Unveiling the Future of Power Grids: AEMO's Specification for Grid-Forming Inverters
Power electronic’s dream
The growing prevalence of inverter-based resources (IBR) and the gradual retirement of synchronous generators (SG) in power grids worldwide have thrust power system operators into a realm of fresh operational challenges. These hurdles span diverse domains such as system robustness, voltage and frequency control, synchronous inertia, safeguarding power systems, and an array of other intricate phenomena.
Amid this transformative landscape, the emergence of grid-forming inverters emerges as a beacon of promise, offering a pathway to address some of the complex operational intricacies that arise from the heightened integration of IBRs.
In a notable development, the Australian Energy Market Operator (AEMO) released the Voluntary Specification for Grid-Forming Inverters in May. This work is the is the result of collaborative workshops that united stakeholders from various sectors, including Original Equipment Manufacturers (OEMs), developers, Network Service Providers, consultants, and academics.
Diving into the specifics, the specification segments the capabilities of grid-forming inverters into two distinct categories: 'core' and 'additional' capabilities. The former are indispensable for conferring grid-forming status upon a device. This document introduces two classifications of grid-forming inverters: GFM (Grid-Forming Mode) and GFL (Grid-Forming Like).
GFM inverters exhibit rapid response to voltage variations through power injection or absorption. In contrast, GFL inverters mirror this behavior but with a less sustained response. The document meticulously elaborates on their responses to voltage and phase changes, illustrated with illuminating figures.
An illuminating feature of GFM inverters is their contribution of synthetic inertia during system transients, necessitating an energy buffer or headroom. The requisites and anticipated performance during rapid active power changes, especially during frequency shifts, are outlined, underscored by the need for accord on capability enablement with Network Service Providers (NSPs) and AEMO.
Furthermore, the specification underscores the significance of GFM inverters in remote and weaker grid sections. Their role in stabilizing power systems when synchronous connections falter, along with their impact on enhancing the stability of nearby GFL inverters, takes center stage.
The document also delves into the stipulations and anticipated performance of GFM inverters in bolstering the operations of frail grids. Their prowess in furnishing damping power to oscillations and harmonic frequencies is expounded upon, along with an evaluation of oscillation damping characteristics.
Beyond their core functionalities, the document probes the additional capabilities of GFM inverters, casting light on their potential to extend beyond the core functions, incorporating complex tasks like black start capability. The document underscores the importance of operational boundaries, headroom, and energy buffers when harnessing the specification for future services.
Concluding with noteworthy insights, the specification delves into the limitations of grid-forming battery energy storage systems due to thermal constraints. It introduces the concept of overload capability in grid-forming inverters, which empowers them to temporarily operate above continuous rating levels.
In sum, the proposed specification is a treasure trove of insights into the capabilities and anticipated performance of grid-forming inverters for integration into the National Electricity Market (NEM). Its focal point rests on the pivotal role these inverters play in stabilizing power systems and elevating grid reliability. Ensure you explore it further here: