Generalized Δ-Circuit Concept for Integration of Distributed Generators in Online Short-Circuit Calculations

Vojnović

J. Mod. Power Syst. Clean Energy

et al. 2019

Self Cite

We aim to systematically review challenges imposed by emerging distributed energy resources (DERs) to model in two basic distribution management system (DMS) online applications-power flow and short-circuit analysis, as well as to offer a systematic review of potential solutions. In the last decade, electronically coupled DERs became increasingly popular. DERs can employ a wide range of control strategies for power, current, or voltage control, in both normal and faulted conditions. Therefore, DERs cannot be modeled with the traditional PQ (load or generator bus), and PV (generator bus) bus types used for modeling synchronous and induction machines in online power flow calculations. Moreover, because fault currents of DERs are limited to predefined maximal values, electronically coupled DERs cannot be represented with traditional voltage source behind impedance models for online short-circuit calculation (SCC). However, most of the DMS software packages still use the traditional models to represent all DER types, including those that are electronically coupled. This paper shows that there will be high calculation errors in such practice, which makes the system model be an inadequate representation of the system. And this will lead to serious errors in managing, control, and operation of distribution systems. Nonetheless, potential solutions to the challenges are systematically reviewed. Finally, calculation results on a distribution test system with all DER types are used to prove the claim.

Section: Traditional Short-circuit Model and Calculationmentioning

confidence: 99%

“…Depending on the way of the connection to the system, DERs can be divided into four types [88,90]. 1) Type 1: synchronous machine directly connected to the system, e.g.…”

Section: Control Strategies Implemented In Different Dersmentioning

confidence: 99%

Modeling challenges and potential solutions for integration of emerging DERs in DMS applications: power flow and short-circuit analysis

Vojnović

J. Mod. Power Syst. Clean Energy

et al. 2019

Self Cite

“…In contrast, the fault current magnitude from IBDG had been widely reported to be near to its rated current and is also a lot more complicated since it is dependent on the RCI controls. From [18], it was presented that there are a large number of possible RCI controls/fault current controls. However, these vastly different fault current controls had been widely reported to result in difficulties for the microgrid protection based on DOCR, as the need for the IBDG-generated fault current to be picked up by the DOCR is not the priority in an inverter design.…”

Section: Fault Current Analysis For Synchronous Dg and Ibdgmentioning

confidence: 99%

A Novel Reactive Current Injection (RCI) Control for Microgrid Protection with Inverter Based Distributed Generation (IBDG)

et al. 2019

As the development of renewable distributed generations (DGs) is growing rapidly, the autonomous self-healing microgrid had emerged as an effective solution for integrating renewable DGs in the distribution networks. However, before the autonomous self-healing microgrid can be realized, one of the main issues that needs to be resolved is the ability to utilize the most cost-effective protection system-overcurrent relays-to achieve the goal. However, the overcurrent relay is insensitive to the limited fault current contributed by the inverter-based distributed generation (IBDG). Therefore, this paper will propose a novel inverter fault current control with a reactive current injection (RCI) that injects the correct fault current vector, albeit with a limited magnitude, for detection by the cost-effective directional overcurrent relay. This paper will also evaluate the performances of the different RCI controls in delivering an efficient self-healing microgrid protection based on a directional overcurrent relay. The proposed self-healing protection scheme is tested with both a simple distribution test network and also the IEEE 16 bus test system, considering random system parameters like variations in IBDG location, fault location, load capacity and load power factor. Moreover, the performance of the proposed inverter RCI control is also tested under changing weather conditions. Energies 2019, 12, 3371 2 of 19 loads. Even if there were a downstream DG, it would have to cease its operation within 2 s in accordance with IEEE 1547IEEE -2003. At this moment, since the generations of renewable energy DGs only occupy a relatively small amount of the total generation capacity, the impacts of renewable DG disconnection are negligible. However, with the rapid growth of renewable DGs, the installed capacity will hit a substantial level, and any indiscriminate disconnection of renewable DGs may induce grid parameter variations that can lead to serious events such as a wide-scale blackout [7]. For example, it was shown in [8] that the severity of a voltage sag will increase as more renewable DGs are disconnected during a disturbance. Hence, the revision to the existing grid codes and standard are required by considering the renewable DG penetration level, in particular with regard to its response to grid disturbances.As a result, the concept of a low voltage ride through (LVRT) emerges as an alternative solution to prevent renewable DGs from disconnecting during a disturbance. During a fault-induced low voltage condition, instead of ceasing the DGs and interrupting the downstream loads due to the conventional protection intervention, an island can be formed so that the DGs remains energized to power the downstream loads. Once the disturbance is cleared, the DGs and loads will be reconnected to the main grid. Such a process is known as an autonomous self-healing microgrid, where a high reliability and high power quality can be achieved during the process. In fact, the system configuration for an intentional island, which is als...

Int Trans Electr Energ Syst

“…The inverter matrix impedance current vector (IMICV) method has also been employed to determine voltage for a radial system with grid‐connected PV inverters . A generalized delta‐shaped model for IBDG sources was integrated into the backward and forward sweep (BFS) SCC method . BIBC and BCBV matrices for IBDG sources in grid connected or islanded battery energy storage systems have also been proposed .…”

Section: Introductionmentioning

confidence: 99%

“…10 A generalized delta-shaped model for IBDG sources was integrated into the backward and forward sweep (BFS) SCC method. 11 BIBC and BCBV matrices for IBDG sources in grid connected or islanded battery energy storage systems have also been proposed. 12 Loads were converted into impedance and the postfault voltage and SCCs of IBDG sources were calculated.…”

Section: Introductionmentioning

confidence: 99%

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

Kim

2019

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.