Influence of Negative Sequence Injection Strategies on Faulted Phase Selector Performance

Abstract

Renewable power is expected to increase drastically in the coming years due to the energy transition. A large part of the newly installed generators will be connected to the power system through inverters and electronic converters, whose behaviour differs from the generators connected synchronously to the network. One of the main differences is the current contribution during symmetrical and asymmetrical faults which can affect protection systems. New grid codes establish requirements for fast current injection, but the converter’s maximum current limitations during faults make it difficult to establish control strategies for such current contribution. This paper studies the performance of faulted phase selector algorithm of a commercial relay under the current contribution from renewables before unbalanced faults. Two positive and negative sequence current injection strategies in compliance with new Spanish grid code requirements are proposed and tested under fault conditions in HiL (Hardware in the Loop). Test results show that the selected injection strategy affects the fault phase identification algorithm. Furthermore, the negative sequence injection requirements established in the new grid code improve the relay performance when line-to-line faults are applied, but they are not enough to identify all fault types.

Development of a Novel Control Scheme to Achieve the Minimum Unbalance Factor and Real Power Fluctuations under Asymmetrical Faults

“…It also did not discuss the fluctuations in the injected real power. In [11], the authors presented the impact of different k-values on selective fault detection. Two priority injection schemes were discussed.…”

“…Hence, from ( 10) and (11), it is clear that the fluctuations in both real and reactive power cannot be minimized simultaneously. The mathematical expressions for the reference currents corresponding to the minimum real power fluctuations are given in (12).…”

Faulted Phase Selection Multicriteria Algorithm Implemented in Generic Hardware for Centralized P&C in Smart Grids

“…The PV control model includes the fault-ride-through and fast fault current injection requirements defined in the Spanish Grid Code for Type D power park modules [29,30]. Furthermore, a current injection strategy that prioritizes the positive and negative sequence reactive current injection concerning the positive sequence active current injection has been used during this study, as described in [22]. Finally, a synchronous generation (GS) is connected to Bus 2.…”

“…In HiL, RTDS reproduces events that can appear in an electric power system modelled in RSCAD software, generating currents and voltages seen by the relay during a fault and recording the relay behavior. Examples of RTDS test applications can be found in [19][20][21][22]. In this study, RTDS publishes and subscribes sampled values using IEC 61850-9-2 LE profile [23] and GOOSE messages using IEC 61850-8-1.…”

Sequence Control Strategy for Grid-Forming Voltage Source Converters Based on the Virtual-Flux Orientation under Balanced and Unbalanced Faults

“…Some grid codes only require positive sequence current injection under balanced and unbalanced faults [31], but this can provoke an overvoltage in healthy phases during asymmetrical faults and negatively impact the safety of the system [32]. Furthermore, the absence of negative sequence current injection can also have a detrimental impact on the performance of protective systems, as several functions of the protection relays depend on negative sequence magnitudes, which signify imbalanced system conditions [33][34][35].…”