Abstract
The recent growing diffusion of dispersed generation in low voltage (LV) distribution networks is entailing new rules to make local generators participate in network stability. Consequently, national and international grid codes, which define the connection rules for stability and safety of electrical power systems, have been updated requiring distributed generators and electrical storage systems to supply stabilizing contributions. In this scenario, specific attention to the uncontrolled islanding issue has to be addressed since currently required anti-islanding protection systems, based on relays locally measuring voltage and frequency, could no longer be suitable. In this paper, the effects on the interface protection performance of different LV generators’ stabilizing functions are analysed. The study takes into account existing requirements, such as the generators’ active power regulation (according to the measured frequency) and reactive power regulation (depending on the local measured voltage). In addition, the paper focuses on other stabilizing features under discussion, derived from the medium voltage (MV) distribution network grid codes or proposed in the literature, such as fast voltage support (FVS) and inertia emulation. Stabilizing functions have been reproduced in the DIgSILENT PowerFactory 2016 software environment, making use of its native programming language. Later, they are tested both alone and together, aiming to obtain a comprehensive analysis on their impact on the anti-islanding protection effectiveness. Through dynamic simulations in several network scenarios the paper demonstrates the detrimental impact that such stabilizing regulations may have on loss-of-main protection effectiveness, leading to an increased risk of unintentional islanding.
Highlights
In many countries, different grid codes have been recently approved with the scope of defining the connection rules for passive and/or active end-users
Local generators and storages connected to low voltage (LV) and medium voltage (MV) grids are required to participate in supporting the network stability
In the case of wind turbines, the additional active power is retrieved from the blades rotating inertia, in case of static generators the synthetic inertia function could be provided by an associated small scale local storage system
Summary
Different grid codes have been recently approved with the scope of defining the connection rules for passive and/or active end-users. The injected active power regulation (named P/f regulation) is recommended to contribute to the frequency stability of the main grid, whereas the reactive power regulation (named Q/V regulation) is focused on the control of voltage levels in the distribution network [10]. In several network scenarios (considering different imbalance levels between load and generation in the LV portion), stabilizing functions have a role in containing voltage (V) and frequency (f ) variations after the islanding event This inhibits the correct trip of currently required loss-of-main protections, resulting in an uncontrolled islanding operation for a not negligible duration. 2. Present Standard and Requirements for Distributed Generators (DGs) Connected to Low. The DSO can require active users to participate in the network frequency regulation by modulating the active power production.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
