Transient Fault Analysis Method for VSC-Based DC Distribution Networks With Multi-DGs

Abstract

Flexible direct current (dc) distribution networks are the development trend for the future distribution system. However, the protection and control of these networks are vulnerable to complicated dc faults, accurate fault analysis is required. In this article, we propose a three-stage transient fault analysis method to improve the accuracy of fault characteristic calculation for the voltage source converter based dc distribution network with multi distributed generators, which can unify and simplify the calculation process of different transient fault stages. An impedance parameter decoupling approach is proposed based on the dc line parameters, which can avoid the influence of the coupling impedance on fault response. The decoupled equivalent fault circuits are established for accurate fault analysis with flexibility and independence. In addition, a three-stage fault analysis is proposed, which is able to unify the calculation process. Finally, numerical simulations based on PSCAD/EMTDC have been carried out, which well demonstrates the effectiveness of the proposed impedance decoupling approach and the accuracy of the proposed method for fault analysis. Compared with the traditional fault analysis without decoupling, the proposed method stands out the conciseness and correctness.