A fast fault current calculation method for distribution networks connected with inverter interfaced distributed generators

Abstract

The integration of the inverter interfaced distributed generation (IIDG) challenges the conventional fault current calculation methods. The existing fault current calculation methods for distribution networks with IIDG connection generally use nodal admittance matrix and its implicit inverse, which take a longer calculation time and are not suitable for electrical engineering. To simplify the calculation process and reduce the calculation time, a new method was proposed. The new method can estimate fault currents of the feeders with IIDG connection with a higher computation speed, using fault current values obtained in networks without IIDG connection as the initial values in the procedure. The proposed method can obtain results without modifying the node impedance matrix and the calculation time was not affected by the nodes number, which can be used for fast short-circuit current calculation in radial distribution networks with IIDG connection. The new method can be conveniently integrated into software packages for power system analysis and relay protection evaluation. The proposed method can estimate fault currents of the feeders with IIDG connection with a higher computation speed, which is beneficial for electrical engineering. The new method has advantages in calculation time and accuracy of the results in comparison with the conventional bus-oriented methods. The method proposed in this paper can be conveniently integrated into software packages for power system analysis and relay protection evaluation.

Impact of Transformer Topology on Short-Circuit Analysis in Distribution Systems with Inverter-Based Distributed Generations

“…G 2 represents a distributed generator (DG), which can be an SBDG or an IBDG in this work, while [27] tested an SBDG only. [24] Considered fault contributions from unbalanced IBDGs [25] Improved computational speed for fault analysis with IBDGs Many researchers and field operators have developed methods that can calculate the fault currents of transmission systems with synchronous-based generations, as described in [26]. However, the methodology used to deal with the systems with IBDGs has not matured yet.…”

“…Summary [19] Observed that the wind turbine controller may reduce the negative-sequence component of fault currents; injected negative-sequence currents [20] Presented the method that changed the fault current phase angle to minimize the system fault current [21] Quantified the fault current contributions due to IBDGs using steady-state and transient analyses [22] Conducted fault analysis due to IBDGs under balanced conditions [23] Considered IBDG's voltage-dependent control modes for short-circuit analysis of radial and meshed networks [24] Considered fault contributions from unbalanced IBDGs [25] Improved computational speed for fault analysis with IBDGs…”

“…Many fault analysis methods that reflect the characteristics of IBDGs have been studied [21][22][23][24][25]. In [21], the authors calculated the fault current contributions due to IBDGs using the forward-backward sweep method for the steady-state analysis and differential equations for the transient analysis.…”

“…Additionally, in [24], it was highlighted that the fault current contribution due to unbalanced IBDG sources should be considered to achieve accurate short-circuit analysis. Li and Wang [25] reduced the fault current computation time in systems with IBDGs.…”

“…Table 1 summarizes the literature survey results of short-circuit analyses. Several researchers [19][20][21][22][23][24][25] have not considered the interconnection transformer topology, which determines how to link three-phase windings among terminals (e.g., in delta or wye). This transformer topology is a critical factor affecting zero-sequence fault current flows into the fault point.…”