Steady‐state short‐circuit current calculation for internally limited inverter‐based distributed generation sources connected as current sources using the sequence method

Abstract

Summary When inverter‐based distributed generation (IBDG) sources with output current limited by an internal current loop control or other control logic are connected to power system networks, they can affect the short‐circuit current (SCC) despite their small capacities. Therefore, we derive a method to calculate steady‐state SCC from IBDG sources connected to a grid as a current source. To achieve this purpose, this study proposes a method that refers zero‐ and negative‐sequence networks to a positive‐sequence network that includes IBDG sources modeled as a current source. This study also defines positive‐sequence bus impedance and current injection matrices of the network. Subsequently, this study derives new equations that find the positive‐sequence SCC and induced voltages of the network. The proposed method can more accurately calculate SCC that flows from IBDG sources. Thus, accurate SCCs can be used for designing, planning, or maintaining power systems.

The Optimal Allocation of Distributed Generators Considering Fault Current and Levelized Cost of Energy Using the Particle Swarm Optimization Method

“…If a stationary DG is connected to the grid, it works as a current source, so we need to conduct current source analyses in addition to a voltage source analysis. For such an analysis, the detailed current injection method is introduced in other studies [30][31][32]. For example, the current source is located on the transformer side of the positive-sequence circuit, so the fault current can be calculated as:…”

A new load flow and short‐circuit analysis for unbalanced modern distribution system

“…Hence the sum of positive and negative sequence components of j th bus voltage V 0 abc j is calculated using Equation (26). The zero sequence component of the jth bus voltage V 0abc j can be neglected, 11 as in common practice, the single-phase to ground loads are connected to the ungrounded side of transformer in the distribution utility system 11 and therefore the zero sequence currents in transformer are very small as compared with the load currents.…”

“…This method has also not introduced the DGs and various transformer models in the short‐circuit calculations. A sequence component based short‐circuit analysis methods for distribution grid along with IBDGs and unbalanced load models are introduced in References 26 and 27. In the method proposed in Reference 26, a current control strategy based inverter model has been considered during the short‐circuit current calculation.…”

“…A sequence component based short‐circuit analysis methods for distribution grid along with IBDGs and unbalanced load models are introduced in References 26 and 27. In the method proposed in Reference 26, a current control strategy based inverter model has been considered during the short‐circuit current calculation. Both the methods have also made an assumption during the transformation procedure (phase component to sequence component) that the mutual impedances between the phases are equal, which is not the actual case.…”