Summary
The effective management and mitigation of power system oscillations is essential for maintaining power system security. However, Inverter Based Resource (IBR) controllers, particularly in weak/radially connected parts of the network (with low system strength), can become unstable resulting in voltage oscillations known as ‘sub-synchronous controller interactions’ (SSCI) that are typically between 5-25 Hz. In the last several years, it has been observed that the increasing penetration of IBR generation and displacement of synchronous generators in the Australian National Electricity Market (NEM) system has resulted in a wider range of/more frequent poorly damped sub-synchronous oscillations at higher sub-synchronous frequencies. In particular, oscillations in the Victoria (VIC) network have been identified by
Read more Read lessAEMO. While the oscillations have mostly been low in magnitude, there were periods where they persisted for several hours with a voltage magnitude greater than 1% peak-to-peak voltage during planned transmission line outages.
This paper details a three-part structured investigation of the oscillations recently observed in the VIC network, utilising both Phasor Measurement Unit (PMU) data, as well as electromagnetic transient (EMT) models:
• application of a modified Complex Differential Energy Function (CDEF‑V) method for oscillation source location (OSL), applied consistently to both high‑resolution PMU data and wide-area EMT simulation results; • • validation of the identified interaction mechanism through wide‑area time-domain EMT simulations and supporting frequency-domain impedance scans to confirm resonance characteristics under varying system strength; and evaluation of mitigation options through both detuned plant controller settings and advanced local voltage control strategies, with each approach tested in the EMT simulation environment to assess its effectiveness in suppressing the oscillatory mode. Through this investigation, it was determined that under specific dispatch and network conditions, a subset IBRS in the region contributed to the amplification of the observed oscillation mode. The oscillations were accurately reproduced in the wide-area EMT model, and OSL analysis of the PMU data and EMT results are consistent and point to the primary contributors being connected to the VIC network where there is a large amount of IBR generation connected. Furthermore, based on the evaluation of possible mitigation strategies using EMT modelling, it was shown that the combination of a grid-forming (GFM) battery energy storage system (BESS) (system strength solution) and dynamic voltage control (DVC) strategy (tuning solution) effectively reduces the magnitude of the oscillation mode to below an acceptance threshold of 0.1% peak-to-peak voltage.
Additional informations
| Publication type | Session Materials |
|---|---|
| Reference | C4_10938_2026 |
| Publication year | |
| Publisher | CIGRE |
| Country | Australia |
| Study committees |
|
| File size | 1 MB |
| Price for non member | 30 € |
| Price for member | 30 € |
Authors
MOHSENI Nina - AEMO, Australia; OAG Steve - AEMO, Australia; BINET Maddy - AEMO, Australia; SEMSHIKOV Evgenii - AEMO, Australia
Keywords
