Abstract
The accurate transient modeling of faulty DC microgrids is the basis of fault detection, fault location and fault isolation. AC/DC and DC/DC converters keeps their normal control strategies until the fault is detected. However, in existing researches, the influence of the control effect of converters is normally being ignored in the transient characteristics of DC microgrids. This omission reduces the accuracy of the faulty transient model. Thus, this paper proposes a transient modeling method for faulty DC microgrid considering control effect of different DC/AC and DC/DC converters. Firstly, the transient characteristics of different converters (including voltage source converter, boost circuit, bidirectional chopper circuit and buck circuit) are analyzed. And then, the faulty transient model of ring-type DC microgrid is established. Furthermore, the correctness of proposed modeling method is verified by comparing with the Control-hardware-in-loop (CHIL) test system. The results show that the proposed method can not only improve the accuracy of transient analysis of faulty DC microgrid, but also enhance the calculation efficiency.
Highlights
The DC microgrid, which belongs to DC distribution system, is a promising concept in power system [1]
Compared with traditional AC distribution grids, DC microgrids have two unique advantages: 1) There is no concept of “phase” in DC microgrids, which means that the phase synchronization does not need to be considered when AC distributed renewable energies (DERs) are connected [2]; 2) Using DC microgrids to connect with DC devices (such as photovoltaic (PV), energy storage (ES)) can reduce the use of power electronic switches, which makes the distribution systems more efficient and economical [3]
Accurate transient modeling of the faulty DC microgrid is helpful for the selection of the threshold in fault detection [14] and the selection of the parameters of protection devices in fault isolation [15]
Summary
The DC microgrid, which belongs to DC distribution system, is a promising concept in power system [1]. It is necessary to analyze the control effect of converters on Voltage source converters (VSCs) and various DC/DC the fault transient characteristic Under this situation, the transient modeling and analysis microgrids. As analyzed in [18]-[22], the transient of power electronic converters in faulty DC microgrids are current being injected from VSCs can be divided into three accomplished in this paper. Short circuit current provided by the AC system through the modelled and analyzed; 2) A transient modeling method for freewheeling diode in VSCs. Unlike VSCs, there are faulty ring-type DC microgrids is proposed. The analysis in [24] microgrids; Section III analyzes the transient characteristics shows that the ES contributes to faults when the ground of DC/AC converter and DC/DC converter in a faulty ringfaults occur. Line 3-6 Fig. 1 Schematic of a ring-type DC microgrid with distributed energy access
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