An Iraqi-Canadian research team has created a new algorithm that can detect direction change in the line current of renewables-based microgrids. The novel approach can be applied to both grid-forming and grid-following infrastructures.
An international research team has developed a protection scheme for enhancing fault detection in inverter-based microgrids.
The scheme utilizes an algorithm based on modified cumulative sum (MCUSUM) quality control, which is a method for sudden change detection for microgrid protection.
“This method is very effective and owns high speed, even in microgrid protection,” the scientists explained. “But it is not reliable and secure enough for inverted-based microgrids, due to the above-mentioned limitations in such microgrids. So, the modification to CUSUM is proposed in this paper that enables it to detect the direction change.”
The proposed scheme can be used for both grid-forming (GFM) and grid-following (GFL) microgrids, with the related operations being activated via a selector switch. Its core is its ability to detect direction change in the line current at the instant of fault inception, with two relays monitoring the direction changes of the currents at both ends of the line.
“The relays at both ends of the line communicate with each other and share the detected changes,” the team explained. “If a falling flag is detected, the status of 0 will be sent to the other side, whereas a rising flag will prompt a transmission of 1. Then, each relay at both sides of the line will recognize that the fault is within their protection zone considering the fact that the far-end relay produces an opposite flag.”
The novel algorithm was tested through a series of simulations via Typhoon software, with both grid-connected and stand-alone modes being considered. The analysis took into account the grid codes of Germany, Spain, and Ireland, as well as different types of faults at different locations with different fault resistance values.
The scientists claimed the simulations showed the novel approach offers “effective, fast, and selective operation,” while requiring a low computational burden and simple communication infrastructures.
“The proposed method not only addresses the limitations of existing protection strategies but also showcases adaptability in diverse operational scenarios, making it a practical solution for enhancing the reliability of microgrid systems with high renewables penetration,” they concluded.
The novel methodology was introduced in “A cumulative sum-based protection method for inverter-interfaced microgrids,” published in Electric Power Systems Research. The research group comprised academics from Canada’s Toronto Metropolitan University and the Qom University of Technology in Iraq.