Abstract
Circuit breaker (CB) and fault current limiter (FCL) are two major fault protection devices used in mesh-type DC microgrids. This paper proposes the parameters selection method to obtain a reliable and economic configuration scheme of CBs and FCLs applied in mesh-type DC microgrid. The breaking time of CB, the nominal breaking current of CB and the inductance of FCL are selected as three optimization parameters in an evaluation model. Since the reliability of fault protection scheme depends on whether the nominal breaking current of the CB is greater than the line current at the breaking moment of CB, it is necessary to accurately calculate the post-fault line current. Based on this, an accurate transient DC microgrid model is presented in this paper. And then, an improved non-dominated sorting genetic algorithm II (NSGA-II) is used to configure the parameters of CBs and FCLs quickly. Besides, a case study on six-terminal DC microgrid test system shows that the proposed method can obtain accurate post-fault line current and can achieve the parameters selection of CBs and FCLs.
Highlights
The DC microgrid is a promising application in the electric power system
The main contributions of the proposed parameters selection method can be described as following: 1) An evaluation method considering all parameters of Circuit breaker (CB) and fault current limiter (FCL) is developed, and the parameters in hybrid mechanical-solid CB and inductor-type FCL were optimized as an example; 2) An accurate transient DC microgrid model considering the intermediate nodes in mesh-type topology is established in difference equation form; 3) An improved non-dominated sorting genetic algorithm II (NSGA-II) algorithm considering the calculation of non-dominated sorting and crowding distance is proposed to accelerate convergence of iteration in the parameter selection
EVALUATION MODEL OF CBS AND FCLS The short circuit parameters of CBs and FCLs are analyzed
Summary
The DC microgrid is a promising application in the electric power system. Firstly, there are no concepts of phase and reactive power in DC microgrids, so that renewable power generation system can be connected to AC/DC hybrid distribution system through DC microgrid without considering phase synchronization [1]. The transient model of DC microgrid in [13] lacks the consideration of the intermediate nodes Under this situation, a parameters selection method of CBs and FCLs in mesh-type DC microgrid is proposed in this paper. The main contributions of the proposed parameters selection method can be described as following: 1) An evaluation method considering all parameters of CBs and FCLs is developed, and the parameters in hybrid mechanical-solid CB and inductor-type FCL were optimized as an example; 2) An accurate transient DC microgrid model considering the intermediate nodes in mesh-type topology is established in difference equation form; 3) An improved NSGA-II algorithm considering the calculation of non-dominated sorting and crowding distance is proposed to accelerate convergence of iteration in the parameter selection.
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