Buck converter. Finally, three typical pole-to-pole short circuit are calculated, and the results are compared with the PSCAD model to verify the reliability of the simplified circuit. For photovoltaics with Boost converters, a 1Ω pole-to-pole short circuit fault on the output side will cause the peak short-circuit surge current to reach 14.8
$\boldsymbol{I}_{\boldsymbol{N}}$
. For energy storage with bidirectional Buck converters, the short-circuit current rises rapidly within 0.5 ms after short-circuit fault, and the maximum amplitude reaches more than 3kA.