Volume 49

Protection Coordination of Semiconductor Circuit Breakers in Ring-Type 380 V DC Microgrid Naoki Hanaoka, Yuji Higuchi, Naruto Arai, Kazuya Akiyama

Abstract

Ring-type DC microgrids (DCMGs) are attracting attention from the viewpoint of expanding the use of renewable energy and improving power resilience. In the short-circuit protection of ring-type DCMG, the direction of current flow is not determined in the ring wiring. Therefore, the method of setting the trip threshold of the circuit breaker that is included in the main line of the ring-type DCMG in steps, as used in the conventional radiation-type DCMG, does not realize protection coordination. Thus, the purpose of this study was to achieve protection coordination of multiple circuit breakers with the same trip threshold in a simpler way. The authors propose a method of enabling protection coordination by combining a semiconductor circuit breaker (SCCB) with a capacitor as an energy source, which is able to interrupt the circuit as soon as the current reaches a threshold. To verify the method, two SCCBs with a trip threshold set at 30 A were connected in series, and four patterns of capacitors (0, 50, 100, and 150 μF) were connected between the SCCBs. The experimental results showed that when the capacitance was 50 μF or less, the current flowing through the SCCB on the power supply side was higher than the trip threshold, and protection coordination could not be achieved in some cases. On the other hand, when the capacitance was 100 μF or more, the current flowing through the SCCB on the power supply side was smaller than the trip threshold, showing that the protection coordination was successful. The experiments demonstrated that short-circuit protection can be coordinated between SCCBs by connecting two SCCBs in series with the same trip threshold and connecting a capacitor of approximately 100 μF or more between the SCCBs.

Keywords DC microgrid, Protection coordination, Semiconductor circuit breaker, Short-circuit, 3-way SCCB