# 一种基于短路电抗器的直流配网故障保护方法研究Study on Fault Protection of DC Distribution System Based on Short-Circuit Reactor

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This paper analyzes the fault process of a multi-terminal DC power distribution system to obtain the equivalent circuit when the multi-terminal DC power distribution system fails, and then calculates the fault current of the multi-terminal DC power distribution system and analyzes the fault characteristics of the system. Through simulation, it is found that when the system fails, it is difficult to distinguish between bus faults and feeder faults based on the short-circuit current charac-teristics. Therefore, this article proposes to install a series reactor at the outlet of the feeder so that the short-circuit current of the bus fault and the short-circuit current of the feeder fault can be distinguished well in the amplitude characteristics and waveform characteristics, thus providing a criterion for the protection of the multi-terminal DC power distribution system.

1. 引言

2. 网架结构

Figure 1. Structure of multi-terminal DC distribution system

3. 等效电路与短路电流分析

Figure 2. Equivalent circuit of short-circuit fault on the side of AC distribution

Figure 3. Equivalent circuit of short-circuit fault on the side of energy storage

$\left\{\begin{array}{l}{i}_{D}={i}_{B}\\ {E}_{DC}-\left({R}_{batt}+{R}_{LBD}\right){i}_{D}-{L}_{BD}\frac{\text{d}i}{\text{d}t}=0\end{array}$ (1)

$\left\{\begin{array}{l}{i}_{D}={i}_{B}=\frac{{E}_{DC}}{{R}_{batt}+{R}_{LBD}}\left(1-{\text{e}}^{t/{\tau }_{D}}\right)\\ {\tau }_{D}=\frac{{L}_{BD}}{{R}_{batt}+{R}_{LBD}}\end{array}$ (2)

$\left\{\begin{array}{l}{i}_{D}={i}_{B}+{i}_{Bus}\\ {E}_{DC}-\left({R}_{batt}+{R}_{LBD}\right){i}_{D}-{L}_{BD}\frac{\text{d}{i}_{D}}{\text{d}t}-{U}_{d}=0\\ {U}_{d}-{R}_{eqF}{i}_{B}-{L}_{eqF}\frac{\text{d}{i}_{B}}{\text{d}t}-2{R}_{Bus}{i}_{Bus}-{U}_{{C}_{Bus}}=0\\ {i}_{Bus}=\frac{{C}_{Bus}}{2}\frac{\text{d}{U}_{{C}_{Bus}}}{\text{d}t}\end{array}$ (3)

$\left\{\begin{array}{l}{i}_{D}={D}_{1}{\text{e}}^{-{\tau }_{D}t}+{D}_{2}{\text{e}}^{-{\tau }_{D}t}\\ {D}_{1}={i}_{D0}\\ {D}_{2}={i}_{D0}{\tau }_{D}+\frac{{E}_{DC}-\left(2{R}_{Bus}+{R}_{eqF}\right)}{{L}_{eqF}}\\ {\tau }_{D}=\frac{2{R}_{Bus}+{R}_{eqF}}{2{L}_{eqF}}\end{array}$ (4)

4. 改进后的故障特征分析

Figure 4. Structure of multi-terminal DC distribution system with short-circuit reactor installed

Figure 5. Equivalent circuit of short-circuit fault response on the side of AC distribution with short-circuit reactor installed

Figure 6. Equivalent circuit of short-circuit fault response on the side of energy storage with short-circuit reactor installed

5. 仿真算例

Figure 7. Short-circuit current curve without short-circuit reactor installed

Figure 8. Short-circuit current curve with different short-circuit reactor installed

Table 1. Comparison of short-circuit peak value and differential quantity with short-circuit reactor installed

Figure 9. Short-circuit current differential quantity curve with short-circuit reactor installed

6. 结论

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