Protection for DC Distribution System with Distributed Generator

Abstract

DC distribution system has advantages of high power quality, large transmission capacity, high reliability, simple structure, economy and low energy consumption, and so forth. It has been a key part of smart grid nowadays. However, the development of DC distribution system is constrained by the lack of operational experience in DC system, the small interrupting capacity of DC circuit breaker (CB), and the lack of protection schemes for system itself. In this paper, protection for DC distribution system with distributed generator (DG) is fully investigated and verified. Firstly, the electromagnetic transient model of DC distribution system with DG is presented. Simulation based on the electromagnetic transient model is carried out. Both the step response and the steady-state performance verify the accuracy of the model. Then the fault characteristic mechanism is analyzed, and the protection principles and scheme are investigated in detail, including voltage mutation principle as protection starting component, differential current protection principle for DC bus, and two-section current protection for distribution lines. Finally, transient responses with protection scheme are analyzed during faults. The results present that the protection principles and scheme are feasible for DC distribution system with DG.

Protection Principle for a DC Distribution System with a Resistive Superconductive Fault Current Limiter

“…As a result, the AC system is separated from the DC side, and the AC current drops to zero [6]. If a SFCL is not used, the fault characteristic can be divided into four stages [16], which are shown in Figure 3. In the first stage, the capacitor discharges rapidly, and the DC current gets to a large value.…”

“…As we know, before the integration of the SFCL, the overcurrent protection using the peak current could coordinate very well [16]. It can satisfy the requests for protection.…”

“…The time delay can be 0.1 s or more in the DC system [16], considering the coordination with the downstream line and the operation time that the DC circuit breaker takes. However, when the SFCL is installed, the current has already been in the steady state at 0.1 s, and the value is close to the normal value after the fault.…”

“…However, the influence of the SFCL on the fault characteristic and relay protection of the DC distribution system has had no research results till now. At present, most of the research about relay protection of the DC distribution system does not take the current limiters into consideration [11][12][13][14][15][16][17][18]. These protection schemes all apply a great short-circuit current and a low voltage.…”

Protection and energy management of zero net electric energy clusters of buildings

“…The topologies for dc distribution reported in [4], mainly contains radial type and ring type. The path of power flow is certains in radial type and power flow control is also controllable but the reliability is very low.…”