In the rapidly evolving landscape of power grids, the integration of power electronic converters has introduced new challenges and opportunities. Traditional protection methods, once reliable, are now struggling to keep up with the altered fault characteristics of modern grids. This is where the innovative work of Zhaoyi Sha, from the State Key Laboratory for Security and Energy Saving at the China Electric Power Research Institute in Beijing, comes into play.
Sha and his team have developed a groundbreaking protection principle for AC lines based on the multi-stage mutation of total fault current. This method addresses the inadequacies of traditional differential protection, which often fails to meet the requirements when AC lines experience faults. The new approach leverages the characteristic changes in waveform deformation and mutation features of current on both sides of the line post-fault.
“Traditional fast protection based on transient quantities that do not require the extraction of fixed frequency band features, the proposed method overcomes the challenge of accurately extracting fixed transient quantities using the periodic component algorithm under controlled short-circuit current conditions,” Sha explains. This means that the new protection method can accurately identify faults even in the presence of transitional resistance and noise, a significant improvement over conventional methods.
The key to this innovation lies in the use of the matrix gradient algorithm. This algorithm extracts the mutation feature values of total current signals on both sides of the line, describing the degree of mutation in the total current signals. This forms the basis of a longitudinal protection system that is both fast and selective.
To validate their approach, Sha and his team built a simulation model of the converter grid-connected system using PSCAD/EMTDC. The results were impressive: the proposed protection achieved fault identification in less than 7.5 ms and maintained high sensitivity even with a transitional resistance fault of 100 Ω. This level of performance is crucial for the fast response and selectivity required for inverter-interconnected lines.
The implications of this research are vast. As power grids continue to evolve with the integration of more renewable energy sources and advanced technologies, the need for robust and reliable protection methods becomes ever more critical. Sha’s work, published in Zhongguo dianli (which translates to “China Electric Power”), offers a promising solution that could shape the future of power grid protection.
For the energy sector, this means enhanced reliability, reduced downtime, and improved safety. As power grids become more complex, the ability to quickly and accurately identify faults will be essential for maintaining stability and efficiency. Sha’s research paves the way for future developments in this field, offering a glimpse into a future where power grids are not only smarter but also more resilient.
