A Comprehensive Dual Current Control Scheme for Inverter-Based Resources to Enable Correct Operation of Protective Relays

Protection and Monitoring of DESO

“…This is critical and extra care should be taken that in the future such harmonic sources will never be added to the grid. There are two ways for harmonic generation as follows: ■ Fault-triggered harmonic injection in that IBR's start producing harmonics only after fault occurrence [34], [35], and [36]. The problem with this strategy is that the harmonic generator module should rely on a fault detector as a third party, such as [35] and [36], and correct detection of faults in weak grids with low fault levels is not always possible.…”

“…The problem with this strategy is that the harmonic generator module should rely on a fault detector as a third party, such as [35] and [36], and correct detection of faults in weak grids with low fault levels is not always possible. In [34], the occurrence of a fault is detected at the location of the IBR when its terminal voltage drops below 0.9 p.u. Although [19] necessitates that DER's must keep generating during low voltage situations to meet LVRT requirements, the issue arises from the fact that SLG faults in weak or non-effectively grounded grids do not drop the below range also the voltage drop can be caused by other contingencies such as a cut in generation.…”

“…There is a wide body of research working on the development of the negative-sequence current loop to generate currents suitable enough for relays in case of unbalanced faults (e.g., SLG, LL, LLG) as Fig. 12 shows [33] and [34]. Moreover, it should be taken into account that the DC bus usually does not have enough storage capacity for supplying the inverter to make high fault currents.…”

An adaptive virtual impedance fault current limiter for optimal protection coordination of islanded microgrids

“…where k denotes the network X/R ratio. |Z fcl i | is expressed using the network X/R ratio to enable the correct operation of protective functions, such as phase selection and directional elements [26]. The impedance droop characteristic in ( 5) simulates an adaptive VI-FCL that senses the measured IIDG output voltage, v oi , during a fault and outputs a virtual impedance value depending on the fault severity.…”

“…Using Figure 2, $$| {{Z_{fc{l_i}}}} |\ $$can be written as a function of the FCL resistance and the network X/R ratio: $$\begin{equation}\underbrace {\left| {{R_{fc{l_i}}}} \right|\ \sqrt {1 + {k^2}} }_{\left| {{Z_{fc{l_i}}}} \right|} = m\left| {{v_{oi}}} \right| + c\end{equation}$$where k denotes the network X/R ratio. $$| {{Z_{fc{l_i}}}} |$$ is expressed using the network X / R ratio to enable the correct operation of protective functions, such as phase selection and directional elements [26]. The impedance droop characteristic in () simulates an adaptive VI‐FCL that senses the measured IIDG output voltage,$$\ {v_{oi}}$$, during a fault and outputs a virtual impedance value depending on the fault severity.…”