Summary
Islanded microgrids are considered a feasible power supply option especially for servicing communities that are located far or across difficult terrain for connection to the main interconnected power system. These microgrids are typically supplied with power from alternative generation sources such as solar photovoltaic (PV) with backup supply from battery energy storage systems (BESS). Two low power (< 100 kW) islanded microgrid systems that supplies electricity to villages in South Africa is considered. The one microgrid serves residential loads and the other microgrid serves a commercial load. The aim of the study is to assess the frequency response and the under-frequency loading shedding due to the loss of solar
Read more Read lessPV production in islanded microgrids. Power flow and frequency stability analysis is conducted for islanded microgrids using DigSilent Powerfactory simulation software. The first study considers the impact of BESS on the Primary Frequency Response (PFR) of the microgrid. The largest solar PV unit in the microgrid network is tripped and the frequency response due to this trip is analysed to determine whether the frequency remains within acceptable operating limits.
BESS systems have been known to provide droop settings between 1- 5% leading to quite fast and precise control for stabilising the frequency. The frequency range is informed by South
African National Rationalized Specifications (NRS) 048-2 where the compatibility levels of grid frequency for island grids is ± 2.5% (± 1.25 Hz) around the nominal frequency of 50 Hz. The study reveals the amount of the BESS power reserves required to maintain frequency stability in the islanded microgrids. In an interconnected power system, an underfrequency condition below a predefined limit would trigger the underfrequency load shedding (UFLS).
The second study considers a scenario without BESS and the application of UFLS scheme in islanded microgrids. To assess the performance of the UFLS scheme in an islanded microgrid, several UFLS settings are tested for various generation and load scenarios. The study results provide insights on the suitable time delays and frequency settings for implementing effective
UFLS in islanded microgrids.
Additional informations
| Publication type | Session Materials |
|---|---|
| Reference | C6_11271_2026 |
| Publication year | |
| Publisher | CIGRE |
| Country | South Africa |
| Study committees | |
| File size | 635 KB |
| Price for non member | 30 € |
| Price for member | 30 € |
Authors
NOBELA Ntwanano; OLOO Fiona; NDLOVU Given
Keywords
Battery Energy Storage System (BESS), Frequency Stability, Primary Frequency Response (PFR), Under Frequency Load Shedding (UFLS)
