With the widespread adoption of inverter-based resources (IBRs) in power systems, conventional synchronous generators are gradually being replaced, leading to significant changes in the dynamic characteristics of power systems. Particularly in scenarios with high penetration of power electronic devices, ensuring system stability under large disturbances has become a critical challenge. Recently, a research team from Tsinghua University proposed a novel method for calculating the Critical Clearing Time (CCT) sensitivity in power systems with a high proportion of power electronic devices, providing a new tool for stability analysis.
What is Critical Clearing Time (CCT)?
Critical Clearing Time (CCT) refers to the maximum time allowed for clearing a fault while maintaining system stability. CCT provides a quantitative measure of both the severity of a fault and the system's stability. Traditionally, CCT has been used to assess the rotor angle stability of synchronous generators. However, it can also be applied to other types of stability issues.
New Challenges Posed by Power Electronic Devices
Power electronic devices typically have lower overcurrent capabilities and greater control flexibility. These characteristics make the dynamic behavior of power systems more complex during faults. For example, IBRs can usually withstand no more than 20% overcurrent, meaning that current limiting modules are easily triggered during faults, thereby affecting the system's dynamic behavior. Additionally, IBRs can switch control strategies based on different operating conditions, such as Low Voltage Ride-Through (LVRT) modes, further complicating the system's dynamic response.
Core Contributions of the New Method
The research team from Tsinghua University has proposed a new method for calculating CCT sensitivity, specifically considering the effects of current limiting and control switching in power electronic devices. The main contributions of this method include:
- Impact of Current Limiting and Control Switching: The team derived an analytical method for calculating trajectory sensitivity based on sub-trajectory sensitivity and the chain rule, capable of handling trajectories with control switching. Current limiting can be treated as a special type of control switching.
- CCT Sensitivity Under Controlling Periodic Orbits (POs): In some cases, the stability boundary of the system may be controlled by periodic orbits (POs) rather than conventional fixed points (FPs). To address this, the team derived the CCT sensitivity under controlling POs and proposed a corresponding calculation method.
The above research is published in iEnergy , which is a fully open access journal published by Tsinghua University Press. iEnergy publishes peer-reviewed high-quality research representing important advances of significance to emerging power systems. At its discretion, Tsinghua University Press will pay the open access fee for all published papers from 2022 to 2026.
About iEnergy
iEnergy is a quarterly journal launched on March 2022. It has published 4 volumes (13 issues). Authors come from 21 countries, including China, the United States, Australia, etc., and world's top universities and research institutes, including University of Nebraska Lincoln, Columbia University, Imperial College of Science and Technology, Tsinghua University, etc. 12 published articles are written by academicians from various countries. The published papers have also attracted an overwhelming response and have been cited by 179 journals, including top journals in the field of power and energy like Advanced Materials, Advanced Functional Materials, Advanced Energy Materials, etc., from 45 countries.
About Tsinghua University Press
Established in 1980, as a department of Tsinghua University, Tsinghua University Press (TUP) is a leading comprehensive higher education and professional publisher in China. TUP publishes 58 journals and 42 of them are in English. There are 18 journals indexed by SCIE/ESCI. Three of them have the highest impact factor in its field. In 2022, TUP launched SciOpen . As a publishing platform of TUP, SciOpen provides free access to an online collection of journals across diverse academic disciplines and serves to meet the research needs of scientific communities. SciOpen provides end-to-end services across manuscript submission, peer review, content hosting, analytics, identity management, and expert advice to ensure each journal's development.
