Abstract
The calculation of the short-circuit current is an important basis for fault detection and equipment selection in the DC distribution system. This paper proposes a linearized model for modular multilevel converter (MMC) considering different grounding methods and different failure scenarios. This model can be used in different fault conditions before MMC’s block. Under different fault forms, the model has different manifestations. This paper analyzes and models the DC distribution network with two types of faults: inter-pole short circuit and single-pole grounding short circuit. Among them, the modeling and analysis of single-pole grounding short-circuit uses the method of common- and differential-mode (CDM) transformation. To solve such a model, an analytical calculation method is proposed. As a mean of evaluating the effectiveness and accuracy of the proposed model, the analytical calculation solution is compared to the solution produced by PSCAD/EMTDC. A comparison of the results reveals the efficacy of the proposed model.
Highlights
With the continuous development of society, people’s production methods are becoming more and more abundant, and the demand for the use of electric energy is increasing
The calculation of the short-circuit current is an important basis for fault detection and equipment selection in the DC distribution system (Li et al, 2018)
It should be noted that in order to calculate impedance, the Y and YΔ here should be formed according to the following rules: The diagonal element Ynn, in the common-mode admittance matrix is the self-admittance of the bus n in the common-mode network, and its value is equal to the sum of the admittances of the branches connected to the bus
Summary
With the continuous development of society, people’s production methods are becoming more and more abundant, and the demand for the use of electric energy is increasing. As a kind of voltage source converters, MMC has high output waveform quality, and has low switching frequency and low loss (Xu, 2013) It is currently the key research object of DC technology. When a failure occurs at the line, it is difficult to derive the analytical expression of the fault current in the face of a complex multi-terminal DC system, and the calculation method lacks more detailed research. To bridge these gaps, this paper presents the linearized model before MMC’s block in two types of faults.
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