Realization of future low-voltage (LV) microgrids requires that all technical issues, such as power and energy balance, power quality and protection, are solved. One of the most crucial one is the protection of LV microgrid during normal and island operation. In this paper, protection issues of LV microgrids are presented and extensions to the novel LV-microgrid-protection concept has been developed based on simulations with PSCAD simulation software. Essential in the future-protection concept for LV microgrids will be the utilization of high speed, standard, e.g., IEC-61850-based communication to achieve fast, selective, and reliable operation protection.

Microgrids can provide various economic and environmental benefits but their implementation poses great technical challenges in control, protection and energy management. One of the most important technical aspects in microgrids is distribution system protection. This paper first demonstrates a need for and then focuses on the design aspects of the adaptive protection system addressing issues such as: selection of alternative setting groups, components and system architecture; system configuration and programmed logic. The system is based on a centralized controller running the real-time analysis of the data received from the field Intelligent Electronic Devices and communicating with them by means of IEC 61850 communications. The adaptive protection and microgrid control system has been developed and currently being installed at Hailuoto island in Finland.

In this paper voltage and frequency control of islanded microgrid after intentional and unintentional switching events are investigated. The weak low voltage (LV) network based microgrid consists of two inverter based distributed generation (DG) units. One unit is a storage (battery) unit and the other is a photovoltaic (PV) cell. In this case the battery inverter with rapid response is considered to act as a master and it has the main responsibility to control the voltage and frequency in microgrid when islanded from the main distribution network. The studies are performed on a PSCAD simulation software package. Simulation studies show the voltage - active power and frequency - reactive power dependency in weak LV network. The studies also show that in order to maintain frequency balance in islanded microgrid, there is need for a reference sine wave generator inside master unit which imitates the main network phase voltages and gives the input for master units' (battery storage) PLL (phase locked loop) during islanding

The main objective of this paper is to present a comprehensive review of soft open point (SOP), an emerging power electronics technology to maximize future distribution networks’ (DNs) resiliency and flexibility as well as increase hosting capacity for distributed energy resources like photovoltaics and electric vehicles. The SOP is currently an active area of research and ongoing development of new control techniques for SOP and optimization algorithm for the optimal use of SOP in DNs produces new techniques until DN operators use it comprehensively in their systems. The motivation for this work is to present the research that has been completed for the SOP and summarize the duties of SOP in DNs according to the literature and propose advanced duties for SOP according to modern standards. Finally, future research directions are mentioned to pave the way for research in the coming years to drive the DNs towards more flexibility and ‘Robust’ from controllability, stability, and protection structure point of view.

Islanding detection methods can be divided into communication-based and local detection-based methods. Proposed local passive detection methods have traditionally been dependent on the distributed generation unit type. A large nondetection zone (NDZ) near a power balance situation and unwanted distributed generation tripping due to other network events have also been major drawbacks of traditional, passive local islanding detection methods. In this paper, a new passive local multicriteria-based islanding detection algorithm with fault detection and islanding verification logic is presented. This new islanding detection algorithm, measuring voltage unbalance and voltage total harmonic distortion from all phases, is able to detect very fast and selectively islanding situations in a perfect power balance without NDZ with a simultaneous utilization of the available fault detection information and novel islanding verification logic. In addition to the new multicriteria-based islanding detection method, the fault detection information and islanding verification logic could also be used together with any other known passive islanding detection methods, that is, parameters which are not specified in the fault-ride-through (FRT) requirements of the future grid codes, to improve the performance of these methods in terms of reliability and speed of detection.