Fault current calculation method for multi-terminal DC distribution networks considering multiple distributed generation

doi:10.11930/j.issn.1004-9649.202508038

Abstract

Abstract:

In DC distribution networks, short-circuit faults can cause the current to rise to several times the normal operating level in an extremely short period, posing severe challenges to system protection and safe operation. The presence of multiple distributed generators (DGs) in DC distribution networks and the diversity of their grid-connected converters as well as the complex coupling relationships make it difficult to analyze fault characteristics and accurately calculate fault currents, which is unfavorable to the design of protection strategies. To address this issue, this paper proposes a fault current calculation model for DC distribution networks with multiple DGs. First, a fault equivalent circuit of the voltage source converter (VSC) is established, and the fault response characteristics of PV Boost converters, distributed wind power machine-side converters (MSC), energy storage dual active bridge (DAB) converters and VSCs are analyzed to construct multi-scenario fault equivalent circuits. Second, proceeding from the multi-stage transient response process of fault current, a fault current calculation model is built, covering the initial steady-state stage before fault, DC bus discharge stage, diode freewheeling stage and steady-state stage after fault. Then, based on the established multi-stage fault current calculation model, the key factors affecting the peak fault current are analyzed. Finally, taking a multi-terminal DC distribution network with multiple DGs as an example, the theoretical calculation results are compared with the Matlab/Simulink simulation results to verify the accuracy of the proposed model.

Key words: multi-terminal DC distribution network, distributed generation, fault equivalent circuit, fault current calculation, peak current

JIA Dongli, REN Zhaoying, LIU Keyan, YE Xueshun, LI Yuetao, XU Limei. Fault current calculation method for multi-terminal DC distribution networks considering multiple distributed generation[J]. Electric Power, 2026, 59(1): 84-96.

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URL: https://www.electricpower.com.cn/EN/10.11930/j.issn.1004-9649.202508038

https://www.electricpower.com.cn/EN/Y2026/V59/I1/84

Figures/Tables 15

Fig.1 Equivalent circuit of VSC under monopole ground fault

Fig.2 Single-phase equivalent of VSC under ground fault

Fig.3 Equivalent circuit of PV under bipole short-circuit fault

Fig.4 Equivalent circuit of distributed WT under bipole short-circuit fault

Fig.5 Equivalent circuit of energy storage under bipole short-circuit fault

Fig.6 Topology of DC distribution networks with multiple DGs

Table 1 DC distribution network simulation parameters

参数	数值
直流电压/kV	0.75
直流线路长度/km	1.7
直流线路单位长度电感/(mH·km^–1)	0.9
直流线路单位长度电阻/(mΩ·km^–1)	121
光伏Boost变换器开关频率f_PV/kHz	15
储能DAB变换器开关频率f_ES/kHz	10
VSC换流器开关频率f_VSC/kHz	10
直流负载开关频率f_DC/kHz	5
变流器额定有功功率/kW	300

Fig.7 DC capacitor discharge current of DAB converter

Fig.8 Output current of VSC

Fig.9 Short-circuit fault current

Fig.10 DC capacitor discharge current of DAB converter under different transition resistances

Fig.11 VSC output current under different transition resistances

Fig.12 Short-circuit fault current under different transition resistances

Fig.13 Peak fault current

Fig.14 Rise time of peak fault current

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