Design and verification of hardcore reconfigurable relay for islanding detection and subsequent mode adaptation of microgrid

Abstract

Summary Islanding detection is an important factor of the microgrid (MG) protection. Since an MG can work in two modes, ie, grid‐connected and stand‐alone/islanded mode, during any abnormality appearing in the upstream grid, the MG must be decoupled at the point of common coupling and made to operate in the islanded mode to sustain the critical loads. Because of this mode switching, it is necessary to change the pick up current settings of the overcurrent relays (OCRs) at the distributed generators (DGs) to accommodate the changes in the current levels. In this paper, a hardcore reconfigurable multifunctional relay is designed, which is used for the islanding detection as well as mode adaptation within the MG. A modular approach is used to implement the design, which is targeted on field‐programmable gate array (FPGA). Hardware description language, Verilog, is used to develop the optimized hardware. The relay has different submodules viz overcurrent, voltage unbalance, and rate of change of frequency (ROCOF) modules, which are controlled by a soft controller using a multiplexer. Hardware‐in‐loop (HIL) verification for various test cases under different power mismatches is performed on the Real Time Digital Simulator (RTDS) with FPGA setup. The results suggest that the proposed hardcore relay have the capability to identify the islanding event within permissible time and subsequently adapt to the mode of operation effectively.

Evaluation of Passive Islanding Detection Methods for Line to Ground Unsymmetrical Fault in Three Phase Microgrid Systems: Microgrid Islanding Detection Method

“…If the mismatch is too small (less than 15%) the islanding cannot be detected and hence the formation of the NDZ. Figure 4 shows the NDZ for different power mismatch percentages [8,9]. When the reference value is 88% and 110% (as per Table I), under / over voltage and grid RMS Voltage ܸ = 415V, then Vmax = 456V and Vmin = 365V.…”

FPGA implementation of an Islanding detection technique for microgrid using periodic maxima of superimposed voltage components

“…The intentional islanding is mainly performed for some maintenance works within the MG for safety of the working personnel, while the unintentional islanding occurs due to the utility grid blackout by equipment failure, natural disaster or any abnormality in the power system. System stability and power quality within the MG are adversely affected during the unintentional islanding, which can damage the electrical equipment within the islanded section [3,4].…”

Selecting and sizing transformer and AC cable for PV system's safe and reliable operation

“…Fault detection techniques are reported by the previous works. [3][4][5][6][7][12][13][14]16,[24][25][26][27][28][29][30] But other works 3-5,7,12-14 have limited fault detection to DC (PV) side without referencing AC side. On the other hand, previous studies 6,16,24-26 discuss AC (utility) side islanding detection and have proposed multitude of passive islanding detection techniques relying on the detection of V and/or f abnormality at the PCC.…”